JP2023042154A - Permeability test device - Google Patents

Abstract

To enable the measurement of hydraulic conductivity from low permeability ground to medium-high permeability ground with a single permeability test device.SOLUTION: Airtight water tanks for pouring test water in a permeability test device are composed of two sets of airtight water tanks, a first airtight water tank with a small volume located between an outer cylindrical body and an inner cylindrical body using inner and outer double cylinders with different diameters, and a second airtight water tank of large volume located within the inner cylinder. Openings for air inflow and water injection are provided in a lower part of the outer cylinder and a lower part of the inner cylinder, respectively. By connecting the second airtight water tank to the first airtight water tank through the openings for air inflow and water injection in the lower part of the inner cylindrical body, it is possible to measure hydraulic conductivity in low-permeability ground mainly composed of the first airtight water tank, and to measure hydraulic conductivity in medium-to-high-permeability ground in which the first and second airtight tanks are combined.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a configuration of a water permeability test apparatus capable of efficiently measuring the water permeability of various grounds having different water permeability.

As one of the important functions, embankment structures (embankment bodies) such as irrigation embankments and river embankments are required to be safe against water level fluctuations and permeation of rainwater during rainfall. It is the permeability of the ground that governs this hydraulic safety, and in order to properly manage and inspect this, a permeability test device that can measure the permeability of the ground simply and accurately is required. becomes.

Recently, as such a permeability test apparatus, an airtight water tank made of a cylindrical body serving as an apparatus main body, a sealable water supply port provided at the upper end of the airtight water tank, and a sealable water supply port provided at the lower end of the airtight water tank The lower end of an airtight water tank of the same configuration is placed directly in a test hole on the ground side in which a predetermined amount of water is stored, and the lower end of the airtight water tank is maintained at a constant water level using a Marriott siphon system. By functioning as a pipe and a water injection pipe, the water level in the airtight water tank is reduced according to the water permeability of the ground in which the test hole is provided, and the water permeability is measured from the degree of reduction in the water level. is provided (see, for example, Patent Document 1).

According to such a device, when the water level in the test hole is higher than the upper end of the opening on the lower end side of the airtight water tank, the opening is completely blocked by water, and air is trapped in the airtight water tank. does not flow into the test hole, nor does water from the airtight water tank enter the test hole through the opening.

However, when water gradually permeates into the ground through the test hole from the same state, the water level in the test hole drops accordingly, and eventually the upper end of the opening is exposed to the outside air. As a result, air in a bubble state flows into the airtight water tank through the upper end of the opening, and the water in the airtight water tank flows out from the lower end of the opening according to the inflow amount, and is poured into the test hole. Then, when the amount of injected water reaches a predetermined amount equal to or greater than the permeation amount, the water level in the test hole rises again to close the upper end of the opening, and when the upper end of the opening is closed, the constant water level is maintained. .

In other words, in this device, the main body of the cylindrical structure forming an airtight water tank is installed directly in the test hole, and the opening (wall opening) on the lower end side of the device is a conventional Marriott siphon type in-situ permeability test device (patented It functions as a constant water level holding pipe and a water injection pipe of the reference 2). Therefore, unlike the conventional Marriott siphon type in-situ permeability test apparatus, long constant water level holding pipes and water injection pipes are not required. Also, the structure of the airtight water tank itself can be simplified.

As a result, in this device, the permeability test device itself basically consists of a single small-diameter cylindrical body, which significantly reduces the cost. In addition, it is convenient to carry, and it is sufficient to insert it into the test hole of the target ground and place it horizontally on crushed stone or the like filled in the test hole, which facilitates the measurement work. The decrease in the water level in the airtight water tank can also be easily read by making the cylinder forming the apparatus body transparent and marking it with a scale.

However, in the case of this permeability testing device, there is only one cylindrical airtight water tank, which is the main body of the device, and regardless of the water permeability of the target ground, the entire airtight water tank is always filled with water for measurement. Then, a permeability test is carried out. Therefore, the cylindrical volume of the airtight water tank is usually set to a large volume corresponding to highly permeable ground such as a gravel layer.

For this reason, when attempting to measure the permeability of ground with extremely low permeability (low-permeability or impermeable ground) such as a clay layer, for example, water in the test hole will not permeate into the ground. Since it is very slow, the amount of water level drop in the airtight water tank is very small, and there is a problem that it takes a very long time (several hours to several days) for measurement.

Therefore, when trying to realize an appropriate measurement time according to the difference in the permeability of the target ground including such impermeable ground, one method is Prepare three airtight water tanks with different (measured water volume), and use them for three types of permeability test equipment with different measurement areas of hydraulic conductivity: low permeability ground, medium permeability ground, and high permeability ground. It is conceivable to configure

However, in such a case, a geological survey company or the like must purchase each of these three types of permeability test equipment, which is very costly. In addition, since the hydraulic conductivity level of the ground to be measured is not known from the beginning of the measurement work, it is not possible to determine (cannot select) which type of hydraulic tester should be used for measurement. Since it is necessary to bring a type of permeability tester to measure, it only complicates the measurement work and does not shorten the measurement time at all. In addition, multiple water permeability testers are subject to restrictions on where they can be stored when not in use.

Therefore, the inventor of the present application provided a semi-circular arc-shaped partition wall in one cylindrical airtight water tank, and formed two types of large and small airtight water tanks with different capacities through the same arc-shaped partition wall. An opening that functions as a constant water level holding pipe and a water injection pipe similar to the above is provided on the outer peripheral wall of the lower end side, and a large-volume airtight water tank can be used for medium-high permeable ground, and a small-volume airtight water tank can be used for low-permeable ground. A Marriott siphon-type in-situ permeability testing device was proposed (see Patent Document 3, for example).

According to such a configuration, it is possible to appropriately measure the permeability of each of the low permeability ground and the medium-to-high permeability ground with a single permeability test device, so there is no need for a plurality of permeability test devices. The problem associated with doing is resolved.

JP 2012-127673 A JP 2010-163801 A JP 2015-45527 A

However, in the case of the permeability test apparatus of Patent Document 3, even if two types of airtight water tanks having different volumes are structurally integrated, they are completely independent in terms of measurement function, and the airtight water tanks are also mutually compatible. It is not designed to be used in a communicating fashion. Therefore, when measuring, it is necessary to measure individually using two types of large and small airtight water tanks, and it is not always possible to select and measure only one of them. Of course, when the measurement was first performed using a large-volume airtight water tank, the ground to be measured was fortunately medium- or high-permeability ground, or when the measurement was first performed using a small-volume airtight water tank, the ground to be measured It is possible that the ground was fortunately low permeable, but it is a matter of chance, and vice versa with equal probability.

Therefore, basically, it must be assumed that the measurement will be performed twice individually, and the measurement work will be as complicated as when using the above-mentioned multiple permeability test devices, and the measurement time will not necessarily be shortened. do not have.

In addition, in the case of the permeability test apparatus of Patent Document 3, first, the volume of the airtight water tank for medium-to-high permeability ground must be sufficiently large so that it alone can be used, and furthermore, the capacity of the airtight tank for low-permeability ground Since the volume of the airtight water tank is added, the overall size of the airtight water tank (the diameter of the cylindrical body forming the airtight water tank) increases accordingly. As a result, the size of the main body of the apparatus is increased, and the portability and operability during measurement are deteriorated.

Further, in the case of the water permeability test apparatus of Patent Document 3, similarly to the case of the water permeability test apparatus of Patent Document 1, the determination of the constant water level state must be confirmed only by the water level in the test hole. Moreover, it must be determined whether or not the same water level is at the upper end position of the opening for both air inflow and water injection on the lower end side of the airtight water tank. However, the water level in the test hole is a certain dimension (for example, about 5 cm) below the ground surface and cannot be seen horizontally. Also, the water is transparent. Therefore, it is not necessarily easy to determine that the water level in the test hole has reached the upper end position of the opening.

In addition, regarding the installation position of the openings, in the case of a large-volume airtight water tank, a plurality of sets of openings for both air inflow and water injection are provided in a wide range in the circumferential direction except for the small-volume airtight water tank. , It is relatively easy to see, but in the case of a small-volume airtight water tank, since only one opening is provided in a part of the peripheral wall of a large-volume airtight water tank, it cannot be seen at all from the other side. Therefore, determination of a constant water level condition is less straightforward.

The difficulty in judging the constant water level state and the difficulty in seeing it resulted in the deterioration of the accuracy of the hydraulic conductivity measurement data.

Furthermore, regarding the installation of the device main body in the test hole, in the above patent document, a large number of crushed stones are spread in the test hole to form a flat installation surface for the device main body, and a level is placed on the installation surface. Although it is installed vertically, it is not always easy to cover the test hole with a large number of crushed stones to form the installation surface of the main body of the device, and the crushed stones must be removed again after the measurement is completed. . It is also troublesome work to set up vertically on the installation surface using a spirit level.

The present invention was made in order to solve such problems. Two sets of airtight water tanks, a first airtight water tank with a small volume located between the inner cylindrical body and a second airtight water tank with a large volume located in the inner cylindrical body, and an outer cylindrical body and the bottom of the inner cylinder are provided with openings for air inflow and water injection, respectively, and the second airtight water tank is connected to the first airtight water tank through the air inflow and water injection openings at the bottom of the inner cylinder. , making it possible to measure the coefficient of permeability in low-permeability ground centered on the first airtight water tank, and to measure the coefficient of permeability in medium-to-high permeability ground in which the first airtight water tank is combined with the second airtight water tank. It is an object of the present invention to provide a water permeability testing device that is

Therefore, the present invention is provided with the following effective problem-solving means.

(1) Means for Solving the Problems of the Invention of Claim 1 The means for solving the problems of the present invention consists of an airtight water tank for water injection in which water for measurement is stored, and an air inflow and water injection water tank provided at the bottom of the airtight water tank. The bottom of an airtight water tank equipped with openings for air inflow and water injection is submerged in the test hole on the ground side in which a predetermined amount of test water is stored, and the air inflow and water injection openings are Marriott siphon type. It is a permeability testing device that functions as a constant water level holding pipe and a water injection pipe, and measures the permeability of the target ground from the decrease in the water level in the airtight water tank. A first airtight water tank with a small volume located between the outer cylinder and the inner cylinder and a second airtight water tank with a large volume located in the inner cylinder are used. In addition to forming two sets of airtight water tanks, openings for air inflow and water injection are provided in the lower part of the outer cylinder and the lower part of the inner cylinder, respectively, and the inner cylinder has air inflow and water injection openings. Communicate the second airtight water tank with the first airtight water tank through the first airtight water tank, measure the permeability coefficient in the low permeability ground centering on the first airtight water tank, and combine the first airtight water tank with the second airtight water tank It is characterized by being able to measure hydraulic conductivity in medium-high permeability ground.

In the problem-solving means of the present invention, first, an airtight water tank for pouring water in which water for measurement is stored is positioned between an outer cylinder and an inner cylinder by means of inner and outer double cylinders with different diameters. It is composed of two sets of inner and outer airtight water tanks, a first airtight water tank with a small volume and a second airtight water tank with a large volume located in the inner cylindrical body. The lower portion of the outer cylinder and the lower portion of the inner cylinder are provided with openings for air inflow and water injection, respectively. 1. The second inner and outer airtight water tanks communicate with each other.

Therefore, when the permeation test apparatus is installed in a test hole in a predetermined measurement ground whose hydraulic conductivity is unknown, the test water begins to permeate into the measurement ground through the test hole. Then, when the permeation amount reaches a predetermined amount or more, the water level of the test water in the test hole drops below the position of the opening for air inflow in the lower portion of the outer cylindrical body. Then, the opening for air inflow in the lower part of the outer cylindrical body is opened to the atmosphere, and air flows into the first airtight water tank, which has a small volume, from the opening for air inflow, and rises as bubbles. Correspondingly, the negative pressure at the top of the first airtight water tank decreases, and the amount of measurement water corresponding to the amount of decrease flows out from the opening for water injection at the bottom of the outer cylindrical body and is injected into the test hole. . As a result, the test water level in the test hole rises again, and soon the opening for air inflow in the lower part of the outer cylindrical body is blocked by the test water in the test hole, and the inflow of air and the rise of air bubbles due to it are stopped. , water injection into the test hole is also stopped. As a result, the water level of the test water in the test hole returns to the original constant water level state, while the water level of the test water in the first airtight water tank decreases by the amount of water injected into the test hole. Therefore, the hydraulic conductivity of the measured ground is measured from the degree of decrease (elapsed measurement time and the amount of decrease in the measured water during that period).

A decrease in the water level in the first airtight water tank can be read by, for example, providing a water volume scale on the outer circumference of the outer cylindrical body. is formed sufficiently small, and the water tank portion is positioned between the outer cylindrical body and the inner cylindrical body and is formed in a thin ring structure, so that the water level changes greatly and the test hole The amount (decrease) of the measured water injected into the chamber is indicated by a relatively large drop span. Therefore, even if the measurement ground in which the test hole is formed has a low water permeability per unit time and a low permeability coefficient, the scale corresponding to the water level drop can be read easily, and the measurement time can be shortened. be done.

In the case of the means for solving the problems of the present invention, as described above, first, the hydraulic conductivity suitable for low-permeability ground is measured using the first airtight water tank having a small volume (cross-sectional area) on the outer peripheral side of the cylindrical body. will be Then, if the ground to be measured is actually low permeability ground with a low coefficient of permeability and appropriate measurement data can be acquired, the measurement ends there. That is, basically, the volume of the first airtight water tank is sufficient until the water level of the water to be measured in the first airtight water tank drops to the position of the opening for air inflow at the lower part of the inner cylindrical body. It is set to be able to measure the hydraulic conductivity of low-permeability ground.

However, even if the ground has a low permeability with a low coefficient of permeability, it may not be possible to obtain appropriate measurement data depending on the case, and the boundary between low permeability and medium permeability is not always clear. It is not classified. In such a case, the amount of water to be measured in the small-capacity first airtight water tank alone cannot be used. Therefore, in the problem-solving means of the present invention, in addition to the measurement using the measurement water in the first airtight water tank, continuous measurement is performed for a predetermined time using the measurement water in the second airtight water tank. I am making it possible.

That is, in the case of the problem-solving means of the present invention, the airtight water tank for water injection is located in the first airtight water tank with a small volume and the inner cylinder, which is located between the outer cylinder and the inner cylinder. It consists of two sets of airtight water tanks, a second airtight water tank with a large volume, and the first and second inner and outer airtight water tanks are connected via openings for air inflow and water injection in the lower part of the inner cylindrical body. are interconnected.

Therefore, when the water level in the first airtight water tank falls below the position of the air inflow opening at the bottom of the inner cylindrical body, air flows into the second airtight water tank from the air inflow opening, and the second airtight water tank The water to be measured in the airtight water tank is supplied to the first airtight water tank through the opening for water injection in the lower part of the inner cylindrical body, and the water level of the water to be measured in the first airtight water tank is determined by the above-described measurement. is lower than the position of the opening for air inflow at the bottom of the inner cylindrical body, continuous measurement is possible using the measurement water in the second airtight water tank. In other words, basically, the hydraulic conductivity measurement corresponding to the low permeability ground is performed using only the first airtight water tank, but the second airtight water tank is also used when necessary. Such a case is also included in the expression of measurement of hydraulic conductivity in low-permeability ground mainly in the first airtight water tank.

On the other hand, when the ground for measurement in which the test holes are formed is actually medium-to-high permeability ground with a large permeability coefficient, unlike the case of the low permeability ground, the test water in the test holes flows into the ground. Since it continues to permeate into the ground, a large amount of measurement water is required compared to the case of low permeability ground.

Therefore, in such a case, continuous measurement of hydraulic conductivity is performed by combining the first airtight water tank with the second airtight water tank.

That is, in the case of the same measurement, the permeability coefficient is first measured using the first airtight water tank and the openings for air inflow and water injection in the lower part of the outer cylindrical body as in the case of the permeability coefficient measurement of the low permeability ground. Start. However, in the case of medium-to-high permeability ground with a large permeability coefficient, the amount of water injected into the test hole is too large to measure the amount of water up to the opening position for air inflow at the lower part of the cylinder inside the first airtight water tank. Insufficient, the water level in the first airtight water tank soon falls below the position of the opening for air inflow at the bottom of the inner cylindrical body.

When the water level in the first airtight water tank drops below the position of the air inflow opening at the bottom of the inner cylindrical body, air flows into the large-volume second airtight water tank from the air inflow opening. A sufficient amount of water to be measured in the second airtight water tank having the correspondingly large volume flows out into the first airtight water tank from the opening for water injection at the bottom of the inner cylindrical body, and further through the first airtight water tank. Water is injected into the test hole from the water injection opening at the bottom of the outer cylindrical body until the water level reaches a constant level. As a result, the water level of the test water in the test hole reaches a constant level, and when the opening for air inflow in the lower part of the outer cylindrical body is blocked, water is no longer injected from the opening for water injection in the lower part of the outer cylindrical body. stop and the water level in the first airtight water tank rises correspondingly. When the water level in the first airtight water tank rises to the position of the opening for air inflow in the lower part of the inner cylindrical body, the injection of water into the first airtight water tank from the water injection opening in the lower part of the inner cylindrical body also stops. , the water level in the first airtight water tank becomes a constant water level, while the water level in the second airtight water tank stabilizes at a predetermined lowered position. Therefore, the hydraulic conductivity of the medium-to-high permeable ground is appropriately measured from the degree of decrease (elapsed measurement time and decrease in measured water during that period).

That is, in the configuration of the problem-solving means of the present invention, when measuring the water permeability of medium-to-high permeability ground, in addition to the water to be measured in the second airtight water tank, the water to be measured in the first airtight water tank is also continuously measured. The total volume of water measured in the second airtight water tank and the water in the first airtight water tank can be effectively used as the water volume for measuring the permeability of medium-high permeable ground. is. Therefore, compared to the case of using a small-volume first airtight water tank for low-permeability ground and a large-volume second airtight water tank for medium-to-high-permeability ground as completely separate dedicated airtight water tanks, the small-volume It is possible to reduce the overall volume (the diameter of the apparatus body having a cylindrical structure) by the first airtight water tank. Therefore, it becomes easy to handle during the measurement work. Also, since the constant water level is generated in the first airtight water tank portion of the device body, it is very easy to see.

(2) The problem-solving means of the invention of claim 2 The problem-solving means of this invention is the configuration of the problem-solving means of the invention of claim 1,
The air inflow and water injection openings provided in the lower part of the outer cylinder and the lower part of the inner cylinder are separated into an air inflow opening and a water injection opening, respectively, and the air inflow opening is It is characterized in that it is provided at a position higher than the opening for pouring water by a predetermined height.

According to such a configuration, when measuring the coefficient of permeability in the low-permeability ground centered on the first airtight water tank, and when measuring the coefficient of permeability in the medium-high permeability ground in which the first and second airtight water tanks are combined. In either case, when the water level in the first airtight water tank with a small volume becomes lower than the opening position for air inflow provided in the lower part of the inner cylindrical body, the lower part of the inner cylindrical body The provided opening for inflow of air is opened, and the air from the opening flows into the second airtight water tank having a large volume, while the water from the opening for pouring water provided at the lower part of the inner cylinder body flows into the second water tank. The water in the second airtight water tank is poured into the first airtight water tank, and is further poured into the test hole through the opening for water injection provided in the bottom of the first airtight water tank and the outer cylindrical body.

When the water level in the test hole reaches a constant water level, the air inlet opening in the lower part of the outer cylindrical body is blocked by the test water in the test hole, and the inflow of air into the first airtight water tank is stopped. Then, the injection of water from the opening for injection of water in the lower part of the cylindrical body on the outer side is also stopped.

As a result, the water level in the first airtight water tank eventually rises due to the injection of water from the water injection opening provided in the lower part of the inner cylindrical body, and the air inlet opening in the lower part of the inner cylindrical body becomes the first airtight tank. The water in the water tank is blocked, the water injection from the water injection opening provided in the lower part of the inner cylindrical body is stopped, and the water level in the first airtight water tank reaches the level of the air inflow in the lower part of the inner cylindrical body. A constant water level is maintained based on the opening position.

That is, according to the problem-solving means of the present invention, the constant water level is realized also in the first airtight water tank on the testing device side in conjunction with the constant water level in the test hole on the measurement ground side. Moreover, the constant water level position in the test apparatus side first airtight water tank is formed at a predetermined height higher than the opening for pouring water.

Therefore, the constant water level position in the first airtight water tank on the side of the test apparatus is at a position higher than the ground surface by a predetermined dimension or more, and can be sufficiently confirmed from the horizontal direction. Moreover, the constant water level in the first airtight water tank is formed over the entire circumferential direction. Therefore, it can be easily confirmed from any position in the circumferential direction, and the measurement operator can easily and accurately confirm that the water level in the test hole has reached a constant water level state without looking at the state inside the test hole. be able to judge. As a result, the measurement work becomes significantly easier, and the measurement efficiency and measurement accuracy are improved.

In this case, it is preferable that the air inflow opening provided in the lower portion of the inner cylindrical body is provided at a position higher than the air inflow opening provided in the lower portion of the outer cylindrical body by a predetermined height. By doing so, the constant water level position formed in the first airtight water tank becomes sufficiently higher than the ground surface, and the measurement water is quickly poured from the second airtight water tank into the first airtight water tank. Become. In addition, the water injection efficiency is improved.

(3) Means for Solving the Problems of the Invention of Claim 3 The means for solving the problems of the present invention is, in the configuration of the means for solving the problems of the invention of claim 1 or 2, an air inlet provided at the lower part of the outer cylindrical body. and the water injection opening and the air inflow and water injection openings provided in the lower portion of the inner cylindrical body are provided at different positions in the circumferential direction.

The openings for air inflow and water injection provided in the lower part of the outer cylindrical body and the openings for air inflow and water injecting provided in the lower part of the inner cylindrical body are provided at the same positions in the circumferential direction. Since the volume of the first airtight water tank is small, the facing distance is extremely small, and the air that has flowed in from the air inflow opening at the bottom of the outer cylinder mistakenly enters the inner side. There is a risk that the air will be sucked into the air inlet opening at the bottom of the cylinder due to the negative pressure. Therefore, it is not possible to obtain an accurate water level change according to the water permeability level of the measured ground using the second airtight water tank.

However, if the positions in the circumferential direction are different from each other as described above, the rapidly rising air bubbles that flow in from the air inlet opening in the lower part of the outer cylindrical body mistakenly enter the lower part of the inner cylindrical body. Eliminates the risk of being sucked into the opening for cleaning.

(4) Means for solving the problem of the invention of claim 4 The means for solving the problem of the invention is, in the configuration of the means for solving the problem of the invention of claim 1, 2 or 3, near the air inlet on the lower outer circumference of the outer cylindrical body. It is characterized in that a capillary space is provided between the lower outer peripheral surface of the outer cylindrical body and the surface tension is small and the water level rise is large.

According to this structure, the surface tension of the water in the opening portion for air inflow of the outer cylindrical body forming the first airtight water tank is lowered, and a minute amount of water permeates into the opening portion, resulting in an air flow. Air bubbles are easily sucked into the first airtight water tank from the inlet portion. As a result, it is possible to obtain a large number of measurement data (relatively continuous measurement data) in a short period of time even in low-permeability ground with a small permeability coefficient. As a result, accurate measurement with a large amount of data is possible compared to the conventional intermittent measurement data obtained by repeating constant water level realization. Measurement time is also shortened.

It is sufficient that the capillary space is provided corresponding to the opening for air inflow in the lower portion of the outer cylindrical body forming the first airtight water tank, and the entire lower portion of the outer cylindrical body forming the first airtight water tank is sufficient. It is not necessary to provide all the way around. If it is provided over the entire circumference of the lower portion of the outer cylindrical body, the water level rises too much, and the air bubble sucking force is reduced.

(5) Means for Solving the Problems of the Invention of Claim 5 The means for solving the problems of the present invention is a water permeability test device formed in a tubular structure in the configuration of the means for solving the problems of the invention of the above claims 1, 2, 3 or 4. It is characterized in that the main body is suspended above the test hole via a predetermined suspending means whose height is adjustable.

According to such a configuration, during measurement, the main body of the water permeability test apparatus having a cylindrical structure is securely suspended vertically above the test hole in which the test water is stored, and the openings for air inflow and water injection on the lower side are slightly sunk. It becomes possible to easily and accurately set the appropriate measurement start state. Therefore, it is no longer necessary to lay a large number of crushed stones in the test hole to form an installation surface for the main body of the permeability tester, which makes the measurement work much easier. Moreover, since the vertical state is realized more reliably, the measurement accuracy is improved.

As a result, according to the permeability test device of the present invention, from low permeability ground that requires a small amount of water to be measured to medium-to-high permeability ground that requires a medium or large amount of water to be measured, continuous measurement can be performed with a single test device. becomes possible. Moreover, it is possible to shorten the measurement time as much as possible in the low-permeability ground, and it is easy to install in the test hole. Therefore, the total measurement efficiency is greatly improved, and workability is excellent.

In addition, the first airtight water tank for measuring the permeability of low-permeability ground has a small volume (cross-sectional area) and is positioned between the outer cylinder and the inner cylinder and has a ring shape. . Therefore, even if the water level change in the test hole is small, the water level change in the first airtight water tank is shown as a large change. Therefore, even when measuring the water permeability of low-permeability ground, it is easy to read changes in the water level, making measurement easier. Measurement time is also shortened.

Furthermore, the openings for air inflow and water injection provided in the lower part of the outer cylinder and the lower part of the inner cylinder are vertically separated from the air inflow exclusive opening and the water injection exclusive opening, respectively. The opening dedicated to air inflow is provided at a position higher than the opening dedicated to water injection by a predetermined height. Therefore, in the opening for air inflow, the inflow of air and the generation of air bubbles are smooth, and the inflow efficiency is high. In addition, at the opening for water injection, the water flows smoothly and the water injection efficiency is high.

A constant water level corresponding to the constant water level of the test water in the test hole is formed in the first airtight water tank by the opening dedicated to air inflow at the lower part of the inner cylindrical body. The constant water level position in the first airtight water tank is set at a predetermined height above the ground surface where the test hole is located, since the opening dedicated to air inflow is provided at a position higher than the opening dedicated to water injection by a predetermined height. in a high position. And it is formed over the entire circumferential direction in the first airtight water tank. Therefore, it becomes extremely easy to confirm the constant water level compared to conventional confirmation in a test hole. In this respect as well, the measurement work is remarkably facilitated, and the measurement accuracy is improved.

FIG. 2 is a front view showing the configuration of the test device main body portion of the permeability test device according to the first embodiment of the present invention; It is a top view of the same test apparatus main-body part. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, showing the configuration of the test apparatus main body. FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2, showing the configuration of the test apparatus main body. It is a perspective view which shows the structure of the test device main-body part. 1 to 5 above is installed on the test hole of the surface layer above the groundwater to be measured using a tripod which is a hanging support member, and the hydraulic conductivity of the same surface layer is measured. Fig. 10 is a perspective view showing the configurations of the tripod, the test device main body, and the ground-side test hole in a state where the ground is in place; FIG. 7 is an explanatory cross-sectional view showing the relationship between the water level of test water in the test hole in the measurement state of FIG. 6 and the positions of the first air inlet and the first water inlet on the device main body side; In the measurement state of FIG. 6, the relationship between the positions of the first and second air inlets and the positions of the first and second water inlets when the water level in the test hole is constant is shown. It is an enlarged sectional view for explanation shown. In the measurement state of FIG. 6, the water level of the test water in the test hole drops below the position of the first air inlet on the device main body side due to permeation into the ground, and the first air inlet enters the first airtight water tank. 4 is an explanatory enlarged cross-sectional view showing a state in which air flows in and measurement water in a first airtight water tank is correspondingly injected into a test hole through a first water injection port on the device main body side; FIG. In the measurement state of FIG. 6, when the water level of the test water in the test hole drops below the position of the first air inlet on the apparatus main body side due to permeation into the ground, FIG. 4 is an enlarged cross-sectional view for explanation showing an air inflow state in which air flows in, and a transitional state in which the inflowing air is drawn into a first airtight water tank and becomes bubbles; 1 to 5 above is installed on the test hole in the shallow to deep ground above the groundwater to be measured using a tripod that is a suspension support member similar to FIG. Fig. 3 is an explanatory drawing showing the configuration of the shallow to deep ground, the tripod, the main body of the test apparatus, and the shallow to deep ground side test holes when the hydraulic conductivity of the upper shallow to deep ground is being measured. The structure of the water permeability test apparatus main body according to the second embodiment of the present invention, in which a capillary space is provided in the first air inlet portion on the lower side of the test apparatus main body to improve the measurement efficiency of the low permeability ground. 2 is a front view similar to FIG. 1 shown; FIG. FIG. 4 is a cross-sectional view similar to FIG. 3 showing the configuration of the main body of the water permeability test apparatus; Fig. 2 is a perspective view showing the configuration of a capillary space forming member provided in the main body of the water permeability testing apparatus; FIG. 4 is a developed view showing the configuration of a capillary space forming member provided in the main body of the water permeability test apparatus; FIG. 13 is an enlarged cross-sectional view (partially enlarged view of FIG. 13) showing the configuration of the lower part of the water permeability test apparatus main body provided with the capillary space forming member. FIG. 10 is an enlarged cross-sectional view for explaining how the permeability test apparatus in which capillary spaces are formed by a capillary space forming member improves the efficiency of measurement of low permeability ground. It is an explanatory diagram showing the configuration when performing a permeability test of shallow to deep ground above groundwater using a constant water level tank, water pipe, water stop packer, and water injection pipe using a conventional permeability test device (Patent Document 1). be.

<<First embodiment of the present invention>>
1 to 11 show the configuration of a ground permeability testing apparatus according to a first embodiment of the present invention and the implementation state of an on-site permeability test using the same testing apparatus.

<Configuration of the main body of the permeability test device>
First, FIGS. 1 to 8 show the structure of the device main body of the same water permeability testing device and each part of the same device main body.

The permeability testing apparatus 10 according to this embodiment, for example, as shown in FIGS. By coaxially inserting a second cylindrical body 12 having a diameter smaller by the dimension of and having approximately the same length, a double cylinder structure is formed with two inner and outer cylinders, and these first and second cylindrical bodies 11 , 12 are fitted with cover members 11a, 11b, 12a, 12b with high sealability in the respective openings on the upper and lower ends, and are integrated with each other.

In this case, the upper end side lid members 11a and 12a of the first and second cylindrical bodies 11 and 12 are joined and integrated with the respective upper end side openings of the first and second cylindrical bodies 11 and 12 and fixed. On the other hand, the lower end side cover members 11b and 12b are detachably fitted into the respective lower end side openings of the first and second cylindrical bodies 11 and 12, respectively. As a result, as will be described later, it is possible to inject the test water into the first and second cylindrical bodies 11 and 12 with the apparatus body turned upside down. A suspension ring 22 for suspending the main body of the apparatus is fixed to the center of the upper end side lid member 11a of the first cylindrical body 11. As shown in FIG.

A first airtight water tank 13 having a small volume and a ring-shaped (cylindrical) shape is provided between the first cylindrical body 11 having a large outer diameter and the second cylindrical body 12 having a small inner diameter. A second airtight water tank 14 having a sufficiently large volume compared to the first airtight water tank 13 and having a cylindrical shape is formed in the first cylindrical body 11 having a small inner diameter. Injection of the measurement water into the first and second cylindrical bodies 11 and 12 specifically means injection into the first and second airtight water tanks 13 and 14 .

The first and second airtight water tanks 13 and 14 having different volumes are mainly used for measuring the coefficient of permeability of low-permeability ground with a small coefficient of permeability. 13 and a second airtight water tank 14 having a large volume are mainly used for measuring the hydraulic conductivity of medium-to-high permeability ground with a large hydraulic coefficient. The diameter and length of the second cylindrical body 12 are such that an appropriate amount of water can be poured into the test hole 20 (see FIGS. 6 and 7) on the ground side according to the difference in hydraulic conductivity. It is set to a numerical value that achieves the available volume.

The first and second cylindrical bodies 11 and 12 are made of, for example, a highly transparent synthetic resin material (vinyl chloride resin, acrylic resin, etc.). 1. The state of bubble generation (air inflow state) in the second airtight water tanks 13 and 14 and the corresponding decrease in water level (decrease in water volume) can be easily confirmed from the outside. For this purpose, a water volume scale (for example, in units of 1 mm) 19 is provided on the front surface of the first cylindrical body 11 .

At a predetermined height H1 position from the lower end side opening of the outer first cylindrical body 11, first air inlets 15, 15 communicating from the outside (test hole 20) into the first airtight water tank 13 are provided. Also, at a predetermined height H2 position from the lower end side opening of the outer first cylindrical body 11, there are first water injection ports 16, 16 communicating from the inside of the first airtight water tank 13 to the outside (test hole 20). is provided. The first air inlets 15 , 15 are located above the first water inlets 16 , 16 and are provided at positions higher than the first water inlets 16 , 16 by a predetermined height. These two pairs of upper and lower pairs of the first air inlet 15, the first water inlet 16 and the first air inlet 15, the first water inlet 16 are arranged at 180 degrees in the circumferential direction. (left and right sides when viewed in the front view of FIG. 1).

Next, at a predetermined height H3 position from the lower end side opening of the inner second cylindrical body 12, there is a second air inlet 17 communicating from the outer first airtight water tank 13 to the inner second airtight water tank 14. At a predetermined height H4 position from the lower end side opening of the second cylindrical body 12, there is provided a second water inlet 18 communicating from the inside of the inner second airtight water tank 14 to the outer first airtight water tank 13. ing. The second air inlet 17 is located above the second water inlet 18 and is provided at a position higher than the second water inlet 18 by a predetermined height.

The second water inlet 18 is positioned slightly higher than the first water inlets 16, 16 on the first cylindrical body 11 side (the first water inlets 16, 16 and the second air inlets 15, 15 ), on the other hand, the second air inlet 17 is provided at a position sufficiently higher than the first air inlets 15, 15 on the first cylindrical body 11 side. Moreover, the second air inlet 17 and the second water inlet 18 are positioned at 180 degrees in the circumferential direction, and the first air inlets 15, 15 and the first water inlets 16, 16 They are provided at different positions in the circumferential direction by 90 degrees.

The first water inlets 16, 16 of the first cylindrical body 11 and the second water inlet 18 of the second cylindrical body 12 are each formed with a relatively large diameter (for example, 10 mm). The central axis is formed so as to horizontally extend from the radially inner side to the outer side.

On the other hand, the first air inlets 15, 15 of the first cylindrical body 11 and the second air inlet 17 of the second cylindrical body 12 are respectively the first water inlets of the first cylindrical body 11. 15, 15 and the diameter of the second water inlet 18 of the second cylindrical body 12 is slightly smaller (e.g., 8 mm). It is formed so as to extend obliquely with a predetermined ascending inclination angle.

When the diameters of the first air inlets 15, 15 of the first cylindrical body 11 and the diameter of the second air inlet 17 of the second cylindrical body 12 are made relatively small in this manner, these portions , the surface tension of the water on the airtight water tank side can be reduced, and the diameter of air bubbles generated in the measurement water in the first and second airtight water tanks 13 and 14 can be reduced. In that case, if the central axes of the openings of the air inlets 15, 15, and 17 extend obliquely from the radially outer side to the inner upward side at a predetermined ascending inclination angle, each of the air flows Air from the inlet efficiently flows upward into the water to be measured in the first and second airtight water tanks 13 and 14 to smoothly generate a large number of continuous air bubbles. As a result, the measurement water flows smoothly from the first water inlets 16, 16 of the first cylindrical body 11 and the second water inlet 18 of the second cylindrical body 12, and Responsiveness is improved to follow water level drop.

For this reason, according to the same configuration, the followability and responsiveness to the drop in the water level on the side of the test hole 20 are effectively improved, and the diameter of the first water injection ports 16, 16 of the first cylindrical body 11 is made to have a low water permeability. Even if it is narrowed down to some extent so as to correspond to the ground, it can sufficiently follow the water level fluctuation on the test hole 20 side.

Although not shown, each of the first air inlets 15, 15 and the first water inlets 16, 16 of the first cylinder 11 is provided with a predetermined stopcock that can be inserted and removed as an accessory. is provided. This stopcock is placed in the first cylindrical body 11 forming the first airtight water tank 13 and the second cylindrical body 12 forming the second airtight water tank 14 when measuring the hydraulic conductivity, which will be described later. It is for preventing the injected measuring water from flowing out when the measuring water is filled to the full, and each stopcock is at the stage where the lower part of the main body of the water permeability test device 10 is immersed in the test hole 20. It is drained in water so that air does not enter.

Injection of measurement water into the first cylindrical body 11 forming the first airtight water tank 13 and the second cylindrical body 12 forming the second airtight water tank 14 The stopcocks are inserted into the first air inlets 15, 15 and the first water inlets 16, 16, and then the apparatus body is turned upside down. At this time, the second air inlet 17 and the second water inlet 18 of the second cylindrical body 12 will not allow the water to flow to the outside as long as the measurement water is injected into the first and second cylindrical bodies 11 and 12. No shutoff valve is required because the measured water does not flow out.

When the injection of the measurement water into the first cylindrical body 11 forming the first airtight water tank 13 and the second cylindrical body 12 forming the second airtight water tank 14 is completed in this way, Lid members 11b and 12b are fitted and sealed to the lower end openings of the first cylindrical body 11 and the second cylindrical body 12, respectively, and then the apparatus body is returned to its original vertical position, and the lower side is opened. is submerged until the first air inlets 15, 15 and the first water inlets 16, 16 are positioned in the test water W of the test hole 20, and in this state, the stopcock is pulled out. This makes it possible to measure hydraulic conductivity (see state in FIG. 7). An example of the stop cock is shown in FIGS. 7 and 8 of Japanese Patent Application Laid-Open No. 2019-199766.

A water volume scale 19 is provided on the front surface of the first cylindrical body 11 having a large outside diameter for reading changes in the water level in the first and second airtight water tanks 13 and 14 in units of 1 mm, for example. The water level scale 19 is used to confirm the change (decrease) of the water level in the first and second airtight water tanks 13 and 14 .

<Installation structure for the test hole on the measurement ground side of the permeability test device>
The water permeability test apparatus 10 configured as described above is suspended in an accurate vertical state directly above the central portion of the test hole 20 via a tripod 5 having height adjusting means, as shown in FIG. configured to be used

The test hole 20 shown in FIG. 6 is a constant water level hole with a bottomed cylindrical structure having a diameter of 0.3 m and a depth of 0.3 m based on the standards of the Geotechnical Society on the premise of measuring the hydraulic conductivity of the surface ground. It is This test hole 20 is only formed into a cylindrical structure with a bottom after being dug with a shovel, for example, and the bottom is filled with crushed stone (2/3 the height from the bottom) as in the conventional case, and the water permeability test is performed by that. The device installation surface is not formed. Therefore, even if the ground to be measured is low-permeability ground, the penetration of the test water is relatively smooth, and the crushed stone filling portion does not become an obstacle.

The tripod 5 is provided with three sets of shoulders 51, 51, 51 at intervals of 120 degrees with respect to the central tripod main body 9, and the three sets of shoulders 51, 51, 51 are used to open the legs in both directions. Three legs 52, 52, 52 are attached as possible. Each of the legs 52, 52, 52 has a three-joint (three-stage) connection structure in which the diameter is gradually reduced from the connecting portion with the upper shoulder portion 51, 51, 51 to the lower side protruding portion 52a, 52a, 52a. By extending and contracting the connecting portions, the standing height of the entire leg portion can be adjusted as desired. Each connecting portion is provided with a locking mechanism.

A liftable elevator rack 7 is provided vertically through the tripod body 9 at the center between the shoulders 51 , 51 , 51 . The elevator rack 7 is engaged with a predetermined worm (not shown) inside the tripod body 9 at the outer peripheral portion of the main body of the rack, and can be arbitrarily raised and lowered by rotating the worm in both forward and reverse directions. ing. Reference numeral 53 is a height adjusting handle for rotating the worm in both forward and reverse directions.

The elevator rack 7 is provided with a flange portion 6 on the upper end side and a hook 7b for hanging the water permeability test device 10 on the lower end 7a side. Then, the suspension ring 11b at the upper end of the water permeability test device 10 is engaged with the same hook-shaped hook 7b, and the water permeability test device 10 is vertically hung as shown. Suspension of the water permeability test device 10 is performed as follows.

That is, first, the first and second cylindrical bodies 11 and 12 of the water permeability test apparatus 10 shown in FIGS. Then, measuring water is poured into the first and second cylindrical bodies 11 and 12 until they are completely filled. As a result, the first and second airtight water tanks 13 and 14 are filled with the measurement water. In this state, the above-mentioned stopcocks are inserted in advance into the openings 15, 15 for air inflow and the openings 16, 16 for pouring water in the lower part of the first cylindrical body 11, and are reliably sealed.

Next, a predetermined amount of test water is put into the test hole 20 using a bucket or the like, and the water level is accumulated to a predetermined level. Water is stored in the test hole 20 on the premise of this measurement. This is done after judging that the permeation of water inside has reached a predetermined saturation level.

After that, after extending the three legs 52, 52, 52 of the tripod 5 to a predetermined length in consideration of the suspension height, they are opened at equal intervals in three directions, and the lower end side protruding parts 52a, 52a, 52a It is erected so as to be positioned at each vertex of an equilateral triangle surrounding the test hole 20 in which the test water is stored. As a result, the elevator rack 7 is positioned at the center of the circular test hole 20 and extends vertically.

Next, the water permeability test device 10 to which the water to be measured has been completely injected is suspended from the lower end 7a of the elevator rack 7. As shown in FIG.

As a result, as shown in FIG. 10, the permeability test apparatus 10 is positioned in the central part (central part) of the test hole 20 in which the test water is stored, and is suspended in an accurate vertical state directly above it. Become.

Then, the height adjustment handle 53 is operated to adjust the height of the elevator rack 7, and the first air inlets 15, 15 and the first water inlets 16, 16 are provided in the lower part of the first cylindrical body 11. , the lower part of the permeability test device 10 having the second air inlet 17 and the second water inlet 18 in the lower part of the second cylindrical body 12, for example, as shown in FIG. insert into The insertion position into the test hole 20 in which the test water W is stored is such that the water surface of the test water W in the test hole 20 after insertion is the first air inlet 15 at the bottom of the first cylindrical body 11, as shown in the drawing. , 15.

Details of this state are shown enlarged in FIG. In this state, the first air inlets 15, 15 in the lower part of the first cylindrical body 11 are entirely blocked from the upper end to the lower end with the test water W in the test hole 20, and the inflow of air ( There is no draw-in due to the negative pressure in the first airtight water tank 13 , and water is not injected into the test hole 20 from the first water injection ports 16 , 16 . However, the penetration of the test water W into the ground from the test hole 20 has already started.

On the other hand, as the test water W permeates into the ground through the test hole 20 from the state shown in FIG. The surface is lowered (see H0 in FIG. 10), the first air inlets 15, 15 at the bottom of the first cylindrical body 11 are gradually opened, and air flows into the first airtight water tank 13 from the openings. will come to Then, the air that has flowed into the first airtight water tank 13 rises upward inside the water tank 13 as air bubbles. The inflow of air and the rise of air bubbles are caused by the atmospheric pressure acting on the first air inlets 15 and 15 in the lower part of the first cylindrical body 11 and the negative pressure in the first airtight water tank 13 .

That is, when the above-described constant water level surface drops due to the permeation of the test water W into the ground, the first air inlets 15, 15 in the lower part of the first cylindrical body 11 gradually open from above, and the openings 15, 15 The interface of water, which has been partially balanced with the atmospheric pressure, is pushed into the first airtight water tank 13 by the atmospheric pressure and drawn into the first airtight water tank 13 by the negative pressure in the first airtight water tank 13. . As a result, the water interface at the openings 15, 15 gradually becomes a concave interface that extends deeper into the first airtight water tank 13, as shown enlarged in FIG. When it enters, it is pulled upward by the negative pressure in the upper part of the first airtight water tank 13, and rises as air bubbles in the water (so-called piping phenomenon). Then, the air bubbles reaching the upper part of the first airtight water tank 13 reduce the negative pressure in the upper part of the airtight water tank 13, increase the water pressure, and perform corresponding water injection through the first water injection ports 16, 16. It will be.

As a result, the water level of the test water W in the test hole 20 returns to the constant water level state shown in FIG. Then, when the water level of the test water W in the test hole 20 returns to the constant water level state, the test water W blocks the first air inlets 15, 15, and the first water inlets 16, 16 flow into the test hole. Water injection to 20 also stops. The coefficient of permeability is measured from the degree of decrease in the water level in the first airtight water tank 13 during this period.

<Basic Configuration and Operation of Permeability Test Apparatus According to First Embodiment>
As described above, the permeability test apparatus 10 according to the first embodiment includes an airtight water tank for water injection in which water for measurement is stored, and an air inlet and a water inlet provided at the bottom of the airtight water tank. Then, the lower part of the airtight water tank equipped with an air inlet and a water inlet is submerged in the test hole on the ground side in which a predetermined amount of test water is stored, and the air inlet and water inlet are a Marriott siphon type constant water level holding pipe and an inlet. A water permeability test device that functions as a water pipe and measures the permeability of the target ground from the decrease in the water level in the airtight water tank, wherein the airtight water tank is composed of inner and outer double cylinders with different diameters. A first airtight water tank 13 with a small volume located between the outer first cylindrical body 11 and the inner second cylindrical body 12 and the inner second cylindrical body 12 using the body A second airtight water tank 14 having a large capacity is formed into two sets of airtight water tanks, and first airflow ports 15, 15 and a first water injection port 16, 16. A second air inlet 17 and a second water inlet 18 are provided in the lower part of the inner second cylindrical body 12, respectively, and the second air inlet 17 and the second water inlet 18 of the inner second cylindrical body 12 are provided. The second airtight water tank 14 is communicated with the first airtight water tank 13 through the water inlet 18 of No. 2, and the permeability coefficient in the low-permeability ground mainly in the first airtight water tank 13 is measured and the first The combination of the airtight water tank 13 and the second airtight water tank 14 makes it possible to measure the coefficient of permeability in medium-to-high permeability ground.

That is, in the permeability test apparatus 10 according to the first embodiment, first, an airtight water tank for water injection in which water for measurement is stored is formed into a first outer cylinder by inner and outer double cylinders having different diameters. Two inner and outer sets of a first airtight water tank 13 with a small volume located between the body 11 and the inner cylindrical body 12 and a second airtight water tank 14 with a large volume located in the second inner cylindrical body 12 is configured in an airtight water tank. In the lower part of the outer first cylindrical body 11, there are first air inlets 15, 15 and first water inlets 16, 16, and in the lower part of the inner second cylindrical body 12, there are the second An air inlet 17 and a second water inlet 18 are provided, respectively. Two sets of airtight water tanks 13 and 14, inside and outside of 2, communicate with each other.

Therefore, when the water permeability test apparatus 10 is installed in the test hole 20 of the predetermined measurement ground whose hydraulic conductivity is unknown, the test water W starts to permeate into the measurement ground through the test hole 20 . Then, when the amount of permeation reaches or exceeds a predetermined amount, the water level of the test water W in the test hole 20 drops below the position of the first air inlets 15 , 15 below the outer first cylindrical body 11 . Then, the first air inlets 15, 15 at the lower part of the outer first cylindrical body 11 are opened to the atmosphere, and the first air inlets 15, 15 flow into the small-volume first airtight water tank 13. Air flows in and rises as bubbles. Correspondingly, the negative pressure in the upper part of the first airtight water tank 13 is lowered, and an amount of measurement water corresponding to the amount of the decrease flows out from the first water inlets 16, 16 in the lower part of the outer first cylindrical body 11. Then, water is injected into the test hole 20 . As a result, the water level of the test water in the test hole 20 rises again, and soon the first air inlets 15, 15 in the lower part of the outer first cylindrical body 11 are blocked by the test water in the test hole 20, and the air The inflow of water and the rise of air bubbles due to this are stopped, and the water injection into the test hole 20 is also stopped. As a result, the water level of the test water W in the test hole 20 returns to the original constant water level state, while the water level of the measurement water in the first airtight water tank 13 decreases by the amount of water injected into the test hole 20 . . Therefore, the hydraulic conductivity of the measured ground is measured from the degree of decrease (elapsed measurement time and the amount of decrease in the measured water during that period).

A decrease in the water level in the first airtight water tank 13 can be read, for example, from a water volume scale 19 provided on the outer circumference of the outer first cylindrical body 11. In the case of the configuration of this first embodiment, the first The volume (cross-sectional area) of the airtight water tank 13 itself is formed sufficiently small, and the water tank portion is positioned between the outer first cylindrical body 11 and the inner second cylindrical body 12 to form a thin wall. Since it is formed in a ring (cylindrical) structure, the water level changes greatly, and the amount (decrease) of the measurement water injected into the test hole 20 is indicated by a relatively large drop span. Therefore, even when the measurement ground in which the test hole 20 is formed is low permeability ground with a small permeability coefficient and a low permeability per unit time, the scale corresponding to the decrease in water level is easy to read, and the measurement time is reduced. shortened.

In the case of the first embodiment, as described above, first, the first airtight water tank 13 having a small volume (cross-sectional area) on the outer peripheral side of the cylindrical body portion is used to measure the hydraulic conductivity suitable for low-permeability ground. is done. Then, if the ground to be measured is actually low permeability ground with a low coefficient of permeability and appropriate measurement data can be acquired, the measurement ends there. That is, basically, the volume of the first airtight water tank 13 is such that the water level of the water to be measured in the first airtight water tank 13 is equal to the second air inlet opening 17 at the bottom of the second cylindrical body 12 on the inner side. It is set to be able to measure the hydraulic conductivity of low-permeability ground sufficiently until it drops to the position.

However, even if the ground has a low permeability with a low coefficient of permeability, it may not be possible to obtain appropriate measurement data depending on the case, and the boundary between low permeability and medium permeability is not always clear. It is not classified. In such a case, the amount of water to be measured in the small-capacity first airtight water tank 13 alone cannot be used. Therefore, in this embodiment, in addition to the measurement using the measurement water in the first airtight water tank 13, continuous measurement is performed for a predetermined time using the measurement water in the second airtight water tank 14. I am making it possible.

That is, in the case of this embodiment, the airtight water tank for pouring water is the first airtight water tank 13 having a small volume, which is positioned between the outer first cylindrical body 11 and the inner second cylindrical body 12. It is composed of two sets of airtight water tanks, a second airtight water tank 14 with a large volume located in the inner second cylinder 12, and a second air inlet at the bottom of the inner second cylinder 12. The first and second inner and outer airtight water tanks 13 and 14 communicate with each other through the water inlet 17 and the second water inlet 18 .

Therefore, when the water level in the first airtight water tank 13 falls below the position of the second air inlet 17 at the bottom of the inner second cylindrical body 12, the second air inlet 17 flows into the second airtight water tank 14. Air flows into the inside, and the measurement water in the second airtight water tank 14 is supplied into the first airtight water tank 13 through the second water inlet 18 at the bottom of the inner second cylindrical body 12. Therefore, even if the water level in the first airtight water tank 13 is lower than the position of the second air inlet 17 at the bottom of the inner second cylindrical body 12 by the above-described measurement, the second airtightness is achieved. Continuous measurement is possible using the measurement water in the water tank 14 . In other words, basically, the measurement of the hydraulic conductivity corresponding to the low-permeability ground is performed using only the first airtight water tank 13, but the second airtight water tank 14 is also used when necessary. be. Such a case is also included in the expression of measuring the coefficient of permeability in the low-permeability ground mainly in the first airtight water tank 13 .

On the other hand, when the ground for measurement in which the test hole 20 is formed is actually a medium-to-high permeability ground with a large permeability coefficient, unlike the case of the low permeability ground, the test water in the test hole 20 is Since it continues to permeate into the ground, a larger amount of measurement water is required than in the case of low-permeability ground.

Therefore, in such a case, continuous measurement of hydraulic conductivity is performed by combining the first airtight water tank 13 with the second airtight water tank 14 .

That is, in the case of the same measurement, first, as in the case of measuring the hydraulic conductivity of the low-permeability ground, the first air inlets 15, 15 and the first 1. Begin measuring hydraulic conductivity using inlets 16, 16 of No. 1. However, in the case of medium-to-high permeability ground with a large permeability coefficient, the water volume measured up to the position of the second air inlet 17 at the bottom of the second cylindrical body 12 inside the first airtight water tank 13 was tested. The amount of water injected into the hole 20 is insufficient, and the water level in the first airtight water tank 13 drops below the position of the second air inlet 17 below the inner second cylindrical body 12 at an early stage.

When the water level in the first airtight water tank 13 falls below the position of the second air inlet 17 at the bottom of the inner second cylindrical body 12, the second air inlet 17 is opened to a second airtight tank with a large volume. Air flows into the water tank 14, and a sufficient amount of measurement water in the second airtight water tank 14 of the same volume correspondingly flows from the second water inlet 18 at the bottom of the inner second cylindrical body 12 to the second water tank. 1 airtight water tank 13, and then through the first airtight water tank 13 and into the test hole 20 from the first water inlets 16, 16 below the outer first cylindrical body 11 until the water level reaches a constant level. Water is injected. As a result, the water level of the test water in the test hole 20 reaches a constant level, and when the first air inlets 15, 15 below the outer first cylindrical body 11 are blocked, the first outer cylinder 11 is closed. Water injection from the first water injection ports 16, 16 in the lower part of the cylindrical body 11 stops, and the water level in the first airtight water tank 13 rises accordingly. When the water level in the first airtight water tank 13 rises to the position of the second air inlet 17 below the inner second cylindrical body 12, the second water inlet below the inner second cylindrical body 12 is opened. Water injection from 18 into the first airtight water tank 13 also stops, and the water level in the first airtight water tank 13 becomes a constant water level state, while the water level in the second airtight water tank 14 stabilizes at a predetermined lowered position. Therefore, the hydraulic conductivity of the medium-to-high permeable ground is appropriately measured from the degree of decrease (elapsed measurement time and decrease in measured water during that period).

That is, in the configuration of the first embodiment, when measuring the water permeability of the medium-to-high permeability ground, in addition to the water to be measured in the second airtight water tank 14, the water to be measured in the first airtight water tank 13 can also be used continuously, and the total amount of water, which is the sum of the measurement water in the second airtight water tank 14 and the measurement water in the first airtight water tank 13, is the amount of water that measures the water permeability of the medium-to-high permeability ground. can be effectively used as Therefore, compared to the case of using the small volume first airtight water tank 13 for low permeability ground and the large volume second airtight water tank 14 for medium to high water permeability ground as completely separate dedicated airtight water tanks, The overall volume (the diameter of the apparatus body having a cylindrical structure) can be reduced by the small volume of the first airtight water tank 13 . Therefore, it becomes easy to handle during the measurement work. Also, since the constant water level is generated in the first airtight water tank portion of the device body, it is very easy to see.

In the water permeability test apparatus of the first embodiment, the first air inlets 15, 15 and the first water inlets 16, 16 provided in the lower part of the outer first cylindrical body 11 in the above configuration, the inner The second air inlet 17 and the second water inlet 18 provided in the lower part of the second cylindrical body are separated into an opening dedicated to air inflow and an opening dedicated to water injection, respectively. The air inlets 15, 15 and the second air inlet 17 are provided at a predetermined height higher than the first water inlets 16, 16 and the second water inlet 18 dedicated to water injection.

According to such a configuration, when measuring the permeability coefficient in the low permeability ground centering on the first airtight water tank 13, and in the medium-high permeability ground combining the first and second airtight water tanks 13 and 14 In any case during the measurement of the coefficient, the water level in the small-volume first airtight water tank 13 is below the second air inlet 17 provided in the lower part of the inner second cylindrical body 12. When it is lower than the position, the second air inlet 17 provided at the bottom of the inner second cylindrical body 12 is opened, and the air from the second air inlet 17 flows into the large-volume second cylinder. While the water in the second airtight water tank 14 flows into the second airtight water tank 14, the water in the second airtight water tank 14 flows into the first airtight water tank 13 from the second water inlet 18 provided in the lower part of the inner second cylindrical body 12. , and further into the test hole 20 through the first airtight water tank 13 and the first water inlets 16, 16 provided in the lower part of the outer first cylindrical body 11. As shown in FIG.

When the water level in the test hole 20 reaches a constant water level, the first air inlets 15, 15 in the lower part of the outer first cylindrical body 11 are blocked by the test water in the test hole 20, and the first air inlets 15, 15 are closed. The inflow of air into the airtight water tank 13 is stopped, and the water injection from the first water injection ports 16, 16 in the lower part of the first cylindrical body 11 on the outer side is also stopped.

As a result, the water level in the first airtight water tank 13 eventually rises due to the injection of water from the second water inlet 18 provided at the bottom of the inner second cylindrical body 12 , and the inner second cylindrical body 12 The second air inlet 17 at the bottom of the is blocked by the water in the first airtight water tank 13, and water is not injected from the second water inlet 18 provided at the bottom of the inner second cylindrical body 12. Then, the water level in the first airtight water tank 13 is maintained at a constant water level based on the position of the second air inlet 17 at the bottom of the inner second cylindrical body 12 .

In other words, in the first embodiment, the constant water level is realized in the first airtight water tank 13 on the testing apparatus side in conjunction with the constant water level in the test hole 20 on the ground side to be measured. Moreover, the constant water level position in the test apparatus side first airtight water tank 13 is formed at a position higher than the second water inlet 18 by a predetermined height.

Therefore, the constant water level position in the first airtight water tank 13 on the test apparatus main body side is higher than the surface of the ground 21 by a predetermined dimension or more, and can be sufficiently confirmed from the horizontal direction. Moreover, the constant water level in the first airtight water tank 13 is formed over the entire circumferential direction. Therefore, it can be easily confirmed from any position in the circumferential direction, and the measurement operator can easily confirm that the water level in the test hole 20 has reached a constant water level state without looking at the state inside the test hole 20. be able to judge accurately. As a result, the measurement work becomes significantly easier, and the measurement efficiency and measurement accuracy are improved.

In this case, the second air inlet 17 provided in the lower part of the inner second cylindrical body 12 is closer than the first air inlets 15, 15 provided in the lower part of the outer first cylindrical body 11. is also provided at a predetermined high position (sufficiently high position). Therefore, the constant water level position formed in the first airtight water tank 13 becomes sufficiently higher than the surface of the ground 21, and the measurement water is poured into the first airtight water tank 13 from the second airtight water tank 14. faster timing. In addition, the water injection efficiency is improved.

Further, in this first embodiment, the first air inlets 15, 15 and the first water inlets 16, 16 provided in the lower part of the outer first cylindrical body 11 and the inner second The second air inlet 17 and the second water inlet 18 provided in the lower portion of the cylindrical body 12 are provided at different positions in the circumferential direction, for example, by 90 degrees.

The first air inlets 15, 15 and the first water inlets 16, 16 provided in the lower part of the outer first cylindrical body 11 and the inner second cylindrical body 12 are provided in the lower part. If the second air inlet 17 and the second water inlet 18 are provided at the same position in the circumferential direction, they will face each other. The distance is extremely small, and the air that has flowed in from the first air inlets 15, 15 at the bottom of the outer first cylindrical body 11 mistakenly enters the second air inlet 17 at the bottom of the inner second cylindrical body 12. There is a risk of being sucked in by the negative pressure. Therefore, it is not possible to obtain an accurate water level change according to the water permeability level of the measured ground using the second airtight water tank.

However, if the positions in the circumferential direction are different from each other as described above, the rapidly rising air bubbles flowing in from the first air inlets 15, 15 in the lower part of the outer first cylindrical body 11 are erroneously The possibility of being sucked into the second air inlet 17 at the bottom of the inner second cylindrical body 12 is eliminated.

In addition, in the configuration of the first embodiment, as described above, the permeability test apparatus 10 formed in a cylindrical structure as a whole is suspended via a height-adjustable tripod (predetermined suspension support means) 5. It is installed by being suspended above the test hole 20 (see FIGS. 6 and 12).

According to such a configuration, during measurement, the cylindrical water permeability test device 10 is securely suspended vertically above the test hole 20 in which the test water is stored, and the lower first air inlet opening 15, 15 and the first water-injecting openings 16, 16 can be easily and accurately installed in an appropriate measurement start state in which the portions are sunk. Therefore, it is no longer necessary to cover the test hole 20 with a large number of crushed stones to form an installation surface for the permeability tester, which greatly facilitates the measurement work. Moreover, since the vertical state is realized more reliably, the measurement accuracy is improved.

As a result, according to the permeability test apparatus 10 of the first embodiment, a single single Continuous measurement is possible with the test equipment. Moreover, it is possible to shorten the measurement time as much as possible in the low-permeability ground, and it is easy to install in the test hole 20. Therefore, the total measurement efficiency is greatly improved, and workability is excellent.

In addition, the first airtight water tank 13 for measuring the water permeability of the low-permeability ground has a small volume (cross-sectional area) and is located between the outer first cylindrical body 11 and the inner second cylindrical body 12. It has a ring-like (cylindrical) shape. Therefore, even if the water level change in the test hole 20 is small, the water level change in the first airtight water tank 13 is shown as a large change. Therefore, even when measuring the water permeability of low-permeability ground, it is easy to read changes in the water level, making measurement easier. Measurement time is also shortened.

In addition, the first air inlets 15, 15 and the first water inlets 16, 16 provided at the bottom of the outer first cylinder 11 and the inner second cylinder 12 are provided at the bottom. The second air inlet 17 and the second water inlet 18 are separated from each other and separated vertically from the air inlet and the water inlet, respectively. 15, 15 and 17 are provided at a predetermined height higher than openings 16, 16 and 18 dedicated to water injection. Therefore, in the opening for air inflow, the inflow of air and the generation of air bubbles are smooth, and the inflow efficiency is high. In addition, at the opening for water injection, the water flows smoothly and the water injection efficiency is high.

A constant water level corresponding to the constant water level of the test water in the test hole 20 is maintained in the first airtight water tank 13 by the second air inlet 17 dedicated to air inflow at the lower part of the inner second cylindrical body 12 . is formed. The constant water level position in the first airtight water tank 13 is such that the second air inlet 17 dedicated to air inflow at the lower part of the inner second cylindrical body 12 is higher than the second water inlet 18 dedicated to water injection. Since it is provided at a high position, it is located at a predetermined height higher than the ground surface where the test hole 20 is located. And it is formed over the entire circumferential direction inside the first airtight water tank 13 . Therefore, confirmation of the constant water level becomes extremely easy as compared with conventional confirmation in the test hole 20 . In this respect as well, the measurement work is remarkably facilitated, and the measurement accuracy is improved.

<Calculation of hydraulic conductivity from shallow ground to deep ground>
6 to 10 described above, a shallow test hole 20 (diameter 30 cm, depth 30 cm) of the Geotechnical Society standard is formed in the ground surface layer, and the test hole 20 shown in FIGS. 1 to 5 is formed. The method of installing the hydraulic permeability test apparatus 10 having the configuration and calculating the hydraulic conductivity has been described.

However, the permeability test apparatus 10 according to the first embodiment is not limited to the case of the shallow test hole 20 in the ground surface layer, but also the case of a deep test hole of 1 m or more in depth, or deeper than that. It is possible to conduct a permeability test at a wide range of depths from shallow ground to deep ground as shown in FIG.

In the case of a deep test hole with a depth of 1 m or more, for example, the depth of the test hole 20 is divided into the first layer and the second layer, and measurements are sequentially performed in the same manner as in the case of the test hole 20 with a depth of 30 cm. make it

In the case of the shallow ground or deep ground shown in FIG. 11, a boring machine is used to form the test hole 20A to be used. The test hole 20A is excavated step by step to target depths L1 to L4. Then, from the upper first layer No. 1 defined by the excavation depths L1 to L4, the second layer No. 2, the third layer No. 3, and the fourth layer No. 4 are dug down from the top to the bottom. Calculate the hydraulic conductivity step by step. The calculation method of the hydraulic conductivity at each depth is the same as the test hole 20 with a depth of 30 cm already described. As the permeability coefficient obtained in the permeability test, the average value of the cumulative values of the permeability coefficients K1 to K4 at each depth L1 to L4 is used. As a result, a useful permeability test value from the surface layer to the deep layer (1st layer No. 1 to 4th layer No. 4), which is truly necessary in the actual field, can be obtained, not the hydraulic conductivity of the surface layer at a depth of about 30 cm. .

As described above, in the permeability test apparatus of the first embodiment, the first layer No. 1 to fourth layer No. 4 having different depths from L1 to L4 are subjected to the same stepwise permeability test as described above for each layer. By doing this, it becomes possible to conduct a permeability test in a wide area from the shallow layer above the groundwater table to the deep layer (permeability coefficient of any layer can be calculated). Furthermore, the condition of the aspect ratio h/r represented by the ratio of the wet head h to the radius r of the test hole 20A, h/r>10 to 50, can be easily satisfied.

Of course, it is possible to conduct a water permeability test in shallow ground even by using the conventional water permeability test device (Patent Document 1/Japanese Patent Application Laid-Open No. 2012-127673) described above. FIG. 18 shows the configuration in that case.

In FIG. 18, reference numeral 30 denotes a conventional single-tube type water permeability testing apparatus, 31 is a cylindrical body forming an airtight water tank, 32 is an upper end cap of the same extending cylindrical body 31, and 33 is an extending cylindrical body 31. is a lower end cap, 31a is a water volume scale, and 34, 34, .

Reference numeral 40 denotes a constant water level tank of the same size and shape corresponding to the test hole 20 of FIG. 7 of the first embodiment described above. Locking plates 41, 41, . . . for installing the water permeability test device 30 are provided on the inner wall surface of the constant water level tank 40 with a predetermined gap from the bottom surface. A water permeability testing apparatus 30 having a cylindrical structure is installed on the locking plates 41, 41, . . . .

On the other hand, reference numeral 20B denotes a small-diameter test hole dug to predetermined depths L1 to L4 by, for example, a hand auger. This test hole 20B is dug in order from depth L1 to L2, L3, and L4, and the water permeability test is performed in order for each of these depths. Forming the test hole 20B with a hand auger is not easy, a large diameter hole cannot be properly dug, and a constant water level structure test hole such as the test hole 20 in FIG. 7 described above cannot be formed. Therefore, it is impossible to insert the cylindrical water permeability test device 30 into the test hole 20B dug with a hand auger.

Therefore, as described above, a constant water level tank 40 similar to the test hole 20 described above is installed in the upper part of the ground, a thin water pipe 42 is extended from the opening at the bottom, and the bottom side measurement area of the test hole 20B is extended. A water injection pipe 44 is provided. An air-filled water stop packer 43 is provided at the lower part of the water pipe 42 to prevent the measurement water from leaking from the measurement area to the upper layer side. Required air is supplied from an air pump on the ground through an air hose to the air-filled water stop packer 43 .

Also in this case, the permeability test by the permeability test device 30 is basically the same as the above case, and the permeability test is sequentially performed for each of L2, L3, and L4 from the depth L1, and each layer corresponding to each depth Permeability coefficients K1 to K4 of No. 1 to No. 4 are obtained.

However, in the case of this configuration, since the water permeability test device 30 cannot be inserted into the test hole 20B, a constant water level tank 40 must be provided separately. In addition to the water supply pipe 42 and the water injection pipe 44, the packer 43 for stopping water, and an air hose and an air pump associated therewith are required. It is very troublesome to attach the packer 43 for stopping water and to bulge it. Also, if the air pressure of the water stop packer 43 is low, a measurement error will occur due to water leakage. Depending on the type of soil, the walls are prone to collapse.

On the other hand, in the permeability test using the permeability test device 10 of the first embodiment described above, as shown in FIG. By forming the test hole 20A, the permeability test apparatus 10 can be easily inserted, using a tripod 5 equipped with a height adjustment means, and an elevator rack 7 having an effective length according to the depth of the test hole 20A. Suspension support enables easy and accurate positioning at predetermined depths L1 to L4. If necessary, a desired length of suspension chain or suspension rope may be interposed between the hook portion 7b on the elevator rack 7 side and the suspension ring 11b on the device main body side. Unlike excavation by a hand auger, excavation by a boring machine is not restricted by depth or soil quality, and can be freely excavated to the groundwater table.

Therefore, the problem of the conventional water permeability test device 30 described above can be reliably solved. Of course, as the test length increases as shown in FIG. 11, the amount of test water permeating into the ground also increases. Therefore, it goes without saying that the diameters of the first and second cylindrical bodies 11 and 12 are increased and the volumes of the first and second airtight water tanks 13 and 14 are increased in accordance with the test length. .

<<Second embodiment of the present invention>>
Next, FIGS. 12 to 17 show the configuration and operation of a permeability testing apparatus according to a second embodiment of the present invention.

<Configuration of the main body of the permeability test device>
The configuration of the permeability test apparatus 10 according to the second embodiment is, for example, as shown in FIGS. In the configuration of 10, it is positioned at the first air inflow openings 15, 15 on the lower outer periphery of the outer first cylindrical body 11, and is connected to the lower outer peripheral surface of the outer first cylindrical body 11. A capillary space 4 is formed in between, where the surface tension is small and the water level rise is large, and by observing the water level change in this capillary space 4 part, the measurement efficiency of the permeability test in the low permeability ground is improved. and

The first air inlets 15, 15 on the lower outer periphery of the first cylindrical body 11 are provided on the left and right sides of the lower outer periphery of the first cylindrical body 11, respectively. A pair of first water inlets 16, 16 are provided at intervals. 14 (perspective view) and FIG. ) is formed by detachably fitting the capillary space forming member 1 shown in FIG.

As shown in FIG. 14 (perspective view), the capillary space forming member 1 is an elastic member having a C-shaped cross section that is fitted flush with the lower outer periphery of the first cylindrical body 11 with a predetermined elastic pressure. It is composed of a cylinder (an elastic cylinder with a C-shaped cross section having a predetermined dimension larger than the semicircular dimension). The height of the cylindrical body portion 2 is sufficiently high to exceed the upper end of the first air inlets 15, 15 from the upper edge of the lower end lid member 11b of the first cylindrical body 11 in the fitted state. height. Inside the left and right side walls 2a, 2a on the opening side, a ( A shallow capillary space forming groove 3 is provided so that the left and right side walls 2a, 2a on the side of the opening are partially thinned.

As shown in FIGS. 14 and 15 (exploded view), the capillary space forming groove 3 has a generally mountain shape at the portions corresponding to the first air inlets 15, 15 and the first water inlets 16, 16. (isosceles triangle shape), and the upper part of the mountain shape surrounds the first air inlets 15 , 15 . Further, the upper end portion of the mountain shape extends straight upward with a width slightly narrower than the diameter of the first air inlets 15, 15, and is open to the outside from the upper ends of the left and right side walls 2a, 2a. . A rubber member (rubber sheet) 2c having a high sealing property is attached to the inner peripheral surface of the cylindrical body wall except for the capillary space forming groove 3, and the lower part of the first cylindrical body 11 shown in FIGS. When the tubular body 2 is fitted to the outer periphery, the rubber member 2c is used to apply uniform and sufficient pressure due to the elastic force of fitting of the tubular body 2. The peripheral surface portion is fitted flush with good sealing performance. The fitting elastic force of the cylindrical body part 2 is of a level such that it can be easily removed by pulling the cylindrical body part 2 in the direction opposite to that when it was fitted.

In addition, in the portions corresponding to the first water inlets 16, 16 in the lower portion of the mountain-shaped capillary space forming groove 3, upper end side arc portions have the same diameter and coaxially communicate with each other. A water inlet 2b is provided. The shape of the third water inlet 2b may be the same as that of the first water inlets 16,16. However, if it has an inverted U shape and is open downward as it is, the cylindrical body portion 2 of the capillary space forming member 1 will not interfere with the water injection from the first water injection ports 16, 16, and the test hole will not be blocked. Since the water injection distance into 20 can be shortened as much as possible, the water injection efficiency can be increased. In addition, there is an advantage that capillary water easily enters the first air inlets 15, 15.

As a result, in a state where the capillary space forming member 1 is fitted around the lower outer periphery of the first cylindrical body 11, as shown in FIG. A narrow gap-like mountain-shaped capillary space 4 is formed between the inlets 15, 15 and the first water inlets 16, 16 and the lower outer peripheral surface of the first cylindrical body 11, and the mountain-shaped capillary space 4 is formed. The upper portion is open to the outside (atmosphere) from above via a narrow straight capillary space. As a result, a capillary space 4 having a flat gap structure similar to that of a capillary having a small diameter is realized. In this case, the groove surface of the capillary space forming groove 3 and the outer peripheral surface of the first cylindrical body 11 naturally have sufficiently good wettability (a material with a small contact angle is selected).

In this case, the capillary space forming member 1 (the cylindrical body portion 2 thereof) is formed of a transparent synthetic resin material that is elastically deformable when fitted to the outer periphery of the first cylindrical body 1 and has a predetermined rigidity. be done. For the inner rubber member (rubber sheet) 2c, a transparent synthetic resin material such as silicone rubber which is soft and highly sealable is used.

In the case of such a configuration, when the permeation test apparatus 10 is installed in the test hole 20, the lower portion of the first air inlets 15, 15 in the lower part of the outer first cylindrical body 11 spreads in a mountain shape and the test hole A capillary space (capillary structure gap) 4 is formed, which is immersed in the test water in 20, extends straight upward with a width slightly wider than the diameter of the first air inlets 15, 15 at the top, and is open to the atmosphere. , the test water W in the test hole 20 rises to the first air inlets 15, 15 in a mountain shape in a state of a flat water film due to capillary action caused by the capillary space 4. As shown in FIG. Thereby, the level of the test water W in the capillary space 4 is higher than the surface level of the test water W in the test hole 20 by several centimeters. The surface tension of water at the first air inlets 15 , 15 is lowered, and air is easily sucked into the first airtight water tank 13 . In this case, it is possible to form the capillary space 4 around the entire circumference of the lower part of the first cylindrical body 11, but if this is done, the amount of the test water W rising will increase excessively, causing air (bubbles) to be sucked in. power is reduced. Therefore, in the second embodiment, the first air inlets 15, 15 are configured to correspond to the upper portions of the mountain-shaped capillary spaces, and the optimal rising state of the test water W (optimal A negative pressure state (described later) is realized.

With such a configuration, for example, the water permeability of the ground to be measured is low, and only a small amount of water permeates into the ground. Even if the water level does not decrease, the water level of the test water W in the test hole 20 decreases due to the partial increase in the water level in the capillary space 4, and the inflow of air at the first air inlets 15, 15. , relatively smoothly continuous air bubbles are generated in the first airtight water tank 13 . As a result, it has become possible to obtain a large amount of measurement data in a relatively short period of time, even from ground with low permeability and low hydraulic conductivity. Data acquisition can be improved. In addition, since the capillary space forming member 1 is formed in a transparent body like the main body side first and second cylindrical bodies 11 and 12, it is possible to clearly confirm in real time the increase in the water level due to the capillary phenomenon. and measurements can be started as early as possible. From this point as well, the measurement time can be shortened and the efficiency can be improved.

Moreover, since the capillary space forming member 1 can be arbitrarily attached to and detached from (fitted into) the first cylindrical body 11 on the main body side, it can be used as necessary. For example, as will be described later, it is used for the purpose of shortening the measurement time and increasing the efficiency when it is confirmed that the ground is of low permeability in a preliminary test after forming the test hole 20 . Therefore, the capillary space forming member 1 can be added as an optional component in the permeability testing apparatus 10 of the first embodiment.

Here, the result of observing the instant of bubble generation in the first airtight water tank 13 when the capillary space 4 is provided will be explained in detail with reference to FIG. 17 as follows.

That is, when there is a capillary space 4, the test water W has already risen to the first air inlets 15, 15 in a water film state at the start of measurement, while the first air inlets 15, 15 The surface water level (constant water level) in the test hole 20 corresponding to is partially lowered by several centimeters ΔH0 compared to the case without the capillary space 4 in FIG. 10 (see FIG. 17).

When the test water W permeates the ground from this state, although the surface water level in the test hole 20 does not decrease (although it is minute and cannot be determined), the water film rises in a mountain shape in the capillary space 4. A clear change appears in the upper part of the rising water. That is, the penetration (decrease) of several milliliters of water into the ground, which cannot be confirmed as a change in the surface water level in the test hole 20, is one of the water surfaces in the test hole 20 with the highest surface tension. It appears prominently at the top of the rising water (capillary water) in the small capillary space 4 .

As the test water continues to permeate the ground, the rising water in the capillary space 4 is forced into the first airtightness by the negative pressure in the first airtight water tank 13 at the first air inlets 15, 15 where the surface tension is small. It is drawn into the water tank 13. That is, a piping phenomenon occurs due to the difference between the negative pressure in the capillary space 4 and the negative pressure in the first airtight water tank 13 . As a result, air bubbles are generated in the first airtight water tank 13 and rise to the upper part of the first airtight water tank 13 . These bubbles are very small one by one, and they are continuous bubbles with short generation intervals. In the water volume scale 19, a drop of 1 mm level cannot be read until several bubbles are generated. In the case of the water permeability test apparatus of the first embodiment without the capillary space 4, one generated bubble is about the size of a one-yen coin, and several bubbles are generated, and while ascending in the first airtight water tank 13, they become large. Become. However, when there is capillary space 4, the bubble size hardly changes. This is thought to be due to the fact that the bubble pressure is reduced by the amount of the increase due to capillary action. Then, the negative pressure in the first airtight water tank 13 is reduced by the pressure of the raised bubbles, and the corresponding amount of measurement water flows out from the first water inlets 16, 16 and is injected into the test hole 20. . As a result, the water level of the test water W in the test hole 20 returns to the constant water level state, the water level in the capillary space 4 also returns to the original constant water level state, and the first air inlets 15, 15 are blocked. The inflow of air and the generation of air bubbles as described above are eliminated, and the injection of water into the test hole 20 from the first water injection ports 16, 16 is also eliminated.

That is, in the case of the permeability test apparatus of the first embodiment without the capillary space 4, penetration of the test water into the ground directly affects the surface water level in the test hole 20, whereas the capillary space 4 is provided. In the case of the permeability test apparatus of the second embodiment, the permeation of the test water into the ground affects the rising water in the capillary space 4 which has become negative pressure due to capillary action. In this respect, the mechanisms of bubble formation are clearly different between the two methods, and the water permeability test apparatus of the second embodiment having the capillary space 4 is effective when the water permeability of the ground to be measured is low.

As described above, the permeability test apparatus of the first embodiment without the capillary space 4 and the permeability test apparatus of the second embodiment with the capillary space 4 have different mechanisms for generating air bubbles. In the absence of the capillary space 4, the difference between the atmospheric pressure acting on the first air inlets 15 and 15 and the negative pressure in the first airtight water tank 13 causes a piping action to form air bubbles. If there is a capillary space 4, the difference between the negative pressure in the rising water (capillary water) portion due to the capillary space 4 and the negative pressure in the first airtight water tank 13 causes the piping action of bubble formation. That is, since the pressure of the rising water (capillary water) portion due to the capillary space 4 becomes lower than the atmospheric pressure, bubbles are more likely to occur.

The capillary space forming member 1 (cylindrical body portion 2) has a low water permeability of the ground to be measured, and only a small amount of water permeates into the ground. It is used when the surface water level does not drop at all even if the surface water level is observed. Therefore, it does not need to be used in the case of medium-to-high permeability measurement ground. Therefore, the set (fitting to the first cylindrical body 11) is, for example, a preliminary test before the main test in which a test hole 20 is formed, a predetermined amount of water is poured in advance, and the degree of water penetration in the ground is confirmed. It is carried out when it is confirmed that the ground to be measured is low-permeability ground based on the results of .

Then, as for the actual fitting operation on the premise of that, after that, at the start of the main test, the lower part of the water permeability test device 10 is immersed in the test hole 20 in which the necessary test water W is stored, and the immersion is performed. In this state, the first air inlets 15, 15 and the first water inlets 16, 16 may be fitted after the stopcocks are pulled out, or the first air in the first cylindrical body 11 may be inserted first. After fitting above the inlets 15, 15 and the first water inlets 16, 16, the first air inlets 15, 15 and the first air inlets 15, 15 and the first It may be set by sliding it down to a position corresponding to the water inlets 16 , 16 .

Further, in the above description, the mountain-shaped upper end portion of the capillary tube forming groove 3 in the capillary space forming member 1 extends straight upward with a width slightly narrower than the diameter of the first air inlets 15, 15 as an example. However, the diameter may be the same as that of the first air inlets 15, 15, or may be slightly wider. In that case, the mountain-shaped upper end portions of the capillary tube forming grooves 3 extending straight above the first air inlets 15, 15 extend at least a predetermined distance above the first air inlets 15, 15. is sufficient, and it is not necessary to form it higher than necessary. Therefore, it is not necessary to increase the height of the tubular portion 2 of the capillary space forming member 1 more than necessary.

<<Other Embodiments>>
The configurations of the respective parts of the first and second embodiments described above can be modified in various ways according to their purposes, and are by no means limited to the above explanations and display examples in the drawings.

1 is a capillary space forming member, 2 is a cylindrical body portion of the capillary space forming member 1, 3 is a capillary space forming groove, 4 is a capillary space, 5 is a tripod, 7 is an elevator rack, 9 is a tripod body, and 10 is a water permeability test device. , 11 is a first cylindrical body, 12 is a second cylindrical body, 13 is a first airtight water tank, 14 is a second airtight water tank, 15 is a first air inlet, 16 is a first water inlet, 17 is a second air inlet, 18 is a second water inlet, 19 is a water volume scale, 20 is a test hole, and 20A is a test hole.

Claims (5)

Consisting of an airtight water tank for water injection in which water for measurement is stored and an opening for air inflow and water injection provided at the bottom of the airtight water tank, the lower part of the airtight water tank equipped with openings for air inflow and water injection is submerged in the test hole on the ground side in which a predetermined amount of test water is stored, and the air inflow and water injection openings function as Marriott siphon type constant water level holding pipes and water injection pipes to reduce the water level in the airtight water tank. A water permeability test apparatus for measuring the water permeability of a target ground from , wherein the airtight water tank is divided into an outer cylinder and an inner cylinder using inner and outer double cylinders with different diameters It is composed of two sets of airtight water tanks, a first airtight water tank with a small volume located between and a second airtight water tank with a large volume located in the inner cylindrical body. Openings for air inflow and water injection are provided in the lower part of the cylinder, respectively, and the second airtight water tank is communicated with the first airtight water tank through the air inflow and water injection openings in the inner cylinder, Permeability test equipment characterized in that it is possible to measure the coefficient of permeability in low-permeability ground mainly using the first airtight water tank and to measure the coefficient of permeability in medium-to-high-permeability ground in which the first and second airtight tanks are combined. . The air inflow and water injection openings provided in the lower part of the outer cylinder and the lower part of the inner cylinder are separated into an air inflow opening and a water injection opening, respectively, and the air inflow opening is 2. A permeability test apparatus according to claim 1, wherein the apparatus is provided at a position higher than the opening for pouring water by a predetermined height. The air inflow and water injection openings provided in the lower part of the outer cylindrical body and the air inflow and water injecting openings provided in the lower part of the inner cylindrical body are positioned at different positions in the circumferential direction. 3. The permeability test apparatus according to claim 1, wherein the permeation test apparatus is provided at a A capillary space is provided in the vicinity of the air inlet on the lower outer periphery of the outer cylindrical body and has a small surface tension and a large water level rise between the outer cylindrical body and the lower outer peripheral surface of the outer cylindrical body. A water permeability test apparatus according to claim 1, 2 or 3. Claims 1, 2 and 3, characterized in that the main body of the permeability test apparatus formed in a cylindrical structure is suspended from the upper part of the test hole via a predetermined suspending means whose height can be adjusted. Or the water permeability test device according to 4.

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