JP5813066B2 - Permeability test equipment - Google Patents

Description

  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.

  An embankment structure (bank body) such as a pond embankment or river embankment is required to have safety against fluctuations in water level and infiltration of rainwater during rainfall as one of its important functions. It is the water permeability of the ground that dominates this hydraulic safety, and in order to properly manage and inspect this, a water permeability test device that can measure the water permeability of the ground easily and accurately is required. It becomes.

  Recently, as such a water permeability test apparatus, an airtight water tank made of a cylindrical body as the apparatus main body, a sealable water supply port provided on the upper end side of the airtight water tank, and a lower end side of the airtight water tank are provided. An airtight water tank with the same configuration is installed in the ground side test hole that stores a predetermined amount of water, and the opening on the lower end side of the airtight water tank is used as a Marriott Siphon-type constant water level holding pipe and water injection pipe. By making it function, the water level amount in the airtight water tank is reduced according to the water permeability of the ground provided with the test hole, and the water permeability is measured from the degree of decrease in the water level amount. (For example, refer to Patent Document 1).

  According to such an apparatus, the opening provided on the lower end side of the airtight water tank as the apparatus body functions as a constant water level holding pipe and a water injection pipe of a conventional Marriott siphon-type water permeability test apparatus. No constant water level holding pipe or water injection pipe is required.

  As a result, in this apparatus, the apparatus is basically composed of one cylindrical body having a small diameter, and the cost is greatly reduced. In addition, it is convenient to carry, and it is sufficient to insert it into the test hole of the target ground and install it horizontally on the crushed stone filled in the test hole, so the measurement test work becomes remarkably easy, etc. There are great benefits.

JP 2012-127673 A (specifications, pages 5 to 7, FIGS. 1 to 3)

  In the case of the above-mentioned water permeability test apparatus, there is one airtight water tank with a cylindrical structure which is the main body of the apparatus. Regardless of the water permeability of the target ground, water for measurement is always accumulated in one whole airtight water tank, A water permeability test is performed. Therefore, the cylinder volume of the airtight water tank is usually set to a large volume corresponding to a highly permeable ground such as a gravel layer.

  For this reason, when trying to measure the permeability of ground with very low water permeability (impervious ground) such as a clay layer, the penetration of water in the test hole into the ground is very slow. In addition, the amount of water level in the airtight water tank is very small, and there is a problem that the measurement takes a very long time (several hours to several days).

  In order to achieve an appropriate measurement time according to the difference in water permeability of the target ground including such impermeable ground, one method is, for example, large, medium, small and volume (measured water volume). It is conceivable to construct a plurality of types of water permeable devices using a plurality of types of secret water tanks having different types.

  However, in such a case, a geological survey company or the like has to purchase and carry a large number of water permeability test apparatuses, which not only increases the cost but also complicates the measurement work itself.

  The present invention was made to solve such a problem, and the airtight water tank in the apparatus is composed of a plurality of cylindrical spaces having different volumes, and a constant water level holding pipe is provided at the lower end side of each cylindrical space. In addition, the water permeability of the ground to be measured is provided by providing an opening that functions as a water injection pipe and selecting and measuring one of a plurality of cylindrical spaces having the same volume according to the water permeability of the target ground. It is an object of the present invention to provide a water permeation test apparatus capable of measuring water permeability in an appropriate measurement time corresponding to the above.

For this purpose, the present invention comprises the following effective problem solving means.
(1) Problem-solving means of the invention of claim 1 The problem-solving means of the present invention is an airtight water tank having a cylindrical structure in which water for measurement is stored, and a sealable opening provided on the lower end side of the confidential water tank. The airtight water tank having the same configuration is installed in a ground side test hole in which a predetermined amount of water is stored, and the opening on the lower end side functions as a Marriott siphon type constant water level holding pipe and a water injection pipe. A water permeability test apparatus configured to measure water permeability of a target ground from a decrease in the water level in a water tank, wherein the airtight water tank is composed of a plurality of cylindrical spaces having different volumes, and each of the cylinders An opening that functions as the constant water level holding pipe and the water injection pipe is provided at the lower end side of the space, and according to the water permeability of the target ground, one of a plurality of cylindrical spaces having the same volume is selected and measured. Measured by It is characterized in that the water permeability can be measured in an appropriate measurement time corresponding to the water permeability of the ground to be tried.

  According to such a configuration, the water for measurement is stored, and when it becomes the apparatus main body, the airtight water tank portion of the cylindrical structure is composed of a plurality of cylindrical spaces having different volumes, and the lower end side of each cylindrical space In addition, an opening that functions as a Marriott Siphon-type constant water level holding pipe and a water injection pipe is provided.

  Therefore, depending on the water permeability of the target ground, for example, when measuring a ground with a high water permeability, a cylindrical space with a large volume, and when measuring a ground with a low water permeability, a cylindrical body with a small volume By selecting and measuring an optimal volume space of a plurality of cylindrical spaces having different volumes such as a space, the water permeability can be measured in an appropriate measurement time. And if the volume difference in that case is made sufficiently large, it is possible to effectively cope with the measurement of the above-mentioned impermeable ground, and the measurement time can be greatly shortened.

In this case, the plurality of cylindrical spaces having different volumes in the airtight water tank having the cylindrical structure serving as the apparatus main body may be formed by partitioning the inside of one cylindrical body into a plurality of cylindrical spaces having different volumes, for example. Alternatively, a plurality of cylinders having different volumes may be integrated.
(2) The problem solving means of the invention of claim 2 The problem solving means of the invention is the problem solving means of the invention of claim 1, wherein the plurality of cylindrical spaces having different volumes have a common vertical height. The volume is made different by making the inner diameter or the cross-sectional area of the cylindrical body different.

  According to such a configuration, even when the water permeability is constant, the smaller the inner diameter or cross-sectional area of the cylindrical space, the larger the amount of change in the water level drop. Therefore, in the case of ground with low water permeability, if you select a cylindrical space with a small inner diameter or cross-sectional area and put water in and measure it, the amount of change in the water level corresponding to the water level scale is increased accordingly and quickly. Measurement time itself can be effectively shortened.

  In addition, in the case of such a configuration, since each cylindrical space is configured with a common vertical height, the water level scale can be used in common between the cylindrical bodies, and a plurality of water level scales can be used. Need not be provided.

  As a result of the above, according to the water permeability test apparatus of the present invention, even in the case of impermeable ground such as a clay layer, it is possible to effectively and rapidly increase the amount of water level in the airtight water tank. In addition, the water permeability can be accurately measured in a much shorter measurement time than in the past.

  As a result, with the same water permeability test apparatus, measurement can be performed with a wide range and high accuracy from one case where the water permeability of the target ground is high to extremely low.

It is a front view of the test apparatus main body which shows the structure of the water-permeation test apparatus which concerns on Embodiment 1 of this invention. It is a top view of the same test apparatus main body. It is a longitudinal cross-sectional view in the front-back direction center part of the test apparatus main body (cross-sectional view of the AA line cutting part of FIG. 2). It is a horizontal sectional view in the lower end side water injection port portion of the main body of the test apparatus (cross sectional view taken along line BB in FIG. 1). It is an expanded sectional view of the principal part which shows the structure of the 2nd water inlet part of the lower end side of the test apparatus main body. It is explanatory drawing which shows the structure of the test apparatus main body in the state which installs the test apparatus main body in the test hole of the ground side which is a measuring object, and is actually performing the water permeability test, and a ground side test hole (inside of an apparatus main body) The figure of the water-permeable test state of the water-impermeable ground using 2 cylindrical space S2. It is a partially notched top view which shows the structure (water level fall acceleration | stimulation mat | laying state) of the ground side test hole inner periphery part in the water permeability test state of FIG. 6 using the test apparatus main body. It is explanatory drawing which shows the structure of the test apparatus main body in the state which installs the said test apparatus main body in the test hole of the ground side, and is actually performing the water permeability test, and a ground side test hole (the apparatus main body side 1st cylinder) The figure of the water permeability test state of the normal ground using space S1).

FIGS. 1-8 has shown the structure of the water permeability test apparatus of the ground which concerns on embodiment of this invention, and the implementation state of the water permeability test using the test apparatus.
<Configuration of water permeability test device main body>
First, FIGS. 1-5 has each shown the structure of the apparatus main-body part of the same water permeability test apparatus, and each part of the same apparatus main body.

  That is, the water permeability test apparatus 10 according to the first embodiment includes, as shown in FIGS. 1 to 4, for example, a highly transparent acrylic resin, a cylinder having an overall length (height) of h1 and an inner diameter of Φ1. A first cylindrical body (cylindrical body) 10a having a first cylindrical space S1 formed on the inner side thereof, provided inside the cylindrical body portion of the first cylindrical body 10a, and having an overall length of h1 A second cylindrical body (semi-cylindrical body) 14 formed of a semi-cylindrical body having an inner diameter of Φ 2 and having a second cylindrical space S2 formed therein, and the first and second cylindrical bodies 10a, 14 A disc-shaped bottom member 10b having a thickness t1 that forms the bottom of the disc, and a disc-shaped removable lid member 10c having a thickness t2 that forms the lid portions of the first and second cylinders 10a, 14 It is made up of.

  The first and second cylinders 10a and 14 have the same diameters over the entire length from the lower end side to the upper end side in terms of the inner diameter and the outer diameter. Further, the bottom member 10b and the lid member 10c are both formed to have a larger diameter than the outer diameter of the first cylindrical body 10a. And in the predetermined height position h2 part of the bottom member 10b side edge part of the said 1st cylinder 10a, it is 1st, 2nd, 3rd, 4th, 5th, 6th water injection port 11a, 11b. , 11c, 11d, 11e, and 11f are in a state of penetrating from the inner side to the outer side in the radial direction with a predetermined interval in the circumferential direction (in this embodiment, for example, an interval of 60 degrees: see FIGS. 2 and 4) Is provided. The first to sixth water injection ports 11a to 11f are provided with the same height position h2 from the upper surface of the bottom member 10b to the upper end side of the opening (corresponding to a constant water level described later), respectively. Each of them is provided with a water plug (not shown) that can be inserted and removed as a sealing means.

  Of these first to sixth water injection ports 11a to 11f, the first and third to sixth water injection ports 11a and 11c to 11f, excluding the second water injection port 11b, are comparatively about 14 mm in diameter, for example. It has a large aperture and is formed straight (horizontal) from the center axis position outward in the radial direction. On the other hand, only the second water inlet 11b is provided corresponding to the second cylindrical space S2 in the second cylindrical body 14 described above, and the diameter of the second water inlet 11b is a small diameter of about 3 to 5 mm. For example, as shown in detail in FIG. 5, from the outer peripheral surface side opening of the first cylindrical body 10a to the second cylindrical space S2 side of the inner second cylindrical body 14, It is formed with a predetermined upward inclination angle θ.

  As will be described later, the upward inclination angle θ takes the surface tension of the water to be poured into consideration, and reduces the surface tension by setting it to a small diameter as described above, thereby the second cylindrical space S2. The diameter of the air bubbles generated during measurement in the measurement water is reduced so that a large number of continuous air bubbles can be generated smoothly, enabling efficient air inflow and water extraction. The action is made to follow a drop in the water level in the test hole 2 to be described later with good responsiveness. For example, the water contact angle is set to a value around 20 degrees.

As described above, when the water injection port 11b having a reduced diameter and a reduced surface tension of water is inclined so as to descend from the introduction port side to the discharge port side according to the contact angle of water, the passage length itself becomes longer. However, there is a difference in height between the inlet and outlet, and the water at the inlet has energy in position, which moves to the outlet while receiving the pressure of the measured water, and descends. As a result, it gradually flows out while increasing the energy of kinetics. Further, the surface tension of water in the inlet port portion is the smallest when the inclination angle θ in the same portion is set to a water contact angle of about 20 degrees.

  For this reason, according to the same structure, the followability and response to the lowering of the water level (constant water level) on the test hole 2 side described later are greatly improved, and even if the diameter of the water injection port 11b is reduced as described above, the test is sufficiently performed. It is possible to follow the fluctuation of the water level on the hole 2 side.

  The second water injection port 11b is also provided with water injection plugs similar to the first, third to sixth water injection ports 11a, 11c to 11f.

  The lid member 10c is detachably fitted to the upper end opening of the first cylinder 10a, is removed from the upper end of the first cylinder 10a, and Water for water permeability measurement up to the full water position in the first cylindrical space S1 portion in the first cylindrical body 10a in the state where the water injection plugs are inserted into the third to sixth water injection ports 11a, 11c to 11f. (Measurement water) When W2 is introduced, it is fitted thereafter. Further, a level 12 for confirming a horizontal state when the apparatus is installed in the ground 1 side test hole 2 described later is provided at the center of the upper surface of the lid member 10c. The horizontal state at the time of installation is confirmed accurately using the.

  The first, third to sixth water injection ports 11a, 11c to 11f correspond to the water permeability of the normal ground (ground other than the water-impermeable ground) to be measured. The number of water taps to be removed) is adjusted.

  That is, when the water permeability test is performed using the first cylindrical body 10a having a large inner diameter, the water level in the test hole 2 is lowered according to the water permeability size (difference) of the ground 1 to be measured. , The amount of water that can be injected into the test hole 2 within a unit time (water injection speed) is adjusted to an optimum value (see the description of FIG. 8 described later).

  Thus, in the configuration of this embodiment, a plurality of water inlets 11a, 11c to 11f are provided in the circumferential direction of the first cylindrical body 10a, and by selecting the number thereof, the target ground within a certain range. Measured by adjusting the amount of water injected into the test hole 2 (water injection speed) according to the difference in the amount of water per unit time that permeates into the measurement ground 1 from the test hole 2 described later. This makes it possible to measure in an appropriate and efficient measurement time according to the water permeability of the ground.

  However, in this case, even if it is only that, even if it can cope with the difference in water permeability of the ground 1 to some extent, the airtight water tank to be used is only the first cylindrical space S1 in the first cylindrical body 10a, and its volume The inner diameter and the cross-sectional area itself are constant, and regardless of the water permeability of the ground 1 to be measured, the water W2 for measurement is always accumulated in the entire first cylindrical space S1, and the water permeability test is performed. Therefore, the volume, the inner diameter, and the cross-sectional area of the first cylindrical space S1 are set to a large volume, an inner diameter, and a cross-sectional area corresponding to a highly permeable ground such as a gravel layer.

  For this reason, when it is going to measure the water permeability of impermeable ground with extremely low water permeability, such as a clay layer, using only the first cylindrical space S1, water in the test hole 2 into the ground 1 is measured. Since the penetration is extremely slow, the amount of decrease in the water level in the first cylindrical space S1 is extremely small (for example, 1 mm in several hours), and the measurement takes a very long time (several hours to several days). That is, the problem of the conventional example already described remains.

  When an appropriate (practical) measurement time is to be realized according to the difference in water permeability of the measurement target ground 1, as described above, for example, large, medium, small and cylindrical volume, cylinder It is conceivable to manufacture a plurality of types of water permeability test apparatuses having different body inner diameters and perform a water permeability test using the optimum ones among them. However, in such a case, a geological survey company or the like has to purchase and carry a large number of water permeability test apparatuses, which is not only expensive, but also involves considerable complexity in the measurement work itself. There are drawbacks.

  Therefore, in this embodiment, in order to solve such a problem, as described above, the first cylindrical body 10a is disposed inside the first cylindrical body 10a and in the first cylindrical body space S1. And a second cylindrical body 14 having a semicircular cross section having the same vertical length (height) and a much smaller inner diameter than the first cylindrical body 10a. By joining and integrating the end portions 14a and 14b to the inner peripheral surface of the first cylinder 10a, the length (height) h1 in the vertical direction is the same as that of the first cylinder space S1. Thus, a second cylindrical space S2 having a much smaller volume and inner diameter (cross-sectional area) than the first cylindrical space S1 is provided, and a predetermined height position h2 on the lower end side of the second cylindrical space S2 is provided. The diameter is considerably smaller than the first, third to sixth water injection ports 11a, 11c to 11f for the first cylindrical space S1. In addition, a second water injection port 11b as shown in FIG. 5 is provided in the second cylindrical space S2 so as to communicate with a predetermined angle θ ascending (decreasing when viewed in the opposite direction). By measuring the water permeability using the second cylindrical space S2 and the second water inlet 11b, the ground 1 to be measured is a clay layer or the like and has extremely low water permeability, and the first cylindrical space S1 and In the measurement using the first, third to sixth water injection ports 11a, 11c to 11f, the water injection plugs were put on almost all of the first, third to sixth water injection ports 11a, 11c to 11f. Even if only one of them is used, the measurement can be performed as quickly as possible even when the measurement takes several hours to several days.

  In this embodiment, the outer circumferential surface of the first cylindrical body 10a is subjected to a water permeability test in which measurement water W2 is placed in the first cylindrical space S1 from the lower end side to the upper end side. A water scale (water level scale) 13 for reading the change ΔW2 in the amount of the measuring water W2 that decreases is provided. The water scale 13 is an end portion 14b on the left side of the second cylindrical body 14 when viewed from the front. It is provided in a state in contact with the portion, and is commonly used in the first and second cylindrical spaces (see measurement state diagrams 6 and 8 described later).

  The water permeability test apparatus 10 configured as described above is installed in a vertical state in the test hole 2 similar to the conventional one through the bottom member 10b portion, for example, as shown in FIG. 6, FIG. 7 or FIG. used.

  Here, FIG. 6 and FIG. 7 show that the water permeability of the ground 1 to be measured is extremely low, and it takes too much time to measure using the first cylindrical space S1 having a large inner diameter and a large sectional area. Measurement state in the case of impermeable ground that is too much to be practically used (when measuring using the second cylindrical space S2 having an inner diameter and sectional area far smaller than those of the first cylindrical space S1). Show.

Next, FIG. 8 is a case where the water permeability of the ground 1 to be measured is not extremely low, and the measurement can be performed in a relatively normal measurement time even using the first cylindrical space S1 described above. The measurement state is shown.
<Measurement procedure in FIGS. 6 and 7: Measurement in case of impermeable ground with extremely low water permeability>
(1) Creation of test hole As an example, as shown in FIG. 6, for example, as shown in FIG. 6, a bottom having a diameter of about 0.3 m and a depth of about 0.3 m on the ground 1 to be measured based on the standards of the Geotechnical Society A cylindrical test hole (constant water level tank) 2 is dug, and the actual radius of the dug test hole 2 and the depth from the ground surface are measured and recorded.
(2) Filling of crushed stone In the test hole 2, a large number of washed crushed stones (particle size of about 10 mm) 3, 3,... In addition, the absolute amount of measurement water collected in the test hole 2 can be reduced as much as possible.

In this case, the crushed stones 3, 3... Are taken out after measurement, and the crushed stones 3, 3. Use the one stored in the mesh bag.
(3) Injection of a predetermined amount of water into the test hole 2 The test hole 2 functions as a constant water level tank. Therefore, a predetermined amount of water W1 is injected into the test hole 2 using a bucket or the like. Then, after waiting for a while, the injected water W1 penetrates into the ground 1 to some extent, the degree of decrease of the injected water W1 becomes small, and the storage state is stabilized.
(4) Water supply into the second cylindrical space S2 of the water permeability test device 10 In the meantime, the measurement water W2 is supplied into the second cylindrical space S2 of the water permeability test device 10. The water supply is performed up to substantially the upper end. In this state, a water tap is inserted into the second water inlet 11b.
(5) Installation of the water permeability test apparatus 10 in the test hole 2 When a predetermined time has elapsed and the decrease degree of the water W1 in the test hole 2 is reduced and the storage state is stabilized, for example, as shown in FIG. The water permeability test apparatus 10 containing the measurement water W2 is inserted into the test hole 2 and installed on the crushed stones 3, 3. In the same installation state, the level 12 is adjusted so as to be surely in a horizontal state.

  In the subsequent installation state, as shown in the figure, the water level (constant water level) is maintained such that the upper end of the second water inlet 11b is submerged. However, also in this case, the smaller the absolute water amount in the test hole 2 is, the faster the water in the test hole 2 is reduced, and the lowering of the water level in the second cylindrical space S2 on the water permeation device 10 side is also accelerated.

  Therefore, in this embodiment, for example, as shown in FIGS. 6 and 7, the crushed stones 3, 3... In the test hole 2 described above are disposed around the upper surface side of the lower end side bottom member 10 b of the installed water permeable device 10.・ Water level lowering promotion mats 4, 4... Having a fan-shaped block structure having a volume (thickness and width) sufficient to seal a water storage space of about 1/3 of the upper part, for example, water is injected between each other. .., The absolute amount of water W1 stored in the test hole 2 is made as small as possible.

In this case, the water level lowering facilitating mats 4, 4,... May of course be formed integrally with a rubber material or the like that sinks in water to form the gaps 4a, 4a,. Also, the dug up clay can be used in the same form.
(6) Pulling out the water pouring tap of the second water pouring port 11b Thereafter, the water pouring tap of the second water pouring port 11b is pulled out, and the measured water W1 in the second cylindrical space S2 is taken out. In a state where the water injection port 11b is opened, the water level of the water W1 in the test hole 2 is surely stabilized in the illustrated constant water level (see the phantom line).
(7) Main test Then, the measurement test is started when the outflow of the measurement water W2 from the second cylindrical space S2 into the test hole 2 is stopped.

  In the measurement test, the passage of a fixed time (unit time) and the change amount (decrease amount) ΔW2 of the measured water level in the second cylindrical space S2 that is an airtight water tank are read about three times. And based on those average values, the water permeability of the ground 1 is determined.

Of course, in this case, if one of the three readings is abnormal, the test is performed again, and the test is repeated until the three values become substantially similar.
<Measurement procedure in FIG. 8: Measurement of normal ground 1 whose water permeability is not extremely low>
(1) Creation of test hole As an example, for example, as shown in FIG. 8, a bottom having a diameter of about 0.3 m and a depth of about 0.3 m on the ground 1 to be measured based on the standards of the Geotechnical Society A cylindrical test hole (constant water level tank) 2 is dug, and the actual radius of the dug test hole 2 and the depth from the ground surface are measured and recorded.
(2) Filling of crushed stone In the test hole 2, a large number of washed crushed stones (particle size of about 10 mm) 3, 3... 10 installation surfaces are formed, and the absolute amount of measurement water accumulated in the test hole 2 is reduced.

In this case, the crushed stones 3, 3... Are taken out after measurement, and the crushed stones 3, 3. Use the one stored in the mesh bag.
(3) Injection of a predetermined amount of water into the test hole 2 The test hole 2 functions as a constant water level tank. Therefore, a predetermined amount of water W1 is injected into the test hole 2 using a bucket or the like. Then, after waiting for a while, the injected water W1 penetrates into the ground 1 to some extent, the degree of decrease of the injected water W1 becomes small, and the storage state is stabilized.
(4) Water supply to the 1st cylinder space S1 of the water-permeable test apparatus 10 In the meantime, the measurement water W2 is supplied to the 1st cylinder space S1 of the said water-permeable test apparatus 10. FIG. The water supply is performed up to substantially the upper end. In this state, all of the plurality of water inlets 11a, 11c to 11f are inserted with water injection taps.
(5) Installation of the water permeability test apparatus 10 in the test hole 2 When a predetermined time has passed and the decrease degree of water in the test hole 2 is reduced and the storage state is stabilized, for example, as shown in FIG. The water permeability test apparatus 10 containing the measurement water W2 is inserted into the test hole 2 and installed on the crushed stones 3, 3. In the same installation state, the level 12 is adjusted so as to be surely in a horizontal state.

  In the subsequent installation state, as shown in the drawing, the water level (constant water level) is maintained such that the upper ends of the water injection ports 11a, 11c to 11f are submerged.

  In this case, when measuring the above-mentioned impervious ground, since the degree of reduction of the water W1 in the test hole 2 is extremely low, the water level lowering promotion mats 4, 4,. However, in the case of normal ground, there is sufficient water permeability, and since the degree of water reduction in the test hole 2 is high, the water level lowering promotion mats 4, 4,.

However, it can also be used as necessary in the case of ground having low water permeability, among normal ground.
(6) Adjusting the number of water taps to be removed Thereafter, the water level of the water W1 stored in the test hole 2 is constant (constant water level) corresponding to the water permeability (difference) of the measurement target ground 1 itself. ), The number to be extracted from the first, third to sixth water injection ports 11a, 11c to 11f provided on the lower end side of the first cylindrical space S1 (target) Adjust.

That is, when the water permeability is large in sandy ground or the like, the water in the test hole 2 is rapidly reduced, so that the water injection plugs of all the first, third to sixth water injection ports 11a, 11c to 11f are correspondingly provided. On the other hand, when the water injection amount is increased by increasing the water injection amount, the water injection plug of the first water injection port 11a or the third water injection port 11c or the water injection only of the third water injection port 11c is reversed. Finely adjust the water injection volume by removing the stopper.
(7) Main test Then, when the outflow of the measurement water W2 from the first cylindrical space S1 into the test hole 2 is stopped, the measurement test is started.

  In the measurement test, the passage of a fixed time (unit time) and the change amount (decrease amount) ΔW2 of the measured water level in the first cylindrical space S1, which is an airtight water tank, are read about three times. And based on those average values, the water permeability of the ground 1 is determined.

Of course, in this case, if one of the three readings is abnormal, the test is performed again, and the test is repeated until the three values become substantially similar.
<Characteristics, operation, and effect of configuration of this embodiment>
According to the above configuration, the measurement water is stored, and the first and second cylindrical spaces S1 and S2 having greatly different volumes are provided in the airtight water tank portion of the cylindrical structure serving as the apparatus body. Thus, each of the cylindrical spaces S1 and S2 functions as an airtight water tank. In addition, water inlets 11a, 11c to 11f, and 11b for discharging water corresponding to the inflow of air and the inflow of air functioning as the Marriott Siphon-type constant water level holding pipe and the water injection pipe, respectively, are provided on the lower ends thereof. It has been.

  Therefore, according to the difference in water permeability of the target ground, for example, when measuring the ground having high water permeability, the cylindrical space S1 having a large volume, inner diameter and cross-sectional area, and measuring the ground having extremely low water permeability. When carrying out, the cylindrical space S2 having a small volume, inner diameter, and cross-sectional area is arbitrarily selected, such as a plurality of cylindrical spaces S1, S2 having different volumes, inner diameters, and cross-sectional areas. By selecting and measuring, the water permeability can be measured in an appropriate measurement time.

  In the above configuration, the plurality of cylindrical spaces S1, S2 have a common height h1 in the vertical direction, and have different inner diameters or cross-sectional areas (or both) of the cylindrical portions, Each has a different volume.

  According to such a configuration, even when the water permeability is constant, the smaller the inner diameter or the cross-sectional area of the cylindrical spaces S1, S2, the larger the amount of change in the water level decrease. Accordingly, in the case of a ground such as a clay layer with extremely low water permeability, if the cylindrical water space S2 having a particularly small inner diameter or cross-sectional area is selected and the measurement water W2 is put in and measured, the water level scale 13 is correspondingly increased. The amount of change in the water level corresponding to can be made large and fast, and the measurement time itself can be greatly shortened.

  Further, in such a configuration, since the cylindrical spaces S1 and S2 are configured to have the same height in the vertical direction, the water level scale 13 is shared between the cylindrical spaces S1 and S2. It is not necessary to provide a plurality of water level scales.

  Moreover, in the case of this embodiment, the second water injection port 11b provided corresponding to the second cylindrical space S2 in the second cylindrical body 14 has a diameter of 3 as described above. It is formed so as to have a considerably small diameter of ˜5 mm, and the surface tension is made as small as possible.

  Therefore, the size of the bubbles generated in the cylindrical space S2 due to the inflow of air is reduced, the number thereof is increased, and the generated time intervals are very short and continuous. As a result, the reduction of the water level is also promoted.

  In this case, as further shown in FIG. 5, the second water injection port 11b extends from the outer peripheral surface side opening of the first cylinder 10a to the second cylinder space S2 of the inner second cylinder 14. The upward inclination angle θ is set to a value around 20 degrees of water contact angle in consideration of the surface tension of water. If this is done, smoother air inflow and water outflow are realized by the action of the energy at the position and kinetic energy described above without being affected by the surface tension. Will occur very efficiently at short, constant time intervals.

  For this reason, in combination with the fact that the lowering of the water level in the test hole 2 is promoted by the installation of the water level lowering promotion mats 4, 4,. Water W2 is poured. As a result, the water level in the second cylindrical space S2 also decreases with good responsiveness, and the measurement time is greatly shortened.

  As a result, according to the water permeability test apparatus, even in the case of impermeable ground with extremely low water permeability such as a clay layer, the change in the amount of water level in the airtight water tank can be effectively and rapidly increased. Water permeability can be accurately measured in a much shorter measurement time than in the past.

As a result, in the water permeability test apparatus in this embodiment, a single test apparatus can perform measurement in a wide range from the case where the water permeability of the target ground is high to the case of a very low water-impervious ground corresponding to high accuracy. Become.
<Other embodiments>
In the case of the present invention, a plurality of cylindrical spaces S1 and S2 having different volumes, inner diameters, and cross-sectional areas in the cylindrical airtight water tank as the apparatus main body are the same as the conventional one as in the above embodiment. The inside of the first cylindrical body 10a having a large diameter, which is a cylindrical body, may be formed by partitioning the second cylindrical body 14 having the same height h1 and a semicircular cross section having a much smaller inner diameter. However, this may be configured as one device by joining and integrating a plurality of cylindrical bodies having the same height h1 and different inner diameters, for example.

  Further, in the configuration of the above embodiment, only one cylindrical body 14 of the younger brother 2 having a semicircular cross section is provided. However, these are a plurality of two or three, each having a different inner diameter or cross sectional area. It is also possible to form a plurality of cylindrical spaces S2 to S4.

  1 is ground, 2 is a test hole, 3 is crushed stone, 4 is a water level lowering acceleration mat, 10 is a water permeability test device, 10a is a first cylinder, 10b is a bottom member, 10c is a lid member, and 11a to 11f are first To a sixth water inlet, 12 is a level, and 13 is a water volume scale.

Claims (2)

  A ground-side test consisting of an airtight water tank with a cylindrical structure in which water for measurement is stored and a sealable opening provided on the lower end side of the confidential water tank, and storing the predetermined amount of water in the airtight water tank of the same configuration In addition to installing in the hole, the opening on the lower end side functions as a Marriott Siphon-type constant water level holding pipe and water injection pipe, and the water permeability of the target ground is measured from the decrease in the water level in the airtight water tank. The airtight water tank is composed of a plurality of cylindrical spaces having different volumes, and provided with openings serving as the constant water level holding pipe and the water injection pipe on the lower end side of each cylindrical space, By selecting and measuring one of multiple cylindrical spaces with the same volume according to the water permeability of the target ground, the water permeability can be measured at an appropriate measurement time corresponding to the water permeability of the ground to be measured. Measure Permeability test apparatus being characterized in that to allow Rukoto.   2. The plurality of cylindrical spaces having different volumes have the same height in the vertical direction, and have different volumes by changing the inner diameter or the cross-sectional area of the cylindrical portion. Permeability test equipment.

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