JP2003321827A - Method for measuring water permeable anisotropy of ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing water permeable anisotropy of the ground capable of easily obtaining coefficient of permeability in the horizontal direction of the ground and coefficient of permeability in the vertical direction at a low cost. <P>SOLUTION: A boring hole is bored in the ground, and a casing pipe is positioned into the boring hole. A hollow pipe having a packer in an interior wall surface is pressed into the ground directly under from the bottom of the boring hole, and after the packer has been expanded, the ground water in the boring hole is pumped up at a specific pumping rate by a lifting pump installed in the casing pipe, water pressure is measured by pressure sensors installed around both up and down ends of the hollow pipe, and the coefficient of permeability k<SB>v</SB>in the vertical direction is obtained on the basis of the water pressure measure by the pumping rate and both up and down pressure sensors. The hollow pipe is pulled out together with the packer and soil inside thereof to form a naked hole in a mark made by pulling, and the coefficient of permeability in the horizontal direction of the naked hole is obtained by a piezometer method. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of the method for measuring the hydraulic conductivity of in-situ ground, and more specifically, it is a single-hole hydraulic conductivity test, in which the horizontal hydraulic conductivity of in-situ ground and The present invention relates to a method for measuring the anisotropy of permeability of the ground, which measures the hydraulic conductivity in the vertical direction.

[0002]

BACKGROUND ART Generally, natural ground because it has a layer structure, different and permeability in the horizontal direction (k _h) and vertical permeability (k _v), has a so-called "permeability anisotropy" There is a lot of ground.

Conventionally, as a method for measuring the in-situ water permeability coefficient in-situ, a single hole type water permeability test such as a tube method, a piezometer method, an auger method, a packer method, or a tire (Thei
Porous pumping tests such as s) method and Jacob method have been conducted. However, in each of these measuring methods, the hydraulic conductivity in the horizontal direction is dominant, and the hydraulic conductivity in the vertical direction cannot be evaluated.

Under these circumstances, various studies have been conducted on methods for evaluating the horizontal hydraulic conductivity and the vertical hydraulic conductivity, that is, the method for measuring "water permeability anisotropy". For example, (1) Japanese Patent No. 2796748 discloses an example of a single hole type water permeability test for measuring water permeability anisotropy around a single boring hole. According to the invention, a plurality of packers and pressure sensors are alternately installed in the depth direction of a boring hole, a fluctuating water pressure (osmotic flow) due to water injection is generated from one packer section, and a response water pressure propagating into the ground is Measured with a pressure sensor installed in the packer section, and based on the measurement results, numerical analysis was performed using a cylindrical coordinate system permeability distribution model to obtain horizontal and vertical hydraulic conductivity of the ground, and the water permeability anisotropy of the ground. Is a method of measuring.

(2) Japanese Patent No. 2788954 discloses an example of a porous pumping test for measuring the water permeability anisotropy in the entire area around a boring hole. The invention relates to a pumping well and an observation well, which are provided with a screen portion and a blind pipe portion by a casing material and a filling material, and further provided with a water shutoff device for shutting off the flow of water between the screen portions. Groundwater is pumped from the section to generate fluctuations in water pressure in the aquifer of the ground, and the fluctuations in water pressure are measured by water pressure gauges on all screens of the observation well to obtain hydraulic conductivity in the horizontal and vertical directions. This is a method of measuring water permeability anisotropy.

[0006]

However, since the technique of the above (1) employs a numerical analysis by a complex cylindrical coordinate system permeability distribution model for the calculation of the hydraulic conductivity in the horizontal and vertical directions, the technique for the numerical analysis is Only a person with specialized knowledge can carry out the method, and there is a problem that the versatility is poor. Further, there is a problem that the permeability test section of the ground is limited to the depth of the boring hole that was initially drilled.

On the other hand, the above technique (2) has a problem in that the measurement facility becomes large in scale because a plurality of boring holes are excavated to measure the water permeability anisotropy, and the labor and cost of the work increase. .

Further, the porous pumping test as in the technique (2) requires complicated numerical analysis when evaluating the water permeability anisotropy. Therefore, there is a problem in that versatility is poor, since only a person who has specialized knowledge in the numerical analysis can perform the method.

Further, the above technique (2) has a problem that the test section of the hydraulic conductivity of the ground is limited to the depth of the boring hole drilled first, and the continuous permeability in the depth direction of the boring hole. There are problems that cannot be asked for.

In other words, the above techniques (1) and (2) are both i) a complicated method that requires complicated numerical analysis, ii) the cost required for the water permeability test increases, and iii)
Since the test section was limited to the depth of the boring hole, it could not be used as a general means to measure the permeability anisotropy of the ground.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a method for measuring the anisotropy of water permeability of the ground, which can easily and inexpensively determine the hydraulic conductivity in the horizontal direction and the hydraulic conductivity in the vertical direction of the ground.

[0012]

[Means for Solving the Problems] As a means for solving the above-mentioned problems of the prior art, the method for measuring the water permeability anisotropy of the ground according to the invention as set forth in claim 1 has a boring hole cut in the ground. And a casing pipe is installed in the boring hole, and a hollow pipe provided with a packer on the inner wall surface is press-fitted into the ground immediately below from the bottom of the boring hole to expand the packer, and then the casing. The pumping pump installed in the pipe pumps the groundwater in the boring hole at a fixed pumping rate, and the water pressure is measured by pressure sensors installed near the upper and lower ends of the hollow pipe, and the pumping rate and the upper and lower pressures are measured. Based on the water pressure measured by the sensor,

[Equation 3] And to obtain the vertical hydraulic conductivity k _v by using the hollow tube and the packer and the soil inside the hollow tube to form a bare hole in the trace, and to measure the horizontal hydraulic conductivity of the bare hole by the piezometer method. And a step of obtaining.

According to the second aspect of the present invention, there is provided a method for measuring the anisotropy of water permeability of the ground, which comprises the steps of boring a hole in the ground, installing a casing pipe in the boring hole, and providing a packer on the inner wall surface. After pressing the hollow pipe from the bottom of the boring hole into the ground immediately below and expanding the packer, the groundwater in the boring hole is pumped up by the pumping pump installed in the casing pipe to lower the water level. Let
After that, the pumping is stopped and the change in water pressure with time is measured by the pressure sensors installed near the upper and lower ends of the hollow tube, and based on the water pressure at the times t ₁ and t ₂ measured by the upper and lower pressure sensors,

[Equation 4] The step of obtaining the vertical hydraulic conductivity k _v by means of the above, and the hollow tube is pulled out together with the packer and the soil in the hollow tube to form a bare hole in the trace, and the horizontal hydraulic conductivity of the bare hole is obtained by the piezometer method. And a step of obtaining.

According to a third aspect of the present invention, in the method for measuring the water permeability anisotropy of the ground according to the first or second aspect, after the step of obtaining the hydraulic conductivity in the horizontal direction is completed, the casing reaches the bottom depth of the bare hole. The step of inserting the pipe, the step of press-fitting the hollow pipe having the packer on the inner wall surface into the ground immediately below from the bottom of the bare hole to obtain the vertical hydraulic conductivity k _v , and the hollow pipe It is characterized in that the step of extracting with the packer and the soil in the hollow tube to form a bare hole in the trace and obtaining the horizontal hydraulic conductivity of the bare hole by the piezometer method is repeated.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, referring to the drawings,
A method of measuring the water permeability anisotropy of the ground according to the invention described in 3 will be described. 1A to F show, in a schematic procedure, an embodiment of the invention as claimed in claim 1.

First, FIG. 1A shows a stage in which the boring hole 10 is drilled in the ground, and subsequently, FIG. 1B shows the boring hole 1
0 shows a stage in which the casing pipe 1 is installed to protect the hole wall 10a and block horizontal permeation flow of groundwater.

FIG. 1C shows a stage in which a hollow tube 2 having a packer 4 on its inner wall surface is press-fitted into the ground directly below from the bottom of the boring hole 10. In this way, the hollow pipe 2 blocks horizontal permeation flow into the soil 11 inside the hollow pipe 2 to form a test section of vertical hydraulic conductivity.

The outer diameter of the hollow pipe 2 is substantially the same as the inner diameter of the casing pipe 1. In addition, near the peripheral portions of the upper and lower ends of the hollow pipe 2, pressure sensors 3, which respectively measure the water pressures of the groundwater above and below the test section, respectively.
3 is provided.

FIG. 1D shows the stages of a vertical permeability test. At this stage, first, the packer 4 is appropriately expanded by liquid pressure (water pressure) or gas pressure (air pressure), and tends to occur at the boundary between the inner wall surface of the hollow tube 2 and the soil 11 inside thereof. Completely shut off the "water channel". After that, according to the so-called "steady-state method", the pumping pump 6 installed in the casing pipe 1 pumps the groundwater in the boring hole 10 at a constant pumping rate Q to disturb the soil 11 in the hollow pipe 2. Instead, a vertical seepage flow is generated in the soil 11 in the test section. The amount Q of groundwater pumped up by the pumping pump 6 is observed and recorded by a measuring system (not shown) installed on the ground.

Thus, under the condition that the above-mentioned permeation flow is generated, the water pressures above and below the test section are measured by the pressure sensors 3 and 3, and the measurement signal is transmitted via a cable (not shown). Then, it is transmitted to the measurement system, and is observed and recorded.

The pumping amount Q and the upper and lower pressure sensors 3,
Based on the water pressure of each groundwater above and below the test section measured by 3

[0022]

[Equation 5] The hydraulic conductivity k _v in the vertical direction is calculated by. Head difference Δ
h is obtained based on the test sections measured by the pressure sensors 3 and 3, that is, the water pressures at the upper and lower ends of the hollow tube 2.

Incidentally, the calculation of the above [Formula 1] is automatically calculated by the measuring system. Further, the length L of the hollow tube 2 and the numerical value of the water permeation cross-sectional area A of the soil 11 in the hollow tube 2 are set as known values by previously inputting data to the measurement system. The calculation of [Equation 1] is not limited to the calculation by the measurement system, and may be suitably performed by manual calculation by a person.

Next, FIG. 1E shows a stage in which the hollow tube 2 is pulled out together with the packer 4 and the soil 11 in the hollow tube 2 and a bare hole 5 is formed in the trace. In bare hole 5 becomes the horizontal permeability of the test period, the state in which the horizontal flow dominant becomes negligible in the vertical direction of flow, suitable for measuring horizontal permeability k _h Become.

FIG. 1F shows a step of determining a horizontal permeability k _h in the open hole 5 with a piezometer method. The permeability test of the piezometer method is carried out by either the "steady state method" or the "unsteady state method" according to the "Soil investigation method" issued by the Geotechnical Society. Here, the hydraulic conductivity described in the “ground survey method” is an average hydraulic conductivity that includes both horizontal and vertical influences, but as described above, the soil has a layered structure. In addition, since the horizontal permeability is dominant due to the presence and the aspect ratio of the shape of the bare hole 5, the hydraulic conductivity by the piezometer method is used as the horizontal hydraulic conductivity (horizontal permeability).

Thus, the measurement of water permeability anisotropy for the ground layer to which the soil 11 belongs is completed.

2G to I are part of a procedure for continuously measuring the water permeability anisotropy of the soil 12 immediately below the bottom of the open hole 5 after carrying out the invention described in claim 1 above. Is schematically shown. FIG. 2G shows a state immediately after the step of obtaining the horizontal hydraulic conductivity in the bare hole 5 shown in FIG. 1F is completed.

FIG. 2H shows a step of inserting the casing pipe 1 to the bottom depth of the bare hole 5 to protect the hole wall 5a of the bare hole 5 and block the permeation flow from the hole wall 5a. When the casing pipe 1 is inserted, the casing material 1'is added to the upper end portion of the casing pipe 1 as shown in FIG. 2 so that a bare hole portion where the soil is exposed is not formed above the boring hole 10. To For the casing material 1 ', a pipe having a length equal to or greater than the depth L of the bare hole 5 is preferably used.

Next, FIG. 2I shows a step of press-fitting the hollow tube 2 provided with the packer 4 on the inner wall surface thereof into the ground immediately below from the bottom of the mark of the bare hole.

Then, after the step of FIG. 2I is completed, the vertical water permeation is performed by the method of the invention described in claim 1 (steady-state method) or the method of the invention described in claim 2 described later (transient method). Processing similar to the step of obtaining the coefficient k _v shown in FIG. 1D or FIG. 3D described later is performed. Subsequently, the hollow tube 2 is pulled out together with the packer 4 and the soil 12 in the hollow tube 2, a bare hole is formed in the trace, and the horizontal hydraulic conductivity of the bare hole is obtained by the piezometer method. Then, the same processing as the step shown in FIG. 1F is performed (the above is the invention according to claim 3).

Thus, it is possible to measure the water permeability anisotropy of the ground continuously in the vertical direction along the boring hole 10.
That is, the water permeability anisotropy can be continuously measured up to the ground of a desired depth without being limited to the depth of the boring hole excavated first.

Next, FIGS. 3A to 3F show an embodiment of the invention described in claim 2 in a schematic procedure. The description of the parts common to the method for measuring the water permeability anisotropy of the ground described in claim 1 will be omitted.

Since FIGS. 3A to 3C are carried out in the same manner as the steps of FIGS. 1A to 1C showing the procedure of the invention described in claim 1, the description thereof will be omitted.

FIG. 3D shows the stages of the vertical permeability test. At this stage, first, the packer 4 is appropriately expanded by hydraulic pressure (water pressure) or gas pressure (air pressure), and the hollow tube 2
It completely shuts off the "water flow" that tends to occur at the boundary between the inner wall surface of and the soil 14 inside it.

After that, according to the so-called "unsteady method", the groundwater is pumped up by the pumping pump 6 installed in the boring hole 10 to temporarily lower the water level, and then the pumping is stopped and the hollow pipe 2 is closed. Soil 14 in the test section without disturbing soil 14
Generates a permeate flow in the vertical direction. Then, after that, the time-dependent change of the water pressure in the boring hole 10 is measured by the pressure sensors 3 and 3 installed near the upper and lower ends of the hollow tube 2, and the measurement signal is transmitted to the ground via a cable (not shown). It is transmitted to the measurement system (not shown) installed at the station, and is observed and stored.

Then, based on the water pressure at arbitrary times t ₁ and t ₂ measured by the upper and lower pressure sensors,

[0037]

[Equation 6] Permeability coefficient k in the vertical direction_vAsk for. Each time t₁，
t_TwoHead difference at Δh ₁ , Δh_TwoIs the time
t₁, T_TwoPressure sensors provided at the upper and lower ends of the hollow tube 2
Calculate based on each water pressure measured by 3 and 3.

Incidentally, the calculation of [Equation 2] is automatically calculated by the measuring system. Further, the length L of the hollow tube 2 and the numerical value of the water permeation cross-sectional area A of the soil 11 in the hollow tube 2 are set as known values by previously inputting data to the measurement system. The calculation of the above [Equation 2] is not limited to the calculation by the measurement system, and can be suitably performed even if the calculation is performed manually by a person.

3E and 3F show the above-mentioned claim 1.
The same processing as the steps of FIGS. 1E and 1F in the described invention is performed, and the measurement of the water permeability anisotropy of the ground layer to which the soil 14 belongs is completed.

Further, in this embodiment, the continuous water permeability anisotropy in the vertical direction along the boring hole 10 can be measured by the same method as that of the invention described in claim 1. That is, after the step shown in FIG. 3F, the same processing as the steps shown in FIGS. 2H and 2I is performed, and then the steps shown in FIGS. 3D to 3F are performed to change the water permeability anisotropy of the destination ground. taking measurement.

As described above, according to the method for measuring the water permeability anisotropy according to the invention described in claims 1 to 3, the water permeability anisotropy of the ground can be measured by a simple process operation and a simple calculation. can do. In addition, the measuring facility can be smaller than the conventional one, so that the cost can be significantly reduced.

[0042] In addition, since the permeability in the horizontal direction in the sequential order at the same hole (k _h) and vertical permeability of the (k _v) can be measured permeability anisotropy measured ground, in groundwater protection The rational design of the impermeable wall becomes possible, and the cost and the construction period can be shortened by shortening the root length of the impermeable wall. Furthermore, a pumping plan that considers the reduction of the environmental load of the surrounding groundwater by evaluating the groundwater outside the impermeable wall can be formulated.

The water permeability anisotropy can be continuously measured up to the ground of a desired depth without being limited to the depth of the boring hole excavated first.

The preferred embodiments of the present invention have been described above. However, other than the embodiments of the present invention, various applications and modifications usually made by those skilled in the art can be carried out without departing from the gist of the present invention. Add that it is possible. For example, as a means for inserting the hollow pipe into the ground, a hollow pipe having a bit at the lower edge portion thereof may be used for excavation and penetration by rotation.

[0045]

According to the method for measuring soil water permeability anisotropy according to claims 1 to 3 of the present invention, the horizontal and vertical water permeability coefficients of the soil can be easily and inexpensively measured. The water permeability anisotropy can be obtained and investigated.

Further, the water permeability anisotropy can be continuously measured up to the ground of a desired depth without being limited to the depth of the boring hole excavated first.

Further, since the hydraulic conductivity of the ground can be measured by measuring the hydraulic conductivity in the horizontal direction and the hydraulic conductivity in the vertical direction in the same hole in a series of order, it is possible to rationalize the design of the impermeable wall in the countermeasure against groundwater. This will be possible, and eventually the cost and construction period will be shortened by reducing the length of the impermeable wall. Furthermore, a pumping plan that considers the reduction of the environmental load of the surrounding groundwater by evaluating the groundwater outside the impermeable wall can be formulated.

[Brief description of drawings]

1A to 1F are explanatory views showing a schematic procedure of the invention described in claim 1. FIG.

2A to 2I are explanatory views schematically showing a part of the procedure of the method for measuring the water permeability anisotropy of the ground continuously in the vertical direction along the boring hole.

3A to 3F are explanatory diagrams showing a schematic procedure of the invention described in claim 2. FIG.

[Explanation of symbols]

10 Boring Hole 1 Casing Pipe 4 Packer 2 Hollow Tube 6 Pumping Pump 3 Pressure Sensor 5 Bare Holes 10a, 5a Hole Walls 11, 12, 14 Soil k _v Vertical Permeability (Vertical Permeability) L Length of hollow tube Δh Head difference Q Pumped amount A Soil cross-sectional area t ₁ , t ₂ Time Δh ₁ Head difference at time t ₁ Δh ₂ Head difference at time t ₂

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kunimitsu Mori             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute F-term (reference) 2D043 AA05 BA10

Claims (3)

[Claims] 1. A step of boring a boring hole in the ground and constructing a casing pipe in the boring hole, and a hollow pipe having a packer provided on an inner wall surface thereof is press-fitted into the ground immediately below from the bottom of the boring hole. After expanding the packer, the pumping pump installed in the casing pipe pumps the groundwater in the boring hole at a constant pumping amount, and the pressure sensor installed near the upper and lower ends of the hollow pipe And the water pressure measured by the upper and lower pressure sensors, and the following equation The step of obtaining the vertical permeability k _v by means of the step of: extracting the hollow tube together with the packer and the soil inside thereof to form a bare hole in the trace, and the horizontal permeability of the bare hole by the piezometer method. The method for measuring the anisotropy of water permeability of the ground, which comprises the step of: 2. A step of boring a boring hole in the ground and constructing a casing pipe in the boring hole, and a hollow pipe having a packer provided on an inner wall surface thereof is press-fitted into the ground immediately below from the bottom of the boring hole. After expanding the packer, the groundwater in the boring hole is pumped with a pump for pumping the groundwater to lower the water level, and then pumping is stopped to change the water pressure with time of the hollow pipe. Based on the water pressure at time t ₁ and time t ₂ measured by the pressure sensors installed near the upper and lower ends, the following formula The step of obtaining the vertical hydraulic conductivity k _v by means of the step of: extracting the hollow tube with the packer and the soil in the hollow tube to form a bare hole in the trace, and the horizontal hydraulic conductivity of the bare hole by the piezometer method. The method for measuring the anisotropy of water permeability of the ground, which comprises the step of: 3. A step of inserting a casing pipe to the bottom depth of the bare hole after the step of obtaining the hydraulic conductivity in the horizontal direction is completed, and a hollow tube having a packer provided on the inner wall surface thereof is directly under the bare hole. Press-fitting into the ground to determine the vertical hydraulic conductivity k _v , and pulling out the hollow tube together with the packer and the soil in the hollow tube to form a bare hole in the trace, and the bare hole by the piezometer method. The method for measuring the water permeability anisotropy of the ground according to claim 1 or 2, wherein the step of obtaining the horizontal water permeability coefficient of the hole is repeated.