JPH07146193A - Multilayer gap hydraulic pressure measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure gap hydraulic pressure without causing a hydraulic pressure sensor to be affected by a fine soil particle by simultaneously measuring each gap hydraulic pressure of a plurality of water-keeping layers by a drilling hole. CONSTITUTION:In a protection pipe 1, a plurality of connection protection pipe bodies 2 and pipes 12 for measuring distortion are connected by an upper blocking members 3 and a lower blocking members 5. A plurality of hydraulic pressure measurement chambers 4, 4... are demarcated in axial direction while being separated by the upper blocking member 3 and the lower blocking member 5 inside the protection pipe 1. A hydraulic pressure sensor 6 is provided inside each hydraulic pressure measurement chamber 4. Each hydraulic pressure measurement chamber 4 communicates with a drilling hole A by water-guiding holes 8, 8,... formed at the protection pipe 1. A hair-shaped filter part is provided around the water-guiding holes 8 on the outer-periphery surface of the protection pipe 1. Also, annular water-shielding seal parts for shielding a plurality of water-guiding holes 8 communicating with the hydraulic pressure measurement chambers 4 are provided while being separated in axial direction on the outer-periphery surface of the protection pipe 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention analyzes phenomena such as landslides, landslides, and liquefaction of ground to predict the occurrence or measure the pore water pressure required for each aquifer. For a multi-layer pore water pressure measuring device for

[0002]

2. Description of the Related Art Conventionally, a method for measuring the water pressure of groundwater is to estimate the water pressure by inserting a strainered pipe into the borehole and inserting a water level gauge into the pipe to measure the water level. There is known a Casa Grande type water level measuring method, or a method of inserting a piezometer or a pore water pressure gauge to the position of the water layer in the boring hole and sealing the upper and lower sides thereof with a bentonite sealing material.

[0003]

By the way, among the above-mentioned conventional techniques, the Casa Grande type water level measuring method can only measure the groundwater level synthesized by leakage when the ground is heterogeneous and there are multiple aquifers. There are drawbacks and the disadvantage that the pore water pressure for each aquifer cannot be accurately measured because the water pressure is estimated from the measured water level.

Further, the method of inserting a piezometer or a pore water pressure gauge into the borehole requires the provision of a borehole for each aquifer, which is a disadvantage in that a large amount of cost is required. There is a drawback that the possibility of failure is high because it is inserted in, and there is a drawback that the sealing material cannot cope with the fluctuation of the ground and water leaks in the hole, and accurate measurement cannot be performed.

Moreover, the sensor of the pore water pressure gauge is covered with a fine mesh-shaped protective filter. However, the air in the ground easily adheres to the outer surface of the protective filter in the form of bubbles to form an air film. There is a problem that the mesh cannot be accurately measured because it is easily clogged with fine soil particles, and that it can only be measured for a short period of time.

Further, the pore water pressure is related to the landslide phenomenon, but a measuring instrument in which a strain gauge for detecting the landslide and a pore water pressure gauge are integrally assembled has not been provided so far. For this reason, the pore water pressure gauge and the strain gauge are actually installed by boring separate boring holes, which requires a large amount of cost for the boring work and the preparation for measurement is troublesome. There is.

The present invention has been made in view of the above-mentioned drawbacks and problems of the prior art, and it is possible to simultaneously measure the pore water pressure of each of a large number of aquifers by using only one boring hole, and An object of the present invention is to provide a multi-layer pore water pressure measuring device capable of accurate water pressure measurement without being affected by bubbles and soil particles.

It is another object of the present invention to provide a multi-layer pore water pressure measuring device capable of measuring multi-layer pore water pressure and formation strain by utilizing a single boring hole.

[0009]

Means for Solving the Problems The means of the present invention, which is configured to solve the above-mentioned problems, includes a protection tube inserted into a boring hole, and a protection tube which is axially spaced from the protection tube. A plurality of closing members that separate a plurality of water pressure measuring chambers in the protection pipe in the axial direction, water pressure sensors provided in the plurality of closing members and respectively disposed in the plurality of water pressure measuring chambers, and the protection pipe. A plurality of water-conducting holes that are formed to be separated from each other in the axial direction and that communicate each of the plurality of water-pressure measuring chambers with the boring hole, and are provided on the outer peripheral surface of the protective pipe located around the plurality of water-conducting holes. And the hair filter part provided, and the plurality of water pressure measuring chambers are axially attached to the outer peripheral surface of the protection tube so as to abut the hole wall of the boring hole so as to block the plurality of water guiding holes communicating with each other. It is composed of an annular water-impervious seal portion provided separately.

It is preferable that the protection tube is composed of a plurality of connection protection tubes, and that a plurality of strain measuring pipes are provided between the plurality of connection protection tubes.

[0011]

[Function] Each of the water holes communicating with each of the plurality of water pressure measurement chambers is blocked from the other aquifers by the annular impermeable seal part, and the groundwater in one aquifer is only in one water pressure measurement chamber. As a result of the inflow, each water pressure sensor measures the pore water pressure for each aquifer. The hair filter part is bent by water pressure and prevents fine soil particles from entering the water pressure measuring chamber through the water guiding hole.

[0012] By the strain measuring pipes which are integrally assembled in a state of being separated from the protective pipe, it is possible to measure the landslide phenomenon in multiple layers simultaneously with the measurement of the pore water pressure.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. In the figure, reference numeral 1 indicates a protection tube inserted into a boring hole A formed in the ground. Reference numerals 2, 2, ... Show a plurality of connection protection pipe bodies that constitute the protection pipe 1, and each connection protection pipe body 2 is, for example, a female screw portion 2A on the inner surface of both ends of a vinyl chloride pipe.
2A is formed.

.. are connected protection tube bodies 2,
2 shows an upper side closing member for axially connecting 2, ... And defining a water pressure measuring chamber 4 in each connection protection tube 2. Each of the upper closing members 3 is made of a synthetic resin columnar body, and the female screw portion 2A of the connection protection tube body 2 is provided on the outer peripheral surface thereof.
A male threaded portion 3A that is screwed into is formed, a stepped insertion hole 3B is formed at the center, and four insertion holes 3C, 3C, ... Are formed on the outer peripheral side thereof.

On the other hand, reference numerals 5, 5, ... Connect the connection protection pipes 2, 2, ... In the axial direction in a state of facing the upper blocking members 3, and define a water pressure measuring chamber 4. The lower closing member is shown. Each of the lower closing members 5 is made of a cylindrical body made of the same material as the upper closing member 3, and has an outer peripheral surface formed with a male screw portion 5A which is screwed into the female screw portion 2A of the connection protection tube body 2 and has a center portion. And five insertion holes 5B, 5
B, ... Are formed.

Reference numeral 6 denotes a water pressure sensor which is located in the water pressure measuring chamber 4 and which is fitted downward into the stepped insertion hole 3B of the upper blocking member 3. The signal line 6A of the water pressure sensor 6 extends upward through the insertion hole 3B, and the outer peripheral side of the signal line 6A is hermetically sealed by a seal portion 7 filled with a sealant.

Reference numerals 8, 8, ... Depict water guiding holes for introducing groundwater into the water pressure measuring chamber 4. The water guiding holes 8, 8, ...
Is formed of a through hole having a hole diameter of 2 to 5 mm, and is formed in the pipe wall of the connection protection pipe body 2 so as to be separated in the axial direction in the cross direction.

Further, reference numerals 9, 9, ... Denote air vent holes for releasing air in the water pressure measuring chamber 4, and the air vent holes 9, 9 ,. It is formed in the radial direction on the upper end side of the connection protection tube body 2 so as to be located in the vicinity of the water pressure sensor 6.

Reference numerals 10, 10, ... Depict bristle filter portions provided on the outer peripheral surface of the protective tube 1 so as to be spaced apart in the axial direction.
Each of the hair filter parts 10 has a length of about 4 mm and a thickness of about 1 mm.
The denier is composed of 2 denier capillary piles that are planted by using an electrodeposition means, and is formed in a substantially strip shape on the outer peripheral surface of the connection protection pipe body 2 from above the air vent hole 9 to below the lower water guiding hole 8. Has been formed.

Reference numerals 11, 11, ... Depict a plurality of annular watertight seal portions that close the space between the wall of the boring hole A and the protective pipe 1. The annular watertight seal portion 11 is intended to block the water guiding holes 8, 8, ... Which communicate with one water pressure measuring chamber 4 and the water guiding holes 8, 8, ... Which communicate with another water pressure measuring chamber 4. , Protection tube 1
Are arranged on the outer peripheral surface of the so as to be separated from each other in the axial direction. Here, each of the annular water-impervious sealing parts 11 is composed of an expandable and contractible synthetic resin annular bag attached to the outer peripheral surface of the connection protection tube body 2 and a foamable synthetic resin agent filled in the annular bag. By expanding the expandable synthetic resin, it is brought into close contact with the hole wall of the boring hole A.

Reference numerals 12, 12 and 12 denote strain measuring pipes incorporated in the protective tube 1. Each strain measuring pipe 12 is made of the same vinyl chloride pipe as the connection protection pipe body 2 and a strain sensor is attached to the pipe, and the shaft of each connection protection pipe body 2 in which the water pressure sensor 6 is installed. It is located on the upper side in the direction and is connected between the connection protection tubes 2 and 2. The signal line 12A of each strain measuring pipe 12 is extended to the ground along the outer peripheral surface of the protective pipe 1.

Reference numeral 13 in the drawing is an automatic measuring device installed on the ground, and the automatic measuring device 13 includes each water pressure sensor 6 and a signal line 6.
It is also connected via A and the strain gauge of each strain measuring pipe 12 via a signal line 12A.

The apparatus of this embodiment has the above-mentioned structure. Next, the method of using the apparatus will be described. First, after drilling a borehole A in the ground and measuring the depth of the aquifers B, C, and D from the ground, each of the water pressure measurement chambers 4 is located in the aquifers B, C, and D, respectively. So that a plurality of connection protection tubes 2, 2, ...
, And the lower blocking member 5,
Connect using 5, ... A grease or other sealing agent is applied to the connection surface to enhance the water impermeability in order to prevent the groundwater in each of the water retention layers B, C, and D from entering the other water pressure measurement chambers 4. At this time, the strain-measuring pipes 12, 12, 12 are integrally assembled in close proximity to the respective water pressure measuring chambers 4 to form the protective pipe 1.

A water pressure sensor 6 is provided in advance on each upper blocking member 3 while being fitted in the stepped insertion hole 3B.
The signal line 6A is drawn out to the upper end side of the protective tube 1 through the insertion holes 3B and 5B of the upper and lower closing members 3.5 located above. Insertion holes 3B and 5B through which the signal line 6A is inserted
Is sealed by a sealing portion 7 filled with a sealing agent. Further, the signal line 12A of each strain gauge is drawn out to the upper end side along the outer peripheral surface of the protective tube 1.

After the protection tube 1 has been assembled in this manner, the protection tube 1 is expanded while the annular watertight seal portion 11 is expanded.
Is inserted into the boring hole A, and the signal lines 6A of the water pressure sensors 6, 6, 6 and the signal lines 12A of the strain gauge are connected to the automatic measuring instrument 1
Connect to 3.

Thus, each of the three water pressure measuring chambers 4, 4, 4 defined in the protective tube 1 is located in the aquifers B, C, D, respectively, and a pair of upper and lower annular shields are provided. The water seal portions 11 and 11 are in a state of being shielded from the other aquifers C, D, (D, B and B, C). As a result, the groundwater in each of the aquifers B, C, and D will flow only into the respective water pressure measuring chambers 4 communicating with each other through the water guiding holes 8, 8, ... The internal water pressure sensor 6 can measure only the pore water pressure of the groundwater flowing in from the communicating aquifers B, C, and D.

Further, when groundwater flows into the water pressure measuring chamber 4, the pile forming the hair filter part 10 is bent by water pressure, and the pile near the water guiding hole 8 covers the water guiding hole 8 in an arched shape. The fine soil particles mixed in the groundwater are prevented from entering the water pressure measuring chamber 4.

Further, the air in the aquifers B, C, and D penetrates into the respective water pressure measuring chambers 4 as bubbles through the water guiding holes 8 together with the groundwater, and rises to the upper portion in the water pressure measuring chambers 4, As a result of the air bubbles being discharged from the air vent hole 9 to the boring hole A by the water pressure, it is possible to prevent the formation of an air film around the water pressure sensor 6 and the deterioration of the measurement accuracy.

As described above, according to the apparatus of this embodiment, it is possible to measure the interstitial water pressure due to the groundwater in each of the multiple aquifers B, C, and D in a state in which they are cut off from each other. Since a plurality of pipes for strain measurement 12, 12, 12 are incorporated in this, not only pore water pressure but also landslide phenomenon can be measured at the same time.

In this embodiment, vinyl chloride pipes are used as the connection protection pipe body 2 and the strain measuring pipe 12 constituting the protection pipe 1, but metal pipes may be used.

[0031]

Since the present invention is constructed as described above in detail, it has the following effects. (1) Since a plurality of water pressure measurement chambers are defined in one protection tube so as to be separated from each other in the axial direction and a water pressure sensor is arranged in each water pressure measurement chamber, one boring hole is formed. Only by doing so, it becomes possible to simultaneously measure the pore water pressure in a plurality of aquifers, the efficiency of the measurement work can be improved, and the cost for boring holes can be significantly reduced.

(2) The water pressure measuring chamber that communicates with one aquifer through the water guide hole is isolated from other aquifers by the annular impermeable seal portion, and groundwater between the aquifers is mixed to cause pore water pressure. Since it is configured so as to prevent the change of the pressure, the accurate pore water pressure of each can be measured.

(3) Since a ground filter is provided around the opening of the water conduit leading to the aquifer, only groundwater is allowed to pass through but fine soil particles are prevented from flowing in.
It is possible to prevent soil particles from accumulating in the water pressure measurement chamber, and it is possible to accurately measure each pore water pressure over a long period of time.

(4) As described in (1) to (3) above, according to the present invention, a plurality of pore water pressures are simultaneously and accurately measured.
In addition, since it can be measured over a long period of time, it is possible to quantitatively judge multiple pore water pressures, prediction of disasters such as landslides, liquefaction of ground, landslides, research on disaster countermeasures It becomes possible to obtain useful information for prevention, etc.

(5) Furthermore, by incorporating a plurality of strain measuring pipes in the protection tube, it becomes possible to judge the correlation between a plurality of pore water pressures and landslide phenomenon, which was impossible with the prior art.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a multilayer pore water pressure measuring device according to an embodiment of the present invention with a part broken away.

FIG. 2 is an enlarged view of an arrow A in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

4 is a sectional view taken along the line IV-IV in FIG.

[Explanation of symbols]

 1 Protective Tube 2 Connection Protective Tube 3, 5 Closing Member 4 Water Pressure Measuring Chamber 6 Water Pressure Sensor 8 Water Conduction Hole 10 Capillary Filter Section 11 Annular Impermeable Seal Section A Boring Hole

Claims (2)

[Claims] 1. A protective tube inserted into the boring hole, and a plurality of closing members disposed in the protective tube so as to be axially separated from each other and for partitioning a plurality of water pressure measurement chambers in the axial direction in the protective tube. A water pressure sensor provided in each of the plurality of closing members and respectively disposed in each of the plurality of water pressure measuring chambers, and formed in the protection pipe in an axially spaced manner, and each of the plurality of water pressure measuring chambers includes the boring. A plurality of water guiding holes communicating with the holes, a hairy filter portion provided around the plurality of water guiding holes and provided on the outer peripheral surface of the protective tube, and a plurality of the plurality of water pressure measuring chambers communicating with each other Multi-layer pore water pressure measurement comprising an annular watertight seal portion axially spaced from the outer peripheral surface of the protective tube so as to abut the hole wall of the boring hole so as to block the water guiding holes from each other. apparatus. 2. The multi-layer pore water pressure according to claim 1, wherein the protection pipe is composed of a plurality of connection protection pipes, and a plurality of strain measuring pipes are spaced between the plurality of connection protection pipes. measuring device.