JPH0721279B2 - Method of measuring pore water pressure in the ground by forming a special sealing material layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention, in order to know the distribution of the groundwater pressure required to judge the condition of the ground, in order to know the distribution of the groundwater pressure at each depth of the ground ( Regarding the method for measuring the pore water pressure), particularly in the measurement, when a sealing material layer made of a synthetic resin is injected into an appropriate place in the boring hole excavated in the ground to form a sealing material layer which is an impermeable layer, A special mixture is adopted for the sealing material.

《Prior art》 It is necessary to measure the distribution of pore water pressure underground and its change over time in order to know the properties related to the strength and deformation of the ground in the investigation of the foundation of dams, stability of cut slopes, prevention of landslides, etc. However, for this purpose, boring was performed on the required ground, and a highly accurate pore water pressure gauge was installed in the bore hole to measure the pore water pressure.

Therefore, in the above-mentioned conventional method, a large number of boring holes having different depths are drilled and the pore water pressure is measured. Therefore, there is a problem that it takes a lot of time and cost.

Therefore, in order to eliminate the above-mentioned adverse effects, in recent years, it has been practiced to measure the pore water pressure at a plurality of locations with only one boring hole as shown in FIG.

This is a filter material b such as sand is alternately filled through a sealing material c such as mortar or cement milk and a synthetic resin at a pore water pressure measurement position in one boring hole a formed in the ground, These multi-stage filter materials b
Each of the water pressure gauges d is installed therein to measure the water pressure in each layer. Therefore, according to this method, it is troublesome to drill a large number of boring holes and to install a pore water pressure gauge in each of them. And save time and money.

<< Problems to be Solved by the Invention >> However, in the above-mentioned conventional technique shown in FIG. 4, the sealing material c permeates and disappears into the cracks or the concave holes in the boring hole a, resulting in the boring hole a. Since the sealing material layer does not reach the prescribed height due to the lack of the filling amount in the inside, a sufficient sealing effect cannot be obtained, and the pore water of each layer may leak out.

Such a place where the sealant permeates and disappears may occur in a long range on the hole wall of the boring hole a, which becomes a serious obstacle to the work of forming the sealant layer.

Further, the code e of the water pressure gauge d embedded in each layer becomes a water channel, and the pore water pressure of each layer cannot be accurately measured.

In addition to this, when the seal material c penetrates deeply into the filter material b, it also prevents the pore water from reaching the water pressure gauge d, which results in the problem that the water pressure measurement cannot be performed.

The present invention is proposed in view of the above-mentioned problems of the prior art, and in claim (1) thereof, a seal capable of minimizing penetration into a gap due to a recessed hole portion or a crack in a boring hole. It is an object of the present invention to provide a method capable of measuring the pore water pressure in the ground with higher accuracy by using a material and accurately measuring the filling depth of the sealing material. Then, by combining the above-mentioned sealing material with quick-curing property and low heat-generating property, the efficiency of construction and the adverse effects on electric members due to heat generation and the contraction of the sealing material at the time of curing, It is trying to prevent a gap from being generated between the two and to enable more reliable measurement.

<< Means for Solving the Problems >> In order to achieve the above-mentioned object, the present application provides that, in claim (1), water pressure gauges communicating with the water inlet are sectionally incorporated at appropriate intervals, and the lead wire of the water pressure gauge is on the ground side. The step of inserting the water pressure measuring tube guided to the inside of the boring hole, the step of filling at least the filter material into the boring hole, the filling depth of the filter material is measured, and the portion to be covered with the water introducing port is filtered. Laminating the filter material layer and the sealing material layer, including a step of forming a material layer, a step of filling a sealing material with a synthetic resin system, and a step of measuring the filling depth of the sealing material and laminating the sealing material layer. In a method in which the measurement value of each of the water pressure gauges at each depth is detected by a ground-side measuring instrument to which the lead wire is connected, the sealing material made of the synthetic resin system described above. Is a mixture of a curing agent and a main agent such as an epoxy resin that reacts and cures in water after filling, and has a specific gravity greater than that of water and a viscosity at room temperature.
An attempt is made to provide a method for measuring pore water pressure in the ground by forming a special sealing material layer, which is 800 to 9000 cp and is provided with thixotropy. In addition to the content of claim (1), a curing reaction accelerating catalyst and a non-reactive diluent are added to the sealing material so as to combine rapid curing and low heat buildup. There is.

<< Operation >> According to the method for measuring pore water pressure in the ground based on the above-described configuration, the required number of water pressure gauges are built in advance at predetermined positions of the water pressure measurement pipe, and each water pressure gauge is isolated in the measurement pipe. The position of the water gauge is inserted into the boring hole having a predetermined depth, so that the depth of the water pressure gauge in the ground can be accurately specified.

Further, since the work of filling the sealing material with the epoxy resin or the like includes the work of measuring the filling depth, the filling depth of the sealing material layer can be accurately obtained for each filling operation.

Furthermore, in connection with accurately determining the filling depth of the sealing material layer for each filling operation, even if the sealing material penetrates into the cracks or recesses in the boring hole, the sealing material layer will not reach the predetermined depth. The filling work will be continued until it arrives.

Further, in claim (1), since a mixture of a synthetic resin-based main agent and a curing agent is injected as the sealing material, this is cured in water in the boring hole, but its specific gravity is water. Since it does not float because it is heavier, and has a viscosity of 800 to 9000 cp, it does not hinder the pressure-feeding of the mixture, and the thixotropic property of the sealing material is used. Since the fluidity is maintained during the feeding for injection, it is easy to perform injection by the pressure feeding pipe, and at a predetermined place in the boring hole, it is stationary and is not in a state of receiving external mechanical force. In that case, the fluidity of the boring hole is significantly reduced, and the recessed portion or the clearance in the boring hole is to be filled.
At this time, since it hardens without penetrating further through the gaps, the sealing material is not wasted, and the original permeability of the ground is not impaired, and the correct measurement of groundwater pressure is guaranteed. It

Next, in claim (2), the same action as in claim (1) can be achieved, and since a curing reaction accelerating catalyst is added to the mixture as the sealing material, the rapid curing property of the sealing material is obtained. As a result, the construction time can be greatly shortened and a non-reactive diluent is also added separately, so the maximum temperature reached by the reaction heat generated when the mixture of the main agent and the curing agent is cured is reduced. Therefore, without damaging the water pressure gauge or the lead wire, the heat shrinkage due to cooling during curing is small due to the low heat generation property, and as a result, a gap occurs in the contact portion with the water pressure gauge. This prevents the impermeability of the water in the boring hole from being obstructed, and, in addition to having thixotropy as described above, by combining the rapid hardening property as described above, the gap in the boring hole can be prevented. From etc. That the sealing member will be escaped it can be more effectively prevented.

<< Examples >> An example of the present invention will be described in detail below with reference to FIGS.

First, the water pressure measuring pipe 1 is prepared in advance.
As shown in the figure, the water pressure gauges 2 are built into the long tubular body 1a at a predetermined plurality of locations, and at the upper and lower sides of the water pressure gauge 2 there are impermeable walls 3a and 3b made of synthetic resin material or the like. The partition pipe portion 4 is formed by blocking the inside of the pipe body 1a, and the water pressure of the ground water flowing from the water guiding port 5 opened in each partition pipe portion 4 is
Each of the water pressure gauges 2 can be detected.

Each of the lead wires 6 of each of the water pressure gauges 2 passes through the long tubular body 1a, airtightly penetrates the impermeable walls 3a, 3b, and is led out from the upper end opening 1b of the tubular body 1a to the outside, Of course, this lead wire 6 is to be connected to a measuring device on the ground (not shown), and in FIG. 2 of the same above, 1b is an extension pipe body 1c for constructing the long pipe body 1a. It shows the connection part that was continued.

The water pressure measuring tube 1 thus formed is
As shown in (a) of the figure, at a required position of the ground A, the boring hole a excavated to a depth of a predetermined length is inserted and erected at a substantially central position. Therefore, at this time, the boring hole a
Based on the depth of the water and the length of the water pressure measuring pipe 1, each water pressure gauge 2
The depth of can be set to the required position.

Next, in the illustrated example, as shown in the same figure (b), a separately prepared pressure feeding pipe 7 is inserted into the boring hole a and mounted directly above the hole bottom portion a ', and an injection pump (not shown) on the ground is provided. Is operated, a synthetic resin sealing material such as an epoxy resin is supplied by the pressure-feeding pipe 7, whereby the lowest sealing material layer 8 is formed.

Here, at the time of injecting the sealing material such as the epoxy resin, it is preferable that the main agent and the curing agent are delivered by the respective pumps in the required amounts, and these are mixed by the mixer, and then delivered by the pressure feed pipe 7. .

Epoxy resin, urethane resin, etc. can be used as the main component, and the sealing material as a mixture has a specific gravity of 1.05.
It must be larger than water, such as ~ 1.60, and its viscosity must be 800-9000cp at room temperature and thixotropic.

The thixotropy means that when a mechanical external force is applied (for example, when it is injected by the pressure feed pipe 7), it retains fluidity, but when the external force disappears (for example, at a predetermined location). When it is in a stationary state), it means that the fluidity is greatly reduced, but in order to impart such thixotropy, hydrophobicity is added to low viscosity epoxy resin etc. Silica (for example, Cabosil TS720 (trade name of Cabot Co.) or Aerosil R202 (trade name of Aerosil Co.) may be added in an amount of 1 to 6% by weight. In this case, the viscosity is
Adjusted to a range of 2500-7000cp.

Further, in the method of claim (2), a curing reaction accelerating catalyst is used to accelerate the curing reaction of the sealing material.
For this purpose, DMP30 (trade name of Rohm and Haas Company) may be added in the range of 2 to 8 parts by weight with respect to 100 parts by weight of the components such as epoxy resin.

Further, in the above-mentioned claim (2), not only the rapid curing property of the sealing material but also the low exothermic property is intended to be combined.

As is known, in epoxy resins and the like that have fast curing properties, when the sealing material, which is a mixture of the main agent and the curing agent, is cured, the temperature rise due to the reaction heat is large. Aromatic liquid resin such as Epollil L (trade name of Anchor Chemical Co.) or Oligotech 1030 (trade name of Mitsubishi Petroleum Co., Ltd.) is added to 100 parts by weight of the epoxy resin component. It may be added in the range of 40 to 60 parts by weight.

The characteristics of a mixture obtained by adding a thickener to a low-viscosity fast-curing epoxy resin (400 cp) and imparting thixotropy were examined. Its specific gravity was 1.08 and viscosity was 3300 cp (at 20 ° C).
And the curing time is 1 hour and 20 minutes (at 10 ° C),
The maximum temperature reached by the reaction was 63 ° C (30 minutes after the injection).

Compared with this, when using a normal epoxy resin injection material,
If the maximum temperature is 60 ℃, it takes more than 4 hours to cure after mixing the main agent and the curing agent. If you try to shorten the time to cure, the maximum temperature will be too high, such as 200 ℃. Will be lost.

Regarding the sealing material used as described above, if the specific gravity, viscosity, and thixotropic properties are satisfied, the sealing material can be easily transferred by the pressure-feeding pipe 7.
In addition, since the fluidity of the seal material after being injected into the boring hole a is significantly reduced, the recessed holes and cracks of the boring material are closed by the seal material and are not released into the ground through the cracks. There is no such thing as putting it out.

As shown in FIG. 1B, the liquid level sensor 10 for the sealing material is inserted into the boring hole a, and the sealing material is supplied by the pressure pipe 7 via the injection pump installed on the ground. , The liquid level is detected by the liquid level sensor 10
The process is continued until the set depth of is reached, as shown in FIG.

At this time, in consideration of the fact that the sealing material in the pressure-feeding pipe 7 actually drops with the passage of time, the remaining sealing material is pushed by a separately prepared water-pressure feeding pump to remove all the sealing material. The dose is designed to fill the boring hole.

The upper surface of the sealing material layer 8 thus formed is measured by a separately prepared appropriate length measuring means, and the depth of the upper surface corresponds to the lowest water pressure gauge 2 in the water pressure measuring pipe 1.
Check whether it is appropriate for the specified depth of.

When the sealing material layer 8 does not reach the predetermined depth, the sealing material is filled again. On the other hand, when the sealing material layer 8 is filled to the predetermined depth, the sealing material filling operation is finished.

Next, the filter material layer 9 is laminated on the upper surface of the sealing material layer 8, and the layer thickness thereof reaches from the lower order to the upper order of the lowermost water inlet 5 as shown in FIG. The pore water that has entered through the filter material layer 9 is applied so as to reach the water pressure gauge 2 from the water guide port 5. In this case, standard sand can be used as the filter material. The depth of the upper surface of the layer 9 will be measured and compared with the specified depth of the water guide port 5 to confirm its suitability.

As the means for forming the filter material layer 9, sand or the like may be dropped from the opening of the boring hole a, or a long funnel-shaped member may be used for supply.

Next, the work of filling the sealing material with the epoxy resin or the like is performed on the upper surface of the filter material layer 9 as described above, and the work is repeated until the required number of steps is reached, and the steps shown in FIGS. After that, the sealing material injection work is completed.

When such work is completed, in this embodiment, as shown in FIG. 1, the filter material layers 9 are formed in the upper, middle, and lower three stages, and the pore water pressure in each of them is applied to the inside 4 of each partition pipe. It is measured by each water pressure gauge 2 provided, and the measured value can be known by a ground-side measuring device (not shown).

In addition, although the case where the filter material layer 9 is directly laminated on the seal material layer 8 has been shown in the above-mentioned embodiment, in the present invention, for example, bentonite or the like is formed on the seal material layer 8. By forming a water blocking material layer (not shown) by, and by stacking the sealing material layer on this, when forming the sealing material layer,
Including the case where there is an additional laminating step in which the water blocking material layer prevents the sealing material from involuntarily penetrating into the filter material layer 9 made of standard sand or the like. It is a waste.

<< Effect of the Invention >> According to claim (1) of the present application, by inserting the water pressure measuring pipe into the boring hole, it is possible to measure the water pressure at a very highly accurate depth, and to give the measurement result high reliability. Therefore, the cord of the water pressure gauge is not damaged and the cord does not form a water channel.

Further, even if the sealing material penetrates into the cracks in the boring hole, the filling operation is continued until the predetermined depth is reached, so that the impermeable layer can be formed with high accuracy.

Further, it is important to use a mixture of the main agent and the curing agent in the above-mentioned sealing material, and not only satisfy the specific conditions of specific gravity and viscosity, but also impart thixotropy, so that the mixture can be smoothly fed by pressure. Of course, the sealing material that has been injected into the boring hole has reduced fluidity, so that the concave holes and cracks are reliably filled, and
Since the sealing material does not deviate to the cracks or the like, the sealing material is prevented from being wasted, and the undesired water blocking state of the ground is not generated, so that the reliability of the measurement result can be improved. .

Further, according to claim (2), the combination of the fast curing property and the low exothermic property further shortens the construction time,
It was possible to achieve an improvement in waterproofness.

[Brief description of drawings]

FIGS. 1 (a), (b), (c), (d), (e), (f) are longitudinal front views showing the order of steps according to an embodiment of the method for measuring underground pore water pressure according to claim (1) of the present application. Fig. 2 is a partial vertical sectional front view showing an example of a water pressure measuring pipe used for carrying out the above method, Fig. 3 is an enlarged vertical sectional front view of a ground main part in the same state of measuring pore water pressure, and Fig. 4 is conventional. It is a longitudinal cross-sectional front explanatory view of the main part of the ground showing the method for measuring the underground pore water pressure. 1 …… Water pressure measuring tube 2 …… Water pressure gauge 5 …… Water inlet port 6 …… Lead wire 8 …… Seal material layer 9 …… Filter material layer a …… Boring hole

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiko Umeda 4-9-9 Akasaka, Minato-ku, Tokyo Within Japan National Land Development Co., Ltd. (72) Inventor Keisuke Miyauchi 4-9-9 Akasaka, Minato-ku, Tokyo Japan Development Co., Ltd. (56) References JP-A 64-36819 (JP, A) JP-A 52-65101 (JP, A)

Claims (2)

[Claims] 1. A step of inserting a water pressure measuring pipe, in which a water pressure gauge communicating with a water introducing port is divided and incorporated at appropriate intervals, and a lead wire of the water pressure gauge is led to the ground side into the boring hole, and the boring hole. A step of filling at least a filter material into the inside, a step of forming a filter material layer in a portion to be covered with the water inlet by measuring a filling depth of the filter material, and a step of filling a sealing material with a synthetic resin system, Including the step of measuring the filling depth of the sealing material and laminating the sealing material layer, repeating the lamination of the filter material layer and the sealing material layer a plurality of times, and measuring each depth by the ground-side measuring instrument connected with the lead wire. In the method in which the measured value of each of the water pressure gauges is measured, the sealing material by the synthetic resin system described above is composed of a main agent such as an epoxy resin that is reactively cured in water after filling and a curing agent. Pore water pressure in the ground due to the formation of a special sealing material layer characterized by having a specific gravity greater than that of water, a viscosity of 800 to 9000 cp at room temperature, and thixotropic properties. Measuring method. 2. A step of inserting a water pressure measuring pipe, in which water pressure gauges communicating with the water inlet are separated at appropriate intervals, and a lead wire of the water pressure gauge is led to the ground side, into the boring hole, and the boring hole. A step of filling at least a filter material into the inside, a step of forming a filter material layer in a portion to be covered with the water inlet by measuring a filling depth of the filter material, and a step of filling a sealing material with a synthetic resin system, Including the step of measuring the filling depth of the sealing material and laminating the sealing material layer, repeating the lamination of the filter material layer and the sealing material layer a plurality of times, and measuring each depth by the ground-side measuring instrument connected with the lead wire. In the method in which the measured value of each of the water pressure gauges is measured, the sealing material by the synthetic resin system described above is composed of a main agent such as an epoxy resin that is reactively cured in water after filling and a curing agent. It is a compound, the specific gravity is larger than water, the viscosity is 800 ~ 9000 cp at room temperature, and with thixotropic, addition of a curing reaction accelerating catalyst and a non-reactive diluent, A method for measuring pore water pressure in the ground by forming a special sealing material layer, which has both fast curing property and low heat generation property.