JP2544998B2 - Indoor permeability tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an indoor water permeability test apparatus for difficult-to-permeate rocks and the like. More specifically, by setting the same volume on the high-pressure side and the low-pressure side, the transient pulse method can be measured in a short time, and the constant water level method can also be used by devising the piping system. It is about.

This device is a useful technique in indoor permeability tests related to the hydraulic characteristics evaluation of bedrock such as underground space utilization (high-level radioactive waste geological disposal facility, underground oil storage facility, weightless experimental facility, etc.) and hot rock power generation. is there.

[Prior Art] In a conventional test apparatus, a method of measuring a water flow rate and obtaining a water permeability coefficient is widely used as represented by a constant water level method. In this constant water level method, both ends of the specimen (test sample) are kept at a constant pressure head difference, and a hydraulic gradient is applied to the saturated pore water in the specimen so that the flow is in a steady state (the discharge water amount per unit time is stable. It is a method of obtaining the hydraulic conductivity by measuring the amount of discharged water per unit time after the current state).

However, when the constant water level method is applied to a poorly permeable rock, the amount of water discharged from one end of the specimen is extremely small and the test time is long. In addition, since the amount of discharged water is small, the influence of the leakage from the pipe connection portion and the volume change of water due to the room temperature change on the measurement system becomes remarkable, and the measurement accuracy is significantly reduced.

Therefore, the transient pulse method was proposed as a permeability test method for poorly permeable rocks. The evaluation method based on this is derived from the differential equation of one-dimensional unsteady seepage flow. When roughly classified, there are an evaluation method by an approximate solution and an evaluation method by an exact solution. As shown in FIG. 2, the test is carried out using storage tanks 12 and 14 having known volumes V ₁ and V ₂ at both ends of the specimen 10. In the initial state, the pressures P ₁ and P ₂ in each storage tank and the pore water pressure in the specimen are set to be equal (P _INIT ), and a pressure pulse ΔP is applied to the storage tank 12 at the start of the test (t = 0), The hydraulic gradient in the specimen 10 changes with the passage of time, and pressure propagation occurs.
In the evaluation method based on approximate solution, as shown in FIG. 3, P ₁
−P _f (where P _f is the convergent pressure) decreases exponentially with the passage of time, and the hydraulic conductivity can be obtained from the slope α between the time t and the logarithm of P ₁ −P _f .

[Problems to be Solved by the Invention] For example, when designing a geological disposal facility for high-level radioactive waste, it is necessary to accurately predict the groundwater flow in rock for a very long period of time. When considering such a long-term groundwater flow, a poorly permeable rock bed that has been conventionally treated as an impermeable layer or a semi-permeable layer should also be tested, and its permeability should be evaluated.
However, as mentioned above, it is extremely difficult to measure the hardly permeable rock with the existing test equipment by the constant water level method.
The measurement accuracy is poor in reliability.

On the other hand, the evaluation method based on the approximate solution of the transient pulse method requires a storage tank with a relatively large volume compared to the evaluation method based on the exact solution, and it is necessary to confirm the final convergence pressure P _f There is a drawback. In addition, it is difficult to correct the fluctuation of the pore pressure due to the room temperature change by the evaluation method based on the exact solution, and it takes a lot of time for the curve fitting etc. in the evaluation of the hydraulic conductivity, which is inefficient. There is a drawback of.

In any case, a detailed examination has not yet been made on the test method for the hardly permeable rock, and no standard test device has been proposed.

The object of the present invention is to solve the problems of the above-mentioned conventional techniques, and to be able to carry out both the transient pulse method and the constant water level method. It is to provide a water permeability test apparatus.

[Means for Solving the Problems] The present invention includes a pressure vessel for accommodating a specimen therein to apply a restraining pressure, a high-pressure side storage tank and a low-pressure side storage tank, and a pipe provided with these valves and pressure sensors. It is an indoor water permeation test device connected by a system.

The specimen is housed inside the pressure vessel with pressure plates arranged at both ends and the side surfaces covered with a membrane, and the pressure fluid filled inside the pressure vessel by the restraint pressure piping system communicating with the inside of the pressure vessel. Restraint pressure is applied from the outside of the membrane.

The piping system is a high-pressure side and low-pressure side gap pressure piping system that communicates from the high-pressure side and low-pressure side storage tanks to the opposite ends of the specimen of the pressure vessel via the first and second valves, respectively.
A communication path between the first valve and the pressure vessel of the pore pressure piping system and between the second valve and the pressure vessel, which is the high pressure side pressure sensor and the third path.
No. 1 and a low pressure side pressure sensor are connected in series, and a pressure sensor system piping provided with a differential pressure sensor in parallel with the third valve and a pressure vessel side of a high pressure side or low pressure side gap pressure piping system are installed. No. 4 valve, a piping system having fifth and sixth valves respectively connected to the high pressure side and low pressure side storage tanks, between the high pressure side storage tank and the fifth valve, and the low pressure side storage tank and the sixth valve. It consists of a communication piping system that connects between the valves. The volumes of the high-pressure side storage tank and the high-pressure side piping system attached thereto are set to be equal to the volumes of the low-pressure side storage tank and the low-pressure side piping system attached thereto.

Here, the outsides of both storage tanks are surrounded by pipes to automatically circulate a liquid at a constant temperature, and both storage tanks and their surrounding pipes and pressure sensors are placed in a protective container, and the protective container is filled with a heat insulating material to store both of them. It is preferable to control the bath at the same temperature.

[Operation] The transient pulse method or the constant water level method is selectively performed by controlling the opening / closing of each valve, the selection of the piping path associated therewith, and the control of the pressure supply state. The high-pressure side storage tank and the low-pressure side storage tank (both including the piping system) of the same volume make it possible to predict the final converged pressure when performing the transient pulse method, and contribute to shortening the test time.

In addition, the constant temperature control of both storage tanks serves to minimize the decrease in measurement accuracy due to temperature fluctuations.

[Example] FIG. 1 shows an example of an indoor water permeation test apparatus according to the present invention. This device is installed in a test chamber as a whole and includes a pressure vessel 20, a high pressure side storage tank 22, and a low pressure side storage tank 24, which are connected by various piping systems equipped with valves and pressure sensors. Has been done.

The sample 26 is housed inside the pressure vessel 20. A columnar specimen 26 is sandwiched between the top and bottom with pressure plates 27a and 27b, and the periphery is made of rubber (fluorine rubber or chloroprene rubber) membrane 28
Enclose with and tighten with the tightening band 29. The restraining pressure piping system 30 communicates with the space between these and the inner wall of the pressure vessel 20, and the membrane 28 is brought into close contact with the sample 26.

Here, the pressure vessel 20 is fixed to the upper lid 20 with the tightening bolts 21.
It is a structure that can be divided into three parts, a, the body portion 20b, and the bottom lid 20c. With the upper lid 20a and the body portion 20b of the pressure vessel 20 removed, the specimen 26 covered with the membrane 28 is placed on the pressure plate 27b,
The upper pressure plate 27a is covered from above, and the portion where the membrane 28 covers the upper and lower pressure plates 27a and 27b is fixed with the tightening band 29. After that, the pipe 42a for supplying the gap pressure is connected to the pressure plate 27a, and the body 20b of the pressure vessel 20 and the upper lid 20a are attached so as to cover from above. Furthermore, the upper lid of the pressure vessel 20
The shaft pressing shaft 25 attached to the center of 20a is inserted to the upper end of the pressure plate 27a inside the pressure vessel 20 to fix the position of the sample 26. For example, the shaft holding shaft 25 is threaded so that it can be inserted into the pressure vessel by rotating it with a spanner or the like, and a tapered surface and an O ring are used together so that the pressure inside the pressure vessel does not leak during the test. Have a water blocking function.

Here, the upper and lower pressing plates 27a and 27b have a cylindrical shape having substantially the same diameter as the sample 26. One surface of the pressure plates 27a and 27b directly contacts the specimen 26 to apply pore water pressure to the end surface of the specimen. That is, the pressure plates 27a, 27b are connected to the pore water pressure piping system at both ends of the test piece to supply water to the end surface of the test piece 26. The triangular black-painted part in the pressure board is a part that allows the pore water pressure to spread evenly over the end face of the cylindrical specimen. The structure should be open. Also, the side faces of the pressure plates 27a and 27b have a membrane 2
It also makes a surface contact with the upper and lower ends of 8 and plays a role of preventing the pressure fluid (for example, silicone oil) that requires a restraining pressure from directly contacting the specimen 26.

A high pressure side gap pressure piping system 40 having a first valve 31 is connected between the high pressure side storage tank 22 and a lower portion inside the pressure vessel 20. This high-pressure side gap pressure system penetrates the lower pressure plate 27b and
Has reached the bottom surface of. A low pressure side gap pressure piping system 42 having a second valve 32 is connected between the low pressure side storage tank 24 and the pressure vessel 20. The low-pressure side gap pressure system reaches the upper end surface of the sample 26 through the pipe 42a installed in the space inside the pressure vessel and the upper pressure plate 27a. A communication path is provided between the first valve 31 of the high pressure side clearance pressure piping system 40 and the pressure vessel 20 and between the second valve 32 of the low pressure side clearance pressure piping system 42 and the pressure vessel 20. This communication path is a pressure in which the high pressure side pressure sensor 44, the third valve 33 (safety valve of the differential pressure sensor 48) and the low pressure side pressure sensor 46 are in series and the differential pressure sensor 48 is provided in parallel with the third valve. The sensor system piping 50. Further, a fourth valve 34 is incorporated on the pressure vessel 20 side of the high pressure side gap pressure piping system 40. Further, a pipe 52 having a fifth valve 35 is connected to the high pressure side storage tank 22, and a pipe 54 having a sixth valve 36 is connected to the low pressure side storage tank 24. Then, between the high pressure side storage tank 22 and the fifth valve 35, the low pressure side storage tank 24 and the sixth valve
A communication pipe 56 having a seventh valve 37 is connected between 36.

Further, in the present invention, the volumes of the high-pressure side storage tank 22 and the high-pressure side piping system attached thereto are set to be equal to the volumes of the low-pressure side storage tank 24 and the low-pressure side piping system attached thereto.

The entire device is installed in the test room. The test room shall be sealed and isolated from the external environment. Then, by continuously operating the air conditioner, the temperature of the test room is indirectly controlled from the temperature control room adjacent to the test room. The outer walls of both storage tanks 22 and 24 are surrounded by a copper pipe 60, and water having the same temperature as the test room temperature is automatically circulated inside the storage tanks 22 and 24 and their surrounding pipes and pressure sensors, etc. (Not shown) and fill the protective container with heat insulating material. The other pipes should be heat-insulated by making the pipe length as short as possible. As a result, changes in the volume and pressure of the test water due to changes in temperature are minimized.
The high-pressure side storage tank 22 and the low-pressure side storage tank 24 are provided with temperature sensors 62a and 62b, respectively, so that the fluid temperature in the storage tank can be continuously recorded.

Basic test methods by the transient pulse method and the constant water level method are as described above. This device uses the following procedure.

First, the constraining pressure is the pressure that wraps the sample 26 from the periphery, similarly to the transient pulse method and the constant water level method, and is usually applied using silicone oil. This restraining pressure is because the specimen originally existed in the formation,
The pressure is equivalent to the ground pressure at that time. Silicone oil is injected into the pressure vessel by a pump or the like (not shown) from the portion labeled as "restraint pressure" in Fig. 1, and after filling, it is boosted by a commercially available pressurizing device such as a booster pump or the like (not shown). Pressurize to the prescribed pressure. This time,
Since the specimen 26 has pressure plates 27a and 27b at the upper and lower ends and a membrane 28 on the side surface, the silicone oil does not directly contact the specimen, and the membrane 28 and the pressure plate 27a,
The specimen 26 is restrained as a pressure to wrap 27b from the periphery. The filled portion of silicone oil is indicated by dots in FIG.

Then, the pore pressure on both ends of the specimen is usually applied using distilled water or groundwater. The pore water pressure piping system before the test is supplied from the piping system of the fifth valve 35 by a pump or the like (not shown) with the sixth valve 36 closed and all other valves open. Since the gap pressure here is the state before the test, the specimen 26
The pressure is equal at both ends of. Normally, the pore water pressure at this point is about the same as the water pressure the specimen had when it originally existed in the formation. It should be noted that this pore water pressure never exceeds the constraint pressure described above. If the pressure is equal to or higher than the binding pressure, the water used as the pore water pressure pushes the membrane outward and escapes to the binding pressure side, which makes it impossible to grasp the water permeability of the specimen.

In the test by the transient pulse method, after restraining pressure is applied to stabilize the sample 26, the sixth valve 36 is closed and all the other valves are opened. Next, the gap pressure is supplied through the fifth valve 35, and when the predetermined pressure is reached, the fifth valve 35
Close 35. After the pressure in the closed section stabilizes, the third valve 33, the fourth valve 34, and the seventh valve 37 are closed to completely separate the pore water pressure piping system applied to both ends of the specimen 26. After that, the fifth valve 35 is opened and the pressure pulse (several kgf /
cm ² ) is added and the fifth valve 35 is closed immediately. After the pressure in the high-pressure side storage tank 22 has stabilized, the fourth valve 34 is opened and the test is started. Since there is a difference in the pore water pressure applied to both ends of the specimen, the pressure propagates through the specimen from the lower side of the specimen with high pore pressure to the upper side of the specimen with low pore pressure. The pressure change at this time is measured by the differential pressure sensor 48, and the hydraulic conductivity is obtained from the relationship between the time and the pressure change at this time.

In the present invention, since the high-pressure side storage tank and the low-pressure side storage tank are designed to have the same volume including the pipes and the like, the final converged pressure P _f (see FIG. 3) can be predicted, and the test can be performed. Can be implemented in a short time. Further, even if the volume of the test water changes or the pressure changes due to the temperature change, those effects are offset. In the evaluation method based on the approximate solution, since the amount of water stored inside the specimen 26 is ignored, the error increases as the amount of storage in the gap of the specimen 26 increases. The volume of each storage tank is set to approximately 1183 cc in order to minimize this error and enable measurement to the order of 10 ^-7 cm / sec.

The pressure head and back pressure are applied by the constant water level method, but the same piping system as the pore water pressure applied to both ends of the specimen by the transient pulse method can be used, so basically the same equipment is sufficient. In the test by the constant water level method, similarly to the above, after restraining the sample 26 by stabilizing pressure, the first valve 31, the second valve 32, the fourth valve 34, the fifth valve 35, and the sixth valve The valves 36 are opened, and the third valve 33 and the seventh valve 37 are closed. Next, the pressure head is supplied through the fifth valve 35, passes through the first valve 31 and the fourth valve 34, and pressure is applied to the lower end surface of the sample 26. The water discharged from the upper end surface of the specimen 26 is supplied to the second valve 32,
It is measured by a water amount measuring device (not shown) via the low pressure side storage tank 24 and the sixth valve 36. At the time of this test, in order to minimize the effect of bubbles, back pressure due to air is also applied from the measurement system.

As described above, this apparatus can perform the transient pulse method and the constant water level method, and both methods can be continuously performed. This device is 10 ^-7 cm / sec to 10 ^-12 c for transient pulse method.
It has a measuring range of about m / sec, and about 10 ^-4 cm / sec to 10 ^-8 cm / sec by the constant water level method.

In order to prevent lateral flow between the specimen 26 and the membrane 28, it is necessary to apply a pressure difference of 7 kgf / cm ² or more between the restraining pressure and the pressure head based on an experiment to confirm water leakage from the side. It has become.

With this test equipment, it has become possible to measure highly impervious rocks that have been extremely difficult to measure in a short time with high accuracy. The test results are shown in Tables 1 to 4.

Table 1 shows three test specimens measured three times by the constant water level method using the Sanjo Nodoriyama rock from Fukushima Prefecture. From this result, each data is almost equal, 10 ^-8 cm / sec
It can be seen that the constant water level method in order has high reproducibility.

The test results shown in Table 2 are the same as those in Table 1 above, using the Mijo Nohyama rock, four times by the transient pulse method (K-1a to K-1d marked with *), and once by the constant water level method. (K-1e),
The same test piece was repeatedly tested. From this result, it can be seen that the data of both methods are almost equal and the reproducibility of the transient pulse method is high. Also, comparing the test time here, it takes about 3 hours for the constant water level method, but only a few minutes for the transient pulse method, and it is possible to greatly reduce the test time when the transient pulse method is used. .

Table 3 shows the results of two repeated tests by the transient pulse method using Toki granite produced in Gifu Prefecture. The two test data are almost the same, and it can be seen that the reproducibility is high even in the order of 10 ^-10 cm / sec.

Table 4 shows the results obtained by repeating the test twice by the transient pulse method using the crystal schist of the outer zone of Southwest Japan. The two test data are almost the same, and it can be seen that the reproducibility is high even in the order of 10 ^-12 cm / sec.

The apparatus of the present invention can also be used for evaluation based on an exact solution in the transient pulse method. Further, not only water but also other liquids or gases can be measured as the pressure medium, and therefore, it can be used for evaluation of permeability and air permeability of artificial materials such as mortar and synthetic resin.

EFFECTS OF THE INVENTION Since the present invention is a storage tank system (arrangement of piping paths, valves, pressure sensors, differential pressure sensors, etc.) configured as described above, not only the transient pulse method but also the constant water level method is possible. Both methods can be carried out continuously. Further, in the present invention, since the volumes of the high-pressure side storage tank and the low-pressure side storage tank are set equal, including the piping, the convergence point P _{f of the} pressure can be predicted, and thereby the test time can be significantly shortened. Even if a change in volume of the fluid or a change in pressure occurs due to a change in room temperature, the influence can be offset and the measurement accuracy is improved.

In particular, the outsides of both storage tanks are surrounded by pipes to automatically circulate a liquid at a constant temperature, and both storage tanks and their peripheral pipes and pressure sensors are placed in a protective container, and the protective container is filled with a heat insulating material. The measurement accuracy is further improved by configuring so as to be controlled at the same temperature.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an indoor water permeability test apparatus according to the present invention, FIG. 2 is an explanatory view of a transient pulse method,
FIG. 3 is an explanatory diagram of an evaluation method based on an approximate solution. 20 …… pressure vessel, 22 …… high pressure side storage tank, 24 …… low pressure side storage tank, 26 …… specimen.

Claims (2)

(57) [Claims] 1. A pressure vessel having pressure plates arranged at both ends of the specimen and capable of accommodating them while the side surfaces of the specimen are covered with a membrane, and connecting the inside of the pressure vessel to the inside of the pressure vessel. A constraint pressure piping system that applies a constraint pressure to the sample from the outside of the membrane by the pressure fluid that is filled, a high-pressure side and a low-pressure side storage tank, and a high-pressure side and a low-pressure side storage tank, respectively. Through the pressure plate in the pressure vessel to apply the gap pressure to the opposite ends of the test piece, the high and low pressure side gap pressure piping systems, the first valve of the gap pressure piping system and the pressure vessel Between the second valve and the pressure vessel, the high pressure side pressure sensor, the third valve and the low pressure side pressure sensor are in series and
Pressure sensor piping provided with a differential pressure sensor in parallel with the valve, a fourth valve installed on the pressure vessel side of the high pressure side or low pressure side gap pressure piping system, and a high pressure side and low pressure side storage tank, respectively. A pipe system having fifth and sixth valves connected to each other, a high pressure side storage tank and a fifth valve, a low pressure side storage tank and a sixth valve, and a seventh valve An indoor water permeation test device, comprising: a communication pipe system having a high pressure side storage tank and a high pressure side piping system attached thereto, and a low pressure side storage tank and a low pressure side piping system attached thereto. 2. The outside of both storage tanks is surrounded by pipes, a liquid having a constant temperature is automatically circulated therein, and both storage tanks and their peripheral pipes and pressure sensors are housed in a protective container, and a heat insulating material is provided in the protective container. 2. The apparatus according to claim 1, wherein both storage tanks are filled with and are controlled at the same temperature.