A soft-wall permeameter for measuring compression water release and chemical permeability coefficient of clay soil

Abstract

The invention relates to the technical field of geotechnical test instruments, and specifically discloses a soft-wall permeameter for measuring compressed water release and chemical permeability coefficient of clay soil, comprising: a pressure-resistant PVC cylinder, wherein the upper and lower ends of the pressure-resistant PVC cylinder are connected with an upper cover and a base through a connecting piece, a permeation layer is arranged inside the inner cylinder, one side of the upper end of the inner cylinder is connected with a second liquid inlet pipe, the other side of the upper end of the inner cylinder is connected with a second liquid outlet pipe, and the main pipe is further connected with an air compressor through a second three-way pipe; the invention obtains the water release amount of clay samples under different confining pressure conditions by monitoring the flow of each valve; the volume of the clay is reduced due to compression, and the hydraulic transmission oil level in the pressure-resistant PVC cylinder gradually decreases, and the hydraulic transmission oil level decrease speed is monitored to obtain the compression deformation process of the clay samples under different confining pressure conditions; through the monitoring results, a time variation curve of compression-water release of the clay sample is drawn, the law of compressed water release of the weak permeable layer is studied, and the scale effect of the hydraulic parameters of the weak permeable layer is studied by comparing the in-situ test results, which is conducive to the use of permeability test.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical testing instruments, and in particular relates to a soft-wall permeameter for measuring compressed water release and chemical permeability coefficient of clay soil. Background Art

[0002] The geotechnical permeability test is a very important part of the construction and exploration process. It mainly tests the ability of natural landforms to penetrate water. It can determine the permeability coefficient of unsaturated loose rock layers in the aeration zone to determine the internal structure of the terrain. Accurate geotechnical permeability tests allow the construction process to infer the internal structure of different terrains to ensure a safer construction process. Traditional permeameters are not convenient for obtaining the amount of water released by clay samples under different confining pressures, and are not convenient for obtaining the compression deformation process of clay samples under different confining pressures. This is not conducive to obtaining better test results and is not conducive to the use of permeability tests. Summary of the invention

[0003] The object of the present invention is to provide a soft-wall permeameter for measuring the water release under compression and the chemical permeability coefficient of clay soil, so as to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A soft-wall permeameter for measuring compression water release and chemical permeability coefficient of clay soil, comprising:

[0006] A pressure-resistant PVC cylinder, wherein the upper and lower ends of the pressure-resistant PVC cylinder are connected to an upper cover and a base through a connecting piece, an inner cylinder is arranged inside the pressure-resistant PVC cylinder, a permeation layer is arranged inside the inner cylinder, one side of the upper end of the inner cylinder is connected to a liquid inlet pipe 2, the liquid inlet pipe 2 is connected to a water storage tank 1 through a gear pump 1, the other side of the upper end of the inner cylinder is connected to a liquid outlet pipe 2, one end of the liquid outlet pipe 2 is connected to the water storage tank 1, one side of the lower end of the inner cylinder is connected to a liquid inlet pipe 1, the liquid inlet pipe 1 is connected to the water storage tank 2 through a gear pump 2, the other side of the lower end of the inner cylinder is connected to a liquid outlet pipe 1, the liquid outlet pipe 1 is connected to the water storage tank 2, the water storage tank 1 is connected to the pressure-resistant PVC cylinder through a main pipe, the main pipe is connected to a connecting pipe 1 through a three-way pipe 1, the connecting pipe 1 is connected to the water storage tank 2, a valve 2 is installed on the connecting pipe 1, and the main pipe is also connected to an air compressor through a three-way pipe 2.

[0007] Preferably, the permeable layer includes an original core layer and a porous stone layer, the original core layer is arranged at the middle end of the inner cylinder, the porous stone layer is also arranged inside the inner cylinder at the upper and lower ends of the original core layer, an upper permeable layer is arranged at the upper end of the porous stone layer at the upper end, and a lower permeable layer is arranged at the lower end of the porous stone layer at the lower end, the second liquid inlet pipe is connected to the upper permeable layer, the second liquid outlet pipe is connected to the upper permeable layer, the first liquid inlet pipe is connected to the lower permeable layer, the first liquid outlet pipe is connected to the lower permeable layer, and the upper and lower ends of the inner cylinder are both provided with O-rings.

[0008] Preferably, the liquid outlet pipe 2 is connected to a transverse pipe through a tee pipe 3, the water storage tank 1, the water storage tank 2 and the transverse pipe are all connected to a conductivity meter, a valve 5 is installed on the liquid outlet pipe 2 near the base, a valve 9 is also installed on the liquid outlet pipe 2 near the water storage tank 1, and a valve 10 is installed on the transverse pipe.

[0009] Preferably, the water tank one and the water tank two are both provided with injection holes, the water tank one and the water tank two are both installed with pressure sensors, a pressure limiting valve one is installed on one side of the water tank one, and a pressure limiting valve two is installed on one side of the water tank two.

[0010] Preferably, a valve four is installed on the liquid inlet pipe two near the base, a valve six is ​​installed on the liquid outlet pipe one near the base, and a valve seven is installed on the liquid inlet pipe one near the base.

[0011] Preferably, the inner cylinder is connected with a vertical pipe, the vertical pipe passes through the base and is installed with a valve 1, a valve 8 is installed on the main pipe near the upper cover, and a valve 3 is installed on the main pipe near the water storage tank 1.

[0012] Preferably, a pressure limiting valve three is installed in the middle of the upper end of the upper cover.

[0013] Preferably, the connecting piece includes a threaded rod and a nut, the threaded rod is installed between the upper cover and the base, the nut is threadedly connected to the threaded rod, and the pressure-resistant PVC cylinder can be installed between the upper cover and the base by setting the threaded rod and the nut.

[0014] Preferably, hydraulic transmission oil is provided inside the pressure-resistant PVC cylinder.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention monitors the flow of each valve to facilitate obtaining the water release amount of the clay sample under different confining pressure conditions; because the clay is compressed and the volume is reduced, the hydraulic transmission oil level in the pressure-resistant PVC cylinder will gradually decrease, and the compression deformation process of the clay sample under different confining pressure conditions can be obtained by monitoring the hydraulic transmission oil level decrease speed; through the monitoring results, the time variation curve of the compression-water release of the clay sample is drawn, the compression and water release law of the weak permeable layer is studied, and the in-situ test results are compared to study the scale effect of the hydraulic parameters of the weak permeable layer, so as to obtain better test results, facilitate comparison of different permeability tests, and be beneficial to the use of permeability tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0018] In the figure: 1. Pressure-resistant PVC cylinder; 2. Upper cover; 3. Base; 4. Inner cylinder; 5. Water storage tank 1; 6. Water storage tank 2; 7. Main pipe; 8. Liquid inlet pipe 2; 9. Liquid outlet pipe 2; 10. Gear pump 1; 11. Valve 4; 12. Valve 5; 13. Valve 9; 14. Valve 10; 15. Conductivity meter; 16. Valve 3; 17. Pressure limiting valve 1; 18. Valve 6; 19. Gear pump 2; 20. Pressure sensor; 21. Valve 2; 22. Pressure limiting valve 2; 23. Liquid injection hole; 24. Air compressor; 25. Scale; 26. Valve 8; 27. Pressure limiting valve 3; 28. Threaded rod; 29. ​​Nut;

[0019] 41. Original core layer; 42. Porous stone layer; 43. O-ring; 44. Liquid outlet pipe 1; 45. Liquid inlet pipe 1; 46. Valve 7; 47. Valve 1. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example:

[0022] See also Figure 1 As shown, a soft-wall permeameter for measuring compression water release and chemical permeability coefficient of clay soil comprises:

[0023] A pressure-resistant PVC cylinder 1, the upper and lower ends of the pressure-resistant PVC cylinder 1 are connected to an upper cover 2 and a base 3 through a connecting piece, an inner cylinder 4 is arranged inside the pressure-resistant PVC cylinder 1, a permeation layer is arranged inside the inner cylinder 4, one side of the upper end of the inner cylinder 4 is connected to a liquid inlet pipe 8, the liquid inlet pipe 8 is connected to a water storage tank 5 through a gear pump 10, the other side of the upper end of the inner cylinder 4 is connected to a liquid outlet pipe 9, one end of the liquid outlet pipe 9 is connected to the water storage tank 5, and one side of the lower end of the inner cylinder 4 is connected to a liquid inlet pipe 8. Tube 1 45, the liquid inlet pipe 1 45 is connected to the water tank 2 6 through the gear pump 2 19, the other side of the lower end of the inner cylinder 4 is connected to the liquid outlet pipe 1 44, the liquid outlet pipe 1 44 is connected to the water tank 2 6, the water tank 1 5 is connected to the pressure-resistant PVC cylinder 1 through the main pipe 7, the main pipe 7 is connected to the connecting pipe 1 through the three-way pipe 1, the connecting pipe 1 is connected to the water tank 2 6, the connecting pipe 1 is installed with a valve 21, and the main pipe 7 is also connected to the air compressor 24 through the three-way pipe 2, which can play an air compression role.

[0024] refer to Figure 1 As shown, the permeable layer includes an original core layer 41 and a porous stone layer 42. The original core layer 41 is arranged at the middle end of the inner cylinder 4. A porous stone layer 42 is also arranged inside the inner cylinder 4 at the upper and lower ends of the original core layer 41. An upper permeable layer is arranged at the upper end of the upper porous stone layer 42, and a lower permeable layer is arranged at the lower end of the lower porous stone layer 42. The inlet pipe 8 is connected to the upper permeable layer, the outlet pipe 9 is connected to the upper permeable layer, the inlet pipe 45 is connected to the lower permeable layer, and the outlet pipe 44 is connected to the lower permeable layer. O-rings 43 are arranged at the upper and lower ends of the inner cylinder 4.

[0025] refer to Figure 1 As shown, the liquid outlet pipe 29 is connected to the cross pipe through the three-way pipe, the water storage tank 15, the water storage tank 26 and the cross pipe are all connected to the conductivity meter 15, the liquid outlet pipe 29 is installed with a valve 5 12 near the base 3, the liquid outlet pipe 29 is also installed with a valve 9 13 near the water storage tank 15, and the cross pipe is installed with a valve 14.

[0026] refer to Figure 1 As shown, water tank 1 5 and water tank 2 6 are both provided with a liquid injection hole 23, and water tank 1 5 and water tank 2 6 are both installed with a pressure sensor 20, and a pressure limiting valve 17 is installed on one side of water tank 1 5, and a pressure limiting valve 2 22 is installed on one side of water tank 2 6.

[0027] refer to Figure 1 As shown, a valve four 11 is installed on the liquid inlet pipe two 8 near the base 3, a valve six 18 is installed on the liquid outlet pipe one 44 near the base 3, and a valve seven 46 is installed on the liquid inlet pipe one 45 near the base 3.

[0028] refer to Figure 1As shown, the inner cylinder 4 is connected to a vertical pipe, which passes through the base 3 and is installed with a valve 47, a valve eight 26 is installed on the main pipe 7 near the upper cover 2, and a valve three 16 is installed on the main pipe 7 near the water storage tank 5.

[0029] refer to Figure 1 As shown, a pressure limiting valve 3 27 is installed in the middle of the upper end of the upper cover 2.

[0030] refer to Figure 1 As shown, the connecting piece includes a threaded rod 28 and a nut 29. The threaded rod 28 is installed between the upper cover 2 and the base 3. The nut 29 is threadedly connected to the threaded rod 28. The pressure-resistant PVC cylinder 1 can be installed between the upper cover 2 and the base 3 by setting the threaded rod 28 and the nut 29.

[0031] refer to Figure 1 As shown, hydraulic transmission oil is arranged inside the pressure-resistant PVC cylinder 1 .

[0032] ①Compression water release test

[0033] Add a certain amount of fresh water into two water storage tanks one and two;

[0034] Open valves 1, 4, 5, 6, 7, and 9, and use a gear pump to circulate the fresh water in the two water storage tanks 1 and 2 to infiltrate the porous stone, so that the porous stone and the inlet and outlet pipes are saturated, and then close valves 4, 6, 7, and 9;

[0035] Open valve eight to pressurize the pressure-resistant PVC cylinder, and adjust pressure-limiting valve three to subject the original soil sample to different degrees of confining pressure;

[0036] Open valve ten, monitor the flow through valve ten, and obtain the water release amount of the clay sample under different confining pressure conditions; because the clay is compressed and its volume decreases, the hydraulic transmission oil level in the pressure-resistant PVC cylinder will gradually decrease, and the hydraulic transmission oil level decrease rate is monitored to obtain the compression deformation process of the clay sample under different confining pressure conditions;

[0037] Based on the monitoring results, the time variation curve of compression and water release of clay samples was drawn to study the law of compression and water release of weak permeable layers.

[0038] It should be noted that the valves not mentioned in the article were in the closed state during the test, and the same is true for the following text.

[0039] ②Physical penetration test

[0040] Add a certain amount of fresh water into two water storage tanks one and two;

[0041] Open valves 4, 5, 6, 7, and 9, and use the gear pump to circulate the liquid in the two water storage tanks to soak the porous stone, so that the porous stone and the inlet and outlet pipes are saturated, and then close valve 4;

[0042] Open valves 2 and 8 to increase the pressure in water storage tank 2 and the pressure-resistant PVC cylinder. By adjusting pressure-limiting valves 2 and 3, the lower end of the clay sample is subjected to different degrees of head pressure and the clay sample is ensured to be tightly fitted with the flexible latex sleeve.

[0043] Open valve ten and monitor the flow through valve ten to obtain the overflow of clay samples under different head pressures. Calculate the hydraulic parameters of clay media, study the physical seepage mechanism of aquitard at laboratory scale, compare with the in-situ test results, and study the scale effect of hydraulic parameters of aquitard.

[0044] ③Chemical permeation test

[0045] Add fresh water to the first water storage tank, and add a solution of a certain concentration to the second water storage tank;

[0046] Open valves 4, 5, 6, 7, and 9, and use a gear pump to circulate the fresh water in water storage tank 1 and the solution in water storage tank 2 to infiltrate the porous stone, so that the porous stone and the inlet and outlet pipes are saturated. At this time, both ends of the clay sample are subjected to a certain degree of concentration gradient;

[0047] The pressure sensor is used to monitor the pressure change of the water storage tanks 1 and 2, and the conductivity meter is used to invert the concentration change of the solution in the water storage tanks 1 and 2;

[0048] Based on the monitoring results, the pressure and solution concentration curves at both ends of the clay sample were drawn to evaluate the membrane performance of the aquitard;

[0049] Repeatedly change the solution concentration in the second water storage tank to study the dynamic change of the chemical permeability coefficient of the clay sample with the solution concentration;

[0050] The pressure in the pressure-resistant PVC cylinder was repeatedly changed to study the changing characteristics of the chemical permeability coefficient of clay samples under different confining pressure conditions (or under conditions of changing porosity of clay soil).

[0051] ④Ultrafiltration test

[0052] In addition to the chemical permeability test, the ultrafiltration test can also evaluate the chemical permeability coefficient (i.e., membrane performance capacity) of clay samples, and is more in line with the main research purpose of this study to clarify the "salt storage" potential of the weak permeable layer in the North China Plain. The steps are as follows:

[0053] Add fresh water to the first water storage tank, and add a solution of a certain concentration to the second water storage tank;

[0054] Open valves 4, 5, 6, 7, and 9, and use a gear pump to circulate the fresh water in water storage tank 1 and the solution in water storage tank 2 to infiltrate the porous stone, so that the porous stone and the inlet and outlet pipes are saturated, and then close valve 4. At this time, both ends of the clay sample are subjected to a certain degree of concentration gradient;

[0055] Open valves 2 and 8 to increase the pressure in water storage tank 2 and the pressure-resistant PVC cylinder. By adjusting pressure-limiting valves 2 and 3, the lower end of the clay sample is subjected to different degrees of head pressure and the clay sample is tightly fitted with the flexible latex sleeve. At this time, the high-concentration salt water overflows to the fresh water end under the action of the head pressure.

[0056] Open valve ten, monitor the flow through valve ten and the conductivity of the solution, and obtain the overflow of the clay sample under different head pressures and the change in solution concentration after passing through the clay sample.

[0057] Based on the monitoring results, the solution concentration change curves of the salt water end and filtrate of the clay sample were drawn, the membrane performance of the weak permeable layer was evaluated from the perspective of the salt resistance of the clay sample, the "salt storage" potential of the weak permeable layer was analyzed, and compared with the results of the chemical permeation test;

[0058] The solution concentration in the second water storage tank was repeatedly changed to study the dynamic variation of the chemical permeability coefficient of the clay sample with the solution concentration.

[0059] The present invention monitors the flow of each valve to facilitate obtaining the water release amount of the clay sample under different confining pressure conditions; because the clay is compressed and the volume is reduced, the hydraulic transmission oil level in the pressure-resistant PVC cylinder will gradually decrease, and the compression deformation process of the clay sample under different confining pressure conditions can be obtained by monitoring the hydraulic transmission oil level decrease speed; through the monitoring results, the time variation curve of the compression-water release of the clay sample is drawn, the compression and water release law of the weak permeable layer is studied, and the in-situ test results are compared to study the scale effect of the hydraulic parameters of the weak permeable layer, so as to obtain better test results, facilitate comparison of different permeability tests, and be beneficial to the use of permeability tests.

[0060] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A soft-wall permeameter for measuring compression water release and chemical permeability coefficient of clay soil, characterized in that: include: A pressure-resistant PVC cylinder (1), wherein the upper and lower ends of the pressure-resistant PVC cylinder (1) are connected to an upper cover (2) and a base (3) through a connecting piece, an inner cylinder (4) is arranged inside the pressure-resistant PVC cylinder (1), and a permeable layer is arranged inside the inner cylinder (4), one side of the upper end of the inner cylinder (4) is connected to a second liquid inlet pipe (8), and the second liquid inlet pipe (8) is connected to a water storage tank (5) through a gear pump (10), the other side of the upper end of the inner cylinder (4) is connected to a second liquid outlet pipe (9), and one end of the second liquid outlet pipe (9) is connected to the first water storage tank (5), and one side of the lower end of the inner cylinder (4) is connected to a first liquid inlet pipe (45), and the first liquid inlet pipe (45) is connected to a water storage tank (5) through a gear pump (19). The second water storage tank (6) is connected to the other side of the lower end of the inner cylinder (4), and the first liquid outlet pipe (44) is connected to the second water storage tank (6). The first water storage tank (5) is connected to the pressure-resistant PVC cylinder (1) through a main pipe (7). The main pipe (7) is connected to a connecting pipe (1) through a tee pipe (1), and the connecting pipe (1) is connected to the second water storage tank (6). A valve (21) is installed on the connecting pipe (1). The main pipe (7) is also connected to an air compressor (24) through a tee pipe (2). The air compressor (24) is used to increase the pressure of the second water storage tank (6) and the pressure-resistant PVC cylinder (1), and to add a solution of a certain concentration to the second water storage tank (6) when performing a chemical permeation test and an ultrafiltration test. The second liquid outlet pipe (9) is connected to a transverse pipe via a three-way pipe, the first water storage tank (5), the second water storage tank (6) and the transverse pipe are all connected to a conductivity meter (15), a valve five (12) is installed on the second liquid outlet pipe (9) near the base (3), a valve nine (13) is also installed on the second liquid outlet pipe (9) near the first water storage tank (5), and a valve ten (14) is installed on the transverse pipe; A valve 4 (11) is installed on the second liquid inlet pipe (8) near the base (3), a valve 6 (18) is installed on the first liquid outlet pipe (44) near the base (3), and a valve 7 (46) is installed on the first liquid inlet pipe (45) near the base (3); The inner cylinder (4) is connected to a vertical pipe, the vertical pipe passes through the base (3) and is installed with a valve 1 (47), a valve 8 (26) is installed on the main pipe (7) near the upper cover (2), and a valve 3 (16) is installed on the main pipe (7) near the water storage tank 1 (5).

2. The soft-wall permeameter for measuring water release and chemical permeability coefficient of clay soil under compression according to claim 1, characterized in that: The permeable layer comprises an original core layer (41) and a porous stone layer (42); the original core layer (41) is arranged at the middle end of the inner cylinder (4); the porous stone layer (42) is also arranged inside the inner cylinder (4) at the upper and lower ends of the original core layer (41); an upper permeable layer is arranged at the upper end of the porous stone layer (42) at the upper end; a lower permeable layer is arranged at the lower end of the porous stone layer (42) at the lower end; the second liquid inlet pipe (8) is connected to the upper permeable layer; the second liquid outlet pipe (9) is connected to the upper permeable layer; the first liquid inlet pipe (45) is connected to the lower permeable layer; the first liquid outlet pipe (44) is connected to the lower permeable layer; and the upper and lower ends of the inner cylinder (4) are both provided with O-rings (43).

3. The soft-wall permeameter for measuring the water release and chemical permeability coefficient of clay soil under compression according to claim 2, characterized in that: The water storage tank 1 (5) and the water storage tank 2 (6) are both provided with a liquid injection hole (23), the water storage tank 1 (5) and the water storage tank 2 (6) are both installed with a pressure sensor (20), a pressure limiting valve 1 (17) is installed on one side of the water storage tank 1 (5), and a pressure limiting valve 2 (22) is installed on one side of the water storage tank 2 (6).

4. The soft-wall permeameter for measuring water release and chemical permeability coefficient of clay soil under compression according to claim 3, characterized in that: A pressure limiting valve 3 (27) is installed in the middle of the upper end of the upper cover (2).

5. The soft-wall permeameter for measuring water release and chemical permeability coefficient of clay soil under compression according to claim 4, characterized in that: The connecting piece comprises a threaded rod (28) and a nut (29); the threaded rod (28) is installed between the upper cover (2) and the base (3); and the nut (29) is threadedly connected to the threaded rod (28).

6. The soft-wall permeameter for measuring water release and chemical permeability coefficient of clay soil under compression according to claim 1, characterized in that: Hydraulic transmission oil is arranged inside the pressure-resistant PVC cylinder (1).

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