A permeability coefficient testing device suitable for unloading seepage conditions

Abstract

The present invention provides a permeability coefficient testing device suitable for use under unloading seepage conditions, comprising a rubber sleeve for covering a sample, a confining pressure chamber, a water supply tank, an upper pore pressure volume controller, a confining pressure volume controller, and a lower pore pressure volume controller. The base of the confining pressure chamber is provided with a water supply port connected to the water supply tank, an upper hole connected to the upper pore pressure volume controller, a lower hole connected to the lower pore pressure volume controller, and a confining pressure hole connected to the confining pressure volume controller. The confining pressure chamber is provided with a sample support seat and a sample cover. The confining pressure chamber cover is provided with a pressing block for pressing the sample cover, a pressing block driving structure for driving the pressing block to rise and fall, and a pressing force detector for detecting the pressure exerted by the pressing block on the sample cover. The present invention has the advantage of accurate confining pressure data and solves the problem of poor test accuracy caused by the existing constant pressure measurement method.

Description

Technical Field

[0001] The present application relates to the technical field of indoor geotechnical testing, and in particular to a permeability coefficient testing device suitable for use under unloading seepage conditions. Background Art

[0002] As shallow urban underground space development approaches saturation, underground engineering projects are expanding into deeper areas, resulting in a surge in deep foundation pits exceeding 30 meters in depth. Water-rich soft soil areas, such as those in Shanghai, feature alternating clay and sand layers, forming a multi-aquifer system with an average confined water level of 7 to 9 meters below ground level. During deep foundation pit excavation, the stress level of the soil decreases under unloading, far below the initial stress state. This change in stress causes the soil to expand and rebound, increasing the porosity and resulting in a heave at the pit bottom. Simultaneously, a high confined water level remains within the confined layer during excavation, increasing the water gradient from the confined layer to the excavation surface and triggering upward seepage from the confined layer to the overlying aquitard. As the excavation surface approaches the aquitard-confined aquifer interface, the effective stress in the soil further decreases. The increased porosity leads to an increase in the soil permeability coefficient, resulting in significant upward seepage, potentially leading to risks such as sudden outbursts in the foundation pit. On the other hand, geological surveys have shown that coastal soft soil areas contain extensive silt layers. The permeability of silt layers lies between that of clay and sand, and their permeability develops more complexly under unloading conditions. Therefore, accurately measuring the permeability coefficient of soil during unloading is crucial for assessing the risk of sudden inrush from foundation pits.

[0003] Current research on the permeability characteristics of soils under different stress states primarily considers changes in the permeability coefficient during loading. The compression modulus and rebound modulus of soil vary significantly during loading and unloading, resulting in distinct nonlinear deformation characteristics. Furthermore, in practice, the pressures on the side and top surfaces of soil are different and well-known. Existing permeability tests employ confining pressure through water, with the pressures on the side and top surfaces being the same, resulting in poor sample accuracy. During unloading permeability tests, the volume of air within the confining pressure chamber significantly impacts the accuracy of the sample structure. Prolonged testing of a single sample can lead to the water in the volume controller running out, necessitating the test to be stopped and the water in the upper hole volume controller (for receiving water) channeled through the confining pressure chamber to the lower hole volume controller (for delivering water). This approach not only reduces test efficiency but also causes reverse osmosis, resulting in poor sample accuracy. Summary of the Invention

[0004] The first purpose of the present invention is to provide a permeability coefficient testing device suitable for unloading seepage conditions in which pressure measurement and top pressure are applied independently, thereby solving the problem of poor test accuracy caused by the same confining pressure as the existing constant pressure measurement.

[0005] The second purpose of the present invention is to further provide a permeability coefficient testing device suitable for unloading seepage conditions with low air content in confined pressure water, thereby solving the problem of poor test accuracy caused by high air content in confined pressure water.

[0006] The third purpose of the present invention is to provide a permeability coefficient testing device suitable for unloading seepage conditions that can perform uninterrupted tests, thereby solving the problem of poor test accuracy caused by stopping reverse osmosis to replenish water when the test water volume is insufficient.

[0007] In order to achieve the above-mentioned invention objectives, the present invention adopts the following technology: a permeability coefficient testing device suitable for unloading seepage conditions, comprising a rubber sleeve for covering a sample, a confined pressure chamber, a water supply tank, an upper pore pressure volume controller, a confined pressure volume controller and a lower pore pressure volume controller, the confined pressure chamber comprising a confined pressure chamber base and a confined pressure chamber cover provided with an exhaust valve and detachably sealed and connected to the chamber base, the confined pressure chamber base and the confined pressure chamber cover enclose a sealed confined pressure chamber, the confined pressure chamber base is provided with a water supply port connected to the water supply tank, an upper hole connected to the upper pore pressure volume controller, a lower hole connected to the lower pore pressure volume controller and a confined pressure hole connected to the confined pressure volume controller, a sample support seat and a sample cover are provided in the confined pressure chamber, and the confined pressure chamber is characterized in that a pressing block for pressing the sample cover, a pressing block driving structure for driving the pressing block to rise and fall, and a pressing force detector for detecting the pressure generated by the pressing block on the sample cover. When in use, the rubber sleeve is put on the sample, the sample is placed on the sample support seat and covered with the sample cover, the upper end of the rubber sleeve is put on the sample cover, and the lower end is put on the sample support seat, the water in the water supply tank is input into the confining pressure chamber through the water supply port to fill the confining pressure chamber and then the exhaust valve is closed, the confining pressure volume controller pressurizes the confining pressure chamber to the set first side confining pressure value to apply pressure to the surrounding surface of the sample and presses the sample cover to the first top surface confining pressure value through the pressing block to apply pressure to the top surface of the test, and inputs water with a set first water inlet pressure into the sample through the lower hole through the lower hole pressure volume controller, and the water penetrates through the sample and is output from the upper hole to the upper hole pressure volume controller, and the upper hole pressure volume controller maintains the set first water outlet pressure. Pressure, calculate the first permeability coefficient according to the existing permeability calculation formula; the confining pressure volume controller pressurizes the confining pressure chamber to the set second side confining pressure value to apply pressure to the circumference of the sample and presses the sample cover to the second top surface confining pressure value through the pressing block to apply pressure to the top surface of the test, and inputs water of the set second water inlet pressure into the sample through the lower hole through the lower hole pressure volume controller. After the water penetrates through the sample, it is output from the upper hole to the upper hole pressure volume controller, and the upper hole pressure volume controller is maintained at the second water outlet pressure received. The second permeability coefficient is calculated according to the existing permeability calculation formula. The same method is used to reduce the confining pressure value, input pressure and output pressure in turn, so as to obtain the permeability coefficient under various pressures when the sample is depressurized. The top surface of the sample is independently pressurized by water instead of being controlled by the confining pressure volume controller at the same value on the same circumference, so that the pressure on the side and top surfaces of the sample is close to the actual pressure, thereby making the measured decompression confining pressure data more accurate.

[0008] Preferably, the water supply tank is provided with a water pump for outputting the water in the water supply tank, a vacuum pump for evacuating the water supply tank and a vibrator for causing the water in the water supply tank to shake, and the outlet end of the water pump is connected to the water supply port.

[0009] Preferably, the lower pore pressure volume controller includes a three-way valve of the lower pore pressure volume controller, a threaded rod of the lower pore pressure volume controller, a guide rod of the lower pore pressure volume controller, a motor of the lower pore pressure volume controller for driving the threaded rod of the lower pore pressure volume controller to rotate, a drive block of the lower pore pressure volume controller threadedly connected to the threaded rod of the lower pore pressure volume controller, a locking switching structure of the lower pore pressure volume controller, a first cylinder of the lower pore pressure volume controller, a first piston of the lower pore pressure volume controller connected in a sliding seal in the first cylinder of the lower pore pressure volume controller, one end of which is connected to the lower pore pressure volume controller. The first piston is connected together and the other end is passed through the first piston rod of the lower pore pressure volume controller in the lower pore pressure volume controller driving block, the first pressure sensor of the lower pore pressure volume controller, the second cylinder of the lower pore pressure volume controller, the second piston of the lower pore pressure volume controller connected in the second cylinder of the lower pore pressure volume controller with a sliding seal, the second piston of the lower pore pressure volume controller at one end is connected together with the second piston of the lower pore pressure volume controller and the other end is passed through the second piston rod of the lower pore pressure volume controller and the second pressure sensor of the lower pore pressure volume controller, the lower pore pressure volume controller The first piston isolates the first liquid storage chamber of the lower pore pressure volume controller part in the first cylinder of the lower pore pressure volume controller part, the first pressure sensor of the lower pore pressure volume controller part is used to detect the pressure in the first liquid storage chamber of the lower pore pressure volume controller part, the first liquid storage chamber of the lower pore pressure volume controller part is connected to a branch hole of the three-way valve of the lower pore pressure volume controller part, the second piston of the lower pore pressure volume controller part isolates the second liquid storage chamber of the lower pore pressure volume controller part in the second cylinder of the lower pore pressure volume controller part, the second pressure sensor of the lower pore pressure volume controller part is used to detect the pressure in the second liquid storage chamber of the lower pore pressure volume controller part The pressure of the lower pore pressure volume controller part, the second liquid storage chamber of the lower pore pressure volume controller part is connected with another branch hole of the three-way valve of the lower pore pressure volume controller part, and the total port of the three-way valve of the lower pore pressure volume controller part is connected with the lower hole, and the locking switching structure of the lower pore pressure volume controller part is used to make the lower pore pressure volume controller part drive block only be fixed with one of the first piston rod of the lower pore pressure volume controller part and the second piston rod of the lower pore pressure volume controller part at the same time, and the guide rod of the lower pore pressure volume controller part is penetrated into the drive block of the lower pore pressure volume controller part to prevent the drive block of the lower pore pressure volume controller part from rotating;The upper pore pressure volume controller includes an upper pore pressure volume controller three-way valve, an upper pore pressure volume controller threaded rod, an upper pore pressure volume controller guide rod, an upper pore pressure volume controller motor that drives the upper pore pressure volume controller threaded rod to rotate, an upper pore pressure volume controller drive block threadedly connected to the upper pore pressure volume controller threaded rod, an upper pore pressure volume controller first cylinder, an upper pore pressure volume controller first piston slidingly sealed and connected in the upper pore pressure volume controller first cylinder, an upper pore pressure volume controller first piston rod with one end connected to the upper pore pressure volume controller first piston and the other end fixed to the upper pore pressure volume controller drive block, an upper pore pressure volume controller The first pressure sensor of the device part, the second cylinder of the upper pore pressure volume controller part, the second piston of the upper pore pressure volume controller part which is connected in a sliding seal in the second cylinder of the upper pore pressure volume controller part, the second piston rod of the upper pore pressure volume controller part which is connected to the second piston of the upper pore pressure volume controller part at one end and fixed to the driving block of the upper pore pressure volume controller part at the other end, and the second pressure sensor of the upper pore pressure volume controller part, the first piston of the upper pore pressure volume controller part isolates the first liquid storage chamber of the upper pore pressure volume controller part in the first cylinder of the upper pore pressure volume controller part, the first pressure sensor of the upper pore pressure volume controller part is used to detect the pressure in the first liquid storage chamber of the upper pore pressure volume controller part, the upper pore pressure volume controller part The first liquid storage chamber of the upper pore pressure volume controller is connected to a branch hole of the three-way valve of the upper pore pressure volume controller, the second piston of the upper pore pressure volume controller isolates the second liquid storage chamber of the upper pore pressure volume controller in the second cylinder of the upper pore pressure volume controller, the second pressure sensor of the upper pore pressure volume controller is used to detect the pressure in the second liquid storage chamber of the upper pore pressure volume controller, the second liquid storage chamber of the upper pore pressure volume controller is connected to another branch hole of the three-way valve of the upper pore pressure volume controller, the total port of the three-way valve of the upper pore pressure volume controller is connected to the upper hole, and the guide rod of the upper pore pressure volume controller is passed through the drive block of the upper pore pressure volume controller to prevent the drive block of the upper pore pressure volume controller from rotating. ; The first liquid storage chamber of the lower pore pressure volume controller part is connected with the first liquid storage chamber of the upper pore pressure volume controller part through the first valve, and the second liquid storage chamber of the lower pore pressure volume controller part is connected with the second liquid storage chamber of the upper pore pressure volume controller part through the first valve; when in use, water is delivered through the first liquid storage chamber of the lower pore pressure volume controller part and water is received through the first liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment. After the water in the first liquid storage chamber of the lower pore pressure volume controller part is delivered or the first liquid storage chamber of the upper pore pressure volume controller part is filled, the first valve is opened and water is delivered through the second liquid storage chamber of the lower pore pressure volume controller part and water is received through the second liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment;The process of resetting the driving block of the lower pore pressure volume controller to drive the second piston rod of the lower pore pressure volume controller resets the first liquid storage chamber of the lower pore pressure volume controller, and the process of resetting the driving block of the upper pore pressure volume controller resets the first liquid storage chamber of the upper pore pressure volume controller and the second liquid storage chamber of the upper pore pressure volume controller, so that the water in the first liquid storage chamber of the lower pore pressure volume controller flows back to the first liquid storage chamber of the upper pore pressure volume controller, and the first valve is closed; after the water in the second liquid storage chamber of the lower pore pressure volume controller is delivered or the second liquid storage chamber of the upper pore pressure volume controller is filled, the second valve is opened and the lower pore pressure volume controller is opened at the same time. The first liquid storage chamber of the upper pore pressure volume controller sends water and receives water through the first liquid storage chamber of the upper pore pressure volume controller to perform a permeability coefficient test experiment; the process of resetting the lower pore pressure volume controller drive block to drive the first piston rod of the lower pore pressure volume controller resets the second liquid storage chamber of the lower pore pressure volume controller, and the process of resetting the upper pore pressure volume controller drive block resets the second liquid storage chamber of the upper pore pressure volume controller and the first liquid storage chamber of the upper pore pressure volume controller, so that the water in the second liquid storage chamber of the lower pore pressure volume controller flows back to the second liquid storage chamber of the upper pore pressure volume controller, and the second valve is closed; repeat the above process to conduct an uninterrupted infiltration system test sample. It can avoid insufficient water and interruption of the test by returning the water in the first liquid storage chamber of the upper pore pressure volume controller to the lower pore pressure volume controller through the confining pressure chamber. It is equivalent to reverse osmosis of the sample, which will affect the accuracy of the test data and the test efficiency.

[0010] Preferably, the first piston of the upper pore pressure volume controller is located at the upper end of the first cylinder of the upper pore pressure volume controller, the second piston of the upper pore pressure volume controller is located at the upper end of the second cylinder of the upper pore pressure volume controller, the first piston of the lower pore pressure volume controller is located at the upper end of the first cylinder of the lower pore pressure volume controller, and the second piston of the lower pore pressure volume controller is located at the upper end of the second cylinder of the lower pore pressure volume controller. The cylinders are arranged vertically so that the volume of the liquid storage chamber can be maintained at the current state when not in use.

[0011] Preferably, the first cylinder of the upper pore pressure volume controller part and the second cylinder of the upper pore pressure volume controller part are connected side by side, and the first cylinder of the lower pore pressure volume controller part and the second cylinder of the lower pore pressure volume controller part are connected side by side. It is convenient to drive and has a compact structure.

[0012] Preferably, when the volume of the first liquid storage chamber of the upper pore pressure volume controller is at its maximum, the height of the first liquid storage chamber of the upper pore pressure volume controller is less than 5 cm; when the volume of the second liquid storage chamber of the upper pore pressure volume controller is at its maximum, the height of the liquid storage chamber of the upper pore pressure volume controller is less than 5 cm; when the volume of the first liquid storage chamber of the lower pore pressure volume controller is at its maximum, the height of the first liquid storage chamber of the lower pore pressure volume controller is less than 5 cm; when the volume of the second liquid storage chamber of the lower pore pressure volume controller is at its maximum, the length of the second liquid storage chamber of the lower pore pressure volume controller is less than 5 cm. This can shorten the time it takes for the liquid storage chambers to reset.

[0013] Preferably, the locking and switching structure of the lower pore pressure volume controller includes a first fixed lock of the lower pore pressure volume controller and a second fixed lock of the lower pore pressure volume controller. The first fixed lock of the lower pore pressure volume controller is used to fix the lower pore pressure volume controller drive block and the first piston rod of the lower pore pressure volume controller together. The second fixed lock of the lower pore pressure volume controller is used to fix the lower pore pressure volume controller drive block and the second piston rod of the lower pore pressure volume controller together. Only one of the first fixed lock of the lower pore pressure volume controller and the second fixed lock of the lower pore pressure volume controller remains in a locked state at the same time. A specific technical solution for the locking and switching structure of the lower pore pressure volume controller is provided.

[0014] Preferably, the first fixed lock of the lower pore pressure volume controller part includes a first locking pin of the lower pore pressure volume controller part hinged on the upper end of the first piston rod of the lower pore pressure volume controller part, a first locking hole of the lower pore pressure volume controller part arranged on the side of the driving block of the lower pore pressure volume controller part, and a first driving cylinder of the lower pore pressure volume controller part for driving the first locking pin of the lower pore pressure volume controller part to insert and pull out the locking hole of the lower pore pressure volume controller part. When the first locking pin of the lower pore pressure volume controller part is inserted into the first locking hole of the lower pore pressure volume controller part, the piston rod of the lower pore pressure volume controller part is fixed to the lower pore pressure volume controller part together with the driving block of the lower pore pressure volume controller part. The second fixing lock of the lower pore pressure volume controller includes a second locking pin of the lower pore pressure volume controller hinged on the upper end of the second piston rod of the lower pore pressure volume controller, a second locking hole of the lower pore pressure volume controller provided on the side of the driving block of the lower pore pressure volume controller, and a second driving cylinder of the lower pore pressure volume controller for driving the second locking pin of the lower pore pressure volume controller into and out of the locking hole of the lower pore pressure volume controller. When the second locking pin of the lower pore pressure volume controller is inserted into the second locking hole of the lower pore pressure volume controller, the piston rod of the lower pore pressure volume controller is fixed together with the driving block of the lower pore pressure volume controller. A specific technical solution for the locking structure is provided.

[0015] As a preferred method, a pressure sensor in the confining pressure chamber is also included to input the water inlet pressure at the bottom of the sample, so as to re-measure the water inlet pressure and improve the accuracy of the test.

[0016] Preferably, a flow meter is used at the upper port or the lower port to accurately measure the amount of water permeated during the test.

[0017] The present invention has the following beneficial effects: constant pressure and pressure measurement can simulate actual sample testing; the amount of air contained in the confined pressure water is small; when the water volume is insufficient, the test can be carried out without stopping and the water can be recycled; and the accuracy during the test is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the present invention;

[0019] Figure 2 is a schematic diagram of an upper pore pressure volume controller and a lower pore pressure volume controller;

[0020] Figure 3 yes Figure 2 A local enlarged schematic diagram of point A;

[0021] Figure 4 yes Figure 2 A local enlarged schematic diagram of point B;

[0022] Figure 5 It is a cross-sectional schematic diagram of the confining pressure chamber.

[0023] In the figure: sample 1, rubber sleeve 2, confining pressure chamber 3, water supply tank 4, upper pore pressure volume controller 5, confining pressure volume controller 6, lower pore pressure volume controller 7, confining pressure chamber pressure sensor 8, confining pressure chamber base 9, exhaust valve 10, confining pressure chamber cover 11, water supply port 12, upper hole 13, lower hole 14, confining pressure hole 15, sample support seat 16, sample cover 17, pressing block 18, water pump 19, vacuum pump 20, vibrator 21, three-way valve of lower pore pressure volume controller 22, threaded rod of lower pore pressure volume controller 24, motor of lower pore pressure volume controller 25, lower pore pressure volume controller The device driving block 26, the first cylinder 27 of the lower pore pressure volume controller, the first piston 28 of the lower pore pressure volume controller, the first piston rod 29 of the lower pore pressure volume controller, the first pressure sensor 30 of the lower pore pressure volume controller, the second cylinder 31 of the lower pore pressure volume controller, the second piston 32 of the lower pore pressure volume controller, the second piston rod 33 of the lower pore pressure volume controller, the second pressure sensor 34 of the lower pore pressure volume controller, the first liquid storage chamber 35 of the lower pore pressure volume controller, the frame 36 of the lower pore pressure volume controller, the second liquid storage chamber 37 of the lower pore pressure volume controller, the upper The three-way valve 38 of the pore pressure volume controller part, the threaded rod 39 of the upper pore pressure volume controller part, the motor 40 of the upper pore pressure volume controller part, the drive block 41 of the upper pore pressure volume controller part, the first cylinder 42 of the upper pore pressure volume controller part, the first piston 43 of the upper pore pressure volume controller part, the first piston rod 44 of the upper pore pressure volume controller part, the first pressure sensor 45 of the upper pore pressure volume controller part, the second cylinder 46 of the upper pore pressure volume controller part, the second piston 47 of the upper pore pressure volume controller part, the second piston rod 48 of the upper pore pressure volume controller part, and the second pressure sensor 49 of the upper pore pressure volume controller part , the first liquid storage chamber 50 of the upper pore pressure volume controller part, the second liquid storage chamber 51 of the upper pore pressure volume controller part, the frame 52 of the upper pore pressure volume controller part, the first valve 53, the second valve 54, the first fixed lock 55 of the lower pore pressure volume controller part, the second fixed lock 56 of the lower pore pressure volume controller part, the first locking pin 57 of the lower pore pressure volume controller part, the first locking hole 58 of the lower pore pressure volume controller part, the first driving cylinder 59 of the lower pore pressure volume controller part, the second locking pin 60 of the lower pore pressure volume controller part, the second locking hole 61 of the lower pore pressure volume controller part, and the second driving cylinder 62 of the lower pore pressure volume controller part. DETAILED DESCRIPTION

[0024] The present invention will be described below with reference to the accompanying drawings and specific embodiments. The anchor rod is tilted in a state where one end connected to the inner retaining wall is higher than the other end, and the lower end of the anchor rod is lower than the bottom of the inner pit.

[0025] See also Figures 1 to 5A permeability coefficient testing device suitable for unloading seepage conditions includes a rubber sleeve 2 for covering a sample 1, a confining pressure chamber 3, a water supply tank 4, an upper pore pressure volume controller 5, a confining pressure volume controller 6, a lower pore pressure volume controller 7, and a confining pressure chamber pressure sensor 8 inputted into the bottom of the sample to check the water inlet pressure.

[0026] The confined pressure chamber includes a base 9 and a cover 11 removably and hermetically connected to the base, which is equipped with an exhaust valve 10. The base and cover enclose a sealed confined pressure chamber. The base is equipped with a water supply port 12 connected to the water supply tank, an upper hole 13 connected to the upper pore pressure volume controller, a lower hole 14 connected to the lower pore pressure volume controller, and a confined pressure hole 15 connected to the confined pressure volume controller. A sample support 16 and a sample cover 17 are provided within the confined pressure chamber. The cover is equipped with a pressing block 18 for pressing the sample cover, a pressing block drive structure for driving the pressing block up and down, and a pressing force detector for detecting the pressure exerted by the pressing block on the sample cover.

[0027] The water supply tank is equipped with a water pump 19 to output the water in the water supply tank, a vacuum pump 20 to evacuate the water supply tank, and a vibrator 21 to cause the water in the water supply tank to vibrate. The outlet of the water pump is connected to the water supply port. During operation, the vacuum pump and vibrator first work to remove air from the water in the water supply tank, and then the water is input into the confining pressure chamber.

[0028] When in use, the rubber sleeve is put on the sample, the sample is placed on the sample support seat and covered with the sample cover, the upper end of the rubber sleeve is put on the sample cover, and the lower end is put on the sample support seat, the water in the water supply tank is input into the confining pressure chamber through the water supply port to fill the confining pressure chamber and then the exhaust valve is closed, the confining pressure volume controller pressurizes the confining pressure chamber to the set first side confining pressure value to apply pressure to the surrounding surface of the sample and presses the sample cover to the first top surface confining pressure value through the pressing block to apply pressure to the top surface of the test, and inputs water with a set first water inlet pressure into the sample through the lower hole through the lower hole pressure volume controller, and the water penetrates through the sample and is output from the upper hole to the upper hole pressure volume controller, and the upper hole pressure volume controller maintains the set first water outlet pressure. Pressure, calculate the first permeability coefficient according to the existing permeability calculation formula; the confining pressure volume controller pressurizes the confining pressure chamber to the set second side confining pressure value to apply pressure to the circumference of the sample and presses the sample cover to the second top surface confining pressure value through the pressing block to apply pressure to the top surface of the test, and inputs water of the set second water inlet pressure into the sample through the lower hole through the lower hole pressure volume controller. After the water penetrates through the sample, it is output from the upper hole to the upper hole pressure volume controller, and the upper hole pressure volume controller is maintained at the second water outlet pressure received. The second permeability coefficient is calculated according to the existing permeability calculation formula. The same method is used to reduce the confining pressure value, input pressure and output pressure in turn, so as to obtain the permeability coefficient under various pressures when the sample is depressurized. The top surface of the sample is independently pressurized by water instead of being controlled by the confining pressure volume controller at the same value on the same circumference, so that the pressure on the side and top surfaces of the sample is close to the actual pressure, thereby making the measured decompression confining pressure data more accurate.

[0029] The confining pressure volume controller is an existing structure.

[0030] The lower pore pressure volume controller includes a three-way valve 22 of the lower pore pressure volume controller, a vertically arranged lower pore pressure volume controller threaded rod 24, a lower pore pressure volume controller guide rod, a lower pore pressure volume controller motor 25 for driving the lower pore pressure volume controller threaded rod to rotate, a lower pore pressure volume controller drive block 26 threadedly connected to the lower pore pressure volume controller threaded rod, a lower pore pressure volume controller locking switching structure, a lower pore pressure volume controller first cylinder 27, a lower pore pressure volume controller first piston 28 slidingly sealed and connected to the lower pore pressure volume controller first cylinder, a lower pore pressure volume controller first piston 28 at one end connected to the lower pore pressure volume controller first piston and the other end passing through the lower pore pressure body The volume controller driver block includes the first piston rod 29 of the lower pore pressure volume controller, the first pressure sensor 30 of the lower pore pressure volume controller, the second cylinder 31 of the lower pore pressure volume controller, the second piston 32 of the lower pore pressure volume controller, which is slidingly and sealably connected to the second cylinder 31 of the lower pore pressure volume controller, the second piston rod 33 of the lower pore pressure volume controller, one end of which is connected to the second piston of the lower pore pressure volume controller and the other end is inserted into the drive block 31 of the lower pore pressure volume controller, and the second pressure sensor 34 of the lower pore pressure volume controller. The first piston of the lower pore pressure volume controller isolates the first liquid storage chamber 35 of the lower pore pressure volume controller within the first cylinder 31 of the lower pore pressure volume controller. The lower pore pressure volume controller motor and the first cylinder 31 of the lower pore pressure volume controller are connected to the lower pore pressure volume controller frame 36. The lower pore pressure volume controller guide rod is parallel to the lower pore pressure volume controller threaded rod. The lower pore pressure volume controller guide rod is fixed to the lower pore pressure volume controller frame. The first pressure sensor of the lower pore pressure volume controller is used to detect the pressure in the first liquid storage chamber of the lower pore pressure volume controller. The first liquid storage chamber of the lower pore pressure volume controller is connected to a branch hole of the three-way valve of the lower pore pressure volume controller. The second piston of the lower pore pressure volume controller isolates the second liquid storage chamber 37 of the lower pore pressure volume controller in the second cylinder of the lower pore pressure volume controller. The second pressure sensor of the lower pore pressure volume controller is used to detect the pressure in the second liquid storage chamber of the lower pore pressure volume controller. The second liquid storage chamber of the lower pore pressure volume controller is connected to another branch hole of the three-way valve of the lower pore pressure volume controller. The total port of the three-way valve of the lower pore pressure volume controller is connected to the lower hole. The locking switching structure of the lower pore pressure volume controller is used to make the driving block of the lower pore pressure volume controller only fixed to one of the first piston rod and the second piston rod of the lower pore pressure volume controller at the same time.The guide rod of the lower pore pressure volume controller is arranged in the driving block of the lower pore pressure volume controller to prevent the driving block of the lower pore pressure volume controller from rotating; the upper pore pressure volume controller includes an upper pore pressure volume controller three-way valve 38, an upper pore pressure volume controller threaded rod 39, an upper pore pressure volume controller guide rod, an upper pore pressure volume controller motor 40 for driving the upper pore pressure volume controller threaded rod to rotate, an upper pore pressure volume controller driving block 41 threadedly connected to the upper pore pressure volume controller threaded rod, an upper pore pressure volume controller first cylinder 42, an upper pore pressure volume controller first piston 43 connected in a sliding seal in the first cylinder of the upper pore pressure volume controller, and one end of the upper pore pressure volume controller first piston connected to the upper pore pressure volume controller. The first piston rod 44 of the upper pore pressure volume controller, one end of which is fixed to the upper pore pressure volume controller drive block, the first pressure sensor 45 of the upper pore pressure volume controller, the second cylinder 46 of the upper pore pressure volume controller, the second piston 47 of the upper pore pressure volume controller, which is slidingly sealed and connected to the second cylinder of the upper pore pressure volume controller, the second piston rod 48 of the upper pore pressure volume controller, one end of which is connected to the second piston of the upper pore pressure volume controller and the other end is fixed to the upper pore pressure volume controller drive block, and the second pressure sensor 49 of the upper pore pressure volume controller. The first piston of the upper pore pressure volume controller isolates a first liquid storage chamber 50 of the upper pore pressure volume controller within the first cylinder of the upper pore pressure volume controller. The first pressure sensor of the upper pore pressure volume controller is used to detect the pressure in the first liquid storage chamber of the upper pore pressure volume controller. The first liquid storage chamber of the upper pore pressure volume controller is connected to a branch hole of the three-way valve of the upper pore pressure volume controller. The second piston of the upper pore pressure volume controller isolates a second liquid storage chamber 51 of the upper pore pressure volume controller within the second cylinder of the upper pore pressure volume controller. The upper pore pressure volume controller motor and the first cylinder of the upper pore pressure volume controller are connected to the upper pore pressure volume controller frame 52. The upper pore pressure volume controller guide rod is parallel to the upper pore pressure volume controller threaded rod. The upper pore pressure volume controller guide rod is fixed to the upper pore pressure volume controller frame.The second pressure sensor of the upper pore pressure volume controller part is used to detect the pressure in the second liquid storage chamber of the upper pore pressure volume controller part. The second liquid storage chamber of the upper pore pressure volume controller part is connected to another branch hole of the three-way valve of the upper pore pressure volume controller part. The total port of the three-way valve of the upper pore pressure volume controller part is connected to the upper hole. The guide rod of the upper pore pressure volume controller part is passed through the driving block of the upper pore pressure volume controller part to prevent the driving block of the upper pore pressure volume controller part from rotating; the first liquid storage chamber of the lower pore pressure volume controller part is connected to the first liquid storage chamber of the upper pore pressure volume controller part through the first valve 53, and the second liquid storage chamber of the lower pore pressure volume controller part is connected to the first liquid storage chamber of the upper pore pressure volume controller part through the first valve 53. The second liquid storage chamber is connected to the second liquid storage chamber of the upper pore pressure volume controller part through the second valve 54; when in use, water is delivered through the first liquid storage chamber of the lower pore pressure volume controller part and water is received through the first liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment. After the water in the first liquid storage chamber of the lower pore pressure volume controller part is delivered or the first liquid storage chamber of the upper pore pressure volume controller part is filled, the first valve is opened and water is delivered through the second liquid storage chamber of the lower pore pressure volume controller part and water is received through the second liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment; the lower pore pressure volume controller part drive block is reset to drive the lower The process of the second piston rod of the pore pressure volume controller part resets the first liquid storage chamber of the lower pore pressure volume controller part, and the process of resetting the driving block of the upper pore pressure volume controller part resets the first liquid storage chamber of the upper pore pressure volume controller part and the second liquid storage chamber of the upper pore pressure volume controller part, so that the water in the first liquid storage chamber of the lower pore pressure volume controller part flows back to the first liquid storage chamber of the upper pore pressure volume controller part, and the first valve is closed; after the water in the second liquid storage chamber of the lower pore pressure volume controller part is delivered or the second liquid storage chamber of the upper pore pressure volume controller part is filled, the second valve is opened and water is delivered through the first liquid storage chamber of the lower pore pressure volume controller part and The permeability coefficient test experiment is carried out by receiving water through the first liquid storage chamber of the upper pore pressure volume controller; the process of resetting the lower pore pressure volume controller drive block to drive the first piston rod of the lower pore pressure volume controller resets the second liquid storage chamber of the lower pore pressure volume controller, and the process of resetting the upper pore pressure volume controller drive block resets the second liquid storage chamber of the upper pore pressure volume controller and the first liquid storage chamber of the upper pore pressure volume controller, so that the water in the second liquid storage chamber of the lower pore pressure volume controller flows back to the second liquid storage chamber of the upper pore pressure volume controller, and the second valve is closed; the above process is repeated to conduct uninterrupted permeability system test sample. This can avoid insufficient water and interruption of the test by returning the water in the first liquid storage chamber of the upper pore pressure volume controller to the lower pore pressure volume controller through the confining pressure chamber. This is equivalent to reverse osmosis of the sample, which will affect the accuracy of the test data and the test efficiency.

[0031] The first piston of the upper pore pressure volume controller is located at the upper end of the first cylinder of the upper pore pressure volume controller, the second piston of the upper pore pressure volume controller is located at the upper end of the second cylinder of the upper pore pressure volume controller, the first piston of the lower pore pressure volume controller is located at the upper end of the first cylinder of the lower pore pressure volume controller, and the second piston of the lower pore pressure volume controller is located at the upper end of the second cylinder of the lower pore pressure volume controller. The first cylinder of the upper pore pressure volume controller and the second cylinder of the upper pore pressure volume controller are connected side by side, and the first cylinder of the lower pore pressure volume controller and the second cylinder of the lower pore pressure volume controller are connected side by side. When the volume of the first liquid storage chamber of the upper pore pressure volume controller part is at its maximum state, the height of the first liquid storage chamber of the upper pore pressure volume controller part is less than 5 cm; when the volume of the second liquid storage chamber of the upper pore pressure volume controller part is at its maximum state, the height of the liquid storage chamber of the upper pore pressure volume controller part is less than 5 cm; when the volume of the first liquid storage chamber of the lower pore pressure volume controller part is at its maximum state, the height of the first liquid storage chamber of the lower pore pressure volume controller part is less than 5 cm; when the volume of the second liquid storage chamber of the lower pore pressure volume controller part is at its maximum state, the length of the second liquid storage chamber of the lower pore pressure volume controller part is less than 5 cm.

[0032] The locking switching structure of the lower pore pressure volume controller part includes a first fixed lock 55 of the lower pore pressure volume controller part and a second fixed lock 56 of the lower pore pressure volume controller part. The first fixed lock of the lower pore pressure volume controller part is used to fix the lower pore pressure volume controller part drive block together with the first piston rod of the lower pore pressure volume controller part, and the second fixed lock of the lower pore pressure volume controller part is used to fix the lower pore pressure volume controller part drive block together with the second piston rod of the lower pore pressure volume controller part. Only one of the first fixed lock of the lower pore pressure volume controller part and the second fixed lock of the lower pore pressure volume controller part remains in a locked state at the same time. The first fixing lock of the lower pore pressure volume controller part includes a first locking pin 57 of the lower pore pressure volume controller part hinged on the upper end of the first piston rod of the lower pore pressure volume controller part, a first locking hole 58 of the lower pore pressure volume controller part provided on the side of the driving block of the lower pore pressure volume controller part, and a first driving cylinder 59 of the lower pore pressure volume controller part for driving the first locking pin of the lower pore pressure volume controller part to insert into and pull out from the locking hole of the lower pore pressure volume controller part. When the first locking pin of the lower pore pressure volume controller part is inserted into the first locking hole of the lower pore pressure volume controller part, the piston rod of the lower pore pressure volume controller part is fixed together with the driving block of the lower pore pressure volume controller part. The second fixing lock of the lower pore pressure volume controller includes a second locking pin 60 hinged to the upper end of the second piston rod of the lower pore pressure volume controller, a second locking hole 61 provided on the side of the lower pore pressure volume controller drive block, and a second driving cylinder 62 of the lower pore pressure volume controller that drives the second locking pin of the lower pore pressure volume controller into and out of the locking hole. When the second locking pin of the lower pore pressure volume controller is inserted into the second locking hole, the piston rod of the lower pore pressure volume controller is fixed to the lower pore pressure volume controller drive block. A flow meter is used for the upper or lower port.

Claims

1. A permeability coefficient testing device suitable for unloading seepage conditions, comprising a rubber sleeve for covering a sample, a confined pressure chamber, a water supply tank, an upper pore pressure volume controller, a confined pressure volume controller and a lower pore pressure volume controller, the confined pressure chamber comprising a confined pressure chamber base and a confined pressure chamber cover provided with an exhaust valve and detachably and sealedly connected to the chamber base, the confined pressure chamber base and the confined pressure chamber cover enclose a sealed confined pressure chamber, the confined pressure chamber base is provided with a water supply port connected to the water supply tank, an upper hole connected to the upper pore pressure volume controller, a lower hole connected to the lower pore pressure volume controller and a confined pressure hole connected to the confined pressure volume controller, a sample support seat and a sample cover are provided in the confined pressure chamber, characterized in that, The confined pressure chamber cover is provided with a pressing block for pressing the sample cover, a pressing block driving structure for driving the pressing block to rise and fall, and a pressing force detector for detecting the pressure generated by the pressing block on the sample cover. When in use, the rubber sleeve is sleeved on the sample, the sample is placed on the sample support seat and the sample cover is covered. The upper end of the rubber sleeve is sleeved on the sample cover and the lower end is sleeved on the sample support seat. The water in the water supply tank is input into the confined pressure chamber through the water supply port to fill the confined pressure chamber and then the exhaust valve is closed. The confined pressure volume controller pressurizes the confined pressure chamber to the set first side confining pressure value to apply pressure to the surrounding surface of the sample and presses the sample cover to the first top surface confining pressure value through the pressing block to apply pressure to the top surface of the test. Water with a set first water inlet pressure is input into the sample through the lower hole through the lower hole pressure volume controller. After the water penetrates through the sample, it is output from the upper hole to the upper hole pressure volume controller and the upper hole pressure volume controller maintains at the set first water outlet pressure. According to the existing permeability calculation formula, the water is calculated. Calculate the first permeability coefficient; the confining pressure volume controller pressurizes the confining pressure chamber to the set second side confining pressure value to apply pressure to the circumference of the sample and presses the sample cover to the second top surface confining pressure value through the pressing block to apply pressure to the top surface of the test; the lower hole pressure volume controller inputs water of the set second water inlet pressure into the sample through the lower hole; after the water penetrates through the sample, it is output from the upper hole to the upper hole pressure volume controller and the upper hole pressure volume controller is maintained at the second water outlet pressure received; the second permeability coefficient is calculated according to the existing permeability calculation formula; the same method is used to reduce the confining pressure value, input pressure and output pressure in turn, so as to obtain the permeability coefficient under various pressures when the sample is depressurized; the top surface of the sample is independently pressurized by water instead of being controlled at the same value on the same circumference by the confining pressure volume controller, so that the pressure on the side and top surfaces of the sample is close to the actual pressure, thereby making the measured decompression confining pressure data more accurate.

2. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 1, characterized in that: The water replenishment tank is provided with a water pump for outputting the water in the water replenishment tank, a vacuum pump for evacuating the water replenishment tank, and a vibrator for causing the water in the water replenishment tank to shake, and the outlet end of the water pump is connected to the water replenishment port.

3. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 1, characterized in that: The lower pore pressure volume controller comprises a three-way valve of the lower pore pressure volume controller, a threaded rod of the lower pore pressure volume controller, a guide rod of the lower pore pressure volume controller, a motor of the lower pore pressure volume controller for driving the threaded rod of the lower pore pressure volume controller, a driving block of the lower pore pressure volume controller threadedly connected to the threaded rod of the lower pore pressure volume controller, a locking switching structure of the lower pore pressure volume controller, a first cylinder of the lower pore pressure volume controller, a first piston of the lower pore pressure volume controller connected in a sliding seal in the first cylinder of the lower pore pressure volume controller, and one end of the first piston of the lower pore pressure volume controller. The first piston rod of the lower pore pressure volume controller part is connected together and the other end of which is passed through the lower pore pressure volume controller part driving block, the first pressure sensor of the lower pore pressure volume controller part, the second cylinder of the lower pore pressure volume controller part, the second piston of the lower pore pressure volume controller part which is slidingly sealed and connected in the second cylinder of the lower pore pressure volume controller part, the second piston of the lower pore pressure volume controller part which is connected together with the second piston of the lower pore pressure volume controller part and the other end of which is passed through the lower pore pressure volume controller part driving block, and the second piston rod of the lower pore pressure volume controller part and the second pressure sensor of the lower pore pressure volume controller part, the first active The plug is inserted into the first cylinder of the lower pore pressure volume controller to isolate the first liquid storage chamber of the lower pore pressure volume controller. The first pressure sensor of the lower pore pressure volume controller is used to detect the pressure in the first liquid storage chamber of the lower pore pressure volume controller. The first liquid storage chamber of the lower pore pressure volume controller is connected to a branch hole of the three-way valve of the lower pore pressure volume controller. The second piston of the lower pore pressure volume controller is inserted into the second cylinder of the lower pore pressure volume controller to isolate the second liquid storage chamber of the lower pore pressure volume controller. The second pressure sensor of the lower pore pressure volume controller is used to detect the pressure in the second liquid storage chamber of the lower pore pressure volume controller. force, the second liquid storage chamber of the lower pore pressure volume controller part is connected to another branch hole of the three-way valve of the lower pore pressure volume controller part, and the total port of the three-way valve of the lower pore pressure volume controller part is connected to the lower hole, and the locking switching structure of the lower pore pressure volume controller part is used to make the lower pore pressure volume controller part drive block only be fixed with one of the first piston rod of the lower pore pressure volume controller part and the second piston rod of the lower pore pressure volume controller part at the same time, and the guide rod of the lower pore pressure volume controller part is arranged in the drive block of the lower pore pressure volume controller part to prevent the drive block of the lower pore pressure volume controller part from rotating;The upper pore pressure volume controller includes an upper pore pressure volume controller three-way valve, an upper pore pressure volume controller threaded rod, an upper pore pressure volume controller guide rod, an upper pore pressure volume controller motor that drives the upper pore pressure volume controller threaded rod to rotate, an upper pore pressure volume controller drive block threadedly connected to the upper pore pressure volume controller threaded rod, an upper pore pressure volume controller first cylinder, an upper pore pressure volume controller first piston slidingly sealed and connected in the upper pore pressure volume controller first cylinder, an upper pore pressure volume controller first piston rod with one end connected to the upper pore pressure volume controller first piston and the other end fixed to the upper pore pressure volume controller drive block, an upper pore pressure volume controller The first pressure sensor of the device part, the second cylinder of the upper pore pressure volume controller part, the second piston of the upper pore pressure volume controller part which is connected in a sliding seal in the second cylinder of the upper pore pressure volume controller part, the second piston rod of the upper pore pressure volume controller part which is connected to the second piston of the upper pore pressure volume controller part at one end and fixed to the driving block of the upper pore pressure volume controller part at the other end, and the second pressure sensor of the upper pore pressure volume controller part, the first piston of the upper pore pressure volume controller part isolates the first liquid storage chamber of the upper pore pressure volume controller part in the first cylinder of the upper pore pressure volume controller part, the first pressure sensor of the upper pore pressure volume controller part is used to detect the pressure in the first liquid storage chamber of the upper pore pressure volume controller part, the upper pore pressure volume controller part The first liquid storage chamber of the upper pore pressure volume controller is connected to a branch hole of the three-way valve of the upper pore pressure volume controller, the second piston of the upper pore pressure volume controller isolates the second liquid storage chamber of the upper pore pressure volume controller in the second cylinder of the upper pore pressure volume controller, the second pressure sensor of the upper pore pressure volume controller is used to detect the pressure in the second liquid storage chamber of the upper pore pressure volume controller, the second liquid storage chamber of the upper pore pressure volume controller is connected to another branch hole of the three-way valve of the upper pore pressure volume controller, the total port of the three-way valve of the upper pore pressure volume controller is connected to the upper hole, and the guide rod of the upper pore pressure volume controller is passed through the drive block of the upper pore pressure volume controller to prevent the drive block of the upper pore pressure volume controller from rotating. ; The first liquid storage chamber of the lower pore pressure volume controller part is connected with the first liquid storage chamber of the upper pore pressure volume controller part through the first valve, and the second liquid storage chamber of the lower pore pressure volume controller part is connected with the second liquid storage chamber of the upper pore pressure volume controller part through the second valve; when in use, water is delivered through the first liquid storage chamber of the lower pore pressure volume controller part and water is received through the first liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment. After the water in the first liquid storage chamber of the lower pore pressure volume controller part is delivered or the first liquid storage chamber of the upper pore pressure volume controller part is filled, the first valve is opened and water is delivered through the second liquid storage chamber of the lower pore pressure volume controller part and water is received through the second liquid storage chamber of the upper pore pressure volume controller part to perform a permeability coefficient test experiment;The process of resetting the driving block of the lower pore pressure volume controller to drive the second piston rod of the lower pore pressure volume controller resets the first liquid storage chamber of the lower pore pressure volume controller, and the process of resetting the driving block of the upper pore pressure volume controller resets the first liquid storage chamber of the upper pore pressure volume controller and the second liquid storage chamber of the upper pore pressure volume controller, so that the water in the first liquid storage chamber of the lower pore pressure volume controller flows back to the first liquid storage chamber of the upper pore pressure volume controller, and the first valve is closed; after the water in the second liquid storage chamber of the lower pore pressure volume controller is delivered or the second liquid storage chamber of the upper pore pressure volume controller is filled, the second valve is opened and the lower pore pressure volume controller is opened at the same time. The first liquid storage chamber of the upper pore pressure volume controller receives water through the first liquid storage chamber of the upper pore pressure volume controller to perform a permeability coefficient test experiment; the process of resetting the lower pore pressure volume controller drive block to drive the first piston rod of the lower pore pressure volume controller resets the second liquid storage chamber of the lower pore pressure volume controller, and the process of resetting the upper pore pressure volume controller drive block resets the second liquid storage chamber of the upper pore pressure volume controller and the first liquid storage chamber of the upper pore pressure volume controller, thereby allowing the water in the second liquid storage chamber of the lower pore pressure volume controller to flow back to the second liquid storage chamber of the upper pore pressure volume controller, and closing the second valve; repeating the above process to conduct an uninterrupted permeability system test sample.

4. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 3, characterized in that: The first piston of the upper pore pressure volume controller part is located at the upper end of the first cylinder of the upper pore pressure volume controller part, the second piston of the upper pore pressure volume controller part is located at the upper end of the second cylinder of the upper pore pressure volume controller part, the first piston of the lower pore pressure volume controller part is located at the upper end of the first cylinder of the lower pore pressure volume controller part, and the second piston of the lower pore pressure volume controller part is located at the upper end of the second cylinder of the lower pore pressure volume controller part.

5. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 3 or 4, characterized in that: The first cylinder of the upper pore pressure volume controller part and the second cylinder of the upper pore pressure volume controller part are connected side by side, and the first cylinder of the lower pore pressure volume controller part and the second cylinder of the lower pore pressure volume controller part are connected side by side.

6. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 2 or 3, characterized in that: When the volume of the first liquid storage chamber of the upper pore pressure volume controller part is at its maximum state, the height of the first liquid storage chamber of the upper pore pressure volume controller part is less than 5 cm; when the volume of the second liquid storage chamber of the upper pore pressure volume controller part is at its maximum state, the height of the liquid storage chamber of the upper pore pressure volume controller part is less than 5 cm; when the volume of the first liquid storage chamber of the lower pore pressure volume controller part is at its maximum state, the height of the first liquid storage chamber of the lower pore pressure volume controller part is less than 5 cm; when the volume of the second liquid storage chamber of the lower pore pressure volume controller part is at its maximum state, the length of the second liquid storage chamber of the lower pore pressure volume controller part is less than 5 cm.

7. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 2 or 3, characterized in that: The locking switching structure of the lower pore pressure volume controller part includes a first fixed lock of the lower pore pressure volume controller part and a second fixed lock of the lower pore pressure volume controller part. The first fixed lock of the lower pore pressure volume controller part is used to fix the lower pore pressure volume controller part drive block and the first piston rod of the lower pore pressure volume controller part together. The second fixed lock of the lower pore pressure volume controller part is used to fix the lower pore pressure volume controller part drive block and the second piston rod of the lower pore pressure volume controller part together. Only one of the first fixed lock of the lower pore pressure volume controller part and the second fixed lock of the lower pore pressure volume controller part remains in a locked state at the same time.

8. The permeability coefficient testing device suitable for unloading seepage conditions according to claim 7, characterized in that: The first fixing lock of the lower pore pressure volume controller part includes a first locking pin of the lower pore pressure volume controller part hinged on the upper end of the first piston rod of the lower pore pressure volume controller part, a first locking hole of the lower pore pressure volume controller part provided on the side of the driving block of the lower pore pressure volume controller part, and a first driving cylinder of the lower pore pressure volume controller part for driving the first locking pin of the lower pore pressure volume controller part to insert and pull out the locking hole of the lower pore pressure volume controller part. When the first locking pin of the lower pore pressure volume controller part is inserted into the first locking hole of the lower pore pressure volume controller part, the piston rod of the lower pore pressure volume controller part is fixed together with the driving block of the lower pore pressure volume controller part; The second fixed lock of the lower pore pressure volume controller part includes a second locking pin of the lower pore pressure volume controller part hinged on the upper end of the second piston rod of the lower pore pressure volume controller part, a second locking hole of the lower pore pressure volume controller part arranged on the side of the driving block of the lower pore pressure volume controller part, and a second driving cylinder of the lower pore pressure volume controller part for driving the second locking pin of the lower pore pressure volume controller part to insert and pull out the locking hole of the lower pore pressure volume controller part. When the second locking pin of the lower pore pressure volume controller part is inserted into the second locking hole of the lower pore pressure volume controller part, the piston rod of the lower pore pressure volume controller part is fixed together with the driving block of the lower pore pressure volume controller part.

9. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 1, 2 or 3, characterized in that: It also includes a confining pressure chamber pressure sensor that inputs into the bottom of the specimen to check the water inlet pressure.

10. A permeability coefficient testing device suitable for unloading seepage conditions according to claim 1, 2 or 3, characterized in that: The upper port or the lower hole uses a flow meter.

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