Fluid-solid coupling and seepage test system of surrounding rock under complex action

Abstract

The present application belongs to the field of rock mechanics test of engineering rock mass, and relates to a gas-solid coupling and seepage test system under complex action, which comprises a seepage medium supply module, a seepage coupling module, a transient method test module and a steady method test module; the seepage medium supply module is used for providing seepage medium or blowing medium to the system; the seepage coupling module is a rock mechanics testing machine; the transient method test module calculates the permeability of a sample by measuring the differential pressure change of the inlet and outlet of the triaxial chamber of the testing machine, and is suitable for low-permeability medium; the steady method test module tests the fluid flow at the outlet of the triaxial chamber of the testing machine based on the principle of the steady method, and is suitable for high-permeability medium. The present application can test both liquid seepage medium and gas seepage medium, and overcomes the problem that the previous seepage test function is single and a set of system can only test one kind of medium; the present application realizes the coupling test of different media and rocks with the same set of device, and solves the problem that the comparison test standards of the influence of different seepage media on rock mass degradation are not unified.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rock mechanics testing of engineering rock mass, and particularly relates to a fluid-solid coupling and seepage testing system of surrounding rock under complex action. BACKGROUND

[0002] Due to the continuous improvement of engineering technology and the development needs of underground engineering construction, the problems faced by deep engineering construction are becoming more and more complex. In particular, the complex coupling conditions of deep temperature, stress, seepage, engineering disturbance and the like lead to more complex and variable problems of surrounding rock disaster. Deep buried transportation engineering, deep buried long tunnel engineering, deep buried hydropower engineering, deep geological carbon sequestration engineering of salt water layer, deep geological disposal engineering of high-level radioactive waste, deep energy storage engineering, deep shale gas exploitation and geothermal exploitation engineering, and deep drilling engineering, etc. not only involve seepage, but also face the coupling of complex temperature field, stress field and excavation condition disturbance, further deteriorate the mechanical properties of surrounding rock and accelerate the unstable state, leading to the problem of prominent seepage and engineering disaster induced by different disaster states under different complex conditions. Different engineering states have different complexities of occurrence conditions. For example, the construction technology problem and construction safety problem of coal tunnel under complex conditions are more prominent. If the surrounding rock of coal tunnel cannot be fully understood, it is difficult to propose an effective solution to the safety problem of coal tunnel construction, leading to the delay of construction period, the increase of construction cost, and even the occurrence of serious safety accidents in the process of tunnel construction, causing huge losses. Therefore, the development of effective testing equipment and the implementation of testing of the seepage evolution of cap rock under different deep engineering conditions and various complex coupling are still one of the difficult problems to be broken through in the research of deep engineering construction.

[0003] In the construction of underground rock mass engineering, the interaction between seepage medium (such as gas or liquid) and rock mass will inevitably occur, and the seepage medium will cause the deterioration of the mechanical properties of the rock mass, while the deterioration process of the rock mass will also cause the change of the seepage characteristics. That is to say, whether the mechanical behavior of the rock mass deteriorates or the seepage characteristics change, it will have a very adverse effect on the engineering. Therefore, the test and evaluation of the fluid-solid coupling mechanical deterioration and seepage evolution characteristics of the rock mass are important contents of the engineering construction research. However, how to effectively implement the test of the mechanical deterioration and seepage evolution under the fluid-solid coupling is a difficult problem to be solved in rock mechanics test. Although the MTS815 rock mechanics testing machine is an advanced equipment for rock mechanics test in this field, it can only carry out the test function of liquid medium at present, and it cannot realize the coupling test of gas and rock mass, nor can it realize the test of both liquid and gas seepage medium in one system. In addition, when the MTS815 rock mechanics testing machine is used for the test of liquid seepage process, once the confining pressure medium enters the seepage test module during the test process, it cannot be judged whether it enters the test module from the top or the bottom of the rock sample, and the structure of the module is complex and cannot be cleaned, so the confining pressure medium remains in the seepage module, which leads to the results obtained by using the module thereafter not meeting the actual situation, and even being wrong results. Moreover, during the test process of the MTS815 rock mechanics test system, many valves need to be operated manually, and if one valve is operated incorrectly, it will lead to the waste of the test before the test, and even the damage of the equipment. The operation during the test process is difficult, the process is complex, the cost is high, and it is time-consuming and laborious. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the MTS815 rock mechanics test system, and to provide a fluid-solid coupling and seepage test system of surrounding rock under complex action, which can realize the convenient exchange of liquid and gas medium, and can timely find the failure position of the sample protection layer during the test process, so as to terminate the test in time.

[0005] The technical scheme adopted by the present application is:

[0006] The fluid-solid coupling and seepage test system of surrounding rock under complex action comprises a seepage medium supply module, a seepage coupling module, a transient method test module and a steady-state method test module.

[0007] The seepage medium supply module 1 is used to supply seepage medium or purging medium to the system.

[0008] The seepage coupling module is a rock mechanics testing machine, which comprises a triaxial chamber, and the triaxial chamber is provided with a seepage medium inlet at the top end and a seepage medium outlet at the bottom end.

[0009] The transient method test module comprises an upstream branch pipe, a pressure sensor 1, a pressure chamber 1, a downstream branch pipe, a pressure sensor 2, a pressure chamber 2 and a differential pressure sensor;

[0010] The inlet end of the upstream branch pipe is connected with the seepage medium outlet of the seepage medium supply module, and the outlet end of the upstream branch pipe is connected with the seepage medium inlet of the triaxial chamber; the pressure chamber 1 is connected with the upstream branch pipe through a pressure branch 1, and the pressure sensor 1 is connected with the connecting passage between the upstream branch pipe and the pressure chamber 1, for detecting the pressure of the upstream branch pipe.

[0011] The inlet end of the downstream branch pipe is connected with the seepage medium outlet of the seepage medium supply module, and the outlet end of the downstream branch pipe is connected with the seepage medium outlet of the triaxial chamber; the pressure chamber 2 is connected with the downstream branch pipe through a pressure branch 2, and the pressure sensor 2 is connected with the connecting passage between the downstream branch pipe and the pressure chamber 2, for detecting the pressure of the downstream branch pipe.

[0012] The differential pressure sensor is arranged between the upstream branch pipe and the downstream branch pipe, for detecting the differential pressure between the upstream branch pipe and the downstream branch pipe.

[0013] The steady state method test module is connected with the downstream branch pipe, for testing the fluid flow rate of the seepage medium outlet of the triaxial chamber.

[0014] Further, the steady state method test module comprises a flow meter 1, a flow meter 2 and an electromagnetic three-way valve 1.

[0015] The flow meter 1 and the flow meter 2 are respectively connected with the steady state test main line through steady state test branch pipes, and the electromagnetic three-way valve 1 is installed at the intersection of the steady state test main line and the steady state test branch pipes, for selecting one of the flow meter 1 and the flow meter 2 to be communicated with the steady state test main line.

[0016] Further, the flow meter 1 is a soap bubble flow meter.

[0017] Further, a steady state pressure reducing valve, a steady state stop valve 1 and a steady state stop valve 2 are arranged on the steady state test main line.

[0018] The steady state stop valve 2 and the steady state pressure reducing valve are connected in parallel on the steady state test main line, and are connected in series with the steady state stop valve 1.

[0019] Further, a temperature stabilizing module is arranged between the seepage medium supply module and the transient method test module.

[0020] The temperature stabilizing module comprises a temperature sensor 1, a heater, a stop valve 13, a pressure stabilizer, a pressure reducing valve 2 and a temperature sensor 2, which are sequentially connected in series on the medium flow passage.

[0021] Further, a drying module and a stop valve fourteen are arranged between the seepage medium supply module and the temperature and pressure stabilizing module, and the drying module and the stop valve fourteen are connected in parallel on the medium flow passage.

[0022] The drying module comprises a dryer, a stop valve four is arranged between an inlet end of the dryer and a medium outlet of the seepage medium supply module, and a stop valve five is arranged between an outlet end of the dryer and a medium inlet of the temperature and pressure stabilizing module.

[0023] Further, a vacuum module is further included, the vacuum module comprises a vacuum pump, the vacuum pump is connected to the communication passage of the dryer and the seepage medium supply module through a vacuum branch pipe, and a stop valve three for controlling the closure of the vacuum branch pipe is arranged on the vacuum branch pipe.

[0024] Further, the seepage medium supply module comprises a medium supply main pipeline, a compressor, a pressure increasing valve, a three-way valve, a gas source and a one-way valve.

[0025] One end of the medium supply main pipeline is a medium inlet, and the other end is a medium outlet; the one-way valve is arranged at the medium outlet of the medium supply main pipeline.

[0026] The compressor is connected in communication with the medium inlet of the medium supply main pipeline through a medium supply branch pipe one, and a pressure increasing valve is arranged on the medium supply branch pipe one.

[0027] The gas source is connected in communication with the medium inlet of the medium supply main pipeline through a medium supply branch pipe two, a stop valve one is installed on the medium supply branch pipe two, and the stop valve one is located between the gas source and the medium inlet of the medium supply main pipeline.

[0028] The gas source and the medium supply branch pipe one are connected in communication through the three-way valve, the outlet of the pressure increasing valve is connected with the inlet of the three-way valve, one of the outlets of the three-way valve is connected with the inlet of the gas source, and the other outlet is connected in communication with the inlet of the medium supply main pipeline.

[0029] Further, a data acquisition and display module is included, the data acquisition and display module is connected with the pressure sensor one, the pressure sensor two and the pressure difference sensor, and is used for real-time acquisition and storage of parameters of each sensor.

[0030] Further, an automatic control module is further included, the automatic control module comprises a controller, an input port of the controller is connected with the pressure sensor one and the pressure sensor two, and an output port of the controller is connected with valves for controlling the opening and closing of the seepage medium supply module, the transient method test module and the steady state method test module respectively.

[0031] The beneficial effects of the present application are:

[0032] (1) The liquid seepage medium and the gas medium can be tested, the problem that the seepage test function is single and a set of system can only test one medium is overcome, the coupling test of different media and rocks in the same set of devices is realized, and the problem that the comparison test standard of the influence of different seepage media on rock mass deterioration is not unified is solved.

[0033] (2) The continuous change test of seepage evolution state from low permeability (10- 21 m 2 ) to high permeability (10- 13 m 2 ) in the whole process of rock mass from the complete state to the micro-crack, then to the crack development and formation of rock mass, and to the gradual deterioration of rock mass is realized.

[0034] (3) The test operation is simple, the equipment or sample is not damaged in the test process, and the same test state can be tested for many times in the test process, so that the test cost is reduced, and the reliability of the test result is guaranteed.

[0035] (4) The mutual feedback test of mechanics and different seepage media under the coupling of different excavation and mining and other construction and operation modes in the simulation of engineering construction and operation process is realized, the influence of the in-situ environment state of the rock mass in the deep underground is reflected, and the problem of the single simulation of the engineering construction state and the seepage coupling medium is overcome. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The gas-solid coupling and seepage test system structure schematic diagram of surrounding rock under complex action provided by the application is shown in the figure.

[0037] Figure 2 The photo of the plaster rock sample in the test example is shown in the figure.

[0038] Figure 3 The seepage measuring point distribution diagram of the plaster rock sample in the test example in the permeability test process is shown in the figure.

[0039] Figure 4 The stress-strain curve diagram of the plaster rock sample under four different confining pressures and permeability conditions at room temperature in the test example is shown in the figure.

[0040] Figure 5 The change relation diagram of the permeability of the plaster rock sample in each confining pressure group in the whole loading process is shown in the figure.

[0041] Figure 6 The characteristic curve diagram of the permeability of the plaster rock under different confining pressures and the change of the loading stress at room temperature in the test example is shown in the figure.

[0042] In the figure, 1-permeation medium supply module; 11-compressor; 12-pressure increasing valve; 13-three-way valve; 14-gas source; 15-check valve; 16-check valve one; 17-check valve two; 18-pressure reducing valve one;

[0043] 2-vacuum module; 21-vacuum pump; 22-vacuum branch; 23-check valve three;

[0044] 3-drying module; 31-dryer; 32-check valve four; 33-check valve five;

[0045] 4-data acquisition and display module;

[0046] 5-transient method test module; 51-upstream branch; 52-pressure sensor one; 53-pressure chamber one; 54-downstream branch; 55-pressure sensor two; 56-pressure chamber two; 57-pressure difference sensor; 58-check valve six; 59-check valve seven; 510-check valve eight; 511-check valve nine; 512-check valve ten; 513-check valve eleven; 514-check valve twelve; 515-safety valve one; 516-safety valve two;

[0047] 6-warming and pressure stabilizing module; 61-temperature sensor one; 62-heater; 63-pressure stabilizer; 64-pressure reducing valve two; 65-temperature sensor two; 66-check valve thirteen;

[0048] 7-steady state method test module; 71-flow meter one; 72-flow meter two; 73-electromagnetic three-way valve one; 74-steady state pressure reducing valve; 75-steady state check valve one; 76-steady state check valve two; 77-electromagnetic three-way valve two;

[0049] 8-permeation coupling module; 81-triaxial chamber; 82-sample;

[0050] 9-check valve fourteen. DETAILED DESCRIPTION

[0051] The present application will be further described below in conjunction with the accompanying drawings, examples and test examples: Figures 1-6

[0052] Examples

[0053] As shown in the figure is a gas-solid coupling and permeation test system for surrounding rock under complex action of the present application, comprising a permeation medium supply module 1, a permeation coupling module 8, a transient method test module 5 and a steady state method test module 7; wherein the permeation medium supply module 1 is used to provide pressure-stable permeation medium or flushing medium to the system. Figure 1

[0054] ​​Specifically, the seepage medium supply module 1 is used to supply seepage medium or flushing medium to the system; the seepage medium supply module 1 comprises a medium supply main pipe, a compressor 11, a booster valve 12, a three-way valve 13, a gas source 14 and a check valve 15; one end of the medium supply main pipe is a medium inlet, and the other end is a medium outlet; the compressor 11 is connected to the medium inlet of the medium supply main pipe through a medium supply branch pipe one, and the check valve 15 is arranged at the medium outlet of the medium supply main pipe; the booster valve 12 is arranged between the compressor 11 and the three-way valve 13.

[0055] In order to realize the diversification of the gas supply mode, the gas source 14 is arranged on a medium supply branch pipe two, and the inlet of the gas source 14 is connected to the three-way valve 13, and the outlet of the gas source 14 is connected to the check valve 15 through a stop valve one 16.

[0056] The stop valve two 17 and the pressure reducing valve 18 for changing the gas supply mode are further arranged at the inlet end of the check valve 15, and the stop valve two 17 and the pressure reducing valve 18 are connected to the check valve 15 in parallel.

[0057] In this way, the seepage medium supply module 1 can supply gas through the compressor 11 alone, supply gas through the gas source 14 alone, and supply gas to the gas source 14 through the compressor 11 and then supply gas to the system. The gas supply mode can be selected according to the actual situation, and backup can be formed between the gas supply modes.

[0058] The seepage coupling module 8 is a rock mechanics testing machine, which comprises a triaxial chamber, the top end of the triaxial chamber is provided with a seepage medium inlet, and the bottom end is provided with a seepage medium outlet. The reason for choosing the triaxial chamber is that, compared with the uniaxial compression test, the triaxial compression test can consider the effect of confining pressure, is more in line with the stress state of the surrounding rock of underground engineering, and can more truly reflect the real mechanical properties of the surrounding rock of underground engineering.

[0059] The transient method test module 5 comprises an upstream branch pipe 51, a pressure sensor one 52, a pressure chamber one 53, a downstream branch pipe 54, a pressure sensor two 55, a pressure chamber two 56 and a differential pressure sensor 57.

[0060] Specifically, the inlet end of the upstream branch pipe 51 is connected with the seepage medium outlet of the seepage medium supply module 1 to form a medium flow passage, and the outlet end is connected with the seepage medium inlet of the triaxial chamber 81; the pressure chamber one 53 is connected with the upstream branch pipe 51 through the pressure branch one, and the pressure sensor one 52 is connected with the connecting passage between the upstream branch pipe 51 and the pressure chamber one 53 to detect the pressure of the upstream branch pipe 51. The inlet end of the downstream branch pipe 54 is connected with the seepage medium outlet of the seepage medium supply module 1 to form a medium flow passage, and the outlet end is connected with the seepage medium outlet of the triaxial chamber 81; the pressure chamber two 56 is connected with the downstream branch pipe 54 through the pressure branch two, and the pressure sensor two 55 is connected with the connecting passage between the upstream branch pipe 51 and the pressure chamber two 56 to detect the pressure of the downstream branch pipe 54. The differential pressure sensor 57 is connected between the upstream branch pipe 51 and the downstream branch pipe 54 to detect the pressure difference between the upstream branch pipe 51 and the downstream branch pipe 54.

[0061] It should be noted here that in order to ensure that the volume of the upstream branch pipe 51 and the downstream branch pipe 54 is equivalent and to reduce the floor area, the pressure chamber one 53 and the pressure chamber two 56 in the module are symmetrically arranged, the pressure sensor one 52 and the pressure sensor two 55 are symmetrically arranged, and the upstream branch pipe 51 and the downstream branch pipe 54 are also symmetrically arranged.

[0062] Specifically, the maximum range of the pressure sensor one 52 and the pressure sensor two 55 is 10 MPa. The maximum range of the differential pressure sensor 57 is 700 kPa, and the accuracy is 0.001 kPa. The pressure chamber one 53 and the pressure chamber two 56 are special high-pressure steel cylinders with a volume of 0.5 L and a maximum pressure of 40 MPa. In order to avoid the triaxial chamber pressure oil entering the gas seepage test system and causing the pressure in the pipeline to exceed the safety pressure of the pressure sensor and the differential pressure sensor, thereby damaging the system, a safety valve two 516 is arranged on the upstream branch pipe 51, and a safety valve one 515 is arranged on the downstream branch pipe 54.

[0063] In addition, in order to better control the medium flow in the upstream branch pipe 51 and the downstream branch pipe 54, a stop valve ten 512 is arranged at the inlet end of the upstream branch pipe, a stop valve nine 511 and a stop valve six 58 are arranged at the outlet end of the upstream branch pipe 51 and the inlet end of the downstream branch pipe, respectively; a stop valve eight 510 and a stop valve seven 59 are arranged on the pipelines where the pressure chamber one 53 and the pressure chamber two 56 are located, and a stop valve twelve 514 is arranged at the free end of the downstream branch pipe 54.

[0064] It should be noted that the transient method test module 5 is designed based on the principle of the transient method, which calculates the permeability of the sample by measuring the pressure difference between the inlet and outlet of the sample 82, and is suitable for low-permeability media.

[0065] In order to improve the accuracy of measurement and the scope of application, the application also provides a steady state method test module 7 connected to the downstream branch pipe 54 for testing the fluid flow of the bottom end outlet of the triaxial chamber 81.

[0066] Specifically, the steady state method test module 7 comprises a flowmeter one 71, a flowmeter two 72 and an electromagnetic three-way valve one 73; the flowmeter one 71 and the flowmeter two 72 are respectively connected to the steady state test main line through the steady state test branch pipe, and the electromagnetic three-way valve one 73 is installed at the intersection of the steady state test main line and the steady state test branch pipe for selecting one of the flowmeter one 71 or the flowmeter two 72 to be in communication with the steady state test main line. When the seepage flow is small and short, the flowmeter one 71 with high sensitivity is selected, and the flowmeter one 71 is a soap bubble flowmeter (SFFM); when the seepage flow is large and long, the flowmeter two 72 is selected, and the flowmeter one 71 uses a conventional flowmeter. In addition, the steady state test main line is also provided with a steady state pressure reducing valve 74, a steady state stop valve one 75 and a steady state stop valve two 76; the steady state stop valve two 76 and the steady state pressure reducing valve 74 are connected in parallel on the steady state test main line and are connected in series with the steady state stop valve one 75. In order to be connected with other performance testing equipment of the sample, an electromagnetic three-way valve two 77 can also be installed between the electromagnetic three-way valve one 73 and the steady state test main line, which is used as an expansion end.

[0067] It should be noted that the steady state method test module 7 is designed based on the principle of the steady state method, which can test the seepage flow of the fluid medium at the outlet end of the sample 82 and is suitable for high permeability medium.

[0068] The application integrates the transient method test module and the steady state method test module in one test system, which can measure the seepage flow of low permeability medium and the seepage flow of high permeability medium, and has a wide range of use.

[0069] In order to improve the temperature of the seepage medium and ensure the stability of the system pressure, a heating and pressure stabilizing module 6 is arranged between the seepage medium supply module 1 and the transient method test module 5; the heating and pressure stabilizing module 6 comprises a temperature sensor one 61, a heater 62, a stop valve thirteen 66, a pressure stabilizer 63, a pressure reducing valve two 64 and a temperature sensor two 65 connected in sequence on the medium flow passage.

[0070] The advantages of this design are that the heater 62 can effectively improve the temperature of the seepage medium, and in the case of insufficient air pressure, the temperature of the seepage medium can be improved to ensure the stability of the air pressure. Moreover, it is convenient to operate and simple in structure.

[0071] In order to dry the seepage medium and the pipeline of the system, improve the accuracy of the test, a drying module 3 and a stop valve fourteen 9 are arranged between the seepage medium supply module 1 and the heating and pressure stabilizing module 6, and the drying module 3 and the stop valve fourteen 9 are connected in parallel on the medium flow passage.

[0072] Specifically, the drying module 3 includes a dryer 31, a stop valve four 32 is arranged between the inlet end of the dryer 31 and the medium outlet of the seepage medium supply module 1, and a stop valve five 33 is arranged between the outlet end of the dryer 31 and the medium inlet of the heating and pressure stabilizing module 6.

[0073] In order to detect the sealing of the whole system, a vacuum module 2 is also arranged, the vacuum module 2 includes a vacuum pump 21, the vacuum pump 21 is connected to the communication passage of the drying module 31 and the seepage medium supply module 1 through a vacuum branch pipe 22, and a stop valve four 23 for controlling the closure of the vacuum branch pipe 22 is arranged on the vacuum branch pipe 22.

[0074] Further, a data acquisition and display module 4 is also included, the data acquisition and display module 4 is connected with the pressure sensor one 52, the pressure sensor two 55 and the differential pressure sensor 57, and is used for real-time acquisition and storage of sensor parameters.

[0075] The data acquisition and display module 4 is mainly composed of an acquisition card, a computer system and a software system, and the working principle of the module belongs to the prior art, so it will not be described again.

[0076] In order to automatically control and avoid manual opening of each valve, improve the accuracy of the test, an automatic control module (not shown in the figure) is also included, the automatic control module includes a controller, the input port of the controller is connected with the pressure sensor one 52 and the pressure sensor two 55, and the output port is connected with the valves for controlling the opening and closing of the seepage medium supply module 1, the transient method test module 5 and the steady state method test module 7. In addition, the automatic control module also makes the operation of the system simple.

[0077] The test system is not only suitable for gas medium, but also suitable for liquid medium, realizes the coupling test of different media and rocks with the same device, and solves the problem that the comparison test standards of the influence of different seepage media on rock mass are not unified. When it is a liquid medium, the liquid enters from the supply main pipeline through the compressor 11, at this time, only the gas source 14 and the drying module 3 need to be closed.

[0078] Test example

[0079] In this test example, the fluid-solid coupling and seepage test system under complex action in the embodiment is adopted, the gas-solid coupling and seepage test of the gypsiferous rock sample taken from the cover layer rock of underground gas storage is carried out, so as to reveal the evolution law of the gypsiferous rock in the gas-solid coupling seepage mechanics behavior. The seepage medium in the test process is nitrogen.

[0080] (I) sample preparation:

[0081] The paste rock is polished in the laboratory according to the standard of "Standard Test Methods for Engineering Rock Mass" and "Regulations for Rock Test of Water Conservancy and Hydropower Engineering", and the standard sample for indoor rock mechanics experiment is made, the sample size is diameter and height ФxH = 38x76mm, and artificial penetration holes with a diameter of 3mm are prepared at both ends of the sample, as shown in Figure 2 The sample is stored dry before the experiment.

[0082] (II) experimental equipment

[0083] MTS815 rock mechanics testing machine is used.

[0084] (III) test method

[0085] (1) The paste rock sample wrapped with heat shrink film is installed in the triaxial chamber.

[0086] (2) The confining pressure of the paste rock sample is loaded, and the confining pressure at this time comes from the pressure oil in the triaxial chamber. The pressure oil surrounds the side of the paste rock sample and exerts pressure on it. The confining pressure loading rate is 3MPa / min. When the target confining pressure value is reached, the seepage medium supply module 1 is started to apply air pressure to both ends of the paste rock sample. The air pressure value is set to 1.5MPa. After the air pressure is stabilized for 30min, the first seepage test is carried out, and the permeability at this point is regarded as the permeability before axial loading, i.e. the initial point.

[0087] (3) After the initial point permeability test is completed, axial loading is carried out, and the pressure comes from the triaxial test shaft. The axial loading rate is controlled by LVDT, and the control rate is 0.08mm / min.

[0088] (4) The seepage test points are evenly distributed in the loading process. When the specified stress point is reached, the LVDT is stabilized, and the transient method is used to test the permeability parameters at the stress point.

[0089] In this process, more than 10 measurement points are ensured in the whole process of loading and destroying the paste rock sample, of which 1 permeability measurement point is ensured at the peak stress point, and more than 3 permeability measurement points are ensured after the peak stress. The distribution of the permeability measurement points is shown in Figure 3 .

[0090] (5) After the above steps are completed, the mechanical behavior data and permeability data parameters are obtained, and the data is processed.

[0091] It should be noted that the target confining pressure value in step (2) is 4, which is 5 MPa, 15 MPa, 25 MPa and 35 MPa, that is, the above test is done 4 times, the test method is the same, the difference is only that the target confining pressure is different, in order to more accurately obtain the mechanical behavior characteristics and permeation data of the paste rock sample.

[0092] Transient method for calculating permeability K P The formula is as follows:

[0093] ΔP(t)=ΔP0e ωt ;

[0094]

[0095] In the formula, ΔP(t) refers to the pressure difference between the two ends of the sample at time t, unit MPa; ΔP0 is the initial pressure difference between the two ends of the sample, unit MPa; t refers to the duration of one permeation, unit s; μ refers to the dynamic viscosity coefficient of the permeation medium nitrogen, unit Pa·s; η refers to the gas compression coefficient of nitrogen, unit Pa -1 ; V1, V2 refer to the volume of the upper and lower gas pressure end buffer gas cylinders, unit m 3 ; A refers to the cross-sectional area of the sample, unit m 2 ; L refers to the height of the sample, unit m.

[0096] (IV) Test results and analysis

[0097] As Figure 4 shown in the figure are the stress-strain curves of the paste rock sample under four different confining pressure permeation conditions at room temperature. As can be seen from the figure, the brittle failure and ductile failure characteristics of the paste rock are obvious.

[0098] Under the permeation condition, the deformation stage of the paste rock sample after axial loading is in turn crack compression stage, crack generation and expansion stage, stress oscillation stage, macroscopic crack penetration failure stage or strain hardening stage. Under different confining pressures, the strength and deformation characteristics of the paste rock sample are shown in Table 1:

[0099] Table 1 Strength and deformation characteristic parameters of paste rock under conventional loading-permeation loading

[0100]

[0101]

[0102] Note: Conventional loading means that in step (2) of the test method, no gas pressure is applied; axial strain and hoop strain are measured by axial extensometer and hoop extensometer respectively; stress is measured by force sensor.

[0103] As can be seen from Table 1, the peak deviatoric stress under conventional loading state and under permeation condition has no big difference; the gas pressure weakening effect affects the residual strength of the paste rock.

[0104] As Figure 5 The change relation of permeability of each confining pressure group paste rock sample in the whole loading process is shown.

[0105] The change characteristic curve of paste rock permeability with loading stress under different confining pressures at room temperature is shown. Figure 6 It can be seen from the figure that the permeability mainly presents the change of first falling, then rising, finally tending to be stable or continuing to rise.

[0106] In summary, the application not only solves the test problem of fluid-solid coupling mechanical mutual feedback under different mining methods in the simulation of deep underground coal mining, but also solves the test problem of surrounding rock mechanical degradation process in the simulation of deep underground energy storage engineering operation.

[0107] Those skilled in the art will realize that the embodiments described herein are for the purpose of helping the reader understand the principles of the application and should be understood as not limiting the scope of protection of the application to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations according to the technical inspiration disclosed in the application without departing from the essence of the application, and these modifications and combinations are still within the scope of protection of the application.

Claims

1. A fluid-solid coupling and seepage test system of surrounding rock under complex action, characterized by: The system comprises a seepage medium supply module (1), a seepage coupling module (8), a transient method test module (5) and a steady method test module (7); The seepage medium supply module (1) is used for providing seepage medium for the system, and the seepage medium is liquid or gas; The seepage coupling module (8) is a rock mechanics testing machine, and the rock mechanics testing machine comprises a triaxial chamber (81), the top end of the triaxial chamber (81) is provided with a seepage medium inlet, and the bottom end of the triaxial chamber (81) is provided with a seepage medium outlet; The transient method test module (5) comprises an upstream branch pipe (51), a pressure sensor one (52), a pressure chamber one (53), a downstream branch pipe (54), a pressure sensor two (55), a pressure chamber two (56) and a differential pressure sensor (57); The inlet end of the upstream branch pipe (51) is connected with the seepage medium outlet of the seepage medium supply module (1), and the outlet end of the upstream branch pipe (51) is connected with the seepage medium inlet of the triaxial chamber (81); the pressure chamber one (53) is connected with the upstream branch pipe (51) through a pressure branch one, and the pressure sensor one (52) is connected on the connecting passage between the upstream branch pipe (51) and the pressure chamber one (53) and is used for detecting the pressure of the upstream branch pipe (51); The inlet end of the downstream branch pipe (54) is connected with the seepage medium outlet of the seepage medium supply module (1), and the outlet end of the downstream branch pipe (54) is connected with the seepage medium outlet of the triaxial chamber (81); the pressure chamber two (56) is connected with the downstream branch pipe (54) through a pressure branch two, and the pressure sensor two (55) is connected on the connecting passage between the downstream branch pipe (54) and the pressure chamber two (56) and is used for detecting the pressure of the downstream branch pipe (54); The differential pressure sensor (57) is arranged between the upstream branch pipe (51) and the downstream branch pipe (54) and is used for detecting the differential pressure between the upstream branch pipe (51) and the downstream branch pipe (54); A temperature stabilizing module (6) is arranged between the seepage medium supply module (1) and the transient method test module (5); the temperature stabilizing module (6) comprises a temperature sensor one (61), a heater (62), a stop valve thirteen (66), a pressure stabilizer (63), a pressure reducing valve two (64) and a temperature sensor two (65) which are sequentially connected in series on a medium flow passage; A drying module (3) and a stop valve fourteen (9) are arranged between the seepage medium supply module (1) and the temperature stabilizing module (6), and the drying module (3) and the stop valve fourteen (9) are connected in parallel on the medium flow passage; the drying module (3) comprises a dryer (31), a stop valve four (32) is arranged between the inlet end of the dryer (31) and the medium outlet of the seepage medium supply module (1), and a stop valve five (33) is arranged between the outlet end of the dryer (31) and the medium inlet of the temperature stabilizing module (6); The steady method test module (7) is connected with the downstream branch pipe (54) and is used for testing the fluid flow of the seepage medium outlet of the triaxial chamber (81).

2. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 1, characterized in that: The steady method test module (7) comprises a flowmeter one (71), a flowmeter two (72) and an electromagnetic three-way valve one (73). The flowmeter one (71) and the flowmeter two (72) are connected to the steady state test main line through the steady state test branch respectively, the electromagnetic three-way valve one (73) is installed at the intersection of the steady state test main line and the steady state test branch, and is used for selecting one of the flowmeter one (71) and the flowmeter two (72) to be communicated with the steady state test main line.

3. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 2, characterized in that: The flowmeter one (71) is a soap bubble flowmeter.

4. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 3, characterized in that: A steady state pressure reducing valve (74), a steady state stop valve one (75) and a steady state stop valve two (76) are further arranged on the steady state test main line. The steady state stop valve two (76) and the steady state pressure reducing valve (74) are connected in parallel on the steady state test main line and are connected in series with the steady state stop valve one (75).

5. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 1, characterized in that: The vacuum module (2) further comprises a vacuum pump (21) connected to the communication passage of the dryer (31) and the seepage medium supply module (1) through a vacuum branch (22), and a stop valve three (23) is arranged on the vacuum branch (22) to control the closure of the vacuum branch (22).

6. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 1, characterized in that: The seepage medium supply module (1) comprises a medium supply main line, a compressor (11), a pressure increasing valve (12), a three-way valve (13), an air source (14) and a check valve (15). One end of the medium supply main line is a medium inlet, and the other end is a medium outlet; the check valve (15) is arranged at the medium outlet of the medium supply main line; The compressor (11) is connected to the medium inlet of the medium supply main line through a medium supply branch one, and the pressure increasing valve (12) is arranged on the medium supply branch one; The air source (14) is connected to the medium inlet of the medium supply main line through a medium supply branch two, and the stop valve one (16) is arranged on the medium supply branch two, and the stop valve one (16) is located between the air source (14) and the medium inlet of the medium supply main line; The air source (14) and the medium supply branch one are connected through the three-way valve (13), the outlet of the pressure increasing valve (12) is connected with the inlet of the three-way valve (13), one of the outlets of the three-way valve (13) is connected with the inlet of the air source (14), and the other outlet is connected with the inlet of the medium supply main line.

7. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 1, characterized in that: The data acquisition and display module (4) is connected with the pressure sensor one (52), the pressure sensor two (55) and the differential pressure sensor (57), and is used for real-time acquisition and storage of sensor parameters.

8. The fluid-solid coupling and seepage test system for surrounding rock under complex action according to claim 1, characterized in that: The automatic control module further comprises a controller, an input port of the controller is connected with the pressure sensor one (52) and the pressure sensor two (55), and an output port of the controller is connected with valves for starting and stopping the seepage medium supply module (1), the transient method test module (5) and the steady state method test module (7) respectively.

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