Fluid-solid coupling and seepage testing system for surrounding rock under complex action

Abstract

The invention belongs to the field of rock mechanics testing of engineering rock mass, and relates to a gas-solid coupling and seepage testing system under complex action, which comprises a seepage medium supply module, a seepage coupling module, a transient method testing module and a steady state method testing module, the seepage medium supply module is used for providing a seepage medium or a purging medium for the system; the seepage coupling module is a rock mechanics testing machine, and the transient method testing module calculates the permeability of a sample by measuring the pressure difference change between the inlet and the outlet of a triaxial chamber of the testing machine, and is suitable for a low-permeability medium; the steady-state method testing module tests the fluid flow at the outlet of the triaxial chamber of the testing machine based on a steady-state method principle, and is suitable for a high-permeability medium. According to the invention, both the liquid seepage medium and the gas seepage medium can be tested, and the problems that the previous seepage test function is single and only one medium test can be carried out by one set of system are solved; the coupling test of different media and rocks in the same set of device is realized, and the problem of non-uniform comparison test standards of the influence of different permeable media on the deterioration of the rock mass is solved.

Description

Technical Field

[0001] The present invention belongs to the field of rock mechanics testing of engineering rock masses, and particularly relates to a fluid-solid coupling and seepage testing system for surrounding rocks under complex actions. Background Art

[0002] Due to the continuous improvement of engineering technology levels and the development needs of underground engineering construction, the problems faced by deep geological engineering construction are becoming increasingly complex. In particular, complex coupling conditions such as deep temperature, stress, seepage, and engineering disturbances make the surrounding rock catastrophe problems more complex and variable. Deep-buried transportation engineering, deep-buried extra-long tunnel engineering, deep-buried hydropower engineering, deep geological carbon sequestration engineering in deep saline aquifers, deep geological disposal engineering of high-level radioactive waste, deep energy storage engineering, deep shale gas extraction and geothermal extraction engineering, and deep drilling engineering, etc., not only involve seepage, but also face the coupling effects of complex temperature fields, stress fields, and excavation condition disturbances, further deteriorating the mechanical properties of the surrounding rock and accelerating the unstable state, resulting in prominent seepage problems and engineering disaster problems of different catastrophe states induced by different complex conditions. The engineering states are different, and the complexity of the occurrence conditions varies. For example, in the case of a coal-crossing tunnel under complex conditions, its construction technical problems and construction safety problems are more prominent. If the surrounding rock of the coal-crossing tunnel cannot be fully understood, it is difficult to propose an effective solution to the construction safety problem of the coal-crossing tunnel, resulting in delays in the construction period, increased construction costs, and even serious work safety accidents during the tunnel construction process, causing huge losses. Therefore, developing effective testing equipment and realizing tests that can effectively achieve the seepage evolution of cap rocks under different deep geological engineering conditions and various complex coupling effects is still one of the difficult problems that need to be urgently solved in the research of deep geological engineering construction.

[0003] In the construction of underground rock mass engineering, it is inevitable to encounter the interaction between seepage media (such as gas or liquid) and rock mass. The seepage media will cause the mechanical properties of the rock mass to deteriorate, and the deterioration process of the rock mass will also cause changes in seepage characteristics. That is to say, whether it is the deterioration of the mechanical behavior of the rock mass or the change of seepage characteristics, it may have extremely adverse effects on the project. Therefore, testing and evaluating the mechanical deterioration of fluid-solid coupling and the continuous evolution characteristics of seepage in rock mass is an important content of engineering construction research. However, how to effectively implement the mechanical deterioration and seepage evolution tests under fluid-solid coupling is a difficult problem to overcome in rock mechanics tests. Although the MTS815 rock mechanics testing machine is an advanced equipment for rock mechanics testing in this field, at present, it can only carry out the testing function of liquid media. It can neither realize the coupling test of gas and rock mass, nor can it realize the test of liquid or gas permeation media in a set of systems. 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, it is impossible to judge whether it enters the test module from the top or the bottom of the rock specimen, and the structure of this module is complex and cannot be cleaned, so that the confining pressure medium remains in the permeation module, resulting in the results measured by using this module not conforming to the actual situation, or even being wrong results. Moreover, during the testing process of the MTS815 rock mechanics test system, there are many operating valves, all of which need to be completed manually. If one valve is operated incorrectly, the test will be wasted, and even the equipment may be damaged. The operation of the test process is difficult, the process is complex, the cost is high, and it is time-consuming and laborious. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the MTS815 rock mechanics test system, and provide a fluid-solid coupling and seepage test system for surrounding rock under complex actions, which can realize the convenient interchange of liquid and gas media, and can timely detect the failure parts of the specimen protective layer during the test, so as to terminate the test in time.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A fluid-solid coupling and seepage test system for surrounding rock under complex actions includes 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 provide seepage medium or flushing medium for the system;

[0008] The seepage coupling module is a rock mechanics testing machine, and the rock mechanics testing machine includes a triaxial chamber. There is a seepage medium inlet at the top of the triaxial chamber and a seepage medium outlet at the bottom of the triaxial chamber;

[0009] The transient method testing module includes an upstream branch pipe, a first pressure sensor, a first pressure chamber, a downstream branch pipe, a second pressure sensor, a second pressure chamber, and a differential pressure sensor;

[0010] The inlet end of the upstream branch pipe is connected to the seepage medium outlet of the seepage medium supply module, and the outlet end of the upstream branch pipe is connected to the seepage medium inlet of the triaxial chamber; the first pressure chamber is connected to the upstream branch pipe through a first pressure branch, and the first pressure sensor is connected to the connection path between the upstream branch pipe and the first pressure chamber for detecting the pressure of the upstream branch pipe;

[0011] The inlet end of the downstream branch pipe is connected to the seepage medium outlet of the seepage medium supply module, and the outlet end of the downstream branch pipe is connected to the seepage medium outlet of the triaxial chamber; the second pressure chamber is connected to the downstream branch pipe through a second pressure branch, and the second pressure sensor is connected to the connection path between the downstream branch pipe and the second pressure chamber 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 pressure difference between the upstream branch pipe and the downstream branch pipe;

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

[0014] Furthermore, the steady-state method testing module includes a first flowmeter, a second flowmeter, and a first electromagnetic three-way valve;

[0015] The first flowmeter and the second flowmeter are respectively connected to the steady-state test main road through steady-state test branch pipes, and the first electromagnetic three-way valve is installed at the intersection of the steady-state test main road and the steady-state test branch pipes for selecting one of the first flowmeter and the second flowmeter to communicate with the steady-state test main road.

[0016] Furthermore, the first flowmeter is a soap bubble flowmeter.

[0017] Furthermore, a steady-state pressure reducing valve, a first steady-state stop valve, and a second steady-state stop valve are also arranged on the steady-state test main road;

[0018] The second steady-state stop valve and the steady-state pressure reducing valve are connected in parallel on the steady-state test main road and are connected in series with the first steady-state stop valve.

[0019] Furthermore, a heating and pressure stabilizing module is arranged between the seepage medium supply module and the transient method testing module;

[0020] The heating and pressure stabilizing module includes a first temperature sensor, a heater, a thirteenth stop valve, a voltage stabilizer, a second pressure reducing valve, and a second temperature sensor that are sequentially connected in series on the medium flow path.

[0021] Further, a drying module and a fourteenth stop valve are provided between the seepage medium supply module and the heating and pressure stabilizing module, and the drying module and the fourteenth stop valve are connected in parallel on the medium flow path;

[0022] The drying module includes a dryer. A fourth stop valve is provided between the inlet end of the dryer and the medium outlet of the seepage medium supply module, and a fifth stop valve is provided between the outlet end of the dryer and the medium inlet of the heating and pressure stabilizing module.

[0023] Further, a vacuum module is further included. The vacuum module includes a vacuum pump. The vacuum pump is connected to the communication path between the dryer and the seepage medium supply module through a vacuum branch pipe, and a third stop valve for controlling the closing of the vacuum branch pipe is provided on the vacuum branch pipe.

[0024] Further, the seepage medium supply module includes a medium supply main pipeline, a compressor, a pressure increasing valve, a three-way valve, a gas source, and a check valve;

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

[0026] The compressor is connected to the medium inlet of the medium supply main pipeline through a first medium supply branch pipe, and a pressure increasing valve is provided on the first medium supply branch pipe;

[0027] The gas source is connected to the medium inlet of the medium supply main pipeline through a second medium supply branch pipe, and a first stop valve is installed on the second medium supply branch pipe. The first stop valve is located between the gas source and the medium inlet of the medium supply main pipeline;

[0028] The gas source is connected to the first medium supply branch pipe through a three-way valve. The outlet of the pressure increasing valve is connected to the inlet of the three-way valve. One outlet of the three-way valve is connected to the inlet of the gas source, and the other outlet is connected to 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 to a first pressure sensor, a second pressure sensor, and a differential pressure sensor, and is used for real-time acquisition and storage of the parameters of each sensor.

[0030] Further, an automatic control module is further included. The automatic control module includes a controller. The input port of the controller is connected to the first pressure sensor and the second pressure sensor, and the output port of the controller is respectively connected to the 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.

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

[0032] (1) It realizes the test for both liquid seepage medium and gas medium, overcomes the problem of single seepage test function before, that is, a set of systems can only conduct tests for one medium; it realizes the coupling test of different media and rocks with the same set of devices, and solves the problem of inconsistent comparison test standards for the deterioration effects of different seepage media on rock masses.

[0033] (2) It realizes the continuous change test of the seepage evolution state of rocks from the intact state to the appearance of microcracks, then from the development of cracks to the formation of rock masses, and finally to the gradual deterioration of rock masses, from low permeability (10- 21 m 2 ) to high permeability (10- 13 m 2 ).

[0034] (3) The test operation is simple, the equipment or samples will not be damaged during the test, and the same test state can be tested multiple times during the test, which not only reduces the test cost but also ensures the reliability of the test results.

[0035] (4) It realizes the mutual feedback test of mechanics and different seepage media under the coupling of various construction and operation methods such as different excavations and mining during the process of simulating engineering construction and operation, reflects the influence of the in-situ environment state of deep underground where the rock mass is located, and overcomes the problem of the singularity of simulating engineering construction states and seepage coupling media before. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the gas-solid coupling and seepage test system for surrounding rocks under complex actions provided by the present invention;

[0037] Figure 2 It is a photo of the gypsum rock sample in the test example;

[0038] Figure 3 It is a distribution diagram of seepage measurement points of the gypsum rock sample during the permeability test in the test example;

[0039] Figure 4 It is a stress-strain curve diagram of the gypsum rock sample under four different confining pressure seepage conditions at room temperature in the test example;

[0040] Figure 5 It is a change relationship diagram of the permeability of the gypsum rock sample in each confining pressure group during the whole loading process in the test example;

[0041] Figure 6 It is a characteristic curve diagram of the change of the permeability of the gypsum rock with the loading stress under different confining pressures at room temperature in the test example.

[0042] In the figure, 1 - seepage medium supply module; 11 - compressor; 12 - booster valve; 13 - three-way valve; 14 - gas source; 15 - check valve; 16 - stop valve 1; 17 - stop valve 2; 18 - pressure reducing valve 1;

[0043] 2 - vacuum module; 21 - vacuum pump; 22 - vacuum branch pipe; 23 - stop valve 3;

[0044] 3 - drying module; 31 - dryer; 32 - stop valve 4; 33 - stop valve 5;

[0045] 4 - data acquisition and display module;

[0046] 5 - transient method testing module; 51 - upstream branch pipe; 52 - pressure sensor 1; 53 - pressure chamber 1; 54 - downstream branch pipe; 55 - pressure sensor 2; 56 - pressure chamber 2; 57 - differential pressure sensor; 58 - stop valve 6; 59 - stop valve 7; 510 - stop valve 8; 511 - stop valve 9; 512 - stop valve 10; 513 - stop valve 11; 514 - stop valve 12; 515 - safety valve 1; 516 - safety valve 2;

[0047] 6 - heating and pressure stabilizing module; 61 - temperature sensor 1; 62 - heater; 63 - voltage stabilizer; 64 - pressure reducing valve 2; 65 - temperature sensor 2; 66 - stop valve 13;

[0048] 7 - steady state method testing module; 71 - flowmeter 1; 72 - flowmeter 2; 73 - electromagnetic three-way valve 1; 74 - steady state pressure reducing valve; 75 - steady state stop valve 1; 76 - steady state stop valve 2; 77 - electromagnetic three-way valve 2;

[0049] 8 - seepage coupling module; 81 - triaxial cell; 82 - specimen;

[0050] 9 - stop valve 14. Detailed implementation manners

[0051] The present invention will be further described below in conjunction with Figure 1-6 the attached drawings, embodiments and test examples:

[0052] Embodiment

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

[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 includes a main medium supply pipeline, 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 main medium supply pipeline is a medium inlet, and the other end is a medium outlet; the compressor 11 is connected to the medium inlet of the main medium supply pipeline through a first medium supply branch pipe, and the check valve 15 is arranged at the medium outlet of the main medium supply pipeline; the booster valve 12 is arranged between the compressor 11 and the three-way valve 13.

[0055] In order to achieve diversification of the gas supply mode, the gas source 14 is arranged on the second medium supply branch pipe, 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 first stop valve 16.

[0056] A second stop valve 17 and a pressure reducing valve 18 for changing the gas supply mode are further arranged at the inlet end of the check valve 15, and the second stop valve 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 alone through the compressor 11, or supply gas alone through the gas source 14, or first supply gas from the compressor 11 to the gas source 14 and then supply the gas to the system. The gas supply mode can be selected according to the actual situation, and a backup can be formed between the gas supply modes.

[0058] The seepage coupling module 8 is a rock mechanics testing machine, and the rock mechanics testing machine includes a triaxial cell. The top end of the triaxial cell is provided with a seepage medium inlet, and the bottom end is provided with a seepage medium outlet. The reason for choosing the triaxial cell 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 testing module 5 includes an upstream branch pipe 51, a first pressure sensor 52, a first pressure chamber 53, a downstream branch pipe 54, a second pressure sensor 55, a second pressure chamber 56 and a differential pressure sensor 57.

[0060] Specifically, the inlet end of the upstream branch pipe 51 is connected to the seepage medium outlet of the seepage medium supply module 1 to form a medium circulation path, and the outlet end is connected to the seepage medium inlet of the triaxial chamber 81; the first pressure chamber 53 is connected to the upstream branch pipe 51 through the first pressure branch, and the first pressure sensor 52 is connected to the connection path between the upstream branch pipe 51 and the first pressure chamber 53 to detect the pressure of the upstream branch pipe 51. The inlet end of the downstream branch pipe 54 is connected to the seepage medium outlet of the seepage medium supply module 1 to form a medium circulation path, and the outlet end is connected to the seepage medium outlet of the triaxial chamber 81; the second pressure chamber 56 is connected to the downstream branch pipe 54 through the second pressure branch, and the second pressure sensor 55 is connected to the connection path between the upstream branch pipe 51 and the second pressure chamber 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 upstream branch pipe 51 and the downstream branch pipe 54 have a comparable volume and reduce the floor area, the first pressure chamber 53 and the second pressure chamber 56 in this module are symmetrically arranged, the first pressure sensor 52 and the second pressure sensor 55 are symmetrically arranged, and the upstream branch pipe 51 and the downstream branch pipe 54 are also symmetrically arranged.

[0062] Specifically, the maximum measuring ranges of the first pressure sensor 52 and the second pressure sensor 55 are both 10 MPa. The maximum measuring range of the differential pressure sensor 57 is 700 kPa, and the accuracy is 0.001 kPa. The first pressure chamber 53 and the second pressure chamber 56 are special high-pressure steel cylinders with a volume of 0.5 L and a maximum tolerable pressure of 40 MPa. In order to prevent the pressure oil in the triaxial chamber from 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 and thus damaging the system, a second safety valve 516 is provided on the upstream branch pipe 51, and a first safety valve 515 is provided on the downstream branch pipe 54.

[0063] In addition, in order to better control the medium circulation in the upstream branch pipe 51 and the downstream branch pipe 54, a tenth stop valve 512 is provided at the inlet end of the upstream branch pipe, and a ninth stop valve 511 and a sixth stop valve 58 are respectively provided at the outlet end of the upstream branch pipe 51 and the inlet end of the downstream branch pipe; an eighth stop valve 510 and a seventh stop valve 59 are respectively provided on the pipelines where the first pressure chamber 53 and the second pressure chamber 56 are located, and a twelfth stop valve 514 is provided 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 transient method principle. It calculates the permeability of the specimen by measuring the change in the pressure difference at both ends of the inlet and outlet of the specimen 82 and is applicable to low-permeability media.

[0065] To improve the measurement accuracy and applicable range, the present invention further provides a steady-state method test module 7, which is connected to the downstream branch pipe 54 and used to test the fluid flow rate at the bottom outlet of the triaxial chamber 81.

[0066] Specifically, the steady-state method test module 7 includes a first flowmeter 71, a second flowmeter 72 and a first electromagnetic three-way valve 73. The first flowmeter 71 and the second flowmeter 72 are respectively connected to the steady-state test main road through the steady-state test branch pipes. The first electromagnetic three-way valve 73 is installed at the intersection of the steady-state test main road and the steady-state test branch pipes and is used to select one of the first flowmeter 71 or the second flowmeter 72 to communicate with the steady-state test main road. When the seepage is of small flow rate and short time, the first flowmeter 71 with high sensitivity is selected. The first flowmeter 71 is a soap bubble flowmeter (SFFM). When the seepage is of large flow rate and long time, the second flowmeter 72 is selected, and the first flowmeter 71 uses a conventional flowmeter. In addition, a steady-state pressure reducing valve 74, a first steady-state stop valve 75 and a second steady-state stop valve 76 are also arranged on the steady-state test main road. The second steady-state stop valve 76 and the steady-state pressure reducing valve 74 are connected in parallel on the steady-state test main road and are connected in series with the first steady-state stop valve 75. In order to be connected to the equipment for detecting other properties of the test sample, a second electromagnetic three-way valve 77 can also be installed between the first electromagnetic three-way valve 73 and the steady-state test main road, and the second electromagnetic three-way valve 77 is used as an extension end.

[0067] It should be noted that the steady-state method test module 7 is designed based on the steady-state method principle. It can test the permeation flow rate of the fluid medium at the outlet end of the test sample 82 and is applicable to high-permeability media.

[0068] The present invention integrates the transient method test module and the steady-state method test module in a test system, which can measure both the permeation flow rate of low-permeability media and that of high-permeability media, and has a wide range of applications.

[0069] To increase the temperature of the seepage medium and ensure the system pressure stability at the same time, 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 includes a first temperature sensor 61, a heater 62, a thirteenth stop valve 66, a voltage stabilizer 63, a second pressure reducing valve 64 and a second temperature sensor 65 connected in series in the medium flow passage.

[0070] The advantages of such a design are as follows: The temperature of the seepage medium can be effectively increased by heating the seepage medium with the heater 62. When the air pressure is insufficient, the air pressure stability can be ensured by increasing the temperature of the seepage medium. And it is convenient to operate and has a simple structure.

[0071] To dry the seepage medium and the system pipeline and improve the accuracy of the test, a drying module 3 and a stop valve XIV 9 are provided between the seepage medium supply module 1 and the heating and pressure stabilizing module 6. The drying module 3 and the stop valve XIV 9 are connected in parallel on the medium flow path.

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

[0073] To detect the tightness of the entire system, a vacuum module 2 is also provided. The vacuum module 2 includes a vacuum pump 21. The vacuum pump 21 is connected to the communication path between the dryer 31 and the seepage medium supply module 1 through a vacuum branch pipe 22. A stop valve IV 23 for controlling the closing of the vacuum branch pipe 22 is provided on the vacuum branch pipe 22.

[0074] Furthermore, a data acquisition and display module 4 is also included. The data acquisition and display module 4 is connected to a pressure sensor I 52, a pressure sensor II 55, and a differential pressure sensor 57, and is used to collect and store the parameters of each sensor in real time.

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

[0076] For automatic control, to avoid manually opening each valve and 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 to the pressure sensor I 52 and the pressure sensor II 55, and the output port is respectively connected to 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 this system simple.

[0077] This test system is applicable not only to gas media but also to liquid media, realizing the coupling test of different media and rocks with the same set of devices, and solving the problem of non-uniform comparison test standards for the influence of different seepage media on the deterioration of rock masses. When it is a liquid medium, the liquid enters through the supply main pipeline via the compressor 11. At this time, only the gas source 14 and the drying module 3 need to be closed.

[0078] Test Example

[0079] This test example uses the fluid-solid coupling and seepage test system for surrounding rocks under complex actions in the embodiment to conduct gas-solid coupling and seepage tests on gypsum rock samples taken from the caprock of an underground gas storage to reveal the evolution law of the seepage mechanical behavior of gypsum rock under gas-solid coupling. The seepage medium during the test is nitrogen.

[0080] (1) Specimen preparation:

[0081] The gypsum rock is finely processed and polished indoors in accordance with the "Standard for Engineering Rock Mass Test Methods" and the "Rock Test Regulations for Water Conservancy and Hydropower Projects" to make standard specimens for indoor rock mechanics experiments. The specimen size is a diameter and height of Ф×H = 38×76 mm, and artificial infiltration holes with a diameter of 3 mm are prepared at both ends of the specimen. The specimen is as Figure 2 shown. The specimen is stored dry before the experiment.

[0082] (2) Experimental equipment

[0083] An MTS815 rock mechanics testing machine is used.

[0084] (3) Test method

[0085] (1) Install the gypsum rock specimen wrapped with heat shrink film in the triaxial chamber.

[0086] (2) Apply confining pressure to the gypsum rock specimen. At this time, the confining pressure comes from the pressure oil in the triaxial chamber. The pressure oil surrounds the gypsum rock specimen and exerts pressure on it. The confining pressure loading rate is 3 MPa / min. After loading to the target confining pressure value, start the seepage medium supply module 1 to apply air pressure to both ends of the gypsum rock specimen. The air pressure value is set to 1.5 MPa. After stabilizing the air pressure for 30 min, conduct the first seepage test, and regard the permeability at this point as the permeability before axial loading, that is, this point is the initial point.

[0087] (3) After the initial point permeability test is completed, conduct axial loading. At this time, the pressure comes from the triaxial test shaft and is loaded until the specimen deforms and fails. The axial loading rate is controlled by LVDT, and the control rate is 0.08 mm / min.

[0088] (4) During the loading process, the seepage test points are evenly distributed throughout the loading process. When reaching the specified stress point and the LVDT stabilizes the force, use the transient method to test the seepage parameters at this stress point.

[0089] During this process, try to ensure that there are more than 10 measurement points throughout the process of loading and damaging the gypsum rock specimen, including 1 seepage measurement point at the peak stress point and more than 3 seepage measurement points after the peak stress. The seepage measurement point distribution diagram is as Figure 3 shown.

[0090] (5) After completing the above steps, obtain the mechanical behavior data and seepage data parameters and conduct data processing.

[0091] It should be noted that there are four target confining pressure values in step (2), namely 5 MPa, 15 MPa, 25 MPa, and 35 MPa. That is, the above tests were conducted four times, and the test method was the same each time, with the only difference being the target confining pressure, in order to more accurately obtain the mechanical behavior characteristics and permeability data of the gypsum rock specimens.

[0092] Calculation of permeability K by transient method P The formula is as follows:

[0093] ΔP(t) = ΔP 0 e ωt ;

[0094]

[0095] In the formula, ΔP(t) refers to the pressure difference at both ends of the specimen at time t, with the unit of MPa; ΔP 0 is the initial pressure difference at both ends of the specimen, with the unit of MPa; t refers to the duration of one penetration, with the unit of s; μ refers to the dynamic viscosity coefficient of the permeating medium nitrogen, with the unit of Pa·s; η refers to the gas compression coefficient of nitrogen, with the unit of Pa -1 ; V 1 、V 2 refer to the volumes of the upper and lower gas pressure end buffer gas cylinders, with the unit of m 3 ; A refers to the cross-sectional area of the specimen, with the unit of m 2 ; L refers to the height of the specimen, with the unit of m.

[0096] (IV) Test results and analysis

[0097] As Figure 4 shown are the stress-strain curves of gypsum rock specimens under four different confining pressure penetration conditions at room temperature. It can be seen from the figure that the brittle failure and ductile failure characteristics of gypsum rock are relatively obvious.

[0098] Under the penetration condition, after axial loading, the deformation stages of the gypsum rock specimen are successively the crack compaction stage, the crack generation and propagation stage, the stress oscillation stage, the macroscopic crack penetration and failure stage, or the strain hardening stage. Under different confining pressures, the strength and deformation characteristics of the gypsum rock specimen are shown in Table 1:

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

[0100]

[0101]

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

[0103] As can be seen from Table 1, there is not much difference in the peak deviatoric stress between the conventional loading state and the seepage condition; the gas pressure weakening effect affects the residual strength of gypsum rock.

[0104] As Figure 5 shown is the variation relationship of the permeability of gypsum rock specimens in each confining pressure group during the whole loading process. It can be seen from the figure that the confining pressure inhibits the macroscopic level of permeability: the trends of the permeability curves under different confining pressures are different, but from the overall permeability level, as the confining pressure increases, the overall permeability level decreases.

[0105] As Figure 6 shown is the characteristic curve of the permeability of gypsum rock varying with the loading stress under different confining pressures at room temperature. It can be seen from the figure that the permeability mainly shows a change of first decreasing, then increasing, and finally tending to be stable or continuing to increase.

[0106] In summary, the present invention not only solves the test problem of the fluid-solid coupling mechanical interaction under different mining methods in the simulation of deep underground coal mine mining, but also solves the test problem of the mechanical deterioration process of surrounding rocks in the simulation of the operation of deep underground energy storage projects.

[0107] Those of ordinary skill in the art will realize that the embodiments described herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not deviate from the essence of the present invention according to these technical revelations disclosed by the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A fluid-solid coupling and seepage test system for surrounding rock under complex effects, characterized by: It comprises a seepage medium supply module (1), a seepage coupling module (8), a transient method test module (5) and a steady-state method test module (7); The seepage medium supply module 1 is used to provide the seepage medium to the system; The seepage coupling module (8) is a rock mechanics testing machine, comprising a triaxial chamber (81), a seepage medium inlet being arranged at the top end of the triaxial chamber (81), and a seepage medium outlet being arranged at the bottom end of the triaxial chamber (81); The transient method test module (5) comprises an upstream branch pipe (51), a pressure sensor 1 (52), a pressure chamber 1 (53), a downstream branch pipe (54), a pressure sensor 2 (55), a pressure chamber 2 (56) and a differential pressure sensor (57); The inlet end of the upstream branch pipe (51) is connected to the seepage medium outlet of the seepage medium supply module (1), and the outlet end of the upstream branch pipe (51) is connected to the seepage medium inlet of the triaxial chamber (81); the pressure chamber 1 (53) is connected to the upstream branch pipe (51) via the pressure branch 1, and the pressure sensor 1 (52) is connected to the connection path between the upstream branch pipe (51) and the pressure chamber 1 (53) for detecting the pressure of the upstream branch pipe (51); The inlet end of the downstream branch pipe (54) is connected to the seepage medium outlet of the seepage medium supply module (1), and the outlet end of the downstream branch pipe (54) is connected to the seepage medium outlet of the triaxial chamber (81); the second pressure chamber (56) is connected to the downstream branch pipe (54) through the second pressure branch; the second pressure sensor (55) is connected to the connection path between the downstream branch pipe (54) and the second pressure chamber (56) for detecting the pressure of the downstream branch pipe (54); The pressure difference sensor (57) is arranged between the upstream branch pipe (51) and the downstream branch pipe (54) and is used to detect the pressure difference between the upstream branch pipe (51) and the downstream branch pipe (54); The steady-state method test module (7) is connected to the downstream branch pipe (54) and is used to test the fluid flow rate at the seepage medium outlet of the triaxial chamber (81).

2. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 1, characterized in that: The steady-state method test module (7) comprises a flow meter 1 (71), a flow meter 2 (72) and an electromagnetic three-way valve 1 (73); The flowmeter 1 (71) and the flowmeter 2 (72) are respectively connected to the steady-state test main line through the steady-state test branch pipe, and the electromagnetic three-way valve 1 (73) is installed at the intersection of the steady-state test main line and the steady-state test branch pipe, and is used to select one of the flowmeter 1 (71) and the flowmeter 2 (72) to be connected to the steady-state test main line.

3. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 2, characterized in that: The flow meter 1 (71) is a soap bubble flow meter.

4. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 3, characterized in that: A steady-state pressure reducing valve (74), a steady-state stop valve 1 (75) and a steady-state stop valve 2 (76) are also provided on the steady-state test main circuit; The second steady-state stop valve (76) and the steady-state pressure reducing valve (74) are connected in parallel on the steady-state test main circuit, and are connected in series with the first steady-state stop valve (75).

5. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as described in any one of claims 1 to 4, characterized in that: A heating and voltage stabilization module (6) is provided 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 1 (61), a heater (62), a stop valve 13 (66), a pressure stabilizer (63), a pressure reducing valve 2 (64) and a temperature sensor 2 (65) which are sequentially connected in series on a medium flow passage.

6. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 5, characterized in that: A drying module (3) and a stop valve 14 (9) are provided between the seepage medium supply module (1) and the heating and pressure stabilizing module (6), and the drying module (3) and the stop valve 14 (9) are connected in parallel to 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 heating and pressure stabilizing module (6).

7. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 6, characterized in that: The invention also comprises a vacuum module (2), wherein the vacuum module (2) comprises a vacuum pump (21), wherein the vacuum pump (21) is connected to a communication passage between the dryer (31) and the seepage medium supply module (1) via a vacuum branch pipe (22), and a stop valve (23) for controlling the closing of the vacuum branch pipe (22) is arranged on the vacuum branch pipe (22).

8. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 1, characterized in that: The seepage medium supply module (1) comprises a medium supply main line, a compressor (11), a booster valve (12), a three-way valve (13), an air source (14) and a one-way valve (15); One end of the main medium supply line is a medium inlet, and the other end is a medium outlet; the one-way valve (15) is arranged at the medium outlet of the main medium supply line; The compressor (11) is connected to the medium inlet of the medium supply main line through a medium supply branch pipe 1, and a boost valve (12) is provided on the medium supply branch pipe 1; The gas source (14) is connected to the medium inlet of the medium supply main line through the medium supply branch pipe 2, and a stop valve 1 (16) is installed on the medium supply branch pipe 2, and the stop valve 1 (16) is located between the gas source (14) and the medium inlet of the medium supply main line; The gas source (14) is connected to the medium supply branch pipe 1 through a three-way valve (13), the outlet of the boost valve (12) is connected to the inlet of the three-way valve (13), one of the outlets of the three-way valve (13) is connected to the inlet of the gas source (14), and the other outlet is connected to the inlet of the medium supply main pipe.

9. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 1, characterized in that: It comprises a data acquisition and display module (4), which is connected to a pressure sensor 1 (52), a pressure sensor 2 (55) and a pressure difference sensor (57) and is used for real-time acquisition and storage of parameters of each sensor.

10. The fluid-solid coupling and permeability testing system for surrounding rock under complex action as claimed in claim 1, characterized in that: The system also includes an automatic control module, which includes a controller, wherein the input port of the controller is connected to a pressure sensor 1 (52) and a pressure sensor 2 (55), and the output port of the controller is respectively connected to valves for controlling the opening and closing of a seepage medium supply module (1), a transient method test module (5), and a steady-state method test module (7).

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