A multiphase rock triaxial compression-shear seepage test system and test method

Abstract

The present invention relates to a multiphase rock triaxial compression and shear seepage test system and test method, comprising a triaxial compression and shear test module and a loading control and acquisition module. The triaxial compression and shear test module uses a detachably connected upper cylinder and a lower cylinder to form a shear seepage chamber, and pushes the lower cylinder and the upper cylinder to move relative to each other through a slide rail device and a shear oil cylinder, transmitting independent shear pressure to the sample, using a loading and control module to provide independent axial, annular and shear pressures, and using an air pressure module to provide fluid pressure, ultimately overcoming the technical difficulties of multi-field coupled seepage testing of multiphase medium rock mass under the combined action of triaxial compression and shear with applied confining pressure, while having transient and steady-state test conditions, realizing seepage testing of multiphase medium rock mass from ultra-low permeability to high permeability, with simple operation, high measurement accuracy and accurate data acquisition.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and in particular to a multiphase rock triaxial compression-shear seepage test system and test method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The construction and operation environment of deep underground projects, such as dam foundations, tunnel excavation, mine shafts, radioactive waste storage, carbon dioxide geological storage, unconventional energy oil and gas extraction, geothermal resource development and other facilities, is often under the complex coupling of multiple fields and phases such as high ground stress, high permeability pressure and high temperature. The environment is harsh, and the engineering facilities are subjected to both compressive stress and shear stress. A large number of cracks develop on the surface and inside the rock mass, providing channels for fluid migration, which ultimately leads to the frequent occurrence of engineering disasters.

[0004] To understand and manage the engineering hazards encountered in deep rock mass engineering, laboratory experiments can be used to study the various mechanical properties of rock. The impact of the complex stress state of deep multiphase rock masses on structural stability is common in all types of rock mass engineering. Therefore, conducting indoor triaxial rock compression-shear-seepage coupled experiments is an effective way to theoretically describe the rock mass fracture process and permeability characteristics in engineering, and to explore the evolution, internal mechanisms, and influencing factors of rock compression-shear seepage.

[0005] The test devices or systems in the existing technology all meet the requirements for studying and testing the seepage laws of rocks under conventional triaxial conditions, and can also reflect the stress-seepage coupling characteristics of deep rock masses. However, deep rock masses often undergo simultaneous compressive stress and shear stress under triaxial stress conditions. The existing devices are difficult to test and analyze the multi-field coupled compressive-shear seepage laws. Summary of the Invention

[0006] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a multiphase rock triaxial compression and shear seepage test system and test method, which overcomes the technical difficulties of multi-field coupled seepage test of multiphase medium rock under the combined action of triaxial compression and shear. The seepage characteristics of multiphase rock can be tested using transient method and steady-state method under the conditions of triaxial compression and shear multi-field coupling under the application of confining pressure, thereby realizing the seepage test of multiphase medium rock from ultra-low permeability to high permeability.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A first aspect of the present invention provides a multiphase rock triaxial compression-shear seepage test system, comprising:

[0009] The triaxial compression-shear test module includes an axial compression cylinder, a fluid self-balancing chamber, a shear seepage chamber, and a shear slide device arranged from top to bottom with their axes coinciding;

[0010] The shear seepage chamber includes a detachably connected upper cylinder and a lower cylinder, which form a sample placement area inside after the two are connected; the axial pressure cylinder is connected to the self-balancing piston rod in the fluid self-balancing chamber, and the bottom of the self-balancing piston rod is toward the top of the sample placement area, which is used to provide axial pressure to the sample placement area; the inner walls of the upper cylinder and the lower cylinder form an annular pressure loading chamber, and the annular pressure loading chamber provides annular pressure through the loading control and acquisition module; the top of the upper cylinder is connected to the slider, and the lower cylinder is connected to the shear slide device, the slider is slidably connected to the shear slide device, and the shear cylinder is connected to the side of the lower cylinder, and the shear cylinder pushes the lower cylinder and the upper cylinder to move relative to each other to transmit shear pressure to the sample placement area;

[0011] The loading control and acquisition module uses the loading and unloading combination pump to provide axial pressure, annular pressure and shear pressure to the triaxial compression and shear test module through the pipeline, and uses the air pressure module to provide fluid pressure to the triaxial compression and shear test module through the pipeline to obtain the test data of the sample.

[0012] The axial pressure cylinder includes an axial pressure piston rod that moves along the axis of the cylinder barrel, and the fluid self-balancing chamber includes a self-balancing piston rod that moves along the axis of the cylinder barrel. The axial pressure piston rod and the self-balancing piston rod are connected and fixed by pins; the depression at the bottom of the axial pressure piston rod matches the protrusion at the top of the self-balancing piston rod, and the cross-sectional area of ​​the axial pressure piston rod and the self-balancing piston rod are the same.

[0013] A flow channel is provided inside the self-balancing piston rod, which connects the interior of the cylinder of the fluid self-balancing chamber, the sample placement area, and the loading control and acquisition module; a porous contact surface is provided at the bottom of the self-balancing piston rod, which is used to contact the specimen in the shear seepage chamber.

[0014] The bottom of the lower cylinder is connected to the bottom piston through a bottom flange.

[0015] The shearing slide device includes a guide rail, which is slidably connected to the slider. The bottom of the guide rail is connected to the lower cylinder after passing through the upper cylinder through a connecting bolt rod. The area of ​​the upper cylinder to accommodate the connecting bolt rod is provided with a strip hole. When the lower cylinder is pushed by the shear cylinder to move along the guide rail, the connecting bolt rod moves along the strip hole.

[0016] The loading control and acquisition module includes a loading and unloading combination pump and a circulating air injection pump. The loading and unloading combination pump is connected to the axial pressure cylinder, the shear cylinder and the two annular pressure fluid interfaces opened on the lower cylinder through pipelines. The circulating air injection pump is connected to the fluid self-balancing chamber and the bottom piston through pipelines.

[0017] The circulating gas injection pump and the gas source are connected in parallel to share a set of gas pipelines to form a gas pressurization module. A control valve and a gas pressure sensor are provided on the pipeline between the two, and a control valve is provided on the pipelines at the outlets of both.

[0018] The outlet pipe of the gas pressurization module is equipped with a pressure reducing valve. The pipe connecting the gas pressurization module to the fluid self-balancing chamber is equipped with a control valve, a vacuum pump, an upstream standard chamber, and a gas pressure sensor. The fluid self-balancing chamber is connected to the sample placement area. The pipe connecting the gas pressurization module to the bottom piston is equipped with a control valve, a gas pressure sensor, and a downstream standard chamber. The system also features a temperature sensor, a displacement sensor, and a data acquisition and monitoring console, which together enable real-time monitoring of system parameters such as pressure, deformation, flow rate, and temperature under transient and steady-state permeability test conditions.

[0019] A second aspect of the present invention provides a test method for implementing a triaxial compression-shear seepage test of multiphase rock based on the above system, comprising the following steps:

[0020] (1) Place the sample in the sample placement area and connect and fix the upper cylinder, lower cylinder, bottom flange and bottom piston of the shear seepage chamber in sequence;

[0021] (2) Start the gas source and circulating gas injection pump, inject high-pressure gas, and perform a sealing check;

[0022] (3) After the sealing meets the requirements, the vacuum pump is started to vacuum degas the shear seepage chamber and the seepage pipeline system;

[0023] (4) The loading and unloading combination pump is started to provide the set axial pressure and annular pressure to the sample according to the test requirements; the gas source and circulating gas injection pump are started, and the gas is injected into the sample surface inside the shear seepage chamber through the upstream standard chamber using the control valve according to the test requirements. The gas flows through the sample into the downstream standard chamber. After a period of time, the upstream and downstream air pressures reach equilibrium. The air pressure data is obtained during the upstream and downstream air pressure equilibrium process at both ends of the sample to obtain the sample permeability under the initial conditions;

[0024] (5) The loading and unloading combination pump is started to provide shear pressure to the shear cylinder and load it to the set value; the gas pressurization module is started to increase the gas pulse upstream, and the control valve is used to keep the upstream and downstream gas pressures balanced according to the test requirements. At this stage, the pulse attenuation seepage test is completed; the upstream and downstream gas pressure changes and seepage time during the seepage process are recorded to obtain the sample permeability under shear loading conditions;

[0025] (6) Repeat step (5) to increase the gas pressure pulse on the sample until the set pressure level is reached, and obtain the gas seepage law under the shear pressure condition;

[0026] (7) According to the test requirements, repeat steps (5)-(6) under each set shear loading pressure condition to obtain the influence of shear pressure change on the seepage of the sample.

[0027] Compared with the existing technology, one or more of the above technical solutions have the following beneficial effects:

[0028] The shear seepage chamber and the shear slide device are dynamically mounted and fixed. Through lateral shear loading, the triaxial shear seepage test conditions of complete multiphase medium rock under applied confining pressure are realized. The seepage law under the conditions of combined compression and shear and multi-field coupling complex stress state can be accurately measured.

[0029] The circulating gas injection pump is connected in parallel with the gas source pipeline, which can simultaneously monitor the flow rate and flow data under the premise of gas pressurization. It has two types of permeability measurement methods: transient method and steady-state method, and realizes the multiphase medium rock test from ultra-low permeability to high permeability, greatly shortening the measurement time and improving the permeability measurement accuracy.

[0030] The fluid self-balancing chamber and the shear seepage chamber form an integrated combined seal, which organically combines the high-pressure gas pressure and the annular pressure seal, greatly simplifying the sample sealing operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 It is a schematic structural diagram of a multiphase rock triaxial compression-shear seepage test system provided by one or more of the present inventions;

[0033] Figure 2 It is a schematic diagram of a three-dimensional combined cross-sectional structure of a triaxial shear seepage chamber provided by one or more of the present inventions;

[0034] Figure 3 It is a schematic diagram of the stress structure of a multiphase rock sample provided by one or more of the present inventions;

[0035] Figure 4 is a schematic diagram of the installation process of the test piece during one or more test processes provided by the present invention;

[0036] In the figure: 1-1 axial pressure cylinder; 1-2 pin connection; 1-3 fixing bolt rod; 1-4 fluid self-balancing chamber; 1-5 guide rail; 1-6 slider; 1-7 connecting bolt rod; 1-8 porous contact surface; 1-9 upper cylinder structure; 1-10 lower cylinder structure; 1-11 annular pressure loading chamber; 1-12 integrated annular pressure transmission rubber sleeve; 1-13 sealing groove; 1-14 annular pressure fluid interface; 1-15 test specimen; 1-16 shear cylinder; 1-17 bottom flange; 1-18 bottom piston; 2-1 high-precision pressure loading and unloading combination pump; 2-2 high-precision double-cylinder circulating air injection pump; 2-3 acquisition and monitoring console; 2-4 gas source; 2-5 control valve; 2-6 pressure reducing valve; 2-7 vacuum pump; 2-8 upstream standard chamber; 2-9 gas pressure sensor; 2-10 downstream standard chamber; 2-11 displacement sensor; 2-12 temperature sensor. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] As described in the background technology, the test devices or systems in the existing technology meet the requirements for research and testing of seepage laws under conventional triaxial conditions of rocks, such as the thermal-fluid-solid coupled triaxial servo seepage device for gas-containing coal independently developed by Xu Jiang et al., the coal rock triaxial creep-seepage-adsorption-desorption experimental device developed by Wang Dengke et al., and the rock stress-seepage coupled true triaxial test system developed by Yin Liming et al. These devices or systems meet the requirements for research on seepage laws under conventional triaxial conditions of rocks, and can also reflect the stress-seepage coupling characteristics of deep rock masses. However, deep rock masses often bear compressive stress and shear stress at the same time under triaxial stress conditions. It is difficult for existing devices to conduct experiments and tests on multi-field coupled compression-shear seepage laws.

[0041] The Chinese patent application number 201910023638.X discloses a device and method for direct shear-seepage testing of rocks. The device can use a triaxial testing instrument to perform shear-seepage tests on prefabricated jointed rock specimens, simulating the shear failure of rocks under natural conditions. However, the device is mainly based on the modification of the specimen, which destroys the natural structure of the original rock. The measured seepage direction coincides with the shear surface direction, and the permeability properties on the shear surface are mainly measured, ignoring the influence of other pores and cracks inside the rock on the permeability. It has certain deviations and limitations. The device is also unable to meet the reaction force balance of the gas on the axially loaded piston rod, which is easy to cause test errors. The connection position is sealed by means of an adhesive sealing device, which is a cumbersome process, and it is impossible to measure the circumferential deformation of the specimen, and the data collection is not accurate enough.

[0042] Chinese patent application number 201810223211.X discloses a true triaxial rock shear seepage test apparatus that enables real-time testing of shear failure and seepage in rock specimens under triaxial stress, ensuring seepage in the shear direction during rock shear. However, the fluid seepage direction of this apparatus aligns with the shear plane, allowing only the permeability characteristics of the shear plane to be measured. Furthermore, the use of a rubber sleeve holder to seal the specimen is cumbersome, making specimen replacement difficult. Under high pressure, sealing risks may exist, resulting in inaccurate data collection.

[0043] Chinese patent application number 202110274901.X discloses a test device and test method for shear seepage testing. It can test water permeability using both transient and steady-state methods, and can simultaneously measure the permeability of rock samples at the initial and later stages of loading. However, the device can only conduct seepage tests under shear loading conditions, and cannot meet the stress state requirements of simultaneous compression and shear under triaxial loading conditions. It can only measure water permeability, and the sealing form cannot meet the requirements for gas permeability determination. The sealing method using a sealing strip group is relatively cumbersome, and the test operation is relatively complicated.

[0044] In the June 2008 issue of the Chinese Journal of Rock Mechanics and Engineering, Volume 27, Issue 6, Xia Caichu, Wang Wei, Wang Xiaorou, et al. published an article titled "Development of a Rock Joint Shear-Seepage Coupling Test System" (pp. 1285-1291). This paper describes a self-developed rock joint shear-seepage coupling test system capable of studying the stress-seepage coupling characteristics of joints under steady-state and transient seepage water pressure. However, the device can only load normal and tangential forces and cannot simulate the compressive-shear seepage characteristics under triaxial stress conditions. Furthermore, the designed seepage shear cell can only effectively isolate high-pressure seepage water but cannot guarantee a gas seal, making it unsuitable for gas seepage tests.

[0045] In the May 2015 issue of the Chinese Journal of Rock Mechanics and Engineering, Vol. 34, Supplement 1, Xu Jiang, Liu Yixin, Yin Guangzhi, et al. published a paper titled "Development of a Coal Rock Shear-Seepage Coupling Test Device" (pp. 2987–2995). This device can be used to study the shear failure mechanism and shear-seepage coupling characteristics of coal and rock masses under the combined effects of compressive shear stress and hydraulic head pressure. However, this device can only apply normal and shear loads, making it incapable of simulating the compressive-shear seepage characteristics under triaxial stress conditions. Furthermore, the sample sealing method is complex, making it inconvenient for testing.

[0046] In the April 2018 issue of Mining Safety and Environmental Protection, Vol. 45, No. 2, Wang Pengfei, Wang Gang, Li Wenxin, et al. published "Development and Application of a True Triaxial Shear Seepage Test System" (pp. 40-43). This system can conduct true triaxial shear failure seepage tests under three-dimensional unequal stress conditions. The system places a steel plate and nitrile rubber at the bottom of the axial direction, creating a height difference during loading to induce shear failure in the coal. However, because the seepage direction of this system coincides with the shear direction, it cannot measure the seepage characteristics within intact rock, nor can it measure circumferential deformation. The sample loading and sealing methods are complex, making testing inconvenient.

[0047] The devices or systems provided in the above-mentioned prior art are mostly for seepage testing of rock joint surfaces, and the seepage direction is mostly consistent with the shear surface direction. However, it is still impossible to accurately measure the seepage characteristics of intact porous multiphase medium rocks under compression and shear conditions.

[0048] Secondly, since it is difficult to solve the sealing problem of multiphase rock specimens under the simultaneous action of confining pressure and compression and shear, the current instruments are unable to realize the multi-field coupled complex stress state under the combined action of compression and shear of multiphase medium rock. Only uniaxial compression and shear tests and triaxial seepage tests of multiphase medium rock can be carried out. Triaxial compression and shear seepage tests under confining pressure cannot be realized.

[0049] Furthermore, current testing instruments only offer a single method for measuring permeability, capable of performing transient or steady-state permeability tests. This makes it impossible to test multiphase rock masses ranging from ultra-low to high permeabilities. This results in long measurement times and the potential for significant measurement errors.

[0050] Therefore, the following embodiment provides a multiphase rock triaxial compression and shear seepage test system and test method, which overcomes the technical difficulties of multi-field coupled seepage testing of multiphase medium rock under the combined action of triaxial compression and shear. The seepage characteristics of multiphase rock can be tested using transient and steady-state methods under the conditions of triaxial compression and shear multi-field coupling under applied confining pressure, thereby realizing seepage testing of multiphase medium rock masses with a range of ultra-low permeability to high permeability.

[0051] Example 1:

[0052] like Figures 1-4As shown, a multiphase rock triaxial compression-shear seepage test system includes:

[0053] The triaxial compression-shear test module includes an axial compression cylinder, a fluid self-balancing chamber, a shear seepage chamber, and a shear slide device arranged from top to bottom with their axes coinciding;

[0054] The shear seepage chamber includes a detachably connected upper cylinder and a lower cylinder, which form a sample placement area when connected; the axial pressure cylinder is connected to the self-balancing piston rod in the fluid self-balancing chamber, and the bottom of the self-balancing piston rod is toward the top of the sample placement area, which is used to provide axial pressure to the sample placement area; the inner walls of the upper cylinder and the lower cylinder form an annular pressure loading chamber, and the annular pressure loading chamber provides annular pressure through the loading control and acquisition module; the top of the upper cylinder is connected to the slider, and the lower cylinder is connected to the shear slide device, the slider is slidably connected to the shear slide device, and the shear cylinder is connected to the side of the lower cylinder, and the shear cylinder pushes the lower cylinder and the upper cylinder to slide relative to each other to transmit shear pressure to the sample placement area; the lower cylinder is connected to the bottom flange and the bottom piston;

[0055] The loading control and acquisition module uses the loading and unloading combination pump to provide axial pressure, annular pressure and shear pressure to the triaxial compression and shear test module through the pipeline, and uses the air pressure module to provide fluid pressure to the triaxial compression and shear test module through the pipeline to obtain the test data of the sample.

[0056] Specifically:

[0057] like Figure 1-3 As shown in the figure, the triaxial compression-shear test module is the core part of the system, which is used to provide a closed space for triaxial loading of rock specimens, a shear loading test space, and a seepage test space; the loading control and acquisition module is used to provide the system's axial pressure, annular pressure, shear pressure, and fluid pressure loading, and real-time monitoring of parameters such as pressure, deformation, flow, and temperature in the seepage system.

[0058] The triaxial compression-shear test module includes an axial compression cylinder 1-1, a fluid self-balancing chamber 1-4, a shear seepage chamber, a shear slide device and a shear cylinder 1-16 arranged from top to bottom.

[0059] The axial pressure cylinder 1-1 includes a cylinder head, a cylinder barrel and an axial pressure piston rod. The bottom of the piston rod adopts an upward concave structure. When pressurized, the axial pressure is loaded by injecting high-pressure fluid to push the piston rod.

[0060] The fluid self-balancing chamber 1-4 includes a cylinder head, a cylinder barrel and a self-balancing piston rod. The top of the piston rod is designed as an upward convex structure. The upper surface area of ​​the piston rod is the same as the area of ​​the bottom of the piston rod. The force acting on the upper surface of the piston is equal to the force acting on the bottom of the piston rod, but in opposite directions, thereby achieving self-balancing of the axial fluid pressure.

[0061] In this embodiment, a flow channel is provided within the self-balancing piston rod, connecting the loading control and collection modules, the sample placement area, and the interior of the cylinder. A porous contact surface 1-8 is provided at the bottom of the piston rod for contact with the specimen 1-15 within the shear seepage chamber.

[0062] In this embodiment, the cylinder barrel of the axial pressure cylinder 1-1 and the cylinder head of the fluid self-balancing chamber 1-4 are both designed with an extended structure, and the two are connected and fixed by fasteners. In this embodiment, the connection is fixed by a fixing bolt rod 1-3; the bottom of the axial pressure piston rod is designed as a concave structure with holes on both sides, and the top of the self-balancing piston rod is designed as a convex structure with holes on both sides, and the two are fixed by a pin connection 1-2.

[0063] The shear cylinder 1-16 comprises a cylinder head, a cylinder barrel, and a shear piston rod. When pressurized, high-pressure fluid is injected to push the piston rod, thereby applying shear pressure. In this embodiment, the shear cylinder 1-16 is laterally mounted on the upper cylinder structure 1-9 of the shear seepage chamber, and the shear piston rod is located in the middle of the same side of the lower cylinder structure 1-10 of the shear seepage chamber, enabling relative shear sliding between the upper and lower cylinder structures of the shear seepage chamber.

[0064] The shear seepage chamber is interrupted in the middle, including the upper cylinder structure 1-9, the lower cylinder structure 1-10, the bottom flange 1-17 and the bottom piston 1-18, which are used for triaxial loading and shear loading of the sample; sealing grooves are respectively opened at the bottom of the upper cylinder structure 1-9 and the top of the lower cylinder structure 1-10 to realize dynamic surface sealing, and the two together form an annular pressure loading chamber 1-11. The interior of the annular pressure loading chamber 1-11 is the sample 1-15 placement area, which is designed as an up and down staggered structure for assisting shear loading and ensuring that the shear pressure is quickly loaded to the sample surface; the lower cylinder structure 1-10 of the shear seepage chamber opens two annular pressure fluid interfaces 1-14 for adding and unloading annular pressure; the bottom piston 1-18 passes through the bottom flange 1-17 and maintains a static seal together with the lower cylinder structure 1-10, and the three are fixedly connected by bolts.

[0065] In this embodiment, annular grooves are provided at the top of the upper cylinder structure 1-9 and the bottom of the lower cylinder structure 1-10, which are used to install and fix the integrated annular pressure transfer rubber sleeve 1-12 inside the annular pressure loading chamber 1-11, to ensure that the high-pressure gas inside the sample is isolated from the high-pressure fluid in the annular pressure loading chamber 1-11, so that the annular pressure is transmitted to the surface of the sample 1-15; a fluid outflow pipe is opened inside the bottom piston 1-18, which is connected to the annular pressure loading chamber 1-11.

[0066] The shear slide device includes a slider 1-6, a guide rail 1-5, and a connecting bolt rod 1-7, which are used to assist the shear loading and sliding of the lower cylinder structure. The slider 1-6 is fixed to the top of the shear seepage chamber upper cylinder structure 1-9 by bolts; the guide rail 1-5 is mounted on the slider 1-6, and the guide rail 1-5, the shear seepage chamber upper cylinder structure 1-9, and the lower cylinder structure 1-10 are provided with bolt holes. The three are fixed by the connecting bolt rod 1-7. The upper cylinder structure 1-9 of the shear seepage chamber has a strip hole at the same position to provide displacement margin for shear sliding, ensuring that the upper cylinder structure 1-9 is fixed during the shear loading process. Under the action of shear pressure, the lower cylinder structure 1-10 drives the slide rail through the connecting bolt rod 1-7 to achieve sliding in the shear direction.

[0067] like Figure 1-3 As shown, the loading control and acquisition module includes a loading and unloading combination pump and a circulating air injection pump, which in this embodiment are a high-precision pressure loading and unloading combination pump 2-1 and a high-precision double-cylinder circulating air injection pump 2-2 respectively. The loading and unloading combination pump is connected to the axial pressure cylinder 1-1, the shear cylinder 1-16 and the two annular pressure fluid interfaces 1-14 opened in the lower cylinder structure 1-10 through pipelines, and the circulating air injection pump is connected to the fluid self-balancing chamber 1-4 and the bottom piston 1-18 through pipelines.

[0068] The circulating gas injection pump and the gas source 2-4 are connected in parallel to share a set of gas pipelines to form a gas pressurization module. A control valve 2-5 and a gas pressure sensor 2-9 are provided on the pipeline between the two, and a control valve 2-5 is provided on the pipelines at the outlets of both.

[0069] A pressure reducing valve 2-6 is provided on the outlet pipe of the gas pressurizing module; a control valve 2-5, a vacuum pump 2-7, an upstream standard chamber 2-8 and a gas pressure sensor 2-9 are respectively provided on the pipe connecting the gas pressurizing module and the fluid self-balancing chamber 1-4, and the fluid self-balancing chamber 1-4 is connected to the sample placement area; a control valve 2-5, a gas pressure sensor 2-9 and a downstream standard chamber 2-10 are respectively provided on the pipe connecting the gas pressurizing module and the bottom piston 1-18.

[0070] Gas source 2-4 provides various high-pressure gases for testing; control valve 2-5 and pressure reducing valve 2-6 control pipeline pressure section by section; vacuum pump 2-7 evacuates the seepage pipeline system and the specimen placement area; a high-precision dual-cylinder circulating gas injection pump 2-2, in conjunction with upstream standard chamber 2-8, downstream standard chamber 2-10, and control valves, achieves the test conditions for transient and steady-state permeability determination. The data acquisition and monitoring console 2-3, operating simultaneously with various sensors, enables real-time dynamic monitoring and control of test system data such as gas pressure, axial displacement, circumferential deformation, and temperature.

[0071] It also has a temperature sensor 2-12 for obtaining the ambient temperature of the test site, and the acquisition monitoring console 2-3 is connected with each sensor, valve, loading and unloading combination pump and gas pressurization module to obtain the information collected by each component and issue control instructions to each component.

[0072] In the above structure, the specimen placement area is located in the shear seepage chamber, which is composed of two annular pressure loading chambers arranged upper and lower. The upper annular pressure loading chamber is fixed, and the lower annular pressure loading chamber is pushed by the shear cylinder and slides relative to the upper annular pressure loading chamber to achieve shearing of the specimen.

[0073] The system is equipped with a shear seepage chamber and a shear slide device with dynamic mounting and fixing. Through lateral shear loading, it realizes the triaxial shear seepage test conditions of complete multiphase medium rock under applied confining pressure, and can accurately measure the seepage law under the conditions of combined compression and shear and complex stress states of multi-field coupling.

[0074] The system connects a high-precision circulating gas injection pump in parallel with the gas source pipeline, which can simultaneously monitor flow velocity and flow data under the premise of gas pressurization. It has two types of permeability measurement methods: transient method and steady-state method, and realizes multiphase medium rock testing from ultra-low permeability to high permeability, greatly shortening the measurement time and improving the permeability measurement accuracy.

[0075] The system is equipped with an integrated combined sealing structure of a fluid self-balancing chamber and a shear seepage chamber, which realizes an integrated sample sealing condition, organically combines high-pressure gas pressure with annular pressure sealing, and greatly simplifies the sample sealing operation.

[0076] Example 2:

[0077] Based on the method of conducting the test on the multiphase rock triaxial compression-shear seepage test system given in Example 1, the permeability of coal rocks with different fluids under triaxial compression-shear stress conditions with confining pressure can be measured as an example. Figure 1-4 As shown, the following steps are included:

[0078] (1) The multiphase rock triaxial compression-shear seepage test instrument was assembled and the connections between the modules were completed;

[0079] (2) Install the integrated annular pressure transfer rubber sleeve 1-12, place the sample in it, and connect and fix the upper cylinder structure 1-9, the lower cylinder structure 1-10, the bottom flange 1-17 and the bottom piston 1-18 of the shear seepage chamber in sequence;

[0080] (3) Open the gas source 2-4 and the high-precision double-cylinder circulating gas injection pump 2-2, inject high-pressure gas, adjust the control valve 2-5 in the pipeline, and use a leak detection liquid to check the sealing;

[0081] (4) After the air tightness meets the requirements, adjust the pipeline control valve, turn on the vacuum pump 2-7, and vacuum degas the shear seepage chamber and the seepage pipeline system;

[0082] (5) Start the high-precision pressure loading and unloading combination pump 2-1 to provide axial pressure and confining pressure to the system and stabilize the pressure at a certain value; open the gas source 2-4, start the high-precision double-cylinder circulating gas injection pump 2-2, open the pressure reducing valve 2-6, adjust the control valve, and inject the gas into the surface of the rock sample inside the shear seepage chamber through the upstream standard chamber 2-8. After a period of time, the gas passes through the sample and flows from the gas outlet channel into the downstream standard chamber 2-10. During the test, ensure that the gas pressure is less than the confining pressure;

[0083] (6) After a period of stabilization, the upstream air pressure gradually decreases, the downstream air pressure gradually increases, and finally reaches equilibrium. During the stabilization of the upstream and downstream air pressures at both ends of the sample, the air pressure data is collected, the seepage time is recorded, and the permeability of the sample under the initial conditions is calculated;

[0084] (7) Start the high-precision pressure loading and unloading combination pump 2-1, set the loading rate, and provide shear pressure to the system and load it to the set value. Add gas pulses to the upstream and adjust the control valve. At this time, the upstream air pressure gradually decreases and the downstream air pressure gradually increases. When the upstream and downstream gas pressures finally reach equilibrium, the pulse attenuation seepage test is completed at this stage. Calculate the permeability of the sample under shear loading conditions;

[0085] (8) Repeat step (7) and increase the gas pressure pulse on the sample until the predetermined pressure level is reached, and finally obtain the gas seepage law under the shear pressure condition.

[0086] (9) Repeat steps (7)-(8) for each shear loading pressure condition, and finally obtain the influence of shear pressure change on the seepage of the sample.

[0087] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multiphase rock triaxial compression-shear seepage test system, characterized by: include: The triaxial compression-shear test module includes an axial compression cylinder, a fluid self-balancing chamber, a shear seepage chamber, and a shear slide device arranged from top to bottom with their axes coinciding; The shear seepage chamber includes a detachably connected upper cylinder and a lower cylinder, which form a sample placement area inside after the two are connected; the axial pressure cylinder is connected to the self-balancing piston rod in the fluid self-balancing chamber, and the bottom of the self-balancing piston rod is toward the top of the sample placement area, which is used to provide axial pressure to the sample placement area; the inner walls of the upper cylinder and the lower cylinder form an annular pressure loading chamber, and the annular pressure loading chamber provides annular pressure through the loading control and acquisition module; the top of the upper cylinder is connected to the slider, and the lower cylinder is connected to the shear slide device, the slider is slidably connected to the shear slide device, and the shear cylinder is connected to the side of the lower cylinder, and the shear cylinder pushes the lower cylinder and the upper cylinder to move relative to each other to transmit shear pressure to the sample placement area; The shearing slide device includes a guide rail, which is slidably connected to the slider. The bottom of the guide rail is connected to the lower cylinder after a connecting bolt rod passes through the upper cylinder. The upper cylinder is provided with a strip hole in the area where the connecting bolt rod passes. When the lower cylinder is pushed by the shearing cylinder to move along the guide rail, the connecting bolt rod moves synchronously along the strip hole. Annular grooves are provided at the top of the upper cylinder structure and the bottom of the lower cylinder structure, and an integrated ring pressure transmission rubber sleeve is installed and fixed inside the ring pressure loading chamber to isolate the high-pressure gas inside the sample from the high-pressure fluid in the ring pressure loading chamber; Sealing grooves are respectively provided at the bottom of the upper cylinder and the top of the lower cylinder to realize dynamic surface sealing. The integrated sealing structure of the fluid self-balancing chamber and the shear seepage chamber realizes integrated sample sealing conditions and organically combines high-pressure gas pressure and annular pressure sealing. The loading control and acquisition module uses a loading and unloading combination pump to provide axial pressure, annular pressure, and shear pressure to the triaxial compression and shear test module, and uses an air pressure module to provide fluid pressure to the triaxial compression and shear test module, and obtains the test data of the sample; The circulating gas injection pump is connected in parallel with the gas source and shares a set of gas pipelines to form a gas pressurization module; The pipeline between the gas pressurization module and the triaxial compression and shear test module is equipped with a pressure reducing valve, a control valve, a vacuum pump, an upstream standard chamber, a downstream standard chamber, a pressure sensor, a displacement sensor and a temperature sensor for providing sample monitoring under transient and steady-state permeability test conditions; The gas pressurization module is started to increase the gas pulse upstream, and the control valve is used to keep the upstream and downstream gas pressures balanced according to the test requirements. At this stage, the pulse attenuation seepage test is completed; the upstream and downstream gas pressure changes and the seepage time during the seepage process are recorded to obtain the sample permeability of the pulse at this stage under shear loading conditions.

2. A multiphase rock triaxial compression-shear seepage test system according to claim 1, characterized in that: The axial pressure oil cylinder includes an axial pressure piston rod moving along the cylinder axis, and the fluid self-balancing chamber includes a self-balancing piston rod moving along the cylinder axis. The axial pressure piston rod and the self-balancing piston rod are connected and fixed by pins.

3. A multiphase rock triaxial compression-shear seepage test system according to claim 2, characterized in that: The depression at the bottom of the axial pressure piston rod matches the protrusion at the top of the self-balancing piston rod, and the cross-sectional areas of the axial pressure piston rod and the self-balancing piston rod are the same.

4. The multiphase rock triaxial compression-shear seepage test system according to claim 1, characterized in that: A flow channel is provided inside the self-balancing piston rod, and the flow channel connects the inside of the cylinder of the fluid self-balancing chamber, the sample placement area and the loading control and collection module.

5. The multiphase rock triaxial compression-shear seepage test system according to claim 4, characterized in that: The bottom of the self-balancing piston rod is provided with a porous contact surface, and the porous contact surface is used to contact the test piece in the shear seepage chamber.

6. The multiphase rock triaxial compression-shear seepage test system according to claim 1, characterized in that: The loading control and acquisition module includes a loading and unloading combination pump and a circulating air injection pump. The loading and unloading combination pump is connected to the axial pressure cylinder, the shear cylinder and the two annular pressure fluid interfaces opened in the lower cylinder barrel through pipelines. The circulating air injection pump is connected to the fluid self-balancing chamber and the bottom piston through pipelines.

7. A test method for implementing triaxial compression-shear seepage testing of multiphase rock based on the system according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Place the sample in the sample placement area and connect and fix the upper cylinder, lower cylinder, bottom flange and bottom piston of the shear seepage chamber in sequence; (2) Start the gas source and circulating gas injection pump, inject high-pressure gas, and perform a sealing check; (3) After the sealing meets the requirements, the vacuum pump is started to vacuum degas the shear seepage chamber and the seepage pipeline system; (4) The loading and unloading combination pump is started to provide the set axial pressure and annular pressure to the sample according to the test requirements; the gas source and circulating gas injection pump are started, and the gas is injected into the sample surface inside the shear seepage chamber through the upstream standard chamber using the control valve according to the test requirements. The pressure value is less than the annular pressure, and the gas flows through the sample into the downstream standard chamber. When the upstream and downstream pressures reach equilibrium, the pressure data is obtained during the upstream and downstream pressure equilibrium process at both ends of the sample to obtain the sample permeability under the initial conditions; (5) The loading and unloading combination pump is started to provide shear pressure to the shear cylinder and load it to the set value; the gas pressurization module is started to increase the gas pulse upstream, and the control valve is used to keep the upstream and downstream gas pressures balanced according to the test requirements. At this stage, the pulse attenuation seepage test is completed; the upstream and downstream gas pressure changes and the seepage time during the seepage process are recorded to obtain the sample permeability of the pulse at this stage under the shear loading condition; (6) Repeat step (5) to increase the gas pressure pulse on the sample until the set pressure level is reached, and obtain the gas seepage law under the shear pressure condition; (7) According to the test requirements, repeat steps (5)-(6) under each set shear loading pressure condition to obtain the influence of shear pressure change on the seepage of the sample.

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