Dynamic-fluid coupling induced earthquake simulation test device and test method

Abstract

The present invention provides a dynamic-fluid coupling-induced earthquake simulation test device and test method. The test device of the present invention includes a dynamic true triaxial electromagnetic Hopkinson bar system, a sealing loading system, and a data monitoring and control system. The dynamic true triaxial electromagnetic Hopkinson bar system is used to act on a simulated fault sample to simulate the true triaxial stress state and multiaxial and multi-directional dynamic disturbance of an underground fault; the sealing loading system is used to pressurize the fluid and inject it into the simulated fault sample, and seal the fluid under the dynamic and static combined loading of the simulated fault sample; the sealing loading system cooperates with the dynamic true triaxial electromagnetic Hopkinson bar system to load dynamic disturbance on the simulated fault sample containing fluid, simulate the stress state of the fault in an underground engineering project involving fluid activity, and conduct a dynamic-fluid coupling-induced earthquake simulation test. The present invention can simulate the true triaxial stress state and multiaxial and multi-directional dynamic disturbance of an underground fluid-containing fault.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering of fluid activities, and in particular to a dynamic-fluid coupling-induced earthquake simulation test device and a test method. Background Art

[0002] Underground engineering projects with fluid activities (carbon storage, geothermal mining, hydraulic fracturing and wastewater treatment, etc.) induce medium to large earthquakes, causing great harm to social development. Dynamic-fluid coupling-induced underground fault instability is one of the key internal causes of medium to large earthquakes. During the implementation of the above-mentioned underground engineering projects, operations such as blasting, excavation and hydraulic fracturing will produce strong dynamic disturbances on the faults. At the same time, fluid injection will reduce the effective stress of the fault and reduce its friction coefficient. The coupling effect of the two will cause fault instability, thereby inducing medium to large earthquake events. However, the current experimental devices for studying dynamic disturbance-induced earthquakes cannot inject fluids, and the experimental devices that can study fluid-injected earthquakes cannot perform dynamic disturbances, especially multi-axis and multi-directional dynamic disturbances. The current experimental devices cannot perform dynamic-fluid coupling-induced earthquake simulation tests. Therefore, it is urgent to develop a dynamic-fluid coupling-induced earthquake simulation test device to conduct dynamic-fluid coupling-induced earthquake simulation tests, explore the dynamic-fluid coupling-induced earthquake mechanism, and provide strong guarantees for the safe implementation of underground projects such as carbon sequestration, geothermal extraction and hydraulic fracturing. Summary of the invention

[0003] In order to solve the problems in the prior art, the present invention provides a dynamic-fluid coupling-induced earthquake simulation test device and test method, which can accurately simulate the tectonic stress state of underground faults and the dynamic-fluid coupling effect they are subjected to, and reveal the physical mechanism of dynamic-fluid coupling-induced earthquakes.

[0004] The dynamic-fluid coupling induced earthquake simulation test device of the present invention comprises a dynamic true triaxial electromagnetic Hopkinson bar system, a sealing loading system, and a data monitoring and control system, wherein:

[0005] The dynamic true triaxial electromagnetic Hopkinson bar system is used to act on a simulated fault sample to simulate the true triaxial stress state and multiaxial and multidirectional dynamic disturbance of an underground fault;

[0006] The sealing loading system is used to pressurize and inject fluid into the simulated fault specimen, and seal the fluid under the combined dynamic and static loading of the simulated fault specimen;

[0007] The sealed loading system cooperates with the dynamic true triaxial electromagnetic Hopkinson bar system to realize dynamic disturbance loading on the simulated fault sample containing fluid, simulate the stress state of the fault in the underground engineering project involving fluid activity, and conduct a dynamic-fluid coupling induced earthquake simulation test;

[0008] The data monitoring and control system is used to control the dynamic true three-axis electromagnetic Hopkinson bar system and the sealing loading system, and record and store test data.

[0009] The sealing loading system includes a sealing chamber, a fixture system, a fluid injection system and an acoustic emission system.

[0010] The sealed chamber is arranged in the central reference square box of the dynamic true three-axis electromagnetic Hopkinson rod system, and the six faces are respectively connected to the six square rods of the dynamic true three-axis electromagnetic Hopkinson rod system in the X direction, the Y direction, and the Z direction through the clamp system; the clamp system includes two fixed clamps correspondingly connected to the two square rods in the Z direction, two fluid injection clamps connected to one of the square rods in the X direction and one of the square rods in the Y direction and used for fluid inlet and outlet, and two slidable clamps connected to another square rod in the X direction and another square rod in the Y direction,

[0011] The fixture bodies of the fixed fixture, the fluid injection fixture and the slidable fixture are sealed and connected to the sealing chamber. One side of the fixture body is provided with a groove for connecting the square rod, and the other side is provided with a metal pressure head. The six metal pressure heads are respectively arranged in contact with the six surfaces of the simulated fault sample.

[0012] The fluid injection system comprises a fluid pipeline structure which is arranged on the fluid injection fixture and is connected to the simulated fault sample and can inject the fluid into the cross section of the simulated fault sample;

[0013] The acoustic emission system comprises an acoustic emission detection element arranged on the metal pressure head, and the fixture body is also provided with a signal line channel for leading out a signal line of the acoustic emission detection element.

[0014] Furthermore, the dynamic true triaxial electromagnetic Hopkinson bar system includes a rod system, a loading frame system, an electromagnetic pulse emission system and a static loading system, wherein the loading frame system includes a cross-support platform, a central reference square box arranged in the middle of the cross-support platform, and also includes lateral support rods arranged in the X and Y directions of the cross-support platform, and a Z-direction loading frame arranged vertically in the middle of the cross-support platform. The loading frame system is used to provide a test platform and guide the centering of multi-axis and multi-directional rods; the rod system includes six square rods in the X, Y and Z directions arranged on the loading frame system and a square rod fixing support frame for fixing the square rods. The rod system is used as a load for applying static force and dynamic disturbance propagation to simulated fault specimens. body; the electromagnetic pulse emission system is arranged at one end of the square rod away from the central reference square box to provide dynamic disturbance for the test; the static loading system includes a static loading end baffle, a static loading frame and a static loading cylinder arranged on the static loading end baffle, the static loading cylinder can drive the static loading frame to move toward or away from the square rod, the static loading system is used to apply static loading to the simulated fault specimen through the square rod, the dynamic true triaxial electromagnetic Hopkinson rod system also includes a displacement detection element and a force detection element arranged on the static loading end baffle, which are used to monitor the force and displacement of the six axial square rods during the test, and a strain detection element arranged on the square rod for monitoring the strain of the square rod during the dynamic loading process.

[0015] Furthermore, the data monitoring and control system includes a control module for controlling the electromagnetic pulse emission system, the static loading system and the fluid injection system, and a data monitoring and acquisition module. The data monitoring and acquisition module includes an acoustic emission monitoring system connected to the acoustic emission system, a displacement monitoring system connected to the displacement monitoring element, and a force monitoring system and a stress wave monitoring system of the force monitoring element arranged on the square rod.

[0016] Furthermore, the sealed bin includes a sealed bin body composed of 5 square metal base plates and a sealed bin cover sealedly connected to the sealed bin body, the sealed bin body and the sealed bin cover are both provided with mounting holes for installing the fixture system in the middle, the upper surface of the sealed bin body is provided with a boss, the outer side wall of the boss is provided with a first O-type rubber sealing ring, the inner side of the boss is provided with a second O-type rubber sealing ring, and each edge of the upper surface of the boss is provided with a plurality of bolt holes, the lower surface of the sealed bin cover is provided with a groove corresponding to the boss, the side walls of the groove are respectively sealed and connected to the boss through the first O-type rubber sealing ring and the second O-type rubber sealing ring, and the sealed bin cover is fixedly connected to the sealed bin body through waterproof bolts and bolt holes.

[0017] Furthermore, the acoustic emission detection element includes an acoustic emission probe, a spring and an acoustic emission pressure block. A plurality of through holes are provided on the metal pressure head, and a mounting groove connected to a plurality of through holes is provided on the rear end of the metal pressure head. The acoustic emission pressure block is arranged in the mounting groove, and the acoustic emission probe is arranged at the front end of the through hole that can contact the square rod. One end of the spring is connected to the acoustic emission probe, and the other end is connected to one end of the acoustic emission pressure block.

[0018] Furthermore, the metal pressure head of the slidable clamp is provided with a sliding roller slidably connected to the clamp body near the rear end of the square rod, and the clamp body is also provided with limit plates on both sides of the metal pressure head. A limit spring is provided between the limit plate and the clamp body. The two sides of the metal pressure head are in contact with the limit plates. When the fault of the simulated fault specimen moves, the metal pressure head can be driven to slide relative to the clamp body.

[0019] Furthermore, the fluid pipeline structure includes a fluid channel arranged in the clamp body, a fluid interface connected to the fluid channel is arranged on the clamp body, and a fluid injection pipeline is arranged on the metal pressure head, and the fluid injection pipeline is sealed and connected to the fluid channel.

[0020] The present invention also provides a method for simulating an earthquake induced by a dynamic-fluid coupling effect, which is implemented based on the dynamic-fluid coupling effect induced earthquake simulating test device and comprises the following steps:

[0021] S1: Fix the simulated fault specimen in the sealed chamber so that the contact surfaces of the square rod, the fixture system and the simulated fault specimen are parallel;

[0022] S2: Calculate the initial three-dimensional stress state based on the deep ground stress, start the static loading system, and perform static loading in three directions synchronously to ensure that all contact surfaces are in full contact and maintain a constant state by using displacement control. Then start the fluid injection system to inject liquid into the sealed chamber to make the pore pressure in the sealed chamber reach the design value.

[0023] S3: Load the stress in the X, Y and Z directions to the design value at a certain rate and maintain the load for the set time;

[0024] S4: Using an electromagnetic pulse transmitting system, synchronous electromagnetic pulses are applied in the three directions of X, Y and Z to achieve three-axis six-directional stress fluctuation load disturbance synchronous loading;

[0025] S5: The data monitoring and control system collects and records the test data during the test, including displacement, force, acoustic emission and stress wave data, and analyzes the earthquake mechanism induced by dynamic-fluid coupling.

[0026] Furthermore, step S6 is also included, which draws the fault displacement, fault shear stress, and effective normal stress on the fault during the fault slip process of the simulated fault sample based on the displacement, force, acoustic emission and stress wave data, records the seismic moment and moment magnitude of each seismic event, and studies the induced earthquake process of underground faults under the action of dynamic-fluid coupling.

[0027] Furthermore, the fault displacement The calculation method is:

[0028]

[0029] in,

[0030] The total axial displacement measured by the displacement sensing element of the axis where any slidable fixture is located;

[0031] , is the elastic deformation of the square rod, is the static force difference before and after loading, is the square bar stiffness;

[0032] , is the axial deformation of the rock sample, is the average strain, is the sample length; is the fault angle,

[0033] Fault shear stress The calculation method is:

[0034]

[0035] in, is the maximum principal stress in the Z direction, is the minimum principal stress in the X direction,

[0036] Effective normal stress The calculation method is:

[0037]

[0038] is the pore pressure;

[0039] Seismic moment The calculation method is:

[0040]

[0041] The number of acoustic emission detection elements, is the serial number of the acoustic emission detection element, ,

[0042] The P-wave amplitude of the i-th acoustic emission detection element,

[0043] The distance from the i-th acoustic emission detection element to the earthquake source,

[0044] Moment magnitude The calculation method is: .

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can realize fluid sealing under dynamic and static combined loading through the sealing loading system, and cooperate with the dynamic true triaxial electromagnetic Hopkinson bar system provided in the present invention to simulate the true triaxial stress state and multi-axial and multi-directional dynamic disturbance of underground fluid-containing faults, so as to more comprehensively study the activation characteristics of underground faults under dynamic-fluid coupling, and help to reveal the earthquake mechanism induced by dynamic-fluid coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the present invention or the solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 It is a structural block diagram of the test device of the present invention;

[0048] Figure 2 It is a schematic diagram of the overall structure of the test device of the present invention;

[0049] Figure 3 This is a schematic structural diagram of an embodiment of a sealing loading system of the present invention;

[0050] Figure 4 This is a schematic structural diagram of an embodiment of a sealed chamber of the present invention;

[0051] Figure 5 This is a structural schematic diagram of an embodiment of a fixing fixture of the present invention;

[0052] Figure 6 This is a schematic diagram of the internal structure of the fixing fixture of the present invention;

[0053] Figure 7 This is a schematic structural diagram of an embodiment of a movable clamp of the present invention;

[0054] Figure 8 This is a schematic structural diagram of an embodiment of a fluid injection fixture of the present invention;

[0055] Fig. 9This is a schematic diagram of the plane of the earthquake test induced by dynamic-fluid coupling;

[0056] Fig.10 Schematic diagram of the stress state of the earthquake model induced by dynamic-fluid coupling.

[0057] Reference numerals:

[0058] 11-cross support platform; 12-lateral support rod; 13-center reference square box; 14-Z-direction loading frame; 21-square rod; 22-fixed support frame; 31-static loading cylinder; 32-static loading end baffle; 33-static loading frame; 41-electromagnetic pulse launch chamber; 42-launch chamber support frame; 5-sealed chamber; 51-sealed chamber body; 52-sealed chamber cover; 53-boss; 54-sealing ring; 55-waterproof bolt; 61-fixed fixture; 611-pressure head; 612-clamp body; 613-clamp sealing ring; 62-fluid injection clamp; 621-fluid injection pipeline; 622-fluid interface; 623-fluid pipeline sealing ring; 63-slidable clamp; 631-limiting spring; 632-limiting plate; 633-sliding roller; 71-acoustic emission probe; 72-spring; 73-acoustic emission pressure block; 74-signal line channel; 75-signal line channel sealing ring; 9-simulated fault sample. DETAILED DESCRIPTION

[0059] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0060] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it mutually exclusive, independent, or alternative to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0061] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

[0062] like Figure 1-Figure 8As shown, the dynamic-fluid coupling induced earthquake simulation test device of the present invention includes a dynamic true triaxial electromagnetic Hopkinson bar system, a sealing loading system, and a data monitoring and control system, wherein:

[0063] The dynamic true triaxial electromagnetic Hopkinson bar system is used to act on a simulated fault sample to simulate the true triaxial stress state and multiaxial and multidirectional dynamic disturbance of an underground fault;

[0064] The sealing loading system is used to pressurize and inject fluid into the simulated fault specimen, and seal the fluid under the combined dynamic and static loading of the simulated fault specimen;

[0065] The sealed loading system cooperates with the dynamic true triaxial electromagnetic Hopkinson bar system to realize dynamic disturbance loading on the simulated fault sample containing fluid, simulate the stress state of the fault in the underground engineering project involving fluid activity, and conduct a dynamic-fluid coupling induced earthquake simulation test;

[0066] The data monitoring and control system is used to control the dynamic true three-axis electromagnetic Hopkinson bar system and the sealing loading system, and record and store test data.

[0067] The sealing loading system includes a sealing chamber, a fixture system, a fluid injection system and an acoustic emission system.

[0068] The sealing chamber is arranged in the central reference square box of the dynamic true three-axis electromagnetic Hopkinson rod system, and the six faces are respectively connected to the six square bars of the dynamic true three-axis electromagnetic Hopkinson rod system in the X direction, Y direction and Z direction through a clamp system; the clamp system includes two fixed clamps 61 correspondingly connected to the two square bars in the Z direction, two fluid injection clamps 62 connected to one of the square bars in the X direction and one of the square bars in the Y direction and used for fluid in and out, and two slidable clamps 63 connected to the other square bar in the X direction and the other square bar in the Y direction. The clamp bodies 612 of the fixed clamps 61, the fluid injection clamps 62 and the slidable clamps 63 are sealed and connected to the sealing chamber through a clamp sealing ring 613. A groove for connecting the square bars is provided on one side of the clamp body 612, and a metal pressure head 611 is provided on the other side. The six metal pressure heads 611 are respectively arranged in contact with the six faces of the simulated fault sample, as shown in FIG. Figure 3-Figure 5 shown.

[0069] The fluid injection system comprises a fluid pipeline structure which is arranged on the fluid injection fixture and is connected to the simulated fault sample and can inject the fluid into the cross section of the simulated fault sample;

[0070] The acoustic emission system comprises an acoustic emission detection element arranged on the metal pressure head, and the fixture body is also provided with a signal line channel for leading out a signal line of the acoustic emission detection element.

[0071] The data monitoring and control system of this example includes a control module for controlling the electromagnetic pulse emission system, the static loading system and the fluid injection system, and a data monitoring and acquisition module. The data monitoring and acquisition module includes an acoustic emission monitoring system connected to the acoustic emission system, a displacement monitoring system connected to the displacement monitoring element, and a force monitoring system and a stress wave monitoring system of the force monitoring element arranged on the square rod.

[0072] like Figure 2 As shown, the dynamic true triaxial electromagnetic Hopkinson bar system includes a bar system, a loading frame system, an electromagnetic pulse emission system and a static loading system, wherein the loading frame system includes a cross support platform 11, a central reference square box 13 arranged in the middle of the cross support platform 11, and also includes a transverse support rod 12 arranged in the X direction and Y direction of the cross support platform 11, and a Z-direction loading frame 14 vertically arranged in the middle of the cross support platform 11, and the loading frame system is used to provide a test platform and guide the centering of multi-axis multi-directional bars; the bar system includes six square bars 21 in the X direction, Y direction, and Z direction arranged on the loading frame system and a square bar fixing support frame 22 for fixing the square bars 21, and the bar system is used as a carrier for applying static force and dynamic disturbance propagation to the simulated fault specimen. In this example, the cross-section of the square bar 21 is a square with a side length of 50 mm.

[0073] The electromagnetic pulse emission system is arranged at one end of the square rod 21 away from the central reference square box 13 to provide dynamic disturbance for the test, and includes an electromagnetic pulse emission chamber 41 and an emission chamber support frame 42 supporting the electromagnetic pulse emission chamber 41 .

[0074] The static loading system includes a static loading end baffle 32, a static loading frame 33 and a static loading cylinder 31 arranged on the static loading end baffle 32. The static loading cylinder 31 can drive the static loading frame 33 to move toward or away from the square rod 21. The static loading system is used to apply static loading to the simulated fault specimen through the square rod 21.

[0075] The dynamic true three-axis electromagnetic Hopkinson bar system also includes a displacement detection element and a force detection element arranged on the static loading end baffle, which are used to monitor the force and displacement of the six axial square bars during the test, and a strain detection element arranged on the square bar for monitoring the strain of the square bar during the dynamic loading process. The force detection element in this example is a pressure sensor, the displacement detection element adopts a displacement sensor, and the strain detection element is a strain gauge. The present invention can feedback pressure and stroke data through pressure sensors and displacement sensors to ensure that the static force remains relatively stable during the test process.

[0076] like Figure 3 and Figure 4As shown, the sealed bin includes a sealed bin body 51 and a sealed bin cover 52 sealedly connected to the sealed bin body 51. The outer dimensions of the sealed bin in this example are 180mm×180mm×180mm. The sealed bin body 51 is welded from five square metal bottom plates with a thickness of 40mm. A circular mounting hole is opened in the center of each face for installing the fixture system. A 20mm wide and 20mm high boss 53 is cut out on the top side of the side plate of the sealed bin body 51 in this example. A sealing ring 54 is arranged on the inner and outer center lines of the boss 53. The sealing ring in this example includes a first O-type rubber sealing ring arranged on the outer side wall of the boss 53 and a second O-type rubber sealing ring arranged on the inner side of the boss. Five bolt holes are arranged on the center line of the boss 53 on each side for fixing the sealed bin cover 52. Correspondingly, the sealing chamber cover 52 is a square metal plate of 180mm×180mm×40mm, and a groove corresponding to the boss 53 is provided on the lower surface. The side walls of the groove are sealed and connected to the boss through the first O-type rubber sealing ring and the second O-type rubber sealing ring respectively. The sealing chamber cover 52 is fixedly connected to the sealing chamber body 51 through the waterproof bolts 55 and the bolt holes.

[0077] like Figure 5-Figure 6 As shown, in this example, acoustic emission detection elements are arranged on the fixed fixture 61, the fluid injection fixture 62 and the slidable fixture 63 of the fixture system, and the acoustic emission detection elements include an acoustic emission probe 71, a spring 72 and an acoustic emission pressure block 73. Four through holes are opened on the metal pressure head 611 for arranging four acoustic emission probes 71, and a mounting groove connected to a plurality of through holes is arranged at the rear end of the metal pressure head 611. The acoustic emission pressure block 73 is arranged in the mounting groove, and the acoustic emission probe 71 is arranged at the front end of the through hole that can contact the square rod 21. One end of the spring 72 is connected to the acoustic emission probe 71, and the other end is connected to one end of the acoustic emission pressure block 73, so that the acoustic emission probe 71 can be stably installed in the through hole and can reliably contact the simulated fault sample 9. In addition, in this example, a signal line channel 74 is provided on the fixture body 612 and passes through the fixture body 612, so that the signal line of the acoustic emission detection element can be led out to the signal acquisition device of the acoustic emission system. A signal line channel sealing ring 75 that seals the signal line channel 74 is also sleeved on the acoustic emission pressure block 73 that cooperates with the metal pressure head 611 and the signal line channel 74 of the fixture body 612.

[0078] like Figure 7As shown, the metal pressing head 611 of the slidable clamp 63 is provided with a sliding roller 633 slidably connected to the clamp body 612 near the rear end of the square rod 21, and the clamp body 612 is also provided with limit plates 632 on both sides of the metal pressing head 611. A limit spring 631 is provided between the limit plate 632 and the clamp body 612. The two sides of the metal pressing head 611 are in contact with the limit plate 632. When the fault of the simulated fault specimen 9 moves, the metal pressing head 611 can be driven to slide relative to the clamp body 612.

[0079] like Figure 8 As shown, the fluid pipeline structure includes a fluid channel arranged in the clamp body, a fluid interface 622 connected to the fluid channel is arranged on the clamp body 612, a fluid injection pipeline 621 is arranged on the metal pressure head 611, and the fluid injection pipeline 621 is sealed and connected to the fluid channel through a fluid pipeline sealing ring 623.

[0080] The fluid injection system of this example serves to pressurize the fluid and inject it into the rock sample. It also includes a double-acting high-precision constant-flow and constant-pressure pump connected to the fluid interface 622, and a pressure-resistant pipeline and other structures for injecting the fluid at a controllable pressure and flow rate. It can provide a fluid pressure of 0 to 50 MPa, and the pressure and flow rate of the injected fluid can be accurately controlled during the test.

[0081] The acoustic emission system of this example also includes a preamplifier connected to the output end of the acoustic emission detection element, the output end of the preamplifier is connected to the input end of the acoustic emission monitoring system, and the acoustic emission monitoring system and the acoustic emission system are mainly used to track, monitor and record acoustic emission events during the test.

[0082] The data monitoring and acquisition module also includes signal processing equipment such as a multi-channel high-speed synchronous recorder, a Wheatstone bridge and a strain signal amplifier, which are respectively connected to the output ends of the displacement sensor, pressure sensor and strain gauge to ensure that the test data is recorded and stored completely and effectively.

[0083] The present invention also provides a method for simulating earthquakes induced by dynamic-fluid coupling, which is implemented based on the dynamic-fluid coupling induced earthquake simulation test device and is used to simulate the stress state of faults in underground engineering projects involving fluid activities. Since operations such as blasting, excavation, hydraulic fracturing and earthquakes will produce strong dynamic disturbances on the faults, and fluid injection will reduce the effective stress of the faults and lower their friction coefficient, the coupling effect of the two will cause the faults to become unstable, thereby inducing medium to large earthquake events.

[0084] The test method of the present invention comprises the following steps:

[0085] S1: Fix the simulated fault sample in the sealed chamber, and then install the test device of the present invention, so that the contact surface of the square rod, the fixture system and the simulated fault sample are parallel. Use high-precision measuring tools to align the rod system so that the error is less than 0.1mm; connect the fluid injection system and the acoustic emission system; test the airtightness of the sealing loading system to ensure the system is sealed.

[0086] Preparation of simulated fault specimens:

[0087] The rock samples obtained on site were cut and polished into cube specimens with a side of 50 mm, and cut along the diagonal of one of the faces into Fig. 9 Two triangular prism-shaped specimens are shown. Two holes with a diameter of 2 mm are drilled into the cross section at the designed position of one of the specimens for injecting fluid, and the cross section is polished to simulate the fault roughness.

[0088] The sealing loading system installation of the present invention includes:

[0089] Install the fixture system, install the acoustic emission probe 71 in the corresponding hole of the metal pressure head 611, install the signal line in the wire groove on the metal pressure head 611, install the spring 72 and the acoustic emission pressure block 73, inject glue into the wire groove for sealing, pull the acoustic emission signal line out through the signal line channel 74, install the signal line channel sealing ring 75 and the fluid pipeline sealing ring 623, install the whole consisting of the metal pressure head 611 and the acoustic emission pressure block 73 into the fixture body 612, and install the fixture sealing ring 613 on each fixture.

[0090] Install the sealing ring 54 on the top of the sealing chamber body 51, install the fixed clamp 61 on the bottom of the sealing chamber body 51 and the sealing chamber cover 52, and install the fluid injection clamp 62 and the slidable clamp 63 on the two adjacent surfaces of the sealing chamber body 51 respectively; put in the simulated fault sample 9, install the fluid injection pipeline 621 in the fluid injection clamp 62 and the simulated fault sample 9; insert the square rods 21 in each direction into the grooves on each clamp body, and adjust the position of the simulated fault sample 9; cover the sealing chamber cover 52, connect the upper clamp to the square rod 21, and install the waterproof bolt 55; connect the fluid pressurization system to the fluid interface 622 on the fluid injection clamp 62, and connect each acoustic emission signal line to the acoustic emission monitoring system.

[0091] S2: Calculate the initial three-dimensional stress state based on the deep ground stress, start the static loading system, and perform static loading in three directions simultaneously to ensure that all contact surfaces are in full contact and maintain a constant state using displacement control. Then start the fluid injection system to inject liquid into the sealed chamber to make the pore pressure in the sealed chamber reach the design value.

[0092] S3: Load the stress in X, Y and Z directions to the design value at a certain rate and maintain the load for a set time.

[0093] In this example, the Z and X directions are loaded synchronously to the minimum principal stress value; then the Z direction is kept constant by force control, and the X direction is loaded synchronously to the maximum principal stress value; finally, the Z and X directions are kept constant by force control, and the Y direction is loaded to the design value.

[0094] S4: Using the electromagnetic pulse transmission system, synchronous electromagnetic pulses are applied in the three directions of X, Y and Z to achieve synchronous loading of stress fluctuations in three axes and six directions. The schematic diagram of the stress state of the earthquake model induced by dynamic-fluid coupling is shown in Fig.10 shown.

[0095] Before executing step S4, a stress wave characteristic debugging step is also included: starting the electromagnetic pulse emission system and debugging the ideal stress wave characteristic by changing the voltage and the discharge current.

[0096] In step S4, when the three directions have reached the designed initial stress state, the load is maintained for half a minute, and an electromagnetic pulse emission system is used to apply three-way synchronous electromagnetic pulses in the X, Y and Z directions using the voltage and current data of ideal stress wave characteristics to achieve three-axis six-way stress wave load disturbance synchronous loading.

[0097] S5: The data monitoring and control system collects and records the test data during the test, including displacement, force, acoustic emission and stress wave data, and analyzes the earthquake mechanism induced by dynamic-fluid coupling.

[0098] In this example, while executing step S4, the acoustic emission system and the data monitoring and acquisition module are synchronously triggered to record the displacement, force, acoustic emission and stress wave data during the test, and the fault displacement, fault shear stress, effective normal stress on the fault, and seismic moment and moment magnitude of each earthquake event at each moment are calculated by the following formula.

[0099] Fault displacement The calculation method is:

[0100]

[0101] in,

[0102] is the total axial displacement measured by the displacement sensor of the axis where any slidable fixture is located;

[0103] , is the elastic deformation of the square rod, is the static force difference before and after loading, is the square bar stiffness;

[0104] , is the axial deformation of the rock sample, is the average strain, is the sample length; is the fault angle, which is 45° in this case.

[0105] Fault shear stress The calculation method is:

[0106]

[0107] in, is the maximum principal stress in the Z direction, is the minimum principal stress in the X direction,

[0108] Effective normal stress The calculation method is:

[0109]

[0110] is the pore pressure;

[0111] Seismic moment The calculation method is:

[0112]

[0113] The number of acoustic emission detection elements is 24 in total for the clamping system in 6 directions in this example. is the serial number of the acoustic emission detection element, ,

[0114] The P-wave amplitude of the i-th acoustic emission detection element,

[0115] The distance from the i-th acoustic emission detection element to the earthquake source,

[0116] Moment magnitude The calculation method is:

[0117]

[0118] Preferably, the present invention also includes step S6, based on the displacement, force, acoustic emission and stress wave data, drawing the fault displacement, fault shear stress, and effective normal stress on the fault during the fault slip process of the simulated fault sample, recording the seismic moment and moment magnitude of each seismic event, and studying the induced earthquake process of underground faults under the action of dynamic-fluid coupling.

[0119] As can be seen from the above, the present invention has the following innovative features:

[0120] The present invention can achieve fluid sealing under dynamic and static combined loading through a sealing loading system. In conjunction with the dynamic true triaxial electromagnetic Hopkinson bar system provided in the present invention, the true triaxial stress state and multiaxial and multidirectional dynamic disturbance of underground fluid-containing faults can be simulated, and the activation characteristics of underground faults under dynamic-fluid coupling can be studied more comprehensively, which is helpful to reveal the mechanism of earthquake induced by dynamic-fluid coupling.

[0121] The specific implementation modes described above are preferred implementation modes of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the specific implementation modes, and all equivalent changes made according to the present invention are within the protection scope of the present invention.

Claims

1. A dynamic-fluid coupling induced earthquake simulation test device, characterized in that: It includes a dynamic true triaxial electromagnetic Hopkinson rod system, a sealed loading system, and a data monitoring and control system. The dynamic true triaxial electromagnetic Hopkinson bar system is used to act on a simulated fault sample to simulate the true triaxial stress state and multiaxial and multidirectional dynamic disturbance of an underground fault; The sealing loading system is used to pressurize and inject fluid into the simulated fault specimen, and seal the fluid under the combined dynamic and static loading of the simulated fault specimen; The sealed loading system cooperates with the dynamic true triaxial electromagnetic Hopkinson bar system to realize dynamic disturbance loading on the simulated fault sample containing fluid, simulate the stress state of the fault in the underground engineering project involving fluid activity, and conduct a dynamic-fluid coupling induced earthquake simulation test; The data monitoring and control system is used to control the dynamic true three-axis electromagnetic Hopkinson bar system and the sealing loading system, and record and store test data. The sealing loading system includes a sealing chamber, a fixture system, a fluid injection system and an acoustic emission system. The sealed chamber is arranged in the central reference square box of the dynamic true three-axis electromagnetic Hopkinson rod system, and the six faces are respectively connected to the six square rods of the dynamic true three-axis electromagnetic Hopkinson rod system in the X direction, the Y direction, and the Z direction through a clamp system; the clamp system includes two fixed clamps correspondingly connected to the two square rods in the Z direction, two fluid injection clamps connected to one of the square rods in the X direction and one of the square rods in the Y direction and used for fluid inlet and outlet, and two slidable clamps connected to another square rod in the X direction and another square rod in the Y direction, The fixture bodies of the fixed fixture, the fluid injection fixture and the slidable fixture are sealed and connected to the sealing chamber. One side of the fixture body is provided with a groove for connecting the square rod, and the other side is provided with a metal pressure head. The six metal pressure heads are respectively arranged in contact with the six surfaces of the simulated fault sample. The fluid injection system comprises a fluid pipeline structure which is arranged on the fluid injection fixture and is connected to the simulated fault sample and can inject the fluid into the cross section of the simulated fault sample; The acoustic emission system comprises an acoustic emission detection element arranged on the metal pressure head, and the fixture body is also provided with a signal line channel for leading out a signal line of the acoustic emission detection element.

2. The dynamic-fluid coupling induced earthquake simulation test device according to claim 1, characterized in that: The dynamic true triaxial electromagnetic Hopkinson bar system includes a bar system, a loading frame system, an electromagnetic pulse emission system and a static loading system, wherein the loading frame system includes a cross support platform, a central reference square box arranged in the middle of the cross support platform, and also includes transverse support bars arranged in the X and Y directions of the cross support platform, and a Z-direction loading frame vertically arranged in the middle of the cross support platform. The loading frame system is used to provide a test platform and guide the centering of multi-axis and multi-directional bars; The rod system includes six square rods arranged in the X, Y and Z directions on the loading frame system and a square rod fixing support frame for fixing the square rods. The rod system is used as a carrier for applying static force to the simulated fault specimen and propagating dynamic disturbances. The electromagnetic pulse emission system is arranged at one end of the square rod away from the central reference square box to provide dynamic disturbances for the test. The static loading system includes a static loading end baffle, a static loading frame and a static loading cylinder arranged on the static loading end baffle. The static loading cylinder can drive the static loading frame to move toward or away from the square rod. The static loading system is used to apply static loading to the simulated fault specimen through the square rod. The dynamic true three-axis electromagnetic Hopkinson bar system also includes a displacement detection element and a force detection element arranged on the static loading end baffle, which are used to monitor the force and displacement of the six axial square bars during the test, and a strain detection element arranged on the square bar for monitoring the strain of the square bar during dynamic loading.

3. The dynamic-fluid coupling induced earthquake simulation test device according to claim 2 is characterized in that: The data monitoring and control system includes a control module for controlling the electromagnetic pulse emission system, the static loading system and the fluid injection system, and a data monitoring and acquisition module. The data monitoring and acquisition module includes an acoustic emission monitoring system connected to the acoustic emission system, a displacement monitoring system connected to the displacement monitoring element, and a force monitoring system and a stress wave monitoring system connected to the force monitoring element arranged on the square rod.

4. The dynamic-fluid coupling induced earthquake simulation test device according to claim 1, characterized in that: The sealed bin includes a sealed bin body composed of 5 square metal base plates and a sealed bin cover sealedly connected to the sealed bin body. The sealed bin body and the sealed bin cover are both provided with mounting holes for installing the fixture system in the middle. A boss is provided on the upper surface of the sealed bin body. The outer wall of the boss is provided with a first O-type rubber sealing ring. The inner side of the boss is provided with a second O-type rubber sealing ring. A plurality of bolt holes are provided on each edge of the upper surface of the boss. A groove corresponding to the boss is provided on the lower surface of the sealed bin cover. The side walls of the groove are sealedly connected to the boss through the first O-type rubber sealing ring and the second O-type rubber sealing ring respectively. The sealed bin cover is fixedly connected to the sealed bin body through waterproof bolts and bolt holes.

5. The dynamic-fluid coupling induced earthquake simulation test device according to claim 1, characterized in that: The acoustic emission detection element includes an acoustic emission probe, a spring and an acoustic emission pressure block. A plurality of through holes are opened on the metal pressure head, and a plurality of mounting grooves connected with the through holes are provided at the rear end of the metal pressure head. The acoustic emission pressure block is arranged in the mounting groove, and the acoustic emission probe is arranged at the front end of the through hole that can contact the square rod. One end of the spring is connected to the acoustic emission probe, and the other end is connected to one end of the acoustic emission pressure block.

6. The dynamic-fluid coupling induced earthquake simulation test device according to claim 5, characterized in that: The metal pressure head of the slidable clamp is provided with a sliding roller slidably connected to the clamp body near the rear end of the square rod. The clamp body is also provided with limit plates on both sides of the metal pressure head. A limit spring is provided between the limit plate and the clamp body. The two sides of the metal pressure head are in contact with the limit plates. When the fault of the simulated fault specimen moves, the metal pressure head can be driven to slide relative to the clamp body.

7. The dynamic-fluid coupling induced earthquake simulation test device according to claim 5, characterized in that: The fluid pipeline structure includes a fluid channel arranged in the clamp body, a fluid interface connected to the fluid channel is arranged on the clamp body, a fluid injection pipeline is arranged on the metal pressure head, and the fluid injection pipeline is sealed and connected to the fluid channel.

8. A method for simulating earthquakes induced by dynamic-fluid coupling, implemented based on the dynamic-fluid coupling induced earthquake simulating test device according to any one of claims 2 to 7, characterized in that: The steps include: S1: Fix the simulated fault specimen in the sealed chamber so that the contact surfaces of the square rod, the fixture system and the simulated fault specimen are parallel; S2: Calculate the initial three-dimensional stress state based on the deep ground stress, start the static loading system, and perform static loading in three directions synchronously to ensure that all contact surfaces are in full contact and maintain a constant state by using displacement control. Then start the fluid injection system to inject liquid into the sealed chamber to make the pore pressure in the sealed chamber reach the design value. S3: Load the stress in the X, Y and Z directions to the design value at a certain rate and maintain the load for the set time; S4: Using an electromagnetic pulse transmitting system, synchronous electromagnetic pulses are applied in the three directions of X, Y and Z to achieve three-axis six-directional stress fluctuation load disturbance synchronous loading; S5: The data monitoring and control system collects and records the test data during the test, including displacement, force, acoustic emission and stress wave data, and analyzes the earthquake mechanism induced by dynamic-fluid coupling.

9. The method for simulating earthquake induced by dynamic-fluid coupling according to claim 8, characterized in that: The method also includes step S6, which draws the time variation curve of fault displacement, fault shear stress and effective normal stress on the fault during the fault slip process of the simulated fault sample based on the displacement, force, acoustic emission and stress wave data, records the seismic moment and moment magnitude of each seismic event, and studies the induced earthquake process of underground faults under the action of dynamic-fluid coupling.

10. The method for simulating earthquake induced by dynamic-fluid coupling according to claim 9, characterized in that: Fault displacement The calculation method is: in, The total axial displacement measured by the displacement sensing element of the axis where any slidable fixture is located; , is the elastic deformation of the square rod, is the static force difference before and after loading, is the square bar stiffness; , is the axial deformation of the rock sample, is the average strain, is the sample length; is the fault angle, Fault shear stress The calculation method is: in, is the maximum principal stress in the Z direction, is the minimum principal stress in the X direction, Effective normal stress The calculation method is: is the pore pressure; Seismic moment The calculation method is: The number of acoustic emission detection elements, is the serial number of the acoustic emission detection element, , The P-wave amplitude of the i-th acoustic emission detection element, The distance from the i-th acoustic emission detection element to the earthquake source, Moment magnitude The calculation method is: 。

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