High- and low-frequency combined dynamic disturbance-induced earthquake simulation test device and test method

Abstract

The present invention provides a high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device and test method. The test device of the present invention includes a static loading system, a dynamic disturbance system, a fixture system, and a data monitoring and control system. The static loading system and the dynamic disturbance system can simulate the stress state of the high- and low-frequency combined dynamic disturbance that the fault is subjected to under complex stress conditions. The response characteristics of the simulated fault specimen under the high- and low-frequency combined dynamic disturbance are obtained through the data monitoring and control system, thereby realizing earthquake induction simulation under the high- and low-frequency combined dynamic disturbance. The present invention also provides a test method based on the high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device, which can simulate the micro-fracture accumulation, energy release and earthquake induction process of deep faults under the superposition of high- and low-frequency dynamic disturbances.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering for fluid activities, and in particular to a high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device and a test method. Background Art

[0002] In the field of underground engineering, the mechanisms of earthquake induction and their dynamic response have long been a key concern for both academics and engineers. Deep engineering, in particular, significantly increases the risk of induced earthquakes due to the complex stress environment and energy accumulation, posing a serious threat to personnel safety and engineering stability.

[0003] Traditional earthquake simulation testing methods, which mostly rely on single-frequency or purely static loading, are unable to accurately reproduce the complex dynamic characteristics of actual earthquakes, such as the superposition of high- and low-frequency perturbations, nonlinear responses, and rupture evolution. High-frequency perturbations primarily simulate localized transient energy releases from blasting and fractures, while low-frequency perturbations can simulate regional slow deformations caused by natural earthquakes or engineering disturbances. The coupling of these two factors is a key factor in the development of medium- to large-scale earthquakes.

[0004] Existing test equipment generally lacks the ability to load multi-frequency coupled disturbances, making it difficult to fully explore the critical conditions, failure modes, and evolution mechanisms of induced earthquakes, thus limiting the development of related prevention and control technologies. Therefore, it is urgent to develop a test device for simulating earthquakes induced by high- and low-frequency combined dynamic disturbances. This device can be used to conduct simulation tests of high- and low-frequency combined dynamic disturbances to reveal the mechanism of earthquakes induced by these combined dynamic disturbances, optimize dynamic disaster prediction models for deep engineering projects, and provide strong guarantees for the safe implementation of underground projects. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present invention provides a high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device and test method, which can accurately simulate the tectonic stress state of underground faults and the effects of high- and low-frequency combined dynamic disturbances on them, and reveal the induced earthquake mechanism under high- and low-frequency combined dynamic disturbances.

[0006] The high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device of the present invention includes a static loading system, a dynamic disturbance system, a fixture system, and a data monitoring and control system. The simulated fault specimen is provided with a 45-degree oblique fault. The 45-degree oblique fault divides the simulated fault specimen into a sliding upper plate and a fixed lower plate that fit together. The outer surface of the fixed lower plate is arranged in the Z-axis direction and the X-axis direction, respectively, and the sliding upper plate is arranged in the Z+ axis direction and the X+ axis direction, respectively.

[0007] The static loading system includes a static loading frame and a static loading device arranged on the static loading frame, which is used to provide X-axis and Z-axis biaxial four-directional static loading to the simulated fault specimen;

[0008] The dynamic disturbance system includes a low-frequency disturbance device and a high-frequency disturbance device, which are used to provide biaxial dynamic disturbance in the X-axis and Z-axis directions to the simulated fault specimen;

[0009] The fixture system is arranged in the static loading frame, and is used to limit and fix the simulated fault specimen, and transmit the static load and dynamic disturbance to the simulated fault specimen;

[0010] The data monitoring and control system is used to control the static loading system and the dynamic disturbance system, and monitor and store test data through the data acquisition element and the monitoring system connected to the data acquisition element.

[0011] The static loading system and dynamic disturbance system can simulate the stress state of the fault under complex stress conditions caused by high- and low-frequency combined dynamic disturbances. The response characteristics of the simulated fault specimen under high- and low-frequency combined dynamic disturbances are obtained through the data monitoring and control system, thereby realizing earthquake-induced simulation under high- and low-frequency combined dynamic disturbances.

[0012] Furthermore, the static loading device includes two first static servo cylinders vertically arranged on the static loading frame and corresponding to the Z-axis surface of the simulated fault specimen, and two second static servo cylinders horizontally arranged on the static loading frame and corresponding to the X-axis surface of the simulated fault specimen. The static loading piston rods of the first static servo cylinder and the second static servo cylinder are respectively connected to the clamping system. A vertical first hollow part is provided in the middle of the first static servo cylinder, and a horizontal second hollow part is provided in the middle of the second static servo cylinder. The first hollow part and the second hollow part serve as channels for the dynamic disturbance transmission rod.

[0013] Furthermore, the clamping system includes a pressure plate that is fitted with the X-axis surface and the Z-axis surface of the simulated fault specimen, and also includes a connecting plate arranged on the upper surface of the pressure plate, and the connecting plate is provided with a roller on the side close to the pressure plate, and the connecting plate is slidingly connected to the pressure plate through the roller and the limit member, and also includes a conversion head arranged on the other side of the connecting plate, and the conversion head is respectively connected to the static loading piston rod of the first static servo cylinder or the second static servo cylinder.

[0014] Furthermore, the data monitoring and control system includes a control system and a data acquisition and detection system. The data acquisition and detection system includes a force detection element and a force monitoring system connected to the output end of the force detection element, a displacement detection element and a displacement detection system connected to the displacement detection element, an acoustic emission detection element and a strain detection element. The force detection element is arranged between the conversion head and the static loading piston rod, and the displacement detection element is linked to the static loading piston rod; the acoustic emission detection element and the strain detection element are respectively arranged near the oblique 45-degree fault of the simulated fault specimen.

[0015] Furthermore, the fixture system also includes a piston orienting member, an orienting rod and an orienting sleeve, one end of the piston orienting member is connected to the static loading piston rod, and the other end is connected to the orienting rod. The orienting rod is arranged in the orienting sleeve and can move radially in the orienting sleeve. The orienting sleeve is fixed on the static loading frame, and the displacement detection element is arranged on the orienting rod. When the fault of the simulated fault specimen moves, it can drive the pressure plate to slide, thereby driving the orienting rod to move radially in the orienting sleeve. The displacement data of the simulated fault specimen can be monitored through the displacement detection element connected to the orienting rod.

[0016] Furthermore, the dynamic disturbance system includes a dynamic disturbance cylinder arranged in the Z+ direction of the static loading frame, an electromagnetic emission chamber and a dynamic disturbance force transmission rod arranged in the X+ direction of the static loading frame. The dynamic disturbance cylinder is fixed to the static loading frame through a disturbance cylinder frame, and is arranged corresponding to the first static servo cylinder for applying low-frequency disturbance. The piston rod of the dynamic disturbance cylinder is connected to one end of the dynamic disturbance force transmission rod in the Z+ direction. The electromagnetic emission chamber is arranged on the static loading frame through an electromagnetic Hopkinson rod frame, and is arranged corresponding to the second static servo cylinder in the X+ direction for applying high-frequency disturbance. The electromagnetic emission chamber is connected to one end of the dynamic disturbance force transmission rod in the X+ direction. The other end of the dynamic disturbance force transmission rod passes through the first hollow part or the second hollow part and is in contact with the simulated fault specimen.

[0017] Furthermore, the dynamic disturbance system also includes a force transmission rod conversion head and a disturbance pressure block. The clamp system is provided with a through hole for the force transmission rod conversion head and the disturbance pressure block to pass through. The disturbance pressure block is fixed to the other end of the dynamic disturbance force transmission rod through the force transmission rod conversion head. The dynamic disturbance force transmission rod is in contact with the outer surface of the simulated fault specimen through the disturbance pressure block.

[0018] The present invention also provides a high- and low-frequency combined dynamic disturbance-induced earthquake simulation test method, which is implemented based on the high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device and includes the following steps:

[0019] S1: Calculate the initial fault stress state based on the deep ground stress, start the static loading system, and use the displacement-controlled force loading method to apply a certain initial stress to the simulated fault specimen in four directions along the two axes to ensure that the simulated fault specimen is centered and fixed. Then start the data acquisition and monitoring system to record the data during the experiment.

[0020] S2: In the X-direction and Z-direction, the position of the fixed footwall is kept fixed, and the static loading system is loaded synchronously to the design value. After stabilization, the stress in the X+ direction is kept constant, and the stress in the Z+ direction is gradually increased until the fault slips at an oblique angle of 45 degrees. The critical shear stress of the fault is calculated.

[0021] S3: Gradually reduce the Z+ stress to reduce the fault shear stress to 80%~90% of the critical fault shear stress;

[0022] S4: starting the low-frequency disturbance device of the dynamic disturbance system to apply low-frequency dynamic disturbance to the simulated fault specimen according to a predetermined magnitude and frequency;

[0023] S5: Maintain low-frequency dynamic disturbance, start the high-frequency disturbance device, and apply high-frequency impact disturbance to the simulated fault specimen according to the set loading path to achieve biaxial and two-directional high- and low-frequency combined dynamic disturbance loading;

[0024] S6: 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 the high- and low-frequency combined dynamic disturbance.

[0025] Furthermore, step S7 is also included, which draws the time variation curve of 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 the underground fault under the action of high- and low-frequency combined dynamic disturbance.

[0026] Compared with the prior art, the beneficial effects of the present invention are: the present invention can perform biaxial four-directional static loading on large-scale rock samples through the static loading system. In addition, through the dynamic perturbation system, it can perform biaxial two-directional high- and low-frequency combined dynamic perturbation loading on simulated fault samples. The device can simulate the stress state of the high- and low-frequency combined dynamic perturbation that the fault is subjected to under deep complex stress conditions, and is particularly suitable for studying the response characteristics and fracture evolution process of deep fracture structures under multi-source dynamic perturbations.

[0027] The experimental method based on the high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device can simulate the micro-fracture accumulation, energy release and earthquake induction process of deep faults under the superposition of high- and low-frequency dynamic disturbances, and can be used to systematically study the earthquake incubation and triggering mechanism under the action of high- and low-frequency combined dynamic disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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 any creative work.

[0029] Figure 1 This is a structural diagram of the test device of the present invention;

[0030] Figure 2 Schematic diagram of the overall structure of the test device of the present invention;

[0031] Figure 3 Schematic diagram of the internal structure of the test device of the present invention;

[0032] Figure 4 This is a structural diagram of an embodiment of a clamp system of the present invention;

[0033] Figure 5 This is a schematic structural diagram of an embodiment of a simulated fault specimen of the present invention;

[0034] Figure 6 Schematic diagram of the stress state of a simulated fault specimen under high- and low-frequency combined dynamic disturbances.

[0035] Reference numerals:

[0036] 1-static loading system; 11-static loading frame; 12-first static servo cylinder; 13-first static loading piston rod; 14-second static servo cylinder; 15-second static loading piston rod; 16-cylinder cover; 2-dynamic disturbance system; 21-disturbance cylinder frame; 22-dynamic disturbance cylinder; 23-electromagnetic Hopkinson bar frame; 24-electromagnetic emission chamber; 25-dynamic disturbance force transmission rod; 3-fixture system; 31-conversion head; 32-connecting plate; 33-roller; 34-pressure plate; 35-limiting part; 36-piston orientation part; 37-orientation rod; 38-orientation sleeve; 4-simulated fault specimen; 41-sliding upper plate; 42-fixed lower plate; 5-data monitoring and control system; 51-acoustic emission detection element; 52-strain detection element; 53-force detection element; 54-displacement detection element. DETAILED DESCRIPTION

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as 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 for the purpose of describing specific embodiments only 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 accompanying drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of the present invention and the accompanying drawings are used to distinguish different objects, not to describe a specific order.

[0038] References to "embodiments" in this disclosure mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to mutually exclusive, independent, or alternative embodiments to other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this disclosure may be combined with other embodiments.

[0039] 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 with reference to the accompanying drawings.

[0040] like Figures 1-6 As shown, the high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device of the present invention includes a static loading system 1, a dynamic disturbance system 2, a clamping system 3, and a data monitoring and control system 5, wherein the simulated fault sample 4 is provided with a 45-degree oblique fault, and the 45-degree oblique fault divides the simulated fault sample 4 into a sliding upper plate 41 and a fixed lower plate 42 that fit together, and the outer surfaces of the fixed lower plate 42 are respectively arranged in the Z-axis direction and the X-axis direction, and the sliding upper plate 41 is respectively arranged in the Z+ axis direction and the X+ axis direction.

[0041] like Figure 2 and Figure 3 As shown, the static loading system includes a static loading frame 11 and a static loading device arranged on the static loading frame 11. The static loading device includes a vertical bidirectional loading system and a horizontal bidirectional loading system, providing biaxial four-directional static loading.

[0042] The static loading frame 11 in this example is integrally cast. The vertical bidirectional loading system consists of two sets of 500T first static servo cylinders 12 arranged vertically, and the horizontal bidirectional loading system consists of two sets of 200T second static servo cylinders 14 arranged horizontally. The first static loading piston rod 13 of the first static servo cylinder 12 and the second static loading piston rod 15 of the second static servo cylinder 14 are respectively connected to the clamping system 3. The first static servo cylinder 12 has a vertical first hollow portion in the middle, and the second static servo cylinder 14 has a horizontal second hollow portion in the middle. The first and second hollow portions serve as channels for the dynamic disturbance transmission rod. For simplicity of description, the first static loading piston rod 13 and the second static loading piston rod 15 are collectively referred to as the static loading piston rod.

[0043] The dynamic perturbation system 2 of this example includes a perturbation cylinder frame 21, a dynamic perturbation cylinder 22 arranged in the Z+ direction of the static loading frame, an electromagnetic emission chamber 24 arranged in the X+ direction of the static loading frame, and a dynamic perturbation force transmission rod 25. The dynamic perturbation cylinder 22 is fixed to the static loading frame 11 through the perturbation cylinder frame 21 and is correspondingly arranged with the first static servo cylinder 12 for applying low-frequency perturbations. The piston rod of the dynamic perturbation cylinder 22 is connected to one end of the dynamic perturbation force transmission rod 25 in the Z+ direction. The electromagnetic emission chamber 24 is arranged on the static loading frame 11 through an electromagnetic Hopkinson bar frame 23 and is correspondingly arranged with the second static servo cylinder 14 in the X+ direction for applying high-frequency perturbations. The electromagnetic emission chamber 24 is connected to one end of the dynamic perturbation force transmission rod 25 in the X+ direction. The other end of the dynamic perturbation force transmission rod 25 passes through the first hollow portion or the second hollow portion and is in contact with the simulated fault specimen 4.

[0044] Preferably, the dynamic disturbance system also includes a force transmission rod conversion head and a disturbance pressure block. The clamp system is provided with a through hole for the force transmission rod conversion head and the disturbance pressure block to pass through. The disturbance pressure block is fixed to the other end of the dynamic disturbance force transmission rod 25 through the force transmission rod conversion head. The dynamic disturbance force transmission rod 25 is reliably contacted and connected with the outer surface of the simulated fault specimen through the disturbance pressure block.

[0045] The dynamic disturbance cylinder 22 in this example is a set of 10T dynamic hydraulic cylinders, which can provide a maximum of 100kN, 0~50Hz long-term low-frequency dynamic disturbance; the horizontally configured electromagnetic launch chamber 24 can provide a maximum of 250kN, up to 500s -1 Instantaneous high-frequency dynamic disturbances of strain rate.

[0046] like Figure 2-Figure 4As shown, the fixture system 3 of this example serves to transmit static loads and dynamic disturbances to the specimen. It includes a pressure plate 34, which is positioned in contact with the X- and Z-axis surfaces of the simulated fault specimen 4. It also includes a connecting plate 32, which is positioned on the upper surface of the pressure plate 34. A roller 33 is provided on the side of the connecting plate 32 near the pressure plate 34. The connecting plate 32 and the pressure plate 34 are slidably connected via the roller 33 and a stopper 35. The stopper in this example is a stopper spring, which serves as a limiter. It is worth noting that the fixed lower plate of the simulated fault specimen 4 in this example needs to be fixed in position on its placement surface in the X-direction. Therefore, the X-direction pressure plate and the connecting plate are directly fixedly connected in this example, without the use of rollers.

[0047] A conversion head 31 is located on the other side of the connecting plate 32, away from the rollers 33. This conversion head 31 is connected to the static loading piston rod of the first or second static servo cylinder. The static loading piston rod applies a static load to the fixture system, which is then transferred to the four surfaces of the simulated fault specimen in contact with it.

[0048] like Figure 1-Figure 5 As shown, the data monitoring and control system of this example includes a control system and a data acquisition and detection system. The data acquisition and detection system includes a force detection element 53 and a force monitoring system connected to the output end of the force detection element 53, a displacement detection element 54 and a displacement detection system connected to the displacement detection element 54, an acoustic emission detection element 51 and an acoustic emission monitoring system connected to the acoustic emission detection element, and a strain detection element 52 and a strain monitoring system connected to the strain monitoring element. The force detection element 53 is arranged between the conversion head 31 and the static loading piston rod, and the displacement detection element 54 is linked to the static loading piston rod. The acoustic emission detection element 51 and the strain detection element 52 are respectively arranged near the oblique 45-degree fault of the simulated fault specimen. In this example, the acoustic emission detection element 51 can be an acoustic emission sensor, the strain detection element 52 can be a strain gauge, etc., the displacement detection element 54 can be various mainstream displacement sensors on the market, and the force detection element can be a force sensor, etc.

[0049] The acoustic emission monitoring system in this example includes an acoustic emission probe, a preamplifier and an acoustic emission monitoring and analysis system, which is mainly used to track, monitor and record acoustic emission events during the test.

[0050] The control system includes a static servo control module, a low-frequency disturbance control module and an electromagnetic pulse emission control module, which plays a role in accurately controlling static and dynamic disturbance loading.

[0051] The data acquisition and monitoring system also includes a multi-channel synchronous recorder, whose input ends are respectively connected to the displacement detection element, the force detection element, the acoustic emission detection element, and the strain detection element, which can ensure that the test data is recorded and stored completely and effectively.

[0052] In this example, the displacement and force sensors are used to record the vertical force and displacement, and the horizontal force and displacement, respectively, during the test. The acoustic emission and strain sensors are located near the fault to monitor acoustic emission events and stress changes on the fault.

[0053] As an embodiment of the present invention, the displacement detection element 54 of this example is arranged on the self-balancing piston structure of the pressure chamber. Specifically, the clamping system 3 of this example also includes a piston orienting member 36, an orienting rod 37 and an orienting sleeve 38. One end of the piston orienting member 36 is an annular structure, which is sleeved on the static loading piston rod, and the other end is connected to the orienting rod 37. The orienting rod 37 is arranged in the orienting sleeve 38 and can move radially in the orienting sleeve 38. The orienting sleeve 38 is fixed on the static loading frame 11. The displacement detection element 54 is arranged on the orienting rod 37. When the fault of the simulated fault specimen moves, it can drive the pressure plate to slide, thereby driving the orienting rod to move radially in the orienting sleeve. The displacement data of the simulated fault specimen can be monitored through the displacement detection element connected to the orienting rod.

[0054] The present invention also provides a method for simulating earthquakes induced by combined high- and low-frequency dynamic disturbances, which is used to simulate the microfracture accumulation, energy release, and earthquake-inducing processes of deep faults under the combined effects of high- and low-frequency dynamic disturbances. This method includes the following steps:

[0055] S1: Calculate the initial fault stress state based on the deep ground stress, start the static loading system, and use the displacement-controlled force loading method to apply a certain initial stress to the simulated fault specimen in four directions along the two axes to ensure that the simulated fault specimen is centered and fixed. Then start the data acquisition and monitoring system to record the data during the experiment.

[0056] S2: In the X-direction and Z-direction, the position of the fixed footwall is kept fixed, and the static loading system is loaded synchronously to the design value. After stabilization, the stress in the X+ direction is kept constant, and the stress in the Z+ direction is gradually increased until the fault slips at an oblique angle of 45 degrees. The critical shear stress of the fault is calculated.

[0057] S3: Gradually reduce the Z+ stress to reduce the fault shear stress to 80%~90% of the critical fault shear stress;

[0058] S4: starting the low-frequency disturbance device of the dynamic disturbance system to apply low-frequency dynamic disturbance to the simulated fault specimen according to a predetermined magnitude and frequency;

[0059] S5: Maintain low-frequency dynamic disturbance, start the high-frequency disturbance device, and apply high-frequency impact disturbance to the simulated fault specimen according to the set loading path to achieve biaxial and two-directional high- and low-frequency combined dynamic disturbance loading;

[0060] S6: 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 the high- and low-frequency combined dynamic disturbance.

[0061] The following describes the implementation of the present invention in detail: Before executing the test method of the present invention, it is necessary to prepare a simulated fault sample and set up a test environment.

[0062] The preparation method of the simulated fault specimen in this example is:

[0063] The rock samples obtained on site were cut and polished into 400×400×50 mm cubic specimens, and cut into the following shapes along the diagonal lines of the front: Figure 5 The two triangular prism-shaped specimens shown have a 20 mm chamfered edge, a ground cross-section to simulate fault roughness, and ground sides to increase friction, ensuring sufficient friction between the specimen and the fixture.

[0064] Installation of the fixture system: Align and connect the conversion head 31, connecting plate 32, roller 33, and pressure plate 34. The pressure plate is connected to the roller and connecting plate through a limit spring so that it can move with the sliding of the simulated fault. There is no roller under the lower pressure plate.

[0065] Sensor installation: Place the acoustic emission detection element 51 and the strain detection element 52 Figure 5 The position shown is attached to the simulated fault sample 4 and connected to the multi-channel synchronous recorder via a signal line. The simulated fault sample 4 is then placed in the fixture system 3.

[0066] After the hardware environment is built, the simulation test begins.

[0067] Step S1: Calculate the initial fault stress state based on the deep ground stress, start the static servo control module, and use the displacement-controlled force loading method to apply an initial stress of approximately 0.5 MPa to the sample in four directions along both axes to align and fix the sample. Then, start the data monitoring and acquisition system to record the displacement, force, acoustic emission, and stress wave data during the experiment.

[0068] Step S2: Using displacement control mode in the X-direction and Z-direction to keep the fixed lower plate 42 in a fixed position; using force control mode to simultaneously load the X+ direction stress and Z+ stress To transverse stress Reach the design value; after stabilization, maintain the X+ stress in force control mode Constant, gradually increasing Z+ stress Until the fault slips, the critical shear stress of the fault is calculated.

[0069] Fault shear stress The calculation formula is:

[0070]

[0071] : vertical stress;

[0072] : transverse stress;

[0073] : Fault angle, 45°.

[0074] Step S3: Gradually reduce the Z+ stress , reducing the fault shear stress to 80%~90% of the critical fault shear stress.

[0075] Step S4: Start the low-frequency disturbance control module and apply low-frequency dynamic disturbance to the simulated fault sample according to the designed magnitude and frequency.

[0076] Step S5: While maintaining the low-frequency dynamic disturbance, start the electromagnetic pulse emission control module to apply high-frequency impact disturbance to the simulated fault specimen according to the designed loading path to achieve biaxial and bidirectional high- and low-frequency combined dynamic disturbance loading.

[0077] Step S6: Record the displacement, force, acoustic emission and stress wave data during the experiment, and calculate the fault displacement at each moment, the effective normal stress on the fault, and the seismic moment and moment magnitude of each earthquake event.

[0078] Fault displacement The calculation method is:

[0079]

[0080] in,

[0081] : total axial displacement measured by the displacement monitoring element of the vertical axis;

[0082] : is the elastic deformation of the statically loaded piston rod, is the static force difference before and after loading, The stiffness of the piston rod is statically loaded;

[0083] : simulates the axial deformation of the fault specimen, is the average strain, is the length of the simulated fault specimen;

[0084] : Fault angle, in this case 45°.

[0085] seismic moment The calculation method is:

[0086]

[0087] : The number of acoustic emission monitoring elements, a total of 16, is the serial number of the acoustic emission detection element, ,

[0088] : No. The P-wave amplitude of each acoustic emission monitoring element;

[0089] : No. The distance from an acoustic emission monitoring element to the earthquake source.

[0090] moment magnitude The calculation method is:

[0091]

[0092] Preferably, the test method of the present invention also includes step S7: saving and organizing data, drawing the fault displacement, fault shear stress, and effective normal stress on the fault during the fault slip process over time based on the displacement, force, acoustic emission and stress wave data, recording the seismic moment and moment magnitude of each seismic event, and studying the induced earthquake process of underground faults under the action of high- and low-frequency combined dynamic disturbances.

[0093] As can be seen from the above, the present invention has the following innovations:

[0094] The present invention can perform biaxial four-directional static loading on large-scale rock samples through a static loading system. In addition, through a dynamic perturbation system, it can perform biaxial two-directional high- and low-frequency combined dynamic perturbation loading on simulated fault samples. The device can simulate the stress state of the high- and low-frequency combined dynamic perturbation that the fault is subjected to under deep complex stress conditions, and is particularly suitable for studying the response characteristics and fracture evolution process of deep fracture structures under multi-source dynamic perturbations.

[0095] The experimental method based on the high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device can simulate the micro-fracture accumulation, energy release and earthquake induction process of deep faults under the superposition of high- and low-frequency dynamic disturbances, and can be used to systematically study the earthquake incubation and triggering mechanism under the action of high- and low-frequency combined dynamic disturbances.

[0096] The specific implementation manner described above is a preferred implementation manner of the present invention, and is not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific implementation manner. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. High- and low-frequency combined dynamic disturbance-induced earthquake simulation test device, characterized by: It includes a static loading system, a dynamic perturbation system, a fixture system, and a data monitoring and control system. The simulated fault specimen is provided with a 45-degree oblique fault. The 45-degree oblique fault divides the simulated fault specimen into a sliding upper plate and a fixed lower plate that fit together. The outer surface of the fixed lower plate is respectively arranged in the Z-axis direction and the X-axis direction, and the sliding upper plate is respectively arranged in the Z+ axis direction and the X+ axis direction. The static loading system includes a static loading frame and a static loading device arranged on the static loading frame, which is used to provide X-axis and Z-axis biaxial four-directional static loading to the simulated fault specimen; The dynamic disturbance system includes a low-frequency disturbance device and a high-frequency disturbance device, which are used to provide bi-directional dynamic disturbance in the X-axis and Z-axis directions to the simulated fault specimen; The fixture system is arranged in the static loading frame, and is used to limit and fix the simulated fault specimen, and transmit the static load and dynamic disturbance to the simulated fault specimen; The data monitoring and control system is used to control the static loading system and the dynamic disturbance system, and monitors and stores test data through the data acquisition element and the monitoring system connected to the data acquisition element. The static loading system and dynamic perturbation system can simulate the stress state of the fault under complex stress conditions caused by high- and low-frequency combined dynamic perturbations. The response characteristics of the simulated fault specimen under high- and low-frequency combined dynamic perturbations are obtained through the data monitoring and control system, thereby realizing earthquake-induced simulation under high- and low-frequency combined dynamic perturbations. The static loading device includes two first static servo oil cylinders vertically arranged on the static loading frame and corresponding to the Z-axis surface of the simulated fault specimen, and two second static servo oil cylinders horizontally arranged on the static loading frame and corresponding to the X-axis surface of the simulated fault specimen. The static loading piston rods of the first static servo oil cylinder and the second static servo oil cylinder are respectively connected to the clamp system. A vertical first hollow portion is provided in the middle of the first static servo oil cylinder, and a horizontal second hollow portion is provided in the middle of the second static servo oil cylinder. The first hollow portion and the second hollow portion serve as channels for the dynamic disturbance transmission rod. The dynamic disturbance system includes a dynamic disturbance cylinder arranged in the Z+ direction of the static loading frame, an electromagnetic emission chamber and a dynamic disturbance force transmission rod arranged in the X+ direction of the static loading frame. The dynamic disturbance cylinder is fixed to the static loading frame through a disturbance cylinder frame, and is arranged corresponding to the first static servo cylinder for applying low-frequency disturbance. The piston rod of the dynamic disturbance cylinder is connected to one end of the dynamic disturbance force transmission rod in the Z+ direction. The electromagnetic emission chamber is arranged on the static loading frame through an electromagnetic Hopkinson rod frame, and is arranged corresponding to the second static servo cylinder in the X+ direction for applying high-frequency disturbance. The electromagnetic emission chamber is connected to one end of the dynamic disturbance force transmission rod in the X+ direction. The other end of the dynamic disturbance force transmission rod passes through the first hollow part or the second hollow part and is in contact with the simulated fault specimen.

2. The high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device according to claim 1 is characterized in that: The clamping system includes a pressure plate that is fitted with the X-axis surface and the Z-axis surface of the simulated fault specimen, and also includes a connecting plate arranged on the upper surface of the pressure plate. The connecting plate is provided with a roller on the side close to the pressure plate. The connecting plate is slidably connected to the pressure plate through the roller and the limit member. It also includes a conversion head arranged on the other side of the connecting plate, and the conversion head is respectively connected to the static loading piston rod of the first static servo cylinder or the second static servo cylinder.

3. The high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device according to claim 2 is characterized in that: The data monitoring and control system includes a control system and a data acquisition and detection system. The data acquisition and detection system includes a force detection element and a force monitoring system connected to the output end of the force detection element, a displacement detection element and a displacement detection system connected to the displacement detection element, an acoustic emission detection element and a strain detection element. The force detection element is arranged between the conversion head and the static loading piston rod, and the displacement detection element is linked to the static loading piston rod; The acoustic emission detection element and the strain detection element are respectively arranged near the oblique 45-degree fault of the simulated fault specimen.

4. The high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device according to claim 3 is characterized in that: The fixture system further includes a piston orientation member, an orientation rod, and an orientation sleeve. One end of the piston orientation member is connected to the static loading piston rod, and the other end is connected to the orientation rod. The orientation rod is disposed in the orientation sleeve and is capable of radially moving in the orientation sleeve. The orientation sleeve is fixed to the static loading frame. The displacement detection element is disposed on the orientation rod. When the fault of the simulated fault sample moves, it can drive the pressure plate to slide, thereby driving the orientation rod to move radially in the orientation sleeve. The displacement data of the simulated fault sample can be monitored by the displacement detection element connected to the orientation rod.

5. The high- and low-frequency combined dynamic disturbance-induced earthquake simulation test device according to claim 1 is characterized in that: The dynamic disturbance system also includes a force transmission rod conversion head and a disturbance pressure block. The clamp system is provided with a through hole for the force transmission rod conversion head and the disturbance pressure block to pass through. The disturbance pressure block is fixed to the other end of the dynamic disturbance force transmission rod through the force transmission rod conversion head. The dynamic disturbance force transmission rod is in contact with and connected to the outer surface of the simulated fault specimen through the disturbance pressure block.

6. A method for simulating earthquakes induced by a combination of high and low frequency dynamic disturbances, implemented based on the apparatus for simulating earthquakes induced by a combination of high and low frequency dynamic disturbances according to any one of claims 1 to 5, characterized in that: The test method comprises the following steps: S1: Calculate the initial fault stress state based on the deep ground stress, start the static loading system, and use the displacement-controlled force loading method to apply a certain initial stress to the simulated fault specimen in four directions along the two axes to ensure that the simulated fault specimen is centered and fixed. Then start the data acquisition and monitoring system to record the data during the experiment. S2: In the X-direction and Z-direction, the position of the fixed footwall is kept fixed, and the static loading system is loaded synchronously to the design value. After stabilization, the stress in the X+ direction is kept constant, and the stress in the Z+ direction is gradually increased until the fault slips at an oblique angle of 45 degrees. The critical shear stress of the fault is calculated. S3: Gradually reduce the Z+ stress to reduce the fault shear stress to 80%~90% of the critical fault shear stress; S4: starting the low-frequency disturbance device of the dynamic disturbance system to apply low-frequency dynamic disturbance to the simulated fault specimen according to a predetermined magnitude and frequency; S5: Maintain low-frequency dynamic disturbance, start the high-frequency disturbance device, and apply high-frequency impact disturbance to the simulated fault specimen according to the set loading path to achieve biaxial and two-directional high- and low-frequency combined dynamic disturbance loading; S6: 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 the high- and low-frequency combined dynamic disturbance.

7. The test method according to claim 6, characterized in that: The method also includes step S7, which draws a curve of 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 earthquake event, and studies the induced earthquake process of the underground fault under the action of high- and low-frequency combined dynamic disturbance.

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