Biaxial impact loading test device for protrusion-impact composite dynamic disaster

Abstract

The invention provides a biaxial impact loading test device for protrusion-impact composite dynamic disasters, and relates to the technical field of coal rock dynamic disaster tests. Comprising a sealing test cavity, multidirectional static loading devices, one-way impact loading devices, a lateral restraining device, a detachable side wall assembly, a pressure stabilizing type gas supply system and a mechanical driving mechanism, the sealing test cavity is used for loading a sample, and the multidirectional static loading devices are arranged in the X direction and the Z direction of the sealing test cavity respectively. Compared with an existing test device, the device has the advantages that coupling triggering of controllable unloading lateral constraint and impact loading is realized for the first time, so that a coal body failure mode and a gas release process are closer to actual mining conditions; and a high-fidelity and repeatable experiment platform is provided for revealing an inoculation and triggering mechanism of the outburst-impact hybrid dynamic disaster, establishing a risk evaluation index system and calibrating field monitoring and early warning parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal and rock dynamic disaster test, and particularly relates to a test loading device for coal and gas outburst and rock burst under the combined action of high stress, high gas occurrence and engineering disturbance. BACKGROUND

[0002] With the gradual depletion of high-quality coal resources in the shallow part, coal mining in China is continuously advancing to the deep part, and the coal and rock mass around the working face and roadway is generally in a complex environment of high three-dimensional ground stress, high gas pressure, high ground temperature, and is long-term affected by repeated engineering disturbances such as tunneling, mining, lifting, and pressure relief. Under this background, the dynamic disasters such as rock burst and coal and gas outburst are characterized by frequent occurrence, high intensity, and large damage range, and often occur in a combined form. That is, under the action of strong stress redistribution and impact disturbance, the gas desorption in the coal body is accelerated, the cracks are rapidly expanded, and the process of gas seepage is coupled, which induces large-scale fragmentation and high-speed ejection of the coal body, forming a "rock burst and outburst" combined dynamic disaster. In particular, in recent years, a large number of disaster statistics show that outburst and rock burst in deep coal mines often exhibit a combined coupling characteristic, that is, external disturbance or mining impact triggers coal fracture, and gas pressure further amplifies the fracture process and promotes the ejection of the fragments, making the disaster more destructive and more sudden. This kind of disaster has the characteristics of strong suddenness, hidden incubation process, multiple influencing factors and mutual coupling, and is one of the key technical problems restricting the safe and efficient mining of deep coal mines.

[0003] To reveal the incubation and triggering mechanism of such disasters, it is urgent to have a test device that can reconstruct the real working conditions in the laboratory. However, the existing coal and rock dynamics test equipment still has significant shortcomings. First, the existing test devices can only apply uniaxial impact or three-dimensional static load, and cannot realize the superimposed loading mode of "multi-directional static load + unidirectional impact", while the deep coal body is often triggered to fracture under the superimposed loading of high static load and transient dynamic load in real working conditions. Second, the dynamic disaster of deep coal body is often accompanied by significant spatial structure mutation behavior. Typical cases include tunneling head-on advancement, new roadway breakthrough, old roadway reuse, and coal wall exposure in front of the working face, etc. These engineering activities will change the stress distribution and energy re-accumulation in the local area in a short time, thereby significantly changing the fracture initiation position, propagation path and ejection direction. Most test cavities adopt fixed rigid side wall structure, which cannot realize the rapid removal of lateral constraint during loading, and therefore cannot reproduce the stress redistribution and free-air triggering effect caused by the sudden exposure of the coal wall side in the tunneling process.

[0004] In summary, existing technologies still have many shortcomings in simulating complex dynamic disasters in deep coal seams: First, the triaxial stress boundary does not match the actual engineering situation, making it difficult to reproduce the real stress state of "multi-directional static load + unidirectional dynamic load + strong third-direction constraint"; second, the lateral boundary is difficult to remove quickly during the loading process, and cannot form a single-sided free surface corresponding to the processes of roadway excavation and coal wall exposure. Summary of the Invention

[0005] To address the shortcomings of the prior art, the technical problem to be solved by the embodiments of the present invention is to provide a biaxial impact loading test device for protrusion-impact composite dynamic disasters, which is used to construct a force-gas-boundary three-field coupling environment of deep coal seams under high stress, high gas occurrence and transient free-space conditions in the laboratory.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A biaxial impact loading test device for protrusion-impact combined dynamic disasters includes a sealed test chamber, a multi-directional static load loading device, a unidirectional impact loading device, a lateral restraint device, a detachable sidewall assembly, a pressure-stabilized gas supply system, and a mechanical drive mechanism.

[0008] The sealed test chamber is used to load the sample.

[0009] The multi-directional static load loading devices are respectively arranged in the X and Z directions of the sealed test chamber, and are used to apply multi-directional static pressure to the sample inside the sealed test chamber.

[0010] The unidirectional impact loading device is coaxially arranged with the X-axis static load loading device and is used to apply transient impact loads to the specimen inside the sealed test chamber.

[0011] The lateral restraint device and the removable sidewall assembly are arranged in the Y direction of the sealed test chamber.

[0012] The lateral restraint device is used to provide continuous and stable lateral confining pressure on the specimen during test loading.

[0013] The mechanical drive mechanism is used to remove the opening of the self-sealing test chamber of the detachable sidewall assembly.

[0014] The pressure-stabilized gas supply system is used to supply gas into the sealed test chamber.

[0015] As a further improvement of the present invention: the sealed test chamber forms a closed space inside, and the sealed test chamber as a whole is a thickened cavity structure, which forms a closed chamber through flanges, bolts and multi-level sealing rings.

[0016] As a further improvement of the present application, a loading channel is reserved on the outer wall of the sealing test cavity, and an air inlet, an air outlet and a pressure monitoring interface are arranged on the top or bottom of the sealing test cavity.

[0017] As a further improvement of the present application, the stable pressure type gas supply system comprises an air inlet unit and an air outlet unit,

[0018] The air inlet pipeline of the air inlet unit is connected with a gas source, a pressure reducing valve and a total air inlet valve are arranged on the pipeline, the pressure reducing valve is used for preliminary pressure reduction of the gas entering the system, and the total air inlet valve is used for control switching,

[0019] A first branch is arranged downstream of the total air inlet valve, the first branch is connected with a buffer cavity with a larger volume than the sealing test cavity through a first throttle valve, the first throttle valve is used for flow limitation, and the outlet of the buffer cavity is connected with the air inlet of the sealing test cavity through a second throttle valve,

[0020] A second branch is directly connected with the sealing test cavity through a small flow air supplement valve, the small flow air supplement valve is used for slight pressure compensation of the sealing test cavity during the test,

[0021] An air outlet pipeline of the air outlet unit is connected with the air outlet of the sealing test cavity, a stable pressure adjusting valve, a discharge valve and a gas flow meter are arranged on the pipeline in sequence, the stable pressure adjusting valve and the discharge valve are used for controllable gas release when the pressure in the sealing test cavity is too high, and the gas flow meter is used for monitoring the discharge flow of the gas.

[0022] As a further improvement of the present application, a multistage sealing structure is arranged between the inner wall of the sealing test cavity and the loading holes in each direction for sealing, the multistage sealing structure comprises a metal sealing ring, a pressure-resistant rubber ring and a rubberized sealing material.

[0023] As a further improvement of the present application, pressure sensors are arranged on the sealing test cavity and the buffer cavity respectively, and the pressure sensors are installed on the pressure monitoring interface.

[0024] As a further improvement of the present application, the multidirectional static load loading device comprises a static load loading oil cylinder and a loading pressure head, and the static load loading oil cylinder and the loading pressure head are used for applying independently controllable static axial and vertical pressures.

[0025] As a further improvement of the present application, the unidirectional impact loading device comprises an impact rod, an incident rod, a transmission rod and an absorption rod, the impact rod, the incident rod, the transmission rod and the absorption rod are arranged along the same linear direction and are in precise contact,

[0026] The impact rod is used to generate high amplitude stress wave when loading, and the stress wave is firstly transmitted to the incident rod, which is used to propagate and shape the stress wave, and drive the stress wave to directly act on the sample in contact, so that the sample bears transient impact in a very short time,

[0027] The transmission rod is arranged at the back of the sample, and is used to receive the transmission wave after penetrating the sample and guide the transmission wave to the absorption rod,

[0028] The absorption rod dissipates the residual energy through its impedance and energy absorption characteristics, so as to reduce the reflection wave returning to the sample to cause secondary loading.

[0029] As a further improved scheme of the present application, the lateral restraint device comprises a fixed side wall and a reinforcing rib structure connected with the sealed test cavity,

[0030] The detachable side wall assembly comprises a rigid cover plate and a flange sealing structure, and the rigid cover plate is a detachable structure,

[0031] The flange sealing structure is arranged at the outer edge of the rigid cover plate, and is detachably connected with the flange seat of the open end of the sealed test cavity through a plurality of quick locking bolts or quick insertion locking pins distributed in the circumferential direction.

[0032] As a further improved scheme of the present application, the mechanical driving mechanism comprises a hydraulic cylinder, a sliding guide rail, a piston rod and a control console,

[0033] The hydraulic cylinder, the sliding guide rail and the piston rod constitute a linear motion execution mechanism, the hydraulic cylinder is fixedly installed outside the sealed test cavity, the end of the piston rod is connected with the rigid cover plate, and is used to exert a strong pulling force on the rigid cover plate, so that the rigid cover plate is quickly moved out of the opening of the sealed test cavity along the Y direction to complete the removal action, and the sliding guide rail is arranged at the outer edge of the rigid cover plate and is arranged opposite to the sealed test cavity, so as to ensure that the rigid cover plate moves stably and linearly along the Y direction under the driving action without deviation or jamming,

[0034] The control console is connected with the hydraulic cylinder, and is used to control the extension of the piston rod, so that the rigid cover plate is pulled away from the opening of the sealed test cavity in an instant to form a single-face free surface on one side of the sample.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] 1. The authenticity of loading is significantly improved; the independent static loading device is arranged in the X and Z directions respectively, and the transient impact disturbance is additionally superimposed in the X direction, so that the sample presents a complex stress state which is more in line with the stress characteristics of deep coal rock under the combined action of multi-directional static loading and unidirectional impact loading, especially the impact loading in the X direction is coaxially arranged with the static loading, which can further superimose the transient dynamic load on the basis of the existing high static load, form the sudden stress path borne by the coal body under the working conditions such as roadway head-on and mining disturbance in the real scene, at the same time, the thick wall structure and multi-flange fixing mode of the test cavity ensure reliable transmission of loading energy, so that the deformation mode generated in the sample is closer to the stress response of deep coal body in non-uniform field, effectively overcomes the distortion problem of the fracture mode caused by the single loading dimension and idealized boundary conditions of the traditional test device, thereby significantly improves the authenticity and controllability of the composite dynamic disaster simulation.

[0037] 2. The air triggering process is controllable and repeatable; the fixed constraint side wall is arranged on one side of the Y direction to maintain the necessary lateral confining pressure environment, and the movable side wall which can be quickly removed is designed on the other side, and the mechanical driving mechanism is used to realize the instantaneous removal at any preset time, so that the sample suddenly forms a single air at a key node in the stress process, induces the rapid redistribution of internal stress of the coal body and promotes the accelerated expansion of the crack to the free surface direction, the removable side wall structure can realize controlled unloading while maintaining the air tightness of the cavity, without destroying the gas adsorption-desorption environment, and can implement the triggering action at a specific stage of impact loading, static loading or gas flow, thereby realizing the accurate control of the air triggering time, triggering sequence and triggering background conditions, overcoming the defect that the transient change of the air boundary cannot be simulated in the traditional test, and through repeated tests, the differences of the fracture morphology, ejection direction and energy release characteristics under different triggering strategies can be verified, so that the transformation process of the coal body from the constraint state to the air state can be reproduced with high fidelity in the laboratory, which is a key working condition simulation capability that the traditional fixed cavity structure cannot provide.

[0038] 3、Gas adsorption-desorption and mechanical loading coupling are more complete; the application cooperates the design of the sealed test cavity and the stable pressure gas supply system, adopts the sealed test cavity structure and arranges various gas interfaces, so that the sample can establish a stable gas adsorption environment through vacuumizing, injecting gas and other steps before loading, and the internal gas field can be kept from being destroyed during the loading process, ensuring that the sample is always in a real gas occurrence state, the sealing side wall and the loading hole are provided with pressure-resistant sealing components, so that the gas can continuously participate in the mechanical behavior during the sample rupture, crack expansion and free air triggering process, reflect the cooperative failure mechanism of deep coal under the driving of gas adsorption, expansion, desorption and seepage, compared with the traditional test system which cannot guarantee high confining pressure, high sealing and dynamic unloading at the same time, the application realizes the synchronous control of stress field, gas field and boundary conditions, can observe the key processes such as gas pressure difference change, coal desorption behavior and ejection path formation, so that the coupling effect of gas participating in the rupture in the composite dynamic disaster can be more completely presented, and experimental conditions are provided for revealing the physical mechanism of the whole process of deep coal body rupture-ejection. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a structure diagram of a biaxial impact loading test device for a burst-impact composite dynamic disaster Figure One

[0040] Figure 2 It is a structure diagram of a biaxial impact loading test device for a burst-impact composite dynamic disaster Figure Two DETAILED DESCRIPTION

[0041] The technical solutions of the application will be further described in detail in combination with specific embodiments.

[0042] Embodiments of the application are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application.

[0043] Please refer to Figure 1 and Figure 2 ​​The embodiment provides a biaxial impact loading test device for a protrusion-impact composite type dynamic disaster, which comprises a sealed test cavity 10, a multidirectional static load loading device 20, a unidirectional impact loading device 30, a lateral constraint device 40, a detachable side wall assembly 50, a stable pressure type gas supply system 60 and a mechanical driving mechanism, the sealed test cavity 10 is used for loading a test sample, the multidirectional static load loading device 20 is arranged in X and Z directions of the sealed test cavity 10 respectively, and is used for applying multidirectional static pressure to the test sample in the sealed test cavity 10, the unidirectional impact loading device 30 is coaxially arranged with the static load loading device 20 in the X direction, and is used for applying transient impact load to the test sample in the sealed test cavity 10, the lateral constraint device 40 and the detachable side wall assembly 50 are arranged in the Y direction of the sealed test cavity 10, the lateral constraint device 40 is used for providing continuous and stable lateral confining pressure to the test sample during the test loading process, the mechanical driving mechanism is used for driving the detachable side wall assembly 50 to be removed from the opening of the sealed test cavity 10, so that a controlled transient single-face open boundary of the test sample is formed during the loading process, stress redistribution and dynamic instability behavior similar to roadway excavation and working face exposure are induced, and the stable pressure type gas supply system 60 is used for supplying gas to the inside of the sealed test cavity 10.

[0044] The sealed test cavity 10 is internally constituted as a closed space, is a thickened cavity structure as a whole, forms a closed chamber through a flange, bolts and multiple sealing rings, can bear external load and maintain a stable gas pressure environment, the coal sample is placed in the center of the sealed test cavity 10, so that the coal sample can be fully adsorbed through a vacuumizing, aeration and pressure stabilizing process before loading, so as to form an initial environment close to a real gas occurrence state of a deep coal seam.

[0045] Further, the sealed test cavity 10 is provided with a loading channel reserved on an outer wall, and an air inlet 101, an air outlet 102 and a pressure monitoring interface are arranged on the top or the bottom of the sealed test cavity 10.

[0046] In one embodiment, the pressure-stabilized gas supply system 60 includes an intake unit and an exhaust unit. The intake pipe of the intake unit is connected to the gas source 606. A pressure reducing valve 601 and a main intake valve 602 are installed on the pipe. The pressure reducing valve 601 is used to initially reduce the pressure of the gas entering the system, and the main intake valve 602 is used to control the switch. Downstream of the main intake valve 602, there are two branches. The first branch is connected to a buffer cavity 604 with a volume larger than the sealing test chamber 10 via a first throttle valve 603. The first throttle valve 603 is used to limit the flow rate. The outlet of the buffer cavity 604 is connected to the sealing test chamber 10 via a second throttle valve 605. The air inlet 101 of the test chamber 10 is connected; the second branch is directly connected to the sealed test chamber 10 via a small flow air supply valve 611, which is used to provide slight pressure compensation to the sealed test chamber 10 during the test; the exhaust pipe of the exhaust unit is connected to the exhaust port 102 of the sealed test chamber 10, and a pressure regulating valve 607, an exhaust valve 608 and a gas flow meter 609 are installed in sequence on the pipe. The pressure regulating valve 607 and the exhaust valve 608 are used to release gas in a controllable manner when the pressure in the sealed test chamber 10 is too high, and the gas flow meter 609 is used to monitor the gas emission flow rate.

[0047] Furthermore, to ensure the airtightness of the gas adsorption environment, a multi-stage sealing structure is used between the inner wall of the sealed test chamber 10 and the loading holes in each direction. The multi-stage sealing structure includes a metal sealing ring 103, a pressure-resistant rubber ring, and an adhesive sealing material to prevent gas leakage along the loading holes during static and impact loading. The air inlet 101 and exhaust outlet 102 on the sealed test chamber 10 use an integrated welded joint and are connected to the external gas pipeline through a high-pressure hose to ensure flexibility and airtightness during gas transportation.

[0048] Furthermore, pressure sensors 610 are installed on the sealed test chamber 10 and the buffer cavity 604 respectively. The pressure sensors 610 are installed on the pressure monitoring interface. The pressure sensors 610 detect the minute changes in gas pressure in the sealed test chamber 10 and the buffer cavity 604 in real time, so as to reflect the dynamic process of gas release during coal adsorption-desorption behavior and fracturing.

[0049] Furthermore, under static load, impact load, and sidewall disassembly conditions, the effective volume of the sealed test chamber 10 will change rapidly due to the deformation of the sample under pressure, crack opening, or boundary release, resulting in instantaneous pressure fluctuations in the gas within the sealed test chamber 10. To mitigate these gas pressure fluctuations, the buffer cavity 604 and the first throttle valve 603 work together to regulate the flow. The buffer cavity 604 has a volume significantly larger than that of the test chamber. When the pressure inside the chamber suddenly increases, the gas can only flow through the first throttle valve 603 to the buffer cavity 604 at a limited flow rate, thus buffering part of the pressure wave. The absorption in the cavity 604 slows down the pressure rise in the sealed test chamber 10. When the pressure in the sealed test chamber 10 suddenly drops due to air gap or rupture, the gas in the buffer cavity 604 is replenished to the sealed test chamber 10 at a small flow rate through the second throttle valve 605, thus controlling the rate of pressure drop. Through the above-mentioned dual regulation mechanism of "flow restriction and buffering", the pressure change process in the sealed test chamber 10 is smoothed from the original "instantaneous jump" to "slow transition", thereby ensuring that the gas adsorption-desorption process is not disrupted by impact disturbances and maintaining the continuity and stability of the gas pressure field throughout the test.

[0050] In one embodiment, the multi-directional static load loading device 20 includes a static load loading cylinder 201 and a loading head 202, which are used to apply independently controllable static axial and vertical pressures to construct an asymmetric stress state with uneven confining pressure and significant distribution of primary and secondary stresses in the deep coal body, and to simulate the stable static load action in the corresponding direction of the deep surrounding rock and coal pillar.

[0051] In one embodiment, the unidirectional impact loading device 30 mainly includes an impact rod 301, an incident rod 302, a transmission rod 303, and an absorption rod 304. The impact rod 301, incident rod 302, transmission rod 303, and absorption rod 304 are arranged along the same straight line and make precise contact so that the static load and dynamic load are superimposed in the same direction. The transient impact load can be superimposed on the sample through impact to ensure that the impact stress wave can be stably and with low loss transmitted to the sample. It can simulate the impact load induced by engineering such as tunneling face, mining dynamic disturbance, and sudden stress migration, so that the coal sample can bear the transient rapid stress peak on the basis of static load, thereby triggering the typical strong dynamic response during the deep coal body fracture process.

[0052] Furthermore, during loading, a high-amplitude stress wave is generated inside the impact rod 301. This stress wave is first transmitted to the incident rod 302, where it further propagates and is shaped. It then acts directly on the sample in contact with the incident rod, causing the sample to withstand transient impact in a very short time. A transmission rod 303 is provided on the back side of the sample to receive the transmitted wave after it penetrates the sample and guide it to the absorption rod 304. The absorption rod 304 dissipates the remaining energy through its own impedance and energy absorption characteristics, thereby reducing the amount of reflected waves returning to the sample and causing secondary loading.

[0053] Furthermore, the X-direction static load loading device 20 and the unidirectional impact loading device 30 share a loading hole, and the two are independently controlled and do not interfere with each other.

[0054] In one embodiment, the lateral restraint device 40 and the removable sidewall assembly 50 are arranged in the Y direction, but their functions and structures differ, as follows:

[0055] The lateral restraint device 40 includes a fixed sidewall 401 and a reinforcing rib structure 402 connected to the sealed test chamber 10. The fixed sidewall 401 is integrally welded with the main body of the sealed test chamber 10, making it part of the outer shell of the sealed test chamber 10. It has high rigidity and immovability, and is used to provide continuous and stable lateral confining pressure during the test loading process. It does not participate in any action or disassembly.

[0056] The detachable sidewall assembly 50 is independent of the main body of the sealing test chamber 10 and consists of a rigid cover plate 501 and a flange sealing structure 502. The rigid cover plate 501, being a detachable structure, has a flange sealing structure 502 on its outer edge. It is detachably connected to the flange seat at the opening end of the sealing test chamber 10 via several quick-locking bolts or quick-insertion locking pins distributed circumferentially. Multiple O-rings or gradient sealing gaskets are arranged between the contact surfaces of the two, thus forming a reliable, highly airtight seal during installation and tightening. Because it is not a welded structure, the rigid cover plate 501 can be detached from the sealing test chamber 10 when needed, while the fixed sidewall 401 never detaches. With this assembly structure, the rigid cover plate 501 maintains a complete seal during gas adsorption, pressure stabilization, and loading processes, maintaining a stable gas pressure field inside the chamber.

[0057] Furthermore, the mechanical drive mechanism of the detachable sidewall assembly 50 is connected to the back of the rigid cover plate 501, applying a strong pulling force to cause the rigid cover plate 501 to move rapidly out of the opening of the sealed test chamber 10 in the Y direction, completing the "removal" action. The aforementioned drive mechanism is a mechanical drive structure that can provide high thrust, short stroke, and fast response. It can ensure a sufficiently high action speed when instantly removing the sidewall, so that the constraint on one side of the sample suddenly disappears and forms a free surface, reconstructing the key triggering condition of "sudden emptiness" in deep dynamic disasters such as tunnel excavation, structural exposure, or mining disturbance.

[0058] Furthermore, the sealing surface of the rigid cover plate 501 is provided with a composite structure of rubber sealing ring and metal sealing ring to ensure that gas does not leak during the adsorption stage.

[0059] In one embodiment, the mechanical drive mechanism includes a hydraulic cylinder 503, a sliding guide rail 504, a piston rod 505, and a control panel 506. The hydraulic cylinder 503, sliding guide rail 504, and piston rod 505 constitute a linear motion actuator. The hydraulic cylinder 503 is mounted and fixed on the outside of the sealed test chamber 10, and the end of its piston rod 505 is connected to a rigid cover plate 501 to apply a pushing or pulling force to the rigid cover plate 501. The outer edge of the rigid cover plate 501 is provided with a sliding guide rail 504 opposite to the sealed test chamber 10. The sliding guide rail 504 ensures that the rigid cover plate 501 moves smoothly and linearly in the Y direction under the driving action, without deviation or jamming. The control panel 506 is connected to the hydraulic cylinder 503 and can quickly drive the piston rod 505 to extend according to the trigger command, so that the rigid cover plate 501 is pulled away from the opening of the sealed test chamber 10 in an instant, forming a single-sided free surface on one side of the sample. This mechanical drive mechanism can provide reliable clamping while maintaining a sealed state and achieve high-speed unloading when needed, thus meeting the requirements of simulated tunnel excavation and sudden exposure of deep structures.

[0060] The unloading action can be precisely triggered by the control system based on indicators such as time thresholds, abnormal acoustic emission, sudden strain changes, electrical signal changes, or impact loading stages. After the sealed sidewall is rapidly pulled away by the drive mechanism, the free surface of the coal sample is exposed. The internal stress field redistributes rapidly in a short time, and the local high-stress zone transforms into a fracture source. The fracture accelerates its penetration towards the free surface, accompanied by rapid desorption and even ejection of gas, realistically reproducing the dynamic instability process induced by open space in deep engineering.

[0061] In summary, by comprehensively constructing the multi-directional static load, unidirectional impact load, controllable free-space triggering, and sealed gas adsorption and desorption conditions of this invention, a comprehensive working condition of "high static load, high gas content, constrained-free-space transient, and superimposed impact disturbance" that closely approximates the actual conditions of deep coal seams can be formed. This allows the coal body fracturing process to be fully presented from micro-crack initiation, unstable crack propagation, gas desorption and ejection to macroscopic destruction, and it possesses repeatability and controllability. This provides a novel experimental platform for the theoretical research, prediction, early warning, and engineering application of disasters such as coal and gas outbursts and rockbursts.

[0062] The experimental procedure of this invention includes:

[0063] 1. Sample preparation and cavity sealing: Place the prepared cubic coal sample in the center of the sealed test cavity 10, fix it with the positioning device, install the detachable side wall assembly 50 and check the sealing performance of the sealed test cavity 10.

[0064] 2. Vacuuming and gas adsorption: Vacuuming is performed on the sealed test chamber 10 through pipelines, followed by the introduction of gas and pressure stabilization to bring the coal sample to adsorption equilibrium.

[0065] 3. Bidirectional static load loading: Each static load loading device 20 applies load independently to gradually establish the real stress environment of the deep coal body.

[0066] 4. Removal of detachable sidewall assembly 50 and impact loading triggering: According to the test plan, the detachable sidewall assembly 50 can be removed first and then impacted, or the two can be set to be triggered simultaneously. Instantaneous exposure can significantly change the coal body fracture path and gas ejection behavior.

[0067] 5. Dynamic fracture response observation; record fracture morphology, ejection behavior and pressure changes, and conduct multi-field analysis when necessary, in conjunction with acoustic emission, DIC, fiber optic and other monitoring methods.

[0068] 6. Unloading and sample removal: Remove static load, release gas from inside the sealed test chamber 10, disassemble the detachable side wall assembly 50, and remove the sample residue for damage morphology analysis.

[0069] During the static-dynamic load superposition process, the internal stress of the sample gradually concentrates towards the principal stress direction. With the arrival of the impact stress wave, the internal microcracks rapidly expand, and energy continuously accumulates. After the detachable sidewall assembly 50 is removed, one side of the sample loses its constraint, and internal stress unloading occurs. Cracks begin to rapidly penetrate towards the free surface, and coal fragments may be ejected in a directional manner under the coupling effect of rapid gas desorption and dynamic load, thus fully presenting the evolution process of deep complex dynamic disasters. Through the above structure and process, this invention achieves a unified simulation capability of multi-directional static load, impact disturbance, instantaneous free space, and gas adsorption-desorption coupling, which is difficult to possess simultaneously with traditional devices. This enables the laboratory to realistically reconstruct the entire process of deep coal body fracturing and ejection, providing a reliable physical experimental platform for the study of coal and rock dynamic disaster mechanisms, model calibration, and engineering prediction.

[0070] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A biaxial impact loading test device for protrusion-impact combined dynamic disasters, characterized in that, It includes a sealed test chamber, a multi-directional static load loading device, a unidirectional impact load loading device, a lateral restraint device, a detachable sidewall assembly, a pressure-stabilized gas supply system, and a mechanical drive mechanism. The sealed test chamber is used to load the sample. The multi-directional static load loading devices are respectively arranged in the X and Z directions of the sealed test chamber, and are used to apply multi-directional static pressure to the sample inside the sealed test chamber. The unidirectional impact loading device is coaxially arranged with the X-axis static load loading device and is used to apply transient impact loads to the specimen inside the sealed test chamber. The lateral restraint device and the removable sidewall assembly are arranged in the Y direction of the sealed test chamber. The lateral restraint device is used to provide continuous and stable lateral confining pressure on the specimen during test loading. The mechanical drive mechanism is used to remove the opening of the self-sealing test chamber of the detachable sidewall assembly. The pressure-stabilized gas supply system is used to supply gas into the sealed test chamber.

2. The biaxial impact loading test device for protrusion-impact composite dynamic disasters according to claim 1, characterized in that, The sealed test chamber has a closed space inside. The sealed test chamber is a thickened cavity structure and is formed by flanges, bolts and multi-level sealing rings.

3. The biaxial impact loading test device for protrusion-impact composite dynamic disasters according to claim 1, characterized in that, The outer wall of the sealed test chamber has a reserved loading channel, and the top or bottom of the sealed test chamber is provided with an air inlet, an exhaust outlet and a pressure monitoring interface.

4. The biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 3, characterized in that, The pressure-stabilized gas supply system includes an intake unit and an exhaust unit. The intake pipe of the intake unit is connected to the gas source. A pressure reducing valve and a main intake valve are installed on this pipe. The pressure reducing valve is used to initially reduce the pressure of the gas entering the system, and the main intake valve is used for control. Downstream of the main intake valve are two branches. The first branch is connected to a buffer cavity with a volume larger than the sealing test chamber via a first throttle valve. The first throttle valve is used to limit the flow rate. The outlet of the buffer cavity is connected to the intake port of the sealing test chamber via a second throttle valve. The second branch is directly connected to the sealing test chamber via a low-flow air supply valve, which is used to provide minor pressure compensation to the sealing test chamber during the test. The exhaust pipe of the exhaust unit is connected to the exhaust port of the sealed test chamber. A pressure regulating valve, an exhaust valve and a gas flow meter are installed in sequence on the pipe. The pressure regulating valve and the exhaust valve are used to release gas in a controllable manner when the pressure in the sealed test chamber is too high. The gas flow meter is used to monitor the gas emission flow rate.

5. The biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 4, characterized in that, The inner wall of the sealed test chamber is sealed with loading holes in each direction using a multi-stage sealing structure, which includes a metal sealing ring, a pressure-resistant rubber ring, and an adhesive sealing material.

6. The biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 4, characterized in that, Pressure sensors are respectively installed on the sealed test chamber and the buffer cavity, and the pressure sensors are mounted on the pressure monitoring interface.

7. The biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 1, characterized in that, The multi-directional static load loading device includes a static load loading cylinder and a loading head, which are used to apply independently controllable static axial and vertical pressures.

8. The biaxial impact loading test device for protrusion-impact composite dynamic disasters according to claim 1, characterized in that, The unidirectional impact loading device includes an impact rod, an incident rod, a transmitting rod, and an absorbing rod, which are arranged along the same straight line and connected by precision contact. The impact rod is used to generate a high-amplitude stress wave during loading and to first transmit the stress wave to the incident rod. The incident rod is used to propagate and shape the stress wave and drive it to act directly on the sample in contact with it, so that the sample can withstand transient impact in a very short time. The transmission rod is disposed on the back of the sample to receive the transmitted wave after it penetrates the sample and guide it to the absorption rod. The absorbing rod dissipates residual energy through its own impedance and energy absorption characteristics, thereby reducing the secondary loading caused by reflected waves returning to the sample.

9. A biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 1, characterized in that, The lateral restraint device includes a fixed sidewall and a reinforcing rib structure connected to the sealed test chamber. The detachable sidewall assembly includes a rigid cover plate and a flange sealing structure, wherein the rigid cover plate is a removable structure. The flange sealing structure is located on the outer edge of the rigid cover plate and is detachably connected to the flange seat at the opening end of the sealing test chamber by a number of quick-locking bolts or quick-insertion locking pins distributed in the circumferential direction.

10. A biaxial impact loading test device for protrusion-impact combined dynamic disasters according to claim 9, characterized in that, The mechanical drive mechanism includes a hydraulic cylinder, a sliding guide rail, a piston rod, and a control panel. The hydraulic cylinder, sliding guide rail, and piston rod constitute a linear motion actuator. The hydraulic cylinder is mounted and fixed on the outside of the sealing test chamber, and its piston rod end is connected to a rigid cover plate. This piston rod applies a strong pulling force to the rigid cover plate, causing it to quickly move out of the sealing test chamber opening along the Y-axis, completing the removal action. The sliding guide rail is located on the outer edge of the rigid cover plate and is arranged opposite to the sealing test chamber to ensure that the rigid cover plate moves smoothly and linearly along the Y-axis under the driving action, without deviation or jamming. The control panel is connected to the hydraulic cylinder and is used to control the extension of the piston rod, so that the rigid cover plate is pulled away from the opening of the sealed test chamber in an instant, forming a single-sided free surface on one side of the sample.

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