A physical simulation test system and test method for coal rock mass water immersion fracture instability

Abstract

The present invention provides a physical simulation test system and test method for water-immersed cracking and instability of coal-rock mass, belonging to the field of underground mining technology. The system includes a physical model, a biaxial loading device, a hydraulic jack, a rigid pressure plate, a combination plate, a water pressure control system, a pressure sensor, a displacement sensor, an acoustic emission sensor and a resistance test probe. The physical model is provided with pressure sensors and resistance test probes buried around the preset goaf and tunnel, and a water pipe is buried behind the goaf. The biaxial loading device can load the physical model in the horizontal and vertical directions. The rigid pressure plate is placed behind the physical model, and the combination plate is placed in front of the physical model and connected and fixed with the rigid pressure plate by high-strength bolts. The combination plate is provided with a tunnel excavation opening at the preset position of the physical model, and the water pressure control system is connected to the preset goaf of the physical model through a water pipe. It can be used to study the internal water diffusion law of coal-rock mass in the goaf, the water-weakening mechanism, and the design of coal pillar width.

Description

Technical Field

[0001] The invention relates to the technical field of underground mining, and in particular to a physical simulation test system and test method for water-immersed cracking and instability of coal and rock masses. Background Art

[0002] The hydrogeological conditions of coal mines are mostly complex. After the underground coal resources are mined, a large area of ​​goaf will be left, which may cause water accumulation, and in severe cases, it will pose a threat to the mine. In order to prevent the impact of water damage in the goaf, coal mines generally set up water-proof coal pillars in the goaf. Although the water-proof coal pillars have reduced the troubles caused by mine water damage to a certain extent, the peat-containing coal pillars are significantly weakened by water immersion. Long-term water immersion of the coal pillars will lead to a reduction in the effective size of the pre-designed water-proof coal pillars, which seriously threatens the safe production of coal mines. In addition, with the application of pumped storage technology and underground reservoir technology in abandoned mines, coal rock mass, as the bearing structure of underground space, is inevitably affected by long-term immersion or dry-wet cycle. Therefore, in order to reasonably design the size of the water-proof coal pillars, ensure the safe mining of the adjacent working faces of the goaf and the stable operation of the underground reservoir, it is very important to obtain the internal water migration law and weakening instability mechanism of the coal rock mass under the coupling of load and immersion.

[0003] At present, the research on water-weakening instability of coal rock mass in goaf area mostly adopts indoor rock mechanics test or the combination of indoor test and numerical simulation. In rock mechanics test, the coal rock sample is usually immersed in water for a period of time, then taken out and placed in the testing machine for testing. However, the coal rock mass in goaf area is usually subjected to the combined action of water immersion and load; and this method does not consider the damage caused to coal rock by excavation disturbance in actual engineering. The method of combining indoor test and numerical simulation is generally to obtain the water diffusion law and mechanical parameter degradation law of water-immersed rock sample through indoor test, so as to establish the corresponding water diffusion equation, mechanical parameter degradation equation, constitutive equation, etc. Finally, secondary development is carried out in numerical calculation software according to the established equation, so as to realize the simulation of water-weakening instability of coal rock mass in goaf area. In this method, the influence of excavation disturbance on coal rock mass and the change of diffusion coefficient are usually not considered, and the established equation is usually based on some assumptions and simplification of engineering problems, which is difficult to truly reflect the mechanical properties of coal rock mass in mine.

[0004] Therefore, there is a need for a physical simulation test system and method for coal rock mass water-soaked fracture and instability that can take into account the actual stress, excavation disturbance, water immersion and water migration laws of the coal rock mass. Summary of the invention

[0005] In view of this, the present invention provides a physical simulation test system and test method for coal rock mass water immersion, fracture and instability, which simulate the water migration process in coal rock mass in water-logged goafs with different burial depths under three-dimensional stress, the weakening and instability process of coal pillars due to water immersion, and the influence of water accumulation in goafs on the stress field and displacement field of adjacent tunnels.

[0006] To this end, the present invention provides the following technical solutions:

[0007] A physical simulation test system for coal rock mass water immersion fracture instability, comprising:

[0008] A physical model placed on the fourth actuator of the biaxial loading device, a control system for manipulating the actuator group of the biaxial loading device to apply loads to the left, right, top and bottom surfaces of the physical model, a combination plate arranged in front of the physical model, and a rigid pressing plate fixed to the back of the physical model by a hydraulic jack;

[0009] The physical model is provided with a goaf and a tunnel; the opening side of the goaf is provided in front of the physical model;

[0010] The goaf and the middle part of the tunnel serve as water-proof coal pillars;

[0011] Sensors are arranged inside and outside the lane;

[0012] Pairs of resistance test probes are provided in the waterproof coal pillar;

[0013] A water pipe is provided on the non-opening side of the goaf of the physical model;

[0014] The sensor and the resistance test probe are connected to the data acquisition system via a data transmission line.

[0015] Furthermore, the physical model is obtained by a 3D printer.

[0016] Furthermore, the biaxial loading device comprises:

[0017] Load frame and actuator assembly;

[0018] The actuator group is fixed on the loading frame and connected to the control system.

[0019] Furthermore, the combined plate comprises: an observation area made of a transparent material and a fixing area made of a metal material;

[0020] The combined plate is provided with bolt holes in the fixing area;

[0021] Bolts pass through the bolt holes to connect the combined plate and the rigid pressing plate;

[0022] The observation area is provided with a tunnel excavation opening at the tunnel position.

[0023] Furthermore, the tunnel internal sensors include: a displacement sensor and an acoustic emission sensor.

[0024] Furthermore, the tunnel external sensor includes: a pressure sensor.

[0025] Furthermore, the rigid pressing plate is provided with threading holes and rigid pressing plate bolt holes;

[0026] The transmission data lines of the pressure sensor and the resistance test probe are connected to the data acquisition system through the threading holes;

[0027] The water pipe is connected to the water pressure control system through the threading hole.

[0028] Furthermore, a camera films the test process through the observation area.

[0029] A test method for a coal rock mass water immersion fracture instability physical simulation test system comprises the following steps:

[0030] S1. Make a physical model using a 3D printer;

[0031] The method of making a physical model by a 3D printer comprises:

[0032] Preset the location of goaf and tunnels in the physical model;

[0033] According to the positions of the preset goaf and tunnel, burying pressure sensors, resistance test probes and water pipes in the physical model;

[0034] S2, placing the physical model on the actuator of the biaxial loading device, and applying a preload force on the physical model through the actuator group of the biaxial loading device;

[0035] S3, one end of the hydraulic jack is fixed in the wall, and the other end applies a preset pressure to the physical model through a rigid pressure plate;

[0036] S4, the transmission data lines of the pressure sensor and the resistance test probe are connected to the data acquisition system through the threading holes on the rigid pressing plate; the water pipe is connected to the water pressure control system through the threading holes;

[0037] S5, controlling the actuator group of the biaxial loading device through the control system to apply loads to the left, right, top and bottom surfaces of the physical model to set values;

[0038] S6. Excavate to a preset depth at the preset goaf location in the physical model; after excavation, a water stop strip is pasted around the goaf opening;

[0039] S7, connecting and fixing the combined plate to the rigid pressing plate at the rear of the physical model by bolts;

[0040] S8, injecting water into the goaf through a water pressure control system to a preset position;

[0041] S9, excavating to a preset depth at a preset tunnel position through the tunnel excavation opening on the combined plate;

[0042] S10, arranging displacement sensors and acoustic emission sensors in the lane; connecting transmission data lines of the displacement sensors and acoustic emission sensors to a data acquisition system;

[0043] S11, controlling the actuator group of the biaxial loading device through the control system to maintain the load on the left, right, top and bottom surfaces of the physical model until the water-proof coal pillar between the goaf and the tunnel is completely destroyed;

[0044] During the physical simulation test of coal-rock mass water-immersion fracture and instability, the data acquisition system continuously monitors the pressure and displacement signals of the tunnel surrounding rock and the resistivity and acoustic emission signals of the waterproof coal pillar;

[0045] The process of tunnel excavation until the waterproof coal pillar is completely destroyed is filmed by camera.

[0046] Advantages and positive effects of the present invention:

[0047] 1) The present invention uses 3D printing technology to make physical models. Compared with the traditional manual layered compaction or filling method, the printing effect is uniform and can accurately simulate the structure and physical and mechanical properties of the strata where the goaf and tunnels are located.

[0048] 2) The present invention applies loads and constraints on the boundaries of the physical model through a biaxial loading device, a hydraulic jack, a rigid pressure plate and a combined plate, and can simulate three-dimensional geostress conditions in actual engineering.

[0049] 3) The present invention can simulate the excavation process of adjacent tunnels after water accumulation in the goaf and the progressive destruction process of the waterproof coal pillar under the action of long-term water immersion by designing the excavation of goafs and tunnels and injecting water into the goafs.

[0050] 4) The present invention can simulate the rise and fall of water levels in underground reservoirs by filling and pumping water from the goaf through a water pressure control system, and can be used to study the deterioration and instability mechanism of coal rock mass under the action of dry-wet cycles.

[0051] 5) The present invention can simulate different actual working conditions by adjusting the position and size of the goaf and the tunnel.

[0052] 6) The present invention realizes real-time monitoring of water diffusion inside the waterproof coal pillar and the moisture content of the coal pillar by burying a resistance test probe in the physical model, thereby obtaining a more accurate diffusion law of groundwater in the waterproof coal pillar.

[0053] 7) The present invention arranges pressure sensors, displacement sensors and acoustic emission sensors around and inside adjacent tunnels in the goaf to monitor the stress field and displacement field of adjacent tunnels and the progressive fracture of the waterproof coal pillar during the process of water-insulating and fracture of the waterproof coal pillar.

[0054] 8) The present invention not only prevents the outflow of water in the goaf by arranging a combined plate in front of the physical model, but also enables tunnel excavation under the condition of water filling in the goaf through the tunnel excavation opening on the combined plate.

[0055] 9) The present invention arranges a camera in front of the observation area of ​​the transparent material to realize image recording of the deformation and destruction process of the waterproof coal pillar and the surrounding rock of the tunnel during the test.

[0056] 10) The images of stress, displacement, acoustic emission, resistivity and coal pillar destruction process obtained by the data acquisition system of the present invention can be used to explore the destruction mechanism of water-soaked coal and rock in mines, which is helpful to optimize mine design, especially the design of water-proof coal pillars, which is of great significance to further improve the stability and safety of mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0058] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0059] Figure 2 is a cross-sectional view of an embodiment of the present invention;

[0060] Figure 3 It is a partial enlarged view of the physical model of the embodiment of the present invention;

[0061] Figure 4 Schematic diagram of the connection between the rigid pressing plate and the combined plate in an embodiment of the present invention;

[0062] In the figure, 1. loading frame; 2. actuator group; 2-1. first actuator; 2-2. second actuator; 2-3. third actuator; 2-4. fourth actuator; 3. combination plate; 3-1. fixing area; 3-2. observation area; 3-3. tunnel excavation; 4. bolt; 5. rigid pressure plate; 5-1. bolt hole; 5-2. threading hole; 6. hydraulic jack; 7. physical model; 8. goaf; 9. water pipe; 10. tunnel; 11. pressure sensor; 12. resistance test probe; 13. displacement sensor; 14. acoustic emission sensor; 15. control system; 16. camera; 17. water pressure control system; 18. data acquisition system. DETAILED DESCRIPTION

[0063] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0064] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0065] The present invention provides a physical simulation test system for coal rock mass water-soaked cracking and instability, which uses a real three-dimensional physical model test to conduct research and simulate the tunnel excavation process to more accurately understand the coal rock mass water-soaked weakening and instability mechanism in actual engineering.

[0066] Combination Figure 1-Figure 4 , the physical simulation test system for coal rock mass water immersion fracture instability further explains:

[0067] The physical simulation test system for coal rock mass water-immersion fracture instability in this embodiment includes: a physical model 7, a biaxial loading device, a hydraulic jack 6, a rigid pressure plate 5, a combination plate 3, a water pressure control system 17, a data acquisition system 18, a control system 15, a pressure sensor 11, a displacement sensor 13, an acoustic emission sensor 14 and a resistance test probe 12. The biaxial loading device includes a loading frame 1 and an actuator group 2, the actuator group 2 is fixed on the loading frame and connected to the control system through a data line; the actuator group includes a first actuator 2-1, a second actuator 2-2, a third actuator 2-3, and a fourth actuator 2-4, which can load the top surface, bottom surface, left surface and right surface of the physical model respectively.

[0068] The physical model 7 is a cubic block printed by a 3D printer of rock-similar materials and coal-rock-similar materials. Pressure sensors 11 and resistance test probes 12 are buried around the goaf 8 and tunnels 10 preset in the physical model 7. The pressure sensor 11 is used to monitor the pressure changes around the tunnels, and the resistance test probes 12 are used to monitor the diffusion of moisture inside the coal-rock mass.

[0069] The physical model 7 is placed on the fourth actuator 2-4 of the biaxial loading device; a water pipe 9 is buried behind the goaf 8; the water pressure control system 17 is connected to the preset goaf 8 of the physical model 7 through the water pipe 9;

[0070] After the tunnel 10 is excavated, a displacement sensor 13 and an acoustic emission sensor 14 are arranged inside the tunnel. The displacement sensor 13 is used to monitor the horizontal and vertical deformation of the tunnel, and the acoustic emission sensor 14 is used to monitor the acoustic emission signal of coal rock mass fracture;

[0071] The rigid pressing plate 5 is provided with threading holes 5-2; and a bolt hole 5-1 is arranged at each of the four corners;

[0072] The rigid pressing plate 5 is fixed behind the physical model 7 by a hydraulic jack 6;

[0073] The combined plate 3 is placed in front of the physical model 7, with transparent material used in the observation area 3-2 and steel plate used in the fixed area 3-1; a tunnel excavation opening 3-3 is reserved at the preset tunnel position in the observation area; the steel plate 3-1 is provided with 4 bolt holes; the rigid pressing plate and the combined plate are connected and fixed by bolts 4;

[0074] The data acquisition system 18 is connected to the pressure sensor, the displacement sensor, the acoustic emission sensor and the resistance test probe respectively through data transmission lines.

[0075] The camera 16 is installed in front of the physical model to record the weakening and instability process of the coal rock mass.

[0076] In this embodiment, the physical model making process includes:

[0077] 1. Carry out uniaxial, triaxial, shear, splitting and other mechanical tests and mineral composition analysis on the coal and rock mass obtained on site;

[0078] 2. Based on the physical and mechanical properties of the coal and rock mass obtained in step 1, determine the similarity ratio, select the configuration materials, and determine the material ratio according to the similar material theory and similarity criteria;

[0079] In this embodiment, the simulation materials include: sand, clay minerals, gypsum, cement, lime, barite powder, bentonite, calcium carbonate, coal, and iron powder;

[0080] 3. Place the configured similar materials into the nozzle of the 3D printer and use the 3D printer to make a model similar to the one on site;

[0081] In this embodiment, the observation area 3-2 is made of high-strength glass, which is embedded in the steel plate frame of the fixed area 3-1 and fixed with high-strength sealant;

[0082] The physical simulation test system for coal-rock mass water-immersion fracture and instability includes the following test steps:

[0083] (1) A cubic physical model 7 is made using a 3D printer of rock-like materials and coal-rock-like materials, and a pressure sensor 11 and a resistance test probe 12 are buried around the preset goaf 8 and tunnel 10, and a water pipe 9 is buried behind the preset goaf 8;

[0084] (2) After the physical model 7 is solidified, it is moved to the fourth actuator 2-4 of the biaxial loading device, and the control system 15 is used to control the actuator group 2 of the biaxial loading device to apply a preload force to the physical model 7;

[0085] (3) The rigid pressing plate 5 is fixed to the back of the physical model 7 by means of the hydraulic jack 6, and the hydraulic jack 6 is manipulated to apply a certain pressure to the rigid pressing plate 5. The other end of the hydraulic jack 6 is fixed to the wall. The transmission data lines of the pressure sensor 11 and the resistance test probe 12 in the physical model 7 are connected to the data acquisition system 18 through the threading hole 5-2 of the rigid pressing plate 5. The water pipe 9 behind the preset goaf 8 is also connected to the water pressure control system 17 through the threading hole 5-2 of the rigid pressing plate 5.

[0086] (4) The actuator group 2 of the biaxial loading device is controlled by the control system 15 to apply loads to the physical model 7 in the horizontal and vertical directions to the set values, and then excavation is performed in the preset goaf 8 of the physical model 7. After excavation to the set depth, water stop strips are pasted around the opening of the goaf 8, and then the combined plate 3 is connected and fixed to the rigid pressure plate 5 at the rear of the physical model 7 by high-strength bolts 4;

[0087] (5) Water is injected into the goaf 8 through the water pressure control system 17. After the water is injected to a preset position, excavation is performed at a preset position of the tunnel 10 of the combined plate 3 to a specified depth. A displacement sensor 13 and an acoustic emission sensor 14 are arranged in the tunnel 10. Then, the transmission data lines of the displacement sensor 13 and the acoustic emission sensor 14 are connected to the data acquisition system 18;

[0088] (6) The load is maintained until the waterproof coal pillar between goaf 8 and tunnel 10 is completely destroyed. During the excavation of tunnel 10 until the waterproof coal pillar is weakened by water, the stress and displacement of the surrounding rock of tunnel 10 are continuously monitored. At the same time, the moisture distribution and fracture acoustic emission signals of the waterproof coal pillar are monitored. The process of tunnel excavation until the waterproof coal pillar is weakened by water is filmed by a camera.

[0089] The test system and method of the present invention comprehensively consider the damage caused by goaf and tunnel excavation to the coal rock mass and the influence of water diffusion on the weakening of the coal rock mass, and can simulate the progressive destruction process of the waterproof coal pillar under three-dimensional ground stress, and explore the weakening and instability mechanism of the water-soaked coal rock mass. Through the test system and method of the present invention, the pressure of the surrounding rock and the water content change of the waterproof coal pillar during the tunnel excavation under continuous stress and immersion can be monitored; as well as the acoustic emission signal and water content change during the crushing of the waterproof coal pillar under continuous pressure, and the pressure and displacement change of the tunnel surrounding rock; based on the results of the physical model test, the non-uniform distribution of water and the dynamic changes of the dry-wet interface caused by the seepage and diffusion process under the water-rock interaction, and the influence of these changes on the stability of the waterproof coal pillar and the tunnel surrounding rock, thereby providing theoretical support for the design of the size of the waterproof coal pillar.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test method for a physical simulation test system for coal rock mass water immersion fracture instability, characterized in that: include: S1. Make a physical model using a 3D printer; Preset the location of goaf and tunnels in the physical model; According to the preset positions of goaf and tunnels, pressure sensors, resistance test probes and water pipes are embedded in the physical model; S2, placing the physical model on the actuator of the biaxial loading device, and applying a preload force on the physical model through the actuator group of the biaxial loading device; S3, one end of the hydraulic jack is fixed in the wall, and the other end applies a preset pressure to the physical model through a rigid pressure plate; S4, the transmission data lines of the pressure sensor and the resistance test probe are connected to the data acquisition system through the threading holes on the rigid pressing plate; the water pipe is connected to the water pressure control system through the threading holes; S5, controlling the actuator group of the biaxial loading device through the control system to apply loads to the left, right, top and bottom surfaces of the physical model to set values; S6. Excavate to a preset depth at the preset goaf location in the physical model; after excavation, a water stop strip is pasted around the goaf opening; S7, connecting and fixing the combined plate to the rigid pressing plate at the rear of the physical model by bolts; S8, injecting water into the goaf through a water pressure control system to a preset position; S9, excavating to a preset depth at a preset tunnel position through the tunnel excavation opening on the combined plate; S10, arranging displacement sensors and acoustic emission sensors in the lane; connecting transmission data lines of the displacement sensors and acoustic emission sensors to a data acquisition system; S11, controlling the actuator group of the biaxial loading device through the control system to maintain the load on the left, right, top and bottom surfaces of the physical model until the water-proof coal pillar between the goaf and the tunnel is completely destroyed; During the physical simulation test of coal-rock mass water-immersion fracture and instability, the data acquisition system continuously monitors the pressure and displacement signals of the tunnel surrounding rock and the resistivity and acoustic emission signals of the waterproof coal pillar; The system comprises: A physical model placed on the fourth actuator of the biaxial loading device, a control system for manipulating the actuator group of the biaxial loading device to apply loads to the left, right, top and bottom surfaces of the physical model, a combination plate arranged in front of the physical model, and a rigid pressing plate fixed to the back of the physical model by a hydraulic jack; The physical model is provided with a goaf and a tunnel; the opening side of the goaf is provided in front of the physical model; The goaf and the middle part of the tunnel serve as water-proof coal pillars; Sensors are arranged inside and outside the lane; A pair of resistance test probes are arranged in the waterproof coal pillar; A water pipe is provided on the non-opening side of the goaf of the physical model; The sensor and the resistance test probe are connected to the data acquisition system via a data transmission line.

2. The test method of a physical simulation test system for coal rock mass water immersion fracture instability according to claim 1 is characterized in that: The biaxial loading device comprises: Load frame and actuator assembly; The actuator group is fixed on the loading frame and connected to the control system.

3. The test method of a physical simulation test system for coal rock mass water immersion fracture instability according to claim 1 is characterized in that: The combined plate comprises: an observation area made of transparent material and a fixing area made of metal material; The combined plate is provided with bolt holes in the fixing area; Bolts pass through the bolt holes to connect the combined plate and the rigid pressing plate; The observation area is provided with a tunnel excavation opening at the tunnel position.

4. The test method of a physical simulation test system for coal rock mass water immersion fracture instability according to claim 1 is characterized in that: The internal sensors of the tunnel include: a displacement sensor and an acoustic emission sensor.

5. The test method of a physical simulation test system for coal rock mass water immersion fracture instability according to claim 1 is characterized in that: The tunnel external sensor includes: a pressure sensor.

6. The test method of a physical simulation test system for coal rock mass water immersion fracture instability according to claim 1 is characterized in that: The rigid pressing plate is provided with threading holes and rigid pressing plate bolt holes; The transmission data lines of the pressure sensor and the resistance test probe are connected to the data acquisition system through the threading holes; The water pipe is connected to the water pressure control system through the threading hole.

7. The test method of the physical simulation test system for coal rock mass water immersion fracture instability according to claim 3 is characterized by: The system also includes: a camera shoots the process of tunnel excavation in the test until the waterproof coal pillar is completely destroyed through the observation area.

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