Device and method for simulating engineering vibroflotation induced karst roof damage and surface collapse

Abstract

The invention provides a device and method for simulating engineering vibroflotation induced karst roof damage and surface collapse, and belongs to the technical field of geotechnical engineering and geological disaster physical simulation. The device comprises a karst stratum simulation system, a covering layer rock-soil simulation system, an underground water seepage simulation system, a pile foundation / drilling construction vibroflotation load simulation system and a monitoring and measuring system. A karst covering layer-karst rock layer-karst cavity stratum structure is constructed, and a double-water-level water-rich environment and three-dimensional ground stress loading are combined, so that the damage process of vibroflotation load to a karst cave top plate and catastrophe evolution of surface collapse in pile foundation or drilling construction are truly simulated. The method comprises the steps of karst stratum preparation, load application, data monitoring and the like, key parameters can be flexibly adjusted, and multivariate monitoring data can be obtained. The device solves the problem that the damage process of the karst cave roof is difficult to simulate in the prior art, has the advantages of simple structure, convenience in operation, high experimental accuracy and the like, and is suitable for karst collapse mechanism research and disaster prevention and control.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering and geological disaster physical simulation, and in particular to a device and method for simulating engineering vibration-induced karst roof destruction and ground collapse. Background Art

[0002] Overburden karst collapse refers to a karst dynamic geological phenomenon in which the rock and soil cover system above concealed karst caves and cavities undergoes deformation and failure due to natural or human factors, altering the mechanical state and stability of the overburden system, ultimately causing it to collapse and form sinkholes (cavities) on the surface. my country is one of the countries with the most extensive and highly developed karst formations in the world, with numerous caves and karst fissures. Urban development inevitably leads to the construction of numerous major projects, such as buildings and transportation lines, in areas with karst development. Vibro-impact loads generated by pile foundations and drilling construction have a significant impact on the stability of overburden karst geological structures, significantly increasing the risk of karst collapse. Karst collapse has already affected over 30 large and medium-sized cities and 420 counties and cities in my country. Karst collapse induced by pile foundations and drilling construction is particularly prominent in large cities such as Wuhan, Shenzhen, and Guangzhou. It severely restricts the sustainable development of karst areas, threatens national public security, and threatens the lives and property of citizens. It is a major geological hazard that urgently needs to be addressed during my country's urbanization process.

[0003] Karst collapses are characterized by multiple causes and mechanisms, and are highly spatially hidden and sudden. Their mechanisms and catastrophic evolution remain unclear. Simulating the occurrence of karst collapses through indoor model experiments and obtaining key information on their evolution is an effective means of revealing the essential characteristics and patterns of these disasters. This can provide a scientific basis for pre-disaster assessment and prediction of karst collapses, potentially addressing the technical challenges of safe karst collapse prevention and control in areas of intense human activity. CN114563263B discloses an experimental method for an apparatus for simulating karst collapse induced by engineering impact under a seepage environment. The technical solution comprises a test chamber, an impact condition simulation, and a water level control assembly. A first test chamber filled with soil is connected to a second test chamber below via a simulated karst cave hole at its bottom. The impact condition simulation assembly is mounted above the first simulation chamber and comprises a support member and a drill rod. A drop hammer is provided at the upper end of the support member to strike the drill rod directly below it, causing the drill bit to impact the soil. Water distribution chambers are provided on both sides of the first test chamber through filter baffles and connected to the water level control assembly. The second test chamber is connected to the water level control assembly via a water pipe. The water level control assembly includes a water tank and an elevator. This apparatus and method can simulate the process of karst collapse induced by engineering impact under a seepage environment. However, this apparatus and method are designed for conditions where karst crack openings develop upward to the bottom of the overburden soil. This makes it difficult to simulate the role of the rock roof in the collapse development process when the karst openings have not developed to the bottom of the overburden. Consequently, this method has limited reference value for the karst roof destruction-seepage type collapse model. Summary of the Invention

[0004] In response to the above-mentioned technical deficiencies, the purpose of the present invention is to provide a device and method for simulating engineering vibration-induced karst roof destruction and ground collapse. By combining structures such as karst cracks and cavities and the complex ground stress and groundwater environment in which they are located, the device and method can realistically simulate the complex catastrophic process of ground collapse caused by vibration-induced destruction of the roof of covered karst caves during pile foundation and drilling construction.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A device for simulating engineering vibration-induced karst roof destruction and ground collapse, comprising a karst stratum simulation system, an overburden rock and soil simulation system, a groundwater seepage simulation system, a pile foundation / drilling construction vibration load simulation system, and a monitoring and measurement system; the overburden rock and soil simulation system is connected to the upper part of the karst stratum simulation system to form a karst overburden-karst rock layer-karst cavity stratum structure; the overburden rock and soil simulation system and the karst stratum simulation system are respectively connected to the groundwater seepage simulation system via pipelines, and a dual-water-level water-rich environment of porous groundwater and karst groundwater under different working conditions is provided to the overburden rock and soil simulation system and the karst stratum simulation system via the groundwater seepage simulation system; the pile foundation / drilling construction vibration load simulation system is arranged on the upper part of the overburden rock and soil simulation system to apply vibration load to the overburden rock and soil simulation system; the monitoring and measurement system is used to obtain information on changes in key physical and mechanical parameters during the simulation process.

[0007] Preferably, the karst formation simulation system includes a platform base, a karst formation simulation box, a ground stress loading device, a karst groundwater channel, a karst gas channel, and a karst negative pressure control box; the karst formation simulation box is fixed on the platform base; the karst formation simulation box includes a first box body, the top of which is provided with an opening; the first box body is provided with a mounting hole for the ground stress loading device; a detachable flexible sealing layer is embedded in the inner side of the first box body; the interior of the first box body is filled with a karst rock layer; the karst rock layer is provided with at least one karst cave space with a simulation structure prefabricated by a melting dissolution method or an air bag method; the karst rock layer above the karst cave space is configured as a karst cave roof; the karst groundwater channel connects the bottom of the karst cave space and the groundwater seepage simulation system; the karst gas channel connects the top of the karst cave space and the karst negative pressure control box; the karst groundwater, exhaust and vacuum negative pressure conditions in the karst cave space are coordinated and controlled by the groundwater seepage simulation system and the karst negative pressure control box;

[0008] The ground stress loading device includes a reaction frame and multiple loading modules; the reaction frame includes columns and diaphragms; the columns are vertically fixed on the platform base, the diaphragms are arranged above the platform base in parallel and at intervals, and the upper ends of the columns are fixedly connected to the diaphragms; the first box is arranged in the middle of the frame structure composed of the platform base, the columns and the diaphragms; a flexible sealing pad is provided at the bottom of the diaphragm, and the lower end surface of the flexible sealing pad abuts the top of the first box and the karst rock layer; the diaphragm and the flexible sealing pad within the range above the karst rock layer are provided with at least one first opening; an iris rotary valve and a sealing ring for adjusting the shape and size of the opening are installed in the first opening; the loading module includes a loading A pressure plate and multiple power devices; the ground stress loading device mounting holes are configured with multiple power devices; the loading pressure plate is placed between the inner wall of the first box and the flexible sealing layer; the power device is placed outside the first box, and one end is configured with a protruding rod, the front end of the protruding rod passes through the ground stress loading device mounting hole and is fixedly connected to the loading pressure plate; multiple power devices are installed in a linear array on the loading pressure plate; the loading module is configured as a horizontal bidirectional loading module and a bottom vertical loading module; the horizontal bidirectional loading module is arranged on the side of the first box; the bottom vertical loading module is arranged at the bottom of the first box; the end of the power device away from the protruding rod is fixed to a column or platform base.

[0009] Preferably, the covering layer geotechnical simulation system includes a second box body; the top of the second box body is set to an opening; the second box body is fixed to the upper end of the diaphragm; the internal space of the second box body is separated by two groups of porous permeable panels and geotextiles, forming water tanks on both sides and a middle geotechnical simulation box; the plane size and position of the geotechnical simulation box correspond to the top of the karst formation simulation box, and the geotechnical simulation box is used to fill the karst covering layer geotechnical body; at least one second opening is set at the bottom of the geotechnical simulation box, corresponding to the first opening of the diaphragm and the flexible sealing layer, and connected to the iris rotary valve and sealing ring at the first opening; a group of water supply and drainage outlets and valves with different flow rates are set at the bottom of the water tanks on both sides, and the water supply and drainage outlets and valves are connected to the groundwater seepage simulation system.

[0010] Preferably, the groundwater seepage simulation system includes a water supply box, a pipeline, a porous groundwater level control box, and a karst groundwater level control box. The water supply box is connected to the porous groundwater level control box and the karst groundwater level control box respectively through pipelines. The porous groundwater level control box is connected to the water supply and drainage outlets and valves through pipelines to control the porous groundwater conditions of the karst overburden in the geotechnical simulation box; the karst groundwater level control box is connected to the karst groundwater channel of the karst formation simulation system through pipelines to control the karst groundwater conditions in the cave space, thereby realizing the simulation of dual-level water-rich conditions of the porous groundwater in the overburden and the karst groundwater.

[0011] Preferably, the pile foundation / drilling construction vibration load simulation system includes a driving device, a driving device controller, a model pile, and a model drill rod; the driving device is arranged above the overburden rock and soil simulation system; the driving device is equipped with an action rod, and the end of the action rod is installed with a model pile or a model drill rod; the other end of the model pile or model drill rod is buried in the overburden rock and soil, or embedded in the karst rock layer; depending on the experimental requirements, the end of the action rod of the driving device can also directly contact the surface of the overburden rock and soil to apply a vibration load to the overburden; the driving device is connected to the driving device controller; the driving device is one of an impact hammer, a drill rig, and an actuator; the model pile and the model drill rod are respectively prepared from similar materials designed according to similarity theory based on the prototype, at least to ensure that the size and mechanical properties are similar.

[0012] Preferably, the monitoring and measurement system is a contact system or a non-contact system; the contact system includes an embedded earth pressure gauge, a pore water pressure gauge, a strain gauge, a settlement mark, an acceleration sensor, an acoustic emission sensor, a high-density electrical electrode as a monitoring element and a corresponding acquisition instrument; the non-contact system includes a laser displacement meter and a corresponding acquisition instrument, a digital photographic measurement device, and a geological radar, which is used to obtain stress, pore water pressure, strain, acceleration, ground displacement in the cover soil, apparent resistivity distribution characteristics of the cover rock and soil and the cave roof, ground deformation and collapse process, soil cave development status and collapse process, karst rock layer stress and strain, three-dimensional acoustic emission characteristics of cave roof destruction, and cave water vapor pressure information.

[0013] A method for simulating engineering vibration-induced karst roof destruction and ground collapse, comprising the following steps:

[0014] 1) Prepare rock fluid-solid coupling similarity materials based on the properties of the karst rock layer and the experimental similarity ratio, cast the karst rock layer according to the experimental design dimensions, and during the casting process, use the melting dissolution method or the air bag method to simultaneously prepare a karst cave space consistent with the prototype morphology. Reserve interfaces for karst groundwater channels and karst gas channels at the bottom and top of the karst space, respectively. If there are cracks and broken zones in the cave roof, grouting reinforcement, or geotextile reinforcement conditions must be prefabricated during the casting process. When the original rock is used as the karst stratum, rock samples must be selected according to experimental requirements and processed into a size that can be loaded into the karst stratum simulation box. During the karst rock layer preparation process, corresponding monitoring elements are embedded at the designed location according to the experimental monitoring plan. Prepare similar materials for model piles and model drill rods, and prefabricate the model piles and model drill rods.

[0015] 2) hoisting the karst stratum into the karst stratum simulation box, connecting the karst groundwater channel and the karst gas channel in the cave space, installing the flexible sealing pad, the diaphragm, and the iris rotary valve and sealing ring in the first opening, positioning and fixing the overburden geotechnical simulation system on the top of the diaphragm, passing the iris rotary valve and sealing ring from the first opening at the bottom of the diaphragm through the second opening at the bottom of the geotechnical simulation box and sealing and fixing them, adjusting the iris rotary valve to a predetermined opening shape and size, connecting the water tank water supply and drainage port and valve to the groundwater seepage simulation system, laying the overburden geotechnical mass in layers in the geotechnical simulation box until the overburden thickness is designed, and simultaneously burying the monitoring elements at the corresponding positions according to the experimental plan. During the preparation of the karst stratum and overburden geotechnical mass, model piles or model drill rods are simultaneously buried according to experimental requirements;

[0016] 3) Start the groundwater seepage simulation system and the karst negative pressure control box, and slowly supply water to the cave space and the geotechnical simulation box respectively. When the cave space is full of water, stop the karst water supply. When the geotechnical simulation box reaches the predetermined water level, stop the water supply. Maintain a stable water level and let it stand for a period of time to fully saturate it. Start the ground stress loading device and apply three-dimensional ground stress to the karst stratum according to the experimental design. Continue to start the groundwater seepage simulation system and slowly apply water pressure to the cave space to the experimental design value. Select and install the pile foundation / drilling construction vibration load simulation system drive device, drive device controller, and remaining monitoring devices according to experimental requirements;

[0017] 4) Start the monitoring and measurement system to measure ambient acoustic emission, initial geological radar or apparent resistivity signals, apply vibration load according to the experimental plan, record the applied disturbance load parameters, as well as the sinking height of the model pile, the upper end of the model drill rod or the ground under the vibration impact, and the soil collapse. Regularly measure the geological radar or apparent resistivity signals until the cave roof is destroyed and the overburden rock and soil are completely destroyed and collapsed;

[0018] 5) After the collapse develops stably and the monitoring data is stable, conduct the final geological radar or apparent resistivity signal measurement, shut down the monitoring and measurement system, dismantle the pile foundation / drilling construction vibration load simulation system, slowly drain the groundwater in the overburden rock and soil simulation box and the cave space, carefully clean the collapsed soil in the collapse pit, fill the collapse pit with foam glue, and after the foam glue is formed, excavate the overburden rock and soil in the overburden rock and soil simulation box, take out the foam glue molded body, perform three-dimensional modeling on the foam glue molded body, and record the shape and size of the collapse pit.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention solves the problem of realistically simulating the destruction process of the cave roof caused by the vibration load generated by pile foundation / drilling construction in the karst collapse disaster by constructing a karst cover layer-karst rock layer-karst cavity stratum structure. It can realize the whole disaster process of the pile foundation / drilling construction disaster, including the stratum stabilization stage, the vibration load disturbance stage, the cave roof destruction and exposure of the cave space stage, and the ground collapse stage. At the same time, the horizontal bidirectional and bottom vertical loading modules are used to provide a three-dimensional stress environment of the karst stratum. The groundwater seepage simulation system is used to simulate the complex double-water-level water-rich environment of the groundwater in the karst development area. It can reflect the destruction process of the cave roof under the combined action of multiple load effects such as ground stress, water pressure and vibration force and the resulting cover layer collapse disaster evolution, so that the simulated experimental environment is more in line with the natural environment and the accuracy of the experiment is improved.

[0021] (2) The experimental device and method proposed in the present invention have the advantages of simple structure, strong scalability, easy assembly and disassembly, and simple experimental operation. They can meet the experimental requirements of simulating various working conditions by simply and flexibly adjusting key parameters such as the properties of karst strata, the properties and thickness of the cave roof, the morphology, size and location of the cave, the type and thickness of the cap layer, the ground stress state of the karst stratum, groundwater conditions, and the type of pile foundation / drilling construction load.

[0022] (3) During the experiment, the present invention deploys a variety of monitoring elements to obtain soil stress, pore water pressure, strain, acceleration, ground displacement, ground collapse development, karst rock layer stress and strain, cave roof damage acoustic emission characteristics, and cave water and gas pressure and other multi-information changes. At the same time, with the help of geophysical exploration methods such as high-density electrical method and geological radar, the development status of soil caves and the collapse process are clarified, which helps to reveal the mechanism of karst collapse induced by karst roof damage-seepage effect, and assists in accurate assessment of collapse risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention;

[0024] Figure 2 It is a flowchart of the present invention.

[0025] in:

[0026] 1. Karst formation simulation system; 2. Platform base; 3. Karst formation simulation box; 301. First box; 302. Flexible sealing layer; 303. Ground stress loading device mounting hole; 4. Karst rock layer; 401. Cave space; 402. Cave roof; 5. Ground stress loading device; 501. Reaction frame; 502. Column; 503. Diaphragm; 504. Flexible sealing pad; 505. First opening; 506. Iris rotary valve and sealing ring; 507. Horizontal bidirectional loading module; 508. Bottom vertical loading module; 509. Power device; 5010. Extension rod; 5011. Loading plate; 6. Karst groundwater channel; 7. Karst gas vent Channel; 8. Karst negative pressure control box; 9. Overburden geotechnical simulation system; 10. Second box; 11. Porous permeable board and geotextile; 12. Water tank; 13. Geotechnical simulation box; 14. Overburden geotechnical body; 15. Water supply and drainage outlet and valve; 16. Second opening; 17. Groundwater seepage simulation system; 18. Water supply tank; 19. Pipeline; 20. Porous groundwater level control box; 21. Karst groundwater level control box; 22. Porous groundwater; 23. Karst groundwater; 24. Karst gas; 25. Pile foundation / drilling construction vibration load simulation system; 2501. Drive device; 2502. Drive device controller; 2503. Model pile, model drill rod. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] like Figure 1 、 Figure 2 As shown, a device for simulating engineering vibration-induced karst roof destruction and ground collapse includes a karst stratum simulation system 1, an overburden rock and soil simulation system 9, a groundwater seepage simulation system 17, a pile foundation / drilling construction vibration load simulation system 25, and a monitoring and measurement system; the overburden rock and soil simulation system 9 is connected to the upper part of the karst stratum simulation system 1 to form a karst overburden-karst rock layer 4-karst cavity stratum structure; the overburden rock and soil simulation system 9 and the karst stratum simulation system 1 are respectively connected to the groundwater seepage simulation system 17 through pipelines, and the groundwater seepage simulation system 17 provides a dual water-rich environment of porous groundwater 22 and karst groundwater 23 under different working conditions to the overburden rock and soil simulation system 9 and the karst stratum simulation system 1; the pile foundation / drilling construction vibration load simulation system 25 is set on the upper part of the overburden rock and soil simulation system 9 for applying vibration load to the overburden rock and soil simulation system 9; the monitoring and measurement system is used to obtain information on changes in key physical and mechanical parameters during the simulation process.

[0029] In this embodiment, the karst formation simulation system 1 includes a platform base 2, a karst formation simulation box 3, a ground stress loading device 5, a karst groundwater channel 6, a karst gas channel 7, and a karst negative pressure control box 8; the karst formation simulation box 3 is fixed on the platform base 2; the karst formation simulation box 3 includes a first box body 301, and the top of the first box body 301 is provided with an opening; the first box body 301 is provided with a ground stress loading device mounting hole 303; the inner side of the first box body 301 is embedded with a detachable flexible sealing layer 302; the interior of the first box body 301 is filled with a karst rock layer 4 prepared from original rock or rock fluid-solid coupling similar materials; the karst rock layer 4 is provided with at least one melt dissolution method or air bag. The karst space 401 of the simulated structure is prefabricated by the method, and the shape of the karst space 401 is consistent with the actual one; the karst rock layer 4 above the karst space 401 is configured as the karst cave roof 402, and the karst rock layer 4 within the range of the karst cave roof 402 can be prefabricated with cracks and broken zones, grouting reinforcement, geotextile reinforcement and other conditions according to experimental requirements; the karst groundwater channel 6 connects the bottom of the karst space 401 and the groundwater seepage simulation system 17; the karst gas channel 7 connects the top of the karst space 401 and the karst negative pressure control box 8; the karst groundwater 23, exhaust and vacuum negative pressure conditions of the karst space 401 in the karst space 401 are coordinated and controlled by the groundwater seepage simulation system 17 and the karst negative pressure control box 8;

[0030] The ground stress loading device 5 includes a reaction frame 501 and multiple loading modules; the reaction frame 501 includes a column 502 and a diaphragm 503; the column 502 is vertically fixed on the platform base 2, and the diaphragm 503 is arranged above the platform base 2 in parallel and spaced apart, and the upper end of the column 502 is fixedly connected to the diaphragm 503; the first box body 301 is arranged in the middle of the frame structure composed of the platform base 2, the column 502 and the diaphragm 503; a flexible sealing gasket 504 is provided at the bottom of the diaphragm 503, and the lower end surface of the flexible sealing gasket 504 abuts the top of the first box body 301 and the karst rock layer 4; the diaphragm 503 and the flexible sealing gasket 504 in the range above the karst rock layer 4 are provided with at least one first opening 505; an iris rotary valve and a sealing ring 506 for adjusting the shape and size of the opening are installed in the first opening 505; the loading module includes a loading pressure plate 5011 and multiple power devices 509; The force device 509 is a hydraulic loading cylinder or a servo motor; the ground stress loading device mounting hole 303 is configured with multiple power devices 509; the loading pressure plate 5011 is placed between the inner wall of the first box body 301 and the flexible sealing layer 302; the power device 509 is placed outside the first box body 301, and one end is provided with an extension rod 5010, the front end of the extension rod 5010 passes through the ground stress loading device mounting hole 303 and is fixedly connected to the loading pressure plate 5011; multiple power devices 509 are installed in a linear array on the loading pressure plate 5011; the loading module is configured as a horizontal bidirectional loading module 507 and a bottom vertical loading module 508; the horizontal bidirectional loading module 507 is arranged on the side of the first box body 301; the bottom vertical loading module 508 is arranged at the bottom of the first box body 301; the end of the power device 509 away from the extension rod 5010 is fixed on the column 502 or the platform base 2.

[0031] In this embodiment, the covering layer geotechnical simulation system 9 includes a second box body 10; the top of the second box body 10 is set to be an opening; the second box body 10 is fixed to the upper end of the diaphragm 503; the internal space of the second box body 10 is separated by two groups of porous permeable panels and geotextiles 11, forming two side water tanks 12 and a middle geotechnical simulation box 13; the plane size and position of the geotechnical simulation box 13 correspond to the top of the karst formation simulation box 3, and the geotechnical simulation box 13 is used to fill the karst covering layer geotechnical body 14; at least one second opening 16 is set at the bottom of the geotechnical simulation box 13, corresponding to the first opening 505 of the diaphragm 503 and the flexible sealing layer 302, and connected to the iris rotary valve and sealing ring 506 at the first opening 505; a group of water supply and drainage outlets and valves 15 with different flow rates are set at the bottom of the water tanks 12 on both sides, and the water supply and drainage outlets and valves 15 are connected to the groundwater seepage simulation system 17.

[0032] In this embodiment, the groundwater seepage simulation system 17 includes a water supply tank 18, a pipeline 19, a porous groundwater 22 water level control box 20, and a karst groundwater 23 water level control box 21. The water supply tank 18 is connected to the porous groundwater 22 water level control box 20 and the karst groundwater 23 water level control box 21 through the pipeline 19 respectively. The porous groundwater 22 water level control box 20 is connected to the water supply and drainage outlet and the valve 15 through the pipeline 19 to control the conditions of the porous groundwater 22 in the karst overburden layer in the geotechnical simulation box 13; the karst groundwater 23 water level control box 21 is connected to the karst groundwater channel 6 of the karst formation simulation system 1 through the pipeline 19 to control the conditions of the karst groundwater 23 in the cave space 401, thereby realizing the simulation of the dual water level rich conditions of the porous groundwater 22 in the overburden layer and the karst groundwater 23.

[0033] In this embodiment, the pile foundation / drilling construction vibration load simulation system 25 includes a driving device 2501, a driving device controller 2502, and a model pile or model drill rod 2503; the driving device 2501 is arranged above the overburden rock and soil simulation system 9; the driving device 2501 is equipped with an action rod, and the end of the action rod is installed with a model pile or model drill rod 2503; the other end of the model pile or model drill rod 2503 is buried in the overburden rock and soil body 14, or embedded in the karst rock layer 4; depending on the experimental requirements, the end of the action rod of the driving device 2501 can also directly contact the surface of the overburden rock and soil body 14 to apply a vibration load to the overburden; the driving device 2501 is connected to the driving device controller 2502; the driving device 2501 is one of an impact hammer, a drill rig, and an actuator; the model pile or model drill rod 2503 is prepared from similar materials designed according to similarity theory based on the prototype, at least to ensure that the size and mechanical properties are similar.

[0034] In this embodiment, the monitoring and measurement system is a contact system or a non-contact system; the contact system includes an embedded soil pressure gauge, a pore water pressure gauge, a strain gauge, a settlement mark, an acceleration sensor, an acoustic emission sensor, a high-density electrical electrode as a monitoring element and a corresponding acquisition instrument; the non-contact system includes a laser displacement meter and a corresponding acquisition instrument, a digital photographic measurement device, and a geological radar, which is used to obtain stress, pore water pressure, strain, acceleration, ground displacement in the cover soil, apparent resistivity distribution characteristics of the cover rock and soil body 14 and the cave roof 402, ground deformation and collapse process, soil cave development status and collapse process, stress and strain of the karst rock layer 4, three-dimensional acoustic emission characteristics of the destruction of the cave roof 402, and cave water and gas pressure information.

[0035] A method for simulating engineering vibration-induced karst roof destruction and ground collapse, comprising the following steps:

[0036] 1) Based on the properties of the karst rock layer 4 and the experimental similarity ratio, rock fluid-solid coupling similar materials are prepared, and the karst rock layer 4 is cast according to the experimental design dimensions. During the casting process, a karst cave space 401 consistent with the prototype morphology is simultaneously prepared using a melting dissolution method or an air bag method. Interfaces for a karst groundwater channel 6 and a karst gas channel 7 are reserved at the bottom and top of the karst space, respectively. If the cave roof 402 has cracks and broken zones, grouting reinforcement, or geotextile reinforcement conditions are required, it must be prefabricated during the casting process. When the original rock is used as the karst stratum, rock samples must be selected according to experimental requirements and processed into a size that can be loaded into the karst stratum simulation box 3. During the preparation of the karst rock layer 4, corresponding monitoring elements are embedded at the designed location according to the experimental monitoring plan. Similar materials for model piles or model drill rods 2503 are prepared and prefabricated.

[0037] 2) The karst stratum is hoisted and placed into the karst stratum simulation box 3, the karst groundwater channel 6 and the karst gas channel 7 in the karst cave space 401 are connected, the flexible sealing gasket 504, the diaphragm 503, and the iris rotary valve and sealing ring 506 in the first opening 505 are installed, the overburden geotechnical simulation system 9 is positioned and fixed on the top of the diaphragm 503, the iris rotary valve and sealing ring 506 are passed through the first opening 505 at the bottom of the diaphragm 503 and sealed, the iris rotary valve is adjusted to a predetermined opening shape and size, the water tank 12 water supply and drainage port and the valve 15 are connected to the groundwater seepage simulation system 17, the overburden geotechnical mass 14 is laid in layers in the geotechnical simulation box 13 until the overburden thickness is designed, and the monitoring elements are simultaneously buried at the corresponding positions according to the experimental plan. During the preparation of the karst stratum and the overburden geotechnical mass 14, model piles or model drill rods 2503 are simultaneously buried according to experimental requirements;

[0038] 3) Start the groundwater seepage simulation system 17 and the karst negative pressure control box 8, and slowly supply water to the cave space 401 and the geotechnical simulation box 13 respectively. When the cave space 401 is full of water, stop the karst water supply. When the geotechnical simulation box 13 reaches a predetermined water level, stop the water supply. Maintain a stable water level and let it stand for a period of time to fully saturate it. Start the ground stress loading device 5 and apply three-dimensional ground stress to the karst stratum according to the experimental design. Continue to start the groundwater seepage simulation system 17 and slowly apply water pressure to the cave space 401 to the experimental design value. Select and install the driving device 2501, driving device controller 2502, and remaining monitoring devices of the pile foundation / drilling construction vibration load simulation system 25 according to the experimental requirements;

[0039] 4) Start the monitoring and measurement system to measure ambient acoustic emission, initial geological radar or apparent resistivity signals, apply vibro-load according to the experimental plan, record the applied disturbance load parameters, as well as the sinking height of the upper end of the model pile or model drill rod 2503 or the ground under the vibro-load and the soil collapse, and regularly measure the geological radar or apparent resistivity signals until the cave roof 402 is destroyed and the overburden rock and soil 14 is completely destroyed and collapsed;

[0040] 5) After the collapse develops stably and the monitoring data is stable, perform the final geological radar or apparent resistivity signal measurement, shut down the monitoring and measurement system, remove the pile foundation / drilling construction vibration load simulation system 25, slowly drain the groundwater in the overburden rock and soil simulation box 13 and the cave space 401, carefully clean the collapsed soil in the collapse pit, fill the collapse pit with foam, and after the foam is formed, excavate the overburden rock and soil 14 in the overburden rock and soil simulation box 13, remove the foam molded body, perform three-dimensional modeling on the foam molded body, and record the shape and size of the collapse pit.

[0041] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A device for simulating engineering vibration-induced karst roof destruction and ground collapse, characterized in that: The invention comprises a karst stratum simulation system (1), an overburden rock and soil simulation system (9), a groundwater seepage simulation system (17), a pile foundation / drilling construction vibration impact load simulation system (25), and a monitoring and measurement system; the overburden rock and soil simulation system (9) is connected to the upper part of the karst stratum simulation system (1) to form a karst overburden-karst rock layer (4)-karst cavity stratum structure; the overburden rock and soil simulation system (9) and the karst stratum simulation system (1) are respectively connected to the groundwater seepage simulation system (17) through pipelines. The invention relates to a method for providing a double-water-rich environment of porous groundwater (22) and karst groundwater (23) under different working conditions to the covering layer geotechnical simulation system (9) and the karst stratum simulation system (1) through the groundwater seepage simulation system (17); a pile foundation / drilling construction vibration load simulation system (25) is arranged on the upper part of the covering layer geotechnical simulation system (9) to apply vibration load to the covering layer geotechnical simulation system (9); and a monitoring and measurement system is used to obtain information on changes in key physical and mechanical parameters during the simulation process.

2. The device for simulating engineering vibration-induced karst roof destruction and ground collapse according to claim 1, characterized in that: The karst formation simulation system (1) comprises a platform base (2), a karst formation simulation box (3), a ground stress loading device (5), a karst underground water channel (6), a karst gas channel (7), and a karst negative pressure control box (8); the karst formation simulation box (3) is fixed on the platform base (2); the karst formation simulation box (3) comprises a first box body (301), the top of which is provided with an opening; the first box body (301) is provided with a ground stress loading device mounting hole (303); a detachable flexible sealing layer (302) is embedded in the inner side of the first box body (301); the interior of the first box body (301) is filled with karst rock formation (4) The karst rock layer (4) is provided with at least one karst cave space (401) of a simulation structure prefabricated by a melting dissolution method or an air bag method; the karst rock layer (4) above the karst cave space (401) is configured as a karst cave roof (402); the karst groundwater channel (6) is connected to the bottom of the karst cave space (401) and the groundwater seepage simulation system (17); the karst gas channel (7) is connected to the top of the karst cave space (401) and the karst negative pressure control box (8); the karst groundwater (23), exhaust and vacuum negative pressure conditions of the karst cave space (401) in the karst cave space (401) are coordinated and controlled by the groundwater seepage simulation system (17) and the karst negative pressure control box (8); The ground stress loading device (5) comprises a reaction frame (501) and a plurality of loading modules; the reaction frame (501) comprises a column (502) and a diaphragm (503); the column (502) is vertically fixed on the platform base (2); the diaphragm (503) is arranged above the platform base (2) in parallel and at intervals; the upper end of the column (502) is fixedly connected to the diaphragm (503); the first box (301) is arranged in a frame consisting of the platform base (2), the column (502) and the diaphragm (503); The bottom of the transverse diaphragm (503) is provided with a flexible sealing pad (504), and the lower end surface of the flexible sealing pad (504) abuts against the top of the first box (301) and the karst rock layer (4); the transverse diaphragm (503) and the flexible sealing pad (504) above the karst rock layer (4) are provided with at least one first opening (505); an iris rotary valve and a sealing ring (506) for adjusting the shape and size of the opening are installed in the first opening (505); the loading module includes a loading pressure plate (501 1) and multiple power devices (509); multiple power devices (509) are configured corresponding to the ground stress loading device mounting holes (303); the loading pressure plate (5011) is placed between the inner wall of the first box (301) and the flexible sealing layer (302); the power device (509) is placed outside the first box (301), and one end is configured with a protruding rod (5010), the front end of the protruding rod (5010) passes through the ground stress loading device mounting hole (303) and is fixedly connected to the loading pressure plate (5011) ; Multiple power devices (509) are installed in a linear array on the loading plate (5011); the loading module is configured as a horizontal bidirectional loading module (507) and a bottom vertical loading module (508); the horizontal bidirectional loading module (507) is arranged on the side of the first box (301); the bottom vertical loading module (508) is arranged at the bottom of the first box (301); the end of the power device (509) away from the extension rod (5010) is fixed to the column (502) or the platform base (2).

3. The device for simulating engineering vibration-induced karst roof destruction and ground collapse according to claim 2, characterized in that: The overburden geotechnical simulation system (9) comprises a second box (10); the top of the second box (10) is set to be open; the second box (10) is fixed to the upper end of the transverse partition (503); the internal space of the second box (10) is divided by two groups of porous permeable plates and geotextiles (11), forming water tanks (12) on both sides and a geotechnical simulation box (13) in the middle; the plane size and position of the geotechnical simulation box (13) correspond to the top of the karst formation simulation box (3), and the geotechnical simulation box (13) is used to fill the rock. The invention relates to a rock and soil body (14) of a soluble overburden layer; at least one second opening (16) is provided at the bottom of the rock and soil simulation box (13), corresponding to the first opening (505) of the diaphragm (503) and the flexible sealing layer (302), and connected to the iris rotary valve and the sealing ring (506) at the first opening (505); a group of water supply and drainage ports and valves (15) with different flow rates are respectively provided at the bottom of the water tanks (12) on both sides, and the water supply and drainage ports and valves (15) are connected to the groundwater seepage simulation system (17).

4. The device for simulating engineering vibration-induced karst roof destruction and ground collapse according to claim 3, characterized in that: The groundwater seepage simulation system (17) comprises a water supply box (18), a pipeline (19), a porous groundwater (22) water level control box (20), and a karst groundwater (23) water level control box (21). The water supply box (18) is connected to the porous groundwater (22) water level control box (20) and the karst groundwater (23) water level control box (21) through the pipeline (19), and the porous groundwater (22) water level control box (20) is connected to the karst groundwater (23) water level control box (21) through the pipeline (19). The water supply and drainage outlet is connected to the valve (15) to control the conditions of the karst cover layer pore groundwater (22) in the geotechnical simulation box (13); the karst groundwater (23) water level control box (21) is connected to the karst groundwater channel (6) of the karst formation simulation system (1) through the pipeline (19) to control the conditions of the karst groundwater (23) in the cave space (401), thereby realizing the simulation of the dual water level rich conditions of the cover layer pore groundwater (22) and the karst groundwater (23).

5. The device for simulating engineering vibration-induced karst roof destruction and ground collapse according to claim 4, characterized in that: The pile foundation / drilling construction vibration load simulation system (25) includes a driving device (2501), a driving device controller (2502), and a model pile or model drill rod (2503); the driving device (2501) is arranged above the overburden rock and soil simulation system (9); the driving device (2501) is equipped with an action rod, and the end of the action rod is installed with the model pile or model drill rod (2503); the other end of the model pile or model drill rod (2503) is buried in the overburden rock and soil body (14), or embedded in the karst rock layer (4); Depending on the experimental requirements, the end of the action rod of the driving device (2501) can also directly contact the surface of the covering rock and soil (14) to apply a vibratory load to the covering layer; the driving device (2501) is connected to the driving device controller (2502); the driving device (2501) is one of an impact hammer, a drill, and an actuator.

6. The device for simulating engineering vibration-induced karst roof destruction and ground collapse according to claim 5, characterized in that: The monitoring and measuring system is a contact system or a non-contact system; the contact system includes an embedded earth pressure gauge, a pore water pressure gauge, a strain gauge, a settlement mark, an acceleration sensor, an acoustic emission sensor, a high-density electrical method electrode as a monitoring element and a corresponding acquisition instrument; the non-contact system includes a laser displacement meter and a corresponding acquisition instrument, a digital photographic measurement device, and a geological radar, which is used to obtain stress, pore water pressure, strain, acceleration, ground displacement, apparent resistivity distribution characteristics of the covering layer rock and soil and the cave roof, ground deformation and collapse process, soil cave development state and collapse process, stress and strain of the karst rock layer (4), three-dimensional acoustic emission characteristics of the destruction of the cave roof (402), and cave water and gas pressure information.

7. A method for simulating engineering vibration-induced karst roof destruction and ground collapse, characterized in that: The following steps are involved: 1) According to the properties of the karst rock layer (4) and the experimental similarity ratio, a rock fluid-solid coupling similar material is prepared, and the karst rock layer (4) is cast according to the size of the experimental design. During the casting process, a karst cave space (401) consistent with the prototype shape is simultaneously prepared by a melting dissolution method or an air bag method. The karst groundwater channel (6) and the karst gas channel (7) interfaces are reserved at the bottom and top of the karst space respectively. When the cave roof (402) has cracks and broken zones, grouting reinforcement, and geotextile reinforcement conditions, it needs to be prefabricated during the casting process. When the original rock is used as the karst stratum, rock samples need to be selected according to the experimental requirements and processed into a size that can be loaded into the karst stratum simulation box (3). During the preparation of the karst rock layer (4), corresponding monitoring elements are buried at the designed position according to the experimental monitoring plan. Similar materials of the model pile or model drill rod (2503) are prepared and the model pile or model drill rod (2503) is prefabricated; 2) hoisting the karst stratum into the karst stratum simulation box (3), connecting the karst underground water channel (6) and the karst gas channel (7) in the cave space (401), installing the flexible sealing pad (504), the diaphragm (503) and the iris rotary valve and the sealing ring (506) in the first opening (505), positioning and fixing the overburden geotechnical simulation system (9) on the top of the diaphragm (503), and passing the iris rotary valve and the sealing ring (506) through the geotechnical simulation box from the first opening (505) at the bottom of the diaphragm (503). (13) The second opening (16) at the bottom is sealed and fixed, the iris rotary valve is adjusted to the predetermined opening shape and size, the water tank (12) water supply and drainage outlet and the valve (15) are connected to the groundwater seepage simulation system (17), the covering rock and soil body (14) is laid in layers in the rock and soil simulation box (13) until the covering layer has a designed thickness, and the monitoring element is buried in the corresponding position according to the experimental plan. During the preparation of the karst stratum and the covering rock and soil body (14), the model pile or model drill rod (2503) is buried according to the experimental requirements; 3) Start the groundwater seepage simulation system (17) and the karst negative pressure control box (8), and slowly supply water to the cave space (401) and the geotechnical simulation box (13), respectively. When the cave space (401) is full of water, stop the karst water supply. When the geotechnical simulation box (13) reaches a predetermined water level, stop the water supply. Maintain a stable water level and let it stand for a period of time to fully saturate it. Start the ground stress loading device (5), apply three-dimensional geostress to the karst stratum according to the experimental design, continue to start the groundwater seepage simulation system (17), and slowly apply water pressure to the cave space (401) to the experimental design value. Select and install the pile foundation / drilling construction vibration load simulation system (25) drive device (2501), drive device controller (2502), and remaining monitoring devices according to experimental requirements; 4) starting the monitoring and measurement system, performing environmental sound emission, initial geological radar or apparent resistivity signal measurements, applying a vibration load according to the experimental plan, recording the applied disturbance load parameters, as well as the sinking height of the upper end of the model pile or model drill rod (2503) or the ground under the vibration action and the soil collapse, and regularly performing geological radar or apparent resistivity signal measurements until the cave roof (402) is destroyed and the overburden rock and soil (14) is completely destroyed and collapsed; 5) After the collapse develops stably and the monitoring data is stable, the final geological radar or apparent resistivity signal measurement is carried out, the monitoring and measurement system is turned off, the pile foundation / drilling construction vibration load simulation system (25) is removed, the groundwater in the overburden rock and soil simulation box (13) and the cave space (401) is slowly drained, the collapsed soil in the collapse pit is carefully cleaned, and the collapse pit is filled with foam glue. After the foam glue is formed, the overburden rock and soil (14) in the overburden rock and soil simulation box (13) is excavated, the foam glue molded body is taken out, and the foam glue molded body is three-dimensionally modeled to record the shape and size of the collapse pit.

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