A water inrush and sand inrush model test device and method containing prefabricated cracks

Abstract

The present application belongs to the technical field of geotechnical engineering simulation test, and discloses a water inrush and sand collapse model test device and method containing prefabricated cracks, which comprises a model box and a model. The model is formed by filling and pressing simulation materials in the model box. The model box comprises a back plate, and an excavation simulation extraction plate is pluggably connected to the bottom of the back plate. The excavation simulation extraction plate is extracted to form a free surface at the bottom of the model. A plurality of through holes are formed in the middle of the back plate. A crack prefabricating assembly comprises a rotating disc, a crack extraction plate and a cover plate. The rotating disc is fixedly connected to the crack extraction plate, and the rotating disc is rotatably connected to the through holes. The crack extraction plate is extracted to form a crack cavity in the model. The crack cavity is filled with simulation materials to form a prefabricated crack. The cover plate is used to block the through holes. A plurality of mounting holes are formed in the back plate, and a pressure sensor or a water pipe joint is mounted on the mounting hole. The present application has the technical effect of simulating the crack collapse induced by excavation unloading and monitoring the pressure value change in the whole process of crack collapse.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering simulation and testing technology, specifically relating to a test device and method for a water inrush and sand collapse model with prefabricated cracks. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Water inrush and sand bursting are common and highly dangerous geological hazards in the construction of underground engineering projects (such as tunnels, mines, and foundation pits). Their occurrence is closely related to the development of rock mass fissures. Fissures are not only the main channels for groundwater migration and sand seepage, but also largely control the triggering conditions, development process, and final scale of water inrush and sand bursting.

[0004] To explore the mechanism by which fractures affect disaster evolution, existing technology discloses a simulation test device for initiating sand collapse in a single fracture, including a sand source box, an angle adjustment device, a single fracture simulation device, and a head control device. The sand source box is installed on the angle adjustment device, the single fracture simulation device is installed at one end of the sand source box, and the head control device is installed at the other end of the sand source box. The angle adjustment device changes the angle of the single fracture simulation device relative to the horizontal plane, and the single fracture simulation device simulates fractures with different openings, widths, and lengths. The head control device provides a gradually increasing head height to the sand body in the sand source box until sand collapse is initiated and the water-sand mixture in the single fracture simulation device begins to move.

[0005] The above has the following defects: The above scheme triggers sand breach by monotonically increasing water head pressure, which cannot reflect the evolution characteristics and critical conditions of excavation-induced water inrush and sand breach disasters, and cannot provide reliable experimental data support for disaster prevention and control design based on excavation conditions. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a test device and method for a water inrush and sand collapse model with pre-fabricated cracks, which can solve the technical problem in the prior art that it cannot reflect the excavation-induced water inrush and sand collapse disaster.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a test device for a water inrush and sand collapse model with prefabricated fractures is provided, including a model box, prefabricated fracture components, an excavation simulation panel, and a model; the model is formed by filling and compacting simulated materials inside the model box and then curing them. The model box includes a base box and a back plate. An excavation slot is opened at the bottom of the back plate. The excavation simulation pull plate can be plugged and unplugged into the excavation slot. When the excavation simulation pull plate is pulled out of the excavation slot, a free surface is formed at the bottom of the model. Multiple through holes are opened in the middle of the back plate. The prefabricated crack component includes a rotating disk, a crack removal plate, and a cover plate. The rotating disk is fixedly connected to the crack removal plate and rotatably connected to the through holes. The crack removal plate is pulled out to form a crack cavity in the model. Simulated material is filled into the crack cavity to form a prefabricated crack. The cover plate is used to seal the through holes. The back panel also has several mounting holes for installing pressure sensors or water pipe connectors.

[0008] Furthermore, the mounting holes are opened in at least three layers. A layer of pressure sensor mounting holes is set between the mounting groove and the through hole, a layer of pressure sensor mounting holes is set at the top of the through hole, and the topmost mounting hole is used to install water pipe connectors.

[0009] Furthermore, the base box and the back panel are assembled into a box with an open top. Sealing strips are installed at the joint between the base box and the back panel, sealant is applied, and then the joint is pressed tightly with a sealing strip. Sealing grooves are provided on the inner walls of the mounting holes and through holes, and sealing strips are installed in the sealing grooves.

[0010] Furthermore, the model box is made of transparent material, and a camera acquisition device is installed in front of the model box. Both the camera acquisition device and the pressure sensor are connected to the mobile terminal, and both the image data and pressure data have time-series characteristics.

[0011] Furthermore, a bushing is provided on the outer periphery of the rotating disk, and the diameter of the bushing is equal to that of the through hole.

[0012] Furthermore, a locking device is installed on the rotating disk to lock the angle of the rotating disk.

[0013] Furthermore, the length of the excavation trench is equal to the length of the back plate, and the size of the simulated excavation plate is consistent with the size of the excavation trench.

[0014] Secondly, a test method for the aforementioned water inrush and sand collapse model test device with pre-fabricated fractures is provided, the specific steps of which include: Assemble the model box, insert the excavation simulation plate into the excavation trench, insert the fracture plate into the through hole, install the water pipe joint and pressure sensor, and verify the sealing performance of the model box. Set and fix the angles of multiple rotating disks, and then fill and compact simulation material into the model box to obtain the model; The crack removal plate forms a prefabricated crack cavity. Simulated material is filled into the cavity and compacted. A cover plate is installed to seal the through hole, resulting in multiple prefabricated cracks with set inclination angles. A set amount of water is injected into the model box, and the box is allowed to stand until the readings of each pressure sensor stabilize. Finally, the excavation simulation plate is removed, and the camera acquisition equipment and pressure sensors are activated to continuously acquire image data and pressure data.

[0015] Furthermore, after water is injected into the model box, the water injection is stopped when the pressure sensor reading installed below the fissure begins to rise from the initial value, so that the fissure is filled with water, while the rock mass below the fissure remains in a critical state of not being fully permeated.

[0016] Furthermore, by replaying the image data, the process from sand bursting to complete sand bursting was identified, the pressure changes upstream and downstream of the fracture during the corresponding time period were found, the pressure difference upstream and downstream of the fracture at the time of sand bursting was calculated, and the critical hydraulic gradient at the time of sand bursting due to water inrush was calculated.

[0017] Compared with the prior art, the advantages and positive effects of this invention are: This invention discloses a test device for a water inrush and sand collapse model with pre-fabricated fractures. By detachably connecting excavation simulation plates to the bottom of a backplate, after model fabrication, these plates are removed to create a free surface at the bottom of the model, simulating the unloading process during excavation in rock mass. Multiple fracture plates are rotatably connected to the middle of the backplate, creating multiple pre-fabricated fractures with different or identical inclination angles within the model. Installation holes are made in the backplate to install water pipe joints and pressure sensors, allowing for the acquisition of pressure changes throughout the entire process of sand collapse induced by excavation and unloading. This invention solves the technical problem of existing technologies that trigger sand collapse within fractures by gradually increasing water head pressure, which only reflects the influence of water pressure on sand collapse but not the sand collapse induced by excavation and unloading. It effectively simulates sand collapse induced by excavation and unloading, monitors pressure changes throughout the entire process, and provides reliable experimental data support for disaster prevention and control design based on excavation conditions. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a perspective view of the model box of Embodiment 1 or Embodiment 2 of the present invention; Figure 2 This is a rear view of the model box of Embodiment 1 or Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the rotating disk and the slit extraction plate in Embodiment 1 or Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the cover plate of Embodiment 1 or Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the bushing in Embodiment 1 or Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the locking device according to Embodiment 1 or Embodiment 2 of the present invention; Figure 7This is a flowchart of the test method of Embodiment 2 of the present invention; In the picture: 1. Model; 2. Front plate; 3. Side plate; 4. Bottom plate; 5. Back plate; 51. Mounting hole; 52. Excavation simulation plate pull-out; 53. Through hole; 6. Crack prefabrication component; 61. Rotary disk; 62. Liner ring; 63. Crack pull-out plate; 64. Cover plate; 65. Turntable; 66. Locking bolt. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] Example 1 This embodiment discloses a test device for a water inrush and sand collapse model containing pre-fabricated fractures, such as... Figures 1 to 3 As shown, the system includes a model box, a precast fracture component 6, an excavation simulation panel 52, and model 1. Model 1 is constructed by filling and compacting a simulated material similar to the rock or soil mass of the study area within the model box, followed by curing. It can be understood that by using a simulated material similar to the soil or rock mass of the study area to prepare model 1, the real rock or soil environment is replicated.

[0023] In this embodiment, as Figure 1 and Figure 2 As shown, the model box includes a base box and a back plate 5. The back plate is installed on the back of the base box, and an excavation slot is opened at the bottom of the back plate 5. The excavation simulation pull plate 52 can be plugged into the excavation slot. It should be noted that after the model 1 is completed, the excavation simulation pull plate 52 is pulled out of the excavation slot, forming a free surface at the bottom of the model 1, thereby simulating the situation of excavation and unloading in the rock mass.

[0024] like Figure 2 As shown, multiple through holes 53 are opened in the middle of the back plate, such as... Figure 3 , Figure 4As shown, the fracture prefabrication component 6 includes a rotating disk 61, a fracture removal plate 63, and a cover plate 64. The rotating disk 61 is fixedly connected to the fracture removal plate 63, and the rotating disk 61 is rotatably connected to the through hole 53. It should be noted that the rotating disk 61 is rotatably connected to the through hole 53. Rotating the rotating disk 61 can drive the fracture removal plate 63 to rotate inside the model box. Before filling with simulation material, rotating multiple rotating disks 61 can adjust the tilt angle of multiple fracture removal plates 63. Then, simulation material is filled to form multiple fracture cavities with different or the same tilt angle in the model 1. Simulation material is then filled into the fracture cavities to form multiple fractures with different or the same tilt angle. Finally, the cover plate 64 is sealed on the through hole 53.

[0025] like Figure 2 As shown, the back plate also has several mounting holes 51 for mounting pressure sensors or water pipe connectors. It should be noted that the water pipe connectors installed in the mounting holes are used to connect external water pipes. Before filling with simulated material similar to rock or soil, after installing the pressure sensor, rotating disk 61, and excavation simulation plate 52 in their respective positions, water can be injected into the model box through the water pipe connectors to verify the seal. After completing the crack fabrication, before removing the excavation simulation plate 52, a set amount of water is injected into the top of the model through the water pipe connectors. Then, the excavation simulation plate 52 is removed to conduct a simulation test of water inrush and sand collapse under excavation unloading conditions.

[0026] In this embodiment, after the excavation simulation plate 52 is removed, the pressure changes of the model are obtained throughout the entire process of sand collapse caused by excavation unloading by monitoring the pressure changes of multiple pressure sensors.

[0027] Understandably, existing technologies that trigger sand erosion within fissures by gradually increasing water head pressure only reflect the effect of water pressure on sand erosion and cannot reflect sand erosion induced by excavation unloading. This embodiment, however, by setting up a rotating disk, fissure extraction plate, and excavation simulation extraction plate, can create fissures with different inclination angles in the rock or soil model to be excavated, and simulate sand erosion induced by excavation unloading. It monitors the pressure changes in the model throughout the entire sand erosion process, providing reliable experimental data support for disaster prevention and control design based on excavation conditions.

[0028] like Figure 2As shown, in this embodiment, the mounting holes 51 are provided in at least three layers, and the number of mounting holes 51 in each layer corresponds to the number of through holes 53. A layer of mounting holes 51 is provided between the mounting groove and the through holes 53 for installing pressure sensors to monitor pressure changes downstream of the simulated fracture. A layer of mounting holes 51 is provided on top of the through holes 53 for installing pressure sensors to monitor pressure changes upstream of the simulated fracture. The topmost mounting hole 51 is used to install a water pipe connector for injecting a set amount of water into the top of the model. When the pressure monitoring values ​​upstream and downstream of the fracture are stable, the top of the fracture in the model is in a critical state of water saturation.

[0029] Understandably, after injecting a set amount of water into the top of the model through the water pipe joint at the top mounting hole 51, and then removing the excavation simulation plate 52, a free surface appears at the bottom of the model, causing a change in the model's stress environment, especially a significant change in the stress environment at the bottom of the cracks. It should be noted that the model is filled with a compacted simulated material similar to the rock or soil mass of the study area, and thus possesses internal stress. However, with the disappearance of the support at the bottom of the model, the internal stress within the model also changes, and the water saturation at the top of the model also changes. In the upper part of the model, water seeps downwards through the cracks under pressure, causing changes in the upstream and downstream pressures of the cracks.

[0030] It is also understandable that after removing the excavation simulation plate 52, monitoring the pressure changes upstream and downstream of the fracture can obtain the pressure value changes of the model throughout the entire process of sand collapse induced by the simulated excavation unloading.

[0031] like Figure 1 As shown, the basic housing of the model box also includes a front panel 2, side panels 3, and a bottom panel 4. The basic housing and the back panel 5 are assembled together to form a top-opening housing. Similar simulated materials are filled into the model box from the top of the housing. In this embodiment, the front panel 2, side panels 3, bottom panel 4, and back panel 5 are fixed together with bolts. Sealing strips are installed at the joints between adjacent panels, sealant is applied, and sealing strips are used to press them together to ensure the airtightness of the model box. After the model is completed, a set amount of water is injected into the model to avoid the situation where water saturation cannot be achieved in the model due to poor sealing, which would affect the experimental process.

[0032] In this embodiment, the thickness of the back plate 5 is greater than that of other plates. A sealing groove is provided on the inner wall of the mounting hole and through hole to install a sealing strip. This enhances the sealing effect of the connection between the pressure sensor, water pipe joint, rotating disk, cover plate and back plate, ensuring that water in the model can permeate from the upstream to the downstream of the crack, and preventing water from permeating through the through hole and mounting hole, which would affect the test results.

[0033] It should also be noted that this embodiment monitors water pressure changes in the model using pressure sensors, but water pressure changes cannot be used to conversely prove that a sudden water inrush and sand breach has occurred. Therefore, as follows... Figure 1 As shown, the model box in this embodiment is made of transparent material, such as acrylic. In this embodiment, a camera acquisition device (not shown) is installed in front of the model box. After the excavation simulation panel 52 is removed, the camera acquisition device is activated to capture the scene changes of sudden water inrush and sand collapse.

[0034] In this embodiment, both the camera acquisition device and the pressure sensor are communicatively connected to a mobile terminal, such as a computer, to transmit the acquired image and pressure data to the computer for analysis and storage. It should be noted that both the image and pressure data have temporal characteristics. By observing the image data, the time points of occurrence and termination of fissure water inrush and sand collapse can be determined. Based on the same temporal characteristics, the pressure data for the corresponding time period can be found. Analyzing the pressure data allows for the acquisition of pressure data during the simulated excavation unloading-induced fissure water inrush and sand collapse stage.

[0035] In this embodiment, the video acquisition device may be a camera or a webcam.

[0036] like Figure 3 , Figure 5 As shown, the crack prefabrication assembly 6 also includes a bushing 62, which is disposed on the outer periphery of the rotating disk 61. The bushing 62 is used to reduce the friction between the rotating disk 61 and the back plate 5 when the rotating disk 61 rotates. In this embodiment, the bushing 62 is made of polytetrafluoroethylene (PTFE), nylon, or silicone wear-resistant material.

[0037] It should be noted that when filling the model box with similar simulated materials, the filling is usually done in layers and compacted. To prevent the cracked pull plate 63 from rotating due to collisions when filling with similar simulated materials, this embodiment can also be designed with a locking device. Specifically, as shown in the example... Figure 6 As shown, a turntable 65 is coaxially fixed to the outside of the rotating disk. The diameter of the turntable is larger than that of the rotating disk. A threaded hole facing the back plate is opened on the turntable. The locking bolt 66 is screwed into the threaded hole. When the locking bolt is tightened, the end of the locking bolt presses against the outer surface of the back plate. The friction force locks the turntable, rotating disk, and slit plate at the current angle, so as to avoid the slit plate from rotating when filling similar simulated materials, which would affect the test process.

[0038] It is understandable that by preparing fracture extraction plates of different thicknesses and widths, fracture tests with different inclination angles, thicknesses, and widths can be achieved. Before filling with similar simulated materials, the corresponding fracture extraction plate can be replaced. Furthermore, in this embodiment, angles are marked on the rotating disk with an accuracy of 1°, and pointers are marked on the back plate outside the through-hole to facilitate changing the inclination angle of the fracture extraction plate.

[0039] In some implementations, handles are fixedly connected to the outside of the turntable and the outside of the excavation simulation panel to facilitate the removal or placement of the fissure panel and the excavation simulation panel from the model box.

[0040] It is important to note that in this embodiment, the length of the excavation trench is equal to the length of the back plate, and the dimensions of the excavation simulation panel 52 are consistent with the dimensions of the excavation trench. This design prevents the model from falling after the excavation simulation panel is removed because the model is compacted between the various panels of the box body during the filling process. Even if a completely free surface is formed at the bottom of the model, the model will not fall. By forming a completely free surface at the bottom of the model, the process of cracking and sand collapse induced by excavation unloading can be simulated more realistically.

[0041] Example 2 This embodiment discloses a test method for a water inrush and sand collapse model test device with pre-fabricated fractures, utilizing methods such as... Figures 1 to 6 The embodiment 1 disclosed in the figure shows a water inrush and sand collapse model test device with pre-fabricated fractures, such as Figure 7 As shown, the specific steps include: Assemble the model box, insert the excavation simulation plate 52 into the excavation trench, insert the rotating disk and the crack plate into the through hole, and install the water pipe joint and pressure sensor; seal all connection gaps, and then fill with water to check the sealing performance.

[0042] Understandably, injecting water into the model box through the water pipe joint to check the sealing of the model box can ensure that after the simulated excavation and unloading, water can seep from the upstream to the downstream of the crack, avoiding water seepage from the connection gaps, through holes, or installation holes, which would affect the test results.

[0043] Then, according to the experimental requirements, the angles of multiple rotating disks were set, the inclination angle of the cracks was set, and then the angles of multiple rotating disks were fixed. Then, simulated materials similar to rock or soil were filled and compacted in layers into the model box to obtain the model. Then, the rotating disk and the fissure extraction plate 63 are removed to form a prefabricated fissure cavity. The cavity is filled with a simulated material similar to rock or soil and compacted. The cover plate is installed to seal the through hole 53, resulting in multiple prefabricated fissures with set inclination angles. A set amount of water is injected into the model box, and the box is allowed to stand until the readings of each pressure sensor stabilize. Finally, the excavation simulation plate is removed, and the camera acquisition equipment and pressure sensors are activated to continuously acquire image data and pressure data.

[0044] In this embodiment, after water is injected into the model box, water injection is stopped when the pressure sensor reading installed below the fissure begins to rise from its initial value. This ensures that the fissure is filled with water while the rock mass below the fissure remains in a critical state where it is not fully permeated. After the pressure sensor readings stabilize, the excavation simulation plate is removed. It should be noted that this setting is to simulate the critical state of the rock mass before excavation, where the upper part of the rock mass is water-saturated, while the lower part is dense, preventing water from permeating downwards through the fissure. After the excavation simulation plate 52 is subsequently removed, a free surface appears at the bottom of the model, disrupting the original stress environment. The stress in the rock mass below the fissure naturally decreases, allowing water in the model to permeate downwards.

[0045] In this embodiment, image data and pressure data of the model during the occurrence of water inrush and sand collapse in the fissure are continuously acquired simultaneously using a camera acquisition device and a pressure sensor. Since both the image data and pressure data contain time-series signals, the process from the occurrence of sand collapse to complete sand collapse can be locked by image playback. The pressure value changes upstream and downstream of the corresponding fissure during the corresponding time process can be found, and these pressure value changes can be used as a reference for actual construction.

[0046] It should be noted that, in this embodiment, after locking the pressure changes upstream and downstream of the crack when sand collapse occurs, the pressure difference between the upstream and downstream of the crack can be calculated. Dividing this pressure difference by the seepage path length can calculate the critical hydraulic gradient when the crack experiences water inrush and sand collapse, which can be used as a reference for the early warning threshold in actual excavation construction.

[0047] The seepage path length is determined by trigonometric functions based on the preset width of the crack extraction plate and the rotation angle of the rotating disk.

[0048] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A test apparatus for a water inrush and sand collapse model with pre-fabricated fractures, characterized in that, It includes a model box, precast crack components, excavation simulation slabs, and a model; the model is formed by filling and compacting simulated materials inside the model box and then curing them. The model box includes a base box and a back plate. An excavation slot is opened at the bottom of the back plate. An excavation simulation pull plate can be plugged into the excavation slot. When the excavation simulation pull plate is pulled out of the excavation slot, an open surface is formed at the bottom of the model. The back plate has multiple through holes in the middle. The fissure prefabrication component includes a rotating disk, a fissure pull plate, and a cover plate. The rotating disk is fixedly connected to the fissure pull plate and rotatably connected to the through holes. Pulling out the fissure pull plate forms a fissure cavity in the model. The fissure cavity is filled with simulated material to form a prefabricated fissure. The cover plate is used to seal the through holes. The back plate is also provided with several mounting holes, on which pressure sensors or water pipe connectors are installed.

2. The water inrush and sand bursting model test device with pre-fabricated fractures as described in claim 1, characterized in that, The mounting holes are provided in at least three layers. A layer of pressure sensor mounting holes is provided between the mounting groove and the through hole, a layer of pressure sensor mounting holes is provided at the top of the through hole, and the topmost mounting hole is used to install a water pipe connector.

3. The water inrush and sand bursting model test device with pre-fabricated fractures as described in claim 1, characterized in that, The basic box and the back panel are assembled into a box with an open top. A sealing strip is installed at the connection gap between the basic box and the back panel, sealant is applied, and a sealing strip is used to press it tightly. Sealing grooves are provided on the inner walls of the mounting holes and through holes, and sealing strips are installed in the sealing grooves.

4. The water inrush and sand bursting model test device with pre-fabricated fractures as described in claim 1, characterized in that, The model box is made of transparent material. A camera acquisition device is installed in front of the model box. Both the camera acquisition device and the pressure sensor are connected to the mobile terminal for communication, and both the image data and the pressure data have time-series characteristics.

5. The water inrush and sand bursting model test device with pre-fabricated fractures as described in claim 1, characterized in that, A bushing is provided on the outer periphery of the rotating disk, and the diameter of the bushing is equal to that of the through hole.

6. The water inrush and sand burst model test device with pre-fabricated fractures as described in claim 5, characterized in that, The rotating disk is equipped with a locking device to lock the angle of the rotating disk.

7. The water inrush and sand bursting model test device with pre-fabricated fractures as described in claim 1, characterized in that, The length of the excavation trench is equal to the length of the back plate, and the size of the excavation simulation plate is consistent with the size of the excavation trench.

8. The test method for a water inrush and sand collapse model test device with pre-fabricated fractures as described in claims 1-7, characterized in that, The specific steps include: Assemble the model box, insert the excavation simulation plate into the excavation trench, insert the crack plate into the through hole, install water pipe joints and pressure sensors, and verify the sealing performance of the model box; The angles of the multiple rotating disks are set and fixed, and then the model box is filled with compacted simulation material to obtain the model; The fissure plate is removed to form a prefabricated fissure cavity. Simulated material is filled into the cavity and compacted. A cover plate is installed to seal the through hole, resulting in multiple prefabricated fissures with a set inclination angle. A set amount of water is injected into the model box, and the box is allowed to stand until the readings of each pressure sensor stabilize. Finally, the excavation simulation plate is removed, and the camera acquisition equipment and pressure sensors are activated to continuously acquire image data and pressure data simultaneously.

9. The test method for a water inrush and sand collapse model test device with pre-fabricated fractures as described in claim 8, characterized in that, After water is injected into the model box, the water injection is stopped when the pressure sensor reading installed below the fissure starts to rise from the initial value, so that the fissure is filled with water, while the rock mass below the fissure remains in a critical state of not being fully permeated.

10. The test method for a water inrush and sand collapse model test device with pre-fabricated fractures as described in claim 8, characterized in that, The image data is replayed to pinpoint the process from sand bursting to complete sand bursting. The pressure changes upstream and downstream of the fracture during the corresponding time period are found. The pressure difference upstream and downstream of the fracture when sand bursting occurs is calculated, and the critical hydraulic gradient when the fracture experiences water inrush and sand bursting is calculated.

Images