Simulation test device for catastrophe mechanism of surface collapse induced by tunnel excavation in karst area

Abstract

The invention relates to a simulation test device for a catastrophe mechanism of surface collapse induced by tunnel excavation in a karst area. The device comprises a covering layer simulation box, a karst pipeline system, a karst water cavity simulation box, a tunnel simulation assembly, a water level control box, a water supply system, a multi-parameter monitoring system and a bearing steel frame. A karst hole structure is arranged at the bottom of the covering layer simulation box and is connected with the karst water cavity simulation box through a karst pipeline system; the tunnel simulation assembly is connected with the karst pipeline system through a communication pipeline, and is provided with an electric adjusting valve and an electromagnetic flowmeter to quantitatively control the underground water leakage rate; the multi-parameter monitoring system comprises a displacement sensor, a pore water pressure sensor and the like and is used for synchronously collecting multi-dimensional data such as displacement and earth surface displacement. According to the invention, the underground water leakage process caused by tunnel excavation can be accurately simulated, the association rule of the underground water leakage rate and the surface collapse development mode is disclosed, and a theoretical basis is provided for disaster early warning and protection design of karst area tunnel engineering.

Description

Technical Field

[0001] The invention relates to the technical field of karst geological engineering disaster simulation, in particular to a karst area tunnel excavation-induced ground collapse disaster mechanism simulation test device. Background Art

[0002] Ground collapse refers to a geological disaster in which the overlying soil layer suddenly loses its stability and collapses due to natural or human factors. It is typically characterized by its suddenness, concealment, and frequent fluctuations in groundwater levels. Tunnel excavation in karst areas can lead to significant groundwater leakage, triggering ground collapse hazards in the tunnel site. These hazards damage tunnels, buildings, farmland, and other facilities, leading to traffic disruptions, housing damage, and casualties, posing a serious threat to the safety of projects and personnel in karst areas. Studying its mechanism can reveal the mechanisms of collapse instability and quantify the impact of disturbances such as tunnel excavation and water level fluctuations on soil cavity expansion, providing a scientific basis for setting disaster warning thresholds and optimizing tunnel construction design.

[0003] Current research often relies on a combination of numerical simulation and field monitoring, but this is plagued by technical bottlenecks such as distorted numerical model parameter values ​​and delayed field monitoring data. Physical model experiments are also an important tool for studying ground collapse in karst areas, as they can realistically reproduce the complex coupled geological and mechanical processes and achieve efficient and controllable simulation of karst structures and catastrophic factors. However, current experimental devices for studying ground collapse in karst areas primarily focus on the development of cavities and collapse in the overburden layer. There is limited research on the impact of groundwater environmental changes caused by factors such as tunnel excavation on collapse, and the influence of karst conduits is generally not considered. Consequently, there is a lack of quantitative research on the relationship between karst collapse and factors such as tunnel leakage and groundwater level fluctuations. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A test device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas, comprising: The cover layer simulation box is used to simulate the covering soil layer above the karst cave entrance. A row of replaceable perforated cover plates are installed at the bottom. By changing the hole size of the cover plates, karst cave entrances of different diameters can be simulated. The karst pipeline system consists of a funnel-shaped pipeline, a vertical pipeline, a horizontal pipeline and a ball valve, with the upper end connected to the overburden simulation box and the lower end connected to the karst water cavity simulation box; The karst water cavity simulation box is used to simulate the confined water layer and is connected to the water level control box through the water inlet pipe; The tunnel simulation component includes a main tunnel and a connecting pipe. The connecting pipe is connected to the karst pipeline system and is equipped with an electric regulating valve and an electromagnetic flow meter to form a closed-loop flow control system for quantitatively controlling the groundwater leakage rate. The water level control box is symmetrically located on both sides of the overburden simulation box, and the water level is adjusted by a slide rail overflow device; Water supply system, including water supply tank and water pump, supplies water to the water level control box; A multi-parameter monitoring system, including displacement sensors, soil pressure sensors, pore water pressure sensors, geological radar, high-speed cameras, and a monitoring platform, layered within the overburden layer; The load-bearing steel frame supports the covering layer simulation box, karst water cavity simulation box and water level control box in layers.

[0006] Both ends of the cover layer simulation box are provided with permeable plates with small holes, and a gauze layer is set between the permeable plates and the soil layer to simulate surface runoff and prevent clogging.

[0007] As a further solution of the present invention: a sealing ring is used to seal the perforated cover plate and the covering layer simulation box, and the diameter of the hole in the cover plate can be adjusted in the range of 5-50 mm.

[0008] As a further solution of the present invention: the vertical pipelines of the karst pipeline system are connected to the horizontal pipelines through a three-way interface to form an expandable pipeline network, and ball valves are installed on the vertical pipelines to simulate different leakage effects.

[0009] As a further solution of the present invention: an openable and closable slag discharge hole is provided at the bottom of the karst water cavity simulation box for discharging mud, sand and sediment.

[0010] As a further solution of the present invention: the electric regulating valve of the tunnel simulation component can be adjusted according to the preset water inflow curve ( Figure 7 ) Dynamically adjust the leakage rate to simulate water gushing conditions at different tunnel construction stages.

[0011] As a further solution of the present invention: the overflow device moves vertically via a slide rail, and the water level control accuracy reaches ±1mm.

[0012] As a further solution of the present invention: the multi-parameter monitoring system further includes: Air pressure sensors are installed in the funnel-shaped pipe to monitor the changes in air pressure in the karst pipe; The geological radar scans the surface of the cover layer at fixed intervals to detect the development morphology of soil holes; The collapse process was recorded by a high-speed camera at a frame rate of ≥1000 fps.

[0013] As a further solution of the present invention: the displacement sensors, soil pressure sensors and pore water pressure sensors are arranged in layers along the longitudinal plane of the karst cave entrance, and the layer spacing is 1 / 10-1 / 5 of the thickness of the covering layer.

[0014] An operating method of a device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in a karst area comprises the following steps: Step (1): Based on the similarity ratio of the similarity model, configure the appropriate test cover soil, determine the size of the cover hole, install the cover, and then place the cover soil into the cover simulation box. Displacement sensors, soil pressure sensors, and pore water pressure sensors are layered in the soil; a water level sensor is installed in the water level control box; an air pressure sensor is installed at the hole-shaped pipe, and flow meters are installed on the connecting pipe and the main tunnel. Step (2): Adjust the karst pipeline valve and the connecting pipeline valve to the designed size, adjust the overflow device to the designed height, continuously add water from the water supply tank to the water level control box through the water pump, open the valve between the water level control box and the karst water cavity simulation box, and supply water to the rock cavity water cavity simulation box to the designed height; turn off the water pump; Step (3): Turn on all deployed monitoring instruments, open the drainage valve of the rock cavity water tank simulation box, open the valve of the connecting pipe according to the design working conditions, and set the water flow rate of the connecting pipe to simulate the leakage of cave groundwater at different locations and different rates; Step (4): During the test, the development of soil holes in the covering soil layer was detected by geological radar every hour; Step (5): If the ground does not collapse after one drainage, repeat steps (2) and (3) until the soil collapse occurs; Step (6): Stop drainage, turn off the test instrument, and export the monitoring data.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The tunnel simulation component simulates tunnel drainage, which can explore the relationship between groundwater leakage and ground collapse caused by tunnel excavation; The deployment of multi-source monitoring equipment can record test phenomena in multiple dimensions, thereby more fully exploring the catastrophic mechanism of karst ground collapse induced by tunnel excavation; It can provide reference for the fields of ground collapse disaster monitoring and early warning in karst areas, tunnel engineering construction, etc., and promote the scientific and intelligent prevention and control of ground collapse disasters in karst areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the experimental device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas.

[0018] Figure 2 Schematic diagram of the overburden simulation box.

[0019] Figure 3 Schematic diagram of the karst pipeline simulation system.

[0020] Figure 4 Schematic diagram of the karst water cavity simulation box.

[0021] Figure 5 Schematic diagram of tunnel simulation components.

[0022] Figure 6 Schematic diagram of the excavation sequence of the cross-wall tunnel method.

[0023] Figure 7 Schematic diagram of tunnel water inflow-time curve.

[0024] Figure 8 Diagram of the layout of the covering soil layer monitoring instruments.

[0025] In the figure: 1-1. Cover layer simulation box, 1-2. Permeable board, 1-3. Drain valve of cover layer simulation box, 1-4. Cover plate of karst cave entrance, 2-1. Funnel-shaped pipe, 2-2. Karst pipe valve, 2-3. Vertical pipe, 2-4. Horizontal pipe, 3-1. Karst water cavity simulation box, 3-2. Water inlet valve, 3-3. Karst water cavity water inlet pipe, 3-4. Karst water cavity water supply valve, 3-5. Slag discharge hole, 4-1. Main tunnel, 4-2 .Connecting pipes, 4-3. Connecting pipe valves, 5-1. Water level control box, 5-2. Overflow device, 5-3. Slide rail, 5-4. Overflow pipe, 5-5. Return pipe, 6-1. Water supply tank, 6-2. Water pump, 6-3. Water supply pipe, 7. Load-bearing steel frame, 8-1. Water level sensor, 8-2. Displacement sensor, 8-3. Soil pressure sensor, 8-4. Pore water pressure sensor, 8-5. Air pressure sensor, 8-6. Electromagnetic flowmeter. DETAILED DESCRIPTION

[0026] In the description of the present application, it needs to be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0027] In the description of the present application, it needs to be understood that the terms "installation", "connection", "arrangement" should be understood broadly, for example, it can be fixedly connected, arranged, or detachably connected, arranged, or integrally connected, arranged, unless otherwise explicitly specified and limited. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Please refer to Figures 1 to 8 In the embodiments of the present application, a simulation test device for mechanism of tunnel excavation induced ground collapse disaster in karst area includes a cover layer simulation box, a karst pipeline system, a karst water cavity simulation box, a tunnel simulation assembly, a water level control box, a water supply box, a multi-parameter monitoring system and a load-bearing steel frame.

[0030] Preferably, the cover layer simulation box is used for simulating the overburden soil layer above the karst cave entrance, and the cover layer simulation box is a box-shaped device with an open top and is composed of transparent organic glass, which facilitates observation of test phenomena; a water-permeable plate with small holes is arranged at each end of the cover layer simulation box, which is used for simulating surface runoff; the water-permeable plate is composed of transparent organic glass, and gauze is used to separate the water-permeable plate and the soil layer during the test process, so that the water-permeable plate can permeate water and will not be blocked; a row of circular holes are formed at the bottom of the cover layer simulation box for installing a perforated cover plate, and a sealing ring is used between the cover plate and the cover layer simulation box for sealing, and different hole diameters of the karst cave entrance can be simulated by changing the hole size of the cover plate; two drain valves are arranged at the side edges of the cover layer simulation box for draining water in the box.

[0031] Preferably, the karst pipeline system consists of four parts: a funnel-shaped pipeline, a vertical pipeline, a transverse pipeline and a ball valve, which is used to simulate the karst pipeline and serve as a channel for water migration and soil migration; the upper end of the karst pipeline system is connected to the cover layer simulation box by a funnel-shaped pipeline, and a small hole is opened in the funnel-shaped pipeline to connect a thin tube to connect to the air pressure sensor; the lower end of the funnel-shaped pipeline is connected to the vertical pipeline, and a ball valve is installed on the vertical pipeline to simulate the different leakage effects of the karst pipeline itself by changing the degree of opening and closing of the valve; at the same time, a transverse pipeline can be set through a three-way interface to connect different vertical pipelines; the lower end of the karst pipeline system is connected to the karst water cavity simulation box through a vertical pipeline.

[0032] Preferably, the karst water cavity simulation box is used to simulate the pressurized water layer; a hole is opened on the upper surface of the karst water cavity simulation box to connect to the karst pipeline; two slag discharge holes that can be opened and closed freely are opened on the lower surface for drainage and mud discharge; a valve is opened on the side surface for drainage, and the water level control boxes on both sides are connected through the water inlet pipe.

[0033] Preferably, the tunnel simulation component is used to simulate a tunnel, and consists of a connecting pipe and a main tunnel. Figure 6 This is a schematic diagram of a common tunnel excavation method. When the excavation of the upper left part of the tunnel causes tunnel water inrush, groundwater leaks out of the tunnel in large quantities and is discharged from the tunnel entrance. The tunnel simulation component can simulate the function of the tunnel as a groundwater drainage channel after tunnel excavation causes groundwater leakage in the karst cave, without involving the tunnel's load-bearing function or interaction with the stratum. The main tunnel is connected to the karst pipeline system through a connecting pipe. An electric regulating valve is installed on the connecting pipe to quantitatively control the speed of groundwater leakage through the tunnel, and an electromagnetic flowmeter is installed. During the test, the actual tunnel water inrush curve ( Figure 7 ) Set the leakage rates of different connecting pipes to simulate the water gushing situation when different engineering measures are taken, and observe the changes in the monitoring data of the cover layer; the main tunnel is open at one end and closed at the other end, and an electromagnetic flowmeter is installed at the open end to measure the flow rate and flow rate of tunnel drainage.

[0034] Preferably, the water level control box is provided on each side of the cover layer simulation box, and is connected to the karst water cavity simulation box, the overflow device and the water pump through pipes respectively. The water level control box can supply water to the karst water cavity simulation box; the overflow device is installed on a slide rail fixed to the load-bearing steel frame, and the height of the water level in the water level control box is controlled by moving the position of the overflow device on the slide rail; the overflow device is connected to the water level control box and the water supply tank through a pipe. When the water level in the water level control box reaches the height of the overflow device, the water can flow back to the water supply tank through the overflow device.

[0035] Preferably, the water supply system includes a water supply tank, a water pump and a water pipeline. The water supply tank is placed under the karst water cavity simulation box and is connected to the water pump via a pipeline to supply water to the water level control boxes on both sides.

[0036] Preferably, the multi-parameter monitoring system includes a water level sensor, a displacement sensor, an earth pressure sensor, a pore water pressure sensor, an air pressure sensor, a geological radar, a flow sensor, a high-speed camera, and a monitoring platform. A water level sensor is arranged in the water level control box to monitor water level changes; a displacement sensor, an earth pressure sensor, and a pore water pressure sensor are arranged in layers on the longitudinal plane of the karst cave entrance in the cover layer simulation box to monitor displacement, earth pressure, and pore water pressure at different depths; an air pressure sensor is connected to the funnel-shaped hole of the karst pipeline system through a thin tube to monitor the internal air pressure; an electromagnetic flow sensor is arranged in the connecting pipeline and the main tunnel to monitor the flow of groundwater leakage in the connecting pipeline and the tunnel, and the flow rate is calculated based on the pipe diameter. The above monitoring equipment is connected to the monitoring platform on the computer. During the test, a geological radar is used to detect the development of soil holes on the surface of the cover layer at fixed time intervals; a high-speed camera is set up in front of the test box to record the collapse process.

[0037] Preferably, the load-bearing steel frame is made of stainless steel and is divided into two layers. The upper layer is used to place the cover layer simulation box, and the lower layer is used to place the karst water cavity simulation box and the water level control box. The size of the load-bearing steel frame should be able to meet the load-bearing requirements of the test device.

[0038] An operating method of a device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in a karst area comprises the following steps: Step 1: Based on the similarity ratio of the similarity model, configure the test cover soil and determine the size of the cover hole. The number of karst cave openings can be designed according to the working conditions. In this embodiment, the number of karst cave openings is 4. Install the cover, and then put the cover soil into the cover simulation box. Displacement sensors 8-2, soil pressure sensors 8-3 and pore water pressure sensors 8-4 are layered on the plane where each karst cave opening is located in the soil; install a water level sensor 8-1 in the water level control box; install an air pressure sensor 8-5 at the leaky pipe 2-1, and install flow meters on the connecting pipe 4-2 and the main tunnel 4-1; and assume a high-definition camera in front of the simulation test device.

[0039] Step 2: The karst pipeline system can be considered as two groups of pipelines, one with transverse pipelines and the other without transverse pipelines. Adjust the sizes of the karst pipeline valve 2-2 and the connecting pipeline valve 4-3, adjust the overflow device 5-2 to the designed height, and continuously add water from the water supply tank 6-1 to the water level control box 5-1 through the water supply pipe 6-3 via the water pump 6-2. Open the karst water cavity inlet valve 3-2 between the water level control box and the karst water cavity simulation box to supply water to the rock cavity water cavity simulation box 3-1 to the designed height. Turn off the water pump 7. Step 3: Turn on all deployed monitoring instruments, open the drainage valves 3-4 of the rock cavity water tank simulation box, open the valves of the connecting pipes according to the design working conditions, and set the water flow rate of the connecting pipes to simulate the situation of groundwater leakage in different locations and at different rates in the cave; Step 4: During the test, the development of soil holes in the covering soil layer was detected by geological radar every hour; Step 5: If the ground does not collapse after one drainage, repeat steps 2 and 3 until the soil collapse occurs; Step 6: Stop drainage, turn off the test instrument, and export the monitoring data.

[0040] It should be noted that the present invention is a simulation test device for the mechanism of ground collapse disaster induced by tunnel excavation in karst areas. All components are universal standard parts or components known to technical personnel in this field. Its structure and principles can be known to technical personnel through technical manuals or through conventional experimental methods.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0042] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A test device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas, characterized by: include: The cover layer simulation box (1-1) is used to simulate the covering soil layer above the karst cave entrance. A row of replaceable perforated cover plates (1-4) are provided at the bottom thereof. By changing the hole size of the cover plates, karst cave entrances of different apertures can be simulated. The karst pipeline system is composed of a funnel-shaped pipeline (2-1), a vertical pipeline (2-3), a horizontal pipeline (2-4) and a ball valve (2-2), with the upper end connected to the overburden simulation box and the lower end connected to the karst water cavity simulation box; The karst water cavity simulation box (3-1) is used to simulate the confined water layer and is connected to the water level control box through the water inlet pipe (3-3); A tunnel simulation component includes a main tunnel (4-1) and a connecting pipe (4-2), wherein the connecting pipe (4-2) is connected to the karst pipe system and is provided with an electric regulating valve (4-3) and an electromagnetic flow meter (8-6), forming a closed-loop flow control system for quantitatively controlling the groundwater leakage rate; The water level control box (5-1) is symmetrically arranged on both sides of the cover layer simulation box, and the water level height is adjusted by the slide rail overflow device (5-2); A water supply system, comprising a water supply tank (6-1) and a water pump (6-2), supplies water to the water level control box; A multi-parameter monitoring system, including displacement sensors (8-2), soil pressure sensors (8-3), pore water pressure sensors (8-4) layered in the overburden, as well as geological radar, high-speed cameras and a monitoring platform; The load-bearing steel frame (7) supports the covering layer simulation box, the karst water cavity simulation box and the water level control box in layers.

2. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: Permeable plates (1-2) with fine holes are provided at both ends of the cover layer simulation box (1-1), and a gauze layer is provided between the permeable plates and the soil layer to simulate surface runoff and prevent clogging.

3. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: A sealing ring is used to seal the perforated cover plate (1-4) and the covering layer simulation box, and the diameter of the hole in the cover plate can be adjusted within a range of 5-50 mm.

4. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The vertical pipeline (2-3) of the karst pipeline system is connected to the horizontal pipeline (2-4) through a three-way interface to form an expandable pipeline network, and the ball valve (2-2) is installed on the vertical pipeline to simulate different leakage effects.

5. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The bottom of the karst water cavity simulation box (3-1) is provided with an openable and closable slag discharge hole (3-5) for discharging mud, sand and sediment.

6. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The electric regulating valve (4-3) of the tunnel simulation component can dynamically adjust the leakage rate according to the preset water inrush curve (Figure 7) to simulate the water inrush conditions at different tunnel construction stages.

7. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The overflow device (5-2) moves vertically via a slide rail (5-3), and the water level control accuracy reaches ±1mm.

8. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The multi-parameter monitoring system further comprises: An air pressure sensor (8-5) is arranged in the funnel-shaped pipe (2-1) to monitor the air pressure changes in the karst pipe; The geological radar scans the surface of the cover layer at fixed intervals to detect the development morphology of soil holes; The collapse process was recorded by a high-speed camera at a frame rate of ≥1000 fps.

9. The device for simulating the mechanism of ground collapse disaster induced by tunnel excavation in karst areas according to claim 1, characterized in that: The displacement sensor (8-2), soil pressure sensor (8-3) and pore water pressure sensor (8-4) are arranged in layers along the longitudinal plane of the karst cave entrance, with the layer spacing being 1 / 10–1 / 5 of the thickness of the covering layer.

10. A test method based on the device according to any one of claims 1 to 9, characterized in that: Including steps: (a) Adjust the overflow device (5-2) to the target height and inject water into the water level control box (5-1) to make the karst water cavity simulation box (3-1) reach the preset water pressure; (b) Open the electric regulating valve (4-3) and set the leakage rate, and simultaneously start the multi-parameter monitoring system; (c) Use geological radar to scan the internal structure of the cover layer at regular time intervals; the scanning interval is 1 hour, and the scanning data is temporally and spatially correlated with the real-time displacement data of the displacement sensor (8-2); (d) When a single drainage does not induce collapse, steps (a)–(c) are repeated until collapse occurs.

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