Test system and test method for simulating water and mud bursting disasters of karst tunnel

Abstract

The invention belongs to the technical field of disaster simulation, and particularly discloses a test system and a test method for simulating water and mud bursting disasters of a karst tunnel, and the system comprises a seepage simulation box, a tunnel test unit, a water pressure monitoring device, a mud and sand flow monitoring device, a water tank water supply system and an atomization spraying device. The seepage simulation box comprises a box body, a first cover plate and universal wheels; a tunnel hole is formed in the front plate surface of the box body and is used for mounting a tunnel test unit; the interior of the box body is filled with different materials in a layered mode to simulate karst rock geologic bodies and non-karst rock geologic bodies, and rock stratum permeability parameters are regulated and controlled so as to reproduce evolution of a corrosion channel and the waterproof characteristic of a non-karst rock layer. The test system disclosed by the invention combines accurate water supply, extreme rainfall simulation, karst boundary difference modeling and double-hole coupling monitoring means, reveals critical conditions and a propagation mechanism of water inrush and mud inrush disasters caused when a tunnel passes through soluble and non-soluble rock mass interfaces, and provides a reliable test basis for disaster chain prevention and control in karst area tunnel construction and operation.

Description

Technical Field

[0001] The present invention relates to the technical field of disaster simulation, and in particular to a test system and a test method for simulating water and mud burst disasters in karst tunnels. Background Art

[0002] Karst areas, where complex underground networks have formed due to the long-term dissolution of soluble rocks, present extremely high risks when tunnels pass through the interface between soluble and non-soluble rocks. On the one hand, intense dynamic groundwater recharge creates a "water-conducting-water-blocking" binary structure between the dissolution channels and the impermeable boundaries, leading to severe distortion of the seepage field. On the other hand, high-pressure water flows through fissures that split the surrounding rock, driving mud and sand from the dissolution channels into the tunnel, triggering a sudden increase in seepage pressure in adjacent chambers and cracking of the lining, creating a chain reaction of disasters. However, existing model test systems, due to their use of homogeneous materials, static water supply, and fragmented monitoring, result in ambiguous critical thresholds for disasters and a reliance on empirical control designs. Breaking through the "homogeneous, static, and single-dimensional" technical bottleneck and constructing a test system that integrates layered heterogeneous simulation, dynamic environmental reproduction, and multi-dimensional monitoring has become a core requirement for achieving precise control in karst tunnels.

[0003] The traditional test system has the following limitations: First, it does not simulate the permeability difference between soluble rock and non-soluble rock in layers, and cannot accurately control the development of dissolution channels and the strength of water-blocking boundaries; second, the water supply method is single, and it is difficult to dynamically simulate the multi-condition coupling effects of high-pressure sudden surges or rainfall infiltration in karst areas; third, the monitoring dimension is limited, and there is a lack of synchronous quantitative analysis of water pressure mutations, mud and sand migration, and seepage instability in adjacent caverns during water and mud inrush.

[0004] Therefore, there is an urgent need to construct a model test system that can reproduce the hydrogeological characteristics of the interface, dynamically control the seepage boundary, and realize multi-dimensional disaster linkage, so as to reveal the triggering mechanism and chain effect of sudden water and mud disasters, and provide scientific support for the safe construction of karst tunnels and disaster early warning. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a test system and test method for simulating water and mud inrush disasters in karst tunnels, which solves the problems mentioned in the above background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a test system for simulating sudden water and mud disasters in karst tunnels, the test system comprising a seepage simulation box, a tunnel test unit, a water pressure monitoring device, a mud and sand flow monitoring device, a water tank water supply system, and an atomizing spray device for simulating rainfall.

[0007] The seepage simulation box comprises a box body, a first cover plate made of transparent material, and universal wheels; a tunnel hole is formed in the front plate surface of the box body and used for mounting a tunnel test unit to simulate a horizontal double-hole tunnel; a drainage interface is arranged on the first cover plate and used for plugging the tunnel hole in the front plate surface.

[0008] Preferably, the box body is internally layered with soluble rock simulation material and non-soluble rock simulation material to simulate soluble rock and non-soluble rock regions respectively, and the junction of the two forms a soluble rock and non-soluble rock interface; the development characteristics of the soluble rock region and the water-resisting boundary effect of the non-soluble rock region are controlled by adjusting the permeability coefficients of the simulation materials in the respective layers.

[0009] Preferably, the box body is internally layered with soluble rock simulation material and non-soluble rock simulation material to simulate soluble rock and non-soluble rock regions respectively, and the junction of the two forms a soluble rock and non-soluble rock interface; the development characteristics of the soluble rock region and the water-resisting boundary effect of the non-soluble rock region are controlled by adjusting the permeability coefficients of the simulation materials in the respective layers.

[0010] Preferably, the soil-separating and water-permeating plate comprises a perforated steel plate and a composite soil-separating layer; the composite soil-separating layer is made of a mixture of steel wire mesh and non-woven fabric and is fixed to the surface of the perforated steel plate.

[0011] Preferably, the seepage simulation box is provided with a plurality of universal wheels with brakes at the bottom of the box body, which are used for conveniently moving and accurately positioning the entire test system.

[0012] Preferably, the water supply system of the water tank comprises a water tank and a staged pressure adjusting module; the water tank is independently arranged on the left side of the box body and is in communication with the inside of the box body through a controllable flow rate pipeline; the water tank and the box body are further provided with a staged pressure adjusting module, and the pressure and flow rate of the water supply are flexibly controlled through the staged pressure adjusting module to adapt to various groundwater recharge conditions and simulate the groundwater seepage environment under the condition of high pressure and rich water in karst regions.

[0013] Preferably, the atomizing and spraying device comprises atomizing nozzles; a plurality of atomizing nozzles form an array of atomizing nozzles arranged at the top of the box body; when the opening degree of the atomizing nozzles is adjusted to 90%, an extreme rainfall environment is simulated.

[0014] Preferably, the tunnel test unit is provided with a grouting ring for simulating grouting reinforcement, and water pressure collectors are embedded in the inner and outer sides of the grouting ring to realize monitoring of the water pressure response under different reinforcement states.

[0015] Preferably, the water pressure monitoring equipment is embedded in the soluble rock and non-soluble rock interface, the soluble rock seepage path, and the tunnel surrounding rock region to monitor the dynamic water pressure changes in the water inrush process in real time; the mud and sand flow monitoring device is connected with the drainage interface of the first cover plate and can monitor the mud and sand concentration, flow rate, and cumulative flow rate data in real time to quantify the scale of mud inrush disasters and their cascading effects on the tunnel seepage field.

[0016] In another aspect, to achieve the above object, the present application also provides the following technical solutions: a test method for simulating water and mud inrush disasters of karst tunnels, comprising the following steps:

[0017] S1, the tunnel test unit is installed in parallel in the middle of the box by using a prefabricated fixed support, the inner circle of the grouting ring hole end of the tunnel test unit is aligned with the two tunnel holes of the front plate surface of the box, glass glue is sealed on the grouting ring close to the glass surface periphery, then the first cover plate with a drainage interface is covered, and it is ensured that the double-hole axis is horizontally aligned;

[0018] S2, water pressure monitoring equipment is pre-buried in the left and right hole grouting rings respectively, and is arranged at intervals of 90° along the ring, with 4 measuring points per hole; a tunnel face water baffle is installed on the side of the tunnel formed by the tunnel test unit in the full-face curtain grouting area, then similar material simulating lining is attached to the inner wall of the grouting ring on the tunnel side of the tunnel face water baffle, to simulate the lining of the tunnel; a distributed optical fiber sensor is pre-buried in the left hole erosion channel, to monitor the water pressure gradient in real time; a pore pressure gauge and a strain gauge are pre-buried in the left hole surrounding rock and the lining structure, to quantify the pressure transmission coefficient of the right hole water inrush to the left hole;

[0019] S3, fluorescent tracer particles are injected into the right hole water inrush source area, the path of the mud sand migrating along the erosion channel to the left hole is recorded by a high-speed camera; a 3D dynamic model of the cross-hole migration of the mud sand is constructed by using image processing software;

[0020] S4, soluble rock layer is laid in the box by using soluble rock simulation material, including using modified gypsum as the main material, adding foaming agent and retarder, forming multi-level pore structure by controlling foaming rate, simulating erosion channel network, pre-buried soluble salt crystal as "sacrificial template", in the test, the salt crystal is dissolved by water flow to form a dynamically expanding erosion channel, clay, fine sand and water are mixed to make mud mortar, which is pre-filled into the pore structure to simulate the occurrence state of the mud sand in the karst area, the fluorescent tracer particles are mixed into the mud sand, the migration trajectory is recorded by a high-speed camera, and the flow rate and diffusion range are quantified;

[0021] Non-soluble rock layer is laid below the soluble rock layer by using non-soluble rock simulation material, including using dense clay-bentonite composite material, coating epoxy resin sealant at the boundary to prevent interlayer leakage, embedding replaceable high-density polyethylene water-resistant sheet to simulate the anti-inrush capacity of the water-resistant boundary;

[0022] S5, high-pressure dynamic water supply and rainfall simulation configuration, the water tank in the water supply system of the water tank is installed on the left side of the box, connected to the right hole karst interface zone through a high-pressure pipeline, the water supply pressure is adjusted to 1.2 MPa by a staged pressure adjustment module, the karst pipeline inrush is simulated, and the instantaneous flow peak value is recorded;

[0023] Install atomizing spray head on the top of the box to form an array of atomizing spray heads, adjust the opening of the atomizing spray head to 90%, simulate extreme rainfall intensity of 100mm / h, and synchronously control the rainfall and high pressure gushing through the PID controller to simulate the synergistic effect of surface rainfall infiltration and underground gushing.

[0024] S6, maintain the right hole high pressure gushing 1.2MPa and rainfall 100mm / h for 25 minutes; through the data acquisition system connected with the water pressure monitoring equipment and the mud flow monitoring device, the water pressure of the right hole dissolution channel, the left hole surrounding rock seepage pressure, the water flow from the tunnel hole and the mud flow data are collected in real time;

[0025] S7, end the test, simulate the seepage field distribution of the horizontal double-hole karst tunnel under the condition of high pressure gushing-rainfall coupling during the tunnel construction period and the drainage capacity and mud flow of the tunnel under the condition of the water retaining plate of the tunnel face;

[0026] Remove the water retaining plate of the tunnel face near the tunnel side in the full-face curtain grouting area, repeat the high pressure gushing test, record the water pressure of the right hole dissolution channel, the left hole surrounding rock seepage pressure, the water flow from the tunnel hole and the mud flow data; simulate the seepage field distribution of the horizontal double-hole karst tunnel under the condition of high pressure gushing-rainfall coupling during the tunnel construction period and the total drainage capacity and mud flow of the tunnel.

[0027] The beneficial effects of the present application are:

[0028] 1) The present application accurately simulates the layered hydrogeological structure, in order to more truly reflect the hydrogeological environment of the karst area, the present system constructs a test model based on a layered structure, and adopts a composite design of soluble rock layer and non-soluble rock layer. The soluble rock layer is composed of modified gypsum material and precast artificial dissolution channels to simulate the characteristics of karst development; the non-soluble rock layer is simulated by dense clay composite material to simulate the water-resisting rock layer. The layered design breaks through the limitation of the traditional homogeneous model in reducing the geological structure, is closer to the real karst stratum combination, and effectively improves the geological adaptability and reliability of the test results.

[0029] 2) The present application accurately reproduces the simulation of high pressure dynamic seepage environment, by configuring a multi-stage adjustable pressure water supply unit (pressure adjusting range is 0.1-1.5MPa) and a variable intensity rainfall device (10-100mm / h), the present system can simulate multiple coupling conditions such as typical high pressure recharge, gushing water flow and surface heavy rainfall in karst area. The dynamic water supply system supports water pressure mutation simulation (for example, 0.5MPa suddenly rises to 1.2MPa), so as to capture the critical trigger pressure (such as 0.8MPa) of water and mud gushing event, and provide quantitative analysis basis for disaster warning. The system uses PID control algorithm to link the electric valve, maintains the water level within ±5mm, effectively reduces the manual control error, and significantly improves the repeatability and operation efficiency of the test.

[0030] 3) The present application realizes quantitative tracking and visual analysis of the whole process of disasters through a multi-dimensional monitoring system, integrates various sensing and tracking methods, and builds a full-factor data acquisition platform. Fiber optic pressure sensors are arranged in the dissolution channel, surrounding rock fissures and structural lining area to obtain real-time water pressure change information; combined with fluorescent marker particles and high-speed imaging systems, the dynamic tracking of mud and sand migration paths is realized. By setting up seepage pressure and strain linkage monitoring of adjacent caverns, the cross-cavern propagation law of water and mud inrush disasters is revealed, supporting chain effect analysis. On this basis, a "seepage-mud-sand-structure" three-field coupling model is built to realize accurate prediction of the disaster expansion path and provide decision support for tunnel group disaster prevention design. In addition, the system also supports 3D dynamic simulation display, which can intuitively present the disaster development hotspots and realize the visualization and intelligent extension from test to engineering. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The structure schematic diagram of the test system for simulating karst tunnel water and mud inrush disasters of the embodiment of the present application;

[0032] Figure 2 The cross-sectional structure schematic diagram of the embodiment of the present application for measuring the drainage capacity and mud and sand flow of the tunnel under the water retaining condition of the working face during the construction period;

[0033] Figure 3 The cross-sectional structure schematic diagram of the embodiment of the present application for measuring the total drainage capacity and mud and sand flow of the tunnel during the construction period;

[0034] Figure 4 The structure schematic diagram of the fixed support of the embodiment of the present application;

[0035] Figure 5 The schematic diagram of the connection with the external water supply when simulating the horizontal double-hole karst tunnel under the condition of high-pressure gushing-rainfall coupling of the embodiment of the present application;

[0036] In the figure, 1-box, 2-tunnel hole, 3-fixed support, 4-first cover plate, 5-water tank, 6-soil-proof water-permeable plate, 7-overflow port, 8-omni-directional wheel, 9-tunnel test unit, 10-water retaining plate, 11-soluble rock simulation material, 12-non-soluble rock simulation material, 13-atomizing nozzle, 14-soluble rock and non-soluble rock interface, 15-staged pressure regulation module, 16-high-speed camera, 17-data acquisition system. DETAILED DESCRIPTION

[0037] With reference to the drawings and the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts are within the scope of the present application.

[0038] It should be noted that the embodiments and features in the present application can be combined with each other without conflict. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0039] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and thus cannot be understood as indicating or implying that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus cannot be understood as limiting the present application. In addition, the terms "first", "second", and the like are only used to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrange", "mount", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] In view of the technical status of the existing karst tunnel water and mud inrush disaster model test system, although the existing researches focus on the simulation test of the disaster of tunnel passing through water-rich fracture zone or karst development area, there are still the following key problems: 1) the permeability performance of karst junction zone is insufficient, and the mainstream simulation system generally adopts homogeneous surrounding rock material for structure design, and lacks simulation support for the layered structure of soluble rock and non-soluble rock. Due to the neglect of the coupling characteristics of the permeability difference (such as the development condition of the dissolution channel network and the impermeability of the water-resisting zone), it is difficult to truly reflect the complex hydrogeological behavior of the karst intersection zone, thereby limiting the in-depth exploration of the water and mud inrush disaster inducing mechanism. 2) The dynamic water supply and extreme working condition simulation capability are insufficient, and the traditional model system mostly adopts constant water head or one-way water supply at the bottom, which is difficult to meet the reproduction demand of the dynamic conditions such as high-pressure water recharge (pressure range 0.1-1.0 MPa), strong rainfall infiltration (10-100 mm / h) and sudden inrush in karst area. In addition, the overflow regulation capacity of the existing device is limited, and the water level control error is generally above ±20 mm, which is difficult to guarantee the stability of the seepage field in the test process, thereby affecting the accuracy and reliability of the hydraulic response data, and weakening the identification ability of the disaster water pressure critical threshold (such as 0.5-1.2 MPa). 3) The monitoring dimension of the disaster process is limited, and the multi-parameter linkage monitoring mechanism is lacking, and most of the existing test systems mainly focus on the change of the hydraulic parameters in the single chamber, such as water pressure or flow rate, and ignore the dynamic coordination process of the multi-dimensional disaster chain in the water and mud inrush evolution process. For example, the distributed sensing device is not embedded in the soluble rock-non-soluble rock junction zone, surrounding rock fracture and supporting structure, so that the pressure jump, mud and sand migration path and seepage field coupling effect between multiple chambers cannot be synchronously perceived and analyzed. The data of key parameters such as the water pressure transmission coefficient (0.3-0.8) between adjacent chambers and the mud and sand outflow concentration (0-100 g / L) are missing, which seriously restricts the quantitative research on the disaster expansion path and chain damage mechanism.

[0042] Embodiment 1

[0043] In view of the above, in order to solve the problems of the existing model system in simulating the water and mud inrush disaster of karst tunnel, a technical scheme is provided: a test system for simulating the water and mud inrush disaster of karst tunnel, the test system comprises a seepage simulation box, a tunnel test unit 9, a water pressure monitoring device (not shown in the figure), a mud and sand flow monitoring device (not shown in the figure), a water tank water supply system and a simulated rainfall atomizing and spraying device.

[0044] As Figure 1As shown, the seepage simulation box includes a box body 1, a first cover plate 4 made of transparent material arranged on the front plate surface of the box body, and universal wheels 8; the front plate surface of the box body 1 is provided with two tunnel holes 2 located on the same horizontal line, for embedding a double-hole tunnel test unit to reproduce a double-hole tunnel construction scene. The first cover plate 4 is provided with a drainage interface for plugging the tunnel holes 2 on the front plate surface.

[0045] Further, the box body 1 is filled with soluble rock simulation material 11 and non-soluble rock simulation material 12 for simulating soluble rock and non-soluble rock areas, respectively, and the junction thereof forms a soluble rock and non-soluble rock junction 14; the development characteristics of the dissolution channel in the soluble rock area and the water-resisting boundary effect in the non-soluble rock area are controlled by adjusting the permeability coefficients of the simulation materials in each layer.

[0046] Among them, the soluble rock material (selecting modified gypsum as the main material, adding foaming agent and retarder, forming multi-stage pore structure by controlling foaming rate to simulate dissolution channel network; embedding soluble salt crystals as "sacrificial template", in the test, the water flow dissolves the salt crystals to form a dynamically expanding dissolution channel; mixing clay, fine sand and water to make mud mortar, pre-filling into the pore structure to simulate the occurrence state of mud sand in karst area; mixing fluorescent tracer particles into mud sand, recording the migration trajectory by high-speed camera, quantifying flow rate and diffusion range), non-soluble rock material (using dense clay-bentonite composite material to simulate water-resisting boundary area, setting waterproof sealant at the boundary to prevent interlayer leakage), reproducing the geological characteristics of different karst development stages.

[0047] Further, in terms of water level regulation, the box body is provided with an overflow port 7 with a diameter of 50 mm at the lower right corner, and a valve is arranged on the overflow port for regulating the water level height in the seepage simulation box; the opening degree is adjusted by a PID system to ensure that the water level is controlled within a range of ±5 mm error.

[0048] Further, the tunnel test structure includes a grouting ring for simulating the grouting reinforcement effect and a full-face curtain grouting layer, wherein the grouting ring is made of cement-bentonite mixture (with impermeability not less than P8 grade), and micro pressure sensors (range 0-1 MPa, measurement error ±0.5%) are embedded in the inside and outside of the grouting ring; a waterproof baffle 10 with waterproof coating is installed at the tunnel face for simulating water stopping and protection in the construction stage.

[0049] Further, in terms of mud sand monitoring, the system integrates multiple sensors: an electromagnetic flowmeter is installed at the drainage end (measurement range 0-100 L / s, accuracy ±1%); a laser particle size analyzer can detect the particle size distribution of mud sand in real time (0.1-10 mm); a turbidity sensor monitors the concentration of mud slurry (range 0-100 g / L). All sensor data are collected through RS485 bus and transmitted to an external analysis terminal in real time to realize the linkage monitoring and modeling of water pressure, flow rate and mud sand data.

[0050] The box further comprises a soil-separating and water-permeable plate 6, which is arranged in parallel to the right side wall of the box. The soil-separating and water-permeable plate 6 comprises a perforated steel plate (thickness 3 mm, hole diameter 10 mm, hole spacing 50 mm, uniformly distributed as a support framework) and a composite soil-separating layer. The composite soil-separating layer is made of a mixture of steel mesh and non-woven fabric, with a total thickness of 20 mm, and is fixed to the surface of the perforated steel plate. Further, the composite soil-separating layer is fixed to the surface of the perforated steel plate by epoxy resin adhesion, realizing the functions of water permeability and soil impermeability, and is arranged in parallel to the right side of the box to control the seepage boundary conditions of the model test.

[0051] Further, to enhance the visualization effect, the front panel of the box is made of three independent transparent materials spliced together, and the first sealing cover plate is also made of transparent material, allowing for multi-angle observation of the disaster evolution path and groundwater seepage process of water and mud inrush phenomena. To ensure good structural stability and service life of the entire test device, the rear panel, two side panels and bottom panel of the box are made of metal materials (such as steel plates). Necessary bearing capacity and mechanical strength are provided to meet the test requirements under high-pressure water supply and long-time operation conditions.

[0052] Further, a plurality of universal wheels 8 with brakes are installed at the bottom of the seepage simulation box, which are used for convenient movement and precise positioning of the entire test system. A locking brake mechanism is also provided to meet the flexible arrangement requirements in the laboratory environment.

[0053] Further, the water tank water supply system comprises a water tank 5 and a staged pressure regulation module 15. The water tank 5 is independently arranged on the left side of the box and is in communication with the inside of the box through a controllable flow rate pipeline. The water tank 5 and the box 1 are also provided with a staged pressure regulation module 15, which is used to flexibly control the pressure and flow rate of water supply to adapt to various groundwater recharge conditions, and to simulate the groundwater seepage environment under the condition of high pressure and water-rich in karst areas.

[0054] Further, in terms of water supply, the independent water tank structure arranged on the left side of the box has a volume of 500L. By integrating a multi-stage adjustable pressure water supply module (adjustment range: 0.1-1.0MPa), cooperating with a frequency conversion pump and an electromagnetic valve joint control, precise adjustment of the flow rate within the range of 0-50L / min is realized. The system supports high-pressure gushing water supply mode, i.e. water is injected to the bottom of the model or the karst boundary through high-strength pressure-resistant pipelines (pressure resistance up to 1.5MPa), to reproduce the situation of gushing water in karst tunnels. At the same time, the atomizing and spraying device comprises atomizing nozzles 13, and a plurality of atomizing nozzles 13 form an atomizing nozzle array arranged at the top of the box. The nozzle opening can be adjusted to 90%, simulating rainfall intensity of 100mm / h, and simulating extreme rainfall environment. The entire water supply and rainfall simulation process is coordinated and controlled by a PID controller, realizing synchronous coupling simulation of surface rainfall infiltration and underground water inrush.

[0055] Further, the tunnel test unit is provided with a grouting ring for simulating grouting reinforcement, and water pressure collectors are embedded in the inner and outer sides of the grouting ring to realize water pressure response monitoring under different reinforcement states.

[0056] Further, the water pressure monitoring device is embedded in the soluble rock and non-soluble rock interface 14, the soluble rock seepage path and the tunnel surrounding rock area to monitor the dynamic water pressure change in the water inrush process in real time; the mud and sand flow monitoring device is connected with the drainage interface of the first cover plate, and can monitor the mud and sand concentration, flow rate and cumulative flow data in real time, and quantify the mud inrush disaster scale and its cascading influence on the tunnel seepage field.

[0057] Through the design of the seepage model box structure in the embodiment of the application, when the tunnel test structure is placed in the seepage model box and aligned with the two horizontal tunnel holes of the front plate of the box, the application can simulate horizontal double-hole tunnels; then the left water tank water supply system and the top atomizing nozzle device are used, combined with the multi-stage pressure control unit, the application can simulate complex conditions such as high-pressure underground water supply, rainfall infiltration and karst pipe gushing; then the water pressure sensors embedded in the soluble rock and non-soluble rock interface, the tunnel surrounding rock and the inner and outer surfaces of the grouting ring collect the water pressure at the embedded position, and the water quantity collecting device connected with the drainage pipe on the first cover plate collects the flow at the drainage pipe, so that the water pressure, gushing quantity and seepage field change of a karst tunnel (i.e. a horizontal double-hole tunnel composed of two tunnel test structures) in the stage of tunnel excavation (i.e. the construction period) under high-pressure dynamic seepage environment can be truly tested. Among them, the water pressure collecting device can select the existing water pressure gauge in the market, and these devices can accurately measure the water pressure. The water quantity collecting device can use the water flow meter widely sold in the market, which can monitor the change of water flow in real time, ensuring the accuracy and stability of data collection.

[0058] Embodiment 2

[0059] Considering that the traditional model test system is mostly designed based on homogeneous surrounding rock, the difference in permeability of the interface between soluble rock and non-soluble rock (such as the development characteristics of the dissolution channel and the strength of the water-resisting boundary) is not simulated in layers, which leads to the inability to reproduce the dissolution-water-resisting coupling effect and the difficulty in revealing the triggering mechanism of the water and mud inrush disaster. To solve the above problems, the embodiment of the present application proposes a layered interface hydrogeological simulation technology. For the layered structure of soluble rock and non-soluble rock (the soluble rock layer mainly uses modified gypsum as the main material, adds a foaming agent and a retarder, forms a multi-pore structure by controlling the foaming rate, embeds soluble salt crystals as "sacrificial templates", forms a dynamically expanding dissolution channel by dissolving the salt crystals in the water flow in the test, and mixes clay, fine sand and water to make mud mortar, which is pre-filled into the pore structure to simulate the occurrence state of the mud sand in the karst area, and the fluorescent tracer particles are mixed into the mud sand, the migration trajectory is recorded by a high-speed camera, and the flow rate and diffusion range are quantified; the non-soluble rock layer uses a dense clay-bentonite composite material to simulate the water-resisting boundary area, and a waterproof sealant is arranged at the boundary to prevent interlayer leakage); a standardized slot is reserved at the interface, different permeability material modules (such as high-permeability dissolution modules and low-permeability water-resisting modules) can be quickly replaced, and the stage characteristics of karst development are reproduced; a water pressure sensor is pre-embedded in the soluble rock layer (a distributed optical fiber sensor is arranged every 200mm along the dissolution channel to monitor the water pressure gradient change in real time) and the non-soluble rock layer (a micro osmometer is pre-embedded at the water-resisting boundary to quantify the water pressure decay rate of the water-resisting layer), a dissolution-water-resisting coupling effect model is constructed through the synchronous collection of water pressure data and permeability parameters, and the critical condition of water and mud inrush triggering is revealed.

[0060] Considering that the triggering of the karst tunnel water and mud inrush disaster is closely related to the high-pressure water-rich environment, especially the dynamic recharge and inrush water effect of the groundwater in the karst area through the dissolution pipeline or the crack grid, which affects the construction process and construction safety during the tunnel construction period, and the existing model test system mostly uses a single water supply mode (such as a fixed water head or bottom water inlet), which cannot accurately simulate the coupling effect of multiple working conditions such as high-pressure water-rich recharge (0.1-1.0 MPa), karst pipeline inrush (flow rate 0.1-2.0 m / s) and rainfall infiltration (10-100 mm / h), which leads to a significant deviation between the test results and the actual hydrogeological conditions. To solve the above problems, the embodiment of the present application proposes a high-pressure water-rich dynamic water supply system, such as Figure 1The water tank structure shown is independently arranged on the left side of the tank body, and a multi-stage pressure control unit is arranged therein, including a variable frequency water pump, an electromagnetic valve and a pressure sensor. Water flow is directly injected to the bottom of the tank body or the karst interface zone through a high-pressure pipeline, simulating the instantaneous high pressure and flow mutation of the karst pipeline gushing. A PID controller is used to adjust the frequency of the water pump and the opening of the valve to maintain constant water pressure and reproduce the stable recharge of deep groundwater in the karst area. An array of atomizing nozzles is installed on the top of the tank body, and the nozzle opening is adjusted to 90%, simulating an extreme rainfall intensity of 100 mm / h. The PID controller is used to synchronously control the rainfall and high-pressure gushing to simulate the synergistic effect of surface rainfall infiltration and underground gushing. Through the above structural design, the application can realize dynamic simulation of multiple working conditions of karst area high-pressure gushing, continuous recharge and rainfall infiltration, break through the limitations of traditional static water supply, and accurately capture the critical threshold of disaster triggering.

[0061] In the present application, in order to accurately simulate the triggering mechanism of water and mud inrush disasters in karst tunnel construction period, the embodiment of the present application reproduces the dynamic evolution process of grouting reinforcement, face water stop and surrounding rock seepage field by controlling the specific design of the tunnel test structure. In an embodiment of the present application, the tunnel test structure for construction period simulation structure includes the whole of the grouting ring and the full-face curtain grouting area, the face water stop plate and the embedded water pressure acquisition device, which are modularly combined to adapt to the engineering requirements of different karst development stages. For example Figure 2 and Figure 3 As shown in the figure, when the tunnel test structure is a simulated construction period grouting ring and full-face curtain grouting area: the grouting ring adopts a cement-bentonite-nano silicon dioxide composite material to simulate the rock mass in the grouting reinforcement area in the construction period, and to block the seepage path of the dissolution channel of the karst interface zone; the full-face curtain grouting area covers an area of 2 times the diameter in front of the tunnel face, and high-pressure grouting pipelines (not shown in the figure) are used to inject grout into the karst interface zone to simulate the construction period advanced curtain grouting process; the face water stop plate is tightly attached to the front end of the full-face curtain grouting area and aligned with the dissolution channel area of the karst interface zone to prevent high-pressure underground water gushing; the water pressure acquisition device is embedded at the positions of the inner and outer surfaces of the grouting ring (one measuring point is arranged every 120° along the ring direction to monitor the water pressure distribution at the contact surface between the grouting reinforcement area and the surrounding rock), and the dissolution channel of the karst interface zone (a distributed sensor is embedded in the dissolution channel to real-time acquire the dynamic water pressure gradient in the water inrush process). The test methods for different test pipe structures are different, and the specific process of the test method is described in detail in the following text, which will not be described here.

[0062] Considering that the traditional model test system only focuses on the water pressure or flow change of a single chamber, the sudden change of water pressure in the water and mud gushing process, the migration path of mud and sand, and the synchronous monitoring of the seepage instability of adjacent chambers are lacking. For example, the sensor layout is limited, distributed sensors are not pre-embedded in the karst interface zone, surrounding rock fissures and lining structures, and the pressure transmission coefficient or mud and sand inflow of adjacent chambers cannot be quantified; the data is isolated, water pressure, mud and sand flow and structure strain data are not collected in linkage, leading to insufficient research on disaster propagation path and chain effect; visualization is lacking, real-time visualization observation of mud expansion path is difficult, and it is difficult to capture the dynamic process of mud and sand migration along the dissolution channel or surrounding rock fissure. In view of this, in order to solve the above problems, the embodiment of the present application proposes a multi-dimensional disaster chain monitoring technology, which mainly includes the following three aspects: first, the distributed sensor network is used, the detection of the karst interface zone (water pressure sensor is arranged every 200mm along the dissolution channel, and the water pressure gradient change in the water gushing process is monitored in real time; the electromagnetic flowmeter and turbidity sensor are installed at the outlet of the dissolution channel, and the mud and sand concentration and flow rate are quantified); the monitoring of adjacent chambers (the surrounding rock fissure piezometer is pre-embedded in the surrounding rock fissure of the adjacent chamber, and the water pressure transmission coefficient is monitored). Secondly, the tracer particle injection system is used for the mud and sand migration path tracking technology, that is, fluorescent tracer particles are injected in the water and mud gushing source area (karst interface zone), the migration trajectory of mud and sand along the dissolution channel or surrounding rock fissure is recorded by a high-speed camera (not shown in the figure), and 3D visualization reconstruction is combined with particle motion data and box transparent observation window. A three-dimensional dynamic model of the mud and sand migration path is constructed by using image processing software, and the disaster expansion hot area is labeled. Finally, the synchronous acquisition system (water pressure, mud and sand flow, strain and tracer particle position data are synchronously acquired by a multi-channel data acquisition instrument) is used.

[0063] The embodiment of the present application includes the following advantages:

[0064] 1. Precise control ability of interface zone development simulation, by layering soluble rock and non-soluble rock materials in the model and introducing adjustable permeability parameter control mechanism, the embodiment realizes precise replication of the dissolution channel evolution characteristics and water-resisting boundary effect of the karst interface area. Compared with the traditional homogeneous medium test method, this technology breaks through the limitation of its geological structure difference simulation, and can provide a more realistic geological condition experiment basis for the water and mud gushing disaster triggering mechanism research.

[0065] 2. Multi-scenario coupling reproduction ability in high-pressure water-rich environment. The system is configured with an independent water supply tank on the left side of the box, integrating a multi-stage pressure regulating unit (pressure regulation range 0.1-1.0 MPa, flow range 0-50 L / min), combined with the atomizing nozzle device arranged on the top, through the PID closed-loop control system, to realize the synchronous regulation and control of extreme rainfall process and underground high-pressure water inrush process. This embodiment can flexibly simulate the coupling influence of various hydrological conditions including high-pressure sudden inrush, surface rainfall infiltration, underground water recharge, etc., truly restore the complex hydrodynamic process in karst area, and reveal the hydraulic critical value characteristics in disaster evolution.

[0066] 3. Multi-parameter linkage monitoring and disaster process coupling analysis ability. The system pre-buries water pressure monitoring elements in key positions such as karst interface zone and surrounding rock area, and combines high-precision mud monitoring devices integrating electromagnetic flowmeter, laser particle size analyzer and turbidity sensor, to realize synchronous acquisition and analysis of key physical quantities such as water and pressure inrush, mud movement and tunnel seepage evolution. By constructing a "seepage-mud inrush" disaster correlation model, the disaster chain conduction path and its mutual influence mechanism can be revealed.

[0067] 4. Strong adaptability of visual observation design and modular structure. The front panel adopts a three-section transparent material splicing structure, which facilitates real-time observation of water and mud inrush diffusion behavior and seepage path. Key components such as karst interface zone module, soil isolation and water permeation structure, and tunnel test unit are detachable structures, supporting quick replacement of different permeability materials and tunnel section forms according to requirements, effectively improving test flexibility and parameter adaptation range, and providing support for engineering verification under multi-stage karst development conditions.

[0068] 5. Portable and improved operation automation level. The model is configured with heavy-duty universal wheel sets at the bottom, and is provided with brake locking mechanism, facilitating flexible movement and precise positioning of the device in the experimental space. At the same time, the right side overflow system adopts electric valve, and maintains water level dynamic stability through PID control module (control error within ±5 mm), effectively simplifying water level regulation process and reducing operator burden.

[0069] 6. Simulation of disaster early warning ability during tunnel construction period. The test tunnel module includes grouting ring structure and tunnel face water retaining device, combined with distributed optical fiber water pressure sensing network arranged inside the structure, to realize dynamic monitoring of the whole process of seepage field evolution during construction stage, providing scientific experimental support for disaster identification, prevention and early warning during karst tunnel design and construction period.

[0070] Example 3

[0071] As Figure 2 , Figure 3 and Figure 5As shown, the system provided by this application simulates the sudden water and mud disasters in a horizontal double-hole karst tunnel under the coupling of high-pressure sudden surge and heavy rainfall, revealing the disaster triggering mechanism and the chain effect of seepage and instability in adjacent caverns, and verifying the effectiveness of the layered simulation and multi-dimensional monitoring technology of the karst junction zone. Among them, the tunnel test unit is the grouting ring of the rock mass in the grouting reinforcement area during the construction period and the entire curtain grouting area of ​​the whole section. The test method includes the following steps:

[0072] S1, using prefabricated fixed bracket 3, such as Figure 4 As shown, the tunnel test unit 9 is installed parallel to the middle of the box body, so that the inner circle of the grouting ring of the tunnel test unit is aligned with the two tunnel holes 2 on the front panel of the box body, and the glass glue is applied to the grouting ring close to the periphery of the glass surface to seal it, and then the first cover plate 4 with a drainage interface is covered to ensure that the axes of the two holes are horizontally aligned;

[0073] S2. Pre-embed water pressure monitoring equipment within the grouting rings of the left and right tunnels, arranged at 90° intervals along the annulus, with four measuring points per tunnel. Install a face water retaining plate 10 (removable) on the tunnel side formed by the tunnel test unit near the full-section curtain grouting area. Then, similar material simulating the lining is attached to the inner wall of the grouting ring on the tunnel side of the face water retaining plate to simulate the tunnel lining. Pre-embed distributed fiber optic sensors within the dissolution channel of the right tunnel to monitor the water pressure gradient in real time. Pre-embed piezometers and strain gauges within the surrounding rock and lining structure of the left tunnel to quantify the pressure transfer coefficient of the water inrush from the right tunnel to the left tunnel.

[0074] S3: Fluorescent tracer particles were injected into the water inrush source area of ​​the right cave, and the migration path of mud and sand along the dissolution channel to the left cave was recorded using a high-speed camera 16; a 3D dynamic model of mud and sand migration across the cave was constructed using image processing software;

[0075] S4. A soluble rock layer was laid within the chamber using soluble rock simulation material 11. This included using modified gypsum as the primary material, adding a foaming agent and a retarder, and controlling the foaming rate to form a multi-level pore structure to simulate a network of dissolution channels. Soluble salt crystals were pre-buried as a "sacrificial template." During the experiment, water dissolved the salt crystals to form dynamically expanding dissolution channels. A mud mortar made from a mixture of clay, fine sand, and water was pre-filled into the pore structure to simulate the occurrence of mud and sand in karst areas. Fluorescent tracer particles were mixed into the mud and sand, and their migration trajectory was recorded using a high-speed camera to quantify the flow rate and diffusion range.

[0076] A non-soluble rock layer is laid below the soluble rock layer using non-soluble rock simulation material 12, including a dense clay-bentonite composite material, epoxy resin sealant is applied at the boundary to prevent interlayer leakage, and replaceable high-density polyethylene waterproof sheets are embedded to simulate the anti-surge capability of the waterproof boundary;

[0077] S5, high pressure dynamic water supply and rainfall simulation configuration, the water tank in the water tank supply system is installed on the left side of the box, connected to the right hole karst interface zone through high pressure pipeline, the staged pressure regulating module (variable frequency water pump + electromagnetic valve) adjusts the water supply pressure to 1.2 MPa, simulates the sudden gushing of karst pipeline, and records the instantaneous flow peak value;

[0078] The atomizing spray head is installed on the top of the box to form an array of atomizing spray heads, the opening of the atomizing spray head is adjusted to 90%, the extreme rainfall intensity of 100 mm / h is simulated, the rainfall and high pressure sudden gushing are synchronously controlled through the PID controller, the synergistic effect of surface rainfall infiltration and underground sudden gushing is simulated;

[0079] S6, start the variable frequency water pump, maintain the right hole high pressure sudden gushing 1.2 MPa and rainfall 100 mm / h for 25 minutes; through the data acquisition system 17 connected with the water pressure monitoring equipment and the mud and sand flow monitoring device, the water pressure of the right hole dissolution channel, the left hole surrounding rock seepage pressure, the water flow from the tunnel hole, and the mud and sand flow data are collected in real time;

[0080] S7, end the test, simulate the seepage field distribution of the horizontal double-hole karst tunnel under the condition of high pressure sudden gushing-rainfall coupling during the tunnel construction period and the drainage capacity and mud and sand flow of the tunnel under the condition of the water retaining plate of the working face;

[0081] The water retaining plate of the working face near the tunnel side in the full-face curtain grouting area is removed, the high pressure sudden gushing test is repeated, the water pressure of the right hole dissolution channel, the left hole surrounding rock seepage pressure, the water flow from the tunnel hole, and the mud and sand flow data are recorded; the seepage field distribution of the horizontal double-hole karst tunnel under the condition of high pressure sudden gushing-rainfall coupling during the tunnel construction period and the total drainage capacity and mud and sand flow of the tunnel are simulated.

[0082] Through the above test method, the present application precisely reproduces the dissolution-water resistance coupling effect between the double holes through the layered design of soluble rock stratum (artificial dissolution channel + permeability regulation) and non-dissolution rock stratum (dense water-resisting boundary), breaks through the limitation of single-hole model; the top water tank (multi-stage pressure control) and the array of atomizing spray heads (extreme rainfall simulation) on the top of the box are linked to realize the multi-working condition coupling of the right hole high pressure sudden gushing (1.2 MPa) and the surface heavy rainfall (100 mm / h), accurately capture the critical threshold of cross-hole disaster; the synchronous monitoring of the water pressure of the right hole dissolution channel, the left hole surrounding rock seepage pressure, and the mud and sand cross-hole migration path reveals the cross-hole propagation mechanism of the horizontal double-hole water and mud inrush disaster. The triggering mechanism of the water and mud inrush disaster under the condition of high pressure sudden gushing-rainfall coupling and the chain effect of the seepage instability of the adjacent chambers of the horizontal double-hole karst tunnel are maximally restored.

[0083] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A test system for simulating water and mud inrush disasters in karst tunnels, characterized in that: The test system comprises a seepage simulation box, a tunnel test unit (9), a water pressure monitoring device, a mud and sand flow monitoring device, a water tank water supply system, and an atomizing spray device for simulating rainfall; the seepage simulation box comprises a box body (1), a first cover plate (4) made of a transparent material, and universal wheels (8); a tunnel hole (2) is provided on the front panel of the box body (1) for installing the tunnel test unit to simulate a horizontal double-hole tunnel; a drainage interface is provided on the first cover plate (4) for blocking the tunnel hole (2) on the front panel.

2. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: The box (1) is filled with soluble rock simulation materials (11) and non-soluble rock simulation materials (12) in layers for respectively simulating soluble rock and non-soluble rock areas, with the soluble rock and non-soluble rock interface (14) formed at their junction. The development characteristics of the dissolution channel in the soluble rock area and the water-isolating boundary effect in the non-soluble rock area are controlled by adjusting the permeability coefficient of each layer of simulation material.

3. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: An overflow port (7) is provided at the lower right corner of the box body, and a valve is provided on the overflow port for regulating the water level in the seepage simulation box; a soil-isolating water-permeable plate (6) is also provided in the box body, and the soil-isolating water-permeable plate is arranged parallel to the right side wall of the box body.

4. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 3, characterized in that: The soil-isolating and water-permeable plate (6) comprises a perforated steel plate and a composite soil-isolating layer; the composite soil-isolating layer is made of a mixture of steel wire mesh and non-woven fabric, and is fixed on the surface of the perforated steel plate.

5. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: A plurality of universal wheels (8) with brakes are installed at the bottom of the seepage simulation box body, which are used to conveniently move and accurately position the entire test system.

6. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: The water tank water supply system comprises a water tank (5) and a graded pressure regulating module (15); the water tank (5) is independently arranged on the left side of the tank body and communicates with the interior of the tank body through a controllable flow rate pipeline; a graded pressure regulating module (15) is also arranged between the water tank (5) and the tank body (1); the graded pressure regulating module (15) is used to flexibly control the pressure and flow rate of the water supply to adapt to various groundwater recharge conditions, and is used to simulate the groundwater seepage environment under high-pressure and water-rich conditions in karst areas.

7. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: The atomizing spray device comprises an atomizing nozzle (13), wherein a plurality of atomizing nozzles (13) form an atomizing nozzle array and are arranged on the top of the box body. When the opening of the atomizing nozzle is adjusted to 90%, it is used to simulate an extreme rainfall environment.

8. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: The tunnel test unit is equipped with a grouting ring for simulating grouting reinforcement. Water pressure collectors are embedded inside and outside the grouting ring to monitor the water pressure response under different reinforcement conditions.

9. The test system for simulating water and mud inrush disasters in karst tunnels according to claim 1, characterized in that: The water pressure monitoring equipment is pre-buried at the interface (14) between soluble rock and non-soluble rock, the soluble rock seepage path and the tunnel surrounding rock area, and monitors the dynamic water pressure changes during the water inrush process in real time; the mud and sand flow monitoring device is connected to the drainage interface of the first cover plate, and can monitor the mud and sand concentration, flow velocity and accumulated flow data in real time, and quantify the scale of the mud inrush disaster and its chain reaction effect on the tunnel seepage field.

10. A test method for a test system for simulating water and mud inrush disasters in karst tunnels according to any one of claims 1 to 9, characterized in that: The steps include: S1. Use a prefabricated fixing bracket (3) to install the tunnel test unit (9) parallel to the middle of the box, align the inner ring of the grouting ring of the tunnel test unit with the two tunnel holes (2) on the front panel of the box, and seal the grouting ring close to the periphery of the glass surface with glass glue, then cover it with the first cover plate (4) with a drainage interface, and ensure that the axes of the two holes are horizontally aligned; S2. Water pressure monitoring equipment was embedded in the grouting rings of the left and right tunnels, arranged at 90° intervals along the annulus, with four measuring points in each tunnel. A face water retaining plate was installed on the tunnel side formed by the tunnel test unit near the full-section curtain grouting area. A similar material simulating the lining was then attached to the inner wall of the grouting ring on the tunnel side of the face water retaining plate to simulate the tunnel lining. Distributed fiber optic sensors were embedded in the dissolution channel of the right tunnel to monitor the water pressure gradient in real time. Piezometers and strain gauges were embedded in the surrounding rock and lining structure of the left tunnel to quantify the pressure transfer coefficient of the water inrush from the right tunnel to the left tunnel. S3, injecting fluorescent tracer particles into the water inrush source area of ​​the right cave, and using a high-speed camera (16) to record the path of mud and sand migrating along the dissolution channel to the left cave; using image processing software to construct a 3D dynamic model of mud and sand migration across the cave; S4. A soluble rock simulation material (11) is used to lay a soluble rock layer in the box, including using modified gypsum as the main material, adding a foaming agent and a retarder, forming a multi-level pore structure by controlling the foaming rate, simulating a dissolution channel network, and pre-buried soluble salt crystals as a "sacrificial template". In the experiment, the salt crystals are dissolved by water flow to form a dynamically expanding dissolution channel. Clay, fine sand, and water are mixed to form a mud mortar, which is pre-filled into the pore structure to simulate the occurrence state of mud and sand in the karst area. Fluorescent tracer particles are mixed into the mud and sand, and the migration trajectory is recorded by a high-speed camera to quantify the flow rate and diffusion range. A non-soluble rock layer is laid below the soluble rock layer using non-soluble rock simulation materials (12), including using a dense clay-bentonite composite material, coating the boundary with epoxy resin sealant to prevent interlayer leakage, and embedding a replaceable high-density polyethylene waterproof sheet to simulate the anti-surge capability of the waterproof boundary; S5, high-pressure dynamic water supply and rainfall simulation configuration: The water tank in the water supply system is installed on the left side of the tank body and connected to the karst junction zone of the right cave through a high-pressure pipeline. The graded pressure regulation module adjusts the water supply pressure to 1.2MPa to simulate the sudden surge in the karst pipeline and record the instantaneous flow peak; Atomizing nozzles were installed on the top of the box to form an atomizing nozzle array. The nozzle opening was adjusted to 90% to simulate an extreme rainfall intensity of 100 mm / h. The rainfall and high-pressure surge were synchronously controlled by a PID controller to simulate the synergistic effect of surface rainfall infiltration and underground surge. S6, maintaining a high-pressure surge of 1.2 MPa and a rainfall of 100 mm / h in the right tunnel for 25 minutes; collecting data on the water pressure in the right tunnel's erosion channel, the seepage pressure of the surrounding rock in the left tunnel, the amount of water flowing out of the tunnel hole, and the amount of mud and sand flow in real time through a data acquisition system (17) connected to a water pressure monitoring device and a mud and sand flow monitoring device; S7. End the test and simulate the seepage field distribution of the horizontal twin-hole karst tunnel during the tunnel construction period under the coupling conditions of high-pressure sudden surge and rainfall, as well as the drainage volume and mud and sand flow rate of the tunnel under the condition of face water retaining; remove the face water retaining plate near the tunnel side in the full-section curtain grouting area, repeat the high-pressure sudden surge test, and record the water pressure of the right hole karst channel, the seepage pressure of the left hole surrounding rock, the amount of water flowing out of the tunnel hole, and the mud and sand flow rate data; simulate the seepage field distribution of the horizontal twin-hole karst tunnel during the tunnel construction period under the coupling conditions of high-pressure sudden surge and rainfall, as well as the total drainage volume and mud and sand flow rate of the tunnel.

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