Testing device and method for stratum seepage erosion damage induced by tunnel local leakage

Abstract

The invention relates to a test device and method for inducing stratum seepage erosion damage by tunnel local leakage, and the test device comprises two aspects: 1, the test device for inducing stratum seepage erosion damage by tunnel local leakage comprises a model box, a tunnel model is arranged on the model box in a penetrating manner, and a tunnel damage simulation device is arranged on the tunnel model; a measuring frame system is arranged in the model box, a sand layer position tracing system is arranged in the model box, a water level control system is arranged on the model box, a water and sand collecting system is arranged on one side of the model box, a data monitoring system is arranged on the model box, and the data monitoring system comprises a plurality of water pressure sensors, a plurality of soil pressure sensors and a camera. 2, the test method for stratum seepage erosion damage induced by tunnel local seepage is used for testing through the test device; aiming at the continuous water and soil loss catastrophe condition induced by tunnel local degradation, the real-time monitoring of the transmission rule of the stratum stress, the pore pressure and the stratum deformation in the water and soil loss is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of stratum stability analysis, and in particular to a device and method for testing stratum seepage erosion damage induced by local leakage in tunnels. Background Art

[0002] Water and sand leakage are common geotechnical issues during tunnel operation. In severe cases, they can lead to safety risks such as ground collapse and continuous damage to the tunnel structure. With the continuous expansion of urban underground space development, incidents of subway tunnels being penetrated by external operations are becoming increasingly frequent, increasing the risk of large-scale water and sand leakage in tunnels. Currently, scholars have studied the soil and water loss hazards caused by leakage in shield tunnel joints. Related experimental studies are as follows:

[0003] Zheng Gang et al. first defined the maximum gap width at which soil particles can form a stable soil skeleton as the critical gap width for tunnel opening. They also conducted experimental studies on the soil erosion and evolution of different graded sands below the groundwater level when they leaked through gaps of different widths, clarifying the mechanical behavior of soil particles forming arches and arch failures. (Journal article number: 1000-6915(2014)12-2458-14, Journal title: Experimental study and numerical simulation of the development process of water and sand leakage disasters in underground engineering) To further clarify the different states of water and soil erosion, Zheng Gang et al. optimized the experimental device (refer to the journal mentioned below: Experimental study on the water and soil erosion law outside the tunnel under different segment openings). Figure 6 ), conducted three types of tests on Tianjin fine sand and Fujian standard sand: leakage, soil erosion, and water and sand leakage. They clarified the mechanism of gradual sand loss at shield tunnel joints, analyzed the critical segment openings for leakage, erosion, and water and sand leakage, and proposed a method for assessing soil loss status. However, these experimental analyses did not consider the location of tunnel leakage joints and only corresponded to leakage at the tunnel vault. (Journal Article Number: 1000–4548(2018)06–0969–09, Journal Title: Experimental Study on the Law of Soil and Water Loss Outside Tunnels Under Different Segment Openings)

[0004] In order to analyze the location of the leak, Lu et al. designed a model test device for shield tunnel leakage under constant water pressure for underwater shield tunnels (Journal Article Number: 1000–6915(2019)05–0993–12, Journal Name: Model Test Study on the Leakage Law of Underwater Shield Tunnel Joints, and referred to their journal Figure 1 a and Figure 4), using the geometric similarity ratio Cl=55, Xiamen standard sand was selected as the test soil sample, and the critical crack width of different leakage positions was first analyzed, and the amount of water and sand leakage of tunnel through cracks and staggered cracks under the critical crack width condition, as well as the initial grading and convergent grading of sand leakage were compared. Afterwards, the settlement and deformation law of the stratum during the tunnel leakage process was studied, and the settlement form of the stratum and the change of soil pressure at the leakage position during the leakage process were clarified, revealing the influence of leakage on the stress of the soil around the leakage and the deformation of the stratum. Based on the critical crack width, Zhang Zhiguo et al. conducted an experimental study on the influence of factors such as leakage position, cover thickness, and water level on the change of stratum settlement and pore water pressure, and designed a seepage tracer device (the journal name in the "China Journal of Highway and Transportation" is: Model test and discrete element analysis of soil and water loss induced by leakage in shield tunnel joints, refer to the journal's Figure 1 a and Table 2), exploring the distribution of the seepage field and the changing patterns of its streamlines. While the above experimental analyses considered the impact of leak location on soil erosion, they focused on erosive damage, emphasizing the eventual formation of a stable soil arch at the leak location. However, insufficient research has been conducted on the catastrophic effects of widespread tunnel leakage and sand collapse.

[0005] In order to study the problem of water and sand gushing, Liu Chengyu et al. designed a set of visual test devices to simulate the water and sand gushing in underground engineering (Journal Article Number: 1000-7598 (2019) 03-0843-09, Journal Name: Model Test Study on the Leakage Law of Underwater Shield Tunnel Joints, and refer to their journal Figure 1 ), the settlement law induced by water and sand inrush under different thickness-span ratios and different fine particle contents in sand was studied. The test selected standard sand as filling fine particles, 5~10mm coarse sand as skeleton coarse particles, and the test sand was mixed in different proportions. The test results clearly showed that the soil sand burst is correlated with the thickness-span ratio and the soil particle size. The stratum settlement range induced by the circular inrush is approximately circular on the plane, and the side is funnel-shaped, approximately a quadratic surface, and the settlement range after the soil sand burst is related to the settlement slope angle. Subsequently, Liu Chengyu et al. conducted an experimental study on the stratum settlement induced by underground pipeline damage (Journal Article Number: 1000-7598 (2019) 03-0843-09, Journal Name: Model Test Study on the Leakage Law of Underwater Shield Tunnel Joints, and referred to their journal Figure 2 (and Table 2) analyzed the effects of full-flow velocity within the pipeline, pipeline damage dimensions, soil gradation, and water and soil height on surface settlement induced by seepage erosion under full-flow conditions. The main influencing factors of pipeline damage-induced surface settlement were identified, and a prediction model for ground settlement induced by underground pipeline damage was proposed. However, the above experiments did not monitor the settlement and damage process of soil particles within the stratum; they only focused on the surface settlement amount and the final surface settlement curve.

[0006] At present, there are few studies on the continuous soil and water loss disasters induced by local deterioration of tunnels, and there is a lack of monitoring research on the movement of soil particles within the stratum under disaster conditions such as water inrush and sand inrush. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide a test device and method for seepage erosion and damage of formations induced by local leakage in tunnels, so as to study the continuous soil and water loss disaster induced by local deterioration of tunnels and realize real-time monitoring of the development and transmission laws of formation stress, pore pressure and formation deformation (migration of soil particles inside the formation) during the soil and water loss process (in the case of water inrush and sand inrush).

[0008] To achieve the above object, the present invention is implemented through the following two aspects:

[0009] In the first aspect, the present invention provides a test device for tunnel local leakage-induced stratum seepage erosion and damage, comprising a model box, a tunnel model being installed on the model box, a tunnel damage simulation device being installed on the tunnel model, a measuring frame system being installed inside the model box, the measuring frame system comprising a plurality of linearly arranged measuring main frames, each of the measuring main frames being provided with a plurality of linearly arranged movable measuring rods, a sand layer position tracing system being provided inside the model box, a water level control system being provided on the model box, a water and sand collection system being provided on one side of the model box, and a data monitoring system being provided on the model box, the data monitoring system comprising a plurality of water pressure sensors being linearly distributed and mounted on the movable measuring rods, a plurality of soil pressure sensors being linearly distributed and mounted on the movable measuring rods, and a camera being installed on one side of the model box.

[0010] Preferably, the model box includes a bottom plate, side plates installed at the left and right ends of the bottom plate, and test observation windows installed at the front and rear ends of the bottom plate.

[0011] As an example, the tunnel model is a PVC pipe.

[0012] Preferably, the tunnel destruction simulation device includes a rubber water-stop rod inserted in a local deterioration position of the tunnel model and a pull rope tied to one end of the rubber water-stop rod and passing through one side hole of the tunnel model.

[0013] Preferably, the measuring main frame is fixed to the model box by bolts, a sliding groove is provided on the measuring main frame, a mounting steel plate is provided on the top of the movable measuring rod, the movable measuring rod passes through the sliding groove and the mounting steel plate is fixed to the measuring main frame by nuts and bolts.

[0014] Preferably, the sand layer position tracing system includes several test soil sample layers filled in the model box, and a colored sand layer is provided on one side or both sides of the test soil sample layer.

[0015] Preferably, the water level control system includes a water inlet system and a drainage system, the water inlet system includes a cover plate covering the model box, a water inlet pipe inserted on the cover plate, and a number of overflow holes arranged linearly and opened on both sides of the model box, the drainage system includes a sand unloading port baffle opened on both sides of the model box, the sand unloading port baffle is located below the several overflow holes, and a drainage hole valve is provided on the sand unloading port baffle.

[0016] Preferably, a side of the tunnel model protruding from the model box is provided as a drainage pipe, and the water-sand collection system is composed of the drainage pipe and a water-sand collection box provided on one side of the drainage pipe.

[0017] Preferably, the apparatus further includes a data acquisition system electrically and signal-connected to the data monitoring system, the data acquisition system comprising a micro-osmotic pressure data acquisition instrument electrically and signal-connected to the water pressure sensor, a static strain tester electrically and signal-connected to the soil pressure sensor, a digital image processing system electrically and signal-connected to the camera, and a host computer for receiving and analyzing the collected data from the micro-osmotic pressure data acquisition instrument, the static strain tester, and the digital image processing system, wherein the water pressure sensor is a micro-pore water pressure sensor, the soil pressure sensor is a micro-pore soil pressure sensor, and the camera is a high-speed camera. The water pressure sensor is fixed to a movable measuring rod by a plastic strap, and the soil pressure sensor is adhered to the movable measuring rod by nano double-sided tape.

[0018] In a second aspect, the present invention provides a method for testing local leakage-induced stratum seepage erosion damage in tunnels, wherein the test is conducted using the apparatus for testing local leakage-induced stratum seepage erosion damage in tunnels as described in the first aspect, and the method comprises the following steps:

[0019] S1: Perform local penetration degradation operation on the tunnel model;

[0020] S2: Install water pressure sensors and earth pressure sensors on the movable measuring rod of the measuring frame system;

[0021] S3: Fix the tunnel model on the model box;

[0022] S4: Use a rubber water stopper with a pull rope to seal the deteriorated position of the tunnel model. The pull rope extends from a hole at one end of the tunnel model to block the overflow hole and close the drain hole valve.

[0023] S5: Fix the main measuring frame of the measuring frame system on the test monitoring section;

[0024] S6: Setting the soil cover height of the tunnel model, i.e., using a layered method to fill each layer of soil sample, and arranging a colored sand layer on one or both sides of each test soil sample layer, and then injecting water through a water level control system to saturate the soil sample in the model box;

[0025] S7: Arrange the water and sand collection system, set up and debug the high-speed camera on the front side of the model box, and connect the data acquisition system;

[0026] S8: The test begins. The pull rope is pulled to remove the rubber water stopper. Water and sand above the deteriorated position of the tunnel model flow into the tunnel model and then into the water and sand collection box through the drainage pipe at the tunnel model entrance. The water and sand collection boxes are replaced at regular intervals and numbered until only water flows out of the tunnel. The test ends.

[0027] S9: Open the drain hole valve and the sand discharge port baffle in sequence to drain water and unload soil;

[0028] S10: weigh, record, filter, dry, and calculate the water quality of each water and sand collection box in sequence;

[0029] S11: Screening the dried sand in each collection box for particle size to clarify the stratum loss characteristics during the stratum soil and water loss process;

[0030] S12: Processing the images captured by the high-speed camera through a digital image system to obtain the migration pattern of sand particles during the process of soil erosion and damage in the stratum, and revealing the stratum collapse process from a microscopic level;

[0031] S13: Combining the monitoring data of stratum water and soil pressure during stratum damage and the results of digital image processing of stratum collapse, the mechanism of continuous water and soil loss caused by local deterioration of the tunnel can be revealed from the microscopic phenomena and mechanical mechanisms of stratum collapse.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The advantages of the present invention include:

[0034] A. Its core advantages are: studying the continuous soil and water loss disasters induced by local deterioration of tunnels, realizing real-time monitoring of the development and transmission laws of stratum stress, pore pressure and stratum deformation (migration of soil particles within the stratum) during the soil and water loss process (under the conditions of water inrush and sand inrush), revealing the occurrence, development and evolution of tunnel leakage and sand burst disasters, clarifying the influence of factors such as cover height, leakage location, leakage area and initial water level on soil and water loss, and exploring the mechanical mechanism of progressive stratum destruction induced by local deterioration of shield tunnels.

[0035] B. It can simulate different degradation forms such as shield tunnel joint degradation (square through-holes), concrete lining corrosion degradation (approximately circular through-holes), and tunnel breakdown degradation (circular through-holes). It can also further consider the impact of factors such as tunnel degradation degree, degradation location, stratum particle size, water head height, and stratum water replenishment on stratum damage characteristics;

[0036] C. It can not only monitor and analyze the soil arching effect during the process of small-scale stratum instability and damage, but also study the flow damage characteristics caused by large-scale continuous soil erosion;

[0037] D. Using a measuring frame system to fix soil and water pressure sensors, real-time monitoring of the development and transmission patterns of formation stress and pore pressure during soil erosion can be achieved, solving the problem of monitoring the internal mechanical field of the formation during soil flow and destruction.

[0038] E. The test observation windows in front and behind the model box are made of transparent acrylic glass plates, which can be used as observation windows during the test process. At the same time, the tunnel deterioration position is close to the observation window of the model box. Combined with the colored sand layer installed in the stratum, it can realize the direct observation of the macroscopic phenomenon of soil particle movement in the deep stratum during soil erosion;

[0039] F. With the help of high-speed cameras and digital image processing systems, the migration paths of soil particles during stratum collapse can be tracked, and millimeter-level stratum displacement can be captured. This overcomes the limitations of direct macroscopic observation data and reveals the stratum collapse process from a microscopic perspective.

[0040] G. By regularly replacing the water and sand collection box, the entire process of tunnel water and sand leakage as the development of stratum damage can be monitored. By screening the sand in the water and sand collection box, the characteristics of stratum loss and damage can be further clarified. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the 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.

[0042] Figure 1 This is a schematic structural diagram of a test device for tunnel local leakage-induced stratum seepage erosion damage, provided in Example 1 of the present invention;

[0043] Figure 2 This is a schematic structural diagram of a test device for tunnel local leakage-induced stratum seepage erosion damage (the test observation window shows a transparent effect) provided in Example 1 of the present invention;

[0044] Figure 3 This is a schematic diagram of the exploded structure of a test device for tunnel local leakage-induced stratum seepage erosion damage provided by Example 1 of the present invention;

[0045] Figure 4 This is a schematic diagram of the exploded structure of a test device for local leakage-induced stratum seepage erosion damage in a tunnel provided by Example 1 of the present invention, omitting the measuring frame system and the sand layer position tracing system;

[0046] Figure 5 is a schematic structural diagram of a measuring frame system provided in Example 1 of the present invention;

[0047] Figure 6 Schematic diagram of the structure of the tunnel model and tunnel destruction simulation device provided in Example 1 of the present invention;

[0048] Figure 7 This is a structural rendering of a test device for conducting tests on formation seepage erosion and damage caused by local leakage in tunnels, provided in Example 3 of the present invention;

[0049] Figure 8 This is a graph showing the water leakage, sand leakage, and surface settlement curves of a test device for local tunnel leakage-induced stratum seepage erosion damage, provided in Example 3 of the present invention;

[0050] Figure 9 The present invention provides a device for testing stratum seepage erosion damage caused by local leakage in a tunnel, which is provided in Example 3 of the present invention. The device is used to test stratum damage phenomena, stratum displacement, and stratum damage contours.

[0051] Figure 10 This is a rendering of the soil pressure variation during the stratum destruction process of a test device for stratum seepage erosion damage induced by local leakage in a tunnel provided by Example 3 of the present invention.

[0052] Included in the diagram are:

[0053] 1. Model box; 11. Bottom plate; 12. Side plate; 13. Test observation window; 2. Tunnel model; 21. Rubber water stop rod; 22. Pull rope; 4. Measuring frame system; 41. Measuring main frame; 411. Sliding groove; 42. Movable measuring rod; 421. Mounting steel plate; 60. Cover plate; 61. Water inlet pipe; 62. Overflow hole; 63. Sand discharge port baffle; 64. Drain hole valve; 7. Water and sand collection system; 71. Drainage pipe; 72. Water and sand collection box. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solution in this embodiment of the present invention in conjunction with the drawings in this embodiment of the present invention. Obviously, the embodiment described is only one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0055] Example 1:

[0056] See also Figures 1 to 6 Embodiment 1 of the present invention provides a test device for local leakage-induced stratum seepage erosion and damage in a tunnel, comprising a model box 1, a tunnel model 2 being provided on the model box 1, a tunnel damage simulation device being provided on the tunnel model 2, a measuring frame system 4 being provided inside the model box 1, the measuring frame system 4 comprising a plurality of linearly arranged measuring main frames 41, each measuring main frame 41 being provided with a plurality of linearly arranged movable measuring rods 42, a sand layer position tracing system being provided inside the model box 1, a water level control system being provided on the model box 1, a water and sand collection system 7 being provided on one side of the model box 1, and a data monitoring system being provided on the model box 1, the data monitoring system comprising a plurality of water pressure sensors being linearly distributed and mounted on the movable measuring rods 42, a plurality of soil pressure sensors being linearly distributed and mounted on the movable measuring rods 42, and a camera being mounted on one side of the model box 1.

[0057] The model box 1 includes a bottom plate 11 , side plates 12 installed at the left and right ends of the bottom plate 11 , and test observation windows 13 installed at the front and rear ends of the bottom plate 11 .

[0058] More specifically, the front and rear ends of the model box 1 are constructed with 15mm-thick transparent acrylic glass panels as test observation windows 13. The bottom panel 11 and left and right side panels 12 are constructed from 10mm-thick steel plates. The bottom panel 11 and side panels 12 can be integrally formed or connected by bolts. The test observation windows 13 are first connected using M12 bolts, and then the seams are sealed with gaskets and waterproof sealant.

[0059] Tunnel model 2 is a PVC pipe.

[0060] More specifically, in this embodiment, the tunnel model 2 is simulated using a PVC tube with an outer diameter of 110 mm and a wall thickness of 6 mm. A test observation window 13 is located in the middle of the model box 1 and penetrates the front and rear transparent acrylic glass plates. The central axis of the tunnel model 2 is 315 mm away from the bottom of the model box 1. In other embodiments, the tunnel model 2 can be a square tube or a tube of other shapes.

[0061] The tunnel damage simulation device includes a rubber water-stopping rod 21 (not shown in the drawings) inserted into a local deterioration position of the tunnel model 2 and a pull rope 22 tied to one end of the rubber water-stopping rod 21 and passed through one side hole of the tunnel model 2 .

[0062] More specifically, when the test starts, the rubber water-stopping rod 21 is pulled out of the local deterioration position of the tunnel model 2 by the pulling rope 22, thereby realizing the tunnel local deterioration leakage operation.

[0063] The measuring main frame 41 is fixed to the model box 1 by bolts. A sliding groove 411 is provided on the measuring main frame 41. A mounting steel plate 421 is provided on the top of the movable measuring rod 42. The movable measuring rod 42 passes through the sliding groove 411 and the mounting steel plate 421 is fixed to the measuring main frame 41 by nuts and bolts.

[0064] More specifically, the length × width × thickness of the measuring main frame 41 is 1270mm × 40mm × 10mm, with a 6mm wide sliding groove 411 in the middle. Both ends of the measuring main frame 41 are fastened to the model box 1 by M8 bolts. A movable measuring rod 42 is provided on the measuring main frame 41. The top of the movable measuring rod 42 is a 25mm × 25mm × 5mm cube mounting steel plate 421. Bolts with a diameter of 5mm are provided on both sides of the mounting steel plate 421. A steel rod with a diameter of 6mm and a length of 500mm is welded downward from the center of the mounting steel plate 421. The installation process of the measuring main frame 41 is to first pass the lower steel rod of the movable measuring rod 42 through the sliding groove 411 of the measuring main frame 41, slide the fixing rod to the required layout position of the data monitoring system, and fix it to the measuring main frame 41 by the bolts and nuts on the mounting steel plate 421 at the top of the sliding fixing rod.

[0065] The sand layer position tracing system comprises several test soil sample layers filled in the model box 1 , and a colored sand layer is provided on one side or both sides of the test soil sample layer.

[0066] More specifically, during the filling process of the test box soil sample layer, the sand layer position tracing system is composed of a 10 mm thick colored sand layer evenly arranged at intervals of 110 mm on the inner side of the test observation window 13 in front and behind the model box 1 to realize the visualization of the stratum profile collapse process.

[0067] The water level control system includes a water inlet system and a drainage system. The water inlet system includes a cover plate 60 covering the model box 1, a water inlet pipe 61 inserted on the cover plate 60, and several overflow holes 62 arranged linearly and opened on both sides of the model box 1. The drainage system includes a sand discharge port baffle 63 opened on both sides of the model box 1. The sand discharge port baffle 63 is located below the several overflow holes 62, and a drainage hole valve 64 is provided on the sand discharge port baffle 63.

[0068] More specifically, the function of the water inlet pipe 61 of the water level control system is to inject water into the sand layer position tracing system through the water inlet pipe 61 before the test begins. Only after the test soil sample layer in the model box 1 is saturated with water can the tunnel damage simulation device be used for testing. The function of the overflow hole 62 of the water level control system is to maintain the test set water level. Before the test, the overflow hole 62 located below the test set water level must be sealed with a rubber plug, and then the soil sample is filled. If water needs to be replenished during the test, it is necessary to continuously replenish water to the model box 1 through the water pipe to ensure that the overflow hole 62 at the test set water level continues to overflow, that is, the water head height remains unchanged. The function of the sand discharge port baffle 63 of the water level control system is to open the drain hole valve 64 when the test is completed and the model box 1 needs to be drained, so as to quickly drain the test soil sample layer in the model box 1; and further open the sand discharge port baffle 63 to remove the test soil sample layer.

[0069] A side of the tunnel model 2 protruding from the model box 1 is provided as a drainage pipe 71 , and the water-sand collection system 7 is composed of the drainage pipe 71 and a water-sand collection box 72 provided on one side of the drainage pipe 71 .

[0070] More specifically, the function of the water and sand collection system 7 is to monitor water leakage, sand leakage and changes in particle size in the formation by regularly replacing the water and sand collection box 72 during the test.

[0071] Example 2:

[0072] Example 2 of the present invention provides a method for testing local leakage-induced stratum seepage erosion damage in tunnels, which is conducted using a test apparatus for local leakage-induced stratum seepage erosion damage in tunnels as described in Example 1, and includes the following steps:

[0073] S1: Before the test begins, the tunnel model 2 is processed and a local penetration degradation operation is performed on the tunnel model 2 according to the test settings;

[0074] The local penetration degradation operation simulates a certain area or part of the tunnel model 2 being penetrated to form a penetration opening, thereby causing degradation performance such as a decrease in strength or an increase in permeability of the tunnel model 2. The number of penetration openings is determined according to the specific test settings.

[0075] S2: Installing water pressure sensors and earth pressure sensors at designated locations on the movable measuring rod 42 of the measuring frame system 4 according to the test monitoring settings;

[0076] S3: Fix the tunnel model 2 on the model box 1;

[0077] The specific processing process is as follows: inserting the tunnel model 2 after local through-degradation processing into the reserved holes of the front and rear test observation windows 13 of the model box 1, adjusting the local degradation position of the tunnel model 2 according to the test settings, that is, rotating the angle of the tunnel model 2 to adjust the specific position of the local degradation, and fixing the tunnel model 2, that is, sleeved with a hollow circular ring piece with multiple bolt holes on the tunnel model 2, and provided with a hollow circular ring piece with multiple bolt holes in the model box 1, and fastening the hollow circular ring piece of the tunnel model 2 and the hollow circular ring piece arranged in the model box 1 by bolts to achieve the fixation of the tunnel model 2 and the sealing of the joint between the tunnel model 2 and the model box 1;

[0078] S4: Use a rubber water stopper with a drawstring 22 having a diameter slightly larger than the tunnel opening to seal the deteriorated position of the tunnel model 2. The drawstring 22 extends from a hole at one end of the tunnel model 2. Use rubber water stoppers to block the overflow holes 62 on both sides of the model box 1 below the test set water level. Close the overflow holes 62, lock and seal the sand discharge port baffle 63, and the drain hole valve 64.

[0079] S5: According to the test monitoring setting, the measurement main frame 41 of the measurement frame system 4 is fixed to the test monitoring section, which refers to the cross section along the width direction of the model box 1;

[0080] S6: Setting the soil cover height of the tunnel model 2, i.e., using a layered method to fill each layer of soil sample, and arranging a colored sand layer on one or both sides of each test soil sample layer, and then injecting water through the water level control system to saturate the soil sample in the model box 1;

[0081] The specific processing process is as follows: according to the test setting, the cover height of the tunnel model 2 is set, and the soil sample is filled in a layered manner. After calculating the required weight of each test soil sample layer according to the density control method, the soil is evenly filled in the model box 1, and the filled soil is compacted and leveled according to the filling height of each layer. Then, a 10mm thick layer of colored sand is evenly arranged on one side of the test observation window 13 to realize the visualization of the stratum collapse. Among them, when filling the next layer of soil, the surface of the current soil is scraped to increase the contact between the layered filling soils. According to this step, the filling is continued to the test set height;

[0082] After the soil sample is filled, the water level control system injects water to saturate the soil sample in the model box 1, that is, the water inlet pipe 61 of the water level control system is opened so that the water level is slightly higher than the soil cover height (such as Figure 2 The effect shown is Figure 2 The observation window in the middle test shows the transparent effect, and the thin layer on the top of the soil represents the water level);

[0083] S7: Arrange the water-sand collection system 7, set up and debug the high-speed camera on the front side of the model box 1, and connect the water pressure sensor, soil pressure sensor, and high-speed camera of the data monitoring system to the data acquisition system electrically and signal-wise, so that the host computer receives the monitoring data of the three;

[0084] S8: The test begins. The pull rope 22 is pulled to remove the rubber water stopper. Water and sand above the deteriorated position of the tunnel model 2 flow into the tunnel model 2 and into the water and sand collection box 72 through the drainage pipe 71 at the entrance of the tunnel model 2. The water and sand collection boxes 72 are replaced at regular intervals and numbered until only water flows out of the tunnel. The test ends.

[0085] S9: After the test, the drain hole valve 64 and the sand discharge port baffle 63 are opened in sequence to drain water and unload soil;

[0086] The specific processing process is as follows: after the test is completed, the drain hole valve 64 on the sand discharge port baffle 63 is first opened to quickly drain the soil in the test box. Then, the fastening bolts on the sand discharge port baffle 63 are removed, and the soil in the test box is removed from the sand discharge port of the model box 1. Then, the measurement main frame 41 fixed on the top of the model box 1 is removed, and finally, the tunnel model 2 is removed.

[0087] S10: weigh, record, filter, dry, and calculate the water quality of each water and sand collection box 72 in sequence;

[0088] The specific processing process is as follows: the water and sand collection boxes 72 are weighed and recorded in sequence, and then the sand in each water and sand collection box 72 is filtered out through a sieve with a mesh smaller than the minimum particle size of the test soil sample, and the sand is placed in a high-temperature drying box for drying. The mass of the dried sand in each water and sand collection box 72 is recorded, and the mass of the water in the water and sand collection box 72 is obtained by subtracting the mass of the dried sand from the total mass of the water and sand collection box 72;

[0089] S11: Screening the dried sand in each collection box for particle size to clarify the stratum loss characteristics during the stratum soil and water loss process;

[0090] S12: Processing the images captured by the high-speed camera through a digital image system to obtain the migration pattern of sand particles during the process of soil erosion and damage in the stratum, and revealing the stratum collapse process from a microscopic level;

[0091] S13: Combining the monitoring data of stratum water and soil pressure during stratum damage and the results of digital image processing of stratum collapse, the mechanism of continuous water and soil loss caused by local deterioration of the tunnel can be revealed from the microscopic phenomena and mechanical mechanisms of stratum collapse.

[0092] The test method for tunnel local leakage-induced stratum seepage erosion damage in Example 2 of the present invention has the following advantages:

[0093] A. Its core advantages are: studying the continuous soil and water loss disasters induced by local deterioration of tunnels, realizing real-time monitoring of the development and transmission laws of stratum stress, pore pressure and stratum deformation (migration of soil particles within the stratum) during the soil and water loss process (under the conditions of water inrush and sand inrush), revealing the occurrence, development and evolution of tunnel leakage and sand burst disasters, clarifying the influence of factors such as cover height, leakage location, leakage area and initial water level on soil and water loss, and exploring the mechanical mechanism of progressive stratum destruction induced by local deterioration of shield tunnels.

[0094] B. It can simulate different degradation forms such as shield tunnel joint degradation (square through-holes), concrete lining corrosion degradation (approximately circular through-holes), and tunnel breakdown degradation (circular through-holes). It can also further consider the impact of factors such as tunnel degradation degree, degradation location, stratum particle size, water head height, and stratum water replenishment on stratum damage characteristics;

[0095] C. It can not only monitor and analyze the soil arching effect during the process of small-scale stratum instability and damage, but also study the flow damage characteristics caused by large-scale continuous soil erosion;

[0096] D. Using the measuring frame system 4 to fix the earth pressure sensor and water pressure sensor, real-time monitoring of the development and transmission of formation stress and pore pressure during soil erosion can be achieved, solving the problem of monitoring the internal mechanical field of the formation during soil flow and destruction.

[0097] E. The test observation windows 13 in front and behind the model box 1 are made of transparent acrylic glass plates, which can be used as observation windows during the test process. At the same time, the tunnel deterioration position is close to the observation window of the model box 1. Combined with the colored sand layer set in the stratum, it can realize the direct observation of the macroscopic phenomenon of soil particle movement in the deep stratum during the soil erosion process;

[0098] F. With the help of high-speed cameras and digital image processing systems, the migration paths of soil particles during stratum collapse can be tracked, and millimeter-level stratum displacement can be captured. This overcomes the limitations of direct macroscopic observation data and reveals the stratum collapse process from a microscopic perspective.

[0099] G. By regularly replacing the water and sand collection box 72, the entire process of tunnel water and sand leakage as the ground damage develops can be monitored. By screening the sand in the water and sand collection box 72, the characteristics of ground loss and damage can be further clarified.

[0100] Example 3:

[0101] Example 3 of the present invention uses the specific parameters of Example 1 to build a test device for local leakage-induced stratum seepage erosion and damage in tunnels. After the test device is built, the test method for local leakage-induced stratum seepage erosion and damage in tunnels is used to conduct a test. The test is based on the working condition of a maximum cover thickness of 440 mm. The layout principles of the water and earth pressure monitoring points (i.e., water pressure sensors, earth pressure sensors) and cameras in the tunnel transverse and longitudinal sections are as follows:

[0102] Existing tests have shown that the phenomenon of soil sand burst is related to the sand particle size and the tunnel thickness-span ratio (the ratio of the soil layer thickness to the tunnel model diameter). The failure angle of the settlement surface after the soil sand burst is approximately 9° greater than the natural angle of repose of the soil or close to the saturated internal friction angle of the soil. The internal friction angle of sand is approximately 30°. Therefore, the maximum radius of the stratum failure monitoring range at each burial depth can be taken as twice the tunnel burial depth. According to the survey, the stratum failure form is funnel-shaped. Therefore, the layout of the water and soil pressure monitoring points (i.e., water pressure sensors and soil pressure sensors) is generally inverted triangle shape.

[0103] 1) Formation stress monitoring points

[0104] Taking into account the ground failure monitoring radius and the layout of the monitoring points, stress monitoring points (i.e., earth pressure sensors) were installed at intervals of 110 mm vertically and 150 mm horizontally throughout the tunnel's longitudinal and transverse sections. Furthermore, as changes in ground stress around the tunnel caused by localized ground failure are a primary cause of tunnel structural failure, earth pressure sensors were deployed within the tunnel opening, at the arch crown, arch base, and along the arch haunches on both sides to monitor actual changes in ground stress around the tunnel.

[0105] 2) Water pressure monitoring points

[0106] This test is a constant head test. Therefore, theoretically, water pressure only varies within the opening. The closer to the head height, the less pronounced the change. Therefore, the water pressure monitoring range is smaller than the earth pressure monitoring range, and only areas with significant ground disturbance are monitored. In the tunnel's transverse and longitudinal sections, piezometers (i.e., water pressure sensors) are deployed horizontally at intervals of 150 mm and vertically at intervals of 110 mm, using the tunnel vault as the reference point. A piezometer (i.e., water pressure sensor) is also installed at the tunnel opening to monitor water pressure changes at the opening.

[0107] 3) High-speed camera deployment points

[0108] The high-speed camera is placed in front of the test chamber. The camera height and distance from the test chamber are adjusted so that the camera can look level with the test chamber. The camera is focused and the camera shooting frequency is set.

[0109] The arrangement of water and earth pressure monitoring points (i.e. water pressure sensors and earth pressure sensors) in the tunnel transverse and longitudinal sections is as follows: Figure 7 The monitoring equipment and quantity required for the test are summarized in Table 1.

[0110] Table 1 Monitoring instruments required for the test

[0111] Monitoring equipment Miniature earth pressure sensor Water pressure sensor High-speed cameras Digital image processing system Osmotic pressure data acquisition instrument, static strain tester quantity 80 11 2 1 80 channels

[0112] Therefore, the experimental results of the embodiment 3 of the present invention using a test device for tunnel local leakage induced stratum seepage erosion damage test are as follows ( Figure 8-10 shown):

[0113] 1. With the help of the water and sand collection system 7, the amount of water and sand leakage during the formation destruction process can be monitored. In addition, if well-graded sand is used, the data of the change of sand particle size of the leaking sand with the leakage time can also be monitored and analyzed;

[0114] 2. With the help of high-speed cameras, real-time monitoring of surface settlement curves, stratum displacement cloud maps and damage contours can be achieved;

[0115] 3. With the help of the colored sand layer, the surface subsidence process can be observed with the naked eye.

[0116] 4. With the help of the data monitoring system, real-time monitoring of the deep stratum mechanical field can be achieved.

[0117] From the above test results, it can be concluded that the device and method for testing seepage erosion and damage of formations induced by local leakage in tunnels can realize the microscopic real-time monitoring of the displacement of the formation flow damage process and the mechanical field inside the formation. The monitoring technology is sophisticated and the operation is simple.

[0118] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. 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 device for local leakage-induced stratum seepage erosion damage in tunnels, characterized in that: The invention comprises a model box (1), wherein a tunnel model (2) is provided on the model box (1), wherein a tunnel destruction simulation device is provided on the tunnel model (2), wherein a measuring frame system (4) is provided inside the model box (1), wherein the measuring frame system (4) comprises a plurality of linearly arranged measuring main frames (41), wherein each of the measuring main frames (41) is provided with a plurality of linearly arranged movable measuring rods (42), wherein a sand layer position tracing system is provided inside the model box (1), wherein a water level control system is provided on the model box (1), wherein a water and sand collecting system (7) is provided on one side of the model box (1), and wherein a data monitoring system is provided on the model box (1), wherein the data monitoring system comprises a plurality of water pressure sensors which are linearly distributed and mounted on the movable measuring rods (42), a plurality of soil pressure sensors which are linearly distributed and mounted on the movable measuring rods (42), and a camera which is mounted on one side of the model box (1).

2. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The model box (1) comprises a bottom plate (11), side plates (12) installed at the left and right ends of the bottom plate (11), and test observation windows (13) installed at the front and rear ends of the bottom plate (11).

3. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The tunnel model (2) is a PVC pipe.

4. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The tunnel destruction simulation device comprises a rubber water-stopping rod (21) inserted into a local deterioration position of a tunnel model (2) and a pull rope (22) tied to one end of the rubber water-stopping rod (21) and passing through a side hole of the tunnel model (2).

5. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The measuring main frame (41) is fixed to the model box (1) by bolts, a sliding groove (411) is provided on the measuring main frame (41), a mounting steel plate (421) is provided on the top of the movable measuring rod (42), the movable measuring rod (42) passes through the sliding groove (411), and the mounting steel plate (421) is fixed to the measuring main frame (41) by nuts and bolts.

6. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The sand layer position tracing system comprises several test soil sample layers filled in a model box (1), and a colored sand layer is provided on one side or both sides of the test soil sample layer.

7. The device for testing stratum seepage erosion damage induced by local leakage in tunnels according to claim 1, characterized in that: The water level control system comprises a water inlet system and a drainage system. The water inlet system comprises a cover plate (60) covering the model box (1), a water inlet pipe (61) inserted into the cover plate (60), and a plurality of overflow holes (62) arranged linearly and opened on both sides of the model box (1). The drainage system comprises sand discharge port baffles (63) opened on both sides of the model box (1), the sand discharge port baffles (63) being located below the plurality of overflow holes (62), and a drainage hole valve (64) being provided on the sand discharge port baffles (63).

8. The device for testing stratum seepage erosion damage induced by local leakage in tunnels according to claim 1, characterized in that: The side of the tunnel model (2) protruding from the model box (1) is provided as a drainage pipe (71), and the water-sand collection system (7) is composed of the drainage pipe (71) and a water-sand collection box (72) provided on one side of the drainage pipe (71).

9. The device for testing stratum seepage erosion damage caused by local leakage in tunnels according to claim 1, characterized in that: The invention also includes a data acquisition system electrically and signal-connected to the data monitoring system, wherein the data acquisition system includes a micro-osmotic pressure data acquisition instrument electrically and signal-connected to the water pressure sensor, a static strain tester electrically and signal-connected to the soil pressure sensor, a digital image processing system electrically and signal-connected to the camera, and a host computer for receiving and analyzing the collected data from the micro-osmotic pressure data acquisition instrument, the static strain tester, and the digital image processing system, wherein the water pressure sensor is a micro-pore water pressure sensor, the soil pressure sensor is a micro-pore soil pressure sensor, and the camera is a high-speed camera. The water pressure sensor is fixed to a movable measuring rod (42) by a plastic strap, and the soil pressure sensor is adhered to the movable measuring rod (42) by a nano double-sided adhesive tape.

10. A test method for local leakage-induced stratum seepage erosion damage in tunnels, characterized in that: The test is conducted using a test device for tunnel local leakage-induced stratum seepage erosion damage according to any one of claims 1 to 9, comprising the following steps: S1: Perform local penetration degradation operation on the tunnel model (2); S2: Installing a water pressure sensor and an earth pressure sensor on the movable measuring rod (42) of the measuring frame system (4); S3: Fixing the tunnel model (2) on the model box (1); S4: Using a rubber water stopper with a pull rope (22) to seal the deteriorated position of the tunnel model (2), the pull rope (22) extends from a hole at one end of the tunnel model (2), and the overflow hole (62) is blocked, and the drain hole valve (64) is closed; S5: Fixing the measuring main frame (41) of the measuring frame system (4) on the test monitoring section; S6: Setting the soil cover height of the tunnel model (2), i.e., using a layered method to fill each layer of soil sample, and arranging a colored sand layer on one side or both sides of each test soil sample layer, and then injecting water through a water level control system to saturate the soil sample in the model box (1); S7: Arrange the water and sand collection system (7), set up and debug the high-speed camera on the front side of the model box (1), and connect the data acquisition system; S8: The test starts, the pull rope (22) is pulled to bring out the rubber water stopper, and the water and sand above the deteriorated position of the tunnel model (2) flow into the tunnel model (2), and flow into the water and sand collection box (72) through the drainage pipe (71) at the entrance of the tunnel model (2). The water and sand collection box (72) is replaced at regular time intervals and numbered until only water flows out of the tunnel, and the test ends; S9: Open the drain hole valve (64) and the sand discharge port baffle (63) in sequence to drain water and unload soil; S10: weighing, recording, sieve filtering, drying, and calculating the water quality of each water and sand collection box (72) in sequence; S11: Screening the dried sand in each collection box for particle size to clarify the stratum loss characteristics during the stratum soil and water loss process; S12: Processing the images captured by the high-speed camera through a digital image system to obtain the migration pattern of sand particles during the process of soil erosion and damage in the stratum, and revealing the stratum collapse process from a microscopic level; S13: Combining the monitoring data of stratum water and soil pressure during stratum damage and the results of digital image processing of stratum collapse, the mechanism of continuous water and soil loss caused by local deterioration of the tunnel can be revealed from the microscopic phenomena and mechanical mechanisms of stratum collapse.

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