Device and method for testing constant pressure difference seepage-shear coupling performance of soil-lining interface

Abstract

The invention relates to the technical field of geotechnical engineering test equipment, and provides a soil-lining interface constant pressure difference seepage-shear coupling performance test device and method.The device comprises a main controller, a sensor array used for monitoring the stress field distribution state, a data acquisition system, a shear box and a confining pressure box internally provided with a confining pressure cavity; the shear box is located in the confining pressure cavity, the bottom of the shear box is in sliding connection with the confining pressure box, shear loading devices are arranged on the top and the two opposite side faces of the shear box respectively, permeable stones are arranged on the inner top wall and the inner bottom wall of the shear box respectively, and the top and the bottom of one side of the shear box are connected with a water supply pipeline and a water drainage pipeline respectively. The communicating ends of the water supply and drainage pipelines and the shear box are respectively positioned on the opposite sides of the two permeable stones. According to the invention, independent loading and stable maintenance of normal pressure, interface shear force and constant seepage pressure difference across the interface direction are realized, and the problems that the functions of the existing test equipment are separated and constant pressure difference seepage and shear load coupling performance test cannot be realized are solved.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing equipment technology, specifically to a device and method for testing the constant pressure difference seepage-shear coupling performance of soil-lining interface. Background Technology

[0002] Under conditions of sudden rise in groundwater level caused by extreme rainfall, the high pore water pressure gradient (large seepage pressure difference) formed at the tunnel soil-lining interface and the interfacial shear stress generated by relative soil movement will strongly couple. This seepage-shear coupling effect is a key mechanism for inducing interface sealing failure, seepage channel expansion, and even segment uplift failure. Accurately quantifying the comprehensive performance parameters of the interface (seepage shear strength, seepage flow evolution) under the coupled action of constant pressure difference seepage and shear load has become a key requirement for assessing such water hazard risks in shield tunnels and ensuring long-term safety.

[0003] Current soil-structure interface performance testing primarily relies on traditional equipment with separate functions. While standard direct shear apparatus can apply normal pressure and shear force, it cannot independently apply and stably maintain a constant seepage pressure differential across the interface. Permeameters, although capable of measuring seepage parameters, lack the ability to apply controllable shear loads. These devices and processes cannot achieve synchronous coupling of shear loading and seepage loading under constant seepage pressure gradient conditions. Furthermore, it is difficult to accurately measure the change in seepage flow at the interface with shear displacement and its impact on the real-time degradation of interfacial frictional strength and cohesive strength under this complex coupling environment. In addition, existing methods lack the ability to simulate the deteriorating effect of wet-dry cycles on interfacial coupling performance under constant seepage pressure gradients, resulting in a lack of reliable experimental data to support key mechanical and permeability constitutive parameters. Summary of the Invention

[0004] To address the problems in the background technology and overcome the technical bottleneck in testing the coupling performance of constant pressure differential seepage and shear load, this patent proposes a testing device and method for the coupling performance of constant pressure differential seepage and shear load at the soil-lining interface. The technical solution is as follows: A soil-lining interface constant pressure differential seepage-shear coupling performance testing device includes a main controller, a sensor array for monitoring the stress field distribution, a data acquisition system, a shear box for placing tunnel segment samples, and a confining pressure chamber with an internal confining pressure cavity. The confining pressure cavity is connected to an oil supply pipeline and an oil discharge pipeline. The shear box is located inside the confining pressure cavity, and its bottom is slidably connected to the confining pressure chamber. Shear loading devices are respectively provided on the top and opposite sides of the shear box. The top and bottom walls of the shear box are respectively provided with permeable stones, and the top and bottom of one side of the shear box are respectively connected to a water supply pipeline and a drainage pipeline. The water supply pipeline and the drainage pipeline are connected to the opposite sides of the two permeable stones at their respective ends. The data acquisition system is connected to the sensor array, and the main controller is connected to both the data acquisition system and the shear loading device. Preferably, it also includes a confining pressure / permeability control center, wherein the ends of the oil supply pipeline, water supply pipeline, drainage pipeline and oil discharge pipeline away from the shear box are respectively connected to the confining pressure / permeability control center, and valves are respectively provided on the oil supply pipeline, water supply pipeline, drainage pipeline and oil discharge pipeline, and the confining pressure / permeability control center is respectively connected to the valves and the main controller.

[0005] Preferably, the confining pressure / permeability control center includes a water tank, an oil tank, a water pump, an oil pump, and a controller. The water supply pipeline and the drainage pipeline are each connected to the water tank via a water pump. Electromagnetic flow meters are installed on the drainage pipeline and the water supply pipeline. The oil supply pipeline and the oil discharge pipeline are each connected to the oil tank via an oil pump. The controller is connected to the main controller, the oil pump, the water pump, the electromagnetic flow meters, and the valves.

[0006] Preferably, the confining pressure box is located inside the shear main shell, and the bottom of the confining pressure box is fixedly connected to the bottom wall of the shear main shell by bolts. The confining pressure / permeability control center is located outside the shear main shell.

[0007] Preferably, the shear box includes an upper shear box and a lower shear box located at the bottom of the upper shear box. The bottom of the upper shear box and the top of the lower shear box are respectively provided with arc grooves. After the upper shear box and the lower shear box are connected, the arc grooves of the upper and lower shear boxes are spliced ​​together to form a positioning groove for positioning and placing tunnel segment samples.

[0008] Preferably, the shear loading device includes an upper shear loading device, an upper shear driving device, and a lower shear driving device. The lower shear driving device and the upper shear driving device are located on opposite sides of the shear box. The upper shear driving device is connected to the side of the upper shear box, and the lower shear driving device is connected to the side of the lower shear box. The upper shear loading device is connected to the top surface of the upper shear box, and the bottom of the lower shear box is slidably connected to the confining pressure box. The sliding direction of the shear box is consistent with the driving direction of the upper shear loading device and the lower shear loading device.

[0009] Preferably, the sensor array includes a confining pressure sensor, multiple soil pressure sensors, an upper osmotic pressure sensor, a lower osmotic pressure sensor, a shear force sensor, a first displacement sensor, a second displacement sensor, and multiple pore water pressure sensors; The confining pressure sensor is fixed to the wall of the confining pressure cavity. Multiple soil pressure sensors are buried in layers inside the soil sample. The upper osmotic pressure sensor is located at the connection between the water supply pipeline and the shear box. The lower osmotic pressure sensor is located at the connection between the drainage pipeline and the shear box. The shear force sensor and the first displacement sensor are located at the bottom of the shear box. The second displacement sensor is located at the top of the confining pressure cavity and corresponds to the position of the shear box. Multiple pore water pressure sensors are buried in layers inside the soil sample.

[0010] A method for testing the constant pressure differential seepage-shear coupling performance of soil-lining interface includes the following steps: S1. Set up the test device clipboard Based on the engineering geological conditions, remolded soil is prepared as a soil sample, or field soil samples are taken, and the moisture content and compaction of the soil samples are adjusted to the required state for the test. A flexible film is used to wrap the outer wall of the tunnel segment sample to form a hydraulic transfer boundary and seal both ends of the tunnel segment sample; soil samples are layered and filled to the target height on the permeable stone base located at the bottom of the shear box; the tunnel segment sample wrapped with the flexible film is placed in the shear box and the soil samples are filled until completion. S2, Establishment of Initial Stress State Pre-set confining pressure is applied by injecting confining oil into the confining pressure chamber through the oil supply pipeline, achieving isobaric consolidation of the soil sample in the shear box; simultaneously, water is injected into the shear box through the water supply pipeline to apply a hydrostatic pressure benchmark value to the saturated soil zone and the lining back cavity. p 0, simulate the steady-state environment of groundwater; apply confining pressure and hydrostatic pressure until the soil stress field reaches a uniform distribution; Confining pressure is collected in real time using a sensor array. s conf Monitoring the normal stress of each soil layer s n Monitoring infiltration pressure p i and drainage pressure p o To determine whether the soil stress field is uniformly distributed, the condition for determining whether the soil stress field is uniformly distributed is: the normal stress in each layer of the soil... s n With confining pressure s conf Deviation ≤ 5%, and satisfy p i = p o = p 0; S3, Constant water pressure differential loading By adjusting the injection and drainage pressures of the water supply and drainage pipelines, the infiltration and drainage pressures are regulated, thereby establishing a target hydraulic gradient between the infiltration and drainage boundaries and maintaining the fluctuation range of the osmotic pressure difference Δp < 1 kPa, thus achieving the constancy of the hydraulic gradient during the seepage process. The formula for calculating the osmotic pressure difference is as follows: (1) In the formula, Δ p For the constant seepage pressure difference at the soil-lining interface, p i This refers to the infiltration boundary water pressure, which is the pressure at the interface between the water supply pipeline and the shear box. po This refers to the water pressure at the drainage boundary, i.e., the pressure at the interface between the drainage pipe and the shear box.

[0011] S4, seepage-shear coupling loading The shear loading devices located on both sides of the shear box are activated. Under the condition of maintaining a constant osmotic pressure difference Δp, a horizontal shear load is applied along the contact interface between the soil sample and the tunnel segment sample. The shear displacement and the shear force value at the soil-lining interface are monitored by a sensor array to achieve complete spatiotemporal coupling between the seepage field and the stress field. Specifically, the action of the shear loading device is controlled by the displacement rate control equation, while ensuring that the seepage field satisfies Darcy's law and that the mechanical loading and seepage action interact continuously and simultaneously. The loading process must satisfy the condition of complete temporal overlap. The displacement rate control equation is: (2) In the formula, v s δ is the shear displacement rate, t is the shear displacement, and t is the shear loading time. The formula for determining whether the loading process satisfies the condition of complete temporal overlap is: (3) In the formula, t s t is the movement time of the shearing component. Δp The duration of the seepage effect; While applying shear load, adjust the infiltration pressure and drainage pressure to control fluctuations in osmotic pressure differential caused by displacement: (4) In the formula, Δ p Where δ is the osmotic pressure difference and δ is the shear displacement. e δ This is the error threshold; S5. Synchronous Monitoring and Data Recording The following data monitored by the sensor array are acquired in real time through the data acquisition system: soil-lining interface shear force Fs, shear displacement ẟ, soil sample settlement ΔH, seepage flow Q, and seepage path pressure field p(x, t). All data are stored in a unified time step. S6. Performance Parameter Calculation The following characteristic curves and evolution parameters are dynamically generated based on real-time acquired data streams: a) Intensity characteristic curve τ-δ; b) Seepage response curve Q- p; c) Deformation evolution curve ε v -δ;d) Conductivity curve k eff-γ The calculation formula is as follows: (5) (6) (7) (8) In the formula, τ is the interfacial shear stress, and A c ε represents the contact area between the soil sample and the pipe segment. v Let H0 be the initial thickness of the soil sample, and k be the volumetric strain. eff The effective permeability coefficient is given by γ, where γ is the shear strain, Q is the seepage flow rate, L is the seepage path length (i.e., the distance between the two permeable stones), and A is the permeability coefficient. s Where Δp is the cross-sectional area of ​​the seepage flow, and Δp is the seepage pressure difference. The peak value of the interfacial friction coefficient, the residual friction coefficient, the critical shear displacement, and the hydraulic weakening rate were calculated based on the four curves. The calculation formulas are as follows: (9) (10) (11) (12) In the formula, μ p μ is the peak value of the friction coefficient. r δ is the residual friction coefficient. cr η is the critical shear displacement. ω This refers to the hydraulic weakening rate, i.e., the rate at which seepage weakens the friction coefficient. m r / m p The ratio of residual friction coefficient to peak value (dimensionless). The four curves and four values ​​provide a basis for the analysis of seepage-shear coupling performance.

[0012] Preferably, step S2 specifically involves monitoring the confining pressure using a confining pressure sensor, monitoring the soil normal stress using a soil pressure sensor, monitoring the infiltration pressure using an upper osmotic pressure sensor, and monitoring the drainage pressure using a lower osmotic pressure sensor. Specifically, step S3 involves adjusting the infiltration pressure and drainage pressure by changing the power of the water pumps connected to the water supply pipeline and drainage pipeline, respectively. Specifically, step S4 involves monitoring the shear displacement using a first displacement sensor and monitoring the shear force value at the soil-lining interface using a shear force sensor. Specifically, step S5 involves monitoring the soil sample settlement using a second displacement sensor, measuring the seepage flow rate using an electromagnetic flowmeter at the drainage pipe, and monitoring the seepage path pressure field using a pore water pressure sensor.

[0013] Preferably, step S4 specifically involves, based on real-time volumetric strain ε vThe changes in soil pore structure are inverted, and the water pump is linked to maintain a constant seepage pressure difference, controlling the seepage pressure difference fluctuation to be less than or equal to 0.1 kPa / mm. When the shear displacement δ>2 mm, the flexible membrane sealing reinforcement mechanism is activated to ensure the boundary leakage Q during the seepage-shear coupling process. leak <10⁻⁶ m 3 / s.

[0014] Preferably, a two-field coupling analysis is performed based on the curve obtained in step S6, and the analysis includes quantification of the conduction weakening effect: through k eff - c Real-time curve capture of shear strain γ and its effect on permeability coefficient k eff The nonlinear attenuation effect, if k eff / k o If the percentage is less than 30%, it is determined that the tunnel segment shear deformation has led to a deterioration in the sealing function. k o The original permeability coefficient; Hydraulic weakening risk warning: When the hydraulic weakening rate or ω When the pressure difference is greater than 0.05 kPa, it indicates that the friction coefficient loss rate caused by the unit seepage pressure difference exceeds the critical threshold, directly triggering a strong seepage-shear coupling risk alarm.

[0015] The beneficial effects of this invention are as follows: This invention achieves independent loading and stable maintenance of normal pressure, interfacial shear force, and constant seepage pressure differential across the interface, solving the problem of existing testing equipment's functional separation and inability to perform coupled performance testing of constant pressure differential seepage and shear load. Simultaneously, it captures high-precision correlation data of the dynamic evolution of interfacial seepage flow and shear force displacement response during this seepage-shear coupling process. The testing method of this invention provides fundamental experimental evidence for characterizing the constitutive relationship and seepage conductivity of the interface under complex coupled loads, providing important parameter support for high-precision numerical simulation of tunnel seepage-structure interaction under extreme rainfall disasters, and can directly serve engineering safety design and risk decision-making. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the testing device of the present invention; Figure 2 This is a schematic diagram of the stress state of the tunnel segment sample of the present invention; Figure 3 This is a schematic diagram of the force state of the shear box of the present invention; Figure 4 This is a schematic diagram showing the structural relationship between the upper and lower shear boxes of the present invention.

[0017] The diagram labels are as follows: 1. Shear main shell; 2. Confining pressure box; 3. Confining pressure cavity; 4. Upper shear box; 5. Lower shear box; 6. Permeable stone; 7. Tunnel segment sample; 8. Target height; 9. Upper shear loading device; 10. Upper shear drive device; 11. Lower shear drive device; 12. Confining pressure / permeability control center; 13. Oil supply pipeline; 14. Oil discharge pipeline; 15. Water supply pipeline; 16. Drainage pipeline; 17. Slide rail; 18. Shear force / displacement sensor; 19. Arc groove; 20. Valve; 21. Positioning groove; 22. Third displacement sensor; 23. First shear force sensor. Detailed Implementation

[0018] To make the present invention clearer and more understandable, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the given embodiments are only one of the implementation methods and do not represent all embodiments.

[0019] In this article, terms such as "inner," "outer," "upper," "lower," "front," "back," "left," and "right" are established based on the positional relationships shown in the attached figures. Depending on the attached figures, the corresponding positional relationships may also change. Therefore, they should not be interpreted as an absolute limitation on the scope of protection.

[0020] Combined with appendix Figure 1 - Appendix Figure 4 The soil-lining interface constant pressure differential seepage-shear coupling performance testing device includes a main controller, a sensor array for monitoring the stress field distribution, a data acquisition system, a shear box for placing tunnel segment samples 7, and a confining pressure chamber 2 with a confining pressure cavity 3 inside. The confining pressure chamber 3 is connected to an oil supply pipeline 13 and an oil discharge pipeline 14. The shear box is located inside the confining pressure chamber 3, and the bottom of the shear box is slidably connected to the confining pressure chamber 2. Shear loading devices are respectively provided on the top and opposite sides of the shear box. The top and bottom walls of the shear box are respectively provided with permeable stones 6, and the top and bottom of one side of the shear box are respectively connected to a water supply pipeline 15 and a drainage pipeline 16. The water supply pipeline 15 and the drainage pipeline 16 are respectively located on opposite sides of the two permeable stones 6 when they communicate with the inside of the shear box. The data acquisition system is connected to the sensor array, and the main controller is connected to both the data acquisition system and the shear loading device.

[0021] Specifically, when the tunnel segment sample 7 is placed in the shear box, the axial direction of the tunnel segment sample 7 is set along the front-to-back direction of the shear box, and the loading direction of the shear loading device located on both sides is parallel to the radial direction of the tunnel segment sample 7; the sliding direction of the shear box is consistent with the loading direction of the shear loading device located on both sides.

[0022] Specifically, it also includes a confining pressure / permeability control center 12. The ends of the oil supply pipeline 13, water supply pipeline 15, drainage pipeline 16, and oil discharge pipeline 14 away from the shear box are respectively connected to the confining pressure / permeability control center 12. Valves 20 are respectively provided on the oil supply pipeline 13, water supply pipeline 15, drainage pipeline 16, and oil discharge pipeline 14. The confining pressure / permeability control center 12 is connected to the valves 20 and the main controller respectively.

[0023] More specifically, the confining pressure / permeability control center 12 includes a water tank, an oil tank, a water pump, an oil pump, and a controller. The water supply pipeline 15 and the drainage pipeline 16 are each connected to the water tank via a water pump. Electromagnetic flow meters are installed on the drainage pipeline 16 and the water supply pipeline 15. The oil supply pipeline 13 and the oil discharge pipeline 14 are each connected to the oil tank via an oil pump. The controller is connected to the main controller, the oil pump, the water pump, the electromagnetic flow meters, and the valve 20. Water is stored and discharged through the water tank. The water in the water tank is pumped into the shear box using the water supply pipeline 15 and the water pump on it. The water in the shear box is pumped back to the water tank using the water pump on the drainage pipeline 16 and the water pump on it. The flow rate of water passing through the pipeline is obtained using the electromagnetic flow meters. Confining pressure oil is stored and discharged through the oil pumps. The oil in the oil tank is pumped into the confining pressure chamber 3 using the oil supply pipeline 13 and the oil pump on it. The oil in the confining pressure chamber 3 is pumped back to the oil tank using the oil discharge pipeline 14 and the oil pump on it. More specifically, to prevent the water pumped back to the water tank from being mixed with soil, a filter can be installed between the water tank and the drainage pipe 16.

[0024] Specifically, the confining pressure box 2 is located inside the shear main shell 1, and the bottom of the confining pressure box 2 is fixedly connected to the bottom wall of the shear main shell 1 by bolts. The confining pressure / permeability control center 12 is located outside the shear main shell 1.

[0025] Specifically, the shearing box includes an upper shearing box 4 and a lower shearing box 5 located at the bottom of the upper shearing box 4. The bottom of the upper shearing box 4 and the top of the lower shearing box 5 are respectively provided with arc grooves 19. After the upper shearing box 4 and the lower shearing box 5 are connected, the arc grooves 19 of the upper and lower shearing boxes 5 are spliced ​​to form a positioning groove 21 for positioning and placing the tunnel segment sample 7. The positioning groove 21 restricts the position of the tunnel segment sample 7, ensuring accurate positioning. The positioning grooves 21 are located on the front and rear sides of the shearing box, respectively. More specifically, the upper shearing box 4 and the lower shearing box 5 are connected by circumferential bolts with graded pre-tightening.

[0026] Specifically, the shear loading device includes an upper shear loading device 9, an upper shear driving device 10, and a lower shear driving device 11. The lower shear driving device 11 and the upper shear driving device 10 are located on opposite sides of the shear box. The upper shear driving device 10 is connected to the side of the upper shear box 4, and the lower shear driving device 11 is connected to the side of the lower shear box 5. The upper shear loading device 9 is connected to the top surface of the upper shear box 4, and the bottom of the lower shear box 5 is slidably connected to the confining pressure box 2. The sliding direction of the shear box is consistent with the driving direction of the upper shear loading device 9 and the lower shear loading device. The upper shear driving device 10 applies a horizontal shear load to the upper shear box 4, and the lower shear driving device 11 applies a horizontal shear load to the lower shear box 5. The upper shear loading device 9 is mainly used to limit the position of the shear box foundation to prevent the shear box from moving directly with the upper shear driving device 10 or the lower shear driving device 11 without deformation. More specifically, the shear loading device is an electro-hydraulic servo loading system, which is a physical performance testing instrument used in the fields of mechanics and civil engineering; the bottom of the lower shear box 5 is slidably connected to the confining pressure box 2 via a slide rail 17.

[0027] Specifically, the sensor array includes a confining pressure sensor, multiple soil pressure sensors, an upper osmotic pressure sensor, a lower osmotic pressure sensor, a shear force / displacement sensor 18, a second displacement sensor, and multiple pore water pressure sensors. The shear force / displacement sensor 18 is a shear force sensor and a first displacement sensor. The confining pressure sensor is fixed to the wall of the confining pressure cavity 3. Multiple soil pressure sensors are buried in layers inside the soil sample, that is, distributed vertically within the soil sample. The upper osmotic pressure sensor is located at the connection between the water supply pipe 15 and the shear box, and the lower osmotic pressure sensor is located at the connection between the drainage pipe 16 and the shear box. The shear force sensor and the first displacement sensor are located at the bottom of the shear box, and the second displacement sensor is located at the top inside the confining pressure cavity 3, corresponding to the position of the shear box. Multiple pore water pressure sensors are arranged in layers within the soil sample.

[0028] More specifically, mounting holes are pre-drilled at equal intervals on the side wall of the shear box, through which the earth pressure sensor is installed inside the shear box. Both the first displacement sensor and the second displacement sensor are LVDT sensors.

[0029] A method for testing the constant pressure differential seepage-shear coupling performance of soil-lining interface includes the following steps: S1. Set up the test device clipboard Based on the engineering geological conditions, remolded soil is prepared as a soil sample, or field soil samples are taken, and the moisture content and compaction of the soil samples are adjusted to the required state for the test. A flexible film is used to wrap the outer wall of the tunnel segment sample 7 to form a hydraulic transfer boundary and seal both ends of the tunnel segment sample 7. Soil samples are layered and filled to the target height 8 on the permeable stone base 6 located at the bottom of the shear box. The tunnel segment sample 7 wrapped with the flexible film is placed in the shear box and the soil samples are filled until completion.

[0030] Specifically, a first shear force sensor 23 and a third displacement sensor 22 are attached to the outer wall of the tunnel segment sample 7. The first shear force sensor 23 and the third displacement sensor 22 are connected to the data acquisition system. The first shear force sensor 23 and the third displacement sensor 22 are used to detect the shear force value and shear displacement at the soil-lining interface of the tunnel segment sample 7. The core purpose is to provide additional local (near the tunnel segment sample 7) information dimension to improve the accuracy of the entire testing device.

[0031] S2, Establishment of Initial Stress State Confining pressure oil is injected into the confining pressure chamber 3 through the oil supply pipeline 13 to apply a preset confining pressure, thereby achieving isobaric consolidation of the soil sample in the shear box. Simultaneously, water is injected into the shear box through the water supply pipeline 15 to apply a hydrostatic pressure reference value p0 to the saturated soil area (the soil sample area located above the bottom permeable stone 6) and the lining back cavity (the closed cavity formed between the outer wall of the tunnel segment sample 7 and the flexible membrane), simulating the steady-state environment of groundwater. Confining pressure and hydrostatic pressure are applied until the soil stress field reaches a uniform distribution. Specifically, water is pumped into the shear box through the water supply pipeline 15 using the water pump of the confining pressure / permeability control center 12, and water is discharged from the shear box using the water pump of the drainage pipeline 16. The water injection pressure and drainage pressure are applied by the two water pumps respectively. More specifically, the water pump on the water supply pipeline 15 is a high-pressure water pump, and the water pump on the drainage pipeline 16 is a low-pressure water pump. The confining pressure σ is collected in real time using a sensor array. conf Monitoring the normal stress σ of each soil layer n Monitoring infiltration pressure p i and drainage pressure p o To determine whether the soil stress field is uniformly distributed, the condition for determining whether the soil stress field is uniformly distributed is: the normal stress σ in each layer of the soil... n With confining pressure σ conf Deviation ≤ 5%, and satisfy p i =p o =p0; Specifically, the confining pressure is monitored by a confining pressure sensor, the soil normal stress is monitored by a soil pressure sensor, the infiltration pressure is monitored by an upper osmotic pressure sensor, and the drainage pressure is monitored by a lower osmotic pressure sensor.

[0032] S3, Constant water pressure differential loading By adjusting the injection and drainage pressures of the water supply pipe 15 and the drainage pipe 16, the infiltration pressure and drainage pressure are regulated, thereby establishing a target hydraulic gradient between the infiltration boundary (the interface between the top permeable stone 6 and the saturated soil sample area) and the drainage boundary (the interface between the bottom permeable stone 6 and the saturated soil sample area), and maintaining the fluctuation range of the seepage pressure difference Δp <1 kPa, thus achieving the constancy of the hydraulic gradient during the seepage process; the formula for calculating the seepage pressure difference is as follows: (1) In the formula, Δ p For the constant seepage pressure difference at the soil-lining interface, p i This refers to the infiltration boundary water pressure, specifically the pressure at the interface between the water supply pipe 15 and the shear box. p o This refers to the water pressure at the drainage boundary, i.e., the pressure at the interface between the drainage pipe 16 and the shear box.

[0033] Specifically, the infiltration pressure and drainage pressure are adjusted by changing the power of the water pumps connected to the water supply pipeline 15 and the drainage pipeline 16, respectively. The data acquisition system receives data monitored by the upper and lower osmotic pressure sensors in real time (data accuracy 0.1%FS) and transmits the data to the main controller. The main controller dynamically adjusts the output power of the two water pumps through a closed-loop PID algorithm to maintain the fluctuation range of the osmotic pressure difference.

[0034] S4, seepage-shear coupling loading The shear loading devices located on both sides of the shear box are activated. Under the condition of maintaining a constant osmotic pressure difference Δp, a horizontal shear load is applied along the contact interface between the soil sample and the tunnel segment sample 7. The shear displacement and the shear force value at the soil-lining interface are monitored by a sensor array to achieve complete spatiotemporal coupling between the seepage field and the stress field. Specifically, the shear displacement is monitored by a first displacement sensor, and the shear force value at the soil-lining interface is monitored by a shear force sensor. Specifically, the action of the shear loading device is controlled by the displacement rate control equation, while ensuring that the seepage field satisfies Darcy's law and that the mechanical loading and seepage action interact continuously and simultaneously. The loading process must satisfy the condition of complete temporal overlap. The displacement rate control equation is: (2) In the formula, v s ẟ represents the shear displacement rate, t represents the shear displacement, and t represents the shear loading time. The formula for determining whether the loading process satisfies the condition of complete temporal overlap is: (3) In the formula, t s t is the movement time of the shearing component. ΔpThe duration of the seepage effect; While applying shear load, the infiltration pressure and drainage pressure are adjusted. The water supply pipeline 15 and drainage pipeline 16, together with their respective connected water pumps and valves 20, form a dynamic boundary compensation system to control the fluctuation of osmotic pressure difference caused by displacement. (4) In the formula, Δp is the osmotic pressure difference, δ is the shear displacement, and ε is the osmotic pressure difference. δ The error threshold is set to 0.1 kPa / mm.

[0035] S5. Synchronous Monitoring and Data Recording The following data monitored by the sensor array are acquired in real time through the data acquisition system: soil-lining interface shear force Fs, shear displacement δ, soil sample settlement ΔH, seepage flow Q, and seepage path pressure field p(x, t). All data are stored in a unified time step. Specifically, the soil sample settlement is monitored by a second displacement sensor, the seepage flow is measured by an electromagnetic flowmeter at the drainage pipe 16, and the seepage path pressure field is monitored by a pore water pressure sensor.

[0036] More specifically, the soil-lining interface shear force value Fs is detected in real time by a shear force sensor, and the original voltage signal is converted into a physical quantity Fs (unit: kN) by a data acquisition system; the shear displacement is continuously monitored by a first displacement sensor with an accuracy of 0.1% for the horizontal displacement change of the shear box, and the real-time displacement is recorded with the shear start time as the reference ẟ=0; the soil sample settlement is measured by a second displacement sensor, that is, by measuring the front and rear position changes of the top surface of the upper shear box 4 by the second displacement sensor, specifically by the initial distance H between the top surface of the upper shear box 4 and the second displacement sensor. o and the spacing H after deformation t We obtain, and then obtain, the soil thickness compression (i.e., soil sample settlement) ΔH, ΔH = H o -H t The soil sample settlement is cross-validated by the displacement feedback data of the top surface of the upper shear box 4; the seepage flow rate is accurately measured by the electromagnetic flowmeter of the drainage pipeline 16, which measures the drainage volume per unit time (Q=V / Δt), and the spatial pressure distribution of the seepage path pressure field p(x,t) is collected in real time by a micro pore water pressure sensor array (deployed at least 3 measuring points in the soil sample seepage path).

[0037] The data acquisition system adopts a millisecond-level multi-channel synchronization system to synchronously acquire various data monitored by the sensor at a sampling rate of 200Hz, ensuring that the timestamps are completely aligned and forming a five-dimensional coupled dataset [Fs, δ, ΔH, Q, Δp].

[0038] S6. Performance Parameter Calculation The following characteristic curves and evolution parameters are dynamically generated based on real-time acquired data streams: a) Intensity characteristic curve τ-δ; b) Seepage response curve Q- p; c) Deformation evolution curve εv-δ; d) Conductivity curve k eff-γ The calculation formula is as follows: (5) (6) (7) (8) In the formula, τ is the interfacial shear stress, Ac is the soil sample-segment contact area, and ε is the interfacial shear stress. v Let H0 be the initial thickness of the soil sample, and k be the volumetric strain. eff The effective permeability coefficient is given by γ, where γ is the shear strain, Q is the seepage flow rate, L is the seepage path length (i.e., the distance between the two permeable stones), and A is the permeability coefficient. s Where Δp is the cross-sectional area of ​​the seepage flow, and Δp is the seepage pressure difference. The peak value of the interfacial friction coefficient, the residual friction coefficient, the critical shear displacement, and the hydraulic weakening rate were calculated based on the four curves. The calculation formulas are as follows: (9) (10) (11) (12) In the formula, μ p μ is the peak value of the friction coefficient. r δ is the residual friction coefficient. cr η is the critical shear displacement. ω This refers to the hydraulic weakening rate, i.e., the rate at which seepage weakens the friction coefficient. m r / m p The ratio of residual friction coefficient to peak value (dimensionless). The four curves and four values ​​provide a basis for the analysis of seepage-shear coupling performance.

[0039] Specifically, four dynamic curves—the strength characteristic curve (τ-δ), the seepage response curve (Q-δ), and the seepage response curve (Q-δ). p), Deformation evolution curve (ε) v -δ), conduction characteristic curve (k eff-γ —This provides the core basis for coupling performance analysis. Those skilled in the art can make the following judgments based on conventional knowledge: A. Extracting the peak value μ of the interfacial friction coefficient from the τ-δ curve. p With residual value μr (Formulas (9)-(10)) directly assess the shear strength degradation characteristics; B. Identify the critical shear displacement δ using the Qp curve. cr (Formula (11)) predicts the critical point of interface instability when the seepage flow increases sharply; C. Utilizing ε v -δ curve analysis of the compressive effect of volumetric variation on the seepage channel (such as ε caused by shear dilatation) v When the Q value decreases (<0), the stability of the lining against buoyancy is related.

[0040] The determination method in this application breaks through the conventional two-field coupling analysis: Quantification of the transmission weakening effect: via k eff-γ The curve (Formula (8)) captures the effect of shear strain γ on permeability coefficient k in real time. eff The nonlinear attenuation effect, if k eff / k o (k) o If the original permeability coefficient is less than 30%, it is determined that the shear deformation of the tunnel segments has led to a significant deterioration in the sealing function. Hydraulic weakening risk warning: Based on the hydraulic weakening rate η defined for the first time in this application ω When η ω When the value is >0.05 / kPa (Equation (12)), it indicates that the friction coefficient loss rate caused by the unit seepage pressure difference exceeds the critical threshold, directly triggering a strong seepage-shear coupling risk alarm. This parameter, combined with δ cr With k eff-γ Based on the curve characteristics, a closed-loop feedback judgment mechanism of "seepage-induced strength degradation - deformation-accelerated seepage" was constructed, providing an irreplaceable quantitative indicator for tunnel water hazard prevention and control.

[0041] Specifically, step S4 involves, based on real-time volumetric strain εv inversion of soil pore structure changes, linking water pumps to maintain a constant seepage pressure difference, controlling seepage pressure difference fluctuations to be less than or equal to 0.1 kPa / mm, and activating a flexible membrane sealing enhancement mechanism when shear displacement ẟ > 2 mm to ensure boundary leakage Q during seepage-shear coupling. leak <10⁻⁶m 3 / s.

[0042] Although embodiments of the invention have been shown and described, those skilled in the art will be able to make various changes, modifications, substitutions and alterations to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A soil-lining interface constant pressure differential seepage-shear coupling performance testing device, characterized in that: The system includes a main controller, a sensor array for monitoring the stress field distribution, a data acquisition system, a shear box for placing tunnel segment samples (7), and a confining pressure box (2) with a confining pressure cavity (3) inside. The confining pressure cavity (3) is connected to an oil supply line (13) and an oil discharge line (14). The shear box is located inside the confining pressure cavity (3). The bottom of the shear box is slidably connected to the confining pressure box (2). Shear loading devices are provided on the top and opposite sides of the shear box. The top and bottom walls of the shear box are provided with permeable stones (6). The top and bottom of one side of the shear box are connected to a water supply line (15) and a drainage line (16). The water supply line (15) and the drainage line (16) are connected to the opposite sides of the two permeable stones (6). The data acquisition system is connected to the sensor array. The main controller is connected to the data acquisition system and the shear loading device.

2. The soil-lining interface constant pressure difference seepage-shear coupling performance testing device according to claim 1, characterized in that: It also includes a confining pressure / permeability control center (12), wherein the oil supply pipeline (13), water supply pipeline (15), drainage pipeline (16) and oil discharge pipeline (14) are respectively connected to the confining pressure / permeability control center (12) at the ends away from the shear box, and valves (20) are respectively provided on the oil supply pipeline (13), water supply pipeline (15), drainage pipeline (16) and oil discharge pipeline (14), and the confining pressure / permeability control center (12) is respectively connected to the valves (20) and the main controller.

3. The soil-lining interface constant pressure difference seepage-shear coupling performance testing device and method according to claim 2, characterized in that: The confining pressure / permeability control center (12) includes a water tank, an oil tank, a water pump, an oil pump, and a controller. The water supply pipeline (15) and the drainage pipeline (16) are respectively connected to the water tank through a water pump. Electromagnetic flow meters are installed on the drainage pipeline (16) and the water supply pipeline (15). The oil supply pipeline (13) and the oil discharge pipeline (14) are respectively connected to the oil tank through an oil pump. The controller is connected to the main controller, the oil pump, the water pump, the electromagnetic flow meter, and the valve (20).

4. The soil-lining interface constant pressure difference seepage-shear coupling performance testing device according to claim 1, characterized in that: The shearing box includes an upper shearing box (4) and a lower shearing box (5) located at the bottom of the upper shearing box (4). The bottom of the upper shearing box (4) and the top of the lower shearing box (5) are respectively provided with arc grooves (19). After the upper shearing box (4) and the lower shearing box (5) are connected, the arc grooves (19) of the upper and lower shearing boxes (5) are spliced ​​to form a positioning groove (21) for positioning and placing the tunnel segment sample (7).

5. The soil-lining interface constant pressure difference seepage-shear coupling performance testing device according to claim 4, characterized in that: The shear loading device includes an upper shear loading device (9), an upper shear driving device (10), and a lower shear driving device (11). The lower shear driving device (11) and the upper shear driving device (10) are located on opposite sides of the shear box. The upper shear driving device (10) is connected to the side of the upper shear box (4), and the lower shear driving device (11) is connected to the side of the lower shear box (5). The upper shear loading device (9) is connected to the top surface of the upper shear box (4), and the bottom of the lower shear box (5) is slidably connected to the confining pressure box (2). The sliding direction of the shear box is consistent with the driving direction of the upper shear loading device (9) and the lower shear loading device.

6. The soil-lining interface constant pressure difference seepage-shear coupling performance testing device according to claim 1, characterized in that: The sensor array includes a confining pressure sensor, multiple soil pressure sensors, an upper osmotic pressure sensor, a lower osmotic pressure sensor, a shear force sensor, a first displacement sensor, a second displacement sensor, and multiple pore water pressure sensors. The confining pressure sensor is fixed to the wall of the confining pressure cavity (3). Multiple soil pressure sensors are buried in layers inside the soil sample. The upper osmotic pressure sensor is located at the connection between the water supply pipeline (15) and the shear box. The lower osmotic pressure sensor is located at the connection between the drainage pipeline (16) and the shear box. The shear force sensor and the first displacement sensor are located at the bottom of the shear box. The second displacement sensor is located at the top inside the confining pressure cavity (3) and corresponds to the position of the shear box. Multiple pore water pressure sensors are buried in layers inside the soil sample.

7. A method for testing the constant pressure difference seepage-shear coupling performance of the soil-lining interface, implemented based on the constant pressure difference seepage-shear coupling performance testing device for the soil-lining interface as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Set up the test device clipboard Based on the engineering geological conditions, remolded soil is prepared as a soil sample, or field soil samples are taken, and the moisture content and compaction of the soil samples are adjusted to the required state for the test. A flexible film is used to wrap the outer wall of the tunnel segment sample (7) to form a hydraulic transmission boundary and seal both ends of the tunnel segment sample (7); soil samples are layered and filled to the target height (8) on the permeable stone (6) base located at the bottom of the shear box; the tunnel segment sample (7) wrapped with the flexible film is placed in the shear box and the soil samples are filled until completion. S2, Establishment of Initial Stress State Confining pressure oil is injected into the confining pressure chamber (3) through the oil supply pipeline (13) to apply the preset confining pressure, thereby achieving isobaric consolidation of the soil sample in the shear box; at the same time, water is injected into the shear box through the water supply pipeline (15) to apply the hydrostatic pressure reference value p0 to the soil saturation zone and the back cavity of the lining, simulating the steady-state environment of groundwater; confining pressure and hydrostatic pressure are applied until the soil stress field reaches a uniform distribution; The confining pressure σ is collected in real time using a sensor array. conf Monitoring the normal stress σ of each soil layer n Monitoring infiltration pressure p i and drainage pressure p o To determine whether the soil stress field is uniformly distributed, the condition for determining whether the soil stress field is uniformly distributed is: the normal stress σ in each layer of the soil... n With confining pressure σ conf Deviation ≤ 5%, and satisfy p i =p o =p0; S3, Constant water pressure differential loading By adjusting the injection pressure and drainage pressure of the water supply pipeline (15) and drainage pipeline (16), the infiltration pressure and drainage pressure are adjusted, thereby establishing a target hydraulic gradient between the infiltration boundary and the drainage boundary, and maintaining the fluctuation range of the osmotic pressure difference Δp <1kPa, thus achieving the constancy of the hydraulic gradient during the seepage process; the formula for calculating the osmotic pressure difference is as follows: （1） S4, seepage-shear coupling loading Start the shear loading device located on both sides of the shear box. Under the condition of maintaining a constant osmotic pressure difference Δp, apply a horizontal shear load along the contact interface of the soil sample-tunnel segment sample (7). Monitor the shear displacement and the shear force value of the soil-lining interface through the sensor array to achieve the spatiotemporal coupling effect of the seepage field and the stress field. Specifically, the action of the shear loading device is controlled by the displacement rate control equation, while ensuring that the seepage field satisfies Darcy's law and that the mechanical loading and seepage action interact continuously and simultaneously. The loading process must satisfy the condition of complete temporal overlap. The displacement rate control equation is: （2） In the formula, v s δ is the shear displacement rate, t is the shear displacement, and t is the shear loading time. The formula for determining whether the loading process satisfies the condition of complete temporal overlap is: （3） In the formula, t s t is the movement time of the shearing component. Δp The duration of the seepage effect; While applying shear load, adjust the infiltration pressure and drainage pressure to control fluctuations in osmotic pressure differential caused by displacement: （4） In the formula, Δp is the osmotic pressure difference, δ is the shear displacement, and ε is the osmotic pressure difference. δ This is the error threshold; S5. Synchronous Monitoring and Data Recording The following data monitored by the sensor array are acquired in real time through the data acquisition system: soil-lining interface shear force Fs, shear displacement δ, soil sample settlement ΔH, seepage flow Q, and seepage path pressure field p(x, t). All data are stored in a unified time step. S6. Performance Parameter Calculation The following characteristic curves and evolution parameters are dynamically generated based on real-time acquired data streams: a) Intensity characteristic curve τ-δ; b) Seepage response curve Q- p; c) Deformation evolution curve ε v -δ;d) Conductivity curve k eff-γ The calculation formula is as follows: （5） （6） （7） （8） In the formula, τ is the interfacial shear stress, Ac is the soil sample-segment contact area, and ε is the interfacial shear stress. v Let H0 be the initial thickness of the soil sample, and k be the volumetric strain. eff The effective permeability coefficient is given by γ, shear strain is given by Q, seepage flow rate is given by L, seepage path length is given by the distance between the two permeable stones, As is given by the seepage cross-sectional area, and Δp is given by the seepage pressure difference. The peak value of the interfacial friction coefficient, the residual friction coefficient, the critical shear displacement, and the hydraulic weakening rate were calculated based on the four curves. The calculation formulas are as follows: （9） （10） （11） （12） In the formula, μ p μ is the peak value of the friction coefficient. r δ is the residual friction coefficient. cr η is the critical shear displacement. ω This refers to the hydraulic weakening rate, i.e., the rate at which seepage weakens the friction coefficient. μ r / μ p The ratio of residual friction coefficient to peak value; The four curves and four values ​​provide a basis for the analysis of seepage-shear coupling performance.

8. The method for testing the constant pressure difference seepage-shear coupling performance of the soil-lining interface according to claim 7, characterized in that: Specifically, step S2 involves monitoring the confining pressure using a confining pressure sensor, the soil normal stress using a soil pressure sensor, and the infiltration pressure using an upper osmotic pressure sensor and a drainage pressure using a lower osmotic pressure sensor. Specifically, step S3 involves adjusting the infiltration pressure and drainage pressure by changing the power of the water pumps connected to the water supply pipeline (15) and drainage pipeline (16), respectively. Specifically, step S4 involves monitoring the shear displacement using a first displacement sensor and monitoring the shear force value at the soil-lining interface using a shear force sensor. Specifically, step S5 involves monitoring the soil sample settlement using a second displacement sensor, measuring the seepage flow rate using an electromagnetic flowmeter at the drainage pipe (16), and monitoring the seepage path pressure field using a pore water pressure sensor.

9. The method for testing the constant pressure difference seepage-shear coupling performance of the soil-lining interface according to claim 8, characterized in that: Specifically, step S4 involves, based on real-time volumetric strain ε v The changes in soil pore structure are inverted, and the water pump is linked to maintain a constant seepage pressure difference, controlling the seepage pressure difference fluctuation to be less than or equal to 0.1 kPa / mm. When the shear displacement δ>2 mm, the flexible membrane sealing reinforcement mechanism is activated to ensure the boundary leakage Q during the seepage-shear coupling process. leak <10⁻⁶ m 3 / s.

10. The method for testing the constant pressure difference seepage-shear coupling performance of the soil-lining interface according to claim 7, characterized in that, Based on the curve obtained in step S6, a two-field coupling analysis is performed, including the quantification of the conduction weakening effect: through k eff-γ Real-time curve capture of shear strain γ and its effect on permeability coefficient k eff The nonlinear attenuation effect, if k eff / k o If the percentage is less than 30%, it is determined that the tunnel segment shear deformation has led to a deterioration in the sealing function, where k o The original permeability coefficient; Hydraulic weakening risk warning: When the hydraulic weakening rate η ω When the pressure difference is greater than 0.05 kPa, it indicates that the friction coefficient loss rate caused by the unit seepage pressure difference exceeds the critical threshold, directly triggering a strong seepage-shear coupling risk alarm.

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