A test system and method for localized grouting and water shut-off in water-rich sandy gravel formations

Abstract

This invention discloses a localized grouting and water-blocking test system and method for highly water-rich sandy gravel formations, relating to the technical field of grouting simulation systems. The test system includes: a sandy gravel formation simulation module comprising multiple vertically placed model boxes of different diameters, each filled with sandy gravel media; a localized grouting module comprising a grout storage tank, a grout delivery pipe, ball bearings, and a retractable grouting sleeve connected in sequence; a constant-temperature water supply module to create a highly water-rich environment for the sandy gravel media; a data acquisition module including pressure sensors and flow sensors; and a data analysis module electrically connected to the data acquisition module, including pressure analysis and flow analysis modules. The sandy gravel formation simulation system enables effective simulation of formations at different scales. Furthermore, during numerical simulation, considering the dilution of grout concentration due to the water-rich environment, a grout density field is introduced to comprehensively analyze the grout penetration and fracturing processes during grouting.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grouting simulation, in particular to a system and method for localized grouting and water plugging test in extremely water-rich sandy pebble stratum. BACKGROUND

[0002] The extremely water-rich sandy pebble stratum is a common stratum in tunnel construction, which has the characteristics of large porosity, high permeability, low strength, high water content, and poor self-stability, and is prone to induce water gushing and sand collapse disasters in the construction process, which seriously threatens the safety of tunnel construction. Grouting is one of the important technical means to control the disaster of sand collapse. Grouting in water-rich sand layer can improve the strength and impermeability of the sand layer, thereby achieving the purpose of reinforcement, water stopping, and seepage prevention. However, due to the loose structure and large porosity of the sandy pebble stratum, the diffusion law of the grout in the stratum is complex, which can easily cause excessive concentration or insufficient diffusion of the grout, making it difficult to form effective plugging or reinforcement, thereby affecting the grouting effect. Therefore, a more accurate and scientific grouting test system is needed to deeply study the diffusion law of the grout in the extremely water-rich sandy pebble stratum and optimize the grouting parameters in order to achieve better grouting effect.

[0003] For the grouting test system in water-rich sandy pebble stratum, the current model test system usually adopts fixed grouting port and fixed diameter model design, which cannot flexibly adjust the grouting position and the diameter change of the grouted medium. In addition, due to the influence of seepage effect and water-rich environment, cement particles are deposited at the grouting port before reaching the grouting position, and the grout is diluted, which makes it difficult to effectively plug and reinforce the grouted medium. Therefore, it is necessary to improve the existing model test system in order to simulate the diffusion behavior of the grout in the actual grouting process. In addition, the existing grouting simulation method for extremely water-rich sandy pebble stratum does not fully consider the influence of water-rich environment on the dilution of grout concentration, and it is difficult to effectively predict the grout diffusion range, reinforcement and water plugging effect in the grouting process. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a system and method for localized grouting and water plugging test in extremely water-rich sandy pebble stratum, which realizes effective simulation of different scale strata through a sandy pebble stratum simulation system. At the same time, when numerical simulation is carried out, the dilution of grout concentration due to the influence of water-rich environment is considered, and the grout density field is introduced to realize comprehensive analysis of the process of grout penetration and splitting in the grouting process.

[0005] The technical scheme of the present application is as follows:

[0006] In the first aspect of the present application, a system for localized grouting and water plugging test in extremely water-rich sandy pebble stratum is provided, comprising:

[0007] The sand pebble stratum simulation module comprises a plurality of model boxes with different diameters arranged vertically, and the model boxes are filled with sand pebble medium.

[0008] The localized grouting module comprises a grout storage tank, a grout conveying pipeline, a ball and a telescopic grouting casing arranged in sequence, and the telescopic grouting casing is arranged at the bottom of the model box.

[0009] The constant-temperature water supply module comprises a water tank and a water conveying pipeline, and the water tank is connected with the model box through the water conveying pipeline to create a water-rich environment for the sand pebble medium.

[0010] The data acquisition module comprises a pressure sensor and a flow sensor, wherein the pressure sensor is used for monitoring the grout pressure, the sand pebble medium soil pressure and the pore water pressure, and the flow sensor is used for measuring the grouting amount and the water discharge amount.

[0011] The data analysis module is electrically connected with the data acquisition module and comprises a pressure analysis module and a flow analysis module, wherein the pressure analysis module is used for analyzing the grout phase fraction field, the velocity field and the pressure field, and the flow analysis module is used for analyzing the grouting plugging efficiency.

[0012] In some embodiments of the present application, the diameters of the plurality of model boxes gradually decrease from top to bottom, the adjacent model boxes are connected in a sealed manner through flanges and bolts, and the top of the uppermost model box and the bottom of the lowermost model box are blocked through upper and lower baffles, respectively.

[0013] In some embodiments of the present application, a water outlet is arranged on the upper baffle, the water outlet is connected with the water conveying pipeline, and a layer of water-permeable stone is arranged at the position of the water outlet in the uppermost model box.

[0014] In some embodiments of the present application, the telescopic grouting casing comprises a plurality of casings with diameters gradually increasing from inside to outside, and each casing is provided with a pair of buckles and a plurality of clamping grooves, the buckles and the clamping grooves are clamped according to different lengths to adjust the length of the telescopic grouting casing.

[0015] In some embodiments of the present application, the outermost casing of the telescopic grouting casing is provided with a ball, the ball is arranged in the flange, and the ball can roll in the flange to drive the rotation of the telescopic grouting casing.

[0016] In some embodiments of the present application, a constant-temperature heater is arranged in the water tank, the constant-temperature heater starts heating when the water temperature is lower than the set temperature, and the constant-temperature heater stops heating when the water temperature reaches the set temperature.

[0017] In some embodiments of the present application, the pressure sensor comprises a pressure gauge, a soil pressure gauge and a pore water pressure gauge; the pressure gauge is arranged on the slurry conveying pipeline near the grouting port; the soil pressure gauge and the pore water pressure gauge are arranged in layers as the sand and gravel medium is filled; and the flow sensor comprises a flow meter arranged on the slurry conveying pipeline and the water outlet pipeline.

[0018] In the second aspect of the present application, a localized grouting and water plugging test method for water-rich sand and gravel stratum is provided, comprising:

[0019] Water is injected into the model box, and when the water outlet pipeline starts to discharge water, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium;

[0020] The cement-sodium silicate double-liquid slurry is injected into the model box at a set ratio and a set speed, and when the water in the water outlet pipeline stops flowing out or discharging the slurry, the grouting is stopped;

[0021] The data acquisition module records the data changes of each sensor in the grouting process in real time to obtain the variation rules of the grouting pressure, the soil pressure, the pore water pressure, the flow at the slurry and water outlet pipeline with time, and calculates the water plugging efficiency of the test;

[0022] After the grouting is completed, the model box is opened after the slurry is initially set, the sand and gravel and the stone body of the slurry inside the model box are taken out, and standard curing is performed on them. After the curing is completed, the diffusion range is checked, the strength of the stone body is determined, and the permeability is measured.

[0023] In some embodiments of the present application, a sand and gravel medium calculation model is constructed, the slurry state is initialized, a slurry density equation, a momentum equation and a continuity equation are constructed based on the data obtained in the test, the slurry concentration field, the pressure field and the velocity field are obtained by solving the above equations, and thus the numerical simulation of the slurry diffusion range is realized.

[0024] In some embodiments of the present application, the numerical simulation process specifically comprises:

[0025] A slurry density equation is constructed, and the slurry density field at the current time step is obtained by solving according to the initial boundary value condition;

[0026] Based on the initialized slurry velocity and pressure, the PISO cycle iteration is performed by solving the momentum equation and the continuity equation to obtain the slurry velocity field and the pressure field at the current time step;

[0027] The time when the sand and gravel medium is split is determined according to the data of the soil pressure gauge. If the current time step has not reached the time required for splitting, the above steps are repeated for iterative calculation. If the splitting time has been reached, the porosity is updated, and other conditions remain unchanged, and the iteration is continued until the grouting is completed.

[0028] After the simulation ends, the slurry density field obtained by numerical simulation is used to depict the diffusion process of the slurry, and the diffusion progress of the slurry is compared with the pore water pressure depicted by the simulation, so as to verify the accuracy of the simulation result.

[0029] The one or more technical solutions of the present application have the following beneficial effects:

[0030] (1) The sand and pebble stratum simulation system of the present application can effectively simulate different scale strata, introduces a variable-diameter injected medium structure, can simulate the change of the diameter of the filled karst pipeline under different geological conditions, and creates a constant-temperature water-rich environment for the stratum through the constant-temperature water supply module; the localized grouting module can freely adjust the grouting pipe opening, and realizes constant-speed grouting for different strata; finally, the data acquisition and analysis module is used to obtain various data in the grouting process, the slurry density field is introduced, the fluid mechanics equation is combined, and the slurry density field, velocity field and pressure field are obtained by numerical calculation, so as to analyze the diffusion form of the slurry and the water plugging effect.

[0031] (2) The present application uses a telescopic sleeve as a grouting device, and the grouting port is fixed on a rotatable ball, which allows it to rotate 360 degrees in the horizontal direction. The grouting pipe is composed of multiple telescopic sleeves that can move vertically. Through this device, the grouting port can be flexibly positioned and adjusted in the horizontal and vertical directions, and the grouting position can be flexibly adjusted according to the test requirements to realize directional grouting operation in a specific area.

[0032] (3) The present application provides a grouting numerical simulation method for extremely water-rich sand and pebble medium considering the dilution of slurry concentration, introduces the slurry density field to represent the change of slurry concentration, and solves the slurry water density field, velocity field and pressure field by combining the data of the micro soil pressure gauge and the pore water pressure gauge placed in the model with the fluid mechanics equation, to analyze the slurry penetration and diffusion and splitting process during grouting. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Figure is a water-rich sand and pebble stratum localized grouting and water plugging test system of the present application;

[0034] Figure 2 Figure is a structure schematic diagram of the sand and pebble stratum simulation module of the present application;

[0035] Figure 3 Figure is a structure schematic diagram of the telescopic grouting sleeve of the localized grouting module;

[0036] Figure 4 Figure is a flow chart of the water-rich sand and pebble stratum localized grouting and water plugging test method of the present application.

[0037] In the figure: 1, sand and pebble stratum simulation module; 2, localized grouting module; 3, constant temperature water supply module; 4, waste liquid collection module; 5, data acquisition module; 6, model box; 7, baffle; 8, grout conveying pipeline; 9, water outlet pipeline; 10, water-permeable stone; 11, water conveying pipeline; 12, ball; 13, telescopic grouting sleeve; 14, buckle; 15, clamping groove; 16, earth pressure cell; 17, pore water pressure meter. DETAILED DESCRIPTION

[0038] The application will be further described below in combination with the drawings and examples.

[0039] Example 1

[0040] In a typical embodiment of the application, a localized grouting and water plugging test system for water-rich sand and pebble stratum is provided, as shown in Figure 1 and Figure 2 , comprising:

[0041] The sand and pebble stratum simulation module 1 comprises a plurality of model boxes 6 of different diameters arranged vertically, and the model boxes 6 are filled with sand and pebble medium;

[0042] The localized grouting module 2 comprises a grout storage tank, a grout conveying pipeline 8 and a telescopic grouting sleeve 13 connected in sequence, and the telescopic grouting sleeve 13 is installed at the bottom of the model box 6;

[0043] The constant temperature water supply module 3 comprises a water tank and a water conveying pipeline 11, and the water tank is connected to the model box 6 through the water conveying pipeline 11 to create a water-rich environment for the sand and pebble medium;

[0044] The data acquisition module 5 comprises a pressure sensor and a flow sensor, the pressure sensor is used to monitor the grout pressure, the earth pressure of the sand and pebble medium and the pore water pressure; and the flow sensor is used to measure the grouting amount and the water outlet amount;

[0045] The data analysis module is electrically connected to the data acquisition module 5, comprising a pressure analysis module and a flow analysis module, the pressure analysis module is used to analyze the grout phase fraction field, velocity field and pressure field; and the flow analysis module is used to analyze the grouting plugging efficiency.

[0046] In the embodiment, the diameters of the plurality of model boxes 6 gradually decrease from top to bottom, the adjacent model boxes 6 are connected in airtight manner by flanges and bolts, the top of the uppermost model box and the bottom of the lowermost model box are blocked by the baffles 7, that is, the top of the uppermost model box is blocked by the upper baffle and the bottom of the lowermost model box is blocked by the lower baffle. A through hole is arranged at the coaxial position of the upper baffle and the lower baffle, and a slurry feeding pipeline 8 and a water outlet pipeline 9 are connected to the through hole. The slurry feeding pipeline 8 is connected to the localized grouting module 2, and the water outlet pipeline 9 is connected to the waste liquid collecting module 4, so as to realize the inflow and outflow of the slurry. The through hole on the upper baffle serves as a water outlet, and a layer of water-permeable stone 10 is arranged at the position of the uppermost model box corresponding to the water outlet, which can prevent the sand and gravel medium from flowing out under the action of grouting pressure and blocking the slurry outlet. A through hole is arranged at the lower position of the side wall of the model box 6, and a water feeding pipeline 11 is connected to the through hole, so as to facilitate the water flowing into the sand and gravel medium in the model box and creating a water-rich environment for the sand and gravel medium.

[0047] As shown in Figure 1 and Figure 3 , the slurry storage tanks of the localized grouting module 2 are provided with two, respectively storing cement and water glass, and a grouting motor is arranged on each of the two slurry storage tanks. The grouting motor drives the piston to compress the air in the slurry storage tank, so that the slurry in the slurry storage tank flows out at a constant speed along the slurry feeding pipeline, and finally is injected into the sand and gravel medium in the model box through the telescopic grouting sleeve 13.

[0048] Further, the telescopic grouting sleeve 13 includes a plurality of sleeves with diameters gradually increasing from inside to outside. Each sleeve is provided with a pair of buckles 14 and a plurality of clamping grooves 15. The buckles 14 and the clamping grooves 15 are matched according to different lengths to adjust the length of the telescopic grouting sleeve 13. Further, the outermost sleeve of the telescopic grouting sleeve 13 is provided with a ball 12. The ball 12 is installed in the flange and can roll in the flange to drive the telescopic grouting sleeve 13 to rotate.

[0049] Specifically, a spherical groove is opened at a position above the horizontal center line of the flange. The size of the groove is slightly larger than the ball 12. The groove is used to place the ball 12. Lubricating oil is applied between the ball 12 and the groove, so that the ball can roll 360° on the horizontal plane, and at the same time, the sand and gravel medium in the model box is prevented from extruding from the gap. A through hole is drilled through the axis of the ball. The diameter of the through hole is the same as the diameter of the largest sleeve and penetrates the entire ball. The through hole is used to place the outermost sleeve of the telescopic grouting sleeve 13. The telescopic grouting sleeve 13 includes pipelines with different diameters. The multi-stage sleeves gradually increase in diameter from inside to outside. Each sleeve is provided with a pair of buckles 14 and a plurality of clamping grooves 15. The buckles and the clamping grooves can be matched according to different lengths, so as to realize multi-stage adjustment of the length of the grouting pipe.

[0050] In the embodiment, the water tank is provided with water level scale, and a constant temperature heater is arranged in the water tank to set the heating temperature. When the water temperature is lower than the set temperature, the constant temperature heater starts heating. When the water temperature reaches the set temperature, the constant temperature heater stops heating, so as to realize dynamic control of the water temperature. The water tank is connected to the through hole in the side wall of the model box 6 through the water conveying pipeline 11, and the water pump is arranged in the water tank to pump the constant temperature water in the water tank to the model box, so as to create a very water-rich environment for the sand and gravel stratum.

[0051] In the embodiment, the pressure sensor includes a pressure gauge, a soil pressure meter 16 and a pore water pressure meter 17. The pressure gauge is arranged at the position of the slurry conveying pipeline 8 close to the grouting port to measure the slurry pressure at the grouting port. The soil pressure meter 16 and the pore water pressure meter 17 are buried in layers when the sand and gravel medium is filled, and each model box is arranged with one layer in the middle. The soil pressure meter and the pore water pressure meter are arranged at intervals to monitor the changes of the soil pressure and the pore water pressure, as shown in FIG. 3. Figure 2 The flow sensor includes flow meters arranged on the slurry conveying pipeline 8 and the water outlet pipeline 9 to measure the changes of the grouting amount and the water outlet amount respectively, so as to facilitate the evaluation of the water plugging effect. The data of the above-mentioned sensors can be transmitted to the data acquisition instrument in real time, which is convenient for subsequent data analysis.

[0052] The data analysis system includes a pressure analysis module and a flow analysis module. The pressure analysis module analyzes the changes of the soil pressure to determine whether the soil splitting is caused by grouting. If the soil pressure shows a trend of growth and sudden decline, it indicates that the soil has experienced a seepage-splitting process. Combined with the three equations of fluid mechanics, the slurry phase fraction field, velocity field and pressure field are solved. When the slurry diffuses to the pore water pressure meter buried point, the pore water pressure will suddenly increase. The changes of the pore water pressure are analyzed to determine the diffusion range of the slurry, which is verified and analyzed by the numerical simulation results. The flow analysis module analyzes the changes of the water amount in the water outlet pipeline before and after grouting to analyze the grouting plugging efficiency.

[0053] The use method of the very water-rich sand and gravel stratum localized grouting and water plugging test system provided in the embodiment is as follows:

[0054] Step 1: Take the dry density of sand and gravel as the control index of the filled soil, and fill the sand and gravel into the model box in layers and compact them in layers to reach the dry density of the original soil. When the sand and gravel is filled to the middle of each model box, the soil pressure meter and the pore water pressure meter are buried, and the pressure sensor is connected to the data acquisition instrument.

[0055] Step 2: When the medium is filled to the position close to the grouting port, adjust the ball and the multi-stage sleeve to move the grouting port to the set position, continue to fill the sand and gravel to the position where the filling height is level with the grouting port, place a layer of sand screen at the grouting port, and then continue to fill and compact, and fix the grouting pipe in the model box.

[0056] Step 3: After the sand and gravel filling is completed, a layer of water-permeable stone is covered, and the flanges between the model boxes are fixed by bolting.

[0057] Step 4: After the pipeline is connected, when the water in the water tank reaches the set temperature, the water pump is turned on to inject water into the sand and gravel medium. When the water outlet pipeline starts to discharge water, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium.

[0058] Step 5: Set the proportion and injection speed of the cement-silicate double liquid slurry, turn on the double liquid grouting motor and valve, and inject the double liquid slurry into the model box according to the set proportion and speed. When the water in the water outlet pipeline stops flowing or discharging slurry, stop grouting.

[0059] Step 6: The data acquisition system records the data changes of each sensor in real time during the grouting process to obtain the variation rules of grouting pressure, soil pressure, pore water pressure, slurry and water flow at the water outlet pipeline with time, and calculate the water plugging efficiency of this test.

[0060] Step 7: After grouting is completed, after the slurry is initially set, the model box is opened, the sand and gravel and the stone body of the slurry inside the model box are taken out, and standard curing is performed. After curing is completed, the diffusion range is checked, the strength of the stone body is measured, and the permeability is determined.

[0061] Example 2

[0062] In a typical embodiment of the present application, a method for localized grouting and water plugging in a water-rich sand and gravel formation is provided, as shown in Figure 4 , comprising:

[0063] Water is injected into the model box, and when the water outlet pipeline starts to discharge water, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium;

[0064] The cement-silicate double liquid slurry is injected into the model box according to the set proportion and speed. When the water in the water outlet pipeline stops flowing or discharging slurry, stop grouting;

[0065] The data acquisition module records the data changes of each sensor in real time during the grouting process to obtain the variation rules of grouting pressure, soil pressure, pore water pressure, slurry and water flow at the water outlet pipeline with time, and calculate the water plugging efficiency of the test;

[0066] After grouting is completed, after the slurry is initially set, the model box is opened, the sand and gravel and the stone body of the slurry inside the model box are taken out, and standard curing is performed. After curing is completed, the diffusion range is checked, the strength of the stone body is measured, and the permeability is determined.

[0067] Further, a sand pebble medium calculation model is constructed, a slurry state is initialized, a slurry density equation, a momentum equation and a continuity equation are constructed based on the data obtained in the test, the slurry concentration field, the pressure field and the velocity field are obtained by solving the above equations, so that the numerical simulation of the slurry diffusion range is realized.

[0068] The numerical simulation process specifically includes:

[0069] 1. Construct a sand pebble medium calculation model, initialize the porosity of the sand pebble medium according to the porosity obtained in the test process, discretize by constructing a river basin grid, and initialize the slurry density, velocity, pressure and viscosity field according to the slurry ratio;

[0070] 2. Construct a slurry density equation, and solve the slurry density field at the current time step according to the initial boundary value condition;

[0071] The slurry density equation is:

[0072]

[0073] Wherein, ρ is the slurry density, t is the time, v is the slurry velocity, D is the slurry diffusion coefficient, S = Qρ0 is the source term, Q is the grouting speed, and ρ0 is the initial slurry density;

[0074] Initial condition:

[0075] ρ(x, y, z, 0) = 0

[0076] Boundary condition:

[0077] ρ(x0, y0, z0, t) = ρ0

[0078] ρ(x1, y1, z1, t) = 0

[0079] Wherein, x0, y0, z0 are the grouting port positions, and x1, y1, z1 are the grouting port positions.

[0080] 3. Based on the initialized slurry velocity and pressure, the slurry velocity field and pressure field at the current time step are obtained by solving the momentum equation and the continuity equation through the PISO cycle iteration;

[0081] The momentum equation is:

[0082]

[0083] Wherein, φ is the porosity of the sand pebble medium, ρ is the slurry density, t is the time, v is the slurry velocity, p is the slurry pressure, g is the gravity vector, and μ is the viscosity.

[0084] The continuity equation is:

[0085]

[0086] where v is the velocity.

[0087] 4. Determine the time of splitting of the sand pebble medium according to the data of the earth pressure meter. If the current time step does not reach the time required for splitting, repeat the above steps for iterative calculation. If the splitting time has been reached, update the porosity φ'=1, and other parameters remain unchanged, and continue to iterate until the grouting end time.

[0088] 5. After the simulation is completed, the diffusion process of the slurry is depicted through the slurry density field of the current time step, and the slurry diffusion progress depicted by the pore water pressure is compared. If they are consistent, the precise simulation of the slurry diffusion form is achieved, and the feasibility of the test device is verified.

[0089] The above describes the specific embodiments of the present application in combination with the drawings, but is not a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications or variations made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A system for localized grouting and water plugging test in a very water-rich sandy cobble stratum, characterized in that, The sand and pebble stratum simulation module comprises a plurality of model boxes of different diameters arranged vertically, and the model boxes are filled with sand and pebble medium. The localized grouting module comprises a grout storage tank, a grout conveying pipeline, a ball and a telescopic grouting casing connected in sequence, and the telescopic grouting casing is installed at the bottom of the model box. The constant-temperature water supply module comprises a water tank and a water conveying pipeline, and the water tank is connected with the model box through the water conveying pipeline to create an extremely water-rich environment for the sand and pebble medium. The data acquisition module comprises a pressure sensor and a flow sensor, the pressure sensor is used for monitoring the grout pressure, the soil pressure and the pore water pressure of the sand and pebble medium, and the flow sensor is used for measuring the grouting amount and the water outflow amount. The data analysis module is electrically connected with the data acquisition module and comprises a pressure analysis module and a flow analysis module, the pressure analysis module is used for analyzing the grout phase fraction field, the velocity field and the pressure field, and the flow analysis module is used for analyzing the grouting plugging efficiency. The diameters of the plurality of model boxes gradually decrease from top to bottom, the adjacent model boxes are connected in a sealed manner through flanges and bolts, the top of the uppermost model box and the bottom of the lowermost model box are blocked through upper and lower baffles respectively.

2. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 1, characterized in that, The upper baffle is provided with a water outlet connected with the water conveying pipeline, and a layer of water-permeable stone is arranged at the position of the water outlet in the uppermost model box.

3. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 2, characterized in that, The telescopic grouting casing comprises a plurality of casings with diameters gradually increasing from inside to outside, each casing is provided with a pair of buckles and a plurality of clamping grooves, the buckles and the clamping grooves are matched according to different lengths to adjust the length of the telescopic grouting casing.

4. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 1, characterized in that, The outermost casing of the telescopic grouting casing is provided with a ball, the ball is installed in the flange, and the ball can roll in the flange to drive the telescopic grouting casing to rotate.

5. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 4, characterized in that, A constant-temperature heater is arranged in the water tank, when the water temperature is lower than the set temperature, the constant-temperature heater starts heating, and when the water temperature reaches the set temperature, the constant-temperature heater stops heating.

6. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 1, characterized in that, The pressure sensor comprises a pressure gauge, a soil pressure gauge and a pore water pressure gauge, the pressure gauge is arranged at the position of the grouting port of the grout conveying pipeline, and the soil pressure gauge and the pore water pressure gauge are buried in layers when the sand and pebble medium is filled.

7. The extremely water-rich sandy cobble stratum localized grouting and water plugging test system according to claim 1, characterized in that, The method comprises the following steps:

8. A method for localized grouting and water plugging test in a water-rich sandy cobble stratum, using the test system according to any one of claims 1-7, characterized in that, Water is injected into the model box, when the water outlet pipeline starts to discharge water, the water level in the water tank is read to calculate the initial porosity of the sand and pebble medium; Cement-silicate double-liquid slurry is injected into the model box at a set ratio and a set speed, and the grouting is stopped when the water in the water outlet pipeline stops flowing out or the slurry is discharged; The data acquisition module records the data changes of each sensor in the grouting process in real time to obtain the change rules of the grouting pressure, the soil pressure, the pore water pressure, the slurry and the flow at the water outlet pipeline with time, and the water plugging efficiency of the test is calculated; After the grouting is completed, the model box is opened after the slurry is initially cured, the sand and pebble and the stone body of the slurry in the model box are taken out, and the stone body is standardly maintained, and the diffusion range, the strength and the permeability of the stone body are checked after the maintenance is completed. ​ 9. The method for localized grouting and water plugging test of extremely water-rich sandy cobble stratum according to claim 8, characterized in that, A sand pebble medium calculation model is constructed, a slurry state is initialized, a slurry density equation, a momentum equation and a continuity equation are constructed based on the data obtained in the test, the slurry concentration field, the pressure field and the velocity field are obtained by solving the above equations, and thus the numerical simulation of the slurry diffusion range is realized.

10. The method for localized grouting and water plugging test of extremely water-rich sandy cobble stratum according to claim 8, characterized in that, The numerical simulation process specifically includes: A slurry density equation is constructed, and the slurry density field at the current time step is obtained by solving the initial boundary value condition; Based on the initialized slurry velocity and pressure, the slurry velocity field and the pressure field at the current time step are obtained by solving the momentum equation and the continuity equation through PISO cycle iteration; The time when the sand pebble medium is split is determined according to the data of the soil pressure gauge, if the current time step has not reached the time required for splitting, the above steps are repeated for iterative calculation, if the splitting time has been reached, the porosity φ' is updated to 1, and other parameters remain unchanged, and the iteration is continued until the grouting end time; After the simulation is completed, the diffusion process of the slurry is depicted by the slurry density field obtained by numerical simulation, and the diffusion progress of the slurry is depicted by the pore water pressure obtained by the test simulation, and the accuracy of the test simulation result is verified.

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