Localized grouting and water plugging test system and method for extremely water-rich sandy gravel stratum

Abstract

The invention discloses an extremely water-rich sandy gravel stratum localized grouting and water plugging test system and method, and relates to the technical field of grouting simulation systems.The test system comprises a sandy gravel stratum simulation module which comprises a plurality of vertically-arranged model boxes with different diameters, and the model boxes are filled with sandy gravel media; the localized grouting module comprises a slurry storage tank, a slurry conveying pipeline, a ball and a telescopic grouting sleeve which are connected in sequence; the constant-temperature water supply module is used for creating an extremely water-rich environment for the sandy gravel medium; the data acquisition module comprises a pressure sensor and a flow sensor; the data analysis module is electrically connected with the data acquisition module and comprises a pressure analysis module and a flow analysis module; effective simulation of stratums with different scales is realized through the sandy gravel stratum simulation system, and meanwhile, during numerical simulation, the slurry concentration is diluted due to the influence of a water-rich environment, and a slurry density field is introduced, so that the processes of slurry permeation and splitting in the grouting process are comprehensively analyzed.

Description

Technical Field

[0001] The invention relates to the technical field of grouting simulation, and in particular to a localized grouting and water blocking test system and method for extremely water-rich sand and gravel formations. Background Art

[0002] The extremely water-rich sand and gravel stratum is a common stratum in tunnel construction. This stratum has the characteristics of large porosity, high permeability, low strength, high water content, and poor self-stabilization ability. It is very easy to induce water gushing and sand bursting disasters during construction, which seriously threatens the safe construction of tunnels. Grouting is one of the important technical means to control sand bursting and landslide disasters. Grouting in the water-rich sand layer can improve the strength and impermeability of the sand layer, thereby achieving the purpose of reinforcement, water stopping, and anti-seepage. However, due to the loose structure and large porosity of the sand and gravel stratum, the diffusion law of the slurry in the stratum is complex, which easily causes excessive concentration or insufficient diffusion of the slurry, making it difficult to form an effective plugging or reinforcement, thereby affecting the grouting effect. To this end, a more accurate and scientific grouting test system is needed to deeply study the diffusion law of the slurry in the extremely water-rich sand and gravel stratum and optimize the grouting parameters to achieve better grouting effects.

[0003] For the grouting test system of water-rich sand and gravel formations, the current model test system usually adopts a model design with a fixed grouting port and a fixed diameter, which cannot flexibly adjust the grouting position and the diameter change of the injected medium. Secondly, due to the infiltration effect and the influence of the water-rich environment, cement particles are deposited at the grouting port before reaching the grouting position, and the slurry is diluted, making it difficult to effectively plug and reinforce the injected medium. Therefore, it is urgent to improve the existing model test system in order to simulate the diffusion behavior of the slurry during the actual grouting process. In addition, the existing grouting simulation method for extremely water-rich sand and gravel formations does not fully consider the influence of the water-rich environment on the dilution of the slurry concentration, and it is difficult to effectively predict the slurry diffusion range, reinforcement and water plugging effects during the grouting process. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a localized grouting and water plugging test system and method for extremely water-rich sand and gravel formations. The sand and gravel formation simulation system is used to effectively simulate formations of different scales. At the same time, when performing numerical simulation, the slurry concentration is diluted by the water-rich environment, and a slurry density field is introduced to comprehensively analyze the slurry penetration and splitting process during the grouting process.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect of the present invention, a localized grouting and water blocking test system for extremely water-rich sand and gravel formations is provided, comprising:

[0007] The sand-pebble formation simulation module comprises a plurality of model boxes of different diameters placed vertically, wherein the model boxes are filled with sand-pebble media;

[0008] A localized grouting module, comprising a grout storage tank, a grout delivery pipeline, a ball bearing and a retractable grouting sleeve connected in sequence, wherein the retractable grouting sleeve is installed at the bottom of the model box;

[0009] A constant temperature water supply module, comprising a water tank and a water pipeline, wherein the water tank is connected to the model box through the water pipeline to create a water-rich environment for the sand and gravel medium;

[0010] The data acquisition module includes a pressure sensor and a flow sensor. The pressure sensor is used to monitor the slurry pressure, the soil pressure of the sand and gravel medium, and the pore water pressure; the flow sensor is used to measure the grouting volume and the water output;

[0011] The data analysis module is electrically connected to the data acquisition module and includes a pressure analysis module and a flow analysis module. The pressure analysis module is used to analyze and obtain the slurry phase fraction field, velocity field and pressure field; the flow analysis module is used to analyze the grouting plugging efficiency.

[0012] In some embodiments of the present invention, the diameters of the multiple model boxes gradually decrease from top to bottom, adjacent model boxes are tightly connected by flanges and bolts, and the top of the topmost model box and the bottom of the bottommost model box are sealed by upper and lower baffles respectively.

[0013] In some embodiments of the present invention, a water outlet is provided on the upper baffle plate, the water outlet is connected to a water pipeline, and a layer of permeable stone is provided at the position of the water outlet in the uppermost model box.

[0014] In some embodiments of the present invention, the retractable grouting sleeve comprises a plurality of sleeves whose diameters increase successively from the inside to the outside, and each sleeve is provided with a pair of buckles and a plurality of pairs of slots, and the buckles and slots are engaged according to different lengths to adjust the length of the retractable grouting sleeve.

[0015] In some embodiments of the present invention, the outermost sleeve of the retractable grouting sleeve is provided with a ball, and the ball is installed in a flange. The ball can roll in the flange to drive the retractable grouting sleeve to rotate.

[0016] In some embodiments of the present invention, a constant temperature heater is provided 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.

[0017] In some embodiments of the present invention, the pressure sensor includes a pressure gauge, an earth pressure gauge and a pore water pressure gauge; the pressure gauge is arranged on the grouting pipeline near the grouting port; the earth pressure gauge and pore water pressure are buried in layers when the sand and gravel medium is filled; the flow sensor includes a flow meter arranged on the grouting pipeline and the water outlet pipeline.

[0018] In a second aspect of the present invention, a method for localized grouting and water blocking test in extremely water-rich sand and gravel formations is provided, comprising:

[0019] Water is injected into the model box. When water starts to flow out of the outlet pipe, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium.

[0020] Inject cement-water glass double liquid slurry into the model box according to the set ratio and set speed. When the water in the outlet pipe stops flowing out or the slurry is discharged, stop grouting;

[0021] The data acquisition module records the data changes of each sensor in the grouting process in real time, obtains the change rules of grouting pressure, soil pressure, pore water pressure, slurry and flow rate at the outlet pipe over time, and calculates the water blocking efficiency of the test;

[0022] After the grouting is completed, wait for the slurry to initially set, open the model box, take out the sand, gravel and slurry stone body inside the model box, and perform standard curing on it. After the curing is completed, check its diffusion range, measure the strength and permeability of the stone body.

[0023] In some embodiments of the present invention, a sand and gravel medium calculation model is constructed, the slurry state is initialized, and the slurry density equation, momentum equation and continuity equation are constructed based on the data obtained from the experiment. By solving the above equations, the slurry concentration field, pressure field and velocity field are obtained, thereby realizing the numerical simulation of the slurry diffusion range.

[0024] In some embodiments of the present invention, the numerical simulation process specifically includes:

[0025] Construct the slurry density equation and solve it according to the initial boundary value conditions to obtain the slurry density field at the current time step;

[0026] Based on the initialized slurry velocity and pressure, the momentum equation and continuity equation are solved and PISO loop iteration is performed to obtain the slurry velocity field and pressure field of the current time step;

[0027] The time when the sand-pebble medium splits is determined based on the soil pressure gauge data. If the current time step does not reach the time required for splitting, repeat the above steps and perform iterative calculations. If the splitting time has been reached, update the porosity, and keep other parameters unchanged, and continue iterating until the grouting ends.

[0028] After the simulation, the slurry density field obtained by numerical simulation depicts the slurry diffusion process, which is compared with the slurry diffusion progress depicted by the pore water pressure obtained by experimental simulation to verify the accuracy of the experimental simulation results.

[0029] One or more technical solutions of the present invention have the following beneficial effects:

[0030] (1) The present invention realizes effective simulation of strata of different scales through a sand and gravel stratum simulation system, introduces a variable diameter injected medium structure, can simulate the diameter change of the filling karst pipe under different geological conditions, and creates a constant temperature and water-rich environment for the stratum through a constant temperature water supply module; the grouting pipe mouth can be freely adjusted through a localized grouting module to realize constant speed grouting for different strata; finally, various data in the grouting process are obtained through a data acquisition and analysis module, the slurry density field is introduced, and the slurry density field, velocity field, and pressure field are obtained by combining the fluid mechanics equation and numerical calculation, and the diffusion morphology and water plugging effect of the slurry are analyzed.

[0031] (2) The present invention adopts a retractable sleeve as a grouting device. The grouting port is fixed on a rotatable ball bearing, allowing it to rotate 360 ​​degrees in the horizontal direction. The grouting pipe is composed of a multi-stage sleeve that can be retracted up and down and can move vertically. Through this device, the grouting port can be flexibly positioned and adjusted in the horizontal and vertical directions. The grouting position can be flexibly adjusted according to the test requirements to achieve directional grouting operations in specific areas.

[0032] (3) The present invention provides a numerical simulation method for grouting in extremely water-rich sand and gravel media taking into account the dilution of slurry concentration. The slurry density field is introduced to characterize the change in slurry concentration. The data from the micro-soil pressure gauge and pore water pressure gauge placed in the model are combined with the fluid mechanics equation to solve the slurry water density field, velocity field, pressure field, etc., and the slurry penetration, diffusion and splitting process during the grouting process are analyzed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a diagram of the localized grouting and water blocking test system for the extremely water-rich sand and gravel stratum of the present invention;

[0034] Figure 2 It is a structural schematic diagram of the sand and gravel formation simulation module of the present invention;

[0035] Figure 3 It is a structural schematic diagram of a retractable grouting sleeve of a localized grouting module;

[0036] Figure 4 This is a flow chart of the localized grouting and water blocking test method for extremely water-rich sand and gravel formations.

[0037] In the figure: 1. Sand and gravel formation 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. Slurry pipeline; 9. Water outlet pipeline; 10. Permeable stone; 11. Water pipeline; 12. Ball; 13. Retractable grouting sleeve; 14. Buckle; 15. Slot; 16. Earth pressure gauge; 17. Pore water pressure gauge. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] Example 1

[0040] In a typical embodiment of the present invention, a localized grouting and water blocking test system for extremely water-rich sand and gravel formations is proposed, such as Figure 1 and Figure 2 As shown, including:

[0041] The sand-pebble formation simulation module 1 comprises a plurality of vertically placed model boxes 6 of different diameters, wherein the model boxes 6 are filled with sand-pebble media;

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

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

[0044] Data acquisition module 5, including a pressure sensor and a flow sensor, wherein the pressure sensor is used to monitor slurry pressure, sand and gravel medium soil pressure and pore water pressure; the flow sensor is used to measure grouting volume and water output;

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

[0046] In this embodiment, the diameters of the multiple model boxes 6 gradually decrease from top to bottom, and the adjacent model boxes 6 are sealed by flanges and bolts. The top of the top model box and the bottom of the bottom model box are blocked by baffles 7, that is, the top of the top model box is blocked by the upper baffle, and the bottom of the bottom model box is blocked by the lower baffle. A through hole is provided at the coaxial position of the upper baffle and the lower baffle, respectively, which is connected to the slurry delivery pipeline 8 and the water outlet pipeline 9. The slurry delivery pipeline 8 is connected to the localized grouting module 2, and the water outlet pipeline 9 is connected to the waste liquid collection module 4 to achieve the inflow and outflow of slurry. The through hole on the upper baffle is used as a water outlet. A layer of permeable stone 10 is arranged at the position of the water outlet in the top model box, which can prevent the sand and gravel medium from losing under the action of the grouting pressure and thus blocking the slurry outlet. A through hole is provided at the lower position of the side wall of the model box 6, which is connected to the water delivery pipeline 11, so that water can flow into the sand and gravel medium in the model box, creating a very water-rich environment for it.

[0047] like Figure 1 and Figure 3 As shown, the localized grouting module 2 is provided with two slurry storage tanks, which store cement and water glass respectively. Grouting motors are respectively provided on the two slurry storage tanks. The grouting motors drive the pistons to compress the air in the slurry storage tanks, so that the slurry in the slurry storage tanks flows out at a constant speed along the slurry delivery pipeline, and finally is injected into the sand and gravel medium in the model box through the retractable grouting sleeve 13.

[0048] Furthermore, the retractable grouting sleeve 13 includes a plurality of sleeves whose diameters increase from the inside to the outside, and each sleeve is provided with a pair of buckles 14 and a plurality of pairs of slots 15, and the buckles 14 and the slots 15 are engaged according to different lengths to adjust the length of the retractable grouting sleeve 13. Furthermore, the outermost sleeve of the retractable grouting sleeve 13 is provided with a ball 12, and the ball 12 is installed in the flange, and the ball 12 can roll in the flange to drive the retractable grouting sleeve 13 to rotate.

[0049] Specifically, a spherical groove is opened at a position slightly above the horizontal midline of the flange, the size of the groove is slightly larger than the ball 12, the groove is used to place the ball 12, and lubricating oil is applied between the ball 12 and the groove, so that the ball can roll 360 degrees on the horizontal plane, while preventing the sand and gravel medium in the model box from squeezing out 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 runs through the entire ball, for placing the outermost sleeve of the telescopic grouting sleeve 13. The telescopic grouting sleeve 13 includes pipes of different diameters, and the diameter of the multi-stage sleeve gradually increases from the inside to the outside. Each sleeve is provided with a pair of buckles 14 and multiple pairs of slots 15, and the buckles and slots can be matched according to different lengths, thereby realizing multi-stage adjustment of the length of the grouting pipe.

[0050] In this embodiment, the water tank is provided with a water level scale, and a constant temperature heater is provided in the water tank, and the heating temperature can be set. 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, thereby realizing dynamic control of the water temperature. The water tank is connected to the through hole on the side wall of the model box 6 through a water delivery pipeline 11, and a water pump is placed in the water tank, and the constant temperature water in the water tank can be pumped into the model box, thereby creating a water-rich environment for the sand and gravel formation.

[0051] In this embodiment, the pressure sensor includes a pressure gauge, an earth pressure gauge 16 and a pore water pressure gauge 17; the pressure gauge is arranged at a position near the grouting port of the grouting pipeline 8, and can measure the slurry pressure at the grouting port; the earth pressure gauge 16 and the pore water pressure gauge 17 are buried in layers when the sand and gravel medium is filled, and one layer is arranged in the middle of each model box. The earth pressure gauge and the pore water pressure gauge are arranged at intervals to monitor the changes in earth pressure and pore water pressure, such as Figure 2 As shown in ; the flow sensor includes flow meters arranged on the grouting pipeline 8 and the water outlet pipeline 9, which are used to measure the changes of grouting volume and water outlet volume respectively, so as to judge the water plugging effect. The data of the above sensors can be transmitted to the data acquisition instrument in real time, so as to facilitate the subsequent data analysis.

[0052] The data analysis system includes a pressure analysis module and a flow analysis module. The pressure analysis module determines whether grouting causes soil splitting by analyzing the change in soil pressure. If the soil pressure shows a trend of increasing and then suddenly decreasing, it indicates that the soil has undergone a permeation-splitting process. Combining the three major equations of fluid mechanics, the slurry phase fraction field, velocity field, pressure field, etc. are solved; when the slurry diffuses to the buried point of the pore water pressure gauge, the pore water pressure will increase suddenly. By analyzing the change in pore water pressure, the slurry diffusion range is determined and verified with the numerical simulation results. The flow analysis module analyzes the grouting plugging efficiency by analyzing the change in water volume in the outlet pipe before and after grouting.

[0053] The method of using the localized grouting and water blocking test system for extremely water-rich sand and gravel formations provided in this embodiment is as follows:

[0054] Step 1: Take the dry density of sand and gravel as the control index of the filling soil, fill the sand and gravel into the model box layer by layer, and compact it layer by layer to reach the dry density of the original soil. When filling the sand and gravel to the middle of each model box, bury the soil pressure gauge and pore water pressure gauge, and connect the pressure sensor and data acquisition instrument.

[0055] Step 2: When the medium is filled to the position close to the grouting port, adjust the ball and multi-stage sleeve, move the grouting port to the set position, continue to fill with sand and gravel until the filling height is flush with the grouting port, place a layer of sand net 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, cover it with a layer of permeable stone and fix the flanges between the model boxes with bolts.

[0057] Step 4: After connecting the pipes, wait until the water in the water tank reaches the set temperature, turn on the water pump, and inject water into the sand and gravel medium. When the outlet pipe starts to discharge water, read the water level in the water tank and calculate the initial porosity of the sand and gravel medium.

[0058] Step 5: Set the ratio and injection speed of cement-water glass dual-liquid slurry, turn on the dual-liquid grouting motor and valve, and inject the dual-liquid slurry into the model box at the set ratio and set speed. When the water in the outlet pipe stops flowing out or the slurry is discharged, stop grouting.

[0059] Step 6: The data acquisition system records the data changes of each sensor during the grouting process in real time, obtains the change patterns of grouting pressure, soil pressure, pore water pressure, slurry and flow rate at the outlet pipe over time, and calculates the water blocking efficiency of this test.

[0060] Step 7: After the grouting is completed and the slurry is initially solidified, open the model box, take out the sand, gravel and slurry stone body inside the model box, and perform standard curing on it. After the curing is completed, check its diffusion range and measure the strength and permeability of the stone body.

[0061] Example 2

[0062] In a typical embodiment of the present invention, a localized grouting and water blocking test method for extremely water-rich sand and gravel formations is provided, such as Figure 4 As shown, including:

[0063] Water is injected into the model box. When water starts to flow out of the outlet pipe, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium.

[0064] Inject cement-water glass double liquid slurry into the model box according to the set ratio and set speed. When the water in the outlet pipe stops flowing out or the slurry is discharged, stop grouting;

[0065] The data acquisition module records the data changes of each sensor in the grouting process in real time, obtains the change rules of grouting pressure, soil pressure, pore water pressure, slurry and flow rate at the outlet pipe over time, and calculates the water blocking efficiency of the test;

[0066] After the grouting is completed, wait for the slurry to initially set, open the model box, take out the sand, gravel and slurry stone body inside the model box, and perform standard curing on it. After the curing is completed, check its diffusion range, measure the strength and permeability of the stone body.

[0067] Furthermore, a sand and gravel medium calculation model is constructed to initialize the slurry state. Based on the data obtained from the experiment, the slurry density equation, momentum equation and continuity equation are constructed. By solving the above equations, the slurry concentration field, pressure field and velocity field are obtained, thereby realizing the numerical simulation of the slurry diffusion range.

[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 during the test process; construct a watershed grid and discretize it; initialize the slurry density, velocity, pressure, and viscosity fields according to the slurry ratio;

[0070] 2. Construct the slurry density equation and solve it according to the initial boundary conditions to obtain the slurry density field at the current time step;

[0071] The slurry density equation is:

[0072]

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

[0074] Initial conditions:

[0075] ρ(x,y,z,0)=0

[0076] Boundary conditions:

[0077] ρ(x0,y0,z0,t)=ρ0

[0078] ρ(x1,y1,z1,t)=0

[0079] Among them, x0, y0, z0 are the positions of the grouting port, and x1, y1, z1 are the positions of the grouting outlet;

[0080] 3. Based on the initialized slurry velocity and pressure, the momentum equation and continuity equation are solved and PI SO loop iteration is performed to obtain the slurry velocity field and pressure field of the current time step;

[0081] The momentum equation is:

[0082]

[0083] Among them, φ is the porosity of the sand and gravel 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 when the sand and gravel medium splits according to the soil pressure gauge data. If the current time step does not reach the time required for splitting, repeat the above steps and perform iterative calculations. If the splitting time has been reached, update the porosity φ' = 1, and keep the others unchanged, and continue iterating until the grouting ends.

[0088] 5. After the simulation, the diffusion process of the slurry is characterized by the slurry density field of the current time step, and compared with the slurry diffusion progress characterized by the pore water pressure. If they are consistent, the accurate simulation of the slurry diffusion morphology is achieved, and the feasibility of the experimental device is verified.

[0089] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A localized grouting and water blocking test system for extremely water-rich sand and gravel formations, characterized in that: include: The sand-pebble formation simulation module comprises a plurality of model boxes of different diameters placed vertically, wherein the model boxes are filled with sand-pebble media; A localized grouting module, comprising a grout storage tank, a grout delivery pipeline, a ball bearing and a retractable grouting sleeve connected in sequence, wherein the retractable grouting sleeve is installed at the bottom of the model box; A constant temperature water supply module, comprising a water tank and a water pipeline, wherein the water tank is connected to the model box through the water pipeline to create a water-rich environment for the sand and gravel medium; The data acquisition module includes a pressure sensor and a flow sensor. The pressure sensor is used to monitor the slurry pressure, the soil pressure of the sand and gravel medium, and the pore water pressure; the flow sensor is used to measure the grouting volume and the water output; The data analysis module is electrically connected to the data acquisition module and includes a pressure analysis module and a flow analysis module. The pressure analysis module is used to analyze and obtain the slurry phase fraction field, velocity field and pressure field; the flow analysis module is used to analyze the grouting plugging efficiency.

2. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations according to claim 1 is characterized in that: The diameters of the multiple model boxes gradually decrease from top to bottom, and adjacent model boxes are tightly connected via flanges and bolts. The top of the uppermost model box and the bottom of the lowermost model box are sealed by an upper baffle and a lower baffle respectively.

3. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations according to claim 2 is characterized in that: The upper baffle is provided with a water outlet, the water outlet is connected to a water delivery pipeline, and a layer of permeable stone is provided at the position of the water outlet in the uppermost model box.

4. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations according to claim 1 is characterized in that: The retractable grouting sleeve comprises a plurality of sleeves whose diameters increase successively from the inside to the outside. A pair of buckles and a plurality of pairs of slots are arranged on each sleeve. The buckles and slots are engaged according to different lengths to adjust the length of the retractable grouting sleeve.

5. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations as claimed in claim 4 is characterized in that: The outermost sleeve of the telescopic grouting sleeve is provided with a ball, and the ball is installed in the flange. The ball can roll in the flange to drive the telescopic grouting sleeve to rotate.

6. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations according to claim 1, 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.

7. The localized grouting and water blocking test system for extremely water-rich sand and gravel formations according to claim 1 is characterized in that: The pressure sensor includes a pressure gauge, an earth pressure gauge and a pore water pressure gauge; the pressure gauge is arranged on the grouting pipeline near the grouting port; the earth pressure gauge and pore water pressure are buried in layers when the sand and gravel medium is filled; the flow sensor includes a flow meter arranged on the grouting pipeline and the water outlet pipeline.

8. A method for localized grouting and water blocking test in extremely water-rich sand and gravel formations, using the test system as described in any one of claims 1 to 7, characterized in that: include: Water is injected into the model box. When water starts to flow out of the outlet pipe, the water level in the water tank is read to calculate the initial porosity of the sand and gravel medium. Inject cement-water glass double liquid slurry into the model box according to the set ratio and set speed. When the water in the outlet pipe stops flowing out or the slurry is discharged, stop grouting; The data acquisition module records the data changes of each sensor in the grouting process in real time, obtains the change rules of grouting pressure, soil pressure, pore water pressure, slurry and flow rate at the outlet pipe over time, and calculates the water blocking efficiency of the test; After the grouting is completed, wait for the slurry to initially set, open the model box, take out the sand, gravel and slurry stone body inside the model box, and perform standard curing on it. After the curing is completed, check its diffusion range, measure the strength and permeability of the stone body.

9. The method for localized grouting and water blocking test in extremely water-rich sand and gravel formations as claimed in claim 8, characterized in that: A sand and gravel medium calculation model is constructed to initialize the slurry state. Based on the experimental data, the slurry density equation, momentum equation and continuity equation are constructed. By solving the above equations, the slurry concentration field, pressure field and velocity field are obtained, thereby realizing the numerical simulation of the slurry diffusion range.

10. The method for localized grouting and water blocking test in extremely water-rich sand and gravel formations according to claim 8, characterized in that: The numerical simulation process specifically includes: Construct the slurry density equation and solve it according to the initial boundary value conditions to obtain the slurry density field at the current time step; Based on the initialized slurry velocity and pressure, the momentum equation and continuity equation are solved and PISO loop iteration is performed to obtain the slurry velocity field and pressure field of the current time step; The time when the sand-pebble medium splits is determined based on the soil pressure gauge data. If the current time step does not reach the time required for splitting, repeat the above steps and perform iterative calculations. If the splitting time has been reached, update the porosity φ' = 1, and keep other parameters unchanged, and continue iterating until the grouting ends. After the simulation, the slurry density field obtained by numerical simulation depicts the slurry diffusion process, which is compared with the slurry diffusion progress depicted by the pore water pressure obtained by experimental simulation to verify the accuracy of the experimental simulation results.

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