Grouting experiment platform for simulating complex surrounding rock environment of tunnel

Abstract

The utility model discloses a grouting experiment platform for simulating a complex surrounding rock environment of a tunnel, which comprises a cubic model box body formed by welding a plurality of independent steel plates, a front / rear side plate of the cubic model box body is provided with regular through holes and is externally connected with a water storage tank, and the water storage tank regulates and controls dynamic water pressure through a bottom water outlet and an external water pressure supply system; a detachable cover plate and a ground stress simulation system are arranged at the top of the model box body, the ground stress simulation system comprises a portal frame, a hydraulic jack and a bearing plate, and stratum stress is reproduced through hydraulic loading and pressure monitoring; the grouting equipment injects grout into the simulation tunnel through the pressure stirring barrel and the grouting guide pipe. The device can accurately simulate a seepage field and a stress field of a complex surrounding rock, and is used for analyzing a grouting liquid diffusion rule in a laboratory, optimizing grouting parameters and reducing site construction risks.

Description

Grouting test platform simulating complex surrounding rock environment of tunnel Technical Field

[0001] This utility model relates to the field of civil engineering technology. More specifically, this utility model relates to a grouting experimental platform simulating the complex surrounding rock environment of a tunnel. Background Technology

[0002] At present, tunnel excavation reinforcement often adopts the method of injecting a mixture of cement and water glass grout into the front of the tunnel face. This method can achieve effective reinforcement results in areas with weak water abundance, but under complex surrounding rock conditions with strong water abundance, weak soil cementation, and the influence of dynamic water, the grouting reinforcement effect is not good. Problems include the effective reinforcement volume in the soil behind the tunnel face being far lower than expected, the grouting volume being far greater than estimated, increased input of manpower and materials, and impact on work progress.

[0003] Under complex surrounding rock physical conditions, the lack of an experimental platform that can simulate the on-site stress and water pressure environment makes it difficult to identify key factors affecting the grouting reinforcement efficiency, such as the non-directional loss of grout, and also makes it impossible to accurately grasp the grout direction and the reasons why the grouting volume far exceeds the actual estimate. Summary of the Invention

[0004] One objective of this invention is to provide a grouting experimental platform that simulates complex surrounding rock conditions in tunnels, comprising:

[0005] The model box is a cubic structure made of multiple independent steel plates welded together. It has regularly distributed through holes on its front and rear side plates. Water storage tanks are welded and fixed to the outer surfaces of the front and rear side plates respectively. The water storage tanks cover the through hole area and have water outlets with valves at the bottom. The top of the water storage tank on the rear side plate is connected to an external water pressure supply system through a pipe. The center of the water storage tank on the front side plate has an installation port that matches the outer diameter of the simulated tunnel.

[0006] The model box has a removable cover with a sealing strip on one side panel and an upper cover that is fixed to the metal edging with bolts on the top.

[0007] The ground stress simulation system includes a gantry frame welded and fixed to the edge of the upper cover plate, a hydraulic jack installed in the center of the gantry frame, and a pressure plate connected to the hydraulic jack via a ball joint.

[0008] A water pressure simulation system, comprising a water storage container connected to a water tank via a hose to a rear panel;

[0009] The grouting equipment includes a grouting hose that is horizontally connected to the simulated tunnel face via a grouting conduit. The other end of the grouting hose is connected to a pressure mixing tank. The pressure mixing tank is inserted into the tunnel face of the box body at a horizontal or slightly inclined angle via the grouting conduit. The pressure mixing tank is connected to an air compressor.

[0010] Preferably, the system also includes a monitoring system, which includes a flow velocity sensor embedded in the arch of the simulated tunnel and a pressure sensor installed between the bearing plate and the simulated tunnel. The flow velocity sensor and the pressure sensor are respectively connected to an external data acquisition terminal.

[0011] Preferably, the through holes are a regularly arranged circular array of holes, all located in the central area of ​​the front and rear side plates.

[0012] Preferably, the water storage tank is fixed to the outer surface of the front / rear side panel by welding, and its bottom outlet is equipped with an openable and closable valve, while the top of the water storage tank on the rear side panel is equipped with a water inlet;

[0013] The water storage container is equipped with a flow regulating valve at the bottom, and the two ends of the hose are sealed and connected by quick connectors.

[0014] Preferably, the inner diameter of the tunnel model mounting opening of the water tank on the front side panel is adapted to the outer diameter of the simulated tunnel, and the two are connected by a sealing ring.

[0015] The tunnel model was 3D printed using PETG material.

[0016] Preferably, the pressure sensor uses a thin-film strain gauge, which is wrapped with a plastic outer membrane and then coated with a waterproof polyurethane coating with a thickness of 0.2~0.5mm.

[0017] The model box has an inspection port on one side, which is 2 / 3 the height of the model box and is sealed with a removable cover.

[0018] Preferably, the edge of the detachable cover plate is fixed to the metal edging with bolts, the flange is embedded in the center of the upper cover plate and the sealing ring is made of nitrile rubber.

[0019] A vertical guide sleeve is welded to the center of the flange, and its inner diameter is clearance-fitted with the outer diameter of the pressure column of the ground stress simulation system.

[0020] Preferably, the gantry frame is welded to the upper surface edge of the top cover plate;

[0021] The lower end of the bearing column in the geostress simulation system is connected to the bearing plate via a ball joint.

[0022] Preferably, the air inlet pipe and slurry outlet pipe of the pressure mixing tank are equipped with an air pressure gauge and a pressure gauge, respectively, and the grouting pipe is connected to the slurry outlet of the pressure mixing tank through a high-pressure ball valve.

[0023] Preferably, the flow velocity sensor is buried at a height of 0.5 to 1.0 times the tunnel diameter above the arch of the simulated tunnel, and its measurement range is 0 to 5 m / s.

[0024] This utility model has at least the following beneficial effects:

[0025] This utility model uses simulated ground stress and dynamic water conditions to conduct grouting tests on the simulated tunnel face inside the main box, effectively and intuitively reflecting the morphology of the grouting reinforced body under grouting reinforcement operation, and reflecting the effectiveness of grouting reinforcement under complex strata in advance, which is beneficial for the operation adjustment of the pre-grouting position before construction.

[0026] Meanwhile, the simulated geological environment inside the box can be preset and the ground stress and dynamic water conditions can also be changed according to the on-site construction environment. Under different operating conditions, it can intuitively reflect the actual effect of on-site grouting. Through the data feedback of the monitoring system, it is convenient for technicians to adjust the working conditions, improve the working safety factor of on-site workers, and the trial and error cost is lower and the safety level is higher than that of direct on-site grouting test.

[0027] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0028] Figure 1 is a side connection diagram of the grouting test platform according to one of the technical solutions of this utility model;

[0029] Figure 2 is a schematic diagram of the model box structure of one of the technical solutions of this utility model;

[0030] Figure 3 is a schematic diagram of the structure of a geostress simulation system according to one of the technical solutions of this utility model.

[0031] The markings in each of the attached figures are as follows:

[0032] 1. Air compressor; 2. Agitator; 3. Pressure mixing tank; 4. Top cover plate; 5. Metal edging; 6. Simulated tunnel; 7. Water tank on the front panel; 8. Water outlet; 9. Grouting pipe; 10. Removable cover plate; 11. Gantry frame; 12. Hydraulic jack; 13. Flange; 14. Pressure column; 15. Pressure plate; 16. Vertical guide sleeve; 17. Water tank on the rear panel; 18. Support frame; 19. Water storage container; 20. Flow rate sensor; 21. Pressure sensor. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0034] It should be noted that, unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the reagents and materials are commercially available unless otherwise specified. In the description of this utility model, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0035] As shown in Figures 1-3, this utility model provides a grouting experimental platform simulating a complex surrounding rock environment in a tunnel, comprising:

[0036] The model box is a cubic structure welded from multiple independent steel plates. Its front and rear side plates have regularly distributed through holes. Water tanks are welded and fixed to the outer surfaces of the front and rear side plates, covering the through hole areas and having outlets 8 with valves at the bottom. The top of the water tank 17 on the rear side plate is connected to an external water pressure supply system via a pipe. The center of the water tank 7 on the front side plate has an installation port adapted to the outer diameter of the simulated tunnel 6. Specifically, the model box is a cubic structure welded from multiple independent steel plates, with steel plate thickness selectable from 8 to 12 mm, and the cube side length can be... The diameter of the through holes on the front and rear side panels is 10-20mm and the spacing between the holes is 50-100mm. The outer surfaces of the front and rear side panels are welded and fixed with water tanks. The water tanks can be made of 304 stainless steel with a thickness of 3-5mm. The bottom is equipped with a water outlet 8 with a valve. The valve can be a ball valve. The top of the water tank 17 on the rear side panel is connected to the external water pressure supply system through a pressure-resistant hose. The center of the water tank 7 on the front side panel is equipped with an installation port that matches the outer diameter of the simulated tunnel 6. A rubber sealing ring can be set on the edge of the installation port.

[0037] The model box has a removable cover plate 10 with a sealing strip on one side panel, and an upper cover plate 4 fixed to the metal edging 5 by bolts on the top. Specifically, a rectangular opening with a height of 200-300mm is opened in the middle of one side panel of the model box, covered by a steel plate with a sealing strip. The sealing strip can be made of nitrile rubber and is fixed by bolts. The upper cover plate 4 is fixed to the metal edging 5 on the top of the box by bolts. The metal edging 5 is made of L-shaped angle steel. During assembly, the water tanks on the front and rear side panels are... 17 is welded to the outer surface of the steel plate, completely covering the through hole area. The detachable cover plate 10 is fixed to the open with bolts. The top cover plate 4 is connected to the metal edging 5 with bolts. During operation, the water storage tank 17 of the rear side plate is connected to the external water pressure system through the pipe. Water flows in from the top of the water storage tank 17 of the rear side plate and enters the tank through the through hole to simulate dynamic water conditions. Excess water flows out from the bottom outlet 8 of the water storage tank 7 of the front side plate. The tank is filled with simulated surrounding rock soil samples. Soil samples are filled and later excavation observation is carried out through the inspection port.

[0038] The ground stress simulation system includes a gantry frame 11 welded and fixed to the edge of the upper cover plate 4, a hydraulic jack 12 installed at the center of the gantry frame 11, and a pressure plate 15 connected to the hydraulic jack 12 via a ball joint. Specifically, the gantry frame 11 is welded from H-beams, the hydraulic jack 12 can be an electric hydraulic jack, and the pressure plate 15 is a rectangular steel plate with dimensions adapted to the internal cross-section of the box. The bottom is machined to have a rough surface to enhance contact with the soil. During assembly, the gantry frame 11 is welded... The jack is attached to the edge of the upper surface of the cover plate 4 and is vertically installed at the center of the gantry frame 11. The pressure plate 15 is connected to the lower end of the jack piston rod through a ball joint to ensure that the pressure plate 15 can be adjusted horizontally. During operation, oil is supplied to the jack through the hydraulic pump station, and the jack piston rod extends downward to push the pressure plate 15 to apply vertical pressure to the soil inside the box. By adjusting the oil pressure of the jack, the geostress environment at different strata depths can be simulated, and the stress loading rate is controlled at 0.05~0.2MPa / min.

[0039] The water pressure simulation system includes a water storage container 19 connected to a water tank 17 on the rear panel via a flexible hose. Specifically, the water storage container 19 is mounted on a height-adjustable bracket 18. The water storage container 19 can be a polyethylene plastic water tank with an outlet 8 at the bottom, connected to a rubber hose with an inner diameter of 25-32mm. The hose is sealed to the top opening of the water tank 17 on the rear panel via a quick-connect fitting. The bracket 18 is made of welded steel pipe, and its height can be adjusted via a threaded sleeve, with an adjustment range of 0.5-2 meters. During assembly, the water storage container 19 is fixed to the rear of the model box via the bracket 18, and one end of the flexible hose is connected to the outlet of the water storage container 19. Water inlet 8 is connected to the top inlet of the water storage tank 17 on the rear side plate. A sealing clamp is installed at the connection. During operation, water is injected into the water storage container 19 to the set water level. The valve of the water outlet 8 of the water storage container 19 is opened, and the water flows into the water storage tank 17 on the rear side plate through the hose. It then flows evenly into the soil sample inside the tank through the through hole of the rear side plate, forming a stable seepage field from back to front. By adjusting the height of the support 18 of the water storage container 19, the water level difference can be changed, which can simulate different water pressure environments. The water flow rate is monitored by the flow rate sensor 20 (such as electromagnetic flow rate sensor 20) embedded in the tank. The flow rate range can be controlled between 0.01 and 0.1 m / s.

[0040] The grouting equipment includes a grouting hose horizontally connected to the simulated tunnel face via a grouting conduit 9. The other end of the grouting hose is connected to a pressure mixing tank 3. The pressure mixing tank 3 is inserted into the tunnel face within a box at a horizontal or slightly inclined angle via the grouting conduit 9. An air compressor 1 is connected to the pressure mixing tank 3. Specifically, the pressure mixing tank 3 is a cylindrical stainless steel container equipped with an electric agitator 2, and has a feed inlet and a pressure gauge at the top. The pressure gauge has a range of 0~1.6. For the grouting pipe 9, a piston-type air compressor can be used as the air compressor 1. The length of the grouting pipe 9 is made of seamless steel pipe, and its length is determined according to the height of the box. The front end of the pipe is processed into a cone shape, and the tail end is connected to the grout outlet of the pressure mixing tank 3 through a quick connector. The pressure mixing tank 3 is connected to the grouting pipe 9 through a grouting hose. The grouting pipe 9 is inserted into the "face" of the simulated tunnel 6 at a horizontal or slightly inclined angle and fixed to the installation port of the face with a sealing ring. The air compressor 1 is connected to the air inlet of the mixing tank through an air pipe. During operation, the cement-water glass grout is first added to the mixing tank according to the design ratio. The agitator 2 is started and stirred evenly. The air outlet and liquid outlet valves of the mixing tank are closed. The air compressor 1 is turned on to pressurize the tank to 0.3~0.6 MPa (set according to experimental requirements). The liquid outlet valve is opened, and the grout is injected into the "face" of the simulated tunnel 6 through the grouting hose and grouting pipe 9 under pressure. The grouting rate is controlled by the valve opening and maintained at 5~20 MPa. L / min. After grouting is completed, close the valves of air compressor 1 and mixing tank, and conduct excavation observation after the grout has solidified.

[0041] In the aforementioned technical solution, the synergistic effect of the model box, the ground stress simulation system, the water pressure simulation system, and the grouting equipment allows for the simulation of ground stress and hydrodynamic conditions in complex surrounding rock of tunnels under laboratory conditions. This provides a direct view of the morphology of the reinforced body and the grout flow trend after grouting at the tunnel face. Adjustable stress loading and water pressure simulation can adapt to the grouting experiment requirements under different geological conditions, providing data support for optimizing grouting schemes before construction. Compared to direct on-site testing, this platform reduces trial-and-error costs, improves operational safety, and facilitates the analysis of issues such as abnormal grout volume and grout loss by technical personnel, providing a scientific basis for the reinforcement of tunnels in complex geological formations.

[0042] In another technical solution, a monitoring system is also included, comprising a flow velocity sensor 20 embedded in the arch of the simulated tunnel 6 and a pressure sensor 21 disposed between the pressure plate 15 and the simulated tunnel 6. The flow velocity sensor 20 and the pressure sensor 21 are respectively connected to an external data acquisition terminal. Specifically, the flow velocity sensor 20 can be an electromagnetic flow velocity sensor 20 or an ultrasonic flow velocity sensor 20. The housing material can be stainless steel or engineering plastic, resistant to water and soil pressure. The size of the flow velocity sensor 20 is adapted to the inner diameter of the simulated tunnel 6, such as a diameter of 10~15mm and a length of 50~80mm. Sensor 21 can be a resistance strain gauge pressure sensor, installed at the center of the bottom of the pressure plate 15, and led out of the housing via wires. During assembly, after filling the model housing with simulated surrounding rock soil samples to the installation height of the simulated tunnel 6, the flow velocity sensor 20 is horizontally buried in the soil at the arch of the simulated tunnel 6, with the axis of the flow velocity sensor 20 parallel to the water flow direction and 50~100mm away from the outer wall of the tunnel. It is led out from the reserved hole on the side wall of the housing via wires. The external data acquisition terminal can be a multi-channel data acquisition instrument or an industrial control computer, equipped with data acquisition software, supporting real-time data display and storage functions. Yes, the data acquisition terminal is placed in a stable position outside the model box and connected to the flow velocity sensor 20 and pressure sensor 21 via shielded wires. Waterproof connectors are used at the connection points. During operation, the flow velocity sensor 20 monitors the water flow velocity under dynamic water conditions inside the box in real time, and the pressure sensor 21 monitors the stress value transmitted by the pressure plate 15 in real time. The signals are converted into electrical signals and transmitted to the data acquisition terminal. The terminal records the data at a sampling frequency of 0.1~1Hz, forming a flow velocity-time curve, which facilitates subsequent analysis of water flow characteristics under different water pressure conditions. Before starting the water pressure simulation system, first... After completing the installation of the flow velocity sensor 20 and debugging of the data acquisition terminal to ensure normal connection, when the water storage container 19 injects water into the water storage tank 17 on the rear side plate of the model box, the water flows into the soil through the through hole, forming a seepage field from back to front. The flow velocity sensor 20 synchronously monitors the water flow velocity in this area. By adjusting the height of the support 18 of the water storage container 19 to change the water level difference, the change in flow velocity data can be observed. For example, for every 0.1 meter increase in water level difference, the flow velocity increases by 0.005~0.01m / s. Combined with the diffusion pattern of the grout during the grouting process, the influence of the dynamic water velocity on grout loss and reinforcement effect is analyzed.

[0043] In this technical solution, the monitoring system collects flow velocity data under dynamic water conditions in real time, providing a quantitative basis for analyzing the causes of non-directional grout loss in complex surrounding rock environments. This allows experimental personnel to intuitively grasp the correlation between water flow velocity and grouting effect. Through data feedback, the simulation parameters of ground stress and water pressure can be optimized, improving the accuracy and reliability of grouting experiments. This provides scientific data support for predicting grout direction and adjusting grouting schemes during on-site construction, reducing problems such as excessive grouting volume and insufficient reinforcement effect caused by unreasonable parameters.

[0044] In another technical solution, the through holes are a regularly arranged circular array, all located in the central area of ​​the front and rear side plates. Specifically, the diameter of the circular holes can be selected as 10~20mm, the array is arranged in a row and column manner, and the horizontal and vertical hole spacing is 50~100mm, forming a rectangular distribution area that covers 60%~80% of the area of ​​the front and rear side plates. The through holes are machined by mechanical drilling, and the hole edges are deburred. During assembly, the center of the circular array of the front and rear side plates is aligned with the geometric center of the model box to ensure that the water flow is evenly distributed when passing through the array. During operation, the water in the water storage tank 17 of the rear side plate seeps into the soil inside the box through the circular array, forming a stable dynamic water seepage field. The regular distribution of the array can avoid soil erosion caused by concentrated water flow and ensure the uniformity of dynamic water simulation.

[0045] The grouting conduit 9 can be made of seamless steel pipe with a smooth inner wall to reduce grout flow resistance. The front end is machined into a 45° chamfer to facilitate insertion into the simulated tunnel 6 "face".

[0046] In the above technical solution, during the dynamic water simulation process, the water in the water storage tank 17 of the rear side plate seeps into the soil evenly through a circular array of holes. The regularly arranged array of holes can control the water flow velocity distribution error on the cross-section of the tank to within ±10%, providing stable hydrodynamic conditions for the grouting experiment. During grouting, the grout in the pressure mixing tank 3 is injected into the tunnel face through the grouting conduit 9. The ratio of the inner diameter to the outer diameter of the conduit can balance the grout flow resistance and the strength of the conduit structure. For example, a ratio of 1:1.3 can ensure sufficient grouting flow rate and avoid deformation of the conduit due to excessive pressure. The ratio of the conduit length to the tunnel diameter is determined according to the experimental similarity ratio, so that the pressure loss of the grout in the conduit is controlled within a reasonable range, ensuring that the grouting pressure at the tunnel face meets the experimental set value.

[0047] In another technical solution, the water storage tank is fixed to the outer surface of the front / rear side panels by welding. The bottom outlet 8 of the water storage tank is equipped with an openable and closable valve, and the top of the water storage tank 17 on the rear side panel is equipped with an inlet. Specifically, the water storage tank can be fixed to the outer surface of the front and rear side panels by full welding, completely covering the circular through hole area. The bottom edge of the water storage tank is equipped with an outlet 8 with a diameter of 25~50mm, which is equipped with an openable and closable valve. The valve can be a manual ball valve or a butterfly valve to control the discharge of water. The top center of the water storage tank 17 on the rear side panel is equipped with an inlet with a diameter that is compatible with the external hose. It can be connected by a threaded interface or a flange to ensure a sealed connection with the hose of the water pressure simulation system. During assembly, the welded joint between the water storage tank and the side panel is treated with anti-corrosion to prevent water leakage.

[0048] The bottom of the water storage container 19 is equipped with a flow regulating valve, and the two ends of the hose are sealed by quick connectors. Specifically, the flow regulating valve can be a manual throttle valve or an electric regulating valve, used to control the water flow rate into the model box. The hose is made of pressure-resistant rubber with an inner diameter of 25~32mm. The two ends are connected to the water outlet 8 at the bottom of the water storage container 19 and the water inlet at the top of the water tank 17 on the rear side plate, respectively. Stainless steel quick connectors are installed at the connection points. The quick connectors have built-in O-ring seals to ensure sealing performance. The water storage container 19 is placed on an adjustable height bracket 18. The height of the bracket 18 can be adjusted from 0.5 to 2 meters. By changing the water level difference between the water storage container 19 and the model box, different water pressure environments can be simulated.

[0049] In the above technical solution, before the experiment, close the valves at the bottom outlets 8 of the water tank 7 on the front side panel and the water tank 17 on the rear side panel. Fill the water tank 19 with water through the top. Open the flow regulating valve at the bottom of the water tank 19. The water flows through the hose into the water tank 17 on the rear side panel. After the water level stabilizes, slowly open the valve at the bottom outlet 8 of the water tank 7 on the front side panel. Adjust the flow regulating valve to balance the inlet and outlet flow rates, forming a stable water flow condition from back to front. The water flow rate can be adjusted by changing the height of the support 18 of the water tank 19 (e.g., for every 0.1 meter increase, the water level difference increases by 0.1 MPa) or by adjusting the opening of the flow regulating valve (e.g., for every 10% increase in valve opening, the flow rate increases by 5~10 L / min).

[0050] In another technical solution, the inner diameter of the tunnel model mounting opening of the water tank 7 on the front side panel is adapted to the outer diameter of the simulated tunnel 6, and the two are connected by a sealing ring. Specifically, the inner diameter of the tunnel model mounting opening of the water tank 7 on the front side panel is adapted to the outer diameter of the simulated tunnel 6, and the dimensional tolerance between the two can be controlled within ±1~2mm to ensure a tight fit. An annular groove is provided on the inner side of the mounting opening for embedding the sealing ring. The sealing ring can be made of nitrile rubber or silicone rubber with a cross-sectional diameter of 5~8mm. It is fixed in the groove by pressing. During assembly, the outer diameter of the simulated tunnel 6 is aligned with the mounting opening, and it is slowly pushed in to make the sealing ring elastically deform, forming a waterproof sealing interface to prevent grout or water from leaking from the interface during the grouting process.

[0051] The tunnel model is made of PETG material by 3D printing. Specifically, resistance strain gauge pressure sensors 21 are uniformly pasted on the outer wall of the tunnel model. The distance between the resistance strain gauge pressure sensors 21 is 100~200mm. After pasting, the model is wrapped with transparent plastic film and fixed with waterproof tape to prevent cement slurry from corroding the resistance strain gauge pressure sensors 21.

[0052] In the above technical solution, before the experiment, the model parameters are calculated based on the elastic modulus and similarity ratio of the tunnel on site. The tunnel model is designed and printed using 3D modeling software. The model is installed in the installation port of the water storage tank 7 on the front side plate to ensure that the sealing ring is fully compressed. Then, the soil sample inside the box is filled. During the filling process, the wire of the pressure sensor 21 is led out from the reserved hole in the box and connected to the external data acquisition instrument. During the grouting process, the model bears the stress of the surrounding soil and the grout diffusion pressure. The pressure sensor 21 monitors the strain data of the outer wall of the model in real time. The stress state of the prototype tunnel during grouting reinforcement can be reflected by the similarity ratio conversion.

[0053] In another technical solution, the pressure sensor 21 uses a thin-film strain gauge, which is wrapped with a plastic outer film and then coated with a waterproof polyurethane coating with a thickness of 0.2~0.5mm. Specifically, the pressure sensor 21 uses a thin-film strain gauge, the substrate material of which can be polyimide and the sensing grid material is constantan alloy. The strain gauge is coated with a waterproof polyurethane coating with a thickness of 0.2~0.5mm. The coating is uniformly covered on the surface of the strain gauge by brushing or spraying to form a waterproof barrier. During assembly, the strain gauge is first pasted on the outer wall of the simulated tunnel 6 at a designated position with epoxy resin adhesive. The pasting direction is perpendicular to the tunnel axis and the spacing is 100~200mm. After the adhesive has cured, the polyurethane coating is applied in 2~3 layers. The drying time of each layer is not less than 2 hours to ensure that the coating is free of bubbles and has no missed areas.

[0054] The model box has an inspection port on one side, the height of which is 2 / 3 of the height of the model box, and it is equipped with a removable cover plate for sealing. Specifically, the removable cover plate 10 is a whole piece of steel plate with a sealing strip on the edge, and is fixed to the side plate by bolts with a bolt spacing of 200~300mm.

[0055] In the above technical solution, when the pressure sensor 21 is working, the stress change of the soil around the simulated tunnel 6 is transmitted to the strain gauge through the tunnel wall, causing the resistance value of the strain gauge's sensitive grid to change. This change is converted into a voltage signal and recorded by the data acquisition instrument. The waterproof polyurethane coating can effectively prevent cement slurry and moisture from intruding, ensuring that the sensor works stably in a humid environment. The measurement error is controlled within ±1.5%. The support structure of the detachable cover plate 10 bears the self-weight of the cover plate and the lateral pressure of the soil, avoiding the cover plate from failing to seal due to deformation under stress. For example, after the soil is compacted, the support structure can control the displacement of the cover plate within the range of 1~2mm.

[0056] In another technical solution, the edge of the detachable cover plate 10 is fixed to the metal edging 5 by bolts, and the flange 13 is embedded in the center of the upper cover plate 4 and the sealing ring is made of nitrile rubber. Specifically, the edge of the detachable cover plate 10 is fixed to the metal edging 5 on the top of the box by bolts. The metal edging 5 is made of L-shaped angle steel and welded to the open edge of the box. The bolt spacing is set to 200~300mm to ensure that the cover plate is tightly connected to the box. During assembly, the cover plate is first placed on the metal edging 5, the bolts are inserted after aligning with the bolt holes, and the bolts are tightened gradually in 2~3 times using a diagonal tightening method to make the cover plate evenly stressed and avoid deformation due to stress concentration.

[0057] A vertical guide sleeve 16 is welded to the center of the flange 13, and its inner diameter is clearance-fitted with the outer diameter of the pressure column 14 of the ground stress simulation system. Specifically, the flange 13 is embedded in the center of the upper cover plate 4 and adopts a circular steel structure. The flange 13 has an annular groove inside which a nitrile rubber sealing ring is embedded. The sealing ring has a cross-sectional diameter of 8~12mm. During installation, it is embedded into the groove by a press-fitting process to ensure tight contact with the detachable cover plate 10 and the pressure column 14. The vertical guide sleeve 16 is welded to the center of the upper surface of the flange 13 and is made of seamless steel pipe. Its inner diameter is clearance-fitted with the outer diameter of the pressure column 14, with a clearance value of 0.5~2mm. The sleeve height is 150~200mm, and the inner wall is ground to ensure a surface roughness Ra≤3.2μm.

[0058] In the above technical solution, during the in-situ stress simulation, the hydraulic jack 12 applies vertical pressure to the bearing column 14 through the gantry frame 11. The bearing column 14 moves downward along the axis of the guide sleeve. The clearance fit of the inner wall of the sleeve allows for minor centering adjustments while limiting lateral displacement, ensuring that the stress is vertically transmitted to the bearing plate 15 and the soil. The nitrile rubber sealing ring undergoes compression deformation after the cover plate bolts are tightened, forming a sealing interface to prevent soil particles or water from overflowing from the connection between the cover plate and the box body during grouting. The verticality error of the guide sleeve is controlled within 0.1°, ensuring that the axis of the bearing column 14 is consistent with the direction of in-situ stress loading, and the stress transmission error is ≤3%.

[0059] In another technical solution, the gantry frame 11 is welded to the edge of the upper surface of the upper cover plate 4; specifically, the gantry frame 11 is made of H-beams and welded to the edge of the upper surface of the upper cover plate 4, the width of the flange plate is consistent with the width of the edge of the upper cover plate 4 to ensure sufficient welding area, the span of the gantry frame 11 is 70%~80% of the width of the upper cover plate 4, the height is 200~300mm, and its section moment of inertia satisfies the deflection ≤L / 500 under the maximum design load;

[0060] The lower end of the bearing column 14 of the geostress simulation system is connected to the bearing plate 15 via a ball joint. Specifically, the lower end of the bearing column 14 is connected to the bearing plate 15 via a ball joint. The diameter of the ball joint is 1.5 to 2 times the diameter of the bearing column 14. The outer shell of the ball joint is made of cast steel, and the inner surface is hardened to HRC40 to 45. The surface of the ball is plated with hard chrome to improve wear resistance and corrosion resistance. The swing angle range of the ball joint is ±15°, which can compensate for the tilt of the bearing plate 15 caused by uneven soil deformation and ensure uniform pressure transmission. During assembly, the ball is connected to the lower end of the bearing column 14 via flange bolts, and the outer shell is welded to the bearing plate 15. A rubber sealing ring is set at the connection to prevent mud intrusion.

[0061] In the above technical solution, when the ground stress is applied, the hydraulic jack 12 transmits the vertical force to the ball joint through the bearing column 14. When the bearing plate 15 tilts due to local soil deformation, the ball joint automatically adjusts its angle to keep the axis of the bearing column 14 consistent with the loading direction of the jack. For example, when the local compression difference of the soil causes the bearing plate 15 to tilt by 5°, the ball joint can compensate for the angle by rotating itself, so that the pressure distribution unevenness coefficient is controlled within ±5%. The rigid structure of the gantry frame 11 ensures that the elastic deformation under the maximum loading pressure (such as 2MPa) is ≤2mm, thus ensuring the stability of the loading process.

[0062] In another technical solution, the air inlet pipe and slurry outlet pipe of the pressure mixing tank 3 are respectively equipped with a pneumatic gauge and a pressure gauge. The grouting conduit 9 is connected to the slurry outlet of the pressure mixing tank 3 through a high-pressure ball valve. Specifically, the pneumatic gauge has a range of 0~1.6MPa and is installed on the air inlet pipe near the air inlet of the mixing tank to monitor the gas pressure input by the air compressor 1. The pressure gauge has a range of 0~2.5MPa and is installed on the slurry outlet pipe near the slurry outlet of the mixing tank to display the grouting pressure in real time. The instrument housing is made of cast aluminum and covered with a transparent impact-resistant protective cover. The dial diameter is 100 mm. ~150mm, making it easy for experimental personnel to read data. The grouting conduit 9 is connected to the grout outlet of the pressure mixing tank 3 through a high-pressure ball valve. The high-pressure ball valve can be made of stainless steel and has manual opening, closing and locking functions. The inlet end of the ball valve is welded and fixed to the grout outlet of the mixing tank through a flange, and the outlet end is connected to the external thread at the front end of the grouting conduit 9 through an internal thread. The connection is wrapped with PTFE raw material tape to ensure a seal. The grouting conduit 9 is a seamless steel pipe with a wall thickness of 3~5mm. The length is determined according to the height of the model box, usually 1.5~2.5 meters. A quick connector is set at the tail of the conduit for easy disassembly.

[0063] Before the experiment, close the high-pressure ball valve and all valves in the mixing tank. Add the cement-water glass grout mixed according to the ratio into the tank, ensuring the grout volume does not exceed 80% of the mixing tank's capacity. Start the mixer 2, setting the speed to 50-200 r / min and stirring for 3-5 minutes until the grout is uniform. Turn on the air compressor 1 and pressurize the mixing tank through the air inlet pipe, observing the pressure gauge reading. Stop pressurizing when the pressure reaches the experimental set value. Slowly open the high-pressure ball valve, and the grout, under air pressure, is injected into the simulated tunnel 6 "face" through the grout outlet pipe and grouting conduit 9. Simultaneously observe the pressure gauge reading and control the grouting pressure to remain stable within the range of 0.3-0.6 MPa. Adjust the grouting rate by adjusting the ball valve opening, maintaining it at 5-15 L / min. After grouting is completed, first close the high-pressure ball valve, then release the remaining air pressure in the mixing tank, and disassemble the grouting conduit 9 for cleaning.

[0064] In another technical solution, the flow velocity sensor 20 is buried at a height of 0.5 to 1.0 times the tunnel diameter above the arch of the simulated tunnel 6, and its measurement range is 0 to 5 m / s. Specifically, the flow velocity sensor 20 is buried at a height of 0.5 to 1.0 times the tunnel diameter above the arch of the simulated tunnel 6. The flow velocity sensor 20 adopts the principle of electromagnetic induction. The housing of the flow velocity sensor 20 is made of stainless steel and can withstand water pressure. The cable is a waterproof shielded cable, and the connection between the cable and the body of the flow velocity sensor 20 is sealed to ensure stable signal transmission in humid environments. During installation, after the model box is filled to the installation height of the simulated tunnel 6, a hole is drilled vertically downwards at the predetermined position. The hole diameter is 5-10mm larger than the outer diameter of the sensor, and the hole depth is the length of the flow velocity sensor 20 plus 20-30mm. The flow velocity sensor 20 is placed horizontally into the hole, keeping its axis consistent with the direction of water flow. Fine sand is filled around it to the top of the flow velocity sensor 20, and then 50-100mm thick undisturbed soil is covered and compacted. The cable is led out from the reserved hole on the side wall of the box and connected to the external data acquisition terminal. The acquisition frequency can be adjusted according to the experimental requirements.

[0065] In the above technical solution, before the experiment, the flow velocity sensor 20 is zero-point calibrated through the data acquisition terminal to ensure that the initial reading is 0 m / s. When the water pressure simulation system is started, the water flows into the soil through the through hole of the rear plate, forming a dynamic water condition from back to front. The flow velocity sensor 20 monitors the water flow velocity in real time. When the water level difference is 0.5m, the flow velocity is measured to be about 0.8~1.2m / s. When the water level difference increases to 1.0m, the flow velocity increases to 1.5~2.5m / s accordingly. The data fluctuation range is ≤±5%. Combined with the grouting process, it can be observed that the grout diffusion direction is consistent with the water flow direction, and the greater the flow velocity, the greater the grout loss.

[0066] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A grouting experimental platform simulating complex surrounding rock conditions in tunnels, characterized in that, include: The model box is a cubic structure welded from multiple independent steel plates. It has regularly distributed through holes on its front and rear side plates. Water tanks are welded and fixed to the outer surfaces of the front and rear side plates, covering the through hole areas and having outlets with valves at the bottom. The top of the water tank on the rear side plate is connected to an external water pressure supply system through a pipe. The center of the water tank on the front side plate has an installation port that matches the outer diameter of the simulated tunnel. One side plate of the model box has a removable cover plate with a sealing strip, and the top has an upper cover plate fixed to the metal edging with bolts. The ground stress simulation system includes a gantry frame welded and fixed to the edge of the upper cover plate, a hydraulic jack installed in the center of the gantry frame, and a pressure plate connected to the hydraulic jack via a ball joint; the water pressure simulation system includes a water storage container connected to a water storage tank on the rear side plate via a hose; and grouting equipment includes a grouting hose horizontally connected to the simulated tunnel face via a grouting conduit, the other end of which is connected to a pressure mixing tank. The pressure mixing tank is inserted into the tunnel face of the box at a horizontal or slightly inclined angle via the grouting conduit, and the pressure mixing tank is connected to an air compressor.

2. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, It also includes a monitoring system, which includes a flow velocity sensor embedded in the arch of the simulated tunnel and a pressure sensor installed between the bearing plate and the simulated tunnel. The flow velocity sensor and the pressure sensor are respectively connected to an external data acquisition terminal.

3. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The through holes are a regularly arranged array of circular holes, all located in the central area of ​​the front and rear side panels.

4. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The water storage tank is fixed to the outer surface of the front / rear side panels by welding. The bottom outlet of the tank is equipped with an openable and closable valve, and the top of the water storage tank on the rear side panel is equipped with a water inlet. The bottom of the water storage container is equipped with a flow regulating valve, and the two ends of the hose are sealed and connected by quick connectors.

5. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The inner diameter of the tunnel model mounting opening of the water tank on the front panel is adapted to the outer diameter of the simulated tunnel, and the two are connected by a sealing ring; the tunnel model is made of PETG material using 3D printing.

6. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The pressure sensor uses a thin-film strain gauge, which is wrapped with a plastic outer film and then coated with a waterproof polyurethane coating with a thickness of 0.2~0.5mm. An inspection port is provided on one side of the model box, with the height of the inspection port being 2 / 3 of the height of the model box, and it is equipped with a removable cover plate for sealing.

7. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The detachable cover plate is fixed to the metal edging with bolts. The flange is embedded in the center of the upper cover plate and the sealing ring is made of nitrile rubber. A vertical guide sleeve is welded to the center of the flange, and its inner diameter is clearance-fitted with the outer diameter of the pressure column of the ground stress simulation system.

8. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The gantry frame is welded to the upper edge of the cover plate; the lower end of the bearing column of the ground stress simulation system is connected to the bearing plate by a ball joint.

9. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 1, characterized in that, The air inlet pipe and slurry outlet pipe of the pressure mixing tank are equipped with air pressure gauges and pressure gauges respectively, and the grouting pipe is connected to the slurry outlet of the pressure mixing tank through a high-pressure ball valve.

10. The grouting experimental platform for simulating complex surrounding rock environments in tunnels as described in claim 2, characterized in that, The flow velocity sensor is buried at a height of 0.5 to 1.0 times the tunnel diameter above the arch of the simulated tunnel, and its measurement range is 0 to 5 m / s.

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