Testing device and method for studying influence mechanism of simulated ground grouting on shield tunnel

Abstract

The application provides a test device and method for simulating the influence mechanism of ground grouting on a shield tunnel, and relates to the technical field of test devices, and specifically includes the following: a box is filled with soil in the order of a first soil simulation layer, a second water-rich sand simulation layer and a third soil simulation layer, a water inlet is formed in one side of the box for water injection into the second water-rich sand simulation layer; a grouting pipe is extended into the second water-rich sand simulation layer from outside the box for simulating ground grouting; a segment model is arranged in the second water-rich sand simulation layer of the box for simulating a shield tunnel; stress and strain sensors and displacement sensors are fixed on the segment model for sensing stress and strain and displacement; and the application simulates the ground grouting process to obtain the variation law of the stress and strain and displacement of the segment with time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of test devices, and particularly relates to a test device and method for simulating the influence mechanism of ground grouting on a shield tunnel. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] With the acceleration of urbanization in China, ground transportation facilities have been difficult to bear the increasing traffic volume, and underground space construction has become an important means to alleviate traffic pressure. More and more subways are built, and a series of subway safety problems follow. At present, the tunnel of the subway station is generally constructed by the cut-and-cover method, of which the typical representatives are the mine method and the shield method. The shield method is widely used in urban subway construction due to its safety and efficiency. However, due to the different specific conditions of strata in different regions and the occurrence of groundwater, the shield construction may cause certain safety hazards. For areas with developed groundwater systems, the freezing method can prevent the influence of groundwater during construction. However, as the tunnel usage period becomes longer, regular maintenance and repair are required. If the external environment of the tunnel is unstable or there is a water-rich area, it will pose a potential threat to the safety of the internal chamber.

[0004] At present, the methods of in-hole grouting and ground grouting are generally used to stop water to reduce the permeability coefficient of the soil around the tunnel lining and block the connection between groundwater and the tunnel chamber. Due to the limitations of tunnel space and subway operation time, in-hole grouting is generally used for small-scale reconstruction, limited water inflow, and small grouting volume. Ground grouting is mainly used for water-rich strata around the tunnel, wide reconstruction, and large grouting volume. It can fundamentally transform the tunnel peripheral strata environment and play a decisive role in preventing tunnel water inflow. Ground grouting is performed by drilling and grouting on the ground above the tunnel area to block the nearby loose water-bearing body through stratum seepage. Due to the diffusion of grouting pressure, it will have a certain impact on the tunnel lining structure. If the grouting pressure is too high, it will damage the tunnel structure and even cause safety accidents. If the grouting pressure is too low, the grout cannot effectively fill the gap, and the stratum transformation effect is poor, which cannot play the expected water-blocking role. Therefore, it is of great theoretical and engineering value to study the influence mechanism of ground grouting pressure control on existing tunnel structures, and it has important guiding significance for the safety of the lining structure and the control of stratum stability.

[0005] There is currently no research device for ground grouting on tunnel segments, but the mechanism of grouting pressure transmission from the stratum to the segment is extremely complex and difficult to accurately describe through theoretical research. The existing device cannot simulate the process of external grout diffusion to the tunnel segment. SUMMARY

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a test device and method for studying the influence mechanism of ground grouting on a shield tunnel.

[0007] In order to achieve the above-mentioned purpose, one or more embodiments of the present application provide the following technical solutions:

[0008] The present application provides a test device for studying the influence mechanism of ground grouting on a shield tunnel.

[0009] The test device for studying the influence mechanism of ground grouting on a shield tunnel comprises:

[0010] The box is filled with soil in the order of the first soil simulation layer, the second water-rich sand simulation layer, and the third soil simulation layer. A water inlet is formed on one side of the box for injecting water into the second water-rich sand simulation layer. A grouting pipe extends from the outside of the box into the second water-rich sand simulation layer for grouting to simulate ground grouting.

[0011] A segment model is arranged in the second water-rich sand simulation layer of the box to simulate a shield tunnel.

[0012] Stress-strain sensors and displacement sensors are fixed on the segment model to sense strain and displacement.

[0013] An analysis module obtains the influence mechanism of ground grouting on a shield tunnel based on the sensed strain and displacement.

[0014] The influence mechanism includes the variation of stress-strain and displacement of the segment model with time and the mechanical characteristics of stress, axial force, bending moment, and displacement of the segment model under different grouting pressures.

[0015] Further, the box is made of thick acrylic plates and is provided with a pressure-bearing steel frame around the periphery. A water inlet is formed on one side, and a water outlet is formed at the bottom of the other side.

[0016] The water inlet and the water outlet are provided with water-permeable membranes to prevent fine sand from being lost.

[0017] Further, the grouting pipe is connected with a grouting system through a pipeline.

[0018] The grouting system comprises an air compressor and a grouting cylinder.

[0019] Further, the grouting cylinder is a metal sealed tank for containing grout and serving as a pressure-bearing device for pumping grout.

[0020] Further, the grouting barrel is provided with two valves at the top, one of which is used as an air inlet valve to connect the air compressor, and the other is used as a pressure relief valve; and the bottom is provided with a grout outlet valve connected with the grouting pipe.

[0021] Further, the lower end of the grouting pipe is provided with a small hole in the horizontal direction, and the slurry enters the second water-rich sand layer through the small hole to simulate the diffusion of the slurry in the grouting process.

[0022] Further, the segment model is a tubular structure with open ends, which is prepared by taking the actual shield segment as a prototype and is arranged transversely in the second water-rich sand layer of the box body, and a rubber gasket is used to seal the contact part between the segment model and the side wall of the box body.

[0023] Further, the stress-strain sensors are multiple and are uniformly distributed and fixed on the inner wall and the outer wall of the segment model.

[0024] The displacement sensors are multiple, one end of which is fixed on the horizontal rod inside the segment model, and the other end is in contact with the inner wall of the segment model.

[0025] Further, the analysis module comprises an acquisition instrument and a computer.

[0026] The stress-strain sensors and the displacement sensors are both connected with the acquisition instrument.

[0027] The acquisition instrument acquires the strain monitoring value of the stress-strain sensor and the displacement monitoring value of the displacement sensor.

[0028] The computer obtains the change rule of the stress-strain and displacement of the segment model with time and calculates the stress, axial force, bending moment and displacement mechanical characteristics of the segment model under the action of different grouting pressures.

[0029] The second aspect of the present application provides a test method for studying the influence mechanism of ground grouting on shield tunnels.

[0030] The test method for studying the influence mechanism of ground grouting on shield tunnels adopts the test device provided by the first aspect of the present application to test the influence mechanism of ground grouting on shield tunnels, and the specific steps are as follows:

[0031] Water is continuously injected into the second water-rich sand layer through the water inlet to simulate a water-rich environment.

[0032] Under a preset grouting pressure, grouting is performed on the second water-rich sand layer through the grouting pipe.

[0033] The slurry seepage diffuses to the segment model, and the stress-strain sensor and the displacement sensor perceive the strain and displacement of the segment model.

[0034] Adjusting different grouting pressures to carry out repeated tests, based on the perceived strain and displacement, the influence mechanism of ground grouting on shield tunnel is obtained;

[0035] The influence mechanism includes the stress-strain and displacement of the segment model over time and the stress, axial force, bending moment and displacement mechanical characteristics of the segment model under the action of different grouting pressures.

[0036] The above one or more technical solutions have the following beneficial effects:

[0037] In the present application, the segment model is arranged in the second water-rich sand layer of the box body, and the two ends are in contact with the box body and sealed and waterproofed by using rubber rings, which is more realistic in simulating the ability of the tunnel segment to maintain its stability under the action of the external environment than the prior art.

[0038] In the present application, the permeation and diffusion conditions of different buried depths and different stratum environments are simulated by preparing similar materials and controlling the thickness of each stratum, the pressure control device of the air compressor is used for pressure control, the slurry is relatively constant pressure delivery value grouting pipe, the stratum gap is gradually filled by permeation through the side hole of the grouting pipe, and the valve at the grouting hole of the grouting cylinder can control the grouting test in time, and in the current research, there are few devices for studying the influence of ground grouting on tunnel segments.

[0039] The present application can also test different grouting distances, grouting times and stratum materials, different grouting distances can be realized by changing the position of the pre-buried grouting pipe, thereby changing the distance from the grouting pipe to the segment model, different grouting times are realized by controlling the opening time of the grouting valve from the grouting cylinder to the grouting pipe, and the stratum material is controlled according to the test design scheme to control different soil types and filling thickness, so as to obtain the influence of different grouting distances, grouting times and stratum materials on shield tunnel grouting.

[0040] The advantages of the additional aspects of the present application will be partially given in the following description, partially will become obvious from the following description, or will be known by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and their explanation serve to explain the present application, and do not constitute an improper limitation of the present application.

[0042] Figure 1 It is a device structure diagram of the first embodiment.

[0043] Figure 2 It is a device side view of the first embodiment.

[0044] Figure 3A sensor distribution diagram for the first embodiment.

[0045] Wherein, 1, air compressor; 2, pressure regulating device; 3, pressure gauge; 4, grouting cylinder; 5, platform scale; 6, air inlet valve; 7, pressure relief valve; 8, grout outlet valve; 9, box; 10, water inlet; 11, grouting pipe; 12, stress-strain sensor; 13, rubber gasket; 14, segment model; 15, acquisition instrument; 16, computer; 17, water outlet; 18, crossbar; 19, displacement sensor. DETAILED DESCRIPTION

[0046] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments consistent with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0048] Example One

[0049] In one or more embodiments, a test device for simulating the influence mechanism of ground grouting on shield tunneling is disclosed, as shown in Figure 1 , Figure 2 The test device mainly includes an air compressor 1, a pressure regulating device 2, a pressure gauge 3, a grouting cylinder 4, a platform scale 5, an air inlet valve 6, a pressure relief valve 7, a grout outlet valve 8, a box 9, a water inlet 10, a grouting pipe 11, a stress-strain sensor 12, a displacement sensor 19, a rubber gasket 13, a segment model 14, an acquisition instrument 15, a computer 16, a water outlet 17, and a crossbar 18.

[0050] I. Box 9

[0051] The box 9 is made of thick acrylic plate, and a steel frame is arranged around the box 9 to bear pressure. The soil body is filled in the order of a first simulated soil layer, a second simulated water-rich sand layer, and a third simulated soil layer. In this embodiment, the filled soil body is a combination of clay-sand-clay. In other embodiments, the filler can be in other soil layer forms, such as clay-gravel-clay, clay-sand-clay-gravel-clay, etc.

[0052] The pipe segment model 14 is arranged horizontally in the second water-rich sand layer, and is sealed by a rubber gasket 13; the grouting pipe 11 extends into the second water-rich sand layer from outside the box 9 to perform grouting, and the grouting pipe 11 is fixed on the upper part of the box 9 by the cross bar 18 to simulate ground grouting; the grouting pipe 11 and the pipe segment model 14 are positioned and pre-buried during soil filling, and need to ensure that the soil is substantially consistent and in close contact with the element.

[0053] The grouting pipe 11 is kept at a distance of 1.5 times the outer diameter of the pipe segment model from the pipe segment model 14, and a small hole is arranged at the lower end of the grouting pipe 11 in the horizontal direction, through which the grouting material can enter the soil to simulate the diffusion of grout and the action of the pipe segment during the grouting process.

[0054] A water inlet 10 is arranged on one side of the box 9, and a water outlet 17 is arranged at the bottom of the other side; the water inlet 10 and the water outlet 17 are provided with a water-permeable film to prevent fine sand from being lost.

[0055] In this embodiment, water flows into the water inlet 10, and flows out of the water outlet 17 stably to ensure a water-rich environment, so that the next grouting test can be started; in other embodiments, water can be injected through other water inlets, and if the water outlet position cannot be connected to the water outlet, a porous concrete thin block can be pre-buried on the left side of the box 9 to guide the flow to the lower water outlet 17.

[0056] In other embodiments, the water flowing out of the water outlet 17 is collected as waste water, and the flow rate and flow of the water can be controlled and adjusted according to different test conditions, thereby simulating the flow of underground water during grouting.

[0057] II. Grouting system

[0058] The grouting pipe 11 is connected to a grouting system through a pipeline, and the grouting system includes an air compressor 1, a pressure regulating device 2, a pressure gauge 3, a grouting cylinder 4, a platform scale 5, an air inlet valve 6, a pressure relief valve 7, a grout outlet valve 8, and the grouting cylinder 4.

[0059] The grouting cylinder 4 is a metal sealed tank body for containing grouting liquid, such as cement grout, and serving as a pressure bearing device for pumping grout; the grouting cylinder 4 is placed on the platform scale 5 to facilitate recording the amount of grouting.

[0060] The air compressor 1 serves as a device for providing grouting pressure, and is provided with a pressure regulating device 2 to control the grouting pressure, so that the grout is delivered at a relatively constant pressure into the grouting pipe 11.

[0061] The grouting cylinder 4 is provided with a pressure relief valve 7, and the air inlet valve 6 is connected with the air compressor 1, the pipeline here is an exhaust hose, and the pressure regulating device 2 is arranged; the grouting cylinder 4 is provided with a grouting valve 8 at the bottom of the side, which is connected with the grouting pipe 11, and the pipeline here is a grouting hose; the grouting hose, the grouting cylinder 4, the exhaust hose, the pressure regulating device 2 and the air compressor 1 can be used for simulating the ground grouting process in the actual construction process.

[0062] Three, sensors

[0063] The stress-strain sensors 12 and the displacement sensors 19 are all multiple; the stress-strain sensors 12 are uniformly distributed and fixed on the inner wall and the outer wall of the segment model 14; the displacement sensors 19 are fixed on the horizontal rod inside the segment model 14, and one end is used as the fixed point of displacement, and the other end is in contact with the inner wall of the segment model 14.

[0064] The stress-strain sensors 12 and the displacement sensors 19 are connected with the acquisition instrument 15, and the acquisition instrument 15 is connected with the computer 16; specifically, the stress-strain sensors 12, the displacement sensors 19, the acquisition instrument 15 and the computer 16 can be used for measuring and exporting the strain and displacement of the inner wall of the segment in the test process; in order to ensure the stability of the segment model 8 in the test process, eight groups of stress-strain sensors 12 can be used to measure the strain of the outer wall and the inner wall of the segment model 14, and the stress-strain sensors 12 select three-way strain flowers to measure the strain in the axial direction, the ring direction and the axial and ring direction angle bisector direction; four groups of displacement sensors 19 are used to measure the four-way displacement of the segment model 14.

[0065] The stress-strain sensors 12 need to be pasted flat and closely on the outer and inner walls of the segment model, and the outer wall stress-strain sensors 12 need to be brushed with a waterproof coating to prevent water and slurry from affecting the measurement, and the displacement sensors 19 need to be stably fixed on the horizontal rod inside the segment model 14, and also need to ensure that the measuring head contacts the inner wall of the segment model 14 and can freely stretch and contract within a sufficient range; the sensor wiring fixed on the inner wall of the segment model 14 is stretched out through the inside, and the sensor on the outer wall of the segment model 14 needs to be stretched out from the rubber gasket 13 in advance, and all are connected with the acquisition instrument 15 of the analysis module.

[0066] Four, analysis module

[0067] The acquisition instrument 15 is used to collect the strain monitoring value of the stress-strain sensor 12 and the displacement monitoring value of the displacement sensor 19, and transmit to the computer 16 of the analysis module, and finally the computer 16 obtains the influence mechanism of ground grouting on the shield tunnel according to the strain and displacement data of the segment model 14 in the test process, specifically including the stress-strain and displacement of the segment model with time variation law and the stress, axial force, bending moment and displacement mechanical characteristics of the segment model under the action of different grouting pressures.

[0068] V. Working process or principle of the device

[0069] (1) The setting process of the stress-strain sensor 12 and the displacement sensor 19 is as follows:

[0070] As shown in Figure 3 , 8 points are uniformly arranged along the ring direction of the segment model 14, and 16 stress-strain sensors 12 are fixed at the corresponding positions of the inner and outer walls. A waterproof coating is applied to the outer wall to ensure the normal operation of the outer wall sensor. The displacement sensor 19 is fixed on the crossbar across the middle of the segment model 14, and the measuring heads thereof respectively contact the upper and lower inner walls of the segment model 14 in four directions, and ensure a stretching range of 0.5 cm.

[0071] (2) The box 9 can mainly be used for containing soil, accommodating the segment model 14 and providing a seepage space for grouting. The soil filling process is as follows:

[0072] Firstly, a water-permeable film is arranged at the water inlet 10 and the water outlet 17 to prevent fine sand loss;

[0073] Secondly, fill the soil in the box 9 to a certain height, pre-bury the segment model 14 and the grouting pipe 11 at the set position, fix the grouting pipe 11 on the upper part of the box 9 by the crossbar 18, and fix the segment model 14 in the segment model accommodating area and waterproof seal by the rubber gasket 13. The grouting pipe 11 is fixed on the box 9 by the crossbar 18 to ensure the stability of the grouting pipe 11;

[0074] Finally, according to the implementation scheme, the soil is filled layer by layer, the uniformity of the soil density is ensured as much as possible, the stress-strain sensor 12 fixed on the outer wall of the segment model 14 is protected, and the soil near the grouting pipe 11 is pressed to ensure close combination.

[0075] (3) The grouting cylinder 4 serves as a slurry storage device and has a certain pressure-bearing capacity. Before use, the rubber ring and the bolt are tightly closed, and the air tightness is checked. The specific operation is as follows:

[0076] The air compressor 1 in the grouting system is connected to the grouting cylinder 4 through the air conveying hose, the pressure relief valve 7 and the grout outlet valve 8 are closed, the air inlet valve 6 is opened, the air compressor 1 is started, and the pressure gauge 3 is observed. After the specified pressure value is reached, the pressure regulating device 2 is adjusted to stabilize at the pressure value. Check whether the grouting cylinder 4 has air flow sound, and whether the pressure gauge 3 reading decreases within a period of time. If all the above phenomena occur, the grouting cylinder 4 has good air tightness.

[0077] (4) After checking the pressure relief in the cylinder, the specific operation of the grouting test is as follows:

[0078] Disconnect the air inlet valve 6 from the air compressor 1, open the air inlet valve 6 and the pressure relief valve 7, and pump the slurry from the pressure relief valve 7 into the grouting cylinder 4 by a small water pump. The nozzle should be inserted into the grouting cylinder 4 to prevent the slurry from sticking to the pressure relief valve 7 and affecting the subsequent exhaust pressure relief. The volume of pumped slurry should not exceed 3 / 4 of the volume of the grouting cylinder 4. Record the mass of the slurry by the platform scale 5, then close the pressure relief valve 7, reconnect the air inlet valve 6 to the air compressor 1, start the air compressor 1, and observe the pressure gauge 3. When the pressure reaches the specified value, adjust the pressure regulating device 2 to stabilize at the pressure value. Debug the software and start collecting data. Open the grouting valve 8 to allow the slurry to flow uniformly from the grouting cylinder 4, through the small hole at the lower section of the grouting pipe 11, and into the soil. The slurry diffuses to the pipe segment model 14, causing changes in the stress-strain sensor 12 and displacement sensor 19. The relevant data is collected and recorded. Stop grouting when the monitoring data changes or the soil surface shows signs of grouting. Record the remaining grouting amount of the platform scale 5 again, stop data collection, close the grouting valve 8, air compressor 1, and air inlet valve 6 in turn, and open the pressure relief valve 7 to exhaust. When the pressure gauge 3 shows 0, disconnect the grouting valve 8 from the grouting hose, open the grouting valve 8, and allow the slurry to flow freely into the temporary collection device below. Pump clean water into the cylinder through the pressure relief valve 7 until clean water flows out of the grouting valve 8. Close the grouting valve 8, remove the grouting pipe 11 from the soil, and reconnect it to the grouting valve 8. When sufficient clean water is pumped into the grouting cylinder 4, remove the water pump pipe and close the pressure relief valve 7. Start the air compressor 1 and control the pressure to a small value. Open the air inlet valve 6 and the grouting valve 8 to allow clean water to flow out of the grouting pipe 11. Collect the waste liquid and allow the remaining cement slurry in the grouting pipe 11 to flow out. When the clean water in the grouting cylinder 4 is exhausted, close the grouting valve 8, air compressor 1, and air inlet valve 6 in turn.

[0079] (5) The analysis process is as follows:

[0080] After the test is completed, the collected data is exported to the computer 16 to obtain the strain and displacement changes of the pipe segment model 14 during grouting. The maximum stress value of the measuring point is calculated by formula (1), and the bending moment and axial force at the measuring point are known by formula (2). The mechanical response law of the pipe segment model 14 under the action of grouting pressure is obtained.

[0081] Based on the three strains of the stress-strain sensor 12 in the axial, ring, and axial and ring angle bisector directions, the formula for calculating the maximum stress is:

[0082] (1)

[0083] wherein, , respectively represent the first, third principal stress, , and respectively represent the corresponding strain of the strain rosette in the axial direction (x), the hoop direction (y) and the axial and hoop bisector direction (z), represents the elastic modulus of the segment model material, represents the Poisson's ratio of the segment model material.

[0084] The bending moment M and the axial force N of the tunnel model are calculated according to the following formula:

[0085] (2)

[0086] wherein, b is the unit length of the segment in the longitudinal direction; h is the thickness of the tunnel segment; E is the elastic modulus of the lining material; , respectively represent the strain of the inner wall and the outer wall of the segment in different directions.

[0087] The idea in the embodiment is to rely on the ground grouting scheme for reinforcing the stratum near the tunnel in the actual project, simulate the whole process of ground grouting, monitor the stress, strain and displacement data of the tunnel to study the mechanical response characteristics of the tunnel under the action of different grouting pressures, and apply the same to the actual project.

[0088] Embodiment Two

[0089] In one or more embodiments, a test method for studying the influence mechanism of ground grouting on a shield tunnel is disclosed, which uses the test device disclosed in Embodiment One to test the influence mechanism of ground grouting on a shield tunnel, including:

[0090] Water is continuously injected into the sand layer (second waterproof layer) through the water inlet 10 until a stable water flow flows out of the water outlet 17, simulating a water-rich environment; the air tightness of the grouting cylinder 4 is tested to prepare for the grouting test;

[0091] The air compressor 1 provides grouting pressure to inject the slurry in the grouting cylinder 4 into the soil in the box 9;

[0092] The slurry penetrates and diffuses to the soil around the segment model 14;

[0093] The strain and displacement of the segment model 14 are tested by the stress and strain sensor 12 and the displacement sensor 19 until the strain and displacement monitoring values change suddenly or the soil surface shows the phenomenon of slurry penetration, the grouting is stopped and the grouting equipment is cleaned;

[0094] ​​Adjusting different grouting pressure to carry out repeated test, get the stress-strain and displacement of the pipe model with time variation law; get the stress, axial force, bending moment and displacement of the pipe model under different grouting pressure by formula (1) (2).

[0095] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A test apparatus for studying the influence mechanism of simulating ground grouting on shield tunnels, characterized in that, include: The box is filled with soil in the order of the first imitation soil layer, the second imitation water-rich sand layer, and the third imitation soil layer. A water inlet is opened on one side of the box for injecting water into the second imitation water-rich sand layer. The grouting pipe extends from the outside of the box into the second imitation water-rich sand layer for grouting, and the grouting pipe is fixed to the upper part of the box with a crossbar to simulate ground grouting. The segment model is set in the second simulated water-rich sand layer of the box body to simulate a shield tunnel; Stress-strain sensors and displacement sensors are fixed on the segment model to sense strain and displacement; The analysis module, based on the sensed strain and displacement, obtains the influence mechanism of ground grouting on shield tunnels; The influencing mechanism includes the stress, strain, and displacement of the segment model over time, as well as the stress, axial force, bending moment, and displacement mechanical characteristics of the segment model under different grouting pressures. The segment model is a tubular structure with open ends. It is prepared based on actual shield tunnel segments and is horizontally placed in the second simulated water-rich sand layer of the box body. Rubber gaskets are used to seal the contact part between the segment model and the side wall of the box body. The grouting pipe and the segment model are positioned and pre-embedded during the soil filling process to ensure consistent soil compaction. This allows for testing of different grouting distances, grouting times, and ground materials. Different grouting distances are achieved by changing the position of the pre-embedded grouting pipe, thereby changing the distance between the grouting pipe and the segment model.

2. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 1, characterized in that, The box is made of thick acrylic sheet and has a pressure-bearing steel frame around it. It has a water inlet on one side and a water outlet at the bottom on the other side. The inlet and outlet are equipped with permeable membranes to prevent the loss of fine sand.

3. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 1, characterized in that, The grouting pipe is connected to a grouting system via a pipeline; The grouting system includes an air compressor and a grouting cylinder.

4. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 3, characterized in that, The grouting cylinder is a sealed metal tank used to hold grout and as a pressure-bearing device for grout pumping.

5. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 3, characterized in that, The grouting cylinder has two valves at the top: one is an air inlet valve connected to the air compressor, and the other is a pressure relief valve; the bottom has a grout outlet valve connected to the grouting pipe.

6. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 1, characterized in that, The lower end of the grouting pipe is provided with a small hole in the horizontal direction. The grout enters the second simulated water-rich sand layer through the small hole to simulate the diffusion of grout during the grouting process.

7. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 1, characterized in that, The stress and strain sensors are multiple, evenly distributed and fixed on the inner and outer walls of the tube segment model; The displacement sensor comprises multiple sensors, one end of which is fixed to a crossbar inside the segment model, and the other end is in contact with the inner wall of the segment model.

8. The test apparatus for studying the influence mechanism of simulated ground grouting on shield tunnels as described in claim 1, characterized in that, The analysis module includes a data acquisition device and a computer; Both the stress-strain sensor and the displacement sensor are connected to a data acquisition device; The data acquisition device acquires the strain monitoring values ​​of the stress-strain sensor and the displacement monitoring values ​​of the displacement sensor. The computer obtains the stress, strain, and displacement variation patterns of the segment model over time, and calculates the stress, axial force, bending moment, and displacement mechanical characteristics of the segment model under different grouting pressures.

9. A test method for studying the impact mechanism of simulated ground grouting on shield tunnels, characterized in that, The test, conducted using the testing apparatus described in any one of claims 1-8, simulates the impact mechanism of ground grouting on shield tunnels. The specific steps are as follows: Water is continuously injected into the second simulated water-rich sand layer through the inlet to simulate a water-rich environment. Under the preset grouting pressure, grout is injected into the second simulated water-rich sand layer through the grouting pipe; The grout seeps and diffuses into the segment model, and the strain and displacement of the segment model are sensed by stress-strain sensors and displacement sensors. By adjusting different grouting pressures and conducting repeated tests, the influence mechanism of ground grouting on shield tunnels was obtained based on the sensed strain and displacement. The influencing mechanism includes the stress-strain and displacement variation law of the segment model over time, and the stress, axial force, bending moment and displacement mechanical characteristics of the segment model under different grouting pressures.

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