Test device and test method for simulating instability of excavation face of tunnel under action of seepage

Abstract

The invention discloses a test device and a test method for simulating instability of a tunnel excavation face under the action of seepage, and relates to the technical field of geotechnical engineering. Comprising a model box, one side of the model box is provided with a transparent observation window, and soil for simulating a stratum is arranged in the model box; the tunnel model is positioned in the model box and clings to the observation window; the control device is arranged in the model box and connected with the tunnel model, and the control device is used for controlling the tunnel model to simulate excavation; the image acquisition system is located on the outer side of the model box and records the internal condition of the model box through an observation window; the water tank is arranged on the outer side of the model box and communicates with the model box through a water conveying pipe, and a flow pump is arranged in the water tank; the water storage bin is arranged below the model box, a water inlet hole is formed in the water storage bin, and the model box is communicated with the water storage bin through the tunnel model and the water inlet hole. According to the invention, the excavation face can be withdrawn at an ultra-low speed, and the instability of the tunnel excavation face under the seepage effect is simulated.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering, and in particular to a test device and a test method for simulating the instability of a tunnel excavation face under seepage action. Background Art

[0002] As the construction scale of shield tunnels continues to expand, the engineering problems they face are becoming more and more complex. The stability of the excavation face is an important issue faced in shield tunnel construction. Excavation face instability disasters can cause stratum damage, and in severe cases even cause surface collapse, posing a serious threat to the project site and the surrounding environment. Excavation face instability is difficult to predict, occurs suddenly, and is greatly affected by stratum conditions. Therefore, the need for in-depth research on the instability mechanism of shield tunnel excavation faces and stratum deformation characteristics under complex conditions is becoming more and more urgent.

[0003] As more and more tunnels need to cross rivers, water-rich strata have gradually become the main construction strata for new shield tunnels. Seepage will weaken the stability of the strata and increase the probability of excavation face instability. Therefore, research on tunnel excavation faces under seepage has important engineering significance.

[0004] Therefore, there is an urgent need for a test device and test method that simulates the instability of tunnel excavation face under seepage. Summary of the invention

[0005] The main purpose of the present invention is to provide a test device and a test method for simulating the instability of a tunnel excavation face under the action of seepage, so as to solve the above-mentioned problem.

[0006] To achieve the above-mentioned purpose, the present invention provides a test device and a test method for simulating the instability of a tunnel excavation face under seepage, comprising:

[0007] A model box, wherein a transparent observation window is provided on one side of the model box, and soil simulating a stratum is provided inside the model box;

[0008] A tunnel model, the tunnel model is located in the model box and close to the observation window;

[0009] A control device, which is arranged in the model box and connected to the tunnel model, and is used to control the tunnel model to perform simulated excavation;

[0010] An image acquisition system, the image acquisition system is located outside the model box and records the internal conditions of the model box through the observation window;

[0011] A water tank, which is arranged outside the model box and is connected to the model box through a water pipe, and a flow pump is arranged in the water tank;

[0012] A water storage bin is arranged below the model box, a water inlet hole is arranged on the water storage bin, and the model box is connected with the water storage bin through the tunnel model and the water inlet hole.

[0013] Further, the tunnel model includes a shield shell, an excavation surface and a support block, wherein the shield shell is arranged on the support block, the shield shell is a hollow semi-cylinder, the arc surface of the shield shell is away from the observation window, the excavation surface is arranged in the shield shell and is slidably connected to the shield shell, the shape of the excavation surface is adapted to the shape of the shield shell, and one end of the excavation surface is drivingly connected to the control device;

[0014] The bottom of the shield shell is provided with a shield shell drainage hole, the excavation surface is provided with a seepage hole, the top of the support block is provided with a groove corresponding to the shield shell drainage hole, the bottom of the groove is provided with a through hole, and the through hole is connected with the water inlet hole.

[0015] Furthermore, the control device includes a servo motor and a retraction rod, the retraction rod includes a screw rod and a connecting rod, the screw rod is connected to the output shaft of the servo motor through a coupling, one end of the connecting rod is connected to the moving seat of the screw rod, and the other end is connected to the excavation surface.

[0016] Furthermore, a geotextile is provided on a side of the excavation surface away from the screw rod.

[0017] Furthermore, the image acquisition system includes a camera bracket, a high-speed camera and a lighting device. The camera bracket is arranged on the model box and close to the observation window. The high-speed camera and the lighting device are arranged on the camera bracket.

[0018] Further, a regulating box is provided on one side of the model box, a high drainage hole and a low drainage hole are vertically provided on the side wall of the model box close to the regulating box, a drainage pipe is provided on the high drainage hole and the low drainage hole, the drainage pipe passes through the regulating box and extends into the water storage tank, and an electromagnetic valve is provided on the low drainage hole;

[0019] The control device is arranged in the regulating box, and one end of the tunnel model is located in the model box and the other end extends into the regulating box.

[0020] Furthermore, a plurality of vertical partitions are provided in the water storage bin, the partitions divide the water storage bin into a plurality of areas, and a connecting port is provided at the bottom of the partitions.

[0021] Furthermore, the test device for simulating instability of tunnel excavation face under seepage as claimed in claim 1 comprises the following steps:

[0022] S1. Determine the test parameters, including tunnel diameter, formation parameters, and water head height;

[0023] S2. Lay the ground in the model box according to the test design and bury the test elements;

[0024] S3, hanging the prepared model box to the centrifuge basket, connecting the external water tank, and starting the image acquisition system;

[0025] S4, start the centrifuge, and after reaching the set acceleration, open the water tank to supply water into the model box to keep the water level at a certain height;

[0026] S5. After the water level is adjusted to the test setting requirements, the control device is started to drive the tunnel model to simulate tunnel excavation;

[0027] S6. Collecting stratum parameters during tunnel excavation and taking photos;

[0028] S7. After the tunnel excavation is completed, turn off the water tank and servo motor, slow down and stop the centrifuge, save the data and end the test.

[0029] Furthermore, in step S3, two water tanks are provided, which are respectively arranged on the rotating arms on both sides of the centrifuge shaft; a public computer electrically connected to the flow pump, the control device and the image acquisition system is provided on the top of the centrifuge.

[0030] The present invention has the following beneficial effects:

[0031] 1. The present invention uses a servo motor to provide power, and uses a lead screw to convert angular displacement into linear displacement, and is assisted by a reducer. It can achieve the retreat of the excavation surface at an ultra-slow speed of 0.05 mm / s, so that the high-speed camera can clearly capture the entire process of the development of the unstable zone, thereby greatly improving the accuracy of PIV image analysis.

[0032] 2. In this study, a water tank is installed on each arm of the centrifuge shaft, and a flow pump is used to supply water to the model box. This arrangement shortens the distance between the water tank and the centrifuge arm, reduces the supergravity on the water tank, and reduces the safety hazards of the external water tank. Since the supergravity on the water tank is smaller than that on the model box, the water flow no longer needs to overcome the supergravity, but can use the gravity difference to flow to the model box. Even a low-power water pump can meet the requirements, and a high-power water pump is no longer needed.

[0033] 3. The present invention adjusts the water level in the model box by controlling the switch of the drainage hole through the solenoid valve, thereby simulating the changing seepage effect, making the seepage conditions simulated by the present invention closer to the actual engineering situation, which is conducive to in-depth research on the instability mechanism of the tunnel excavation face under the action of seepage. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is an overall schematic diagram of the test device for simulating the instability of the tunnel excavation face under the action of seepage according to the present invention.

[0035] Figure 2 It is a schematic diagram of a tunnel model of a test device for simulating instability of a tunnel excavation face under seepage action according to the present invention.

[0036] Figure 3 It is a schematic diagram of a regulating box of a test device for simulating instability of a tunnel excavation face under seepage action according to the present invention.

[0037] Figure 4 It is a schematic diagram of the pull-back rod of the test device for simulating the instability of the tunnel excavation face under the action of seepage in the present invention.

[0038] Among them, 1-model box; 2-lighting equipment; 3-high-speed camera; 4-camera bracket; 5-waterproof board; 6-shield; 7-retreat rod; 8-support block; 9-excavation surface; 10-water tank; 11-servo motor; 12-shield drainage hole; 13-through hole; 14-seepage hole; 15-servo motor support block; 16-reducer; 17-public computer; 18-drain pipe; 19-electromagnetic valve; 20-water storage tank; 21-test area; 22-adjusting box; 23-high drainage hole; 24-low drainage hole; 25-partition; 26-screw; 27-connecting rod; 28-support rod. DETAILED DESCRIPTION

[0039] In order to achieve the above-mentioned purpose and effect, the technical means and structures adopted by the present invention are described in detail with reference to the accompanying drawings for the features and functions of the preferred embodiments of the present invention.

[0040] like Figure 1-4 As shown, the present invention provides a test device for simulating the instability of a tunnel excavation face under seepage, comprising:

[0041] The model box 1 has a transparent observation window on one side, and the interior is a test area 21 filled with soil simulating a stratum, and a waterproof board 5 is provided on the top of the test area 21 to prevent water from overflowing.

[0042] The tunnel model comprises a shield shell 6, an excavation face 9 and a support block 8. The support block 8 is arranged in a model box 1. The shield shell 6 is arranged on the support block 8. The shield shell 6 is a hollow semi-cylinder. The opposite side of the arc surface on the shield shell 6 is close to the observation window. The excavation face 9 is arranged in the shield shell 6 and is slidably connected with the shield shell 6. The shape of the excavation face 9 is adapted to the shape of the shield shell 6. One end of the excavation face 9 is drivingly connected to the control device. A shield shell drainage hole 12 is arranged at the bottom of the shield shell 6, a seepage hole 14 is arranged on the excavation face 9, a groove corresponding to the shield shell drainage hole 12 is arranged at the top of the support block 8, and a through hole 13 is arranged at the bottom of the groove.

[0043] The image acquisition system includes a camera bracket 4, a high-speed camera 3 and a lighting device 2. The camera bracket 4 is arranged on the model box 1 and is close to the observation window. The high-speed camera 3 and the lighting device 2 are arranged on the camera bracket 4 and are opposite to the observation window.

[0044] A water tank 10, which is arranged outside the model box 1 and is connected to the test area 21 in the model box 1 through a water pipe. A flow pump is arranged in the water tank 10 to control the water supply from the water tank 10 to the test area 21;

[0045] The water storage bin 20 is arranged below the model box 1 . The water storage bin 20 is provided with a water inlet hole connected to the through hole 13 , so that the water storage bin 20 is connected with the inside of the shield shell 6 to collect the water discharged from the shield shell 6 .

[0046] A regulating box 22 is provided on one side of the model box 1. A high drainage hole 23 and a low drainage hole 24 are vertically provided on the side wall of the model box 1 close to the regulating box 22. A drainage pipe 18 is provided on both the high drainage hole 23 and the low drainage hole 24. The drainage pipe 18 passes through the regulating box 22 and extends into the water storage tank 20. An electromagnetic valve 19 is provided on the low drainage hole 24 or the drainage pipe 18 connected to the low drainage hole 24 to control the opening and closing of the low drainage hole 24. The staff can adjust the water level in the model box 1 by controlling the opening and closing of the low drainage hole 24 to simulate the changing seepage effect.

[0047] One end of the shield shell 6 is located in the model box 1, and the other end extends into the adjustment box 22. A control device is provided on one side of the adjustment box 22 close to the shield shell 6. The control device includes a servo motor 11 and a retraction rod 7. The servo motor 11 is arranged on the servo motor support block 15 so as to adapt to the height of the shield shell 6. The output shaft of the servo motor 11 is connected to the reducer 16, and the output shaft of the reducer 16 is connected to the retraction rod 7. The retraction rod 7 includes a screw rod 26 and a connecting rod 27. The screw rod 26 is connected to the output shaft of the reducer 16 through a coupling. One end of the connecting rod 27 is connected to the moving seat of the screw rod 26, and the other end is connected to a support rod 28. The other end of the support rod 28 is fixedly connected to the excavation surface 9 in the shield shell 6, so that the servo motor 11 can be driven to move the excavation surface 9 in the shield shell 6.

[0048] At the same time, the model box 1, the adjustment box 22 and the water storage tank 20 can be set as multiple areas of an integrated structure to improve the integrity of the device.

[0049] In another embodiment, a plurality of vertical partitions 25 are provided in the water storage tank 20, and the partitions 25 divide the water storage tank 20 into a plurality of areas, and a connecting port is provided at the bottom of the partition 25 to interconnect the plurality of areas. The vertical partitions can be used as auxiliary support structures to improve the overall strength of the device, and by dividing the water storage tank into a plurality of areas, the water flow in the water storage tank 20 can be prevented from forming large fluctuations and impacts during the test, thereby reducing the influence of the fluctuation of the water flow on the test.

[0050] In another embodiment, the side of the excavation face 9 contacting the ground is wrapped with a geotextile to prevent soil from entering the tunnel through the seepage holes 14 .

[0051] The present invention also provides a test method using the test device for simulating tunnel excavation face instability under seepage, comprising the following steps:

[0052] S1. Determine the test conditions such as water head height and formation parameters according to the test requirements, and design the retreat speed of the excavation face. Install the water tank 10 on the rotating shafts on both sides of the centrifuge to ensure that the water tank 10 is firmly installed.

[0053] S2. Install the support block 8 and the shield shell 6, adjust the servo motor support block 15 to a suitable height, install and connect the servo motor 11, the retreat rod 7 and the excavation surface 9 in sequence, and rotate the screw 26 to push the excavation surface 9 to the rightmost side of the shield shell 6.

[0054] S3. Fill the ground according to the designed test conditions and bury the test components. The ground should be filled in layers, and the position and working condition of the test components should be carefully checked to ensure that all components are operating normally.

[0055] S4, hang the model box 1 on the centrifuge basket, debug the camera bracket 4, turn on the lighting equipment 2 and check the lighting effect and the shooting angle of the high-speed camera 3; a public computer 17 electrically connected to the flow pump, control device and image acquisition system is installed on the top of the centrifuge.

[0056] S5, start the public computer 17, prepare the servo debugging software and start data acquisition, turn on the high-speed camera 3, and fill the water tank 10 with water.

[0057] S6, start the centrifuge and accelerate to the set super gravity, open the flow pump to transfer water into the model box 1, observe the water level through the high-speed camera 3, close the electromagnetic valve 19, and raise the water level to the high drainage hole 23.

[0058] S7, after the water level is stable, the continuous shooting function of the high-speed camera 3 is turned on, and the servo motor 11 is turned on at the same time, and the excavation face 9 is controlled to retreat in a set manner through the servo debugging software, so that the stratum in front of the excavation face 9 becomes unstable and damaged.

[0059] S8. After the excavation face 9 is withdrawn to the test set distance, the servo motor 11 is turned off, the water addition into the model box 1 is stopped, and the centrifuge is turned off to end the test. Subsequently, data processing and image PIV analysis are performed to simulate the stratum displacement and stress changes caused by the instability of the tunnel excavation face under the action of stable seepage.

[0060] When simulating the changing seepage effect, take the enhancement of seepage effect as an example, make the water level rise from the low drainage hole 24 to the high drainage hole 23 during the instability process, and correspondingly make the water level drop from the high drainage hole 23 to the low drainage hole 24 to simulate the weakening of seepage effect. A preliminary experiment should be carried out to determine the speed of water level change, and adjust the operating power of the flow pump to ensure that the seepage effect changes according to the set intensity. The preliminary experiment steps are as follows:

[0061] S1. Determine the test conditions such as water head height and formation parameters according to the test requirements, and design the retreat speed of the excavation face. Install the water tank 10 on the rotating shafts on both sides of the centrifuge to ensure that the water tank 10 is firmly installed.

[0062] S2. Install the support block 8 and the shield shell 6, adjust the servo motor support block 15 to a suitable height, install and connect the servo motor 11, the retreat rod 7 and the excavation surface 9 in sequence, and rotate the screw 26 to push the excavation surface 9 to the rightmost side of the shield shell 6.

[0063] S3. Fill the strata according to the designed test conditions. The filling of the strata should be carried out in layers.

[0064] S4, hang the model box 1 on the centrifuge basket, debug the camera bracket 4, turn on the lighting equipment 2 and check the lighting effect and the shooting angle of the high-speed camera 3; a public computer 17 electrically connected to the flow pump, control device and image acquisition system is installed on the top of the centrifuge.

[0065] S5, start the public computer 17, prepare the servo debugging software and start data acquisition, turn on the high-speed camera 3, and fill the water tank 10 with water.

[0066] S6, start the centrifuge and accelerate to the set super gravity, open the flow pump to deliver water to the model box 1, observe the water level through the high-speed camera 3, open the solenoid valve 19, and keep the water level at the low drainage hole 24.

[0067] S7. After the water level is stable, the electromagnetic valve 19 is closed, and the servo motor 11 is turned on to control the excavation surface 9 to retreat in a set manner through the servo debugging software. The water level changes in the test area 21 are monitored by the high-speed camera 3 during the whole process.

[0068] S8. After the excavation surface 9 is withdrawn to the test set distance, the servo motor 11 is turned off, and the water addition into the model box 1 is stopped. The model box 1 is lifted out and the flow pump power is adjusted according to the water level change.

[0069] S9. Repeat steps S6 to S8 until the water level can change according to the test design during the retreat of the excavation surface 9, and prepare for the formal test.

[0070] The formal test steps are as follows:

[0071] S1. Determine the test conditions such as water head height and formation parameters according to the test requirements, and design the retreat speed of the excavation face. Install the water tank 10 on the rotating shafts on both sides of the centrifuge to ensure that the water tank 10 is firmly installed.

[0072] S2. Install the support block 8 and the shield shell 6, adjust the servo motor support block 15 to a suitable height, install and connect the servo motor 11, the retreat rod 7 and the excavation surface 9 in sequence, and rotate the screw 26 to push the excavation surface 9 to the rightmost side of the shield shell 6.

[0073] S3. Fill the ground according to the designed test conditions and bury the test components. The ground should be filled in layers, and the position and working condition of the test components should be carefully checked to ensure that all components are operating normally.

[0074] S4, hang the model box 1 on the centrifuge basket, debug the camera bracket 4, turn on the lighting equipment 2 and check the lighting effect and the shooting angle of the high-speed camera 3; a public computer 17 electrically connected to the flow pump, control device and image acquisition system is installed on the top of the centrifuge.

[0075] S5, start the public computer 17, prepare the servo debugging software and start data acquisition, turn on the high-speed camera 3, and fill the water tank 10 with water.

[0076] S6, start the centrifuge and accelerate to the set super gravity, start the flow pump to transfer water into the model box 1, observe the water level through the high-speed camera 3, open the electromagnetic valve 19, and keep the water level at the low drainage hole 24.

[0077] S7. After the water level is stable, the electromagnetic valve 19 is closed to make the water level in the test area 21 start to rise. At the same time, the servo motor 11 is turned on. The servo debugging software controls the excavation face 9 to retreat in a set manner, causing the stratum in front of the excavation face 9 to become unstable and damaged. During the whole process, the continuous shooting function of the high-speed camera 3 is turned on.

[0078] S8. After the excavation face 9 is withdrawn to the test set distance, the servo motor 11 is turned off, the water addition into the model box 1 is stopped, and the centrifuge is turned off to end the test. Subsequently, data processing and image PIV analysis are performed to simulate the stratum displacement and stress changes caused by the instability of the tunnel excavation face under the action of changing seepage.

[0079] In another embodiment, two water tanks 10 are provided, which are respectively provided on the rotating arms on both sides of the centrifuge shaft. This shortens the distance between the water tank 10 and the rotating arm of the centrifuge, reduces the supergravity on the water tank 10, and reduces the safety hazard of the external water tank 10.

[0080] The above descriptions are only preferred embodiments of the present invention, not all embodiments. Anyone should be aware that any structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, belong to the protection scope of the present invention.

Claims

1. A test device for simulating the instability of tunnel excavation face under seepage, characterized in that: include: A model box (1), wherein a transparent observation window is provided on one side of the model box (1), and soil simulating a stratum is provided inside the model box (1); A tunnel model, the tunnel model being located in the model box (1) and close to the observation window; A control device, the control device being arranged in the model box (1) and connected to the tunnel model, the control device being used to control the tunnel model to perform simulated excavation; An image acquisition system, the image acquisition system being located outside the model box (1) and recording the internal conditions of the model box (1) through the observation window; a water tank (10), the water tank (10) being arranged outside the model box (1) and being connected to the model box (1) via a water pipe, and a flow pump being arranged inside the water tank (10); A water storage bin (20), the water storage bin (20) being arranged below the model box (1), the water storage bin (20) being provided with a water inlet hole, and the model box (1) being connected to the water storage bin (20) via the tunnel model and the water inlet hole.

2. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 1, characterized in that: The tunnel model comprises a shield shell (6), an excavation surface (9) and a support block (8); the shield shell (6) is arranged on the support block (8); the shield shell (6) is a hollow semi-cylinder; the arc surface of the shield shell (6) is away from the observation window; the excavation surface (9) is arranged in the shield shell (6) and is slidably connected to the shield shell (6); the shape of the excavation surface (9) is adapted to the shape of the shield shell (6); and one end of the excavation surface (9) is drivingly connected to the control device; The bottom of the shield shell (6) is provided with a shield shell drainage hole (12), the excavation surface (9) is provided with a seepage hole (14), the top of the support block (8) is provided with a groove corresponding to the shield shell drainage hole (12), the bottom of the groove is provided with a through hole (13), and the through hole (13) is connected to the water inlet hole.

3. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 2, characterized in that: The control device comprises a servo motor (11) and a retreat rod (7), the retreat rod (7) comprises a screw rod (26) and a connecting rod (27), the screw rod (26) is connected to the output shaft of the servo motor (11) via a coupling, one end of the connecting rod (27) is connected to the moving seat of the screw rod (26), and the other end is connected to the excavation surface (9).

4. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 3, characterized in that: A geotextile is provided on the side of the excavation surface (9) away from the screw rod (26).

5. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 1, characterized in that: The image acquisition system comprises a camera bracket (4), a high-speed camera (3) and a lighting device (2); the camera bracket (4) is arranged on the model box (1) and close to the observation window; the high-speed camera (3) and the lighting device (2) are arranged on the camera bracket (4).

6. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 1, characterized in that: A regulating box (22) is arranged on one side of the model box (1); a high drainage hole (23) and a low drainage hole (24) are vertically arranged on a side wall of the model box (1) close to the regulating box (22); drainage pipes (18) are arranged on the high drainage hole (23) and the low drainage hole (24); the drainage pipes (18) pass through the regulating box (22) and extend into the water storage bin (20); and a solenoid valve (19) is arranged on the low drainage hole (24); The control device is arranged in the regulating box (22); one end of the tunnel model is located in the model box (1) and the other end extends into the regulating box (22).

7. The test device for simulating instability of tunnel excavation face under seepage as claimed in claim 1, characterized in that: A plurality of vertical partitions (25) are arranged in the water storage bin (20), and the partitions (25) divide the water storage bin (20) into a plurality of areas. A communication port is arranged at the bottom of the partitions (25).

8. A test method for simulating the instability of tunnel excavation face under seepage, characterized in that: The test device for simulating instability of tunnel excavation face under seepage action as claimed in claim 1 comprises the following steps: S1. Determine the test parameters, including tunnel diameter, formation parameters, and water head height; S2. Laying the ground in the model box (1) according to the test design and burying the test elements; S3, hanging the prepared model box (1) on the centrifuge basket, connecting the external water tank (10), and starting the image acquisition system; S4, starting the centrifuge, and after reaching the set acceleration, opening the water tank (10) to supply water into the model box (1) so that the water level is maintained at a certain height; S5. After the water level is adjusted to the test setting requirements, the control device is started to drive the tunnel model to simulate tunnel excavation; S6. Collecting stratum parameters during tunnel excavation and taking photos; S7. After the tunnel excavation is completed, the water tank (10) and the servo motor (11) are turned off, the centrifuge is decelerated and stopped, the data is saved and the test is ended.

9. The test method for simulating instability of tunnel excavation face under seepage as claimed in claim 8, characterized in that: In step S3, two water tanks (10) are provided, which are respectively arranged on the rotating arms on both sides of the centrifuge shaft; a public computer (17) electrically connected to the flow pump, the control device and the image acquisition system is provided on the top of the centrifuge.

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