Model test device and test method for excavation face instability under seepage confined water conditions

Abstract

The invention discloses a model test device and a test method for shield excavation face instability under seepage and confined water conditions. The model tunnel of the model test device is closely attached to the inner side of the front face of a model box, the excavation face loading system is located on the left side of the model box, the excavation face loading system is connected to the model tunnel, a water level control system is installed at the lower part of the model box, the excavation face loading system is driven by an engine connected to an active shaft to move a driven shaft, the driven shaft is connected to the outer plate of the shield tunnel, i.e., the tunnel excavation face, so as to control the forward and backward movement of the excavation panel, the excavation face of the tunnel excavation face system is water-permeable, the excavation face loading system can control the displacement of the excavation face, the water level control system is located below the excavation face loading system, the water level control system can control the seepage and the size of confined water, the invention can realize vertical and horizontal seepage and can realize confined water conditions, compared with the existing model box, the invention can provide and control the size of confined water, and is simple and practical.

Description

Technical Field

[0001] The invention relates to the field of rock, soil and underground engineering tunnels, and in particular to a model test device and a test method for excavation face instability under seepage pressure water conditions. Background Art

[0002] With the continuous development of underground structures in my country, urban subways are increasingly accepted as a new mode of transportation. Most urban subways use shield excavation. If the support pressure of shield excavation is too large, the soil in front of the excavation face will rise. If the support pressure is too small, the soil in front of the excavation face will settle or even collapse. The mechanical effect of groundwater seepage on the soil cannot be underestimated. The existing research methods mainly include analytical solutions of theoretical analysis. Analytical solutions often require some assumptions for the convenience of calculation and solution, resulting in errors in the results. In terms of numerical analysis, the mechanical and physical parameters of the soil are often approximate, so there will be large discrepancies in the results of numerical calculations. Model tests can more realistically reflect the actual force distribution of the soil, and model tests are irreplaceable. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a model test device and test method for excavation face instability under seepage and pressurized water conditions, which can ensure that under the action of seepage and pressurized water, the displacement of the excavation face can be accurately controlled and the deformation of the stratum caused by the instability of the excavation face under the action of seepage can be observed.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: a model test device for excavation face instability under seepage confined water conditions, including a model box, a model tunnel, an excavation face loading system, a water level control system and a reading control device, and the specific structure and connection relationship are as follows:

[0005] The model tunnel is close to the inner side of the front of the model box, the excavation surface loading system is located on the left side of the model box, the excavation surface loading system is connected to the model tunnel, the water level control system is installed below the model box, the reading control device is connected to the perforated metal pipe at the bottom of the model box, and the excavation surface loading system is partially separated from the model tunnel by a partition plate inside the model box. The front side of the model box is made of organic glass, the right side panel is set as a switchable box door, and the bottom of the model box is set as a permeable layer composed of perforated metal pipes, so that water can evenly penetrate into the box body. The model tunnel includes a symmetrical semicircular tunnel and an excavation The panel, the model tunnel is installed on the inner side of the plexiglass, the outer side plate of the model tunnel simulates the shield tunnel excavation surface, the shield tunnel excavation surface is made of permeable stone and is permeable, the excavation surface loading system includes a transmission mechanism, the engine of the transmission mechanism is connected to the active shaft, the active shaft is connected to the driven shaft, the driven shaft is connected to the outer side plate of the shield tunnel, that is, the tunnel excavation surface, so as to control the forward and backward movement of the excavation panel, the water level control system includes a water tank, a flow pump, a perforated metal pipe and a pressure gauge, the water tank is connected to the flow pump on the left side in the model box, and the perforated metal pipe is connected to the water tank and the pressure gauge.

[0006] The partition plate is provided with three water leakage holes, which are respectively located at 1D, 2D and 3D of the upper part of the tunnel.

[0007] The front side of the model box is made of organic glass, and the left side, right side and rear side are made of steel plates. The organic glass on the front side of the model box can clearly observe the deformation of the soil, and the right side panel is set as a switchable box door to facilitate loading and taking soil.

[0008] The shield tunnel excavation surface is made of permeable stone.

[0009] The water level control system includes six pressure gauges and six electronic displays.

[0010] The test method of the model test device for excavation face instability under seepage confined water conditions, the specific test operation steps are as follows:

[0011] 1) The soil samples used for the test are loaded into the model box in layers using the sand-rain method;

[0012] 2) Open the saturation hole, add water to the top of the soil sample, and observe whether water flows out of the saturation hole;

[0013] 3) When water flows out of the saturated hole, close it. For the root test, add water to the leaking holes at positions 1D, 2D and 3D, and turn on the flow pump to adjust to the required water head height;

[0014] 4) When the pressure gauge is observed to be stable, the excavation surface loading system is started, the main rotating shaft drives the driven shaft, and the driven shaft drives the permeable surface to retreat. The excavation surface loading system can accurately control the retreat distance and speed of the permeable surface;

[0015] 5) Observe the displacement law of soil caused by the instability of the shield tunnel excavation face under seepage confined water conditions through plexiglass.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. The model box tunnel is a semicircular tunnel installed on plexiglass, which allows the test process and soil layer changes to be well observed during the test.

[0018] 2. The retreat or advance speed of the tunnel excavation face can be controlled by the excavation face loading system.

[0019] 3. The tunnel excavation surface can move forward to simulate over-excavation in actual projects, and can move backward to simulate under-excavation in actual projects.

[0020] 4. The tunnel excavation surface uses a permeable surface, which can more realistically simulate the horizontal lateral seepage of an actual shield tunnel.

[0021] 5. The model box can apply overlying water pressure, and the overlying water pressure can be applied to a maximum of 3D height.

[0022] 6. Pressurized water can be applied to the model box, and the required pressurized water volume can be adjusted and controlled by using a flow pump and a pressure gauge.

[0023] 7. The model box can simulate the seepage conditions of the soil. The overlying water pressure and flow pump are turned on at the same time, which can truly simulate the seepage process in actual engineering.

[0024] 8. The experimental instrument has a simple structure, easy-to-purchase accessories, high degree of automation and high test accuracy, and has a good market application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the model test device for excavation face instability under seepage confined water conditions described in the present invention.

[0026] Figure 2 It is a top view of the model test device for excavation face instability under seepage confined water conditions described in the present invention.

[0027] Figure 3 1-1 is a cross-sectional view of the model test device for excavation face instability under seepage confined water conditions described in the present invention.

[0028] Marked in the figure are: model box 1, model tunnel 2, excavation face loading system 3, water level control system 4, tunnel excavation face 5, engine 6, main rotating shaft 7, driven shaft 8, partition plate 9, water tank 10, flow pump 11, perforated metal pipe 12, pressure gauge 13, saturation hole 14, leakage hole 15, and plexiglass 16. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] like Figures 1 to 3 As shown, the model test device for excavation face instability under seepage confined water conditions of the present invention comprises a model box 1, a model tunnel 2, an excavation face loading system 3, a water level control system and a reading control device, and the specific structure and connection relationship are as follows:

[0031] The model tunnel 2 is located on the inner side of the front of the model box 1, the excavation surface loading system 3 is located on the left side of the model box 1, the excavation surface loading system 3 is connected to the model tunnel 2, the water level control system 4 is installed below the model box 1, the reading control device is connected to the perforated metal pipe 12 at the bottom of the model box, and the excavation surface loading system 3 is partially separated from the model tunnel 2 by a partition plate 9 on the inside of the model box 1. The front of the model box 1 is organic glass 16, and the right side panel is set as a switchable box door. The bottom of the model box 1 is set as a permeable layer composed of perforated metal pipes 12, so that water can evenly penetrate into the box body. The model tunnel 2 includes a symmetrical semicircular tunnel and an excavation panel 5. The model tunnel 2 is installed on the inner side of the organic glass 16. The outer panel of the model tunnel 2 simulates the shield tunnel excavation surface 5, and the shield tunnel excavation surface 5 is permeable. The excavation face loading system 3 includes a transmission mechanism, the engine 6 of the transmission mechanism is connected to the driving shaft 7, the driving shaft 7 is connected to the driven shaft 8, the driven shaft 8 is connected to the outer plate of the shield tunnel, that is, the tunnel excavation face 5, so as to control the forward and backward movement of the excavation panel 5. The water level control system includes a water tank 10, a flow pump 11, a perforated metal pipe 12 and a pressure gauge 13. The water tank 10 is connected to the flow pump 11 at the bottom of the left side of the model box 1, the perforated metal pipe 12 is connected to the water tank 10 and the pressure gauge 13, and the saturation hole 14 is located at the bottom of the right side of the model box 1.

[0032] The partition plate is provided with three water leakage holes, which are respectively located at 1D, 2D and 3D of the upper part of the tunnel (D is the diameter of the tunnel).

[0033] The front side of the model box is made of organic glass, and the left side, right side and rear side are made of steel plates. The organic glass on the front side of the model box can clearly observe the changes of the soil, and the right side panel is set as a switchable box door to facilitate loading and taking soil.

[0034] The tunnel excavation face system includes a symmetrical semicircular tunnel and a permeable panel.

[0035] The tunnel excavation surface 5 is made of permeable stone.

[0036] The excavation face loading system includes an engine, a main rotating shaft and a driven shaft.

[0037] The water level control system comprises one water tank, one flow pump, six perforated metal pipes and six pressure gauges.

[0038] The test method of the refined model test device for shield tunnel excavation face instability under seepage confined water conditions described in the present invention has the following specific operating steps:

[0039] 1) The soil samples used in the test are loaded in layers into the model box 1 using the sand-rain method;

[0040] 2) Open the saturation hole 14, add water to the top of the soil sample, and observe whether water flows out of the saturation hole 14.

[0041] 3) When water flows out of the saturation hole 14, close it. For the root test, add water to the leakage holes 15 at the positions 1D, 2D and 3D. Turn on the flow pump 11 and adjust it to the required water head height.

[0042] 4) When the pressure gauge 13 is observed to be stable, the excavation surface loading system 3 is started, the main rotating shaft 7 drives the driven shaft 8, and the driven shaft 8 drives the excavation panel 5 to retreat. The excavation surface loading system 3 can accurately control the retreat distance and speed of the permeable surface 5;

[0043] 5) Observe the displacement law of soil caused by the instability of the shield tunnel excavation face under the condition of seepage confined water through the organic glass 16.

[0044] When only vertical seepage needs to be considered during the test, proceed as follows:

[0045] After the permeable panel is covered with an impermeable plastic sheet instead of the permeable surface, the corresponding water pressure is applied on the upper part of the soil sample, and the flow pump is turned on for testing.

[0046] When horizontal lateral seepage is required during the test, the following method shall be followed:

[0047] After placing a waterproof steel plate at the bottom of the model box and sealing it on all sides, the corresponding water pressure is applied on the top of the soil sample for testing.

[0048] The model test device for excavation face instability under seepage and confined water conditions is easy to process, the materials are easy to obtain, the structural assembly parts are simple, and tests of different confined water sizes and horizontal, lateral and vertical seepage can be carried out. The advance and retreat of the excavation face can be accurately controlled, and the monitoring data is accurate, which accurately simulates the instability of the shield excavation face under the actual seepage and confined water.

[0049] The above description is only a preferred embodiment of the present invention and is not limited to the present invention. It should be pointed out that for technicians and ordinary people in this field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A model test device for excavation face instability under seepage confined water conditions, comprising a model box, a model tunnel, an excavation face loading system, a water level control system and a reading control device, characterized in that: The specific structure and connection relationship are as follows: The model tunnel is close to the inner side of the front of the model box, the excavation surface loading system is located on the left side of the model box, the excavation surface loading system is connected to the model tunnel, the water level control system is installed below the model box, the reading control device is connected to the metal pipe with holes at the bottom of the model box, and the excavation surface loading system is partially separated from the model tunnel by a partition plate inside the model box. The front side of the model box is made of organic glass, the right side panel is set as a switchable box door, and the bottom of the model box is set as a permeable layer composed of metal pipes with holes, so that water can evenly penetrate into the box body. The model tunnel includes a symmetrical semicircular tunnel. The model tunnel is installed on the inner side of the organic glass, the outer side plate of the model tunnel simulates the tunnel excavation surface, the tunnel excavation surface is water-permeable, the excavation surface loading system includes a transmission mechanism, the engine of the transmission mechanism is connected to the active shaft, the active shaft is connected to the driven shaft, the driven shaft is connected to the outer side plate of the shield tunnel, i.e., the tunnel excavation surface, so as to control the forward and backward movement of the tunnel excavation surface, the water level control system includes a water tank, a flow pump, a metal pipe with holes and a pressure gauge, the water tank is connected to the flow pump on the left side in the model box, and the metal pipe with holes is connected to the water tank and the pressure gauge; The model box is supplied with pressurized water, and the required pressurized water volume is adjusted and controlled by using a flow pump and a pressure gauge; The model box simulates the seepage conditions of the soil, and the overlying water pressure and flow pump are turned on at the same time, truly simulating the seepage process in actual engineering; The saturation hole is located at the bottom right side of the model box; The perforated metal pipe is located below the model tunnel and extends along the tunnel excavation direction, and the holes of the perforated metal pipe are arranged along the length direction; The partition plate is provided with three water leakage holes, which are respectively located at 1D, 2D and 3D in the upper part of the tunnel, where D is the diameter of the tunnel; The front side of the model box is made of organic glass, and the left side, right side and rear side are made of steel plates. The front side of the model box uses organic glass to clearly observe the changes of the soil, and the right side panel is set as a switchable box door to facilitate loading and taking soil; The reading control device includes six pressure gauges and six electronic displays; The specific test steps are as follows: 1) The soil samples used for the test are loaded into the model box in layers using the sand-rain method; 2) Open the saturation hole, add water to the top of the soil sample, and observe whether water flows out of the saturation hole; 3) When water flows out of the saturated hole, close it. Add water to the leaking holes at positions 1D, 2D and 3D according to the test requirements. Turn on the flow pump and adjust it to the required water head height. 4) When the pressure gauge is observed to be stable, the excavation face loading system is started. The main rotating shaft drives the driven shaft, and the driven shaft drives the tunnel excavation face to retreat. The excavation face loading system can accurately control the retreat distance and speed of the tunnel excavation face; 5) Observe the displacement law of soil caused by instability of tunnel excavation face under seepage pressure water conditions through organic glass; When only vertical seepage needs to be considered during the test, the following method is used: the tunnel excavation surface is blocked with a waterproof plastic sheet, the corresponding water pressure is applied to the upper part of the soil sample, and the flow pump is turned on for the test; When horizontal transverse seepage is required during the test, the following method is used: after placing an impermeable steel plate at the bottom of the model box and sealing it on all sides, apply corresponding water pressure on the upper part of the soil sample for testing; It is capable of conducting tests on different sizes of pressurized water and horizontal, lateral and vertical seepage.

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