Test device for simulating swelling stratum tunnel heaving floor

Abstract

The utility model discloses a tunnel floor heave test device for simulating an expansive stratum, and belongs to the technical field of tunnel model tests. Comprising a model box and a tension loading frame, the model box is internally filled with test soil and a tunnel model, and the tunnel model is buried at the lower part of the model box; the tension loading frame comprises a horizontal bottom plate, the bottom plate is rectangular, the side length of the bottom plate is larger than the width of the tunnel model, the four corners of the bottom plate are connected with vertically upward tie bars respectively, and the tops of the four tie bars are connected with a top plate; the top plate is connected with a vertically upward main tie bar, and a vertically upward pulling force is applied to the pulling force loading frame through the main tie bar; the tension loading frame is buried in the model box, the bottom plate is located under the center of the tunnel model, the center of the bottom plate right faces the center of the tunnel model, and the tunnel model penetrates out of the tie bars.

Description

Technical Field

[0001] The utility model belongs to the technical field of tunnel model tests, and in particular relates to a tunnel floor drum test device simulating expansive strata. Background Art

[0002] In tunnel engineering, expansive soil is a dangerous geological soil. It will show different degrees of expansion and contraction during water absorption and water loss, and has the characteristics of cracks and over-consolidation. These characteristics will have a significant negative impact on tunnel construction and subsequent safe operation. The existence of expansive soil may lead to the dissipation of over-consolidation pressure during construction, and the water absorption and expansion of the soil will cause the redistribution of surrounding rock stress, which will lead to surrounding rock collapse, resulting in loss of life and property. Engineering practice shows that the expansion force generated by the volume expansion of expansive surrounding rock after absorbing water may cause cracks in the tunnel lining, causing great trouble to the maintenance and safety of the tunnel.

[0003] At present, the research on the damage mechanism of expansive surrounding rock to tunnel structure is mainly carried out from two aspects: numerical simulation and on-site monitoring. Numerical simulation methods usually need to make assumptions and simplifications on the actual situation, which may lead to differences between the model and the actual situation and affect the accuracy of the results. In addition, different parameter selection or model assumptions may also lead to large differences in simulation results. In comparison, model tests simulate the real situation by building a physical model, which can more realistically simulate the tunnel surrounding rock environment and stress conditions, intuitively observe and explain the mechanical behavior and structural characteristics of the model, and through fine control of the test conditions, including loading conditions, environmental conditions, etc., it can comprehensively study and evaluate the response and impact of tunnel engineering.

[0004] At present, there are relatively few test equipment for the damage mechanism of expansive soil tunnels, especially for the most common bottom heave damage in expansive soil tunnels, which makes it difficult to conduct relevant tests. Utility Model Content

[0005] Aiming at the most common floor heave damage in expansive soil tunnels, a test device simulating the floor heave of tunnels in expansive strata was proposed. The test device can simulate the stress of the tunnel invert structure and the deformation of the surrounding rock during the expansion of the expansive soil at the bottom of the tunnel, so as to study the deformation of the floor heave of the expansive soil tunnel.

[0006] To this end, the utility model adopts the following technical solutions:

[0007] A tunnel floor drum test device for simulating expansive strata, comprising a model box and a tension loading frame;

[0008] The model box is used to fill the test soil and the tunnel model, and the tunnel model is buried in the lower part of the model box;

[0009] The tension loading frame comprises a horizontal bottom plate, which is rectangular and has a side length greater than the width of the tunnel model. The four corners of the bottom plate are respectively connected to vertically upward tension bars, and the tops of the four tension bars are connected to the top plate; the top plate is connected to vertically upward main tension bars, and the vertically upward tension is applied to the tension loading frame through the main tension bars; the tension loading frame is buried in the model box, the bottom plate is located directly below the center of the tunnel model, the center of the bottom plate is directly opposite to the center of the tunnel model, and the tunnel model passes through the tension bars;

[0010] Several mechanical sensors are connected inside the tunnel model, and the sensor signals are connected to the host computer.

[0011] Furthermore, a horizontal beam is provided above the model box, a first fixed pulley is fixed at the center of the beam, the first fixed pulley is located directly above the tension loading frame, a second fixed pulley is fixed on the outer end of the beam, the second fixed pulley is arranged side by side with the first fixed pulley; the main tensioning bar on the tension loading frame is vertically upward, bypasses the first fixed pulley and the second fixed pulley, and is connected to a load loading device.

[0012] Furthermore, the load loading device includes a loading tray and weights, the head end of the main tensioning rod is connected to the center position of the loading tray, and the loading tray is used to place the weights.

[0013] Furthermore, the mechanical sensors include micro strain gauges, earth pressure cells and linear displacement meters; the micro strain gauges are used to measure the internal forces and bending moments of the tunnel model lining, the earth pressure cells are used to measure the earth pressure of the tunnel model and the changes in earth pressure of the surrounding rock; the linear displacement meters are placed inside the tunnel model to measure the vertical bottom drum value of the tunnel section.

[0014] The beneficial effects of the utility model are:

[0015] 1. In view of the lack of a tunnel floor drum test device for expansive strata in the field of tunnel test technology, the utility model fills this gap, solves the problem that it is difficult to apply partial expansion force to the tunnel from the bottom of the tunnel in model tests, and can realize an intuitive simulation of the working condition of the tunnel bottom being subjected to the expansion force.

[0016] 2. The model box and loading structure in the utility model are made of simple materials and can be quickly assembled. Compared with the traditional test tunnel loading method, it can not only achieve accurate graded loading but also effectively reduce the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the tunnel floor drum deformation test device of the utility model;

[0018] Figure 2 It is a structural schematic diagram of the model box of the utility model;

[0019] Figure 3It is a structural schematic diagram of the tension loading frame of the utility model;

[0020] Figure 4 It is a structural schematic diagram of the load loading system of the utility model;

[0021] Figure 5 It is a structural schematic diagram of the bottom plate of the utility model;

[0022] In the figure: 1-model box, 2-tension loading frame, 21-bottom plate, 22-tension rod, 23-top plate, 4-first fixed pulley, 5-second fixed pulley, 6-main tension rod, 7-weight, 8-crossbeam. DETAILED DESCRIPTION

[0023] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments:

[0024] like Figure 1 As shown, the utility model includes a test model box 1, which is composed of a box frame welded by channel steel and a transparent organic glass panel. According to the test design, the channel steel is assembled into a rectangular model box 1 frame of corresponding length, width and height. The four sides of the model box 1 frame are bonded with transparent organic glass of corresponding size by glass glue. The upper and lower bottom surfaces of the model box 1 may not be sealed according to the test conditions.

[0025] like Figure 2 and 3 As shown, it also includes a support frame, which is composed of two vertical columns and a cross beam 8. A support plate is provided under the vertical column, and the support plate is a solid I-shaped cast iron block material, which serves to fix and support the vertical column. The vertical column is a solid cast iron cylinder, the lower end of which is welded to the center of the support plate surface, and the upper end is welded with a steel ring, the inner contour of the steel ring fits the outer contour of the cross beam 8, and is used to place and fix the cross beam 8. The two vertical columns are symmetrically placed on both sides of the long side of the model box 1, and the spacing between the two vertical columns can be flexibly adjusted according to the size of the model box 1, and the spacing between the vertical column support plate and the outer edge of the model box 1 should be no less than 30cm, which is used to observe the test phenomenon of tunnel model changes during the test. The crossbeam 8 is a solid cast iron cylinder, with both ends inserted into the steel rings on the upper part of the vertical columns. The length of the crossbeam 8 is set according to the test needs and is at least 50 cm longer than the distance between the two vertical columns. The length of one side of the crossbeam 8 must be at least 50 cm longer than the connection with the vertical column, providing operating space for the installation of the weights 7 in the loading system.

[0026] like Figure 3As shown, the tension loading frame 2 includes a bottom plate 21, a tie rod 22 and a top plate 23. The bottom plate 21 is a rectangular cast iron plate with a thickness of not less than 1.5 cm to ensure that it does not deform when a force is applied. The length and width are related to the test tunnel model. The single-side extension length along the span direction of the tunnel cross section must be greater than 2 cm to ensure that the tunnel invert is evenly stressed. Through holes are reserved at the four corners of the bottom plate 21 for connection with the tie rod 22. The tie rod 22 uses stainless steel wire ropes wrapped with a polymer outer skin material. The lower ends of the four tie rods 22 are respectively connected to the four holes reserved in the bottom plate 21, and the upper part passes through the top plate 23 and is connected to the main tie rod 6. The length of the tie rod 22 is determined according to the position of the test bottom plate 21 and the fill height. The size of the top plate 23 is consistent with that of the bottom plate 21, and the same holes are reserved at the corresponding positions of the bottom plate 21. The material is a cast iron steel plate with a thickness of not less than 1 cm. The function of the top plate 23 is to ensure that the force direction of the four tie bars 22 always remains vertically upward. The first fixed pulley 4 is fixedly suspended at the center of the beam 8, and the second fixed pulley 5 is fixedly suspended at the longer end of the beam 8 at a position not less than 30 cm outward from the vertical upright. After the lower end of the main tie bar 6 is fixedly connected to the four tie bars 22, the upper end first passes through the first fixed pulley 4 to change its force direction from vertical to horizontal, and then passes through the second fixed pulley 5 to change its force direction from horizontal to vertical, and finally connects to the loading tray.

[0027] The working principle of the device is as follows: by loading weights 7 on the loading tray, firstly, a vertical downward pulling force is applied to the main tie bar 6, and the main tie bar 6 converts the vertical downward pulling force into a horizontal pulling force through the second fixed pulley 5 fixed on the cross beam 8, and then converts the horizontal pulling force into a vertical upward pulling force through the first fixed pulley 4. The whole process only changes the direction of the pulling force but does not change its magnitude. The main tie bar 6 evenly transmits the pulling force to the four tie bars 22 connected to its ends, and the direction of the force on the four tie bars 22 is converted from oblique to vertical upward through the four holes of the top plate 23. The four tie bars 22 transmit the pulling force to the bottom plate 21 through the bottom plate 21 connected to its ends, so that the bottom plate 21 obtains a vertical upward force, which is transmitted to the tunnel invert by the surrounding rock. By adding weights 7 step by step, the working condition of simulating the tunnel bottom being subjected to different expansion forces can be achieved.

Claims

1. A tunnel floor drum test device simulating expansive strata, characterized in that: It comprises a model box (1) and a tension loading frame (2); The model box (1) is used to fill test soil and a tunnel model, and the tunnel model is buried in the lower part of the model box (1); The tension loading frame (2) comprises a horizontal bottom plate (21), the bottom plate (21) is rectangular and has a side length greater than the width of the tunnel model, the four corners of the bottom plate (21) are respectively connected to vertically upward tension bars (22), and the tops of the four tension bars (22) are connected to a top plate (23); the top plate (23) is connected to vertically upward main tension bars (6), and vertically upward tension is applied to the tension loading frame (2) through the main tension bars (6); the tension loading frame (2) is buried in the model box (1), the bottom plate (21) is located directly below the center of the tunnel model, the center of the bottom plate (21) is directly opposite to the center of the tunnel model, and the tunnel model passes through the tension bars (22); Several mechanical sensors are connected inside the tunnel model, and the sensor signals are connected to the host computer.

2. The device for testing the tunnel floor drum simulating an expansive stratum according to claim 1, characterized in that: A horizontal crossbeam (8) is provided above the model box (1), a first fixed pulley (4) is fixed at the center of the crossbeam (8), the first fixed pulley (4) is located directly above the tension loading frame (2), a second fixed pulley (5) is fixed on the outer end of the crossbeam (8), the second fixed pulley (5) and the first fixed pulley (4) are arranged side by side; the main tensioning bar (6) on the tension loading frame (2) is connected to a load loading device after passing through the first fixed pulley (4) and the second fixed pulley (5) vertically upward.

3. The device for testing tunnel floor drum in simulated expansive strata according to claim 2, characterized in that: The load loading device comprises a loading tray and a weight (7), the head end of the main tensioning rod (6) is connected to the center position of the loading tray, and the loading tray is used to place the weight (7).

4. The device for testing tunnel floor drum in simulated expansive strata according to claim 1, characterized in that: The mechanical sensors include micro strain gauges, earth pressure cells and linear displacement meters; the micro strain gauges are used to measure the internal forces and bending moments of the tunnel model lining, the earth pressure cells are used to measure the earth pressure of the tunnel model and the changes in earth pressure of the surrounding rock; the linear displacement meters are placed inside the tunnel model to measure the vertical bottom drum values ​​of the tunnel section.

Images