Tunnel primary support mechanical model test device and method based on air bag combined control

Abstract

The invention discloses a tunnel primary support mechanical model test device and method based on air bag combined control, and relates to the field of tunnel construction model tests.The tunnel primary support mechanical model test device comprises a test box, a tunnel primary support model and an air bag assembly, similar surrounding rock materials are filled between the outer side of the tunnel primary support model and the test box; the tunnel primary support model is provided with a sensor assembly, and the sensor assembly is used for monitoring mechanical property parameters of the tunnel primary support model; the air bag assembly is installed in the tunnel primary support model and comprises a plurality of air bags, and each air bag is provided with an air valve and used for simulating the instant unloading process of tunnel step-by-step excavation. According to the invention, a plurality of groups of air bags are used for inflation and deflation, so that the process of instant unloading and step-by-step excavation of a tunnel can be simulated, tunnel construction primary support and surrounding rock mechanics space-time response law test working conditions under various construction methods can be completed, and the test accuracy and test efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of tunnel construction model testing, and in particular to a tunnel primary support mechanical model testing device and method based on airbag combination control. Background Art

[0002] During tunnel construction, affected by complex factors such as geological conditions and construction quality, the instantaneous unloading caused by the drilling and blasting method may cause loosening of surrounding rock, significant deformation of primary support, and other precursory characteristics that can easily lead to structural instability. Tunnel safe construction technology under complex construction environments requires a lot of scientific research. Clarifying the mechanical response characteristics of primary support during tunnel construction through mechanical tests is an important way to study the precursors of primary support instability.

[0003] At present, the test methods related to tunnel construction simulation are mainly model tests based on the principle of similarity. The surrounding rock is simulated by preparing similar materials by calculating the scale, and the lining model materials are selected by scaling the mechanical properties of the primary support to achieve accurate simulation of the construction process. In reality, according to construction environmental factors such as cross-sectional dimensions and surrounding rock conditions, commonly used construction methods can be divided into upper and lower step methods, center partition (CD) methods, etc. This requires accurate monitoring of the relationship between commonly used methods and surrounding rock stability and primary support stability during the model test process. In the prior art, there is a test device that uses a ring mechanical loading device instead of surrounding rock to simulate surrounding rock pressure. The advantages of this method are small workload, high controllability, and the ability to explore the mechanical response mode of the lining under construction and operation conditions. However, this type of device cannot accurately simulate the progressive influence of surrounding rock and soil on lining stress during tunnel excavation. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a tunnel primary support mechanical model test device and method based on airbag combination control. The use of multiple sets of airbags to inflate and deflate can simulate the process of instantaneous unloading and step-by-step excavation of the tunnel. It can complete the test conditions of the temporal and spatial response laws of the primary support and surrounding rock mechanics of tunnel construction under various construction methods, and can improve the accuracy and efficiency of the test.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, embodiments of the present invention provide a tunnel primary support mechanical model test apparatus based on airbag combination control, comprising a test chamber, a tunnel primary support model, and an airbag assembly. The tunnel primary support model is laterally disposed within the test chamber, and the space between the outer side of the tunnel primary support model and the test chamber is filled with similar surrounding rock material. The tunnel primary support model is provided with a sensor assembly for monitoring mechanical performance parameters of the tunnel primary support model.

[0007] The airbag assembly is installed inside the tunnel primary support model. The airbag assembly includes multiple airbags, each of which is equipped with an air valve to simulate the instantaneous unloading process of step-by-step tunnel excavation.

[0008] As a further implementation method, in the inflated state, the outer surface of the airbag fits with the mechanical model of the primary branch of the tunnel, and the inner contact surfaces of adjacent airbags fit with each other.

[0009] As a further implementation, the airbag is made of double-layer composite rubber.

[0010] As a further implementation, the sensor assembly includes a resistance strain gauge and an earth pressure gauge, and a plurality of the resistance strain gauge and the earth pressure gauge are arranged along the circumference of the tunnel primary support model.

[0011] As a further implementation method, the sensor assembly also includes a pull-rope displacement meter, and a support frame for installing the pull-rope displacement meter is fixed on the top of the test box. The rope ends of the pull-rope displacement meter are fixed at the arch top and arch waist positions of the tunnel primary support model.

[0012] As a further implementation, the support frame includes a frame, and the frame is provided with a mounting groove; the pull-wire displacement meter is arranged in the mounting groove.

[0013] As a further implementation, the test box includes a test box body having a box-shaped structure, and two opposing baffles of the test box body are provided with installation openings for the tunnel primary support model;

[0014] The tunnel primary support model is connected to the baffle through a flange plate.

[0015] As a further implementation method, the tunnel primary support model and baffle are made of acrylic material.

[0016] In a second aspect, an embodiment of the present invention further provides a tunnel primary support mechanical model test method based on airbag combination control, using the test device, including:

[0017] Fill the test chamber with similar surrounding rock material, and simultaneously calculate the pressure of the similar material on the tunnel primary support mechanical model. Inflate the airbag according to the pressure value; the inflation pressure is equal to the pressure of the similar material on the tunnel primary support model.

[0018] The airbag is unloaded and deflated according to the set excavation method. During the deflation process, the displacement, strain and soil pressure of the tunnel primary support mechanical model are monitored.

[0019] As a further implementation method, the airbags at the set positions are deflated according to the up-and-down step excavation method or the CD excavation method.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The test device of the present invention includes a test box, a tunnel primary support model and an airbag assembly. The tunnel primary support model is arranged in the test box along the horizontal direction. The airbag assembly is installed inside the tunnel primary support model. The number of airbags in the airbag assembly can be adjusted according to the excavation method. By using airbags at different positions to deflate to perform instantaneous unloading simulation, the influence law of the mechanical response process of the tunnel primary support model can be analyzed.

[0022] (2) The pull-rope displacement meter of the present invention is arranged on the top of the test box, the resistance strain gauges are arranged on the arch top, the arch shoulders on both sides, the arch waists on both sides, the arch feet on both sides, and the arch bottom positions on the outer surface of the tunnel primary support model, and the soil pressure gauge is arranged inside the filled surrounding rock similar material, corresponding to the arch top, the arch shoulders on both sides, the arch waists on both sides, the arch feet on both sides, and the arch bottom positions on the outer surface of the tunnel primary support model; the tunnel mechanical properties are monitored by the pull-rope displacement meter, the resistance strain gauge and the soil pressure gauge; and during the filling process of the surrounding rock similar material, the pressure of the surrounding rock on the tunnel primary support model is collected in real time by burying the soil pressure gauge, and the pressure in the air bag is monitored by the air pressure sensor integrated on the air valve, and the air valve is fed back using the real-time collected soil pressure, so that the air pressure in the air bag and the soil pressure reach a dynamic relative balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 is a schematic structural diagram of a test device according to one or more embodiments of the present invention;

[0025] Figure 2 is a schematic structural diagram of a test chamber according to one or more embodiments of the present invention;

[0026] Figure 3 is a schematic structural diagram of an airbag assembly according to one or more embodiments of the present invention;

[0027] Figure 4 is a schematic diagram of the distribution of sensor components according to one or more embodiments of the present invention;

[0028] Figure 5 It is a schematic diagram of the structure of a carrier according to one or more embodiments of the present invention.

[0029] Among them, 1. test box, 1-1. test box body, 1-2. tunnel primary support model, 1-3. baffle, 1-4. positioning hole, 1-5. drainage hole;

[0030] 2. Airbag combination, 2-1, first airbag, 2-2, second airbag, 2-3, third airbag, 2-4, fourth airbag;

[0031] 3. Carrying frame, 3-1. Frame, 3-2. Mounting slot, 3-3. Column;

[0032] 4. Sensor assembly, 4-1. Pull-rope displacement meter, 4-2. Resistance strain gauge, 4-3. Soil pressure gauge. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0034] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0035] Example 1:

[0036] This embodiment provides a tunnel primary support mechanical model test device based on airbag combination control, such as Figure 1 and Figure 2 As shown, it includes a test box 1, a tunnel primary support model 1-2 and an airbag assembly 2. The tunnel primary support model 1-2 is arranged horizontally in the test box 1, and the outer side of the tunnel primary support model 1-2 and the space between the test box 1 are used to fill with similar surrounding rock materials; the airbag assembly 2 is installed inside the tunnel primary support model 1-2 to simulate the instantaneous unloading process of step-by-step tunnel excavation.

[0037] Specifically, the test chamber 1 includes a test chamber body 1-1. In this embodiment, the test chamber body 1-1 is a rectangular box-shaped structure. The tunnel primary support model 1-2 is positioned in the middle of the test chamber body 1-1 along its width. The test chamber body 1-1 is surrounded by baffles 1-3 to form a closed structure, with a bottom plate installed at the bottom and an open structure at the top. The front and rear sides of the test chamber body 1-1 form a support frame composed of a grid-like steel plate, and baffles 1-3 are installed inside the support frame. The baffles 1-3 are made of acrylic. The grid-like support frame ensures the support performance of the front and rear sides of the test chamber body 1-1, and facilitates observation of the internal conditions of the test chamber 1 without affecting the overall structural strength of the test chamber 1.

[0038] like Figure 2As shown, the grid-shaped support frame is provided with multiple positioning holes 1-4 on its edge, which are used to cooperate with the baffle 1-3. Several drainage holes 1-5 are provided near the bottom on the left and right sides of the test box body 1-1 for draining water during the simulated water environment test.

[0039] The front and rear baffles 1-3 are provided with mounting openings, into which the tunnel primary support model 1-2 is assembled. In this embodiment, in order to simulate cracking and brittle failure during the test, the tunnel primary support model 1-2 is made of acrylic material. It has an elastic range and brittle failure, and its strength meets the requirements after scale conversion. It can be used to simulate the surrounding rock collapse caused by the failure of the primary support concrete. The shape of the tunnel primary support model 1-2 is designed according to the shape of the tunnel. It has flange plates at both ends. The flange plates and the baffles 1-3 are attached to the inner surface of the baffles 1-3, and the tunnel primary support model 1-2 is connected to the test box body 1-1 by bolts.

[0040] The airbag assembly 2 is filled in the tunnel primary branch model 1-2. When the airbag assembly 2 is inflated, it can generate pressure on the tunnel primary branch model 1-2. Multiple groups of airbag assemblies 2 are arranged in the transverse direction (in the direction of the axis of the tunnel primary branch model 1-2). Each group of airbag assemblies 2 includes multiple airbags, such as Figure 3 As shown, multiple airbags are arranged in sequence along the circumferential direction of the tunnel primary support model 1-2 to form a structural form that is compatible with the tunnel primary support model 1-2; each airbag is equipped with an air valve, which controls the inflation and deflation of the airbag; the airbag deflation process is used to simulate the influence of the instantaneous unloading of the drilling and blasting method on the mechanical response process of the surrounding rock and the primary support.

[0041] In this embodiment, each group of airbag assemblies 2 includes four airbags, namely the first airbag 2-1 and the second airbag 2-2 on the upper side and the third airbag 2-3 and the fourth airbag 2-4 on the lower side; each of the above airbags has two contact surfaces on the inner side. Taking the first airbag 2-1 as an example, in the inflated state, one contact surface of the first airbag 2-1 is in contact with the second airbag 2-2, and the other contact surface of the first airbag 2-1 is in contact with the third airbag 2-3; the outer surface of the first airbag 2-1 is in contact with the inner wall of the tunnel primary branch model 1-2.

[0042] In this embodiment, the airbag is made of double-layer composite rubber, in which the outer layer is chloroprene rubber and the inner layer is silicone rubber, which has high elasticity and fatigue resistance. Through valve control, the airbag in the specified area can be completely depressurized within 0.1 seconds, simulating the instantaneous unloading process of the drilling and blasting method.

[0043] The tunnel primary support model 1-2 is equipped with a sensor assembly 4, which includes a pull-rope displacement meter 4-1, a resistance strain gauge 4-2 and an earth pressure gauge 4-3. Figure 4As shown, resistance strain gauges 4-2 and earth pressure gauges 4-3 are arranged at certain intervals along the circumferential direction of the tunnel primary support model 1-2; in this embodiment, resistance strain gauges 4-2 are arranged at the arch crown, spandrels on both sides, haunches on both sides, arch feet on both sides, and arch bottom positions on the outer surface of the tunnel primary support model 1-2, and the earth pressure gauges 4-3 are set inside the filled surrounding rock-similar material and are located at the arch crown, spandrels on both sides, haunches on both sides, arch feet on both sides, and arch bottom positions on the outer surface of the tunnel primary support model 1-2; the monitoring surfaces of the resistance strain gauges 4-2 and the earth pressure gauges 4-3 are parallel to the tangent line of the outer surface of the tunnel primary support model 1-2 to ensure the accuracy of data monitoring.

[0044] The rope displacement meter 4-1 is installed on the support frame 3, and the rope ends of the rope displacement meter 4-1 are glued to the surface of the arch top and arch waist of the tunnel primary support model 1-2 by structural adhesive. Figure 5 As shown, the carrier frame 3 includes a skeleton 3-1 and a mounting groove 3-2. The skeleton 3-1 is in a cross structure. A column 3-3 is installed at the end of the skeleton 3-1, and the end of the column 3-3 is fixedly connected to the test box body 1-1; the mounting groove 3-2 is arranged on the upper surface of the skeleton 3-1, so the mounting groove 3-2 also forms a cross structure to facilitate the measurement of displacement data in different directions; the purpose of setting the mounting groove 3-2 is to improve the universality of the carrier frame 3, which can be applied to the adjustment of the installation position of the sensor under different scales.

[0045] This embodiment uses a pull-rope displacement meter 4-1 to obtain displacement information, which is used to analyze the spatial changes in the surrounding rock above the primary support during each instantaneous unloading of drilling and blasting excavation. The displacement values ​​of each step in the excavation process are then correlated in chronological order, allowing the temporal characteristics of the changes in the surrounding rock near the face and the primary support during the construction of different drilling and blasting methods to be obtained. If the primary support fails at any stage, the critical displacement at the time of failure can also be obtained. The strain information obtained by the resistance strain gauge 4-2 can be used to calculate the bending moment of the primary support and further calculate the safety factor. The safety factor calculated for each excavation step can be used to observe the spatial distribution characteristics of the safety factor after instantaneous unloading of the excavation. By connecting the safety factor distribution of each step in chronological order of excavation, the temporal characteristics of the changes in the surrounding rock near the face and the primary support during drilling and blasting excavation can be obtained. The soil pressure meter 4-3 can be used to monitor the spatiotemporal characteristics of the stress redistribution of the primary support after instantaneous unloading.

[0046] Therefore, by extracting the displacement, strain, and earth pressure throughout the entire construction process, the spatiotemporal characteristics of the mechanical response of the surrounding rock near the tunnel face and the entire primary support in each excavation cycle are explored, providing theoretical support for the optimization of construction methods.

[0047] In this embodiment, the air valve is installed with an air pressure sensor. During the filling process of surrounding rock similar materials, the pressure of the surrounding rock on the primary support model is collected in real time through the embedded soil pressure gauge 4-3. At the same time, the pressure in the air bag is monitored by the air pressure sensor integrated on the air valve. The real-time collected soil pressure is used to provide feedback to the air valve, so that the air pressure in the air bag and the soil pressure reach a dynamic relative balance.

[0048] Example 2:

[0049] This embodiment provides a tunnel primary support mechanical model test method based on airbag combination control, using the test device described in Example 1, including the following steps:

[0050] Step 1: Install the test device.

[0051] The opening of the baffle 1-3 and the tunnel primary support model 1-2 are designed according to different scales, burial depths, and cross-sectional dimensions; the baffle 1-3 is connected to the main body of the test box 1, and the tunnel primary support model 1-2 is connected to the baffle 1-3. The airbag assembly 2 is designed and placed according to the corresponding excavation method, and then the various sensors and the support frame 3 are installed.

[0052] Step 2: Fill the test box 1 with similar surrounding rock materials. During the filling process, calculate the pressure of the similar material on the primary support, and inflate the airbag as the filling progresses. The inflation pressure is equal to the pressure of the similar material on the primary support model. After the filling is completed, if it is necessary to simulate a water-containing environment, water is injected into the similar material according to the test design. After completion, the sensor is calibrated and reset.

[0053] Step 3: Test unloading and monitoring.

[0054] Taking the arrangement of two airbag assemblies 2 in the transverse direction as an example, a detailed description is given:

[0055] (1) For the up-and-down step excavation method:

[0056] Minute 0: First, the first airbag 2-1 and the second airbag 2-2 in the first row are deflated and withdrawn to simulate the first step excavation;

[0057] 90th minute: The first airbag 2-1 and the second airbag 2-2 of the second row are deflated and withdrawn to simulate the excavation of the second step up. At the same time, the third airbag 2-3 and the fourth airbag 2-4 of the first row are deflated and withdrawn to simulate the excavation of the first step down.

[0058] 180th minute: The third airbag 2-3 and the fourth airbag 2-4 of the second row were deflated and withdrawn to simulate the excavation of the second step down, completing a cycle.

[0059] The data logger collects data from the 0th minute to the 180th minute, collects the data and analyzes them.

[0060] (2) For CD excavation method:

[0061] Minute 0: First row first airbag 2-1 deflated and withdrawn;

[0062] 25th minute: The third airbag 2-3 of the first row is deflated and the airbag is withdrawn;

[0063] 50th minute: The second airbag in the first row is deflated at 2-2 and the airbag is withdrawn;

[0064] 75th minute: The fourth airbag 2-4 of the first row is deflated and the airbag is withdrawn;

[0065] 100th minute: The first airbag in the second row is deflated 2-1 and the airbag is withdrawn;

[0066] 125 minutes: The third airbag in the second row, 2-3, was deflated and the airbag was withdrawn;

[0067] 150 minutes: The second airbag in the second row was deflated 2-2 and the airbag was withdrawn;

[0068] 175 minutes: The fourth airbag 2-4 in the second row was deflated and the airbag was withdrawn;

[0069] 180th minute: Stop recording data.

[0070] During the test, the displacement, strain, soil pressure and other mechanical parameters of each part of the tunnel primary support model 1-2 were monitored according to the test requirements.

[0071] Due to the scale effect, the actual time and the scaled time are in a square relationship. The instantaneous nature of airbag deflation can better simulate the instantaneous unloading characteristics of drilling and blasting construction.

[0072] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. The tunnel primary support mechanical model test device based on airbag combination control is characterized by: The test chamber comprises a test chamber, a tunnel primary support model, and an airbag assembly. The tunnel primary support model is laterally arranged in the test chamber, and the space between the outer side of the tunnel primary support model and the test chamber is filled with similar surrounding rock materials. The tunnel primary support model is provided with a sensor assembly for monitoring the mechanical performance parameters of the tunnel primary support model. The airbag assembly is installed inside the tunnel primary support model. The airbag assembly includes multiple airbags, each of which is equipped with an air valve to simulate the instantaneous unloading process of step-by-step tunnel excavation.

2. The tunnel primary support mechanical model test device based on airbag combination control according to claim 1 is characterized in that: In the inflated state, the outer surface of the airbag fits the mechanical model of the primary branch of the tunnel, and the inner contact surfaces of adjacent airbags fit each other.

3. The tunnel primary support mechanical model test device based on airbag combination control according to claim 2 is characterized in that: The airbag is made of double-layer composite rubber.

4. The tunnel primary support mechanical model test device based on airbag combination control according to claim 1 is characterized in that: The sensor assembly includes a resistance strain gauge and an earth pressure gauge, and a plurality of the resistance strain gauge and the earth pressure gauge are arranged along the circumference of the tunnel primary support model.

5. The tunnel primary support mechanical model test device based on airbag combination control according to claim 4 is characterized in that: The sensor assembly also includes a pull-rope displacement meter. A support frame for installing the pull-rope displacement meter is fixed on the top of the test box. The rope ends of the pull-rope displacement meter are fixed to the arch top and arch waist positions of the tunnel primary support model.

6. The tunnel primary support mechanical model test device based on airbag combination control according to claim 5 is characterized in that: The supporting frame includes a frame, and the frame is provided with a mounting groove; the pull-wire displacement meter is arranged in the mounting groove.

7. The tunnel primary support mechanical model test device based on airbag combination control according to claim 1 is characterized in that: The test box includes a test box body with a box-shaped structure, and two opposing baffles of the test box body are provided with installation openings for the tunnel primary support model; The tunnel primary support model is connected to the baffle through a flange plate.

8. The tunnel primary support mechanical model test device based on airbag combination control according to claim 7 is characterized in that: The tunnel primary support model and baffle are made of acrylic material.

9. The tunnel primary support mechanical model test method based on airbag combination control is characterized by: The test device according to any one of claims 1 to 8 comprises: Fill the test chamber with similar surrounding rock material, and simultaneously calculate the pressure of the similar material on the tunnel primary support mechanical model. Inflate the airbag according to the pressure value; the inflation pressure is equal to the pressure of the similar material on the tunnel primary support model. The airbag is unloaded and deflated according to the set excavation method. During the deflation process, the displacement, strain and soil pressure of the tunnel primary support mechanical model are monitored.

10. The tunnel primary support mechanical model test method based on airbag combination control according to claim 9 is characterized in that: Deflate the airbags at the set positions according to the up-down step excavation method or the CD excavation method.

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