Experimental device and method for instability mechanism of tunnel face of weak surrounding rock tunnel

Abstract

The invention discloses a weak surrounding rock tunnel face instability mechanism experiment device and method. A stratum environment simulation system is arranged above a model box system, and a tunnel excavation simulation system is installed in the model box system; in the stratum environment simulation system, a base of a hydraulic jack is fixedly arranged on a force transmission plate, a counter-force beam is fixedly arranged on the model box system, and a telescopic rod of the hydraulic jack is rotationally connected with the counter-force beam. According to the invention, a weak surrounding rock tunnel face instability mechanism reduced scale model test is carried out, a hydraulic jack is used for applying a load acting on a force transmission plate, the force transmission plate is used for transmitting the load to a position above a stratum so as to simulate surrounding rock overlying loads at different burial depths, and gradual unloading is carried out through a displacement control method so as to realize tunnel face instability failure whole process simulation. The stratum deformation evolution rule and the geometrical characteristics of a plastic instability area in the tunnel instability state are researched, and the method can be used for simulating the stability and instability characteristics of tunnel faces with different section forms, excavation forms and using functions.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of soft weak surrounding rock tunnel face instability mechanism experimental device and method thereof, belong to tunnel technical field. BACKGROUND

[0002] With the innovation of tunnel design concept and construction technology, tunnel mechanized large section excavation technology is widely concerned due to its advantages such as less disturbance to surrounding rock, simple process and effective labor saving. In recent years, the number of cases of tunnel mechanized large section excavation in soft surrounding rock has also increased, such as Zhengwan railway, Sichuan-Tibet railway and Chenglan railway. However, in the V-grade soft surrounding rock area, the use of mechanized large section excavation construction is prone to face instability and other accidents. How to control the stability of soft surrounding rock tunnel face has become an important problem in the safety construction of tunnel mechanized large section excavation. In actual engineering, if the stability of the face and the potential instability range can be accurately judged, and reasonable pre-reinforcement measures are taken, the probability of accidents can be effectively reduced, and the risk analysis and control level of soft surrounding rock tunnel mechanized large section construction can be improved.

[0003] Full-face method and micro-bench method are commonly used excavation methods for tunnel mechanized large section construction. The use of reasonable pre-reinforcement measures to maintain the stability of the tunnel face is an important guarantee for the safety of soft surrounding rock tunnel large section excavation construction. Current scholars have conducted research on the stability of soft surrounding rock large section tunnel face, and have obtained many meaningful results. However, most of the existing research is based on full-face method. For the background of tunnel mechanized large section excavation construction, there is less research on the instability mechanism of face under micro-bench construction conditions considering different excavation methods (such as full-face, micro-bench method, etc.) and different section forms of face instability. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a soft weak surrounding rock tunnel face instability mechanism experimental device and method thereof. By conducting a soft weak surrounding rock tunnel face instability mechanism scale model test, the whole process of tunnel face instability and failure is simulated by gradually unloading through displacement control method, and the deformation evolution law of the tunnel under instability state and the geometric characteristics of the plastic instability area are studied.

[0005] Preferably, the present application provides a soft weak surrounding rock tunnel face instability mechanism experimental device, which comprises a model box system, a stratum environment simulation system, a tunnel excavation simulation system, a tunnel lining system and an information acquisition system. The stratum environment simulation system is installed above the model box system, the tunnel excavation simulation system and the tunnel lining system are installed in the model box system, and the information acquisition system is arranged on one side of the model box system.

[0006] The stratum environment simulation system comprises a plurality of hydraulic jacks, a counter-force beam and a force transmission plate. The bases of the plurality of hydraulic jacks are fixedly arranged on the force transmission plate, and the counter-force beam is fixedly arranged on the model box system. The telescopic rods of the plurality of hydraulic jacks are rotatably connected to the counter-force beam.

[0007] Preferably, the tunnel excavation simulation system comprises a force transmission device, a connecting rod and a support baffle. The force transmission device is fixedly connected to the support baffle through the connecting rod.

[0008] Preferably, the information collection system comprises lighting equipment, high-definition shooting equipment and a notebook computer. The lighting equipment and the high-definition shooting equipment are arranged on one side of the model box system, and the high-definition shooting equipment is electrically connected to the notebook computer.

[0009] Preferably, the force transmission plate comprises a horizontal plate, a left U-shaped rod and a right U-shaped rod. The left U-shaped rod and the right U-shaped rod are fixedly arranged on the two sides of the horizontal plate, respectively. One end of the counter-force beam is fixedly arranged on the left U-shaped rod, and the other end of the counter-force beam is fixedly arranged on the right U-shaped rod.

[0010] Preferably, the counter-force beam is a straight rod, and the horizontal plate is a planar plate.

[0011] Preferably, the bottom simulation device applies a load on the force transmission plate through the hydraulic jacks, transmits the load to the stratum above through the force transmission plate, and adjusts the force applied on the force transmission plate by the jacks to simulate the overburden load of the surrounding rock at different buried depths.

[0012] Preferably, the force transmission device comprises an L-shaped rod, the connecting rod is a straight rod, and the support baffle is a semicircular plate. The shape of the support baffle can be adjusted to simulate the two large-section excavation methods of the micro-step method and the full-face method under the condition of mechanized construction.

[0013] Preferably, the tunnel lining system adopts a structure in which a semicircular organic glass shell with a diameter of D=200mm is connected to a rectangular plate. The tunnel excavation simulation system is arranged in the tunnel lining device. The tunnel lining device is linked to the model box through a clamping groove and a bolt. Different shapes of lining plates, such as circular, horseshoe-shaped and three-centered circular shapes, can be replaced to simulate different forms of tunnels, such as shield tunnels, railway tunnels and highway tunnels, to simulate the lining of different tunnels in reality. The tunnel excavation simulation system is arranged in the tunnel lining device.

[0014] Preferably, a method for testing the instability mechanism of a tunnel face in soft surrounding rock comprises the following steps:

[0015] A lubricating liquid is applied to the inside of the model box of the device for testing the instability mechanism of a tunnel face in soft surrounding rock according to any one of claims 1-8.

[0016] The model soil is filled into the model box.

[0017] The model soil is simulated to be excavated and unloaded, whether the instability of the tunnel face is unstable is judged, if the tunnel face is not unstable, the load plate is loaded step by step until the tunnel face is unstable;

[0018] Collect the data of the tunnel destruction process through the information collection system.

[0019] Preferably, the data of the tunnel destruction process collected by the information collection system is processed by using the open source digital image velocimetry technology, the pressure generated by the filling soil above the tunnel face and the influence of the excavation of the excavation face on the destruction of the tunnel face are obtained, and the instability mechanism of the tunnel face of the soft surrounding rock is analyzed; wherein the influence of the excavation of the excavation face on the destruction of the tunnel face includes the relationship between the displacement of the baffle of the tunnel excavation simulation system and the rupture of the rupture surface of the tunnel face, and the instability mechanism of the tunnel face of the soft surrounding rock includes the principle of the rupture of the rupture surface of the tunnel face under the joint action of the pressure generated by the filling soil above the tunnel face and the displacement of the supporting baffle in the tunnel excavation simulation system.

[0020] The present application has the following beneficial effects:

[0021] The present application provides a tunnel face instability mechanism experimental device and method for soft surrounding rock, which simulates the whole process of tunnel face instability and destruction by gradually unloading through displacement control method by carrying out the tunnel face instability mechanism scale model test of soft surrounding rock, and studies the stratum deformation evolution law and the geometric characteristics of the plastic instability area under the instability state of the tunnel. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the embodiments will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor on the premise of not paying creative labor.

[0023] Figure 1 is a tunnel model test schematic diagram of micro-step excavation and a full-face excavation tunnel model test schematic diagram in some embodiments of the present application;

[0024] Figure 2 is a structural diagram of a model box system in some embodiments of the present application;

[0025] Figure 3 is a structural diagram of a tunnel excavation simulation system in some embodiments of the present application;

[0026] Figure 4 is a structural diagram of a stratum environment simulation system in some embodiments of the present application;

[0027] Figure 5 is a structural diagram of a tunnel lining system in some embodiments of the present application;

[0028] The following are the meanings of the reference numerals in the attached diagram: 1-Model box system; 2-Tunnel excavation simulation system; 3-Lighting equipment; 4-High-definition shooting equipment; 5-Geological environment simulation system; 6-Model box; 7-Tunnel device; 8-Hydraulic jack; 9-Reaction beam; 10-Force transmission plate; 11-Force transmission device; 12-Connecting rod; 13-Support baffle; 14-Model box; 15-Reserved tunnel hole. Detailed Implementation

[0029] In this invention, the terms "first" and "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0030] See Figure 1 This application provides an experimental device for the instability mechanism of tunnel face in weak surrounding rock, including a model box system, a geological environment simulation system, a tunnel excavation simulation system and an information acquisition system. The geological environment simulation system is installed above the model box system, the tunnel excavation simulation system is installed in the model box system, and the information acquisition system is set on one side of the model box system.

[0031] The geological environment simulation system includes several hydraulic jacks, reaction beams, and force transmission plates. The bases of the hydraulic jacks are fixed on the force transmission plates, and the reaction beams are fixed on the model box system. The telescopic rods of the hydraulic jacks are rotatably connected to the reaction beams. In addition, the pressure of the hydraulic jacks can be adjusted to simulate the geological pressure above the tunnel at different burial depths.

[0032] Furthermore, the tunnel excavation simulation system includes a force transmission device, a connecting rod, and a support baffle. The force transmission device is fixedly connected to the support baffle through the connecting rod, and different tunnel excavation methods can be simulated by replacing different force transmission devices.

[0033] Furthermore, the information acquisition system includes lighting equipment, high-definition shooting equipment, and a laptop computer. The lighting equipment and high-definition shooting equipment are located on one side of the model box system, and the high-definition shooting equipment is electrically connected to the laptop computer.

[0034] Furthermore, the force transmission plate includes a horizontal plate, a left U-shaped rod, and a right U-shaped rod. The left U-shaped rod and the right U-shaped rod are fixedly installed on both sides of the horizontal plate, and one end of the reaction beam is fixedly installed on the left U-shaped rod, while the other end of the reaction beam is fixedly installed on the right U-shaped rod.

[0035] Furthermore, the reaction beam is a straight bar, and the cross plate is a flat plate.

[0036] Furthermore, the force transmission device includes an L-shaped rod, a straight connecting rod, and a semi-circular plate as the supporting baffle.

[0037] Furthermore, the model box system includes a fully transparent acrylic model box with dimensions of 1000mm x 600mm x 1000mm and a tunnel device, with tunnel openings inside the model box.

[0038] Furthermore, the tunnel lining system adopts a structure that connects a semi-circular plexiglass shell with a diameter of D=200mm and a rectangular plate. Different types of tunnels can be simulated by replacing the semi-circular plexiglass shells of different shapes, and different tunnel excavation cross sections can be simulated by replacing the tunnel lining devices of different shapes. The tunnel excavation simulation system is set in the tunnel device.

[0039] There are many models of hydraulic jacks, lighting equipment, high-definition shooting equipment, and laptops available in the prior art. Those skilled in the art can select according to actual needs, and no examples will be given in this embodiment.

[0040] Model Test Similarity Material Configuration: Based on typical working conditions and combined with existing literature on similarity material configuration methods for weak surrounding rock model tests, barite, quartz sand, petrolatum, and gypsum were selected as raw materials. These low-cost, readily available, and easily prepared materials were used to formulate the mixture required for the model test, serving as the model soil. The model materials were determined according to the first similarity theorem and elasticity mechanics, ensuring that the elastic modulus and other physical parameters of the model materials basically conformed to the set similarity ratios: cohesive strength similarity ratio Cc=60, soil weight similarity ratio C=1, elastic modulus similarity ratio Ce=1, Poisson's ratio similarity ratio Cu=1, and internal friction angle similarity ratio C=1. In accordance with the "Railway Tunnel Design Code" (TB10003-2016) for Class V surrounding rock, clay was selected as the test material, and its specific mechanical parameters are shown in Table 1.

[0041] Table 1. Similar test materials and original parameters of surrounding rock

[0042]

[0043] Model box configuration: the model size is 1 / 60 of the original size, that is, the geometric similarity ratio CL=60. The initial model box size is 1000mmx600mmx1000mm. The model box is a full transparent organic glass model box with a reserved tunnel hole. In order to facilitate the observation of the instability characteristics of the surrounding rock in front of the working face, only half of the tunnel structure is selected. The tunnel device adopts a semicircular organic glass shell structure with a diameter of D=200mm to realize the simulation of the model tunnel lining, and different tunnel excavation sections can be simulated by replacing different shaped tunnel lining devices. Since the invention only studies the instability characteristics of the working face under the action of excavation unloading, the influence of the rigidity of the lining structure on the instability mechanism of the tunnel working face is not considered.

[0044] A support baffle is arranged in front of the working face, and the tunnel excavation is simulated by moving the support baffle. The support baffle has two forms and is used to simulate full-face method and micro-step method excavation respectively.

[0045] Information acquisition system construction: the information acquisition system includes lighting equipment, high-definition shooting equipment, open-source digital image velocimetry technology post-processing software, and notebook computers, etc. The high-definition shooting equipment is placed at the side of the tunnel model box to record the deformation characteristics of the surrounding rock in front of the working face during the tunnel excavation unloading process. After the test is completed, the digital image velocimetry technology post-processing software is used to analyze the movement law of the soil in the whole process of the working face instability, and then the failure mode of the stratum in front of the working face is captured.

[0046] Experimental material placement: Vaseline lubricating liquid is applied to the inside of the model box and the edge of the support baffle using a brush to reduce the friction between the model box and the test material and between the model box and the baffle, thereby reducing the influence of the boundary effect. When placing the filled soil, first fill the tunnel underlying soil layer evenly, then place the tunnel lining structure, and tamp the filled soil into layers into the model box. After the model is built, the model box is maintained without disturbance to form a uniformly distributed stress field. In order to study the instability mechanism of the tunnel working face under deep burial conditions, the tunnel burial depth is set to 600mm, which is 3 times the diameter of the hole.

[0047] Tunnel excavation unloading simulation: displacement control method is used to control the tunnel excavation during the test, and the support baffle is moved to adjust the support pressure of the working face. For full-face method excavation, the support baffle is controlled to be pulled back at a uniform displacement interval to release the support pressure of the working face. During the tunnel excavation process, the deformation characteristics of the surrounding rock in front of the working face are recorded until the tunnel working face loses stability. For micro-step method excavation, the upper and lower support baffles are controlled to move respectively to simulate the tunnel working face excavation process. During the tunnel excavation process, the deformation characteristics of the surrounding rock in front of the working face are recorded until the tunnel working face loses stability. Different transmission devices can be replaced to simulate different tunnel excavation methods.

[0048] Gradual loading at the top of the model: If no instability occurs when the support baffle completely detaches from the tunnel face, loading is applied to the top of the model using jacks and reaction beams. Gradual loading is employed, recording the deformation characteristics of the surrounding rock in front of the tunnel face during the loading process, until instability occurs at the tunnel face. Additionally, the pressure of the hydraulic jacks can be adjusted to simulate the ground pressure above the tunnel at different burial depths. Three specific working conditions are initially set, as shown in Table 2.

[0049] Table 2. Tunnel face instability model tests under different excavation methods

[0050]

[0051] An experimental method for studying the instability mechanism of tunnel faces in weak surrounding rock is described below:

[0052] Step 1: Install the model box system;

[0053] Step 2: Install the tunnel excavation simulation system;

[0054] Step 3: Install the formation simulation system;

[0055] Step 4: Fill the model box with model soil;

[0056] Step 5: Simulate excavation and unloading of the model soil until the working face becomes unstable;

[0057] Step 6: If the working face is not unstable, gradually increase the load on the force transmission plate until the working face becomes unstable;

[0058] Step 7: After the experiment, data on the tunnel destruction process are collected using the information acquisition system;

[0059] Step 8: Repeat steps 1 to 7 above, processing the tunnel failure data collected by the information acquisition system using open-source digital image velocimetry technology to obtain the pressure generated by the backfill soil above the tunnel face and the impact of excavation on the tunnel face failure. Analyze the instability mechanism of the tunnel face in weak surrounding rock tunnels. The impact of excavation on tunnel face failure includes the relationship between the displacement of the baffle in the tunnel excavation simulation system and the rupture of the tunnel face fracture surface. The instability mechanism of the tunnel face in weak surrounding rock tunnels includes the principle that the pressure generated by the backfill soil above the tunnel face and the displacement of the support baffle in the tunnel excavation simulation system cause the rupture of the tunnel face fracture surface. The pressure generated by the strata above the tunnel face is simulated using pressure provided by hydraulic jacks.

[0060] A specific embodiment of an experimental method for studying the instability mechanism of a weak surrounding rock tunnel face: the full transparent organic glass model box is fixed on the base by bolts; a semicircular organic glass shell structure tunnel device with a diameter of D=200mm is installed in the full transparent organic glass model box as a model tunnel lining; the model soil with a good ratio is filled in the full transparent organic glass model box, and the connecting rod and the support baffle are installed during the filling process; after the installation is completed, the force transmission device is connected with the connecting rod, the support baffle is moved through the force transmission device, and the tunnel excavation is simulated. There are two kinds of excavation methods, micro-step and full-face, and different support baffle styles and link rod arrangement methods are used correspondingly. After the filling is completed, the force transmission plate is covered above the model soil, and then the reaction beam is fixed and connected with the model box by bolts, and then the hydraulic jack is installed in the middle of the force transmission plate and the reaction beam, and the loading is realized at the top of the model by controlling the jack and the reaction beam. The high-definition shooting equipment is placed at the side of the model box, and the lighting equipment including the lighting lamp is placed on both sides of the model box, and the high-definition shooting equipment is used to record the deformation characteristics of the surrounding rock in front of the tunnel face during the tunnel excavation unloading process. The excavation face construction process is started, the support baffle is moved to simulate the tunnel excavation by controlling the force transmission device, and the loading is realized at the top of the model box by controlling the jack and the reaction beam. After the test is completed, the deformation characteristics of the surrounding rock in front of the tunnel face are collected through the information acquisition system, and the influence of the top loading and the tunnel excavation on the instability of the face is analyzed. The above steps are repeated, different top loads, excavation methods, excavation unloading processes and other parameters are set, and the face stability test under different conditions is completed. The data of the tunnel failure process collected by the information acquisition system is processed by using the open source digital image velocimetry technology, the pressure generated by the filling soil above the face and the influence of the face excavation on the face failure are obtained, and the instability mechanism of the weak surrounding rock tunnel face is analyzed; wherein the influence of the face excavation on the face failure includes the relationship between the displacement of the baffle of the tunnel excavation simulation system and the rupture of the face rupture surface, and the instability mechanism of the weak surrounding rock tunnel face includes the principle of the rupture of the face rupture surface caused by the combined action of the pressure generated by the filling soil above the face and the displacement of the support baffle in the tunnel excavation simulation system. After the digital image velocimetry technology is used for post-processing software analysis of the motion law of the soil in the whole process of the face instability, the failure mode of the stratum in front of the face is captured.

[0061] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

[0062] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the application being indicated by the following claims.

[0063] Finally, it should be noted that: first, in the description of the present application, it should be pointed out that, unless otherwise specified and limited, the terms "mounting", "connection", "connection", "fitting" should be understood broadly, which can be mechanical connection or electrical connection, or the communication between two elements, or direct connection, "up", "down", "left", "right" and the like are only used to indicate the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change;

[0064] Secondly: the present application discloses the structure involved in the embodiment of the present application in the drawings, and other structures can refer to the usual design; the above specific embodiments further illustrate the purpose, technical scheme and beneficial effects of the present application, and it should be understood that the above is only a specific embodiment of the present application, and is not used to limit the protection scope of the present application, any modification, equivalent replacement, improvement, etc. made on the basis of the technical scheme of the present application shall be included in the protection scope of the present application.

Claims

1. A soft surrounding rock tunnel face instability mechanism experimental device, characterized in that, The experimental device comprises a model box system, a stratum environment simulation system, a tunnel excavation simulation system, a tunnel lining system and an information acquisition system. The stratum environment simulation system comprises a plurality of hydraulic jacks, a counter-force beam and a force transmission plate, the bases of the plurality of hydraulic jacks are fixedly arranged on the force transmission plate, the counter-force beam is fixedly arranged on the model box system, and the telescopic rods of the plurality of hydraulic jacks are rotatably connected to the counter-force beam.

2. The experimental device according to claim 1, wherein The tunnel excavation simulation system comprises a force transmission device, a connecting rod and a support baffle, the force transmission device is fixedly connected to the support baffle through the connecting rod.

3. The experimental device according to claim 1, wherein The information acquisition system comprises an illumination device, a high-definition shooting device and a notebook computer, the illumination device and the high-definition shooting device are arranged on one side of the model box system, and the high-definition shooting device is electrically connected to the notebook computer.

4. The experimental device according to claim 1, wherein The force transmission plate comprises a horizontal plate, a left U-shaped rod and a right U-shaped rod, the left U-shaped rod and the right U-shaped rod are fixedly arranged on the two sides of the horizontal plate respectively, one end of the counter-force beam is fixedly arranged on the left U-shaped rod, and the other end of the counter-force beam is fixedly arranged on the right U-shaped rod.

5. The experimental device according to claim 4, wherein The counter-force beam is a straight rod, and the horizontal plate is a planar plate.

6. The experimental device according to claim 1, wherein The stratum simulation device applies a load on the force transmission plate through the hydraulic jacks, transmits the load to the stratum above through the force transmission plate, and adjusts the force applied on the force transmission plate by the jacks to simulate the overburden load of the surrounding rock at different depths.

7. The experimental device according to claim 2, wherein The force transmission device comprises an L-shaped rod, the connecting rod is a straight rod, the support baffle is a semicircular plate, and the form of the support baffle is replaced and adjusted to simulate the two large-section excavation methods of the micro-step method and the full-face method under the condition of mechanized construction.

8. The experimental device according to claim 1, wherein The tunnel lining system adopts a structure in which a semicircular organic glass shell with a diameter of D=200 mm and a rectangular plate are connected, and the tunnel lining device is connected to the model box through a clamping groove and a bolt.

9. A method for testing the instability mechanism of a weak surrounding rock tunnel face, characterized in that, The method comprises the following steps: applying lubricating liquid in the model box of the experimental device according to any one of claims 1-8; filling the model box with model soil; simulating excavation unloading of the model soil, judging whether the tunnel face is unstable, and gradually loading the force transmission plate until the tunnel face is unstable if the tunnel face is not unstable; collecting data of the tunnel failure process through the information acquisition system.

10. The method for experimental study on instability mechanism of tunnel face in soft surrounding rock according to claim 8, characterized in that, The method comprises the following steps: The data of tunnel destruction process collected by the information collection system are processed by open source digital image velocimetry technology to obtain the pressure generated by the filling soil above the tunnel face and the influence of the excavation of the excavation face on the destruction of the tunnel face, and analyze the instability mechanism of the tunnel face in soft surrounding rock; wherein the influence of the excavation of the excavation face on the destruction of the tunnel face includes the relationship between the displacement of the baffle of the tunnel excavation simulation system and the rupture of the rupture surface of the tunnel face, and the instability mechanism of the tunnel face in soft surrounding rock includes the principle of the rupture of the rupture surface of the tunnel face under the joint action of the pressure generated by the filling soil above the tunnel face and the displacement of the support baffle in the tunnel excavation simulation system.

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