A test structure for indoor test of surrounding rock-structure stiffness coordination of large deformation tunnels

Abstract

The present invention discloses a large deformation tunnel surrounding rock-structure stiffness coordination indoor test structure, which belongs to the technical field of tunnel structure testing. The test structure includes a reaction frame 1 and a reaction frame 2, and the two reaction frames are connected by four steel strands and bolts to form a square frame; the square frame is sequentially connected and arranged with a yieldable I-beam, a spring, a longitudinal connection structure, a pressure-yielding member, a surrounding rock simulation system and a jack 1 in the direction from the reaction frame 1 to the reaction frame 2; the surrounding rock simulation system includes two square steel plates and a plurality of square surrounding rock simulation bodies clamped between the two square steel plates; four steel strands are respectively passed through the four corners of the two square steel plates and connected and fixed to the reaction frame 2, and the two ends of the steel strands are fixed by bolts. The test structure of the present invention can effectively simulate the surrounding rock and support stress state under the coordinated stiffness of each support structure in a large deformation tunnel.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel structure testing, in particular to a large deformation tunnel surrounding rock-structure stiffness coordination indoor test structure. Background Art

[0002] Tunnel excavation is actually a process of unloading the surrounding rock. The stress release caused by unloading causes the rock to deform into the tunnel, resulting in a decrease in surrounding rock stress and an increase in cracks, which breaks the stable geological stress state, reduces rock constraints, and then creates an air surface. The closed cracks originally existing in the rock reopen, which is specifically manifested as rock fragmentation and volume expansion.

[0003] Tunnel engineering activities break the original stratum balance conditions. In order to seek a new balance, the surrounding rock undergoes stress transfer and deformation transmission. In this process, if the surrounding rock cannot stabilize itself, necessary support measures must be taken. The tunnel support structure is an important measure to ensure the stability of the tunnel surrounding rock. It can provide support resistance to the surrounding rock and limit the deformation of the surrounding rock. According to the concept of the New Austrian Tunneling Method, the self-bearing capacity of the surrounding rock can be utilized, and the surrounding rock and the support structure interact with each other to achieve the purpose of coordinating deformation and stabilizing the surrounding rock. The tunnel support structure mainly includes structures such as advance support, initial support and secondary lining. Among them, the initial support mainly includes structures such as steel arch frames, anchor rods, and shotcrete. When dealing with large deformation tunnels, the use of yield support has a better effect.

[0004] At present, there are obvious deficiencies in the indoor test scheme for the unloading expansion of tunnels and the coordination simulation of the stiffness of supporting structures. The main deficiencies are: (1) there is no simulation test equipment specifically for large deformation tunnels under unloading expansion, and the characteristics of the surrounding rock cannot be simulated; (2) there is no large-scale test equipment for the coordination of supporting structure and surrounding rock deformation. Traditional bench loading or test box loading is small in scale and the simulation is not accurate, so the failure of the lining structure cannot be simulated.

[0005] Based on this, in order to restore the synergistic effect of surrounding rock and various support structures in indoor tests, the present invention seeks to design and provide a large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure, using the various specimens of the indoor test to simulate the various support structures in the tunnel, and achieve a stable state under the coordinated effect of surrounding rock and support stiffness through loading experiments. Summary of the invention

[0006] In order to test the surrounding rock and support stress state under the coordinated stiffness of various support structures of the tunnel in indoor tests and accurately restore the coordinated effect of the surrounding rock and various support structures, the present invention provides a large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure.

[0007] The large deformation tunnel surrounding rock-structure stiffness coordination indoor test structure provided by the present invention comprises two reaction frames, reaction frame one and reaction frame two, the two reaction frames are connected by four steel strands and bolts to form a square frame; in the square frame, yieldable I-beams, springs, longitudinal connection structures, yielding components, surrounding rock simulation systems and jack one are sequentially connected and arranged in the direction from reaction frame one to reaction frame two.

[0008] The surrounding rock simulation system has a multi-layer structure, including two square steel plates and a plurality of square surrounding rock simulation bodies made of surrounding rock simulation materials clamped between the two square steel plates. The length and width of the square steel plates are respectively larger than the length and width of the surrounding rock simulation body. A groove is provided on one side of each surrounding rock simulation body, and a pancake-shaped jack 2 is installed in the groove. All surrounding rock simulation bodies are overlapped and placed in a multi-layer structure in such a way that the side containing the jack 2 faces the reaction frame 1, and four steel strands are respectively passed through the four corners of the two square steel plates and connected and fixed to the reaction frame 2. The two ends of the steel strands are fixed by bolts to realize the fixed installation of the surrounding rock simulation system.

[0009] There are two yieldable I-beams, which are placed side by side, one end of which is connected to a reaction frame 1, and the other end is connected to a spring respectively, the other end of the two springs is connected to one side of the longitudinal connection structure, the other side of the longitudinal connection structure is connected to a pressure-yielding member at the center, the other end of the pressure-yielding member is connected to a square steel plate on one side of the surrounding rock simulation system, the other side of the square steel plate on the surrounding rock simulation system is connected to a jack 1 at the center, and the jack 1 is connected to a reaction frame 2. When the reaction frame 2 and the jack 1 work together to apply a force to the surrounding rock simulation system, the square steel plate transfers the force from the surrounding rock simulation system to the support structure, realizing the simulation of the surrounding rock-support interaction in the tunnel. The yieldable I-beam utilizes the thin web characteristic. When the pressure reaches a certain level, the web will yield and deform, resulting in a large displacement, simulating the failure of the structure.

[0010] A further technical solution is that an anchor rod is further provided in the surrounding rock simulation system, one end of the anchor rod passes through the longitudinal connection structure and is inserted from the center of the square steel plate in a manner perpendicular to the square steel plate and penetrates all the surrounding rock simulation bodies. The other end of the anchor rod is located outside the longitudinal connection structure.

[0011] A further technical solution is that the pressure-releasing member is composed of a steel pipe and a spring located inside the steel pipe. The free length of the spring is the same as the length of the steel pipe. The spring does not need to be fixed inside the steel pipe, and is a structure with certain load-bearing and pressure-releasing composite functions. The specific principle is that when the pressure increases, the steel pipe wall will yield, and then the spring will be elastically stressed. After the spring stroke reaches the maximum value, the entire structure can still continue to transmit the load.

[0012] A further technical solution is that the longitudinal connection structure can select I-beams of different specifications. I-beams of different specifications can simulate different longitudinal connection stiffnesses. If the connected I-beams are relatively small, the connection stiffness is relatively weak and is prone to premature damage.

[0013] A further technical solution is that the surrounding rock simulation material is selected from one of concrete, mortar, organic material or inorganic material or a mixture of two materials. The manufactured surrounding rock simulation body is in the shape of a square brick, and its mechanical properties are similar to those of the surrounding rock.

[0014] A further technical solution is that two square grooves are provided on the surface of the surrounding rock simulation body, and a pancake-shaped jack 2 is installed in each of the two grooves.

[0015] Compared with the prior art, the present invention is beneficial in that:

[0016] (1) The test structure of the present invention can effectively simulate the stress state of the support structure during tunnel excavation and surrounding rock unloading and expansion in a large deformation tunnel, and by coordinating the stiffness of each support structure, find the stiffness selection of the support structure under different surrounding rock deformation levels to ensure the overall stability of the surrounding rock-support structure.

[0017] (2) In the test structure of the present invention, the reaction frame 2 and the jack 1 work together to apply a force to the surrounding rock simulation system, simulating the state of initial ground stress when the surrounding rock is deeply buried.

[0018] (3) The square steel plate near the side of the compression member can be loosened by bolts to release the force in the surrounding rock simulation system. The amount of force released can be controlled by adjusting the tightness of the bolts to simulate the process of surrounding rock stress release in the tunnel.

[0019] (4) When the bolts are loosened, the small pancake-shaped jack 2 acts on the adjacent surrounding rock simulation body, thereby increasing the volume of the surrounding rock simulation system and simulating the surrounding rock unloading and expansion state during tunnel excavation.

[0020] (5) The surrounding rock simulation system is followed by springs, yieldable I-beams and compression member structures, and anchor rods are also provided for reinforcement; the springs are used to simulate the tunnel steel arch support, the compression member is used to simulate the compression support structure (provided when necessary), and the anchor rods are used to simulate the active anchor support, thereby realizing the simulation of various types of support structures in the tunnel.

[0021] (6) The surrounding rock simulation system generates surrounding rock pressure, and the support structure provides support force to resist the surrounding rock pressure. The support structure can be replaced to ensure the effective bearing capacity of the support structure and realize the simulation of surrounding rock-support stiffness coordination.

[0022] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the overall structural diagram of the test structure for the large deformation tunnel surrounding rock-structure stiffness coordination indoor test of the present invention.

[0024] Figure 2 It is an overall top view of the test structure for the large deformation tunnel surrounding rock-structure stiffness coordination indoor test of the present invention.

[0025] Figure 3 It is a schematic diagram of the structure of the surrounding rock simulation body of the present invention.

[0026] Numbers in the figure:

[0027] 1-reaction frame 1, 2-reaction frame 2, 3-steel strand, 4-yieldable I-beam, 5-spring, 6-longitudinal connection structure, 7-pressure-yielding member, 8-jack 1, 9-square steel plate, 10-surrounding rock simulation body; 11-groove, 12-jack 2, 13-bolt, 14-anchor rod. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] like Figure 1-3 As shown, the indoor test structure for the coordinated surrounding rock-structure stiffness of a large deformation tunnel provided by the present invention includes two reaction frames, a reaction frame 1 and a reaction frame 2, a certain distance is reserved between the two reaction frames, and the two reaction frames are connected by four steel strands 3 and fixed by screw plugs to form a square frame. Yieldable I-beams 4, springs 5, longitudinal connection structures 6, yielding members 7, surrounding rock simulation systems and jacks 1 8 are sequentially connected and arranged in the direction from the reaction frame 1 to the reaction frame 2 2 in the square frame.

[0030] The surrounding rock simulation system has a multi-layer structure, including two square steel plates 9 and a plurality of square surrounding rock simulation bodies 10 clamped between the two square steel plates 9. The length and width of the square steel plates 9 are respectively larger than the length and width of the surrounding rock simulation body 10. A groove 11 is provided on one side of each surrounding rock simulation body 10, and a small pancake-shaped jack 12 is installed in the groove. All surrounding rock simulation bodies 10 are overlapped and placed in a multi-layer structure in such a way that the side containing the jack 12 faces the reaction frame 1. Circular holes are provided at the four corners of the two square steel plates 9, and four steel strands 3 are respectively passed through the circular holes at the four corners of the two square steel plates 9 and connected to the reaction frame 22. The two ends of the steel strands are fixed by bolts 13 to achieve fixed installation of the surrounding rock simulation system.

[0031] Preferably, the surrounding rock simulation body 10 is a square brick-shaped simulation body made of a mixture of one or two materials selected from concrete, mortar, organic materials or inorganic materials, and having mechanical properties similar to those of the surrounding rock. Further preferably, two square grooves 11 are provided on the surface of the surrounding rock simulation body, and a pancake-shaped jack 2 12 is installed in each of the two grooves.

[0032] There are two yieldable I-beams 4, which are placed side by side, one end of which is connected to a reaction frame 1, and the other end is connected to a spring 5 respectively. The other ends of the two springs 5 ​​are connected to one side of a longitudinal connection structure 6, which is a square connection plate. The center of the other side of the longitudinal connection structure is connected to a pressure-releasing member 7, and the other end of the pressure-releasing member 7 is connected to a square steel plate 9 on one side of the surrounding rock simulation system. The center of the square steel plate on the other side of the surrounding rock simulation system is connected to a jack 8, and the jack 8 is connected to a reaction frame 2. An anchor rod 14 is also provided in the surrounding rock simulation system, and one end of the anchor rod 14 passes through the longitudinal connection structure 6 and is inserted from the center of the square steel plate 9 in a manner perpendicular to the square steel plate 9 and penetrates all the surrounding rock simulation bodies 10. The other end of the anchor rod is located on the outside of the longitudinal connection structure.

[0033] The longitudinal connection structure 6 can be made of I-beams of different specifications according to actual needs to simulate different longitudinal connection stiffnesses.

[0034] The pressure-releasing member 7 is composed of a steel pipe and a spring inside the steel pipe. The free length of the spring is the same as the length of the steel pipe. The spring does not need to be fixed inside the steel pipe. It is a structure with certain load-bearing and pressure-releasing composite functions.

[0035] The surrounding rock simulation system is followed by a spring 5, a yieldable I-beam 4 and a compression member 7 structure, and an anchor rod 14 is also provided for reinforcement; the spring 5 is used to simulate the tunnel steel arch support, the compression member 7 is used to simulate the compression support structure (set when necessary), and the anchor rod 14 is used to simulate the active anchor support, so as to realize the simulation of various types of support structures in the tunnel.

[0036] When the reaction frame 2 and the jack 1 8 work together to apply force to the surrounding rock simulation system, the square steel plate 9 transfers the force from the surrounding rock simulation system to the support structure, realizing the simulation of the surrounding rock-support interaction in the tunnel. It should be noted that by controlling the magnitude of the applied force, the simulation of the surrounding rock state at different burial depths can be realized, and different magnitudes of initial ground stress of the surrounding rock can be given.

[0037] When the bolts 13 on the square steel plate 9 close to the side of the compression member 7 are loosened, the force in the surrounding rock simulation system can be released. The amount of force released can be controlled by adjusting the tightness of the bolts to simulate the process of surrounding rock stress release in the tunnel. Stress release can achieve the following two situations:

[0038] The first one is to follow the principle of New Austrian Tunneling Method, give full play to the self-bearing capacity of the surrounding rock, release part of the applied force, and realize the joint bearing of the surrounding rock and the supporting structure.

[0039] The second method is that, at the same time as the release, the small pancake-shaped jack 12 in the surrounding rock simulation body plays a role, making the volume of the surrounding rock simulation system larger, thereby simulating the unloading and expansion state of the surrounding rock during tunnel excavation.

[0040] The surrounding rock simulation system generates surrounding rock pressure, and each supporting structure provides supporting force to resist the surrounding rock pressure. The stress state of spring 5 is observed. If spring 5 is damaged during the test, it means that the supporting structure cannot effectively bear the surrounding rock pressure and the supporting structure is damaged. At this time, the supporting structure needs to be replaced to ensure the effective bearing of the supporting structure and realize the simulation of surrounding rock-support stiffness coordination.

[0041] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure, characterized in that: It includes two reaction frames, reaction frame 1 and reaction frame 2, and the two reaction frames are connected by four steel strands and bolts to form a square frame; in the square frame, yieldable I-beams, springs, longitudinal connection structures, yielding components, surrounding rock simulation systems and jack 1 are sequentially connected and arranged in the direction from reaction frame 1 to reaction frame 2; The surrounding rock simulation system comprises two square steel plates and a plurality of square surrounding rock simulation bodies made of surrounding rock simulation materials and clamped between the two square steel plates. A groove is provided on one side of each surrounding rock simulation body, and a pancake-shaped jack 2 is installed in the groove. All surrounding rock simulation bodies are overlapped and placed in a manner that the side containing the jack 2 faces the reaction frame 1 to form a multi-layer structure, and four steel strands are respectively passed through the four corners of the two square steel plates and connected and fixed to the reaction frame 2. Both ends of the steel strands are fixed by bolts to realize the fixed installation of the surrounding rock simulation system. An anchor rod is also provided in the surrounding rock simulation system, and one end of the anchor rod passes through the longitudinal connection structure and is inserted from the center of the square steel plate in a manner perpendicular to the square steel plate and passes through all surrounding rock simulation bodies. There are two yieldable I-beams, which are placed side by side, one end of which is connected to a reaction frame 1, and the other end is respectively connected to a spring, the other end of the two springs is connected to one side of the longitudinal connection structure, the center position of the other side of the longitudinal connection structure is connected to a pressure-yielding member, the other end of the pressure-yielding member is connected to a square steel plate on one side of the surrounding rock simulation system, the center position of the square steel plate on the other side of the surrounding rock simulation system is connected to a jack 1, and the jack 1 is connected to the reaction frame 2; The pressure-releasing member is composed of a steel pipe and a spring located inside the steel pipe, and the free length of the spring is the same as the length of the steel pipe.

2. The large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure according to claim 1, characterized in that: The surrounding rock simulation material is selected from one of concrete, mortar, organic material or inorganic material, or a mixture of two of the two.

3. The large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure as claimed in claim 2, characterized in that: Two square grooves are arranged on the surface of the surrounding rock simulation body, and a pancake-shaped jack 2 is respectively installed in the two grooves.

4. The large deformation tunnel surrounding rock-structure stiffness coordination indoor test test structure according to claim 1, characterized in that: The longitudinal connection structure is selected from I-beams of different specifications.

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