A soft rock large deformation tunnel anchor stress monitoring indoor test structure

Abstract

The application discloses a kind of soft rock large deformation tunnel anchor rod stress monitoring indoor test structure, specifically is: one free end model box, several intermediate section model boxes and one fixed end model box are sequentially assembled into an integral model box by connecting locking structure;Put prefabricated simulation surrounding rock in model box, insert two moving partitions between each surrounding rock, put several air pressure pads between moving partition, air pressure pad is connected to air pressure pump by gas pipe;Anchor rod passes through the hole in the middle of free end model box and fixed end model box, realize the simulation of anchor rod anchoring surrounding rock by anchoring agent, and is fixed by end steel gasket and end nut on both sides.The application not only can effectively simulate the condition that one end of anchor rod is fixed and the other end is stretched with surrounding rock deformation, highly restores the mutual influence between anchor rod and surrounding rock in actual engineering, meanwhile, the structure of the device is simple, convenient to use, beneficial to popularization and low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel testing, and in particular relates to an indoor testing structure for monitoring anchor stress in a soft rock large deformation tunnel. Background Art

[0002] When installing anchor rods in soft rock tunnels with large deformation, there is a situation where the end of the anchor rod is located in a relatively stable load-bearing area or elastic zone, while the rest of the anchor rod is located in the loose zone. At this time, the stress and deformation characteristics of the anchor rod are as follows: the surrounding rock in the loose zone shrinks and deforms inward, while driving the anchor rod to stretch and deform. The end of the anchor rod is located in the stable rock layer, which restricts the overall movement of the anchor rod. In order to restore the stress characteristics of the anchor rod in indoor tests, one end of the anchor rod is fixed, and the other end can be fixed or anchored. Currently, there is no experimental device that can achieve the requirements. Therefore, this experimental structure uses an air pressure cushion as the power to squeeze the surrounding rock and push the anchor rod to stretch, which can effectively achieve the above test requirements. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides an indoor test structure for monitoring anchor stress in soft rock large deformation tunnels.

[0004] The invention discloses an indoor test structure for monitoring anchor stress in a soft rock large deformation tunnel, which comprises a free end model box, a plurality of middle section model boxes and a fixed end model box, which are sequentially assembled into an integral model box through a connecting locking structure.

[0005] Prefabricated simulated surrounding rocks are placed in the model box, two movable partitions are inserted between each surrounding rock, and several air pressure pads are placed between the movable partitions. The air pressure pads are connected to the air pressure pump through an air pipe.

[0006] The anchor rod passes through the middle hole of the free end model box and the fixed end model box, and the anchor rod anchoring surrounding rock is simulated by the anchoring agent, and is fixed on both sides by the end steel gasket and the end nut.

[0007] Furthermore, the steel plate connected to the anchor rod in the free end model box can move freely, realizing the simulation of the anchor rod tail in the actual project, that is, the free surface inside the tunnel.

[0008] Furthermore, all steel plates in the fixed end model box are rigidly connected to simulate the anchor head in actual engineering, that is, the depth of the tunnel surrounding rock. Here, different anchor types are simulated according to whether end anchoring is adopted.

[0009] Furthermore, the air pressure pad is pressurized by an air pump, and the movable partition is squeezed to push the prefabricated simulated surrounding rock, thereby simulating the deformation of the surrounding rock during tunnel construction; at the same time, different air pressures are applied at different locations, and the simulation of uneven surrounding rock deformation is achieved by controlling the amount of movement of the air pressure pad.

[0010] Furthermore, polyurethane foam is added to the gaps between the movable partitions to enhance the pressure transmission efficiency of the air pressure cushion.

[0011] Furthermore, during the loading process of the air pressure cushion, the connection locking structure needs to be released.

[0012] Furthermore, a protective cover is installed on the portion of the anchor rod located between the movable partitions to prevent the anchor rod from being deformed by stress and interfered with by other factors.

[0013] Furthermore, the anchor rod axial force and the relative displacement parameters of the test module should be monitored during the loading test, and the anchor rod axial force test adopts distributed optical fiber testing.

[0014] The beneficial technical effects of the present invention are:

[0015] This invention uses an indoor test method to simulate the stress characteristics of an anchor rod when one end is fixed and the other end stretches as the surrounding rock deforms. Currently, no suitable experimental device can achieve this experimental requirement. This experimental device not only effectively simulates the stress conditions of such anchor rods and closely reproduces the interaction between the anchor rod and the surrounding rock in actual engineering, but also has a simple structure, is easy to use, and is easy to promote and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 It is a top view of the structure of the present invention.

[0018] In the figure: 1-free end model box; 2-fixed end model box; 3-middle section model box; 4-top steel cover; 5-prefabricated simulated surrounding rock; 6-connection locking structure; 7-movable partition; 8-air pressure pad; 9-air pressure pump; 11-anchor rod; 12-end steel gasket; 13-end nut; 14-air pipe; 15-protective cover. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] The present invention provides an indoor test structure for monitoring anchor stress in soft rock large deformation tunnels. Figure 1 、 Figure 2As shown, it includes a free-end model box 1, a fixed-end model box 2, an intermediate-section model box 3, a top steel cover plate 4, a prefabricated simulated surrounding rock 5, a connecting and locking structure 6, a movable partition 7, an air pressure cushion 8, an air pressure pump 9, polyurethane foam, an anchor rod 11, an end steel gasket 12, an end nut 13, and an air pipe 14. Specifically, a free-end model box 1, several intermediate-section model boxes 3, and a fixed-end model box 2 are sequentially assembled into a complete model box (removable) via the connecting and locking structure 6. The number of intermediate-section model boxes 3 can be determined based on the length of the anchor rod 11 to be tested.

[0021] Prefabricated simulated surrounding rock 5 is placed in the model box, with two movable partitions 7 inserted between each surrounding rock. Several air cushions 8 are placed between the movable partitions 7, connected to an air pump 9 via an air pipe 14. The air pump 9 pressurizes the air cushions 8, squeezing the movable partitions 7 and pushing the prefabricated simulated surrounding rock 5, simulating surrounding rock deformation during tunnel construction. Different air pressures are applied at different locations, and the amount of air cushion movement is controlled to simulate uneven surrounding rock deformation.

[0022] The anchor rod 11 passes through the middle hole of the free end model box 1 and the fixed end model box 2, and the anchor rod anchoring surrounding rock is simulated by the anchoring agent, and is fixed on both sides by the end steel gasket 12 and the end nut 13.

[0023] Before the anchor rod 11 passes through all the model test structure frames, it is first pre-treated by grouting and installing monitoring elements. A hole is drilled at the bottom of the anchor rod 11 and concrete is poured to simulate the grouting process of the anchor rod. This allows the anchor rod 11 to better couple with the surrounding rock after entering the surrounding rock, thereby achieving the joint deformation of the anchor rod 11 and the surrounding rock. Several small grooves are opened at appropriate positions around the anchor rod 11 (where the air pressure pad 8 is located), and optical fibers are placed inside the anchor rod to effectively monitor the anchor rod strain while avoiding damage to the optical fiber.

[0024] Furthermore, the steel plate connected to the anchor rod 11 in the free end model box 1 can move freely, thereby simulating the tail of the anchor rod 11 in the actual project, that is, the free surface inside the tunnel.

[0025] Furthermore, all steel plates in the fixed end model box 2 are rigidly connected to simulate the head of the anchor rod 11 in the actual project, that is, the depth of the tunnel surrounding rock. Here, different anchor rod types are simulated according to whether end anchoring is adopted.

[0026] Furthermore, polyurethane foam is added to the gaps between the movable partitions 7 to enhance the pressure transmission efficiency of the air pressure cushion 8.

[0027] Furthermore, the optical fiber is externally connected to a sensor, which measures the strain of the anchor rod by collecting the optical signal changes caused by the air pressure pump 9 pressurizing the air pressure pad 8.

[0028] Furthermore, after the internal installation of the experimental structure is completed, the top steel cover plate 4 is covered and rigidly connected to other structures. During the test, the rigid connection between each box is disconnected to ensure that the surrounding rock only moves and deforms in the expected fixed direction, thereby realizing the restoration of the surrounding rock stress conditions in the actual project.

[0029] Furthermore, during the loading process of the air pressure cushion 8, the connection locking structure 6 needs to be released.

[0030] Furthermore, several small holes should be reserved in the top steel cover plate 4 to ensure the passage of the gas pipe 14.

[0031] Furthermore, a protective cover 15 is installed on the portion of the anchor rod 11 located between the movable partitions 7 to prevent the anchor rod 11 from being deformed by stress and interfered with by other factors.

[0032] Furthermore, the anchor rod axial force and the relative displacement parameters of the test module should be monitored during the loading test, and the anchor rod axial force test adopts distributed optical fiber testing.

[0033] The present invention can control one end of the anchor rod to be fixed, while the other end deforms as the surrounding rock moves and deforms, effectively realizing the test requirements and highly restoring the stress and deformation conditions of the anchor rod in actual engineering, making the test results more convincing. At the same time, the various components of the present invention have low cost, simple assembly, and a wide range of applications.

[0034] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An indoor test structure for monitoring anchor stress in soft rock large deformation tunnels, characterized by: A free end model box (1), a plurality of middle section model boxes (3) and a fixed end model box (2) are sequentially assembled into an integral model box through a connecting locking structure (6); Prefabricated simulated surrounding rocks (5) are placed in the model box, two movable partitions (7) are inserted between each surrounding rock, and several air pressure pads (8) are placed between the movable partitions (7). The air pressure pads (8) are connected to the air pressure pump (9) through the air pipe (14); The anchor rod (11) passes through the middle hole of the free end model box (1) and the fixed end model box (2), and the anchor rod is anchored to the surrounding rock by an anchoring agent, and is fixed on both sides by end steel washers (12) and end nuts (13).

2. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: The steel plate connected to the anchor rod (11) in the free end model box (1) can move freely, thereby simulating the tail of the anchor rod (11) in actual engineering, i.e., the free surface inside the tunnel.

3. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: All steel plates in the fixed end model box (2) are rigidly connected to achieve simulation of the head of the anchor rod (11) in actual engineering, that is, the depth of the tunnel surrounding rock. Here, different anchor rod types are simulated according to whether end anchoring is adopted.

4. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: The air pressure pad (8) is pressurized by an air pressure pump (9), and the movable partition (7) is squeezed to push the prefabricated simulated surrounding rock (5), thereby simulating the deformation of the surrounding rock during tunnel construction; at the same time, different air pressures are applied at different locations, and the simulation of uneven surrounding rock deformation is achieved by controlling the amount of movement of the air pressure pad.

5. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: Polyurethane foam is added to the gaps between the movable partitions (7) to enhance the pressure transmission efficiency of the air pressure cushion (8).

6. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: During the loading process of the air pressure cushion (8), the connection locking structure (6) needs to be released.

7. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: The portion of the anchor rod (11) located between the movable partitions (7) is provided with a protective sleeve (15) to prevent the anchor rod (11) from being deformed by stress and disturbed by other factors.

8. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnels according to claim 1 is characterized in that: During the loading test, the anchor rod axial force and the relative displacement parameters of the test module should be monitored. The anchor rod axial force test adopts distributed optical fiber testing.

Images