Indoor test structure for monitoring stress of soft rock large-deformation tunnel anchor rod

Abstract

The invention discloses a soft rock large-deformation tunnel anchor rod stress monitoring indoor test structure. Specifically, a free end model box, a plurality of middle section model boxes and a fixed end model box are sequentially assembled into an integral model box through connecting and locking structures; prefabricated simulation surrounding rocks are placed in the model box, two movable partition plates are inserted between the surrounding rocks, a plurality of air pressure pads are placed between the movable partition plates, and the air pressure pads are connected to an air pressure pump through air conveying pipes. An anchor rod penetrates through a hole in the middle of the free end model box and a hole in the middle of the fixed end model box, simulation of anchor rod anchoring surrounding rock is achieved through an anchoring agent, and the two sides of the anchor rod are fixed through end steel gaskets and end nuts. The device can effectively simulate the condition that one end of the anchor rod is fixed and the other end of the anchor rod is stretched along with the deformation of the surrounding rock, highly restores the mutual influence effect between the anchor rod and the surrounding rock in actual engineering, and is simple in structural combination, 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 anchoring in a soft rock tunnel with large deformation, there is a situation where the end of the anchor is located in a relatively stable bearing area or elastic area, while most of the rest of the anchor is located in the loose circle. At this time, the stress and deformation characteristics of the anchor are as follows: the surrounding rock in the loose circle shrinks and deforms inward, while driving the anchor to stretch and deform, while the end of the anchor is located in the stable rock layer, limiting the overall movement of the anchor. In order to restore the stress characteristics of the anchor in the indoor test, one end of the anchor is fixed, and the other end can be fixed or anchored. At present, there is no experimental device that can achieve the requirements, so this experimental structure uses air pressure cushions as power to squeeze the surrounding rock and push the anchor to stretch, which can effectively achieve the above test requirements. Summary of the invention

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

[0004] The invention discloses an indoor test structure for monitoring anchor stress in a soft rock large deformation tunnel, which specifically 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 connection 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, so as to simulate the tail of the anchor rod in the actual project, that is, the free surface inside the tunnel.

[0008] Furthermore, all the steel plates in the fixed end model box are rigidly connected to achieve the simulation of the anchor head in the actual project, 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 pressure pump, and the movable partition is squeezed to push the prefabricated simulated surrounding rock, so as to simulate the deformation of the surrounding rock during tunnel construction; at the same time, different air pressures are applied to different parts, 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 affected by other factors.

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

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

[0015] The present invention adopts an indoor test method to simulate the stress characteristics of the anchor rod when one end of the anchor rod is fixed and the other end is stretched as the surrounding rock deforms. Currently, there is no suitable experimental device to achieve the above experimental requirements. This experimental device can not only effectively simulate the stress conditions of the above anchor rod, but also highly restore the mutual influence between the anchor rod and the surrounding rock in the actual project. At the same time, the device has a simple combination of structures, is easy to use, is conducive to promotion and has 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 plate; 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 is 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 a soft rock large deformation tunnel. 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 connection 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, an air pipe 14, etc. Specifically, a free end model box 1, a plurality of intermediate section model boxes 3 and a fixed end model box 2 are sequentially assembled into an integral model box (detachable) through the connection locking structure 6. The number of intermediate section model boxes 3 can be determined according to the length of the tested anchor rod 11.

[0021] Prefabricated simulated surrounding rocks 5 are placed in the model box, two movable partitions 7 are inserted between each surrounding rock, and several air cushions 8 are placed between the movable partitions 7. The air cushions 8 are connected to the air pump 9 through the air pipe 14. The air cushions 8 are pressurized by the air pump 9, and the movable partitions 7 are squeezed to push the prefabricated simulated surrounding rocks 5, so as to simulate the deformation of the surrounding rocks during tunnel construction; at the same time, different air pressures are applied at different locations, and the simulation of uneven surrounding rock deformation is realized by controlling the amount of movement of the air cushions.

[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, the anchor rod 11 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, so that the anchor rod 11 can better couple with the surrounding rock after entering the surrounding rock, thereby realizing the common deformation of the anchor rod 11 and the surrounding rock; a number of 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 strain of the anchor rod 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, so as to simulate the tail of the anchor rod 11 in the actual project, that is, the free surface inside the tunnel.

[0025] Furthermore, all the steel plates in the fixed end model box 2 are rigidly connected to achieve the simulation of 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, and the strain of the anchor rod is measured by collecting the optical signal change 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 the boxes 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, a few 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 force and disturbed by other factors.

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

[0033] The present invention can control one end of the anchor rod to be fixed, while the other end can be deformed as the surrounding rock moves and deforms, thereby 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 component structures 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 clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An indoor test structure for monitoring anchor stress in soft rock large deformation tunnels, characterized in that: 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 connection 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 a plurality of air pressure pads (8) are placed between the movable partitions (7), and the air pressure pads (8) are connected to an air pressure pump (9) through an 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 means of an anchoring agent, and is fixed on both sides by means of end steel washers (12) and end nuts (13).

2. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnel 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, that is, the free surface inside the tunnel.

3. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnel 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 tunnel 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 tunnel 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 tunnel 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 tunnel 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 cover (15) to prevent the anchor rod (11) from being deformed by force and disturbed by other factors.

8. The indoor test structure for monitoring anchor stress in soft rock large deformation tunnel 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, and the anchor rod axial force test should be carried out using distributed optical fiber testing.

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