Tunnel steel arch support structure and secondary yielding control method thereof

Abstract

The invention discloses a tunnel steel arch support structure and a secondary yielding control method thereof. An outer arch ring, an inner arch ring, a first connector and a second connector are connected in a matched mode to form two closed-ring-shaped steel arches so as to adapt to an arch-shaped section tunnel arranged under the condition of large external pressure. Wherein the first connector is connected with the outer section of the outer arch ring and the inner section of the inner arch ring at the same time, and the second connector is only connected with the outer section. The first connector can be contracted in the circumferential direction and the radial direction of the tunnel, the second connector can be contracted in the circumferential direction of the tunnel, and when the steel arch frame is subjected to large surrounding rock pressure, radial contraction is conducted through the first connector, meanwhile, circumferential contraction is conducted through the second connector, yielding contraction of the outer arch ring is achieved, and primary yielding is achieved; when the outer arch ring is attached to the inner arch ring, primary yielding is finished, and if the steel arch is subjected to larger surrounding rock pressure again, the joint I and the joint II are subjected to circumferential shrinkage at the same time, so that common yielding shrinkage of the outer arch ring and the inner arch ring is realized, and secondary yielding is realized.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel support, and in particular to a tunnel steel arch support structure and a pressure relief control method thereof. Background Art

[0002] During the tunnel construction process, it is inevitable to face problems such as high surrounding rock stress and large deformation. The existing strong support measures cannot meet the requirements of surrounding rock deformation control, which can easily cause the support structure to yield and fail, affecting construction safety. In response to this situation, some people have proposed the principle of "yielding pressure support", which means maintaining a certain support resistance. While maintaining the stability of the supported body, the supporting body is allowed to produce a certain displacement to achieve the effect of support and unloading.

[0003] In the document "Tung Chee-hwa, He Pengfei, Qin Zhaoxian. Proposal of shape memory alloy anchor and analysis of pull-out bearing capacity characteristics [J]. China Civil Engineering Journal, 2023.", an anchor made of shape memory alloy is mentioned. It can have a fixed shape in the martensite phase and austenite phase, and can induce phase transformation by changing the temperature of the alloy sheet, so that the shape of the alloy sheet can be restored, and then quickly formed. In the invention patent application "A tunnel steel arch support structure and its pressure-release control method" with publication number CN118462253A, a pressure-release support structure including the above-mentioned memory alloy is recorded. The support structure includes a plurality of alternately arranged segments and joints, which are slidably connected along the length direction of the segment; the joint includes a memory alloy damping block whose volume decreases when the temperature rises and increases when the temperature drops, and the memory alloy damping block fits the segment and changes the friction between the two through volume changes. Therefore, the support structure achieves the "resisting and giving way" compression support effect, ensuring that the tunnel steel arch support structure has both support force and deformation bearing capacity.

[0004] However, this structure also has disadvantages. Its pressure-releasing function comes from the deformation of the memory alloy damping block, which causes the segment and the memory alloy damping block to slide relative to each other, thereby shrinking the tunnel steel arch frame and releasing the internal force of the arch frame. Since the deformation of the memory alloy damping block cannot be restored and re-releasing due to the pressure during the pressure-releasing process, its pressure-releasing function can only occur once, that is, one-time pressure-releasing. Therefore, its pressure-releasing function is limited and is only suitable for situations where the surrounding rock pressure is not very large. However, during tunnel excavation, due to the different tunnel burial depths and soil structures, the surrounding rock pressure of the tunnel section will also be different. Therefore, in the case of large surrounding rock pressure, the pressure-releasing capacity of the above-mentioned pressure-releasing support structure is insufficient and cannot provide sufficient support force, which will also cause structural yield failure and affect construction safety. In addition, different tunnel sections are currently selected during construction for surrounding rock pressures of different intensities, among which the design of the arch section can well support the heavy pressure above and on both sides, and its bearing capacity is also better. Therefore, in order to be suitable for arch sections with stronger bearing capacity, a joint structure with a larger pressure-releasing amount is also required to cooperate with it. Therefore, based on the above problems, a support structure and a pressure relief control method that can provide secondary pressure relief and is more suitable for the arch section are needed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a tunnel support steel arch frame and a secondary pressure relief control method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A tunnel steel arch support structure comprises an outer arch ring abutting against the inner wall of the surrounding rock, and an inner arch ring spaced inside the outer arch ring; the outer arch ring comprises a plurality of spaced outer segments and a plurality of spaced joints 2 connected to the outer segments, and the inner arch ring comprises a plurality of spaced inner segments; adjacent inner segments are connected via joints 1 to form a closed annular structure, and the joints 1 are simultaneously connected to the outer segments, so that each outer segment is connected via joints 1 and 2 to form a closed annular structure; the joints 1 can shrink along the circumference and radial direction of the tunnel, respectively, thereby reducing the circumference of the outer arch ring and the inner arch ring, and reducing the spacing between the outer arch ring and the inner arch ring.

[0007] As a further improvement of the above technical solution: The cross section of the inner segment is U-shaped, and the joint 1 includes a retracting device 1 embedded in the cross section and shrinking along the circumference of the tunnel. The retracting device 1 includes a plate-type damper whose damping effect changes with temperature, a slide plate and a plurality of connecting slide blocks. The plate-type damper is installed between the slide plate and the inner segment, and both ends of the slide plate are provided with sliding holes distributed along the length direction thereof. The connecting slide block, the plate-type damper and the inner segment are fixed by bolts and slidably connected to the slide plate through the sliding holes.

[0008] The connecting sliding block is slidably connected to the top surface of the sliding plate and between the plate-type damper and the inner segment through the sliding hole.

[0009] The joint 1 also includes a retracting device 2 that contracts radially along the tunnel. The retracting device 2 includes a spring damper whose damping effect changes with temperature. The upper end of the spring damper abuts against the bottom of the outer segment, and the lower end abuts against the slide plate.

[0010] The second retracting device also includes a support column vertically penetrating and installed in the middle of the slide plate, and the spring damper is arranged around the support column.

[0011] The plate damper, the spring damper and the memory alloy damping block in the second joint are all electrically connected to a damping control module for controlling the temperature change thereof.

[0012] Each of the outer segments and each of the inner segments is provided with a monitoring device for monitoring the pressure borne by the supporting structure.

[0013] A joint 1 is arranged at the arch and two wall shoulders of the supporting structure, and a joint 2 is installed between two adjacent joints 1.

[0014] A secondary pressure relief control method for a tunnel steel arch support structure as described above comprises the following steps: S1: Before the arch pressure is released, the joint 1 and the joint 2 are in the power-off state. At this time, the damping effect of the two is the greatest, the connecting slider is located at the two ends of the slide plate, and the spring damper is in the relaxation state; S2: The force on the arch frame is determined by the monitoring device. When the force on the outer arch ring is greater than the set value, that is, when pressure relief is required, the damping control module heats the spring damper and the memory alloy damping block to cause the memory alloy to undergo a phase change. The damping of the spring damper and the memory alloy damping block is reduced, so that the outer arch ring is radially and circumferentially retracted to release the pressure on the outer arch ring. S3: When the force on the outer arch ring is less than the set value, the damping control module is powered off to cool the spring damper and the memory alloy damping block. The spring damper and the memory alloy damping block are restored to the maximum damping state, and the spring damper is in a compressed state. S4: Repeat steps S2-S3. When the outer arch ring fits the inner arch ring, the steel arch frame returns to a stable state, and one pressure relief is completed. S5: When the steel arch frame is stressed again, the outer arch ring and the inner arch ring are squeezed at the same time. When the monitoring device determines that the stress on the steel arch frame is greater than the set value, the damping control module heats the plate damper and the memory alloy damping block to make the memory alloy undergo a phase change. The damping of the plate damper and the memory alloy damping block is reduced, so that the outer arch ring and the inner arch ring shrink inward in the circumferential direction. S6: When the force on the steel arch frame is less than the set value, the damping control module is powered off to cool the plate damper and the memory alloy damping block, and the plate damper and the memory alloy damping block are restored to the maximum damping state; S7: Repeat steps S5-S6, and the steel arch frame finally maintains a stable state, completing the second pressure relief.

[0015] As a further improvement of the above technical solution: In S2 and S5: the heating temperature of the plate damper, the spring damper and the memory alloy damping block is controlled between 50° and 60°.

[0016] Compared with the prior art, the advantages of the present invention are: By setting up two pressure reliefs, the steel arch frame can provide more pressure relief, thereby achieving a greater bearing capacity, and the closed-loop arched steel arch frame is more suitable for the arched cross-section tunnel selected when the surrounding rock pressure is large. At the same time, setting up two pressure reliefs can better meet the bearing requirements and cost control requirements of larger surrounding rock pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic three-dimensional diagram of the structure of the tunnel steel arch frame in the embodiment; Figure 2 is a schematic diagram of the structure of the joint 1 in the embodiment (the damping control module is not shown); Figure 3 is a connection diagram of a plate damper and a damping control module in an embodiment; Figure 4 is a schematic structural diagram of a slide plate in an embodiment; Figure 5 is a connection diagram of a spring damper and a damping control module in an embodiment; Figure 6 is a schematic structural stereogram of a joint 2 in the embodiment; Figure 7 Schematic diagram of the connection between the memory damping block and the damping control module in the embodiment.

[0018] The symbols in the figure represent: 1. Outer arch ring; 11. Outer segment; 2. Inner arch ring; 21. Inner segment; 3. Joint 1; 31. Retracting device 1; 311. Plate damper; 312. Slide plate; 3121. Slide hole; 313. Connecting slide block; 314. Bolt; 32. Retracting device 2; 321. Spring damper; 322. Support column; 4. Joint 2; 41. Memory alloy damping block; 5. Damping control module; 6. Monitoring device. DETAILED DESCRIPTION

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

[0020] like Figures 1 to 7 As shown, the tunnel steel arch support structure of this embodiment includes an outer arch ring 1 abutting against the inner wall of the surrounding rock, and an inner arch ring 2 spaced inside the outer arch ring 1; the outer arch ring 1 includes a plurality of spaced outer segments 11 and a plurality of spaced joints 4 connected to the outer segments 11, and the inner arch ring 2 includes a plurality of spaced inner segments 21; adjacent inner segments 21 are connected via joints 3 to form a closed annular structure, and joints 3 are simultaneously connected to the outer segments 11, so that each outer segment 11 is connected via joints 3 and joints 4 to form a closed annular structure; joints 3 can shrink along the circumferential and radial directions of the tunnel, respectively, thereby reducing the circumferences of the outer arch ring 1 and the inner arch ring 2, and reducing the spacing between the outer arch ring 1 and the inner arch ring 2. The present invention is a further development of the invention patent application "A tunnel steel arch support structure and its pressure control method" with publication number CN118462253A. The joint 24 in this application is the joint disclosed in CN118462253A: the joint includes a memory alloy damping block whose volume decreases when the temperature rises and increases when the temperature drops, and the memory alloy damping block fits with the steel arch segment and changes the friction between the two through volume change; it also includes a joint body and a connecting slider; the joint body is provided with sliding grooves distributed along its length direction, and the connecting slider is provided with two groups, which are slidably connected at both ends of the length direction of the joint body through the sliding grooves; the segment is provided with a connecting groove for installing the joint, and the connecting groove is fixedly connected to the connecting slider, the joint body includes a damping surface fit with the connecting groove, and the memory alloy damping block is arranged on the damping surface. Based on the reference "Tung Chee-hwa, He Pengfei, Qin Zhaoxian. Proposal of shape memory alloy anchor and analysis of pull-out bearing capacity characteristics [J]. China Civil Engineering Journal, 2023.", the characteristics of the changes in the characteristics and structure of the memory alloy with temperature are disclosed, which are specifically manifested as follows: the internal characteristics of the memory alloy have recovery ability. When the interior is in the martensite phase, it is in the best state of damping effect. When it is heated to the starting point of the austenite phase transformation, the memory alloy begins to change phases and its damping effect decreases; when the interior of the memory alloy changes to the austenite phase, it can be cooled to the starting point of the reverse martensite phase transformation. The internal crystal phase of the memory alloy changes and recovery stress is generated. The temperature continues to drop to the end point of the reverse martensite phase transformation. The interior of the memory alloy is completely restored to martensite, and the damping effect is restored to the optimal state.

[0021] In this embodiment, the outer arch ring 1, the inner arch ring 2, the joint 1 3 and the joint 2 4 cooperate to form two closed ring steel arch frames to adapt to the arched cross-section with stronger bearing capacity. Among them, the joint 1 3 simultaneously connects the outer segment 11 of the outer arch ring 1 and the inner segment 21 of the inner arch ring 2, and the joint 2 4 only connects the outer segment 11. In addition, the joint 1 3 can shrink along the circumference and radial direction of the tunnel, and the joint 2 4 can shrink along the circumference of the tunnel. Therefore, when the steel arch frame is subjected to surrounding rock pressure, the joint 1 3 is firstly radially shrunk while the joint 2 4 is circumferentially shrunk to achieve the pressure-releasing shrinkage of the outer arch ring 1, which is the first pressure-releasing shrinkage; when the outer arch ring 1 fits the inner arch ring 2, the first pressure-releasing shrinkage ends. If the steel arch frame is subjected to greater surrounding rock pressure, the joint 1 3 is circumferentially shrunk while the joint 2 is also circumferentially shrunk to achieve the pressure-releasing shrinkage of the outer arch ring 1 and the inner arch ring 2, which is the second pressure-releasing shrinkage. By setting up two pressure reliefs, the steel arch frame can provide more pressure relief, thereby achieving a greater bearing capacity, and the closed-loop steel arch frame is also more adaptable to arch sections with stronger bearing capacity, so it can be better used in scenarios with greater surrounding rock pressure.

[0022] In this embodiment, the cross-section of the inner segment 21 is U-shaped, and the joint 3 includes a retracting device 31 embedded in the cross-section and shrinking along the circumference of the tunnel. The retracting device 31 includes a plate-type damper 311 whose damping effect changes with temperature, a slide plate 312 and a plurality of connecting sliders 313. The plate-type damper 311 is installed between the slide plate 312 and the inner segment 21. Both ends of the slide plate 312 are provided with sliding holes 3121 distributed along its length direction. The connecting slider 313, the plate-type damper 311 and the inner segment 21 are fixed by bolts 314 and are slidably connected to the slide plate 312 through the sliding holes 3121. The joint 3 is connected to the inner segment 21 through the retracting device 31. The plate damper 311 is made of memory alloy. Since the characteristics and structure of the memory alloy change with temperature, the damping effect of the plate damper 311 is reduced by increasing the temperature, and the friction between the retracting device 31 and the inner segment 21 is reduced. The inner segment 21 drives the connecting slider 313 and the plate damper 311 to slide along the slide hole 3121 relative to the slide plate 312, so that the inner arch ring 2 shrinks and releases the internal force of the arch frame. After achieving the expected effect, the temperature of the plate damper 311 is reduced to restore its damping effect and finally reach a static equilibrium state. The damping effect of the plate damper 311 is controlled by temperature, thereby changing the friction and position between the inner segment 21 and the joint 3, thereby achieving controllable compression shrinkage.

[0023] In this embodiment, the connecting slider 313 is slidably connected to the top surface of the slide plate 312 and between the plate damper 311 and the inner segment 21 through the slide hole 3121. The connecting slider 313 includes at least two pieces, which are used to protect the plate damper 311 and the slide plate 312 from damage, and provide a mounting basis for the sliding connection between the inner segment 21 and the retracting device 1 31.

[0024] In this embodiment, the joint 1 3 also includes a retracting device 2 32 that shrinks radially along the tunnel. The retracting device 2 32 includes a spring damper 321 whose damping effect changes with temperature. The upper end of the spring damper 321 abuts against the bottom of the outer segment 11, and the lower end abuts against the slide plate 312; the retracting device 2 32 also includes a support column 322 that is vertically penetrated and installed in the middle of the slide plate 312, and the spring damper 321 is arranged around the support column 322. The spring damper 321 is also made of memory alloy. Therefore, its damping is regulated by controlling the temperature change of the spring damper 321, thereby realizing contraction in the radial direction of the tunnel, so that the distance between the outer arch ring 1 and the inner arch ring 2 is reduced, and in this process, the first-level pressure-releasing contraction is completed by the synchronous circumferential contraction of the joint 2 4; and the support column 322 installed through the middle of the slide plate 312 is used to provide an installation basis for the spring damper 321 to prevent it from lateral deformation, and a base is also installed at the bottom of the support column 322 to prevent the joint 1 3 from falling off in the radial direction, thereby ensuring that the retraction device 2 32 can smoothly achieve radial contraction.

[0025] In this embodiment, the plate damper 311, the spring damper 321 and the memory alloy damping block 41 in the joint 2 4 are all electrically connected to the damping control module 5 for controlling their temperature changes. Each outer segment 11 and each inner segment 21 is provided with a monitoring device 6 for monitoring the pressure borne by the support structure. The surrounding rock pressure borne by the outer arch ring 1 and the inner arch ring 2 is monitored by the monitoring device 6, and the temperature change of the plate damper 311, the spring damper 321 and the memory alloy damping block 41 is controlled by the damping control module 5, so as to adjust the change of the damping effect, thereby realizing that the pressure relief amount can be adjusted according to the size of the surrounding rock pressure during the pressure relief process, and accurate pressure relief control is achieved.

[0026] In this embodiment, a joint 1 3 is arranged at the arch top and two wall shoulders of the supporting structure, and a joint 2 4 is installed between two adjacent joints 1 3. According to the stress conditions of the steel arch support structure, in this embodiment, a joint 1 3 is arranged at the arch top, two wall shoulders, two wall sides and arch bottom of the supporting structure, and a joint 2 4 is installed between two adjacent joints 1 3, so that the outer arch ring 1 and the inner arch ring 2 both form a closed arch style to adapt to the arch section tunnel; and the outer arch ring 1 itself can have the ability to resist the surrounding rock pressure by yielding; and by adding multiple joints 1 3 and joints 2 4, each joint can be individually regulated according to the stress and yielding requirements. In order to ensure that the steel arch frame can smoothly achieve two yielding, it is necessary to ensure that the outer arch ring 1 can continue to deform with the inner arch ring 2 after completing radial contraction and fitting the inner arch ring 2, so a joint 2 4 is installed between two adjacent joints 1 3. When the radial contraction of joint 1 3 is completed, joint 2 4 has not reached the pressure relief limit and still retains the circumferential pressure relief. Therefore, when the retraction device 1 31 of joint 1 3 and the inner segment 21 perform the circumferential contraction of the inner arch ring 2 along the tunnel, joint 2 4 can also follow the circumferential contraction of the outer arch ring 1 in the tunnel, thereby ensuring the feasibility of the device. The secondary pressure relief control method of the tunnel steel arch support structure as described above in this embodiment includes the following steps: S1: before the arch pressure is released, the joint 1 3 and the joint 2 4 are in the power-off state, at which time the damping effect of the two is the greatest, the connecting slider 313 is located on the two ends of the slide plate 312, and the spring damper 321 is in the relaxation state; S2: According to the monitoring device 6, the stress of the arch frame is judged. The pressure of the outer arch ring 1 is between 1.5 and 2 MPa. In this embodiment, the set value is 1.5 MPa. When the stress of the outer arch ring 1 is greater than the set value 1.5 MPa, it is necessary to release the pressure. The damping control module 5 heats the spring damper 321 and the memory alloy damping block 41 to make the memory alloy undergo phase change. The damping of the spring damper 321 and the memory alloy damping block 41 is reduced. Therefore, the outer arch ring 1 is forced to shrink radially and circumferentially under the pressure of the surrounding rock, and the pressure of the outer arch ring 1 is released. In this process, the surrounding rock pressure corresponding to the pressure release amount per millimeter needs to be measured on site. It is assumed that the surrounding rock pressure corresponding to the deformation amount of 1 mm on site is 1 Kpa, that is, every time the surrounding rock pressure increases by 1 Kpa, each spring damper 321 of the outer arch ring 1 needs to shrink by 1 mm, and the corresponding joints 4 at different positions shrink by π / 2 mm and 1 mm respectively according to the arc length formula and geometric relationship.

[0027] S3: When the force on the outer arch ring 1 is less than the set value 1.5Mpa, there is no need to shrink the pressure, so the damping control module 5 is powered off to cool the spring damper 321 and the memory alloy damping block 41, and the spring damper 321 and the memory alloy damping block 41 are restored to the maximum damping state, and the spring damper 321 is in a compressed state; S4: Repeat steps S2-S3 to keep the surrounding rock pressure on the outer arch ring 1 at about 1.5 MPa. When the outer arch ring 1 fits the inner arch ring 2, the spring damper 321 reaches the maximum pressure relief, and the steel arch frame returns to a stable state, completing a pressure relief. S5: When the steel arch frame is stressed again, the outer arch ring 1 and the inner arch ring 2 are squeezed at the same time. At this time, the outer arch ring 1 and the inner arch ring 2 jointly resist the surrounding rock pressure. The surrounding rock pressure that can be borne at this time is greater than the surrounding rock pressure that the outer arch ring 1 alone bears during the first-level pressure relief. Therefore, when the monitoring device 6 determines that the force on the steel arch frame is greater than the set value 1.8Mpa, the damping control module 5 heats the plate damper 311 and the memory alloy damping block 41 to cause the memory alloy to undergo a phase change, and the damping of the plate damper 311 and the memory alloy damping block 41 is reduced, so that the outer arch ring 1 and the inner arch ring 2 are simultaneously circumferentially retracted; S6: When the stress on the steel arch is less than the set value 1.8 MPa, the damping control module 5 is powered off to cool the plate damper 311 and the memory alloy damping block 41, and the plate damper 311 and the memory alloy damping block 41 are restored to the maximum damping state; S7: Repeat steps S5-S6, and the steel arch frame finally maintains a stable state, completing the second pressure relief.

[0028] In this embodiment, in S2 and S5: the heating temperature of the plate damper 311, the spring damper 321 and the memory alloy damping block 41 is controlled between 50° and 60°.

[0029] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A tunnel steel arch support structure, characterized in that: The invention comprises an outer arch ring (1) abutting against the inner wall of the surrounding rock, and an inner arch ring (2) arranged at intervals inside the outer arch ring (1); the outer arch ring (1) comprises a plurality of outer segments (11) arranged at intervals and a plurality of second joints (4) arranged at intervals and connected to the outer segments (11); the inner arch ring (2) comprises a plurality of inner segments (21) arranged at intervals; adjacent inner segments (21) are connected via first joints (3) to form a closed annular structure, and the first joints (3) are simultaneously connected to the outer segments (11), so that each outer segment (11) is connected via the first joints (3) to the second joints (4) to form a closed annular structure; the first joints (3) can shrink along the circumferential direction and radial direction of the tunnel respectively, thereby reducing the circumference of the outer arch ring (1) and the inner arch ring (2), and reducing the distance between the outer arch ring (1) and the inner arch ring (2).

2. The tunnel steel arch support structure according to claim 1 is characterized in that: The cross section of the inner segment (21) is U-shaped. The joint (3) comprises an inner retracting device (31) embedded in the cross section and retracted along the circumferential direction of the tunnel. The inner retracting device (31) comprises a plate-type damper (311) whose damping effect changes with temperature, a slide plate (312) and a plurality of connecting slide blocks (313). The plate-type damper (311) is installed between the slide plate (312) and the inner segment (21). Both ends of the slide plate (312) are provided with sliding holes (3121) distributed along the length direction thereof. The connecting slide blocks (313), the plate-type damper (311) and the inner segment (21) are fixed by bolts (314) and are slidably connected to the slide plate (312) through the sliding holes (3121).

3. The tunnel steel arch support structure according to claim 2 is characterized in that: The connecting sliding block (313) is slidably connected to the top surface of the sliding plate (312) and between the plate-type damper (311) and the inner segment (21) through the sliding hole (3121).

4. The tunnel steel arch support structure according to claim 2 is characterized in that: The joint 1 (3) further comprises a retracting device 2 (32) that contracts in the radial direction of the tunnel, the retracting device 2 (32) comprising a spring damper (321) whose damping effect varies with temperature, the upper end of the spring damper (321) abutting against the bottom of the outer segment (11), and the lower end abutting against the slide plate (312).

5. The tunnel steel arch support structure according to claim 4 is characterized in that: The second retracting device (32) further comprises a support column (322) vertically penetrating and installed in the middle of the slide plate (312), and the spring damper (321) is arranged around the support column (322).

6. The tunnel steel arch support structure according to claim 4, characterized in that: The plate-type damper (311), the spring damper (321) and the memory alloy damping block (41) in the second joint (4) are all electrically connected to a damping control module (5) for controlling the temperature change thereof.

7. The tunnel steel arch support structure according to any one of claims 1 to 6, characterized in that: Each of the outer segments (11) and each of the inner segments (21) is provided with a monitoring device (6) for monitoring the pressure borne by the supporting structure.

8. The tunnel steel arch support structure according to any one of claims 1 to 6, characterized in that: A joint 1 (3) is arranged at the arch and two wall shoulders of the supporting structure, and a joint 2 (4) is installed between two adjacent joints 1 (3).

9. A secondary pressure relief control method for a tunnel steel arch support structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: before the arch pressure is released, the first joint (3) and the second joint (4) are in a power-off state, at which time the damping effect of the two is the greatest, the connecting slider (313) is located on the two ends of the slide plate (312), and the spring damper (321) is in a relaxed state; S2: judging the magnitude of the force on the arch frame according to the monitoring device (6), when the force on the outer arch ring (1) is greater than the set value, i.e. when pressure relief is required, heating the spring damper (321) and the memory alloy damping block (41) through the damping control module (5) causes the memory alloy to undergo a phase change, thereby reducing the damping of the spring damper (321) and the memory alloy damping block (41), thereby causing the outer arch ring (1) to retract radially and circumferentially, thereby releasing the pressure on the outer arch ring (1); S3: When the force applied to the outer arch ring (1) is less than a set value, the damping control module (5) is powered off to cool the spring damper (321) and the memory alloy damping block (41), so that the spring damper (321) and the memory alloy damping block (41) are restored to a maximum damping state, and the spring damper (321) is in a compressed state; S4: Repeat steps S2-S3, and when the outer arch ring (1) fits the inner arch ring (2), the steel arch frame returns to a stable state, completing one pressure release; S5: When the steel arch frame is subjected to stress again, the outer arch ring (1) and the inner arch ring (2) are squeezed at the same time. When the monitoring device (6) determines that the stress on the steel arch frame is greater than the set value, the damping control module (5) heats the plate damper (311) and the memory alloy damping block (41) to cause the memory alloy to undergo a phase change, and the damping of the plate damper (311) and the memory alloy damping block (41) is reduced, so that the outer arch ring (1) and the inner arch ring (2) are circumferentially retracted. S6: When the force on the steel arch frame is less than the set value, the damping control module (5) is powered off to cool the plate damper (311) and the memory alloy damping block (41), so that the plate damper (311) and the memory alloy damping block (41) are restored to a maximum damping state; S7: Repeat steps S5-S6, and the steel arch frame finally maintains a stable state, completing the second pressure relief.

10. The secondary pressure relief control method for a tunnel steel arch support structure according to claim 9, characterized in that: In S2 and S5: the heating temperature of the plate damper (311), the spring damper (321) and the memory alloy damping block (41) is controlled between 50° and 60°.

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