A multi-stage pressure-released supporting structure and a supporting method applied to underground engineering

Abstract

The application discloses a multistage pressure-releasing supporting structure applied to underground engineering, and relates to the technical field of underground engineering, in particular to a multistage pressure-releasing supporting structure applied to underground engineering.

Description

Technical Field

[0001] This invention relates to a multi-stage pressure relief support structure, and more particularly to a multi-stage pressure relief support structure applied to underground engineering, belonging to the field of tunnel surrounding rock support technology. Background Technology

[0002] During the construction of tunnels in soft rock with high ground stress and large deformation, the loose texture and poor stability of soft rock increase the difficulty of deformation control. Under the combined action of the surrounding rock's own weight and the disturbance caused by tunnel construction, there is a risk of settlement and instability at the top of the surrounding rock. To address the problem of significant large deformation in tunnels with weak surrounding rock, the main control measures currently adopted include: large-section steel frame technology, retractable support technology, early high-strength concrete technology, long anchor cable and bolt technology, and double-layer initial support technology.

[0003] In highway and railway tunnels, rigid connection methods using only U-shaped steel arch bolts are unsuitable for complex geological conditions with high ground stress and large deformation in soft rock. For friction-retractable U-shaped steel arch connections using cable clamps, their resistance to large deformations of the surrounding rock is generally considered limited, and the arch retraction speed during stress release is slow. Unlike in coal mine roadways where they serve as temporary supports, steel arches in tunnels must function as permanent load-bearing structures. Although some existing support structures can achieve a certain degree of deformation adaptability, they cannot achieve multi-level, layered pressure relief for more complex soft rock deformation situations, thus failing to effectively release surrounding rock pressure. Some pressure relief devices in support structures cannot flexibly deform and contract under stress and are at risk of damage. Furthermore, they cannot provide suitable support reaction forces to the surrounding rock, potentially causing loosening and failure of both the steel arch and the surrounding rock.

[0004] Under complex geological conditions of high ground stress and large deformation of soft rock, it is necessary to propose a multi-stage pressure relief support structure and support method for underground engineering to address the problems of the inability of the support structure and the surrounding rock to coordinate deformation and the inability to achieve multi-stage orderly release of surrounding rock pressure. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a multi-stage pressure-relief support structure and method for underground engineering, enabling multi-stage and orderly release of surrounding rock pressure. This achieves the aforementioned technical objectives and effects.

[0006] This invention is achieved through the following technical solution:

[0007] A multi-stage pressure-relief support structure for underground engineering is characterized by comprising a U-shaped steel arch frame, pressure-relief device A, pressure-relief device B, a rigid support structure, pressure-relief anchors, and a foamed concrete layer. The outer ring support structure is formed by connecting multiple U-shaped steel arch frames with pressure-relief device A. The pressure-relief anchors are fixed in the surrounding rock, and the bottom plate of the pressure-relief anchors is in contact with the outer surface of the surrounding rock. A foamed concrete layer is sprayed around the pressure-relief anchors. The U-shaped steel arch frames in the outer ring support structure are in contact with the foamed concrete layer. The bottom of the pressure-relief device B is welded to the inner side of the U-shaped steel arch frame in the outer ring support structure. The rigid support structure is in the inner ring, located inside the pressure-relief device B and with a distance between them. The rigid support structure is composed of multiple U-shaped steel arch frames connected together. Connecting plates are welded to the ends of the outer ring U-shaped steel arch frames, and adjacent U-shaped steel arch frames are fixed by bolts.

[0008] Preferably, the pressure-relieving device A includes a welded steel plate, a connecting steel plate with a connector, bolts and nuts A, steel bars with different pre-made holes, a hydraulic device, short bolts and nuts B, a telescopic rod with a connector, and a spring. The hydraulic device includes a hexagonal cylinder, a sealed rotating piston, a damping hole, and hydraulic oil. Welded steel plates are welded to opposite sides of a pair of U-shaped steel arches. The welded steel plates are connected to the connecting steel plate via bolts and nuts A. The steel bars are connected to the connector via short bolts and nuts B on one side and to other steel bars on the other side in sequence. The hexagonal cylinder in the hydraulic device is connected to the inner hexagonal hole, and the sealed rotating piston is connected to the outer hexagonal hole. Adjacent steel bars can rotate relative to each other. The spring is located between the washers of the telescopic rod, and the telescopic rod is connected to the connecting steel plate via short bolts and nuts B.

[0009] Preferably, the connecting steel plate with connecting bodies has two pairs of connecting bodies along the long side of the steel bar connecting body, the distance between one pair of connecting bodies is shorter than the distance between the other pair of connecting bodies by the thickness of one steel bar, and the telescopic rod connecting body is located at the four corners of the connecting steel plate.

[0010] Preferably, there are four types of steel bars with different pre-made holes: one type has large hexagonal holes on both sides, one type has small hexagonal holes on both sides, one type has a round hole on one side and a large hexagonal hole on the other side, and one type has a round hole on one side and a small hexagonal hole on the other side.

[0011] Preferably, in the hydraulic device, a vertical sealing steel plate is welded to the bottom of the hexagonal cylinder and sealed to the top of the rotating piston. The rotating piston has a cylindrical body in the middle and hexagonal cylinders on both sides. The vertical sealing steel plate is connected to the cylinder. There are multiple damping holes on the sealing steel plate. The hydraulic oil is in chambers A and B. When stationary, the sealing steel plate on the rotating piston is at a 180-degree angle to the vertical sealing steel plate in the hexagonal cylinder.

[0012] Preferably, the pressure relief device B includes a cylindrical cylinder, a sealed sliding connecting rod piston, a high-strength spring, an emulsion, a safety valve, and a steel wire pressure sensor. The high-strength spring is located between the cylindrical cylinder and the steel wire pressure sensor, and in its natural state, the bottom plate of the sealed sliding connecting rod piston is located at half of the cylindrical cylinder, and the emulsion occupies one-third of the cylindrical cylinder.

[0013] Preferably, the top plate of the pressure-relief device B is spaced apart from the steel arch frame in the rigid support structure by a pressure-relief distance.

[0014]

[0015] The pressure relief distance can be obtained as follows:

[0016]

[0017] In the formula, a is the radius of a portion of the outer ring support structure, b is the radius of a portion of the rigid support structure, c is the length of the pressure relief device B after it is fully contracted, m is the pressure relief distance between the top plate of the pressure relief device B and the steel arch frame in the rigid support structure, L is the distance between the outer ring support structure and the rigid support structure, h is the deformation length of each pressure relief device A, d is the thickness of the earth pressure gauge, all in meters; n is the number of pressure relief devices A, and k is the correction coefficient.

[0018] Preferably, the steel wire pressure sensor consists of a pressure plate, an electromagnetic excitation coil, a steel wire, a rear cover plate, and a bracket.

[0019] Preferably, the pressure-relief anchor bolt includes a top plate with a nut, an anchor bolt, a bottom plate, a cylindrical cylinder, a sealed sliding connecting rod piston, a high-strength spring, an emulsion, and a safety valve. The top plate with the nut is tightened onto the anchor bolt, the high-strength spring is located between the top plate and the bottom plate, the cylindrical cylinder is welded to the bottom plate, and the emulsion occupies half of the volume of chambers D, E, and F in the cylindrical cylinder.

[0020] A multi-stage pressure relief support method for underground engineering includes the following steps:

[0021] Step 1 - First-level pressure relief: First, multiple pressure relief anchors are evenly driven into the surrounding rock, and an energy-absorbing foam concrete layer is sprayed around the pressure relief anchors. The surrounding rock load is first transferred to the pressure relief anchors and the foam concrete layer. The high-strength spring and the foam concrete layer are compressed first. As compression continues, the D-cylinder sealed sliding connecting rod piston is first subjected to force. As the surrounding rock load increases, the bearing capacity reaches the limit and the safety valve is opened, and the emulsion flows out from the safety valve. Then, the E-cylinder and F-cylinder sealed sliding connecting rod pistons are compressed. Finally, the top plate presses on the top of the cylindrical cylinder, and the pressure relief of the pressure relief anchor ends.

[0022] Step 2 - Secondary Pressure Relief: Erect each section of the U-shaped steel arch frame using the arch frame installation trolley, and install pressure relief device A between the welded steel plates to form the outer ring support structure; the surrounding rock load is transferred to the U-shaped steel arch frame of the outer ring support structure. The spring in pressure relief device A is stressed first. As the deformation increases, the spring is compressed, the telescopic rod contracts, and the steel bars rotate relative to each other, causing the hexagonal cylinder and the sealed rotating piston to rotate relative to each other. Due to the pressure, depending on the relative rotation direction of the hexagonal cylinder and the rotating piston, the hydraulic oil can enter chamber B from chamber A through the damping hole, or it can enter chamber A from chamber B, realizing the pressure relief contraction of pressure relief device A. At this time, pressure relief device A is not fully contracted.

[0023] Step 3 - Three-stage pressure relief: Pressure relief devices B are uniformly welded onto the U-shaped steel arch of the outer ring support structure to form a buffer layer; as deformation increases, when the steel wire pressure sensor at the top of pressure relief device B connects with the bottom of the inner U-shaped steel arch, pressure relief device B and pressure relief device A are subjected to force and contraction together. The high-strength spring is compressed first, and compression stops when chamber C is filled with emulsion. When the surrounding rock pressure reaches a certain value, the safety valve will be opened, and the emulsion will flow out from the safety valve. The spring continues to compress, and when the bottom of the sealed sliding connecting rod piston connects with the bottom of the cylindrical cylinder, the spring stops compressing, achieving the effect that the resistance to deformation increases with the increase of the support structure deformation. Pressure relief ends when pressure relief devices B and A are fully contracted.

[0024] Step 4: The remaining surrounding rock pressure is borne by the rigid support structure.

[0025] The beneficial effects of this invention are:

[0026] (1) The pressure relief distance between the top plate of the pressure relief device B and the steel arch frame in the rigid support structure can be obtained through theoretical calculation. This allows for more accurate control of the shrinkage of the steel arch frame, enabling the pressure relief structure to achieve a better buffering effect and further release the surrounding rock pressure.

[0027] (2) The pressure support structure adopts U-shaped steel arch frame. U-shaped steel arch frame has good geometric parameters and cross-sectional shape, high tensile strength and compressive strength, good toughness, high support force and high support strength.

[0028] (3) This pressure relief support device adopts double-layer initial support technology and retractable support technology. It achieves multi-level and layered pressure relief by pressure relief anchor, energy-absorbing foam concrete layer, outer ring support structure, pressure relief device B, and inner ring rigid support structure. It can achieve the effect that as the support structure deforms, the resistance to its deformation also increases, thereby effectively releasing the surrounding rock load.

[0029] (4) The new multi-stage pressure relief anchor can achieve a better buffering effect. The inner ring rigid support structure can prevent the steel arch frame and surrounding rock from loosening and breaking.

[0030] (5) The pressure relief device A can flexibly follow the bending deformation and shrinkage of the steel arch frame, and will not be damaged by excessive force from the steel arch frames at both ends; the steel wire pressure sensor on the pressure relief device B can monitor the deformation degree of the surrounding rock in real time, and play an early warning role. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the present invention.

[0032] Figure 2 This is a schematic diagram of the pressure relief device A of the present invention.

[0033] Figure 3 This is a schematic diagram of steel bars with different pre-made holes according to the present invention.

[0034] Figure 4 This is a schematic diagram of the overall hydraulic device of the present invention.

[0035] Figure 5 This is a cross-sectional view of the hydraulic device of the present invention.

[0036] Figure 6 This is an exploded view of the hexagonal cylinder body and the sealed rotating piston of the hydraulic device of the present invention.

[0037] Figure 7 This is a longitudinal section view of the pressure relief device B of the present invention.

[0038] Figure 8 This is a longitudinal section view of the pressure anchor bolt of the present invention.

[0039] Figure 9 This is a schematic diagram of the local distance length of the present invention.

[0040] In the diagram: 1. U-shaped steel arch frame; 2. Pressure relief device A; 21. Welded steel plate; 22. Connecting steel plate with connector; 23. Bolt and nut A; 24. Steel bar; 25. Hydraulic device; 251. Hexagonal cylinder; 252. Sealed rotary piston; 253. Damping hole; 254. Hydraulic oil; 26. Short bolt and nut B; 27. Telescopic rod with connector; 28. Spring; 3. Pressure relief device B; 31. Cylindrical cylinder; 32. Sealed sliding connecting rod piston; 33. High-strength spring; 34. Emulsion; 35. Safety valve; 36. Steel wire pressure sensor; 4. Rigid support structure; 5. Pressure relief anchor bolt; 51. Top plate with nut; 52. Anchor bolt; 53. Bottom plate; 6. Foamed concrete layer. Detailed Implementation

[0041] The following is in conjunction with the appendix Figure 1-9 The present invention will be described in detail below:

[0042] A multi-stage pressure-relief support structure for underground engineering is characterized by comprising a U-shaped steel arch frame 1, a pressure-relief device A2, a pressure-relief device B3, a rigid support structure 4, pressure-relief anchors 5, and a foamed concrete layer 6. The outer ring support structure is formed by connecting multiple sections of U-shaped steel arch frames 1 with the pressure-relief device A2. The pressure-relief anchors 5 are fixed in the surrounding rock, and the bottom plate of the pressure-relief anchors 5 is in contact with the outer surface of the surrounding rock. The pressure-relief anchors 5 are surrounded by a foamed concrete layer 6. The U-shaped steel arch frames 1 in the outer ring support structure are in contact with the foamed concrete layer 6. The bottom of the pressure-relief device B3 is welded to the inner side of the U-shaped steel arch frame 1 in the outer ring support structure. The rigid support structure 4 is in the inner ring, located inside the pressure-relief device B3 and with a distance between them. The rigid support structure 4 is composed of multiple sections of U-shaped steel arch frames 1 connected together. The ends of the outer ring U-shaped steel arch frames 1 are welded with connecting plates, and adjacent sections of U-shaped steel arch frames 1 are fixed by bolts.

[0043] Preferably, the pressure relief device A2 includes a welded steel plate 21, a connecting steel plate 22 with a connecting body, bolts and nuts A23, steel bars 24 with different pre-made holes, a hydraulic device 25, short bolts and nuts B26, a telescopic rod 27 with a connecting body, and a spring 28. The hydraulic device 25 includes a hexagonal cylinder 251, a sealed rotating piston 252, a damping hole 253, and hydraulic oil 254. Welded steel plates 21 are welded to opposite sides of a pair of U-shaped steel arches 1. The welded steel plates 21 and the connecting steel plate 22 are connected by bolts and nuts A23. The steel bars 24 are connected to the connecting body on one side and to other steel bars on the other side in sequence through short bolts and nuts C27. The hexagonal cylinder 251 in the hydraulic device 25 is connected to the inner hexagonal hole, and the sealed rotating piston 252 is connected to the outer hexagonal hole. Adjacent steel bars 24 can rotate relative to each other. The spring 28 is located between the washers of the telescopic rod 27. The telescopic rod 27 is connected to the connecting steel plate 22 through short bolts and nuts B26.

[0044] Preferably, the connecting steel plate 22 with connecting body, the steel bar 24 connecting body has two pairs of connecting bodies along the long side, the distance between one pair of connecting bodies is shorter than the distance between the other pair of connecting bodies by the thickness of one steel bar 24, and the telescopic rod 28 connecting body is located at the four corners of the connecting steel plate 22.

[0045] Preferably, the steel strips 24 with different pre-made holes are of four types: one with large hexagonal holes on both sides, one with small hexagonal holes on both sides, one with a round hole on one side and a large hexagonal hole on the other side, and one with a round hole on one side and a small hexagonal hole on the other side.

[0046] Preferably, in the hydraulic device 25, a vertical sealing steel plate is welded to the bottom of the hexagonal cylinder 251 and sealed to the top of the cylinder 251. The sealed rotating piston 252 is cylindrical in the middle and connected to hexagonal cylinders on both sides. The vertical sealing steel plate is connected to the cylinder. There are multiple damping holes 253 on the sealing steel plate. The hydraulic oil 254 is located in chambers A and B. When stationary, the sealing steel plate on the rotating piston 252 is at a 180-degree angle to the vertical sealing steel plate in the hexagonal cylinder 251.

[0047] Preferably, the pressure relief device B3 includes a cylindrical cylinder 31, a sealed sliding connecting rod piston 32, a high-strength spring 33, an emulsion 34, a safety valve 35, and a steel wire pressure sensor 36. The high-strength spring 33 is located between the cylindrical cylinder 31 and the steel wire pressure sensor 36, and in its natural state, the bottom plate of the sealed sliding connecting rod piston 32 is located at half of the cylindrical cylinder 31, and the emulsion 34 occupies one-third of the cylindrical cylinder 31.

[0048] Preferably, the top plate of the pressure-relief device B3 is spaced apart from the steel arch frame in the rigid support structure by a pressure-relief distance.

[0049]

[0050] The pressure relief distance can be obtained as follows:

[0051]

[0052] In the formula, a is the radius of a portion of the outer ring support structure, b is the radius of a portion of the rigid support structure 4, c is the length of the pressure relief device B3 after it is fully contracted, m is the pressure relief distance between the top plate of the pressure relief device B3 and the steel arch frame in the rigid support structure 4, L is the distance between the outer ring support structure and the rigid support structure 4, h is the deformation length of each pressure relief device A2, d is the thickness of the earth pressure gauge, all in meters; n is the number of pressure relief devices A2, and k is the correction coefficient.

[0053] Preferably, the steel wire type pressure sensor 36 consists of a pressure plate, an electromagnetic excitation coil, a steel wire, a rear cover plate, and a bracket.

[0054] Preferably, the pressure-relief anchor 5 includes a top plate 51 with a nut, an anchor 52, a bottom plate 53, a cylindrical cylinder 31, a sealed sliding connecting rod piston 32, a high-strength spring 33, an emulsion 34, and a safety valve 35. The top plate 51 with the nut is tightened onto the anchor 52. The high-strength spring 33 is located between the top plate 51 and the bottom plate 53. The cylindrical cylinder 31 is welded onto the bottom plate 53. The emulsion 34 occupies half of the volume of chambers D, E, and F in the cylindrical cylinder 31, respectively.

[0055] The following is in conjunction with the appendix Figure 1-9 Detailed explanation of the usage process of this invention:

[0056] 1. First, drive multiple pressure-relief anchor bolts 5 evenly into the surrounding rock, and spray an energy-absorbing foam concrete layer 6 around the pressure-relief anchor bolts 5.

[0057] 2. Use the arch frame installation trolley to erect each section of U-shaped steel arch frame 1, and install the pressure relief device A2 between the welded steel plates 21 to form the outer ring support structure.

[0058] 3. Weld pressure relief device B3 uniformly onto the U-shaped steel arch frame 1 of the outer ring support structure to form a buffer layer.

[0059] 4. At a certain distance from the pressure relief device B3, use the arch frame installation trolley to erect each section of U-shaped steel arch frame 1 according to the pre-assembled pattern, so that the rectangular connecting plates at both ends of the U-shaped steel arch frame 1 are connected together, and the inner ring rigid support structure 4 is formed by bolt rigid connection.

[0060] The following is in conjunction with the appendix Figure 1-9 Detailed explanation of the working principle of this invention:

[0061] Achieving Level 1 Pressure Relief: During the construction of a high-stress soft rock tunnel with large deformation, the soft rock will undergo very large extrusion deformation, releasing the surrounding rock load and causing the surrounding rock to converge into the tunnel. The surrounding rock load is first transferred to the pressure relief anchor 5 and the foamed concrete layer 6. The high-strength spring 33 and the foamed concrete layer 6 are compressed first. As compression continues, the D-cylinder sealed sliding connecting rod piston 32 is first subjected to force. As the surrounding rock load increases, the bearing capacity reaches the limit and the safety valve 35 is opened, and the emulsion 34 flows out from the safety valve 35. Then, the E-cylinder and F-cylinder sealed sliding connecting rod pistons 32 are compressed. Finally, the top plate 51 presses on the top of the cylindrical cylinder, and the pressure relief of the pressure relief anchor 5 ends.

[0062] 2. Achieving secondary pressure relief: The surrounding rock load is then transferred to the U-shaped steel arch frame 1 of the outer support structure. The spring 28 in the pressure relief device A2 is stressed first. As the deformation increases, the spring 28 is compressed, the telescopic rod 27 retracts, and the steel bars 24 rotate relative to each other, causing the hexagonal cylinder 251 and the sealed rotating piston 252 to rotate relative to each other. Due to the pressure, depending on the relative rotation direction of the hexagonal cylinder 251 and the rotating piston 252, the hydraulic oil 254 can enter the B chamber from the A chamber through the damping hole 253, or it can enter the A chamber from the B chamber, thus achieving the pressure relief contraction of the pressure relief device A2. At this time, the pressure relief device A2 is not fully contracted.

[0063] 3. Achieving three-stage pressure relief: As deformation increases, when the steel wire pressure sensor 36 at the top of the pressure relief device B3 connects with the bottom of the inner U-shaped steel arch 1, the pressure relief device B3 and the pressure relief device A2 are jointly compressed. The high-strength spring 33 is compressed first, and compression stops when chamber C is filled with emulsion 34. When the surrounding rock pressure reaches a certain value, the safety valve 35 is opened, and the emulsion 34 flows out from the safety valve 35. The spring 33 continues to compress. When the bottom of the sealed sliding connecting rod piston 32 connects with the bottom of the cylindrical cylinder 31, the spring 33 stops compressing, achieving the effect that the resistance to deformation increases with the increase of the support structure deformation. The pressure relief ends when the pressure relief device B3 and the pressure relief device A2 are fully contracted.

[0064] 4. The remaining surrounding rock pressure is borne by the rigid support structure 4. This ensures that the support structure and the surrounding rock deform in a high-stress soft rock tunnel with large deformation, releasing the surrounding rock load, while also maintaining the integrity of the tunnel support structure and cross-section, thus preventing loosening and damage to the tunnel surrounding rock.

[0065] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A multi-stage pressure relief support structure for underground engineering, characterized in that, The outer ring support structure includes a U-shaped steel arch frame (1), a pressure-relief device A (2), a pressure-relief device B (3), a rigid support structure (4), a pressure-relief anchor rod (5), and a foamed concrete layer (6). The outer ring support structure is formed by connecting multiple sections of U-shaped steel arch frames (1) with pressure-relief devices A (2). The pressure-relief anchor rod (5) is fixed in the surrounding rock, and the bottom plate of the pressure-relief anchor rod (5) is in contact with the outer surface of the surrounding rock. A foamed concrete layer (6) is sprayed around the pressure-relief anchor rod (5). The U-shaped steel arch frame in the outer ring support structure (1) 1) It is connected to the foamed concrete layer (6). The bottom of the pressure relief device B (3) is welded to the inner side of the U-shaped steel arch frame (1) in the outer ring support structure. The rigid support structure (4) is in the inner ring, located inside the pressure relief device B (3) and there is a gap between it and the pressure relief device B (3). The rigid support structure (4) is composed of multiple U-shaped steel arch frames (1) connected together. The ends of the outer ring U-shaped steel arch frames (1) are welded with connecting plates. The adjacent U-shaped steel arch frames (1) are fixed by bolt connection.

2. The multi-stage pressure relief support structure for underground engineering according to claim 1, characterized in that, The pressure relief device A (2) includes a welded steel plate (21), a connecting steel plate (22) with a connector, bolts and nuts A (23), steel bars (24) with different pre-made holes, a hydraulic device (25), short bolts and nuts B (26), a telescopic rod (27) with a connector, and a spring (28). The hydraulic device (25) includes a hexagonal cylinder (251), a sealed rotating piston (252), a damping hole (253), and hydraulic oil (254). Welded steel plates (21) are welded to opposite sides of a pair of U-shaped steel arches (1). (21) is connected to the connecting steel plate (22) by bolt and nut A (23). The steel bar (24) is connected to the connecting body by short bolt and nut B (26) on one side and connected to other steel bars on the other side. The hexagonal cylinder (251) in the hydraulic device (25) is connected to the inner hexagonal hole. The sealed rotating piston (252) is connected to the outer hexagonal hole. Adjacent steel bars (24) can rotate relative to each other. The spring (28) is located between the washers of the telescopic rod (27). The telescopic rod (27) is connected to the connecting steel plate (22) by short bolt and nut B (26).

3. A multi-stage pressure relief support structure for underground engineering according to claim 2, characterized in that, The connecting steel plate (22) with connecting body, the steel bar (24) connecting body has two pairs of connecting bodies along the long side, the distance between one pair of connecting bodies is shorter than the distance between the other pair of connecting bodies by the thickness of one steel bar (24), and the telescopic rod (27) connecting body is located at the four corners of the connecting steel plate (22).

4. A multi-stage pressure relief support structure for underground engineering according to claim 2, characterized in that, The steel strips (24) with different pre-made holes are of four types: one with large hexagonal holes on both sides, one with small hexagonal holes on both sides, one with a round hole on one side and a large hexagonal hole on the other side, and one with a round hole on one side and a small hexagonal hole on the other side.

5. A multi-stage pressure relief support structure for underground engineering according to claim 2, characterized in that, The hydraulic device (25) has a vertical sealing steel plate in the hexagonal cylinder (251) with its bottom welded to the cylinder (251) and its top sealed to the sealed rotating piston (252). The sealed rotating piston (252) has a cylinder in the middle and hexagonal cylinders on both sides. The cylinder is connected to a vertical sealing steel plate. There are multiple damping holes (253) on the sealing steel plate. The hydraulic oil (254) is located in chambers A and B. When stationary, the sealing steel plate on the rotating piston (252) is at a 180-degree angle to the vertical sealing steel plate in the hexagonal cylinder (251).

6. A multi-stage pressure relief support structure for underground engineering according to claim 1, characterized in that, The pressure relief device B (3) includes a cylindrical cylinder (31), a sealed sliding connecting rod piston (32), a high-strength spring (33), an emulsion (34), a safety valve (35), and a steel wire pressure sensor (36). The high-strength spring (33) is located between the cylindrical cylinder (31) and the steel wire pressure sensor (36), and in its natural state, the bottom plate of the sealed sliding connecting rod piston (32) is located at half of the cylindrical cylinder (31), and the emulsion (34) occupies one-third of the cylindrical cylinder (31).

7. A multi-stage pressure relief support structure for underground engineering according to claim 6, characterized in that, The top plate of the pressure relief device B(3) is spaced apart from the steel arch frame in the rigid support structure by a pressure relief distance, which is... The pressure relief distance can be obtained as follows: In the formula, a is the radius of a portion of the outer ring support structure, b is the radius of a portion of the rigid support structure (4), c is the length of the pressure relief device B (3) after it is fully contracted, m is the pressure relief distance between the top plate of the pressure relief device B (3) and the steel arch frame in the rigid support structure (4), L is the distance between the outer ring support structure and the rigid support structure (4), h is the deformation length of each pressure relief device A (2), d is the thickness of the earth pressure gauge, all in m; n is the number of pressure relief devices A (2), and k is the correction coefficient.

8. A multi-stage pressure relief support structure for underground engineering according to claim 6, characterized in that, The steel wire pressure sensor (36) consists of a pressure plate, an electromagnetic excitation coil, a steel wire, a rear cover plate, and a bracket.

9. A multi-stage pressure relief support structure for underground engineering according to claim 1, characterized in that, The pressure-relief anchor rod (5) includes a top plate (51) with a nut, an anchor rod (52), a bottom plate (53), a cylindrical cylinder (31), a sealed sliding connecting rod piston (32), a high-strength spring (33), an emulsion (34), and a safety valve (35). The top plate (51) with the nut is tightened onto the anchor rod (52). The high-strength spring (33) is located between the top plate (51) and the bottom plate (53). The cylindrical cylinder (31) is welded onto the bottom plate (53). The emulsion (34) occupies half of the volume of chambers D, E, and F in the cylindrical cylinder (31).

10. A multi-stage pressure relief support method for underground engineering, implemented using the multi-stage pressure relief support structure described in any one of claims 1-9, characterized in that, Specifically, the steps include the following: Step 1: Achieve first-level pressure relief; First, drive multiple pressure relief anchors (5) evenly into the surrounding rock, and spray an energy-absorbing foam concrete layer (6) around the pressure relief anchors (5); The surrounding rock load is first transferred to the pressure relief anchors (5) and the foam concrete layer (6). The high-strength spring (33) and the foam concrete layer (6) are compressed first. When compression continues, the D-cylinder sealed sliding connecting rod piston (32) is compressed first. As the surrounding rock load increases, the bearing capacity reaches the limit safety valve (35) and is opened. The emulsion (34) flows out from the safety valve (35). Then the E-cylinder and F-cylinder sealed sliding connecting rod pistons (32) are compressed. Finally, the top plate (51) presses on the top of the cylindrical cylinder, and the pressure relief of the pressure relief anchors (5) ends. Step 2: Achieve secondary pressure relief; Use the arch frame installation trolley to erect each section of U-shaped steel arch frame (1), and install pressure relief device A (2) between the welded steel plates (21) to form an outer ring support structure; The surrounding rock load is transferred to the outer ring support structure U-shaped steel arch frame (1), the spring (28) in the pressure relief device A (2) is stressed first, as the deformation increases, the spring (28) is compressed, the telescopic rod (27) contracts, and the steel bars (24) rotate relative to each other, driving the hexagonal cylinder (251) and the sealed rotating piston (252) to rotate relative to each other. Due to the pressure, according to the relative rotation direction of the hexagonal cylinder (251) and the rotating piston (252), the hydraulic oil (254) can enter the B chamber from the A chamber through the damping hole, or enter the A chamber from the B chamber, to achieve the pressure relief contraction of the pressure relief device A (2). At this time, the pressure relief device A (2) is not fully contracted. Step 3: Achieve three-level pressure relief; uniformly weld pressure relief device B (3) to the U-shaped steel arch frame (1) of the outer ring support structure to form a buffer layer; as deformation increases, when the steel wire pressure sensor (36) at the top of the pressure relief device B (3) is connected to the bottom of the inner U-shaped steel arch frame (1), the pressure relief device B (3) and the pressure relief device A (2) are subjected to force and contraction together. The high-strength spring (33) in the pressure relief device B (3) is compressed first, and stops when the C chamber is filled with emulsion (34). When the surrounding rock pressure reaches a certain value, the safety valve (35) will be opened, and the emulsion (34) will flow out from the safety valve (35). The spring (33) will continue to compress. When the bottom of the sealed sliding connecting rod piston (32) is connected to the bottom of the cylindrical cylinder (31), the spring (33) will no longer compress, thus achieving the effect that the resistance to deformation increases as the support structure deforms. The pressure relief ends when the pressure relief device B (3) and the pressure relief device A (2) are fully contracted. Step 4: The remaining surrounding rock pressure is borne by the rigid support structure (4).

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