A multi-directional yielding expansion head anchor rod and a yielding control method thereof

Abstract

This invention discloses a multi-directional pressure-yielding enlarged-head anchor bolt and its pressure-yielding control method. The multi-directional pressure-yielding enlarged-head anchor bolt includes an anchor bolt member. A sleeve is fitted on the outer wall of one end of the anchor bolt member, and a first shape memory alloy is disposed inside the sleeve. An enlarged anchor head is disposed on the outer wall of the other end of the anchor bolt member. The enlarged anchor head includes a support plate and a pressure-yielding device. The support plate is disposed outside the anchor bolt member through the pressure-yielding device, and a second shape memory alloy is disposed inside the pressure-yielding device. A pressure monitoring device is disposed on the outer surface of the support plate, and the pressure monitoring device is signal-connected to the first shape memory alloy and the second shape memory alloy. This invention achieves controllable pressure yielding in both axial and circumferential directions, while significantly improving the pull-out bearing capacity and anchoring reliability of the anchor bolt by combining the enlarged-head structure. It can adapt to complex surrounding rock conditions such as high ground stress and non-uniform deformation, effectively releases multi-directional surrounding rock pressure, and significantly improves the support effect.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering support structures, and particularly relates to an enlarged head anchor bolt and its pressure relief control method. Background Technology

[0002] As a common technique in underground engineering support, yielding anchor technology can effectively control surrounding rock deformation and release some of the pressure caused by deformation by adjusting the yielding structure, thus restoring the surrounding rock to dynamic equilibrium. Currently, the construction process of yielding anchors often uses friction damping structures to achieve yielding, but this method has its shortcomings. High temperatures are easily generated during friction yielding, leading to metal fatigue. Furthermore, most yielding anchors have a limited yielding function, only providing yielding in one direction, resulting in limited bearing capacity. Faced with complex surrounding rock conditions such as high ground stress, non-uniform deformation, and unstable soil and rock structures, common yielding anchor technologies are insufficient to alleviate the pressure from deformation in multiple directions, leading to anchor failure and the risk of rock collapse. Therefore, there is an urgent need to develop a multi-directional yielding anchor structure capable of releasing surrounding rock stress in multiple directions and adapting to complex non-uniform deformation, to address the many shortcomings of existing yielding anchor technologies. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a multi-directional pressure relief enlarged head anchor bolt with stronger pull-out bearing capacity and more comprehensive pressure relief function, as well as its pressure relief control method. This can solve the problem that the existing pressure relief anchor bolts are difficult to adapt to complex and ever-changing surrounding rock pressure, resulting in pressure relief failure.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0005] A multi-directional pressure-yielding enlarged head anchor bolt includes an anchor bolt member. A sleeve is fitted onto the outer wall of one end of the anchor bolt member. A first shape memory alloy is disposed within the sleeve to drive the anchor bolt member to move relative to the sleeve to achieve pressure yielding. An enlarged anchor head is disposed on the outer wall of the other end of the anchor bolt member. The enlarged anchor head includes a support plate and a pressure-yielding device. The support plate is disposed outside the anchor bolt member via the pressure-yielding device. A second shape memory alloy is disposed within the pressure-yielding device to drive the support plate to move to achieve pressure yielding. Multiple support plates are evenly arranged around the anchor bolt member. A pressure monitoring device is disposed on the outer surface of the support plate. The pressure monitoring device is signal-connected to the first shape memory alloy and the second shape memory alloy.

[0006] In this invention, two independent temperature-controlled pressure-relief systems are constructed using a first shape memory alloy and a second shape memory alloy, respectively, in the axial and circumferential directions. This replaces the traditional friction damping method, fundamentally avoiding the risks of high-temperature fatigue and fracture. Simultaneously, the circumferential pressure-relief function is integrated into an expandable anchor head. When the expandable anchor head opens, the support plate tightly engages with the surrounding rock and soil, significantly improving the pull-out bearing capacity of the anchor rod. The pressure monitoring device can sense the axial tensile force and circumferential shear stress of the surrounding rock in real time and precisely initiate pressure-relief actions in the corresponding directions as needed, achieving bidirectional intelligent pressure relief. This design combines the geometric anchoring advantages of the expandable head with the deformation release advantages of bidirectional controllable pressure relief, enabling the anchor rod to both anchor firmly and expand, resulting in significant improvements in anchoring reliability and support accuracy, with effects significantly superior to traditional pressure-relief anchor rods.

[0007] In the aforementioned multi-directional pressure-relief enlarged-head anchor bolt, preferably, the enlarged anchor head further includes a support frame and a push plate. The push plate is sleeved outside the anchor bolt member and located between the sleeve and the pressure-relief device. One end of the support frame is hinged to the push plate, and the other end is hinged to the pressure-relief device (located on the pressure-relief sleeve of the pressure-relief device). By moving the push plate axially along the anchor bolt member, and through the linkage of the support frame, the pressure-relief device is driven to swing, thereby converting the linear motion of the push plate into the radial opening motion of the support plate. This mechanism has a simple design, clear force transmission, and can ensure that multiple support plates open synchronously and smoothly, achieving reliable enlargement of the anchor head.

[0008] In the aforementioned multi-directional pressure-relief enlarged-head anchor bolt, preferably, a spring is also provided between the sleeve and the pusher plate. The spring is sleeved outside the anchor bolt component, and the spring is in a compressed state before the enlarged-head anchor bolt is driven into the soil. When the anchor bolt is pushed into a larger diameter section at the bottom of the hole, the pre-compressed spring releases its elastic potential energy, actively pushing the pusher plate forward, providing initial driving force for the opening of the enlarged anchor head, ensuring that the anchor head can automatically and quickly open and anchor even in the absence of large-diameter hole constraints. This spring-driven release mechanism is responsive and reliable, requiring no additional external operation.

[0009] In the aforementioned multi-directional pressure-relief enlarged head anchor bolt, preferably, the anchor bolt member is further provided with a stop block. The anchor bolt member has a telescopic groove at the stop block, and the stop block is telescopically positioned within the telescopic groove. One side of the stop block is an arc surface that facilitates the sliding of the push plate, and the other side is a vertical surface that prevents the push plate from sliding back. When the push plate slides towards the arc surface of the stop block, the stop block retracts into the telescopic groove, allowing the push plate to slide past. After the push plate has passed the stop block, the stop block extends out of the telescopic groove and locks the push plate through the vertical surface, preventing the push plate from sliding back. This stop block structure forms a one-way self-locking mechanism. After the push plate moves forward and opens the anchor head under the action of spring force or gravity, it is locked by the vertical surface of the stop block and cannot retract. This structure ensures that once the enlarged anchor head is opened, it is permanently locked in the working state, effectively preventing accidental retraction of the anchor head due to external disturbances and ensuring the long-term reliability of the anchoring.

[0010] In the aforementioned multi-directional pressure-relief enlarged head anchor bolt, preferably, the anchor bolt member is further provided with a stop plate for limiting the position of the pressure-relief device. One end of the pressure-relief device near the anchor bolt member is hinged to the stop plate at the junction of the anchor bolt member and the stop plate. The stop plate provides a precise endpoint for the swing of the pressure-relief device. When the push plate pushes the pressure-relief device to swing and abut against the stop plate, the pressure-relief device is exactly at a 90° perpendicular angle to the anchor bolt member, and the support plate reaches its maximum extended position. This design ensures that the enlarged anchor head can be extended to the preset optimal force angle and size each time, guaranteeing a stable output of anchoring force.

[0011] In the aforementioned multi-directional pressure-relief enlarged-head anchor bolt, preferably, each support plate has pressure monitoring devices at both ends of its outer surface, and each support plate has two sets of pressure-relief devices, respectively located at both ends of the support plate. The ends of each pressure-relief device are hinged to the support plate and the anchor bolt component, respectively. This "two-point support" method ensures that the support plate maintains stable posture and uniform force distribution even under non-uniform surrounding rock pressure, avoiding the risk of tilting or jamming that can occur with single-point support. The multi-point pressure monitoring devices can more comprehensively and accurately collect pressure signals from different parts of the support plate, providing richer data for pressure relief control. Furthermore, the "two-point support" method allows the support plate to tilt, meaning the pressure-relief strokes of the two pressure-relief devices are inconsistent. By monitoring the stress at different locations using pressure monitoring devices, the pressure-relief strokes of the pressure-relief devices at different locations can be controlled to regulate the state of the support plate. This approach is applicable to more pressure-relief scenarios, such as when the upper and lower ends of the same support plate experience different forces. In this case, the pressure-relief devices can be used to tilt the support plate to meet the pressure-relief requirements of the different forces at the upper and lower ends. This configuration means that the pressure-relief mode of the present invention is not limited to axial and circumferential directions, and can be applied to a wider range of usage scenarios.

[0012] In the aforementioned multi-directional pressure-relief enlarged head anchor bolt, preferably, the pressure-relief device includes a pressure-relief sleeve and a pressure-bearing rod. The pressure-bearing rod is slidably disposed within the pressure-relief sleeve. The second shape memory alloy is disposed within the pressure-relief sleeve and connected to the pressure-bearing rod. The pressure-relief sleeve is disposed on the anchor bolt member, and the pressure-bearing rod is connected to the support plate. This structure cleverly integrates the pressure-relief function within the connector, resulting in a compact structure. When the second shape memory alloy contracts due to heat, it pulls the pressure-bearing rod back into the pressure-relief sleeve, thereby precisely and controllably causing the support plate to retract inward, achieving circumferential pressure relief.

[0013] In the aforementioned multi-directional pressure-relief enlarged head anchor bolt, preferably, the first shape memory alloy is disposed inside the sleeve and fitted outside the anchor bolt member. A pressure plate is provided inside the sleeve and fitted outside the anchor bolt member. One end face of the first shape memory alloy abuts against the pressure plate, and the other end face abuts against the inner end face of the sleeve. By rotating the pressure plate, the preload of the first shape memory alloy can be easily adjusted and axially limited. When the first shape memory alloy shrinks due to heat, the axial sliding of the anchor bolt member relieves pressure. The overall structure has advantages such as simple structure, direct and efficient force transmission path.

[0014] In the aforementioned multi-directional pressure-yielding enlarged-head anchor bolt, preferably, the enlarged-head anchor bolt further includes a controller. The controller is connected to the first shape memory alloy and the second shape memory alloy via a temperature-controlled wire, and the pressure monitoring device is signal-connected to the controller. This design constructs a complete "monitoring-judgment-execution" closed-loop control system. The pressure monitoring device acts as the sensing layer, collecting surrounding rock stress data in real time; the controller acts as the decision-making layer, determining when and in which direction to initiate pressure yielding and issuing commands; the regulating device and temperature-controlled wire act as the execution layer, precisely heating and controlling the deformation of the shape memory alloy. The entire pressure yielding process achieves intelligent, automated, and precise control.

[0015] As a general technical concept, the present invention also provides a pressure relief control method for the above-mentioned multi-directional pressure relief enlarged head anchor rod, comprising the following steps: after the enlarged head anchor rod is driven into the soil, the enlarged anchor head is in an expanded state, and the first shape memory alloy and the second shape memory alloy are both in an expanded state. When the pressure monitoring device detects that the soil pressure exceeds a set threshold, the first shape memory alloy and / or the second shape memory alloy are contracted by adjusting the temperature, so as to sink the anchor rod and / or close the support plate to relieve stress by pressure relief, until the soil pressure detected by the pressure monitoring device is lower than the set threshold.

[0016] The aforementioned pressure relief control method has a clear logic. Based on the magnitude and direction of the surrounding rock stress, it intelligently selects to initiate axial pressure relief, circumferential pressure relief, or simultaneous bidirectional pressure relief. Throughout the pressure relief process, dynamic adjustment is achieved through real-time stress signals fed back by a pressure monitoring device until the surrounding rock stress returns to a safe equilibrium state. When the shape memory alloy fully contracts to its limit state, all pressure relief strokes are exhausted, and the anchor bolt automatically transforms into rigid support, providing the final ultimate bearing capacity and ensuring the safety of long-term support.

[0017] In specific implementation, the axial tensile force monitoring range of the pressure monitoring device can be set between 2MPa and 2.5MPa. When the axial tensile force is detected to be greater than 2MPa, axial pressure relief is initiated. The circumferential shear stress monitoring range can be set between 1.5MPa and 2MPa. When the circumferential shear stress is detected to be greater than 1.5MPa, circumferential pressure relief is initiated. The heating temperature of the first shape memory alloy and the second shape memory alloy is preferably controlled between 50° and 60°. Within this temperature range, the alloy can undergo a stable and controllable phase transformation, gradually shrinking from an expanded state (which can be disc-shaped) until it reaches a cylindrical shape or the shrinkage limit, at which point pressure relief stops and it becomes a rigid support.

[0018] The multi-directional pressure-yielding enlarged-head anchor bolt of this invention improves and innovates upon traditional pressure-yielding anchor bolts. By combining the pressure-yielding function with an adjustable enlarged-head structure, and employing a multi-directional pressure-yielding structure, the axial slip and circumferential contraction can be adjusted according to the surrounding rock stress, releasing the axial tensile force and circumferential shear stress of the surrounding rock, achieving a dual-degree-of-freedom pressure-yielding function in both the axial and circumferential directions. When the anchor bolt's pressure-yielding function reaches its limit, it can automatically switch to rigid support. Simultaneously, it uses a shape memory alloy with temperature-controlled phase change to achieve active pressure-yielding, replacing the traditional rod friction damping method, effectively avoiding the risk of high-temperature fatigue and fracture. This pressure-yielding anchor bolt with an enlarged-head structure significantly improves anchoring reliability and support accuracy, has a higher ultimate pull-out bearing capacity, and can better adapt to complex surrounding rock conditions such as high ground stress and non-uniform deformation. Its pressure-yielding efficiency and synergistic bearing effect with the surrounding rock are significantly better than traditional pressure-yielding anchor bolts.

[0019] Compared with the prior art, the advantages of the present invention are as follows: The multi-directional pressure relief enlarged head anchor bolt of the present invention can achieve bidirectional pressure relief, with strong adaptability. It integrates two independent shape memory alloy temperature control pressure relief systems in the axial and circumferential directions. It can release axial tensile force and circumferential shear stress individually or in combination according to the real-time stress of the surrounding rock, perfectly solving the problem of multi-directional pressure release under complex geological conditions, and making the pressure relief function more comprehensive.

[0020] The multi-directional pressure-yielding enlarged-head anchor bolt of this invention has strong anchoring force and good synergy. Combined with the enlarged-head structure, the support plate, after opening, forms a huge end-bearing capacity and frictional resistance with the soil and rock mass, greatly improving the anchor bolt's pull-out bearing capacity. Simultaneously, the pressure-yielding process allows for moderate deformation of the surrounding rock and release of pressure, ultimately creating a favorable situation where the surrounding rock and anchor bolt cooperate in bearing the load.

[0021] The multi-directional pressure-relief enlarged head anchor bolt and pressure-relief control method of this invention rely on temperature control drive, which is stable and reliable. It uses the temperature-controlled phase change of shape memory alloy as the driving force for pressure relief, replacing the traditional friction damping method. The process is smooth, impact-free, and does not generate high temperatures, fundamentally avoiding the risk of metal fatigue and fracture, and the system has extremely high stability and reliability.

[0022] The multi-directional pressure relief enlarged head anchor bolt and pressure relief control method of the present invention are equipped with a pressure monitoring device and a controller to form a closed-loop control system. It can sense the changes in surrounding rock stress in real time and automatically and accurately start and control the pressure relief process according to a preset threshold, so as to keep the surrounding rock pressure within a safe range and realize the intelligent and precise support. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the three-dimensional structure of the enlarged head anchor bolt of the multi-directional pressure relief according to the present invention.

[0025] Figure 2 This is a three-dimensional structural diagram of the multi-directional pressure-relief enlarged head anchor rod of the present invention before enlargement.

[0026] Figure 3 This is a schematic diagram of the structure of the multi-directional pressure-relief enlarged head anchor bolt of the present invention in the unpressure-relief state (a pressure-relief device in the figure shows an internal structural schematic diagram).

[0027] Figure 4 This is a schematic diagram of the structure of the multi-directional pressure-relief enlarged head anchor bolt of the present invention under the pressure-relief limit state (a pressure-relief device in the figure shows a schematic diagram of its internal structure).

[0028] Figure 5 for Figure 3 Enlarged detail of point A in the middle.

[0029] Figure 6 This is a schematic diagram of the structure of the multi-directional pressure-relief enlarged head anchor rod of the present invention when the support plate is tilted.

[0030] Figure 7 This is a schematic diagram of the structure of the pressure-relief device in the multi-directional pressure-relief enlarged head anchor bolt of the present invention in the unpressure-relief state.

[0031] Figure 8 This is a schematic diagram of the pressure-relief device in the multi-directional pressure-relief enlarged head anchor bolt of the present invention under the pressure-relief limit state.

[0032] Figure 9 This is a schematic diagram illustrating the application of the multi-directional pressure-relief enlarged head anchor bolt of the present invention.

[0033] Legend 1. Anchor bolt; 11. Pressure plate; 12. Stop block; 13. Stop plate; 14. Expansion groove; 2. Sleeve; 3. Pressure relief device; 31. Pressure relief sleeve; 32. Pressure bearing rod; 33. Second shape memory alloy; 4. Support frame; 5. Support plate; 6. Push plate; 7. Pressure monitoring device; 8. Spring; 9. First shape memory alloy; 10. Bolt; 100. Controller; 200. Temperature control wire. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] Example: like Figures 1-9As shown, the multi-directional pressure-relief enlarged head anchor bolt of this embodiment includes an anchor bolt member 1. A sleeve 2 is fitted on the outer wall of one end of the anchor bolt member 1. A first shape memory alloy 9 (which is disc-shaped when not under pressure and cylindrical when under pressure limit) is provided inside the sleeve 2 to drive the anchor bolt member 1 to move relative to the sleeve 2 to achieve pressure relief. An enlarged anchor head is provided on the outer wall of the other end of the anchor bolt member 1. The enlarged anchor head includes a support plate 5 and a pressure-relief device 3. The support plate 5 is disposed outside the anchor bolt member 1 through the pressure-relief device 3. A second shape memory alloy 33 (which is disc-shaped when not under pressure and cylindrical when under pressure limit) is provided inside the pressure-relief device 3 to drive the support plate 5 to move to achieve pressure relief. Multiple support plates 5 are evenly arranged around the anchor bolt member 1. A pressure monitoring device 7 is provided on the outer surface of the support plate 5. The pressure monitoring device 7 is signal-connected to the first shape memory alloy 9 and the second shape memory alloy 33.

[0039] In this embodiment, the enlarged anchor head also includes a support frame 4 and a push plate 6. The push plate 6 is sleeved outside the anchor rod 1 and is located between the sleeve 2 and the pressure relief device 3. One end of the support frame 4 is hinged to the push plate 6, and the other end is hinged to the pressure relief sleeve 31 of the pressure relief device 3, so that the support frame 4 is not affected when the pressure-bearing rod 32 moves.

[0040] In this embodiment, a spring 8 is also provided between the sleeve 2 and the pusher plate 6. The spring 8 is sleeved outside the anchor rod 1. Before the enlarged head anchor rod is driven into the soil, the spring 8 is in a contracted state. The spring 8 is used to drive the pusher plate 6 to move downward along the axial direction of the anchor rod 1. In addition, the pusher plate 6 can also be driven to slide forward by the weight of the support plate 5 to complete the self-locking.

[0041] In this embodiment, the anchor rod 1 is also provided with a stop block 12. The anchor rod 1 is provided with a telescopic groove 14 at the stop block 12. The stop block 12 can be telescopically disposed in the telescopic groove 14. One side of the stop block 12 is an arc surface that facilitates the sliding of the push plate 6, and the other side is a vertical surface that prevents the push plate 6 from sliding back. When the push plate 6 slides toward the arc surface of the stop block 12, the stop block 12 retracts into the telescopic groove 14, allowing the push plate 6 to slide past. After the push plate 6 slides past the stop block 12, the stop block 12 extends out of the telescopic groove 14 and locks the push plate 6 through the vertical surface, preventing the push plate 6 from sliding back.

[0042] In this embodiment, the anchor rod 1 is also provided with a stop plate 13 for limiting the position of the pressure relief device 3. The end of the pressure relief device 3 near the anchor rod 1 is hinged at the junction of the stop plate 13 and the anchor rod 1.

[0043] In this embodiment, each support plate 5 has a pressure monitoring device 7 at both ends of its outer surface, and each support plate 5 has two sets of pressure relief devices 3, which are respectively located at both ends of the support plate 5. The two ends of the pressure relief devices 3 are hinged to the support plate 5 and the anchor rod 1, respectively. Two sets of pressure relief devices 3 are used, and two push plates 6 are matched accordingly.

[0044] like Figure 7 , Figure 8 As shown, in this embodiment, the pressure relief device 3 includes a pressure relief sleeve 31 and a pressure bearing rod 32. The pressure bearing rod 32 is slidably disposed in the pressure relief sleeve 31. The second shape memory alloy 33 is disposed in the pressure relief sleeve 31 and connected to the pressure bearing rod 32. The pressure relief sleeve 31 is disposed on the anchor rod 1, and the pressure bearing rod 32 is connected to the support plate 5.

[0045] In this embodiment, the first shape memory alloy 9 is disposed inside the sleeve 2 and sleeved outside the anchor rod 1. The sleeve 2 is provided with a pressure plate 11, which is sleeved outside the anchor rod 1. One end face of the first shape memory alloy 9 abuts against the pressure plate 11, and the other end face abuts against the inner end face of the sleeve 2.

[0046] In this embodiment, the enlarged head anchor bolt also includes a controller 100. The controller 100 is connected to the first shape memory alloy 9 and the second shape memory alloy 33 via a temperature control wire 200, and the pressure monitoring device 7 is signal-connected to the controller 100.

[0047] The pressure control method of the multi-directional pressure relief enlarged head anchor rod described in this embodiment includes the following steps: After the enlarged head anchor rod is driven into the soil, the enlarged anchor head is in an expanded state, and the first shape memory alloy 9 and the second shape memory alloy 33 are both in an expanded state. When the pressure monitoring device 7 detects that the soil pressure exceeds the set threshold, the first shape memory alloy 9 and / or the second shape memory alloy 33 are contracted by adjusting the temperature, so that the anchor rod 1 sinks and / or the support plate 5 closes, so as to relieve the pressure and release the stress until the soil pressure detected by the pressure monitoring device 7 is lower than the set threshold.

[0048] Specifically, in use, several support plates 5 are connected and installed with pressure-relieving devices 3 via bolts 10. The other end of each pressure-relieving device 3 is installed on the anchor rod 1. The pressure-relieving device 3 is connected and hinged to the push plate 6 via the support frame 4, thus completing the installation of the enlarged anchor head. The anchor rod 1 is then inserted into the sleeve 2, which contains several shape memory alloy discs (i.e., the first shape memory alloy 9). A pressure plate 11 is screwed into the tail of the anchor rod 1 to abut against the end face of the shape memory alloy discs. At this point, the enlarged anchor head assembly is complete (e.g., ...). Figure 2 (As shown), then the assembled anchor rod is driven into the pre-expanded anchor hole. Anchoring can then be performed once the release device has fully expanded the support plate 5 (as shown). Figure 9(As shown). The pressure monitoring device 7 applies pressure to the anchor bolt by monitoring the deformation of the surrounding rock, so that the controller 100 controls the temperature of the shape memory alloy large disc and the shape memory alloy small disc (i.e., the second shape memory alloy 33) to implement axial and circumferential pressure relief functions. According to the stress generated in different directions of the surrounding rock, the controller controls the temperature of the shape memory alloy large disc and the shape memory alloy small disc to implement axial and circumferential pressure relief functions, and controls the anchor bolt to slide axially and contract circumferentially. As the surrounding rock continues to deform, until the shape memory alloy large disc and the shape memory alloy small disc are completely transformed from a disc shape into a cylinder shape, the anchor bolt reaches the maximum pressure relief limit and automatically transforms into a rigid support structure.

[0049] In this embodiment, the expansion and self-locking mechanism of the expanded anchor head is as follows: A spring 8 in a pre-compressed state is provided between the sleeve 2 and the push plate 6. The anchor rod 1 is provided with a telescopic groove 14, inside which is a stop block 12. One side of the stop block 12 is an arc surface, and the other side is a vertical surface. When the anchor rod has not entered the predetermined anchor hole, the spring 8 is in a contracted state, and the support plate 5 is fitted against the circumferential periphery of the anchor rod 1. Figure 2 As shown. When the anchor bolt is inserted as... Figure 9 After the rear half of the hole, which has a larger diameter, is shown, the support plate 5 loses the constraint of the hole wall, the spring 8 releases its elastic force, and combined with the gravity of the enlarged anchor head, pushes the push plate 6 forward. When the push plate 6 passes the stop block 12, it slides over its arc surface and presses the stop block 12 into the telescopic groove 14. After sliding over, the stop block 12 pops out, and its vertical surface locks the push plate 6, achieving one-way self-locking, and the push plate 6 cannot retract. At the same time as the push plate 6 moves forward, the support frame 4 pushes the pressure relief device 3 to swing until the bottom end of the pressure relief device 3 abuts against the pre-set stop plate 13. At this time, the pressure relief device 3 is perpendicular to the anchor rod 1 at 90°, and the support plate 5 is fully extended, as shown. Figure 1 As shown, the anchor head expands and locks. In addition to the drive of spring 8, in the absence of spring 8 or in the case of spring 8 failure, the gravity of support plate 5 can also serve as a release source, driving push plate 6 forward to complete self-locking.

[0050] After anchoring is completed, the pressure relief phase begins. Pressure monitoring device 7 monitors the axial tensile force and circumferential shear force transmitted from the surrounding rock in real time.

[0051] When the axial tensile force exceeds a set threshold (e.g., 2 MPa), the controller 100 determines that axial pressure relief is required. It heats the first shape memory alloy 9 via a temperature-controlled wire 200 (controlled between 50° and 60°), causing it to undergo a phase change and gradually contract, from its initial expanded state (e.g., ...). Figure 3 (As shown) thinner and shorter (as shown) Figure 4(As shown). One end face of the first shape memory alloy 9 abuts against the inner end face of the sleeve 2, and the other end face is fixed relative to the anchor rod 1 by the pressure plate 11. Therefore, its contraction provides space for the anchor rod 1 to slide towards the orifice. Under the huge axial tensile force of the surrounding rock, the anchor rod 1 slides downward (towards the orifice) relative to the sleeve 2, generating axial displacement, thereby actively releasing part of the axial tensile force of the surrounding rock. The pressing process continues until the axial tensile force monitored by the pressure monitoring device 7 drops below 2 MPa.

[0052] When the circumferential shear stress exceeds a set threshold (e.g., 1.5 MPa), the controller 100 determines that circumferential pressure relief is required. It heats the second shape memory alloy 33 located within the pressure relief sleeve 31 via a temperature control wire 200, causing it to shrink (e.g., ...). Figure 4 , Figure 8 (As shown). One end of the second shape memory alloy 33 is fixed relative to the pressure relief sleeve 31, and the other end is connected to the pressure-bearing rod 32. Its contraction will pull the pressure-bearing rod 32 back into the pressure relief sleeve 31. Since the pressure relief sleeve 31 is fixed to the anchor rod 1, and the pressure-bearing rod 32 is hinged to the support plate 5, this action directly drives the support plate 5 to close in the axial direction of the anchor rod 1, reducing the effective diameter of the enlarged anchor head, thereby actively releasing the circumferential shear stress of the surrounding rock. The process continues until the circumferential stress drops below 1.5 MPa.

[0053] like Figure 6 As shown, when the pressure monitoring device 7 at the upper and lower ends of the support plate 5 detects that the upper and lower ends of the support plate 5 are subjected to different forces, the two pressure relief devices 3 of the support plate 5 can be controlled to contract different strokes so that the support plate 5 can tilt, thereby meeting the pressure relief requirements in more scenarios.

[0054] like Figure 3 , Figure 7 As shown, when no pressure is applied, both the first shape memory alloy 9 and the second shape memory alloy 33 are in an expanded state; as Figure 4 , Figure 8 As shown, both the anchor bolt and the support plate 5 continuously contract as the pressure is released. When both reach their contraction limits, that is, when they completely transform from an expanded state into a compact cylindrical shape, the axial sliding stroke of the anchor bolt 1 and the circumferential contraction stroke of the support plate 5 both reach their limits, and the pressure release function ends. At this time, the entire anchor bolt automatically transforms into a rigid support structure without the pressure release function, providing the final ultimate pull-out bearing capacity and ensuring the safety of the project.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-directional pressure-relief enlarged head anchor bolt, comprising an anchor bolt component (1), characterized in that, A sleeve (2) is fitted on the outer wall of one end of the anchor rod (1). A first shape memory alloy (9) is provided inside the sleeve (2) to drive the anchor rod (1) to move relative to the sleeve (2) to achieve pressure relief. An enlarged anchor head is provided on the outer wall of the other end of the anchor rod (1). The enlarged anchor head includes a support plate (5) and a pressure relief device (3). The support plate (5) is located outside the anchor rod (1) through the pressure relief device (3). A second shape memory alloy (33) is provided inside the pressure relief device (3) to drive the support plate (5) to move to achieve pressure relief. Multiple support plates (5) are evenly arranged around the anchor rod (1). A pressure monitoring device (7) is provided on the outer surface of the support plate (5). The pressure monitoring device (7) is connected to the first shape memory alloy (9) and the second shape memory alloy (33) via signal connection.

2. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, The enlarged anchor head also includes a support frame (4) and a push plate (6). The push plate (6) is sleeved on the outside of the anchor rod (1). The push plate (6) is located between the sleeve (2) and the pressure relief device (3). One end of the support frame (4) is hinged to the push plate (6), and the other end is hinged to the pressure relief device (3).

3. The multi-directional pressure-relief enlarged head anchor bolt according to claim 2, characterized in that, A spring (8) is also provided between the sleeve (2) and the push plate (6). The spring (8) is sleeved outside the anchor rod (1). Before the enlarged head anchor rod is driven into the soil, the spring (8) is in a contracted state.

4. The multi-directional pressure-relief enlarged head anchor bolt according to claim 2, characterized in that, The anchor rod (1) is also provided with a stop block (12). The anchor rod (1) is provided with a telescopic groove (14) at the stop block (12). The stop block (12) is telescopically disposed in the telescopic groove (14). One side of the stop block (12) is an arc surface that facilitates the sliding of the push plate (6), and the other side is a vertical surface that prevents the push plate (6) from sliding back. When the push plate (6) slides toward the arc surface of the stop block (12), the stop block (12) retracts into the telescopic groove (14) to allow the push plate (6) to slide past. After the push plate (6) slides past the stop block (12), the stop block (12) extends out of the telescopic groove (14) and clamps the push plate (6) through the vertical surface to prevent the push plate (6) from sliding back.

5. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, The anchor rod (1) is also provided with a stop plate (13) for limiting the position of the pressure relief device (3). The end of the pressure relief device (3) near the anchor rod (1) is hinged at the junction of the stop plate (13) and the anchor rod (1).

6. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, Each of the support plates (5) has a pressure monitoring device (7) at both ends of its outer surface. Each support plate (5) has two sets of pressure relief devices (3). The two sets of pressure relief devices (3) are respectively located at both ends of the support plate (5). The two ends of the pressure relief devices (3) are respectively hinged to the support plate (5) and the anchor rod (1).

7. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, The pressure relief device (3) includes a pressure relief sleeve (31) and a pressure-bearing rod (32). The pressure-bearing rod (32) is slidably disposed in the pressure relief sleeve (31). The second shape memory alloy (33) is disposed in the pressure relief sleeve (31) and connected to the pressure-bearing rod (32). The pressure relief sleeve (31) is disposed on the anchor rod (1). The pressure-bearing rod (32) is connected to the support plate (5).

8. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, The first shape memory alloy (9) is disposed inside the sleeve (2) and sleeved outside the anchor rod (1). The sleeve (2) is provided with a pressure plate (11), which is sleeved outside the anchor rod (1). One end face of the first shape memory alloy (9) abuts against the pressure plate (11), and the other end face abuts against the inner end face of the sleeve (2).

9. The multi-directional pressure-relief enlarged head anchor bolt according to claim 1, characterized in that, The enlarged head anchor also includes a controller (100), which is connected to the first shape memory alloy (9) and the second shape memory alloy (33) via a temperature control wire (200), and the pressure monitoring device (7) is signal connected to the controller (100).

10. A method for controlling the pressure relief of a multi-directional pressure-relief enlarged head anchor bolt as described in any one of claims 1-9, characterized in that, The process includes the following steps: After the enlarged head anchor rod is driven into the soil, the enlarged anchor head is in an expanded state, and the first shape memory alloy (9) and the second shape memory alloy (33) are both in an expanded state. When the pressure monitoring device (7) detects that the soil pressure exceeds the set threshold, the first shape memory alloy (9) and / or the second shape memory alloy (33) are contracted by adjusting the temperature, so that the anchor rod (1) sinks and / or the support plate (5) closes, so as to release the stress until the soil pressure detected by the pressure monitoring device (7) is lower than the set threshold.

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