Self-locking prestressed compensation anchor rod and construction method thereof

Abstract

The application discloses a self-locking prestress compensation anchor rod and a construction method, belongs to the technical field of rock and soil anchoring, and solves the problems that the existing compensation anchor rod cannot be self-locked and the compensation stroke and the bearing capacity are difficult to be considered simultaneously. The anchor rod comprises a rod body, an anchor head assembly, a prestress compensation mechanism and a self-locking mechanism. The compensation mechanism adopts a composite disc spring group which is composed of multiple disc springs in a mixed manner of superposition and matching, is sleeved on a guide shaft, and has high bearing capacity and large stroke. The self-locking mechanism is a ratchet-pawl type or a wedge-shaped clamping piece type, and is automatically locked after compensation. The rod body is provided with a hollow grouting channel, and forms a mechanical-chemical composite anchoring system. During construction, grouting is firstly performed and then solidification is waited, and then tensioning is performed to the initial pre-compression state for locking. When the surrounding rock creeps, the disc spring group automatically rebounds to compensate for the loss of prestress, and when the surrounding rock expands or is impacted, the disc spring group is further compressed to absorb energy. The application has the advantages of compact structure, strong self-adaptability, and can effectively solve the problem of long-term maintenance of prestress in deep high-stress and large-deformation strata.

Description

Technical Field

[0001] This invention relates to the field of geotechnical anchoring engineering technology, and in particular to a self-locking prestressed compensating anchor and its construction method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In deep engineering and tunnel rock support, prestressed anchors, as core support components, rely on their long-term effective prestress to ensure the stability of the engineering structure. However, existing prestressed anchors generally face the problem of prestress loss during their service life. The main reasons for this include: soil and rock creep, anchor material relaxation, anchor slippage, and temperature changes. The continuous attenuation of prestress leads to a decline in support effectiveness and may even cause engineering disasters.

[0004] To address the aforementioned issues, over-tensioning or repeated tensioning is often used in engineering for compensation, but this is complex to operate and cannot achieve real-time, long-term automatic compensation. In recent years, springs fitted onto anchor bolts have been widely used for prestress compensation, and techniques utilizing disc springs for prestress compensation have also emerged. However, these techniques have the following specific problems: Although springs or disc springs are used to compensate for prestress, that is, the elasticity of springs or disc springs is used to compensate for prestress, the anchor bolts are not self-locking. In other words, they are not locked in time after prestress compensation. If they cannot be locked, the surrounding rock will continue to creep, resulting in insufficient long-term maintenance of the anchor bolts' bearing capacity. Furthermore, existing technologies often employ simple stacking (parallel) or pairing (series) combinations, which have significant limitations: simple stacking can provide high load-bearing capacity, but the compensation stroke (deformation) is extremely small; simple pairing can provide a larger stroke, but the load-bearing capacity is limited by the single disc spring. This makes it difficult for existing disc spring compensation devices to simultaneously meet the dual requirements of high load-bearing capacity and large relief / compensation stroke in deep high-stress environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a self-locking prestressed compensation anchor system that is compact, highly adaptable, possesses both high bearing capacity and long-stroke compensation capability, and can reliably self-lock, thereby solving the core problem of insufficient long-term prestress maintenance capability of existing technologies under complex geological conditions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A self-locking prestressed compensating anchor bolt, comprising: Anchor bolt body: consists of a free section and an anchoring section connected in sequence; Anchor head assembly: Located at the exposed end of the free section, used for tensioning and locking prestress; Prestress compensation mechanism: includes a protective sleeve and a guide shaft. The protective sleeve is circumferentially fitted around the exposed end of the free section. The protective sleeve is connected to the anchor head assembly. An elastic component is installed inside the protective sleeve. The elastic component is coaxially fitted on the guide shaft. One end of the elastic component is in contact with the anchor head assembly. The elastic component applies force along the axial direction of the anchor rod body. The elastic component is composed of multiple disc springs in a stacked and mating combination manner. Self-locking mechanism: Installed on the anchor head assembly, the self-locking mechanism can lock the free section. Under the action of external force, the self-locking mechanism can slide in the tensioning direction and automatically lock in the opposite direction to adjust and lock the position of the free section. After the anchor rod body is tensioned and locked, the elastic component is in an initial pre-compression state. When the prestress of the anchor rod body decreases due to the creep of the surrounding rock, the elastic component automatically rebounds to compensate for the lost prestress. When the prestress of the anchor rod increases suddenly due to the expansion of the surrounding rock or the impact load, the elastic component is further compressed to absorb energy and the free section of the anchor rod is relocked by the self-locking mechanism, realizing bidirectional adjustment of peak shaving and valley filling.

[0007] As described above, a self-locking prestressed compensating anchor bolt includes an anchor head assembly comprising an anchor, and a ratchet-pawl type self-locking mechanism. The free section is provided with multiple continuous toothed grooves in a circumferential direction. The ratchet-pawl type self-locking mechanism includes a ratchet and a pawl that cooperates with the ratchet. The pawl is positioned on the side of the ratchet away from the surrounding rock. The ratchet is rotatably fixed inside the anchor. A portion of the ratchet extends from the inner surface of the anchor to engage with the toothed groove of the free section. One end of the pawl is connected to the inner surface of the anchor via a connecting rod, and the other end of the pawl is connected to the anchor via a spring. Under normal conditions, the spring pulls the pawl to keep it in the ready-to-engage position.

[0008] As described above, in a self-locking prestressed compensating anchor bolt, the pawl is placed between the elastic component and the ratchet, and the pawl is spaced apart from the elastic component so that when the elastic component rebounds, it first pushes the anchor bolt to move and then triggers the pawl to engage with the ratchet and lock it in place.

[0009] As described above, in a self-locking prestressed compensation anchor bolt, the elastic component is a composite butterfly spring assembly, in which 2 to 3 disc springs are stacked in the same direction to form a stacked unit, and two or more stacked units are connected in series in opposite directions to form a composite butterfly spring assembly. The total compensation stroke of the elastic component is 5mm to 100mm, and the maximum compensation force is 30% to 50% of the design prestress value.

[0010] As described above, in a self-locking prestressed compensating anchor bolt, the disc spring is made of 60Si2Mn or 50CrVA, and is subjected to carburizing and quenching heat treatment, with a Dacromet coating or phosphate anti-corrosion layer on its surface; the outer diameter of the disc spring is less than or equal to 250 mm, and the thickness is 0.2 mm to 14 mm.

[0011] As described above, in a self-locking prestressed compensating anchor bolt, the protective sleeve is a polyethylene corrugated pipe or a stainless steel corrugated pipe, with both ends sealed to the anchor bolt body and the anchor head assembly, respectively. The protective sleeve is filled with an anti-corrosion medium, which is an anti-corrosion grease.

[0012] As described above, a self-locking prestressed compensating anchor bolt is provided with a high-strength prestressed steel strand as the anchor bolt body, and a hollow grouting channel extending axially is provided inside the anchor bolt body. The anchoring section of the anchor rod is provided with at least two grout outlet holes evenly distributed along the circumference, and the grout outlet holes are connected to the hollow grouting channel.

[0013] In the self-locking prestressed compensating anchor bolt described above, the surface hardness of the guide shaft is higher than the hardness of the disc spring material.

[0014] As described above, a self-locking prestressed compensating anchor bolt has a self-locking mechanism that is a wedge-shaped clamp-type self-locker, including a clamp and a tapered anchor hole that cooperates with the clamp. The inner surface of the clamp is provided with serrations or threads to cooperate with the anchor bolt body. When the elastic component rebounds, it pushes the clamp to move inward toward the tapered anchor hole, so that the clamp and the anchor bolt body are automatically wedge-locked. This solution has a more compact structure and is suitable for installation scenarios with limited space.

[0015] As described above, in a self-locking prestressed compensating anchor bolt, the anchor head assembly further includes a bearing plate and a platform. The platform is placed circumferentially at the exposed end of the free section, and the bearing plate is placed at the end of the platform away from the surrounding rock. The anchor is in contact with the bearing plate, and the anchor is a wedge-type anchor or a nut-type anchor.

[0016] As a further technical solution, a grout stopper is also included. The grout stopper is set at the opening of the hollow grouting channel to seal the opening after grouting is completed, prevent grout backflow, and ensure grout compactness.

[0017] Secondly, the present invention also provides a construction method for a self-locking prestressed compensating anchor bolt, comprising the following: Based on the design prestress value and estimated surrounding rock deformation in the engineering design, determine the number of overlapping pieces and pairs of the elastic components, and assemble the elastic components and self-locking mechanism. Drill to the designed depth and clean the hole; The assembled anchor rod is inserted into the borehole to the design depth, so that the anchoring section is located at the design anchoring position; Epoxy resin modified cement-based grout is injected through the hollow grouting channel of the anchor rod body, so that the grout flows out from the grout outlet to fill the gap between the borehole and the anchor rod and the surrounding rock fissures. The grouting pressure is maintained at 2-3 MPa. Grouting is stopped when the grout returns from the hole and the concentration is consistent with the injected grout. The grouting channel opening is then sealed with a grout stop plug. After the grout has solidified, the anchor rod is tensioned to the designed prestress value, compressing the elastic components to the initial pre-compression state, and the self-locking mechanism automatically enters the locking state; the tensioning equipment is removed, the protective sleeve is installed and anti-corrosion medium is injected, and the anchor installation is completed.

[0018] The construction method of a self-locking prestressed compensation anchor bolt as described above also includes a supplementary tensioning step during the service life of the anchor bolt: when the prestress loss of the anchor bolt is detected to exceed the threshold, a supplementary tensioning force is applied through the anchor head assembly to recompress the elastic component to the set prestress state.

[0019] The beneficial effects of the present invention are as follows: (1) Adaptive compensation and reliable self-locking: The present invention sets a self-locking mechanism and a prestress compensation mechanism at the exposed end of the free section of the anchor rod. In a limited space, it can not only perform prestress compensation on the anchor rod, but also ensure the stable locking of the prestress after each compensation by setting a ratchet-pawl type or wedge-shaped clamp type self-locking mechanism, which is not affected by vibration and prevents prestress retraction; the guide shaft ensures the axial stability of the elastic component in high-load reciprocating motion and improves the overall reliability of the device.

[0020] (2) High load-bearing capacity and large stroke are achieved simultaneously: The elastic component adopts a composite combined disc spring group, which is composed of multiple disc springs in a stacked and paired manner. The composite combined disc spring group has a unique nonlinear elastic characteristic of "parallel load increase and series stroke increase". It can provide high compensation force (up to hundreds of kilonewtons) and sufficient stroke (5mm to 100mm) in a limited space. It automatically adapts to the deformation of surrounding rock creep, expansion and other deformations, and compensates for prestress loss in real time. It avoids manual periodic tensioning and significantly improves the long-term effectiveness of the support. It also breaks through the bottleneck of traditional disc spring application and can simultaneously meet the stringent requirements of high load-bearing capacity and large deformation in deep high ground stress environment. The composite combined disc spring group has high damping characteristics and can absorb the energy of sudden loads such as rock bursts and rockbursts, prevent brittle fracture of anchor bolts and realize the "pressure relief" function. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1This is a cross-sectional view of a self-locking prestressed compensating anchor bolt according to one or more embodiments of the present invention.

[0023] Figure 2 This is an enlarged view of a portion of the structure of a self-locking prestressed compensating anchor bolt according to one or more embodiments of the present invention. Figure 1 .

[0024] Figure 3 This is an enlarged view of a portion of the structure of a self-locking prestressed compensating anchor bolt according to one or more embodiments of the present invention. Figure 2 .

[0025] Figure 4 This is a flowchart of a construction method for a self-locking prestressed compensating anchor bolt according to one or more embodiments of the present invention.

[0026] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0027] The components are: 1. Anchor rod body; 11. Free section; 12. Anchoring section; 13. Tooth groove; 2. Elastic component; 3. Protective sleeve; 4. Self-locking mechanism; 41. Pin; 42. Spring; 43. Ratchet; 44. Pawl; 5. Hollow grouting channel; 6. Grout outlet hole; 7. Bearing plate; 8. Platform; 9. Anchor; 10. Guide shaft; 11. Grout stop plug. Detailed Implementation

[0028] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. As described in the background section, existing compensating anchor rods can achieve prestress compensation but cannot self-lock. To solve the above technical problem, this invention proposes a self-locking prestress compensation anchor rod.

[0030] Example 1 In a typical embodiment of the present invention, reference is made to Figure 1 , Figure 2 As shown, a self-locking prestressed compensating anchor bolt includes: Anchor rod body 1: includes a free section 11 and an anchoring section 12 connected in sequence; Anchor head assembly: Located at the exposed end of free section 11, used for tensioning and locking prestress; Prestress compensation mechanism: includes protective sleeve 3, which is sleeved around the exposed end of free section 11 in the circumferential direction. Protective sleeve 3 is connected to anchor head assembly. Elastic component 2 is installed inside protective sleeve 3. One end of elastic component 2 is in contact with anchor head assembly. Elastic component 2 applies force along the axial direction of anchor rod body 1. Elastic component 2 is composed of multiple disc springs in a stacked and paired manner. Self-locking mechanism: Installed on the anchor head assembly, the self-locking mechanism can lock the free section 11, and under the action of external force, the self-locking mechanism can adjust and lock the position of the free section 11; After the anchor rod body 1 is tensioned and locked, the elastic component 2 is in an initial pre-compression state, that is, the compression amount is 20% to 40% of the total compensation stroke. When the prestress of the anchor rod body 1 decreases due to the creep of the surrounding rock, the elastic component 2 automatically rebounds to compensate for the lost prestress. When the prestress of the anchor rod increases suddenly due to the expansion of the surrounding rock or the impact load, the elastic component 2 is further compressed to absorb energy, and the free section of the anchor rod is relocked by the self-locking mechanism to achieve bidirectional adjustment of peak shaving and valley filling.

[0031] In this embodiment, the anchor rod body 1 is made of φ25 mm high-strength prestressed steel strand with an ultimate bearing capacity of 400 kN. The anchor rod body 1 is formed by using a seamless steel pipe as the core tube and then twisting multiple high-strength steel wires on the outer layer. The anchor rod body 1 is provided with a hollow grouting channel 5 inside. The anchoring section 12 is provided with multiple rows of grout outlet holes 6 with a set diameter, such as Φ8 mm. Each row is provided with 4 grout outlet holes 6. The grout outlet holes 6 are connected to the hollow grouting channel 5. The grout outlet holes 6 in each row are spaced apart. The grout flows to the periphery of the anchoring section of the anchor rod body through the hollow grouting channel 5 and the grout outlet holes to perform anchoring.

[0032] In addition, the outer diameters of the free section 11 and the anchoring section 12 of the anchor rod body 1 are the same. The free section 11 of the anchor rod body is provided with multiple continuous toothed grooves 13 in a circumferential direction. The ratchet 44 in the self-locking mechanism can be engaged in the toothed grooves 13 of the free section 11. The width of the toothed grooves 13 is adapted to the width of the teeth in the ratchet 43. The length of the toothed groove section is less than or equal to the length of the free section 11.

[0033] It should be noted that the anchor rod body 1 uses a seamless steel pipe as its core tube, possessing sufficient radial stiffness. Because the anchor rod body 1 uses a seamless steel pipe as its core tube and is outer-layered with high-strength steel wire, the free section 11 has sufficient radial stiffness to withstand machining. The toothed groove 13 is formed as follows: multiple continuous annular grooves are machined on the outer surface of the free section 11 by turning or rolling. The groove depth is 15% to 25% of the outer steel wire diameter (approximately 0.5 mm to 1.5 mm), and the groove width matches the tooth width of the ratchet 43. The machining depth of the toothed groove 13 does not penetrate the outer steel wire, thus not weakening the tensile bearing capacity of the anchor rod body 1. In another optional embodiment, a pre-fabricated rigid sleeve (such as made of 40Cr material, with an inner diameter that is interference-fitted with the outer diameter of the free section) can also be fitted over the free section 11. The two ends of the sleeve are fixed to the free section 11 by welding, set screws, or keyways. Both of the above-mentioned tooth groove formation methods ensure reliable meshing between ratchet 43 and free section 11.

[0034] It should be noted that the elastic component 2 is a composite butterfly spring assembly. Every 2 to 3 disc springs are stacked in the same direction to form a stacked unit. Two or more stacked units are connected in series in opposite directions. The total load-bearing capacity is 2 to 3 times that of a single disc spring, and the total deformation is more than 2 times that of a single disc spring. Specifically, the composite disc spring assembly uses the existing A-series disc springs, with a single disc specification of Φ71×Φ36.5×4 mm, a single disc deformation of 1.6 mm, and a load capacity of 30 kN. The disc springs are made of 60Si2Mn (silicon manganese spring steel) or 50CrVA (high-strength alloy spring steel), and are subjected to carburizing and quenching heat treatment, with a Dacromet coating or phosphate anti-corrosion layer on the surface.

[0035] In this embodiment, the combination of multiple disc springs is as follows: every 2 to 3 disc springs are stacked in the same direction to form a stacked unit, and two or more stacked units are connected in series in opposite directions. In this embodiment, a composite combination of "2 stacks + 5 connections" is adopted, specifically: every 2 disc springs are stacked (connected in parallel) in the same direction to form a stacked unit with a load-bearing capacity of 60. kN; Five composite units are connected in reverse series (connected in series), maintaining a total load-bearing capacity of 60kN and a total deformation of 1.6mm × 5 = 8mm. Through this combination, the composite disc spring assembly utilizes its unique nonlinear elastic characteristics of "parallel load increase and series range increase" to simultaneously provide high compensation force (up to hundreds of kN) and sufficient stroke within a limited space. It automatically adapts to deformations such as creep and expansion of the surrounding rock, compensates for prestress loss in real time, avoids manual periodic tensioning, and significantly improves the long-term effectiveness of the support. Compared with pure composite or pure parallel design, the composite design breaks through the bottleneck of traditional disc spring applications and can simultaneously meet the stringent requirements of high load-bearing capacity and large deformation in deep high ground stress environments. Elastic component 2 has high damping characteristics and can absorb the energy of sudden loads such as rock bursts and rockbursts, prevent brittle fracture of anchor bolts, and achieve the "pressure relief" function.

[0036] In this embodiment, the elastic component 2 is designed with a prestress of 200kN. During initial installation, the disc spring assembly is pre-compressed by 2mm (in the initial pre-compression state, the compression amount is about 25% of the total compensation stroke), and the reserve compensation stroke is 6mm.

[0037] Additionally, it should be noted that the multiple disc springs in the elastic component 2 are coaxially sleeved on the guide shaft 10, as shown in the reference. Figure 2 As shown, the guide shaft 10 guides the movement of the elastic component. The surface hardness of the guide shaft 10 is higher than that of the disc spring material, specifically 30% to 50% higher. The end of the guide shaft away from the surrounding rock is fixed.

[0038] In this embodiment, the anchor head assembly includes a bearing plate 7, a base 8, and an anchor 9. The anchor 9 is a wedge-type anchor or a nut-type anchor. The base 8 is fixed circumferentially to the exposed end of the free section. One end of the base 8 abuts against the surrounding rock. The free section extends beyond the base 8. The base 8 is an existing structural component. The bearing plate 7 is placed at the end of the base 8 away from the surrounding rock. The anchor 9 can specifically be a locking nut. The locking nut has a set length to ensure the setting space for the ratchet 43 and the pawl 44. The protective sleeve 3 is detachably connected to the locking nut. Specifically, it can be a snap-fit ​​connection or a threaded connection. One end of the locking nut abuts against the bearing plate 7, and one end of the elastic component abuts against the end of the locking nut away from the bearing plate 7. Regarding the self-locking mechanism 4, in this embodiment, refer to... Figure 3As shown, the self-locking mechanism 4 adopts a ratchet-pawl type self-locking mechanism. The free section 11 is provided with multiple continuous toothed grooves in a circumferential direction. The ratchet-pawl type self-locking mechanism includes a ratchet 43 and a pawl 44 that cooperates with the ratchet 43. The pawl 44 is placed on the side of the ratchet 43 away from the surrounding rock. The ratchet 43 is rotatably fixed inside the anchor 9. Part of the ratchet 43 extends out from the inner surface of the anchor to engage in the toothed groove 13 of the free section 11. One end of the pawl 44 is connected to the inner surface of the anchor 9, and the other end of the pawl 44 is connected to the outer surface of the anchor through a spring 42. The function of the spring 42 is to hold the pawl. The pawl 44 is placed between the elastic component 2 and the ratchet 43. The end of the pawl 44 closest to the anchor 9 away from the surrounding rock allows the pawl 44 to engage with the spring. The spacing between the elastic components 2 is set, and the pawl 44 is connected to the inner surface of the anchor 9 through a connecting rod. The pawl 44 can be engaged between two adjacent teeth of the ratchet 43. Under normal conditions, one tooth of the ratchet is engaged in one of the tooth grooves of the free section to lock the position of the free section. When the prestress is lost, when the elastic component rebounds and pushes the anchor and the bearing plate 7 toward the surrounding rock, the pawl 44 immediately engages between the teeth of the ratchet 43 to prevent the bearing plate 7 from retracting, thereby achieving self-locking. It can be used in vibration environments that require stronger locking feedback, such as slopes in high-intensity earthquake zones. The integrated ratchet-type mechanical self-locking mechanism ensures the stable locking of the prestress after each compensation, is not affected by vibration, and prevents prestress shrinkage.

[0039] Thus, the operation of elastic component 2 is as follows: Surrounding rock pushes outward → Elastic component 2 is compressed → Energy storage; Surrounding rock retraction → Elastic component 2 rebounds → Pawl locks in place → Prestress is maintained; The surrounding rock is pushed outward again → the anchor 9 moves outward → the pawl 44 slides over the ratchet 43 again → the elastic component is further compressed → more energy is stored; The surrounding rock retracts again → the elastic component 2 rebounds again → the pawl 44 locks into a new position again → the prestress is increased again.

[0040] It needs to be explained that the triggering mechanism for the pawl's "immediate engagement" is as follows: The reason why the pawl 44 can automatically and immediately engage with the adjacent teeth of the ratchet 43 when the anchor 9 moves back is based on the synergistic effect of the following three mechanisms: 1) Spring preload bias - the spring 42 is always in a pre-stretched state, applying a constant bias torque to the pawl 44 in the direction of the root of the ratchet 43 teeth, so that the default mechanical state of the pawl 44 is "tending to engage with the tooth groove"; 2) Follow-up triggering - the pawl 44 is fixed to the anchor 9 by the connecting rod, and when the disc spring assembly rebounds, it pushes the anchor 9 to move towards the surrounding rock. At the same time, the pawl 44 moves synchronously with the anchor 9, and the tip of the pawl 44 slides along the inclined surface of the tooth back of the ratchet 43; once the pawl 44 slides past the tooth top, the biasing force of the spring 42 immediately causes it to spring into the adjacent tooth groove - the whole process does not require external control or electrical signal triggering, and is completed automatically by mechanical force; 3) Tooth shape directionality design - the tooth shape of the ratchet 43 is asymmetrical: the tooth back is an inclined surface (allowing the pawl to slide in the tensioning direction), and the tooth surface is an approximately vertical stop surface (preventing the pawl from retracting in the direction of the surrounding rock), thus forming a motion constraint of "one-way passage, reverse locking". In summary, as long as the rebound force of the disc spring group is generated and the anchor 9 undergoes a slight displacement, the pawl 44 will automatically spring into the tooth groove of the ratchet 43 under the drive of the above three mechanisms, realizing the prestress compensation locking function of "instant response, automatic locking, and irreversibility".

[0041] It should be noted that the protective sleeve 3 is a ring structure. The inner diameter of the protective sleeve 3 is larger than the outer diameter of the free section. The outer diameter of the protective sleeve 3 is adapted to the size of the bearing plate 7. The protective sleeve 3 is fixedly connected to the bearing plate 7. The protective sleeve 3 is made of HDPE (high-density polyethylene) corrugated pipe with an inner diameter of 80 mm and a length of 300 mm. The end away from the anchor 9 is sealed. The inside is filled with anti-corrosion medium, which is anti-corrosion grease.

[0042] The anchor bolt provided in this embodiment has a compact overall structure and strong adaptability, which can effectively solve the problem of difficulty in maintaining prestress for a long time in deep high-stress and large-deformation strata. Through the composite combination of "overlapping + mating" disc spring group, "parallel load increase and series range increase" are achieved. When the prestress decreases due to the creep of the surrounding rock, the disc spring group automatically rebounds to compensate for the loss; when the surrounding rock expands or is impacted, the disc spring group further compresses to absorb energy, realizing bidirectional adjustment, realizing dynamic, large-stroke compensation and energy regulation of prestress, and combined with the mechanical self-locking mechanism, thereby significantly improving the long-term anchoring performance of the anchor bolt under the conditions of large deformation and dynamic disturbance in deep surrounding rock.

[0043] In addition, all compensation and self-locking components are integrated near the anchor head, requiring no external power. Combined with the hollow grouting design, anchor installation, prestressing application, automatic compensation, and grouting reinforcement can be completed in one go after drilling, forming a "mechanical-chemical" composite anchoring system, which greatly improves construction efficiency and support quality.

[0044] Example 2 refer to Figure 4 As shown in the figure, this embodiment provides a construction method for a self-locking prestressed compensation anchor bolt, and the specific steps are as follows: Anchor bolt design and prefabrication: Based on the engineering design prestress value of 200 kN and the estimated surrounding rock creep of 5 mm, the performance parameters of the composite disc spring assembly were determined; The combination of "2-layer stacking + 5-layer assembly" is adopted, and the assembly of each component of the anchor bolt is completed. The protective sleeve 3 is installed on the outside of the assembled disc spring assembly and anti-corrosion grease is injected. Drilling: Drill holes with a diameter of φ90 mm into the rock mass, with the depth matching the designed length of the anchor bolt, and clean the holes; Anchor rod body 1 installation: Slowly push the prefabricated anchor rod body 1 into the borehole to the design depth, so that the anchoring section is located at the design anchoring position; Grouting: Pressure grouting is performed through the hollow grouting channel 5 of the anchor rod body 1, injecting existing epoxy resin modified cement-based grout, with the grout pressure maintained at 2-3 MPa. The grout flows out through the grout outlet 6, filling the gap between the borehole and the anchor rod, as well as the surrounding rock fissures. When grout returns to the borehole and its concentration is consistent with the injected grout, grouting is stopped, and the grouting channel opening is immediately sealed with a grout stop plug 11.

[0045] Prestressing and Locking: After the grout has cured, use a through-hole jack to tension the anchor rod 1 to the design value of 200 kN. During tensioning, the composite disc spring assembly 2 is compressed to the initial pre-compression state (compression amount of about 2 mm, approximately 25% of the total compensation stroke). Tighten the anchor 9, at which point the pawl 44 of the self-locking mechanism 4 automatically locks into place between the teeth of the ratchet 43.

[0046] Installation complete: Remove the tensioning equipment to complete the installation of the entire anchor bolt. At this point, the composite disc spring assembly is in its initial pre-compression state, ready to compensate for any potential future prestress loss.

[0047] Work process and effect verification: During the service life of the anchor bolt: The service life of the anchor bolt also includes a tensioning step: when the prestress loss of the anchor bolt is detected to exceed the threshold, a tensioning force is applied through the anchor head assembly to recompress the composite disc spring assembly to the set prestress state; During the service life of the anchor bolt: when the prestress decreases by approximately 20% (i.e., a decrease of 40 kN) due to rock creep, the composite disc spring assembly 2 will automatically rebound by approximately 4 mm, pushing the anchor head assembly outward to compensate for the lost prestress. If the prestress increases due to rock expansion, the disc spring assembly will further compress to absorb energy, while the self-locking mechanism 4 always ensures that the steel strand will not retract.

[0048] Re-tensioning maintenance procedure: During the service life of the anchor bolt, when the prestress loss of the anchor bolt exceeds 20% of the design threshold, a re-tensioning force is applied through the anchor head assembly to recompress the elastic component 2 back to the set initial pre-compression state, restoring the design prestress level. The re-tensioning process does not require removing the anchor bolt; it only requires applying additional torque to the anchor 9, making the operation simple and efficient.

[0049] The above construction method enables the construction of self-locking prestressed compensation anchor bolts. By setting up elastic components, the compensation stroke and bearing capacity of the elastic components are effectively improved, the prestress compensation is enhanced, and the anchor bolts automatically adapt to deformations such as creep and expansion of the surrounding rock, thereby compensating for prestress loss in real time, avoiding the need for manual periodic tensioning, and significantly improving the long-term effectiveness of the support.

[0050] This embodiment is structurally similar to Embodiment 1, except that the self-locking mechanism 4 is replaced with a wedge-shaped clamp-type self-locking device. This self-locking device includes a clamp and a conical anchor hole that engages with the clamp. The inner surface of the clamp has serrations that engage with the anchor rod body 1. When the elastic component 2 rebounds, it pushes the clamp to move inward into the conical anchor hole, automatically wedging and locking the clamp with the anchor rod body 1. Compared to the ratchet-pawl type of Embodiment 1, this embodiment has fewer components and a more compact radial dimension, making it particularly suitable for applications with limited anchor head installation space, such as narrow tunnel sections or existing structure reinforcement projects. Its working principle is as follows: during tensioning, the clamp is in a relaxed state within the conical anchor hole, allowing the anchor rod body 1 to move in the tensioning direction; when prestress is lost and the elastic component rebounds, pushing the clamp, the clamp automatically clamps the anchor rod body 1 under the wedging action of the conical anchor hole, achieving unidirectional self-locking.

[0051] 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 self-locking prestressed compensating anchor bolt, characterized in that, include: Anchor bolt body: consists of a free section and an anchoring section connected in sequence; Anchor head assembly: Located at the exposed end of the free section, used for tensioning and locking prestress; Prestress compensation mechanism: includes a protective sleeve and a guide shaft. The protective sleeve is circumferentially fitted around the exposed end of the free section. The protective sleeve is connected to the anchor head assembly. An elastic component is installed inside the protective sleeve. The elastic component is coaxially fitted on the guide shaft. One end of the elastic component is in contact with the anchor head assembly. The elastic component applies force along the axial direction of the anchor rod body. The elastic component is composed of multiple disc springs in a stacked and mating combination manner. Self-locking mechanism: Installed on the anchor head assembly, the self-locking mechanism can lock the free section. Under the action of external force, the self-locking mechanism can slide in the tensioning direction and automatically lock in the opposite direction to adjust and lock the position of the free section. After the anchor rod body is tensioned and locked, the elastic component is in an initial pre-compression state. When the prestress of the anchor rod body decreases due to the creep of the surrounding rock, the elastic component automatically rebounds to compensate for the lost prestress. When the prestress of the anchor rod increases suddenly due to the expansion of the surrounding rock or the impact load, the elastic component is further compressed to absorb energy and the free section of the anchor rod is relocked by the self-locking mechanism, realizing bidirectional adjustment of peak shaving and valley filling.

2. The self-locking prestressed compensating anchor bolt according to claim 1, characterized in that, The anchor head assembly includes an anchor, and the self-locking mechanism is a ratchet-pawl type self-locking mechanism. The free section is provided with multiple continuous toothed grooves in a circumferential direction. The ratchet-pawl type self-locking mechanism includes a ratchet and a pawl that cooperates with the ratchet. The pawl is placed on the side of the ratchet away from the surrounding rock. The ratchet is rotatably fixed inside the anchor. Part of the ratchet extends from the inner surface of the anchor to engage with the toothed groove of the free section. One end of the pawl is connected to the inner surface of the anchor through a connecting rod, and the other end of the pawl is connected to the anchor through a spring. Under normal conditions, the spring pulls the pawl to keep it in the ready-to-engage position.

3. A self-locking prestressed compensating anchor bolt according to claim 2, characterized in that, The pawl is positioned between the elastic component and the ratchet, with a distance between the pawl and the elastic component, such that when the elastic component rebounds, it first pushes the anchor to move before triggering the pawl to engage and lock the ratchet.

4. A self-locking prestressed compensating anchor bolt according to claim 1 or 2, characterized in that, The elastic component is a composite butterfly spring assembly. Every 2 to 3 disc springs are stacked in the same direction to form a stacked unit. Two or more stacked units are connected in opposite directions to form a composite butterfly spring assembly. The total compensation stroke of the elastic component is 5mm to 100mm, and the maximum compensation force is 30% to 50% of the design prestress value.

5. A self-locking prestressed compensating anchor bolt according to claim 4, characterized in that, The disc spring is made of 60Si2Mn or 50CrVA, and is subjected to carburizing and quenching heat treatment. The surface is coated with Dacromet coating or phosphate anti-corrosion layer. The outer diameter of the disc spring is less than or equal to 250 mm, and the thickness is 0.2 mm to 14 mm.

6. A self-locking prestressed compensating anchor bolt according to claim 1, characterized in that, The protective sleeve is a polyethylene corrugated pipe or a stainless steel corrugated pipe, with both ends sealed to the anchor rod body and the anchor head assembly, respectively. The protective sleeve is filled with an anti-corrosion medium, which is an anti-corrosion grease.

7. A self-locking prestressed compensating anchor bolt according to claim 1, characterized in that, The anchor rod body is a high-strength prestressed steel strand, and the interior of the anchor rod body is provided with a hollow grouting channel extending along the axial direction; The anchoring section of the anchor rod is provided with at least two grout outlet holes evenly distributed along the circumference, and the grout outlet holes are connected to the hollow grouting channel.

8. A self-locking prestressed compensating anchor bolt according to claim 1, characterized in that, The surface hardness of the guide shaft is higher than that of the disc spring material.

9. A self-locking prestressed compensating anchor bolt according to claim 2, characterized in that, The anchor head assembly also includes a bearing plate and a platform. The platform is placed circumferentially at the exposed end of the free section, and the bearing plate is placed at the end of the platform away from the surrounding rock. The anchor is in contact with the bearing plate, and the anchor is a wedge-type anchor or a nut-type anchor.

10. A self-locking prestressed compensating anchor bolt according to claim 1, characterized in that, The self-locking mechanism is a wedge-shaped clip-type self-locking device, including a clip and a tapered anchor hole that cooperates with the clip. The inner surface of the clip is provided with serrations or threads to cooperate with the anchor rod body. When the elastic component rebounds, it pushes the clip to move inward to the tapered anchor hole, so that the clip and the anchor rod body are automatically wedge-locked.

11. A self-locking prestressed compensating anchor bolt according to claim 7, characterized in that, It also includes a grout stopper, which is placed at the opening of the hollow grouting channel to seal the opening after grouting is completed.

12. A construction method for a self-locking prestressed compensating anchor bolt according to any one of claims 1-11, characterized in that, Includes the following: Based on the design prestress value and estimated surrounding rock deformation in the engineering design, determine the number of overlapping pieces and pairs of the elastic components, and assemble the elastic components and self-locking mechanism. Drill to the designed depth and clean the hole; The assembled anchor rod is inserted into the borehole to the design depth, so that the anchoring section is located at the design anchoring position; Epoxy resin modified cement-based grout is injected through the hollow grouting channel of the anchor rod body, so that the grout flows out from the grout outlet to fill the gap between the borehole and the anchor rod and the surrounding rock fissures. The grouting pressure is maintained at 2-3 MPa. Grouting is stopped when the grout returns from the hole and the concentration is consistent with the injected grout. The grouting channel opening is then sealed with a grout stop plug. After the grout has solidified, the anchor rod is tensioned to the designed prestress value, compressing the elastic components to the initial pre-compression state, and the self-locking mechanism automatically enters the locking state; the tensioning equipment is removed, the protective sleeve is installed and anti-corrosion medium is injected, and the anchor installation is completed.

13. The construction method according to claim 12, characterized in that, The anchor bolt service life also includes a tensioning step: when the prestress loss of the anchor bolt is detected to exceed the threshold, a tensioning force is applied through the anchor head assembly to recompress the elastic component to the set prestress state.

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