Anchoring rod with multiple force resistance lines
By designing anchor bolts with multi-level stress defense lines, the problem of anchor bolts breaking when the internal stress of the rock suddenly increases was solved, and the continuous support capacity of the anchor bolts was realized when the internal force of the surrounding rock increases, thus avoiding the occurrence of engineering accidents.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CITIC GENERAL INST OF ARCHITECTURAL DESIGN & RES
- Filing Date
- 2023-12-24
- Publication Date
- 2026-06-26
AI Technical Summary
Existing anchor bolts are prone to breakage when the internal stress of the rock suddenly increases, leading to a chain reaction in the anchor bolt system and causing engineering accidents.
Design an anchor bolt with multi-level force protection, including core reinforcement, large sleeve, small sleeve, limiting structure and auxiliary force transmission structure. The interlocking of the limiting end plates provides multi-level support force, ensuring that the anchor bolt can continue to function when the internal force of the surrounding rock increases.
When the internal forces of the surrounding rock increase, the anchor bolts extend their service life through a multi-level force defense mechanism, avoid sudden safety incidents, provide greater support capacity, and continue to play a role after the internal forces of the surrounding rock are released.
Smart Images
Figure CN117738709B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of anchoring technology, and more specifically to an anchor bolt with multi-level stress protection. Background Technology
[0002] With the rapid development of transportation networks, the construction of tunnels and slope engineering is often involved in the process. Rock anchors, as an important anchoring and support technology for rock tunnels and slope engineering, are being widely used in the support and disaster prevention of various projects.
[0003] Currently, conventional anchor bolts are designed with their strength based on an estimated anchoring force. However, in actual engineering projects, scenarios such as tunnel rockbursts, mine blasting, and slope blasting can cause a sudden increase in rock internal stress. This sudden increase in surrounding rock internal force may exceed the tensile bearing capacity of the anchor bolt, causing it to break and triggering a chain reaction throughout the entire anchor bolt system, leading to engineering accidents. Summary of the Invention
[0004] Based on the above description, the present invention provides an anchor bolt with multi-level stress protection lines to solve the problem in related technologies where anchor bolts may break when the internal stress of the rock suddenly increases, exceeding the tensile bearing capacity of the anchor bolt, thereby causing a chain reaction in the entire anchor bolt system and triggering engineering accidents.
[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:
[0006] This application provides an anchor bolt with multi-level stress protection lines, and the technical solution adopted is as follows:
[0007] An anchor bolt with multi-level stress protection lines includes:
[0008] Core reinforcement;
[0009] A large sleeve is coaxially fitted around the core steel reinforcement and fixed to the rock wall;
[0010] A small sleeve is coaxially sleeved outside the core steel bar and distributed axially with the first sleeve on the core steel bar. One end of the small sleeve is placed inside the large sleeve, and the other end of the small sleeve is fixed to the core steel bar.
[0011] A limiting structure includes a large sleeve limiting end plate connected to the large sleeve and a small sleeve limiting end plate connected to the small sleeve. The large sleeve limiting end plate is located between the small sleeve limiting end plate and the end of the small sleeve that is fixed to the core reinforcement. The projections of the large sleeve limiting end plate and the small sleeve limiting end plate on the axial direction of the core reinforcement intersect. The structure is adapted to limit the distance by which the large sleeve and the small sleeve move away from each other along the axial direction of the core reinforcement by the cooperation of the large sleeve limiting end plate and the small sleeve limiting end plate.
[0012] Auxiliary force transmission structure, which includes:
[0013] - A large sleeve end cap steel plate, located at the end of the large sleeve away from the small sleeve, through which the core reinforcing bar passes and is connected to the reinforcing bar nut;
[0014] - A steel support plate is located at the end of the large sleeve away from the small sleeve and is encircled outside the large sleeve. A stiffening rib is provided between the steel support plate and the large sleeve. The steel support plate is fixed to the rock wall by anchor bolts.
[0015] - An inner sleeve is provided inside the large sleeve and encircled outside the core reinforcing bar. A stiffening rib inside the large sleeve is provided between the inner sleeve and the large sleeve, and the stiffening rib inside the large sleeve is connected to the end plate of the large sleeve.
[0016] Preferably, the large sleeve limiting end plate is annularly arranged outside the large sleeve and integrally cast with the large sleeve; the small sleeve limiting end plate is annularly arranged outside the small sleeve and welded and fixed to the small sleeve; the small sleeve limiting end plate is placed inside the large sleeve; the inner diameter of the large sleeve limiting end plate is smaller than the outer diameter of the small sleeve limiting end plate; and the large sleeve limiting end plate and the small sleeve limiting end plate are spaced apart by a set distance along the axial direction of the core reinforcing bar.
[0017] Preferably, the outer edge of the small sleeve limiting end plate is 30mm away from the outer surface of the small sleeve, the inner edge of the large sleeve limiting end plate is 30mm away from the inner surface of the large sleeve, the inner edge of the large sleeve limiting end plate is 3-8mm away from the outer surface of the small sleeve, and the outer surface of the small sleeve limiting end plate is 3-8mm away from the inner surface of the large sleeve.
[0018] Preferably, the inner diameter of the small sleeve is 5-8 mm larger than the diameter of the core reinforcing bar, and the small sleeve and the core reinforcing bar are connected and fixed by an annular steel block anchor.
[0019] Preferably, the space between the small sleeve and the core reinforcing bar is filled with semi-solid grease.
[0020] Preferably, the space between the small sleeve limiting end plate and the large sleeve limiting end plate is filled with semi-solid grease.
[0021] Preferably, the large sleeve end cap steel plate has a through hole in the center for the core reinforcing bar to pass through, the diameter of the through hole is 2mm larger than the diameter of the core reinforcing bar, and the inner diameter of the inner sleeve is 2-5mm larger than the diameter of the core reinforcing bar.
[0022] Preferably, the core reinforcing bar is HRB400 or HRB500 hot-rolled ribbed steel bar, and the large sleeve, the small sleeve, the large sleeve limiting end plate and the small sleeve limiting end plate are all made of Q355B or Q390B low alloy high strength steel.
[0023] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:
[0024] In this application, the anchor bolt has one end of the small sleeve anchored together with the core reinforcement in a concrete anchor block, while the large sleeve is fixed to the rock wall. When the force in the surrounding rock area where the anchor bolt acts increases and outward deformation occurs, the core reinforcement undergoes tensile deformation under the external force. The limiting end plates of the large sleeve and the small sleeve approach each other. When the designed free displacement limit is reached, the limiting end plates of the large sleeve and the small sleeve come into contact with each other. At this time, the core reinforcement has not reached its ultimate tensile bearing capacity and can still provide anchoring force. The large sleeve and the small sleeve also provide anchoring force at this time under the interlocking action of the limiting end plates of the large sleeve and the small sleeve, playing the role of a second-level defense line. Ultimately, they jointly provide greater support force, allowing the anchor bolt to continue to function. For surrounding rock where stress may increase, such as in sudden disaster scenarios like tunnel rockbursts, mine blasting, and slope blasting, the anchor bolt has the following advantages: The anchor bolt deforms accordingly with the development of internal forces in the surrounding rock, releasing some of the surrounding rock stress and potentially reaching a new equilibrium point as the axial force of the core reinforcement increases; the anchor bolt has good ductility, allowing for observation of rock mass deformation before sudden collapse, providing timely warnings and preventing sudden safety incidents; the free section of the anchor bolt (the part not anchored in the anchor body) is designed as a second-level defense, allowing the outer sleeve to share the load with the core reinforcement, achieving greater support capacity; even after the core reinforcement is broken, the large and small sleeve systems can continue to bear the load independently, and after the large deformation releases the internal forces in the surrounding rock, a new equilibrium may be reached, allowing the anchor bolt to continue functioning. Attached Figure Description
[0025] Figure 1 A schematic diagram of the structure of an anchor bolt with multi-level stress defense lines anchored to rock mass, provided in an embodiment of the present invention;
[0026] Figure 2 A schematic diagram of an anchor bolt with multi-level force defense lines provided in an embodiment of the present invention;
[0027] Figure 3 for Figure 2 Sectional view along line AA;
[0028] Figure 4 This is a schematic diagram of the stress-strain curve of the core steel bar in the anchor rod with multi-level stress defense line provided in Embodiment 1 of the present invention.
[0029] The attached diagram lists the components represented by each number as follows:
[0030] 1. Large sleeve; 2. Small sleeve; 3. Large sleeve limiting end plate; 4. Small sleeve limiting end plate; 5. Core reinforcement; 6. Reinforcing bar nut; 7. Large sleeve end plate; 8. Large sleeve external stiffening rib; 9. Steel support plate; 10. Large sleeve internal stiffening rib; 11. Inner sleeve; 12. Steel block anchor body; 13. Anchor bolt. Detailed Implementation
[0031] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0033] It is understood that spatial relation terms such as "below," "under," "below," "below," "above," "above," etc., can be used here to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below" or "below" of the other element or feature will be oriented "above" the other element or feature. Therefore, the exemplary terms "below" and "below" can include both upper and lower orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.
[0034] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have the transmission of electrical signals or data between them.
[0035] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.
[0036] Reference Figure 1-4 As shown in the figure, this application provides an anchor bolt with a multi-level stress defense line, which includes a free section and an anchoring section.
[0037] Reference Figure 1-3 As shown, the anchor bolt includes a core reinforcing bar 5, a large sleeve 1, a small sleeve 2, a limiting structure, and an auxiliary force transmission structure. The large sleeve 1 is coaxially sleeved outside the core reinforcing bar 5 and fixed to the rock wall. The small sleeve 2 is coaxially sleeved outside the core reinforcing bar 5 and is distributed axially with the first sleeve in the core reinforcing bar 5. One end of the small sleeve 2 is placed inside the large sleeve 1, and the other end of the small sleeve 2 is fixed to the core reinforcing bar 5. The limiting structure includes a large sleeve limiting end plate 3 connected to the large sleeve 1 and a small sleeve limiting end plate 4 connected to the small sleeve 2. The large sleeve limiting end plate 3 is located between the small sleeve limiting end plate 4 and the end of the small sleeve 2 fixed to the core reinforcing bar 5, and the projections of the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4 in the axial direction of the core reinforcing bar 5 intersect. This is suitable for limiting the distance that the large sleeve 1 and the small sleeve 2 move away from each other along the axial direction of the core reinforcing bar 5 by the cooperation of the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4. The auxiliary force transmission structure includes a large sleeve end plate 7, a steel support plate 9, and an inner sleeve 11. The large sleeve end plate 7 is located at the end of the large sleeve 1 away from the small sleeve 2. The core steel bar 5 passes through the large sleeve end plate 7 and is connected to the steel bar nut 6. The steel support plate 9 is located at the end of the large sleeve 1 away from the small sleeve 2 and is encircled outside the large sleeve 1. An outer stiffening rib 8 is provided between the steel support plate 9 and the large sleeve 1. The steel support plate 9 is fixed to the rock wall by anchor bolts 13. The inner sleeve 11 is located inside the large sleeve 1 and is encircled outside the core steel bar 5. An inner stiffening rib 10 is provided between the inner sleeve 11 and the large sleeve 1, and the inner stiffening rib 10 is connected to the large sleeve end plate 7.
[0038] Reference Figure 1-3As shown, during anchor installation, the end of the core steel bar 5 closest to the small sleeve 2, i.e. the end where the small sleeve 2 is fixed to the core steel bar 5, is anchored in the concrete anchor body to form an anchoring section. The part of the anchor rod in the anchor hole that is not anchored in the concrete anchor body is a free section. The length of the free section is variable, and after being stretched by a set distance, the large sleeve 1 and the small sleeve 2 can form a second-level stress defense line.
[0039] Reference Figure 1-3 As shown, the large sleeve limiting end plate 3 is arranged in a circular ring outside the large sleeve 1 and is integrally cast with the large sleeve 1. The small sleeve limiting end plate 4 is arranged in a circular ring outside the small sleeve 2 and is welded and fixed to the small sleeve 2. The small sleeve limiting end plate 4 is placed inside the large sleeve 1. The inner diameter of the large sleeve limiting end plate 3 is smaller than the outer diameter of the small sleeve limiting end plate 4. The large sleeve limiting end plate 3 and the small sleeve limiting end plate 4 are spaced apart along the axial direction of the core steel bar 5.
[0040] Reference Figure 1-3 As shown, the large sleeve end plate 7 is welded to the end of the large sleeve 1. The inner sleeve 11 is coaxial with the large sleeve 1 and three large sleeve inner stiffening ribs 10 are welded between the inner sleeve 1 and the large sleeve 1. The large sleeve end plate 7 and the large sleeve inner stiffening ribs 10 are welded and fixed. The steel support plate 9 is welded to the outer wall of the large sleeve 1 with full penetration slit welding. Six large sleeve outer stiffening ribs 8 are welded between the steel support plate 9 and the large sleeve 1 to ensure the transmission of axial force on the end of the large sleeve. The steel support plate 9 is fixed to the surrounding rock wall by three M16 anchor bolts 13. The core steel bar 5 passes through one end of the large sleeve end plate 7 and is threaded. It is fixed to the center position of the large sleeve end plate 7 by steel bar nuts 6.
[0041] Reference Figure 1-3 As shown, furthermore, the distance between the small sleeve limiting end plate 4 and the end of the small sleeve 2 located inside the large sleeve 1 is 30mm, in order to ensure welding quality.
[0042] Reference Figure 1-3 As shown, specifically, the inner diameter of the small sleeve 2 is 5-8 mm larger than the diameter of the core reinforcing bar 5, and the small sleeve 2 and the core reinforcing bar 5 are connected and fixed by a ring-shaped steel block anchor 12; the outer edge of the small sleeve limiting end plate 4 is 30 mm away from the outer surface of the small sleeve 2. Figure 1 The value 'a' marked in the middle is 30mm from the inner edge of the large sleeve limiting end plate 3 to the inner surface of the large sleeve 1. Figure 1The distance between the inner edge of the large sleeve limiting end plate 3 and the outer surface of the small sleeve 2 is 3-8 mm (specifically 5 mm). The distance between the outer surface of the small sleeve limiting end plate 4 and the inner surface of the large sleeve 1 is 3-8 mm (specifically 5 mm). A through hole for the core reinforcing bar 5 to pass through is opened in the center of the large sleeve end plate 7. The diameter of the through hole is 2 mm larger than the diameter of the core reinforcing bar 5. The inner diameter of the inner sleeve 11 is 2-5 mm larger than the diameter of the core reinforcing bar 5. The core reinforcing bar 5 is HRB400 or HRB500 hot-rolled ribbed steel bar. The large sleeve 1, small sleeve 2, large sleeve limiting end plate 3, and small sleeve limiting end plate 4 are all made of Q355B or Q390B low alloy high-strength steel. The appropriate diameter of the core reinforcing bar 5, the thickness of the steel plate of each component, the size of the stiffening rib, the specifications of the connectors, and the size of the weld leg are selected according to the design requirements.
[0043] Furthermore, semi-solid grease is filled between the small sleeve 2 and the core steel bar 5, and semi-solid grease is filled between the small sleeve limiting end plate 4 and the large sleeve limiting end plate 3.
[0044] During anchor installation in this embodiment, the small sleeve 2, with the small sleeve limiting end plate 4 welded to it, is first interlocked with the large sleeve 1. The other end of the large sleeve 1 is then welded to the large sleeve end cap steel plate 7, the three large sleeve inner stiffening ribs 10, the inner sleeve 11, the six large sleeve outer stiffening ribs 8, and the steel support plate 9. Then, the core reinforcing bar 5 is inserted into the small sleeve 2 and the large sleeve 1. The design displacement between the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4 is pre-reserved as needed. The steel block anchor body 12 is welded to the core reinforcing bar 5 and to the right end of the small sleeve 2, fixing the right end of the small sleeve 2. The gap between the small sleeve 2 and the core reinforcing bar 5 is filled with semi-solid grease to ensure the free stretching of the core reinforcing bar 5. The gap between the small sleeve limiting end plate 4 and the large sleeve limiting end plate 3 is also filled with semi-solid grease to ensure that the large sleeve 1 and the small sleeve 2 can slide relative to each other in the early stages of anchor stress. The anchor bolt anchoring section was installed and grouted according to standard construction procedures. Grouting was poured into the drilled section at the right end of the small sleeve 2 as part of the anchoring section. Subsequently, three M16 anchor bolts 13 were used to fix the steel support plate 9 to the surrounding rock wall; the core steel bar 5 was fixed to the center of the large sleeve end plate 7 using steel bar nuts 6, completing the installation. Since most of the free section of the anchor bolt device was exposed to the air and not grouted, anti-corrosion and anti-rust treatment was required for all components before installation.
[0045] The working principle of this invention: When the force in the surrounding rock area where the anchor bolt acts increases and outward deformation occurs, the core steel bar 5 undergoes tensile deformation under the action of external force, and the large sleeve 1 moves to the left (see attached diagram). Figure 1(In the placement method), when the designed free displacement limit is reached, the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4 come into contact with each other. At this time, the core steel bar 5 has not reached the ultimate tensile bearing capacity and can still provide anchoring force. The large sleeve 1 and the small sleeve 2 also provide anchoring force at this time under the interlocking action of the end plates, playing the role of the second-level defense line, and finally jointly providing greater support force, so that the anchor can continue to play a role. When the core steel bar 5 is broken, the large sleeve 1 and the small sleeve 2 system can still continue to bear the load independently. After the internal force of the surrounding rock is released after the large deformation, a new equilibrium may be reached, so that the anchor can continue to play a role.
[0046] Example 1:
[0047] Reference Figure 4 As shown, the core reinforcing bar 5 is made of HRB400 grade hot-rolled ribbed steel bar with a diameter of 28mm, a yield strength of 400MPa, an ultimate strength of 540MPa, and a total elongation of 7.5% under maximum force; the small sleeve 2 is made of Q355B with an inner diameter of 34mm, an outer diameter of 50mm, and a wall thickness of 8mm; the large sleeve 1 is made of Q355B with an inner diameter of 120mm, an outer diameter of 140mm, and a wall thickness of 10mm; the small sleeve limiting end plate 4 is made of Q355B with a thickness of 16mm; the large sleeve limiting end plate 3 is made of Q355B with a thickness of 16mm; the Q355B low-alloy high-strength steel has a yield strength of 345MPa, a yield shear strength of 199MPa, and an ultimate strength of 470MPa. The free section of the anchor bolt device is designed to be 1.25m long. A 50mm gap is left between the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4, meaning the designed elongation rate of the core reinforcement 5 during free deformation is 4%. When the large sleeve 1 moves to the left by the designed distance of 50mm, the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4 come into contact. At this point, the elongation rate of the core reinforcement 5 is 4%, and the axial force of the core reinforcement 5 is approximately 246kN to 332kN. The stress state is as follows: Figure 4 In section CD shown, the large sleeve 1 and the small sleeve 2 participate in the stress of the anchor rod through the interlocking of the large sleeve limiting end plate 3 and the small sleeve limiting end plate 4, and the second-level stress system begins to work; when the core steel bar 5 reaches its ultimate strength, the stress state is as follows: Figure 4 At point D, the axial force of core reinforcement 5 is approximately 332 kN. Large sleeve 1 and small sleeve 2 reach a yield state, providing an axial force of approximately 363 kN, and the total bearing capacity of the anchor bolt is approximately 695 kN. When core reinforcement 5 fractures, the stress state is as follows: Figure 4 As shown in section DE, the large sleeve 1 and small sleeve 2 system can individually provide an ultimate bearing capacity of approximately 495 kN. All other connectors meet the corresponding strength requirements.
[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. An anchor bolt with multi-level stress protection lines, characterized in that, include: Core reinforcement (5); A large sleeve (1) is coaxially sleeved outside the core steel bar (5) and fixed to the rock wall; Small sleeve (2) is coaxially sleeved outside the core steel bar (5) and distributed axially with the large sleeve (1) on the core steel bar (5). One end of the small sleeve (2) is placed inside the large sleeve (1), and the other end of the small sleeve (2) is fixed to the core steel bar (5). The limiting structure includes a large sleeve limiting end plate (3) connected to the large sleeve (1) and a small sleeve limiting end plate (4) connected to the small sleeve (2). The large sleeve limiting end plate (3) is located between the small sleeve limiting end plate (4) and the end of the small sleeve (2) that is fixed to the core steel bar (5). The projections of the large sleeve limiting end plate (3) and the small sleeve limiting end plate (4) on the axial direction of the core steel bar (5) intersect. It is suitable for limiting the distance by which the large sleeve (1) and the small sleeve (2) move away from each other along the axial direction of the core steel bar (5) by the cooperation of the large sleeve limiting end plate (3) and the small sleeve limiting end plate (4). Auxiliary force transmission structure, which includes: - A large sleeve end plate (7) is located at the end of the large sleeve (1) away from the small sleeve (2), and the core steel bar (5) passes through the large sleeve end plate (7) and is connected to the steel bar nut (6). - A steel support plate (9) is located at one end of the large sleeve (1) away from the small sleeve (2) and is encircled outside the large sleeve (1). A large sleeve external stiffening rib (8) is provided between the steel support plate (9) and the large sleeve (1). The steel support plate (9) is fixed to the rock wall by anchor bolts (13). - Inner sleeve (11), which is located inside the large sleeve (1) and encircled outside the core steel bar (5), and a large sleeve inner stiffening rib (10) is provided between the inner sleeve (11) and the large sleeve (1), and the large sleeve inner stiffening rib (10) is connected to the large sleeve end plate (7).
2. The anchor bolt with multi-level force protection line according to claim 1, characterized in that: The large sleeve limiting end plate (3) is arranged in a circular ring outside the large sleeve (1) and is integrally cast with the large sleeve (1). The small sleeve limiting end plate (4) is arranged in a circular ring outside the small sleeve (2) and is welded and fixed to the small sleeve (2). The small sleeve limiting end plate (4) is placed inside the large sleeve (1). The inner diameter of the large sleeve limiting end plate (3) is smaller than the outer diameter of the small sleeve limiting end plate (4). The large sleeve limiting end plate (3) and the small sleeve limiting end plate (4) are spaced apart by a distance along the axial direction of the core steel bar (5).
3. The anchor bolt with multi-level force protection line according to claim 2, characterized in that: The outer edge of the small sleeve limiting end plate (4) is 30mm away from the outer surface of the small sleeve (2), the inner edge of the large sleeve limiting end plate (3) is 30mm away from the inner surface of the large sleeve (1), the inner edge of the large sleeve limiting end plate (3) is 3~8mm away from the outer surface of the small sleeve (2), and the outer surface of the small sleeve limiting end plate (4) is 3~8mm away from the inner surface of the large sleeve (1).
4. The anchor bolt with multi-level force protection lines according to claim 1, characterized in that: The inner diameter of the small sleeve (2) is 5-8 mm larger than the diameter of the core steel bar (5), and the small sleeve (2) and the core steel bar (5) are connected and fixed by an annular steel block anchor (12).
5. The anchor bolt with multi-level force protection lines according to claim 1, characterized in that: The space between the small sleeve (2) and the core steel bar (5) is filled with semi-solid grease.
6. The anchor bolt with multi-level force protection lines according to claim 2, characterized in that: The space between the small sleeve limiting end plate (4) and the large sleeve limiting end plate (3) is filled with semi-solid grease.
7. The anchor bolt with multi-level force protection lines according to claim 1, characterized in that: The large sleeve end plate (7) has a through hole in the center for the core steel bar (5) to pass through. The diameter of the through hole is 2 mm larger than the diameter of the core steel bar (5). The inner diameter of the inner sleeve (11) is 2-5 mm larger than the diameter of the core steel bar (5).
8. The anchor bolt with multi-level force protection line according to claim 1, characterized in that: The core steel bar (5) is HRB400 or HRB500 hot-rolled ribbed steel bar, and the large sleeve (1), the small sleeve (2), the large sleeve limiting end plate (3) and the small sleeve limiting end plate (4) are all made of Q355B or Q390B low alloy high strength steel.