A multi-stage extrusion anchor rod with a non-spacing cylindrical friction platform

Abstract

The utility model discloses a kind of multi-stage extrusion anchoring anchor rod of spacing-free cylindrical friction platform, belong to geotechnical engineering anchoring technical field, including anchor rod main body, sleeve, hexagonal bushing, three groups of extrusion circular platform, three groups of cylindrical friction platform and elastic claw;Each component is assembled without spacing with anchor rod main body as shaft and is embedded in sleeve, anchor rod main body is equipped with rectangular spline, sleeve inner wall is equipped with annular positioning boss, hexagonal bushing is opened pre-groove, extrusion circular platform is gradient taper angle, cylindrical friction platform is equipped with laser texture pit and DLC coating, and elastic claw contains claw piece.The utility model solves the problems of traditional anchor rod assembly cumbersome, large space occupation, etc., while simplifying structure, anchoring force is improved by more than 30%, assembly efficiency is improved by 50%, suitable for narrow space high-stress anchoring scene.

Description

Technical Field

[0001] This utility model belongs to the field of geotechnical engineering anchoring technology, specifically relating to a multi-stage extrusion anchor rod with a gapless cylindrical friction table. Background Technology

[0002] In geotechnical engineering anchoring operations, multi-stage extrusion friction anchors are widely used due to their stable anchoring force. However, traditional multi-stage extrusion friction anchors have significant drawbacks and are difficult to adapt to the anchoring requirements in confined spaces: First, the axial spacing between the multi-stage frustums of traditional multi-stage anchors needs to be reserved to avoid assembly interference, resulting in an excessively long overall anchor length, making it impossible to install in confined anchoring spaces such as thin coal seams and shallow slopes; Second, the friction frustums often adopt a conical structure design, which not only involves complex processing technology but also places extremely high demands on assembly coaxiality, increasing processing and assembly costs; Third, the spacing between the frustums can easily cause gaps in debris filling, leading to stress concentration problems and affecting anchoring stability and service life. Utility Model Content

[0003] (a) Technical problems to be solved

[0004] This utility model aims to overcome the shortcomings of the prior art and solve the following core technical problems:

[0005] How to shorten the overall length of the anchor bolt to fit into a narrow space while ensuring the continuity of multi-stage compression and the uniformity of debris filling through a tight connection design without gaps;

[0006] How to optimize the structure of the friction table, and change the traditional conical friction table to a cylindrical structure, simplifying the processing technology while ensuring that the friction anchoring effect is not reduced;

[0007] How can we improve the overall stability of anchor bolts by using structural adaptation design to avoid stress concentration and assembly deviation problems that may be caused by gapless connections?

[0008] (II) Technical Solution

[0009] To achieve the above objectives, this utility model provides a multi-stage extrusion anchor bolt using a gapless cylindrical friction table, the specific technical solution of which is as follows:

[0010] A multi-stage extrusion anchor bolt with a gapless cylindrical friction table includes an anchor bolt body, a sleeve, a hexagonal liner, three sets of extrusion frustums, three sets of cylindrical friction tables, and elastic claws; the anchor bolt body is the central axis, and the hexagonal liner, the three sets of extrusion frustums, the three sets of cylindrical friction tables, and the elastic claws are assembled sequentially from the front end to the rear end along the axial direction of the anchor bolt body without any gap, and all components are coaxially embedded inside the sleeve;

[0011] The anchor rod body is provided with a rectangular spline; the inner wall of the sleeve is provided with three annular positioning bosses, which are respectively limited by three sets of extrusion frustums; the outer surface of the hexagonal liner is provided with an axial pre-groove along the hexagonal edge; the three sets of extrusion frustums are gradient cone angle structures, and the diameter of the large end increases sequentially along the rear end direction of the anchor rod body; the outer diameter of the three sets of cylindrical friction tables is consistent with the diameter of the large end of the corresponding three sets of extrusion frustums, the inner hole is provided with a spline groove that mates with the rectangular spline, and the outer cylindrical surface is provided with a laser-textured pit array; the elastic claw is evenly distributed with claw plates in the circumference.

[0012] Furthermore, the rear end faces of the first extrusion stage and the front end face of the first cylindrical friction stage, the rear end face of the first cylindrical friction stage and the front end face of the second extrusion stage, the rear end face of the second extrusion stage and the front end face of the second cylindrical friction stage, the rear end face of the second cylindrical friction stage and the front end face of the third extrusion stage, and the rear end face of the third extrusion stage and the front end face of the third cylindrical friction stage are all in close contact with each other, with no axial gap.

[0013] Furthermore, the anchor bolt body is made of 40Cr alloy steel, with a rectangular spline module of 2, a number of teeth of 6, and a spline groove depth of 2mm and a width of 4mm.

[0014] Furthermore, the sleeve is made of Q690 low-alloy high-strength steel, with an inner diameter of φ50mm and a wall thickness of 5mm. The inner wall is treated with gas nitriding, with a nitriding depth of 0.3mm.

[0015] Furthermore, the hexagonal liner has a bimetallic composite structure, with an inner layer of Q235 low-carbon steel core tube and an outer layer of H62 copper alloy. The axial pre-grooves are 1.5mm deep and 2mm wide, and there are 6 grooves in total.

[0016] Furthermore, all three extrusion frustums are made of 42CrMo alloy steel. The first extrusion frustum has a cone angle of 45°, the second extrusion frustum has a cone angle of 37°, and the third extrusion frustum has a cone angle of 30°. The length of each frustum is 13mm, and the diameter of the large end is φ45mm, φ47.5mm, and φ49mm, respectively.

[0017] Furthermore, all three sets of cylindrical friction stages are made of 42CrMo alloy steel, with a length of 13mm. The outer cylindrical surface is also coated with a 2μm thick DLC coating, and the laser-textured pit array has a pit diameter of 50μm, a depth of 10μm, and a spacing of 100μm.

[0018] Furthermore, the elastic claw is made of 65Mn spring steel with an outer diameter of φ49mm, a claw length of 8mm, a thickness of 1mm, and a gap of ≤0.1mm between it and the anchor rod body (1) after pre-compression.

[0019] (III) Beneficial Effects

[0020] Compared with the prior art, the present invention has the following significant advantages:

[0021] 1. More compact structure: The gapless and tight connection design shortens the sleeve length by more than 40mm compared with the traditional structure, which can adapt to the anchoring needs of narrow spaces such as thin coal seams and shallow slopes, expanding the applicable scenarios by 30%;

[0022] 2. Simplified processing and assembly: Compared with the traditional conical friction table, the three sets of cylindrical friction tables have lower processing accuracy requirements (cylindricity tolerance of ±0.03mm is sufficient) and improve processing efficiency by 40%; the gapless design reduces assembly and positioning steps, and the assembly time of a single anchor rod is shortened from the traditional 8 minutes to 4 minutes.

[0023] 3. Stable anchoring performance: Gradient cone angle extrusion combined with the deepened pre-groove of hexagonal liner achieves directional crushing of the liner. The laser textured coating of the cylindrical friction table ensures a friction coefficient ≥0.55, and the ultimate pull-out resistance is 30% higher than that of the traditional non-spaced cone friction table structure.

[0024] 4. More uniform stress distribution: The extrusion frustum and the cylindrical friction table fit together without gap, and with the annular positioning boss, the stress transmission is continuous. The maximum stress peak is reduced from 1200MPa in the traditional structure to 950MPa, avoiding local overload fracture. Attached Figure Description

[0025] Figure 1 : Cross-sectional view of the overall structure of this utility model;

[0026] Figure 2 Schematic diagram of the cross-section of a hexagonal liner tube;

[0027] Figure 3 Schematic diagram of laser texturing on the surface of a cylindrical friction stage;

[0028] Figure 4 : Schematic diagram of the circumferential structure of the elastic claw.

[0029] The markings in the diagram are as follows: 1-Anchor bolt body, 11-Rectangular spline; 2-Sleeve, 21-Annular positioning boss; 3-Hexagonal liner, 31-Pre-groove; 41-First extrusion frustum, 42-Second extrusion frustum, 43-Third extrusion frustum; 51-First cylindrical friction table, 52-Second cylindrical friction table, 53-Third cylindrical friction table, 54-Laser textured pit; 6-Elastic claw, 61-Claw plate. Detailed Implementation

[0030] 1. Manufacturing process of key components

[0031] Anchor bolt body (1): 40Cr alloy steel bar is quenched at 850℃ and tempered at 550℃. After turning, it is knurled to form a rectangular spline (11). The spline accuracy meets the GB / T1144-20016 standard.

[0032] Sleeve (2): Q690 steel strip is welded into a tube blank by high frequency, and then precisely cold-drawn to an inner diameter of φ50mm. It is then subjected to gas nitriding treatment at 520℃ for 4 hours. The inner wall ring positioning boss (21) is machined by electric spark, with a boss width of 5mm.

[0033] Hexagonal liner (3): Q235 core tube and H62 copper alloy strip are rolled into hexagonal composite tube (outer diameter φ48mm) by a composite rolling mill, and 6 axial pre-grooves (31) are laser-cut, with the groove opening rounded by R0.5mm.

[0034] Extruded frustum (41, 42, 43): 42CrMo steel billet is formed in one step by cold extrusion die, with cone angles of 45°, 37°, and 30° respectively, and the large end diameters are 45mm, 47.5mm, and 49mm respectively, with end face parallelism ≤0.02mm.

[0035] Cylindrical friction tables (51, 52, 53): 42CrMo steel billets are machined into cylinders of φ45mm×13mm, φ47.5mm×13mm, and φ49mm×13mm, and spline grooves are broached in the inner hole; the outer cylindrical surface is processed with a pit array (54) by fiber laser processing, and then coated with physical vapor deposition (DLC).

[0036] Elastic claw (6): 65Mn spring steel plate is stamped and formed, and then quenched at 830℃ and tempered at 400℃. The claw piece (61) is pre-pressed and shaped to have a gap of ≤0.1mm with the φ25mm cylinder.

[0037] 2. Overall Assembly Process

[0038] Horizontal fixed sleeve (2), insert the anchor rod body (1) from the front end of the sleeve until the rod body is completely penetrated;

[0039] Insert the hexagonal liner (3) along the anchor rod body (1) so that the front end of the liner abuts against the front end limiting surface of the sleeve;

[0040] The first extrusion platform (41), the first cylindrical friction platform (51), the second extrusion platform (42), the second cylindrical friction platform (52), the third extrusion platform (43), and the third cylindrical friction platform (53) are sequentially installed to ensure that the end faces of each component fit tightly together and that the front end of the extrusion platform abuts against the corresponding annular positioning boss (21).

[0041] An elastic claw (6) is embedded behind the third cylindrical friction table (53) and fixed by a retaining spring at the rear end of the sleeve (2);

[0042] Use a dial indicator to check the coaxiality of the anchor body (1) and the sleeve (2) to ensure that the coaxiality is ≤0.05mm, and then complete the assembly.

[0043] 3. Anchoring process

[0044] When the anchor bolt is subjected to tensile load, the anchoring force transfer process is as follows:

[0045] First-stage anchoring: The load is transferred to the first extrusion frustum (41), which quickly cuts into the hexagonal liner (3) at a 45° cone angle. The copper alloy outer layer breaks in a directional manner along the pre-groove (31), and the debris fills the gap between the sleeve (2) and the cylindrical friction table. The first cylindrical friction table (51) transfers the load through the spline, and the laser-textured pit (54) engages with the debris, providing approximately 25% of the total anchoring force.

[0046] Second-stage anchoring: With increased load, the second extrusion frustum (42) further extrudes the liner, expanding the damage range; the second cylindrical friction platform (52) generates higher frictional resistance due to its larger outer diameter (φ47.5mm), providing approximately 40% of the total anchoring force;

[0047] Third-level anchoring: When the load reaches its peak, the third extrusion frustum (43) completes deep extrusion and the debris is tightly filled; the third cylindrical friction platform (53) (φ49mm) forms a high-strength friction pair with the inner wall of the sleeve (2), providing about 35% of the total anchoring force; at the same time, the elastic claw (6) clamps the spline to suppress creep.

[0048] 4. Performance Verification Results

[0049] Pull-out tests on Φ50mm×450mm mortar anchors show that the performance of this invention is as follows:

[0050] Ultimate pull-out resistance: 255kN, which is 30.1% higher than the traditional non-pitched conical friction table anchor rod (196kN); Assembly time: 4 minutes / piece, which is 50% shorter than the traditional structure;

[0051] Space occupancy: The sleeve length is 210mm, which is 16% shorter than the traditional 250mm; the anchoring force attenuation rate after 100 days of static placement is 5.3%, which meets the long-term support requirements.

Claims

1. A multi-stage extrusion anchor bolt with a gapless cylindrical friction table, characterized in that, The system includes an anchor body (1), a sleeve (2), a hexagonal liner (3), three sets of extrusion frustums (41, 42, 43), three sets of cylindrical friction tables (51, 52, 53), and an elastic claw (6). The anchor body (1) is the central axis. The hexagonal liner (3), the three sets of extrusion frustums (41, 42, 43), the three sets of cylindrical friction tables (51, 52, 53), and the elastic claw (6) are assembled sequentially from the front end to the rear end along the axial direction of the anchor body (1) without any gaps. All components are coaxially embedded inside the sleeve (2). The anchor rod body (1) is provided with a rectangular spline (11); the inner wall of the sleeve (2) is provided with three annular positioning bosses (21), which are respectively limited by three sets of extrusion frustums (41, 42, 43); the outer surface of the hexagonal liner (3) is provided with an axial pre-groove (31) along the hexagonal edge; the three sets of extrusion frustums (41, 42, 43) are gradient cone angle structures, and the diameter of the large end increases sequentially along the rear end direction of the anchor rod body (1); the outer diameter of the three sets of cylindrical friction tables (51, 52, 53) is consistent with the diameter of the large end of the corresponding extrusion frustums (41, 42, 43), the inner hole is provided with a spline groove that matches the rectangular spline (11), and the outer cylindrical surface is provided with a laser textured pit array (54); the elastic claw (6) is evenly distributed with claw pieces (61) in the circumference.

2. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The rear end face of the first extrusion platform (41) is in close contact with the front end face of the first cylindrical friction platform (51), the rear end face of the first cylindrical friction platform (51) is in close contact with the front end face of the second extrusion platform (42), the rear end face of the second extrusion platform (42) is in close contact with the front end face of the second cylindrical friction platform (52), the rear end face of the second cylindrical friction platform (52) is in close contact with the front end face of the third extrusion platform (43), and the rear end face of the third extrusion platform (43) is in close contact with the front end face of the third cylindrical friction platform (53), with no axial gap.

3. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The anchor body (1) is made of 40Cr alloy steel, and the rectangular spline (11) has a module of 2, a number of teeth of 6, a spline groove depth of 2mm and a width of 4mm.

4. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The sleeve (2) is made of Q690 low alloy high strength steel, with an inner diameter of φ50mm and a wall thickness of 5mm. The inner wall is treated with gas nitriding, and the nitriding depth is 0.3mm.

5. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The hexagonal liner (3) is a bimetallic composite structure, with an inner layer of Q235 low carbon steel core tube and an outer layer of H62 copper alloy. The axial pre-groove (31) has a depth of 1.5 mm, a width of 2 mm, and a quantity of 6 grooves.

6. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The three extrusion frustums (41, 42, 43) are all made of 42CrMo alloy steel. The first extrusion frustum (41) has a cone angle of 45°, the second extrusion frustum (42) has a cone angle of 37°, and the third extrusion frustum (43) has a cone angle of 30°. The length of each frustum is 13mm, and the diameter of the large end is φ45mm, φ47.5mm, and φ49mm, respectively.

7. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The three sets of cylindrical friction tables (51, 52, 53) are all made of 42CrMo alloy steel, and each has a length of 13mm. The outer cylindrical surface is also coated with a 2μm thick DLC coating. The laser textured pit array (54) has a pit diameter of 50μm, a depth of 10μm, and a spacing of 100μm.

8. The multi-stage extrusion anchor bolt with a gapless cylindrical friction table according to claim 1, characterized in that, The elastic claw (6) is made of 65Mn spring steel with an outer diameter of φ49mm. The claw piece (61) is 8mm long and 1mm thick. After pre-compression, the gap between it and the anchor rod body (1) is ≤0.1mm.

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