Design method of multi-section energy-absorbing anchor rod of bamboo-like structure

Abstract

The invention discloses a design method of a multi-section energy-absorbing anchor rod of a bamboo-like structure, and relates to the technical field of bionic mechanical metamaterials. The anchor rod comprises an anchoring sleeve, an end cover, an outer sleeve, a pull rod, an energy absorption assembly and a pre-tightening assembly. The core innovation of the anchor rod is that the energy-absorbing body adopts a bionic multi-stage structural design, and the energy-absorbing performance of the anchor rod is improved through various energy-consuming mechanisms. The energy-absorbing body is composed of a multi-cell energy-absorbing pipe which adopts Voronoi cell elements in gradient distribution to develop bamboo-like structure section morphology, a mechanical gradient structure which is sparse inside and dense outside is formed in combination with an SLM forming process, and energy-absorbing sections with different wall thicknesses are arranged according to a bamboo joint shape. The overall energy absorption characteristic of the anchor rod is improved by applying five energy consumption mechanisms including the excellent energy absorption characteristic of the voronoi energy absorption pipe, step-by-step crushing of the bamboo joint type assembly, friction between crushing expansion of the energy absorption pipe and the cylinder wall, drawing friction of a preset conical structure of the pull rod on the inner side of the energy absorption assembly and plastic deformation of the rigid anchor rod. Compared with a traditional anchor rod, the energy absorption efficiency is improved, and the anti-impact stability is high.

Description

Technical Field

[0001] The present invention relates to a design method of an energy-absorbing bolt, specifically a design method of an energy-absorbing bolt with a bamboo-like structure and multiple energy dissipation mechanisms. Background Technique

[0002] Five main configurations are derived from the structural design of energy-absorbing bolts: friction energy dissipation type, plastic deformation type, energy absorber component type, multi-point anchoring coordination type, and constant group yielding type. Specifically: The Cone bolt dissipates energy by providing resistance through the friction between the tail cone and the anchoring agent; the Garford bolt dissipates energy by converting kinetic energy into heat through the friction between the bolt body and the anchor hoop; the NPR bolt improves the bolt's anti-impact, anti-shear, and energy absorption performance by applying the characteristic of lateral expansion during uniaxial tension of a negative Poisson's ratio structure (i.e., structural plastic deformation); the D-shaped bolt disperses energy impact through the coordinated action of multiple anchoring segments, and the J energy-release bolt combines the slip ability of the Cone bolt and the multi-point anchoring ability of the D-shaped bolt to improve the overall energy absorption efficiency by superimposing energy dissipation; the NPR constant resistance energy-absorbing bolt and the CRLD bolt achieve the "yielding" function through yield components or energy absorber components, allowing the surrounding rock to deform moderately while stably absorbing energy. However, the bolts with the above single energy dissipation mechanism have various disadvantages as follows: For the friction energy dissipation type bolt, under long-term high stress or impact load, the friction surface is easily worn, resulting in resistance attenuation, and the heat generated by friction may cause local temperature rise, affecting the performance of the anchoring agent. For the plastic deformation type bolt, under repeated impact loads, the material is prone to fatigue fracture. For the multi-point anchoring coordination type bolt, the multiple anchoring segments rely on precise installation and uniform load distribution. For the constant resistance yielding type bolt, the yield components are prone to cumulative damage after multiple impacts and need to be frequently replaced, resulting in high maintenance costs. For the energy absorber component type bolt, the repeated friction or deformation of its metal structure is prone to fatigue cracks, reducing the reliability of energy absorption.

[0003] To address the drawbacks of single-energy-absorbing mechanism energy-absorbing bolts, this patent designs a bionic multi-stage energy-absorbing bolt starting from the bionic design of the energy-absorbing component and the coordinated action of multiple energy-consuming mechanisms. First, the bamboo structure cross-section has a unique cell arrangement form (which can be represented as a Voronoi polycell structure). Similar structures disperse stress through multi-stage deformation, thereby reducing stress concentration and improving the fatigue strength under load. When the structure is crushed, the full folding of the bamboo-like structure can be used to enhance the energy dissipation characteristics. This biomechanical feature is very suitable for being introduced into the design of the energy-absorbing component of the energy-absorbing bolt. On the other hand, the bionic design inspiration of this patent comes from the multi-stage structure of bamboo. Its unique cell distribution arrangement makes its bending resistance, compressive resistance, and energy-absorbing characteristics show excellent performance. The core performance requirements of the energy-absorbing bolt focus on impact toughness, high energy absorption efficiency, and controllable large deformation ability, and the bionic superstructure of the bamboo structure provides an innovative direction for this. By adding multiple sections of bamboo-like structures, the performance of the bolt can be optimized. At the same time, the bamboo-like structure energy-absorbing component is placed inside the cylinder structure, and energy is dissipated by the crushing and expansion of the energy-absorbing component and the friction with the cylinder wall. There is a cone at the end of the tie rod. After the bamboo-like structure section is compacted, the cone generates extrusion friction energy consumption by pulling and rubbing inside the section. After these energy-consuming mechanisms are completed, energy is absorbed by the tensile energy absorption of the tie rod. In this way, a multiple energy-absorbing mechanism of the bamboo-like structure energy-absorbing bolt is realized. Summary of the Invention

[0004] The object of the present invention is to design a multi-section energy-absorbing bolt design method with a bamboo-like structure. A multi-cell energy-absorbing tube component with a bamboo-like structure cross-section morphology is designed by using gradient-distributed Voronoi cells. By regulating the gradient and quantity of Voronoi cells inside the bamboo-like structure cross-section morphology, multi-stage deformation is used to disperse stress, thereby reducing stress concentration and improving the fatigue strength under load. At the same time, according to the arrangement characteristics of the bamboo node structure, the layout form of multi-section energy-absorbing components with different wall thicknesses is designed. Facing the changes in rock bursts, the thinner energy-absorbing sections are crushed and even compacted first. For different impact loads, there are corresponding energy-absorbing tubes being crushed, which can achieve more efficient and stable energy absorption, thereby optimizing the performance of the bolt. During the crushing process, since the bamboo-like structure energy-absorbing body component is placed inside the cylinder structure, the crushed and expanded energy-absorbing body contacts the stable sleeve of the energy-absorbing structure, generating extrusion friction for energy dissipation. Even after all sections are compacted, through the conical nut installed at the tail of the energy-absorbing rod, extrusion friction energy consumption can still be generated by pulling and rubbing on the inner side of the energy-absorbing section. After the above energy-consuming mechanisms act, the tensile plastic deformation of the rigid bolt continues to provide the anchoring energy absorption function. Through the above multi-stage energy dissipation mechanism, the impact resistance and energy absorption performance of the bolt are improved.

[0005] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] A design method for a multi-segment energy-absorbing bolt with a bamboo-like structure, characterized in that it includes an anchoring sleeve housing, an anchoring end closing cover, a bolt main body tension rod, an anchor head end sleeve, an energy-absorbing body, and pads, pre-tightening nuts, tapered nuts and gaskets installed at the ports;

[0007] The anchoring sleeve housing is sleeved on the anchoring end of the bolt main body tension rod, and together with the anchoring end closing cover, forms a sealed cavity to prevent gravel or soil from entering the interior; the anchoring end of the bolt is inserted into the roadway wall, and the other end passes through the anchor head end sleeve and the energy-absorbing body assembly, and is threadedly connected to the pre-tightening nut and the tapered nut; an energy-absorbing body assembly is installed on the tension rod inside the anchoring end, and the energy-absorbing body assembly is installed in a bamboo joint-like manner through the energy-absorbing body and the pad, and is fixed by the pre-tightening nut, the tapered nut and the gasket; the pre-tightening nut applies a pre-tightening force to limit the outer end of the energy-absorbing bolt, so that the components arranged at the outer end of the energy-absorbing bolt are restricted on the anchor head end sleeve; one end of the anchor head end sleeve has a through hole for fixing on the roadway wall; when rock burst occurs, the rod body is subjected to the tensile force generated by the rock burst squeezing the surrounding rock, and axially slides relative to the anchoring sleeve to absorb the kinetic energy generated by the rock burst; when the rod body slides relative to the sleeve, the energy-absorbing device begins to be squeezed by the pad to absorb the kinetic energy generated by the rock burst; the energy-absorbing device is composed of a multi-cell energy-absorbing tube with a bamboo-like structure cross-section morphology developed by using gradient-distributed Voronoi cells, and is installed inside the anchoring end and the anchor head end in the form of multi-segment energy-absorbing components with different wall thicknesses. The wall thickness of the cell is 0.15 - 0.6 mm, and the cell size changes in a gradient manner, with the cell size near the rod body being larger than that of the outside.

[0008] The energy-absorbing multi-cell tube is made of 316L stainless steel, and the bamboo-like structure multi-cell energy-absorbing tube is integrally manufactured by 3D printing.

[0009] Compared with the prior art, the advantages of the design method for a multi-segment energy-absorbing bolt with a bamboo-like structure of the present invention are as follows: 1. The energy absorption efficiency is improved. The voronoi gradient multi-cell structure shows excellent performance in bending resistance, compressive resistance and energy absorption characteristics through a hierarchical deformation mechanism, and the energy absorption density is significantly improved compared with the traditional thin-walled structure. 2. The energy dissipation is stable and the energy absorption process is evenly dispersed. The multi-segment design with different wall thicknesses enables the bolt to be gradually compacted in multiple segments when facing changes in rock burst. 3. The deformation mode is controllable. The gradient design guides the deformation to expand from the inside to the outside. The energy-absorbing body is crushed and expanded to squeeze the sleeve. Even after all segments are compacted, the tapered nut at the end of the tension rod can still generate extrusion friction energy consumption by pulling and rubbing on the inner side of the energy-absorbing tube, and the rigid tension rod stretching deformation continues to provide the anchoring energy absorption function. 4. Good environmental adaptability. 316L stainless steel is resistant to the corrosion environment in the mine, and the structure can still effectively absorb energy under small-amplitude axial deviation impacts. Description of the Drawings

[0010] Figure 1 It is a cross-sectional view of the energy-absorbing bolt of the present invention.

[0011] Figure 2 External energy absorption component diagram.

[0012] Figure 3 Internal energy absorption component diagram of the anchor.

[0013] Figure 4 It is a cross-sectional view of the energy absorbers of each part of the energy absorption component of the energy absorption anchor bolt.

[0015] The labels in the figure are:

[0016] 1 Pre-tightening nut 2 Tapered nut 3 Gasket 4 Backing plate 5 Energy absorber 6 Anchor head end sleeve 7 Tie rod 8 Anchoring sleeve 9 Anchoring end closure cap Ⅰ Internal energy absorption component of the anchor Ⅱ External energy absorption component Specific implementation mode

[0017] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. In this embodiment, the energy absorption anchor bolt adopts a multi-cell energy absorption tube assembly with a multi-cell structure cross-section morphology of Voronoi cells distributed in a multi-stage gradient as the core energy absorption unit. Through the synergistic action of gradient structure design, multi-stage energy dissipation mechanism and mechanical metamaterial characteristics, multi-stage dissipation of impact energy and uniform stress distribution are achieved.

[0018] As Figure 1 , 2 As shown in Figures 2 and 3, the energy absorption anchor bolt is composed of the following components: The tie rod (7) of the anchor bolt body is made of high-strength alloy steel, runs through the whole length of the anchor bolt, and threads are provided on the surfaces at both ends for connecting the pre-tightening nut (1), tapered nut (2), and gasket (3). The anchoring sleeve (8) is fixed to the formation in cooperation with cement mortar, etc., sleeved on the anchoring end of the tie rod (7), and a sealed cavity is formed on the outside through the anchoring end closure cap (9). The energy absorber assembly is divided into an internal energy absorber assembly (Ⅰ) and an external energy absorber assembly (Ⅱ), and both energy absorber assemblies are composed of an energy absorber (5) and a backing plate (4). The energy absorber (5) is composed of a multi-cell energy absorption tube with a multi-cell structure cross-section morphology of Voronoi cells distributed in a gradient. The multi-cell tubes are isolated by the backing plate (4), sleeved in the anchor head end sleeve (6) and the anchoring sleeve (8), and arranged in the form of a multi-stage energy absorption component with different wall thicknesses and different cell sizes in a gradient. The backing plate (4) has holes for clearance fit with the tie rod (7), and the outside of the backing plate (4) has a clearance fit with the sleeves (6, 8). The structural energy absorption assembly applies an initial pre-tightening force through the nuts (1, 2) and the gasket (3). The external energy absorption assembly (Ⅱ) is close to the anchor head end sleeve (6), and the internal energy absorption assembly (Ⅰ) is fixed inside the anchoring sleeve (8).

[0019] As Figure 4, as shown in Table 1, Table 1 is the structural parameter table of the energy absorber, including the number of Voronoi seed points, gradient, and structural wall thickness. The multi-cell energy-absorbing tube with a bamboo-like structure cross-sectional morphology developed using gradient-distributed Voronoi cells is designed according to the following parameters: The cells are generated by randomly distributing seed points to generate a Voronoi diagram, and the seed point density changes along the radial gradient (the distance between the seed points from the center of the anchor rod to the outer wall decreases) to form a non-uniform distribution of large inner cells and small outer cells. The energy absorber (5) is formed by 3D printing with 316L stainless steel. When rock bursts occur, the deformation of the surrounding rock forces the tie rod (7) to axially slide relative to the anchor sleeve (8), driving the backing plate (4) to squeeze the energy absorber (5). During the complete crushing process of the energy absorber (5), elastic buckling occurs in the inner cells and plastic collapse occurs in the outer layer. At the same time, due to the multi-segment form arrangement of different wall thicknesses in the energy-absorbing group, the crushing process shows step-by-step compaction, and for different impact loads, there are corresponding energy-absorbing tube crushings to achieve more efficient and stable energy absorption. During this period, the crushed and expanded energy absorber (5) will contact the energy-absorbing structure stabilizing sleeves (6, 8), generating extrusion friction and producing a tube expansion effect. Then, after all segments are compacted, it is still possible to generate extrusion friction energy consumption through the conical nut (2) at the end of the tie rod (7) by pulling and rubbing inside the energy absorber (5). After the above energy-consuming mechanisms take effect, the rigid tie rod (7) undergoes overall tensile plastic deformation and continues to provide the function of anchoring and energy absorption. These five energy-absorbing mechanisms achieve the step-by-step dissipation and uniform transfer of impact energy, improving the impact resistance and fatigue resistance of the anchor bolt.

[0020] The above embodiments are only specific examples for further detailed description of the purpose, technical solutions, and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the scope of the disclosure of the present invention are included in the protection scope of the present invention.

[0021] Energy absorber 1 Energy absorber 2 Energy absorber 3 Energy absorber 4 Energy absorber 5 Energy absorber 6 Number of seed points 80 120 160 120 120 120 Gradient (n) 2 2 2 0 1 3 Thickness value (mm) 0.248 0.212 0.187 0.186 0.199 0.216

[0022] Table 1 Structural parameters of the energy absorber.

Claims

1. A design method for a multi-segment energy-absorbing anchor rod with a bamboo-like structure, characterized in that: Design a Voronoi polycell energy absorber with a gradient distribution. The energy absorber forms a multi-level cell structure through a bamboo-section-like cross-sectional morphology, where the cell size varies radially in a gradient manner, with the internal cell size being larger than the external one, and the cell wall thickness being 0.15 - 0.6 mm. Arrange the energy-absorbing tubes in a bamboo-joint-like manner into a multi-segment energy-absorbing assembly. Each segment of the energy absorber has a different wall thickness and is installed in the two end sleeves. Set tapered nuts at both ends of the tie rod of the anchor rod body, and apply a pre-tightening force through the pre-tightening nuts and washers to fix the energy-absorbing assembly and the backing plate in the sleeve. Through the gradual crushing of the energy-absorbing pipe fittings in the energy-absorbing assembly, the crushing and expansion of the energy absorber, the friction between the energy absorber and the sleeve, the pulling and friction of the tapered nut after compaction, and the plastic deformation of the rigid tie rod, multi-level energy dissipation is achieved.

2. The design method of a multi-segment energy-absorbing anchor rod with a bamboo-like structure according to claim 1, characterized in that: The generation of the Voronoi polycell energy-absorbing tube cells is based on the random distribution of seed points, and the density of the seed points varies radially in a gradient manner. The distance between the seed points decreases from the inside to the outside, forming a non-uniform distribution structure with the cell size gradually decreasing from the inside to the outside, and controlling the outward expansion of the structural crushing.

3. The design method of a multi-segment energy-absorbing anchor rod with a bamboo-like structure according to claim 1, characterized in that: The gradient cell structure of the energy absorber realizes multi-level deformation, disperses stress, reduces stress concentration, and improves the fatigue strength under load by regulating the number and gradient distribution of the seed points.

4. A design method for a multi-segment energy-absorbing anchor rod with a bamboo-like structure according to claim 1, characterized in that: The multi-segment energy-absorbing assembly is separated by the backing plate and arranged in the sleeve in the form of a multi-segment energy-absorbing assembly with different wall thicknesses and different cell size gradients. When the energy absorber crushes and expands, it contacts the inner wall of the sleeve to generate frictional energy dissipation.

5. A design method for a multi-segment energy-absorbing anchor rod with a bamboo-like structure according to claim 1, characterized in that: The anchor rod tie rod is made of high-strength alloy steel, with threads provided at both ends to connect the pre-tightening nuts and the tapered nuts. After the energy absorber is compacted, the tapered nut pulls and frictions on the inner wall of the energy absorber to dissipate energy, and at the same time, the rigid tie rod generates plastic deformation to dissipate energy.

6. The design method of a multi-segment energy-absorbing anchor rod with a bamboo-like structure according to claim 1, characterized in that: The energy absorber is made of 316L stainless steel material and is integrally formed by the selective laser melting (SLM) 3D printing process.

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