A roadway negative Poisson's ratio gradient energy absorption support device

Abstract

The present invention relates to the field of roadway surrounding rock support in underground engineering, and specifically relates to a roadway negative Poisson's ratio gradient energy absorption support device, which includes a negative Poisson's ratio gradient energy absorption structure. Compared with the conventional chiral negative Poisson's ratio structure, the deformation regularity and controllability are enhanced. Considering the special working conditions of coal mines, the shape of the connecting rod member is changed, and the connecting rod member is a double-helix connecting rod member. Moreover, compared with the traditional hexagonal honeycomb structure, the defect that the honeycomb structure fails too quickly after being compressed is overcome. At the same time, the deformation advantage of the concave shape and the rigid advantage of the chiral circular node are combined. The present invention can adopt gradient design in both two-dimensional and three-dimensional structures. Through the non-uniform distribution of spatial parameters, the bottleneck of the traditional structure in energy absorption efficiency and environmental adaptability is broken through. It is especially suitable for the non-uniform load scenario of coal mine underground engineering, can intensively enhance the strength of a certain area, change the deformation mode of the structure, and enable the structure to be customized according to the requirements of different application scenarios.

Description

Technical Field

[0001] The present invention relates to the field of roadway surrounding rock support in underground engineering, and particularly to a roadway negative Poisson's ratio gradient energy-absorbing support device. Background Art

[0002] The geological conditions of coal mine roadways are complex, and the surrounding rock stress has a gradient distribution. Traditional static support structures are difficult to match the gradient distribution of surrounding rock stress, resulting in an increased risk of roof collapse; in the prior art, some patent applications for roadway support using negative Poisson's ratio structures have been disclosed, such as: Chinese patents CN206972264U, CN118934015A, etc. However, in these patents, the existing negative Poisson's ratio structures are directly used without improvement, and the existing negative Poisson's ratio structures have the following problems:

[0003] 1. After the single cells are connected by ligaments, some form triangular concave structures, some form quadrilateral concave structures, and some form concave structures of other shapes. However, these concave structures only emphasize periodic arrangement but do not solve the problem of uncontrollable deformation. Under non-uniform stress, the triangular concave structure will also undergo non-uniform deformation locally, resulting in stress concentration and premature failure of the structure; while the traditional concave structure formed by four ligaments can only generate negative Poisson's ratio deformation under unidirectional stress, and it is prone to instability under stress in the other direction, and is not suitable for complex coal mine stress environments or other complex stress environments.

[0004] 2. Adjacent energy-absorbing layers are connected by cylindrical connecting rods; such cylindrical straight rods are prone to overall instability, and the load transfer is single. Only axial loads can be transferred in one rod direction, making it difficult to effectively resist multi-directional impacts (such as roof pressure and lateral rock bursts), and it is prone to fracture under complex load conditions. The traditional straight rod shape can only dissipate energy through simple twisting and axial compression deformation under impact, and the proportion of plastic deformation energy is relatively low. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present invention discloses a roadway negative Poisson's ratio gradient energy-absorbing support device, which can produce a negative Poisson's ratio effect without instability and can be applied to complex stress environments.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a roadway negative Poisson's ratio gradient energy-absorbing support device, including a support bracket, and a negative Poisson's ratio gradient energy-absorbing structure is provided on the outer surface of the support bracket. The negative Poisson's ratio gradient energy-absorbing structure includes a plurality of energy-absorbing layers and connecting rod members stacked in sequence;

[0008] The energy absorption layer described above includes a number of four-chiral structural unit cells. Each four-chiral structural unit cell includes a circular node and four ligaments arranged in sequence along the circumferential direction of the circular node. Each ligament extends out tangentially from the circular node, and adjacent four-chiral structural unit cells are connected by ligaments, forming a star-shaped concave structure.

[0009] The two circular nodes corresponding to adjacent energy absorption layers are at an angle of 180 degrees to each other. Adjacent energy absorption layers are connected by four connecting rods. The axis of the connecting rod forms an inclination angle with the normal direction of the energy absorption layer, and each group of connecting rods is axially symmetrically distributed on the horizontal projection plane.

[0010] As a further technical solution, the connecting rod is a double-helix connecting rod, which is composed of two spiral metal rods with opposite helix directions and is compounded by a prestressed winding process.

[0011] As a further technical solution, the pitch P of the double-helix connecting rod and the diameter d of the double-helix connecting rod satisfy the relationship: 2d ≤ P ≤ 8d, and the helix angle β of the double-helix connecting rod is controlled within the range of 20° - 60°.

[0012] As a further technical solution, a connecting hole is provided on the circular node, and a conical connecting head is provided at the end of the double-helix connecting rod. The conical connecting head is inserted into the connecting hole.

[0013] As a further technical solution, among several layers of energy absorption layers, the diameter of the circular nodes of the four-chiral structural unit cells in the upper energy absorption layer and the lower energy absorption layer is greater than the diameter of the circular nodes of the four-chiral structural unit cells in the middle layer;

[0014] Or the diameter of the circular nodes of the four-chiral structural unit cells in the upper energy absorption layer and the lower energy absorption layer is less than the diameter of the circular nodes of the four-chiral structural unit cells in the middle layer.

[0015] Or the diameter of the circular nodes of the four-chiral structural unit cells in the energy absorption layer gradually decreases from top to bottom;

[0016] Or the diameter of the circular nodes of the four-chiral structural unit cells in the energy absorption layer gradually increases from top to bottom.

[0017] Or the diameters of all the circular nodes of the four-chiral structural unit cells in the energy absorption layer from top to bottom are equal.

[0018] As a further technical solution, among several layers of energy absorption layers, the thicknesses of the circular nodes of different energy absorption layers are equal or unequal.

[0019] As a further technical solution, among several layers of energy absorption layers, a connecting hole is provided on the circular node, and a clamping column is provided at the end of the connecting rod. The clamping column is inserted into the connecting hole.

[0020] As a further technical solution, among the several energy-absorbing layers, the energy-absorbing layer and the connecting rod member are made of a metal matrix composite material, wherein the elastic modulus E of the energy-absorbing layer material 1 and the elastic modulus E of the connecting rod member material 2 satisfy the relational expression: 0.2 ≤ E 1 / E 2 ≤ 5, ensuring that the high modulus region bears the main load and the low modulus region dissipates the remaining energy; and the yield strength of the energy-absorbing layer material is greater than or equal to 80% of the connecting rod member material.

[0021] As a further technical solution, among the several energy-absorbing layers, the energy-absorbing layer and the rod of the structure can use materials with different strengths.

[0022] As a further technical solution, the top of the support bracket uses a corrugated steel beam.

[0023] The beneficial effects of the present invention are as follows:

[0024] The roadway negative Poisson's ratio gradient energy-absorbing support device proposed by the present invention can customize the gradient according to the stress field distribution under non-uniform loads in coal mines (for example, a small diameter and thick wall in the central area to resist high pressure, and a large diameter and thin wall in the edge area to adapt to the deformation of the surrounding rock), reducing the risk of local buckling. And the adjacent four chiral structure unit cells of the negative Poisson's ratio gradient energy-absorbing structure are connected by ligaments and form a star-shaped concave structure. When the star-shaped concave planar geometric configuration is subjected to a single-directional force (for example, a vertical force), the ligament pulls the circular ring node tangentially, triggering a transverse contraction (negative Poisson's ratio effect), and the stress concentrates and is evenly distributed in the stress-bearing area, avoiding local stress concentration. Compared with the traditional four chiral concave structures, the star-shaped concave structure can generate negative Poisson's ratio effects in both horizontal and vertical directions without instability. The gradient design further optimizes the deformation and force transmission paths: changing the diameters of the large and small rings to achieve hierarchical energy absorption and deformation adaptation, and changing the thickness to achieve the regional matching of the support effect and energy dissipation.

[0025] 2. The present invention designs the connecting rod member into a double-helix connecting rod member, which is composed of two spiral metal rods with opposite helix directions and is compounded by a prestressed winding process; it overcomes the problems of easy overall instability, single load transmission, and low plastic deformation ability of the traditional straight rod structure; the geometric characteristics of the spiral rod enhance the bending and torsional stiffness, and the critical buckling load is higher than that of the traditional straight rod. At the same time, more energy can be dissipated through plastic torsional deformation. The use of the double-helix rod effectively improves the stability of the structure under multi-directional surrounding rock loads and rock bursts, and the proportion of plastic deformation energy increases significantly. The rod can cooperate with the energy-absorbing layer to dissipate energy in stages through torsional deformation. Description of the Drawings

[0026] Figure 1Schematic diagram of the combined state of the four-chirality structure unit cell, connecting rod member, and embedded clamping structure disclosed in Example 1;

[0027] Figure 2 Schematic diagram of two four-chirality structure unit cells disclosed in Example 1;

[0028] Figure 3 Schematic diagram of a single four-chirality structure unit cell disclosed in Example 1;

[0029] Figure 4 Schematic diagram of the combined state of the four-chirality structure unit cell, connecting rod member, and embedded clamping structure disclosed in Example 1;

[0030] Figure 5 Top view of the roadway negative Poisson's ratio gradient energy-absorbing support device disclosed in Example 1;

[0031] Figure 6 Side view of the roadway negative Poisson's ratio gradient energy-absorbing support device disclosed in Example 1;

[0032] Figure 7 Three-dimensional structure schematic diagram of the roadway negative Poisson's ratio gradient energy-absorbing support device disclosed in Example 1;

[0033] Figure 8 Schematic diagram of the combined state of the four-chirality structure unit cell, connecting rod member, and embedded clamping structure disclosed in Example 2 Figure 1 ;

[0034] Figure 9 Schematic diagram of the combined state of the four-chirality structure unit cell, connecting rod member, and embedded clamping structure disclosed in Example 2 Figure 2 ;

[0035] Figure 10 Schematic diagram of the combined state of the four-chirality structure unit cell, connecting rod member, and embedded clamping structure disclosed in Example 2 Figure 3 ;

[0036] Figure 11 Three-dimensional schematic diagram of the negative Poisson's ratio gradient structure disclosed in Example 2;

[0037] Figure 12 Two-dimensional schematic diagram of the negative Poisson's ratio gradient structure disclosed in Example 2;

[0038] Figure 13 Schematic diagram of the uniform gradient negative Poisson's ratio structure formed in Example 1 or Example 2;

[0039] Figure 14 Schematic diagram of the positive gradient negative Poisson's ratio structure formed in Example 1 or Example 2;

[0040] Figure 15 Schematic diagram of the negative Poisson's ratio structure with a negative gradient formed in Example 1 or Example 2;

[0041] Figure 16 Schematic diagram of the negative Poisson's ratio structure with a central positive gradient formed in Example 1 or Example 2;

[0042] Figure 17 Schematic diagram of the negative Poisson's ratio structure with a central negative gradient formed in Example 1 or Example 2;

[0043] Figure 18 Schematic diagram of the application state of the negative Poisson's ratio gradient structure in the underground engineering support device in Example 1 or Example 2 Figure 1 ;

[0044] Figure 19 Schematic diagram of the application state of the negative Poisson's ratio gradient structure in the underground engineering support device in Example 1 or Example 2 Figure 2 ;

[0045] In the figure: 1. Tetra-chiral structure unit cell; 1-1. Circular node; 1-2. Ligament; 2. Cylindrical connecting rod member; 3. Embedded clamping structure; 4. Double-helix connecting rod member; 5. Steel support. Detailed implementation manners

[0046] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0047] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the present invention clearly states otherwise, the singular forms are also intended to include the plural forms. In addition, 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;

[0048] Example 1

[0049] This example discloses a roadway negative Poisson's ratio gradient energy-absorbing support device. When the roadway negative Poisson's ratio gradient energy-absorbing support device is stretched, the dimension in the vertical direction increases instead, and it has the negative Poisson's ratio effect. The specific structure is as follows:

[0050] The roadway negative Poisson's ratio gradient energy absorption support device includes a support bracket, and a negative Poisson's ratio gradient energy absorption structure is arranged on the outer surface of the support bracket. The negative Poisson's ratio gradient energy absorption structure includes a plurality of energy absorption layers stacked in sequence. Adjacent energy absorption layers are connected to form a three-dimensional structure, and the three-dimensional structure forms an adjustable network structure through a specific hole distribution and rigid unit layout; each energy absorption layer includes a plurality of tetra-chiral structure unit cells 1 arranged and combined to achieve the energy absorption effect.

[0051] As Figure 1 , Figure 2 , Figure 3 , Figure 4 shown, each tetra-chiral structure unit cell 1 includes a circular node 1-1 and four ligaments 1-2; each ligament 1-2 extends tangentially from the circular node 1-1. The geometric parameters of each unit cell are controlled by different variables, and each ligament 1-2 extends tangentially from the circular node 1-1.

[0052] As Figure 1 shown, the width of the circular node 1-1 and the ligaments 1-2 in the tetra-chiral structure unit cell 1 is b, the length of the ligament 1-2 is l, the thickness of the circular node 1-1 and the ligaments 1-2 is t, and the cross-section in the thickness direction of the unit cell can be square or circular.

[0053] Furthermore, in this embodiment, in the same energy absorption layer, adjacent tetra-chiral structure unit cells 1 are connected by ligaments 1-2 to form a star-shaped concave structure to enhance its mechanical properties; as Figure 13As shown, the star-shaped concave structure formed in this embodiment is an octagonal star-shaped concave structure. Specifically, four adjacent chiral quadruple structure unit cells 1 are adjacent to each other through ligaments 1-2. One ligament 1-2 of the chiral quadruple structure unit cell 1 in the upper left corner is connected to one ligament 1-2 of the chiral quadruple structure unit cell 1 in the upper right corner, and an obtuse angle is formed between the two ligaments; another ligament 1-2 of the chiral quadruple structure unit cell 1 in the upper left corner is connected to one ligament 1-2 of the chiral quadruple structure unit cell 1 in the lower left corner, and an obtuse angle is formed between the two ligaments; another ligament 1-2 of the chiral quadruple structure unit cell 1 in the lower left corner is connected to one ligament 1-2 of the chiral quadruple structure unit cell 1 in the lower right corner, and an obtuse angle is formed between the two ligaments; another ligament 1-2 of the chiral quadruple structure unit cell 1 in the lower right corner is connected to one ligament 1-2 of the chiral quadruple structure unit cell 1 in the upper right corner, and an obtuse angle is formed between the two ligaments; each chiral quadruple structure unit cell 1 is connected in the same way to form a star-shaped concave structure. Compared with traditional honeycomb structures of other shapes, this star-shaped concave structure has excellent impact resistance. It can produce lateral contraction when stressed vertically, causing the structure to effectively gather at the stressed part, which macroscopically shows an increase in regional density, significantly different from traditional structures. At the same time, compared with the positive Poisson's ratio honeycomb structure that undergoes crushing deformation under slight stress, this negative Poisson's ratio structure has an anti-indentation effect that can effectively resist the generation of indentations.

[0054] Furthermore, adjacent energy-absorbing layers are fixedly connected by four groups of cylindrically-shaped connecting rods 2 that are symmetrically distributed in space; the four cylindrically-shaped connecting rods 2 are all inclined in the chiral quadruple structure unit cell 1, with two of the cylindrically-shaped connecting rods 2 having a relatively large inclination angle and the other two having a relatively small inclination angle; that is, the axis of the cylindrically-shaped connecting rod 2 forms an adjustable inclination angle θ of 15°-75° with the normal direction of the energy-absorbing layer, and each group of cylindrically-shaped connecting rods 2 is axially symmetrically distributed on the horizontal projection plane; the inclination angle is determined according to the position of the round rod connector and the connection unit cell and the distance between the two surface layers. In the design, it is recommended to set the connection position of the connecting rod at the junction of the ligament and the ring, as this symmetrical layout is beneficial to enhancing the rotational effect of the connecting rod on the ligament. Because the ligaments are designed to form this concave star-shaped shape, the angles formed by the four ligaments and the ring are different, and the angles formed by each cylindrically-shaped connecting rod 2 after connecting the two surface layers will also be different.

[0055] Furthermore, the cylindrically-shaped connecting rod 2 in this embodiment is cylindrical, and of course, it can also be designed to be square.

[0056] Furthermore, the negative Poisson's ratio characteristic of the roadway negative Poisson's ratio gradient energy-absorbing support device is achieved through three-dimensional configuration design. The three-dimensional configuration follows the design rules of the two-dimensional configuration. At the same time, the two circular node 1-1 corresponding to each layer are 180 degrees apart from each other, and cylindrical connecting rods 2 are added between different energy-absorbing layers. The cylindrical connecting rod 2 forms an angle θ with the plane of the circular node 1-1.

[0057] Furthermore, the gradient of the above-mentioned roadway negative Poisson's ratio gradient energy-absorbing support device can also be designed; the roadway negative Poisson's ratio gradient energy-absorbing support device can be designed by setting the aperture diameter and thickness of the circular node 1-1 of each four-chiral structure unit cell 1, as follows:

[0058] Define the reference diameter of the central circular node 1-1 as D 0 , the size of the circular node 1-1 can be enlarged and reduced according to a certain multiple ratio to achieve different gradient arrangements; design different circular node diameters. At the part where the diameter increases, the section moment of inertia of the circular node can be increased to enhance the local bending and compressive resistance; at the part where the diameter decreases, the plastic deformation of the ligament is the main factor to adapt to the dynamic displacement of the surrounding rock. The gradient change of the circular ring diameter will change the pore distribution of the honeycomb structure. The small diameter (high density) in the central area enhances the bearing capacity, and the large diameter (low density) in the edge area improves the deformation adaptability. The small diameter area bears the load first and triggers plastic deformation, and the large diameter area absorbs the residual energy through elastic rebound to achieve hierarchical energy absorption.

[0059] By adjusting the printing layer number and layer thickness layer by layer through 3D printing, the linear decrease of the thickness of the circular node 1-1 from 1.6 mm at the center to 0.8 mm at the edge is realized to match the yield strength requirements of different regions. In this embodiment, the thickness gradient is designed. At the position where the thickness increases, the cross-sectional area of the material can be directly increased to enhance the anti-yield ability of the node, while the thin-walled area absorbs energy through elastoplastic deformation, and the thick-walled area bears the main load through high stiffness. The thick-walled area (such as t = 1.6 mm) is used for the high-pressure central area to provide high-strength support and can be used to resist high-speed impact loads such as rock bursts; the thin-walled area (such as t = 0.8 mm) is used for the edge area to dissipate energy through deformation. It can also be used to absorb low-frequency vibrations.

[0060] For the negative Poisson's ratio gradient structure, taking the aperture gradient setting as an example, the gradient design can be divided into three regions according to the position relationship of the circular node 1-1 from bottom to top. The diameters of the circular node 1-1 in each region satisfy:

[0061] The diameter D of the circular node 1-1 in area I (transition area) 1 =D 0 (1 - ΔD);

[0062] The diameter D of the circular node 1-1 in area II (central area) 2 =D0 ;

[0063] The diameter D of the circular node 1-1 in Zone Ⅲ (edge zone) 3 = D 0 (1 + ΔD);

[0064] where D 0 is the reference diameter of the circular node 1-1, and ΔD is the diameter difference of the circular node 1-1. The geometric parameter variation between adjacent unit cells

[0065] is between 15% - 25%, and the maximum does not exceed 30% of the previous-level unit.

[0066] The negative Poisson's ratio gradient structure can be divided into different arrangement orders such as uniform gradient, positive gradient, negative gradient, central positive gradient, and central negative gradient according to different partition arrangements. Among them, the negative Poisson's ratio structure with uniform gradient is as Figure 13 shown; in the several energy-absorbing layers described, the diameters and thicknesses of all the four-chirality structure unit cell circular nodes in the energy-absorbing layers from top to bottom are equal, constituting a negative Poisson's ratio structure with uniform gradient; the negative Poisson's ratio structure with positive gradient is as Figure 14 shown. In the several energy-absorbing layers described, the diameters of the four-chirality structure unit cell circular nodes in the energy-absorbing layers gradually decrease from top to bottom, and the thickness remains unchanged; the negative Poisson's ratio structure with negative gradient is as Figure 15 shown. In the several energy-absorbing layers described, the diameters of the four-chirality structure unit cell circular nodes in the energy-absorbing layers gradually increase from top to bottom, and the thickness remains unchanged; the negative Poisson's ratio structure with central positive gradient is as Figure 16 shown. The diameters of the four-chirality structure unit cell circular nodes in the upper and lower energy-absorbing layers are smaller than those in the middle layer, and the thickness remains unchanged; the negative Poisson's ratio structure with central negative gradient is as Figure 17 shown; in the several energy-absorbing layers described, the diameters of the four-chirality structure unit cell circular nodes in the upper and lower energy-absorbing layers are larger than those in the middle layer, and the thickness remains unchanged; among them, the central gradient means that in addition to being arranged according to the gradient, each layer forms a structure according to the relationship of central symmetry.

[0067] In the structure, the ligament 1-2 is responsible for pulling the circular node 1-1 to move through deformation, and the circular node 1-1 is responsible for connecting each layer of rods and ensuring the overall stability of the structure; uniform structures (such as honeycombs and metallic foams) are prone to local stress concentration under impact loads, leading to premature failure. For example, due to the multi-stable rebound characteristics of traditional negative stiffness structures, the energy absorption efficiency is only 50% - 70% of that of gradient structures. At the same time, the geological conditions of coal mine roadways are complex, and the surrounding rock stress also has a gradient distribution. Traditional static support structures are difficult to match the gradient distribution of the surrounding rock stress, resulting in an increased risk of roof collapse. After designing different gradients, different gradient designs can be used according to different structures and loading conditions.

[0068] By changing the structural impedance through gradient aperture or thickness, the reflection-transmission coordinated dissipation of stress waves is achieved, and the non-uniform stress field of coal mine tunnels (such as high stress areas in the center and low stress areas at the edges) is matched, so that the structure can reasonably share stress, reduce stress peaks, and reduce local buckling. In the coal mine support energy absorption layer, the diameter of the transition zone ring node 1-1 is reduced by 15%-25% to withstand high pressure, and the diameter of the edge zone is increased to release deformation.

[0069] The energy absorbing layer and the cylindrical connecting rod 2 are made of metal matrix composite materials, wherein the elastic modulus E of the energy absorbing layer material is 1 The elastic modulus E of the connecting rod material 2 Satisfy the relationship: 0.2≤E 1 / E 2 ≤5, ensuring that the high modulus area bears the main load and the low modulus area dissipates the residual energy. And the yield strength of the energy absorption layer material is not less than 80% of the material of the cylindrical connecting rod 2. The energy absorption layer and the connecting rod of the structure can be made of materials of different strengths, such as aluminum alloy or fiber reinforced composite material for the energy absorption layer, and stainless steel for the rod, to ensure that the structure will not produce compression deformation when the load is small; when subjected to impact, it can effectively transfer the load and guide the deformation of the energy absorption layer.

[0070] Furthermore, the manufacturing method of the negative Poisson's ratio gradient structure is to manufacture the negative Poisson's ratio gradient structure by 3D printing or mold casting, as follows:

[0071] When the 3D printing method is used for manufacturing, the energy absorbing layer is printed first, and then the energy absorbing layer is stacked by manufacturing connecting rods and connecting and assembling the embedded clamping structure 3 to form an overall negative Poisson's ratio gradient structure.

[0072] The structure can be modularly assembled to form different structures; when cylindrical or square connecting rods are used, each ring node 1-1 is connected between adjacent modules through an embedded snap-fit ​​structure 3, which is provided with four spiral holes, and the embedded snap-fit ​​structure 3 can be connected by bolts or welding.

[0073] like Figure 18 , Figure 19 As shown, the gradient negative Poisson's ratio structure is used in the trapezoidal cross-section anti-impact corrugated steel support 5, and the top is combined with a corrugated steel beam to form a new type of honeycomb-like composite sandwich structure; the small-aperture thick-walled circular ring node 1-1 (D=9.6mm, t=1.6mm) is used in the central area of ​​the tunnel to resist the high pressure of the roof, and the large-aperture thin-walled structure (D=14.4mm, t=0.8mm) in the edge area is adapted to the deformation of the surrounding rock and reduce the amount of maintenance.

[0074] Under the impact of surrounding rock, the upper honeycomb panel can quickly absorb the impact energy and deform and yield stably. At the same time, the overall structure of the upper panel converges inward, enhancing the shear buckling bearing capacity and flexural stability of the structure, and avoiding the instability and collapse of the lower bracket.

[0075] Embodiment 2

[0076] This embodiment discloses another roadway negative Poisson's ratio gradient energy-absorbing support device. The main difference between this roadway negative Poisson's ratio gradient energy-absorbing support device and that of Embodiment 1 lies in the different shape of the connecting member. As Figure 8 、 Figure 9 、 Figure 10 shown, in this embodiment, the connecting member is designed as a double-helix connecting member 4. The double-helix connecting member 4 in this embodiment is composed of two spiral metal rods with opposite helix directions compounded by a prestressed winding process. The pitch P of the double-helix connecting member 4 and the diameter d of the double-helix connecting member 4 satisfy the relational expression: 2d ≤ P ≤ 8d, and the helix angle β is controlled within the range of 20° - 60°; the double-helix connecting member 4 is used to replace the original cylindrical connecting member 2, and the connecting inclination direction and the connection sequence between the layers remain unchanged. This embodiment only changes the shape of the connecting member.

[0077] When the double-helix connecting member 4 is adopted, tapered connection heads can be arranged at both ends to be matched and fitted with the quadrilateral connection holes at the central nodes of the gradient chiral unit cells on the energy-absorbing layer. The taper angle of the tapered head is designed to be 5° - 15° to ensure radial compressive stress is generated during prestressed assembly and enhance the friction of the contact surface. The assembly gap is controlled within 0.02 - 0.05 mm, which not only ensures smooth assembly but also avoids loosening. For the specific structure after connection, see Figure 11 、 Figure 12 .

[0078] Furthermore, the cylindrical connecting rod 2 in Embodiment 1 can only transmit axial loads. However, in coal mine support, it is often necessary to resist multi-directional impacts (such as roof pressure and lateral rock bursts). The straight rod structure is prone to overall instability, and the critical buckling load is lower than that of the double-helical rod. Compared with the cylindrical connecting rod 2 in Embodiment 1, the double-helical connecting rod member 4 preferentially generates controllable torsional deformation under axial compression, guiding the rod to undergo torsional deformation rather than fracture under impact loads, increasing the proportion of plastic deformation energy. At the same time, it better guides the rotation of the chiral unit cells, significantly enhancing the lateral impact resistance of the structure. That is: in this embodiment, the connecting rod member is designed as the double-helical connecting rod member 4, which is composed of two helical metal rods with opposite helix directions compounded by a prestressed winding process, overcoming the problems of easy overall instability, single load transmission, and low plastic deformation ability of the traditional straight rod structure; the geometric characteristics of the helical rod enhance the bending and torsional stiffness, and the critical buckling load is higher than that of the traditional straight rod. At the same time, more energy can be dissipated through plastic torsional deformation. The use of the double-helical rod member effectively improves the stability of the structure under multi-directional surrounding rock loads and rock bursts, the proportion of plastic deformation energy increases significantly, and the rod can cooperate with the energy absorption layer to dissipate energy in stages through torsional deformation.

[0079] The remaining structure of this embodiment is the same as that of Embodiment 1 and will not be elaborated here.

[0080] Furthermore, the structures disclosed in the above Embodiment 1 or Embodiment 2 can be applied not only to roadway support devices but also to various engineering fields such as sandwich composite plates and impact energy absorption devices, especially in the fields of energy absorption and deformation. In the anti-collision structure of mining equipment, the gradient pore size can trigger plastic deformation in stages: the small pore size area (pore diameter D < 10 mm) preferentially buckles to absorb high-energy impacts, and the large pore size area (pore diameter D > 15 mm) dissipates residual energy through elastic rebound. The pore size gradient is designed in coordination with the helix angle (β = 20° - 60°), enabling the energy absorption frequency band to achieve a certain noise reduction and vibration absorption effect within the coal mine machinery vibration range (10 - 200 Hz).

[0081] In summary, the present invention provides a roadway negative Poisson's ratio gradient energy absorption support device, including two-dimensional and three-dimensional structural configurations. Compared with the conventional chiral negative Poisson's ratio structure, the two-dimensional structure of the present invention enhances the deformation regularity and controllability. Considering the special working conditions of coal mines, the connecting rod adopts the double-helical connecting rod member 4; compared with the traditional hexagonal honeycomb structure, it overcomes the defect of the honeycomb structure having too fast failure after compression; at the same time, it combines the deformation advantage of concavity and the rigid advantage of the chiral circular node. The present invention can adopt gradient design in both two-dimensional and three-dimensional structures. Through the non-uniform distribution of spatial parameters, it breaks through the bottleneck of the traditional structure in energy absorption efficiency and environmental adaptability, and is especially suitable for the non-uniform load scenarios of coal mine underground engineering. It can intensively enhance the strength of a certain area and change the deformation mode of the structure, enabling the structure to be customized according to the requirements of different application scenarios.

[0082] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A tunnel negative Poisson's ratio gradient energy absorption support device, characterized in that: It includes a support bracket, and a negative Poisson's ratio gradient energy absorption structure is arranged on the outer surface of the support bracket, and the negative Poisson's ratio gradient energy absorption structure includes a plurality of sequentially stacked energy absorption layers and connecting rods; The energy absorption layer includes a plurality of four-chirality structure unit cells, each of which includes a ring node and four ligaments arranged in sequence along the circumference of the ring node, each ligament extending from the tangent direction of the ring node, and adjacent four-chirality structure unit cells are connected by ligaments to form a star-shaped concave structure; Two ring nodes corresponding to adjacent energy absorbing layers are at an angle of 180 degrees to each other. Adjacent energy absorbing layers are connected by four connecting rods. The axes of the connecting rods form an inclined angle with the normal direction of the energy absorbing layer. Each group of connecting rods is axially symmetrically distributed on the horizontal projection plane. The negative Poisson's ratio gradient structure is divided into uniform gradient, positive gradient, negative gradient, central positive gradient and central negative gradient according to the different partition arrangements; among several energy absorbing layers, the thickness of the ring nodes of different energy absorbing layers is equal or unequal; The connecting rod is a double-helix connecting rod, which is formed by compounding two spiral metal rods with opposite rotation directions through a prestressed winding process.

2. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: The pitch P of the double helical connecting rod and the diameter d of the double helical connecting rod satisfy the relationship: 2d≤P≤8d, and the helix angle β of the double helical connecting rod is controlled within the range of 20°-60°.

3. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: A connecting hole is arranged on the ring node, and a conical connecting head is arranged at the end of the double-helix connecting rod, and the conical connecting head is inserted into the connecting hole.

4. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: Among the plurality of energy absorbing layers, the node diameters of the four-chiral structure unit cell rings in the upper energy absorbing layer and the lower energy absorbing layer are larger than the node diameters of the four-chiral structure unit cell rings in the middle layer; or the node diameters of the four-chiral structure unit cell rings in the upper energy absorbing layer and the lower energy absorbing layer are smaller than the node diameters of the four-chiral structure unit cell rings in the middle layer; Or the diameter of the ring nodes of the unit cell of the four-chiral structure in the energy-absorbing layer gradually decreases from top to bottom; Or the diameter of the ring nodes of the unit cell of the four-chiral structure in the energy-absorbing layer gradually increases from top to bottom; Or the diameters of all the four-chiral structure unit cell ring nodes in the energy absorbing layer from top to bottom are equal.

5. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: A connecting hole is arranged on the node of the ring, and a clamping column is arranged at the end of the connecting rod, and the clamping column is inserted into the connecting hole.

6. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: The energy absorbing layer and the connecting rod are made of metal-based composite materials, wherein the elastic modulus E1 of the energy absorbing layer material and the elastic modulus E2 of the connecting rod material satisfy the relationship: 0.2≤E1 / E2≤5, ensuring that the high modulus area bears the main load and the low modulus area dissipates the residual energy; and the yield strength of the energy absorbing layer material is greater than or equal to 80% of the connecting rod material.

7. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: The energy absorbing layer and the connecting rod are made of materials with different strengths.

8. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: The top of the support bracket is made of a corrugated steel beam.

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