Roadway negative Poisson's ratio gradient energy absorption supporting device

Abstract

The invention relates to the field of roadway surrounding rock supporting in underground engineering, in particular to a roadway negative Poisson's ratio gradient energy-absorbing supporting device which comprises a negative Poisson's ratio gradient energy-absorbing structure, compared with a conventional chiral negative Poisson's ratio structure, deformation regularity and controllability are enhanced, the shape of a connecting rod piece is changed in combination with the special working condition of a coal mine, and the supporting effect of the roadway negative Poisson's ratio gradient energy-absorbing supporting device is improved. The connecting rod piece is a double-spiral connecting rod piece; compared with a traditional hexagonal honeycomb structure, the defect that the honeycomb structure is too fast in failure after being pressed is overcome; and meanwhile, the concave deformation advantage and the chiral ring node rigidity advantage are combined. Gradient design can be adopted in a two-dimensional structure and a three-dimensional structure, through non-uniform distribution of spatial parameters, the bottleneck of a traditional structure in energy absorption efficiency and environmental adaptability is broken through, the structure is particularly suitable for a non-uniform load scene of coal mine underground engineering, the strength of a certain area can be intensively enhanced, the deformation mode of the structure can be changed, and the energy absorption efficiency is improved. And the structure can be customized according to different application scene requirements.

Description

Technical Field

[0001] The invention relates to the field of tunnel surrounding rock support in underground engineering, and in particular to a tunnel negative Poisson's ratio gradient energy absorption support device. Background Art

[0002] The geological conditions of coal mine tunnels are complex, and the surrounding rock stress has a gradient distribution. The traditional static support structure is difficult to match the surrounding rock stress gradient distribution, resulting in an increased risk of roof collapse. In the prior art, some patent applications for tunnel support using negative Poisson's ratio structures are disclosed, such as: Chinese patents CN206972264U, CN118934015A, etc. However, these patents directly use the existing negative Poisson's ratio structure without improving the negative Poisson's ratio structure. The existing negative Poisson's ratio structure has the following problems: 1. After the unit 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 the condition of non-uniform force, the triangular concave structure will also undergo non-uniform deformation locally, causing the structure to easily produce stress concentration and fail prematurely. The concave structure formed by the traditional four ligaments can often only produce negative Poisson's ratio deformation for force in one direction, and is prone to instability when force is applied in the other direction. It is not suitable for complex coal mine force environments or other complex force environments.

[0003] 2. Adjacent energy-absorbing layers are connected by cylindrical connecting rods; this cylindrical straight rod is prone to overall instability, and the load transmission is single, and one rod direction can only transmit axial loads, which makes it difficult to effectively resist multi-directional impacts (such as roof pressure and lateral rock bursts), and it is easy to break when subjected to 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 low. Summary of the invention

[0004] In order to solve the technical problems existing in the prior art, the present invention discloses a tunnel negative Poisson's ratio gradient energy absorption support device, which can produce a negative Poisson's ratio effect without losing stability and can be applied to complex stress environments.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a tunnel negative Poisson's ratio gradient energy absorption support device, comprising a support bracket, 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 comprises 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; The two ring nodes corresponding to adjacent energy absorbing layers are at an angle of 180 degrees to each other. The 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.

[0006] As a further technical solution, 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.

[0007] 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°.

[0008] As a further technical solution, a connecting hole is provided on the ring node, and a conical connecting head is provided at the end of the double-helix connecting rod, and the conical connecting head is inserted into the connecting hole.

[0009] As a further technical solution, among the several energy absorbing layers, the node diameter of the four-chiral structure unit cell ring in the upper energy absorbing layer and the lower energy absorbing layer is larger than the node diameter of the four-chiral structure unit cell ring in the middle layer; Alternatively, 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.

[0010] 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; Alternatively, the diameter of the ring nodes of the four-chiral structure unit cell in the energy absorption layer gradually increases from top to bottom.

[0011] Alternatively, the diameters of all the tetrachirality structure unit cell ring nodes in the energy absorbing layer from top to bottom are equal.

[0012] As a further technical solution, among the several energy absorbing layers, the thicknesses of the ring nodes of different energy absorbing layers are equal or unequal.

[0013] As a further technical solution, in several energy absorbing layers, connection holes are provided on the ring nodes, and clamping columns are provided at the ends of the connecting rods, and the clamping columns are inserted into the connection holes.

[0014] As a further technical solution, among the several layers of energy absorbing layers, the energy absorbing layers and connecting rods 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.

[0015] As a further technical solution, among the several energy absorbing layers, the energy absorbing layers and rods of the structure may be made of materials with different strengths.

[0016] As a further technical solution, the top of the support bracket adopts a corrugated steel beam. The beneficial effects of the present invention are as follows: The negative Poisson's ratio gradient energy absorption support device for the tunnel proposed in the present invention can customize the gradient according to the stress field distribution under the non-uniform load of the coal mine (such as small diameter thick wall in the center area to resist high pressure, large diameter thin wall in the edge area to adapt to the deformation of the surrounding rock), reducing the risk of local buckling. The adjacent four-chiral structural unit cells of the negative Poisson's ratio gradient energy absorption structure are connected by ligaments to form a star-shaped concave structure. When the star-shaped concave plane geometric configuration is subjected to force in a single direction (for example, when subjected to vertical force), the ligaments pull the ring nodes tangentially to trigger lateral contraction (negative Poisson's ratio effect), and the stress is concentrated and evenly distributed in the stressed area to avoid local stress concentration. Compared with the traditional four-chiral concave structure, the star-shaped concave structure can produce a negative Poisson's ratio effect without instability when subjected to force in both the horizontal and vertical directions. The gradient design further optimizes the deformation and force transmission path: changing the diameter of the large and small rings to achieve hierarchical energy absorption and deformation adaptation, and changing the thickness to achieve regional matching of support effect and energy dissipation.

[0017] 2. The present invention designs the connecting rod into a double-helix connecting rod, which is composed of two spiral metal rods with opposite rotation directions through a prestressed winding process; it overcomes the problems of easy overall instability of the traditional straight rod structure, single load transmission, and low plastic deformation capacity; the geometric characteristics of the spiral rod enhance the bending and torsional rigidity, 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 double-helix rods effectively improves the stability of the structure under multi-directional surrounding rock loads and impact ground pressure, and the proportion of plastic deformation energy is significantly increased. The rods can dissipate energy in stages through torsional deformation in coordination with the energy absorption layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the combined state of the four-chiral structure unit cell, the connecting rod and the embedded clamping structure disclosed in Example 1; Figure 2 Schematic diagram of two tetrachirality structure unit cells disclosed in Example 1; Figure 3 is a schematic diagram of a single four-chiral structure unit cell disclosed in Example 1; Figure 4 It is a schematic diagram of the combined state of the four-chiral structure unit cell, the connecting rod and the embedded clamping structure disclosed in Example 1; Figure 5 It is a top view of the tunnel negative Poisson's ratio gradient energy absorption support device disclosed in Example 1; Figure 6 It is a side view of the tunnel negative Poisson's ratio gradient energy absorption support device disclosed in Example 1; Figure 7 It is a schematic diagram of the three-dimensional structure of the negative Poisson's ratio gradient energy absorption support device for the tunnel disclosed in Example 1; Figure 8 Schematic diagram of the combination state of the four-chiral structure unit cell, the connecting rod and the embedded clamping structure disclosed in Example 2 Figure 1 ; Fig. 9 Schematic diagram of the combination state of the four-chiral structure unit cell, the connecting rod and the embedded clamping structure disclosed in Example 2 Figure 2 ; Fig.10 Schematic diagram of the combination state of the four-chiral structure unit cell, the connecting rod and the embedded clamping structure disclosed in Example 2 Figure 3 ; Fig.11 is a three-dimensional schematic diagram of the negative Poisson's ratio gradient structure disclosed in Example 2; Fig.12 is a two-dimensional schematic diagram of the negative Poisson's ratio gradient structure disclosed in Example 2; Fig.13 A schematic diagram of a negative Poisson's ratio structure of a uniform gradient formed in Example 1 or Example 2; Fig.14 A schematic diagram of a negative Poisson's ratio structure of a positive gradient formed in Example 1 or Example 2; Fig.15 A schematic diagram of a negative Poisson's ratio structure of a negative gradient formed in Example 1 or Example 2; Fig.16 A schematic diagram of a negative Poisson's ratio structure of a central positive gradient formed in Example 1 or Example 2; Fig.17 A schematic diagram of a negative Poisson's ratio structure of a central negative gradient formed in Example 1 or Example 2; Fig.18 Schematic diagram of the application state of the negative Poisson's ratio gradient structure in Example 1 or Example 2 in the underground engineering support device Figure 1 ; Fig.19Schematic diagram of the application state of the negative Poisson's ratio gradient structure in Example 1 or Example 2 in the underground engineering support device Figure 2 ; In the figure: 1. Four-chiral structure unit cell; 1-1. Ring node; 1-2. Ligament; 2. Cylindrical connecting rod; 3. Embedded snap-in structure; 4. Double helix connecting rod; 5. Steel bracket. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof; Example 1 This embodiment discloses a tunnel negative Poisson's ratio gradient energy absorption support device. When the tunnel negative Poisson's ratio gradient energy absorption support device is stretched, its vertical dimension increases instead, and it has a negative Poisson's ratio effect. The specific structure is as follows: The tunnel negative Poisson's ratio gradient energy absorption support device comprises 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 comprises a plurality of energy absorption layers stacked in sequence, and adjacent energy absorption layers are connected to form a three-dimensional structure. The three-dimensional structure is an adjustable network structure formed by a specific hole distribution and a rigid unit layout; each energy absorption layer comprises a plurality of four-handed structure unit cells 1 arranged and connected to achieve an energy absorption effect. like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, each unit cell 1 of the four-chiral structure includes a ring node 1-1 and four ligaments 1-2; each ligament 1-2 extends tangentially from the ring node 1-1, wherein the geometric parameters of each unit cell are controlled by different variables, and each ligament 1-2 extends tangentially from the ring node 1-1; like Figure 1 As shown, the width of the ring node 1-1 and the ligament 1-2 in the quadrilateral structure unit cell 1 is b, the length of the ligament 1-2 is l, the thickness of the ring node 1-1 and the ligament 1-2 is t, and the unit cell thickness direction can be set to have two cross-sections: square and circular.

[0021] Furthermore, in this embodiment, in the same energy absorption layer, adjacent four-chiral structure unit cells 1 are connected by ligaments 1-2 to form a star-shaped concave structure to enhance its mechanical properties; Fig.13 As shown, the star-shaped concave structure formed in this embodiment is an octagonal star-shaped concave structure. Specifically, four adjacent four-chirality structure unit cells 1 are adjacent to each other through ligaments 1-2. One ligament 1-2 of the four-chirality structure unit cell 1 in the upper left corner is connected to one ligament 1-2 of the four-chirality 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 four-chirality structure unit cell 1 in the upper left corner is connected to one ligament 1-2 of the four-chirality structure unit cell 1 in the lower left corner, and the two ligaments are connected to each other. An obtuse angle is formed between the ligaments; another ligament 1-2 of the four-chiral structure unit cell 1 in the lower left corner is connected to a ligament 1-2 of the four-chiral 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 four-chiral structure unit cell 1 in the lower right corner is connected to a ligament 1-2 of the four-chiral structure unit cell 1 in the upper right corner, and an obtuse angle is formed between the two ligaments; each four-chiral 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, the star-shaped concave structure has excellent impact resistance and can produce lateral contraction when subjected to vertical force, so that the structure can effectively gather to the force-bearing part. Macroscopically, it is manifested as an increase in regional density, which is significantly different from the traditional structure. At the same time, compared with the positive Poisson's ratio honeycomb structure, which is crushed and deformed when subjected to slight force, the anti-indentation effect of this negative Poisson's ratio structure can effectively resist the generation of indentations.

[0022] Furthermore, adjacent energy-absorbing layers are fixedly connected by four groups of cylindrical connecting rods 2 that are symmetrically distributed in space; the four cylindrical connecting rods 2 are all tilted in the four-chiral structure unit cell 1, of which two cylindrical connecting rods 2 have relatively large tilt angles, and the other two have relatively small tilt angles; that is, the axis of the cylindrical connecting rod 2 forms an adjustable tilt angle θ of 15°-75° with the normal direction of the energy-absorbing layer, and each group of cylindrical connecting rods 2 is axially symmetrically distributed on the horizontal projection plane; the tilt angle is determined according to the position of the circular rod connecting member and the connecting unit cell and the distance between the two surface layers. When designing, it is recommended to set the connection position of the connecting rod at the intersection of the ligament and the ring, so that the symmetrical layout is conducive to enhancing the rotation effect of the connecting rod on the ligament. Because the ligament is designed to form a concave star shape, the angles formed by the four ligaments and the ring are different, and the angle formed by each cylindrical connecting rod 2 after connecting the two surface layers will also be different.

[0023] Furthermore, the cylindrical connecting rod 2 in this embodiment is cylindrical, and can of course also be designed to be square.

[0024] Furthermore, the negative Poisson's ratio characteristic of the negative Poisson's ratio gradient energy absorption support device of the tunnel is realized through a three-dimensional configuration design, and the three-dimensional configuration follows the design rules of the two-dimensional configuration. At the same time, the two corresponding ring nodes 1-1 of each layer are at an angle of 180 degrees to each other, and cylindrical connecting rods 2 are added between different energy absorption layers, and the cylindrical connecting rods 2 form an angle θ with the plane of the ring nodes 1-1.

[0025] Furthermore, the gradient of the above-mentioned negative Poisson's ratio gradient energy absorption support device for the tunnel can also be designed; the negative Poisson's ratio gradient energy absorption support device for the tunnel can be designed by setting the aperture and thickness of the ring node 1-1 of each quadrilateral structure unit cell 1, as follows: The central ring node 1-1 reference diameter is defined as D0. The size of the ring node 1-1 can be enlarged or reduced according to a certain multiple ratio to achieve different gradient arrangements. Different ring node diameters are designed to increase the cross-sectional inertia moment of the ring node in the area with increased diameter, and enhance the local bending and compression resistance. In the area with reduced diameter, the plastic deformation of the ligament is dominant to adapt to the dynamic displacement of the surrounding rock. The gradient change of the 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 takes the load first and triggers plastic deformation. The large diameter area absorbs the residual energy through elastic rebound to achieve graded energy absorption.

[0026] Through 3D printing, the number of printing layers and layer thickness are adjusted layer by layer to achieve a linear decrease in the thickness of the ring node 1-1 from 1.6mm in the center to 0.8mm at the edge to match the yield strength requirements of different areas. This embodiment designs a thickness gradient, which can directly increase the cross-sectional area of ​​the material at the location where the thickness increases, and enhance the node's anti-yield ability. The thin-walled area absorbs energy through elastic-plastic deformation, and the thick-walled area bears the main load through high stiffness. The thick-walled area (such as t=1.6mm) is used in 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=0.8mm) is used in the edge area to dissipate energy through deformation. It can also be used to absorb low-frequency vibrations.

[0027] The negative Poisson's ratio gradient structure takes the aperture gradient setting as an example. The gradient design can be divided into three areas according to the position relationship of the ring node 1-1 from bottom to top. The diameter of the ring node 1-1 in each area satisfies: The diameter of the ring node 1-1 in zone I (transition zone) is D1=D0(1-ΔD); The diameter of the ring node 1-1 in zone II (central zone) is D2=D0; The diameter of the ring node 1-1 in zone III (edge ​​zone) is D3=D0(1+ΔD); Among them, D0 is the reference diameter of the ring node 1-1, ΔD is the diameter difference of the ring node 1-1, and the distance between adjacent unit cells is The geometric parameter change is between 15% and 25%, and the maximum does not exceed 30% of the previous level unit.

[0028] The negative Poisson's ratio gradient structure can be divided into different arrangements according to the partition arrangement, such as uniform gradient, positive gradient, negative gradient, central positive gradient and central negative gradient. Among them, the negative Poisson's ratio structure of uniform gradient is as follows: Fig.13 As shown; in the several layers of energy absorbing layers, all the four-chiral structure unit cell ring nodes in the energy absorbing layers from top to bottom have equal diameters and thicknesses, forming a negative Poisson's ratio structure with a uniform gradient; the negative Poisson's ratio structure with a positive gradient is as shown Fig.14 As shown, in the several layers of energy absorption layers, the diameter of the node of the four-chiral structure unit cell ring in the energy absorption layer gradually decreases from top to bottom, and the thickness remains unchanged; the negative Poisson's ratio structure with a negative gradient is shown in Fig.15 As shown, in the several layers of energy absorption layers, the diameter of the node of the four-chiral structure unit cell ring in the energy absorption layer increases gradually from top to bottom, and the thickness remains unchanged; the negative Poisson's ratio structure with a positive gradient in the center is as shown in Fig.16 As shown, the node diameters of the four-chiral structure unit cell rings in the upper and lower energy absorption layers are smaller than those in the middle layer, and the thickness remains unchanged; the negative Poisson's ratio structure with a negative gradient in the center is shown in Fig.17 As shown; among the several layers of energy absorbing layers, the node diameter of the four-chiral structure unit cell ring in the upper energy absorbing layer and the lower energy absorbing layer is larger than the node diameter of the four-chiral structure unit cell ring in the middle layer, and the thickness remains unchanged; wherein, the central gradient means that in addition to being arranged according to a gradient, each layer forms a structure according to a relationship of symmetry along the center.

[0029] In the structure, ligament 1-2 is responsible for pulling the ring node 1-1 to move through deformation, and the ring 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 foam metals) are prone to local stress concentration under impact loads, leading to premature failure. For example, due to the multi-stable rebound characteristics, the energy absorption efficiency of traditional negative stiffness structures is only 50%-70% of that of gradient structures. At the same time, the geological conditions of coal mine tunnels are complex, and the surrounding rock stress also has a gradient distribution. Traditional static support structures are difficult to match the surrounding rock stress gradient distribution, resulting in an increased risk of roof collapse. After designing different gradients, different gradient designs can be used according to different structures and stress conditions.

[0030] 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.

[0031] The energy absorbing layer and the cylindrical connecting rod 2 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 not less than 80% of the material of the cylindrical connecting rod 2. The energy absorbing 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 absorbing 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 absorbing layer.

[0032] 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: 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.

[0033] 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.

[0034] like Fig.18 , Fig.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.

[0035] Under the impact of surrounding rocks, the upper honeycomb panel can quickly absorb the impact energy and stably deform and give way. At the same time, the upper panel structure as a whole converges inward, enhancing the structure's shear buckling bearing capacity and bending stability, and avoiding the instability and collapse of the lower support.

[0036] Example 2 This embodiment discloses another tunnel negative Poisson's ratio gradient energy absorption support device. The difference between this tunnel negative Poisson's ratio gradient energy absorption support device and embodiment 1 is mainly that the shape of the connecting rod is different, such as Figure 8 , Fig. 9 , Fig.10 As shown, in this embodiment, the connecting rod is designed as a double helical connecting rod 4. The double helical connecting rod 4 in this embodiment is composited by two spiral metal rods with opposite rotation directions through a prestressed winding process. The pitch P of the double helical connecting rod 4 and the diameter d of the double helical connecting rod 4 satisfy the relationship: 2d≤P≤8d, and the helix angle β is controlled within the range of 20°-60°. The double helical connecting rod 4 is used to replace the original cylindrical connecting rod 2, and the inclination direction of the connection and the connection order between the surface layers remain unchanged. This embodiment only changes the shape of the connecting member.

[0037] When a double-helix connecting rod 4 is used, conical connectors can be provided at both ends to match and fit with the quadrilateral connecting holes of the central nodes of the gradient chiral unit cells on the energy absorbing layer. The cone angle of the conical head is designed to be 5°-15° to ensure radial compressive stress during prestressed assembly and enhance contact surface friction. The assembly clearance is controlled at 0.02-0.05mm, which ensures smooth assembly and avoids looseness. For the specific structure after connection, see Fig.11 , Fig.12 .

[0038] Furthermore, the cylindrical connecting rod 2 in Example 1 can only transmit axial loads, while coal mine support often needs to resist multi-directional impacts (such as roof pressure and lateral rock bursts), and 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 Example 1, the double helical connecting rod 4 preferentially produces controllable torsional deformation during axial compression, guiding the rod to preferentially undergo torsional deformation rather than fracture under the impact load, increasing the proportion of plastic deformation energy, and better guiding the rotation of the chiral cell, so that the structure's ability to resist lateral impact is significantly improved. That is: this implementation designs the connecting rod into a double helical connecting rod 4, which is composed of two spiral metal rods with opposite hand directions through a prestressed winding process, overcoming the problems of the traditional straight rod structure being prone to overall instability, single load transmission, and low plastic deformation capacity; the geometric characteristics of the spiral rod enhance the bending and torsional stiffness, and the critical buckling load is increased compared to the traditional straight rod, and more energy can be dissipated through plastic torsional deformation. The use of double-helix rods effectively improves the stability of the structure under multi-directional surrounding rock loads and impact ground pressure. The proportion of plastic deformation energy is significantly increased, and the rods can dissipate energy in a graded manner through torsional deformation and coordinated energy-absorbing layers.

[0039] The remaining structures of this embodiment are the same as those of Embodiment 1 and will not be described in detail here.

[0040] Furthermore, the structure disclosed in the above-mentioned embodiment 1 or embodiment 2, in addition to being used in tunnel support devices, can also be applied to various engineering fields such as sandwich composite panels and impact energy absorption devices, especially in the field of energy absorption and deformation. In the anti-collision structure of mining equipment, the gradient aperture can trigger plastic deformation in a graded manner: the small aperture area (aperture D <10mm) preferentially buckles to absorb high-energy impacts, and the large aperture area (aperture D>15mm) dissipates residual energy through elastic rebound. The aperture gradient and the helix angle (β=20°-60°) are designed in coordination, so that the energy absorption frequency band can be within the vibration range of coal mine machinery (10-200Hz), achieving a certain noise reduction and vibration absorption effect.

[0041] In summary, the present invention provides a negative Poisson's ratio gradient energy absorption support device for a tunnel, including two-dimensional and three-dimensional structural configurations, wherein the two-dimensional structure of the present invention enhances deformation regularity and controllability compared with conventional chiral negative Poisson's ratio structures, and in combination with the special working conditions of coal mines, the connecting rod adopts a double-helix connecting rod 4; compared with the traditional hexagonal honeycomb structure, it overcomes the defect of the honeycomb structure failing too quickly after being compressed; and at the same time combines the deformation advantage of the concave shape and the rigidity advantage of the chiral circular ring nodes. The present invention can adopt a gradient design in both two-dimensional and three-dimensional structures, and through the non-uniform distribution of spatial parameters, it breaks through the bottleneck of traditional structures in energy absorption efficiency and environmental adaptability, and is particularly suitable for non-uniform load scenarios of underground coal mine projects, and can focus on enhancing the strength of a certain area and changing the deformation mode of the structure, so that the structure can be customized according to the needs of different application scenarios.

[0042] The above description is only a preferred embodiment of the present invention and is 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 in 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; The two ring nodes corresponding to adjacent energy absorbing layers are at an angle of 180 degrees to each other. The 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.

2. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1, characterized in that: 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.

3. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 2, 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°.

4. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 2, 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.

5. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1 or 2, 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.

6. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1 or 2, characterized in that: Among the several energy absorbing layers, the thicknesses of the ring nodes of different energy absorbing layers are equal or unequal.

7. 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.

8. The tunnel negative Poisson's ratio gradient energy absorption support device according to claim 1 or 2, 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.

9. 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.

10. 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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