Self-locking and framework-adjusting negative poisson's ratio composite anchor rod and method of use

Abstract

This invention discloses a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor and its usage method. The composite anchor includes: an anchor body, at least one set of self-locking units and skeleton units; the self-locking unit is a cylindrical negative Poisson's ratio structure I, fixed at both ends to the anchor body, and expands radially under axial force; the skeleton unit is a cylindrical negative Poisson's ratio structure II, sleeved on, with one end fixed to the anchor body and the other end adjustable for axial movement and positioning; the negative Poisson's ratio structure II has pre-fabricated breakpoints or weakened nodes or is in a critical deformation state, so that it can break under axial force. This invention can not only form a widely distributed and complex three-dimensional metal skeleton before grouting, significantly improving the shear strength and integrity of the grouting stone body, but also expand radially and actively squeeze the surrounding grout body or borehole wall for self-locking, thereby greatly improving the interfacial friction and mechanical interlocking force, making it suitable for complex geological environments.

Description

Technical Field

[0001] This invention relates to roadway support technology, belonging to the field of mine safety engineering, and specifically to a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor and its usage method. Background Technology

[0002] As a commonly used load-bearing component in geotechnical engineering, underground engineering, and structural reinforcement, the core function of anchor bolts is to connect structures or soil and rock masses to deep stable strata. Through the tensile and shear resistance of the bolt, external loads (such as earth pressure, water pressure, structural loads, etc.) are transferred to deep stable soil and rock layers, thereby achieving the purpose of stabilization, reinforcement, or anchoring. They are widely used in tunnel support, mine roadways, slope reinforcement, and building structure reinforcement projects. Existing anchor types include ordinary steel bar anchors, prestressed anchors, and mechanical expansion anchors. Ordinary steel bar anchors and prestressed anchors mainly use materials with a positive Poisson's ratio. When subjected to axial tension, these anchors exhibit a radial "neckback" effect, leading to debonding at the anchorage interface. Furthermore, they are prone to anchorage force attenuation due to surrounding rock creep or grout deterioration, making it difficult to effectively convert axial tension into radial constraint force. While mechanical expansion anchors can provide radial pressure, they are mostly rigid structures and lack the ability to adaptively adjust to changes in load. In particular, during the anchoring process, relying solely on the anchor's own expansion is unsuitable for complex and demanding environments, as secondary reinforcement is not performed. Therefore, based on the existing problems with existing anchors, there is an urgent need for a composite anchor that coordinates expansion self-locking with skeleton transformation. Summary of the Invention

[0003] The purpose of this invention is to provide a negative Poisson's ratio composite anchor bolt with self-locking and skeleton adjustment. It can not only form a three-dimensional metal skeleton with a wide distribution and complex shape before grouting, which significantly improves the shear strength and integrity of the grouting stone body, but also expand radially and actively squeeze the surrounding grouting body or borehole wall to achieve self-locking, thereby greatly improving the interface friction and mechanical interlocking force, and is suitable for complex geological environments.

[0004] To achieve the above objectives, a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt is provided, comprising: Anchor bolt body; At least one set of self-locking units and skeleton units; The self-locking unit is a cylindrical negative Poisson's ratio structure I, which is sleeved and fixed at both ends to the anchor rod body; The skeleton unit is a cylindrical negative Poisson's ratio structure II, which is fitted and fixed at one end to the anchor rod body, while the other end can be adjusted to move axially and be positioned. Among them, the negative Poisson's ratio structure I expands radially when subjected to axial force, while the negative Poisson's ratio structure II is provided with pre-fabricated breakpoints or weakened nodes or is in a critical deformation state, so that it can break when subjected to axial force.

[0005] In some examples of the present invention, the prefabricated breakpoint or weakened node includes a circumferentially arranged cut component I and a circumferentially arranged cut component II; Both cut component I and cut component II include multiple cuts at different locations, which cause the negative Poisson's ratio structure II to break into block-like or strip-like shapes.

[0006] In some examples of the present invention, the negative Poisson's ratio structure I and negative Poisson's ratio structure II are one or more combinations of concave structure, perforated plate structure, and chiral structure; When negative Poisson's ratio structure I and negative Poisson's ratio structure II have the same structural form, the cylindrical radial thickness of negative Poisson's ratio structure II is smaller than that of negative Poisson's ratio structure I.

[0007] In some examples of the present invention, there are gaps between the negative Poisson's ratio structure I, the negative Poisson's ratio structure II and the anchor body; An isolation layer to prevent adhesion is applied to the inner wall of negative Poisson's ratio structure I and negative Poisson's ratio structure II, or to the outer wall of the anchor body.

[0008] In some examples of the present invention, the isolation layer is a solvent-modified asphalt coating, a thin film layer formed after spraying or brushing and drying.

[0009] In some examples of the present invention, ring bodies II are fixed at both ends of the negative Poisson's ratio structure II; It also includes adjustment components corresponding to the skeleton unit; The adjusting component has a pair of fixed rings and multiple circumferentially arranged guide rods; A pair of fixing rings are fixed to the anchor body and located at the end of the negative Poisson's ratio structure II. Each guide rod passes through the ring body II and the fixing ring at both ends and is fixed by a pair of axially arranged nuts with threaded limits.

[0010] In some examples of the present invention, the adjusting component further includes a pair of clamping plates located between the fixed ring and the ring body II; Each clamping plate is fixed with an L-shaped pressure block. One end of the pressure block can press against the ring II, so that the ring II can move axially synchronously with the clamping plate. Both ends of the guide rod pass through the clamping plate and the fixing ring, and are then fixed by a pair of axially arranged nuts with threaded limits.

[0011] In some examples of the present invention, multiple self-locking units and skeleton units are arranged side by side with intervals, or arranged in an alternating manner; The negative Poisson's ratio structure II has ring bodies II fixed at both ends; It also includes adjustment components corresponding to the skeleton unit; The adjustment component includes a traction rope, a pair of fixing rings, and a positioning rod; A pair of fixing rings are fixed to the anchor body and located at the end of the negative Poisson's ratio structure II. The ring body II of the negative Poisson's ratio structure II, which is away from the orifice, is fixed to one of its fixing rings. Multiple positioning rods are fixedly connected at one end to the ring body II near the orifice of the negative Poisson's ratio structure II, and at the other end slide through the fixing ring and are fixed by nuts. The ring II of the negative Poisson's ratio structure II near the orifice is connected to the ring II of another adjacent negative Poisson's ratio structure II near the orifice by a taut traction rope; the traction rope closest to the orifice extends to the outside of the orifice and can be lifted by a traction device.

[0012] A method for using a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt specifically includes the following steps: Step S1: Drill anchor bolt holes in the surrounding rock according to the design requirements and clean the drill holes; Adjust the skeleton units to bring the negative Poisson's ratio structure II to a critical deformation state; Insert the self-locking and skeleton-adjustable negative Poisson's ratio composite anchor into the borehole to prevent the middle skeleton unit from prematurely triggering dispersion; Step S2: Apply critical dispersion tension to the anchor bolt body or skeleton unit. Under the action of this tension, the negative Poisson's ratio structure II undergoes over-limit tension, and the skeleton unit breaks, disperses, or undergoes extreme plastic expansion, "exploding" inside the borehole, transforming from a cylindrical structure into a three-dimensional metal skeleton with a wide distribution range and complex shape, thus completing the skeleton transformation. Step S3: While maintaining the dispersed state of the skeleton units, inject grout into the hole. Under pressure, the grout fills the borehole and fully wraps the anchor body, self-locking unit and the three-dimensional metal skeleton scattered around it. The grout seeps into the fractured surrounding rock along the gaps. Once the grout has completely solidified, it forms a high-strength composite reinforcement consisting of the anchor bolt body, a negative Poisson's ratio structure I tightly wrapped by the solidified grout, a dispersed negative Poisson's ratio structure II remnant, and grouting stone body. Then, a preload is applied to the anchor bolt body to lock it in place; Step S4: When the surrounding rock undergoes rheological or expansion deformation, causing the anchor bolt body to be stretched, the anchor bolt body will drive the negative Poisson's ratio structure I to stretch axially in sync. Based on the negative Poisson's ratio effect, the negative Poisson's ratio structure I will generate radial expansion, actively squeezing the surrounding grout or borehole wall, increasing the normal stress at the anchoring interface, and thus significantly improving the interface friction and mechanical interlocking force, completing the expansion self-locking function of the borehole.

[0013] In some examples of the present invention, in step S2, a tensioning device is installed at the orifice to apply a critical dispersion tension to the anchor bolt body. The tension value is set to be greater than the ultimate tensile strength of the negative Poisson's ratio structure II, but less than the yield strength of the anchor bolt body. By applying the critical dispersion tension to the anchor bolt body, multiple sets of skeleton units are blown open to complete the skeleton transformation. or A traction device is installed at the orifice to pull the traction rope closest to the orifice. Multiple traction ropes connected in series drive the moving end of the adjacent negative Poisson's ratio structure II to move axially. The series linkage enables multiple sets of skeleton units to explode and complete the skeleton transformation.

[0014] Compared with existing technologies, this self-locking and skeleton-adjustable negative Poisson's ratio composite anchor has the following advantages: 1. The skeleton unit is designed with pre-fabricated breakpoints or weakened nodes or is in a critical deformation state. It is then blasted open before grouting and transformed into a three-dimensional metal skeleton with a wide distribution and complex shape. The injected grout can solidify with the skeleton to form a reinforced structure similar to "reinforced concrete". This significantly improves the shear strength and integrity of the grouting stone body and is suitable for loose and broken surrounding rock, fault fracture zone or extremely soft rock layer. 2. When the surrounding rock undergoes expansion deformation, causing the anchor bolt body 10 to be stretched, the self-locking unit can expand radially and actively squeeze the surrounding grout or borehole wall to achieve self-locking, significantly increasing the normal stress of the anchoring interface, thereby greatly improving the interface friction and mechanical interlocking force. It can be applied to intact surrounding rock, jointed and fractured rock mass or high ground stress rock mass. 3. Set skeleton units and self-locking units on the anchor bolt body. Utilize two completely different enhancement modes, "expansion self-locking" and "skeleton transformation". Expansion self-locking actively expands to cope with high stress and large deformation. Skeleton transformation uses pre-tension failure to reconstruct the negative Poisson's ratio structure into a three-dimensional skeleton to greatly improve the grouting strength of the fracture zone. This effectively ensures the reliable triggering of the NPR effect and the ultimate bearing safety of the connection nodes, and significantly improves the engineering adaptability of the anchor bolt in complex geological environments. 4. An adjustment component is set up. After the negative Poisson's ratio structure II is adjusted to the critical deformation state by the nut, the critical dispersion tension is applied to the anchor body or the skeleton unit in two different ways, so that the skeleton unit will break, disperse or undergo extreme plastic expansion, which is more practical. In addition, the traction rope is used to link multiple skeleton units in series, which can facilitate personnel operation and avoid the expansion and self-locking of the self-locking unit when the anchor body is stretched too much. Attached Figure Description

[0015] Figure 1 This is an overall schematic diagram of the present invention; Figure 2 This is the overall front view of the present invention; Figure 3 This is a front view of the self-locking unit in this invention, which expands radially and locks itself under axial tensile force. Figure 4 This is a front view of the self-locking unit in this invention being blown open by axial tensile force to form a three-dimensional metal skeleton; Figure 5 This is a schematic diagram of the cut in the negative Poisson's ratio structure II of this invention; Figure 6 This is a schematic diagram of an example of the adjusting component in this invention; Figure 7 This is a schematic diagram of the assembly of a pressure plate and a guide rod in one example of an adjusting component; Figure 8 This is a front view of another example of the adjusting component in this invention; Figure 9 This is a front view of the perforated plate structure with negative Poisson's ratio in this invention; Figure 10 This is a front view of the chiral structure with negative Poisson's ratio in this invention; In the diagram: 10. Anchor bolt body; 20. Self-locking unit; 21. Negative Poisson's ratio structure I; 22. Ring body I; 30. Skeleton unit; 31. Negative Poisson's ratio structure II; 31.1. Notch; 32. Ring body II; 40. Retaining ring; 51. Pressure plate; 52. Guide rod; 53. Nut; 54. Pressure block; 55. Positioning rod; 60. Towing rope. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0018] Example 1

[0019] like Figures 1 to 4 As shown, this self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt includes: Anchor bolt body 10; At least one set of self-locking unit 20 and skeleton unit 30; The self-locking unit 20 is a cylindrical negative Poisson's ratio structure I21, which is sleeved and fixed at both ends to the anchor rod body 10; The skeleton unit 30 is a cylindrical negative Poisson's ratio structure II 31, which is sleeved and fixed at one end to the anchor rod body 10, and the other end can be adjusted to move axially and be positioned. Among them, the negative Poisson ratio structure I21 expands radially when subjected to axial force, and the negative Poisson ratio structure II31 is provided with pre-fabricated breakpoints or weakened nodes or is in a critical deformation state, so that it can break when subjected to axial force. Specifically, the anchor body 10 can be made of high-strength steel bars, precision-rolled threaded steel bars, or other metal materials suitable for engineering anchoring; In the self-locking unit 20, the negative Poisson's ratio structure I21 is fixedly connected to the anchor body 10 at both ends. It can expand radially under the axial tension of the anchor body 10. For example, the negative Poisson's ratio structure I21 is fixed with ring body I22 at both ends. The ring body I22 is fixedly connected to the fixed ring 40. The fixed ring 40 is welded to the anchor body 10. The welding adopts continuous annular fillet weld or carbon dioxide gas shielded welding to ensure the continuity and airtightness of the connection. By increasing the effective welding area and providing radial constraint, the shear stress concentration factor of the weld interface is significantly reduced, ensuring the reliability of anchoring force transmission. When this self-locking and skeleton-adjustable negative Poisson's ratio composite anchor is used, the self-locking unit 20 and the skeleton unit 30 can be in multiple groups, which can be arranged side by side with intervals of the same type, or the two can be arranged alternately in sequence, which can reduce the risk of overall buckling instability of the structure during stress or installation; initially, the negative Poisson's ratio structure II 31 is provided with prefabricated breakpoints or weakened nodes or is in a critical deformation state, so that it can break when subjected to axial force. Insert the negative Poisson's ratio composite anchor into the borehole, and avoid premature triggering and dispersion of the skeleton unit 30 during the installation process; Before grouting, a tensioning device is installed at the borehole opening to apply a critical dispersion tensile force to the anchor bolt body 10. This tensile force is set to be greater than the ultimate tensile strength of the negative Poisson's ratio structure II 31, but less than the yield strength of the anchor bolt body 10. Alternatively, a tensioning device is installed at the borehole opening to apply a force to one end of the negative Poisson's ratio structure II 31 of the skeleton unit 30. This tensile force is greater than the ultimate tensile strength of the negative Poisson's ratio structure II 31. Under this tensile force, the negative Poisson's ratio structure II 31 undergoes over-stretching, and the skeleton unit 30 fractures, disperses, or undergoes extreme plastic expansion, "exploding" inside the borehole, transforming from a cylindrical structure into a widely distributed and complex three-dimensional metal skeleton, such as... Figure 4 As shown; While maintaining the dispersed state of the skeleton unit 30, immediately inject high-strength cement grout or modified chemical grout into the hole using a penetration grouting process; the grout fills the borehole under pressure and fully wraps the anchor body 10, the self-locking unit 20, and the three-dimensional metal skeleton scattered around it. The grout seeps into the fractured surrounding rock fissures along the skeleton gaps; after the grout reaches the design strength, install the tray and anchor nut, and use a torque wrench or tensioning equipment to apply the conventional design pre-tightening force to the anchor body 10 for locking. The applied pre-tightening force should be less than the yield strength or ultimate tensile strength of the negative Poisson's ratio structure I21; after construction, this negative Poisson's ratio composite anchor enters the long-term monitoring and service stage. When the surrounding rock undergoes rheological or expansion deformation, the self-locking unit 20 automatically triggers "expansion self-locking," such as... Figure 3 As shown; When the surrounding rock undergoes expansion deformation, causing the anchor bolt body 10 to be stretched, the anchor bolt body 10 will drive the negative Poisson's ratio structure I21 to stretch axially in sync. At this time, based on the negative Poisson's ratio effect, the negative Poisson's ratio structure I21 will generate radial expansion, actively squeezing the surrounding grout or borehole wall. This squeezing action can significantly increase the normal stress of the anchoring interface, thereby greatly improving the interface friction and mechanical interlocking force, achieving the adaptive reinforcement effect of "the greater the tension, the thicker the diameter, and the tighter the anchoring". It can be applied to intact surrounding rock, jointed and fractured rock mass or high ground stress rock mass. For the negative Poisson's ratio structure I21 with "expansion self-locking mechanism", it is advisable to select a negative Poisson's ratio structure with continuous deformation and good stability, such as an inward hexagonal structure or a perforated plate structure. Taking the inward hexagonal structure as an example, its structure is a funnel-shaped hexagonal structure with the middle concave inward, and the inward hexagons are connected to each other in the axial direction and offset by half a position in the circumferential direction, finally forming a cylindrical structure. The skeleton unit 30 is provided with prefabricated breakpoints or weakened nodes or is in a critical deformation state, so that it is blown open before grouting and transformed into a three-dimensional metal skeleton with a wide distribution and complex shape. The injected grout can solidify with the skeleton to form a reinforced structure similar to "reinforced concrete", which significantly improves the shear strength and integrity of the grouting stone body. It can be applied to loose and broken surrounding rock, fault fracture zone or extremely soft rock layer. This negative Poisson's ratio composite anchor can utilize two distinct enhancement modes: "expansion self-locking" and "skeleton transformation". Through expansion self-locking, it actively expands to cope with high stress and large deformation. Skeleton transformation utilizes pre-tension failure to reconstruct the negative Poisson's ratio structure into a three-dimensional skeleton to significantly improve the grouting strength of the fracture zone, effectively ensuring the reliable triggering of the NPR effect and the ultimate bearing safety of the connection nodes, and significantly improving the engineering adaptability of the anchor in complex geological environments. Furthermore, such as Figure 5 As shown, the prefabricated breakpoint or weakened node includes a circumferentially arranged cut component I and a circumferentially arranged cut component II; Both cut assembly I and cut assembly II include multiple cuts 311 at different locations, so that when the negative Poisson's ratio structure II 31 is broken, it forms a block-like or strip-like shape; Specifically, the incision 311 can be a V-shaped structure, and the number of incisions 311 should not be too many to avoid the negative Poisson's ratio structure II 31 forming a block / strip that separates independently; The notch 311, as a prefabricated break or weakening node, enables the negative Poisson's ratio structure II 31 to break preferentially from this point when subjected to axial tensile force, forming a relatively complete block or strip structure, that is, a certain degree of controllable destruction, so as to achieve the corresponding predicted dispersion effect, so as to fully combine with the grouting liquid and increase the shear strength. The critical deformation state of the negative Poisson's ratio structure II 31 can be obtained through experimental data. That is, the negative Poisson's ratio structure II 31 of the same specification and material is placed on the test platform, the lower end is fixed, and the upper end is fixedly connected to the tensile end of the tensile equipment. An axial tensile test is carried out to obtain the test data when the negative Poisson's ratio structure II 31 is broken. Multiple tests are carried out to eliminate abnormal test data, and finally the minimum limit value of the test data is obtained. In the initial state of the negative Poisson's ratio structure II 31, one end of the negative Poisson's ratio structure II 31 is fixed, and the other end is moved axially and positioned to complete the setting of the critical deformation state of the negative Poisson's ratio structure II 31.

[0020] Furthermore, such as Figure 3 , Figure 9 , Figure 10 As shown, the negative Poisson's ratio structure I21 and negative Poisson's ratio structure II31 are in the form of one or more combinations of concave structure, perforated plate structure, and chiral structure; When negative Poisson's ratio structure Ⅰ21 and negative Poisson's ratio structure Ⅱ31 have the same structural form, the cylindrical radial thickness of negative Poisson's ratio structure Ⅱ31 is smaller than that of negative Poisson's ratio structure Ⅰ21. Specifically, such as Figure 3 As shown, the concave structure is a funnel-shaped hexagonal structure formed by the center approaching inward, and the concave hexagons are connected to each other in the axial direction and offset by half a position in the circumferential direction, finally forming a cylindrical structure. like Figure 9 As shown, this negative Poisson's ratio structure can be a perforated plate structure. The perforated plate structure has semicircular ends and an inward-curving arc strip in the middle, which smoothly transitions to the semicircular ends. In the axial and circumferential directions, adjacent perforated plate structures are arranged at 90° intervals and staggered from each other. Figure 10 As shown, the negative Poisson's ratio structure can be a chiral structure, which is a rectangular hole. In the axial and circumferential directions, adjacent chiral structures are arranged at 90° intervals and staggered from each other. The four adjacent chiral structures are filled with square holes. In addition, the negative Poisson's ratio structure I21 and negative Poisson's ratio structure II31 can also be a rotating structure or a star-shaped structure. The negative Poisson's ratio structure I21 and negative Poisson's ratio structure II31 are in the form of one or more combinations of concave structure, perforated plate structure, and chiral structure. However, when the anchor body 10 is subjected to axial tensile force, the negative Poisson's ratio structure II31, which is in the critical deformation state, will first explode to form a complex three-dimensional metal skeleton, while the negative Poisson's ratio structure I21 will not respond. When the structural forms are the same, the negative Poisson's ratio structure with a smaller radial thickness should be blasted open first, before the negative Poisson's ratio structure with a larger radial thickness. In some examples of the present invention, there are gaps between the negative Poisson's ratio structure I 21, the negative Poisson's ratio structure II 31 and the anchor body 10; An isolation layer that prevents adhesion is applied to the inner wall of negative Poisson's ratio structure I21 and negative Poisson's ratio structure II31, or to the outer wall of anchor body 10. Furthermore, the isolation layer is a thin film layer formed by solvent-modified asphalt coating.

[0021] Specifically, the inner diameters of the negative Poisson's ratio structures I21 and II31 are slightly larger than the outer diameter of the anchor body 10, with a deformation gap reserved between them. An isolation layer is applied to the inner wall of the negative Poisson's ratio structures I21 and II31 or the outer wall of the anchor body 10. This isolation layer ensures that the inner side of the corresponding negative Poisson's ratio structure does not adhere to the anchor body 10 or the bonding material during the corresponding cylindrical deformation. The isolation layer uses solvent-modified asphalt coating, which forms a thin film after spraying or brushing and drying.

[0022] Example 2

[0023] As an example of the assembly of skeleton unit 30, such as Figure 6 , Figure 7 As shown, ring bodies II 32 are fixed at both ends of the negative Poisson's ratio structure II 31; This negative Poisson's ratio composite anchor also includes an adjustment component corresponding to the skeleton unit 30; The adjusting component has a pair of fixed rings 40 and a plurality of circumferentially arranged guide rods 52; A pair of fixing rings 40 are fixed on the anchor body 10 and located at the end of the negative Poisson's ratio structure II 31. Each guide rod 52 passes through the ring body II 32 and the fixing rings 40 at both ends and is fixed by a pair of axially arranged nuts 53 with threaded limit. Specifically, the fixing ring 40 is used to weld onto the anchor body 10, and the negative Poisson ratio structure II 31 and the ring body II 32 can be an integral structure; The following is an example of the guide rod 52 passing through the ring body II 32 and the fixing ring 40 and being fixed by the nuts 53 arranged above and below; A pair of nuts 53 are threadedly connected to the guide rod 52 and are located on the outside of the ring body II 32 and the fixing ring 40, respectively. The upper nut 53 is used to fix the guide rod 52 on the fixing ring 40, and the lower nut 53 is used to limit the ring body II 32 on the guide rod 52. The nuts 53 can be rotated to adjust the negative Poisson ratio structure II 31 axially. After the adjustment is completed, the negative Poisson ratio structure II 31 of the skeleton unit 30 is fixedly connected to the anchor body 10, and the negative Poisson ratio composite anchor is placed in the borehole. Although this method can adjust the negative Poisson's ratio structure II31 axially to bring it to the critical deformation state, there is a problem that the pressure of the nut 53 on the ring II32 can easily cause the negative Poisson's ratio structure II31 to be unstable under force. The reason is that the point of action of the negative Poisson's ratio structure II31 depends on the number of guide rods 52. For example, when there are four guide rods 52, when adjusting the negative Poisson's ratio structure II31 axially, the point of action is concentrated at the ring II32 where the guide rods 52 are located, which is prone to local instability of the negative Poisson's ratio structure II31 and the risk of it going out of the critical state. Furthermore, such as Figure 6 , Figure 7 As shown, the adjusting component also includes a pair of clamping plates 51 located between the fixed ring 40 and the ring body II 32; Each clamping plate 51 is fixed with an L-shaped pressure block 54. One end of the pressure block 54 can press against the ring body II 32, so that the ring body II 32 can move axially synchronously with the clamping plate 51. Both ends of the guide rod 52 pass through the clamping plate 51 and the fixing ring 40 and are then fixed by a pair of axially arranged nuts 53 with threaded limit. Specifically, the middle part of the clamping plate 51 has a semi-circular structure to wrap around the outside of the anchor rod body 10, which is a "C" shaped clamping plate, which can facilitate the assembly of the clamping plate 51 between the fixing ring 40 and the ring body II 32; there can be four guide rods 52, which pass through the clamping plate 51 in pairs. The following is an example of the guide rod 52 passing through the pressure plate 51 and the fixing ring 40 and being fixed by the nuts 53 arranged above and below; The upper nut 53 is used to fix the guide rod 52 on the fixing ring 40, and the lower nut 53 is used to limit the pressure plate 51 on the guide rod 52. When the lower nut 53 is rotated, the pressure plate 51 moves on the guide rod 52. The multiple pressure blocks 54 on the pressure plate 51 will act on the ring body II 32 so that the negative Poisson's ratio structure II 31 can withstand a uniform axial force. The negative Poisson's ratio structure II 31 will undergo controlled deformation and be locked in the critical state of imminent failure, reducing the risk of deviating from the critical state. After the negative Poisson's ratio structure II 31 is in the critical deformation state, the fixing ring 40 can be welded to the anchor body 10. In addition, each pressure block 54 can be rotatably installed on the pressure plate 51. During assembly, the pressure block 54 rotates to avoid contact with the ring body II 32. After the pressure plate 51 is assembled between the fixing ring 40 and the ring body II 32, the pressure block 54 is rotated to act on the ring body II 32. In this example, after the negative Poisson's ratio structure II 31 is adjusted to the critical deformation state by nut 53, the negative Poisson's ratio composite anchor is placed in the borehole, and a tensioning device is installed at the borehole opening to apply a critical dispersion tension to the anchor body 10. This tension value is set to be greater than the ultimate tensile strength of the negative Poisson's ratio structure II 31, but less than the yield strength of the anchor body 10. Finally, the negative Poisson's ratio structure II 31 explodes and transforms into a three-dimensional metal skeleton with a wide distribution range and complex shape.

[0024] As an example of the assembly of skeleton unit 30, such as Figure 8 As shown, multiple self-locking units 20 and skeleton units 30 are arranged side by side with intervals or staggered. The negative Poisson's ratio structure II31 has ring bodies II32 fixed at both ends; This negative Poisson's ratio composite anchor also includes an adjustment component corresponding to the skeleton unit 30; The adjustment component includes a traction rope 60, a pair of fixing rings 40, and a positioning rod 55; A pair of fixing rings 40 are fixed on the anchor body 10 and located on the end side of the negative Poisson's ratio structure II 31. The ring body II 32 of the negative Poisson's ratio structure II 31 away from the orifice is fixed on one of its fixing rings 40. Multiple positioning rods 55 are fixedly connected at one end to the ring body II 32 near the orifice of the negative Poisson's ratio structure II 31, and at the other end slide through the fixing ring 40 and are fixed by the nut 53. The ring II 32 of the negative Poisson's ratio structure II 31 near the orifice is connected to the ring II 32 of another adjacent negative Poisson's ratio structure II 31 near the orifice by a taut traction rope 60; the traction rope 60 closest to the orifice extends to the outside of the orifice and can be lifted by a traction device. Specifically, in the above example, when the negative Poisson's ratio structure II 31 is adjusted to the critical deformation state by nut 53, a tensioning device is used at the borehole to apply a critical dispersed tensile force to the anchor body 10. The anchor body 10 is subjected to force, which drives the negative Poisson's ratio structure II 31 to break through the ultimate tensile strength and explode. The problem is that this negative Poisson's ratio composite anchor is located inside the borehole, and the operator stretches the anchor body 10. On the one hand, it is impossible to directly obtain whether the skeleton unit 30 is completely in the exploded state. On the other hand, when the anchor body 10 is stretched too much, it is easy to affect the expansion self-locking of the self-locking unit 20. The explanation will be based on the upper part of the negative Poisson's ratio structure II31 near the orifice. The lower end of the negative Poisson ratio structure II31 is directly fixedly connected to the fixed ring 40 through the ring body II32. The fixed ring 40 can be welded to the anchor body 10. First, fix the fixing ring 40 to the anchor body 10. The positioning rod 55 can be a bolt structure, which is fixedly connected to the ring body II 32 at the upper end of the negative Poisson ratio structure II 31. The upper end passes through the fixing ring 40 and is positioned by the nut 53. The ring body II 32 at the upper end of the negative Poisson ratio structure II 31 in the upper skeleton unit 30 is connected to the ring body II 32 at the upper end of the negative Poisson ratio structure II 31 in the lower skeleton unit 30 through the traction rope 60. The uppermost traction rope 60 is led out to the outside. After the skeleton unit 30 is installed on the anchor body 10, the nut 53 is rotated to drive the negative Poisson's ratio structure II 31 to move axially through the positioning rod 55, so that the negative Poisson's ratio structure II 31 is in a critical deformation state. The negative Poisson's ratio composite anchor is placed in the borehole, and the uppermost traction rope 60 is pulled by the traction device. Assuming that the skeleton unit 30 is divided into three groups A, B, and C from top to bottom, the corresponding traction rope A is led out from the skeleton unit A to the outside of the borehole, the traction rope B is connected between the skeleton units A and B, and the traction rope C is connected between the skeleton units B and C. When traction rope A is pulled, the negative Poisson's ratio structure II 31 in skeleton unit A is pulled and explodes to form a three-dimensional metal skeleton. At the same time, traction rope B pulls the negative Poisson's ratio structure II 31 in skeleton unit B, and traction rope C pulls the negative Poisson's ratio structure II 31 in skeleton unit C. This series structure allows skeleton units A, B, and C to explode to form a three-dimensional metal skeleton, and the operator can judge the situation by the tension of traction rope A, which is more efficient.

[0025] Example 3

[0026] When using this self-locking and skeleton-adjustable negative Poisson's ratio composite anchor, the specific steps include: Step S1, hole formation and cleaning; According to the design requirements, anchor bolt holes are drilled in the surrounding rock, and high-pressure air or water is used to clean the rock powder and slag inside the holes to ensure the cleanliness of the hole walls and to ensure the bonding quality between the grout and the surrounding rock.

[0027] Step S2, anchor bolt assembly and installation; The self-locking unit 20 and the skeleton unit 30 are installed on the anchor body 10 to form this negative Poisson's ratio composite anchor. After determining the overall mass of this composite anchor, it is inserted into the borehole, and the skeleton unit 30 is prevented from being prematurely triggered and dispersed during the installation process. Step S3: Apply axial force to skeleton unit 30; A tensioning device is installed at the orifice to apply a critical dispersed tensile force to the anchor body 10. This tensile force value is set to be greater than the ultimate tensile strength of the negative Poisson's ratio structure II 31, but less than the yield strength of the anchor body 10; or a tensioning device is installed at the orifice to apply a force to one end of the negative Poisson's ratio structure II 31 of the skeleton unit 30, and this tensile force value is greater than the ultimate tensile strength of the negative Poisson's ratio structure II 31. Under this tensile force, the negative Poisson's ratio structure II 31 undergoes excessive tensile stress, and the skeleton unit 30 fractures, disperses, or undergoes extreme plastic expansion, "exploding" inside the borehole, transforming from a cylindrical structure into a three-dimensional metal skeleton with a wide distribution and complex shape. Step S4, permeation grouting and wrapping; While maintaining the dispersed shape of the skeleton unit 30, high-strength cement grout or modified chemical grout is immediately injected into the hole using a penetration grouting process. Under pressure, the grout fills the borehole and fully wraps the anchor body 10, the self-locking unit 20, and the three-dimensional metal skeleton scattered around it. The grout seeps into the fractured surrounding rock fissures along the gaps. The negative Poisson's ratio structure I21 in the self-locking unit 20 does not respond, forming an external anchoring system of "surrounding rock-grouting body-sleeve"; Step S5: The composite solidifies and forms. Once the grout has completely solidified, a high-strength composite reinforcement is formed inside the borehole, consisting of the anchor bolt body 10, a negative Poisson's ratio structure I 21 tightly wrapped by the solidified grout, the dispersed negative Poisson's ratio structure II 31 remnants, and the grouting stone body. This significantly improves the integrity of the grout body in a fractured environment.

[0028] After the grout reaches the design strength, install the tray and anchor nut, and use a torque wrench or tensioning tool to apply the conventional design pre-tightening force to the anchor body 10 for locking. The applied pre-tightening force should be less than the yield strength or ultimate tensile strength of the negative Poisson's ratio structure I21. After construction, this negative Poisson's ratio composite anchor enters the long-term monitoring and service stage. When the surrounding rock undergoes rheological or expansion deformation, the "expansion self-locking" cycle is automatically triggered. That is, the anchor body 10 will drive the negative Poisson's ratio structure I21 to elongate axially in sync. At this time, based on the negative Poisson's ratio effect, the negative Poisson's ratio structure I21 will generate radial expansion, actively squeezing the surrounding grout or borehole wall. This squeezing action can significantly increase the normal stress of the anchoring interface, thereby greatly improving the interface friction and mechanical interlocking force, and achieving the adaptive reinforcement effect of "the greater the tension, the thicker the diameter, and the tighter the anchoring". To address the complex dynamic mechanical environment and strong disturbance characteristics of deep rock masses, several self-locking units 20 and skeleton units 30 can be staggered along the axial direction of the anchor bolt. The specific construction steps for using this negative Poisson's ratio composite anchor bolt must follow the pre-tensioning process based on the skeleton transformation mechanism. That is, when the anchor bolt body 10 is stretched, a critical pre-tensioning force between the strengths of negative Poisson's ratio structure I 21 and negative Poisson's ratio structure II 31 is applied to selectively induce the skeleton units 30 to break and disperse, allowing them to fully mix with the grouting fluid to form a reinforced stone body. Meanwhile, the self-locking units 20 maintain structural integrity under this tension, thus enabling them to continue to perform radial expansion and active tensile anchoring functions during the anchor bolt's service life.

[0029] The foregoing description, with reference to preferred embodiments, details an exemplary implementation of a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt proposed by the present invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed by the present invention, without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt, characterized in that, include: Anchor bolt body (10); At least one set of self-locking unit (20) and skeleton unit (30); The self-locking unit (20) is a cylindrical negative Poisson's ratio structure I (21), which is sleeved and fixed at both ends to the anchor rod body (10); The skeleton unit (30) is a cylindrical negative Poisson ratio structure II (31), which is fitted and fixed at one end to the anchor rod body (10), and the other end can be adjusted to move axially and be positioned. Among them, the negative Poisson ratio structure I (21) expands radially when subjected to axial force, and the negative Poisson ratio structure II (31) is provided with prefabricated break points or weakened nodes or is in a critical deformation state, so that it can break when subjected to axial force.

2. The self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 1, characterized in that, The prefabricated breakpoint or weakened node includes circumferentially arranged cut component I and circumferentially arranged cut component II; Both cut assembly I and cut assembly II include multiple cuts (311) at different locations, and the cuts (311) cause the negative Poisson ratio structure II (31) to break into blocks or strips.

3. The self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 1, characterized in that, The negative Poisson ratio structure I (21) and negative Poisson ratio structure II (31) are in the form of one or more combinations of concave structure, perforated plate structure, and chiral structure; When negative Poisson ratio structure I (21) and negative Poisson ratio structure II (31) have the same structural form, the cylindrical radial thickness of negative Poisson ratio structure II (31) is smaller than that of negative Poisson ratio structure I (21).

4. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to any one of claims 1 to 3, characterized in that, There is a gap between the negative Poisson's ratio structure I (21), the negative Poisson's ratio structure II (31) and the anchor body (10); An isolation layer that prevents adhesion is applied to the inner wall of negative Poisson ratio structure I (21) and negative Poisson ratio structure II (31), or to the outer wall of anchor body (10).

5. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 4, characterized in that, The isolation layer is a solvent-modified asphalt coating, a thin film layer formed after spraying or brushing and drying.

6. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 1, characterized in that, The negative Poisson's ratio structure II (31) has rings II (32) fixed at both ends. It also includes adjustment components corresponding to the skeleton unit (30); The adjusting component has a pair of fixed rings (40) and a plurality of circumferentially arranged guide rods (52); A pair of fixing rings (40) are fixed on the anchor body (10) and located at the end of the negative Poisson ratio structure II (31). Each guide rod (52) passes through the ring body II (32) and the fixing ring (40) at both ends and is fixed by a pair of axially arranged nuts (53) threaded limit.

7. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 6, characterized in that, The adjusting component also includes a pair of clamping plates (51) located between the fixed ring (40) and the ring body II (32); Each clamping plate (51) is fixed with an L-shaped clamping block (54). One end of the clamping block (54) can press against the ring body II (32) so that the ring body II (32) can move axially synchronously with the clamping plate (51). Both ends of the guide rod (52) pass through the clamping plate (51) and the fixing ring (40) and are then fixed by a pair of axially arranged nuts (53) with threaded limit.

8. A self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 1, characterized in that, Multiple self-locking units (20) and skeleton units (30) are arranged side by side with intervals or staggered. The negative Poisson's ratio structure II (31) has rings II (32) fixed at both ends. It also includes adjustment components corresponding to the skeleton unit (30); The adjustment component has a traction rope (60), a pair of fixing rings (40), and a positioning rod (55); A pair of fixing rings (40) are fixed on the anchor body (10) and located on the end side of the negative Poisson's ratio structure II (31). The ring body II (32) of the negative Poisson's ratio structure II (31) away from the orifice is fixed on one of its fixing rings (40). Multiple positioning rods (55) are fixedly connected at one end to the ring body II (32) near the orifice of the negative Poisson's ratio structure II (31), and at the other end slide through the fixing ring (40) and are fixed by the nut (53); The ring II (32) of the negative Poisson's ratio structure II (31) near the orifice is connected to the ring II (32) of another adjacent negative Poisson's ratio structure II (31) near the orifice by a taut traction rope (60); the traction rope (60) closest to the orifice extends to the outside of the orifice and can be lifted by a traction device.

9. A method of using a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 6 or 8, characterized in that, Specifically, the following steps are included: Step S1: Drill anchor bolt holes in the surrounding rock according to the design requirements and clean the drill holes; Adjust the skeleton unit (30) to make the negative Poisson ratio structure II (31) be in the critical deformation state; Insert the self-locking and skeleton-adjustable negative Poisson's ratio composite anchor into the borehole to prevent the middle skeleton unit (30) from prematurely triggering dispersion; Step S2, apply critical dispersion tension to the anchor body (10) or skeleton unit (30). Under the action of this tension, the negative Poisson's ratio structure II (31) undergoes over-limit tension, and the skeleton unit (30) undergoes fracture, dispersion or extreme plastic expansion, "exploding" inside the borehole, transforming from a cylindrical structure into a three-dimensional metal skeleton with a wide distribution range and complex shape, thus completing the skeleton transformation. Step S3: While maintaining the dispersed state of the skeleton unit (30), grout is injected into the hole. The grout fills the borehole under pressure and fully wraps the anchor body (10), the self-locking unit (20) and the three-dimensional metal skeleton scattered around it. The grout seeps into the fractured surrounding rock along the gaps. Once the grout has completely solidified, a high-strength composite reinforcement is formed, consisting of the anchor bolt body (10), a negative Poisson's ratio structure I (21) tightly wrapped by the solidified grout, a dispersed negative Poisson's ratio structure II (31) remnant, and the grouting stone body. Then, a preload is applied to the anchor bolt body (10) to lock it in place; Step S4: When the surrounding rock undergoes rheological or expansion deformation, causing the anchor body (10) to be stretched, the anchor body (10) will drive the negative Poisson's ratio structure I (21) to stretch axially in sync. Based on the negative Poisson's ratio effect, the negative Poisson's ratio structure I (21) will generate radial expansion, actively squeezing the surrounding grout or borehole wall, increasing the normal stress of the anchoring interface, and thus significantly improving the interface friction and mechanical interlocking force, completing the expansion self-locking effect on the borehole.

10. The method of using a self-locking and skeleton-adjustable negative Poisson's ratio composite anchor bolt according to claim 9, characterized in that, In step S2, Tensioning equipment is installed at the orifice to apply critical dispersion tension to the anchor body (10). The tension value is set to be greater than the ultimate tensile strength of the negative Poisson's ratio structure II (31), but less than the yield strength of the anchor body (10). By applying critical dispersion tension to the anchor body (10), multiple skeleton units (30) are blown open to complete the skeleton transformation. or A traction device is installed at the orifice to pull the traction rope (60) closest to the orifice. Multiple traction ropes (60) connected in series drive the moving end of the adjacent negative Poisson ratio structure II (31) to move axially. The series linkage enables multiple sets of skeleton units to explode and complete the skeleton transformation.

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