An anchor device based on negative Poisson's ratio structural theory and its application

Abstract

The present invention discloses an anchor rod based on the negative Poisson's ratio structural theory and with a self-anchoring device and its application, including a drill bit section and an anchor rod body section. The drill bit section includes a drill bit, a drill rod joint and a drill rod. The anchor rod body section includes a grouting conduit, a bellows, a strut and a steel strand. The present invention makes full use of the negative Poisson's ratio structural theory, and adds a strut to the bellows, so that when the steel strand is subjected to axial tension, the strut can push the bellows to separate up and down, thereby increasing the pressure between the bellows and the soil, achieving the effect of increasing the tangential friction of the anchor rod, and the used bellows can fully utilize the tangential friction between the pipe and the soil. The present invention has a fast construction speed, is easy to operate, is detachable, has a clean and environmentally friendly construction site, and is suitable for different engineering geological conditions such as sandy soil layers, clay soil layers, silt soil layers, pebble layers and miscellaneous fill soil layers.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering, in particular to the field of anchor rod technology, and more particularly to an anchor rod device based on negative Poisson's ratio structural theory and application thereof. Background Art

[0002] In order to meet the needs of increasingly developed projects and solve the problems of engineering disasters caused by the failure of supporting materials, many scholars at home and abroad have proposed various types of anchor force forms. At present, there are mainly the following measures: 1) Mechanical anchoring, that is, using a wedge to drive into the wedge gap at the head of the rod body to squeeze the borehole wall to provide anchoring force, such as: wedge-type anchor, inverted wedge-type anchor, shell-expanding anchor, etc.; 2) Bonding anchoring, that is, the rod body is made of steel bars or wire ropes, and is anchored by cement mortar and other bonding materials, such as cement anchors, resin anchors, hollow grouting anchors, etc.; 3) Friction anchoring, that is, anchoring is carried out by the friction between the anchor rod body and the soil, such as: seam-tube anchor, expansion-tube anchor, etc. The above anchor bolt anchoring methods have been widely used in different geotechnical engineering fields at home and abroad, such as successfully solving the support problems of fully mechanized caving coal top tunnels and broken surrounding rock tunnels. However, these support methods still belong to the field of traditional Poisson's ratio structural theory, that is, plastic hardening material structure, which is difficult to meet the disaster control requirements of surrounding rock in large deformation.

[0003] The traditional definition of Poisson's ratio is the ratio of negative transverse strain to longitudinal strain when the structure is subjected to longitudinal tension or compression, that is, when the structure is subjected to longitudinal tension, it will produce a compressive effect in the transverse direction. Similarly, when the structure is subjected to longitudinal compression, it will produce a tensile effect in the transverse direction. The negative Poisson's ratio is the ratio of positive transverse strain to longitudinal strain. Compared with the traditional Poisson's ratio structure, the negative Poisson's ratio structure has excellent tensile performance, shear performance, fracture resistance, impact resistance, energy absorption and seismic isolation and other mechanical properties. In order to improve the mechanical properties of anchor rods during slope support, an anchor rod device is proposed based on the negative Poisson's ratio structure theory, which can provide new technical methods for related geotechnical engineering fields such as foundation pit support in my country. Summary of the invention

[0004] In view of the above existing needs, the purpose of the present invention is to overcome the shortcomings of complex construction procedures in ordinary anchor construction, and combined with the structural characteristics of negative Poisson's ratio, a new anchor device is proposed. This device effectively increases the anchoring force of the anchor, can enhance the anti-overturning ability in foundation pit construction, and the device is easy to install, has a wide range of applications, and has relatively complete functions.

[0005] The present invention adopts the following technical solution:

[0006] An anchor rod device based on negative Poisson's ratio structural theory includes a drill bit section and an anchor rod body section. The drill bit section includes a drill bit 1, a drill rod joint 2 and a drill rod 3, wherein the drill bit 1 is connected to the drill rod 3 by the drill rod joint 2; wherein the drill bit 1 drives the entire drill rod 3 to be pushed forward, and the drill rod joint 2 is connected to the drill rod 3 by threads; during the process of the drill bit 1 driving the drill rod 3 to be pushed forward, the drill bit 1 plays a role of connecting the drill bit 1 and the drill rod 3, and also plays a role of waterproofing and anti-seepage, thereby preventing the corrugated pipe 5 and the support rod 6 from being eroded by groundwater.

[0007] The bolt body section includes a grouting conduit 4, a corrugated pipe 5, a support rod 6 and a steel strand 7. The bolt body section is in the form of a sleeve, the corrugated pipe 5 is sleeved inside the drill pipe 3, wherein the grouting conduit 4 is fixed in the space between the corrugated pipe 5 and the drill pipe 3. The steel strand 7 is fixed in the middle of the corrugated pipe 5 through a radial support rod 6.

[0008] The drill bit 1 drives the entire drill rod 3 to be pushed forward. After the entire drill rod 3 completes the pushing process, cement slurry 8 is poured into the space between the drill rod 3 and the corrugated pipe 5 through the grouting conduit 4, and the drill rod joint 2 and the drill rod 3 are slowly pulled out.

[0009] The grouting conduits 4 are distributed inside the drill rod joint 2 and the drill rod 3, and are respectively distributed along the drill rod circumferential directions of 0°, 90°, 180°, and 270°. The drill rod 3 is provided with a bellows 5, wherein the bellows 5 is composed of two completely identical half bellows; when the steel strand 7 is subjected to the force of being pulled out of the soil, the support rod 6 is driven to move; the support rod 6 is composed of two metal clips, wherein the two metal clips are firmly fixed on the steel strand 7 and the bellows 5, and four support rods 6 are distributed circumferentially along the bellows 5, which are respectively distributed in four directions of 45°, 135°, 225°, and 315° along the circumferential direction. Due to the special structure and distribution of the support rod 6, when the steel strand 7 is subjected to the force of being pulled out of the soil, the support rod 6 will push the two bellows 5 to separate upward and downward respectively, so that the entire bellows 5 produces the same mechanical properties as the negative Poisson's ratio structure, at which time the axial force and tangential friction between the anchor rod and the soil will increase, so that the anchor rod is firmly fixed in the soil. When the force of the steel strand is greater, the friction between the bellows and the soil will also increase accordingly, and the device greatly increases the ability of the anchor rod to be anchored in the soil.

[0010] Furthermore, the speed of grouting of the conduit 4 is appropriate to the speed of pulling out the drill rod 3, ensuring that the space between the bellows and the soil is completely filled. After the grouting process is completed, the drill rod joint 2 and the drill rod 3 are completely pulled out. At this time, a baffle 9 and an anchor 10 are installed at the end of the drill rod 3, and the anchor 10 is passed through the steel strand and then anchored. When the steel strand 7 is subjected to the force of being pulled out of the soil, the support rod 6 inside the bellows 5 will also be subjected to this force. Due to the special structure of the support rod 6, the bellows 5 will be separated from top to bottom, and the pressure and tangential friction between the bellows and the cement slurry will increase accordingly. The bellows 5 is composed of two identical half bellows, and a certain adhesive material can be applied to the joint, but the material bonding force should not be too large. The steel strand 7 and the support rod 6 are fixedly connected to ensure that the support rod 6 will not produce axial movement, and all components of the anchor rod body section need to be waterproof and anti-seepage.

[0011] In the drill bit section, the drill bit 1 is composed of cement slurry to ensure the rigidity of the drill bit. When the overall construction of the anchor rod is completed, the drill bit part is retained inside the soil body in consideration of the convenience of construction and engineering cost. The inner and outer walls of the bellows 5 should be coated with asphalt binder material to form an anti-corrosion and waterproof layer. The wall thickness of the bellows 5 is between 5 and 10 mm, and the wave pitch is between 50 and 100 mm, so that it can withstand a certain internal pressure and ensure that it can provide sufficient tangential friction between the pipe and the soil when the steel strand 7 is subjected to tension. The anchor rod length applicable to the present invention should be not less than 1m and not more than 5m, because an excessively long anchor rod length will cause excessive resistance when the anchor rod is pushed in, causing local buckling of the drill rod or damage to the pipe body. An anchor rod that is too short will cause insufficient anchoring force after self-anchoring and fail, and cannot meet the requirements for the use of the anchor rod.

[0012] The present invention provides a novel anchor rod device based on the negative Poisson's ratio structural theory. The anchor rod is divided into two parts for connection through a drill rod joint, so that it can be easily installed during anchor rod construction. Compared with the prior art, the present invention has the following significant features:

[0013] 1. The present invention makes full use of the negative Poisson's ratio structural theory and adds a support rod to the corrugated pipe, so that when the steel strand is subjected to axial tension, the support rod can push the corrugated pipe to separate up and down, thereby increasing the pressure between the corrugated pipe and the soil, thereby achieving the effect of increasing the tangential friction of the anchor rod, and the corrugated pipe used can fully utilize the tangential friction between the pipe and the soil.

[0014] 2. The present invention performs grouting between the drill rod and the bellows, so that the bellows is in full contact with the soil, thereby increasing the tangential friction of the entire anchor rod, thereby enhancing the pull-out resistance of the anchor rod, shortening the length of the anchor rod, and reducing engineering costs.

[0015] 3. In the present invention, since the anchor and the anchor rod body are connected by a baffle, it can be ensured that if the anchor needs to be removed after the construction is completed, it is only necessary to remove the anchor and the baffle and push the steel strand into the soil. The diameter of the corrugated pipe will be reduced, and the pipe-soil interface will be separated, so that the anchor can be removed.

[0016] 4. The invention has a fast construction speed and convenient operation. The whole operation can be completed by a single person, the engineering cost is low, labor is saved, the construction site is clean and environmentally friendly, and it is suitable for different engineering geological conditions such as sandy soil layers, clay soil layers, silt soil layers, pebble layers and miscellaneous fill soil layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the three-dimensional structure of a new type of anchor before grouting based on the negative Poisson's ratio structural theory.

[0018] Figure 2 It is a schematic diagram of the three-dimensional structure of a new type of anchor after grouting based on the negative Poisson's ratio structural theory.

[0019] Figure 3 This is a side view of a new type of anchor based on negative Poisson's ratio structural theory before grouting.

[0020] Figure 4 It is a side view of a new type of anchor bolt after grouting based on negative Poisson's ratio structural theory.

[0021] Figure 5 yes Figure 3 Schematic diagram of the structure of the AA section.

[0022] Figure 6 yes Figure 4 Schematic diagram of the structure of the middle BB section.

[0023] Figure 7 It is a schematic diagram of a single strut before and after being subjected to force; a is when the strut is not subjected to force, and b is when the strut is subjected to force. DETAILED DESCRIPTION

[0024] The following is combined with Figures 1 to 7 The specific embodiments of the present invention are described in detail.

[0025] Figure 1The figure shows a three-dimensional schematic diagram of a new anchor device based on the negative Poisson's ratio structural theory before grouting. According to its construction sequence and structural characteristics, the anchor is divided into a drill section and an anchor rod section. In this embodiment, before the anchor jacking construction, the bellows 5 is first spliced ​​by two identical half bellows, and then each support rod 6 is fixed on the steel strand 7, and the support rods 6 are distributed in sequence along the axial direction of the bellows to ensure that when the steel strand 7 is pulled, the support rod 6 can provide sufficient thrust to separate the bellows. After that, the drill bit interface 2 is connected to the drill rod 3, and after the grouting conduit 4 is fixed at the specified position inside the drill rod 3, the bellows 5 is inserted into the drill rod 3, and the drill bit interface 2 is connected to the drill bit 1. Then the drill bit 1 is placed at the predetermined position and jacking begins. During the jacking construction process, the jacking should be slow to ensure the integrity of the bellows 5 to avoid cracking or even damage.

[0026] Reference Figure 2 As shown, it is a three-dimensional schematic diagram of a new type of anchor device after grouting based on the negative Poisson's ratio structural theory. The anchor rod body includes a drill rod joint 2, a drill rod 3, a grouting conduit 4, a bellows 5, a support rod 6, and a steel strand 7. After the drill rod completes the jacking process, cement slurry 8 is poured from the grouting conduit 4 into the space between the drill rod 3 and the bellows 5, and the drill rod joint 2 and the drill rod 3 are slowly pulled out to ensure that the space between the bellows and the soil is completely filled. When the grouting process is completed, a baffle 9 is added to the end of the bellows, and the connection needs to be sealed with sealing materials. After standing for 12 hours, the cement slurry in the pipe solidifies and reaches a certain strength, and then an anchor 10 is added behind the baffle 9. The anchor 10 is passed through the steel strand and then anchored. Reference Figure 4 As shown, the steel strand 7 produces axial displacement, so that when the support rod 6 is subjected to the tension of the steel strand, it pushes the bellows 3 to separate the two bellows, and then the anchor rod enters the self-anchoring state and has a certain pull-out resistance.

[0027] refer to Figure 7 As shown in , after the steel strand is subjected to tension, the strut 6 can produce a lateral positive displacement due to the ductility and compressibility of the two joints fixed on the steel strand 7 and its working clip, and the cumulative deformation of multiple struts 6 can meet the requirement of pushing the bellows to separate.

[0028] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. An anchor device based on negative Poisson's ratio structural theory, characterized in that: It includes a drill bit section and an anchor rod body section; the drill bit section includes a drill bit, a drill rod joint and a drill rod, wherein the drill bit is connected to the drill rod by the drill rod joint; wherein the drill bit drives the entire drill rod to be pushed forward, and the drill rod joint is connected to the drill rod by a thread; during the process of the drill bit driving the drill rod to be pushed forward, the drill bit and the drill rod are connected, and the drill rod joint is waterproof and anti-seepage; The bolt body section includes a grouting conduit, a corrugated pipe, a support rod and a steel strand; the bolt body section is in the form of a casing, the corrugated pipe is sleeved inside the drill pipe, wherein the grouting conduit is fixed in the space between the corrugated pipe and the drill pipe; the steel strand is fixed in the middle of the corrugated pipe through a radial support rod; The drill bit drives the entire drill rod to push forward. After the entire drill rod completes the pushing forward process, cement slurry is poured into the space between the drill rod and the bellows through the grouting conduit, and the drill rod joint and the drill rod are slowly pulled out at the same time; The grouting conduits are distributed inside the drill pipe joint and the drill pipe, and are respectively distributed along the drill pipe circumference at 0°, 90°, 180°, and 270°; When the steel strand is subjected to the force of being pulled out of the soil, the support rod will be driven to move; the support rod is composed of two metal clips, wherein the two metal clips are firmly fixed on the steel strand and the corrugated tube, and four support rods are distributed circumferentially along the corrugated tube, which are distributed in four directions of 45°, 135°, 225° and 315° along the circumferential direction. When the support rod is subjected to the force of the steel strand being pulled out of the soil, the support rod will push the two corrugated tubes to separate upward and downward respectively, so that the entire corrugated tube produces the same mechanical properties as the negative Poisson's ratio structure, at this time, the axial force and tangential friction between the anchor rod and the soil will increase, so that the anchor rod is fixed in the soil; when the force of the steel strand is greater, the friction between the corrugated tube and the soil will also increase accordingly, and the device greatly increases the ability of the anchor rod to be anchored in the soil; The speed of grouting the guide tube is appropriate to the speed of pulling out the drill rod, ensuring that the space between the bellows and the soil is completely filled; when the grouting process is completed, the drill rod joint and the drill rod are completely pulled out, at this time, a baffle and an anchor are installed at the end of the drill rod, the anchor is passed through the steel strand, and then anchored; when the steel strand is subjected to the force of being pulled out of the soil, the support rod inside the bellows will also be subjected to this force, and due to the structure of the support rod, it will cause the bellows to separate up and down, and the pressure and tangential friction between the bellows and the cement slurry will increase accordingly; the bellows consists of two identical upper and lower half bellows.

2. The anchor device based on negative Poisson's ratio structural theory according to claim 1, characterized in that: The inner and outer walls of the corrugated pipe are coated with asphalt bonding material to form an anti-corrosion and waterproof layer.

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