Similar model test anchor cable with negative Poisson's ratio structure and manufacturing method thereof

Abstract

The invention discloses a similar model test anchor cable with a negative Poisson's ratio structure and a manufacturing method of the similar model test anchor cable. The anchor cable comprises a tray (2), a fastening nut (3), a cone (4), a sleeve (5), a steel wire (6), an axial force monitoring device (7) and a steel wire lock catch (8), and the sleeve (5) is a main body of the anchor cable and is in a hollow barrel shape; the tray (2) is a quadrangular prism of which the bottom surface is a square with a hole, and is used for transmitting the deformation of the test block (1) to the sleeve (5). The diameter of one end of the cone (4) is slightly larger than the inner diameter of the sleeve (5), and the diameter of the other end is slightly smaller than the inner diameter of the sleeve (5). One end of a steel wire (6) penetrates through a small hole of the cone (4) and then is fixed by a steel wire lock catch (8), and the other end of the steel wire (6) penetrates through the sleeve (5) and then is integrally arranged in an anchor cable drill hole of a test block (9). And the tray (2) and the fastening nut (3) are screwed on the sleeve (5) exposed out of the test block (9). According to the invention, the constant resistance end and the anchoring end are easy to install and apply pre-tightening force, and the applicability is wide.

Description

Technical Field

[0001] The invention relates to the field of tunnel physical model test reinforcement support structure, in particular to a similar model test anchor cable with a negative Poisson's ratio structure and a manufacturing method thereof. Background Art

[0002] With the rapid development of the world economy, human demand for energy and available space is increasing and gradually expanding underground. However, during tunnel excavation, the complex geological environment and deep high stress conditions cause rocks to exhibit significant time-effect deformation such as creep, which significantly threatens the safety of underground projects. This time-effect deformation poses a huge threat to the safety of underground projects. In recent years, due to the deterioration of rock conditions and the increasing complexity of the environment, the number of tunnel collapse accidents has shown an increasing trend year by year, and has become one of the most common and most serious geological disasters. In order to ensure the safety of underground excavation projects, system anchor cables are currently the main means of controlling the surrounding rock of underground projects. Therefore, in order to effectively control the deformation of the surrounding rock and ensure the stability of the underground space, it is of great significance to deeply study the control mechanism of tunnel deformation by anchor cable support.

[0003] In order to deeply study the rock deformation, support structure stability and tunnel collapse mechanism during tunnel excavation, physical model test has become a common method in tunnel engineering research. This method can truly simulate the characteristics of geological structure and engineering structure in the laboratory, and directly observe the rock deformation, support structure response and stress changes inside the tunnel. By precisely controlling the test parameters, physical model test can effectively study the influence of key variables on engineering behavior. In addition, the scaled model can simulate the behavior of large-scale engineering in a short time, thus overcoming the time and space limitations of field observation.

[0004] With the development of similar model test anchor cables, scholars have achieved certain research results in making similar model test anchor cables, but there are some limitations or defects:

[0005] (1) The installation process of similar model test anchors is limited by the model space and traditional manufacturing methods, especially in complex structures or small-scale models. The mechanical properties of similar model test anchor materials are difficult to fully meet the similarity ratio requirements, and the coupling effect between them and the surrounding rock often deviates, resulting in a lack of accuracy in their bearing characteristics.

[0006] (2) Due to the limitations of model size and test conditions, the monitoring results of stress and deformation are not accurate enough to effectively simulate the long-term bearing characteristics of the field and anchor cables. The simplification of the test environment and loading conditions may further deviate from the actual engineering situation, thus affecting the reliability of the results.

[0007] (3) Currently, most anchor model tests are large-scale physical model tests, which have high test design complexity, high operation difficulty and long test cycle. Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] One of the technical problems to be solved by the present invention is that the existing similar model test anchor cables cannot simultaneously meet the requirements of applying preload and constant resistance to large deformation. Another technical problem to be solved by the present invention is that the existing similar model test anchor cables cannot provide the relationship between the thickness of the sleeve and the constant resistance while maintaining the force transmission characteristics similar to those of the on-site anchor cables.

[0010] (II) Technical solution

[0011] In order to solve the above technical problems, the first aspect of the present invention proposes a similar model test anchor cable with a negative Poisson's ratio structure, which is used to be inserted into the anchor cable drill hole reserved in the test block for testing, and is characterized in that: the anchor cable includes a tray, a fastening nut, a cone, a sleeve, a steel wire, an axial force monitoring device and a steel wire lock buckle, wherein the sleeve is the main body of the anchor cable and is a hollow cylinder; the tray is a quadrangular prism with a square bottom surface, and a cylindrical hole is left between the top surface and the bottom surface, which is used to transfer the deformation of the test block to the sleeve; The cone is piston-shaped, with different diameters at both ends, one end having a diameter slightly smaller than the inner diameter of the sleeve, and the other end having a diameter slightly larger than the inner diameter of the sleeve; a small hole is reserved at the bottom of the cone for the steel wire to pass through; one end of the steel wire passes through the small hole of the cone and is fixed with a wire lock, and the other end passes through the sleeve and is installed as a whole into the anchor cable drilling hole of the test block, and is fixed with a wire lock 8 after bypassing the nut inside the axial force monitoring device; the axial force monitoring device is tightly attached to the tray; the tray and the fastening nut are screwed on the sleeve exposed from the test block.

[0012] According to a preferred embodiment of the present invention, the interior of the sleeve is a smooth curved surface, and the exterior is a spiral surface.

[0013] According to a preferred embodiment of the present invention, the small diameter end of the cone is inserted into the sleeve. When the cone slides under tension, the large diameter end of the cone and the sleeve generate friction resistance, thereby providing constant resistance for the anchor cable. At the same time, the diameter of the large diameter end of the cone is slightly larger than the inner diameter of the sleeve, thereby causing the sleeve to deform, thereby generating a negative Poisson's ratio effect.

[0014] According to a preferred embodiment of the present invention, at the opening of one end of the sleeve where the sleeve contacts the cone, the inner wall of the sleeve is designed to be a smooth slope that fits the shape of the cone, so as to facilitate the cone to move into the sleeve when sliding begins.

[0015] According to a preferred embodiment of the present invention, the axial force monitoring device is connected to a strain gauge, and the strain of the test block is monitored in real time by the strain gauge.

[0016] According to a preferred embodiment of the present invention, the fastening nut is used to transfer the prestress applied by the similar model test anchor cable to the surrounding medium, and at the same time can control the tension of the similar model test anchor cable, thereby adjusting the anchoring force.

[0017] The second aspect of the present invention provides a method for manufacturing a similar model test anchor cable with a negative Poisson's ratio structure, which is used to manufacture the similar model test anchor cable as described above, and is characterized in that it comprises the following steps:

[0018] S1. Model the similar model test anchor cable based on the negative Poisson's ratio anchor cable used in actual engineering;

[0019] S2, 3D printing of the tray, fastening nut and sleeve of the anchor cable of similar model test using thermoplastic polyurethane elastomer material;

[0020] S3, 3D printing the cone of the anchor cable of similar model test using aluminum alloy material;

[0021] S4, assembling the 3D printed tray, fastening nut, cone, sleeve, steel wire, axial force monitoring device and steel wire lock buckle. Anchor cable Anchor cable According to a preferred embodiment of the present invention, step S1 includes:

[0022] S1.1. Based on the on-site monitoring data, obtain the on-site stress boundary conditions and on-site displacement variation law of the on-site tunnel or anchor unit, and determine the similarity constant that the physical model test should satisfy based on the similarity law of the physical model test;

[0023] S1.2, design the specific dimensions of the anchor cable for the similar model test;

[0024] S1.3. Establish a three-dimensional digital model of the similar model test anchor cable.

[0025] The third aspect of the present invention provides a method for performing an anchor tensile test on a similar model test anchor using the negative Poisson's ratio anchor, characterized in that it comprises the following steps:

[0026] T1. Conducting a cable tensile test on similar model test anchor cables with different sleeve sizes to obtain the constant resistance of the similar model test anchor cable and the relationship curve between the sleeve thickness and the axial force of the similar model test anchor cable; obtaining the length of the similar model test anchor cable from the geometric similarity ratio, and determining the length and geometric size of the sleeve;

[0027] T2. Conduct multiple tensile tests on the similar model test anchor cable with determined size to verify whether it meets the similarity requirements;

[0028] T3. Install the similar model test anchor cable in the reserved anchoring borehole of the test block to conduct a small anchoring test.

[0029] (III) Beneficial effects

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The 3D printing anchor cable method provided by the present invention overcomes the problems of insufficient holding force accuracy and uneven holding force in the traditional method, and also solves the problem that it is difficult to meet the breaking similarity ratio in the physical model test. Similarities are made in terms of anchor cable size, anchor cable axial force and anchor cable force transmission to obtain similar anchor cables suitable for conducting small-scale tests.

[0032] (2) The similar model test anchor provided by the present invention is easy to install at both the constant resistance end and the anchoring end, and the pre-tightening force can be applied by tightening the fastening nut and the wire lock buckle, which solves the problem that the traditional similar anchor can only apply the pre-tightening force at the constant resistance end.

[0033] (3) The thermoplastic polyurethane elastomer material used in the present invention is reusable, and the cone is made of aluminum alloy. After the cone slides inside the sleeve, the sleeve can still be used next time.

[0034] (4) The present invention has strong applicability. The axial force ranges of the anchor cable obtained by calculating the breaking similarity constants in different physical model tests are different. The axial force of the anchor cable can be changed by changing the thickness of the sleeve. The axial force range that this anchor cable can provide is relatively large and has strong applicability.

[0035] (5) The present invention can adjust the sleeve length according to the corresponding geometric conditions of the physical model so that it satisfies the strain similarity constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of a similar model test anchor cable and a test block with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0037] Figure 2 It is a structural schematic diagram of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0038] Figure 3 It is a schematic structural diagram of a tray of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0039] Figure 4 It is a schematic structural diagram of a fastening nut of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0040] Figure 5It is a schematic structural diagram of a cone of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0041] Figure 6 It is a schematic diagram of the assembly relationship between the cone, steel wire and steel wire lock buckle of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0042] Figure 7 and Figure 8 They are respectively a three-dimensional structural schematic diagram and a cross-sectional schematic diagram of a sleeve of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0043] Fig. 9 It is a schematic diagram of the assembly dimensions of a sleeve and a cone of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0044] Fig.10 This is a relationship diagram between the thickness of the sleeve and the axial force of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0045] Fig.11 It is a schematic diagram of the installation of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0047] Figure 1 This is a schematic diagram of a similar model test anchor cable and test block structure with a negative Poisson's ratio structure according to an embodiment of the present invention. Figure 1 As shown, an anchor cable drilling hole 12 is reserved in the test block 9. The similar model test anchor cable 1 inserted into the anchor cable drilling hole 12 is a composite structure, and its two ends are an anchoring end and a constant resistance end, respectively. The anchoring end is inserted into the test block 9, and the constant resistance end opposite to the anchoring end extends out of the anchor cable drilling hole 12. The anchoring end includes an axial force monitoring device 7 and a wire lock buckle 8, and the constant resistance end includes a tray 2, a fastening nut 3, a cone 4, a sleeve 5 and a wire lock buckle 8. The sleeve 5 is the main body of the anchor cable and is a hollow cylinder.

[0048] Figure 2 Schematic diagram of the structure of a similar model test anchor cable with a negative Poisson's ratio structure in the above embodiment. Figure 2As shown, the similar model test anchor cable 1 of the present invention comprises a tray 2, a fastening nut 3, a cone 4, a sleeve 5, a steel wire 6, an axial force monitoring device 7 and a steel wire lock 8. One end of the steel wire 6 passes through the small hole of the cone 4 and is fixed with the steel wire lock 8, and the other end passes through the sleeve 5 and is installed as a whole into the anchor cable drilling hole of the test block 9, and then the tray 2 and the fastening nut 3 are screwed onto the exposed sleeve 5, and the other end of the steel wire 6 passes through the anchor cable drilling hole and the tray, bypasses the nut inside the axial force monitoring device 7 and is fixed with the steel wire lock 8, and the axial force monitoring device 7 is close to the tray 2.

[0049] Figure 3 Schematic diagram of the structure of the tray of the similar model test anchor cable with negative Poisson's ratio structure in the above embodiment. Figure 3 As shown, the tray 2 is a quadrangular prism with a square bottom surface, and a cylindrical hole is left between the top surface and the bottom surface. The diameter of the circular hole is equal to the outer diameter of the sleeve. The height of the quadrangular prism is relatively small and it is in the shape of a flat plate, which plays the role of transmitting the deformation of the test block 1 to the sleeve 5.

[0050] Figure 4 Schematic diagram of the structure of the fastening nut of the similar model test anchor cable with negative Poisson's ratio structure in the above embodiment. Figure 4 As shown, the fastening nut 3 is a regular hexahedron with a circular hole in the middle, the diameter of the circular hole is equal to the outer diameter of the sleeve, the thickness is relatively thin, and the size is slightly smaller than the tray 2. By tightening the fastening nut 3, the prestress applied by the similar model test anchor cable 1 can be transferred to the surrounding medium, and at the same time, the tension of the similar model test anchor cable 1 can be controlled, thereby adjusting the anchoring force.

[0051] Figure 5 Schematic diagram of the structure of the cone of the similar model test anchor cable with negative Poisson's ratio structure in the above embodiment. Figure 5 As shown, the cone 4 is piston-shaped, with different diameters at both ends, one end having a diameter slightly smaller than the inner diameter of the sleeve 5, and the other end having a diameter slightly larger than the inner diameter of the sleeve 5. When installing, the end with a slightly smaller diameter is inserted into the sleeve 5 and stuck. As an example, the size of the cone 4 is a circle with a diameter of 12.5 mm in the lower section, a circle with a diameter of 5.6 mm in the upper section, a height of 15 mm, and a circular hole with a diameter of 2 mm in the middle opening penetrating the cone 4, so that the steel wire 6 can pass through when installing the anchor cable 1 of the similar model test.

[0052] Figure 6 The figure is a schematic diagram of the assembly relationship between the cone, steel wire and steel wire lock buckle of a similar model test anchor cable with a negative Poisson's ratio structure in the above embodiment. Figure 6As shown, the similar model test anchor cable 1 provided by the present invention is easy to install at both the constant resistance end and the fixed end, and the pre-tightening force can be applied by tightening the fastening nut 3 and the wire lock buckle 8. The axial force monitoring device 7 is connected to the strain gauge, and the pre-tightening force can be applied to the similar model test anchor cable 1 by tightening the fastening nut 3 or the nut in the axial force monitoring device 7 with a wrench, and the data displayed by the strain gauge software can be monitored in real time.

[0053] Therefore, the present invention can solve the problem that the conventional similar model test anchor cable can only apply pre-tightening force at the constant resistance end.

[0054] Figure 7 and Figure 8 They are respectively a three-dimensional structural schematic diagram and a cross-sectional schematic diagram of a sleeve of a similar model test anchor cable with a negative Poisson's ratio structure in the above embodiment. Figure 7 and Figure 8 As shown, the inside of the sleeve is a smooth curved surface, and the outside is a spiral surface. At the same time, at the opening of the end where the sleeve 5 contacts the cone 4, the inner wall of the sleeve 5 is designed to be a smooth slope that fits the shape of the cone, so that the cone 4 can move toward the inside of the sleeve when the sliding starts. Figure 8 The lower part of the sleeve or Fig. 9 On the left side of the sleeve, it can be seen that the thickness of the sleeve wall 5 gradually changes to fit the large diameter end of the cone 4. If the inner diameter of the sleeve opening is not processed as above, the large diameter end of the cone 4 slides into the sleeve, which will cause a large squeeze on the sleeve opening and easily cause the sleeve 5 to crack. Therefore, the above design is to allow the cone 4 to slide in smoothly at the beginning, and to prevent the sleeve 5 from cracking at this end.

[0055] The small end of the cone 4 is inserted into the sleeve 5. When the cone 4 is subjected to tension and slides, the large diameter end and the sleeve 5 generate friction resistance, thereby providing a constant resistance similar to the model test anchor 1. At the same time, the diameter of the large diameter end of the cone 4 is slightly larger than the inner diameter of the sleeve 5, so that the sleeve 5 is deformed, thereby generating a negative Poisson's ratio effect. As an example, the internal thread radius of the inner nut is 6.4mm, the distance between the two parallel sides of the regular hexagon is 20mm, and the thickness is 8mm. The tray is 5mm thick, the side length is 30mm, and the internal circle size is 12.6mm.

[0056] Fig. 9 1 is a schematic diagram of the assembly dimensions of the sleeve and cone of a similar model test anchor cable with a negative Poisson's ratio structure in the above embodiment. Fig. 9 As shown, as an example, the outer diameter of the sleeve 5 is 12.5 mm, the inner diameter can be 7, 7.5, 8, 8.5 mm respectively, the length is 40 mm, the thread is 20 turns, divided into 40 small sections, and scaled inward by 0.85.

[0057] From the structure in the above figure, it can be seen that the similar model test anchor cable 1 of the present invention can simulate the characteristics of a negative Poisson's ratio anchor cable with a large elongation and constant resistance after being subjected to force. When an axial external load (tension) acts on the constant resistance end of the similar model test anchor cable 1, the sleeve 5 produces a displacement in the opposite direction to the anchoring section, which is equivalent to the sliding of the cone 4 relative to the inner wall of the sleeve 5. This sliding is the elongation deformation of the similar model test anchor cable 1.

[0058] The following is a method for manufacturing a similar model test anchor cable having a negative Poisson's ratio structure of the present invention. The method of the present invention comprises the following steps:

[0059] S1. Model the similar model test anchor cable based on the negative Poisson's ratio anchor cable used in actual engineering.

[0060] Specifically, the structure and size of the similar model test anchor cable of the present invention are determined according to the negative Poisson's ratio anchor cables used in actual projects.

[0061] S1.1. First, the present invention obtains the on-site stress boundary conditions and on-site displacement variation law of the on-site tunnel or anchoring unit based on the on-site monitoring data, and determines the similarity constants that the physical model test should satisfy based on the similarity law of the physical model test.

[0062] Similarity constants include the breaking similarity constant C F , geometric similarity constant C l Similar constant C to bulk density γ The similar anchor breaking load can be determined based on the similarity constant.

[0063] A specific similarity ratio design is carried out based on the basic structure of the similarity model test anchor cable 1. The axial geometric similarity and mechanical similarity of the similarity model test anchor cable 1 are carried out, and the breaking similarity constant C of the anchor cable is F Need to meet:

[0064]

[0065] Where: C F is the breaking similarity constant, C γ is the heavy similarity constant, C l is the geometric similarity constant.

[0066] The similarity ratio of the breaking load of the anchor cable can be obtained through calculation. The breaking load of the anchor cable with negative Poisson's ratio in the actual project is used to determine the breaking load of the anchor cable 1 in the similar model test, i.e. the constant resistance.

[0067] As a specific example, in formula (1), the bulk density similarity constant C γ Set to 1:1, set the geometric similarity constant C l is 10:1, and the breaking similarity constant C of the anchor cable can be obtained through calculation.F It is 1000:1.

[0068] From the on-site tensile test, it can be seen that the effective elongation of the constant resistance large deformation anchor cable is 25% to 30%, and the constant resistance is basically stable at 350kN, which can ensure that the anchor cable has a good constant resistance while undergoing large deformation. According to the equation, the breaking similarity ratio of the constant resistance large deformation anchor cable is calculated to obtain the axial force of the similar anchor cable to be 350N.

[0069] Preferably, the similar model test anchor cable 1 achieves a constant resistance effect through the friction resistance between the cone 4 and the sleeve 5, wherein the diameter of one end of the cone 4 is slightly larger than the inner diameter of the sleeve 5, thereby providing a constant resistance through friction.

[0070] S1.2. Carry out specific dimension design for similar model test anchor cable 1.

[0071] The diameter of cone 4, the thickness of sleeve 5 and the length of sleeve 5 are the main factors affecting the constant resistance and elongation of similar model test anchor 1. Therefore, the size of cone 4 is determined, and a three-dimensional digital model of similar model test anchor 1 with different sleeve 5 thicknesses is established. The model includes tray 2, fastening nut 3, cone 4, sleeve 5 and steel wire 6.

[0072] The inner diameter of the sleeve 5 is slightly smaller than the maximum diameter of the cone 4, so that the cone can generate greater friction when sliding.

[0073] S1.3. Establish a three-dimensional digital model of the anchor cable 1 for similar model test.

[0074] The geometrical dimensions, spatial shapes and structural data of similar model test anchor cables 1 with different sleeve 5 thicknesses to be prepared are determined according to similarity theory, and then a three-dimensional digital model of the similar model test anchor cable 1 is established based on the geometrical dimensions, spatial shapes and structural data using modeling software.

[0075] S2. Use thermoplastic polyurethane elastomer material to 3D print the tray 2, fastening nut 3 and sleeve 5 of the similar model test anchor cable.

[0076] The parts are 3D printed according to the three-dimensional digital model obtained in step S1. The tray 2, the fastening nut 3, and the sleeve 5 are 3D printed with thermoplastic polyurethane elastomer material, and the model is checked and the printing size error is corrected.

[0077] S3. Use aluminum alloy material to 3D print the cone of the anchor cable for similar model test.

[0078] To achieve the constant resistance large deformation effect, the material hardness of the cone 4 is greater than that of the sleeve 5. The 3D printing material of the cone 4 can be selected from aluminum alloy material or resin material for printing, and the model is checked and the printing size error is corrected. Preferably, the cone 4 is printed with aluminum alloy material.

[0079] S4, assembling the 3D printed tray 2, the fastening nut 3, the sleeve 5, the cone 4, the steel wire 6, the axial force monitoring device 7 and the steel wire lock 8.

[0080] One end of the steel wire 6 passes through the small hole of the cone 4 and is fixed with a wire lock buckle 8. The other end passes through the sleeve 5 and the whole is installed into the anchor cable hole of the test block 9. Then the tray 2 and the fastening nut 3 are screwed onto the exposed sleeve 5. The other end of the steel wire 6 passes through the anchor cable hole and the tray, bypasses the nut inside the axial force monitoring device 7 and is fixed with a wire lock buckle 8. The axial force monitoring device 7 is close to the tray 2.

[0081] The following describes the steps of using the negative Poisson's ratio anchor cable of the present invention to perform an anchor cable tensile test on a similar model test anchor cable:

[0082] T1. Conduct anchor cable tensile tests on similar model test anchor cables 1 with different sleeve 5 sizes to obtain the relationship curve between the constant resistance of similar model test anchor cables 1 and the sleeve 5 thickness, as well as the axial force of similar model test anchor cables 1. The thickness of sleeve 5 can be determined from the constant resistance of similar model test anchor cables 1 through the relationship curve. The length of similar model test anchor cables 1 can be obtained from the geometric similarity ratio, and the elongation of the on-site anchor cables and similar model test anchor cables 1 is consistent from the strain similarity ratio, and finally the length and geometric size of the anchor cable sleeve are determined.

[0083] Specifically, the sliding of the cone 4 relative to the inner wall of the sleeve 5 is the deformation or elongation of the similar model test anchor 1, and the total length of the sleeve 5 is the elongation of the similar model test anchor 1. Therefore, the length dimension of the sleeve 5 can be obtained through the length and elongation of the similar model test anchor 1.

[0084] Fig.10 This is a relationship diagram between the thickness of the sleeve and the axial force of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention.

[0085] like Fig.10 As shown, similar model test anchor cables 1 with different sleeve 5 sizes are subjected to anchor cable tensile tests to obtain a relationship curve between the constant resistance of the similar model test anchor cable 1 and the thickness of the sleeve 5 and the axial force of the similar model test anchor cable 1.

[0086] Specifically, a static tensile test was performed using a tensile loading device. The test used a constant loading rate for tensile loading, and the loading rate was 11.0 mm / min, and the following results were obtained: Fig.10 The tensile curve of the similar model test anchor cable 1 is shown. Among them, the constant resistance of the similar anchor cable with a sleeve thickness of 7 mm is about 350N, which meets the test requirements.

[0087] T2. After the size is determined, multiple tensile tests are performed on the similar model test anchor cable 1 with the determined size to verify whether it meets the similarity requirements.

[0088] T3. Install the similar model test anchor cable 1 in the reserved anchor borehole 12 of the tunnel physical model test block 9 to carry out an indoor small-scale anchor test.

[0089] Specifically, one end of the steel wire 6 passes through the cone 4 and is fixed with a wire lock 8, the other end of the steel wire 6 passes through the sleeve 5, the cone 4 is pressed against one end of the sleeve 5, the sleeve 5 and the other end of the steel wire 6 pass through the reserved anchor drill hole 12 when the tunnel physical model test block 9 is cast, the tray 2 and the fastening nut 3 are passed through the sleeve 5 in turn, the tray 2 is pressed against the tunnel physical model test block 9, and the fastening nut 3 is screwed on the sleeve 5 to tightly fit the tray 2.

[0090] Fig.11 The installation diagram of a similar model test anchor cable with a negative Poisson's ratio structure according to an embodiment of the present invention is shown. Specifically, the other end of the steel wire 6 passes through the hole-containing screw 10 and is fixed by the steel wire lock buckle 8. The hole-containing screw 10 is tightened into the axial force monitoring device 7. The other end of the axial force monitoring device 7 is fixed to the axial force monitoring bracket 11 by the hole-containing screw 10. The strain gauge can be connected to monitor the tension of the similar model test anchor cable 1 during the test in real time, and the specific value of the preload force can be checked through the strain gauge.

[0091] Specifically, the pre-tightening force can be applied to the anchor cable 1 in the similar model test by tightening the fastening nut 3 or tightening the axial force monitoring device 7 .

[0092] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A similar model test anchor cable with a negative Poisson's ratio structure, used for inserting into an anchor cable drill hole (12) reserved in a test block (9) for testing, characterized in that: The anchor cable (1) comprises a tray (2), a fastening nut (3), a cone (4), a sleeve (5), a steel wire (6), an axial force monitoring device (7) and a steel wire lock buckle (8), wherein: The sleeve (5) is the main body of the anchor cable (1) and is in the shape of a hollow cylinder; The tray (2) is a quadrangular prism with a square bottom surface, and a cylindrical hole is left between the top surface and the bottom surface, which is used to transfer the deformation of the test block (1) to the sleeve (5); The cone (4) is piston-shaped, with different diameters at both ends, one end having a diameter slightly smaller than the inner diameter of the sleeve (5), and the other end having a diameter slightly larger than the inner diameter of the sleeve (5); a small hole is reserved at the bottom of the cone (4) to allow the steel wire (6) to pass through; One end of the steel wire (6) passes through the small hole of the cone (4) and is fixed with a steel wire lock buckle (8), and the other end passes through the sleeve (5) and is installed as a whole into the anchor cable drilling hole (12) of the test block (9), passes around the nut inside the axial force monitoring device (7) and is fixed with a steel wire lock buckle (8); The axial force monitoring device (7) is in close contact with the tray (2); The tray (2) and the fastening nut (3) are screwed onto the sleeve (5) that exposes the test block (9).

2. The similar model test anchor cable with negative Poisson's ratio structure as claimed in claim 1, characterized in that: The sleeve (5) has a smooth curved surface inside and a spiral surface outside.

3. The similar model test anchor cable with negative Poisson's ratio structure as claimed in claim 1, characterized in that: The small diameter end of the cone (4) is inserted into the sleeve (5). When the cone (4) is subjected to a tensile force and slides, the large diameter end of the cone (4) and the sleeve (5) generate friction resistance, thereby providing a constant resistance for the anchor cable (1). At the same time, the diameter of the large diameter end of the cone (4) is slightly larger than the inner diameter of the sleeve (5), thereby causing the sleeve (5) to deform, thereby generating a negative Poisson's ratio effect.

4. The similar model test anchor cable with negative Poisson's ratio structure as claimed in claim 3, characterized in that: At the opening of one end of the sleeve (5) where it contacts the cone (4), the inner wall of the sleeve (5) is designed to be a smooth slope that fits the shape of the cone, so as to facilitate the cone (4) to move into the interior of the sleeve (5) when sliding begins.

5. The similar model test anchor cable with negative Poisson's ratio structure as claimed in claim 1, characterized in that: The axial force monitoring device (7) is connected to a strain gauge, and the strain of the test block (1) is monitored in real time via the strain gauge.

6. The similar model test anchor cable with negative Poisson's ratio structure as claimed in claim 1, characterized in that: The fastening nut (3) is used to transfer the prestress applied by the anchor cable (1) to the surrounding medium, and can also control the tension of the anchor cable (1), thereby adjusting the anchoring force.

7. A method for manufacturing a similar model test anchor cable with a negative Poisson's ratio structure, used for manufacturing a similar model test anchor cable as claimed in any one of claims 1 to 6, characterized in that: The steps include: S1. Model the similar model test anchor cable based on the negative Poisson's ratio anchor cable used in actual engineering; S2. Using thermoplastic polyurethane elastomer material, 3D printing is performed on a tray (2), a fastening nut (3) and a sleeve (5) of a similar model test anchor cable; S3, using aluminum alloy material to 3D print the cone (4) of the anchor cable of the similar model test; S4, assembling the 3D printed tray (2), the fastening nut (3), the cone (4), the sleeve (5), the steel wire (6), the axial force monitoring device (7) and the steel wire lock (8).

8. The method for manufacturing a similar model test anchor cable with a negative Poisson's ratio structure according to claim 7, characterized in that: Step S1 includes: S1.

1. Based on the on-site monitoring data, obtain the on-site stress boundary conditions and on-site displacement variation law of the on-site tunnel or anchor unit, and determine the similarity constant that the physical model test should satisfy based on the similarity law of the physical model test; S1.2, carrying out specific size design for the anchor cable (1); S1.

3. Establishing a three-dimensional digital model of the anchor cable (1).

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