Friction type extensible anchor rod capable of automatically measuring extension displacement

Abstract

The invention discloses a friction type extensible anchor rod capable of automatically measuring extension displacement, and relates to the technical field of tunnel engineering supporting. The friction type extensible anchor rod comprises an anchor rod body, a damping block, a spring, a force sensor, a sleeve, a damping tube and a processor, the force sensor is hollow, and the spring and the force sensor are arranged on a suspended section of the anchor rod body in a sleeving mode and are in sliding fit with the suspended section; one end of the spring abuts against the conical surface, the other end of the spring abuts against the annular force measuring end face, away from one side of the anchoring section, of the force sensor, the end face of the other side of the force sensor abuts against the gasket, and the processor is in communication connection with the force sensor and is used for calculating elongation displacement according to the output force value of the force sensor. Therefore, data can be collected on site, the elongation displacement of the anchor rod can be obtained through a calculation formula, the purposes of avoiding potential safety hazards of measurement, reducing manual participation and more accurately measuring the elongation displacement of the anchor rod are achieved, and the practical engineering problem can be solved from the aspect of engineering practice.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering support technology, specifically relating to a friction-type extendable anchor bolt that automatically measures elongation displacement. Background Technology

[0002] Tunnels in soft rock formation typically experience significant deformation, making rock bolts an essential support measure. While ordinary rigid rock bolts provide sufficient anchoring force, their limited elongation deformation makes them unsuitable for the large deformations required in soft rock tunnels. Therefore, an extendable rock bolt has been developed. This type of rock bolt utilizes a damping device consisting of a damping block, a sleeve, and a damping tube. When the rock bolt is subjected to tension (from the outward expansion of the surrounding rock on the free side due to changes in its mechanical properties), the damping block is pulled to compress the damping tube into the sleeve (which remains stationary relative to the free rock side). This causes the damping tube to deform away from the center of the rock bolt, creating resistance between the damping block and the damping tube, thus achieving the purpose of tunnel support.

[0003] Currently, extendable rock bolts have been widely used in soft rock tunnel support. However, existing research on extendable rock bolts is limited to indoor studies on the elongation and axial force of the bolts. Research on the elongation displacement of rock bolts in the field is almost non-existent (i.e., existing research on the elongation displacement of rock bolts is only based on numerical simulations, and there is no technical solution for automatically measuring the elongation displacement of rock bolts). This means that if the elongation displacement of rock bolts needs to be measured manually, which is inconvenient in actual production and obviously has problems such as low feasibility, insufficient accuracy, and certain safety hazards.

[0004] Therefore, those skilled in the art urgently need to provide an automatic measurement technology for the elongation displacement of extendable anchor bolts, so as to avoid measurement safety hazards, reduce manual intervention, and more accurately measure the elongation displacement of anchor bolts. Summary of the Invention

[0005] The purpose of this invention is to provide a friction-type extendable anchor bolt for automatically measuring elongation displacement, in order to solve the problems of poor convenience, low feasibility, insufficient accuracy, and certain safety hazards in existing anchor bolt elongation displacement measurement schemes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a friction-type extendable anchor rod for automatically measuring elongation displacement, comprising an anchor rod, a damping block, a spring, a force sensor, a sleeve, a damping tube, and a processor. The anchor rod includes an anchoring section and a suspended section bounded by a gasket. The damping block includes a straight tube section and a tapered tube section. The cross-sectional area of ​​the tapered tube section on the side closer to the anchoring section is smaller than the cross-sectional area on the other side. The force sensor is hollow inside.

[0008] The straight pipe section, the tapered pipe section, the spring, and the force sensor are sequentially sleeved on the suspended section along the direction from the suspended section to the anchoring section. The straight pipe section is limited to the suspended end of the suspended section. The spring and the force sensor are slidably engaged with the suspended section. One end of the spring abuts against the tapered surface of the tapered pipe section, and the other end of the spring abuts against the annular force-measuring end face of the force sensor on the side away from the anchoring section. The other end face of the force sensor abuts against the gasket.

[0009] The damping block, the sleeve, and the damping tube constitute a damping device that does not affect the movement of the spring;

[0010] The processor, communicatively connected to the force sensor, is used to calculate the elongation displacement x based on the output force value F1 of the force sensor according to the following formula:

[0011]

[0012] In the formula, F2 represents the frictional resistance value of the damping device, and k represents the spring stiffness.

[0013] Based on the above-mentioned invention, a novel extendable anchor rod is provided for automatic measurement of elongation displacement based on a force sensor and a spring. The anchor rod includes an anchor rod, a damping block, a spring, a force sensor, a sleeve, a damping tube, and a processor. The force sensor is hollow inside. The spring and the force sensor are fitted onto the suspended section of the anchor rod and slide in contact with the suspended section. One end of the spring abuts against a conical surface, and the other end abuts against the annular force-measuring end face of the force sensor on the side furthest from the anchoring section. The other end face of the force sensor abuts against a gasket. The processor is communicatively connected to the force sensor and is used to calculate the elongation displacement based on the output force value of the force sensor. This allows for on-site data collection and calculation of the anchor rod's elongation displacement, achieving the goals of avoiding measurement safety hazards, reducing manual intervention, and more accurately measuring the anchor rod's elongation displacement. It also enables more practical exploration and analysis, allowing for the solution of real-world engineering problems from an engineering perspective, rather than merely remaining at the level of numerical simulation, thus facilitating practical application and promotion.

[0014] In one possible design, the sleeve is intermittently fitted onto the suspended section and located between the conical surface and the annular force-measuring end face;

[0015] The damping tube is disposed between the outer wall of the suspended section and the inner wall of the sleeve, and is attached to the inner wall of the sleeve, with gaps between it and the suspended section and the spring, respectively.

[0016] In one possible design, the minimum gap between the sleeve and the suspended section is 2 mm, and the minimum gap between the damping tube and the suspended section is 1 mm.

[0017] In one possible design, the wire diameter of the spring is smaller than the minimum gap between the damping tube and the suspended section.

[0018] In one possible design, the frictional resistance value is the maximum of a first frictional force value and a second frictional force value, wherein the first frictional force value refers to the value of the maximum static frictional force generated between the damping block and the inner wall of the sleeve, and the second frictional force value refers to the value of the maximum static frictional force generated between the damping block and the damping tube.

[0019] In one possible design, the first frictional force value P1 is calculated according to the following formula:

[0020] P1=β×μ1×E×ε×A1

[0021] In the formula, β represents the preset reduction coefficient, μ1 represents the static friction coefficient between the damping block and the inner wall of the sleeve, E represents the elastic modulus of the sleeve, ε represents the circumferential strain of the sleeve when it expands, and A1 represents the contact area between the damping block and the inner wall of the sleeve.

[0022] In one possible design, the contact area A1 between the damping block and the inner wall of the sleeve is obtained as follows:

[0023] A two-dimensional rectangular coordinate system is established with the axis of the sleeve as the origin and the cross-section of the sleeve as the XY plane. The intersection of the axis of the straight pipe segment and the XY plane is located on the Y-axis of the two-dimensional rectangular coordinate system, and the intersection of the axis of the damping pipe before deformation and the XY plane is also located on the Y-axis of the two-dimensional rectangular coordinate system.

[0024] Based on the two-dimensional rectangular coordinate system, establish the equation of the inner circumferential cross-section ellipse of the sleeve after deformation, as shown below:

[0025]

[0026] In the equation, D1 represents the diameter of the straight pipe section, D3 represents the inner diameter of the sleeve before deformation, and ρ represents the thickness of the damping tube.

[0027] Based on the two-dimensional rectangular coordinate system, establish the equation of the outer circumferential cross-section circle of the straight pipe segment after the sleeve deformation:

[0028] Based on the equations of the inner circumferential cross-section ellipse and the outer circumferential cross-section circle, a system of equations is established and solved to obtain a pair of intersection points, and the arc length of the pair of intersection points is also calculated.

[0029] According to the arc length The contact area A1 between the damping block and the inner wall of the sleeve is calculated using the following formula:

[0030]

[0031] In the formula, L1 represents the length of the straight pipe segment.

[0032] In one possible design, the second frictional force value P2 is calculated according to the following formula:

[0033]

[0034] In the formula, β represents the preset reduction coefficient, π represents pi, μ2 represents the static friction coefficient between the damping block and the damping tube, E represents the elastic modulus of the sleeve, ε represents the circumferential strain of the sleeve when it expands, L1 represents the length of the straight pipe section, D2 represents the outer diameter of the damping tube before deformation, and d represents the inner diameter of the damping tube before deformation.

[0035] In one possible design, the spring stiffness k is calculated according to the following formula:

[0036]

[0037] In the formula, G represents the shear modulus of the spring material. The wire diameter of the spring is represented by D, the coil diameter of the spring is represented by n, and the effective number of coils of the spring is represented by n.

[0038] In one possible design, a nut is fixed to the suspended end of the suspended section to limit the straight pipe section.

[0039] The beneficial effects of the above scheme are:

[0040] (1) This invention provides a novel extendable anchor rod for automatic measurement of elongation displacement based on a force sensor and a spring. The anchor rod includes an anchor rod, a damping block, a spring, a force sensor, a sleeve, a damping tube, and a processor. The force sensor is hollow inside. The spring and the force sensor are sleeved on the suspended section of the anchor rod and slide in contact with the suspended section. One end of the spring abuts against a conical surface and the other end abuts against the annular force measuring end face of the force sensor on the side away from the anchoring section. The other end face of the force sensor abuts against a gasket. The processor is connected to the force sensor and is used to calculate the elongation displacement based on the output force value of the force sensor. This allows data to be collected on-site and the elongation displacement of the anchor rod to be obtained through calculation formulas. This achieves the purpose of avoiding measurement safety hazards, reducing manual intervention, and measuring the elongation displacement of the anchor rod more accurately. It also allows for more practical discussion and research analysis, enabling the solution of practical engineering problems from an engineering perspective, rather than just remaining in numerical simulation.

[0041] (2) Automatic measurement can be realized, filling the technological gap: At present, there are no anchor rods on the market with automatic measurement of elongation displacement. This technology integrates force sensor, damping device and spring system, and combines algorithm to calculate anchor rod elongation displacement in real time, which solves the problems of low efficiency and poor accuracy of traditional manual measurement, and fills the gap in automatic monitoring technology in the field of soft rock tunnel support.

[0042] (3) Improve engineering safety and efficiency: Automation technology reduces manual on-site operations, avoids safety hazards caused by manual measurement during tunnel construction, and real-time data acquisition and analysis can quickly provide feedback on the stress state of anchor bolts, providing immediate support for engineering decisions and significantly improving support efficiency.

[0043] (4) It can combine theory and practice to optimize design verification: Traditional research relies on numerical simulation and lacks on-site measured data support. This technology accurately calculates the displacement through measured data and formulas, providing a real basis for anchor performance analysis and promoting the deep integration of theoretical research and practical engineering applications.

[0044] (5) Improved accuracy and reliability: Force sensors can accurately collect data, and by selecting the appropriate force sensor, measurement errors can be minimized.

[0045] (6) It can promote the development of intelligent support technology: This technology introduces an automated monitoring solution to the field of tunnel support, lays the foundation for the subsequent development of intelligent anchor bolt systems that integrate the Internet of Things and big data analysis, helps the industry upgrade towards digitalization and intelligence, and facilitates practical application and promotion. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of a friction-type extendable anchor rod for automatically measuring elongation displacement, provided in an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram illustrating the operation of a friction-type extendable anchor bolt provided in an embodiment of the present invention.

[0049] Figure 3 A simplified diagram of the force sensor provided in an embodiment of the present invention.

[0050] Figure 4 This is a schematic diagram of the damping tube before and after deformation, provided in an embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the damping device before and after deformation, provided in an embodiment of the present invention. Detailed Implementation

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these embodiments without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0053] It should be understood that although the terms "first" and "second", etc., may be used herein to describe various objects, these objects should not be limited by these terms. These terms are only used to distinguish one object from another. For example, the first object may be referred to as the second object, and similarly, the second object may be referred to as the first object, without departing from the scope of the exemplary embodiments of the invention.

[0054] It should be understood that the term "and / or" that may appear in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, or A and B exist simultaneously. Another example is A, B and / or C, which can mean that any one of A, B, and C or any combination thereof exists. The term " / and" that may appear in this document describes another relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone or A and B exist simultaneously. In addition, the character " / " that may appear in this document generally indicates that the related objects before and after it are in an "or" relationship.

[0055] Example

[0056] like Figures 1-5 As shown, the friction-type extendable anchor bolt provided in this embodiment, which automatically measures elongation displacement, includes, but is not limited to, an anchor bolt 1, a damping block 2, a spring 3, a force sensor 4, a sleeve 5, a damping tube 6, and a processor 7. The anchor bolt 1 includes, but is not limited to, an anchoring section 11 and a suspended section 12 bounded by a gasket 10. The damping block 2 includes, but is not limited to, a straight tube section 21 and a tapered tube section 22. The cross-sectional area of ​​the tapered tube section 22 on the side closest to the anchoring section 11 is smaller than the cross-sectional area on the other side. The force sensor 4 is hollow inside. The aforementioned anchor bolt 1, damping block 2, sleeve 5, and damping tube 6 are all conventional configurations of existing extendable anchor bolts, and their structural relationships will not be elaborated here.

[0057] The straight pipe section 21, the tapered pipe section 22, the spring 3, and the force sensor 4 are sequentially sleeved on the suspended section 12 along the direction from the suspended section 12 to the anchoring section 11. The straight pipe section 21 is confined to the suspended end of the suspended section 12. The spring 3 and the force sensor 4 are slidably engaged with the suspended section 12. One end of the spring 3 abuts against the tapered surface of the tapered pipe section 22, and the other end of the spring 3 abuts against the annular force-measuring end face of the force sensor 4 on the side away from the anchoring section 11. The other end face of the force sensor 4 abuts against the gasket 10. Figures 1-2As shown, a nut 8 is specifically fixed at the suspended end of the suspended section 12 to limit the straight pipe section 21. Since the spring 3 and the force sensor 4 are respectively slidably engaged with the suspended section 12, when the surrounding rock on the free side expands outward due to changes in mechanical properties in practice, it will push the gasket 10, the force sensor 4, and the sleeve 5 to move outward as a whole. The damping block 2 will not move because it is limited, thereby compressing the annular force measuring end face of the force sensor 4 and pushing the spring 3 and the sleeve as a whole towards the damping block 2. Then, the reaction force value of the spring 3 and the sleeve as a whole on the annular force measuring end face can be measured by the force sensor 4 as the original measurement data.

[0058] The damping block 2, the sleeve 5, and the damping tube 6 constitute a damping device that does not affect the movement of the spring 3. To ensure that the movement of the spring 3 is not affected, preferably, the sleeve 5 is loosely fitted onto the suspended section 12 and located between the conical surface and the annular force-measuring end face; the damping tube 6 is disposed between the outer wall of the suspended section 12 and the inner wall of the sleeve 5, and is attached to the inner wall of the sleeve 5, with gaps between it and both the suspended section 12 and the spring 3. Figure 1 As shown in detail, the minimum gap between the sleeve 5 and the suspended section 12 is 2mm, and the minimum gap between the damping tube 6 and the suspended section 12 is 1mm; the wire diameter of the spring 3 (i.e., the diameter of the spring helix) is smaller than the minimum gap between the damping tube 6 and the suspended section 12, for example, 0.8mm. Furthermore, as... Figure 1 As shown, the outer diameter of the sleeve 5 is, for example, 50 mm and the thickness is 5 mm, and the outer diameter of the damping tube 6 is, for example, 12 mm and the thickness is 2 mm.

[0059] The processor 7 is communicatively connected to the force sensor 4 and is used to calculate the elongation displacement x according to the output force value F1 of the force sensor 4 using the following formula:

[0060]

[0061] In the formula, F2 represents the frictional resistance value of the damping device, and k represents the spring stiffness of the spring 3. Figure 3As shown, when the annular force measuring end face of the force sensor 4 compresses and pushes the spring 3 and the sleeve as a whole to move toward the damping block 2, since the friction-type extendable anchor rod is a constant resistance anchor rod, the sleeve 5 will only move toward the damping block 2 when the thrust generated (that is, the output force value F1 of the force sensor 4) reaches the preset force value of the damping device. The preset force value of the damping device is denoted as F2 (i.e., the frictional resistance value of the damping device). This F2 will act on the force sensor 4 due to the interaction of forces. Therefore, when the thrust F1 is greater than F2, the annular force measuring end face of the force sensor 4 will squeeze the sleeve 5 and compress the spring 3. The force on the annular force measuring end face is the sum of the frictional resistance and the elastic force generated by the spring 3 on the force sensor 4 due to compression. That is, the elastic force F3 generated by the spring 3 due to compression can be obtained by the following formula: F3 = F1 - F2. Then, the compression of the spring 3 can be solved by Hooke's law. According to the relative displacement, the compression of the spring 3 is equal to the displacement of the sleeve 5, which is the elongation displacement of the anchor rod: x = (F1 - F2) ÷ k (this elongation displacement can be used to judge the stress condition of the anchor rod and the on-site support condition, etc., which is of great significance for actual engineering).

[0062] The frictional resistance value F2 can be determined through the following theoretical analysis: According to the working principle of the anchor bolt, when the damping block 2 enters the sleeve 5, it simultaneously squeezes the sleeve 5 and the damping tube 6, thereby causing the damping tube 6 to compress and deform, and the sleeve 5 to expand outward. Through the mutual compression and contact of the three, two constant frictional forces can be obtained. That is, the frictional resistance of the damping device is mainly the maximum static frictional force between the damping block 2 and the damping tube 6 and the maximum static frictional force between the damping block 2 and the inner wall of the sleeve 5. Specifically, this frictional resistance is the maximum frictional force generated between the damping block 2 and the damping tube 6, and between the damping block 2 and the inner wall of the sleeve 5. Therefore, specifically, the frictional resistance value is the maximum value between the first frictional force value and the second frictional force value, where the first frictional force value refers to the value of the maximum static frictional force generated between the damping block 2 and the inner wall of the sleeve 5, and the second frictional force value refers to the value of the maximum static frictional force generated between the damping block 2 and the damping tube 6.

[0063] To simplify the problem, a theoretical model can be established to presuppose the frictional resistance value F2 and make the following assumptions: (1) The damping block 2 is an incompressible rigid linear strain hardening material, which is a rigid body material; (2) The wall thickness of the sleeve 5 remains unchanged throughout the deformation process; (3) The mutual compression deformation between the tapered section of the damping block 2 and the sleeve 5 and the damping tube 6 is ignored.

[0064] For the damping block 2 and the damping tube 6: when the straight tube segment 21 of the damping block 2 contacts the damping tube 6, the damping tube 6 is squeezed into a single piece and tightly pressed between the damping block 2 and the sleeve 5. At this time, the contact area between the damping block 2 and the damping tube 6 can be regarded as a rectangle; the length of this rectangle is the length L1 of the straight tube segment 21 of the damping block 2, and the width is B. The width of the squeezed damping tube 6 is slightly smaller than the original diameter, so it can be multiplied by a coefficient α1 (this coefficient is less than 1); correspondingly, α1×D2 is the width of the rectangle, i.e., B; thus, the contact area between the damping block 2 and the damping tube 6 can be calculated as A2=L1×B=L1×α1×D2, where L1 represents the length of the straight tube segment 21, D2 represents the outer diameter of the damping tube 6, and α1 represents the compression deformation coefficient.

[0065] like Figure 4 As shown, in its initial state, the damping tube 6 is a hollow thin-walled tube (e.g., Figure 4 (As shown on the left); when compressed by the damping block 2, the damping tube 6 becomes a thin plate with a certain thickness, which can be regarded as a cuboid (e.g., ...). Figure 4 (As shown on the right side); the length of the cuboid is equal to the length of the original damping tube; if the initial thickness of the damping tube 6 is ρ, then the thickness after compression deformation is 2×ρ, which is twice the original thickness, and the width is α1×D2. Considering that the volume of the damping tube before and after the change is constant, the compression deformation coefficient can be calculated, that is, the following equation can be established accordingly:

[0066]

[0067] In the equation, π represents the mathematical constant pi, and d represents the inner diameter of the damping tube 6 before deformation. The aforementioned equation can be rewritten as follows using ρ=(D2-d): This allows for the attainment of a constant frictional force between the damping block 2 and the damping tube 6.

[0068]

[0069] In the formula, μ2 represents the static friction coefficient between the damping block 2 and the damping tube 6, E represents the elastic modulus of the sleeve 5, and ε represents the circumferential strain of the sleeve 5 when it expands.

[0070] Furthermore, considering the differences in processing technology and lining roughness of the sleeve 5 in practical applications, when the damping block 2 enters the sleeve 5, the sleeve 5 will be compressed and deformed into an approximately elliptical shape. Therefore, the actual circumferential strain is less than the ideal value. Combining these factors, the actual measured frictional resistance is less than the value obtained from the above formula. That is, the constant frictional force between the damping block 2 and the damping tube 6 can be modified as follows:

[0071]

[0072] In the formula, β represents the reduction coefficient, which ranges from 0.6 to 0.9. The specific value depends on the manufacturing process of the sleeve 5. When the deformation differs greatly from the theoretical value due to the excessive error in the inner wall size of the sleeve 5, the value of β is lower. Otherwise, it needs to be a higher value.

[0073] In summary, the second frictional force value P2 can be calculated, but is not limited to, according to the following formula:

[0074]

[0075] In the formula, β represents the preset reduction coefficient, π represents pi, μ2 represents the static friction coefficient between the damping block 2 and the damping tube 6, E represents the elastic modulus of the sleeve 5, ε represents the circumferential strain of the sleeve 5 when it expands, L1 represents the length of the straight pipe section 21, D2 represents the outer diameter of the damping tube 6 before deformation, and d represents the inner diameter of the damping tube 6 before deformation.

[0076] For the damping block 2 and the sleeve 5: the straight pipe section 21 of the damping block 2, the inner wall of the sleeve 5, and the damping tube 6 can be projected onto the same plane; in the projection diagram of the damping block 2 before and after sliding, an XY axis coordinate system is established with the initial state center of the sleeve 5 as the origin, as follows: Figure 5 As shown; using analytical geometry, the contact area A1 between the damping block 2 and the inner wall of the sleeve 5 can be calculated.

[0077] like Figure 5 As shown, in the initial state, the damping block 2 is located above the sleeve 5 (e.g., Figure 5 (As shown on the left side), the center of the sleeve 5 is the coordinate axis of the circle, which is represented by O. The dashed line represents the straight pipe segment 21 of the damping block 2, the blue line represents the inner wall of the sleeve 5, and the yellow line represents the outer diameter of the damping tube 6. According to the working principle of the anchor rod, after the damping block 5 enters the sleeve 5, the damping tube 6 is squeezed and deformed; the damping tube 6 becomes a tile near the straight pipe segment 21 of the damping block 2, and the contact position between the damping block 2 and the damping tube 6 is at point A on the Y-axis; at the same time, the other side of the damping block 2 contacts the inner wall of the sleeve 5 at point B on the Y-axis. The high rigidity of the damping block 2 makes the inner wall elliptical during the sliding process; the major axis of the ellipse is the sum of the diameter of the damping block 2 and the thickness of the damping tube 6, that is, the length of the BE line segment; the minor axis of the ellipse is approximately the original diameter of the inner wall of the sleeve; after compressing the damping tube 6, the center of the circle changes to position O′ (e.g., Figure 5As shown on the right side, the length of line segment OO′ is 2×ρ. The equation of the deformed sleeve ellipse can then be established as follows:

[0078]

[0079] In the equation, D1 represents the diameter of the straight pipe section 21, and D3 represents the inner diameter of the sleeve 5 before deformation.

[0080] Figure 5 The length of line segment AE shown on the right is 2×ρ, and the length of line segment AB is D1. The circular equation of the straight pipe segment 21 of the damping block 2 can then be expressed as: in this way Figure 5 The coordinates of points C and D shown on the right side can be obtained by solving the equations of the sleeve ellipse and the circle mentioned above, and the length of the arc from point C to point D can be calculated. This allows us to obtain the contact area between the damping block 2 and the inner wall of the sleeve 5. and the frictional resistance between the damping block 2 and the sleeve 5 Wherein, μ1 represents the static friction coefficient between the damping block 2 and the inner wall of the sleeve 5.

[0081] In summary, the first frictional force value P1 is calculated according to the following formula:

[0082] P1=β×μ1×E×ε×A1

[0083] In the formula, β represents the preset reduction coefficient, μ1 represents the static friction coefficient between the damping block 2 and the inner wall of the sleeve 5, E represents the elastic modulus of the sleeve 5, ε represents the circumferential strain of the sleeve 5 when it expands, and A1 represents the contact area between the damping block 2 and the inner wall of the sleeve 5. Specifically, the contact area A1 between the damping block 2 and the inner wall of the sleeve 5 can be obtained according to the following steps S100 to S500.

[0084] S100. Establish a two-dimensional rectangular coordinate system with the axis of the sleeve 5 as the origin and the cross-section of the sleeve 5 as the XY plane, wherein the intersection of the axis of the straight pipe segment 21 and the XY plane is located on the Y-axis of the two-dimensional rectangular coordinate system, and the intersection of the axis of the damping pipe 6 before deformation and the XY plane is also located on the Y-axis of the two-dimensional rectangular coordinate system.

[0085] In step S100, the axis of the sleeve 5 is... Figure 5 Point O in the diagram.

[0086] S200. Based on the two-dimensional rectangular coordinate system, establish the equation of the inner circumferential cross-section ellipse of the sleeve 5 after deformation, as shown below:

[0087]

[0088] In the equation, D1 represents the diameter of the straight pipe section 21, D3 represents the inner diameter of the sleeve 5 before deformation, and ρ represents the thickness of the damping pipe 6.

[0089] S300. Based on the two-dimensional rectangular coordinate system, establish the equation of the outer circumferential cross-section circle of the straight pipe segment 21 after the sleeve 5 is deformed:

[0090] S400. Based on the equations of the inner circumferential cross-section ellipse and the outer circumferential cross-section circle, establish a system of equations and solve for a pair of intersection points, and also calculate the arc length of the pair of intersection points.

[0091] In step S400, the pair of intersection points are... Figure 5 Points C and D are shown in the diagram.

[0092] S500. According to the arc length The contact area A1 between the damping block 2 and the inner wall of the sleeve 5 is calculated using the following formula:

[0093]

[0094] In the formula, L1 represents the length of the straight pipe segment 21.

[0095] In addition, the spring stiffness k of the spring 3 can be calculated in advance according to, but is not limited to, the following formula:

[0096]

[0097] In the formula, G represents the shear modulus of the material of the spring 3 (for example, the shear modulus of steel is approximately 79300 MPa). The wire diameter of the spring 3 is represented by D (in mm), the coil diameter of the spring 3 is represented by n (in mm), and the effective number of turns of the spring 3 (i.e., the number of turns involved in deformation) is represented by n.

[0098] In summary, the friction-type extendable anchor bolt provided in this embodiment has the following technical advantages:

[0099] (1) This embodiment provides a novel extendable anchor rod for automatic measurement of elongation displacement based on a force sensor and a spring. It includes an anchor rod, a damping block, a spring, a force sensor, a sleeve, a damping tube, and a processor. The force sensor is hollow inside. The spring and the force sensor are sleeved on the suspended section of the anchor rod and slide in contact with the suspended section. One end of the spring abuts against the conical surface and the other end abuts against the annular force measuring end face of the force sensor on the side away from the anchoring section. The other end face of the force sensor abuts against the gasket. The processor is connected to the force sensor and is used to calculate the elongation displacement based on the output force value of the force sensor. This allows data to be collected on-site and the elongation displacement of the anchor rod to be obtained through calculation formulas. This achieves the purpose of avoiding measurement safety hazards, reducing manual intervention, and measuring the elongation displacement of the anchor rod more accurately. It also allows for more practical discussion and research analysis, so as to solve practical engineering problems from the perspective of engineering practice, rather than just staying in numerical simulation.

[0100] (2) Automatic measurement can be realized, filling the technological gap: At present, there are no anchor rods on the market with automatic measurement of elongation displacement. This technology integrates force sensor, damping device and spring system, and combines algorithm to calculate anchor rod elongation displacement in real time, which solves the problems of low efficiency and poor accuracy of traditional manual measurement, and fills the gap in automatic monitoring technology in the field of soft rock tunnel support.

[0101] (3) Improve engineering safety and efficiency: Automation technology reduces manual on-site operations, avoids safety hazards caused by manual measurement during tunnel construction, and real-time data acquisition and analysis can quickly provide feedback on the stress state of anchor bolts, providing immediate support for engineering decisions and significantly improving support efficiency.

[0102] (4) It can combine theory and practice to optimize design verification: Traditional research relies on numerical simulation and lacks on-site measured data support. This technology accurately calculates the displacement through measured data and formulas, providing a real basis for anchor performance analysis and promoting the deep integration of theoretical research and practical engineering applications.

[0103] (5) Improved accuracy and reliability: Force sensors can accurately collect data, and by selecting the appropriate force sensor, measurement errors can be minimized.

[0104] (6) It can promote the development of intelligent support technology: This technology introduces an automated monitoring solution to the field of tunnel support, lays the foundation for the subsequent development of intelligent anchor bolt systems that integrate the Internet of Things and big data analysis, helps the industry upgrade towards digitalization and intelligence, and facilitates practical application and promotion.

[0105] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A friction-type extendable anchor rod that automatically measures an elongation displacement, characterized by, The anchor rod (1), the damping block (2), the spring (3), the force sensor (4), the sleeve (5), the damping pipe (6) and the processor (7) are included, wherein the anchor rod (1) includes the anchor section (11) and the suspended section (12) which are delimited by the gasket (10), the damping block (2) includes the straight pipe section (21) and the tapered pipe section (22), the cross-sectional area of the tapered pipe section (22) is smaller on one side of the anchor section (11) than on the other side, and the inside of the force sensor (4) is hollow; The straight pipe section (21), the tapered pipe section (22), the spring (3) and the force sensor (4) are sequentially sleeved on the suspended section (12) in the direction from the suspended section (12) to the anchor section (11), wherein the straight pipe section (21) is limited at the suspended end of the suspended section (12), the spring (3) and the force sensor (4) are respectively in sliding fit with the suspended section (12), one end of the spring (3) abuts against the tapered surface of the tapered pipe section (22), the other end of the spring (3) abuts against the annular force measuring end surface of the force sensor (4) away from the anchor section (11), and the other end surface of the force sensor (4) abuts against the gasket (10); The damping block (2), the sleeve (5) and the damping pipe (6) constitute a damping device which does not affect the movement of the spring (3); The processor (7) is in communication connection with the force sensor (4) and is used for calculating the elongation displacement x according to the output force value F1 of the force sensor (4) according to the following formula: In the formula, F2 represents the frictional resistance value of the damping device, and k represents the spring stiffness of the spring (3).

2. A friction-type extendible anchor rod as claimed in claim 1, characterized in that The sleeve (5) is gapingly sleeved on the suspended section (12) and located between the tapered surface and the annular force measuring end surface; The damping pipe (6) is arranged between the outer side wall of the suspended section (12) and the inner side wall of the sleeve (5) and attached to the inner side wall of the sleeve (5) and has a gap with the suspended section (12) and the spring (3) respectively.

3. A friction-type extendible anchor rod as claimed in claim 2, characterized in that The minimum gap size between the sleeve (5) and the suspended section (12) is 2 mm, and the minimum gap size between the damping pipe (6) and the suspended section (12) is 1 mm.

4. A friction-type extendible anchor rod as defined in claim 3, wherein The wire diameter of the spring (3) is smaller than the minimum gap size between the damping pipe (6) and the suspended section (12).

5. A friction-type extendible anchor rod as defined in claim 1, wherein The frictional resistance value adopts the maximum value between a first friction value and a second friction value, wherein the first friction value refers to the value of the maximum static friction generated between the damping block (2) and the inner side wall of the sleeve (5), and the second friction value refers to the value of the maximum static friction generated between the damping block (2) and the damping pipe (6).

6. A friction-type extendible anchor rod as defined in claim 5, wherein The first friction value P1 is calculated according to the following formula: P1 = β × μ1 × E × ε × A1 In the formula, β represents a preset reduction coefficient, μ1 represents a static friction coefficient between the damping block (2) and the inner side wall of the sleeve (5), E represents an elastic modulus of the sleeve (5), ε represents a hoop strain of the sleeve (5) when swelling occurs, and A1 represents a contact area between the damping block (2) and the inner side wall of the sleeve (5).

7. A friction-type extendible anchor rod as defined in claim 6, wherein The contact area A1 between the damping block (2) and the inner side wall of the sleeve (5) is obtained in the following manner: A two-dimensional rectangular coordinate system is established with the axis of the sleeve (5) as the origin and the cross section of the sleeve (5) as the XY plane, wherein the intersection of the axis line of the straight pipe segment (21) and the XY plane is located on the Y axis of the two-dimensional rectangular coordinate system, and the intersection of the axis line of the damping pipe (6) before deformation and the XY plane is also located on the Y axis of the two-dimensional rectangular coordinate system; Based on the two-dimensional rectangular coordinate system, an inner circumferential cross-sectional elliptic equation of the sleeve (5) after deformation is established as follows: In the equation, D1 represents the diameter of the straight pipe segment (21), D3 represents the inner diameter of the sleeve (5) before deformation, and ρ represents the thickness of the damping pipe (6). Based on the two-dimensional rectangular coordinate system, the outer peripheral cross-sectional circle equation of the straight pipe section (21) after the deformation of the sleeve (5) is established: According to the inner circumferential cross-section ellipse equation and the outer circumferential cross-section circle equation, a set of equations is established and a pair of intersection points is obtained by solving the set of equations, and arc length of the pair of intersection points is also calculated According to the arc length The contact area A1 between the damper block (2) and the inner side wall of the sleeve (5) is calculated according to the following formula: In the formula, L1 represents the length of the straight pipe segment (21).

8. A friction-type extendible anchor rod as defined in claim 5, wherein, The second friction value P2 is calculated in the following formula: In the formula, β represents a preset reduction coefficient, π represents a circular constant, μ2 represents a static friction coefficient between the damping block (2) and the damping pipe (6), E represents an elastic modulus of the sleeve (5), ε represents a hoop strain of the sleeve (5) when swelling occurs, L1 represents the length of the straight pipe segment (21), D2 represents the outer diameter of the damping pipe (6) before deformation, and d represents the inner diameter of the damping pipe (6) before deformation.

9. A friction-type extendible anchor rod as defined in claim 1, wherein, The spring stiffness k is calculated in the following formula: In the formula, G represents the shear modulus of the material of the spring (3), represents the wire diameter of the spring (3), D represents the coil diameter of the spring (3), and n represents the effective number of turns of the spring (3).

10. A friction-type extendible anchor rod as defined in claim 1, wherein, A nut (8) is fixed at the overhanging end of the overhanging segment (12) to limit the straight pipe segment (21).

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