Anchoring rod based on self-measuring shear force sensor

Abstract

The application discloses an anchor rod based on self-measurement of shearing force of a force sensor, which comprises three parts of an anchor rod front end, an anchor rod middle end and a force sensor. The anchor rod front end comprises a bolt, a rubber plug, a backing plate, a stop plug, a display and an outer end computer. The anchor rod middle end is provided with a long rectangular groove arranged on the surface of the anchor rod body along the axial direction, and three short rectangular grooves with different depths are arranged equidistantly along the direction perpendicular to the axial direction. The force sensor comprises a fiber sensor and an attitude sensor. According to the method, the corresponding force sensor is arranged at each groove, and the size of the shearing force borne by the anchor rod in actual use is calculated by using the micro-strain detection of the force sensor. The device has the advantages of simple structure, strong practicality and the like, can realize real-time monitoring of the shearing force, improves the accuracy and precision of data, and has an important guiding role for the study of the shearing resistance of the anchor rod in a medium with multiple joints and fissures or under the conditions of large buried depth and high ground stress and the support design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of underground engineering slope, roadway and foundation pit anchoring engineering, and particularly relates to a method for measuring the shear force of an anchor rod. BACKGROUND

[0002] Today, with the continuous development of construction engineering, more and more buildings need to use reinforced concrete structures. In these structures, anchor rods are widely used to support and reinforce concrete structures to ensure the stability and safety of the structures. However, in actual use, anchor rods are often affected by complex loads and mechanical environments, resulting in shear failure of the anchor rods. Therefore, studying the shear problem of anchor rods and proposing effective solutions are crucial to ensuring the structural safety of buildings.

[0003] In many anchoring engineering examples, the common failure modes of anchor rods are tensile-shear failure and tensile-bending failure. The rod body failure is mostly related to the shear displacement of the structural surface, and the mechanical properties of the structural surface have a great relationship with the failure characteristics of the anchor rod. The shear displacement of the structural surface will generate a large shear load on the anchor rod, and some components will produce shear bending deformation, leading to yield failure and failure. However, the current anchor rod support design mostly only considers the axial anchoring effect of the anchor rod, i.e., whether the tensile strength of the anchor rod can meet the engineering design requirements. However, engineering site statistics show that under the conditions of large burial depth and high ground stress, the failure of deep surrounding rock anchor rods is often caused by tensile-shear combined action, rather than pure tensile fracture failure. Domestic and foreign scholars have conducted more research on the stress and failure mechanism of anchor rods under tensile state, but less research on the mechanical properties of anchor rods under shear action. There is a misunderstanding about the understanding of the shear resistance of anchor rods, which is that anchor rods can only play a shear resistance role when the rock mass produces a large relative displacement along the joint surface and the rod surface is in close contact with the surrounding rock, which is a passive support method. In fact, the transverse shear resistance of prestressed anchor rods is still an active support method. After the anchor rod is pre-stressed by the tray and nut, the surrounding rock produces a squeezing effect, causing the joint surface to be subjected to a normal load, thereby changing the shear strength of the joint surface and reinforcing the potential slip surface in the surrounding rock.

[0004] In recent years, more and more attention has been paid to the research on the shear problem of anchor rods. Some researchers have proposed various solutions, some of which have been patented. For example, a "anchor rod shear warning device" has been granted a patent by the China National Intellectual Property Administration.

[0005] The patent mainly relates to a kind of anchor rod shear early warning device, including an anchor rod, a group of strain sensors and a group of data acquisition modules.The anchor rod is fixed in concrete structure by connecting nut, and strain sensor is installed at the both ends of anchor rod, and is connected with central controller by data acquisition module.In actual use, strain sensor can perceive the strain change of anchor rod end, and these change data are transmitted to data acquisition module.Central controller can calculate the shear state of anchor rod according to these data, to warn possible damage risk.This anchor rod shear early warning device has many advantages.First, it can monitor the strain change of anchor rod in real time, and find possible damage risk in time, to guarantee the structural safety of building.Second, it is simple in structure, easy to install, and will not cause any influence to normal use of building.Finally, it can be adjusted according to actual demand, to adapt to different anchor rod sizes and load conditions.

[0006] The measurement of anchor rod shear force is a key and important step in anchor rod shear technology, but there is still a lack of research on anchor rod shear force measurement in research and practice, so it is urgent to carry out research on anchor rod shear force measurement method. SUMMARY

[0007] The present application provides a kind of anchor rod shear force measurement method based on force sensor, to solve the problem of lack of transverse shear test of anchor rod in prior art, realize the all-round research of anchor rod shear force on roadway support.This application has the advantages of simple structure, strong practicality, etc., can carry out shear force real-time monitoring, improve the accuracy and precision of data, and has important guiding role for the shear resistance performance research of anchor rod in multi-joint, fissured medium or under the condition of large buried depth, high ground stress and support design.

[0008] The present application provides a kind of anchor rod based on force sensor self-measured shear force, comprising:

[0009] Anchor rod front end, located outside surrounding rock, including hexagon nut, hemispherical rubber plug, arched pad, stop plug, display, outer end computer.For reducing the shear force generated in the process of anchor rod installation.

[0010] Anchor rod middle end: located inside surrounding rock, including long rectangular groove arranged along axial direction on the surface of anchor rod body and three short rectangular grooves of different depths arranged perpendicular to axial direction, for arranging force sensor.

[0011] Force sensor: located inside the groove of anchor rod middle end, including optical fiber sensor and attitude sensor, for detecting axial and perpendicular to axial shear force.

[0012] The hexagonal nut is internally provided with threads, and can transmit stress concentration of surrounding rock to the hemispherical rubber plug and the arched pad plate, and is used for fixing the anchor rod. The hemispherical rubber plug can adjust the axial direction of stress, correct the stress direction of the anchor rod, and solve the problem of shear damage of the anchor rod due to improper installation angle. The arched pad plate is protruded on one side and recessed on the other side, the arched protruded side is closely attached to the surrounding rock, can disperse stress, and is used for bearing greater internal force of the surrounding rock. The stop plug is wide at the top and narrow at the bottom, and is provided with six fan-shaped holes in the circumferential direction, and is used for maintaining pressure during grouting to fully fill the gap of the surrounding rock.

[0013] The long rectangular groove is arranged along the axial direction of the outer wall of the anchor rod, and is in a strip shape and 10mm deep. The short rectangular grooves are arranged equidistantly along the direction perpendicular to the axial direction, and each short rectangular groove has different depth, the frontmost groove is 10mm deep, the middle groove is 5mm deep, and the last groove is 8mm deep, and is used for arranging the force sensor.

[0014] The groove is arranged according to two different directions of the axial direction and the direction perpendicular to the axial direction, and can be used for measuring shear force of any cross section.

[0015] The short rectangular grooves with different depths are used for detecting shear force at different distances from the center of the anchor rod by controlling the distance between the sensor and the center.

[0016] The anchor rod middle end structure is wrapped with a silica gel protective sleeve as a whole, and is used for protecting the force sensor from external interference.

[0017] The optical fiber sensor and the attitude sensor are arranged in an L shape, are laid in the grooves, and are closely attached to the inside of the grooves. Two force sensors are arranged in each groove, two force sensors are arranged in the long rectangular groove along the axial direction, two force sensors are arranged in the short rectangular groove along the direction perpendicular to the axial direction, and a total of eight force sensors are arranged, so as to improve the measurement accuracy of the force sensor.

[0018] According to the anchor rod force sensor structure for measuring shear force based on force sensor provided by the application, the optical fiber sensor is arranged at the corner of the L-shaped bend, and when the anchor rod is subjected to shear force, a slight strain occurs, so that the shear force of the anchor rod can be measured. The attitude sensor is arranged at the vertical and horizontal directions of the L-shaped, and a column is arranged equidistantly in each direction, and when the anchor rod is subjected to shear force, a slight strain occurs, so that the shear force of the anchor rod can be measured. The two are combined together by using a thin film protective layer, so that the measurement of the anchor rod shear force is more accurate and controllable, and the measurement accuracy is higher than that of ordinary sensors.

[0019] According to the anchor rod force sensor structure for measuring shear force based on force sensor provided by the application, the anchor rod groove and the L-shaped thin film protective layer are provided with a protective adhesive layer, the protective adhesive layer is an epoxy adhesive, and the protective adhesive layer is attached to the force sensor to fix and protect the force sensor.

[0020] According to the anchor rod force sensor structure for measuring shear force based on force sensor provided by the application, the force sensor transmits data to a display, the display is connected to an external computer, the surface micro-strain of an object is calculated, and the size of the anchor rod shear force is measured.

[0021] Compared with the prior art, the anchor rod for measuring shear force based on force sensor provided by the application has the following advantages:

[0022] (1) The anchor rod for measuring shear force based on force sensor provided by the application is provided with corresponding force sensors arranged at each groove, and the deformation of the force sensors is used to detect the size of the shear force of the anchor rod in actual use. The anchor rod has the advantages of simple structure and strong practicality.

[0023] (2) The anchor rod for measuring shear force based on force sensor provided by the application can be monitored in real time, and the accuracy and precision of data are improved.

[0024] (3) The anchor rod for measuring shear force based on force sensor provided by the application has an important guiding role for the shear resistance performance research and support design of the anchor rod in a medium with multiple joints and fissures or under the action of large buried depth and high ground stress. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor. Figures 3-6 The silica gel protective sleeve wrapped around the middle end of the anchor rod in claim 6 has been omitted.

[0026] Figure 1 is a force diagram of the overall structure of the anchor rod based on the self-measured shear force of the force sensor according to the present application;

[0027] Figure 2 is a structure diagram of the anchor rod silica gel protective sleeve based on the self-measured shear force of the force sensor according to the present application;

[0028] Figure 3 is a structure diagram of the overall structure of the anchor rod based on the self-measured shear force of the force sensor according to the present application;

[0029] Figure 4 is a longitudinal section diagram of the anchor rod based on the self-measured shear force of the force sensor according to the present application;

[0030] Figure 5 is a transverse section diagram of the anchor rod based on the self-measured shear force of the force sensor according to the present application;

[0031] Figure 6 is a force sensor diagram of the anchor rod based on the self-measured shear force of the force sensor according to the present application;

[0032] Reference signs:

[0033] 1-1, hexagonal nut; 1-2, hemispherical rubber plug; 1-3, arched pad; 1-4, grout stopper; 2-1, long rectangular groove; 2-2, 10mm short rectangular groove; 2-3, 5mm short rectangular groove; 2-4, 8mm short rectangular groove; 2-5, hollow anchor rod; 2-6, force sensor; 2-7, silica gel protective sleeve; 3-1, attitude sensor; 3-2, optical fiber sensor; 3-3, epoxy resin adhesive; 3-4, thin film protective layer; 4-1, ground stress; 4-2, longitudinal tension; 4-3, transverse extrusion force; 4-4, display; 4-5, external computer. DETAILED DESCRIPTION

[0034] The application will be further described below in conjunction with the drawings and examples.

[0035] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0036] It should be noted that the use of the terms "include", "includes" and / or "including" in this specification is intended to mean that the following elements are present, but not necessarily to the exclusion of other elements. In addition, it should be understood that the use of "including" does not limit the present application to the specific elements unless otherwise defined.

[0037] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are only used to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0038] In this invention, terms such as "fixed," "connected," and "started" should be interpreted broadly, indicating either a fixed connection or an integral connection. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0039] like Figures 2-5 As shown, an anchor rod based on a force sensor for self-measuring shear force includes a front-end structure, a middle-end structure, and a force sensor structure.

[0040] Specifically, the anchor bolt front end structure, located outside the surrounding rock, includes a hexagonal nut 1-1, a hemispherical rubber plug 1-2, an arched pad 1-3, a grout stop plug 1-4, a display 4-4, and an external computer 4-5. These components are used to reduce the shear force generated during anchor bolt installation.

[0041] The anchor bolt mid-end structure, located inside the surrounding rock, includes a long rectangular groove 2-1 arranged along the axial direction on the surface of the anchor bolt body and three short rectangular grooves 2-2 to 2-4 of different depths arranged perpendicular to the axial direction, for arranging force sensors.

[0042] The force sensor, located inside the groove at the middle end of the anchor bolt, includes an optical fiber sensor and an attitude sensor, and is used to detect the axial and perpendicular shear forces of the anchor bolt.

[0043] Specifically, the hexagonal nut 1-1, with internal threads, can concentrate and transfer the stress of the surrounding rock to the hemispherical rubber plug and the pad for fixing the anchor bolt. The hemispherical rubber plug 1-2 can adjust the axial direction of the force, correct the force direction of the anchor bolt, and solve the problem of shear damage to the anchor bolt due to improper installation angle. The arched pad 1-3, with one side protruding and the other side concave, has its arched protruding side in close contact with the surrounding rock, which can disperse stress and withstand greater internal forces in the surrounding rock. The grout stopper 1-4, wider at the top and narrower at the bottom, has six fan-shaped channels arranged in a circumferential direction to maintain the pressure during grouting to fully fill the voids in the surrounding rock.

[0044] Specifically, the long rectangular groove is arranged along the axial direction of the outer wall of the anchor rod, and has a strip shape with a depth of 10 mm. The three short rectangular grooves are arranged equidistantly in a direction perpendicular to the axial direction, and each short rectangular groove has a different depth. The frontmost groove has a depth of 10 mm, the middle groove has a depth of 5 mm, and the last groove has a depth of 8 mm, which are used to arrange the force sensors.

[0045] As a preferred solution, further, a middle-end structure of an anchor rod for measuring shear force by a force sensor, the grooves arranged in two different directions, an axial direction and a direction perpendicular to the axial direction, can be used to measure the shear force of any cross section.

[0046] As a preferred solution, further, a middle-end structure of an anchor rod for measuring shear force by a force sensor, the short rectangular grooves with different depths are used to detect the shear force at different distances from the center of the anchor rod by controlling the distance between the sensor and the center.

[0047] As a preferred solution, further, a middle-end structure of an anchor rod for measuring shear force by a force sensor, the entire anchor rod middle-end structure is wrapped with a silica gel protective sleeve 2-7 to protect the force sensor from external interference. Specifically, the force sensor 2-6 includes an optical fiber sensor and an attitude sensor, which are arranged in an "L" shape and laid in the grooves and closely attached to the inside of the grooves. Two force sensors are arranged in each groove, two in the long rectangular groove along the axial direction, and two in the short rectangular groove along the direction perpendicular to the axial direction, a total of eight, to improve the measurement accuracy of the force sensor.

[0048] As a preferred solution, further, a force sensor structure of an anchor rod for measuring shear force by a force sensor, the optical fiber sensor is arranged at the right angle of the "L" shape, and when the anchor rod is subjected to shear force, a small strain occurs, so that the shear force of the anchor rod can be measured. The attitude sensor is arranged in the vertical and horizontal directions of the "L" shape, and one column is arranged equidistantly in each direction. When the anchor rod is subjected to shear force, a small strain occurs, so that the shear force of the anchor rod can be measured. The two are combined together by a thin film protective layer, which can make the measurement of the anchor rod shear force more accurate and controllable, and the measurement accuracy is higher than that of ordinary sensors.

[0049] As a preferred solution, further, a force sensor structure of an anchor rod for measuring shear force by a force sensor, a protective adhesive layer is provided on the anchor rod groove and the "L" shaped thin film protective layer, which is an epoxy resin adhesive and is attached to the force sensor to fix and protect the force sensor.

[0050] As a preferred solution, further, a kind of anchor rod force sensor structure based on force sensor self-measured shear force, the force sensor transmits data to display, display is connected to the end computer, the shear force of anchor rod is measured by calculating the small strain of object surface.

[0051] A kind of anchor rod using method based on force sensor self-measured shear force, the following steps are taken:

[0052] (1) make a kind of anchor rod based on force sensor self-measured shear force as shown in Figure 3 A kind of anchor rod based on force sensor self-measured shear force is made: a groove is set on the surface of anchor rod along the axial direction, and the groove is through the full length of anchor rod.The depth and width of the groove are about 10mm and 10mm respectively.Three short rectangular grooves are set on the surface of anchor rod perpendicular to the axial direction at equal distance, the front end groove is 10mm deep, the middle end groove is 5mm deep, and the last end groove is 8mm deep, to measure the shear force at different distances from the center.In the long rectangular groove on the surface of anchor rod body, two force sensors are arranged respectively, and one force sensor is arranged in the upper and lower cross sections of the short rectangular groove, a total of eight force sensors are arranged.Epoxy resin adhesive is used to tightly bond the optical fiber, attitude sensor, film protective layer and anchor rod together, so that the force sensor and anchor rod body deform together, and then the strain of the force sensor can be monitored to reflect the strain of the anchor rod body.

[0053] (2) anchor rod anchoring installation: the anchor rod of the force sensor monitoring is anchored in the tunnel, and the arch-shaped backing plate 1-3 and the hemispherical rubber plug 1-2 are installed at the tail, to reduce the pre-shear force generated in the anchor rod due to improper installation angle, to avoid the problem of shear failure of the anchor rod, and to pay attention to the protection of the force sensor lead wire during installation.The force sensors in the four grooves are connected with the display and the external computer respectively, to monitor the small changes of the force sensors in the anchor rod in real time, and to further calculate the shear force of the anchor rod.

[0054] (3) anchor rod stress calculation: as shown in Figure 1 The actual stress of the anchor rod is shear at both ends, to avoid shear failure, the shear force of the anchor rod is monitored in real time.The small changes of the force sensor when subjected to shear force are measured, and the size of the shear force of the object is calculated.When the object is subjected to shear force, the surface of the object will have small strain, which will cause the optical fiber sensor and the attitude sensor to have small strain, and the change data is transmitted to the display, and then the external computer is monitored in real time, the change amount is calculated, and the size of the shear force of the object can be obtained.

[0055] The above only describes the preferred embodiments of the present application and is not used to limit the present application.For those skilled in the art, the present application can have various modifications and changes.Any modification, equivalent replacement, improvement, etc.made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An anchor rod based on a self-measuring force sensor for measuring the shear force, characterized by It comprises: The front end of the anchor rod: located outside the surrounding rock, including hexagonal nut, hemispherical rubber plug, arched pad, stop plug, display, and external computer, used to reduce the shear force generated during the installation of the anchor rod; The middle end of the anchor rod: located inside the surrounding rock, including long rectangular grooves arranged in the axial direction and three short rectangular grooves arranged perpendicular to the axial direction on the surface of the anchor rod body, used to arrange force sensors; The force sensor: located inside the grooves of the middle end of the anchor rod, including fiber optic sensors and attitude sensors, used to detect the axial and perpendicular shear force of the anchor rod, the fiber optic sensors and attitude sensors are arranged in an "L" shape, laid in the grooves, and tightly attached to the inside of the grooves, two force sensors are arranged in each groove, two in the long rectangular grooves in the axial direction and two in the short rectangular grooves perpendicular to the axial direction, a total of eight, to improve the measurement accuracy of the force sensor; The structure of the fiber optic sensor is arranged at the straight angle of the "L" shape, and a small strain will occur when the anchor rod is subjected to shear force, so that the shear force of the anchor rod can be measured, the structure of the attitude sensor is arranged in the vertical and horizontal directions of the "L" shape, and one column is arranged equidistantly in each direction, a small strain will occur when the anchor rod is subjected to shear force, so that the shear force of the anchor rod can be measured, the two are combined together with a thin film protective layer, which can make the measurement of the anchor rod shear force more accurate and controllable, and the measurement accuracy is higher than that of ordinary sensors.

2. The self-measuring anchor rod based on a force sensor according to claim 1, characterized in that, The hexagonal nut is internally threaded, which can transmit the stress concentration of the surrounding rock to the hemispherical rubber plug and the pad, and is used to fix the anchor rod, the hemispherical rubber plug can adjust the axial direction of the stress and correct the stress direction of the anchor rod, solving the problem of shear failure of the anchor rod due to improper installation angle, the arched pad is convex on one side and concave on the other side, the convex side of the arch is tightly attached to the surrounding rock, which can disperse stress and bear greater internal force of the surrounding rock, the stop plug is wide at the top and narrow at the bottom, and six fan-shaped holes are arranged in the circumferential direction, which is used to maintain the pressure during grouting to fully fill the gap of the surrounding rock.

3. The self-measuring anchor rod based on the force sensor according to claim 1, characterized in that, The long rectangular groove is arranged in the axial direction along the outer peripheral wall of the anchor rod, in a strip shape, and has a depth of 10 mm, the short rectangular groove is arranged equidistantly in three in the direction perpendicular to the axial direction, each short rectangular groove has a different depth, the frontmost groove has a depth of 10 mm, the middle groove has a depth of 5 mm, and the last groove has a depth of 8 mm, which is used to arrange the force sensor.

4. The self-measuring anchor rod based on a force sensor according to claim 3, characterized in that, The grooves are arranged in two different directions along the axial direction and perpendicular to the axial direction, which can be used to measure the shear force of any cross section.

5. The self-measuring anchor rod based on the force sensor according to claim 3, characterized in that, The short rectangular grooves with different depths detect the shear force at different distances from the center of the anchor rod by controlling the distance between the sensor and the center.

6. The self-measuring anchor rod based on the force sensor according to claim 3, characterized in that, The middle end structure of the anchor rod is wrapped with a silica gel protective sleeve to protect the force sensor from external interference.

7. The self-measuring anchor rod based on a force sensor according to claim 1, characterized in that, A protective adhesive layer is provided on the grooves of the anchor rod and the "L" shaped thin film protective layer, which is an epoxy resin adhesive and is attached to the force sensor to fix and protect the force sensor.

8. The self-measuring anchor rod based on a force sensor according to claim 1, characterized in that, The force sensor transmits data to a display connected to an external computer, and the size of the anchor rod shear force is measured by calculating the small strain of the object surface.

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