A graded relief anchor bolt device for monitoring preload and its usage method

Abstract

This invention discloses a graded pressure-relief anchor bolt device for monitoring preload and its usage method, belonging to the field of underground engineering support for roadways, tunnels, and culverts. It includes a sleeve, an anchor bolt, and a preload detection tray. The sleeve is located at the front end of the anchor bolt, and the preload detection tray is located at the rear end. The preload detection tray contains a high-elasticity spring, which absorbs energy through compression to further monitor the preload. The sleeve contains multiple sets of end-spherical telescopic rods arranged in stages. These end-spherical telescopic rods coordinate with the annular protrusions on the anchor bolt, enabling the device to simultaneously achieve constant resistance large deformation when large deformation occurs in the surrounding rock, ensuring that the anchor bolt and anchoring structure are not damaged. This invention achieves both pressure relief and preload monitoring, offering versatility, a reasonable structure, cost-effectiveness, and economic efficiency.

Description

Technical Field

[0001] This invention relates to a graded pressure relief anchor bolt device that can monitor preload and its usage method, belonging to the field of underground engineering support such as roadways, tunnels and culverts. Background Technology

[0002] With the rapid increase in demand for mineral resources and the continuous increase in mining intensity, shallow resources are becoming increasingly scarce, and mining at depths of thousands of meters has become the norm. As the depth of coal mining and the burial depth of tunnels and culverts continue to increase, the mining environment and engineering geological conditions become increasingly complex. Under the influence of high ground stress and excavation disturbance, deformation and damage are prone to occur, making support issues an important task in deep mining and tunnel construction.

[0003] Prestressed rock bolts are a widely and efficiently used support method in underground engineering. They apply a certain prestress to the surrounding rock through the anchoring force generated by the anchor head, actively reinforcing the surrounding rock. This requires precise control of the applied prestress. However, because rock bolts are concealed supports, embedded deep within the surrounding rock, it is difficult to detect the magnitude of the prestress simply and effectively. Currently, the commonly used rock bolt force gauge consists of a hand pump, jack, sensor, and digital display instrument. While this method can accurately measure the force on the rock bolt, it has two significant drawbacks: firstly, the installation process is complex, consuming a large amount of manpower and time; secondly, the cost is high, with each rock bolt force gauge costing about ten times that of an ordinary rock bolt. Such a high price means that it is impossible to install all rock bolts together, which limits the effective detection of rock bolts in engineering projects. At the same time, deep roadways or tunnels are affected by high ground stress, weak rock masses, and other factors, making the surrounding rock prone to large deformations. This requires rock bolts to produce large elongation deformations to meet the requirements of large deformations in the surrounding rock. Based on the above problems, there is an urgent need to develop an anchor bolt device that can provide constant support force to effectively control the deformation of the surrounding rock, generate large elongation deformation to meet the requirements of large deformation of the surrounding rock, and accurately monitor the magnitude of prestress. In other words, it is necessary to develop an anchor bolt device that integrates accurate monitoring, constant resistance and deformation relief functions to solve the existing engineering and technical problems. Summary of the Invention

[0004] Technical problem: To address the shortcomings of existing technologies, a graded pressure relief anchor bolt device and its usage method that can monitor prestress are provided. This device can not only accurately monitor the magnitude of the applied prestress, but also provide constant support force and generate large elongation deformation to meet the requirements of large deformation of the surrounding rock.

[0005] Technical solution: To achieve the above technical objective, the present invention provides a graded pressure relief anchor bolt device for monitoring preload, including an anchor bolt, which includes a front section of the anchor bolt head, a middle section of the anchor bolt, and a threaded section of the anchor bolt tail. The front section of the anchor bolt is provided with a sleeve, and the threaded section of the anchor bolt is provided with a preload detection tray and an anti-slip nut in sequence.

[0006] The front section of the anchor bolt includes an annular protruding section and a flat section. The annular protruding section is located at the end of the anchor bolt and has a multi-layered annular protrusion structure. The inner side of the sleeve on the front section of the anchor bolt is provided with multiple rows of spring telescopic clips to match the annular protruding section and form friction. The annular protrusion and the spring telescopic clips in the sleeve interact and coordinate to achieve obstructed sliding between the anchor bolt and the sleeve.

[0007] The preload detection tray set on the threaded section of the anchor bolt is an elastic loading structure. A reserved hole is provided on the inner side of the preload detection tray surrounding the anchor bolt. A lifting disc is provided at the opening of the reserved hole. A high elastic spring is sleeved on the threaded section of the anchor bolt between the lifting disc and the bottom of the cavity. A lifting eye bolt A is provided on the edge of the lifting disc, which moves up and down with the lifting disc in the reserved hole. The lifting eye bolt A is connected to the preload display meter through steel strand.

[0008] 2. The graded pressure relief anchor bolt device for monitoring preload according to claim 1, characterized in that: the sleeve is a hollow rod structure with dimensions matching the anchor hole; the sleeve is divided into a first-stage section and a second-stage section according to its inner diameter, wherein the section near the end is the second-stage section, and the inner diameter of the second-stage section is slightly larger than that of the first-stage section; the section near the end of the second-stage section is a section without spring telescopic clips, and the section near the first-stage section is a section with spring telescopic clips; both the section with spring telescopic clips and the first-stage section have multiple spring telescopic clips arranged in a three-layer ring at equal intervals on their inner sides; the compression degree of the spring clips in the section with spring telescopic clips and the first-stage section is different; the sections without spring telescopic clips and the first-stage section have spring telescopic clips arranged in a ring at equal intervals. The spacing between the annular protrusions of the clip sections is the same as that of the three-layer spring telescopic clips; each cross section is evenly arranged with 4 to 6 square inner grooves. Each spring telescopic clip includes a square inner groove set on the inner wall of the sleeve. A ball-shaped telescopic rod is provided at the end of the square inner groove through spring A. Because the inner diameter of the sleeve I section is slightly smaller than that of the sleeve II section, when the anchor rod slides relative to the sleeve, the annular protrusion on the annular protrusion section of the anchor rod squeezes the ball-shaped telescopic rod at the end of the sleeve I section. Because the spring has a greater degree of contraction, the force required is greater than the force required to squeeze the ball-shaped telescopic rod at the end of the sleeve II section. That is, the resistance encountered by the annular protrusion section of the anchor rod when sliding from the sleeve II section to the sleeve I section increases; the end of the sleeve is provided with a circular cover plate to prevent dust and anchoring agent from entering.

[0009] 3. The graded relief anchor bolt device for monitoring preload according to claim 1, characterized in that: the high elastic spring inside the preload detection tray is only used to monitor the preload of the graded relief anchor bolt device, and its elastic stiffness is large, so that even if the anchor bolt is broken, it cannot be completely compressed in order to monitor the real-time force change of the preload.

[0010] 4. A graded pressure relief anchor bolt device for monitoring preload according to claim 1, characterized in that: the preload display includes a reading instrument panel, the reading instrument panel is provided with a scale, a pointer is connected to the center of the dial via a rotating shaft, a gear is provided coaxially with the pointer, one end of the reading instrument panel is provided with a lifting eye bolt C for fixing the end of the steel strand, the steel strand passes through the lifting eye bolt B into the reading instrument panel, the steel strand passes around the gear and is connected to one end of the spring B, the other end of the spring B is connected to the lifting eye bolt C, a movable screw for adjusting the relationship between the steel strand and the spring B is connected to the steel strand between the lifting eye bolt B and the gear, the movable screw is adjusted by sliding through an adjustment slide on the reading instrument panel.

[0011] 5. A graded pressure relief anchor bolt device for monitoring preload according to claim 4, characterized in that: the direction of the steel strand is changed by the lifting eye bolt B, from perpendicular to the scale to parallel to the reading instrument panel, and the reading is adjusted and the scale is zeroed by sliding the moving screw on the adjustment slide; the scale on the scale is converted and marked by the formula F=kx+a, when the anchor bolt is preloaded, the high elastic spring is compressed, the lifting disc descends accordingly, and then the lifting eye bolt A fixed to one side of its edge pulls the steel strand towards the bottom of the anchor hole, at which time the steel strand pulls the gear to rotate, so that the pointer rotates to the scale corresponding to the force on the anchor bolt.

[0012] 6. The graded pressure relief anchor bolt device for monitoring preload according to claim 1, characterized in that: a retractable structure is provided at the sleeve opening to prevent the annular protrusion section of the anchor bolt from detaching from the sleeve, and the retractable structure at the sleeve opening is connected to the anchor bolt by a rectangular protrusion of a spline structure, thereby allowing the sleeve to rotate with the anchor bolt.

[0013] 7. The method of using a graded relief anchor bolt device for monitoring preload according to any one of claims 1 to 6, characterized in that the steps are as follows:

[0014] Drill anchor holes at the pre-marked location in the surrounding rock, slide the anchor rod from the end of the sleeve into the bottom of the sleeve, and at this time the rectangular protrusion on the middle section of the anchor rod is embedded in the edge of the sleeve, that is, the two can rotate synchronously.

[0015] The circular cover plate is attached to the end of the sleeve to prevent dust and anchoring agent from entering;

[0016] The anchoring agent, curing agent, and the entire pressure-relieving anchor bolt device are fed into the anchor hole, and the anchor bolt is rotated and stirred using a mixer.

[0017] A rectangular protrusion is provided on the middle section of the anchor rod. The rectangular protrusion is embedded in the groove reserved in the sleeve, so the sleeve can rotate with the anchor rod.

[0018] The anchor rod and sleeve are rotated using a mixer to fully mix the putty and hardener to form an anchoring agent colloid.

[0019] After the anchoring agent has cured, a preload testing tray and an anti-slip nut are sequentially installed on the exposed threaded section of the anchor rod outside the anchor hole. The preload is provided by the preload anti-slip nut along the thread helix angle. The applied preload is insufficient to allow the anchor rod to pass the first turn of the spherical telescopic rod.

[0020] When preload is applied via the anti-slip nut along the thread helix angle, the high-elasticity spring is compressed, causing the upper lifting disc to descend. The eye bolt A, fixed to one side of the disc, pulls the steel strand towards the bottom of the anchor hole. At this time, the steel strand pulls the gear, causing the pointer to rotate to the scale corresponding to the force applied to the anchor bolt. The moving bolt slides on the adjustment track to adjust the reading and return the scale to zero. The preload display is pulled by spring B, so the scale should be exactly at 0 when no force is applied. When preload is applied via the anti-slip nut, the lifting disc descends, and the steel strand pulls the pointer to the corresponding position. The descent of the lifting disc pulls the steel strand, indicating the magnitude of the preload.

[0021] When the surrounding rock undergoes large deformation, the anchor bolt is under tension, and the annular protrusion on the anchor bolt and the sleeve will slide relative to each other. The spring changes in coordination to monitor the preload. The annular protrusion on the annular protrusion of the anchor bolt squeezes the end spherical telescopic rod in the sleeve section II, further squeezing the spring A at the bottom of the square inner groove, that is, the sliding of the anchor bolt encounters resistance. When the deformation of the surrounding rock increases further, the force required for the annular protrusion on the annular protrusion of the anchor bolt to squeeze the end spherical telescopic rod in the sleeve section I is greater than the force required to squeeze the end spherical telescopic rod in the sleeve section II. Therefore, the resistance to be overcome by the sliding further increases. If the surrounding rock continues to deform, after further sliding, the annular protrusion of the anchor bolt will be stuck at the end of the sleeve, thus realizing the pressure relief characteristic of the device.

[0022] Similarly, the stress state and stress value of the anchor bolt during the pressure relief process can still be read on the reading instrument panel. In summary, this device can monitor the preload force while also achieving the pressure relief function.

[0023] Beneficial Effects: This invention combines the functions of providing constant support force, generating large elongation deformation to meet the requirements of large deformation of surrounding rock, and accurately monitoring preload. Its beneficial effects are undeniable: 1) It allows for simple and intuitive understanding of the anchor bolt's stress state at the construction site; 2) The device has a simple installation process, does not require excessive manpower or time, is inexpensive, and can effectively test all anchor bolts used in engineering applications; 3) It can generate large expansion and contraction deformation to meet the requirements of large deformation of surrounding rock. Constant resistance is provided through the compression and coordination between the annular protrusion on the anchor bolt and the components on the inner wall of the sleeve, allowing it to deform along with the surrounding rock within allowable limits to meet the requirements of large deformation of surrounding rock; the stress state and magnitude of the anchor bolt are indicated by the compression and pulling of the steel strand by a high-elasticity spring, which drives the pointer to rotate within the reading instrument panel.

[0024] This device achieves pressure relief through spring clips and sleeves, and uses a mechanical structure connected by a heavy-duty spring to monitor the preload. It is low in cost and easy to promote. Finally, this heavy-duty spring is set in the tray, which is very simple to install and retrieve. The tray is adjustable and operable on the outside, and it is also easy to use.

[0025] The anchor bolt device integrates multiple functions, solving the problem that ordinary anchor bolts cannot meet the requirements of large deformation of surrounding rock, and addressing the issues of existing pressure-relieving anchor bolts being unable to apply pre-tightening force or having complex testing procedures and high testing costs after applying pre-tightening force. This invention has a simple structure, accurate data, and stable function, which can greatly improve testing efficiency. Furthermore, the deformation-relieving function of the anchor bolt can effectively reduce the occurrence of accidents and ensure the safety of personnel. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the anchor hole in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a graded pressure relief anchor bolt device for monitoring preload in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the installation of the graded pressure relief anchor bolt device for monitoring preload in an embodiment of the present invention;

[0029] Figure 4(a) is a front view of the preload detection tray in an embodiment of the present invention;

[0030] Figure 4(b) is a three-dimensional schematic diagram of the preload detection tray in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the reading instrument panel in an embodiment of the present invention;

[0032] Figure 6 This is an enlarged schematic diagram of the sliding (pressure relief) sleeve in an embodiment of the present invention;

[0033] Figure 7 This is a schematic cross-sectional view of the sleeve I(II) section in an embodiment of the present invention.

[0034] In the diagram: 1-surrounding rock, 2-preload testing tray, 3-anti-slip thread nut, 4-anchor bolt, 5-anchor hole, 6-lifting disc, 7-high elasticity spring, 8-reading instrument panel, 9-anchor bolt threaded section, 10-anchor bolt middle section, 11-rectangular protrusion, 12-anchor bolt annular protrusion section, 13-end spherical telescopic rod, 14-spring A, 15-circular cover plate, 16-anchoring adhesive binder, 17-sleeve, 18-square inner groove, 19-pointer, 20-eye bolt B, 21-steel strand, 22-spring B, 23-moving screw, 24-adjustment slide, 25-eye bolt C, 26-gear, 27-reserved hole, 28-eye bolt A, 29-scale. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings:

[0036] like Figure 1 and Figure 2 As shown, the present invention discloses a graded pressure relief anchor bolt device for monitoring preload, comprising an anchor bolt 4, the anchor bolt 4 including a front section of the anchor bolt at the head, a middle section of the anchor bolt 10, and a threaded section of the anchor bolt 9 at the tail. A sleeve 17 is provided on the front section of the anchor bolt, and a preload detection tray 2 and an anti-slip nut 3 are sequentially provided on the threaded section of the anchor bolt 9. The front section of the anchor bolt includes an annular protrusion section 12 and a flat section of the anchor bolt. The annular protrusion section 12 is located at the end of the anchor bolt 4, specifically having a multi-layered annular protrusion structure. Multiple rows of spring-loaded telescopic clips are provided inside the sleeve 17 on the front section of the anchor bolt to match and form friction with the annular protrusion section 12. The annular protrusion interacts and coordinates with the spring telescopic clip in the sleeve 17 to achieve obstructed sliding between the anchor rod 4 and the sleeve 17; the preload detection tray 2 set on the threaded section 9 of the anchor rod is an elastic loading structure. A reserved hole 27 is provided on the inner side of the preload detection tray 2 surrounding the anchor rod 4. A lifting disc 6 is provided at the opening of the reserved hole 27. A high elastic spring 7 is sleeved on the threaded section 9 between the lifting disc 6 and the bottom of the cavity. A lifting eye bolt A28 is provided on the edge of the lifting disc 6, which moves up and down with the lifting disc 6 in the reserved hole 27. The lifting eye bolt A28 is connected to a preload display meter through a steel strand 21.

[0037] like Figure 3As shown, the sleeve 17 is a hollow rod body, divided into a sleeve section I and a sleeve section II, with the inner diameter of the sleeve section II being slightly larger than that of the sleeve section I. Because the inner diameter of the sleeve section I is slightly smaller than that of the sleeve section II, when the anchor rod 4 slides relative to the sleeve 17, the force required for the annular protrusion on the annular protrusion section 12 of the anchor rod to compress the end spherical telescopic rod 13 inside the sleeve section I is greater than the force required to compress the end spherical telescopic rod 13 inside the sleeve section II (because the spring has a greater degree of contraction). That is, the resistance encountered by the annular protrusion section 12 of the anchor rod when sliding from the sleeve section II to the sleeve section I increases. The sleeve 17 is provided with a circular cover plate 15 at its end, which can prevent dust and anchoring agent from entering.

[0038] The anchoring agent mortar cartridge, the curing agent cartridge, and the entire anchor rod are fed into the anchor hole 5. The agitator is started to rotate the rod and mix it. A rectangular protrusion 11 is provided on the middle section 10 of the anchor rod. The rectangular protrusion 11 is embedded in the groove reserved in the sleeve 17, so the sleeve 17 can rotate with the anchor rod 4. The agitator drives the rotation of the anchor rod 4 and the sleeve 17 to fully mix the mortar and curing agent to form an anchoring agent colloid. After the anchoring agent has cured, the preload testing tray 2 and the anti-slip nut 3 are sequentially installed on the exposed threaded section 9 of the anchor rod outside the anchor hole. The preload is provided by the preload anti-slip nut 3 along the thread helix angle.

[0039] As shown in Figure 4(a), Figure 4(b) and Figure 5 As shown, the preload detection tray 2 is equipped with a high-elasticity spring 7. The selected high-elasticity spring 7 should have a sufficiently large elastic stiffness so that even if the anchor rod 4 is broken, it cannot be completely compressed. The preload display includes a reading instrument panel 8, which has a scale 29. A pointer 19 is connected to the center of the dial via a rotating shaft. A gear 26 is coaxially mounted on the pointer 19. One end of the reading instrument panel 8 is equipped with a lifting eye bolt C25 for fixing the end of the steel strand 21. The steel strand 21 passes through the lifting eye bolt B20 into the reading instrument panel 8. The steel strand 21 passes around the gear 26 and connects to one end of the spring B22. The other end of the spring B22 is connected to the lifting eye bolt C25. A movable screw 23 is connected to the steel strand 21 between the lifting eye bolt B20 and the gear 26 to adjust the relationship between the steel strand 21 and the spring B22. The movable screw 23 is adjusted by sliding along the adjustment slide 24 on the reading instrument panel 8.

[0040] The direction of the steel strand 21 is changed by the eye bolt B20, from being perpendicular to the dial 29 to being parallel to the reading instrument panel 8. The reading is adjusted and the scale is zeroed by sliding the moving screw 23 on the adjustment slide 24. The scale on the dial 29 is converted and marked by the formula F=kx+a. When the anchor rod 4 is pre-tightened, the high elastic spring 7 is compressed, and the lifting disc 6 descends accordingly. Then, the eye bolt A28 fixed to one side of its edge pulls the steel strand 21 towards the bottom of the anchor hole 5. At this time, the steel strand 21 pulls the gear 26 to rotate, so that the pointer 19 rotates to the scale corresponding to the force on the anchor rod 4.

[0041] like Figure 6 As shown, when the surrounding rock 1 undergoes large deformation, the anchor rod 4 is under tension, and the annular protrusion 12 on it will slip relative to the sleeve 17. The annular protrusion on the annular protrusion 12 of the anchor rod compresses the end spherical telescopic rod 13 in the sleeve II section, further compressing the spring A14 at the bottom of the square inner groove 18, that is, the slippage of the anchor rod 4 encounters resistance. When the deformation of the surrounding rock 1 further increases, because the force required for the annular protrusion on the annular protrusion 12 to compress the end spherical telescopic rod 13 in the sleeve I section is greater than the force required to compress the end spherical telescopic rod 13 in the sleeve II section (because the spring has a greater degree of contraction), the resistance that the slippage needs to overcome further increases. If the surrounding rock 1 continues to deform, after further slippage, the annular protrusion 12 of the anchor rod will be stuck at the end of the sleeve 17 (the end near the anchor hole), thereby realizing the pressure relief characteristic of the device.

[0042] like Figure 7As shown, sleeve 17 is a hollow rod structure with dimensions matching the anchor hole 5. Sleeve 17 is divided into sleeve I and sleeve II sections based on its inner diameter. The section near the end is sleeve II, and its inner diameter is slightly larger than that of sleeve I. Within sleeve II, the section near the end has a springless telescopic clip, while the section near sleeve I has a spring-loaded telescopic clip. Both the spring-loaded and sleeve I sections have multiple spring telescopic clips arranged in a three-layer ring at equal intervals on their inner sides. The spacing between the annular protrusions of the springless, sleeve I, and spring-loaded sections is the same as that of the three-layer spring telescopic clips. Each cross-section has 4-6 square inner grooves 1 evenly distributed. 8. Each spring telescopic clip includes a square inner groove 18 set on the inner wall of the sleeve 17. A ball-shaped telescopic rod 13 is provided in the square inner groove 18 through the spring A. Because the inner diameter of the sleeve I section is slightly smaller than that of the sleeve II section, when the anchor rod 4 slides relative to the sleeve 17, the force required for the annular protrusion on the annular protrusion section 12 of the anchor rod to squeeze the ball-shaped telescopic rod 13 in the sleeve I section is greater than the force required to squeeze the ball-shaped telescopic rod 13 in the sleeve II section (because the spring has a greater degree of contraction). That is, the resistance encountered by the annular protrusion section 12 of the anchor rod when sliding from the sleeve II section to the sleeve I section increases. The sleeve 17 is provided with a circular cover plate 15 at the end to prevent dust and anchoring agent from entering.

Claims

1. A graded yielding anchor device that can monitor pre-tension, characterized by: The anchor rod (4) comprises a front section of the anchor rod with a head, a middle section of the anchor rod (10), and a threaded section of the anchor rod (9) with a tail, wherein the front section of the anchor rod is provided with a sleeve (17), and the threaded section of the anchor rod (9) is sequentially provided with a pre-tightening force detection tray (2) and an anti-slip wire nut (3); The front section of the anchor rod comprises an anchor rod annular protruding section (12) and an anchor rod flat section, the anchor rod annular protruding section (12) is arranged at the end of the anchor rod (4), specifically has a multi-layer annular protruding structure, and the inner side of the sleeve (17) arranged on the front section of the anchor rod is provided with multiple rows of spring retractable clips used to match the anchor rod annular protruding section (12) to form friction, the annular protrusions and the spring retractable clips arranged in the sleeve (17) interact and coordinate to realize the blocked sliding of the anchor rod (4) and the sleeve (17); The pre-tightening force detection tray (2) arranged on the threaded section of the anchor rod (9) is an elastic loading structure, the inner side of the pre-tightening force detection tray (2) surrounding the anchor rod (4) is provided with a reserved hole (27), the opening of the reserved hole (27) is provided with a lifting disc (6), a high-elastic spring (7) is sleeved on the threaded section of the anchor rod (9) between the lifting disc (6) and the bottom of the cavity, the edge of the lifting disc (6) is provided with a lifting eye bolt A (28) moving up and down in the reserved hole (27) along with the lifting disc (6), and the lifting eye bolt A (28) is connected with a pre-tightening force display table through a steel strand (21); The sleeve (17) is a hollow rod structure matching the size of the anchor hole (5), the sleeve (17) is divided into a sleeve I section and a sleeve II section according to the size of the inner diameter, the sleeve II section is close to the end, and the inner diameter of the sleeve II section is slightly larger than that of the sleeve I section, the inner side of the sleeve II section close to the end is a spring retractable clip-free section, and the section close to the sleeve I section is a spring retractable clip section, wherein the spring retractable clip section and the inner side of the sleeve I section are both provided with three layers of annularly arranged spring retractable clips at equal intervals, the compression degree of the spring retractable clips arranged in the spring retractable clip section and the sleeve I section is different, and the spring retractable clip-free section, the sleeve I section and the spring retractable clip section all have the same spacing with the annular protrusions of the three layers of spring retractable clips; 4-6 square inner recesses (18) are uniformly arranged in each cross section, each spring retractable clip comprises a square inner recess (18) arranged on the inner wall of the sleeve (17), and an end spherical telescopic rod (13) is arranged in the square inner recess (18) through a spring A, because the inner diameter of the sleeve I section is slightly smaller than that of the sleeve II section, when the anchor rod (4) relatively slides with the sleeve (17), the annular protrusions on the anchor rod annular protruding section (12) extrude the end spherical telescopic rod (13) in the sleeve I section, because the contraction degree of the spring is larger, the force required is larger than that required for extruding the end spherical telescopic rod (13) in the sleeve II section, that is, the resistance encountered by the anchor rod annular protruding section (12) when sliding from the sleeve II section to the sleeve I section increases; and a circular cover disc (15) is arranged at the end of the sleeve (17) to prevent dust and anchoring agent from entering. The pre-tightening force display table comprises a reading instrument panel (8) provided with a scale disc (29), a pointer (19) connected with the scale disc (29) through a rotating shaft, a gear (26) coaxially arranged on the pointer (19), a hanging ring bolt C (25) arranged on one end of the reading instrument panel (8) and used for fixing an end of a steel strand (21), the steel strand (21) penetrating into the reading instrument panel (8) through a hanging ring bolt B (20), the steel strand (21) being connected with one end of a spring B (22) after winding around the gear (26), the other end of the spring B (22) being connected with the hanging ring bolt C (25), and a moving bolt (23) being connected with the steel strand (21) between the hanging ring bolt B (20) and the gear (26) and used for adjusting the relationship between the steel strand (21) and the spring B (22), the moving bolt (23) being slidably adjusted through a debugging sliding groove (24) opened on the reading instrument panel (8). The steel strand (21) changes the direction through the lifting ring bolt B (20), changes from the direction perpendicular to the dial (29) to the direction parallel to the reading instrument panel (8), adjusts the reading and makes the scale zero through moving the bolt (23) to slide on the adjusting slide (24); the scale on the dial (29) is converted and marked by the formula When the anchor rod (4) is pre-tensioned, the high-elastic spring (7) is compressed under stress, the lifting disc (6) is lowered, and then the lifting ring bolt A (28) fixed on the edge of one side pulls the steel strand (21) to move to the bottom of the anchor hole (5), at this time, the steel strand (21) winds the gear (26) to rotate, and the pointer (19) is rotated to the scale corresponding to the stress of the anchor rod (4).

2. A pre-tension monitored stepped yielding anchor device according to claim 1, characterized in that: The high-elasticity spring (7) arranged in the pre-tightening force detection tray (2) is only used for monitoring the pre-tightening force of the stepped pressure anchor rod device, and has large elastic stiffness. In order to monitor the real-time stress change of the pre-tightening force, the anchor rod (4) cannot be completely compressed even if it is pulled off.

3. A pre-tension monitored graded yielding anchor device according to claim 1, characterized in that: The sleeve (17) is provided with a folding structure at an opening thereof to prevent the anchor rod annular protruding section (12) from being separated from the sleeve (17), and the folding structure at the opening of the sleeve (17) is connected with the anchor rod (4) through the rectangular protrusion (11) of the spline structure, so that the sleeve (17) rotates with the anchor rod (4).

4. The use of a pre-tension monitored stepped yielding anchor rod device according to any one of claims 1 to 3, characterized in that The steps are as follows: Drill the anchor hole (5) at the pre-marked position of the surrounding rock (1), slide the anchor rod (4) into the bottom of the sleeve (17) from the end of the sleeve (17), at this time, the rectangular protrusion (11) on the middle section (10) of the anchor rod is embedded into the edge of the sleeve (17), that is, the two can synchronously rotate; Connect the circular cover disc (15) to the end of the sleeve (17) to prevent dust and anchoring agent from entering; Send the anchoring agent mortar cartridge, curing agent cartridge and whole stepped pressure anchor rod device into the anchor hole (5), and drive the anchor rod (4) to rotate and stir by using the stirrer; The middle section (10) of the anchor rod is provided with the rectangular protrusion (11), the rectangular protrusion (11) is embedded into the reserved groove of the sleeve (17), so that the sleeve (17) can rotate with the anchor rod (4); Drive the rotating anchor rod (4) and sleeve (17) to fully stir the mortar and curing agent to form the anchoring agent cementing body (16) by using the stirrer; After the anchoring agent is cured, the pre-tightening force detection tray (2) and the anti-slip wire nut (3) are sequentially sleeved on the anchor rod threaded section (9) exposed outside the anchor hole, the pre-tightening anti-slip wire nut (3) provides the pre-tightening force along the thread rise angle, and the applied pre-tightening force is insufficient to make the anchor rod (4) pass the first circle of the spherical telescopic rod (13). When the pre-tightening force is provided by the pre-tightening anti-slip nut (3) along the thread rise angle, the high-elasticity spring (7) will be compressed, the upper lifting disc (6) will be lowered, and the lifting ring bolt A (28) fixed on the edge of the lifting disc will pull the steel strand (21) to move towards the bottom of the anchor hole (5). At this time, the steel strand (21) will rotate the gear (26) to make the pointer (19) rotate to the scale corresponding to the force of the anchor rod (4). The moving bolt (23) slides on the adjusting slide (24) to adjust the reading and make the scale zero. The pre-tightening force display table is pulled by the spring B (22), so the scale should be exactly at 0 scale when there is no force. When the pre-tightening force is applied by the anti-slip nut (3), the lifting disc (6) is lowered, the steel strand pulls the pointer (19) to the corresponding position, and the lifting disc (6) is lowered to pull the steel strand, which corresponds to the pre-tightening force. When the surrounding rock (1) deforms greatly, the anchor rod (4) is pulled, the anchor rod ring protruding section (12) on the anchor rod (4) will slide relative to the sleeve (17), and the spring (7) will change to monitor the pre-tightening force. The annular protrusion on the anchor rod ring protruding section (12) extrudes the end spherical telescopic rod (13) in the sleeve II section, further extrudes the spring A (14) at the bottom of the square recess (18), that is, the anchor rod (4) encounters resistance when sliding; when the deformation of the surrounding rock (1) further increases, the annular protrusion on the anchor rod ring protruding section (12) extrudes the end spherical telescopic rod (13) in the sleeve I section, and the force required to extrude the end spherical telescopic rod (13) in the sleeve II section is greater, so the resistance that needs to be overcome during sliding further increases; if the surrounding rock (1) continues to deform, after further sliding, the anchor rod ring protruding section (12) will be stuck at the end of the sleeve (17), so as to realize the pressure relief characteristics of the device. As described above, the stress state and value of the anchor rod (4) during the pressure relief process can still be read on the reading instrument panel (8). As described above, the device can not only monitor the pre-tightening force, but also realize the pressure relief function.

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