Expanding shell prestressed anchor

Abstract

This application provides an expansion-shell type prestressed anchor bolt, comprising: a threaded rod having a front end and a rear end, a wedge sleeve assembled at the front end of the threaded rod, and an expansion shell cooperating with the wedge sleeve. The threaded rod has a first thread, and at least a portion of the threads of the first thread have a second thread. The pitch of the second thread is smaller than the pitch of the first thread, and the wedge sleeve mates with the second thread. The expansion-shell type prestressed anchor bolt provided by this application is easy to install and has high construction efficiency.

Description

Technical Field

[0001] This application relates to the field of anchor bolt technology, and in particular to expansion shell type prestressed anchor bolts. Background Technology

[0002] Rock bolt support is a primary form of support in coal mine roadways. Compared to ordinary mortar rock bolts, expansion shell rock bolts eliminate the setting time of the anchoring agent, meeting the needs of rapid anchoring construction. They also offer higher safety and are widely used in underground engineering support. Expansion shell rock bolts mainly consist of an anchor head, threaded rod, base plate, and fastening nut. The anchor head further comprises a mating expansion shell and a wedge sleeve.

[0003] Early expansion-shell anchor bolts expanded the shell by applying tension along the length of the threaded rod, causing the locking nut at the end of the rod to be pulled away from the roadway wall. Therefore, it was necessary to further tighten the locking nut to maintain the prestress, making the construction process more complicated. Summary of the Invention

[0004] This application provides an expansion-shell type prestressed anchor rod, which is easier to install and helps improve construction efficiency.

[0005] The expansion shell type prestressed anchor bolt provided in this application includes a threaded rod having a front end and a rear end, a wedge sleeve assembled at the front end of the threaded rod, and an expansion shell that mates with the wedge sleeve. The threaded rod has a first thread, and at least a portion of the threads of the first thread have a second thread. The pitch of the second thread is smaller than the pitch of the first thread, and the wedge sleeve mates with the second thread.

[0006] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0007] Optionally, the pitch of the second thread is 0.1 to 0.5 times that of the first thread, the helix angle of the second thread is 0.5 to 3°, and the center of the threaded rod is provided with a grouting hole.

[0008] Optionally, in the length direction of the threaded rod, the expansion shell includes a mating section abutting against the outer periphery of the wedge sleeve and a suspension section located outside the threaded rod. In the circumferential direction of the threaded rod, the expansion shell includes at least two expansion plates. The expansion shell type prestressed anchor rod also includes a retaining ring sleeved on the suspension section, the retaining ring being used to tighten each of the expansion plates.

[0009] Optionally, the retaining ring includes an elastic strip extending circumferentially along the threaded rod, wherein the two ends of the elastic strip overlap each other in the circumferential direction of the threaded rod.

[0010] Optionally, the expansion shell type prestressed anchor rod further includes a clamping member fixed to the front end of the expansion shell. The clamping member is U-shaped and includes two oppositely arranged side walls and a bottom wall connected between the two side walls. The two side walls are respectively fixed to the radial outer side of the expansion shell. The bottom wall is located on one side of the front end of the threaded rod. The rear ends of the two side walls are provided with outwardly curved barb structures.

[0011] Optionally, an expansion gap is provided between two adjacent expansion plates, the expansion gap extends toward the front end of the threaded rod and the width gradually increases, and the outer periphery of the wedge sleeve is provided with a protrusion that is adapted to the shape of the expansion gap.

[0012] Optionally, the protrusion is provided with a backflow groove extending along the length of the threaded rod, so that the grout in the grouting hole can flow back to the rear end of the threaded rod.

[0013] Optionally, the expansion shell type prestressed anchor bolt further includes a support plate, a ball washer, and a fastening nut fixed to the tail end of the threaded rod. The fastening nut engages with the first thread, and the ball washer exerts a squeezing force between the support plate and the fastening nut.

[0014] Optionally, the expansion shell type prestressed anchor rod also includes a support plate, a ball washer, and a fastening nut fixed to the tail end of the threaded rod, wherein the fastening nut and the ball washer are integrally formed with the threaded rod.

[0015] The expansion shell type prestressed anchor provided in this application is easy to install and has high construction efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an embodiment of this application;

[0017] Figure 2 for Figure 1 A sectional view;

[0018] Figure 3 for Figure 1 Exploded view;

[0019] Figure 4 for Figure 3 Enlarged view of area A in the middle;

[0020] Figure 5 for Figure 1 Schematic diagram of the middle retaining ring;

[0021] Figure 6 This is a schematic diagram of another embodiment of the present application.

[0022] The annotations in the figure are explained as follows:

[0023] 1. Threaded rod; 11. Second thread; 12. First thread; 13. Grouting hole; 2. Expansion shell; 21. Fitting section; 22. Suspension section; 23. Expansion plate; 24. Expansion gap; 3. Wedge sleeve; 31. Protrusion; 32. Backflow groove; 4. Snap ring; 41. First thinning section; 42. Second thinning section; 5. Clamping element; 51. Side wall; 52. Bottom wall; 53. Barbed structure; 6. Support plate; 7. Ball pad; 8. Fastening nut. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0026] 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] Expansion shell anchor bolts are installed by mechanically expanding the anchor head and embedding it into the surrounding rock. One type of expansion shell prestressed anchor bolt's anchoring process is as follows: The machine pulls the threaded rod outwards from the borehole. The threaded rod drives the wedge sleeve deeper into the expansion shell, causing the shell to expand and anchor against the borehole wall. During the pulling of the threaded rod, the fastening nut also leaves the inner wall of the roadway along with the threaded rod, therefore it needs to be tightened again to maintain prestress. This installation process is relatively cumbersome, and after installation, the anchor bolt has a long exposed section at the end, requiring further treatment of the exposed section.

[0028] To address the above issues, this application provides an expansion-shell type prestressed anchor rod, which can accelerate construction efficiency.

[0029] refer to Figures 1-6The expansion shell type prestressed anchor bolt of this application includes a threaded rod 1 having a front end and a rear end, a wedge sleeve 3 assembled at the front end of the threaded rod 1, and an expansion shell 2 that cooperates with the wedge sleeve 3. The threaded rod 1 has a first thread 12, and at least a portion of the thread teeth of the first thread 12 are provided with a second thread 11. The pitch of the second thread 11 is smaller than the pitch of the first thread 12, and the wedge sleeve 3 cooperates with the second thread 11.

[0030] In this embodiment, the tail end limiting structure of the threaded rod 1 can adopt existing technology, such as a support plate or nut. The expansion shell 2 in this embodiment can also adopt existing technology. It is not the main improvement point of this embodiment, so it is not limited.

[0031] One installation method of this embodiment is as follows: Anchor holes are drilled in the inner wall of the tunnel, and the front end of the anchor rod is inserted into the anchor holes. At this time, the tail end limiting structure is pressed against the inner wall of the tunnel. The construction equipment directly or through the tail nut drives the threaded rod 1 to rotate. Due to the certain friction between the expansion shell 2 and the inner wall of the anchor hole, the expansion shell 2 will not rotate with the threaded rod 1. A motion mechanism similar to a screw and slider is formed between the wedge sleeve 3 and the threaded rod 1. While the wedge sleeve 3 rotates relative to the threaded rod 1, it moves towards the tail end of the threaded rod 1 and wedges into the expansion shell 2, expanding the expansion shell 2 and completing the anchoring. Those skilled in the art will understand that while the wedge sleeve 3 expands the expansion shell 2, the expansion shell 2 will generate a reaction force on the wedge sleeve 3. The direction of this reaction force is not perpendicular to the threaded rod 1, but has a component towards the front end of the threaded rod 1. This reaction force can generate the prestress of the anchor rod in this embodiment. Thus, by simply rotating the threaded rod 1, prestress is generated while expanding the expansion shell 2, making the operation simple and convenient.

[0032] As the depth of mineral resource mining gradually increases, the pressure on the surrounding rock also rises, which places higher demands on the successful expansion of expansion-shell prestressed anchor bolts. Specifically, regarding the spiral expansion method adopted in this application, if existing standard threaded steel is directly used as the threaded rod 1 in this application, due to limitations in various specifications, a construction machine with significant power and torque is required for expansion during the anchoring process in deep, high-stress surrounding rock. Furthermore, even if the torque of the construction machine is sufficiently high, there is still a risk of breaking the rod tail. Current research on high-strength anchor bolts mainly focuses on the material processing technology of the threaded rod, rather than reducing stress through the overall structural design of the anchor bolt.

[0033] The pull-out force of rebar first increases and then decreases with the pitch. For example, the pitch of left-hand rebar for mining is usually above 11 mm, and some even exceed 40 mm. This large pitch provides the possibility of further machining fine threads on the transverse ribs of existing rebar, for example, designing the second thread 11 to have the same helix direction as the first thread 12, thus making it possible to machine multiple turns of the second thread 11 on the thread teeth of the first thread 12.

[0034] This application reduces the proportion of surrounding rock stress converted into torsional stress in the threaded rod 1 by further machining fine threads on the coarse threads of the existing threaded rod 1, thereby reducing the torsional load that the threaded rod 1 needs to bear during construction from the source. Through improvements to the overall structure of the anchor rod, the limitations of existing mainstream threaded rods in terms of shape, specifications, and torsional strength are overcome, enabling existing mainstream threaded rods to be successfully applied in the spiral opening anchor rod of this application. This reduces the number of anchor rod construction steps while effectively controlling the production cost of the anchor rod.

[0035] For details, please refer to Figure 4 The pitch of the second thread 11 is 0.1 to 0.5 times that of the first thread 12. The threaded rod 1 can be made of construction threaded steel, right-hand fully threaded steel or left-hand threaded steel without longitudinal ribs, and a coarse thread has 2 to 10 fine threaded transverse ribs on its transverse ribs.

[0036] In one embodiment, the rebar has a grouting hole 13 at its center, and after anchoring, grout can be further injected into the anchor hole through the grouting hole 13.

[0037] To further ensure that the threaded rod 1 can withstand sufficiently small torque, in one embodiment, the helix angle of the second thread 11 is 0.5 to 3°.

[0038] Specifically, in one embodiment, along the length of the threaded rod 1, the expansion shell 2 includes a fitting section 21 that abuts against the outer periphery of the wedge sleeve 3 and a suspension section 22 located outside the threaded rod 1. Along the circumferential direction of the threaded rod 1, the expansion shell 2 includes at least two expansion pieces 23. The expansion shell type prestressed anchor also includes a retaining ring 4 sleeved on the suspension section, which is used to tighten each expansion piece 23.

[0039] In this embodiment, the expansion shell 2 is in a segmented form, meaning that each expansion piece 23 is independent of the others. Compared to the integral form, the segmented expansion shell 2 has its tail ends not connected, which facilitates the full expansion of the expansion shell 2 and provides greater anchoring force. During the process of inserting the anchor rod into the anchor hole, in order to ensure that each expansion piece 23 can maintain its initial relative position, in this embodiment, the front end of the expansion shell 2 is fitted onto the wedge sleeve 3, and the rear end of the expansion shell 2 is tightened by the retaining ring 4. This not only maintains the relative positional relationship but also reduces the resistance to the expansion of the tail end of the expansion shell 2.

[0040] After the expansion shell 2 is fully expanded, it may undergo significant deformation. In one embodiment, refer to... Figure 5 The retaining ring 4 includes an elastic strip extending circumferentially along the threaded rod 1. The two ends of the elastic strip overlap each other in the circumferential direction of the threaded rod 1, which can prevent the retaining ring 4 from being over-opened and slipping off.

[0041] In this embodiment, the length of the retaining ring 4 in its straightened state is greater than the circumference of the outer perimeter of the inflated shell 2. When returned to its natural state, the retaining ring 4 is annular, with its two ends overlapping each other. As the inflated shell 2 gradually expands, the overlap length at both ends of the retaining ring 4 gradually decreases, but the retaining ring 4 as a whole still maintains its annular shape, without any partial loops or detachment.

[0042] Specifically, the elastic strip is thinned at both ends, forming a first thinned section 41 and a second thinned section 42 with complementary cross-sectional shapes. The contact surface between the first thinned section 41 and the second thinned section 42 is a sliding surface perpendicular to the length direction of the threaded rod 1. The sliding surface acts as a guide, which facilitates the opening and closing of the retaining ring 4.

[0043] refer to Figure 3 To further ensure that the front end of the expansion shell 2 can smoothly enter the anchor hole, in one embodiment, the expansion shell type prestressed anchor rod also includes a clamping member 5 fixed to the front end of the expansion shell 2. The clamping member 5 is U-shaped and includes two side walls 51 arranged opposite to each other and a bottom wall 52 connected between the two side walls 51. The two side walls 51 are respectively fixed to the radial outer side of the expansion shell 2, and the bottom wall 52 is located on one side of the front end of the threaded rod 1. The rear end of the two side walls 51 is provided with outwardly curved barb structure 53.

[0044] The clamping member 5 is an elongated structure that provides the necessary clamping force to maintain the relative position of each expansion piece 23. This clamping force does not need to be too large, so as not to cause significant resistance to the wedge sleeve 3 entering the expansion shell 2, nor to significantly increase the torque of the threaded rod 1. The barbed structure 53 increases the friction between the expansion shell 2 and the inner wall of the anchor hole, further ensuring that the expansion shell 2 will not rotate with the threaded rod 1.

[0045] refer to Figure 1 An expansion gap 24 is provided between two adjacent expansion plates 23, and the expansion gap 24 extends towards the front end of the threaded rod 1, with its width gradually increasing. The outer periphery of the wedge sleeve 3 is provided with a protrusion 31 that conforms to the shape of the expansion gap 24.

[0046] During the process of inserting the anchor bolt into the anchor hole, the protrusion 31 is supported between two adjacent expansion plates 23, which helps maintain the relative positional relationship of each expansion plate 23. During the anchoring process, the protrusion 31 and the expansion gap 24 cooperate with each other to restrict the rotation of the wedge sleeve 3 and guide the axial movement of the wedge sleeve 3 into the expansion shell 2.

[0047] In one embodiment, the protrusion 31 is provided with a backflow groove 32 extending along the length of the threaded rod 1, so that the grout in the grouting hole 13 can flow back to the rear end of the threaded rod 1, thereby increasing the bonding length between the anchor rod and the grout.

[0048] In one embodiment, the expansion shell type prestressed anchor bolt further includes a support plate 6, a ball pad 7, and a fastening nut 8 fixed to the tail end of the threaded rod 1. The fastening nut 8 is engaged with the first thread 12, and the ball pad 7 exerts a squeezing action between the support plate 6 and the fastening nut 8.

[0049] In another embodiment, reference Figure 6 The expansion-shell type prestressed anchor also includes a support plate 6, a ball washer 7, and a fastening nut 8 fixed to the tail end of the threaded rod 1. The fastening nut 8 and the ball washer 7 are integrally formed with the threaded rod 1. Specifically, the tail end of the threaded rod 1 can be upset to form the fastening nut 8 and the ball washer 7 respectively, and the grouting hole 13 is retained.

[0050] This application provides a method for installing an anchor bolt, wherein the anchor bolt adopts the expansion shell type prestressed anchor bolt of any of the above embodiments, and the installation method includes: rotating the threaded rod to expand the expansion shell 2.

[0051] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0052] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An expansion-shell type prestressed anchor bolt, comprising a threaded rod having a front end and a rear end, a wedge sleeve assembled at the front end of the threaded rod, and an expansion shell cooperating with the wedge sleeve, characterized in that, The threaded rod has a first thread, and at least a portion of the threads of the first thread have a second thread. The pitch of the second thread is less than the pitch of the first thread. The wedge sleeve mates with the second thread. The entire length of the threaded rod has the first thread. The expansion-shell type prestressed anchor bolt includes a fastening nut, which mates with the first thread.

2. The expansion-shell type prestressed anchor bolt according to claim 1, characterized in that, The pitch of the second thread is 0.1 to 0.5 times that of the first thread, and the helix angle of the second thread is 0.5 to 3°.

3. The expansion-shell type prestressed anchor bolt according to claim 1, characterized in that, The threaded rod has a grouting hole at its center.

4. The expansion-shell type prestressed anchor bolt according to claim 2, characterized in that, Along the length of the threaded rod, the expansion shell includes a mating section that abuts against the outer periphery of the wedge sleeve and a suspension section located outside the threaded rod. Along the circumferential direction of the threaded rod, the expansion shell includes at least two expansion plates. The expansion shell type prestressed anchor rod also includes a retaining ring sleeved on the suspension section, the retaining ring being used to tighten each of the expansion plates.

5. The expansion-shell type prestressed anchor bolt according to claim 4, characterized in that, The retaining ring includes an elastic strip extending circumferentially along the threaded rod, wherein the two ends of the elastic strip overlap each other in the circumferential direction of the threaded rod.

6. The expansion-shell type prestressed anchor bolt according to claim 4, characterized in that, The expansion shell type prestressed anchor also includes a clamping member fixed to the front end of the expansion shell. The clamping member is U-shaped and includes two oppositely arranged side walls and a bottom wall connected between the two side walls. The two side walls are respectively fixed to the radial outer side of the expansion shell. The bottom wall is located on one side of the front end of the threaded rod. The rear ends of the two side walls are provided with outwardly curved barb structures.

7. The expansion-shell type prestressed anchor bolt according to claim 4, characterized in that, An expansion gap is provided between two adjacent expansion plates. The expansion gap extends towards the front end of the threaded rod and its width gradually increases. The outer periphery of the wedge sleeve is provided with a protrusion that is adapted to the shape of the expansion gap.

8. The expansion-shell type prestressed anchor bolt according to claim 7, characterized in that, The protrusion is provided with a backflow groove extending along the length of the threaded rod, so that the grout in the grouting hole can flow back to the rear end of the threaded rod.

9. The expansion-shell type prestressed anchor bolt according to claim 1, characterized in that, The expansion-shell type prestressed anchor also includes a support plate and a ball pad fixed to the tail end of the threaded rod, with the ball pad exerting a squeezing force between the support plate and the fastening nut.

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