Expanding shell anchor for soft rock and construction method thereof

Abstract

The invention discloses an expansion shell anchor for soft rock, comprising an expansion shell and an anchor rod, wherein the two ends of the expansion shell are respectively provided with an expansion shell inner wedge and a conical top block, wherein the expansion shell inner wedge and the expansion shell top, the conical top block and the expansion shell bottom all form sliding contact; the anchor rod comprises an anchor rod body, wherein one end of the anchor rod body is fixedly installed with a screw rod through a connecting sleeve, the screw rod and the expansion shell inner wedge are connected through threaded transmission, the top of the connecting sleeve is embedded in the conical top block and presses the supporting flange of the conical top block; the anchor rod is rotated to drive the expansion shell inner wedge and the conical top block to move into the expansion shell until the supporting flange of the conical top block breaks, so that the expansion shell piece is deformed and expanded outward to the surrounding rock hole wall to apply prestress to the rock mass; meanwhile, a construction method of the expansion shell anchor for soft rock is also provided. The invention has low cost, good anchoring effect, high construction efficiency, and can be well applied to soft rock formations.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering anchoring and supporting, and in particular to an expansion shell anchor rod suitable for soft rock formations and a construction method thereof. Background Art

[0002] During the construction of underground projects, mine tunnels, railway tunnels, slope protection and military projects, in order to prevent the ground from deformation, collapse and instability, it is necessary to reinforce the ground. The main measure adopted is to bury mortar anchors or anchors with expansion heads in the ground, and use the tension of the anchors and the concrete grouting body integrated with the anchors to form an integral reinforcement structure for the ground, so as to achieve the purpose of controlling deformation.

[0003] Compared with ordinary mortar anchors, prestressed anchors have the following advantages: 1. By applying prestress to the rock mass between the inner and outer anchor heads, a rock compression zone will be formed; 2) Prestressed anchors are installed continuously in the rock mass, and the overlapping and intersecting compression zones will form a compression bearing layer with a certain thickness; 3) Especially in tunnel engineering, the compression zone formed by the prestressed anchor can form a bearing arch of the rock mass. Under the action of the arch effect, it not only fully mobilizes the self-bearing capacity of the surrounding rock, but also greatly improves the resistance of the surrounding rock outside the arch. Prestressed anchors include fast medicine rolls, expansion shell anchors and other types. Among them, the expansion shell anchor is usually composed of basic components such as the expansion shell, rod body, pad, nut, etc., and other components such as ball pads, grouting pipes, exhaust pipes, grouting plugs, centering devices, etc. are added when necessary. It is a kind of prestressed mechanical anchoring anchor.

[0004] Compared with anchor rods such as quick-roll anchor rods, the rock compression zone formed by the expansion shell anchor rod is larger when the drilling depth and rod length are comparable, and can provide better anchoring effect. At the same time, because there is no need to wait for the anchor body to solidify, the instant prestressing provided by the expansion shell anchor rod is also more advantageous, and by adopting the grouting anchor rod, it can be better applied to soft rock formation environments. For example, the invention patent with application number CN201910265475.6 discloses an extremely soft rock anchor rod structure, including a hollow anchor rod body, a connecting sleeve, an expansion shell anchor head, a slurry stop plug, a pad and a fixing nut, a limiting nut is threadedly mounted on one side of the hollow anchor rod body close to the connecting sleeve, and a through groove located between the limiting nut and the connecting sleeve is provided on the front surface, rear surface, upper surface and lower surface of the hollow anchor rod body, and a moving block located at the through groove is provided inside the hollow anchor rod body, and the moving block can be moved in the limiting nut, and the moving block The front surface, rear surface, upper surface and lower surface are respectively fixedly connected with linkage blocks; the invention has the advantages of good anchor support effect and improved anchor injection efficiency, but the following problems still exist: its improved support effect on soft rock depends on the design of supporting ribs, expansion steel and other components arranged on the hollow rod body, the structure is relatively complex, the production cost is high, and after the operation is completed, the outer end of the hollow anchor rod protrudes to the outside of the anchor hole, and needs to be cut due to process requirements, safety and other factors, which increases the construction steps, reduces the operation efficiency, and makes it difficult to achieve continuous and mechanized operation. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide an expansion anchor with low cost, good anchoring effect and high construction efficiency, which can be well applied in soft rock formations and even in different working conditions, and to introduce a construction method of the expansion anchor for soft rock.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] An expansion shell anchor for soft rock, comprising an expansion shell and an anchor rod, wherein two ends of the expansion shell are respectively provided with an expansion shell inner wedge and a conical top block, wherein the expansion shell inner wedge and the expansion shell top, and the conical top block and the expansion shell bottom all form sliding contact; the anchor rod comprises an anchor rod body, one end of the anchor rod body is fixedly mounted with a screw rod through a connecting sleeve, the screw rod and the expansion shell inner wedge are connected through threaded transmission, the top of the connecting sleeve is embedded in the conical top block and presses the supporting flange of the conical top block; the anchor rod is rotated to drive the expansion shell inner wedge and the conical top block to move into the expansion shell until the supporting flange of the conical top block breaks, so that the expansion shell piece is deformed and expanded outward to the wall of the surrounding rock hole to apply prestress to the rock mass.

[0008] Furthermore, the expansion shell includes an integrally formed expansion shell connection part and two groups of expansion shell plates respectively arranged on both sides of the expansion shell connection part, each group of expansion shell plates is circumferentially arranged on the expansion shell connection part, and a first inner conical surface, an inner annular surface and a second inner conical surface are formed on the upper and lower sides of the inner side of the expansion shell, wherein the first inner conical surface and the second inner conical surface are respectively adapted to the shapes of the inner wedge and the conical top block of the expansion shell.

[0009] Furthermore, the inner wedge of the expansion shell is a conical nut structure, including a cone, a through hole with an internal thread is arranged in the cone, and the outer cone surface of the cone is in sliding contact with the first inner cone surface of the expansion shell.

[0010] Furthermore, the conical top block has a through hole therein and an annular supporting flange adapted to the top of the connecting sleeve is arranged above the through hole, and the outer conical surface of the conical top block is in sliding contact with the second inner conical surface of the expansion shell.

[0011] Furthermore, the expansion shell adopts a split structure, two groups of expansion shell sheets are nested in the same expansion shell connection part, or the same expansion shell connection part is integrally formed with one of the two groups of expansion shell sheets, or one group of expansion shell sheets is integrally formed with an expansion shell connection part and then nested.

[0012] Furthermore, the outer side of the expansion piece has continuously arranged serrations.

[0013] Furthermore, a pad and a driving nut are configured at the end of the anchor rod body, and the two ends of the anchor rod body are fixedly installed with the driving nut and the connecting sleeve respectively, and the driving nut is rotated to rotate the anchor rod body and extrude the conical top block through the connecting sleeve; preferably, the driving nut is configured as a blind nut.

[0014] Furthermore, an independent extrusion head is arranged on the top of the connecting sleeve.

[0015] Furthermore, the anchor rod body is configured as a hollow anchor rod, and a slurry outlet hole is provided on the connecting sleeve.

[0016] Furthermore, an anti-vibration box is arranged between the driving nut and the backing plate, and a pressure-releasing assembly is arranged at the end of the anchor rod body.

[0017] The present invention also provides a construction method based on the soft rock expansion shell anchor, comprising the following steps:

[0018] S1 drilling: drilling anchor holes in the rock mass through the drill bit;

[0019] S2 assembly installation: insert the pre-assembled expansion shell anchor assembly into the anchor hole, so that the pad is close to the rock wall of the anchor hole;

[0020] S3 anchoring: Rotate the drive nut, the anchor rod body rotates to drive the connecting sleeve and the screw to rotate, so that the conical top block moves into the anchor hole to apply preload, and the wedge inside the expansion shell moves to the outside of the anchor hole, thereby achieving close fixation of the expansion shell on the anchor hole and applying prestress to the rock formation.

[0021] The step S3 includes the following sub-steps:

[0022] S31 Initial stage: Rotate the anchor rod to drive the connecting sleeve to squeeze the conical top block inward, so that the conical top block applies pre-tightening force to the expansion shell, and the rotation of the screw rod causes the inner wedge of the expansion shell to slide into the expansion shell, which will push the expansion shell piece to deform outward and close to the surrounding rock hole wall, so that the ends of the outer group of expansion shell pieces are inserted into the surrounding rock hole wall in a barbed hook style, completing the expansion shell fixation;

[0023] S32 intermediate stage: continue to rotate the anchor rod. When the torque exceeds a certain value, the force of the connecting sleeve exceeds the strength limit of the supporting flange of the conical top block, and the supporting flange breaks to make room for the internal space.

[0024] S33 Ending stage: Continue to rotate the anchor rod, the screw will drive the upper end of the anchor rod body to move upward through the connecting sleeve, so that the anchor rod elastically stretches, and applies axial preload force to the inner wedge of the expansion shell, the conical top block and the expansion shell. At this time, the axial preload force is transmitted to the rock wall of the anchor hole through the anchor rod body, the driving nut and the pad, thereby effectively applying prestress to the surrounding rock.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention adopts a unique shell expansion structure with a shell expansion connection part. Compared with the ordinary shell expansion, the shell expansion structure has fewer parts, simpler design, easy to achieve standardized production, low cost, and convenient assembly.

[0027] 2. The serrated structure on the outside of the expansion shell of the present invention has good adhesion to the wall of the surrounding rock hole. In particular, the inner wedge of the expansion shell, the conical top block and the two groups of expansion shell sheets located above and below the expansion shell connection constitute an expansion structure that is close to the wall of the surrounding rock hole. In addition, the group of expansion shell sheets located below has a barb effect of embedding into the soft rock formation. Therefore, the stability of the structure can be maintained even after the expansion shell connection is broken, thereby achieving a good anchoring effect on the soft rock formation.

[0028] 3. The shell expansion connection part of the present invention can also break from the strip groove when the external force exceeds its strength limit, so that the shell expansion piece can expand outward more fully, thereby better adapting to soft rock formations and even different working conditions, and expanding the scope of application.

[0029] 4. The present invention does not need to cut the exposed part of the anchor rod, so the construction steps are simpler. At the same time, the blind hole nut structure is adopted by the driving nut, which is easy to realize continuous, mechanized and automatic operation, and can significantly improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A three-dimensional diagram of the anchoring portion of the soft rock expansion shell anchor rod of the present invention;

[0031] Figure 2 It is a cross-sectional view of the anchoring of the expansion shell anchor for soft rock of the present invention;

[0032] Figure 3 It is a cross-sectional view of the anchoring part when the extrusion head is provided for the expansion shell anchor for soft rock of the present invention;

[0033] Figure 4 This is the overall structure diagram of the expansion shell anchor for soft rock of the present invention;

[0034] Figure 5 This is a structural diagram of the expansion shell anchor for soft rock of the present invention being configured as a hollow anchor body;

[0035] Figure 6 A structural diagram of a seismic box provided for a soft rock expansion shell anchor of the present invention;

[0036] Figure 7 A structural diagram of a pressure-releasing assembly provided for a shell expansion anchor for soft rock according to the present invention;

[0037] Figure 8 A structural diagram of a shell expansion anchor for soft rock provided with an anti-seismic box and a pressure-releasing assembly according to the present invention;

[0038] Fig. 9 This is a construction status diagram of the expansion shell anchor for soft rock of the present invention;

[0039] Fig.10 The present invention is a flowchart of the construction of the expansion shell anchor for soft rock;

[0040] The markings and corresponding parts in the figure are: 1-shell expansion piece, 11-shell expansion connection part, 12-sawtooth, 13-second inner cone, 14-inner annular surface, 15-first inner cone, 2-conical top block, 21-support flange, 3-shell expansion inner wedge, 30-cone, 31-outer cone, 4-anchor rod, 40-slurry outlet hole, 41-connecting sleeve, 42-screw, 5-extrusion head, 6-anchor rod body, 7-shim, 8-drive nut, 80-anti-seismic box, 81-pressure-releasing assembly, 9-anchor hole. DETAILED DESCRIPTION

[0041] The present invention will be described in more detail below in conjunction with the accompanying drawings. It should be noted that the description of the present invention with reference to the accompanying drawings is only illustrative and not restrictive. The various embodiments can be combined with each other to form other embodiments not shown in the following description.

[0042] The expansion shell anchor for soft rock provided by the present invention has not only a simple structure and low production cost, but also good anchoring performance and is suitable for mechanical automation operation, thereby significantly improving construction efficiency.

[0043] The anchor head structure of the soft rock expansion shell anchor is as follows: Figure 1 and Figure 2As shown, it includes an expansion shell and an expansion shell inner wedge 3 and a conical top block 2 arranged at both ends of the expansion shell. The materials of each component are made of alloy steel, cast iron and other materials with certain strength. The expansion shell inner wedge 3 is movably embedded in the top of the expansion shell, and the conical top block 2 is movably embedded in the bottom of the expansion shell. The anchor rod 4 includes an anchor rod body 6, and one end of the anchor rod body 6 is fastened with a screw rod 42 through a connecting sleeve 41. The screw rod 42 is connected to the expansion shell inner wedge 3 through threaded transmission. The top of the connecting sleeve 41 is embedded in the conical top block 2 and presses the supporting flange 21 of the conical top block 2.

[0044] The expansion shell of the expansion shell anchor for soft rock includes an integrally formed expansion shell connection part 11 and expansion shell pieces 1, the expansion shell pieces 1 are in two groups and are respectively arranged on both sides of the expansion shell, the expansion shell pieces 1 of the same group are annularly and evenly arranged on the expansion shell connection part 11, each group of expansion shell pieces 1 has more than two pieces, each expansion shell piece 1 of the same group has the same shape, strip grooves are formed between adjacent expansion shell pieces 1, so that the expansion shell pieces 1 can gradually expand outward, and a first inner cone surface 15, an inner annular surface 14 and a second inner cone surface 13 are formed on the upper and lower sides of the inner side of the expansion shell, wherein the first inner cone surface 15 and the second inner cone surface 13 are respectively adapted to the shapes of the wedge 3 and the conical top block 2 of the expansion shell; in the present embodiment, the number of the expansion shell pieces 1 is four, which effectively increases the contact area with the surrounding rock hole wall, and the outer side of the expansion shell piece 1 has continuously arranged saw teeth 12, which effectively increases the friction with the surrounding rock hole wall, thereby improving the anchoring performance of the expansion shell;

[0045] The expansion shell inner wedge 3 of the expansion shell anchor for soft rock is a conical nut structure, which includes a cone 30, a through hole with an internal thread is arranged in the cone 30, and the outer cone surface 31 of the cone 30 is in sliding contact with the first inner cone surface 15 of the expansion shell. The conical top block 2 has a through hole and an annular support flange 21 adapted to the top of the connecting sleeve 41 is arranged above the through hole. The support flange 21 has the function of limiting the connecting sleeve 41 before breaking, and mainly plays the role of positioning the internal support clamping expansion shell after breaking. The outer cone surface 31 of the conical top block 2 is in sliding contact with the second inner cone surface 13 of the expansion shell.

[0046] Furthermore, the shell expansion connection part 11 can also break from the strip groove when the external force exceeds its strength limit, so that the shell expansion piece 1 can expand outward more fully, so as to better adapt to soft rock formations and even different working conditions, and expand the scope of application. It can be understood that: according to the application scenario and processing and manufacturing requirements, the shell expansion can also be designed as a variety of types of split structures, such as: 1) two groups of shell expansion pieces 1 are nested in the same shell expansion connection part 11; 2) the same shell expansion connection part 11 is integrally formed with one of the two groups of shell expansion pieces 1; 3) a group of shell expansion pieces 1 is integrally formed with an expansion shell connection part 11 and then nested.

[0047] like Figure 3 and Figure 4As shown, the top of the connecting sleeve 41 can be set as an independent extrusion head 5, the top of the extrusion head 5 is in active contact with the support flange 21 above the through hole of the conical top block 2 and has the advantages of easy standardized production and low cost. The other end of the anchor body 6 is provided with a pad 7 and a driving nut 8 to form a set of soft rock expansion anchor fixed in the anchor hole 9;

[0048] By rotating the driving nut 8, the anchor rod body 6 rotates to drive the connecting sleeve 41 and the screw rod 42 to rotate. The top of the connecting sleeve 41 or the extrusion head 5 applies a pressing force inward to the expansion shell by pressing the supporting flange 21 of the conical top block 2. The screw rod 42 drives the inner wedge 3 of the expansion shell to move inwardly of the expansion shell sheet 1 and applies a pressing force outward to the expansion shell. The expansion shell is deformed under the action of the forces at the upper and lower ends. The saw teeth 12 of the upper and lower groups of expansion shell sheets 1 are pressed outwardly against the surrounding rock hole wall. Continuing to rotate will cause the supporting flange 21 of the conical top block 2 to break due to exceeding the strength limit and clamp the conical top block 2 in the lower group of expansion shell sheets 1, so that the stability of the structure is maintained after the expansion shell is tightly pressed against the surrounding rock hole wall, thereby achieving a good prestressing action on the anchor hole 9 and a rock formation compression effect.

[0049] In this embodiment, the driving nut 8 is set as a blind nut, an external thread is set on the anchor rod body 6, and an internal thread is set on the connecting sleeve 41. The anchor rod body 6, the driving nut 8 and the connecting sleeve 41 are all fastened and installed to form an integrated structure. Under the drive of the blind nut, the inner wedge 3 of the expansion shell and the conical top block 2 and the anchor rod body 6 move in opposite directions, that is, the driving nut 8 is rotated, the inner wedge 3 of the expansion shell moves along the screw 42 into the expansion shell (outside the anchor hole 9), and the conical top block 2 and the anchor rod body 6 move into the anchor hole 9, ensuring that the anchor rod body 6 is not exposed;

[0050] Furthermore, if Figure 5 As shown, the anchor rod body 6 can be configured as a hollow anchor rod 4, and a grouting hole 40 is provided on the connecting sleeve 41 to facilitate grouting of the anchor rod 4, thereby enhancing the anchoring performance.

[0051] Furthermore, if Figure 6 As shown, an anti-seismic box 80 is provided between the driving nut 8 and the pad 7 to form a prestressed anti-seismic anchor rod, which is suitable for use in projects with anti-seismic requirements, such as earthquake areas, military projects, etc.;

[0052] Furthermore, if Figure 7 As shown, a yielding assembly 81 is provided at the end of the anchor rod body 6 to form a yielding anchor rod for soft rock that can be prestressed;

[0053] Furthermore, if Figure 8 As shown, an anti-seismic box 80 is arranged between the driving nut 8 and the pad 7 of the yield anchor rod, so that the yield anchor rod can be prestressed and anti-seismic, and the scope of application is further expanded.

[0054] Compared with the existing expansion shell anchor rods, the extremely soft rock expansion shell anchor rod provided by the present invention has fewer expansion shell structural components, simpler design, easy to achieve standardized production, low cost, and convenient assembly. The serration structure 12 on the outside of the expansion shell has good adhesion to the wall of the surrounding rock hole, especially the inner wedge 3 of the expansion shell, the conical top block 2 and the two groups of expansion shell pieces 1 located above and below the expansion shell connection part 11 constitute an expansion structure that is close to the wall of the surrounding rock hole, and the group of expansion shell pieces 1 located below has the effect of embedding in the soft rock formation, so that the stability of the structure can be maintained even after the expansion shell connection part 11 is broken, thereby achieving an excellent anchoring effect on the soft rock formation.

[0055] like Fig. 9 and Fig.10 As shown, the construction process of the present invention is divided into the following steps: 1) drilling: drilling an anchor hole 9 on the rock mass by a drill bit; 2) assembly installation: inserting the pre-assembled shell anchor assembly into the anchor hole 9, so that the pad 7 is close to the rock wall of the anchor hole 9; 3) anchoring: rotating the drive nut 8, the anchor body 6 rotates to drive the connecting sleeve 41 and the screw 42 to rotate, so that the conical top block 2 moves into the anchor hole 9 to apply a pre-tightening force, and the shell inner wedge 3 moves to the outside of the anchor hole 9, thereby realizing the close fixation of the shell on the anchor hole 9 and applying prestress to the rock formation; the anchoring step can be specifically divided into the following sub-steps:

[0056] a) Initial stage: the anchor rod 4 is rotated to drive the connecting sleeve 41 or the extrusion head 5 to squeeze the conical top block 2 inward, so that the conical top block 2 applies a pre-tightening force to the expansion shell, and the screw rod 42 rotates to make the inner wedge 3 of the expansion shell slide into the expansion shell, which will push the expansion shell piece 1 to deform outward and close to the surrounding rock hole wall, so that the ends of the outer group of expansion shell pieces 1 are inserted into the surrounding rock hole wall in a barbed manner, and the expansion shell is fixed;

[0057] b) Intermediate stage: Continue to rotate the anchor rod 4. When the torque exceeds a certain value, the force of the connecting sleeve 41 or the extrusion head 5 exceeds the strength limit of the support flange 21 of the conical top block 2, and the support flange 21 breaks to make room for the internal space.

[0058] c) Ending stage: Continue to rotate the anchor rod 4, the screw rod 42 will drive the upper end of the anchor rod body 6 to move upward through the connecting sleeve 41, so that the anchor rod 4 elastically stretches, and applies axial preload force to the wedge 3 inside the expansion shell, the conical top block 2 and the expansion shell. At this time, the axial preload force is transmitted to the rock wall of the anchor hole 9 through the anchor rod body 6, the driving nut 8 and the pad 7, and the inside of the expansion shell is supported by the wedge 3 inside the expansion shell, the conical top block 2 and the screw rod 42, and the outside of the expansion shell is clamped on the wall of the surrounding rock hole through the sawtooth 12 structure, so that the expansion shell anchor rod can effectively apply prestress to the surrounding rock to form a soft rock compression zone.

[0059] In the existing construction methods of expansion bolts, such as patents with application numbers CN201910265475.6 and CN201510711711.4, the bolt body needs to move outside the anchor hole during construction, resulting in the outer end of the bolt extending outward from the rock mass outside the anchor hole after the operation is completed. Based on factors such as safety and process requirements, the excess bolt body at the exposed end needs to be cut off. Currently, this cutting step relies on manual operation, which not only increases the number of operation steps and reduces construction efficiency, but also causes problems such as increased engineering costs and material waste.

[0060] With the construction method of the expansion shell anchor for soft rock provided by the present invention, the expansion shell is expanded to the rock wall by driving the inner wedge 3 of the expansion shell and the conical top block 2 to move toward each other along the screw of the anchor body 6. During the construction process, the anchor body 6 always stays in the anchor hole 9. Therefore, the construction method does not require a cutting step, the construction steps are simple, and it is easy to realize mechanical automation operation, thereby greatly improving work efficiency.

[0061] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. An expansion shell anchor for soft rock, comprising an expansion shell and an anchor, characterized in that: The two ends of the expansion shell are respectively provided with an expansion shell inner wedge and a conical top block, the expansion shell inner wedge and the top of the expansion shell, the conical top block and the bottom of the expansion shell all form sliding contact, the conical top block has a through hole and an annular support flange is arranged above the through hole; the anchor rod comprises an anchor rod body, one end of the anchor rod body is fixedly mounted with a screw rod through a connecting sleeve, the screw rod and the expansion shell inner wedge are connected by threaded transmission, an independent extrusion head is arranged on the top of the connecting sleeve, the anchor rod body is arranged as a hollow anchor rod, and a slurry outlet hole is arranged on the connecting sleeve, the top of the connecting sleeve is embedded in the through hole of the conical top block and presses the support flange tightly; the anchor rod is rotated to drive the expansion shell inner wedge and the conical top block to move into the expansion shell until the support flange of the conical top block breaks, so that the expansion shell piece is deformed and expanded outward to the wall of the surrounding rock hole to apply prestress to the rock mass.

2. The soft rock expansion anchor as claimed in claim 1, characterized in that: The expansion shell includes an integrally formed expansion shell connection part and two groups of expansion shell plates respectively arranged on both sides of the expansion shell connection part, each group of expansion shell plates is circumferentially arranged on the expansion shell connection part, and a first inner conical surface, an inner annular surface and a second inner conical surface are formed on the upper and lower sides of the inner side of the expansion shell, wherein the first inner conical surface and the second inner conical surface are respectively adapted to the shapes of the inner wedge and the conical top block of the expansion shell.

3. The soft rock expansion anchor as claimed in claim 2, characterized in that: The conical top block has a through hole in it and an annular supporting flange adapted to the top of the connecting sleeve is arranged above the through hole. The outer conical surface of the conical top block is in sliding contact with the second inner conical surface of the expansion shell.

4. The expansion anchor for soft rock according to claim 2 or 3, characterized in that: The inner wedge of the expansion shell is a conical nut structure, including a cone, a through hole with an internal thread is arranged in the cone, and the outer cone surface of the cone is in sliding contact with the first inner cone surface of the expansion shell.

5. The soft rock expansion anchor as claimed in claim 1, characterized in that: The expansion shell adopts a split structure, two groups of expansion shell sheets are nested in the same expansion shell connection part, or the same expansion shell connection part is integrally formed with one of the two groups of expansion shell sheets, or one group of expansion shell sheets is integrally formed with an expansion shell connection part and then nested.

6. The soft rock expansion anchor as claimed in claim 1, 2 or 5, characterized in that: The outer side of the shell expansion sheet is provided with continuously arranged saw teeth.

7. The soft rock expansion anchor as claimed in claim 6, characterized in that: The end of the anchor rod body is provided with a pad and a driving nut, and the two ends of the anchor rod body are respectively fixedly installed with the driving nut and the connecting sleeve, and the driving nut is rotated to rotate the anchor rod body and extrude the conical top block through the connecting sleeve.

8. The soft rock expansion anchor as claimed in claim 7, characterized in that: An anti-vibration box is arranged between the driving nut and the backing plate, and a pressure-releasing assembly is arranged at the end of the anchor rod body.

9. A construction method for a soft rock expansion shell anchor, applicable to the soft rock expansion shell anchor according to any one of claims 1 to 8, characterized in that: The steps include: S1 drilling: drilling anchor holes in the rock mass through the drill bit; S2 assembly installation: insert the pre-assembled expansion anchor into the anchor hole, so that the pad is close to the rock wall at the anchor hole mouth; S3 anchoring: Rotate the drive nut, the anchor rod body rotates to drive the connecting sleeve and the screw to rotate, so that the conical top block moves into the anchor hole to apply preload, and the wedge inside the expansion shell moves to the outside of the anchor hole, thereby achieving close fixation of the expansion shell on the anchor hole and applying prestress to the rock formation.

10. The construction method of the soft rock expansion anchor as claimed in claim 9, characterized in that: The step S3 includes the following sub-steps: S31 Initial stage: Rotate the anchor rod to drive the connecting sleeve to squeeze the conical top block inward, so that the conical top block applies pre-tightening force to the expansion shell, and the rotation of the screw rod causes the inner wedge of the expansion shell to slide into the expansion shell, which will push the expansion shell piece to deform outward and close to the surrounding rock hole wall, so that the ends of the outer group of expansion shell pieces are inserted into the surrounding rock hole wall in a barbed hook style, completing the expansion shell fixation; S32 intermediate stage: continue to rotate the anchor rod. When the torque exceeds a certain value, the force of the connecting sleeve exceeds the strength limit of the supporting flange of the conical top block, and the supporting flange breaks to make room for the internal space. S33 Ending stage: Continue to rotate the anchor rod, the screw will drive the upper end of the anchor rod body to move upward through the connecting sleeve, so that the anchor rod elastically stretches, and applies axial preload force to the inner wedge of the expansion shell, the conical top block and the expansion shell. At this time, the axial preload force is transmitted to the rock wall of the anchor hole through the anchor rod body, the driving nut and the pad, thereby effectively applying prestress to the surrounding rock.

Images