CN111945726A - Construction method of strong unloading broken rock mass prestressed anchor cable - Google Patents
Construction method of strong unloading broken rock mass prestressed anchor cable Download PDFInfo
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- CN111945726A CN111945726A CN202010849965.3A CN202010849965A CN111945726A CN 111945726 A CN111945726 A CN 111945726A CN 202010849965 A CN202010849965 A CN 202010849965A CN 111945726 A CN111945726 A CN 111945726A
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- 239000011435 rock Substances 0.000 title claims abstract description 40
- 238000010276 construction Methods 0.000 title claims abstract description 38
- 238000004873 anchoring Methods 0.000 claims abstract description 89
- 239000002002 slurry Substances 0.000 claims abstract description 39
- 238000005553 drilling Methods 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 8
- 238000007789 sealing Methods 0.000 claims abstract description 6
- 238000004519 manufacturing process Methods 0.000 claims abstract description 4
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 102
- 239000010959 steel Substances 0.000 claims description 102
- 239000011440 grout Substances 0.000 claims description 50
- 239000004570 mortar (masonry) Substances 0.000 claims description 21
- 239000004746 geotextile Substances 0.000 claims description 11
- 239000007788 liquid Substances 0.000 claims description 11
- 239000004568 cement Substances 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000003795 chemical substances by application Substances 0.000 claims description 8
- 229920000742 Cotton Polymers 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 5
- 206010057175 Mass conditions Diseases 0.000 claims description 4
- 239000002390 adhesive tape Substances 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 claims description 3
- 238000009792 diffusion process Methods 0.000 claims description 3
- 230000002093 peripheral effect Effects 0.000 claims description 3
- 238000009941 weaving Methods 0.000 claims description 3
- 238000004062 sedimentation Methods 0.000 claims description 2
- 238000002955 isolation Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 3
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 1
- 238000009412 basement excavation Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/74—Means for anchoring structural elements or bulkheads
- E02D5/76—Anchorings for bulkheads or sections thereof in as much as specially adapted therefor
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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- Civil Engineering (AREA)
- Piles And Underground Anchors (AREA)
Abstract
The invention discloses a construction method of a strong unloading broken rock mass prestressed anchor cable, and belongs to the technical field of rock mass reinforcing prestressed anchor cable construction. The method comprises the following steps: drilling anchor cable holes, manufacturing and installing anchor cable bodies, grouting, constructing anchor piers, locking the anchor cable bodies, and performing grouting and anchor sealing. The anchor cable holes are formed by pipe following hole forming, wall fixing hole forming and grouting according to needs, so that the problems that hole walls are easy to collapse, air leakage of the holes is caused, and grouting loss is serious in the hole forming process under the geological condition of a strong unloading broken rock body are solved, and grouting quality and anchor cable prestress are guaranteed. In the processes of wall-fixing hole forming and grouting according to needs, the hole wall of the anchor cable hole is pre-grouted, so that slurry leakage during grouting of the tensioning section and the anchoring section is avoided, and the grouting quality of the anchoring section and the prestress of the anchor cable are ensured.
Description
Technical Field
The invention relates to a construction method of a strong unloading broken rock mass prestressed anchor cable, and belongs to the technical field of rock mass reinforcing prestressed anchor cable construction.
Background
The strong unloading broken rock mass is a geological condition frequently encountered in water conservancy, highway and railway engineering, and is characterized by mainly comprising the following aspects: firstly, the cracks are developed and broken and loosened, and the hole wall is easy to collapse and drill sticking is easy to occur during hole forming; hardness, compared with the common loose and cracked stratum, the hardness of the rock is higher, and the abrasion of the drilling tool is larger; leakage, deep unloading degree of the side slope, wide crack development, communication, serious pore-forming air leakage and grouting loss; and fourthly, dividing the stratum into a plurality of fault layers, and obviously showing the alternate soft and hard stratum. For the highway and railway engineering, the influence of the tunnel on the engineering construction can be reduced through the tunnel. However, in water conservancy projects, in order to ensure the safety of important permanent buildings such as dams, plants, water inlets and water outlets, slope excavation needs to be carried out, high slopes with the length of more than one hundred meters are often formed, and anchor cables need to be constructed to improve the safety and stability of the slopes.
Chinese patent publication No. CN206438517U discloses a cohesive type prestressed anchor cable suitable for strong unloading developing side slope, which includes an inner anchoring section and a tensioning section, wherein the front end of the inner anchoring section is provided with a guide cap, the tail end of the tensioning section is embedded in a concrete anchor pier, the outer side of the tensioning section is provided with a protective cap, a grout stopping bag is arranged at the boundary between the inner anchoring section and the tensioning section, a corrugated pipe is arranged in the tensioning section, and the inner end of the corrugated pipe is provided with a grout stopping ring. The corrugated pipe is arranged at the stretching section of the bonding type prestressed anchor cable, and the grout stopping ring is arranged at the inner end of the corrugated pipe, so that the steel strand of the anchor cable at the stretching section can be wrapped by cement slurry, and the durability of the anchor cable can be ensured. However, under the geological condition of strong unloading broken rock mass, the hole-forming has the problems that the hole wall is easy to collapse, and the air leakage and grouting loss of the hole-forming are serious, so that the grouting quality and the prestress effect of the anchor cable are difficult to ensure.
Chinese patent publication No. CN103147440A discloses a prestressed anchor cable construction method, which comprises performing low-pressure grouting into the anchor cable hole of the tension section, so that the tension section after grouting becomes a grout-stopping ring for grouting of the inner anchoring section, and the grout-stopping effect can be ensured under any rock mass condition, thereby ensuring the quality of the whole anchor cable. However, when grouting is performed on the tension section, mortar may enter the anchoring section along a rock gap to form slurry string, so that grouting quality of the later anchoring section and prestress of the anchor cable are difficult to guarantee.
Disclosure of Invention
In order to solve the technical problems, the invention provides a construction method of a strong unloading broken rock mass pre-stressed anchor cable.
The invention is realized by the following technical scheme:
a construction method of a strong unloading broken rock mass prestressed anchor cable comprises the following steps:
A. drilling anchor cable holes: after the drilling machine is in place, forming holes by following the pipe, fixing the wall, forming holes and grouting according to needs to form anchor cable holes;
B. manufacturing and installing an anchor cable body: weaving an anchor cable body, directly placing the anchor cable body at the center of the anchor cable hole, and installing a steel pipe assembly at the orifice of the anchor cable hole;
C. grouting: grouting the anchoring section and the tensioning section in sequence, and fixing the steel pipe assembly through mortar;
D. and (3) anchor pier construction: constructing an anchor pier at the orifice position of the anchor cable hole, determining the size of the anchor pier, the internal reinforcing bars of the anchor pier and the type and number of the anchor rods according to the bearing capacity of the anchor pier foundation, ensuring that the anchor pier does not generate settlement deformation when the anchor cable is tensioned, and positioning one end of the steel pipe assembly, which is far away from the anchor cable hole, at the inner side of the anchor pier;
E. locking the anchor cable body: installing an anchor cable body accessory, tensioning the steel strand and unloading and locking the anchor cable body;
F. grouting and sealing the anchor: and (4) filling the pure cement slurry with the same label as that of the anchoring section into the anchor cable hole orifice through the steel pipe assembly, wherein the grouting needs to be compact.
The construction method for forming the hole with the pipe in the step A is to adopt a hole forming mode of an eccentric drill bit and the pipe, the final hole depth of the pipe is determined according to the rock mass condition after the pipe following depth exceeds 20m, and the fault is penetrated when encountering the fault and the drilling is finished to a harder rock mass; the pipe following is performed in a segmented mode, the length of a single pipe following is 1.5-3 m, and the pipe following is pulled out in a segmented mode after drilling is finished.
And B, determining the circulating depth of the straight drill bit according to the collapse condition of the hole wall, controlling the circulating depth to be within the range of 2-5 m, pulling out the straight drill bit after completing one-time drilling, mounting grout stop plugs at the hole bottom and the hole opening of the hole formed by the straight drill bit, mounting a grouting pipe, injecting mortar with low fluidity, adding an early strength agent into the mortar, adding a certain amount of an accelerating agent into the mortar if the grouting amount is large, cleaning the hole by using the drill bit after the mortar reaches a certain strength, and performing the next circulation until the hole wall does not collapse until the designed depth of the anchor cable hole is reached.
B, performing in-hole camera shooting on the anchoring section, if a wider crack is opened on the hole wall, installing a grout stop plug at the boundary of the anchoring section and the tensioning section, then installing a grouting pipe, installing a pressure gauge at the inlet of the grouting pipe, pouring cement paste, wherein the grouting pressure reaches 0.1-0.3MPa, the grout consumption is obviously reduced, and grouting can be finished; drilling a hole in the anchoring section by using a drill bit after the slurry reaches the designed strength; the grout stop plug is a water pressure plug, is tightly contacted with the hole wall after being filled with water, and can be pulled out after pressure relief.
The anchor cable body in the step B comprises a tensioning section, an anchoring section and a grout stopping bag arranged at the boundary of the tensioning section and the anchoring section, wherein the anchoring section is made into a corrugated shape through zinc-lead-free tows alternately arranged on the steel strand at intervals and an isolation frame, and the tensioning section is made into a straight shape through the isolation frame arranged on the steel strand at intervals; each steel strand of the tensioning section is sleeved with a PE sleeve, and one end of the PE sleeve, which is close to the anchoring section, is wound and wrapped by a waterproof adhesive tape; an anchoring section grouting pipe, an anchoring section exhaust slurry return pipe and a tensioning section grouting pipe are laid along the axial direction of an anchor cable hole, one end of the anchoring section grouting pipe penetrates through a slurry stopping bag and extends to the anchoring section, the other end of the anchoring section grouting pipe penetrates through the tensioning section and a steel pipe assembly and extends out of an anchor pier, one end of the anchoring section exhaust slurry return pipe penetrates through the slurry stopping bag and extends to the anchoring section, the other end of the anchoring section exhaust slurry return pipe extends to an anchor cable hole orifice, one end of the tensioning section grouting pipe is located in the tensioning section, and the other end of the tensioning section grouting pipe.
The outer wall of the grouting pipe of the anchoring section is provided with flower holes with the interval of 1m within the range of the anchoring section, and the outer wall of the grouting pipe of the anchoring section is provided with a plurality of grouting ports at the positions corresponding to the grout stopping bags; the middle part of the grouting pipe of the tension section is provided with flower holes with the spacing of 2 m; the steel strand, the anchoring section grouting pipe and the anchoring section exhaust slurry return pipe are tightly wound with cotton wool at the positions corresponding to the slurry stopping bags, and are wrapped with geotextile and tightly bound.
The steel pipe assembly in the step B comprises a steel sleeve, a steel pipe A and a steel pipe B, the steel sleeve is coaxially arranged at the orifice of the anchor cable hole, the steel pipe A and the steel pipe B are arranged on the outer wall of the steel sleeve and communicated with the steel sleeve, and one end, far away from the steel sleeve, of the steel pipe A and the steel pipe B penetrates through the anchor pier.
C, grouting the tensioning section, wherein the grouting liquid is mortar, geotextile wraps the anchor cable of the tensioning section to reduce the diffusion of the grouting liquid to the peripheral rock wall, a grouting pipe of the tensioning section is provided with a flower hole to facilitate the grouting liquid to fill the whole tensioning section, and orifice reverse grouting is adopted as the standard after grouting; and D, before the anchor pier is constructed in the step D, peeling and deoiling one end of the steel strand close to the anchor pier.
And E, the anchor cable body accessory comprises a bearing plate, a working anchor plate and an anchor head protection cover, the bearing plate is arranged on the steel pipe assembly, one side of the bearing plate is provided with a grabbing rib, the grabbing rib is positioned in the anchor pier, the working anchor plate is arranged on the bearing plate through an anchor backing plate, the anchor head protection cover is arranged on the bearing plate, one ends of the working anchor plate, the anchor backing plate and the steel strand, which are exposed out of the anchor cable hole, are all positioned in the anchor head protection cover, and the anchor head protection cover is filled with concrete.
Before the steel strand is tensioned in the step E, a fixed sample frame is arranged on the periphery of the anchor pier to serve as a reference point, and after each stage of tensioning, the settlement value and the tension force value of the anchor cable are observed to check whether the anchor cable has an unloading condition; when the steel strand is tensioned, the steel strand is centered, checked, pre-tightened, compensated and tensioned, then the whole tensioning is carried out, the loading is carried out step by step until the loading reaches the maximum design load, and the unloading locking is carried out.
The invention has the beneficial effects that:
1. the anchor cable holes are formed by pipe following hole forming, wall fixing hole forming and grouting according to needs, so that the problems that hole walls are easy to collapse, air leakage of the holes is caused, and grouting loss is serious in the hole forming process under the geological condition of a strong unloading broken rock body are solved, and grouting quality and anchor cable prestress are guaranteed.
2. In the processes of wall-fixing hole forming and grouting according to needs, the hole wall of the anchor cable hole is pre-grouted, so that slurry leakage during grouting of the tensioning section and the anchoring section is avoided, and the grouting quality of the anchoring section and the prestress of the anchor cable are ensured.
3. The steel strand, the anchoring section grouting pipe and the anchoring section exhaust slurry return pipe are wrapped tightly by cotton wool, geotextile, and bound tightly, so that the slurry-stopping bag is ensured not to leak slurry and can bear pressure; when the anchoring section is grouted, grout can flow out of a grouting opening in the grouting pipe of the anchoring section and fill the grout stopping bag, the grout stopping bag can be in close contact with the rock wall after being filled with the grout, the grout is sealed in the anchoring section, and the purpose of pressure grouting of the anchoring section is achieved.
4. The size of the anchor pier and the reinforcing steel bars are adjusted according to the bearing capacity of the anchor pier foundation, so that the anchor cable is ensured not to have large settlement deformation during tensioning. A plurality of anchor cables in initial construction are subjected to tension manufacturability tests, fixed sample frames are arranged on the periphery of anchor piers to serve as reference points, after each level of tension, settlement values and tension force values of the anchor cables are observed, whether the anchor cables are in an unloading state or not is checked, and the construction quality of the anchor cables is ensured.
5. The anchor cable of the tensioning section wraps the geotextile, so that the cement consumption in grouting of the tensioning section can be reduced, and the construction cost is reduced.
6. The steel strand wires at the orifice section are peeled and deoiled before the anchor pier construction, and after the anchor cable is tensioned and held, the orifice section is sealed and grouted, so that the orifice sealing grout can be enabled to be stressed with the clamping piece in a coordinated manner, and the durability of the anchoring force is improved.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic cross-sectional view taken along A-A of FIG. 1;
FIG. 3 is a construction flow chart of the present invention.
In the figure: 1-guide cap, 2-steel strand, 3-anchoring section grouting pipe, 4-zinc-lead-free strand, 5-isolation frame, 6-anchoring section exhaust and slurry return pipe, 7-lead wire, 8-grout stopping bag, 9-tensioning section grouting pipe, 10-steel sleeve, 11-anchor pier, 12-steel pipe A, 13-grab bar, 14-bearing plate, 15-anchor backing plate, 16-working anchor plate, 17-anchor head protecting cover and 18-steel pipe B.
Detailed Description
The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described.
As shown in figures 1 to 3, the construction method of the strong unloading fractured rock mass prestressed anchor cable comprises the following steps:
A. drilling anchor cable holes: after the drilling machine is in place, hole forming is carried out by following the pipe, hole forming is carried out by wall fixing, and anchor cable holes are formed by grouting according to requirements.
B. Manufacturing and installing an anchor cable body: and weaving an anchor cable body, placing the anchor cable body in the center of the anchor cable hole straightly, and installing a steel pipe assembly at the orifice of the anchor cable hole. The anchor cable body is provided with a guide cap 1 at one end extending into the anchor cable hole.
C. Grouting: and grouting the anchoring section and the tensioning section in sequence, and fixing the steel pipe assembly through mortar.
D. And (3) anchor pier construction: and constructing an anchor pier 11 at the orifice position of the anchor cable hole, determining the size of the anchor pier 11, the internal reinforcement of the anchor pier 11 and the type and number of the anchor rods according to the foundation bearing capacity of the anchor pier, ensuring that the anchor pier 11 does not generate sedimentation deformation when the anchor cable is tensioned, and positioning one end of the steel pipe assembly, which is far away from the anchor cable hole, at the inner side of the anchor pier 11. The bearing capacity of the bedrock is improved through the anchor piers 11.
E. Locking the anchor cable body: installing an anchor cable body accessory, tensioning the steel strand 2 and unloading and locking the anchor cable body;
F. grouting and sealing the anchor: and (4) filling the pure cement slurry with the same label as that of the anchoring section into the anchor cable hole orifice through the steel pipe assembly, wherein the grouting needs to be compact. During the grouting, the steel pipe A12 is used as a grouting pipe, and the steel pipe B18 is used as an exhaust and slurry return pipe.
The construction method for forming the hole with the pipe in the step A is to adopt a hole forming mode of an eccentric drill bit and the pipe, the final hole depth of the pipe is determined according to the rock mass condition after the pipe following depth exceeds 20m, and the fault is penetrated when encountering the fault and the drilling is finished to a harder rock mass; the pipe following is performed in a segmented mode, the length of a single pipe following is 1.5-3 m, and the pipe following is pulled out in a segmented mode after drilling is finished.
And B, determining the circulating depth of the straight drill bit according to the collapse condition of the hole wall, controlling the circulating depth to be within the range of 2-5 m, pulling out the straight drill bit after completing one-time drilling, mounting grout stop plugs at the hole bottom and the hole opening of the hole formed by the straight drill bit, mounting a grouting pipe, injecting mortar with low fluidity, adding an early strength agent into the mortar, adding a certain amount of an accelerating agent into the mortar if the grouting amount is large, cleaning the hole by using the drill bit after the mortar reaches a certain strength, and performing the next circulation until the hole wall does not collapse until the designed depth of the anchor cable hole is reached. The mortar is doped with an early strength agent to shorten the time to be strengthened, and is doped with an accelerating agent to reduce the mortar consumption.
B, performing in-hole camera shooting on the anchoring section, if a wider crack is opened on the hole wall, installing a grout stop plug at the boundary of the anchoring section and the tensioning section, then installing a grouting pipe, installing a pressure gauge at the inlet of the grouting pipe, pouring cement paste, wherein the grouting pressure reaches 0.1-0.3MPa, the grout consumption is obviously reduced, and grouting can be finished; drilling a hole in the anchoring section by using a drill bit after the slurry reaches the designed strength; the grout stop plug is a water pressure plug, is tightly contacted with the hole wall after being filled with water, and can be pulled out after pressure relief.
The anchor cable body in the step B comprises a tensioning section, an anchoring section and a grout stopping bag 8 arranged at the boundary of the tensioning section and the anchoring section, wherein the anchoring section is made into a corrugated shape through zinc-lead-free tows 4 and isolation frames 5 which are alternately arranged on the steel strand 2 at intervals, and the tensioning section is made into a straight line shape through the isolation frames 5 which are alternately arranged on the steel strand 2; each steel strand 2 of the tensioning section is sleeved with a PE sleeve, and one end of the PE sleeve, which is close to the anchoring section, is wound and wrapped by a waterproof adhesive tape; lay anchor section grout pipe 3, anchor section exhaust slurry return pipe 6 and stretch-draw section grout pipe 9 along anchor rope hole axial, the one end of anchor section grout pipe 3 passes only thick liquid package 8 and extends to the anchor section, the other end passes stretch-draw section, the steel pipe assembly extends outside anchor pier 11, the one end of anchor section exhaust slurry return pipe 6 passes only thick liquid package 8 and extends to the anchor section, the other end extends to anchor rope hole drill way, the one end of stretch-draw section grout pipe 9 is located the stretch-draw section, the other end extends to anchor rope hole drill way. When in use, the two ends of the grout stopping bag 8 are firmly bound by the lead wires 7. One end of the PE sleeve, which is close to the anchoring section, is wound and wrapped by a waterproof adhesive tape, so that cement paste is prevented from entering the PE sleeve when the anchoring section is grouted. One end of the grouting pipe 3 of the anchoring section is about 30cm away from the bottom of the anchor cable hole, and the other end of the grouting pipe penetrates through the steel pipe A12. The distance between the pipe orifice of the anchoring section on the anchoring section exhaust pulp return pipe 6 and the pulp stopping bag 8 is not more than 50 cm.
The outer wall of the anchoring section grouting pipe 3 is provided with flower holes with the interval of 1m in the range of the anchoring section, and the outer wall of the anchoring section grouting pipe 3 is provided with a plurality of grouting ports at the positions corresponding to the grout stopping bags 8; the middle part of the grouting pipe 9 of the tension section is provided with flower holes with the spacing of 2 m; the steel strand 2, the anchoring section grouting pipe 3 and the anchoring section exhaust slurry return pipe 6 are tightly wound with cotton wool at the positions corresponding to the slurry stopping bags 8, and are wrapped with geotextile and tightly bound. When the anchor section grouting pipe is used, flower holes are formed in the outer walls of the anchoring section grouting pipe 3 and the tensioning section grouting pipe 9, and therefore slurry can be conveniently diffused. The steel strand 2, the anchoring section grouting pipe 3 and the anchoring section exhaust slurry return pipe 6 are tightly wound with cotton wool at the positions corresponding to the slurry stopping bags 8, and are wrapped with geotextile and tightly bound, so that the slurry stopping bags 8 are ensured not to leak slurry and can bear pressure. Two grouting openings are formed in the position, corresponding to the grout stopping bag 8, of the outer wall of the grouting pipe 3 of the anchoring section, grout can flow out of the two grouting openings when grouting of the anchoring section is conducted, the grout stopping bag 8 is filled, the grout stopping bag 8 can be in close contact with a rock wall after being filled with the grout, the grout is sealed in the anchoring section, and the purpose of pressure grouting of the anchoring section is achieved. The grouting pressure of the anchoring section is 0.3MPa-0.5MPa, and the grouting is closed at the pressure of 0.5MPa after the grouting is returned by the anchoring section exhaust grout return pipe 6, and the grouting closing time is 30 min.
The steel pipe assembly in the step B comprises a steel sleeve 10, a steel pipe A12 and a steel pipe B18, the steel sleeve 10 is coaxially arranged at the orifice of the anchor cable hole, the steel pipe A12 and the steel pipe B18 are arranged on the outer wall of the steel sleeve 10 and are communicated with the steel sleeve 10, and one ends, far away from the steel sleeve 10, of the steel pipe A12 and one end, far away from the steel sleeve 10, of the steel pipe B18 penetrate through the anchor pier 11. The steel sleeve 10 is exposed out of the bedrock for a sufficient length so as to facilitate the construction of the anchor pier 11, the installation of the bearing plate 14 and the tensioning of the anchor cable.
C, grouting the tensioning section, wherein the grouting liquid is mortar, geotextile wraps the anchor cable of the tensioning section to reduce the diffusion of the grouting liquid to the peripheral rock wall, a grouting pipe of the tensioning section is provided with a flower hole to facilitate the grouting liquid to fill the whole tensioning section, and orifice reverse grouting is adopted as the standard after grouting; and D, before the anchor pier 11 is constructed in the step D, peeling and deoiling one end of the steel strand 2 close to the anchor pier 11. After the sealed slurry reaches a certain strength, the steel strand 2 can be better held and wrapped, and the steel strand, the clamping piece and the working anchor plate 16 are stressed cooperatively, so that the durability of the anchoring force is improved.
And E, the anchor cable body accessory comprises a bearing plate 14, a working anchor plate 16 and an anchor head protection cover 17, the bearing plate 14 is arranged on the steel pipe assembly, one side of the bearing plate 14 is provided with a grabbing rib 13, the grabbing rib 13 is positioned in the anchor pier 11, the working anchor plate 16 is arranged on the bearing plate 14 through an anchor backing plate 15, the anchor head protection cover 17 is arranged on the bearing plate 14, one ends of the working anchor plate 16, the anchor backing plate 15 and the steel strand 2, which are exposed out of the anchor cable hole, are all positioned in the anchor head protection cover 17, and the anchor head protection cover 17 is filled with concrete. In use, the bearing plate 14 is welded to the end of the steel casing 10 remote from the anchor cable bore.
Before the steel strand 2 is tensioned in the step E, a fixed sample frame is arranged on the periphery of the anchor pier 11 to serve as a reference point, after each stage of tensioning, the settlement value and the tension force value of the anchor cable are observed, whether the anchor cable has an unloading condition or not is checked, and a tensioning manufacturability test is carried out on a plurality of initially constructed anchor cables; when the steel strand 2 is tensioned, the steel strand 2 is centered, checked, pre-tightened, compensated and tensioned, then the whole tensioning is carried out, the loading is carried out step by step until the loading reaches the maximum design load, and the unloading locking is carried out.
Compared with the prior art, the construction method of the strong unloading broken rock mass prestressed anchor cable provided by the invention has the following beneficial effects:
1. the anchor cable holes are formed by pipe following hole forming, wall fixing hole forming and grouting according to needs, so that the problems that hole walls are easy to collapse, air leakage of the holes is caused, and grouting loss is serious in the hole forming process under the geological condition of a strong unloading broken rock body are solved, and grouting quality and anchor cable prestress are guaranteed.
2. In the processes of wall-fixing hole forming and grouting according to needs, the hole wall of the anchor cable hole is pre-grouted, so that slurry leakage during grouting of the tensioning section and the anchoring section is avoided, and the grouting quality of the anchoring section and the prestress of the anchor cable are ensured.
3. The steel strand 2, the anchoring section grouting pipe 3 and the anchoring section exhaust slurry return pipe 6 are wrapped by cotton wool tightly and geotextile, and are bound tightly, so that the slurry stop bag 8 is ensured not to leak slurry and can bear pressure; when the anchor section is grouted, grout can flow out of a grouting opening in the grouting pipe 3 of the anchor section and fill the grout stopping bag 8, the grout stopping bag 8 can be in close contact with a rock wall after being filled with the grout, the grout is sealed in the anchor section, and the purpose of pressure grouting of the anchor section is achieved.
4. The size of the anchor pier and the reinforcing steel bars are adjusted according to the bearing capacity of the anchor pier foundation, so that the anchor cable is ensured not to have large settlement deformation during tensioning. A plurality of anchor cables in initial construction are subjected to tension manufacturability tests, fixed sample frames are arranged on the periphery of an anchor pier 11 and serve as reference points, after each level of tension, settlement values and tension force values of the anchor cables are observed, whether the anchor cables are in an unloading state or not is checked, and the construction quality of the anchor cables is ensured.
5. The anchor cable of the tensioning section wraps the geotextile, so that the cement consumption in grouting of the tensioning section can be reduced, and the construction cost is reduced.
6. The steel strand wires at the orifice section are peeled and deoiled before the anchor pier construction, and after the anchor cable is tensioned and held, the orifice section is sealed and grouted, so that the orifice sealing grout can be enabled to be stressed with the clamping piece in a coordinated manner, and the durability of the anchoring force is improved.
Claims (10)
1. A construction method of a strong unloading broken rock mass prestressed anchor cable is characterized by comprising the following steps: the method comprises the following steps:
A. drilling anchor cable holes: after the drilling machine is in place, forming holes by following the pipe, fixing the wall, forming holes and grouting according to needs to form anchor cable holes;
B. manufacturing and installing an anchor cable body: weaving an anchor cable body, directly placing the anchor cable body at the center of the anchor cable hole, and installing a steel pipe assembly at the orifice of the anchor cable hole;
C. grouting: grouting the anchoring section and the tensioning section in sequence, and fixing the steel pipe assembly through mortar;
D. and (3) anchor pier construction: constructing an anchor pier (11) at the orifice position of the anchor cable hole, determining the size of the anchor pier (11) and the type and the number of reinforcing bars and anchor rods in the anchor pier (11) according to the foundation bearing capacity of the anchor pier to ensure that the anchor pier (11) does not generate sedimentation deformation when the anchor cable is tensioned, wherein one end of the steel pipe assembly, which is far away from the anchor cable hole, is positioned on the inner side of the anchor pier (11);
E. locking the anchor cable body: installing an anchor cable body accessory, tensioning the steel strand (2) and unloading and locking the anchor cable body;
F. grouting and sealing the anchor: and (4) filling the pure cement slurry with the same label as that of the anchoring section into the anchor cable hole orifice through the steel pipe assembly, wherein the grouting needs to be compact.
2. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: the construction method for forming the hole with the pipe in the step A is to adopt a hole forming mode of an eccentric drill bit and the pipe, the final hole depth of the pipe is determined according to the rock mass condition after the pipe following depth exceeds 20m, and the fault is penetrated when encountering the fault and the drilling is finished to a harder rock mass; the pipe following is performed in a segmented mode, the length of a single pipe following is 1.5-3 m, and the pipe following is pulled out in a segmented mode after drilling is finished.
3. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: and B, determining the circulating depth of the straight drill bit according to the collapse condition of the hole wall, controlling the circulating depth to be within the range of 2-5 m, pulling out the straight drill bit after completing one-time drilling, mounting grout stop plugs at the hole bottom and the hole opening of the hole formed by the straight drill bit, mounting a grouting pipe, injecting mortar with low fluidity, adding an early strength agent into the mortar, adding a certain amount of an accelerating agent into the mortar if the grouting amount is large, cleaning the hole by using the drill bit after the mortar reaches a certain strength, and performing the next circulation until the hole wall does not collapse until the designed depth of the anchor cable hole is reached.
4. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: b, performing in-hole camera shooting on the anchoring section, if a wider crack is opened on the hole wall, installing a grout stop plug at the boundary of the anchoring section and the tensioning section, then installing a grouting pipe, installing a pressure gauge at the inlet of the grouting pipe, pouring cement paste, wherein the grouting pressure reaches 0.1-0.3MPa, the grout consumption is obviously reduced, and grouting can be finished; drilling a hole in the anchoring section by using a drill bit after the slurry reaches the designed strength; the grout stop plug is a water pressure plug, is tightly contacted with the hole wall after being filled with water, and can be pulled out after pressure relief.
5. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: the anchor cable body in the step B comprises a tensioning section, an anchoring section and a grout stopping bag (8) arranged at the boundary of the tensioning section and the anchoring section, wherein the anchoring section is made into a corrugated shape through zinc-lead-free tows (4) and isolating frames (5) which are alternately arranged on the steel strand (2) at intervals, and the tensioning section is made into a straight line shape through the isolating frames (5) which are alternately arranged on the steel strand (2); each steel strand (2) of the tensioning section is sleeved with a PE sleeve, and one end of the PE sleeve, which is close to the anchoring section, is wound and wrapped by a waterproof adhesive tape; lay anchor section grout pipe (3) along anchor rope hole axial, anchor section exhaust slurry return pipe (6) and stretch-draw section grout pipe (9), the one end of anchor section grout pipe (3) is passed and is only starched package (8) and extend to the anchor section, the other end passes the stretch-draw section, the steel pipe assembly extends outside anchor mound (11), the one end of anchor section exhaust slurry return pipe (6) is passed and is only starched package (8) and extend to the anchor section, the other end extends to anchor rope hole drill way, the one end of stretch-draw section grout pipe (9) is located the stretch-draw section, the other end extends to anchor rope hole drill way.
6. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 5, characterized by comprising the following steps: flower holes with the interval of 1m are formed in the range of the anchoring section on the outer wall of the grouting pipe (3) of the anchoring section, and a plurality of grouting ports are formed in the position, corresponding to the grout stopping bag (8), on the outer wall of the grouting pipe (3) of the anchoring section; flower holes with the spacing of 2m are formed in the middle of the tensioning section grouting pipe (9); the steel strand (2), the anchoring section grouting pipe (3) and the anchoring section exhaust slurry return pipe (6) are tightly wound with cotton wool at the positions corresponding to the slurry stopping bags (8), and are wrapped with geotextile and tightly bound.
7. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: and the steel pipe assembly in the step B comprises a steel sleeve (10), a steel pipe A (12) and a steel pipe B (18), the steel sleeve (10) is coaxially arranged at the hole opening of the anchor cable hole, the steel pipe A (12) and the steel pipe B (18) are arranged on the outer wall of the steel sleeve (10) and communicated with the steel sleeve (10), and one end, far away from the steel sleeve (10), of the steel pipe A (12) and the steel pipe B (18) penetrates through the anchor pier (11).
8. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: c, grouting the tensioning section, wherein the grouting liquid is mortar, geotextile wraps the anchor cable of the tensioning section to reduce the diffusion of the grouting liquid to the peripheral rock wall, a grouting pipe of the tensioning section is provided with a flower hole to facilitate the grouting liquid to fill the whole tensioning section, and orifice reverse grouting is adopted as the standard after grouting; and D, before the anchor pier (11) is constructed in the step D, peeling and deoiling one end of the steel strand (2) close to the anchor pier (11).
9. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: and E, the anchor cable body accessory comprises a bearing plate (14), a working anchor plate (16) and an anchor head protective cover (17), the bearing plate (14) is arranged on the steel pipe assembly, one side of the bearing plate (14) is provided with a grabbing rib (13), the grabbing rib (13) is positioned in the anchor pier (11), the working anchor plate (16) is arranged on the bearing plate (14) through an anchor backing plate (15), the anchor head protective cover (17) is arranged on the bearing plate (14), the working anchor plate (16), the anchor backing plate (15), one end, exposed out of the anchor cable hole, of the steel strand (2) is positioned in the anchor head protective cover (17), and the anchor head protective cover (17) is filled with concrete.
10. The construction method of the strongly-unloading fractured rock mass prestressed anchor cable according to claim 1, characterized by comprising the following steps: before the steel strand (2) is tensioned in the step E, a fixed sample frame is arranged on the periphery of the anchor pier (11) to serve as a reference point, the settlement value and the tension value of the anchor cable are observed after each stage of tensioning, and whether the anchor cable is unloaded or not is checked; when the steel strand (2) is stretched, the steel strand (2) is centered and checked, pre-tightened, compensated and stretched, then the whole stretching is carried out, the loading is carried out step by step until the loading reaches the maximum design load, and the unloading locking is carried out.
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