Synchronous cable penetrating and mud jacking construction method after supporting anchor cable hole forming

Abstract

A synchronous cable penetrating and grouting construction method after supporting anchor cable hole forming comprises the steps that after survey lofting, drilling machine hole forming and pre-stressed anchor cable manufacturing are sequentially conducted, an anchor disc at the end of a pre-stressed anchor cable is placed into an anchor cable hole opening, then a hollow drill rod and a rotary spraying drill bit are replaced, and the rotary spraying drill bit is arranged in the anchor disc at the hole opening in a sleeved mode; the spiral drilling machine is started to drive the rotary jet grouting drill bit to drive the anchor disc and the pre-stressed anchor cable to be pushed into the anchor cable hole until the drill bit reaches the designed hole depth; a grouting system on the spiral drilling machine is started, cement paste is injected into the hollow drill rod through a pressure pump, the cement paste is sprayed into the anchor cable hole from the rotary spraying drill bit, grouting is conducted while the rotary spraying drill bit is withdrawn after grouting is continuously conducted till the hole opening is subjected to grout returning, grouting is stopped when drilling is withdrawn to the free section, the hollow drill rod is withdrawn, and cable penetrating and grouting synchronous construction is completed; the effect of synchronous construction of in-hole cable penetrating and grouting is achieved, the problem that manual cable penetrating and grouting are low in efficiency is solved, the construction period can be guaranteed in the miscellaneous fill layer and weathered rock layer construction process, and the construction cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of building foundation pit support, and in particular to a construction method for synchronous cable threading and grouting after hole forming for supporting anchor cables. Background Art

[0002] In underground engineering, ultra-deep foundation pit construction is a sub-project with a high risk of exceeding a certain scale, and foundation pit support is an important guarantee for safe production during the construction period of underground structures. Deep foundation pit support often adopts the solution of retaining piles and sprayed anchor support, and in the pile-anchor support system, anchor cable construction is the key link in the support, and the quality of anchor cable construction is also an important factor affecting the safety of foundation pit support.

[0003] At present, the anchor bolt dry drilling process is mature, using a spiral drill to drill holes, and then manually threading the cable for grouting. However, during the construction process, due to the close connection between the earthwork layered excavation and the foundation pit support process, and the heavy weight of the anchor cable, the high labor intensity and low efficiency of manual threading, the time reserved for support construction is very tight. The construction can be carried out while mechanically threading the cable into the hole and pressure grouting is carried out, but it is difficult to construct in miscellaneous fill layers and solid weathered rock layers, there is no reaction time when encountering unknown underground obstacles, and the cost is high. How to solve the problem of low efficiency of manual threading and grouting, and ensure the construction period and cost while constructing in miscellaneous fill layers and weathered rock layers has become an urgent problem to be solved. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a construction method for synchronous cable threading and grouting after the support anchor cable is bored.

[0005] The technical solution of the present invention is: a construction method for synchronous cable insertion and grouting after supporting anchor cable holes are formed, comprising the following steps:

[0006] ① Use a total station to mark the anchor hole positions on the deep foundation pit slope and spray paint to mark them. The anchor hole position deviation should not exceed 30mm;

[0007] ② Drill a 0.5m deep pilot hole at the marked hole position with a deflection of no more than 3%. After the pilot hole is drilled, use a spiral drill to drill the holes to the designed depth and clean the holes in time;

[0008] ③ A high-strength anchor plate is set at the end of the multi-strand steel strand, and the outer end of the steel strand is fixed with an extrusion anchor. The inner diameter of the anchor plate is between the reducer of the jet-jet drill bit used in the spiral drilling rig;

[0009] ④ After the drilling rig completes drilling and hole cleaning, the anchor plate at the end of the prestressed anchor cable is placed into the hole of the anchor cable hole, and then the drill rod is replaced with a hollow drill rod. The outer end of the hollow drill rod is connected to a rotary jet drill bit, which is inserted into the anchor plate at the hole mouth. The spiral drill is started to drive the rotary jet drill bit to advance the anchor plate and the prestressed anchor cable into the anchor cable hole until the drill bit reaches the designed hole depth and stops advancing; ⑤ Turn on the grouting system on the spiral drill, use the pressure pump to inject cement slurry with a water-cement ratio of 0.5 into the hollow drill pipe, and the pressure is 0.5MPa. The cement slurry is sprayed into the anchor cable hole from the rotary jet drill bit. Continue grouting until the hole mouth returns to the slurry, and then withdraw the rotary jet drill bit while grouting. Stop grouting when the drill is withdrawn to the free section, withdraw the hollow drill pipe, and complete the simultaneous construction of cable threading and grouting;

[0010] ⑥ During the production of prestressed anchor cables, the secondary grouting pipe is tied and fixed on the steel strand. The secondary grouting construction is carried out after the initial setting of the slurry for cable grouting and before the final setting. The secondary grouting pressure is 1.5-3.0MPa. After the secondary grouting is full, the load is maintained for more than 5 minutes.

[0011] Preferably, a centering bracket with an inner diameter larger than the diameter of the jet grouting drill and drill rod is made to meet the requirements of drill withdrawal. During the cable grouting process, the centering brackets are installed at equal intervals between the steel strands, and the hollow drill rod and the jet grouting drill head pass through the center bracket.

[0012] Preferably, the inner end of the secondary grouting pipe is 100-200 mm away from the end of the anchor cable, the inner end of the secondary grouting pipe is sealed, and a plurality of grouting holes are arranged in the anchoring section of the secondary grouting pipe, with a spacing of 300-500 mm between the grouting holes.

[0013] Preferably, a PVC pipe is installed at the end of the steel strand, and the coil of the steel strand is installed in an unwinding bracket, the unwinding bracket is fixed to the ground with anchoring steel bars, and the steel strand is unwound by supporting the unwinding bracket to produce prestressed anchor cables.

[0014] Preferably, an unwinding auxiliary device is arranged outside the unwinding bracket, and the unwinding auxiliary device includes a guide cylinder and two vertical support rods symmetrically welded and fixed on both sides of the guide cylinder. The guide cylinder is arranged toward the unwinding bracket, and the steel strand passes through the guide cylinder.

[0015] Preferably, the waist beam is installed after the secondary grouting. The waist beam is made of two 25b channel steels welded to an iron plate. The gap between the retaining piles and the waist beam is filled with concrete to ensure that the waist beam is close to the vertical retaining piles. The anchor and the waist beam are fixed with gaskets. The gap between the anchor steel waist beam and the bored pile is filled with fine stone concrete with a strength grade of not less than C30. The waist beams between the sections are connected by steel plates welding to form a whole.

[0016] Preferably, tensioning, locking and anchoring are carried out after the waist beam is installed. This is carried out after the anchor cable is 28 days old and the slurry strength reaches 75% of the design strength. Within 48 hours after locking, compensatory tensioning should be carried out when the stress loss exceeds 10%; after tensioning, the remaining anchor bars are cut mechanically and 5-10 cm of exposed anchor bars are left long to prevent slipping; finally, the anchor cable anchor head is protected with M25 cement mortar.

[0017] The beneficial technical effect of the present invention is as follows: the present invention adopts a hollow drill rod with grouting function and a rotary jet drill bit with a nozzle. The grouting system can deliver cement slurry to the rotary jet drill bit through the hollow drill rod. The rotary jet drill bit passes through the centering bracket to support the anchor plate and push the anchor cable bundle into the bottom of the anchor hole. When the grouting system is turned on, cement slurry can be sprayed out from the nozzle of the rotary jet drill bit for pressure grouting, thereby achieving the effect of simultaneous construction of cable threading and grouting in the hole, solving the problem of low efficiency of manual cable threading and grouting, and ensuring the construction period and reducing the construction cost during the construction of miscellaneous fill layers and weathered rock layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the anchor hole drilling construction of the present invention; Figure 2 It is a structural schematic diagram of the cable grouting process of the present invention; Figure 3 It is a schematic diagram of the internal structure of the present invention after construction is completed; Figure 4 It is a schematic diagram of the external three-dimensional structure of the present invention after construction is completed; Figure 5 It is a schematic diagram of the three-dimensional structure after the anchor cable and the rotary jet drill bit of the present invention are connected; Figure 6 It is a three-dimensional structural schematic diagram of the rotary jet drill bit and the hollow drill rod of the present invention; Figure 7 It is a three-dimensional structural schematic diagram of the anchor cable of the present invention; Figure 8 A schematic diagram of the three-dimensional structure of the coiling and uncoiling of the steel strand to make an anchor cable according to the present invention; Fig. 9 and Fig.10 It is a related physical diagram of the present invention.

[0019] In the figure, 01. Auger drill, 11. Anchor drill bit, 12. Solid drill rod, 13. Jet jet drill bit, 131. Nozzle, 14. Hollow drill rod, 02. Anchor cable, 21. Steel strand, 22. Anchor plate, 23. Centering bracket, 24. Secondary grouting pipe, 25. Grouting hole, 26. Exposed anchor bar, 03. Waist beam, 04. Anchor cable hole, 51. Unwinding bracket, 52. Coil of steel strand, 53. Guide tube, 54. Vertical support rod. DETAILED DESCRIPTION

[0020] Embodiment 1, see attached Figure 1-8 A method for synchronous cable grouting after supporting anchor cable holes are formed, which is characterized by comprising the following steps:

[0021] ① Use a total station to mark the position of anchor hole 04 on the slope of the deep foundation pit and spray paint to mark it. The position deviation of anchor hole 04 shall not exceed 30mm;

[0022] ② Drill a 0.5m deep pilot hole at the marked hole position with a deflection of no more than 3%. After the pilot hole is drilled, use the spiral drill 01 to drill the anchor drill bit 11 to the designed depth, and clean the hole in time to clean the soil and gravel in the anchor hole 04 to avoid affecting the solidification effect of the cement slurry in the later stage;

[0023] ③ A high-strength anchor plate 22 is arranged at the end of the multi-strand steel strand 21. The outer side of the anchor plate is evenly distributed with a plurality of circular holes for passing the steel strand 21. The ends of the steel strand pass through the circular holes. The outer ends of the steel strand 21 are fixed by an extrusion anchor. The inner diameter of the anchor plate 22 is between the reducer section of the rotary jet drill 13 used in the spiral drilling machine 01. The outer diameter of the anchor plate is 180 mm, and the diameter of the middle hole is 70 mm. The diameter of the middle hole is between the diameter of the drill reducer section of 50-80 mm.

[0024] ④ After the drilling rig completes drilling and hole cleaning, the anchor plate 22 at the end of the prestressed anchor cable 02 is placed into the hole opening of the anchor cable hole 04, and then the solid drill rod 12 of the anchor drill bit 11 is replaced with a hollow drill rod 14, and the outer end of the hollow drill rod is connected to the rotary jet drill bit 13, and the rotary jet drill bit is inserted into the anchor plate 22 at the hole opening. The rotary jet drill bit 13 with a variable diameter structure can match the anchor plate 22, pushing the anchor plate 22 forward, and starting the spiral drilling rig 01 to drive the rotary jet drill bit 13 to advance with the anchor plate 22 and the prestressed anchor cable 02 into the anchor cable hole 04 until the drill bit reaches the designed hole depth and stops advancing; ⑤ Turn on the grouting system on the spiral drilling machine 01, and use a pressure pump to inject cement slurry with a water-cement ratio of 0.5 into the hollow drill rod 14 at a pressure of 0.5MPa. The cement slurry is sprayed into the anchor hole 04 from the nozzle 131 at the end of the rotary jet drill bit 13 to perform pressure grouting. The grouting is continued until the hole mouth is slurried back, and the rotary jet drill bit 13 is withdrawn while grouting. The grouting is stopped when the drill is withdrawn to the free section, and the hollow drill rod 14 is withdrawn to complete the simultaneous construction of cable threading and grouting; thereby achieving the effect of simultaneous construction of cable threading and grouting in the hole, solving the problem of low efficiency of manual cable threading and grouting, and ensuring the construction period and reducing the construction cost during the construction of miscellaneous fill layers and weathered rock layers.

[0025] ⑥ During the production of the prestressed anchor cable 02, a secondary grouting pipe 24 is tied and fixed on the steel strand 21. The inner end of the secondary grouting pipe is 100-200mm away from the end of the anchor cable 02. The inner end of the secondary grouting pipe 24 is sealed, and a number of grouting holes 25 are set in the anchoring section of the secondary grouting pipe 24. The spacing between the grouting holes 25 is 300-500mm. The secondary grouting construction is carried out after the initial setting of the slurry for cable grouting and before the final setting. The secondary grouting pressure is 1.5-3.0MPa. After the secondary grouting is filled, the load is held for more than 5 minutes. After the cement slurry enters the secondary grouting pipe 24, it is ejected from each grouting hole 25 with uniform pressure. On the basis of the primary grouting, the scope of cement slurry penetration from the anchor cable hole 04 to the foundation is expanded, thereby improving the anchoring strength of the anchor cable 02.

[0026] After the secondary grouting, the waist beam 03 is installed. The waist beam is made of 2 25b channel steels welded together with an iron plate. The gap between the retaining piles and the waist beam 03 is filled with concrete to ensure that the waist beam 03 is close to the vertical retaining piles. The anchor and the waist beam are fixed with gaskets. The gap between the anchor cable 02 steel waist beam 03 and the bored pile is filled with fine stone concrete with a strength grade of not less than C30. The waist beams between the sections are connected by steel plates welding to form a whole.

[0027] After the waist beam 03 is installed, tensioning, locking and anchoring are carried out. This is carried out after the construction age of the anchor cable 02 is 28 days and the slurry strength reaches 75% of the design strength. Within 48 hours after locking, if the stress loss exceeds 10%, compensatory tensioning should be carried out; after tensioning, the remaining exposed anchor bars are cut mechanically and 5-10cm long exposed anchor bars 26 are left to prevent slipping; finally, the anchor head of the anchor cable 02 is protected with M25 cement mortar.

[0028] A centering bracket 23 with an inner diameter larger than the diameter of the jet grouting drill and the drill rod is made to meet the requirements of drilling withdrawal. During the cable grouting process, the centering bracket 23 is installed at equal intervals between the steel strands 21, and the hollow drill rod 14 and the jet grouting drill head 13 pass through the center bracket. The centering bracket 23 has an outer diameter of 180 mm, with a circular hole with an inner diameter of 100 mm in the middle. The end diameter of the jet grouting drill head 13 is 50 mm, the tail diameter is 80 mm, and the diameter of the hollow drill rod 14 is 80 mm, which meets the requirements of the drilling hole diameter of the jet grouting drill head 13.

[0029] A PVC tube is installed at the end of the steel strand 21, and the allowable deviation of the length of the sleeve is +50mm. The coil 52 of the steel strand is installed in the unwinding bracket 51, and the unwinding bracket is fixed to the ground with anchoring steel bars. The steel strand 21 is supported by the unwinding bracket 51 for unwinding, and the prestressed anchor cable 02 is manufactured. An unwinding auxiliary device is arranged on the outside of the unwinding bracket 51, and the unwinding auxiliary device includes a guide cylinder 53 and two vertical support rods 54 symmetrically welded and fixed on both sides of the guide cylinder 53. The guide cylinder 53 is arranged toward the unwinding bracket 51, and the steel strand 21 passes through the guide cylinder 53. The coiled steel strand 21 has a large stress when unwinding, so it will swing left and right due to the stress when unwinding. The guide cylinder 53 can control the swing amount of the steel strand 21, improve the smoothness of the unwinding and unloading of the steel strand 21, and thereby improve the manufacturing efficiency of the anchor cable 02.

Claims

1. A construction method for synchronous cable insertion and grouting after supporting anchor cable drilling, which is characterized by comprising the following steps: Measurement and Stakeout ① Use a total station to mark the anchor hole positions on the deep foundation pit slope and spray paint to mark them. The anchor hole position deviation should not exceed 30mm; Drilling rig hole ② Drill a 0.5m deep pilot hole at the marked hole position with a deflection of no more than 3%. After the pilot hole is drilled, use a spiral drill to drill the holes to the designed depth and clean the holes in time; Prestressed anchor cable production ③ A high-strength anchor plate is set at the end of the multi-strand steel strand, and the outer end of the steel strand is fixed with an extrusion anchor. The inner diameter of the anchor plate is between the reducer of the jet-jet drill bit used in the spiral drilling rig; Cable grouting ④ After the drilling rig completes drilling and hole cleaning, the anchor plate at the end of the prestressed anchor cable is placed into the hole of the anchor cable hole, and then the drill rod is replaced with a hollow drill rod. The outer end of the hollow drill rod is connected to a rotary jet drill bit, which is inserted into the anchor plate at the hole mouth. The spiral drill is started to drive the rotary jet drill bit to advance the anchor plate and the prestressed anchor cable into the anchor cable hole until the drill bit reaches the designed hole depth and stops advancing; ⑤ Turn on the grouting system on the spiral drill, use the pressure pump to inject cement slurry with a water-cement ratio of 0.5 into the hollow drill pipe, and the pressure is 0.5MPa. The cement slurry is sprayed into the anchor cable hole from the rotary jet drill bit. Continue grouting until the hole mouth returns to the slurry, and then withdraw the rotary jet drill bit while grouting. Stop grouting when the drill is withdrawn to the free section, withdraw the hollow drill pipe, and complete the simultaneous construction of cable threading and grouting; Secondary Grouting ⑥ During the production of prestressed anchor cables, the secondary grouting pipe is tied and fixed on the steel strand. The secondary grouting construction is carried out after the initial setting of the slurry for cable grouting and before the final setting. The secondary grouting pressure is 1.5-3.0MPa. After the secondary grouting is full, the load is maintained for more than 5 minutes.

2. According to claim 1, a construction method for synchronous cable insertion and grouting after hole formation of supporting anchor cable, characterized in that: A centering bracket with an inner diameter larger than the diameter of the jet grouting drill and drill rod is made to meet the requirements of drill withdrawal. During the cable grouting process, the centering brackets are installed at equal intervals between the steel strands, and the hollow drill rod and jet grouting drill head pass through the center bracket.

3. The method for synchronously threading and grouting the supporting anchor cable after hole formation according to claim 1 is characterized in that: The inner end of the secondary grouting pipe is 100-200mm away from the end of the anchor cable, the inner end of the secondary grouting pipe is blocked, and a plurality of grouting holes are arranged in the anchoring section of the secondary grouting pipe, and the spacing between the grouting holes is 300-500mm.

4. The method for synchronous cable grouting after hole formation of supporting anchor cable according to claim 1 is characterized in that: A PVC pipe is installed at the end of the steel strand, and the coil of the steel strand is installed in the unwinding bracket. The unwinding bracket is fixed to the ground with anchor steel bars. The steel strand is unwound by supporting the unwinding bracket to produce the prestressed anchor cable.

5. The method for synchronously threading and grouting the supporting anchor cable after hole formation according to claim 1 is characterized in that: An unwinding auxiliary device is arranged outside the unwinding bracket, and the unwinding auxiliary device comprises a guide cylinder and two vertical support rods symmetrically welded and fixed on both sides of the guide cylinder. The guide cylinder is arranged toward the unwinding bracket, and the steel strand passes through the guide cylinder.

6. The method for synchronously threading and grouting the anchor cable after hole formation according to claim 1 is characterized in that: After the secondary grouting, the waist beam is installed. The waist beam is made of two 25b channel steels welded together with an iron plate. The gap between the retaining piles and the waist beam is filled with concrete to ensure that the waist beam is close to the vertical retaining piles. The anchor and the waist beam are fixed with gaskets. The gap between the anchor steel waist beam and the bored pile is filled with fine stone concrete with a strength grade of not less than C30. The waist beams between sections are connected by steel plates welding to form a whole.

7. The method for synchronously threading and grouting the anchor cable after the anchor cable is bored according to claim 6, characterized in that: After the waist beam is installed, tensioning, locking and anchoring are carried out. This is carried out after the anchor cable is 28 days old and the slurry strength reaches 75% of the design strength. Within 48 hours after locking, if the stress loss exceeds 10%, compensatory tensioning should be carried out; after tensioning, the remaining anchor bars are cut mechanically and 5-10cm of exposed anchor bars are left to prevent slipping; finally, the anchor cable anchor head is protected with M25 cement mortar.

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