Construction method for reinforcing existing high-pressure jet expanded-head anchor rod by adopting hollow drill rod

Abstract

The invention discloses a construction method for reinforcing an existing high-pressure jet expanded-head anchor rod by adopting a hollow drill rod, which comprises the following steps of: (1) rotating the hollow drill rod, drilling the hollow drill rod to the underground along the axis direction of the high-pressure jet expanded-head anchor rod, cutting a soil body around the high-pressure jet expanded-head anchor rod, and forming a core rod; the rod body of the high-pressure injection expanded head anchor rod is positioned in the core rod; an annular gap between the hollow drill bit and the core rod forms a jet orifice, and high-pressure water is jetted downwards through the jet orifice to impact a soil body; and (2) the hollow drill rod is rotated, cement paste is jetted to the periphery of the core rod, a cement-soil wrapping body is formed, the cement-soil wrapping body is located on the upper side of the stiffening expansion head of the high-pressure jet expansion head anchor rod, the core rod is wrapped with the cement-soil wrapping body, and the outer diameter of the cement-soil wrapping body is larger than that of the stiffening expansion head. The single high-pressure jet expanded head anchor rod can be reinforced at a time, the construction efficiency is improved, and the construction cost is reduced.

Description

Technical Field

[0001] The invention relates to a construction method for reinforcing an existing high-pressure jet enlarged head anchor rod by using a hollow drill rod. Background Art

[0002] High-pressure jet enlarged head anchor rod is an anchor rod that uses high-pressure fluid to jet cut and expand the soil at the bottom of the anchor hole according to the designed length and pour cement slurry or cement mortar to form a cylindrical grouting body with a larger diameter. The industry standard of the People's Republic of China "Technical Specification for High-pressure Jet Enlarged Head Anchor Rod" (JGJ / T282-2012) stipulates that the compressive strength of the grouting body in the anchor section should generally not be less than 20MPa. High-pressure jet enlarged head anchor rod is based on ordinary anchor rods. It uses clean water and cement slurry or cement slurry to perform high-pressure jet cutting and expansion grouting on the soil outside the anchor hole within a certain length range at the bottom of the anchor hole. Cement slurry is poured in the anchor hole to form an anchor rod with a cylindrical cement soil anchor body with a larger diameter. This process requires pre-empty holes and then injecting pure cement slurry or cement mortar. Construction in soft soil foundations, especially inclined hole construction, is prone to hole collapse, resulting in insufficient bearing capacity of high-pressure jet enlarged head anchor rods and failure to meet design requirements. Therefore, when the bearing capacity of the high-pressure jet enlarged head anchor rod is insufficient, additional piles are usually carried out around the existing high-pressure jet enlarged head anchor rod, and the existing high-pressure jet enlarged head anchor rod is abandoned or used together with the existing high-pressure jet enlarged head anchor rod. However, this construction method may result in the subsequent construction of the high-pressure jet enlarged head anchor rod failing to meet the design requirements, and the additional piles require adjustment of the corresponding frame structure, which increases the construction cost. Therefore, the best solution is to reinforce the existing high-pressure jet enlarged head anchor rod, but the existing reinforcement generally directly constructs jet piles on one side of the existing high-pressure jet enlarged head anchor rod, and uses the later constructed jet piles to increase the friction resistance. The already constructed high-pressure jet enlarged head anchor rod is difficult to position, and the new jet pile cannot bond with the existing high-pressure jet enlarged head anchor rod, and the bonding strength is weak. In order to evenly bear the force, it is usually necessary to construct at least three jet piles around the existing high-pressure jet enlarged head anchor rod, which undoubtedly increases the construction volume and construction cost. Therefore, how to reinforce the existing high-pressure jet enlarged head anchor rod at a low cost still has a strong practical significance. Summary of the invention

[0003] In order to reduce the construction cost of reinforcement and improve the connection strength between the post-construction reinforcement part and the existing high-pressure jet enlarged head anchor rod, the present application proposes a construction method for reinforcing the existing high-pressure jet enlarged head anchor rod using a hollow drill rod, which comprises the following steps:

[0004] (1) Rotate the hollow drill rod and drill the hollow drill rod underground along the axial direction of the high-pressure jet expansion head anchor rod until the hollow drill bit of the hollow drill rod reaches the set depth. The hollow drill rod is a rotary jet drill rod. When the hollow drill rod is drilled underground, the hollow drill bit cuts the soil around the high-pressure jet expansion head anchor rod and forms a core rod. The rod body of the high-pressure jet expansion head anchor rod is located in the core rod, and the hollow drill rod is sleeved on the core rod. The annular gap between the inner wall of the hollow drill bit and the core rod forms an annular injection port, and high-pressure water is sprayed downward through the injection port to impact the soil. The hollow drill rod and the high-pressure jet expansion head anchor rod are coaxially arranged.

[0005] (2) Rotate the hollow drill rod and spray cement slurry around the core rod to form a cement soil inclusion body, which is located on the upper side of the reinforcing enlarged head of the high-pressure jet enlarged head anchor rod, and the cement soil inclusion body is wrapped on the core rod, and the outer diameter of the cement soil inclusion body is greater than the outer diameter of the reinforcing enlarged head. Specifically, the injection pressure of the cement slurry is 20.0-30.0MPa; the pressure of the high-pressure water is 0.2-3.0MPa. The reinforcing enlarged head of the high-pressure jet enlarged head anchor rod can be a steel cage enlarged head or a bladder enlarged head.

[0006] In the present application, the rod body of the high-pressure jet enlarged head anchor rod is specifically made of finely rolled threaded steel, prestressed steel strand or carbon fiber cable. When forming the cement soil inclusion body, the hollow drill rod can be reciprocated multiple times along the axial direction.

[0007] In the present application, a cement-soil inclusion is re-formed on the existing high-pressure jet enlarged head anchor rod by using a hollow drill rod. The cement-soil inclusion is used as a post-construction reinforcement part, which can improve the friction resistance of the high-pressure jet enlarged head anchor rod. Since the cement-soil inclusion is wrapped on the core rod, the cement-soil inclusion constructed later and the existing structure of the high-pressure jet enlarged head anchor rod can form a whole, avoiding the problem of low bonding strength between the post-constructed rotary jet pile and the existing high-pressure jet enlarged head anchor rod in the prior art. Moreover, the cement-soil inclusion is wrapped on the core rod, and at most has only a small amount of eccentricity. Therefore, it is only necessary to supplement the cement-soil inclusion of a set size according to the strength of the existing high-pressure jet enlarged head anchor rod, and the reinforcement of a single high-pressure jet enlarged head anchor rod can be completed at one time, thereby improving construction efficiency and reducing construction costs. Thereby avoiding the problem of low construction efficiency and high construction costs in the prior art that multiple rotary jet piles need to be constructed around the existing high-pressure jet enlarged head anchor rod.

[0008] Furthermore, in order to avoid damage to the rod body in the high-pressure jet enlargement head anchor, the inner diameter of the hollow drill bit is 5-20mm larger than the outer diameter of the ordinary anchoring section of the high-pressure jet enlargement head anchor, and the inner wall of the hollow drill bit is at least 10mm away from the outer wall of any rod body.

[0009] Under the above definition, the hollow drill rod mainly cuts the soil around the high-pressure jet enlarged head anchor rod. Even if there is a construction error, the hollow drill rod will only cut the edge of the cement soil shell of the high-pressure jet enlarged head anchor rod and will not touch the rod body. When the rod body is composed of multiple prestressed steel strands or carbon fiber cables, in this application, each prestressed steel strand or carbon fiber cable is referred to as a rod body.

[0010] Furthermore, the outer diameter of the cement-soil inclusion is 1.2-2 times the outer diameter of the reinforcing enlarged head of the high-pressure jet enlarged head anchor. This design allows the outer diameter of the cement-soil inclusion to outwardly exceed the outer diameter of the reinforcing enlarged head, which can effectively expand the contact area between the reinforced high-pressure jet enlarged head anchor and the underground soil, thereby increasing the friction resistance of the high-pressure jet enlarged head anchor.

[0011] Furthermore, the cement-soil inclusion is connected to the reinforcing enlarged head of the high-pressure jet enlarged head anchor rod. This design enables the newly constructed cement-soil inclusion and the reinforcing enlarged head to form a whole, and jointly resist the external force transmitted by the rod body.

[0012] Furthermore, in order to fully increase the frictional resistance of the high-pressure jetted enlarged head anchor rod, the cement-soil inclusion extends upward to the top of the high-pressure jetted enlarged head anchor rod.

[0013] Specifically, the hollow drill rod includes a rod body and a hollow drill bit installed at the lower end of the rod body. The rod body is a double rod structure, and the rod body includes an inner tube and an outer tube sleeved on the outside of the inner tube. The inner cavity of the inner tube is a water cavity, and a slurry cavity is formed between the inner tube and the outer tube; the inner tube, the outer tube and the hollow drill bit are coaxially arranged; the inner tube and the outer tube can be detachably installed on the hollow drill bit; a through-hole-shaped injection hole is provided at the lower end of the hollow drill rod, the injection hole passes through the outer peripheral surface of the hollow drill rod, the slurry cavity is connected to the injection hole, and the cement slurry in the slurry cavity can be sprayed outward through the injection hole; the water cavity is connected to the inner cavity of the hollow drill bit, and the inner cavity of the hollow drill bit passes downward through the lower end surface of the hollow drill bit.

[0014] This design can easily replace the worn hollow drill bit. The jet nozzle is used to form a water knife with high-pressure water to impact and cut the underground soil and cement soil shell, so as to accelerate the destruction of the underground soil and cement soil shell and improve the construction efficiency. At the same time, the broken underground soil and cement soil shell are conducive to the formation of new cement soil inclusions in subsequent construction.

[0015] Furthermore, the hollow drill bit includes a ring body in the shape of a circular ring, an inner tube and an outer tube extending axially upward are arranged on the upper side of the ring body, an upwardly open injection chamber is formed between the inner tube and the outer tube, the injection hole is arranged on the outer tube, the inner tube is screwed on the inner tube, and the outer tube is screwed on the outer tube. The hollow drill bit can be produced by a one-time molding method, or the inner tube, the outer tube and the ring body can be processed separately, and then the parts are welded together. The inner tube and the outer tube are connected together by a hollow drill bit to simplify the structure of the drill rod. It is preferred to set teeth at the lower end of the ring body to improve cutting efficiency.

[0016] Furthermore, the outer wall of the outer tube does not extend beyond the outer wall of the hollow drill bit. This design can avoid unnecessary excessive wear on the outer tube, thereby increasing the service life of the outer tube.

[0017] Furthermore, the inner diameter of the inner tube is larger than the inner diameter of the hollow drill bit. When the inner diameter of the inner tube is the same as the inner diameter of the hollow drill bit, the wear of the inner wall of the inner tube is roughly the same as the wear of the inner wall of the hollow drill bit. However, as the hollow drill rod is drilled underground, the length of the core rod entering the inner tube becomes longer and longer, and the narrow gap between the core rod and the inner tube may prevent the high-pressure water from spraying downward. When the inner diameter of the inner tube is larger than the inner diameter of the hollow drill bit, a larger annular gap can be formed between the core rod and the inner tube to reduce the pressure loss of the high-pressure water, thereby reducing the pressure required for the high-pressure water. This design can reduce the wear on the inner tube and increase the service life of the inner tube. Preferably, the inner diameter of the inner tube is 2-20 mm larger than the inner diameter of the hollow drill bit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an embodiment of a hollow drill rod.

[0019] Figure 2 yes Figure 1 Enlarged view of part A.

[0020] Figure 3 yes Figure 2 Exploded diagram of .

[0021] Figure 4 It is a schematic diagram of the structure of a high-pressure jet enlarged head anchor rod.

[0022] Figure 5 This is the status diagram when the pile driver is in place.

[0023] Figure 6 yes Figure 5 Enlarged view of part B.

[0024] Figure 7 This is the state diagram of the drill rod when it completes drilling.

[0025] Figure 8 yes Figure 7Magnified view of part C.

[0026] Fig. 9 This is the status diagram when reinforcement is completed. DETAILED DESCRIPTION

[0027] The following first describes the structure of the high pressure jet enlarged head anchor rod 30 that needs to be reinforced. Figure 4 The steel structure of the high-pressure jet enlarged head anchor rod 30 includes a rod body 31 and an enlarged head steel cage 36 fixedly connected to the lower end of the rod body 31. The enlarged head steel cage 36 and the cement soil block 37 around it form a steel cage enlarged head. The rod body 31 extends upward from the ground 100 along the axis of the high-pressure jet enlarged head anchor rod, and there is a cement soil shell 34 formed by cement soil around the rod body 31. Along the axis direction of the high-pressure jet enlarged head anchor rod, the high-pressure jet enlarged head anchor rod is divided into an enlarged head section S, a common anchoring section M and a free section N from bottom to top. The steel cage enlarged head is formed into an enlarged head section S. The enlarged head section S and the common anchoring section M together form an anchoring section. The outer diameter of the common anchoring section is the same as that of the free section. A plastic sleeve 33 is sleeved on the area of ​​the rod body 31 located in the free section, and the centering bracket 32 ​​on the rod body 31 is a plastic part. In this embodiment, each high-pressure jet enlarged head anchor rod is provided with four steel strands, which are dispersedly arranged, each steel strand forms a rod body, and a plastic sleeve is sleeved on the free section area of ​​each steel strand. It can be understood that in other embodiments, the rod body can also be a carbon fiber rope or a precision-rolled threaded steel bar.

[0028] The following is an explanation of the structure of the hollow drill rod. Figure 1-Figure 3 The hollow drill rod is a jet-jet drill rod, specifically comprising a rod body 10 and a hollow drill bit 20 mounted at the lower end of the rod body. The rod body 10 is a double rod structure, comprising an inner tube 11 and an outer tube 12 sleeved outside the inner tube. The inner cavity of the inner tube is a water cavity 13, and a slurry cavity 14 is formed between the inner tube and the outer tube. The inner tube, the outer tube and the hollow drill bit are coaxially arranged.

[0029] The hollow drill bit 20 includes a ring body 21 in the shape of a circular ring, and a center hole 26 extending axially and penetrating through both ends of the ring body is provided in the ring body 21. The center hole is the inner cavity of the hollow drill bit, so that the inner cavity of the hollow drill bit penetrates downwardly through the lower end surface of the hollow drill bit. An inner pipe 22 and an outer pipe 23 extending axially upward are provided on the upper side of the ring body, and an upwardly open injection chamber 24 is formed between the inner pipe and the outer pipe. The outer pipe is located outside the inner pipe, and the injection hole 25 is provided on the outer pipe, and the injection hole penetrates outwardly through the outer wall of the outer pipe. In the axial direction, the top of the inner pipe is lower than the top of the outer pipe, and the injection hole is located within the height range of the inner pipe. The slurry chamber is connected to the injection hole, and the cement slurry in the slurry chamber can be sprayed outward through the injection hole. Teeth 27 are provided at the lower end of the ring body.

[0030] Internal threads are provided on the inner walls of the inner tube and the outer tube, and corresponding external threads are provided on the outer peripheral surfaces of the lower ends of the inner tube and the outer tube. The inner tube is screwed on the inner side of the inner tube, and the outer tube is screwed on the outer side of the outer tube, so that the center hole 26 of the hollow drill bit is connected to the water cavity 13 of the inner tube upward. In this embodiment, the inner tube and the outer tube are integrally formed with the ring body. It can be understood that in another embodiment, the inner tube, the outer tube and the ring body can also be processed separately, and then the inner tube and the outer tube are welded to the ring body.

[0031] To avoid excessive wear on the outer tube, the outer wall of the outer tube does not extend outwardly beyond the outer wall of the hollow drill bit. Specifically, in this embodiment, the outer diameter of the outer tube is the same as the outer diameter of the hollow drill bit. In this embodiment, the inner diameter of the inner tube is 10 mm larger than the inner diameter of the center hole. It can be understood that in other embodiments, the inner diameter of the inner tube can also be 2 mm, 5 mm, 15 mm, 20 mm, or other data between 2-20 mm larger than the inner diameter of the center hole.

[0032] In this embodiment, the inner diameter of the hollow drill bit is 10 mm larger than the outer diameter of the common anchoring section of the high-pressure jet enlarged head anchor rod, and when the hollow drill rod is drilled underground along the axial direction of the high-pressure jet enlarged head anchor rod, the hollow drill rod and the high-pressure jet enlarged head anchor rod are coaxially arranged, and the inner wall of the hollow drill bit and the outer wall of any rod body of the high-pressure jet enlarged head anchor rod have a distance of at least 10 mm. It can be understood that in other embodiments, the inner diameter of the hollow drill bit can also be 5 mm, 15 mm or 20 mm larger than the outer diameter of the common anchoring section, or other distances between 5-20 mm.

[0033] The following is an explanation of the construction method of using hollow drill rods to reinforce existing high-pressure jet enlarged head anchor rods. Figure 5-Figure 9 , the construction method comprises the following steps:

[0034] (1) Install the hollow drill rod on the jet grouting drill 40, rotate the hollow drill rod, and drill the hollow drill rod underground along the axial direction of the high-pressure jet enlarged head anchor rod 30 until the hollow drill bit of the hollow drill rod reaches the set depth. In this embodiment, the set depth is the upper end surface of the steel cage enlarged head. When the hollow drill rod is drilled underground, the hollow drill bit cuts the soil around the high-pressure jet enlarged head anchor rod and forms a core rod 35. All the rod bodies are located in the core rod, and the hollow drill rod is sleeved on the core rod. The hollow drill rod is coaxially arranged with the high-pressure jet enlarged head anchor rod.

[0035] The annular gap between the inner wall of the hollow drill bit and the core rod forms an annular injection port. When the hollow drill rod is drilled downward, high-pressure water enters the water cavity 13 through the first external pipe 61 and is ejected downward through the injection port to crush the soil. At the same time, the high-pressure water cools the hollow drill bit. In this embodiment, the pressure of the high-pressure water is 0.5-1.0 MPa. It can be understood that in other embodiments, the pressure of the high-pressure water can also be other pressure values ​​or pressure ranges between 0.2-3.0 MPa.

[0036] When the hollow drill rod is drilled underground along the axial direction of the high-pressure jet enlarged head anchor rod, there is at least a distance of not less than 10 mm between the inner wall of the hollow drill bit and the outer wall of any rod body of the high-pressure jet enlarged head anchor rod.

[0037] (2) The hollow drill rod is rotated and lifted upward, and the cement slurry enters the slurry chamber 14 through the second external pipe 62, and then enters the injection chamber 24. The cement slurry in the injection chamber 24 is sprayed around the core rod through the injection hole 25 to form a cement soil inclusion 51 wrapped around the core rod. The injection pressure of the cement slurry is 25.0-27.0 MPa. It is understood that the pressure of the cement slurry can also be other pressure values ​​or pressure ranges between 20-30 MPa.

[0038] When the cement slurry is sprayed, the hollow drill rod keeps rotating and can be reciprocated along the axial direction for multiple times as needed.

[0039] The cement soil inclusion 51 is located on the upper side of the steel cage enlarged head and bonded to the steel cage enlarged head. The cement soil inclusion extends upward to the top of the high-pressure jet enlarged head anchor rod. In this embodiment, the outer diameter of the cement soil inclusion is 1.4 times the outer diameter of the steel cage enlarged head. It can be understood that in other embodiments, the outer diameter of the cement soil inclusion can also be 1.2 times, 1.6 times or 2 times the outer diameter of the steel cage enlarged head, or other ratios between 1.2 and 2 times.

[0040] In this embodiment, the stiffening enlarged head is specifically a steel cage enlarged head. It can be understood that in another embodiment, the stiffening enlarged head can also be a capsule-type enlarged head.

Claims

1. A construction method for reinforcing an existing high-pressure jet enlarged head anchor rod using a hollow drill rod, characterized in that: The steps include: (1) rotating the hollow drill rod, drilling the hollow drill rod into the ground along the axial direction of the high-pressure jet expansion head anchor rod, until the hollow drill bit of the hollow drill rod reaches the set depth, the hollow drill rod is a rotary jet drill rod; When the hollow drill rod is drilled underground, the hollow drill bit cuts the soil around the high-pressure jet enlarged head anchor rod and forms a core rod. The rod body of the high-pressure jet enlarged head anchor rod is located in the core rod, and the hollow drill rod is sleeved on the core rod. The annular gap between the inner wall of the hollow drill bit and the core rod forms an annular injection port, and high-pressure water is sprayed downward through the injection port to impact the soil. The hollow drill rod and the high-pressure jet enlarged head anchor rod are coaxially arranged. (2) Rotate the hollow drill rod and spray cement slurry around the core rod to form a cement-soil inclusion. The cement-soil inclusion is located on the upper side of the stiffening enlarged head of the high-pressure jet enlarged head anchor rod, and the cement-soil inclusion is wrapped around the core rod. The outer diameter of the cement-soil inclusion is greater than the outer diameter of the stiffening enlarged head.

2. The construction method according to claim 1, characterized in that: The injection pressure of cement slurry is 20.0-30.0MPa; the pressure of high-pressure water is 0.2-3.0MPa.

3. The construction method according to claim 1, characterized in that: The inner diameter of the hollow drill bit is 5-20 mm larger than the outer diameter of the common anchoring section of the high-pressure jet enlarged head anchor rod, and the inner wall of the hollow drill bit is at least 10 mm away from the outer wall of any rod body.

4. The construction method according to claim 1, characterized in that: The outer diameter of the cement-soil inclusion is 1.2-2 times the outer diameter of the reinforcing enlarged head of the high-pressure jet enlarged head anchor.

5. The construction method according to claim 1, characterized in that: The cement-soil inclusion is connected to the reinforcing enlarged head of the high-pressure jet enlarged head anchor rod.

6. The construction method according to claim 1, characterized in that: The cement-soil inclusion extends upward to the top of the high-pressure jet enlarged head anchor.

7. The construction method according to claim 1, characterized in that: The hollow drill rod comprises a rod body and a hollow drill bit installed at the lower end of the rod body. The rod body is a double rod structure, comprising an inner tube and an outer tube sleeved on the outer side of the inner tube. The inner cavity of the inner tube is a water cavity, and a slurry cavity is formed between the inner tube and the outer tube. The inner tube, the outer tube and the hollow drill bit are coaxially arranged. Both the inner tube and the outer tube can be detachably installed on the hollow drill bit. A through-hole-shaped injection hole is arranged at the lower end of the hollow drill rod, and the injection hole passes through the outer peripheral surface of the hollow drill rod. The slurry cavity is connected to the injection hole, and the cement slurry in the slurry cavity can be sprayed outward through the injection hole. The water cavity is connected to the inner cavity of the hollow drill bit, and the inner cavity of the hollow drill bit passes downward through the lower end surface of the hollow drill bit.

8. The construction method according to claim 7, characterized in that: The hollow drill bit includes a ring body in the shape of an annulus, an inner tube and an outer tube extending axially upward are arranged on the upper side of the ring body, an upwardly open injection cavity is formed between the inner tube and the outer tube, the injection hole is arranged on the outer tube, the inner tube is screwed on the inner tube, and the outer tube is screwed on the outer tube.

9. The construction method according to claim 7, characterized in that: The outer wall of the outer tube does not extend beyond the outer wall of the hollow drill bit.

10. The construction method according to claim 7, characterized in that: The inner diameter of the inner tube is larger than the inner diameter of the hollow drill bit.

Images