Hollow drill rod suitable for reinforcing high-pressure jet expanded-head anchor rod

Abstract

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 comprises an inner pipe, a middle pipe and an outer pipe which are sequentially arranged together in a sleeved mode, an inner cavity of the inner pipe forms a slurry cavity, an air cavity is formed between the inner pipe and the middle pipe, and the outer pipe is connected with the inner pipe. A slurry cavity is formed between the middle pipe and the outer pipe; the inner pipe abuts against the inner wall of the center hole in a sealed mode, so that the water cavity is communicated with the center hole of the hollow drill bit. An injection cavity communicated with the air cavity and the slurry cavity is formed between the lower ends of the middle pipe and the outer pipe and the inner wall of the central hole; the hollow drill bit is provided with a jet hole communicated with the jet cavity, and cement paste and compressed air can be mixed in the jet cavity and then jetted outwards through the jet hole. According to the hollow drill rod, reinforcing parts such as the cement soil expansion head and the anchor rod wrapping body can be formed on the core rod, the reinforcing parts and an original structure are integrated, the construction cost can be reduced, and the connecting strength of the reinforcing parts and an existing high-pressure jet expansion head anchor rod can be improved.

Description

Technical Field

[0001] This utility model relates to a hollow drill rod suitable for reinforcing and strengthening anchor bolts with high-pressure jet enlargement heads. Background Technology

[0002] High-pressure jet grouting enlarged-head anchor bolts are anchor bolts that use high-pressure fluid to jet-cut and enlarge the soil at the bottom of the anchor hole along the designed length, followed by injection of cement grout or cement mortar to form a cylindrical grout body with a larger diameter. The People's Republic of China industry standard "Technical Specification for High-Pressure Jet-Jet Enlarged-Head Anchor Bolts" (JGJ / T282-2012) stipulates that the compressive strength of the grout body in the anchoring section should generally not be less than 20 MPa. High-pressure jet grouting enlarged-head anchor bolts are based on ordinary anchor bolts. The soil outside the anchor hole within a certain length at the bottom is enlarged and grouted using high-pressure jet grouting with water and cement grout or cement grout. Cement grout is then injected into the anchor hole to form a cylindrical cement-soil anchor body with a larger diameter. This process requires pre-forming a hollow hole before injecting pure cement grout or cement mortar. Construction in soft soil foundations, especially with inclined holes, is prone to hole collapse, resulting in insufficient bearing capacity of the anchor bolt and failure to meet design requirements. Therefore, when the bearing capacity of the high-pressure jet grouting head anchor is insufficient, it is usually necessary to add piles around the existing high-pressure jet grouting head anchor, abandoning the existing high-pressure jet grouting head anchor or using it together with the existing high-pressure jet grouting head anchor. However, this construction method may result in the subsequent high-pressure jet grouting head anchor not meeting the design requirements, and the addition of piles requires adjustments to the corresponding frame structure, increasing construction costs. Therefore, the best solution is to reinforce the existing high-pressure jet grouting head anchor. However, the current reinforcement method is generally to directly construct jet grouting piles on one side of the existing high-pressure jet grouting head anchor, using the later-constructed jet grouting piles to increase the frictional resistance. The positioning of the already constructed high-pressure jet grouting head anchor is difficult, and the new jet grouting piles cannot bond with the existing high-pressure jet grouting head anchor due to weak bonding strength. In order to distribute the force evenly, it is usually necessary to construct at least three jet grouting piles around the existing high-pressure jet grouting head anchor, which undoubtedly increases the amount of construction work and construction costs. Therefore, how to reinforce and strengthen the existing high-pressure jet grouting head anchor at low cost still has strong practical significance. Utility Model Content

[0003] To reduce the construction cost of reinforcement and improve the connection strength between the post-construction reinforcement and the existing high-pressure jet enlarged head anchor bolt, this application proposes a hollow drill rod suitable for reinforcement of high-pressure jet enlarged head anchor bolts. The hollow drill rod is a rotary jet drill rod, comprising a rod body and a hollow drill bit installed at the lower end of the rod body. The rod body has a triple-rod structure, comprising an inner tube, a middle tube, and an outer tube sequentially nested together. The middle tube is nested outside the inner tube, and the outer tube is nested outside the middle tube. The inner cavity of the inner tube forms a slurry cavity, and a gas cavity is formed between the inner tube and the middle tube, as well as between the middle tube and the outer tube. The hollow drill bit has a central hole extending axially, which axially penetrates both opposite ends of the hollow drill bit. The inner tube is sealed against the inner wall of the central hole, allowing the water cavity to connect to the central hole of the hollow drill bit. A jetting cavity is formed between the lower ends of the middle tube and the outer tube and the inner wall of the central hole, and both the gas cavity and the slurry cavity are connected to this jetting cavity.

[0004] A through-hole-shaped injection hole is provided on the hollow drill bit, which penetrates the outer circumference of the hollow drill bit. The injection chamber is connected to the injection hole. The cement slurry in the slurry chamber and the compressed air in the air chamber can form a gas-liquid mixture in the injection chamber and be ejected outward through the injection hole.

[0005] When using this hollow drill rod to reinforce and strengthen the high-pressure jet enlarged head anchor bolt, the steps are as follows:

[0006] (1) Rotate the hollow drill rod and drill into the ground along the axis of the high-pressure jet enlarged head anchor rod until the hollow drill bit of the hollow drill rod reaches the set depth; when the hollow drill rod drills into the ground, the hollow drill bit cuts the cement-soil shell of 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 inside 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 jet nozzle, and high-pressure water is sprayed out from the jet nozzle to impact the cement-soil shell; the hollow drill rod and the high-pressure jet enlarged head anchor rod are coaxially set;

[0007] (2) Rotate the hollow drill rod and spray cement slurry around the core rod to form a cement-soil enlarged head. The cement-soil enlarged head is located on the upper side of the stiffening enlarged head of the high-pressure jet enlarged head anchor rod, and the cement-soil enlarged head is wrapped around the core rod. After the construction of the cement-soil enlarged head is completed, rotate the hollow drill rod upward to form an anchor rod wrapping body on the upper side of the cement-soil enlarged head.

[0008] The hollow drill rod in this application is suitable for reinforcing and strengthening high-pressure jet-grooved anchor bolts that use a single precision-rolled threaded steel rod. Specifically, the stiffening enlarged head of the high-pressure jet-grooved anchor bolt can be a steel cage enlarged head or a bladder-type enlarged head.

[0009] Using the hollow drill rod of this application, a cement-soil enlarged head and an anchor bolt wrapping can be re-formed on the core rod. The cement-soil enlarged head and anchor bolt wrapping serve as a post-construction reinforcement, increasing the frictional resistance of the high-pressure jet grouting enlarged head anchor. Since the reinforcement is wrapped around the core rod, the post-construction reinforcement and the original structure of the high-pressure jet grouting enlarged head anchor can be integrated using the existing rod body, avoiding the problem of low bonding strength between the post-construction jet grouting pile and the original high-pressure jet grouting enlarged head anchor in existing technologies. Furthermore, the reinforcement is centered on the existing high-pressure jet grouting enlarged head anchor, eliminating eccentricity. Therefore, only a reinforcement of a predetermined size needs to be added based on the strength of the existing high-pressure jet grouting enlarged head anchor, allowing for one-time reinforcement of a single high-pressure jet grouting enlarged head anchor, improving construction efficiency and reducing costs. This avoids the problems of low construction efficiency and high costs associated with constructing multiple jet grouting piles around the existing high-pressure jet grouting enlarged head anchor, as is common in existing technologies.

[0010] To avoid damage to the hollow drill bit, the centering bracket, the sheath of the free section, and other accessories attached to the high-pressure jet enlarged head anchor are all made of plastic or rubber and other polymer materials. For example, the centering bracket can be made of plastic, and the sheath can be made of rubber or plastic.

[0011] Furthermore, to ensure that all pipes in the rod are subjected to uniform force, the inner pipe, middle pipe, outer pipe, and hollow drill bit are coaxially arranged.

[0012] Furthermore, to facilitate disassembly and replacement of different hollow drill bits, the hollow drill bits are screwed onto the outer wall of the outer tube using a threaded method.

[0013] Furthermore, a stepped portion is formed on the inner wall of the central hole. This stepped portion protrudes radially inward from the inner wall at the lower end of the central hole. The stepped portion has an upward-facing stepped surface, and the inner tube is sealed against this stepped surface. There is a distance between the lower ends of both the middle tube and the outer tube and the stepped surface to form a jet chamber. This structure allows the inner tube to communicate with the inner cavity of the hollow drill bit, while also enabling the cement slurry and compressed air to mix, thereby increasing the impact force of the cement slurry.

[0014] Furthermore, to facilitate positioning, a downward-recessed annular notch is provided on the inner edge of the stepped portion, into which the inner tube is inserted. The annular notch is used to position the inner tube, thereby ensuring the coaxiality of the inner tube and the hollow drill bit.

[0015] Furthermore, to reduce wear on the inner tube, the annular notch extends inward through the inner wall of the stepped portion, and the inner diameter of the inner tube is larger than that of the stepped portion. When the inner diameter of the inner tube is the same as that of the stepped portion, the wear on the inner wall of the inner tube is roughly the same as that on the inner wall of the stepped portion. However, as the hollow drill rod is drilled deeper into the ground, the length of the core rod entering the inner tube increases, and the narrow gap between the core rod and the inner tube may prevent high-pressure water from being ejected downwards. When the inner diameter of the inner tube is larger than that of the stepped portion, 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 high-pressure water. This design can reduce wear on the inner tube and improve its service life. Preferably, the inner diameter of the inner tube is 2-20 mm larger than the inner diameter of the stepped portion.

[0016] Specifically, to prevent the hollow drill rod from cutting into the rod body and causing damage during the downward drilling process, the inner diameter of the stepped part is 2-40mm larger than the outer diameter of the high-pressure jet enlarged head anchor rod.

[0017] Furthermore, a screwing part is provided on the outer circumference of the outer tube. Tools such as wrenches can be clamped on the screwing part to facilitate fixing the rod body and screwing the hollow drill bit onto the rod body. Attached Figure Description

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

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

[0020] Figure 3 This is a schematic diagram of the structure of a hollow drill bit.

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

[0022] Figure 5 This is a diagram showing the state of the anchor bolt after the high-pressure jet enlargement head has been reinforced. Detailed Implementation

[0023] The following describes the structure of the high-pressure jet enlarged head anchor bolt 30 reinforced using this application. Please refer to [link to relevant documentation]. Figure 4The 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 surrounding cement-soil blocks 37 together form a steel cage enlarged head. The rod body 31 extends upward 100 degrees above the ground along the axis of the high-pressure jet-enlarged head anchor rod, and a cement-soil shell 34 is formed around the rod body 31. Along the axial 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 normal anchoring section M, and a free section N from bottom to top. The steel cage enlarged head forms the enlarged head section S, and the enlarged head section S and the normal anchoring section M together form the anchoring section. The outer diameter of the normal anchoring section and the free section are the same. A plastic sleeve 33 is fitted 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, the rod body 31 is specifically made of precision-rolled threaded steel.

[0024] The following describes the structure of the hollow drill pipe; please refer to [link / reference]. Figure 1-Figure 3 The hollow drill rod is a rotary jet grouting drill rod, specifically comprising a rod body 10 and a hollow drill bit 20 installed at the end of the rod body 10. The rod body 10 has a triple rod structure, specifically comprising an inner tube 11, a middle tube 12, and an outer tube 13 sequentially nested together. The middle tube 12 is nested outside the inner tube 11, and the outer tube 13 is nested outside the middle tube 12. The inner cavity of the inner tube forms a water cavity 14, the space between the inner tube and the middle tube forms a slurry cavity 15, and the space between the middle tube and the outer tube forms a gas cavity 16. In this embodiment, the inner tube 11, the middle tube 12, and the outer tube 13 are all steel pipes. Connecting plates extending vertically are provided between the inner tube and the middle tube, and between the middle tube and the outer tube, to connect the inner tube 11, the middle tube 12, and the outer tube 13 into a single unit.

[0025] The hollow drill bit 20 includes a cylindrical body 21 with a central hole 26 extending axially in the center of the body. The central hole extends axially through both opposite ends of the body 21, that is, the central hole 26 extends axially through both opposite ends of the hollow drill bit.

[0026] A stepped portion 24 is formed on the inner wall of the central hole. The stepped portion 24 is formed by radially protruding inward from the inner wall of the lower end of the central hole. The stepped portion 24 has an upward-facing stepped surface 25. Teeth 23 are provided at the lower end of the body. The inner tube, middle tube, outer tube, and hollow drill bit are coaxially arranged.

[0027] The portion of the main body 21 extending upwards beyond the stepped section forms a connecting portion 27. An internal thread is provided on the inner circumferential surface of the connecting portion, and an external thread is provided on the outer circumferential surface of the bottom of the outer tube. The main body 21 is screwed onto the external thread of the outer tube via the aforementioned internal thread, and the inner tube is sealed against the stepped surface, i.e., the inner tube is sealed against the inner wall of the central hole, allowing the water cavity to connect to the central hole of the hollow drill bit. There is a distance between the lower ends of both the middle and outer tubes and the stepped surface, forming an annular injection chamber 18. That is, an injection chamber is formed between the lower ends of the middle and outer tubes and the inner wall of the central hole, and both the air cavity and the slurry cavity are connected to this injection chamber.

[0028] A through-hole-shaped injection hole 22 is provided on the body 21. In the height direction, the injection hole is located above the stepped portion and penetrates the outer peripheral surface of the body 21, that is, the injection hole penetrates the outer peripheral surface of the hollow drill bit. The injection chamber is connected to the injection hole. In this embodiment, the injection hole extends radially. The cement slurry in the slurry chamber and the compressed air in the air chamber can form a gas-liquid mixture in the injection chamber and be ejected outward through the injection hole.

[0029] When using a hollow drill bit to cut the cement-soil shell of a high-pressure jet-enlarged head anchor bolt, a core rod is formed. The rod body is located inside the core rod, and the hollow drill rod is sleeved on the core rod, creating a circular jet nozzle between the inner wall of the stepped hole and the core rod. A water cavity is connected to this jet nozzle, allowing high-pressure water inside the water cavity to be ejected downwards through the jet nozzle, impacting the cement-soil shell 34 to accelerate the cutting of the cement-soil shell and simultaneously cool the hollow drill bit. Under the impact of the high-pressure water, part of the cement-soil shell breaks, which is beneficial for subsequent cement slurry injection.

[0030] For ease of positioning, in this embodiment, a downwardly recessed annular notch 28 is provided on the inner edge of the stepped portion. This annular notch penetrates the inner wall of the stepped portion, and the inner tube is inserted into the annular notch. In this embodiment, the inner diameter of the inner tube is 4mm larger than the inner diameter of the stepped portion to reduce wear on the inner tube and to form a larger annular gap between the inner tube and the core rod to facilitate the passage of high-pressure water. It can be understood that in other embodiments, the inner diameter of the inner tube may also be 2mm, 6mm, 8mm, 10mm, 20mm larger than the inner diameter of the central hole, or other distances between 2 and 20mm.

[0031] To prevent the hollow drill rod from cutting into the rod body and causing damage during downward drilling, the inner diameter of the stepped section is 10mm larger than the outer diameter of the rod body. It is understood that in other embodiments, the inner diameter of the stepped section can also be 2mm, 5mm, 15mm, 25mm, 30mm, or 40mm larger than the outer diameter of the rod body, or other values ​​between 2 and 40mm. In actual construction, due to the existence of certain construction errors, it is recommended that the inner diameter of the stepped section be closer to the upper limit of the above-mentioned range.

[0032] To facilitate the installation of the hollow drill bit, in this embodiment, a screwing part 19 is provided on the outer circumferential surface of the outer tube. Specifically, the screwing part consists of two opposing tangential planes, on which tools such as wrenches can be clamped to facilitate screwing the hollow drill bit onto the outer tube. Of course, the screwing part can also be a regular hexagon or other polygon.

[0033] The following describes the construction method for reinforcing and strengthening high-pressure jet enlarged head anchors using the aforementioned hollow drill rods. Please refer to section 5. This construction method includes the following steps:

[0034] (1) Install the hollow drill rod on the jet grouting drill rig 40, rotate the hollow drill rod, and drill into the ground along the axial direction of the high-pressure jet enlarged head anchor rod until the hollow drill bit of the hollow drill rod reaches the upper end face of the reinforced cage enlarged head. When the hollow drill rod is drilled into the ground, the hollow drill bit cuts the cement-soil shell of the high-pressure jet enlarged head anchor rod and forms a core rod. The rod body 31 is located inside the core rod, and the core rod is inserted into the inner tube through the hollow drill bit 20. When the hollow drill rod is drilled into the ground, the hollow drill rod and the high-pressure jet enlarged head anchor rod are coaxially arranged.

[0035] As the hollow drill rod is drilled downwards, high-pressure water enters the water chamber 14 through the first external pipe 61 and is sprayed downwards through the nozzle to break up the cement-soil shell. At the same time, the high-pressure water cools the hollow drill bit. The pressure of the high-pressure water is controlled between 0.2 and 3.0 MPa.

[0036] (2) Cement slurry enters the slurry chamber 15 through the second external pipe 62, while compressed air enters the air chamber 16 through the third external pipe 63. The compressed air and cement slurry simultaneously enter the injection chamber 18, forming a gas-liquid mixture. This mixture is sprayed out through the injection hole 22 around the core rod, forming a cement-soil enlarged head 51 wrapped around the core rod. This cement-soil enlarged head is located above the reinforcing cage enlarged head of the high-pressure injection enlarged head anchor rod and is connected to the reinforcing cage enlarged head. During the construction of the cement-soil enlarged head, the hollow drill rod continues to rotate and move axially. The hollow drill rod can be reciprocated axially multiple times as needed to form the cement-soil enlarged head. The anchor rod wrapping and the cement-soil enlarged head are constructed continuously.

[0037] After completing the construction of the cement-soil enlarged head, continue to rotate and lift the hollow drill rod upwards, and simultaneously spray a gas-liquid mixture around the core rod to form an anchor rod wrapping body 52 of the cement-soil structure, which wraps around the core rod.

[0038] When constructing the cement-soil enlarged head, the pressure of the cement grout is 20-30 MPa; the pressure of the compressed air is 0.5-0.8 MPa. When constructing the anchor bolt wrapping, the pressure of the cement grout is 10-20 MPa, and the pressure of the compressed air is 0.5-0.8 MPa.

[0039] 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 bladder-type enlarged head.

Claims

1. A hollow drill rod suitable for reinforcing and strengthening anchor bolts with high-pressure jet enlargement heads, characterized in that, The hollow drill rod is a rotary jetting drill rod, comprising a rod body and a hollow drill bit installed at the lower end of the rod body. The rod body has a triple rod structure, comprising an inner tube, a middle tube, and an outer tube that are sequentially nested together. The middle tube is nested outside the inner tube, and the outer tube is nested outside the middle tube. The inner cavity of the inner tube forms a water cavity, the space between the inner tube and the middle tube forms a slurry cavity, and the space between the middle tube and the outer tube forms an air cavity. The hollow drill bit has a central hole extending axially, which axially penetrates both opposite ends of the hollow drill bit. The inner tube is sealed against the inner wall of the central hole, allowing the water cavity to communicate with the central hole of the hollow drill bit. A jetting cavity is formed between the lower ends of the middle tube and the outer tube and the inner wall of the central hole, and both the air cavity and the slurry cavity are connected to the jetting cavity. A through-hole-shaped injection hole is provided on the hollow drill bit, which penetrates the outer circumference of the hollow drill bit. The injection chamber is connected to the injection hole. The cement slurry in the slurry chamber and the compressed air in the air chamber can form a gas-liquid mixture in the injection chamber and be ejected outward through the injection hole.

2. The hollow drill rod according to claim 1, characterized in that, The inner tube, middle tube, outer tube, and hollow drill bit are coaxially arranged.

3. The hollow drill rod according to claim 1, characterized in that, The hollow drill bit is screwed onto the outer wall of the outer tube using a threaded method.

4. The hollow drill rod according to claim 1, characterized in that, A stepped portion is formed on the inner wall of the central hole. The stepped portion is formed by the inner wall of the lower end of the central hole protruding radially inward. The stepped portion has an upward-facing stepped surface. The inner tube is sealed against the stepped surface. There is a distance between the lower ends of the middle tube and the outer tube and the stepped surface to form a jet chamber.

5. The hollow drill rod according to claim 4, characterized in that, The inner edge of the stepped section has a downward-recessed annular notch into which the inner tube is inserted.

6. The hollow drill rod according to claim 5, characterized in that, The annular notch penetrates the inner wall of the stepped section, and the inner diameter of the inner tube is larger than the inner diameter of the stepped section.

7. The hollow drill rod according to claim 4, characterized in that, The inner diameter of the stepped section is 2-40mm larger than the outer diameter of the rod body of the high-pressure jet enlarged head anchor rod.

8. The hollow drill rod according to claim 1, characterized in that, A screwing part is provided on the outer circumferential surface of the outer tube.

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