Multi-layer intermeshing mixing drill string with flow focusing mixing structure and method of construction

Abstract

This invention relates to the field of mixing drilling tools, specifically a multi-layer shear mixing drilling tool with a diversion and focusing mixing structure and its construction method. The mixing drilling tool includes an inner mixing assembly, an outer mixing assembly, an airflow pipe, a powder flow pipe, and a drill bit. The inner mixing assembly has a feeding channel. The airflow pipe and powder flow pipe are arranged side-by-side within the feeding channel. The drill bit is connected to the bottom of the inner mixing assembly, and a diversion connector is provided between the drill bit and the bottom of the inner mixing assembly. A focusing cavity is provided inside the drill bit. The focusing cavity communicates with the bottom of the feeding channel. Proximal nozzles and distal nozzles communicating with the focusing cavity are provided on the left and right sides of the drill bit. A focusing element is provided at the bottom of the focusing cavity. A focusing concave surface is provided on the top surface of the focusing element. The advantage of this invention is that the drilling tool has a focusing structure that allows the airflow and powder flow to be reflected after impacting the focusing concave surface. The secondary gasification formed after reflection improves the uniformity of the mixture and also enhances the spray radius and mixing uniformity of the powder jet mixing pile.

Description

Technical Field

[0001] This invention relates to the field of mixing drilling tools for powder jet grouting, and particularly to a multi-layer shear mixing drilling tool and construction method with a diversion and focusing mixing structure. Background Technology

[0002] In the field of foundation treatment in geotechnical engineering, when the stratum moisture content is high, jet grouting is superior to grouting. In recent years, with the development needs of national economic construction, the requirements for the length and diameter of mixing piles for foundation treatment have continued to increase. This has led to the problem that traditional technical equipment and construction methods are no longer suitable for the needs of modern construction development.

[0003] During construction, problems such as uneven spraying of powder jet grouting piles, incomplete mixing of the pile body, and pipeline blockage often occur, resulting in poor pile quality that fails to meet project construction requirements. Furthermore, frequent blockages in the material delivery pipelines cause delays in the construction period, seriously hindering the development and application of powder jet grouting pile technology. To address these problems, this invention proposes specific improvement measures and technical solutions. Summary of the Invention

[0004] The present invention addresses the technical problems of existing mixing drilling tools, such as frequent blockage of the feeding pipeline, short mixing spray radius, and poor mixing uniformity of powder jet grouting piles. It provides a multi-layer shear mixing drilling tool with a diversion and focusing mixing structure to reduce the blockage of the feeding pipeline, improve the uniformity of mixing spray, enhance the uniformity of the mixing pile body, achieve uniform mixing and continuous pile strength during powder jet grouting pile construction, and thus improve the pile formation quality and efficiency of powder jet grouting piles.

[0005] To achieve the objectives of this invention, the following technical solution is adopted:

[0006] A multi-layer shear mixing drill with a flow-guiding and focusing mixing structure includes an inner mixing assembly, an outer mixing assembly, an airflow pipe, a powder flow pipe, and a drill bit. The outer mixing assembly is rotatably connected to the outer peripheral wall of the inner mixing assembly. A feeding channel is provided inside the inner mixing assembly. The airflow pipe and the powder flow pipe are arranged side by side in the feeding channel. The drill bit is connected to the bottom of the inner mixing assembly, and a flow-guiding connector is provided between the drill bit and the bottom of the inner mixing assembly. A focusing cavity is provided inside the drill bit. The focusing cavity communicates with the bottom of the feeding channel. A proximal nozzle and a distal nozzle communicating with the focusing cavity are respectively provided on the left and right sides of the drill bit. A focusing element is provided at the bottom of the focusing cavity. The top surface of the focusing element has an upward-opening focusing concave surface. The focusing point of the focusing concave surface is located below the horizontal line of the proximal nozzle and the distal nozzle. This drilling tool, with its dual-pipe design, can independently and simultaneously transport gas flow and solid-gas two-phase flow, effectively reducing pipeline blockage. Furthermore, through the concave focusing structure inside the drill bit, the gas flow ejected from the gas flow pipe and the solid-gas two-phase flow ejected from the powder flow pipe are reflected after impacting the focusing concave surface of the focusing element. The two reflected fluids are then focused and mixed at the focal point. The vaporization of the focused mixture causes secondary vaporization of the powder solidifying agent, improving the uniformity of the mixture and enhancing the uniformity of the mixing pile body. This achieves uniformity of mixing and continuity of pile strength during powder jet grouting construction, thereby improving the pile formation quality and efficiency.

[0007] Preferably, the flow guide joint is provided with a first flow guide channel communicating with the airflow pipe, and a second flow guide channel communicating with the powder flow pipe; and the lower ends of both the first and second flow guide channels are flared. The flow guide joint and dual-pipe flow design effectively reduce pipe blockage. Simultaneously, the flared structure design adds power to the solid-gas two-phase flow ejected from the powder flow channel, increasing the ejection range and further reducing the risk of nozzle blockage.

[0008] Preferably, the focusing element is made of hard alloy or ceramic material; the drainage connector is also made of hard alloy or ceramic material. This further ensures the structural strength and service life of the focusing element and the drainage connector.

[0009] Preferably, the proximal nozzle is disposed on one side wall of the drill bit, and the distal nozzle is disposed on the opposite side wall of the drill bit via a nozzle guide, with the proximal and distal nozzles horizontally aligned. By simultaneously disposing of both the proximal and distal nozzles, the distal nozzle can meet the construction requirements of large-diameter powder jetting piles, thereby solving the problem of the limited spray radius of the proximal nozzle and further increasing the construction diameter of the powder jetting piles.

[0010] Preferably, the proximal nozzle and the distal nozzle are made of hard alloy material, which further ensures the structural strength and service life of the nozzle.

[0011] Preferably, the internal stirring assembly includes an upper connector for the internal stirring shaft, an internal stirring shaft, and internal stirring blades. The upper connector for the internal stirring shaft is located on the upper part of the internal stirring shaft, and the internal stirring blades are fixedly sleeved on the outer peripheral wall of the lower part of the internal stirring shaft. The lower end of the internal stirring shaft has a hexagonal shaft structure, and the upper end of the drill bit has a hexagonal sleeve structure. The internal stirring shaft and the drill bit are inserted and locked together by a pin. The structure of the internal stirring assembly facilitates better fixation and locking with the drill bit, which further improves the drilling effect of the drill bit, and also ensures the stability of the stirring action performed by the internal stirring blades.

[0012] Preferably, the external mixing assembly includes an outer pipe upper connector, an outer pipe shaft shoulder sleeve, an outer frame, an outer frame mixing blade, and a sliding sleeve. The outer pipe upper connector and the outer pipe shaft shoulder sleeve are rotatably sleeved on the inner mixing shaft, and the outer pipe upper connector is fixedly connected above the outer pipe shaft shoulder sleeve. A self-aligning roller bearing is provided between the inner cavity of the outer pipe shaft shoulder sleeve and the inner mixing shaft, and the lower part of the self-aligning roller bearing is supported by a bearing seat ring. The bearing seat ring and the sliding sleeve below are both limited by a limiting step on the inner mixing shaft. The inner side of the outer frame is fixedly connected to the outer frame mixing blade. The upper end of the outer frame is connected to the outer pipe shaft shoulder sleeve by bolts, and the lower end of the outer frame is connected to the sliding sleeve by bolts. The outer frame mixing blade is located inside the outer frame and is offset from the inner mixing blade, and they do not interfere with each other when rotating. By cooperating with the inner mixing assembly, multi-layer mutual shear mixing of the powder jet pile can be realized, further improving the mixing uniformity, mixing efficiency, and mixing quality.

[0013] Preferably, the drill bit has a stirring blade on its outer peripheral wall; cutting teeth are embedded at the front end of the drill bit; and a positioning cone is provided at the center of the tip of the drill bit. The cutting teeth can increase drilling capacity and drilling effect, while the positioning cone can drill into the strata first and play a limiting role, which can reduce the rotational vibration of the drill bit and effectively improve the verticality of the mixing pile construction.

[0014] Preferably, the airflow pipe is an independent channel for conveying airflow; the powder flow pipe is an independent channel for conveying solid-gas two-phase flow.

[0015] A construction method for a multi-layer shear mixing drill bit with a diversion and focusing mixing structure, comprising the following steps:

[0016] S1: Connect the top of the multi-layer shear mixing drill bit to the dual-channel swivel and suspend it at the front of the main mast of the multi-layer shear mixing pile drilling rig.

[0017] S2: Fix the solid-gas delivery pipe of the dual-channel faucet to the powder flow pipe, and fix the high-pressure air delivery pipe of the dual-channel faucet to the airflow pipe.

[0018] S3: Start the multi-layer shear mixing pile drilling machine, drive the multi-layer shear mixing drill bit to drill and rotate in both directions, and at the same time, transport the solid-gas mixture and high-pressure air to the bottom of the drill bit through the solid-gas channel of the powder flow pipe and the gas path channel of the air flow pipe.

[0019] S4: Under the action of high-pressure air jetting, the solid-gas mixture and high-pressure air are gathered in the focusing cavity by the focusing concave surface on the focusing part on the lower inner side of the drill bit. The solid-gas mixture is then sprayed into the powder jet mixing pile through the near-end nozzle and the far-end nozzle until the drill tip reaches the design elevation of the pile bottom.

[0020] S5: Continue to drive the multi-layer shear mixing drill bit to lift the drill bit and rotate it in both directions. At the same time, implement or stop the injection of solid-gas mixture into the mixing pile through the near-end nozzle and the far-end nozzle according to the design requirements until the drill tip is lifted to 0.5m above the designed top surface elevation of the mixing pile.

[0021] S6: End the construction of this powder jet grouting pile, move the drilling rig to the next pile position, and repeat the construction steps S3 to S5 above.

[0022] In summary, the advantages of this invention are that the airflow pipe and powder flow pipe of the multi-layer shear mixing drill bit with a diversion and focusing mixing structure have their own independent channels and are arranged side by side inside the inner mixing shaft. The gas ejected from the airflow channel has a diversion effect on the medium in the powder flow channel, which can effectively reduce pipeline blockage. At the same time, it provides additional power to the solid-gas two-phase flow ejected from the powder flow channel, which can reduce the risk of nozzle blockage. The concave focusing mechanism inside the drill bit can cause the gas flow ejected from the airflow channel and the solid-gas two-phase flow ejected from the powder flow channel to be reflected after impacting the focusing concave surface on the focusing element. The two reflected fluids are focused and mixed through the focal point, causing the powder solidifier to undergo secondary gasification, thereby improving the uniformity of the mixture. The positioning cone at the tip of the drill bit can drill into the formation first, which can play a limiting role, thereby reducing the rotational vibration of the drill bit and effectively improving the construction verticality of the mixing pile. The inner and outer mixing components rotate in opposite directions, which can improve the mixing uniformity, mixing efficiency and mixing quality of the powder jet mixing pile construction. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the multi-layer shear mixing drill of the present invention.

[0024] Figure 2 This is a cross-sectional view of the connector on the inner stirring shaft in this invention.

[0025] Figure 3 This is a planar schematic diagram of the connector on the inner stirring shaft in this invention.

[0026] Figure 4 This is a cross-sectional view of the drainage connector in this invention.

[0027] Figure 5 This is a schematic plan view of the drainage connector in this invention.

[0028] Figure 6 This is a cross-sectional view of the drill bit in this invention.

[0029] Figure 7 This is a schematic diagram illustrating the focusing principle of the concave mirror in this invention.

[0030] Figure 8 This is an enlarged view of region C in this invention.

[0031] The labels in the attached diagram are as follows:

[0032] 1. Feeding channel; 2. Airflow pipe; 3. Outer pipe upper connector; 4. Outer pipe shaft shoulder sleeve; 6. Inner stirring shaft upper connector; 10. Powder flow pipe; 11. Inner stirring shaft; 12. Self-aligning roller bearing; 14. Bearing seat ring; 16. Bolt; 17. Outer frame; 18. Outer frame stirring blade; 19. Inner stirring blade; 20. Sliding sleeve; 21. Pin shaft; 22. Drill bit; 221. Focusing chamber; 23. Drainage connector; 231. First drainage channel; 232. Second drainage channel; 24. Drill bit stirring blade; 25. Proximal nozzle; 26. Distal nozzle; 27. Focusing element; 271. Focusing concave surface; 28. Cutting teeth; 29. ​​Positioning top cone; Area B: Drill rod area of ​​the drill bit; Area C: Focusing mixing and gasification area; Area D: Drainage area. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 and Figure 2As shown, a multi-layer shear mixing drill with a flow-focusing mixing structure includes an inner mixing assembly, an outer mixing assembly, an airflow pipe 2, a powder flow pipe 10, and a drill bit 22. The outer mixing assembly is rotatably connected to the outer peripheral wall of the inner mixing assembly (located in area B). A feeding channel 1 is provided inside the inner mixing assembly. The airflow pipe 2 and the powder flow pipe 10 are arranged side by side in the feeding channel 1. The airflow pipe 2 is an independent channel for conveying airflow. The powder flow pipe 10 is an independent channel for conveying a two-phase flow of solid and gas. The drill bit 22 is connected to the bottom of the inner mixing assembly, and a focusing chamber 221 is provided inside the drill bit 22. The focusing chamber 221 communicates with the bottom of the feeding channel 1. A proximal nozzle 25 and a distal nozzle 26 communicating with the focusing chamber 221 are respectively provided on the left and right sides of the drill bit 22 (located in area D). A focusing element 27 is provided at the bottom of the focusing chamber 221 (located in area C). The focusing element 27 is made of hard alloy or ceramic material, further ensuring the structural strength and service life of the focusing element 27. The top surface of the focusing element 27 is provided with an upward-opening focusing concave surface 271; the focusing point of the focusing concave surface 271 (located in area C) is below the horizontal line of the near-end nozzle 25 and the far-end nozzle 26 (located in area D). This drill bit, through its dual-pipe design, can independently and simultaneously transport the gas flow and the solid-gas two-phase flow, effectively reducing pipeline blockage. Furthermore, through the concave focusing structure within the drill bit 22, the gas flow ejected from the airflow pipe 2 and the solid-gas two-phase flow ejected from the powder flow pipe 10 are reflected after impacting the focusing concave surface 271 of the focusing element 27. The two reflected fluids are then focused and mixed at the focal point. The focused mixture vaporizes, causing secondary vaporization of the powder solidifying agent, improving the uniformity of the mixture and enhancing the uniformity of the mixing pile body. This achieves uniform mixing and continuous pile strength during powder jet grouting construction, thereby improving the pile formation quality and efficiency. A flow guide joint 23 is provided between the drill bit 22 and the bottom of the internal mixing assembly. The flow guide joint 23 is made of hard alloy or ceramic material. This further ensures the structural strength and service life of the drainage connector 23. The drainage connector 23 is located within the focusing chamber 221; it has a first drainage channel 231 communicating with the airflow pipe 2, and a second drainage channel 232 communicating with the powder flow pipe 10; both the lower ends of the first and second drainage channels 231 and 232 are flared. The dual-pipe drainage design of the drainage connector 23 effectively reduces pipe blockage, and the flared structure provides additional power to the solid-gas two-phase flow ejected from the powder flow channel, increasing the injection radius and further reducing the risk of nozzle blockage.

[0035] As shown in the figure, the proximal nozzle 25 is mounted on one side wall of the drill bit 22, and the distal nozzle 26 is mounted on the opposite side wall of the drill bit 22 via a nozzle guide, with the proximal nozzle 25 and distal nozzle 26 horizontally aligned. By simultaneously mounting the proximal nozzle 25 and distal nozzle 26, the distal nozzle 26 can meet the construction requirements of large-diameter powder-jet piles, solving the problem of the limited spray radius of the proximal nozzle 25 and further increasing the spraying range. Both the proximal nozzle 25 and distal nozzle 26 are made of hard alloy material, further ensuring the structural strength and service life of the nozzles.

[0036] As shown in the figure, the internal mixing assembly includes an internal mixing shaft upper connector 6, an internal mixing shaft 11, and an internal mixing blade 19. The internal mixing shaft upper connector 6 is located on the upper part of the internal mixing shaft 11, and the internal mixing blade 19 is fixedly sleeved on the outer peripheral wall of the lower part of the internal mixing shaft 11. The lower end of the internal mixing shaft 11 has a hexagonal shaft structure, and the upper end of the drill bit 22 has a hexagonal sleeve structure. The internal mixing shaft 11 and the drill bit 22 are inserted and engaged, and locked together by a pin 21. The structure in the internal mixing assembly facilitates better fixation and locking with the drill bit 22, which further improves the drilling effect of the drill bit 22, and also ensures the stability of the mixing by the internal mixing blade 19.

[0037] As shown in the figure, the external stirring assembly includes an outer tube upper connector 3, an outer tube shaft shoulder sleeve 4, an outer frame 17, an outer frame stirring blade 18, and a sliding sleeve 20. The outer tube upper connector 3 and the outer tube shaft shoulder sleeve 4 are rotatably sleeved on the inner stirring shaft 11, and the outer tube upper connector 3 is fixedly connected above the outer tube shaft shoulder sleeve 4. A self-aligning roller bearing 12 is provided between the inner cavity of the outer tube shaft shoulder sleeve 4 and the inner stirring shaft 11. The lower part of the self-aligning roller bearing 12 is supported by a bearing seat ring 14. The bearing seat ring 14 and the lower sliding sleeve 20 are both limited by the limiting step on the inner stirring shaft 11. The inner side of the outer frame 17 is fixedly connected to the outer frame stirring blade 18. The upper end of the outer frame 17 is connected to the outer tube shaft shoulder sleeve 4 by bolts 16, and the lower end of the outer frame 17 is connected to the lower sliding sleeve 20 by bolts 16. The outer frame stirring blade 18 is located inside the outer frame 17 and is offset from the inner stirring blade 19 and does not interfere with each other when rotating. By combining the external and internal mixing components, multi-layer shear mixing can be implemented, further improving mixing uniformity, mixing efficiency, and mixing quality.

[0038] As shown in the figure, the drill bit 22 has a drill bit mixing blade 24 on its outer peripheral wall; cutting teeth 28 are embedded at the front end of the drill bit 22; and a positioning cone 29 is set at the center of the tip of the drill bit 22. The cutting teeth 28 increase drilling capacity and drilling effect, while the positioning cone 29 allows the drill bit to penetrate the strata first and acts as a limit, which can reduce the rotational vibration of the drill bit 22 and effectively improve the verticality of the construction mixing pile.

[0039] A construction method for a multi-layer shear mixing drill bit with a diversion and focusing mixing structure, comprising the following steps:

[0040] S1: Connect the top of the multi-layer shear mixing drill bit to the dual-channel swivel and suspend it at the front of the main mast of the multi-layer shear mixing pile drilling rig.

[0041] S2: Fix the solid-gas delivery pipe of the dual-channel faucet to the powder flow pipe 10, and fix the high-pressure air delivery pipe of the dual-channel faucet to the airflow pipe 2 (located in area B).

[0042] S3: Start the multi-layer shear mixing pile drilling machine, drive the multi-layer shear mixing drill bit to drill and rotate in both directions. At the same time, through the solid-gas channel of powder flow pipe 10 and the gas passage of air flow pipe 2, the solid-gas mixture and high-pressure air are transported to the bottom of drill bit 22 (in zone C).

[0043] S4: Under the action of high-pressure air jetting, the solid-gas mixture and high-pressure air are gathered in the focusing cavity 221 by the focusing concave surface 271 on the focusing part 27 at the lower inner side of the drill bit 22 (area C). The solid-gas mixture is then sprayed into the powder jet mixing pile through the near-end nozzle 25 and the far-end nozzle 26 until the drill tip reaches the design elevation of the pile bottom.

[0044] S5: Continue to drive the multi-layer shear mixing drill bit to lift the drill bit and rotate it in both directions. At the same time, implement or stop the injection of solid-gas mixture into the mixing pile through the near-end nozzle 25 and the far-end nozzle 26 (in zone D) according to the design requirements until the drill tip is lifted to 0.5m above the design top surface elevation of the mixing pile.

[0045] S6: End the construction of this powder jet grouting pile, move the drilling rig to the next pile position, and repeat the construction steps S3 to S5 above.

[0046] In summary, the advantages of this invention are that the drill bit has independent channels for the airflow pipe 2 and the powder flow pipe 10, which are arranged side-by-side inside the inner mixing shaft 11. The gas ejected from the lower end of the first drainage channel 231 in the drainage connector 23 has a drainage effect on the medium in the powder flow channel, which can effectively reduce pipeline blockage. At the same time, it provides additional power to the solid-gas two-phase flow ejected from the second drainage channel 232, which can reduce the risk of nozzle blockage. The concave focusing mechanism inside the drill bit 22 can cause the gas flow ejected from the airflow channel and the solid-gas two-phase flow ejected from the powder flow channel to be reflected after impacting the focusing concave surface 271 on the focusing member 27. The two reflected fluids are focused and mixed through the focal point, causing the powder solidifying agent to undergo secondary gasification, which improves the uniformity of the mixture. The positioning cone 29 at the tip of the drill bit 22 can drill into the formation first, which plays a limiting role, which can reduce the rotational vibration of the drill bit 22 and effectively improve the verticality of the construction mixing pile. The inner and outer mixing components rotate in opposite directions, which can improve the mixing uniformity, mixing efficiency and mixing quality of the mixing pile construction.

[0047] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A multi-layer shear-mixing drill bit with a diversion and focusing mixing structure, characterized in that, The system includes an inner stirring assembly, an outer stirring assembly, an airflow pipe (2), a powder flow pipe (10), and a drill bit (22). The outer stirring assembly is rotatably connected to the outer peripheral wall of the inner stirring assembly. A feeding channel (1) is provided inside the inner stirring assembly. The airflow pipe (2) and the powder flow pipe (10) are arranged side by side in the feeding channel (1). The drill bit (22) is connected to the bottom of the inner stirring assembly, and a flow guide joint (23) is provided between the drill bit (22) and the bottom of the inner stirring assembly. A focusing cavity is provided inside the drill bit (22). (221); The focusing cavity (221) is connected to the bottom of the feeding channel (1), and the drill bit (22) is provided with a near-end nozzle (25) and a far-end nozzle (26) connected to the focusing cavity (221) on its left and right sides respectively; a focusing element (27) is provided at the bottom of the focusing cavity (221); a focusing concave surface (271) with an upward opening is provided on the top surface of the focusing element (27); the focusing point of the focusing concave surface (271) is located below the horizontal line of the near-end nozzle (25) and the far-end nozzle (26); The internal stirring assembly includes an internal stirring shaft upper connector (6), an internal stirring shaft (11), and an internal stirring blade (19). The internal stirring shaft upper connector (6) is located on the upper part of the internal stirring shaft (11), and the internal stirring blade (19) is fixedly sleeved on the outer peripheral wall of the lower part of the internal stirring shaft (11). The lower end of the internal stirring shaft (11) is a hexagonal shaft structure, and the upper end of the drill bit (22) is a hexagonal sleeve structure. The internal stirring shaft (11) and the drill bit (22) are inserted and engaged, and locked together by a pin (21). The external stirring assembly includes an outer tube upper connector (3), an outer tube shaft shoulder sleeve (4), an outer frame (17), an outer frame stirring blade (18), and a sliding sleeve (20). The outer tube upper connector (3) and the outer tube shaft shoulder sleeve (4) are rotatably sleeved on the inner stirring shaft (11), and the outer tube upper connector (3) is fixedly connected above the outer tube shaft shoulder sleeve (4). A self-aligning roller bearing (12) is provided between the inner cavity of the outer tube shaft shoulder sleeve (4) and the inner stirring shaft (11). The lower part of the self-aligning roller bearing (12) is supported by a bearing seat ring (14). The bearing seat ring (14) and the lower sliding sleeve (20) are both limited by the limiting step on the inner stirring shaft (11). The inner side of the outer frame (17) is fixedly connected to the outer frame stirring blade (18). The upper end of the outer frame (17) is connected to the outer tube shaft shoulder sleeve (4) by bolts (16). The lower end of the outer frame (17) is connected to the sliding sleeve (20) by bolts (16). The outer frame stirring blade (18) is located inside the outer frame (17) and is offset from the inner stirring blade (19) and does not interfere with each other when rotating.

2. The multi-layer shear mixing drill bit with a diversion and focusing mixing structure according to claim 1, characterized in that, The drain connector (23) is provided with a first drain channel (231) that communicates with the airflow pipe (2), and the drain connector (23) is provided with a second drain channel (232) that communicates with the powder flow pipe (10); and the lower end of the first drain channel (231) and the lower end of the second drain channel (232) are both flared structures.

3. The multi-layer shear mixing drill bit with a diversion and focusing mixing structure according to claim 2, characterized in that, The focusing element (27) is made of hard alloy or ceramic material; the drainage connector (23) is made of hard alloy or ceramic material.

4. The multi-layer shear mixing drill bit with a diversion and focusing mixing structure according to claim 1, characterized in that, The proximal nozzle (25) is disposed on one side wall of the drill bit (22), and the distal nozzle (26) is disposed on the side wall of the drill bit (22) opposite to the proximal nozzle (25) through a nozzle guide, and the proximal nozzle (25) and the distal nozzle (26) are horizontally aligned.

5. The multi-layer shear-mixing drill bit with a diversion and focusing mixing structure according to claim 4, characterized in that, The proximal nozzle (25) and the distal nozzle (26) are made of hard alloy material.

6. The multi-layer shear mixing drill bit with a diversion and focusing mixing structure according to claim 1, characterized in that, The drill bit (22) has a drill bit stirring blade (24) on its outer peripheral wall; cutting teeth (28) are embedded at the front end; and a positioning cone (29) is provided at the center of the top part of the drill bit (22).

7. The multi-layer shear mixing drill bit with a diversion and focusing mixing structure according to claim 1, characterized in that, The airflow pipe (2) is an independent channel for conveying airflow; the powder flow pipe (10) is an independent two-phase flow channel for conveying solid gas.

8. A construction method for a multi-layer shear mixing drill bit with a diversion and focusing mixing structure, characterized in that, The multi-layer shear mixing drill bit with the diversion and focusing mixing structure described in any one of claims 1-7 includes the following steps: S1: Connect the top of the multi-layer shear mixing drill bit to the dual-channel swivel and suspend it at the front of the main mast of the multi-layer shear mixing pile drilling rig. S2: Fix the solid gas delivery pipe of the dual-channel faucet to the powder flow pipe (10), and fix the high-pressure air delivery pipe of the dual-channel faucet to the air flow pipe (2); S3: Start the multi-layer shear mixing pile drilling machine, drive the multi-layer shear mixing drill bit to drill and rotate in both directions, and at the same time, transport the solid-gas mixture and high-pressure air to the bottom of the drill bit (22) through the solid-gas channel of the powder flow pipe (10) and the gas path channel of the air flow pipe (2). S4: Under the action of high-pressure air jetting, the solid-gas mixture is gathered in the focusing cavity (221) by the focusing concave surface (271) on the focusing part (27) at the lower inner side of the drill bit (22). The solid-gas mixture is then sprayed into the multi-layer shear mixing pile through the near-end nozzle (25) and the far-end nozzle (26) until the drill tip reaches the design elevation of the pile bottom. S5: Continue to drive the multi-layer shear mixing drill bit to lift the drill bit and rotate it in both directions. At the same time, implement or stop the implementation of injecting solid-gas mixture into the mixing pile through the near-end nozzle (25) and far-end nozzle (26) according to the design requirements until the drill tip is lifted to 0.5m above the design top surface elevation of the mixing pile. S6: End the construction of this multi-layer shear mixing pile, move the drilling rig to the pile position of the next mixing pile, and repeat the construction steps S3 to S5 above.

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