阅读说明：本技术 一种钻孔灌注桩用钻具结构 (Drilling tool structure for cast-in-situ bored pile ) 是由 付建军 李永丰 朱临瑞 白治军 王少华 陈安重 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种钻孔灌注桩用钻具结构,包括第一堵头,以及从上至下依次连接的中空钻杆、第一灌浆接头、转化接头、第二灌浆接头和钻头；第一灌浆接头上开设第一流道,转化接头上开设有第二流道,第二灌浆接头上开设有第三流道,钻头上开设有第四流道,中空钻杆、第一流道、第二流道、第三流道和第四流道依次连通以形成浆料输送通道,第一灌浆接头上设有连通第一流道和外界的第一出浆孔,第四流道与外界连通,第一堵头可沿浆料输送通道的上端进入第二流道中并关闭所述第二流道。本发明可在不提管的情况下,快捷方便地实现钻进过程中钻灌一体与提钻过程中高压旋喷灌浆的转换,适用于地基加固防渗的灌浆工程。(The invention discloses a drilling tool structure for a cast-in-situ bored pile, which comprises a first plug, a hollow drill rod, a first grouting joint, a conversion joint, a second grouting joint and a drill bit, wherein the hollow drill rod, the first grouting joint, the conversion joint, the second grouting joint and the drill bit are sequentially connected from top to bottom; the first grouting connector is provided with a first flow channel, the conversion connector is provided with a second flow channel, the second grouting connector is provided with a third flow channel, the drill bit is provided with a fourth flow channel, the hollow drill rod, the first flow channel, the second flow channel, the third flow channel and the fourth flow channel are sequentially communicated to form a slurry conveying channel, the first grouting connector is provided with a first slurry outlet hole communicated with the first flow channel and the outside, the fourth flow channel is communicated with the outside, and the first plug can enter the second flow channel along the upper end of the slurry conveying channel and close the second flow channel. The invention can quickly and conveniently realize the conversion of drilling and grouting integration in the drilling process and high-pressure rotary spraying grouting in the drilling process under the condition of not lifting the pipe, and is suitable for the grouting engineering of foundation reinforcement and seepage prevention.)

1. A drilling tool structure for a bored pile is characterized by comprising a first plug (6), and a hollow drill rod (1), a first grouting joint (2), a conversion joint (3), a second grouting joint (4) and a drill bit (5) which are sequentially connected from top to bottom; the grouting device is characterized in that a first flow channel (21) is formed in the first grouting connector (2), a second flow channel (31) is formed in the conversion connector (3), a third flow channel (43) is formed in the second grouting connector (4), a fourth flow channel (51) is formed in the drill bit (5), the hollow drill rod (1), the first flow channel (21), the second flow channel (31), the third flow channel (43) and the fourth flow channel (51) are sequentially communicated to form a slurry conveying channel, a first slurry outlet hole (23) for communicating the first flow channel (21) with the outside is formed in the first grouting connector (2), the fourth flow channel (51) is communicated with the outside, and the first plug (6) can enter the second flow channel (31) along the upper end of the slurry conveying channel and close the second flow channel (31).

2. The drilling tool structure for the bored pile according to claim 1, wherein a groove (22) is formed in a side wall of the first grouting joint (2), a first grout outlet (23) is formed in a bottom wall of the groove (22), a nozzle (7) is arranged on the first grouting joint (2), one end of the nozzle (7) is placed in the accommodating hole (23), and the other end of the nozzle (7) is placed in the groove (22).

3. A drill structure for a bored pile according to claim 2, wherein said nozzle (7) is fixed to said first grout joint (2) by means of a nut (8).

4. The drilling tool structure for the bored pile according to claim 1, wherein a sealing member (32) for closing the second flow passage (31) is provided on an inner wall of the second flow passage (31), a through hole (321) extending in an axial direction of the hollow drill rod (1) is provided on the sealing member (32), and the through hole (321) is engaged with the first plug (6).

5. A drill structure for a bored pile according to claim 1, wherein the second grout joint (4) is provided with a one-way structure (41) for automatically controlling one-way entry of hydrostatic slurry into the fourth flow passage (51).

6. The drilling tool structure for the bored pile according to claim 5, wherein the second grouting joint (4) comprises a casing (42) and the one-way structure (41), the casing (42) is connected to the conversion joint (3), an upper portion of the one-way structure (41) extends into an inner cavity of the casing (42) and is fixedly connected to the casing (42), a lower portion of the one-way structure (41) is connected to the drill (5), an upper flow passage (411) and a lower flow passage (412) are formed in the one-way structure (41), an upper end and a lower end of the upper flow passage (411) are sealed, an upper end of the lower flow passage (412) is sealed, a lower end of the lower flow passage (412) is communicated with the fourth flow passage (51), a first hole (413) and a first groove (414) are formed in an upper portion of a side wall of the one-way structure (41), and the first hole (413) and the first groove (414) are oppositely arranged, the first hole (413) is communicated with both the inner cavity of the sleeve (42) and the upper runner (411), the wall of the first groove (414) and the inner wall of the sleeve (42) are enclosed to form a branch runner (418), the bottom wall of the first groove (414) is provided with a second hole (415) communicated with the upper runner (411) and a third hole (416) communicated with the lower runner (412), the second hole (415) is positioned above the first hole (413), a second plug (417) is arranged in the upper runner (411), and the second plug (417) can move up and down under the pushing of static pressure slurry to enable the first hole (413) and the second hole (415) to be communicated or disconnected; the third flow channel (43) is formed when the inner cavity of the sleeve (42), the first hole (413), the upper flow channel (411), the second hole (415), the sub-flow channel (418) and the lower flow channel (412) are communicated.

7. The drilling tool structure for the bored pile according to claim 6, wherein a second groove (419) is formed in an upper portion of a side wall of the one-way structure (41), the second groove (419) extends to an upper end surface of the one-way structure (41) along an axial direction of the hollow drill rod (1), and the first hole (413) is formed in a bottom wall of the second groove (419).

8. A drill structure for a bored pile according to any one of claims 1 to 7, wherein said drill bit (5) includes a connecting portion (52) and a bit portion (53) provided at a lower end of the connecting portion (52), an upper end of the connecting portion (52) is connected to the second grout joint (4), a lower end of the bit portion (53) is provided with a plurality of cutting blades (531) and a plurality of drilling teeth (532), the plurality of cutting blades (531) and the plurality of drilling teeth (532) are circumferentially spaced around a central axis of the drill bit (5), and the plurality of drilling teeth (532) are provided in a space defined by the plurality of cutting blades (531); the fourth flow channel (51) is arranged in the connecting part (52), and a second slurry outlet hole (533) communicated with the fourth flow channel (51) is further formed in the bottom end face of the cutter head part (53).

9. The drilling tool structure for bored piles according to claim 8, wherein the second grout outlet (533) is provided in plurality, the plurality of second grout outlets (533) being circumferentially spaced around the central axis of the drill (5), the second grout outlets (533) being alternately arranged with the cutting blades (531).

Technical Field

The invention relates to the field of foundation reinforcement and seepage-proofing treatment grouting, in particular to a drilling tool structure for a cast-in-situ bored pile.

Background

With the progress of the human society and the improvement of the economic level, large-scale civil engineering construction is more and more, and the engineering construction faces more new challenges while improving the production and life of people. In engineering construction, foundation reinforcement and seepage prevention are common engineering problems and are also key problems in treatment by complex engineering technology and rich engineering experience.

The existing high-pressure jet grouting technology is a grouting technology widely used in foundation reinforcement and seepage prevention engineering in recent years, the traditional high-pressure jet grouting needs to firstly utilize an engineering drilling machine to form holes to a designed depth, and then the high-pressure jet grouting pipe is lowered to the hole bottom to start the high-pressure jet grouting from bottom to top, the actual construction operation process is complicated, the efficiency is low, the engineering requirements under various complex conditions are difficult to meet, 20% -30% of slurry return can be caused, and the environment protection and the resource saving are not facilitated.

CN110004932A discloses a high-pressure jet grouting system without slurry return, wherein, the drilling tool comprises: the double-pipe drilling and spraying fluid director, the drilling and spraying orifice sealer, the double-pipe piston drill rod and the double-pipe drilling and spraying machine are respectively provided with two slurry supply channels, so that an independent slurry supply channel for top-down impact extrusion drilling and grouting and bottom-up injection grouting is formed. The structural design idea is different from that of the invention, and the dual-channel arrangement results in complex drilling tool structure, difficult complete equipment improvement, low construction efficiency and poor operability.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a drilling tool structure for a bored pile, can quickly and conveniently realize the conversion of drilling and grouting integration in the drilling process and high-pressure jet grouting in the drilling process under the condition of not lifting a pipe, and is suitable for grouting engineering for foundation reinforcement and seepage prevention.

In order to solve the technical problems, the invention adopts the following technical scheme:

A drilling tool structure for a bored pile comprises a first plug, a hollow drill rod, a first grouting joint, a conversion joint, a second grouting joint and a drill bit, wherein the hollow drill rod, the first grouting joint, the conversion joint, the second grouting joint and the drill bit are sequentially connected from top to bottom; the grouting device comprises a first grouting joint, a conversion joint, a hollow drill rod, a first runner, a second runner, a third runner, a fourth runner, a first slurry outlet hole, a second slurry outlet hole, a third slurry outlet hole, a fourth runner, a third slurry outlet hole, a fourth slurry outlet hole, a third slurry outlet hole, a fourth slurry outlet hole, a third slurry outlet hole.

The principle that this structure realizes boring and irritates integrative and high pressure jet grouting conversion does: in the drilling process, static pressure slurry is output through a slurry conveying channel to reinforce the whole hole of a soft stratum, after the drilling and grouting are completed, a pipe does not need to be lifted, only a first plug is needed to be put into the conveying channel to plug a second flow channel, high-pressure rotary jet grouting is carried out in the drilling lifting process, a nozzle is installed in a first slurry outlet hole, high-pressure pulse slurry is sprayed out from the nozzle to impact and cut a soil body, so that the slurry and soil body particles form an effective solidified body.

Therefore, the drilling and grouting integrated low (static) pressure grouting method and the high-pressure pulsation rotary spraying grouting method are combined in time sequence and applied to foundation reinforcement and seepage-proofing engineering, so that the advantages of two grouting technologies are exerted, the respective defects are overcome, the maximum stratum application range and the optimal reinforcement and seepage-proofing effect are achieved, and the success rate and the safety of reinforcement and seepage-proofing are ensured.

Compared with the drilling tool disclosed in CN110004932A, the structure has only one conveying channel, the structure is simple, the complete equipment is easy to improve, the practical application operability is strong, and the construction efficiency is greatly improved.

As a further improvement of the above technical solution:

In order to realize that the first grouting joint is adopted for high-pressure pulsation rotary spraying grouting, a groove is formed in the side wall of the first grouting joint, a first grout outlet is formed in the bottom wall of the groove, a nozzle is arranged on the first grouting joint, one end of the nozzle is arranged in the containing hole, and the other end of the nozzle is arranged in the groove.

The structure can avoid the damage to the nozzle in the process of up-and-down movement of the drilling tool.

The nozzle is fixed with the first grouting joint through a nut.

In order to avoid the situation that the first plug is too large to cause the downward movement process to be blocked, a sealing piece for closing the second flow channel is arranged on the inner wall of the second flow channel, a through hole extending along the axial direction of the hollow drill rod is formed in the sealing piece, and the through hole is matched with the first plug.

The second grouting joint is provided with a one-way structure for automatically controlling the static pressure slurry to enter the fourth flow channel in a one-way mode, so that slurry return in the pipe is prevented.

As a specific structural form of the second grouting joint, the second grouting joint comprises a sleeve and the one-way structure, the sleeve is connected with the conversion joint, the upper part of the one-way structure extends into the inner cavity of the sleeve and is fixedly connected with the sleeve, the lower part of the one-way structure is connected with the drill bit, an upper flow passage and a lower flow passage are arranged in the one-way structure, the upper end and the lower end of the upper flow passage are both closed, the upper end of the lower flow passage is closed, the lower end of the lower flow passage is communicated with a fourth flow passage, a first hole and a first groove are arranged on the upper part of the side wall of the one-way structure, the first hole is communicated with the inner cavity of the sleeve and the upper flow passage, a branch flow passage is formed by enclosing the wall of the first groove and the inner wall of the sleeve, a second hole communicated with the upper flow passage and a third hole communicated with the lower flow passage are arranged on the bottom wall of the first groove, and the second hole is positioned above the, a second plug is arranged in the upper flow channel and can move up and down under the pushing of the static pressure slurry so as to enable the first hole and the second hole to be communicated or disconnected; and the third flow channel is formed when the inner cavity of the sleeve, the first hole, the upper flow channel, the second hole, the sub-flow channel and the lower flow channel are communicated.

During drilling, static pressure slurry flows into the upper flow channel from the first hole and pushes the second plug to move upwards, so that the first hole is communicated with the second hole, the static pressure slurry flows out through the third flow channel and the fourth flow channel, and the hole collapse can be effectively prevented by the effect of simultaneously performing mud wall protection on the penetration of surrounding soil bodies. If the slurry return phenomenon occurs, the returned slurry flows into the upper runner from the second hole and pushes the second plug to move downwards, so that the communication between the first hole and the second hole is disconnected, and the slurry return in the pipe is prevented.

The upper portion of the one-way structure side wall is provided with a second groove, the second groove extends to the upper end face of the one-way structure along the axis direction of the hollow drill rod, and the first hole is formed in the bottom wall of the second groove.

The drill bit comprises a connecting part and a cutter head part arranged at the lower end of the connecting part, the upper end of the connecting part is connected with the second grouting joint, the lower end of the cutter head part is provided with a plurality of cutting blades and a plurality of drill teeth, the cutting blades and the drill teeth are arranged around the central axis of the drill bit at intervals in the circumferential direction, and the drill teeth are arranged in a space formed by the cutting blades in a surrounding mode; the fourth runner is arranged in the connecting part, and a second slurry outlet communicated with the fourth runner is further formed in the bottom end face of the cutter head part.

And in the drilling process, the cutter head part destroys the soil body to drill and form a hole, and the cement stable slurry is discharged from the second slurry outlet hole under the action of low-pressure pulse, so that the function of drilling and grouting is realized.

The second grout outlet holes are provided with a plurality of second grout outlet holes which are arranged at intervals in the circumferential direction of the central axis of the drill bit, and the second grout outlet holes and the cutting blades are alternately arranged.

Compared with the prior art, the invention has the advantages that:

The invention can quickly and conveniently realize the super-energy conversion of drilling and grouting integration in the drilling process and high-pressure rotary jet grouting in the drill lifting process, can effectively control the grouting process without slurry return, has high efficiency, environmental protection and energy saving in the construction operation process, and is suitable for the grouting engineering of foundation reinforcement and seepage prevention.

Drawings

Fig. 1 is a sectional view showing a structure of a drilling tool for a bored pile according to an embodiment of the present invention.

Figure 2 is an isometric view of a first grout joint (with no nozzle installed).

Figure 3 is an isometric view of a first grout joint (nozzle installed).

Fig. 4 is a side view of a first grout joint.

Fig. 5 is a front view of a first grout joint.

Fig. 6 is a cross-sectional view of a first grout joint.

Fig. 7 is a top view of a first grout joint.

Fig. 8 is a cross-sectional view of the conversion sub (low pressure grouted state).

Fig. 9 is a cross-sectional view of a conversion joint (high pressure grouted state).

FIG. 10 is a top view of a conversion adapter.

Fig. 11 is a sectional view of a second grout joint.

3 fig. 3 12 3 is 3 a 3 sectional 3 view 3 taken 3 along 3 line 3 a 3- 3 a 3 of 3 fig. 3 11 3. 3

Fig. 13 is a sectional view taken along line B-B of fig. 11.

Fig. 14 is an isometric view of a cannula.

FIG. 15 is an isometric view of a drill bit.

Fig. 16 is a pictorial view of a core of a reinforcing pile formed by pouring in embodiment 1.

Fig. 17 is a pictorial view of a core of a reinforcing pile formed by pouring in embodiment 2.

Illustration of the drawings: 1. a hollow drill rod; 2. a first grout joint; 21. a first flow passage; 22. a groove; 23. a first slurry outlet; 3. converting the linker; 31. a second flow passage; 32. a seal member; 321. a through hole; 4. a second grout joint; 41. a unidirectional structure; 411. an upper flow passage; 412. a lower runner; 413. a first hole; 414. a first groove; 415. a second hole; 416. a third aperture; 417. A second plug; 418. a shunt channel; 419. a second groove; 42. a sleeve; 43. a third flow path; 5. a drill bit; 51. a fourth flow path; 52. a connecting portion; 53. a cutter head portion; 531. a cutting blade; 532. drilling teeth; 533. a second slurry outlet; 6. a first plug; 7. a nozzle; 8. and a nut.

Detailed Description

The invention is further described below with reference to specific preferred embodiments, without thereby limiting the scope of protection of the invention.

As shown in fig. 1, the drilling tool structure for a bored pile according to the present embodiment includes a hollow drill rod 1, a first grouting joint 2, a conversion joint 3, a second grouting joint 4, and a drill bit 5, which are sequentially connected from top to bottom. The second grouting joint 4 is used for low (static) pressure grouting in the drilling process, and the first grouting joint 2 is used for high pressure grouting in the drilling process.

The first grouting joint 2 is provided with a first flow passage 21, the conversion joint 3 is provided with a second flow passage 31, the second grouting joint 4 is provided with a third flow passage 43, the drill bit 5 is provided with a fourth flow passage 51, the hollow drill rod 1, the first flow passage 21, the second flow passage 31, the third flow passage 43 and the fourth flow passage 51 are sequentially communicated to form a slurry conveying passage, the first grouting joint 2 is provided with a nozzle 7 for communicating the first flow passage 21 with the outside, and the fourth flow passage 51 is communicated with the outside.

And, this drilling tool structure for bored concrete pile still includes first end cap 6, and first end cap 6 is preferably the steel ball, and the steel ball can be followed the upper end of thick liquids transfer passage and got into second flow channel 31 and closed second flow channel 31.

As shown in fig. 2 to 7, the first grouting joint 2 has both ends hollow and has threads on the outer circumference, and both ends are threadedly coupled to the hollow drill rod 1 and the conversion joint 3, respectively.

The middle part of the first grouting joint 2 is of a solid structure, the solid structure is provided with a through hole penetrating through the upper end surface and the lower end surface, and the through hole is communicated with the inner cavities at the upper end and the lower end to form a first flow passage 21.

A groove 22 is formed in the side wall of the solid structure, a first slurry outlet 23 communicated with the first flow channel 21 is formed in the bottom wall of the groove 22, one end of the nozzle 7 is arranged in the first slurry outlet 23, and the other end of the nozzle 7 is arranged in the groove 22. The nozzle 7 is fixed to the first grout joint 2 by a nut 8.

The nozzle 7 is fixed on the first grouting joint 2 through a nut and used as a grout outlet during high-pressure injection, grout can effectively impact and cut soil bodies through a high-pressure jet formed by the first grouting joint 2 under high pressure, the high pressure is 20-25 MPa, the nozzle material is titanium carbide nickel molybdenum alloy, the hardness of the nozzle material is up to HRA (high hardness of 90-95), the fineness Ra in the hole is 0.05-0.008 mu m, the inner diameter of the hole is 2-3 mm, the wall thickness of the nozzle material is 1-2 mm, the grout inlet surface in the first grouting joint 2 is a concave arc surface, the diameter of a grout outlet channel is half of the diameter of the first grouting joint 2, the length of a threaded pipe connected with the upper hollow drill rod 1 is 8-12 cm, and the length of a threaded pipe connected with the lower conversion joint 3 is 10-15 cm.

As shown in fig. 8 to 10, the conversion adapter 3 has both ends hollow and the inner circumference is provided with screw threads, and both ends are screw-coupled with the first grout adapter 2 and the second grout adapter 4, respectively.

The middle part of the conversion joint 3 is a solid structure to form a sealing element 32 for closing the second flow channel 31, the solid structure is provided with a through hole 321 penetrating through the upper end surface and the lower end surface of the solid structure, and the diameter of the lower part of the through hole 321 is smaller than that of the first choke plug 6. The through hole is of a funnel-shaped structure, so that the first plug 6 can be conveniently clamped in. When the low-pressure and high-pressure grouting function is converted, only the specially-made steel ball needs to be put into the grouting pipe, falls into the through hole 321 under the action of gravity, and seals the downward slurry outlet channel, so that the conversion of the low-pressure and high-pressure grouting function is realized.

Specifically, after the drilling and grouting are completed, when the low-pressure grouting is converted into the high-pressure grouting, the pipe does not need to be lifted, a joint is disassembled through a vertical shaft grouting pipe faucet of a drilling machine or a grouting pipe orifice, a steel ball with a special diameter is thrown into a slurry conveying channel of a drilling tool structure, the special steel ball falls into a through hole 321 of the conversion joint 3 under the action of gravity, a slurry outlet channel of the multifunctional drill bit is sealed in a one-way mode, slurry can be sprayed out from the first grouting joint only, and therefore the conversion of the low-pressure grouting function is achieved. Wherein the low-pressure grouting pressure is 1-3 MPa during drilling, and the high-pressure rotary jet grouting is 20-25 MPa during drilling.

The slurry inlet surface of the conversion joint 3 is a concave arc surface, the diameter of the specially-made steel ball is 15-20 mm, the diameter of the through hole 321 needs to be 2-3 mm larger than that of the specially-made steel ball, the diameter of the slurry outlet channel needs to be 5-8 mm smaller than that of the specially-made steel ball, the length of the part with the diameter larger than that of the steel ball is 2-3 cm, the length of the slurry outlet channel is 3cm, the length of a threaded pipe connected with the upper first grouting joint 2 is 10-15 cm, and the length of a threaded pipe connected with the lower second grouting joint 4 is 8-12 cm.

As shown in fig. 11-13, the second grouting joint 4 comprises a sleeve 42 and a unidirectional structure 41, and the unidirectional structure 41 can automatically control the hydrostatic slurry to enter the fourth runner 51 in a unidirectional manner.

As shown in fig. 14, the upper end of the sleeve 42 is provided with an external thread connected to the conversion adapter 3, and the lower end of the sleeve 42 is provided with an internal thread.

As shown in fig. 11, the upper portion of the one-way structure 41 extends into the inner cavity of the casing 42, the lower end of the upper portion of the one-way structure 41 is fixedly connected to the casing 42 through an external thread, the lower portion of the one-way structure 41 extends out of the casing 42 and is connected to the drill bit 5, and the lower end of the one-way structure 41 extends into the fourth flow passage 51 of the drill bit 5.

An upper flow passage 411 and a lower flow passage 412 are arranged in the one-way structure 41, the upper end and the lower end of the upper flow passage 411 are both closed, the upper end of the lower flow passage 412 is closed, the lower end of the lower flow passage 412 is communicated with the fourth flow passage 51, a first groove 414 and a second groove 419 are arranged on the upper portion of the side wall of the structure 41, the first groove 414 and the second groove 419 are oppositely arranged, the second groove 419 extends to the upper end face of the one-way structure 41 along the axial direction of the hollow drill rod 1, a first hole 413 is arranged on the bottom wall of the second groove 419, and the first hole 413 is communicated with the inner cavity of the sleeve 42 and the upper flow passage. A branch flow passage 418 is formed by the wall of the first groove 414 and the inner wall of the sleeve 42 in a surrounding manner, a second hole 415 communicated with the upper flow passage 411 and a third hole 416 communicated with the lower flow passage 412 are formed in the bottom wall of the first groove 414, the second hole 415 is positioned above the first hole 413, a second plug 417 is arranged in the upper flow passage 411, the second plug 417 is a movable steel ball, and the second plug 417 can move up and down under the pushing of the static pressure slurry to enable the first hole 413 and the second hole 415 to be communicated or disconnected; the third flow channel 43 is formed when the inner cavity of the sleeve 42, the first hole 413, the upper flow channel 411, the second hole 415, the branch flow channel 418 and the lower flow channel 412 are communicated.

During drilling, static pressure slurry flows into the upper flow channel from the first hole and pushes the second plug to move upwards, so that the first hole is communicated with the second hole, the static pressure slurry flows out through the third flow channel and the fourth flow channel, and the hole collapse can be effectively prevented by the effect of simultaneously performing mud wall protection on the penetration of surrounding soil bodies. If the slurry return phenomenon occurs, the returned slurry flows into the upper flow channel from the second hole, the second plug is pushed to move downwards, and the movable steel ball seals the channel due to gravity and slurry thrust, so that the slurry is prevented from flowing upwards, and the slurry return in the pipe is prevented. The length of the threaded pipe connected with the sleeve 42 and the upper conversion joint 3 is 8-12 cm, and the length of the threaded pipe connected with the one-way structure 41 and the lower multifunctional drill bit 5 is 6-10 cm.

Therefore, the one-way structure 41 can control the grout to only allow the grout to flow out from top to bottom but not allow the grout to flow out from bottom to top, and the grout return in the pipe can be prevented during low-pressure grouting.

As shown in fig. 15, the drill bit 5 includes a connecting portion 52 and a bit portion 53 disposed at a lower end of the connecting portion 52, an upper end of the connecting portion 52 is connected to the second grouting joint 4, a lower end of the bit portion 53 is provided with three cutting blades 531 and two drilling teeth 532, the three cutting blades 531 and the two drilling teeth 532 are all circumferentially spaced and uniformly distributed around a central axis of the drill bit 5, and the two drilling teeth 532 are disposed in a space surrounded by the three cutting blades 531.

The fourth flow passage 51 is opened in the connecting portion 52, and a second slurry outlet 533 communicating with the fourth flow passage 51 is opened on the bottom end surface of the cutter head portion 53. The number of the second slurry outlet holes 533 is three, a plurality of the second slurry outlet holes 533 are circumferentially arranged around the central axis of the drill 5 at intervals, and the second slurry outlet holes 533 are alternately arranged with the cutting blades 531.

The three cutting blades 531 destroy the soil body during downward drilling, and the three second grout outlet holes 533 are grout outlet holes during low-pressure grouting, so that the function of drilling while grouting is realized. The low pressure is 1-3 MPa, the diameter of a grout outlet is 8-12 mm, the length of a blade is 3-6 cm, the average thickness is 1.5cm, the length of a multifunctional drill is 10-15 cm, and the length of a threaded pipe connected with the upper second grouting joint 4 is 6-10 cm.