An integrated construction technique for borehole wall reinforcement and drilling protection in soft formations

Abstract

This invention relates to an integrated construction process for borehole wall reinforcement and drilling protection in soft soil strata, comprising the following steps: S1, in soft and fractured strata, the soft soil layer is pre-compacted using a drill bit, and then the soft soil is cut by the auger blades of the drill bit while drilling a auger hole. Simultaneously, during the pilot hole drilling process, the auger blades are used to complete the hole repair during the hole retraction process; S2, the soft soil in the deformed and collapsed pile hole is re-compacted and cut using a drill bit, while simultaneously replacing the auger blades with larger diameter ones to complete hole enlargement and hole repair during the hole retraction process; S3, the borehole is backfilled layer by layer with well-graded crushed stone material and compacted, and then the hole is formed again using a drill bit; S4, after the drilling is completed, a high-strength steel-reinforced plastic pipe is lowered into the borehole. This invention solves the problems of poor borehole wall stability, high construction technical requirements, and high engineering construction costs in soft soil strata.

Description

Technical Field

[0001] This invention belongs to the field of drilling construction technology, and in particular relates to an integrated construction process for borehole wall reinforcement and drilling protection in soft strata. Background Technology

[0002] Due to the complex geological structure in coastal areas of my country, the borehole structure undergoes uneven deformation during drilling through special strata such as sandy soil, gravel, and silty soil. This results in severe borehole wall collapse and deformation, making drilling difficult and extremely detrimental to foundation reinforcement construction. Furthermore, the drilling fluid's scouring of the borehole wall or the impact and vibration of loose, soft soil layers further exacerbates settlement and deformation, affecting the safety of building foundations.

[0003] The main methods for reinforcing foundations in soft soil include soil replacement, pile foundation construction, and reinforcement. Soil replacement and reinforcement methods are generally complex, involve large amounts of work, have long construction periods, and are costly, and are typically not used except in special circumstances. Pile foundation construction, on the other hand, allows for flexible optimization of the pile foundation structure design based on factors such as the thickness of the soft soil layer, the bearing capacity requirements of the overlying structure, construction quality, and timeline. Therefore, pile foundation construction is frequently used for reinforcing foundations in soft soil. Successful pile foundation construction depends on successfully drilling holes in the soft soil and maintaining the stability of the borehole walls to facilitate the subsequent placement of precast concrete piles, steel piles, or reinforcing cages and the backfilling of concrete. For the unique geological structure of coastal areas, conventional drilling techniques and methods, such as rotary drilling, impact drilling, and manual drilling, still struggle to solve the engineering challenges posed by the soft and thick soil layers, the difficulty of drilling holes in gravel layers, and the long construction period. Meanwhile, in drilling operations in special formations such as soft sandy soil and gravel layers, although the use of drilling flushing fluid and steel casing has advantages in wall protection, it still has shortcomings such as high technical requirements for construction, difficulty in cost control, and low material reuse rate.

[0004] In conclusion, the selection of innovative drilling techniques and supporting equipment is of great significance for improving drilling stability and quality, reducing engineering construction costs, and increasing construction safety. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an integrated construction process for borehole wall reinforcement and drilling protection in soft soil strata, which aims to solve the problems of poor borehole wall stability, high construction technology requirements, and high engineering construction costs in soft soil strata.

[0006] The objective of this invention is achieved through the following technical solution: this integrated drilling and protection construction process for borehole wall reinforcement in soft formations includes the following steps:

[0007] S1. The soft and broken strata are squeezed by the drill bit in advance, and then the soft soil is cut by the auger blades of the drill bit and the hole is drilled in the auger. At the same time, the auger blades of the drill bit are used to complete the hole repair during the drilling process of the pilot hole.

[0008] S2, Secondary rapid hole repair: The drilling tool is used to compact and cut the loose soil in the deformed and collapsed pile hole again. At the same time, the larger diameter spiral blade is replaced to complete the hole enlargement and drilling repair, which prepares for the subsequent backfilling of the hole and secondary extrusion hole formation. At this time, steps S1 and S2 complete the first reinforcement of the soil in the hole wall.

[0009] S3. Backfilling and secondary extrusion drilling: Use crushed stone or gangue material with good particle size distribution to backfill and compact the drilling layer by layer, and use drilling tools to extrude the hole again to achieve the second reinforcement of the pile hole construction in the loose soil layer.

[0010] S4. After the drilling is completed, the high-strength steel-reinforced plastic pipe is lowered into the borehole after the secondary reinforcement is completed. Grouting is then injected into the annular space between the high-strength plastic pipe and the borehole wall to reinforce and protect the borehole, thereby achieving the third reinforcement of the borehole wall in the soft soil layer.

[0011] The beneficial effects of the present invention are as follows: Compared with the prior art, the above-mentioned integrated construction process of drilling and protection for soft soil strata has strong operability, high drilling strength, long service life of the borehole structure, low construction cost, and can avoid the engineering problem of sudden failure of drilling in soft soil strata.

[0012] Preferably, the drilling tool includes a central drill rod, an outer spiral hollow drill rod, and a three-wing pilot drill bit. The central drill rod is sleeved inside the outer spiral hollow drill rod, with one end of the central drill rod flush with one end of the outer spiral hollow drill rod, and the other end of the central drill rod extending beyond the other end of the outer spiral hollow drill rod. The outer circumferential wall of one end of the central drill rod is fixed to the inner circumferential wall of one end of the outer spiral hollow drill rod by a positioning component, and the outer circumferential wall of the other end of the central drill rod is fixed to the inner circumferential wall of one end of the three-wing pilot drill bit. The drill rods are connected and fixed between the walls by tapered thread, and adjacent central drill rods are connected and fixed by internal and external tapered threads. The central drill rod is connected to the active drill rod of the power head drill rig and is provided with drilling power by the power head drill rig. The central drill rod is built into the hollow drill rod of the outer spiral and fixed by the positioning component. The central drill rod is connected to the three-wing pilot drill bit and the adjacent central drill rod by tapered thread. Under the premise of meeting the construction requirements, it has the advantages of convenient disassembly and assembly, low construction cost and high construction efficiency.

[0013] Preferably, the positioning component includes a positioning block and a positioning groove. The positioning block is disposed on the outer circumferential wall of the central drill rod, and one end face of the positioning block is flush with the end face of one end of the central drill rod. The positioning groove is disposed on the inner circumferential wall of the outer spiral hollow drill rod, and one opening of the positioning groove communicates with the end face of one end of the outer spiral hollow drill rod. The central drill rod is inserted into the outer spiral hollow drill rod and fixed by the matching and limiting of the positioning block and the positioning groove. With the above structure, when the central drill rod and the outer spiral hollow drill rod are assembled, the positioning block and the positioning groove can effectively limit and fix the circumferential position, preventing the central drill rod and the outer spiral hollow drill rod from rotating relative to each other.

[0014] Preferably, three positioning blocks and three positioning slots are provided, and they are distributed at equal intervals along the circumferential wall of the central drill rod, with each positioning block and each positioning slot being distributed one-to-one. This distribution of positioning blocks and positioning slots makes the force more uniform and the stability during use better.

[0015] Preferably, the inner circumferential wall of one end of the central drill rod is provided with a first internal thread, and the outer circumferential wall of the other end of the central drill rod is provided with an external thread, and both the first internal thread and the external thread are tapered threads; the above structure makes disassembly and assembly more convenient, and the sealing performance and connection firmness are better.

[0016] Preferably, the external spiral hollow drill rod includes a hollow drill rod body and spiral blades. The spiral blades are welded to the outer peripheral wall of the hollow drill rod body, and the two ends of the spiral blades are flush with the two end faces of the hollow drill rod body. With the above structure, the upper and lower end faces of the spiral blades of adjacent external spiral hollow drill rods can fit together, resulting in better overall integrity.

[0017] Preferably, the three-wing pilot drill bit includes a drill bit body, a drill bit cone, and stepped blades. The drill bit cone is fixed to the bottom of the drill bit body. The top inner circumferential wall of the drill bit body is provided with a second internal thread for threaded connection with the central drill rod. The stepped blades are welded and fixed to the bottom outer circumferential wall of the drill bit body. The above structure facilitates drilling and can achieve the effects of positioning, squeezing, and compaction.

[0018] Preferably, the stepped blades are provided in three pieces and are evenly distributed along the circumferential wall of the drill bit base, and each stepped blade is provided with cutting toughness; it can quickly repair the borehole wall of the deformed and failed soft soil layer. Attached Figure Description

[0019] Figure 1 This is a construction flowchart of the present invention.

[0020] Figure 2 This is a plan view showing the construction effect of the present invention.

[0021] Figure 3 This is a schematic diagram of the drill bit structure of the present invention.

[0022] Figure 4 This is a schematic diagram of the central drill rod structure of the present invention.

[0023] Figure 5 This is a schematic diagram of the external spiral hollow drill rod structure of the present invention. Figure 1 .

[0024] Figure 6 This is a schematic diagram of the external spiral hollow drill rod structure of the present invention. Figure 2 .

[0025] Figure 7 This is a schematic diagram of the three-wing pilot drill bit structure of the present invention. Figure 1 .

[0026] Figure 8 This is a schematic diagram of the three-wing pilot drill bit structure of the present invention. Figure 2 .

[0027] The labels in the attached diagram are as follows: 1. Center drill pipe; 2. Outer spiral hollow drill pipe; 3. Three-wing pilot drill bit; 4. Connecting reference surface; 5. External thread; 6. Cutting toughness; 7. Positioning block; 8. First internal thread; 9. Hollow drill pipe body; 10. Spiral blade; 11. Positioning groove; 12. Second internal thread; 13. Stepped wing; 14. Drill bit cone; 15. Drill bit base; 16. Loose soil layer; 17. Crushed stone backfill layer; 18. Grouting reinforcement layer; 19. High-strength steel reinforcement layer. Detailed Implementation

[0028] The invention will now be described in detail with reference to the accompanying drawings: The construction process of the invention includes the following steps: as shown in the attached drawings. Figure 1 As shown,

[0029] S1. The soft and broken strata are compressed by the drilling tool in advance. The soft soil layer 16 is then cut by the auger blades 10 of the drilling tool and the hole is drilled in a spiral. At the same time, the auger blades 10 of the drilling tool are used to complete the hole repair during the drilling process of the pilot hole to improve the hole wall stability of the pilot hole.

[0030] S2. Secondary rapid hole repair: The drilling tool is used to compact and cut the soft soil in the deformed and collapsed pile hole again. At the same time, the larger diameter spiral blade 10 is replaced to complete the hole enlargement and drilling repair, which prepares for subsequent backfilling of the hole and secondary extrusion hole formation. At this time, steps S1 and S2 complete the first reinforcement of the hole wall soil.

[0031] S3. Backfilling and secondary extrusion drilling: Use crushed stone or gangue material with good particle size distribution to backfill and compact the drilling layer by layer, and use drilling tools to extrude the hole again to achieve the second reinforcement of the pile hole construction in the loose soil layer 16.

[0032] S4. After the drilling is completed, the high-strength steel-reinforced plastic pipe is lowered into the borehole after the secondary reinforcement is completed. Grouting is then injected into the annular space between the high-strength plastic pipe and the borehole wall to reinforce the borehole and achieve the third reinforcement of the borehole wall in the soft soil layer 16, so as to improve the overall strength and quality of the borehole and ultimately achieve integrated drilling and protection construction in the soft soil layer.

[0033] As attached Figure 2 As shown, the engineering plan view after construction of this invention mainly presents, from the outside to the inside, a soft soil layer 16, a crushed stone backfill layer 17, a grouting reinforcement layer 18, a high-strength steel reinforcement layer 19, and a reinforced central borehole. After the crushed stone backfill is completed, an impact extrusion drilling method is used to increase the density and stability of the crushed stone layer on the borehole wall. When lowering the high-strength steel reinforced plastic pipe, the verticality of the pipe should be maintained to avoid uneven extrusion damage to the pipe by the crushed stone layer. After the pipe is lowered, grout is injected layer by layer from bottom to top in the annular space between the pipe and the borehole wall, with the annular space thickness maintained at more than 5 cm, and the grouting layer is cured for at least 24 hours. The crushed stone backfill layer 17 is a layer of crushed stone or gangue material with good particle size distribution backfilled layer by layer, the grouting reinforcement layer 18 is the grout injected in the annular space between the high-strength plastic pipe and the borehole wall, and the high-strength steel reinforcement layer 19 is the high-strength steel reinforced plastic pipe.

[0034] As attached Figures 3 to 8As shown, the drilling tool includes a central drill pipe 1, an outer spiral hollow drill pipe 2, and a three-wing pilot drill bit 3. The central drill pipe 1 is a seamless cylindrical steel pipe, which is sleeved inside the outer spiral hollow drill pipe 2. One end of the central drill pipe 1 is flush with one end of the outer spiral hollow drill pipe 2, and the other end of the central drill pipe 1 extends beyond the other end of the outer spiral hollow drill pipe 2. The outer circumferential wall of one end of the central drill pipe 1 and the inner circumferential wall of one end of the outer spiral hollow drill pipe 2 are fixed by a positioning component. The positioning component can prevent the outer spiral drill pipe 2 from rotating radially along the central drill pipe 1. The outer circumferential wall of the other end of drill rod 1 is connected and fixed to the inner circumferential wall of one end of the three-wing pilot drill bit 3 by a tapered thread connection. Adjacent center drill rods 1 are also connected and fixed by internal and external tapered threads. After one drilling cycle is completed, center drill rod 1 is connected to a new center drill rod 1 and an outer spiral hollow drill rod 2. The interface formed after connection coincides with the connection reference surface 4, thus preventing the outer spiral blades of the upper and lower drill rods from overlapping. Center drill rod 1 is connected to the active drill rod of the power head drilling rig, and the power head drilling rig provides the drilling power. The outer spiral hollow drill rod 2 is the main cutting tool during construction, used for rapid cutting of soft soil layers and borehole repair. The outer spiral hollow drill rod 2 has various outer diameters and blade widths to suit drilling operations in different soft soil layers. During the initial hole formation process, the cone at the front end of the three-wing pilot drill bit 3 plays a role in pre-compression and guiding hole formation. Together with the outer spiral hollow drill rod 2, it cuts the soft soil layer in front to form a hole. After the pilot hole is backfilled, the hollow drill rod with spiral blades and the central drill rod work together to play the role of secondary hole repair and secondary compression hole formation.

[0035] The positioning assembly includes a positioning block 7 and a positioning groove 11. The positioning block 7 is disposed on the outer circumferential wall of the central drill rod 1, and one end face of the positioning block 7 is flush with the end face of one end of the central drill rod 1. The positioning groove 11 is disposed on the inner circumferential wall of the outer spiral hollow drill rod 2, and one opening of the positioning groove 11 is connected to the end face of one end of the outer spiral hollow drill rod 2. The central drill rod 1 is inserted into the outer spiral hollow drill rod 2 along the axial direction and fixed by the matching and limiting of the positioning block 7 and the positioning groove 11. There are three positioning blocks 7 and three positioning grooves 11, which are evenly distributed along the circumferential wall of the central drill rod 1, and each positioning block 7 and each positioning groove 11 are distributed in a one-to-one correspondence. The positioning block is 4mm thick and 20mm high, and cooperates with the positioning groove 11 in the outer spiral hollow drill rod 2 to achieve radial positioning and prevent the central drill rod 1 and the outer spiral hollow drill rod 2 from rotating relative to each other.

[0036] The inner circumferential wall of one end of the central drill rod 1 is provided with a first internal thread 8, and the outer circumferential wall of the other end of the central drill rod 1 is provided with an external thread 5. Both the first internal thread 8 and the external thread 5 are tapered threads; the taper is 0.5°, the thread pitch is 4mm, and the thread section length is 50mm.

[0037] The external spiral hollow drill rod 2 includes a hollow drill rod body 9 and spiral blades 10. The spiral blades 10 are welded to the outer circumferential wall of the hollow drill rod body 9, and both ends of the spiral blades 10 are flush with the end faces of the hollow drill rod body 9. The external spiral hollow drill rod 2 has standardized structural dimensions, allowing for selection of different specifications based on the borehole diameter. The spiral blades 10 have a thickness of 5mm-10mm, a height of 50mm-150mm, and a spiral pitch of 300mm. The entire external spiral hollow drill rod is axially limited and fixed by the threaded connection of the central drill rod 1 to prevent it from sliding axially along the central drill rod 1.

[0038] The three-wing pilot drill bit 3 includes a drill bit body 15, a drill bit cone 14, and stepped blades 13. The drill bit cone 14 is fixed to the bottom of the drill bit body 15. The inner circumferential wall of the top of the drill bit body 15 is provided with a second internal thread 12 for threaded connection with the central drill rod 1. The taper of the second internal thread 12 is 0.5°. The stepped blades 13 are welded and fixed to the outer circumferential wall of the bottom of the drill bit body 15. There are three stepped blades 13, which are evenly distributed along the circumferential wall of the drill bit body 15, and each stepped blade 13 is provided with a cutting bead 6. The drill bit cone 14 is a cone made of alloy steel, which has good heat resistance, wear resistance, and impact resistance for conventional soft soil layers or broken strata. It compresses and compacts the soil in front of the drill bit in advance during the pilot hole construction, thereby improving the working life of the three-wing pilot drill bit 3.

[0039] The assembly process of this drill bit is as follows: First, insert the center drill rod 1 into the outer spiral hollow drill rod 2, and connect it through the positioning block 7 and the positioning groove 11. The end of the center drill rod 1 with the external thread 5 extends out of the outer spiral hollow drill rod 2 and is screwed and fixed with the second internal thread 12 of the drill bit base 15. The lower end of the outer spiral hollow drill rod 2 abuts against the upper end of the drill bit base 15. Then, connect the new center drill rod 1 and the outer spiral hollow drill rod 2 through the positioning block 7 and the positioning groove 11. The end of the center drill rod 1 with the external thread 5 extends out of the outer spiral hollow drill rod 2 and is screwed and fixed with the first internal thread 8 of the old center drill rod 1. Adjacent outer spiral hollow drill rods 2 abut against each other. Finally, according to the actual required drill bit length, connect the first internal thread 8 of the last section of the center drill rod 1 to the active drill rod of the power head drill, and the active drill rod abuts against the last section of the outer spiral hollow drill rod 2.

[0040] This invention is not limited to the above-described embodiments. Any changes made to its shape or material composition, or any structural design using the methods provided by this invention, are considered variations of this invention and should be considered within the scope of protection of this invention.

Claims

1. A construction technique for integrating borehole wall reinforcement and drilling protection in soft formations, characterized in that: The construction process includes the following steps: S1. The soft and broken strata are squeezed by the drill bit (16) in advance, and then the soft soil is cut by the helical blade (10) of the drill bit and the hole is drilled by helical drilling. At the same time, the helical blade (10) of the drill bit is used to complete the hole repair during the pilot hole construction. S2, Secondary rapid hole repair: The drilling tool is used to compact and cut the soft soil in the deformed and collapsed pile hole again. At the same time, the larger diameter spiral blade (10) is replaced to complete the hole enlargement and drilling repair, which prepares for subsequent backfilling of the hole and secondary extrusion hole formation. At this time, steps S1 and S2 complete the first reinforcement of the hole wall soil. S3. Backfilling and secondary extrusion drilling: Use crushed stone or gangue material with good particle size distribution to backfill and compact the drilling layer by layer, and use drilling tools to extrude the hole again to achieve the second reinforcement of the pile hole construction in the soft soil layer (16). S4. After the drilling is completed, the high-strength steel plastic pipe is lowered and placed into the borehole after the secondary reinforcement is completed. Grouting is then injected into the annular space between the high-strength plastic pipe and the borehole wall to reinforce the hole and achieve the third reinforcement of the borehole wall in the soft soil layer (16).

2. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 1, characterized in that: The drilling tool includes a central drill rod (1), an outer spiral hollow drill rod (2), and a three-wing pilot drill bit (3). The central drill rod (1) is sleeved inside the outer spiral hollow drill rod (2), and one end of the central drill rod (1) is flush with one end of the outer spiral hollow drill rod (2). The other end of the central drill rod (1) extends out of the other end of the outer spiral hollow drill rod (2). The outer circumferential wall of one end of the central drill rod (1) is fixed to the inner circumferential wall of one end of the outer spiral hollow drill rod (2) by a positioning component. The outer circumferential wall of the other end of the central drill rod (1) is fixed to the inner circumferential wall of one end of the three-wing pilot drill bit (3) by a tapered thread connection. Adjacent central drill rods (1) are fixed to each other by an inner and outer tapered thread connection. The central drill rod (1) is connected to the active drill rod of the power head drilling machine and is provided with drilling power by the power head drilling machine.

3. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 2, characterized in that: The positioning component includes a positioning block (7) and a positioning groove (11). The positioning block (7) is disposed on the outer circumferential wall of the central drill rod (1), and one end face of the positioning block (7) is flush with the end face of one end of the central drill rod (1). The positioning groove (11) is disposed on the inner circumferential wall of the outer spiral hollow drill rod (2), and one opening of the positioning groove (11) is in communication with the end face of one end of the outer spiral hollow drill rod (2). The central drill rod (1) is inserted into the outer spiral hollow drill rod (2) and fixed by the adaptation and limiting of the positioning block (7) and the positioning groove (11).

4. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 3, characterized in that: There are three of each of the positioning blocks (7) and the positioning grooves (11), which are distributed at equal intervals along the circumferential wall of the central drill rod (1), and each positioning block (7) and each positioning groove (11) are distributed in a one-to-one correspondence.

5. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 2, characterized in that: The inner circumferential wall of one end of the central drill rod (1) is provided with a first internal thread (8), and the outer circumferential wall of the other end of the central drill rod (1) is provided with an external thread (5), and both the first internal thread (8) and the external thread (5) are tapered threads.

6. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 2, characterized in that: The external spiral hollow drill rod (2) includes a hollow drill rod body (9) and a spiral blade (10). The spiral blade (10) is welded to the outer peripheral wall of the hollow drill rod body (9), and the two ends of the spiral blade (10) are flush with the two end faces of the hollow drill rod body (9).

7. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 2, characterized in that: The three-wing pilot drill bit (3) includes a drill bit body (15), a drill bit cone (14), and a stepped wing (13). The drill bit cone (14) is fixed to the bottom of the drill bit body (15). The top inner circumferential wall of the drill bit body (15) is provided with a second internal thread (12) for threaded connection with the central drill rod (1). The stepped wing (13) is welded and fixed to the bottom outer circumferential wall of the drill bit body (15).

8. The integrated construction technology for borehole wall reinforcement and drilling protection in soft formations according to claim 7, characterized in that: The stepped blades (13) are provided in three and are distributed at equal intervals along the circumferential wall of the drill bit body (15), and each stepped blade (13) is provided with cutting toughness (6).

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