Complex High-Strength Boulder Down-the-Hole Drilling and Weak Blasting Impact Drilling Method for Piles

Abstract

This invention relates to a method for constructing complex high-strength boulder pile foundations using down-the-hole drilling and weak blasting impact drilling, comprising the following specific steps: S1, platform replacement and steel casing pre-embedding; S2, installation of the pilot hole guide support and down-the-hole drilling; S3, placement of the settling device and installation of the PVC liner; S4, loading of explosives and deep-hole weak blasting; S5, impact drilling and cast-in-place pile construction. The method for constructing complex high-strength boulder pile foundations using down-the-hole drilling and weak blasting impact drilling involves high efficiency in the installation of prefabricated components, ensures construction quality, and effectively improves the drilling efficiency of cast-in-place piles in boulder strata. It offers numerous construction advantages such as high quality, high efficiency, and high economic benefits, resulting in significant technical benefits.

Description

Technical Field

[0001] This invention relates to a method for constructing complex high-strength boulder pile foundations using down-the-hole drilling and weak blasting impact drilling, belonging to the field of foundation engineering technology. It is applicable to the construction of bridge pile foundations using drilled cast-in-place piles, and is especially applicable to the construction of impact-drilled cast-in-place pile foundations where high-strength boulder strata exist within the pile foundation area. Background Technology

[0002] With rapid economic development and accelerated urbanization, various large-scale infrastructure projects such as highways, railways, bridges, and high-rise buildings are constantly emerging. In these projects, pile foundations, as a common and important foundation type, are widely used. However, in bridge construction areas in canyons and river valleys, unique boulder strata exist due to the long-term erosion and transportation by rivers. Because of the high rock strength, large surface boulders, tightly embedded rock layers, and random spatial distribution of these strata, bridge pile foundation construction under these conditions not only faces drilling difficulties and severe hammer wear, but also inevitably encounters problems such as borehole deviation, hammer jamming, and grout leakage.

[0003] While impact drills possess some breaking ability in boulder strata, they suffer from low drilling efficiency, rough hole walls, and a tendency to produce irregular, staggered holes. Furthermore, when encountering large-diameter or hard boulders, the impact energy may be insufficient to effectively break them, leading to slow construction progress. The "guided drilling combined with" cast-in-place pile drilling technology, developed based on impact drilling techniques, also faces challenges in field implementation, including low guide drilling positioning efficiency and difficulties in sinking the steel casing due to surface boulders. The quality and efficiency of cast-in-place pile drilling directly affect the quality and safety of the entire pile foundation project. In boulder strata, an inappropriate drilling process and compromised drilling quality can reduce the pile's bearing capacity, potentially leading to foundation settlement, structural cracking, and other safety hazards under long-term loads.

[0004] In view of this, to solve the problem of borehole quality for cast-in-place piles in complex, high-strength boulder strata, there is an urgent need to invent a construction method for complex, high-strength boulder pile foundations using down-the-hole drilling and weak blasting impact drilling, which guarantees construction quality, effectively improves pile advance efficiency, and offers significant economic and technical benefits. This will provide reliable technical support for bridge construction under complex geological conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a construction method for complex high-strength boulder down-the-hole drilling and weak blasting impact drilling pile foundations that ensures construction quality, effectively improves the drilling efficiency of cast-in-place piles in boulder strata, and has outstanding economic and technical benefits.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: a construction method for complex high-strength boulder down-the-hole drilling pilot hole weak blasting impact drilling pile foundation, comprising the following steps:

[0007] S1. Platform replacement and steel casing pre-embedding: Pre-embedding steel casing and auxiliary support, unfolding the extended base plate on the auxiliary support; using sand and gravel to backfill to form a sand and gravel backfill layer; embedding the auxiliary support and extended base plate into the sand and gravel backfill layer;

[0008] S2. Installation of the pilot hole guide support and drilling of the hole: Install the pilot hole guide support using the steel casing and its groove, check the verticality of the guide cylinder on the pilot hole guide support, then arrange the down-the-hole drill rig to be in place and fixed, guide and position the drill bit on the down-the-hole drill rig through the guide cylinder on the pilot hole guide support, and the down-the-hole drill rig evenly distributes holes in the circumference within the pile diameter range according to the position of the guide cylinder. The drill bit on the down-the-hole drill rig penetrates the boulder layer and drills down to the schist layer.

[0009] S3. Placement of the sinking device and installation of PVC liner: After drilling is completed, remove the down-the-hole drill and install the sinking device using the pre-installed pilot hole guide bracket. Use the hydraulic system of the sinking device and the positioning cylinder to assist in sinking the PVC liner. The PVC liner is constructed in circumferential order.

[0010] S4. Explosive loading and deep hole weak blasting: After the PVC liner is installed, the sinking device is removed, and the explosive detonator is lowered into the channel of the boulder layer through the PVC liner. The explosive detonator is connected to the detonating cord. After the detonating cord passes through the protective cover, the protective cover is installed at the upper end of the guide tube. Then, the hard rock in the boulder layer is pre-splitting blasted by explosive blasting.

[0011] S5. Impact drilling and cast-in-place pile construction: After blasting, clean the duct and backfill it with sand and gravel. Remove the pilot hole guide support, arrange for the impact drilling rig to enter the site, and use impact drilling to re-drill the pile foundation location. Then carry out the cast-in-place pile construction operation, and disconnect the connecting parts of the auxiliary support and the sliding groove on the steel casing. Remove the auxiliary support and finally remove the steel casing.

[0012] Preferably, in step S1, the outer surface of the steel casing is provided with grooves at equal intervals in the circumference, the grooves are arranged vertically, the bottom of the grooves is a cutting edge structure, and the top of the grooves is provided with reserved bolt holes.

[0013] Preferably, in step S1, the auxiliary support is connected and fixed to the reserved bolt holes at the top of the chute, and an extension base plate is symmetrically provided at the bottom of the auxiliary support through a hinge axis.

[0014] Preferably, in step S2, the guide bracket for the borehole includes a ring beam and a guide cylinder. The ring beam is set at the upper end of the steel casing, and the guide cylinder is set vertically at equal intervals on the inner wall of the ring beam. The outer wall of the guide cylinder abuts against the inner wall of the steel casing. The ring beam is provided with a base corresponding to the slide groove on the steel casing, and the base is fixedly connected to the reserved connection hole at the top of the slide groove by connecting bolts and nuts. The outer surface of the base is also provided with a reserved connection hole.

[0015] Preferably, the settling device includes a support, an annular slide, a fixed top plate, and a hydraulic system. The support is fixed to the base on the guide bracket of the pilot hole by a connecting screw. The supports are connected as a whole by the annular slide. A sliding rod is provided on the annular slide, and the sliding rod can slide along the annular slide. The sliding rod is connected to the fixed top plate, and a positioning cylinder is provided on the top surface of the fixed top plate. The hydraulic system includes a hydraulic lifting rod and a movable base plate. The hydraulic lifting rod is set on the bottom surface of the fixed top plate and is set in a vertical direction. The lower end of the hydraulic lifting rod is connected to the movable base plate. Both the fixed top plate and the movable base plate are provided with through holes with the same inner diameter as the positioning cylinder, and a clamping device is provided on the inner wall of the through hole on the movable base plate.

[0016] Preferably, in step S3, when performing the PVC liner compaction operation, the PVC liner is passed through the through holes on both the fixed top plate and the movable bottom plate simultaneously. The hydraulic lifting rod drives the movable bottom plate to move upward, and then the clamping device on the movable bottom plate clamps the PVC liner. Next, the hydraulic lifting rod drives the movable bottom plate to move downward and presses the PVC liner downward into the hole drilled by the down-the-hole drill. The above process is repeated until the current PVC liner is compacted into place. After the current PVC liner is compacted into place, the fixed top plate and the hydraulic system move along the annular slide to the next construction position, and the compaction operation of the next PVC liner is performed in the same manner.

[0017] Preferably, in step S4, the top of the guide cylinder is provided with a threaded opening, and the protective cover is installed on the threaded opening at the top of the guide cylinder.

[0018] The complex high-strength boulder down-the-hole drilled pilot hole weak blasting impact pile foundation was constructed using the same construction method.

[0019] This invention has the following characteristics and beneficial effects:

[0020] (1) The present invention developed a steel casing pre-embedded sand filling pre-replacement technology. By replacing the crushed stone surface layer with sand and gravel backfill layer and pre-embedding the steel casing, and synchronously backfilling sand and gravel inside the casing, the reverse process not only provides a high-quality foundation platform for subsequent drilling rig construction, but also saves the steel casing burying time. In addition, the stability of the steel casing is guaranteed by the auxiliary support, which improves the efficiency of on-site operation.

[0021] (2) This invention has developed a circumferential precision positioning drilling pilot hole technology for down-the-hole drilling. By setting a pilot hole guide support on the steel casing foundation, the "pilot drilling combined" process is realized efficiently and accurately. Compared with the traditional down-the-hole drilling construction positioning speed, the hole quality is more stable.

[0022] (3) The present invention developed a deep hole blasting technology for assisted sinking of PVC liner. A sinking device is established by using a pre-hole guide support to assist sinking of PVC liner to achieve precise micro blasting of deep holes, which reduces the overall strength of the rock and improves the drilling efficiency of impact drills in boulder strata. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the steel casing structure in this invention;

[0024] Figure 2 This is an elevation view of the steel casing auxiliary support installation in this invention;

[0025] Figure 3 This is a top view of the installation of the steel casing auxiliary support in this invention;

[0026] Figure 4 This is a schematic diagram of the installation of the guide bracket for the pilot hole in this invention;

[0027] Figure 5 yes Figure 4 Cross-sectional view of the middle section (BB);

[0028] Figure 6 yes Figure 4 Sectional view of AA in the middle;

[0029] Figure 7 This is a schematic diagram of the installation of the auxiliary PVC pipe for pressure settling in this invention;

[0030] Figure 8 yes Figure 7 Detailed drawing of point A in the middle;

[0031] Figure 9 This is a top view of the settling device in this invention;

[0032] Figure 10 This is a horizontal sectional view of the through hole;

[0033] Figure 11 This is a schematic diagram of the deep-hole blasting structure in this invention;

[0034] Figure 12 This is a schematic diagram of the pile formation structure in this invention.

[0035] In the diagram: 1-Steel casing; 2-Slide groove; 3-Pre-reserved bolt hole; 4-Pre-reserved connection hole; 5-Auxiliary support; 6-Extended base plate; 7-Hinge shaft; 8-Boulder layer; 9-Sand and gravel backfill layer; 10-Guide cylinder; 11-Ring beam; 12-Down-the-hole drill; 13-Nut; 14-Connecting bolt; 15-Base; 16-Crushed stone surface layer; 17-PVC liner; 18-Support; 19-Connecting screw; 20-Annular slide; 21-Slide rod; 22-Positioning cylinder; 23-Fixed top plate; 24-Hydraulic lifting rod; 25-Modible base plate; 26-Drain; 27-Symplocity layer; 28-Explosive detonator; 29-Protective cap; 30-Detonating cord; 31-Cast pile; 32-Through hole; 33-Clamping device. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0037] like Figures 1 to 12 As shown, the construction method for this complex high-strength boulder down-the-hole drilling pilot hole weak blasting impact pile foundation includes the following steps:

[0038] S1. Platform replacement and steel casing pre-embedding: Large boulders on the surface are removed by blasting. Excavators are used to remove the blasted boulders and surface debris from the site. Steel casing 1 and its auxiliary support 5 are pre-embedded, and the extended base plate 6 on the auxiliary support 5 is deployed. Sand and gravel are used for backfilling to form a sand and gravel backfill layer 9, which serves as the drilling platform. After leveling and compacting, the pile positions are revealed.

[0039] Furthermore, such as Figure 1 As shown, the outer surface of the steel casing 1 is provided with circumferentially spaced grooves 2. The grooves 2 are arranged vertically, the bottom of the grooves 2 is a cutting edge structure, and the top of the grooves 2 is provided with reserved bolt holes 3.

[0040] Furthermore, such as Figure 2 , Figure 3 As shown, the auxiliary support 5 is connected and fixed to the pre-reserved bolt holes 3 at the top of the chute 2, and an extended base plate 6 is symmetrically arranged at the bottom of the auxiliary support 5 through a hinge shaft 7. The auxiliary support 5 and the extended base plate 6 are embedded in the sand and gravel backfill layer 9.

[0041] S2. Installation of the pilot hole guide bracket and drilling of the hole: Install the pilot hole guide bracket using the steel casing 1 and its sliding groove 2. Check the verticality of the guide cylinder 10 on the pilot hole guide bracket. After the check is qualified, arrange the down-the-hole drill rig 12 to be in place and fix the down-the-hole drill rig 12. Guide and position the drill bit on the down-the-hole drill rig 12 through the guide cylinder 10. The down-the-hole drill rig evenly distributes holes in the circumference within the pile diameter range according to the position of the guide cylinder 10. The drill bit on the down-the-hole drill rig 12 penetrates the boulder layer 8 and drills to the schist layer 27, forming the free surface of the boulder layer 8.

[0042] Furthermore, such as Figure 4 , Figure 5 , Figure 6 As shown, the guide bracket for the pilot hole includes a ring beam 11 and a guide cylinder 10. The ring beam 11 is set at the upper end of the steel casing 1. The guide cylinders 10 are vertically and equally spaced on the inner wall of the ring beam 11. The outer wall of the guide cylinder 10 abuts against the inner wall of the steel casing 1. The ring beam 11 is provided with a base 15 corresponding to the slide groove 2 on the steel casing 1. The base 15 is fixedly connected to the reserved connection hole 4 at the top of the slide groove 2 by connecting bolts 14 and nuts 13. The outer surface of the base 15 is also provided with a connection hole.

[0043] S3. Placement of the sinking device and installation of PVC liner 17: After drilling is completed, remove the down-the-hole drill rig 12 and install the sinking device using the pre-installed pilot hole guide bracket. Use the hydraulic system of the sinking device and the positioning cylinder 22 to assist in sinking the PVC liner 17. The PVC liner 17 is constructed circumferentially in sequence. The position of the hydraulic system on the sinking device is synchronously changed along the annular slide 20 with the construction position of the PVC liner 17.

[0044] Furthermore, such as Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the settling device includes a support 18, an annular slide 20, a fixed top plate 23, and a hydraulic system. The support 18 is fixed to the base 15 on the guide bracket of the pilot hole by a connecting screw 19. The supports 18 are connected as a whole by the annular slide 20. A slide rod 21 is provided on the annular slide 20, and the slide rod 21 can slide along the annular slide 20. The slide rod 21 is connected to the fixed top plate 23, and a positioning cylinder 22 is provided on the top surface of the fixed top plate 23. The hydraulic system includes a hydraulic lifting rod 24 and a movable base plate 25. The hydraulic lifting rod 24 is provided on the bottom surface of the fixed top plate 23 and is arranged in a vertical direction. The lower end of the hydraulic lifting rod 24 is connected to the movable base plate 25. Both the fixed top plate 23 and the movable base plate 25 are provided with through holes 32 with the same inner diameter as the positioning cylinder 22, and the inner wall of the through hole 32 on the movable base plate 25 is provided with a clamping device 33.

[0045] During the PVC liner 17 installation, the PVC liner 17 is simultaneously passed through the through holes 32 on both the fixed top plate 23 and the movable bottom plate 25. The hydraulic lifting rod 24 drives the movable bottom plate 25 upward, and then the clamping device 33 on the movable bottom plate 25 clamps the PVC liner 17. Next, the hydraulic lifting rod 24 drives the movable bottom plate 25 downward and presses the PVC liner 17 into the hole drilled by the down-the-hole drill 12. This process is repeated until the current PVC liner 17 is installed in place. After the current PVC liner 17 is installed in place, the fixed top plate 23 and the hydraulic system move along the annular slide 20 to the next construction position, and the next PVC liner 17 installation is performed in the same manner. After the PVC liner 17 is installed, the top end of the PVC liner 17 is flush with the bottom end of the guide cylinder 10.

[0046] S4. Explosive loading and deep-hole weak blasting: After the PVC liner 17 is installed, the sinking device is removed, and the explosive detonator 28 is lowered through the PVC liner 17 into the channel 26 of the boulder layer 8. The explosive detonator 28 is connected to the detonating cord 30. After the detonating cord 30 passes through the protective cover 29, the protective cover 29 is installed at the upper end of the guide tube 10. Then, the hard rock in the boulder layer 8 is pre-splitting blasted by explosive blasting.

[0047] Furthermore, such as Figure 11 As shown, the top of the guide cylinder 10 is provided with a threaded opening, through which a protective cover 29 is installed. The protective cover 29 is installed on the threaded opening at the top of the guide cylinder 10, and a detonating tube through hole is provided in the center of the protective cover 29.

[0048] S5. Impact drilling and construction of cast-in-place pile 31: After the blasting is completed, the duct 26 is cleaned and backfilled with sand and gravel. The guide support for the pilot hole is removed, and the impact drilling rig is brought in and positioned. The impact drilling is used to re-drill the pile foundation location, and then the construction of cast-in-place pile 31 is carried out. The connection between the auxiliary support 5 and the sliding groove 2 on the steel casing 1 is removed, the auxiliary support 5 is removed, and finally the steel casing 1 is removed.

[0049] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A construction method for complex high-strength boulder down-the-hole drilling pilot hole weak blasting impact drilling bored pile foundation, characterized in that, Includes the following steps: S1, Platform replacement and steel casing pre-embedding: Pre-embedding steel casing (1) and auxiliary support (5), unfolding the extended base plate (6) on the auxiliary support (5); using sand and gravel to backfill to form a sand and gravel backfill layer (9); the auxiliary support (5) and the extended base plate (6) are embedded in the sand and gravel backfill layer (9); the outer surface of the steel casing (1) is provided with circumferentially spaced grooves (2), the grooves (2) are set along the vertical direction, the bottom of the grooves (2) is a cutting foot structure, and the top of the grooves (2) is provided with reserved bolt holes (3); S2. Installation of the pilot hole guide bracket and down-the-hole drilling: The pilot hole guide bracket is installed using the steel casing (1) and its groove (2). The pilot hole guide bracket includes a ring beam (11) and a guide cylinder (10). The ring beam (11) is set at the upper end of the steel casing (1). The guide cylinders (10) are vertically and evenly spaced on the inner wall of the ring beam (11). The outer wall of the guide cylinder (10) abuts against the inner wall of the steel casing (1). The ring beam (11) is provided with a base (15) corresponding to the groove (2) on the steel casing (1), and the base (15) is connected by a connecting... The bolts (14) and nuts (13) are fixedly connected to the reserved connection holes (4) at the top of the groove (2); the verticality of the guide cylinder (10) on the pilot hole guide bracket is checked, and then the down-the-hole drill (12) is positioned and fixed. The drill bit on the down-the-hole drill (12) is guided and positioned by the guide cylinder (10) on the pilot hole guide bracket. The down-the-hole drill is evenly distributed in the circumference within the pile diameter range according to the position of the guide cylinder (10). The drill bit on the down-the-hole drill (12) penetrates the boulder layer (8) and drills to the schist layer (27). S3. Placement of the sinking device and installation of the PVC liner (17): After drilling is completed, remove the down-the-hole drill (12), and install the sinking device using the installed pilot hole guide bracket. Use the hydraulic system and positioning cylinder (22) of the sinking device to assist in sinking the PVC liner (17). The PVC liner (17) is constructed circumferentially. The sinking device includes a support (18), an annular slide (20), a fixed top plate (23), and a hydraulic system. The support (18) is fixed to the base (15) on the pilot hole guide bracket by a connecting screw (19). (18) are connected as a whole by an annular slide (20). A slide rod (21) is provided on the annular slide (20). The slide rod (21) can slide along the annular slide (20). The slide rod (21) is connected to the fixed top plate (23). A positioning cylinder (22) is provided on the top surface of the fixed top plate (23). The hydraulic system includes a hydraulic lifting rod (24) and a movable base plate (25). The hydraulic lifting rod (24) is provided on the bottom surface of the fixed top plate (23). The hydraulic lifting rod (24) is set in the vertical direction. The lower end of the hydraulic lifting rod (24) is connected to The movable base plate (25), the fixed top plate (23), and the movable base plate (25) are all provided with through holes (32) with the same inner diameter as the positioning cylinder (22), and the through holes (32) on the movable base plate (25) are provided with clamping devices (33) on their inner walls; when the PVC liner (17) is being pressed down, the PVC liner (17) is passed through the through holes (32) on both the fixed top plate (23) and the movable base plate (25) at the same time, and the hydraulic lifting rod (24) drives the movable base plate (25) to move upward, and then the movable base plate (25) The clamping device (33) clamps the PVC liner (17), and then the hydraulic lifting rod (24) drives the movable base plate (25) to move downward and press the PVC liner (17) into the hole drilled by the down-the-hole drill (12); repeat the above process until the current PVC liner (17) is pressed into place; after the current PVC liner (17) is pressed into place, the fixed top plate (23) and the hydraulic system move along the annular slide (20) to the next construction position, and the pressing operation of the next PVC liner (17) is carried out in the same way; S4. Explosive loading, deep-hole weak blasting; S5. Impact drilling and grouting pile (31) construction.

2. The construction method for complex high-strength boulder down-the-hole drilling and weak blasting impact drilling pile foundation according to claim 1, characterized in that, In step S1, the auxiliary bracket (5) is connected and fixed to the reserved bolt hole (3) at the top of the slide (2), and the bottom of the auxiliary bracket (5) is symmetrically provided with an extension base plate (6) through the hinge shaft (7).

3. The construction method for complex high-strength boulder down-the-hole drilling and weak blasting impact drilling pile foundation according to claim 1, characterized in that, The specific method of step S4 is as follows: After the PVC liner (17) is installed, the sinking device is removed, and the explosive detonator (28) is lowered through the PVC liner (17) into the channel (26) of the boulder layer (8). The explosive detonator (28) is connected to the detonating cord (30). After the detonating cord (30) passes through the protective cover (29), the protective cover (29) is installed at the upper end of the guide tube (10). Then, the hard rock in the boulder layer (8) is pre-splitting blasted by explosive blasting.

4. The construction method for complex high-strength boulder down-the-hole drilling and weak blasting impact drilling pile foundation according to claim 3, characterized in that, In step S4, a threaded opening is provided on the top of the guide cylinder (10), and a protective cover (29) is installed on the threaded opening on the top of the guide cylinder (10).

5. The construction method for complex high-strength boulder down-the-hole drilling and weak blasting impact drilling pile foundation according to claim 3, characterized in that, The specific method of step S5 is as follows: After the blasting is completed, the duct (26) is cleaned and sand and gravel are backfilled into the duct (26). The guide support for the pilot hole is removed, and an impact drilling machine is arranged to enter the site. The pile foundation is drilled again by impact drilling, and then the cast-in-place pile (31) construction operation is carried out. The connection parts of the auxiliary support (5) and the sliding groove (2) on the steel casing (1) are removed, the auxiliary support (5) is removed, and finally the steel casing (1) is removed.

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