A construction method of a multi-edge rock-socketed flared drilled cast-in-place pile

Abstract

The present application belongs to the technical field of bored pile construction, and aims to provide an efficient bored pile construction method, which comprises the steps of measurement and lofting, equipment positioning, multiple small hole pre-drilling, sleeve impact breaking, rotary excavation and repeated sleeve impact, mouth protection and pouring, etc. A plurality of small-diameter air holes are drilled on the outside of the pile hole in advance to form a plurality of air release cavities. Under the impact of the large-tonnage rock breaking hammer head, the breaking effect is not inferior to liquid blasting. Combined with the sleeve impact breaking and secondary slag removal process, the hard rock breaking efficiency, pile end bearing capacity and hole wall stability are significantly improved, and the method can be widely applied in the technical field of bored pile construction.

Description

Technical Field

[0001] This invention belongs to the field of bored pile construction technology, specifically relating to a construction method for multi-sided rock-socketed flared bored piles. Background Technology

[0002] Drilled pile foundations are one of the most important and flexible foundation types in modern construction engineering. They can solve deep foundation problems under almost all geological conditions, but they are also a type of hidden engineering that highly depends on construction experience and management skills. The common construction steps for drilled pile foundations include: surveying and positioning with casing installation, drilling, hole cleaning, lowering the reinforcing cage, and underwater concrete pouring. Drilling is the key step, and common methods include mud wall protection, full casing method, and dry operation method. The main equipment used for drilling includes rotary drilling rigs, long auger drilling rigs, and impact drilling rigs. Rotary drilling rigs are characterized by high efficiency, good hole quality, low mud consumption, and high degree of automation, making them the most mainstream method currently.

[0003] Patent application number "CN201911243746" describes a construction method for rock-socketed bored piles. The method involves first using a cutting-tooth drill to advance the core, and then replacing it with a roller cone drill to extract the core. The roller cone drill, through its densely packed teeth, accelerates the fracture of the core, leading to core breakage. This method is applicable to hard rock, hard rock, uneven rock formations, and sloping rock formations, and can accommodate various pile diameters of rock-socketed bored piles. However, this patent uses complex equipment with high operating costs, and the efficiency improvement is not significant. According to existing technologies and relevant literature, traditional bored piles often face the following problems when entering hard rock formations: 1. Low crushing efficiency: Conventional rotary drilling rigs or impact drills have a slow crushing speed for intact hard rock, which easily causes drill bit wear and long construction cycle; 2. Limited pile end bearing capacity: The bottom area of ​​a circular cross-section pile is fixed, and the side resistance of the rock-socketed section is limited. For structures with high pull-out resistance and horizontal force resistance requirements, it is often necessary to increase the pile diameter or pile length, which significantly increases the cost. 3. Difficulty in protecting the borehole opening: At the junction of rock and soil and in areas with developed karstification, the casing is difficult to effectively protect the borehole opening, which can easily lead to borehole collapse; 4. Difficulty in cleaning debris: Rock chips and gravel produced after impact crushing are difficult to completely remove, affecting the control of sediment at the pile tip.

[0004] While existing technologies include "expanded-base cast-in-place piles" and "rock-socketed piles," these typically require specialized expanded-base drill bits or complete casing wall protection equipment, resulting in high equipment costs, complex processes, and difficulties in achieving rapid and economical multi-stage coordination. Therefore, existing bored cast-in-place pile construction methods need further improvement to meet the requirements for faster bored cast-in-place pile construction. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a construction method for multi-sided rock-embedded borehole piles. By pre-drilling multiple small-diameter air holes on the outside of the pile hole to form multiple air release chambers, the crushing effect can be achieved with the large tonnage impact of the rock-breaking hammer, which is comparable to liquid blasting. At the same time, combined with the shell-hammering crushing and secondary slag removal process, the efficiency of hard rock crushing, pile end bearing capacity and hole wall stability are significantly improved. It can be widely used in the field of borehole pile construction technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a construction method for multi-sided rock-socketed flared bored piles, specifically including the following steps: S1: Measurement and Setting Out and Equipment Placement Design the pile positions of the cast-in-place piles according to the drawings, determine the center point and outer contour line of the pile hole, and mark the "cross" or "star" directional lines at the center point of the pile hole as the reference for subsequent small hole positioning. Small water well drilling rigs or multi-functional down-the-hole drilling rigs are selected as pre-drilling equipment. S2: Pre-drilling of multiple small holes On the outer diameter of the cast-in-place pile, small holes are drilled in four or more directions, including the southeast, northwest and south, using a small water well drilling rig or a multi-functional down-the-hole drilling rig. The drilling depth of the small holes is consistent with the designed pile bottom elevation. The small holes should penetrate the rock to form a release cavity around the hard rock and achieve stress release. S3: Impact Crushing The tracked non-disengaged impact drill is selected for secondary crushing. The non-disengaged design ensures that the impact drill bit can continue to operate without being pulled out of the hole after the rock is crushed, saving auxiliary time. Since the small holes on the outside have formed several cavities around the rock, the impact of the tracked non-disengaged impact drill on the rock will create a liquid explosion effect, which greatly improves the crushing efficiency. S4: Rotary drilling rig for slag removal and repeated clamping After the intact rock is broken into small pieces, a rotary drilling rig or other excavation equipment is used to excavate and clean the pile hole, removing the remaining rock pieces and sediment. Then, an impact drill is lowered again for fine crushing, and this cycle is repeated until the final hole depth is reached, ensuring that the bottom of the hole is flat and free of slag. S5: Mouth protection and grouting After the bored pile hole is completed, a steel casing or concrete wall is installed at the hole opening to prevent the loose soil above from falling. Then, the steel cage is lowered and the pile body is poured using the underwater concrete pouring method. Finally, the construction of the bored pile body is completed.

[0007] As an improvement, in step S2, 6 to 12 small holes are provided along the periphery of the pile diameter to form a polygonal flared structure.

[0008] As an improvement, the diameter of each small hole in step S2 is 80~150mm. When entering below the rock surface, it can be vertically downward or gradually deviated 1~7cm outward from the pile diameter until the final hole depth, thereby forming several "protrusions" or "flared notches" on the circumference of the pile diameter, and forming a multi-faceted or petal-shaped flared end face at the bottom of the pile, which enhances the bearing capacity of the pile body and also greatly improves the pull-out resistance of the pile body.

[0009] As an improvement, the small hole is one of a round hole, a square hole, an elliptical hole, or a polygonal hole, and the small hole is drilled into the rock. The center of the small hole is located on the outer circle of the cast-in-place pile, or at a position offset from the outer circle.

[0010] As an improvement, if the soil layer above the cast-in-place pile is thick, the upper soil layer can be removed first using a rotary drilling rig or a long spiral drilling rig until the rock surface elevation is reached, and then the small hole can be constructed.

[0011] As an improvement, the tracked non-disengaged impact drill in step S3 uses a combined hammer head, which includes a hammer head body, a rotator, and a cable.

[0012] As an improvement, the hammerhead body has a conical structure with a smaller top and a larger bottom, a T-shaped central hammer tooth and four side hammer teeth at the bottom, and an arc-shaped groove on the side.

[0013] As an improvement, the rotator is a cable rotator connector that can rotate 360 ​​degrees independently both up and down, avoiding the phenomenon of wire rope knotting and breaking during construction and achieving continuous advance.

[0014] The beneficial effects achieved by this invention are as follows: A construction method for multi-sided rock-socketed bored piles has the characteristics of high hard rock breaking efficiency, good pile end bearing capacity and borehole wall stability, and simple construction equipment with low cost. Specific beneficial effects are as follows: 1. Significantly improve rock-socketed crushing efficiency: Pre-drill small vertical holes on the outer diameter of the cast-in-place pile, which penetrate the rock matrix, thereby forming a stress-relieving cavity inside the rock. This makes impact crushing of the rock surface less labor-intensive and reduces equipment wear. According to construction practice comparison, the rock-breaking efficiency can be significantly improved by more than 10 times compared with existing construction methods.

[0015] 2. Achieving multi-sided flaring at the bottom significantly improves bearing capacity: When the pre-drilled small hole is inserted into the rock, it is offset to the outside of the pile diameter by 1~7cm. The multi-sided flaring structure naturally formed at the bottom of the pile not only increases the bottom area, but also makes the pile body interlock with the rock layer, increasing the pull-out bearing capacity by 20%~50%.

[0016] 3. Universal construction equipment and low cost: No special underreaming drill bit or full casing equipment is required. Conventional rotary drilling rigs, down-the-hole drills, and impact drills can be combined to complete the task. By using a crawler-type non-disengaged impact drill with a combination hammer and a rotator that can rotate 360 ​​degrees both up and down for cable connection, the phenomenon of wire rope knotting and breaking during construction can be avoided, and continuous crushing progress can be achieved.

[0017] 4. Reliable borehole protection: The combination of multi-sided flaring and borehole casing prevents borehole collapse accidents at the rock-soil interface.

[0018] 5. Thorough cleaning: The percussion (impact-cleaning-re-impact) method ensures the cleanliness of the bottom of the hole, which is beneficial to the quality of the pile end. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the construction method of the multi-sided rock-socketed borehole cast-in-place pile of the present invention; Figure 2 This is a planar sectional view of the multi-sided rock-embedded retaining wall borehole cast-in-place pile of the present invention; Figure 3 This is a schematic diagram of the vertical cross-sectional structure of the multi-sided rock-embedded retaining borehole cast-in-place pile of the present invention; Figure 4 This is a schematic diagram of the forming process of the first embodiment of the multi-sided rock-socketed bored pile of the present invention; Figure 5 This is a schematic diagram of the second embodiment of the multi-sided rock-embedded retaining borehole cast-in-place pile of the present invention; Figure 6 This is a schematic diagram of the forming of the second embodiment of the multi-sided rock-embedded borehole cast-in-place pile of the present invention; Figure 7 This is a schematic diagram of the third embodiment of the multi-sided rock-embedded retaining wall bored pile of the present invention; Figure 8 This is a schematic diagram of the forming of the third embodiment of the multi-sided rock-socketed borehole cast-in-place pile of the present invention; Figure 9 This is a schematic diagram of the combined hammerhead structure of the present invention; Figure 10 This is a top view of the bottom of the combined hammer head of the present invention.

[0020] In the diagram: 1. Cast-in-place pile; 2. Hole; 3. Pile diameter; 4. Pile bottom; 5. Hammer head body; 6. Rotator; 7. Cable; 51. Center hammer tooth; 52. Side hammer tooth; 53. Arc-shaped groove. Detailed Implementation

[0021] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figures 1-3As shown, the present invention discloses a construction method for multi-sided rock-socketed flared bored piles, including surveying and setting out and equipment positioning, multi-hole pre-drilling, impact crushing, rotary drilling and slag removal and repeated impact crushing, joint protection and grouting, etc. The specific steps are described in detail below: S1: Measurement and Setting Out and Equipment Placement According to the design drawings, determine the pile position of pile 1, the center point and outer contour line of the pile hole of pile 1, and mark the "cross" or "star" direction line at the center point of the pile hole as the reference for subsequent small hole positioning. Small water well drilling rigs or multi-functional down-the-hole drilling rigs are selected as pre-drilling equipment. S2: Pre-drilling of multiple small holes Around the outer diameter 3 of the cast-in-place pile 1, small holes 2 are drilled in four or more directions, including east, west, south and north, using a small water well drilling rig or a multi-functional down-the-hole drilling rig. The drilling depth of the small holes 2 is consistent with the designed pile bottom elevation. The small holes 2 will penetrate the rock, thereby forming a release cavity around the hard rock to achieve stress release. S3: Impact Crushing A tracked non-disengaged impact drill was selected for secondary crushing. The non-disengaged design ensures that the impact drill bit can continue to operate without being pulled out of the hole after the rock is crushed, saving auxiliary time. Since the outer small holes 2 have formed several release cavities around the rock, the impact of the tracked non-disengaged impact drill on the rock will create a liquid explosion effect, which greatly improves the crushing efficiency. S4: Rotary drilling rig for slag removal and repeated clamping After the intact rock is broken into small pieces, a rotary drilling rig or other excavation equipment is used to excavate and clean the remaining rock fragments and sediment in the pile hole of the first pile. Then, the impact drill is lowered again for fine crushing. This cycle is repeated until the final hole depth is reached, ensuring that the bottom of the hole is flat and free of slag. S5: Mouth protection and grouting After the first bored pile hole is completed, a steel casing or concrete retaining wall is installed at the hole opening to prevent the loose soil above from falling. Then, the steel cage is lowered and the pile body is poured using the underwater concrete pouring method. Finally, the construction of the bored pile body is completed.

[0023] Furthermore, in step S2, each small hole has a diameter of 80-150mm. When it enters below the rock surface, it gradually deviates 1-7cm, preferably 5-7cm, from the outside of the pile diameter until the final hole depth is reached. This forms several "protrusions" or "flared notches" on the circumference of the pile diameter and a multi-faceted or petal-shaped flared end face at the bottom of the pile, enhancing the bearing capacity of the pile body and significantly improving the pull-out resistance of the pile body. Specifically, 6-12 small holes 2 are provided along the periphery of the pile diameter 3, forming a flared structure of regular hexagon, octagon, or polygon.

[0024] Furthermore, the small hole 2 is one of a round hole, a square hole, an elliptical hole, or a polygonal hole, and the small hole 2 is drilled into the interior of the rock. Specifically, if the soil layer above the cast-in-place pile 1 is thick, the upper soil layer can be removed first using a rotary drilling rig or a long spiral drilling rig until the rock surface elevation is reached, and then the small hole 2 is constructed. More specifically, the center of the small hole 2 is located exactly on the outer circle of the cast-in-place pile 1, or offset from the outer circle by 1 to 5 cm above or below the outer circle, but the small hole 2 must have a portion of its area overlapping with the interior area of ​​the cast-in-place pile 1, thereby ensuring the formation of an effective stress-relieving cavity around the cast-in-place pile and achieving a highly efficient and rapid rock breaking effect.

[0025] Furthermore, such as Figures 9-10 As shown, in step S3, the tracked non-disengaged impact drill uses a combined hammer head, which includes a hammer head body 5, a rotator 6, and a cable 7. Specifically, the hammer head body 5 has a conical structure with a smaller upper part and a larger lower part, with a T-shaped central hammer tooth 51 and four side hammer teeth 52 at the bottom, and an arc-shaped groove 53 on the side. The rotator 6 is a cable rotation connector, which can rotate 360 ​​degrees independently both up and down to avoid the wire rope from getting tangled and broken during construction.

[0026] Based on the above description of the product structure of the present invention, the construction process of the present invention will now be described through the following specific embodiments. Example 1

[0027] Project Background: A bridge foundation with a designed pile diameter of 1.2m and a total depth of 11m for the cast-in-place piles, including a 5.5m depth into slightly weathered granite, requires a pull-out bearing capacity of 1800kN.

[0028] Implementation details: S1. Lay out the center of the cast-in-place pile 1, and determine the positions of four small holes 2 around the cast-in-place pile 1 in a cross direction. The center of each small hole 2 is located on the four symmetrical bisecting points of the outer circle of the cast-in-place pile 1. S2. Use an XY-200 water well drilling rig to drill four small circular holes 2 with a diameter of φ100mm. The holes 2 are located on the pile diameter. Use an SR280 rotary drilling rig to first remove the soil layer to the rock surface, and then continue to drive vertically downward into the rock to a depth of 5.5m, thereby forming four small circular holes with a diameter of 100mm around the hard rock to achieve stress release. S3. A tracked non-disengaged impact drilling rig is selected to perform secondary crushing on the center of the cast-in-place pile 1. A combination hammer head with a T-shaped central hammer tooth and four side hammer teeth is used for impact crushing. The maximum diameter of the hammer head is less than 1.2 meters. Since the outer small holes 2 have formed several release cavities around the rock, the rock impact will form a liquid-like explosion effect, and the drilling speed can reach 30 min / m. S4. Use a rotary drilling rig to remove slag, then perform impact drilling, repeating the cycle twice in total; S5. Lower casing, lower reinforcing cage, underwater pouring of C35 concrete, after the cast-in-place pile is formed, as follows: Figure 4 As shown; S6. Post-pile testing showed that the single pile diameter was 1.2±0.2m, the total depth of the cast-in-place pile was 11±0.5m, and the ultimate tensile strength reached 2200kN, meeting the design requirements. Example 2

[0029] Unlike Example 1, this method is for hard rock layers, such as... Figure 5 As shown, eight small holes 2 are set, with their center points evenly distributed on the outer diameter 3 of the cast-in-place pile 1. The small holes 2 have a circular structure and a diameter of 80-120mm. A multi-functional down-the-hole drill is used for drilling, gradually deviating 5-7cm outwards from the pile diameter when encountering rock layers, forming an octagonal flared end face at the pile bottom. After the cast-in-place pile is formed, it will resemble... Figure 6 As shown. Example 3

[0030] Unlike Example 1, this method is used for particularly hard rock layers, such as... Figure 7 As shown, 10 small holes 2 are set, with the center points of the holes 2 evenly distributed on the outer diameter 3 of the cast-in-place pile 1, offset upwards by 3cm. The holes 2 have a circular structure with a diameter of 80~120mm. A multi-functional down-the-hole drill is used for drilling. When encountering rock layers, the holes gradually deviate 5~7cm outwards from the pile diameter, forming a ten-sided flared end face at the bottom of the pile. After the cast-in-place pile is formed, it looks like... Figure 8 As shown.

[0031] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A construction method for a multi-sided rock-socketed flared bored pile, characterized in that, Includes the following steps: S1: Measurement and Setting Out and Equipment Placement According to the design drawings, determine the pile position of the cast-in-place pile (1), determine the center point and outer contour line of the pile hole, mark the "cross" or "star" direction line at the center point of the pile hole as the reference for subsequent small hole positioning; Small water well drilling rigs or multi-functional down-the-hole drilling rigs are selected as pre-drilling equipment. S2: Pre-drilling of multiple small holes On the outer diameter (3) of the cast-in-place pile (1), small holes (2) are drilled in four or more directions, including the southeast, northwest and south, using a small water well drilling rig or a multi-functional down-the-hole drilling rig. The drilling depth of the small holes (2) is consistent with the design pile bottom elevation and should penetrate the rock, thereby forming a release cavity around the hard rock to achieve stress release. S3: Impact Crushing The tracked non-disengaged impact drill was selected for secondary crushing. The non-disengaged design ensured that the impact drill bit could continue to operate without being pulled out of the hole after the rock was crushed, saving auxiliary time. Since the small holes (2) around the rock have formed several cavities, the impact of the tracked non-disengaged impact drill on the rock will form a liquid explosion effect, which greatly improves the crushing efficiency. S4: Rotary drilling rig for slag removal and repeated clamping After the intact rock is broken into small pieces, a rotary drilling rig or other excavation equipment is used to excavate and clean the pile hole, removing the remaining rock pieces and sediment. Then, an impact drill is lowered again for fine crushing, and this cycle is repeated until the final hole depth is reached, ensuring that the bottom of the hole is flat and free of slag. S5: Mouth protection and grouting After the hole of the cast-in-place pile (1) is completed, a steel casing or concrete wall is set at the hole opening to prevent the loose soil above from falling; then the steel cage is lowered and the pile body is poured using the underwater concrete pouring method, and finally the construction of the cast-in-place pile (1) is completed.

2. The construction method for polygonal rock-socketed flared bored piles according to claim 1, characterized in that, In step S2, 6 to 12 small holes (2) are provided along the periphery of the pile diameter to form a polygonal flared structure.

3. The construction method for polygonal rock-socketed flared bored piles according to claim 2, characterized in that, The diameter of each small hole (2) in step S2 is 80~150mm. When it enters below the rock surface, it can be vertically downward or gradually deviate 1~7cm outward from the outside of the pile diameter until the final hole depth, thereby forming several "protrusions" or "flared notches" on the circumference of the pile diameter (3) and forming a multi-faceted or petal-shaped flared end face at the bottom of the pile (4), which enhances the bearing capacity of the pile body and also greatly improves the pull-out resistance of the pile body.

4. The construction method for polygonal rock-socketed flared bored piles according to claim 2 or 3, characterized in that, The small hole (2) is one of a round hole, a square hole, an elliptical hole or a polygonal hole. The small hole (2) is drilled into the rock. The center of the small hole (2) is located on the outer diameter (3) of the cast-in-place pile (1) or near the outer diameter.

5. The construction method for polygonal rock-socketed flared bored piles according to claim 1, characterized in that, The soil layer above the cast-in-place pile (1) is relatively thick. The upper soil layer can be removed first using a rotary drilling rig or a long spiral drilling rig until it reaches the rock surface elevation, and then the small hole (2) can be constructed.

6. The construction method for polygonal rock-socketed flared bored piles according to claim 1, characterized in that, In step S3, the tracked non-disengaged impact drill uses a combined hammer head, which includes a hammer head body (5), a rotator (6), and a cable (7).

7. The construction method for polygonal rock-socketed flared bored piles according to claim 6, characterized in that, The hammerhead body (5) is a conical structure with a smaller top and a larger bottom. It has a T-shaped central hammer tooth (51) and four side hammer teeth (52) at the bottom, and an arc-shaped groove (53) on the side.

8. The construction method of the multi-sided rock-socketed flared bored pile according to claim 6, characterized in that, The rotator (6) is a cable rotator connector that can rotate 360 ​​degrees independently both up and down, avoiding the phenomenon of wire rope knotting and breaking during construction, and realizing continuous progress.

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