Drilling pile-forming complete-set construction method for large-diameter cast-in-place pile in coastal tidal liquefaction site

Abstract

The invention relates to the technical field of cast-in-place piles, and discloses a coastal tidal liquefaction site large-diameter cast-in-place pile drilling pile-forming complete-set construction method which comprises the steps that (1) a construction site is leveled, a slurry circulating system is built, and the pile position is determined; (2) the pile casing is vibrated and sunk at the pile position; (3) rotary drilling is conducted in the pile casing, and a pile hole is formed; (4) primary hole cleaning is conducted on the pile hole; (5) a steel reinforcement cage is put into the pile hole, the steel reinforcement cage comprises a plurality of main reinforcements which surround at intervals, stirrups surround the peripheries of the main reinforcements, and the steel reinforcement cage defines a cage space; a reinforcing structure is arranged in the cage space and connected with the multiple main reinforcements to limit the main reinforcements from deviating from the cage space to deviate outwards. A pouring guide pipe is put into the pile hole; (6) reverse circulation secondary hole cleaning is conducted on the pile hole, and slurry is discharged into a slurry circulation system to be subjected to multi-layer sedimentation filtration; and (7) after corrosion-resistant concrete is poured into the pile hole through the pouring guide pipe to the set height, the pile casing is pulled out through vibration to be separated from the pile hole, and the concrete in the pile hole is solidified to form a cast-in-place pile.

Description

Technical Field

[0001] The invention relates to the technical field of bored piles, and more specifically, to a complete construction method for drilling and forming large-diameter bored piles in coastal tidal liquefaction sites. Background Art

[0002] The earthwork and pile foundation project of the warehouse (including the turntable) on the south side of Area A of Xiaomo Port Trade and Logistics Park is located in Xiaomo Town, Shenzhen Shenshan Special Cooperation Zone. The project is located on the north side of the first port road in Da'ao Village, Binhai. 100m to the south is the Da'ao River, which flows into the sea alone, and 350m to the south is the Binhai District, which is hydraulically connected with the groundwater of this project. The site is filled with fish ponds. The project covers an area of ​​about 35,000 square meters and a construction area of ​​about 96,000 square meters. A 5-story warehouse and a 4-story truck turntable are built with a height of 41.3m and no basement. The foundation design of the warehouse building adopts bored cast-in-place piles, in which the bottom of the 1800mm diameter engineering piles is embedded in the medium-weathered rock for 11m or slightly weathered rock for 1m, and the average pile length is about 43m. The upper part of the site stratum is distributed from top to bottom with artificial fill, silt sand, silt-containing silt sand, silty clay, silty soil, and pebbles, and the underlying bedrock is various weathered layers of sandstone.

[0003] According to the analysis of the surrounding environment of the site and the survey data, the engineering problems faced by the rotary bored pile construction of this project are mainly that the coastal area is affected by the sea tides, and the groundwater level in the site fluctuates greatly due to the tides, with the maximum change in high and low water levels reaching 4.0m; the deep silt sand layer and silt sand layer distributed on the upper part of the site have a high liquefaction index, the overall liquefaction level is serious, the average thickness is 11m, and the site is distributed in layers.

[0004] During the construction of rotary bored piles, due to the influence of seawater tides, the mud in the pile hole leaks seriously, and problems such as hole collapse and diameter shrinkage often occur. Tides and liquefied soil layers have a great impact on the pile body, resulting in poor pile quality and poor ability of bored piles to resist the influence of tides and liquefied sites. Summary of the invention

[0005] The purpose of the present invention is to provide a complete construction method for drilling and piling large-diameter cast-in-place piles at a coastal tidal liquefaction site, aiming to solve the problem of poor pile quality at a coastal tidal liquefaction site in the prior art.

[0006] The present invention is achieved by drilling and forming a complete set of construction methods for large-diameter cast-in-place piles in coastal tidal liquefaction sites, comprising the following construction steps:

[0007] 1) Level the construction site, build a mud circulation system at the construction site, and determine the pile position at the construction site;

[0008] 2) Lift the casing to the top of the pile position, clamp the casing with a vibrating hammer, and vibrate and sink the casing to a set depth at the pile position;

[0009] 3) Using a rotary drilling rig to drill a silt hole in the casing until the bottom of the silt hole reaches the pebble layer; using a barrel drill to drill into the bearing rock layer in the pebble layer to form a stone layer hole, the silt hole is connected with the stone layer hole up and down to form a pile hole;

[0010] 4) Cleaning the pile hole once, and picking up and discharging the suspended sediment in the pile hole;

[0011] 5) Insert a steel cage into the pile hole, the steel cage comprising a plurality of main bars arranged at intervals, a plurality of stirrups surrounding the outer periphery of the main bars, and the steel cage encloses a cage space; a horizontally arranged reinforcement structure is provided in the cage space, the reinforcement structure is connected to the plurality of main bars, and limits the main bars from deviating from the cage space and deviating outward; insert a perfusion conduit into the pile hole;

[0012] 6) Use a slurry pump to perform reverse circulation secondary hole cleaning on the pile hole, and discharge the mud in the hole cleaning process into the mud circulation system for multi-layer sedimentation and filtration;

[0013] 7) After pouring anti-corrosion concrete into the pile hole to a set height through the pouring conduit, a vibrating hammer is used to vibrate and pull the casing out of the pile hole, and the concrete in the pile hole solidifies to form a cast-in-place pile.

[0014] Optionally, in the construction step 1), the construction steps of the mud circulation system are as follows:

[0015] 1.1) Digging a mud pool on the construction site, wherein the mud pool has an enclosure wall formed at the bottom and surrounding side of the mud pool, and compacting the enclosure wall;

[0016] 1.2) pouring a concrete surface layer on the enclosed wall, wherein the bottom of the concrete surface layer has a steel mesh layer;

[0017] 1.3) A plurality of partition walls are constructed in the mud pool, and the plurality of partition walls are arranged in sequence and spaced apart along the flow direction of the mud in the mud pool, and the plurality of partition walls divide the mud pool into a plurality of sedimentation areas; a convection port is provided in the partition wall, and the height of the convection port in the plurality of partition walls decreases in sequence along the flow direction of the mud in the mud pool.

[0018] Optionally, in the construction step 1.3), the convection openings of adjacent partition walls are staggered along the width direction of the mud pool.

[0019] Optionally, in the construction step 1.1), after the enclosure wall is compacted, a plurality of recessed holes are formed on the enclosure wall, and the plurality of recessed holes are distributed throughout the enclosure wall; a concrete cushion layer is cast on the enclosure wall, and the bottom of the concrete cushion layer is embedded in the recessed holes to form an integrated structure with the enclosure wall;

[0020] The steel mesh layer is laid on the concrete cushion layer, and a plurality of pins are arranged on the steel mesh layer. The plurality of pins are arranged in a plurality of rows on the steel mesh layer to form a plurality of pin rows. The plurality of pin rows are arranged at intervals along the length direction of the mud pool, and the pin rows are extended along the width direction of the mud pool;

[0021] A plurality of the pins are inserted into the concrete cushion layer to form an integrated structure of the steel mesh layer and the concrete cushion layer; the steel mesh layer is in a tensioned state along the width direction of the mud pool, and the steel mesh layer has a spacer located between adjacent rows of pins, and the spacer is in a relaxed folded state along the length direction of the mud pool;

[0022] A concrete surface layer is cast on the concrete cushion layer, the concrete surface layer and the concrete cushion layer are combined up and down to form an integrated structure, and the steel mesh layer is clamped between the concrete cushion layer and the concrete surface layer.

[0023] Optionally, in the construction step 2), after the casing is sunk to a set depth, the casing passes through the silt layer and extends into the pebble layer, and the silt layer contains silt;

[0024] The casing has an upper section extending above the pile position, and the silt sand layer has a surrounding portion enclosed on the outer periphery of the upper section; during the vibration sinking process of the casing, the surrounding portion is squeezed by the vibration of the casing and vibrates downward to be compacted, so that the surrounding portion is concave downward to form a collapse zone, and the collapse zone surrounds the outer periphery of the upper section.

[0025] Optionally, in the construction step 2), the vibratory hammer has two parallel chucks, which clamp the top of the casing and vibrate and squeeze the casing to a set depth. In the process of the casing being vibrated and squeezed to the lower layer, the casing drives the silt on the periphery of the casing to vibrate and squeeze it into a dense state.

[0026] Optionally, in the construction step 3), drill bits with different diameters are used to sequentially expand and drill holes in the pebble layer and the rock layer below until a hole of a set diameter is formed in the rock layer.

[0027] Optionally, in the construction step 5), after the steel cage is completed, a plurality of the reinforcement structures are arranged in the upper part of the cage space, and the plurality of the reinforcement structures are arranged at intervals along the height direction of the cage space;

[0028] The reinforcement structure includes a square-shaped composite hoop, and the circumferential side of the composite hoop has four turning areas. The turning areas bypass the outer side of the main reinforcement and are fixedly connected to the main reinforcement, pressing the main reinforcement from the outside to the inside, and limiting the main reinforcement from deviating from the cage space and deviating outward.

[0029] Optionally, the reinforcement structure includes two orthogonally arranged composite hoops, the two composite hoops are horizontally overlapped up and down, and there are multiple overlapping positions between the two composite hoops, and the multiple overlapping positions are arranged at intervals along the circumference of the composite hoops; the overlapping positions are tied with steel wires to fix the two composite hoops up and down as a whole.

[0030] Optionally, connecting bars are connected between upper and lower adjacent reinforcement structures, the connecting bars are arranged longitudinally, and ends of the connecting bars are respectively connected to the overlapping positions of the upper and lower reinforcement structures.

[0031] Compared with the prior art, the present invention provides a complete set of construction methods for drilling and forming large-diameter cast-in-place piles in coastal tidal liquefaction sites. Through rotary drilling in the casing to form a silt sand hole until it reaches the pebble layer, the influence of the liquefied soil layer is isolated. During the construction process, the liquefied soil layer is effectively prevented from easily collapsing, shrinking, and losing mud due to construction disturbance, thereby ensuring the quality of rotary drilling. Next, in view of the influence of tides and liquefied soil layers on the pile body, a reinforcement structure is set in the cage space to limit the main reinforcement from deviating outward from the cage space, and anti-corrosion concrete is used for pouring, thereby ensuring the quality of the pile and further strengthening the ability of the cast-in-place pile to resist the influence of tides and liquefied sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process of a complete set of construction methods for drilling and piling large diameter cast-in-place piles in a coastal tidal liquefaction site provided by the present invention;

[0033] Figure 2 It is a construction schematic diagram of construction step 2) provided by the present invention;

[0034] Figure 3 It is a structural schematic diagram of the mud pool provided by the present invention;

[0035] Figure 4 It is a cross-sectional schematic diagram of the mud pool provided by the present invention;

[0036] Figure 5 It is a cross-sectional schematic diagram of the mud pool provided by the present invention;

[0037] Figure 6 It is a cross-sectional schematic diagram of the enclosing wall, concrete cushion layer, steel mesh layer and concrete surface layer provided by the present invention;

[0038] Figure 7 It is a partial schematic diagram of the bottom of the vibrating hammer provided by the present invention;

[0039] Figure 8 is a top view schematic diagram of the reinforcement structure provided by the present invention;

[0040] Fig. 9 It is a top view schematic diagram of the reinforcement structure provided by the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] The implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0043] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Reference Figure 1-9 The figure shows a preferred embodiment of the present invention.

[0045] The invention provides a complete set of construction methods for drilling and piling large-diameter cast-in-place piles in a coastal tidal liquefaction site, comprising the following construction steps:

[0046] 1) Level the construction site, build a mud circulation system at the construction site, and determine the pile position at the construction site;

[0047] 2) Lift the casing 100 to the top of the pile position, clamp the casing 100 with a vibrating hammer 300, and vibrate and sink the casing 100 to a set depth at the pile position;

[0048] 3) Using a rotary drilling rig to drill a silt hole in the casing 100 until the bottom of the silt hole reaches the pebble layer 30; using a barrel drill to drill into the bearing rock layer in the pebble layer 30 to form a stone layer hole, the silt hole and the stone layer hole are connected up and down to form a pile hole;

[0049] 4) Clean the pile hole once and remove the suspended sediment in the pile hole;

[0050] 5) Insert a steel cage into the pile hole, the steel cage includes a plurality of main bars 400 arranged at intervals, and the outer periphery of the plurality of main bars 400 surrounds the stirrups 410, and the steel cage encloses a cage space; a horizontally arranged reinforcement structure is provided in the cage space, and the reinforcement structure is connected to the plurality of main bars 400 to limit the main bars 400 from deviating from the cage space and deviating outward; insert a pouring catheter into the pile hole;

[0051] 6) Use a slurry pump to perform reverse circulation secondary hole cleaning on the pile hole, and discharge the mud in the hole cleaning process into the mud circulation system for multi-layer sedimentation and filtration;

[0052] 7) After pouring anti-corrosion concrete into the pile hole to a set height through the pouring conduit, the casing 100 is vibrated and pulled out of the pile hole by a vibrating hammer 300, and the concrete in the pile hole solidifies to form a cast-in-place pile.

[0053] The above-mentioned large-diameter bored pile construction method for coastal tidal liquefaction sites is to drill into the formed silt sand hole in the casing 100 until it reaches the pebble layer 30, isolating the influence of the liquefied soil layer, and effectively avoiding the collapse of the liquefied soil layer due to construction disturbance, shrinkage, mud loss and other problems, thereby ensuring the quality of the bored hole. Then, a reinforcement structure is set in the cage space to limit the main reinforcement 400 from deviating from the cage space and the corrosion-resistant concrete is poured, thereby ensuring the quality of the pile and further strengthening the ability of the bored pile to resist the influence of tides and liquefied sites.

[0054] In construction step 1), the construction steps of the mud circulation system are as follows:

[0055] 1.1) Dig a mud pool 200 on the construction site. The mud pool 200 has an enclosure wall. The enclosure wall is formed at the bottom and the surrounding side of the mud pool 200, and the enclosure wall is compacted;

[0056] 1.2) Casting a concrete surface layer 203 on the enclosed wall, the bottom of the concrete surface layer 203 has a steel mesh layer 202;

[0057] 1.3) A plurality of partition walls 210 are constructed in the mud pool 200. The plurality of partition walls 210 are arranged in sequence and spaced apart along the flow direction of the mud in the mud pool 200. The plurality of partition walls 210 divide the mud pool 200 into a plurality of sedimentation areas. A convection port 211 is provided in the partition wall 210. The height of the convection port 211 in the plurality of partition walls 210 decreases in sequence along the flow direction of the mud in the mud pool 200.

[0058] In this way, the enclosing wall is compacted first to improve its bearing capacity, and then, through the design of the concrete surface layer 203 and the steel mesh layer 202, the mud pool 200 has a certain flexibility, so that the mud pool 200 has the anti-erosion and leakage function to resist tidal changes and the influence of liquefaction sites, and reduce the influence of tides and the upper silt sand layer 10 on the loss of high-quality mud circulating in the mud system.

[0059] In the construction step 1.3), the convection ports 211 of adjacent partition walls 210 are arranged in a staggered manner along the width direction of the mud pool 200. In this way, the mud can be smoothly precipitated in multiple stages, ensuring the reliable supply of high-quality wall protection mud.

[0060] In this embodiment, in the construction step 1.1), after the enclosure wall is compacted, a plurality of recessed holes 2000 are formed on the enclosure wall, and the plurality of recessed holes 2000 are distributed throughout the entire enclosure wall; a concrete cushion layer 201 is cast on the enclosure wall, and the bottom of the concrete cushion layer 201 is embedded in the recessed holes 2000 to form an integrated structure with the enclosure wall;

[0061] A steel mesh layer 202 is laid on the concrete cushion layer 201, and a plurality of pins 204 are arranged on the steel mesh layer 202. The plurality of pins 204 are arranged in a plurality of rows on the steel mesh layer 202 to form a plurality of rows of pins 204. The plurality of rows of pins 204 are arranged at intervals along the length direction of the mud pool 200, and the rows of pins 204 are extended along the width direction of the mud pool 200.

[0062] A plurality of pins 204 are inserted into the concrete cushion layer 201 to form an integrated structure of the steel mesh layer 202 and the concrete cushion layer 201; the steel mesh layer 202 is in a tensioned state along the width direction of the mud pool 200, and the steel mesh layer 202 has a spacer located between adjacent rows of pins 204, and the spacer is in a relaxed folded state along the length direction of the mud pool 200;

[0063] A concrete surface layer 203 is cast on the concrete cushion layer 201, and the concrete surface layer 203 and the concrete cushion layer 201 are combined into an integral structure, and the steel mesh layer 202 is clamped between the concrete cushion layer 201 and the concrete surface layer 203. In this way, the relaxed folded spacer allows the entire concrete surface layer 203 and the steel mesh layer 202 inside it to have better flexibility when subjected to external pressure. This flexibility can reduce cracking or damage caused by stress concentration, thereby improving the overall durability of the mud pool 200. The steel mesh layer 202, the concrete cushion layer 201, and the concrete surface layer 203 form an integral structure through structures such as nails 204, thereby enhancing the overall stability.

[0064] Specifically, a double-layer steel mesh layer 202 is provided at the corners, water level lines and other weak places with complex stress for reinforcement.

[0065] In construction step 2), after the casing 100 sinks to a set depth, the casing 100 passes through the silt layer 10 and extends into the pebble layer 30, and the silt layer 10 contains silt;

[0066] The casing 100 has an upper section extending above the pile position, and the silt layer 10 has a surrounding portion enclosed on the outer periphery of the upper section; during the vibration sinking process of the casing 100, the surrounding portion is squeezed by the vibration of the casing 100 and vibrates downward to be compacted, so that the surrounding portion is concave downward to form a collapse area 40, and the collapse area 40 surrounds the outer periphery of the upper section. In this way, the extra-long casing 100 directly passes through the silt layer 10 and the silt layer 20 containing silt, isolating the influence of the liquefied soil layer, and effectively avoiding the problems of hole collapse, diameter shrinkage, and mud loss caused by construction disturbance in the liquefied soil layer during the construction process, thereby ensuring the quality of rotary drilling.

[0067] The casing 100 isolates the liquefied soil layer, saving the time for frequent mud preparation and hole collapse treatment. The whole process is convenient, fast and efficient.

[0068] Specifically, in construction step 1), positioning piles 50 are constructed, and the positioning piles 50 are located outside the collapse area 40. The casing 100 is sunk using a high-frequency hydraulic vibration hammer 300. When positioning, the pile position is taken as the center, and mutually perpendicular control pile lines are determined. Positioning piles 50 are set at a set distance from the designed pile position to control the center position and verticality of the casing 100, and the casing 100 is hoisted in. However, it was found in the actual construction process that under the excitation of the hydraulic vibration hammer 300, the silt layer 10 around the pile position will cause compaction and collapse toward the center of the casing 100, forming a collapse area 40, and the previously set cross vertical positioning piles will also deviate toward the center of the casing 100, which ultimately results in the center accuracy of the casing 100 not meeting the requirements, and the casing 100 cannot be accurately lowered. After multiple field tests, it was concluded that the compaction collapse occurred within 6m around the casing 100. Therefore, the positioning piles 50 needed to be set outside the affected range. To ensure that the final center position of the casing 100 met the design requirements, the positioning piles 50 were ultimately set 8m around the casing 100 in this project.

[0069] In construction step 2), the vibratory hammer 300 has two parallel chucks 310, and the two chucks 310 clamp the top of the casing 100, vibrate and squeeze the casing 100 to sink to a set depth, and in the process of the casing 100 being vibrated and squeezed into the lower layer, the casing 100 drives the silt sand on the periphery of the casing 100 to vibrate and squeeze into a dense state. In this way, the vibratory hammer 300 can be an ICE high-frequency double-clamp vibratory hammer 300, which is fast and convenient. The casing 100 is smoothly sunk into place and quickly pulled out through the high-frequency excitation effect. On the other hand, the saturated and loose silt sand particles around the pile position are rearranged and compacted under high-frequency forced vibration. This forced compaction increases the relative density of the silt sand, reduces the porosity, and improves the ability to resist soil liquefaction.

[0070] In construction step 3), drill bits with different diameters are used to sequentially expand holes in the pebble layer 30 until a hole of a set diameter is formed in the pebble layer. In this way, the efficiency of hole formation is improved by graded expansion.

[0071] As a preferred embodiment, the spacing of the stirrups 410 is increased for the upper reinforcement cage of the cast-in-place pile. The increased length is from the top of the pile to 1m below the bottom of the liquefied soil layer, and the length of the increased area is determined according to the actual soil layer.

[0072] In construction step 5), after the steel cage is completed, a plurality of reinforcement structures are arranged in the upper part of the cage space, and the plurality of reinforcement structures are arranged at intervals along the height direction of the cage space;

[0073] The reinforcement structure includes a square-shaped composite hoop 420, and the circumference of the composite hoop 420 has four turning areas. The turning areas bypass the outer side of the main reinforcement 400 and are fixedly connected to the main reinforcement 400, pressing the main reinforcement 400 from the outside to the inside, and limiting the main reinforcement 400 from deviating from the cage space and deviating outward. In this way, the composite hoop 420 is used to strengthen the binding effect on the main reinforcement 400 of the steel cage, improve the adverse effects of soil liquefaction on the cast-in-place pile, and also increase the shear resistance of the cast-in-place pile against the cyclic reciprocating horizontal effect of tidal fluctuations. The spacing between the composite hoop 420 is 100mm, and the horizontal is required to fully guarantee the binding effect on the main reinforcement 400.

[0074] Specifically, the reinforcement structure includes two composite hoops 420 arranged orthogonally, the two composite hoops 420 are horizontally overlapped up and down, and there are multiple overlapping positions between the two composite hoops 420, and the multiple overlapping positions are arranged at intervals along the circumference of the composite hoops 420; the overlapping positions are tied with steel wires to fix the two composite hoops 420 up and down as a whole. In this way, the multiple main bars 400 are tied together and formed into a whole through the action of steel wire tying, further enhancing the ability to limit the main bars 400 from deviating from the cage space and deviating outward.

[0075] In this embodiment, connecting ribs 430 are connected between the upper and lower adjacent reinforcement structures, and the connecting ribs 430 are arranged longitudinally, and the ends of the connecting ribs 430 are respectively connected to the overlapping positions of the upper and lower reinforcement structures. In this way, multiple reinforcement structures are connected by connecting ribs 430, further enhancing the ability to limit the main ribs 400 from deviating from the cage space and deviating outward.

[0076] Specifically, a plurality of connecting bars 430 may be arranged between one or more upper and lower adjacent reinforcement structures, and the extending direction of the connecting bars 430 does not pass through the central area of ​​the pile hole to avoid affecting the lowering of the perfusion catheter.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A complete construction method for drilling and forming large-diameter cast-in-place piles in coastal tidal liquefaction sites, characterized in that: The construction steps include: 1) Level the construction site, build a mud circulation system at the construction site, and determine the pile position at the construction site; 2) Lift the casing to the top of the pile position, clamp the casing with a vibrating hammer, and vibrate and sink the casing to a set depth at the pile position; 3) Using a rotary drilling rig to drill a silt hole in the casing until the bottom of the silt hole reaches the pebble layer; using a barrel drill to drill into the bearing rock layer in the pebble layer to form a stone layer hole, the silt hole is connected with the stone layer hole up and down to form a pile hole; 4) Cleaning the pile hole once, and picking up and discharging the suspended sediment in the pile hole; 5) Insert a steel cage into the pile hole, the steel cage comprising a plurality of main bars arranged at intervals, a plurality of stirrups surrounding the outer periphery of the main bars, and the steel cage encloses a cage space; a horizontally arranged reinforcement structure is provided in the cage space, the reinforcement structure is connected to the plurality of main bars, and limits the main bars from deviating from the cage space and deviating outward; insert a perfusion conduit into the pile hole; 6) Use a slurry pump to perform reverse circulation secondary hole cleaning on the pile hole, and discharge the mud in the hole cleaning process into the mud circulation system for multi-layer sedimentation and filtration; 7) After pouring anti-corrosion concrete into the pile hole to a set height through the pouring conduit, a vibrating hammer is used to vibrate and pull the casing out of the pile hole, and the concrete in the pile hole solidifies to form a cast-in-place pile.

2. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site as claimed in claim 1, characterized in that: In the construction step 1), the construction steps of the mud circulation system are as follows: 1.1) Digging a mud pool on the construction site, wherein the mud pool has an enclosure wall formed at the bottom and surrounding side of the mud pool, and compacting the enclosure wall; 1.2) pouring a concrete surface layer on the enclosed wall, wherein the bottom of the concrete surface layer has a steel mesh layer; 1.3) A plurality of partition walls are constructed in the mud pool, and the plurality of partition walls are arranged in sequence and spaced apart along the flow direction of the mud in the mud pool, and the plurality of partition walls divide the mud pool into a plurality of sedimentation areas; a convection port is provided in the partition wall, and the height of the convection port in the plurality of partition walls decreases in sequence along the flow direction of the mud in the mud pool.

3. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site as claimed in claim 2, characterized in that: In the construction step 1.3), the convection openings of adjacent partition walls are staggered along the width direction of the mud pool.

4. The method for drilling and piling large-diameter bored piles at a coastal tidal liquefaction site as claimed in claim 2, characterized in that: In the construction step 1.1), after the enclosure wall is compacted, a plurality of recessed holes are formed on the enclosure wall, and the plurality of recessed holes are distributed throughout the entire enclosure wall; A concrete cushion layer is cast on the enclosing wall, wherein the bottom of the concrete cushion layer is embedded in the recessed hole to form an integrated structure with the enclosing wall; The steel mesh layer is laid on the concrete cushion layer, and a plurality of pins are arranged on the steel mesh layer. The plurality of pins are arranged in a plurality of rows on the steel mesh layer to form a plurality of pin rows. The plurality of pin rows are arranged at intervals along the length direction of the mud pool, and the pin rows are extended along the width direction of the mud pool; A plurality of the pins are inserted into the concrete cushion layer to form an integrated structure of the steel mesh layer and the concrete cushion layer; the steel mesh layer is in a tensioned state along the width direction of the mud pool, and the steel mesh layer has a spacer located between adjacent rows of pins, and the spacer is in a relaxed folded state along the length direction of the mud pool; A concrete surface layer is cast on the concrete cushion layer, the concrete surface layer and the concrete cushion layer are combined up and down to form an integrated structure, and the steel mesh layer is clamped between the concrete cushion layer and the concrete surface layer.

5. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site as claimed in claim 1, characterized in that: In the construction step 2), after the casing is sunk to a set depth, the casing passes through the silt layer and extends into the pebble layer, and the silt layer contains silt; The casing has an upper section extending above the pile position, and the silt sand layer has a surrounding portion enclosed on the outer periphery of the upper section; during the vibration sinking process of the casing, the surrounding portion is squeezed by the vibration of the casing and vibrates downward to be compacted, so that the surrounding portion is concave downward to form a collapse zone, and the collapse zone surrounds the outer periphery of the upper section.

6. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site as claimed in claim 1, characterized in that: In the construction step 2), the vibratory hammer has two parallel chucks, which clamp the top of the casing and vibrate and squeeze the casing to sink to a set depth. In the process of the casing being vibrated and squeezed to the lower layer, the casing drives the silt on the outer periphery of the casing to vibrate and squeeze into a dense state.

7. The method for drilling and piling large-diameter cast-in-place piles for coastal tidal liquefaction sites as claimed in claim 1, characterized in that: In the construction step 3), drill bits with different diameters are used to sequentially expand and drill holes in the pebble layer and the rock layer below until a hole of a set diameter is formed in the rock layer.

8. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site according to any one of claims 1 to 7, characterized in that: In the construction step 5), after the steel cage is completed, a plurality of the reinforcement structures are arranged in the upper part of the cage space, and the plurality of the reinforcement structures are arranged at intervals along the height direction of the cage space; The reinforcement structure includes a square-shaped composite hoop, and the circumferential side of the composite hoop has four turning areas. The turning areas bypass the outer side of the main reinforcement and are fixedly connected to the main reinforcement, pressing the main reinforcement from the outside to the inside, and limiting the main reinforcement from deviating from the cage space and deviating outward.

9. The method for drilling and piling large-diameter bored piles in a coastal tidal liquefaction site as claimed in claim 8, characterized in that: The reinforcement structure includes two orthogonally arranged composite hoops, the two composite hoops are horizontally overlapped up and down, and there are multiple overlapping positions between the two composite hoops, and the multiple overlapping positions are arranged at intervals along the circumference of the composite hoops; the overlapping positions are tied with steel wires to fix the two composite hoops up and down as a whole.

10. The method for drilling and piling large-diameter cast-in-place piles for coastal tidal liquefaction sites as claimed in claim 9, characterized in that: Connecting bars are connected between the upper and lower adjacent reinforcing structures. The connecting bars are arranged longitudinally, and the ends of the connecting bars are respectively connected to the overlapping positions of the upper and lower reinforcing structures.

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