CN107975032B

CN107975032B - Tidal current power generation cast-in-place pile with pile core steel pipe and construction method thereof

Info

Publication number: CN107975032B
Application number: CN201711182102.XA
Authority: CN
Inventors: 何晓宇; 沈坚; 应永良; 金国强; 季大闰
Original assignee: Zhejiang Provincial Institute of Communications Planning Design and Research Co Ltd
Current assignee: Zhejiang Provincial Institute of Communications Planning Design and Research Co Ltd; Zhejiang Shuzhijiaoyuan Technology Co Ltd
Priority date: 2017-11-23
Filing date: 2017-11-23
Publication date: 2019-12-10
Anticipated expiration: 2037-11-23
Also published as: CN107975032A

Abstract

The invention discloses a tidal current power generation filling pile with a pile core steel pipe and a construction method thereof, wherein the filling pile has the advantages of small diameter, strong bending resistance and shearing resistance and simple and convenient construction process, and solves the problems that the conventional diameter filling pile cannot bear overlarge load generated by large tidal current flow velocity in a tidal current energy-rich area, and the large diameter filling pile occupies an overlarge tidal current effective water cross section, so that the utilization of tidal current energy is influenced, and the construction cost of the large diameter filling pile is overhigh. According to the invention, the pile core steel pipe with a certain length is driven into the rock-socketed cast-in-place pile with a conventional diameter, the pile base of the cast-in-place pile is ensured to be embedded 6m below a seabed foundation layer, and the pile core steel pipe and the reinforcement cage can jointly exert stronger bending resistance and shearing resistance under the action of reciprocating loads such as waves and tides, especially in extreme weather, so that the rock-socketed cast-in-place pile is particularly suitable for offshore region engineering foundations such as tidal current power generation pile foundations bearing larger horizontal loads, and has high flexibility and better economic benefits and social benefits.

Description

Tidal current power generation cast-in-place pile with pile core steel pipe and construction method thereof

Technical Field

The invention belongs to the technical field of offshore pile foundation engineering, and particularly relates to a tidal current generation cast-in-place pile with a pile core steel pipe and a construction method thereof.

Background

The seawater generates periodic motion under the action of gravity of the celestial body, and the flow in the horizontal direction is called tidal current. Tidal currents exist in the whole sea, the flow velocity of the open sea is very small, but under the influence of factors such as land and submarine topography, strong tidal currents exist in coastal sea areas, particularly between straits and submarine water channels.

The method for offshore development of tidal current energy mainly combines a tidal current energy generator set and a support carrier, and the support carrier is of a floating type or a fixed type. The floating carrier is fixed on the seabed by the anchoring system, and the mode is easy to maintain, move and recover, is suitable for the complicated submarine topography and is suitable for the environment with larger water depth. However, offshore wind power plants and tidal current power plant construction sea areas in China are in offshore areas with the water depth not more than 30m, so that most of supporting carriers are fixed, and the fixed supporting carriers can be divided into a bottom-sitting type and a pile foundation type. The bottom-sitting type carrier is mostly fixed in a gravity mode, a heavy block or ballast is needed, construction such as seabed leveling and the like needs to be carried out on complex landforms, engineering consumption is large, and the tidal current generator set is inconvenient to overhaul and recover. For the pile foundation type carrier, a pile foundation is driven into the sea bottom to be fixed, the stability is relatively stable, the tidal current energy generator set is fixed on an assembly platform formed by combining the pile foundation and an upper component, the disassembly is convenient, the equipment maintenance is convenient, and the device is suitable for shallow (less than 30m) water areas.

However, for the pile foundation, in the sea area with strong tidal current, the pile foundation can bear large shearing force and bending moment under the periodic action of waves and tidal current, so that high requirements are provided for the stress performance of the pile foundation structure. At present, 70% of offshore wind turbine foundations abroad are single-pile foundations, the single-pile foundations are sunk to the seabed through a steel pipe pile, the diameter of the steel pipe pile is usually 4-6 m, namely, the single-pile foundations are large-diameter pile foundations, however, for large tidal current energy power generation projects with more piles, the large-diameter pile foundations can greatly increase the engineering cost, occupy a large-area overflowing area, affect the tidal current flow speed and flow direction distribution, reduce the tidal current effective water passing cross section, and obviously reduce the benefits of engineering construction.

the Chinese patent with the application number of 201310540280.0 provides a method for improving the bearing capacity of a cast-in-place pile and a cast-in-place pile reinforcing structure, the patent technology is that a group of axial reinforcing holes are drilled on the existing cast-in-place pile, the reinforcing holes are drilled into a foundation layer 1m, then a group of steel pipes are placed into the reinforcing holes, the bottom of each steel pipe is sealed, a group of grouting holes with the diameter of 10mm are split at the interval of 500mm in the length range of 5m from the bottom of each pipe, and secondary grouting is carried out on the bottom of the cast-in-place pile through the steel. The technology can theoretically improve the bearing capacity of the cast-in-place pile, but because the drilling stroke is longer, the requirement on a drilling machine is higher, the strength of the pile per se is influenced to a certain extent in the drilling process, and the bearing capacity of the cast-in-place pile is not improved greatly.

Therefore, for the working environment of the tidal current generator set, the problem that a cast-in-place pile capable of bearing large and periodic wave and tidal current loads and maximally utilizing the water flow cross section is urgently needed to be solved is provided.

Disclosure of Invention

The invention provides a tidal current generation cast-in-place pile with a pile core steel pipe and a construction method thereof, and aims to solve the problems that the conventional cast-in-place pile with the conventional diameter cannot bear the load generated by high-flow-speed tidal current, and the large-diameter cast-in-place pile occupies too much tidal current effective water cross section, so that the utilization of tidal current energy is influenced, and the construction cost of the large-diameter cast-in-place pile is too high.

The tidal current power generation cast-in-place pile comprises a connecting sleeve, an outer sleeve, a pile core steel pipe, a reinforcement cage and a capping steel plate, wherein one end of the connecting sleeve is embedded into a rock face of a seabed bedrock layer, the other end of the connecting sleeve extends into the outer sleeve, the reinforcement cage is arranged in the outer sleeve and extends from the top of the outer sleeve to the bottom of the cast-in-place pile through the connecting sleeve, and the pile core steel pipe is arranged in the reinforcement cage; and after the cast-in-place pile is integrally solidified with the reinforcement cage, the top end of the outer sleeve is welded with a sealing cover through the top steel plate, and the bottom of the cast-in-place pile is 6m below the rock surface of the seabed foundation stratum.

Further, the steel reinforcement cage includes annular welding support frame, stirrup and single main reinforcing bar, single main reinforcing bar arranges in the welding support frame outside along the hoop, and the single main reinforcing bar outside is along vertically binding and having the stirrup.

Furthermore, the welding support frames adopt HPB300 hot rolled steel bars, and the longitudinal distance between every two adjacent welding support frames is 5-8 m.

Furthermore, the stirrups adopt HPB300 hot rolled steel bars, the longitudinal distance between every two adjacent stirrups is 150-200 mm, and the distance between every two stirrups within the range from the pile bottom to the rock surface of the seabed bedrock stratum by 1 time of the pile diameter is encrypted to be 100 mm.

further, the single-row main steel bars adopt hot rolled steel bars of HRB400 grade and above.

Furthermore, two circles of water stop rubber are arranged in the range of 3m at the lower end of the outer sleeve, the thickness of the water stop rubber is the difference between the inner diameter of the outer sleeve and the outer diameter of the connecting sleeve, and the water stop rubber is fixed on the connecting sleeve through a P-shaped rubber gasket by screws.

Furthermore, the top end of the connecting sleeve, the top end of the pile core steel pipe and the bottom end of the auxiliary steel pipe are provided with connecting buckles, and connection and disconnection are performed during release through the connecting buckles.

Furthermore, the connecting sleeve adopts a steel pipe with the model of Q345 and above, the length of the pipe is L1+3.5m, the connecting sleeve is embedded 0.5m below the rock surface of the seabed bedrock layer and extends into the outer sleeve by 3 m; the outer sleeve adopts Q345 and above type steel pipe, and L1 is the maximum distance along the outer sleeve axis direction between outer sleeve bottom and seabed basement rock stratum rock face, and L1 can take 1.5 ~ 3.0m usually.

Furthermore, the capping steel plate comprises two ribbed plates and an upper top plate, the ribbed plates are welded below the upper top plate, and the two ribbed plates are welded in a crossed and vertical mode.

furthermore, the periphery of a gap between the connecting sleeve and the rock surface of the seabed bedrock is provided with mould bag concrete for plugging the contact gap and preventing slurry leakage in the later grouting process.

the construction method of the tidal current power generation cast-in-place pile comprises the following steps:

(1) Positioning an assembly platform by using a construction ship, and controlling the distance between the bottoms of all outer sleeves on the assembly platform and the rock surface of a seabed foundation rock stratum to be 1.5-3 m by using elevation control, so that the top plane of the assembly platform is ensured to be basically horizontal in the positioning process;

(2) Selecting a certain number of outer sleeves which are reasonably arranged on an assembly platform according to design requirements, placing positioning steel pipe piles in the outer sleeves, connecting the positioning steel pipe piles with the outer sleeves through positioning pins with finely adjustable heights, and adjusting the heights of the positioning pins after the placement of all the positioning steel pipe piles is finished to enable the top plane of the assembly platform to meet the designed horizontal requirements;

(3) Inserting the inner sleeve into the outer sleeve, enabling the bottom end of the inner sleeve to be in contact with the rock surface of a seabed bedrock layer, performing primary pore forming through an impact hammer, and sinking the inner sleeve while forming pores, wherein the length of the inner sleeve meets the requirement that the top end of the inner sleeve is slightly higher than the top end of the outer sleeve after the primary pore forming is finished, so that the inner sleeve is sunk in the primary pore forming process and is pulled out after the secondary pore forming is finished;

(4) Secondary pore-forming is carried out through an impact hammer, the inner sleeve is not sunk any more in the pore-forming process at this stage, the depth of the secondary pore-forming is 6m below the rock surface of the seabed bedrock layer, and the inner sleeve is taken out after the secondary pore-forming is finished;

(5) Placing a connecting sleeve, connecting the top of the connecting sleeve with the bottom of an auxiliary steel pipe with the same diameter at the upper part through a connecting buckle before placing, and driving the auxiliary steel pipe and the connecting sleeve into the position which is not less than 0.5m below the surface of the seabed bedrock together in an outer sleeve by using a pile hammer; after the connecting sleeve is in place, pulling out the upper auxiliary steel pipe through the rotary connecting buckle, and further throwing mould bag concrete around a gap between the connecting sleeve and the rock surface of the seabed bedrock layer for plugging;

(6) Removing slag from a rock-socketed pile foundation hole, placing a prefabricated reinforcement cage, inserting a conduit for pouring concrete into the rock-socketed pile foundation hole to perform primary pouring of pile core concrete, wherein the height of a pouring top is 1-2 m higher than the height of the top of a connecting sleeve, the pouring depth is L1+ (10-11) m, the depth is 6m below a rock surface, and the depth is L1+ (4-5) m above the rock surface, and a retarder is added to the poured concrete to prolong the initial setting time;

(7) connecting the pile core steel pipe with an auxiliary steel pipe with the same diameter through a connecting buckle, driving the pile core steel pipe into the pile core concrete by using a pile driving hammer before primary pouring concrete is initially set, enabling the distance from the bottom end of the pile core steel pipe to the bottom of a rock-socketed pile foundation hole to be not more than 0.5m, enabling the length of the pile core steel pipe to be L1+ (9.5-10.5) m, enabling the top elevation of the pile core steel pipe to be not higher than the surface of the primary pouring concrete after release, and finally, rotating and disconnecting the connecting buckle to pull out the upper auxiliary steel pipe;

(8) After the pile core steel pipe is installed, secondary pile core concrete pouring is carried out, the pile core steel pipe is poured to the designed elevation of a pile foundation, a retarder is added into the primary pouring concrete, the time interval of the secondary concrete pouring is strictly controlled, so that no interface exists in the secondary pouring concrete, the integral performance of the cast-in-place pile is ensured, and after the pouring is finished, the top-sealed steel plate is welded with the top of the outer sleeve.

the cast-in-place pile has the advantages of small diameter, strong bending resistance and shearing resistance and simple and convenient construction process. In the one-time pouring process, a pile core steel pipe with the length of L1+ (9.5-10.5) m is driven into the interface of the cast-in-place pile and the seabed base rock stratum and is embedded into the area, which is not less than 5.5m, below the seabed base rock stratum. Compared with the common cast-in-place pile, the cast-in-place pile has the advantages that under the action of reciprocating loads such as waves and tides, particularly in extreme weather, the pile core steel pipe and the reinforcement cage can jointly exert stronger bending resistance and shearing resistance, and the bending resistance and the shearing resistance are stronger than those of the common cast-in-place pile. The pile core steel pipe is additionally arranged in the cast-in-place pile, so that on one hand, the bending resistance of the cast-in-place pile can be greatly improved, the longitudinal structure of the pile core steel pipe is equivalent to the main reinforcements which have the same diameter as the wall thickness of the pile core steel pipe and are arranged in an infinite encryption manner, the size of the cast-in-place pile can be effectively reduced, the number of axial main reinforcements in a reinforcement cage can be effectively reduced, the original densely arranged reinforcement bundles are replaced by single-row main reinforcements with larger intervals, and the quality of concrete cast-in-place molding is greatly; on the other hand, the shearing resistance of the cast-in-place pile can be greatly improved, the annular structure of the pile core steel pipe is equivalent to the stirrups with the diameter equal to the wall thickness of the pile core steel pipe and arranged in an infinite encryption manner, so that the shearing resistance of the cast-in-place pile is greatly improved, and the defect that the existing cast-in-place pile is insufficient in shearing resistance is overcome. In the aspect of construction process, only one process of embedding a pile core steel pipe is added in the construction process of the common cast-in-place pile, so that the method is simple, convenient and quick, and the whole process flow of the cast-in-place pile is not disturbed. The pile core steel pipe is only arranged in the maximum bending and shearing section of the cast-in-place pile, the pile foundation structure is integrally optimized, and the manufacturing cost is saved. Therefore, the cast-in-place pile foundation has the advantages of relatively small diameter, excellent performance and relatively low construction cost, is particularly suitable for offshore area engineering foundations such as tidal current power generation pile foundations bearing large horizontal loads under the environmental conditions of tidal current, waves and the like, has high flexibility, and has relatively good economic benefit and social benefit.

drawings

Fig. 1 is a schematic structural diagram of a tidal current power generation cast-in-place pile of the invention.

fig. 2 is a schematic structural diagram of the water-stopping rubber of the tidal current power generation cast-in-place pile.

Fig. 3 is a schematic diagram of a capping steel plate structure of the tidal current power generation cast-in-place pile of the invention.

fig. 4 is a schematic view of a local structure of a reinforcement cage of the tidal current power generation cast-in-place pile of the invention.

Fig. 5 is a schematic view of a partial structure of a connecting buckle of the tidal current power generation cast-in-place pile.

Fig. 6(a) to fig. 6(g) are schematic diagrams of the construction flow structure of the tidal current power generation cast-in-place pile of the invention in sequence.

Detailed Description

In order to describe the present invention more specifically, the technical solutions and the construction processes thereof will be described in detail below with reference to the accompanying drawings and the detailed description.

as shown in fig. 1, the tidal current power generation cast-in-place pile 1 with the pile core steel pipe comprises a connecting sleeve 3, an outer sleeve 8, a reinforcement cage 7, a capping steel plate 9 and a pile core steel pipe 2, wherein the outer sleeve 8 is connected with an outer frame of an assembly platform into a whole, the reinforcement cage 7 is arranged inside the outer sleeve 8, the top of the outer sleeve 8 is welded with the capping steel plate 9, the lower part of the outer sleeve 8 is lapped with the connecting sleeve 3 through a water stop rubber 6, the connecting sleeve 3 is embedded into a seabed foundation layer 4, the cast-in-place pile 1 is poured from an embedding bottom surface to the top of the outer sleeve 8 in a full-length mode and is fixedly connected with the reinforcement cage 7 into a; and a mould bag concrete 5 is arranged between the seabed foundation layer 4 and the connecting sleeve 3 to block a contact gap and prevent slurry leakage in the later grouting process.

As shown in fig. 4, the reinforcement cage 7 includes a welding support frame 701, a stirrup 702, and a single row of main reinforcements 703, the welding support frame 701 is disposed inside the single row of main reinforcements 703, and the stirrup 702 is disposed around the outside of the single row of main reinforcements 703.

The pile core steel pipe 2 is a Q345 or above type steel pipe, the total length is L1+ 9.5-10.5 m, and L1 is the maximum distance between the bottom end of the outer sleeve 8 and the rock surface of the bedrock layer along the axial direction of the outer sleeve and is embedded 6m below the rock surface of the seabed bedrock layer 4; the welding support frames 701 are HPB300 hot rolled steel bars, and the space between the welding support frames is 5 m-8 m; the stirrups 702 are HPB300 hot rolled steel bars, the distance between the stirrups 702 is 150 mm-200 mm, and the distance between the stirrups in the pile diameter range from the bottom of the pile to 1 time above the rock surface is encrypted to be 100 mm.

Two circles of water stopping rubber 6 are arranged in the range of 3m at the lower end of the outer sleeve 8, and the thickness is the difference between the inner diameter of the outer sleeve 8 and the outer diameter of the connecting sleeve 3. The water stop rubber 6 includes a P-type rubber gasket 601 and a screw 602, and as shown in fig. 2, the P-type rubber gasket 601 is fixed to the connection sleeve 3 by the screw 602.

Connecting buckles 14 are connected between the top end of the connecting sleeve 3, the top end of the pile core steel pipe 2 and the bottom end of the auxiliary steel pipe 10, as shown in fig. 5.

The connecting sleeve 3 is a steel pipe with the model of Q345 or more, the length of the pipe is L1+3.5m, the pipe is embedded 0.5m below the rock surface and extends into the lower end of the outer sleeve 8 by 3 m; the outer sleeve 8 is a Q345 or above type steel pipe, the bottom of the outer sleeve 8 is higher than the rock surface L1m, and the top end of the outer sleeve 8 is connected with the capping steel plate 9 in a welding mode.

As shown in fig. 3, the capping steel plate 9 includes two rib plates 18 and an upper top plate 19, the two rib plates 18 are cross-welded perpendicularly, the rib plates 18 and the upper top plate 19 are welded by a double-sided groove, and the upper top plate 19 and the top of the outer sleeve 8 are welded by a single-sided crevasse.

The concrete construction method of the tidal current power generation cast-in-place pile comprises the following steps:

(1) As shown in fig. 6(a), the overall structural form of the assembly platform 11 and the diameter, number, position and length of the bored pile are designed according to the relevant data such as the geological survey and the tidal current, the assembly platform 11 covers the layout of the outer sleeves 8, and the outer sleeves 8 and the assembly platform 11 form an integral frame structure; positioning the assembly platform 11 by using a construction ship, and enabling the distance between the bottoms of all outer sleeves 8 on the assembly platform 11 and the top surface of the seabed bedrock to be 1.5-3 m through elevation control, wherein the top plane of the assembly platform 11 is ensured to be basically horizontal in the positioning process.

(2) according to design requirements, selecting a certain number of outer sleeves 8 which are reasonably arranged on an assembly platform 11 as construction positioning pile positions in advance, placing positioning steel pipe piles in the positioning steel pipe piles, connecting the positioning steel pipe piles with the outer sleeves 8 through positioning pins with height capable of being finely adjusted, and adjusting the heights of the positioning pins after the placement of all the positioning steel pipe piles is finished to enable the top plane of the assembly platform to meet the design horizontal requirements; and after leveling, welding and fixing the outer sleeve 8 at the construction positioning pile position and the outer frame 11 of the assembly platform.

(3) as shown in fig. 6(b), the inner sleeve 12 is inserted into the outer sleeve 8, so that the bottom end of the inner sleeve 12 contacts with the seabed bedrock surface 4, primary pore-forming is performed by an impact hammer, the inner sleeve 12 sinks while pore-forming is performed, the depth of the primary pore-forming is 0.5m, the length requirement of the inner sleeve 12 meets the requirement that the top end of the inner sleeve 12 is slightly higher than the top end of the outer sleeve 8 after the primary pore-forming is finished, and therefore the sinking of the inner sleeve 12 in the primary pore-forming process and the extraction of the inner sleeve 12.

(4) As shown in fig. 6(c), secondary hole forming is performed by the impact hammer, the inner sleeve 12 does not sink any more in the hole forming process at this stage, the depth of the secondary hole forming is 6m below the seabed bedrock surface 4, and the inner sleeve 12 is taken out after the secondary hole forming is finished.

(5) As shown in fig. 6(d), the connecting sleeve 3 is placed, the top of the connecting sleeve 3 is connected with the bottom of the auxiliary steel pipe 10 with the same diameter as the upper part through the connecting buckle 14 before placing, and the auxiliary steel pipe 10 and the connecting sleeve 3 are driven into the seabed bedrock surface 4 by a pile driving hammer in the outer sleeve 8 to be not less than 0.5 m; the length of the connecting sleeve 3 is L1+3.5m, which is determined by the distance L1 between the bottom end of the outer sleeve 8 and the bedrock rock surface 4, and a circle of water-stopping rubber 6 is respectively arranged on the upper part and the lower part of the outer wall of the connecting sleeve 3 to be used as a slurry leakage prevention measure for later grouting; after the connecting sleeve 3 is in place, the upper auxiliary steel pipe 10 is pulled out through the rotary connecting buckle 14, and then the mold bag concrete 5 is thrown around the gap between the connecting sleeve 3 and the seabed bedrock surface 4 for plugging.

(6) as shown in fig. 6(e), slag removal is carried out on the socketed pile foundation hole, the prefabricated reinforcement cage 7 is placed, then a conduit for pouring concrete is inserted into the socketed pile foundation hole to carry out primary pouring of pile core concrete, the height of a pouring top is 1-2 m higher than the height of the top of the connecting sleeve 3, the pouring depth is L1+ 10-11 m, wherein the height is 6m below a rock surface, the height is L1+ 4-5 m above the rock surface, and retarder needs to be added to the poured concrete to prolong the initial setting time.

(7) as shown in fig. 6(f), the pile core steel pipe 2 and the auxiliary steel pipe 10 with the same diameter are connected through the connecting buckle 14, before the primary pouring concrete is not initially set, the pile core steel pipe 2 is driven into the pile core concrete by using a pile driving hammer, so that the distance from the bottom end of the pile core steel pipe 2 to the bottom of the rock-socketed pile is not more than 0.5m, the length of the pile core steel pipe 2 is L1+ 9.5-10.5 m, the top elevation of the pile core steel pipe 2 after being discharged is not higher than the surface of the primary pouring concrete, finally, the connecting buckle 14 is rotated and disconnected, the upper auxiliary steel pipe 10 is pulled out, and the diameter of the pile core steel pipe 2 is specifically determined.

(8) As shown in fig. 6(g), after the pile core steel tube 2 is installed, secondary pile core concrete pouring is performed, the pile core concrete pouring is performed to the top end of the outer sleeve 8, namely the designed elevation of the pile foundation, the retarder is added into the primary pouring concrete, and the time interval of the two times of concrete pouring is strictly controlled, so that the interface does not exist in the two times of pouring concrete, the overall performance of the cast-in-place pile is not affected, and after the pouring is finished, the capping steel plate 9 and the top of the outer sleeve 8 need to be welded as soon as possible before the concrete is initially set.

The embodiment is a specific implementation mode of the tidal current power generation cast-in-place pile with the pile core steel pipe, which is given based on that the sea area is built in the offshore area with the water depth not more than 30m in the offshore tidal current electric field in China, after the pile foundation is poured and reaches the design strength, the positioning steel pipe pile in the temporary positioning pile for construction is pulled out, the cast-in-place pile construction in the same process is carried out, and after all pile foundation construction is finished and reaches the design strength, a tidal current generator set can be placed in the assembly platform frame.

The embodiments described above are presented to enable a person having ordinary skill in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications can be made to the above-described embodiments and the generic principles defined herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not limited to the above embodiment examples, and those skilled in the art should make improvements and modifications to the present invention based on the disclosure of the present invention within the protection scope of the present invention.

Claims

1. A construction method of a tidal current power generation cast-in-place pile comprises a connecting sleeve, an outer sleeve, a pile core steel pipe, a reinforcement cage and a capping steel plate, wherein one end of the connecting sleeve is embedded into a rock face of a seabed bedrock layer, the other end of the connecting sleeve extends into the outer sleeve, the reinforcement cage is arranged in the outer sleeve and extends from the top of the outer sleeve to the bottom of the cast-in-place pile through the connecting sleeve, and the pile core steel pipe is arranged in the reinforcement cage; the cast-in-place pile is characterized in that cast-in-place concrete is poured from the pile bottom to the top of the outer sleeve through the connecting sleeve and is fixedly integrated with the reinforcement cage, a sealing cover is welded at the top end of the outer sleeve through the capping steel plate, and the pile bottom of the cast-in-place pile is 6m below the rock surface of the seabed foundation layer; the construction method comprises the following steps:

(6) Removing slag from a rock-socketed pile foundation hole, placing a prefabricated reinforcement cage, inserting a conduit for pouring concrete into the rock-socketed pile foundation hole to perform primary pouring of pile core concrete, wherein the height of a pouring top is 1-2 m higher than the height of the top of a connecting sleeve, the pouring depth is L1+ (10-11) m, the depth is 6m below a rock surface, and the depth is L1+ (4-5) m above the rock surface, and a retarder is added to the poured concrete to prolong the initial setting time; l1 is the maximum distance between the bottom end of the outer sleeve and the rock surface of the seabed bedrock stratum along the axial direction of the outer sleeve;