Construction method of pile well type caisson wharf structure

Abstract

The application discloses a construction method of a pile well type caisson wharf structure, which comprises the following steps: sinking prefabricated gravity type caissons to a leveled base bed, arranging a pile foundation system in the gravity type caissons, arranging one pile foundation in each compartment of the gravity type caissons, extending the lower end of the pile foundation into a bearing layer, locating the upper end of the pile foundation in the gravity type caissons, filling backfilling materials in the compartments of the gravity type caissons and tamping to connect the part of the pile foundation in the gravity type caissons and the gravity type caissons into an integrated whole. The construction method of the application improves the adaptability to the foundation, reduces the dredging and leveling process, and can improve the vertical bearing capacity, horizontal shear resistance and overturning resistance of the caisson, effectively prevents the collapse of the land surface, further optimizes the construction process and operation environment, and promotes the quality improvement of the gravity type caisson wharf in the port engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of caisson wharf construction in port engineering construction. More particularly, the present application relates to a construction method of a pile well type caisson wharf structure. BACKGROUND

[0002] With the rapid development of economy at home and abroad, in the process of water and land transportation, ships show a trend of large-scale development. With the increase of cargo demand, the pressure on the port is gradually increasing, and its construction scale is also expanding. At present, the structural form of the wharf mainly includes two categories: pile foundation structure and gravity type caisson structure. The gravity type caisson wharf is suitable for areas with good foundation, has strong adaptability to wharf ground overload and handling process changes, has the advantages of less steel consumption, good engineering durability, etc., and is currently widely used in coastal areas.

[0003] However, the gravity type caisson wharf has relatively high requirements for the bearing capacity of the foundation, and problems such as rapid backfilling of the foundation trench and settlement of the main body of the wharf occur during construction. With the increase of the water depth of the wharf, the cost of the caisson wharf also rises sharply. In the construction process, some corresponding countermeasures are also taken, for example, for the problem of backfilling of the foundation trench, dredging is usually arranged first when the construction plan is developed, and then the foundation trench is excavated. When the bearing capacity of the surface foundation does not meet the requirements, methods such as replacement of the foundation and composite foundation are used for treatment.

[0004] The above still does not fundamentally solve the problem of bearing layer foundation treatment, and with the process of foundation trench excavation and flattening, the project duration and cost are further increased, and ideal economic benefits cannot be achieved. In the face of large engineering quantity and short engineering period, the advantages are still not enough prominent, and it is difficult to meet the increasing demand for fast-paced construction of projects.

[0005] Chinese Patent Publication No. CN202989857U discloses a reinforced gravity type caisson wharf structure, which includes a gravity type caisson wharf main body structure and a plurality of pile foundations. The base bed in the gravity type caisson wharf main body structure is provided with a grouting reinforcement body. The pile foundation is only implanted in part of the bin under the toe of the caisson, and the overall anti-overturning capacity is poor.

[0006] Chinese Patent Publication No. CN216041271U discloses a gravity type caisson wharf structure with anti-slide piles in the foundation base. The left and right sides of the caisson are provided with insertion plates, the number of anti-slide piles is set to multiple, and the outermost anti-slide piles are fixedly connected with a continuous wall. Although this structure improves the overall stability by increasing the contact area of the anti-slide piles with the foundation, it also increases the foundation treatment process, leading to complex and cumbersome construction, and the caisson is suitable for silt geology, and the adaptability to the foundation is not high. SUMMARY

[0007] An object of the present application is to provide a construction method of a pile caisson type caisson wharf structure, which improves the adaptability to the foundation, reduces the dredging and leveling process, and further improves the vertical bearing capacity, horizontal shear resistance and overturning resistance of the caisson, effectively prevents the collapse of the land surface, further optimizes the construction process and working environment, and promotes the quality improvement of the gravity caisson wharf in port engineering.

[0008] In order to achieve the objects and other advantages according to the present application, a construction method of a pile caisson type caisson wharf structure is provided, which comprises the following steps: sinking a prefabricated gravity caisson onto a leveled foundation bed, arranging a pile foundation system in the gravity caisson, wherein the gravity caisson is provided with a plurality of pile foundations, each of the pile foundations is arranged in a corresponding cell of the gravity caisson, the lower end of each of the pile foundations extends into a bearing layer, and the upper end of each of the pile foundations is located inside the gravity caisson, filling backfill material in the cells of the gravity caisson and tamping to connect the part of the pile foundations inside the gravity caisson with the gravity caisson as a whole.

[0009] Preferably, the pile foundation system further comprises an auxiliary mechanism, which comprises a steel casing and an annular fixing plate fixed on the outer wall of the steel casing, a plurality of rib plates are annularly and spacedly arranged on the annular fixing plate, and the rib plates are fixedly connected with the steel casing and the annular fixing plate, respectively. After the gravity caisson is sunk, the auxiliary mechanism is arranged in the cell of the gravity caisson, then a part of the backfill material is filled to connect the auxiliary mechanism with the gravity caisson as a whole, a drilling construction platform is erected, and the pile foundation is constructed in the steel casing, and after the pile foundation is constructed, the backfill material is continuously filled upward in the cell of the gravity caisson.

[0010] Preferably, the outer wall of the gravity caisson is further provided with a blade foot at the bottom end, and the inner side of the blade foot has an inclination angle of 45°-60°. After the gravity caisson is sunk and the auxiliary mechanism is arranged, the bottom plate of the gravity caisson is first poured underwater to form a bottom plate, the auxiliary mechanism is located in the bottom plate, the cell of the gravity caisson is formed into a sealed space by the bottom plate, and then the backfill material is filled and the subsequent pile foundation construction is carried out.

[0011] Preferably, when the auxiliary mechanism is arranged, the top surface of the steel casing is sealed by a sealing steel plate to form a dry construction environment for the pile foundation construction.

[0012] Preferably, a reserved bracket is arranged on the bulkhead of the gravity caisson during prefabrication of the gravity caisson, and the height of the reserved bracket is higher than the height of the steel casing. The reserved bracket is used to erect a construction platform for the pile foundation construction, and the final filling height of the backfill material is higher than the height of the reserved bracket.

[0013] Preferably, the gravity caisson is provided with one or more, the gravity caisson is connected as a whole, the bottom elevation of the gravity caisson is different, and the top elevation is the same; the depth of the pile foundation in the bearing layer is different.

[0014] Preferably, the method comprises the following steps:

[0015] Step one, prefabricate the gravity caisson, steel casing, steel reinforcement cage and reserved bracket in the prefabrication yard, and weld the reserved bracket on the gravity caisson bulkhead according to the design position requirements and quantity, at least two reserved brackets are evenly distributed on each gravity caisson bulkhead, the outer wall of the gravity caisson is provided with a blade foot, and a ring-shaped fixed plate is fixedly arranged on the outer wall of the steel casing after the steel casing is prefabricated, a plurality of rib plates are arranged on the ring-shaped fixed plate in a ring shape, and the rib plates are fixedly connected with the steel casing and the ring-shaped fixed plate respectively;

[0016] Step two, transport the gravity caisson to the installation position of the leveled bed, and lower the gravity caisson to the designed depth through the construction process of earth excavation combined with the blade foot auxiliary sinking, and then adjust the posture of the gravity caisson to the design standard;

[0017] Step three, vertically arrange a steel casing in the center of each compartment of the gravity caisson, the bottom of the steel casing is flush with the bottom end of the gravity caisson, the top surface of the steel casing is provided with a sealing steel plate during arrangement, and the top end of the steel casing is higher than the bottom end of the gravity caisson by not less than 3m;

[0018] Step four, underwater pouring of the bottom plate concrete of the gravity caisson to form the bottom plate of the gravity caisson, the bottom surface of the bottom plate is flush with the bottom end of the steel casing, and the ring-shaped fixed plate and the plurality of rib plates on the steel casing are located in the bottom plate and integrally connected with the bottom plate;

[0019] Step five, water pumping operation is carried out in the gravity caisson compartment to realize the dry construction environment of the pile foundation;

[0020] Step six, fill the backfill material below the reserved bracket in the gravity caisson compartment, then arrange a construction platform on the reserved bracket, remove the sealing steel plate on the steel casing, and construct the pile foundation in the steel casing;

[0021] Step seven, continue to fill the backfill material in the gravity caisson compartment and tamp it to be higher than the height of the reserved bracket to increase the connection strength between the pile foundation and the gravity caisson;

[0022] Step eight, outer facing construction of the gravity caisson;

[0023] Step nine, construction of the upper breast wall and fender member of the gravity caisson.

[0024] Preferably, the gravity type caisson is prefabricated with a pre-embedded steel plate embedded on the inner wall of the bulkhead, and the pre-embedded steel plate is welded with the reserved bracket.

[0025] Preferably, the pile foundation construction comprises the following steps: drilling a hole to the design depth of the pile foundation along the steel casing into the bearing layer below the construction platform, then lowering the reinforcement cage into the hole, and finally pouring concrete in the hole.

[0026] The present application at least includes the following beneficial effects:

[0027] 1. The present application provides a construction method of a pile caisson type caisson wharf structure, which is different from the traditional caisson construction method. Only the soil in the well is excavated to sink the caisson to the depth reached by gravity, which avoids large-area dredging, underwater blasting, ramming and leveling in the early stage, effectively ensures the safety performance of the construction, reduces the workload and cost of foundation treatment, and uses the drilling platform erected on the reserved bracket for pile foundation construction without using a piling ship, thereby reducing offshore operations.

[0028] 2. The pile caisson type caisson wharf structure provided by the present application can make the caisson and the pile foundation system jointly bear the load, so that the stability and durability of the foundation are better than those of the prior art. Even if the connection between a pile foundation and the bottom plate of the caisson is damaged, the remaining nodes can still ensure the connection strength of the lower foundation, and the stability and reliability of the pile caisson structure are better.

[0029] 3. The backfilling material is poured in batches, and the auxiliary mechanism is arranged, so that the position of the pile foundation can be effectively prevented from deviating during grouting, and the connection strength of the lower overall structure is enhanced.

[0030] 4. Compared with the traditional gravity type caisson structure, the lower structure can reduce the height of the caisson, reduce the overturning moment of the entire structure, enhance the anti-overturning, anti-sliding and horizontal shear performance, reduce the cost of the caisson, effectively improve the economic benefit, and be applicable to the construction of large caisson wharf structures on silt, clay and rock and the like.

[0031] Other advantages, objects and features of the present application will be partly embodied in the following description, and will be partly understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a pile caisson type caisson wharf structure of the present application;

[0033] Figure 2 is a sectional view of a gravity type caisson bottom plate of the present application;

[0034] Figure 3This is an elevation view of the connecting component between the gravity caisson bottom plate and the steel casing of the present invention;

[0035] Figure 4 This is a flowchart of the construction method for the pile-well type caisson wharf structure of the present invention;

[0036] Figure 5 This is a schematic diagram of the drilling platform layout for the pile-well type caisson wharf structure of the present invention.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Gravity caisson, 2. Steel casing, 3. Pile foundation, 4. Backfill material, 5. Rib plate, 6. Annular fixing plate, 7. Foundation bed, 8. Bearing layer, 9. Fender components, 10. Breast wall, 11. Reinforcing cage, 12. Cutting edge, 13. Reserved corbel, 14. Construction platform. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0040] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Example

[0042] like Figures 1 to 5 As shown, this invention provides a construction method for a pile-and-well type caisson wharf structure. The wharf structure includes an upper structure and a lower structure. The upper structure of the wharf includes a breast wall 10, a concrete surface layer, etc., and a fender component 9 is also provided at the front end of the wharf. These are all conventional structures. The lower structure of the wharf is different from the conventional structure. The gravity caisson 1 and the pile foundation 3 system together constitute the lower structure of the wharf. The backfill material 4 fills the compartments of the gravity caisson 1. After compaction, the gravity caisson 1 and the pile foundation 3 system are connected into a whole. The pile foundation 3 system includes piles 3 evenly distributed inside the compartments of the gravity caisson 1. This new structure solves the foundation treatment problem and enhances the stability of the gravity caisson 1, greatly improving the safety and durability of the wharf structure.

[0043] The construction method specifically includes the following steps:

[0044] Step one, prefabricate gravity caisson 1, steel casing 2, reinforcement cage 11, reserved bracket 13 in the prefabrication yard. The construction of the prefabrication yard needs to meet the progress requirement of the installation or storage of the prefabricated components. When the caisson is prefabricated, the water inlet, water hole, pull ring and other embedded parts need to be designed reasonably. The concrete surface in the water level change area is treated with anticorrosion to improve the durability of the concrete. The reserved bracket 13 is welded on the bulkhead of the gravity caisson 1 according to the design position and quantity requirements. At least two reserved brackets 13 are evenly distributed on each bulkhead of the gravity caisson 1. The blade foot 12 is arranged at the bottom end of the outer wall of the gravity caisson 1. The ring-shaped fixed plate 6 is fixedly arranged on the outer wall of the steel casing 2 after the steel casing 2 is prefabricated. A plurality of rib plates 5 are arranged on the ring-shaped fixed plate 6 in a ring shape and at intervals. The rib plates 5 are respectively fixedly connected with the steel casing 2 and the ring-shaped fixed plate 6.

[0045] The gravity caisson 1 includes the blade foot 12, the well wall, i.e. the outer wall, the inner partition wall which divides the caisson into a plurality of compartments, the bottom plate (formed by underwater pouring in the later period), the top cover, the air cylinder, the air lock and the manhole. The blade foot 12 is a sharp corner part at the lowermost end of the well wall. The outer side of the blade foot 12 is vertically parallel to the outer wall of the caisson. The inner side of the blade foot 12 is a slope. The inclination angle of the inner side is usually 45°-60°. The blade foot 12 provides protection for the sinking of the caisson structure under complex geological conditions. The steel casing 2, the ring-shaped fixed plate 6 and the rib plate 5 arranged outside the steel casing 2 together form an auxiliary mechanism. The ring-shaped fixed plate 6 is arranged to be close to the bottom plate of the gravity caisson 1. The rib plates 5 are distributed at intervals along the axial direction of the steel casing 2. The ring-shaped fixed plate 6 and the rib plate 5 are connected with the outer wall of the steel casing 2 by welding or fixing bolts. The contact area between the caisson and the steel casing 2 can be increased by arranging the ring-shaped fixed plate 6. The reserved bracket 13 is arranged on the bulkhead of the caisson and is evenly distributed on both sides of the steel casing 2. The structure of the reserved bracket 13 includes a bracket steel shell and concrete poured in the bracket steel shell in the later period. The reserved bracket 13 is connected with the prefabricated caisson by welding a reserved steel plate in the connecting area. The inner wall of the gravity caisson 1 is provided with a reserved steel plate which is welded with the reserved bracket 13 during the prefabrication of the gravity caisson 1. This avoids damage to the caisson caused by the welding of additional structures and the reserved bracket 13, and makes the construction more convenient and fast. After the dry construction platform 14 is formed by pumping water, the construction platform 14 can also be arranged on the reserved bracket 13, which creates a good construction environment for the pile foundation 3 construction, as shown in FIG. 1. Figure 5

[0046] The number of caissons is designed to be one or more according to the design of the wharf shoreline. Connection members are arranged between the multiple caissons to connect them. The bottom elevation of each connected caisson can be differentially arranged according to the undulating condition of the seabed rock. The top elevations of the caissons are the same, which effectively reduces the underwater reef blasting. The soil penetration depth of the pile foundation 3 can be differentially arranged according to the geological condition of the caisson bottom and the stress condition of the caisson. The total vertical bearing capacity of the pile foundation 3 system accounts for 50%-60% of the total vertical load of the wharf, which is appropriate.

[0047] ​Step two, the gravity caisson 1 is transported by a semi-submersible barge, and is transported to the installation position of the leveled foundation 7 by using a floating crane and other lifting equipment, and is lowered to the designed depth by using a dredger and the auxiliary sinking construction procedure of the blade foot 12. Then, the attitude of the gravity caisson 1 is adjusted to the design standard by using an anchor system.

[0048] Step three, a steel casing 2 is vertically arranged in the center of each compartment of the gravity caisson 1. The bottom of the steel casing 2 is flush with the bottom end of the gravity caisson 1. The top surface of the steel casing 2 is sealed by a sealing steel plate when the steel casing 2 is arranged downward. The steel casing 2 has a certain preset height from the bottom plate, and the top end is generally not less than 3m higher than the bottom plate of the gravity caisson 1.

[0049] Step four, the bottom plate concrete of the gravity caisson 1 is poured underwater to form the bottom plate of the gravity caisson 1. The bottom plate and the bottom surface are flush with the bottom end of the steel casing 2. The annular fixing plate 6 and the plurality of rib plates on the steel casing 2 are located in the bottom plate and are integrally connected with the bottom plate by pouring. The pouring of the concrete requires high quality, and must have the characteristics of underwater non-separation, self-compaction, low bleeding, and slow setting.

[0050] Step five, water is pumped out of the gravity caisson 1 to realize the dry construction environment of the pile foundation 3.

[0051] Step six, the backfill material 4 is filled in the compartment of the gravity caisson 1 to below the reserved bracket 13, then the construction platform 14 is arranged on the reserved bracket 13, and the sealing steel plate on the steel casing 2 is removed. The pile foundation 3 is formed in the steel casing 2.

[0052] By using lifting equipment, the drilling machine is lifted and enters along the steel casing 2 to the designed depth of the pile foundation 3 by mechanical drilling to form a pile hole in the bearing layer 8. The drilling depth is determined according to different geological conditions, and a steel reinforcement cage 11 is placed in the pile hole, and then concrete is poured. After the strength of the concrete reaches the requirement, the lower pile foundation 3 system is formed to realize the transmission of vertical load. The steel reinforcement cage 11 includes vertical steel bars and circumferential steel bars. The steel reinforcement cage 11 is implanted to a preset depth of the bearing layer 8 below the foundation 7. After the concrete is poured, the pile foundation 3 is formed to increase the anti-sliding and anti-overturning stability of the lower structure.

[0053] Step seven, the backfill material 4 is continuously filled in the gravity caisson 1 and is tamped to be higher than the height of the reserved bracket 13 to increase the connection strength between the pile foundation 3 and the gravity caisson 1.

[0054] The backfill 4 is filled in each compartment of the caisson, and the thickness of the backfill 4 is greater than the height of the bottom plate and less than the height of the reserved bracket 13 when filled in step six. Preferably, the backfill 4 is poured with water sealing concrete or fixed to make the caisson and the steel casing 2 form an integral structure to form a pile well type caisson wharf structure. In step seven, after the pile foundation 3 is constructed, the backfill 4 is filled again to above the reserved bracket 13, so that the caisson and the pile foundation 3 system form an integral structure, and the thickness of the backfill 4 is determined according to the height of the reserved bracket 13. The reserved bracket 13 buried at the same time plays a role of resisting shear. The backfill 4 is simply leveled and can be used as a pile foundation 3 drilling construction platform 14 with the embedded bracket. The pile foundation 3 is constructed after the drilling machinery is placed on the construction platform 14, which reduces the ship operation at sea and reduces the operation cost while ensuring the pile quality.

[0055] As shown in Figure 2 , there are several compartments in the caisson, and a pile foundation 3 is arranged at the center of each compartment. After the lower pile foundation 3 is poured, the backfill 4 is filled in the compartment of the caisson to effectively prevent the relative displacement between the lower pile foundation 3 and the caisson, and better play the bearing performance of the foundation itself. The advantage of this composite structure is that it combines the gravity caisson 1 and the pile foundation 3 structure. Even if the connection between a pile foundation 3 and the bottom plate of the caisson is damaged, the remaining nodes can still ensure the connection strength of the lower foundation, and better play the stability and reliability of the pile well type caisson structure.

[0056] Step eight, as shown in Figure 5 , the gravity caisson 1 is constructed with an outer facing. The mud surface of the foundation bed 7 around the caisson is removed to the design elevation by a dredger, and the twisted king block or riprap is simply leveled and laid to perform the facing construction, so as to realize the bedding fixation of the lower foundation.

[0057] Step nine, the anchor system is released, and the upper coping 10, the panel and the fender member 9 of the gravity caisson 1 are constructed.

[0058] Although the embodiments of the present application have been disclosed as above, they are not limited to the application and implementation listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application. For those skilled in the art, other modifications can be easily realized, and therefore the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method of constructing a caisson quay structure of a pile caisson type, characterized by, After the prefabricated gravity caisson is sunk to the leveled base, a pile foundation system is arranged in the gravity caisson, which includes a plurality of pile foundations, one of which is arranged in each cell of the gravity caisson, the lower end of the pile foundation extends into the bearing layer, and the upper end of the pile foundation is located in the interior of the gravity caisson, then the interior of the cell of the gravity caisson is filled with backfill and rammed to integrate the part of the pile foundation in the interior of the gravity caisson with the gravity caisson; The pile foundation system further includes an auxiliary mechanism, which includes a steel casing and an annular fixing plate fixed on the outer wall of the steel casing, a plurality of rib plates are arranged on the annular fixing plate in a ring shape, and the rib plates are fixedly connected with the steel casing and the annular fixing plate, after the gravity caisson is sunk, the auxiliary mechanism is arranged in the cell of the gravity caisson first, then a part of the backfill is filled to integrate the auxiliary mechanism with the gravity caisson, a drilling construction platform is erected, and then the pile foundation is constructed in the steel casing, and after the pile foundation is constructed, the backfill is continuously filled upward in the cell of the gravity caisson; The outer wall bottom end of the gravity caisson is further provided with a blade foot, the inner side angle of which is 45°-60°, after the gravity caisson is sunk and the auxiliary mechanism is arranged, the bottom plate of the gravity caisson is first poured underwater to form a bottom plate, the auxiliary mechanism is located in the bottom plate, the interior of the cell of the gravity caisson is formed into a sealed space by the bottom plate, and then the backfill and subsequent pile foundation construction are filled; When the auxiliary mechanism is arranged, the top surface of the steel casing is sealed by arranging a sealing steel plate to form a dry construction environment for the pile foundation construction.

2. The construction method of a caisson quay structure of a pile caisson type according to Claim 1, characterized in that, When the gravity caisson is prefabricated, a reserved bracket is arranged on the bulkhead of the gravity caisson, which is higher than the height of the steel casing, the reserved bracket is used to erect a construction platform for pile foundation construction, and the final filling height of the backfill is higher than the height of the reserved bracket.

3. The construction method of a caisson quay structure of a pile well type according to Claim 1, characterized in that, One or more gravity caissons are arranged, the plurality of gravity caissons are integrated, the bottom elevations of the plurality of gravity caissons are differentially arranged, and the top elevations are the same; and the depths of the pile foundations in the bearing layer are differentially arranged.

4. The construction method of a caisson pier structure according to Claim 1, wherein Specifically includes the following steps: Step one, prefabricate the gravity caisson, steel casing, steel reinforcement cage, and reserved bracket in the prefabrication yard, and weld the reserved bracket on the bulkhead of the gravity caisson according to the design position requirements and quantity, at least two reserved brackets are evenly arranged on each bulkhead of the gravity caisson, a blade foot is arranged at the bottom end of the outer wall of the gravity caisson, and an annular fixing plate is fixedly arranged on the outer wall of the steel casing after the steel casing is prefabricated, a plurality of rib plates are arranged on the annular fixing plate in a ring shape, and the rib plates are fixedly connected with the steel casing and the annular fixing plate; Step two, transport the gravity caisson to the leveled base installation position, and lower the gravity caisson to the designed depth through the earth excavation combined with the blade foot assisted sinking construction process, and adjust the attitude of the gravity caisson to the design standard; Step three, vertically arrange one steel casing in the center of each cell of the gravity caisson, the bottom of the steel casing is flush with the bottom end of the gravity caisson, the top surface of the steel casing is sealed by arranging a sealing steel plate when the steel casing is arranged, and the top end of the steel casing is higher than the bottom end of the gravity caisson by not less than 3m. Step four, pouring the bottom plate concrete of the gravity caisson underwater to form the bottom plate of the gravity caisson, the bottom surface of the bottom plate is flush with the bottom end of the steel casing, the annular fixed plate and the plurality of rib plates on the steel casing are located in the bottom plate and are integrally connected with the bottom plate by pouring; Step five, performing water pumping operation in the gravity caisson compartment to realize dry construction working environment of the pile foundation; Step six, filling backfill material in the gravity caisson compartment below the reserved bracket, then arranging a construction platform on the reserved bracket, and removing the sealing steel plate on the steel casing to form the pile foundation in the steel casing; Step seven, continuously filling backfill material in the gravity caisson compartment and tamping to be higher than the height of the reserved bracket to increase the connection strength between the pile foundation and the gravity caisson; Step eight, construction of the outer facing of the gravity caisson; Step nine, construction of the upper breast wall and fender member of the gravity caisson.

5. The construction method of a caisson pier structure according to Claim 1, wherein The embedded steel plate is embedded in the inner wall of the bulkhead of the gravity caisson during prefabrication, and the embedded steel plate is welded with the reserved bracket.

6. The construction method of a caisson pier structure according to Claim 1, wherein The pile foundation construction comprises drilling a hole in the bearing layer downward along the steel casing to the design depth of the pile foundation, then lowering the reinforcement cage into the hole, and finally pouring concrete in the hole.

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