Device and method for mud preparation and circulation construction based on offshore pile foundation steel casing

Abstract

The application is based on mud preparation and circulation construction device and method of offshore pile foundation steel casing, adopts mud wall protection method to construct offshore bored pile foundation, utilizes adjacent steel casing as new slurry pool, slurry storage pool and waste slurry pool main body, carries out dredging and concrete bottom sealing on the bottom of the steel casing to form a closed steel casing slurry pool; the steel casing of the bored pile foundation is connected with the new slurry pool, circulation pool and waste slurry pool through a pipeline system, mud circulation is realized through liquid level pressure difference and mud pump during the pile foundation drilling and pouring process; mud sand separation system is utilized to purify mud during hole cleaning process, sand and gravel are discharged into a drilling residue box, and the purified mud is discharged into the slurry storage pool; the unqualified mud contaminated by concrete is discharged into the waste slurry pool. The application realizes mud preparation and circulation by utilizing the steel casing and flat link steel pipe, which greatly reduces the engineering quantity of offshore construction platform and mud tank and the work shift of mud ship and circulation equipment.

Description

Technical Field

[0001] This invention relates to the technical field of marine engineering and offshore pile foundation construction such as bridges and wind power foundations, and particularly to a mud preparation and circulation construction device and method based on offshore pile foundation steel casing. Background Technology

[0002] In offshore bored pile construction, a large amount of high-quality bentonite slurry is required to maintain borehole stability, suspend and carry drill cuttings, and cool and lubricate the drill bit. Traditional slurry preparation and circulation methods typically employ two modes:

[0003] Platform-mounted method: A complete set of equipment, including mud tanks, mud pits, mixers, and circulating pumps, is installed on the construction platform or auxiliary vessel. The disadvantages of this method include occupying a large amount of platform space, a large load on the mud tanks, mud spillage causing pollution to the platform and the ocean, numerous limitations, limited mud storage capacity, and significant environmental issues.

[0004] Specialized mud slurry barges: These use specialized mud preparation and circulation barges. Pile foundation construction often involves long periods and significant uncertainties. Specialized mud slurry barges must remain anchored in front of the pile foundation construction platform, resulting in high vessel construction costs. Furthermore, in rough seas, the pipeline connections between the vessel and the platform pose safety and environmental pollution risks.

[0005] The core problem with existing technologies is that mud systems are a necessary auxiliary measure for pile foundation construction, characterized by large space occupation, long duration, high cost, low efficiency, and poor coordination with the main structure. Summary of the Invention

[0006] The present invention aims to address the shortcomings of the prior art by providing a mud preparation and circulation construction device and method based on offshore pile foundation steel casing.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The mud preparation and circulation construction device based on offshore pile foundation steel casing includes a drilling construction platform, drilled cast-in-place pile foundation, new mud pool, waste mud pool, mud storage pool, mud pump, air compressor, mud-sand separation system, drill cuttings box, mud ship and auxiliary mud pump;

[0009] The bored pile foundation, new slurry pool, waste slurry pool, and slurry storage pool all use steel casings as sidewalls. The bottom of the steel casings in the new slurry pool, waste slurry pool, and slurry storage pool are all sealed with bottom concrete, which serves as the bottom wall of the slurry pool. Pipes are connected between the bored pile foundation and the new slurry pool, waste slurry pool, and slurry storage pool, and valves are installed on the pipes. The mud pump is connected between the bored pile foundation and the new slurry pool. The air compressor is connected to the air duct, which extends into the bottom of the new slurry pool. The mud-sand separation system is set on the drilling construction platform and connected to the drill cuttings box. The mud-sand separation system is connected between the bored pile foundation and the slurry storage pool. The auxiliary mud pump is connected between the slurry storage pool and the second and subsequent bored pile foundations.

[0010] There are several slurry storage tanks, which are connected in series by several pipes.

[0011] The inner walls of the steel casings of the new slurry tank, waste slurry tank, and storage tank are marked with elevation and capacity lines.

[0012] The mud pump is connected to the new mud tank through the mud pump inlet pipe, and the mud pump is connected to the bored pile foundation through the mud pump outlet pipe.

[0013] The mud-sand separation system is connected to the bored pile foundation through the mud inlet pipe, the mud-sand separation system is connected to the mud storage tank through the mud outlet pipe, and the bottom of the mud-sand separation system is connected to the drill cuttings box through the mud outlet pipe.

[0014] The construction method for the above-mentioned mud preparation and circulation construction device based on offshore pile foundation steel casing is as follows:

[0015] S1. Calculate the supply, storage, and disposal quantities of mud slurry based on the designed pile foundation structural parameters and construction technology, and determine the capacity requirements of the new mud slurry tank, waste mud slurry tank, and mud storage tank.

[0016] S2. Following the requirements of step S1, construct the new slurry tank, waste slurry tank, and slurry storage tank.

[0017] S3. Welded steel casings are connected by horizontal steel pipes. The horizontal steel pipe connection serves as a conduit for the flow of mud between the steel casings, and valves are installed on the conduit.

[0018] S4. Drain the seawater and debris from the new slurry tank, waste slurry tank, and storage tank; measure the elevation of the bottom sealing concrete; mark the elevation and capacity lines inside the steel casing; and open a through hole on the side wall of the steel casing to connect with the pipeline.

[0019] S5. Determine the mud mix ratio based on geological conditions and construction technology, and prepare the mud in the new mud pool;

[0020] S6. Begin drilling for the first bored pile foundation. Open the valve on the pipeline between the new slurry pool and the first bored pile foundation. As the bored pile foundation is drilled, the mud in the new slurry pool flows into the bored pile foundation through the pipeline under the action of hydraulic differential pressure. When the mud level in the new slurry pool is lower than the pipeline elevation, use a mud pump to continue injecting mud from the new slurry pool into the bored pile foundation. When the mud in the new slurry pool is insufficient, continue to prepare mud and continuously replenish mud into the bored pile foundation through hydraulic differential pressure and mud pump. The mud level in the hole is always higher than the water head height in the hole to ensure the wall protection effect.

[0021] S7. After the drilling depth reaches the design requirements, the sediment at the bottom of the hole is carried out to the outside of the hole by mud circulation until the sediment thickness meets the design requirements. The valve on the pipeline between the slurry storage tank and the drilled pile foundation is opened, and the hole is cleaned by air lift reverse circulation method. The cleaning mud enters the mud-sand separation system for mud purification. The purified mud is injected into the slurry storage tank for storage, and the sediment is discharged into the drill cuttings box. In the initial stage of hole cleaning, mud is continuously added to the drilled pile foundation from the new slurry tank until the mud level in the slurry storage tank exceeds the pipeline elevation. At this time, the mud in the slurry storage tank automatically adds purified mud to the drilled pile foundation under the action of liquid differential pressure.

[0022] S8. After the hole cleaning and reinforcement cage placement are completed, underwater concrete pouring of the pile foundation is carried out. The mud level in the drilled pile foundation rises. When the mud level in the drilled pile foundation exceeds the height of the pipe, the excess mud will automatically flow into the slurry storage tank through the pipe under the action of hydraulic differential.

[0023] S9. Continue drilling for the second bored pile foundation. Open the valve on the pipeline between the slurry storage tank and the second bored pile foundation. As the second bored pile foundation is drilled, the mud in the slurry storage tank flows into the second bored pile foundation through the pipeline under the action of hydraulic differential pressure. When the mud level in the slurry storage tank is lower than the pipeline elevation, use an auxiliary mud pump to inject the mud in the slurry storage tank into the second bored pile foundation. When the mud in the slurry storage tank is insufficient, continue to prepare mud in the new slurry tank and supplement the mud through hydraulic differential pressure and mud pump. The mud level in the second bored pile foundation is always higher than the water head height in the hole to ensure the wall protection effect.

[0024] S10. Following step S9, the drilling construction of other bored pile foundations is carried out in sequence. When the last bored pile foundation is being constructed, all the piles in the remaining steel casings have been formed. A temporary pipeline is set up to connect the last bored pile foundation and the mud boat. As the last bored pile foundation is being poured with concrete, the mud in the hole is discharged into the mud boat and transported to the adjacent pier for recycling.

[0025] The specific operation of step S2 is as follows:

[0026] Excavate the soil to a certain depth inside the steel casing corresponding to the new slurry tank, waste slurry tank, and storage tank. The bottom elevation of the excavated soil should be at least 2m higher than the bottom elevation of the steel casing. Then, pour bottom sealing concrete inside the steel casing to form a bottomed closed space. If a single storage tank does not meet the slurry tank capacity requirements, adjacent steel casings can be modified to increase the number of storage tanks to meet the requirements.

[0027] In step S3, the elevation of the steel pipe horizontal connection is at least 2m higher than the highest water level during construction to ensure the mud level in the drilled pile foundation.

[0028] The specific operation of step S5 is as follows:

[0029] A certain height of fresh water is injected into the new slurry pool. An air compressor is used to send compressed air to the bottom of the new slurry pool through the air duct, causing the fresh water inside to surge. Bentonite is slowly dispersed into the new slurry pool and mixed evenly with the surging fresh water to form bentonite-based slurry. Then, soda ash and polyanionic cellulose are added in proportion and stirred evenly. The freshly mixed slurry is used after it has expanded for 24 hours. The slurry preparation is matched with the drilling progress to ensure that the slurry level in the drilled pile foundation is higher than the water head height in the hole.

[0030] In step S8, the mud entering the slurry storage tank is tested during the concrete pouring process of the pile foundation. When the mud is contaminated by underwater concrete and does not meet the requirements for recycling, the valve on the pipeline between the drilled pile foundation and the slurry storage tank is closed, and the valve on the pipeline between the drilled pile foundation and the waste slurry tank is opened. The waste mud contaminated by concrete flows into the waste slurry tank under the action of hydraulic pressure difference until the pouring is completed. The mud in the waste slurry tank is collected and transported to the land mud plant for treatment by mud barge.

[0031] The beneficial effects of this invention are: This invention utilizes existing offshore pile foundation steel casings as the sidewalls of mud pits, transforming the originally temporary steel structure into a mud container. It eliminates the need to additionally arrange large mud boxes, mud pits, and other equipment on construction platforms or auxiliary vessels, significantly reducing the platform's occupied area and additional load, improving the overall safety and operational convenience of the construction platform, reducing construction costs, simplifying the construction process, and improving recycling efficiency. Attached Figure Description

[0032] Figure 1 Layout diagram for mud preparation;

[0033] Figure 2 Diagram of mud circulation during the drilling of the first hole;

[0034] Figure 3 Diagram showing mud circulation during hole cleaning;

[0035] Figure 4 This is a diagram showing the mud circulation during concrete pouring for pile foundations.

[0036] Figure 5This is a diagram showing the mud circulation during secondary drilling.

[0037] Figure 6 Diagram of mud circulation during final hole concrete pouring;

[0038] In the diagram: 1-Drilled pile foundation; 2-New slurry pool; 3-Waste slurry pool; 4-Slurry storage pool; 5-Pipeline; 6-Valve; 7-Mud pump; 8-Elevation and capacity markings; 9-Steel casing; 10-Air compressor; 11-Air duct; 12-Mud-sand separation system; 13-Drill cuttings box; 14-Bottom sealing concrete; 15-Temporary pipeline; 16-Mud boat; 17-Auxiliary mud pump;

[0039] 701 - Mud pump inlet pipe; 702 - Mud pump outlet pipe;

[0040] 1201 - Mud inlet pipe; 1202 - Mud outlet pipe; 1203 - Mud and sand outlet pipe;

[0041] The following will describe in detail, with reference to the accompanying drawings, embodiments of the present invention. Detailed Implementation

[0042] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0045] Mud preparation and circulation construction device based on offshore pile foundation steel casing, such as Figures 1 to 6 As shown, it includes a drilling construction platform, a drilled pile foundation 1, a new slurry pool 2, a waste slurry pool 3, a slurry storage pool 4, a mud pump 7, an air compressor 10, a mud-sand separation system 12, a cuttings box 13, a mud boat 16, and an auxiliary mud pump 17.

[0046] The drilling platform is a temporary offshore steel structure platform, with steel pipe piles and steel casings as the foundation support. The upper part is equipped with a steel pile top beam, Bailey beam and steel plate composite bridge deck system, providing an offshore operating platform for pile foundation construction equipment and materials.

[0047] The bored pile foundation 1, new grout pool 2, waste grout pool 3, and grout storage pool 4 all use steel casings 9 as sidewalls. The bottom of the steel casings 9 of the new grout pool 2, waste grout pool 3, and grout storage pool 4 is provided with bottom sealing concrete 14, which serves as the bottom wall of the grout pool. The inner wall of the steel casings 9 of the new grout pool 2, waste grout pool 3, and grout storage pool 4 is marked with elevation and capacity lines 8.

[0048] Pipelines 5 connect the bored pile foundation 1 to the new slurry pool 2, the waste slurry pool 3, and the slurry storage pool 4. Valves 6 are installed on the pipelines 5.

[0049] There are several slurry storage tanks 4, and these tanks 4 are connected in series through several pipes 5.

[0050] Pipeline 5 is a closed steel pipe horizontal connection between steel casing 9 and pipe 5. The end of pipe 5 is fully welded to steel casing 9. The inner wall of steel casing 9 has an opening at the position corresponding to the end of pipe 5.

[0051] The mud pump 7 is connected between the bored pile foundation 1 and the new mud pool 2. The mud pump 7 is connected to the new mud pool 2 through the mud pump inlet pipe 701 and to the bored pile foundation 1 through the mud pump outlet pipe 702.

[0052] Air compressor 10 is connected to air duct 11, which extends into the bottom of new slurry tank 2.

[0053] The mud-sand separation system 12 is installed on the drilling platform and connected to the cuttings box 13. The mud-sand separation system 12 is connected between the bored pile foundation 1 and the slurry storage tank 4. The mud-sand separation system 12 is connected to the bored pile foundation 1 through the mud inlet pipe 1201, and to the slurry storage tank 4 through the mud outlet pipe 1202. The bottom of the mud-sand separation system 12 is connected to the cuttings box 13 through the mud outlet pipe 1203.

[0054] The cuttings box 13 is a rectangular steel box made by welding steel plates, used for temporary storage of drilling cuttings and hole cleaning mud and sand.

[0055] An auxiliary mud pump 17 is connected between the slurry storage tank 4 and the second and subsequent bored pile foundations 1. During the drilling of the second and subsequent bored pile foundations 1, the auxiliary mud pump 17 connects the slurry storage tank 4 and the bored pile foundation 1 to replenish mud from the slurry storage tank 4 to the bored pile foundation 1.

[0056] The mud tug 16 is anchored in front of the drilling platform, transporting the discharged mud.

[0057] The construction method for the above-mentioned mud preparation and circulation construction device based on offshore pile foundation steel casing is as follows:

[0058] S1. Technical Preparation:

[0059] Based on the designed pile foundation structural parameters and construction technology, the quantities of mud supply, storage, and waste are calculated to determine the capacity requirements of new mud pit 2, waste mud pit 3, and mud storage pit 4.

[0060] S2. Grout pool construction:

[0061] Following the requirements of step S1, construct the new slurry tank 2, waste slurry tank 3, and slurry storage tank 4. The specific steps are as follows:

[0062] Excavate a certain depth of soil within the steel casings 9 corresponding to the new slurry pool 2, waste slurry pool 3, and slurry storage pool 4 to expand the slurry pool capacity. The bottom elevation of the excavated soil should be at least 2m higher than the bottom elevation of the steel casing 9 to ensure the stability of the soil inside the steel casing 9. Then, pour bottom sealing concrete 14 inside the steel casing 9 to form a bottomed closed space to prevent the slurry from being contaminated by silt, seawater, etc. If a single slurry storage pool 4 does not meet the slurry pool capacity requirements, adjacent steel casings 9 can be modified to increase the number of slurry storage pools 4 to meet the requirements.

[0063] S3, Steel pipe parallel connection:

[0064] A horizontal steel pipe is connected between the welded steel casings 9. The horizontal steel pipe is fully welded to the steel casings 9 to prevent grout leakage. The horizontal steel pipe serves as the pipe 5 for the flow of mud between the steel casings 9. A valve 6 is installed on the pipe 5 to control the flow of mud. The elevation of the horizontal steel pipe is at least 2m higher than the highest water level during construction to ensure the mud level in the drilled pile foundation 1.

[0065] S4. Preparation of the slurry tank:

[0066] Seawater was extracted from the new slurry tank 2, waste slurry tank 3, and storage tank 4. Debris in the slurry tanks was cleaned. The elevation of the bottom sealing concrete 14 was measured. Elevation and capacity markings 8 were engraved inside the steel casing 9. A through hole communicating with the pipe 5 was opened on the side wall of the steel casing 9.

[0067] S5. Mud Preparation:

[0068] The mud mix ratio is determined based on geological conditions and construction technology, and mud preparation is carried out in the new mud pit 2, such as... Figure 1 As shown, the specific steps are as follows:

[0069] A certain height of fresh water is injected into the new slurry pool 2. Compressed air is sent to the bottom of the new slurry pool 2 through the air duct 11 using the air compressor 10, causing the fresh water inside to surge. Bentonite is slowly dispersed into the new slurry pool 2 and mixed evenly with the surging fresh water to form bentonite-based slurry. Additives such as soda ash and polyanionic cellulose are then added in proportion and stirred evenly. The freshly mixed mud is used after it has expanded for 24 hours. The mud preparation is matched with the drilling progress to ensure that the mud level in the drilled pile foundation 1 is higher than the water head height in the hole.

[0070] S6. Mud circulation during the first hole drilling:

[0071] like Figure 2 As shown, drilling for the first bored pile 1 begins. Valve 6 on the pipeline 5 between the new slurry pool 2 and the first bored pile 1 is opened. As the bored pile 1 is drilled, the mud in the new slurry pool 2 flows into the bored pile 1 through the pipeline 5 under the action of hydraulic differential pressure. When the mud level in the new slurry pool 2 is lower than the elevation of the pipeline 5, the mud pump 7 continues to inject the mud from the new slurry pool 2 into the bored pile 1. When the mud in the new slurry pool 2 is insufficient, mud is prepared continuously. Mud is continuously replenished into the bored pile 1 through hydraulic differential pressure and the mud pump 7. The mud level in the hole is always higher than the water head height in the hole to ensure the wall protection effect.

[0072] S7. Mud circulation during hole cleaning:

[0073] After the drilling depth reaches the design requirements, mud circulation is used to carry the sediment from the bottom of the hole to the outside until the sediment thickness meets the design requirements, such as... Figure 3 As shown, the specific steps are as follows:

[0074] Open valve 6 on pipe 5 between slurry storage tank 4 and bored pile 1, and use air-lift reverse circulation method to clean the hole. The cleaning mud carrying a large amount of sediment enters mud-sand separation system 12 through mud inlet pipe 1201 for mud purification. The purified mud is injected into slurry storage tank 4 through mud outlet pipe 1202 for storage, and the sediment is discharged into drill cuttings box 13 through mud-sand outlet pipe 1203. In the initial stage of hole cleaning, mud is continuously replenished into bored pile 1 from new slurry tank 2 until the mud level in slurry storage tank 4 exceeds the elevation of pipe 5, at which point mud preparation is stopped. At this time, the mud in slurry storage tank 4 automatically replenishes the purified mud into bored pile 1 under the action of differential pressure, forming the following circulation loop: mud in bored pile 1 → mud-sand separation system 12 → slurry storage tank 4 → bored pile 1.

[0075] S8. Mud circulation during concrete pouring for pile foundations:

[0076] like Figure 4As shown, after the hole cleaning and steel cage placement are completed, underwater concrete pouring of the pile foundation is carried out. The valve 6 of the pipeline 5 between the drilled pile foundation 1 and the slurry storage tank 4 is opened, and the mud level in the drilled pile foundation 1 rises. When the mud level in the drilled pile foundation 1 exceeds the height of the pipeline 5, under the action of hydraulic differential, the excess mud automatically flows into the slurry storage tank 4 through the pipeline 5.

[0077] During the concrete pouring process of the pile foundation, the mud entering the slurry storage tank 4 is tested. When the mud is contaminated by underwater concrete and does not meet the requirements for recycling, the valve 6 on the pipeline 5 between the drilled pile foundation 1 and the slurry storage tank 4 is closed, and the valve 6 on the pipeline 5 between the drilled pile foundation 1 and the waste slurry tank 3 is opened. The waste mud contaminated by concrete flows into the waste slurry tank 3 under the action of hydraulic pressure difference until the pouring is completed. The mud in the waste slurry tank 3 is collected and transported to the land mud plant for treatment by the mud ship 16.

[0078] S9. Mud circulation during secondary drilling:

[0079] like Figure 5 As shown, drilling of the second bored pile 1 continues. Valve 6 on the pipeline 5 between the slurry storage tank 4 and the second bored pile 1 is opened. As the second bored pile 1 is drilled, the mud in the slurry storage tank 4 flows into the second bored pile 1 through the pipeline 5 under the action of hydraulic differential pressure. When the mud level in the slurry storage tank 4 is lower than the elevation of the pipeline 5, the mud in the slurry storage tank 4 is injected into the second bored pile 1 using the auxiliary mud pump 17. When the mud in the slurry storage tank 4 is insufficient, mud is prepared in the new slurry tank 2. The mud is replenished by hydraulic differential pressure and mud pump 7. The mud level in the second bored pile 1 is always higher than the water head height in the hole to ensure the wall protection effect.

[0080] S10. Mud circulation during final hole concrete pouring:

[0081] Following step S9, drilling of the other bored pile foundations 1 is carried out sequentially. When the last bored pile foundation 1 is being constructed, all the remaining steel casings 9 have already formed piles. A temporary pipe 15 is installed to connect the last bored pile foundation 1 and the mud slurry vessel 16. Figure 6 As shown, with the last bored pile 1 being filled with concrete, the mud in the hole is discharged into the mud boat 16 and transported to the adjacent pier for recycling.

[0082] This invention utilizes existing offshore pile foundation steel casing 9 as the sidewall of the mud pit, transforming the originally temporary steel structure into a mud container. This eliminates the need for additional large mud boxes, mud pits, and other equipment on the construction platform or auxiliary vessels, significantly reducing the platform's footprint and additional load. It also improves the overall safety and operational convenience of the construction platform, reduces construction costs, simplifies the construction process, and increases recycling efficiency.

[0083] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A mud preparation and circulation construction device based on offshore pile foundation steel casing, characterized in that, It includes a drilling construction platform, a drilled pile foundation (1), a new slurry pool (2), a waste slurry pool (3), a slurry storage pool (4), a mud pump (7), an air compressor (10), a mud-sand separation system (12), a cuttings box (13), a mud boat (16), and an auxiliary mud pump (17). The bored pile foundation (1), new slurry pool (2), waste slurry pool (3), and slurry storage pool (4) all use steel casings (9) as sidewalls. The bottom of the steel casings (9) of the new slurry pool (2), waste slurry pool (3), and slurry storage pool (4) is provided with bottom sealing concrete (14), which serves as the bottom wall of the slurry pool. Pipes (5) are connected between the bored pile foundation (1) and the new slurry pool (2), waste slurry pool (3), and slurry storage pool (4). Valves (6) are provided on the pipes (5). Mud pumps ( 7) Connecting the drilled pile foundation (1) and the new slurry tank (2), the air compressor (10) is connected to the air duct (11), the air duct (11) extends into the bottom of the new slurry tank (2), the mud and sand separation system (12) is set on the drilling construction platform and connected to the drill cuttings box (13), the mud and sand separation system (12) is connected between the drilled pile foundation (1) and the slurry storage tank (4), and the auxiliary mud pump (17) is connected between the slurry storage tank (4) and the second and subsequent drilled pile foundations (1).

2. The mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 1, characterized in that, There are several slurry storage tanks (4), and several slurry storage tanks (4) are connected in series through several pipes (5).

3. The mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 2, characterized in that, The inner walls of the steel casings (9) of the new slurry tank (2), waste slurry tank (3), and slurry storage tank (4) are marked with elevation and capacity lines (8).

4. The mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 3, characterized in that, The mud pump (7) is connected to the new mud tank (2) through the mud pump inlet pipe (701), and the mud pump (7) is connected to the bored pile foundation (1) through the mud pump outlet pipe (702).

5. The mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 4, characterized in that, The mud-sand separation system (12) is connected to the bored pile foundation (1) through the mud inlet pipe (1201), the mud-sand separation system (12) is connected to the slurry storage tank (4) through the mud outlet pipe (1202), and the bottom of the mud-sand separation system (12) is connected to the cuttings box (13) through the mud outlet pipe (1203).

6. A construction method for a mud preparation and circulation construction device based on a steel casing for offshore pile foundations as described in any one of claims 1-5, characterized in that, The specific steps are as follows: S1. Calculate the mud supply, storage, and waste volume based on the designed pile foundation structure parameters and construction technology, and determine the capacity requirements of the new mud pit (2), waste mud pit (3), and mud storage pit (4); S2. Following the requirements of step S1, construct the new slurry tank (2), waste slurry tank (3), and slurry storage tank (4). S3. Weld steel pipes are connected horizontally between steel casings (9). The horizontal connection of steel pipes serves as a pipe (5) for mud flow between steel casings (9). Valves (6) are installed on the pipe (5). S4. Extract seawater and debris from the new slurry tank (2), waste slurry tank (3), and storage tank (4), measure the elevation of the bottom sealing concrete (14), mark the elevation and capacity markings (8) inside the steel casing (9), and open a through hole on the side wall of the steel casing (9) to connect with the pipeline (5). S5. Determine the mud mix ratio according to geological conditions and construction technology, and prepare mud in the new mud pool (2); S6. Start drilling construction of the first bored pile foundation (1), open the valve (6) on the pipeline (5) between the new slurry pool (2) and the first bored pile foundation (1). As the bored pile foundation (1) is drilled, the mud in the new slurry pool (2) flows into the bored pile foundation (1) through the pipeline (5) under the action of the hydraulic differential pressure. When the mud level in the new slurry pool (2) is lower than the elevation of the pipeline (5), the mud pump (7) is used to continue to inject the mud in the new slurry pool (2) into the bored pile foundation (1). When the mud in the new slurry pool (2) is insufficient, mud is prepared and mud is continuously added to the bored pile foundation (1) through the hydraulic differential pressure and the mud pump (7). The mud level in the hole is always higher than the water head height in the hole to ensure the wall protection effect. S7. After the drilling depth reaches the design requirements, the sediment at the bottom of the hole is carried out of the hole by mud circulation until the sediment thickness meets the design requirements: open the valve (6) on the pipeline (5) between the slurry storage tank (4) and the drilled grouting pile (1), and use the air lift reverse circulation method to clean the hole. The cleaning mud enters the mud-sand separation system (12) for mud purification. The purified mud is injected into the slurry storage tank (4) for storage, and the sediment is discharged into the drill cuttings box (13). In the early stage of hole cleaning, mud is continuously added to the drilled grouting pile (1) from the new slurry tank (2) until the mud level in the slurry storage tank (4) exceeds the elevation of the pipeline (5). At this time, the mud in the slurry storage tank (4) automatically adds purified mud to the drilled grouting pile (1) under the action of differential pressure. S8. After the hole cleaning and steel cage placement work is completed, underwater concrete pouring of the pile foundation is carried out. The mud level in the drilled pile foundation (1) rises. When the mud level in the drilled pile foundation (1) exceeds the height of the pipe (5), under the action of hydraulic differential, the mud that is higher will automatically flow into the slurry storage tank (4) through the pipe (5). S9. Continue drilling construction of the second borehole cast-in-place pile (1), open the valve (6) on the pipeline (5) between the slurry storage tank (4) and the second borehole cast-in-place pile (1), as the second borehole cast-in-place pile (1) is drilled, the mud in the slurry storage tank (4) flows into the second borehole cast-in-place pile (1) through the pipeline (5) under the action of the hydraulic differential pressure. When the mud level in the slurry storage tank (4) is lower than the elevation of the pipeline (5), the mud in the slurry storage tank (4) is injected into the second borehole cast-in-place pile (1) by the auxiliary mud pump (17). When the mud in the slurry storage tank (4) is insufficient, mud is prepared in the new slurry tank (2) and the mud is supplemented by the hydraulic differential pressure and the mud pump (7). The mud level in the second borehole cast-in-place pile (1) is always higher than the water head height in the hole to ensure the wall protection effect. S10. Drilling construction of other bored pile foundations (1) is carried out in sequence according to step S9. When the last bored pile foundation (1) is being constructed, all the remaining steel casings (9) have been piled. Temporary pipes (15) are set up to connect the last bored pile foundation (1) and the mud boat (16). As the last bored pile foundation (1) is filled with concrete, the mud in the hole is discharged into the mud boat (16) and transported to the adjacent pier for recycling.

7. The construction method of the mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 6, characterized in that, The specific operation of step S2 is as follows: Excavate the soil to a certain depth inside the steel casing (9) corresponding to the new slurry pool (2), waste slurry pool (3), and slurry storage pool (4). The bottom elevation of the excavated soil is at least 2m higher than the bottom elevation of the steel casing (9). Then, pour bottom sealing concrete (14) inside the steel casing (9) to form a bottom-sealed space. If a single slurry storage pool (4) does not meet the slurry pool capacity requirements, the adjacent steel casing (9) can be modified to increase the number of slurry storage pools (4) to meet the requirements.

8. The construction method of the mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 6, characterized in that, In step S3, the elevation of the steel pipe horizontal connection is at least 2m higher than the highest water level during construction to ensure the mud level in the drilled pile foundation (1).

9. The construction method of the mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 6, characterized in that, The specific operation of step S5 is as follows: A certain height of fresh water is injected into the new slurry pool (2). The compressed air is sent to the bottom of the new slurry pool (2) through the air duct (11) using an air compressor (10) to make the fresh water inside surge. Bentonite is slowly dispersed into the new slurry pool (2) and mixed evenly with the surging fresh water to form bentonite-based slurry. Then, soda ash and polyanionic cellulose are added in proportion and stirred evenly. The freshly mixed mud is used after it has expanded for 24 hours. The mud preparation is matched with the drilling progress to ensure that the mud level in the drilled pile foundation (1) is higher than the water head height in the hole.

10. The construction method of the mud preparation and circulation construction device based on offshore pile foundation steel casing according to claim 6, characterized in that, In step S8, the mud entering the slurry storage tank (4) is tested during the concrete pouring process of the pile foundation. When the mud is contaminated by underwater concrete and does not meet the requirements for recycling, the valve (6) on the pipeline (5) between the drilled pile foundation (1) and the slurry storage tank (4) is closed, and the valve (6) on the pipeline (5) between the drilled pile foundation (1) and the waste slurry tank (3) is opened. The waste mud contaminated by concrete flows into the waste slurry tank (3) under the action of hydraulic pressure difference until the pouring is completed. The mud in the waste slurry tank (3) is transported to the land mud plant for treatment by mud boat (16).

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