Construction method of offshore full-offshore pile-free enlarged foundation

Abstract

The invention discloses a construction method of an offshore full-offshore pile-free enlarged foundation. The construction method comprises the following steps that 1, the pile-free enlarged foundation is prefabricated; 2, the pile-free enlarged foundation is transferred to a ship and is shipped to a construction sea area; 3, foundation pit excavation is carried out at the designed position, wherein the step 31 comprises the steps that a virtual plane grid is established, and a workboat is positioned; 32, a covering layer is excavated; (33) a foundation pit is constructed on the seabed; 34, a cushion layer at the bottom of the foundation pit is poured and leveled; 4, the pile-free enlarged foundation is installed in the foundation pit, and the step 4 comprises the substeps that 41, the pile-free enlarged foundation is hoisted and lowered to a cushion layer in the flat tide period; (42) the located pile-free enlarged foundation is accurately located; 43, a gap in the bottom of the bearing platform is filled, and the foundation pit is backfilled to the designed elevation; wherein the step 2 and the step 3 are carried out in no order. According to the construction method, the construction efficiency, the construction quality and the construction safety of the offshore bridge foundation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge foundation construction, and in particular to a construction method for a fully offshore pile-free expanded foundation. Background Art

[0002] The foundation structure of large-scale sea-crossing bridges is key to supporting the entire upper load. Pile foundations are the most adaptable to various geological conditions and are therefore the most widely used. However, the two current mainstream offshore pile foundation construction methods both have shortcomings.

[0003] A common construction method involves building a long trestle from the shore to the foundation site, then constructing a drilling platform for pile foundation construction. This method has significant drawbacks: The trestle is expensive and time-consuming to construct; complex geology leads to inconsistent work efficiency and quality; it relies on a slurry circulation system, increasing costs and potentially polluting the environment; the noise and vibration from impact or rotary drilling operations harm the environment and threaten the platform structure; and repeated drilling and slag removal reduce efficiency.

[0004] Offshore steel pipe composite piles primarily utilize steel casings to support independent steel platforms for construction. These challenges include: weak seabeds or slopes can easily cause the platform to capsize; construction disturbances exacerbate seabed scour; the platform's lack of shelter limits operations to severe sea conditions, resulting in short operating times; and weather emergencies present significant challenges in evacuating hazards. Platform installation relies on large ship-mounted machinery, which has limited space and load capacity, restricting equipment availability.

[0005] For this reason, for hard rock seabed conditions, engineering projects have also attempted to use pile-free expanded foundations. The construction method usually involves first building a large cofferdam, draining the water inside the cofferdam to create a dry working environment, and then cleaning the seabed, tying steel bars, and pouring large volumes of concrete to form the load-bearing foundation blocks. The main disadvantages of this method are low construction efficiency and a complicated process: the construction, water stopping, pumping, and internal operations of the cofferdam require a lot of time and resources. The process is complex and significantly affected by the marine environment, such as tides, wind and waves, resulting in a long overall construction period and high costs. In addition, large-scale offshore cofferdam operations are inherently risky.

[0006] Therefore, with the growing demand for large-scale cross-sea bridge construction, there is an urgent need to find a new construction method for specific marine working conditions to systematically solve the above-mentioned construction technical problems. Summary of the Invention

[0007] The main technical problem to be solved by the present invention is to provide a construction method for offshore bridge foundations, which can complete the foundation construction of large offshore bridges more efficiently, with higher quality and more safety, especially for hard rock seabed working conditions.

[0008] In order to solve the above technical problems, the present invention provides a construction method for a fully offshore pile-free expanded foundation, wherein the pile-free expanded foundation includes a cap and a pier body; the method comprises the following steps:

[0009] Step 1: Prefabricate pile-free expanded foundation;

[0010] Step 2: Transfer the pile-less expanded foundation onto a ship and transport it to the construction sea area by sea;

[0011] Step 3: Excavate the foundation pit at the designed location. This step includes:

[0012] Step 31: Create a virtual plane grid and position the construction vessel;

[0013] Step 32: Excavation of the overburden;

[0014] Step 33: Construct foundation pit on the seabed;

[0015] Step 34: Pour and level the cushion layer at the bottom of the foundation pit;

[0016] Step 4: Install the pile-less expanded foundation into the foundation pit. This step includes:

[0017] Step 41: During low tide, hoist and lower the pile-less expanded foundation to the cushion layer;

[0018] Step 42: Accurately position the pile-free expanded foundation after placement;

[0019] Step 43: Fill the gap at the bottom of the foundation and backfill the foundation pit to the designed elevation;

[0020] Wherein, step 2 and step 3 are performed in no particular order.

[0021] In a preferred embodiment, step 33 adopts a drilling and blasting method, which specifically includes: drilling blasting holes at intervals as required by the design of the foundation pit; placing explosives into the blasting holes, and blasting and excavating the seabed.

[0022] In a preferred embodiment, in step 33, the blasting excavation construction steps specifically include: filling the blasting hole with explosives; blocking the opening of the blasting hole; connecting the detonators of the explosives into a blasting network; detonating the explosives after moving the construction ship to a safe area; and clearing the rubble.

[0023] In a preferred embodiment, in step 2, the pile-less expanded foundation is transported onto the ship using a roll-on / roll-off method.

[0024] In a preferred embodiment, in step 2, the construction steps of transferring the pile-free foundation expansion onto the ship specifically include:

[0025] Step 21: The transport ship docks at the pier, and the ship-to-shore connection and the rail system connecting the prefabricated pedestal to the transport ship deck are installed;

[0026] Step 22: Roll the pile-less expanded foundation onto the ship via the rail system;

[0027] Step 23: After the pile-less expanded foundation is fixed, the ship-shore connection is released and sea transportation begins.

[0028] In a preferred embodiment, step 1 includes:

[0029] Step 11: Construction of the cap, including: positioning the base; installing the cap reinforcement and embedded parts; hoisting the cap formwork; pouring concrete and curing;

[0030] Step 12: Construct the pier body, including: tying the pier body reinforcement; hoisting the pier body formwork; pouring concrete and curing.

[0031] In a preferred embodiment, step 33 uses a combination of dense drilling and rock drilling to break the seabed.

[0032] In a preferred embodiment, step 42 includes: measuring the posture of the pile-less enlarged foundation; and adjusting the posture parameters of the pile-less enlarged foundation including horizontal deviation and verticality using a jack according to the measurement results.

[0033] In a preferred embodiment, the jacks are three-dimensional jacks; in the horizontal direction, several groups of the three-dimensional jacks are symmetrically installed on the periphery of the pedestal; in the vertical direction, the three-dimensional jacks are installed on the top of the support column supported at the bottom of the foundation pit, and the top abuts against the bottom of the corbel extending laterally from the pedestal.

[0034] In a preferred embodiment, in step 43, the construction steps of filling the gap at the bottom of the pedestal include: installing a conduit on the pile-free expanded foundation; the conduit enters the gap between the pedestal and the cushion layer and pours high-strength mortar until the gap is filled; pouring the outer part of the pedestal to the design elevation until the high-strength mortar covers the bottom surface of the foundation pit.

[0035] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0036] The construction method provided by the present invention: (1) significantly improves construction quality by prefabricating the foundation without piles in the factory. In the controlled environment of the prefabrication site, standardized production is carried out using precision molds to ensure high precision, regular shape and good appearance of the components; the concrete mix ratio, mixing, vibration and steam curing processes are standardized to ensure strength, density and durability; the embedded parts are accurately positioned during the construction; the on-site workload is low, reducing on-site human errors. (2) In terms of construction efficiency, factory prefabrication and on-site foundation pit excavation and leveling can be carried out simultaneously, greatly shortening the construction period; the on-site installation process is simplified to hoisting, positioning, connection and grouting, eliminating a large amount of wet work such as steel bar binding, formwork support, concrete pouring, etc., significantly improving construction efficiency; (3) factory-scale production also dilutes mold costs, reduces the investment in turnover materials such as on-site formwork and support frames, and reduces construction cost investment. (4) This construction method has strong adaptability, is less affected by weather and sea conditions, and has significant advantages in areas with limited space. (5) Significant reduction in heavy labor on site, lowering labor demand and intensity, which not only facilitates construction organization and management but also improves construction safety. (6) Complying with green construction and achieving environmental friendliness: factory production reduces noise and dust on site; avoids large amounts of waste generated by formwork dismantling, making waste materials easy to recycle; reduces maintenance water and sewage; and ensures a clean and orderly construction site. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the construction process of the fully offshore pile-free expanded foundation according to an embodiment of the present invention;

[0038] Figure 2 Schematic elevation diagram of a pile-free expanded foundation according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of prefabrication of a pile-free expanded foundation in an embodiment of the present invention;

[0040] Figure 4 Schematic diagram of roll-on / roll-off loading without pile expansion foundation according to an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of excavating the covering layer in an embodiment of the present invention;

[0042] Figure 6 Schematic diagram of blasting seabed rock mass in an embodiment of the present invention;

[0043] Figure 7 Schematic diagram of a foundation pit cushion layer constructed in an embodiment of the present invention;

[0044] Figure 8 Schematic diagram of hanging and placing pile-free enlarged foundation in an embodiment of the present invention;

[0045] Figure 9 A partial schematic diagram of precise positioning of a pile-less expanded foundation in an embodiment of the present invention;

[0046] Figure 10 Schematic diagram of pouring high-strength mortar in an embodiment of the present invention;

[0047] Figure 11 This is a schematic diagram of backfilling gravel according to an embodiment of the present invention.

[0048] The markings in the figure are: 1-pileless expanded foundation, 101-cap, 102-pier, 2-precast pedestal, 3-track system, 301-longitudinal track, 302-transverse track, 4-ship-shore connection, 5-transport ship, 6-grab ship, 7-mud transport ship, 8-cover, 9-foundation pit, 10-blasting hole, 11-explosive material, 12-blocking material, 13-detonator, 14-floating crane, 15-mixing ship, 16-cushion, 17-spreading device, 18-three-dimensional jack, 19-corbel, 20-support column, 21-high-strength mortar, 22-conduit, 23-gravel, 24-guide frame. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0052] like Figures 1 to 11 As shown, an embodiment of the present invention provides a construction method for a fully offshore pile-free expanded foundation, comprising the following steps:

[0053] Step 1: If Figure 3 As shown, prefabricated pile-free expanded foundation 1. Figure 2 The pile-free expanded foundation 1 includes a lower cap 101 and an upper pier 102. This step of construction includes:

[0054] Step 11: Accurately lay out the lines on the prefabricated pedestal 2 and mark the locations of embedded components such as the reinforcement, rigid frame, and hanging point pipes for the pedestal 101. Arrange the bottom layer of pads according to the lines, prioritizing the lower layer of reinforcement. Tie the upper layer of reinforcement to the lower layer to reduce the number of pads required. Apply wax to the top surface of the prefabricated pedestal 2 as a release agent for the bottom of the pedestal 101.

[0055] Step 12: Install the pedestal 101 steel bars and embedded parts such as the rigid frame, lifting lugs and steel strands.

[0056] Step 13: The formwork for pedestal 101 was installed in sections using an 80-ton gantry crane. First, the large formwork on one long side of rectangular pedestal 101 and the small formwork on the two short sides were installed, followed by the large formwork on the other long side. φ40 fine-rolled rebar was used to tie the large and small formwork together.

[0057] Step 14: Sixteen distribution points are located at the top of cap 101 and around pier 102, each equipped with a stringer. Pre-placed concrete holes are left during the reinforcement binding process for cap 101. During the pouring of cap 101, a pump truck pumps concrete into the vertical stringers for layered distribution.

[0058] Step 15: After the concrete of foundation 101 reaches a certain strength, remove the side formwork of foundation 101 and wrap it with water-retaining curing film in time to maintain moisture.

[0059] Step 16: Tie the pier body 102 steel bars through the auxiliary platform. The steel bars are tied in a loose-tying process, from bottom to top and from inside to outside, with the main bars first.

[0060] Step 17: The installation order of the pier body 102 formwork is similar to that of the pedestal 101 formwork. First, install the large formwork on any long side of the pier body 102, then install the small formwork on its two short sides, and finally install the large formwork on the other long side. The formwork sits directly on the concrete of the pedestal 101, and the elevation is adjusted by the spiral legs at the bottom. The formwork is installed from bottom to top in layers and pieces. Each layer is measured, positioned, and accepted using a total station. The layers are reinforced with locating pins to ensure that the joints are flat. The formwork is connected at the corners, and the formwork plate surface is bolted to ensure stability. The pier body 102 is provided with an external formwork on the outside of the side formwork, and the external formwork is provided with a steel mesh operating platform at the top for segment assembly.

[0061] Step 18: The pier body 102 is poured using a sky pump. When pouring the pier body 102, a segmented concrete string tube is set inside the pier body 102 to ensure that the drop height of the concrete meets the requirements.

[0062] Step 19: After the pier body 102 concrete reaches a certain strength, remove the side formwork of the foundation 101 and wrap it with a water-retaining curing film in time to maintain moisture.

[0063] Step 2: If Figure 4 As shown, the pile-less expanded foundation 1 is transferred onto a ship and shipped to the construction sea area. This step of construction includes:

[0064] Step 21: The transport vessel 5 docks at the pier, and the ship-to-shore connection 4 and the track system 3 connecting the prefabricated pedestal 2 to the deck of the transport vessel 5 are installed. The track system 3 includes longitudinal tracks 301 connecting the land and the deck of the transport vessel 5, and transverse tracks 302 connecting the prefabricated pedestal 2 to the longitudinal tracks 301.

[0065] Step 22: The pile-free enlarged foundation 1 on the prefabricated pedestal 2 is transported to the longitudinal track 301 via the transverse track 302. Then, as shown in the figure, the pile-free enlarged foundation 1 is transported to the dock area via the longitudinal track 301.

[0066] Step 23: Use a trolley system to transport the pile-free enlarged foundation 1 to the deck of the transport ship 5 via the longitudinal track 301 .

[0067] Step 24: After the pile-less expanded foundation 1 is in place, it is temporarily fixed on the deck and the trolley system is moved back to the dock area.

[0068] Step 25: After the shipment preparation is completed, the ship-shore connection 4 is removed. The pile-less expansion foundation 1 is shipped to the construction site and prepared for lowering and installation.

[0069] It should be understood that in another embodiment, after the pile-less enlarged foundation 1 is moved to the dock, it can be lifted onto a ship by a large crane to replace the above-mentioned roll-on / roll-off solution.

[0070] Step 3: If Figure 5 、 Figure 6 As shown, excavation of foundation pit is carried out. This step includes:

[0071] Step 31: Preliminary preparation. (1) Pre-excavation measurement. Use a multi-beam echo sounder to scan the seabed and determine the seabed elevation. (2) Establish a virtual plane grid. During construction, excavation is carried out using a strip and layered process. The strip width is 20m, and the strip direction is consistent with the direction of the rising and falling tides. The thickness of the silt and soft soil layer is controlled to 2m.

[0072] Step 32: Positioning the grab boat 6. (1) Initial positioning of the grab boat 6 through the anchoring system. The anchor is a high-grip anchor. Throw an eight-shaped anchor at the bow, and the anchor chain length is selected to be 100m to 200m; throw a cross anchor at the stern, and the anchor chain length is greater than 250m. The anchoring position can be adjusted appropriately according to the on-site conditions. (2) Precise positioning of the grab boat 6 through the plane grid. A DGPS mobile station is installed at the bow and stern of the grab boat 6. Based on the back-field GPS measurement base station, the precise coordinates of the grab boat 6 are read at all times. The reference for precise positioning is the established plane grid of the construction area. Each grab position of the grab boat 6 corresponds to a grid on the plane grid, thereby achieving point positioning.

[0073] Step 33: Figure 5 As shown, the overburden layer 8 is excavated. (1) The grab ship 6 cuts the soil and dredges the mud by the weight of the grab bucket, adopts fan-shaped excavation, and excavates in layers according to the principle of "slope first and then bottom of the trench". The excavation slope is based on the slope of the design drawing, and the excavated mud is unloaded into the mud transport ship 7 moored nearby, and the operation is carried out in a reciprocating cycle. After dredging is completed at each ship position, the dredger is moved to the lower ship position by winding and releasing the anchor chain. (2) The mud transport ship 7 transports the mud to the designated mud dumping area for dumping. The water depth of the dumping route must meet the navigation requirements of the mud transport ship 7 with a full load draft.

[0074] The pile-less expanded foundation 1 is mostly suitable for foundations with higher hardness, so the seabed is broken and constructed to form a foundation pit 9. Preferably, the present embodiment uses the drilling and blasting method to dig the foundation pit 9. Subsequent construction includes:

[0075] Step 34: Drill blasting hole 10 at the designed location of foundation pit 9. (1) Positioning of drilling vessel. The axis of the drilling vessel is arranged along the direction of water flow. Six anchors are set, including two main anchors at the bow with anchor cables of 100 to 200 meters long; there are four side anchors on both sides with anchor cables of 200 meters long. (2) Drilling construction. The drilling vessel arranges holes in a rectangular pattern with a row spacing of 2 meters and a hole spacing of 2.5 meters. The side line is 1.2 meters wide. The high drill frame "one pipe and one drill method" is used. Before drilling, the casing is first lowered, and then the drill tool is lowered along the casing to the bottom for drilling. During the drilling process, the drill rod is lifted while blowing air and water to discharge the debris in the hole.

[0076] Step 35: Figure 6As shown, the seabed is blasted and excavated. (1) Loading explosives 11. Explosives 11 are loaded immediately after the blasting hole 10 is drilled, and the drilling and loading cycle is repeated. The explosives 11 are loaded into a split PVC pipe, which is then tied with tape and loaded into the drilled blasting hole 10. The explosives 11 are not limited to explosives or liquid carbon dioxide. In this embodiment, the explosives 11 are emulsion explosive packs, each section of which is 0.36m long and 110mm in diameter. Double detonators 13 are used in each explosive 11. When the loading length of the blasting hole 10 is greater than 4m, two explosives 11 should be added. (2) Blocking the hole. In order to achieve a better blasting effect and reduce the impact of underwater shock waves, the hole of the blasting hole 10 is blocked with a blockage 12. The blockage 12 is a specially made elongated plastic bag filled with gravel 23 and medium sand with larger particles. The length of the blockage is determined according to the design, but not less than 50 cm. (3) Connecting the blasting network. The above-mentioned detonators 13 are connected in parallel to form a blasting network. The detonators 13 use industrial electronic detonators. The blasting network uses a hole-by-hole blasting technology and a single-hole single-shot method. The delay interval between holes is 25 to 50 ms. After the delay time is set, the detonators 13 are connected in parallel to the busbar of the blasting network. (4) Detonation. The number of blasting holes 10 to be detonated at one time is determined based on the single-hole loading volume and the maximum amount of explosives 11 allowed to be detonated at one time. After the blasting network is connected and tested, the ship is moved to a safe area for detonation. To improve efficiency and ensure safety, blasting is only carried out during the day when visibility is greater than or equal to 1.5 km. The blasting time must be fully coordinated with passing ships at sea. (5) Slag removal. The broken rocks produced by the blasting are grabbed by a grab ship 6 and transported to the designated mud dumping area by a mud transport ship 7 for dumping. (6) Seabed scanning. After the slag is cleaned, multi-beam scanning is performed to check the flatness of the substrate.

[0077] In steps 34 and 35, if blasting is not possible for foundation pit 9, the intensive drilling + rock drilling process is used. The construction process includes: (1) Positioning of the drilling vessel. The axis of the drilling vessel is arranged along the direction of the water flow, and 8 tracked movable drilling rigs are arranged on the drilling vessel, equipped with a GPS navigation and positioning system. (2) Drilling. The drilling vessel performs intensive drilling at a hole spacing of 0.5m×0.5m, with an over-depth of 0.3m. (3) Rock drilling. The spacing of the rock drilling points should take into account the size and shape of the rock drill rods and the thickness and hardness of the rock bed. After the trial drilling is completed, the arrangement can be adjusted according to the experimental results. The rock drilling is about 40 hammers per hour, the hammer spacing is 1m, and the row spacing is 2m. Three shifts are used every day, 24 hours continuously.

[0078] Step 36: Figure 7As shown, the foundation pit cushion layer 16 is constructed. (1) Pouring of cushion layer 16. According to the scanning results and the design elevation of cushion layer 16, a mixing ship 15 and a floating crane 14 are used to set up a guide frame 24 to pour the foundation pit cushion layer 16. The underwater marine engineering non-dispersed concrete flow radius is 5m. The concrete cushion layer 16 is divided into 16 areas and poured in batches. During the pouring process, the base elevation changes are monitored and the backfill elevation is controlled. The measurement is carried out by combining a multi-beam imager and a depth sounder (the sound velocity can be automatically corrected according to the water temperature and salinity). After connecting it to a computer, it can realize data collection and automatic mapping to prevent the base from being uneven. (2) Leveling cushion layer 16. The "guide rail scraping method" is used to level the cushion layer 16. Divers dive and cooperate to complete the work and scrape the cushion layer 16 to the design elevation. (3) Inspection of cushion layer 16. After the concrete pouring of cushion layer 16 is completed, a multi-beam scanning is carried out.

[0079] For ordinary technicians in this technical field, step 2 and step 3 are partially sequential and can be performed simultaneously.

[0080] Step 4: Hoisting and installation of pile-less expanded foundation 1. This step includes:

[0081] Step 41: Install the sling 17. (1) Place the assembled sling 17 on the shelf. Load the sling 17 onto the flatbed barge with a lifting capacity of 1,000 tons, transfer it to the floating crane 14 with a lifting capacity of 5,500 tons, and anchor it. (2) The main hook of the floating crane 14 is lowered, the sling 17 is connected, and the hook is lifted. The flatbed barge exits the construction area.

[0082] Step 42: Lifting the pileless expanded foundation 1. (1) The transport vessel 5 carrying the pileless expanded foundation 1 enters the construction waters and drops anchor. (2) The main hook of the floating crane 14 drops, and the construction workers connect the steel rod bolts of the lifting device 17 to the pileless expanded foundation 1. (3) A trial lift is performed on the pileless expanded foundation 1. After the trial lift is completed, the pileless expanded foundation 1 is lifted to a certain height. The transport vessel 5 winches the cable to the designated position.

[0083] Step 43: Figure 8 As shown, the pile-less expanded foundation 1 is lowered. (1) The floating crane 14 is anchored and moved to the construction position so that the pile-less expanded foundation 1 is located directly above the designed position; (2) During the flat tide period, the floating crane 14 lowers the hook and slowly lowers the pile-less expanded foundation 1; (3) When the pile-less expanded foundation 1 is 1m away from the top of the cushion layer 16, the floating crane 14 is used to fine-tune the pile-less expanded foundation 1 based on the monitoring and measurement results to ensure that the error between its horizontal position and the designed position is within 5cm. (4) After the fine-tuning is completed, the floating crane 14 lowers the pile-less expanded foundation 1 until it is implanted. (5) The diver dives to the bottom of the pedestal 101 to remove the steel bar bolts, and the floating crane 14 lifts the hook and leaves the construction area.

[0084] Step 44: Figure 9As shown, the pile-less enlarged foundation 1 is precisely positioned. (1) After the pile-less enlarged foundation 1 is placed, the posture measurement is performed. (2) According to the measurement results, the posture parameters of the pile-less enlarged foundation 1 are adjusted. The adjustment of the pile-less enlarged foundation 1 uses 4 sets of YDT1000-200 three-dimensional jacks 18, with a horizontal adjustment range of 10 cm, a lifting stroke of 20 cm, and a lifting force of 1000 tons. In this embodiment, the pile-less enlarged foundation 1 weighs 2500 tons after deducting the buoyancy, and the lifting force of the jack is sufficient. The 4 sets of the three-dimensional jacks 18 are symmetrically installed on the periphery of the base 101. In the horizontal direction, several sets of the three-dimensional jacks 18 are symmetrically installed on the periphery of the base 101; in the vertical direction, the three-dimensional jacks 18 are installed on the top of the support column 20 supported at the bottom of the foundation pit 9, and the top is abutted against the bottom of the bracket 19 extending laterally from the base 101. After being positioned, the horizontal deviation of the pile-less enlarged foundation 1 is first adjusted by horizontally extending and retracting each set of three-dimensional jacks 18. When the design requirements are met, each set of three-dimensional jacks 18 is raised or lowered to adjust the verticality of the pile-less enlarged foundation 1.

[0085] Step 45: Figure 10 As shown, high-strength mortar 21 is poured. (1) A guide tube 22 is installed on the pier top platform of the pile-free expanded foundation 1. The pier top platform is installed in advance at the prefabrication site. The guide tube 22 penetrates into the gap between the pedestal 101 and the cushion layer 16 and pours high-strength mortar 21 to fill the gap. After the middle gap is filled, the outer part of the pedestal 101 is poured to the design elevation until the high-strength mortar 21 covers the bottom surface of the foundation pit 9. (2) The guide tube 22 and the pier top platform are removed. (3) After the high-strength mortar 21 reaches the design strength, the diver dives to remove the jack and support column 20.

[0086] Step 46: Pour the core-fill concrete of the pile-less expanded foundation 1.

[0087] Step 47: Figure 11 As shown, a deck barge is used to transport the crushed stone 23, and the foundation pit 9 is backfilled by the cooperation of an excavator and a loader.

[0088] It should be noted that the above-mentioned transport ship 5, grab ship 6, floating crane 14, and mixing ship 15 can all be called construction ships.

[0089] In summary, the construction method provided by the embodiment of the present invention has the following technical advantages: (1) The construction quality is significantly improved by prefabricating the pile-free foundation 1 in the factory. In the controlled environment of the prefabrication site, the standardized production is carried out using precision molds to ensure high precision, regular shape and good appearance of the components; the concrete mix ratio, mixing, vibration and steam curing processes are standardized to ensure strength, density and durability; the embedded parts are accurately positioned during the construction; the on-site workload is low, reducing on-site human errors. (2) In terms of construction efficiency, factory prefabrication and on-site foundation pit 9 excavation and leveling can be carried out simultaneously, greatly shortening the construction period; the on-site installation process is simplified to hoisting, positioning, connection and grouting, eliminating a large number of wet operations such as steel bar binding, formwork support, concrete pouring, etc., significantly improving construction efficiency; (3) Factory-scale production also dilutes the mold cost, reduces the investment in turnover materials such as on-site formwork and support frames, and reduces construction cost investment. (4) This construction method has strong adaptability, is less affected by weather and sea conditions, and has significant advantages in areas with limited space. (5) Significant reduction in heavy labor on site, lowering labor demand and intensity, which not only facilitates construction organization and management but also improves construction safety. (6) Complying with green construction and achieving environmental friendliness: factory production reduces noise and dust on site; avoids large amounts of waste generated by formwork dismantling, making waste materials easy to recycle; reduces maintenance water and sewage; and ensures a clean and orderly construction site.

[0090] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any technical equivalent transformation made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A construction method for a fully offshore pile-less expanded foundation, the pile-less expanded foundation comprising a cap and a pier, characterized in that: The method comprises the following steps: Step 1: Prefabricate pile-free expanded foundation; Step 2: Transfer the pile-less expanded foundation onto a ship and transport it to the construction sea area by sea; Step 3: Excavate the foundation pit at the designed location. This step includes: Step 31: Create a virtual plane grid and position the construction vessel; Step 32: Excavation of the overburden; Step 33: Construct a foundation pit on the seabed; Step 34: Pour and level the cushion layer at the bottom of the foundation pit; Step 4: Install the pile-less expanded foundation into the foundation pit. This step includes: Step 41: During low tide, hoist and lower the pile-less expanded foundation to the cushion layer; Step 42: Accurately position the pile-free expanded foundation after placement; Step 43: Fill the gap at the bottom of the foundation and backfill the foundation pit to the designed elevation; Wherein, step 2 and step 3 are performed in no particular order.

2. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: Step 33 uses the drilling and blasting method, which specifically includes: drilling blasting holes at intervals as required by the foundation pit design; placing explosives into the blasting holes, and excavating the seabed by blasting.

3. The method for constructing a fully offshore pile-free expanded foundation according to claim 2, characterized in that: In step 33, the blasting excavation construction steps specifically include: filling the blasting hole with explosives; blocking the blasting hole opening; connecting the detonators of the explosives into a blasting network; detonating the explosives after the construction vessel moves to a safe area; and clearing the rubble.

4. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: In step 2, the pile-less expanded foundation is transported onto the ship using a roll-on / roll-off method.

5. The method for constructing a fully offshore pile-free expanded foundation according to claim 4, characterized in that: In step 2, the construction steps for transferring the pile-less foundation onto the ship include: Step 21: The transport ship docks at the pier, and the ship-to-shore connection and the rail system connecting the prefabricated pedestal to the transport ship deck are installed; Step 22: Roll the pile-less expanded foundation onto the ship via the rail system; Step 23: After the pile-less expanded foundation is fixed, the ship-shore connection is released and sea transportation begins.

6. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: Step 1 includes: Step 11: Construction of the cap, including: positioning the base; installing the cap reinforcement and embedded parts; hoisting the cap formwork; pouring concrete and curing; Step 12: Construct the pier body, including: tying the pier body reinforcement; hoisting the pier body formwork; pouring concrete and curing.

7. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: Step 33 is to use a combination of intensive drilling and rock drilling to break up the seabed.

8. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: Step 42 includes: measuring the posture of the pile-free expanded foundation; and adjusting the posture parameters of the pile-free expanded foundation including horizontal deviation and verticality using a jack according to the measurement results.

9. The method for constructing a fully offshore pile-free expanded foundation according to claim 8, characterized in that: The jacks are three-dimensional jacks; in the horizontal direction, several groups of the three-dimensional jacks are symmetrically installed on the outer periphery of the pedestal; in the vertical direction, the three-dimensional jacks are installed on the top of the support column supported at the bottom of the foundation pit, and the top abuts against the bottom of the corbel extending laterally from the pedestal.

10. The method for constructing a fully offshore pile-free expanded foundation according to claim 1, characterized in that: In step 43, the construction steps of filling the gap at the bottom of the pedestal include: installing a conduit on the pile-free expanded foundation; the conduit enters the gap between the pedestal and the cushion layer and pours high-strength mortar until the gap is filled; pouring the outer part of the pedestal to the design elevation until the high-strength mortar covers the bottom surface of the foundation pit.

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