What Is a Caisson?

The caisson is a deep foundation type, which is mostly used for docks and breakwaters. It is a box-type structure with a top and no bottom. It has internal partitions that can float in the water. The sinker can be controlled to sink or float by adjusting the ballast water in the tank. During the construction, the box is filled with sand or block of stone, and then the top is covered with a cover to cap the roof. The top cover is equipped with an air lock, which is convenient for personnel, materials and soil to enter and exit the working room, while maintaining a fixed air pressure in the working room.

According to the different conditions of precasting and transporting the caissons, the caissons' shipping process can be summarized as follows.

The caisson hauling is also called towing. A tugboat uses its power and equipment to tow other ships or objects to sail or perform certain operations. A tugboat is called a tugboat. A tugboat usually has its own power plant. The hull is short and wide, has a strong structure, a large draft, and has good maneuverability and stability. A towed vessel or cargo is called a towed vessel or object. There are three main ways of towing: towing, pushing and binding. The so-called belt application is also called a row of tugs. The tug is in front, the tug or cargo is behind, and the tug or tug is connected by a tug. Towing large equipment, cargoes are generally towed. The so-called pushing means the towing method of the towed ship or cargo in front, the pushing wheel behind, and the toe of the hull or side of the towed ship with the head of the pushing wheel. The so-called towing means that the towed ship or cargo is tied to the side of the tug, and the tug is used to tow the ship. It is suitable for short voyages and is generally used in harbors and inland rivers. Its hauling methods include straddle hauling, hauling hauling and mixed delivery. The span drag method has large resistance, slow travel speed, large power consumption, and is prone to wave spray. It is prone to danger under wind and wave conditions, but it is beneficial to the caisson in place. This method is generally used under conditions of short transportation distance and relatively narrow water area. When the transportation distance is long and the water area is large, the dragging method can be used. In places with short transportation distances and relatively narrow water areas, it is common to use a mixed method of spanning and towing, which is relatively easy to control the caissons.

After the caissons are hauled from the prefabrication yard or the storage site to the installation site, take advantage of the ebb tide (cross towing), slowly tow into the installation position, fasten the cable, and when the tide falls to the bottom of the caisson about from the top of the bed, pass the pulley unit Manually retract the cable and sink it after positioning, or open the water valve to sink and sink, tighten the cable while sinking. After sinking on the bed, check the deviation and the width of the seam. If it fails, pump, float and reinstall. When using self-sinking with the tide, the caisson should be properly irrigated, so that the draught before sinking is greater than the stable floating draught, so that the displacement or seam width is unqualified and pumping and floating are required. When reinstalling, the caisson is still in a stable state. After the caisson sinks on the foundation bed, the water inlet valve needs to be opened for irrigation, and like the water inlet valve is set to sink, the water inlet valve is closed after the high tide is filled with water to prevent the caisson from floating with the high tide and increase the caisson resistance. The stability of waves and currents. If the waves are heavy or the current is rapid, if the ropes are used to tighten the ropes manually, and it is still difficult to stabilize the caisson, you can bury the lifting lugs on the top of the caisson, and use a hoisting vessel to lift the caisson. During hoisting, the caisson is filled with water to increase its ability to resist waves and currents. It is aligned with the center of the swing, and the loose hook drops to the caisson ^[1] .