![]() ![]() The caterpillar track system is well established onshore but it gives additional maintenance problems offshore because of the lack of space and high rate of wear and tear. Massive structure and extremely high costĬase 2 Estimated cost: 1.8 times cost of conventional pontoon dredge Used for oil rigs and big offshore cranes in the North Sea stable and effective platform. Reduced water plane area and heavy submerged section reduces the wave effect on the floating structure Tanktesting of models indicated very good damping factors in 2.5 and 3 m simulated wavesĬase 1 B Estimated cost: 1.1 times cost of conventional pontoon dredge The project was aborted because of the political climate in SE Asia. This idea was put forward in an early proposal for an offshore deep-digger bucket dredge in 1972. Elongation of bow to seal off the bow end of the well provides strength and length to protect the pontoon against long waves Plates below the pontoon provide a damping effect. Pontoon bow elongated & stabiliser plates underwater (The articulated L/D idea has yet to be implemented.)Ĭase 1 A Estimated cost: 1.3 times cost of conventional pontoon dredgeģ. ![]() Operating conditions can be varied to suit Andaman Sea conditions of higher waves and periods. Does not cover waves over 1.2 m and period of 8 secs. Buffers operated under certain conditions of wave height and wave period: High waves with low periods (8 secs) and low waves (= 1.2 m) with high periods. Whole digging system including the ladder rests on pneumatic/hydraulic cylinders which absorb the impact of the waves at the digging end Not effective in the open sea anchoring can be a problem high mobility of the dredge means breakwater has to be moved frequentlyĢ. Wave energy is dissipated in the breakwater Clearly, the large environmental impact is a strong limit to its applicability. Although the effectiveness is low, they also have a low cost and they can be easily removed and constructed with unskilled labor and minimal equipment. They are subjected to lower anchor loads, reflect less, and dissipate relatively more than previous FB types. Within the mat category, most are made with tires. The mat and tethered float types are wide, on the order of 10–20 m, but draft is quite small (less than 1.0 m). These shapes aim at increasing the ratio between width and the incident wavelength, and therefore the ability to attenuate the waves, in an economic way. Pontoon-type FBs include several models such as the catamaran type, the Alaska type, and the A-frame type. ![]() Interconnection between adjacent modules and mooring system are primary points of concern for this kind of structures.īarge-type FBs are sometimes built with used barges and ballasted to the desired draft with sand or rock. In the latter case, the efficiency is higher, but the risk of damage is also larger. Connections are either flexible, allowing preferably only the roll along the FB axis, or pre- or posttensioned, to make them act as a single unit. In the former case, the risk of structure sinking is not negligible. They are either empty inside or, more often, filled with a polystyrene or similar materials. A typical module is 15–20 m long, 2.5–5 m wide, and 1–2 m high. Waterway Port Coastal and Ocean Eng., 1985, 111, 2, 304–318, modified.īox type breakwaters are composed of reinforced concrete modules with a rectangular cross-section. ![]() In the schemes: h = water depth, W = width of the pontoon, fr = freeboard of the FB, h s = height of the pontoon, d = draught of the pontoon, and λ = length of the single module forming the FB. ![]()
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