An underwater repair on an offshore concrete gravity platform is to be carried out using tremie concrete. Outline the procedure you would use and the precautions to be taken in carrying out the above...

An underwater repair on an offshore concrete gravity platform is to be carried out using tremie concrete. Outline the procedure you would use and the precautions to be taken in carrying out the above task efficiently. The concrete gravity platform, given in Figure P9.4 [73], is subjected to wind, wave, and ice forces (at the mean water level). The maximum design wind speed is 40 m/s, and the wind is assumed to act over the portion of the platform, exposed to wind action (above mean sea level). The wave regime is equivalent to a significant wave of 10.0-m height and 14.0-s wave period. The ice load is exerted by an ice field of 1.0-m average thickness. Check the adequacy of the design considering API provisions for bearing capacity of the foundation, dynamic amplification of horizontal and rocking motion, and short-term and long-term foundation deformation. Take a factor of safety = 2.5. The deck load is equivalent to 50,000 kN. Assume that the hollow column (vertical leg) is filled with water up to the mean sea level; the caisson at the bottom is approximately cylindrical consisting of two components, viz., (i) a cluster of vertical cylindrical tanks 50 m high, which displace 70% of the volume of seawater occupied by a cylinder of height l = 50 m and radius ro = 45 m. These tanks are filled with oil and the average density of the tanks with their contents is 900 kg/m 3 ; the cylinder is assumed to be a homogeneous solid of this density; and (ii) the portion of the tank, constituting the base and ballast. This part is also assumed to be a homogeneous cylindrical solid 10.0 m high and 90.0 m in diameter with a density of 2000.0 kg/m 3 . Make approximate wind and wave force calculations for the drilling rig, considering the mean diameters of the tapering portion of the platform column. sice = 1.5 MPa. The rectangular platform deck is assumed to be completely impervious to wind on all four sides. The foundation soil is of clay having an undrained shear strength of C = ay, where a = 2.0 kN/m 3 ; effective angle of friction = 20°; and submerged specific weight of 7.9 kN/m 3 . Added mass coefficient = 1.0; G s = 30 MPa; ? s = 0.33; and e o = 0.30. Assume the foundation soil layer to be 100.0 m thick. Initial effective vertical stress is based on the undrained bearing capacity of soil, while the added effective stress is dependent on the drained bearing capacity. Assume any missing data and justify its choice.