Reviews on Mitigation Techniques of Offshore Jack Up Hazard by FEM Analysis

Abstract

It is very well observed that offshore sites mostly contain soft/loose soils may be of sand or clay or may be multiple layer of soil mixture under saturated condition. This particular soil undergoes large deformation on the installation of any offshore structure like jack up. It is also observed that jack up may tilt or sink under its own weight without any lateral load or hydrodynamic pressure or any natural hazard like liquefaction or hurricane. It may undergo punching shear failure due to the presence of soft soil. It may suffer failure due to jack up leg and foundation element connection failure. It gets affected by rotational stiffness, foundation fixity parameters. To overcome this situation, several techniques had been proposed by various researchers. Spudcan, anchors, mud mat, bucket foundation, suction caisson foundation, etc., are used to overcome such difficulties. These techniques of mitigation subsequently affect bearing capacity failure zones of soil. Sinking and tilting effects are due to overlapping of bearing capacity failure zones. Hence, by advancing changing in shape and spacing of jack up legs, sinking and tilting effects can be considerably reduced. In particular research paper, an attempt has been made to investigate the effects of various mitigation techniques by previous researchers. All field and laboratory studies along with soft computing with FEM-based software had been discussed. Considerable researchers had shown that provision of mud mat in jack up bottom increases stability of jack up structure. To visualize the various effects, FEM-based Plaxis 3D program had also been used.