Analysis of Suction Caissons in Soft Clay

Abstract

The cost of establishing any offshore structure is quite expensive. One of the largest expenses in offshore infrastructure is the foundation as environment like wind, wave, and soil or a combination and poses a challenge in most cases. For observation platforms, suction piles offer an unique advantage that it can be reused any number of times by just shifting the location which helps reduce the cost of preliminary infrastructure for potential identification quite feasible. Suction piles or suction buckets are hollow cylindrical steel or concrete caisson, closed at the top and open at the bottom [1]. They are installed by applying suction inside the airtight caisson therefore not difficult for setting up. Once the required data is collected, the pressure inside the caisson is reversed, to be moved to another location. These suction piles resist loads due to the mobilized frictional resistance occurring inside shaft as well as the outside while the bearing resistance comes from the annulus and top plate as it rests on the ground surface (Houlsby and Byrne in Proc. Inst. Civil Eng. Geotech. Eng. 158, 75–82, 2005, [2]). An analysis on the aspect ratio of the caisson for soft clay encountered in the gulf regions is studied in detail [3]. An optimum aspect ratio of the bucket considering various failure conditions is obtained for the gulf regions using numerical computation which can be easily adopted to other location by changing the input parameters. The ratios which are ideal for the gulf regions are also stated in the paper. The suction pile installation has also been studied using a finite element analysis tool, and the failure pattern due to reversal is observed. It is observed that once the suction exceeds the required value, reverse bearing failure occurs causing the bucket to fail.