Numerical modelling of extraction of spudcans

Abstract

A finite element model was developed to simulate the extraction of spudcans embedded in soft clay. The spudcan was assumed to be ‘wished in place'. To simulate the effect of installation, assumptions were made to approximate the stress field and excess pore water pressure field in the soil above the spudcan, and for the effect of installation beneath the spudcan, load was applied on the spudcan until bearing failure of the soil was achieved. Thereafter, the maximum installation load (preload) was reduced to the maintained vertical load, and consolidation of the soil was allowed to occur to simulate the waiting (operational) period of the spudcan. In spite of the simplifying assumptions made in the finite element model, the results show an encouraging measure of agreement with the centrifuge tests results of Purwana et al. The significance of base suction in the extraction of the spudcan is further demonstrated. Parametric studies using marine clay properties show that the ratio of the difference between the breakout force and the top soil resistance at breakout over the maximum installation load depends largely on the soil properties and the waiting time after adjusting for the effect of the geometric size of the spudcan. Hence this may be a plausible way to estimate the force required for the extraction of spudcans embedded in soft clay.