Investigation into the influence of caisson installation process on its capacities in clay

Abstract

The installation process of caisson foundations causes the seabed soil heaving as well as the soil strength remoulding. This paper investigates these two effects by examining the installation process of caissons through large deformation finite element analysis. The short-term undrained bearing capacity of caisson foundations in clay after installation, which is a critical engineering scenario because the long term foundation capacity increases with time due to seabed soil consolidation, is subsequently evaluated. Expressed in terms of bearing capacity envelopes under combined loading, the short-term bearing capacity exhibits significant reduction affected by the two effects (i.e. soil heaving and soil remoulding) during installation. The analysis results show that the caisson foundation capacity under uniaxial vertical load reduces by up to 40.95% when the ratio of caisson skirt length (d) to diameter of the caisson (D) is d/D = 4 while the uniaxial moment capacity reduces by up to 42.21% when d/D = 1. Meanwhile, all failure envelopes shrink due to the influence of installation. The maximum capacity degradation factors of all H-M failure envelopes are always greater than those of the uniaxial vertical, horizontal or moment capacity. The influence of the installation effects on the capacity of caisson post installation is more obviously when V ≤ 0.5Vult.