Wall slope effects on the vertical pull-out capacity of tapered suction caissons

Suction caissons offer certain advantages over other underwater foundation systems by virtue of large bearing capacity, ease of installation, and efficiency. They are typically built with upright walls. The behaviour of upright suction caissons in regard to their applications, installation, load-bearing, etc. has already been investigated by a number of researchers. However, the performance of tapered suction caissons has not been formerly studied. This paper addresses the pull-out capacity of tapered suction caissons under vertical pull-out loads. A numerical approach was used. The finite element model was first calibrated against available test results on upright suction caissons and then used to simulate the pull-out of tapered caissons. It is admitted, however, that further validation of the model against experimental results on tapered suction caissons will increase the acceptability of the results. It was observed that positive wall slopes may noticeably improve the pull-out capacity. A change from local to global failure modes was postulated as the main reason for this improved resistance. With negative wall slopes, however, the pull-out capacity slightly decreased. In addition, effects from the caisson wall slope were investigated for a number of caisson geometries, drainage conditions and soil properties.