Inclined loading capacity of caisson anchor in South China Sea carbonate sand considering the seabed soil loss

Abstract

Seabed soil losses, e.g., seabed trench and general scour, greatly affect the bearing capacity and failure mode of caisson anchors. In this paper, a series of centrifuge model tests have been conducted to investigate the soil loss influence on the anchor capacity in carbonate sand. The semi-model anchor was adopted, and the anchor movement and soil displacement were captured through the particle image velocimetry (PIV) analyses. It is found that the soil loss changes the anchor failure mode, and the anchor capacity decreases accordingly. For the intact seabed, the caisson anchor firstly rotates backward and then forward. With the increase of trench depth, the anchor rotation mode changes from backward to forward. Two types of soil regions are found during the test, i.e., the shear zone and wedge-type region. When the anchor vertical movement is dominant, the shear zone will form near the anchor wall. In other cases, the wedge-type region will be more apparent. Based on the centrifuge test data, the influence of seabed soil loss on the anchor failure mode is assessed, and a modified framework is proposed for predicting the inclined loading capacity of caisson anchor considering seabed soil loss.