Dynamic installation of a torpedo anchor in two-layered clays

The behavior of a torpedo anchor during dynamic installation in two-layered nonhomogeneous clay sediments was investigated through large deformation finite-element (LDFE) alayses. Parametric analyses were undertaken varying the top layer thickness and strength ratio between two layers. The results showed that the location of the demarcation point between the acceleration and deceleration phases of the anchor in the soil relative to the layer interface is the key factor directing the anchor behavior in layered soils including the final embedment depth. Broadly, the anchor behavior in soft-over-stiff clay deposits is somewhat similar to that in single layer clay with strength increasing with depth. In stiff-over-soft clay deposits, the anchor penetrates deeper where the anchor deceleration phase (or the demarcation point) falls within the soft layer. Where the demarcation point lies within the top stiff layer, the anchor
penetration depth decreases with increasing strength ratio, and the anchor penetration is terminated between the two layers for strength ratio ≥ 15. For assessing the anchor embedment depth in two-layered fine-grained ocean sediments in the field, an extended total energy based method, along with a design expression, is proposed.