Undrained vertical pullout capacity of strip plate anchors in two-layered clay

The pullout behavior of plate anchor embedded in clays has received significant attention from researchers, but most existing studies are limited to plate anchors in single layer of undrained clay. In this study, the vertical pullout capacity of horizontal strip anchors in undrained two-layered clay is investigated. A series of finite element analyses were carried out to obtain the stability predictions for a wide range of geometrical and soil properties. Anchor-soil interface conditions of immediate breakaway (vented) and no breakaway (attached) are considered. Results are given in the familiar form of the pullout capacity factors as a function of dimensionless parameters relevant to anchor embedment, relative overlying layer thickness, strength ratio of two soil layers, and soil self-weight. The obtained results are compared with empirical and analytical solutions reported in literature. Simple design equation is proposed for two-layered clays with self-weight representing the anchor capacity. The pullout capacity of the plate anchors is governed by the three failure mechanisms: punching, squeezing, and general shear failures.