Uplift capacity of circular plate anchors in layered soil

Abstract

For anchors embedded in cohesive soil, the uplift capacity remains almost constant when the ratio of anchor embedment depth to anchor diameter (D/B) increases above about 4.5. The uplift capacity of anchors in cohesionless soil increases as D/B increases and the increase is greater with increased density of the cohesionless soil. Then, given that an anchor is embedded in cohesive soil, it may be possible to increase the uplift capacity of the anchor by placing a cohesionless overlay on the clay layer.The purpose of the model tests reported in this note was to investigate the effectiveness of placement of a cohesionless layer over a clay seabed in increasing the uplift capacity of a shallow anchor buried in the clay (D/B < 2.0). The sand overburden did increase the uplift capacity, but to obtain a substantial increase in capacity, a very large anchor displacement is required. In fact, the anchor had to displace through almost the entire clay layer before it mobilized the frictional resistance of the sand overlay. Key words: circular anchor, uplift, layered system.