Capacity of vertical and horizontal plate anchors in sand under normal and shear loading

Plate anchors could be a solution for mooring offshore renewable energy devices in sand. Previous work has focused on the capacity of plate anchors when loaded normal to the plate. However, for field applications the anchor is mostly likely to be installed vertically, but then rotated from a vertical to non-vertical orientation as the mooring line is tensioned. This ‘keying’ process will result in a progressive change in the loading angle at the anchor padeye, such that the plate is subjected to a combination of vertical, horizontal and moment loading. In order to examine the resulting change in capacity due to the changing load inclination, laboratory scale 1g plate anchor tests were conducted in dry loose silica sand to quantify the normal capacity (normal to the plate) and the shear capacity (parallel to the plate). The capacity of the pre-embedded anchor (width, B = 20 mm and length, L = 40 mm) was investigated at four embedment ratios (3, 4, 5 and 6 times the plate width), two plate orientations (horizontal and vertical) and two loading angles (parallel and normal to the plate). The data represent a first step in establishing combined loading failure envelopes for buried plate anchors in sand.