FIELD PULL-OUT EXPERIMENTS OF FLIP-TYPE GROUND ANCHORS DRIVEN IN GROUND OF CLAY AND SAND LAYERS

The pull-out mechanism of square, circular, or rectangularembedded plate anchors in sandy and clayey grounds has been previously studied both in laboratory and field. However, similar experimental researches focusing on flip anchors have not been conducted in either laboratory or field.Therefore, this study aims to provide results of field pull-out experiments of actual flip anchors driven into the ground consisted of a top sand layer and a clay layer underneath. The behavior of pull-out resistance of flip anchors installed in clay is investigated, comparing with the behavior of flip anchors installed in sand. A total of 26 flip anchors were driven into the ground at positions of 2 m pitch grid using a percussion driving device and pulled out using a hydraulic jack. Five sizes of flip anchors were installed in the sand at a depth of 1.0 m or 1.2 m, or clay layer at a depth of 1.8 m. Vane shear tests were conducted in the clay layer to measure the undrained shear strengthcu. The anchors in the sand had a greater pull-out force than the corresponding anchors in the clay. The pressure acting on the anchor increased with decreasing the projected area of the anchor in the sand layer. In contrast, in the clay layer, the pressure was the same regardless of the projected area of the anchor plate. The maximum pull-out forces measured in the clay layer agreed well with the calculated values based on the interpretation of the T-bar penetration test.