Pullout performance of vertical anchors in gravel formation

This study elucidates the behavior of vertical anchors in gravel formation. Seventeen full-scale gravity-grouted anchors were installed in situ in Taichung, Taiwan. Tension, compression and compound anchors were installed. Pullout load testing was conducted for each anchor. Test results were compared and failure mechanisms were examined. The extended failure surfaces of shallow anchors were measured and analyzed. For compression and tension anchors, the angles between the failure plane and tendon were approximately 42° and 53°, respectively. The anchor type also affected the ultimate load for an anchor. For anchors with similar bonded length, the compression anchors with multiple anchorages achieved the highest ultimate load compared with compound anchors and tension anchors. The ultimate load per bonded length increased as total length or overburden ratio in the tension anchor increased. For deep anchors, frictional resistances were > 840 kPa. The ultimate loads obtained in this study were comparable to those obtained by Ostermayer and Scheele.