A 3-D Analysis on the Loading Behaviours of an Under-reamed Anchor in Cohesion-less Soils

Abstract

Abstract This study adopts a constitutive model for sand and a 3-D numerical software, named “FLAC3D” to examine the anchorage behaviours of an under-reamed anchor in sandy soil. A series of pull-out test on model anchors is performed to confirm the results obtained numerical analyses. Test results reveal that the load-movement curves computed numerically are get close to those estimated experimentally. For under-reamed anchors with dimensions of D=0.075m, L/D=4.5, and installed in sandy soil of Dr=70% (Dr: relative density, D: diameter of anchor, L/D: fixed end/diameter ratio), the shape of load-movement relationship on a deep anchor differs from that of a shallow anchor, especially the shape of end resistance-movement curve. However, the friction force, end resistance and total load do not attain peak values at same anchor movement. The end resistance of a shallow anchor displays obviously peak value. However, the peak value the end resistant cannot treasured from a deep anchor. The friction load presents peak and residual values. The mainly pull-out load of a shallow anchor is donated by the friction load, meanwhile the end bearing governs the pull-out load of a deep anchor; overburden depth of 12D is the shallow/deep anchor demarcation. According to the definition of end bearing coefficient, it is categorised to a deep anchor as the overburden surpasses 12D, it is a shallow anchor if the overburden is smaller than 7.5D, and as the overburden equal to 7.5D∼12D, the anchor can be classified as a transit anchor.