Seismic stability analysis of anchored concave slopes

Abstract

Concave-facing profiles are frequently encountered in natural slopes and, more recently, in man-made slopes. The seismic stability of such concave slopes can be effectively improved by employing ground anchors. The concavity of the slope profile can be effective in the design of the soil anchoring system. Using the pseudo-static limit equilibrium (LE) approach and considering a rotational log-spiral failure mechanism, this paper analytically addresses the total anchor load required for the stability of concave soil slopes reinforced with pre-tensioned cable anchors under seismic loading conditions. The concave face of the slope is represented by a circular arc, the curvature of which is expressed by the mid-chord offset (MCO) parameter. A satisfactory agreement was found between the results predicted by the solution and those of the finite element method. The impact of profile concavity on the resulting total anchor load was explored by varying backslope inclination, vertical-to-horizontal seismic coefficient ratio, and the action point of the total anchor load. Further, a design example is presented to illustrate how the load of anchors for a given anchorage layout can be determined using the method. The results generally indicate that a concave slope requires less total anchor load to provide seismic stability compared to an equivalent planar one. However, the concavity impact decreases with increasing horizontal seismic coefficient and backslope inclination. Further, the direction of the vertical seismic coefficient was found to be effective on the impact of concavity.