Stabilization of Coastal Slopes by Anchored Geosynthetic Systems

Coastal slopes are subjected to destabilizing forces from wave action, current scour, and exfiltrating ground water. As such, they are vulnerable to both surficial erosion and shallow sliding failure because of their low shear strength near the surface. One way of increasing the stability of these slopes is to increase the confining stress on the ground surface by means of an anchored geosynthetic system (AGS). This approach is less visually and physically intrusive than traditional “hard armor” methods, which in many instances are prohibited in environmentally sensitive areas such as coastal sand dunes. Theoretical relationships for determining required AGS loads and anchorage lengths are presented that can be used to evaluate stability for different soil conditions and seepage directions. Some important variables affecting AGS performance such as failure depth, surface configuration, anchor orientation, and seepage influence on near-surface stability are also described. The theoretical predictions were examined by conducting laboratory stability tests on saturated sand slopes, which were stabilized by an anchored geosynthetic netting and subjected to parallel seepage and tractive surface stresses. Good agreement was observed between predicted and actual anchor loads at failure.