Stability analyses of reinforced walls subjected to simulated toe scouring

ABSTRACT: Limit-equilibrium-based internal and external stability analyses were performed for two carefully designed and monitored reinforced model walls reported in a companion paper. Failure mechanisms and associated safety factor changes against toe scouring were investigated. Safety factors against various failure modes – reinforcement over-stressing, reinforcement pullout, lateral sliding, overturning and bearing capacity – were derived, based on well-known material properties and theories. It was shown that the ultimate collapse state of the wall with a low reinforcement–facing connection strength was controlled by the pullout of the reinforcement from the facing. A low reinforcement–facing connection impeded the full mobilisation of reinforcement force in the lowermost layer of the reinforcement, which in turn reduced the ductility of the structure and accelerated the failure process. For the wall with high connection strength, the ultimate collapse of the wall was controlled by the bearing capacity failure near the slope toe. The analytical bearing capacity failure state was supported by the experimental observation of the failure wedge below the facing and the reinforced zone. Experimental results also suggested that a transitional wall displacement of D_{h max}/H_t = 0.2–1.0%, signalling rapid wall displacement for further inclined toe cutting (or further toe scouring), is associated with higher internal and external stability safety factors than those suggested in current design guidelines that do not take into account the effects of toe scouring.