Ching Chuan Huang

Investigation of the local strains in a geosynthetic composite

Abstract Effects of the sample treatment and the strain gauge attachment on the local strains developed in a geosynthetic composite which is composed of a core layer of knitted textile needle-punched with two layers of nonwoven geotextile were investigated using a wide-width tensile test apparatus and a photogrammetric technique. It was found that to impregnate both ends of the specimen with epoxy to form stiff areas for clamping was an effective way of preventing slippage of the core knitted textile in the jaws so that uniform deformation of the test specimen could be obtained. It was also found that penetrating strain gauge cement into the geosynthetic composite to create two stiff bases on the geotextile for fixing both ends of the strain gauge provided an efficient manner for monitoring the tensile strain of the geotextile. The tensile strain readings obtained using the suggested installation method was comparable with those measured using the photogrammetric method.

Failure mechanisms of steep-faced geosynthetic-reinforced retaining walls subjected to toe scouring

ABSTRACT Waterfront structures such as seawalls, dikes, and levees are frequently subjected to scouring at the toe of the slope, leading to deteriorated performance and increased failure potential. To this end, some model reinforced steep-faced slopes consisting of a two-dimensional backfill were brought to failure to explore the failure mechanisms of some geosynthetic-reinforced slopes subjected to simulated toe scouring. Results of model tests indicate that in the case of shallow scouring, a reinforcement length (L) increase from 0.4 to 1.0 Ht (Ht, total height of reinforced walls) significantly increases the tolerance against toe scouring-induced failures. In this case, a local bearing capacity failure of facing is the dominant failure mode. In the case of deep scouring, an increase in L beyond 0.7 Ht provides no additional tolerance against toe scouring because the ultimate state is always associated with a global circular sliding in the unreinforced zone. Experimental values of the lateral pressure coefficient (Kt) converted from the measured reinforcement forces indicate that reinforcement forces consistently increase in response to toe scouring up to the final collapsing state and that the reinforcement forces for L = 1.0 Ht mobilize more effectively than those for L = 0.7 Ht.