Interaction of steel geogrids and low-quality, cohesive-frictional backfill and behavior of mechanically stabilized earth (MSE) wall on soft ground

This paper deals with the behavior of MSE test wall consisting of steel grids reinforcement embedded in cohesive-frictional backfill soil that was constructed on soft Bangkok clay. The mechanism of interaction between steel grids reinforcement and low-quality, cohesive-frictional backfill is being modelled and analyzed. Laboratory pullout tests were performed using large pullout box designed for this study. Field pullout tests were also conducted on dummy reinforcements embedded in a full scale mechanically stabilized earth wall utilizing three different backfill materials, namely: clayey sand, lateritic residual soil, and weathered clay backfill. The magnitude of mobilized pullout resistance as well as the strains induced in the reinforcing elements were strongly influenced by the variation of the base pressure of the wall which is, in turn, affected by the arching effects of the reinforcements and the pattern of deformation of the soft clay foundation. Laboratory pullout tests generally provided conservative approximation of actual pullout resistance in comparison to the field pullout test results. Finite element analyses were also done to simulate and verify the load-displacement of the reinforcements and the behavior of the MSE wall. The overall agreement between the experimental and theoretical results were quite satisfactory. The measured wall settlements and lateral movements, after more than a year, were quite excessive but were found to have no adverse effects on the overall wall performance. Thus, it can be concluded that MSE wall and embankment systems using steel grids reinforcements embedded in locally-available, cohesive-frictional backfill soils is a viable and economical alternative scheme for infrastructure construction on soft ground.