PHYSICAL MODEL TESTS ON MECHANICALLY STABILIZED EARTH WALLS WITH GEOCOMPOSITE DRAINAGE UNDER SEEPAGE CONDITION

Both external and internal stabilities are a main concern in design and construction manuals for the mechanically stabilized earth (MSE) wall. Literature showed that the failure of the MSE walls, especially in mountainous areas, is mainly caused by the attack of seasonal heavy rainfall. The seepage through the MSE wall due to the rainfall causes the increase in the lateral stress and the reduction in the effective stress, stiffness and strength of the backfill; hence the reduction in the factors of safety against external and internal failure. This paper investigates the flow and mechanical behaviors of the MSE wall with and without geocomposite grain under seepage condition. The investigation is performed using laboratory physical model tests. It is found that the water pressure significantly controls the performance and the failure of the MSE wall. As the water pressure increases, the settlements in the unreinforced zone increase. The failure of the MSE wall is caused by the piping of the reinforced soil. The geocomposite drainage reduces the water pressure and water content in the reinforced zone, hence the improvement of the stability of the MSE wall. For the same water pressure, the MSE wall with geocomposite drainage sustains lower settlements.