The Flow Response of Reinforced Earth Structures Utilized Fine-Grained Poorly Draining Materials as Backfill

Reinforced earth structures, later known as Mechanically Stabilized Earth (MSE) walls, have been widely employed over four decades due to their ease of installation, quick construction compared to conventional reinforce concrete. Yet, numerous failures of MSE walls structure take place. Most of those failures are frequently attributed to the presence of water within or behind the reinforced zone, flow response inside reinforced earth structures as well. Recently, the use of “high fines” and/or “high plasticity” soils for reinforced fill has become more frequent due to the difficulties in finding an appropriate borrow pit. This paper utilized a well calibrated numerical model to perform series of parametric calculation of MSE incorporated with drainage composite, in which fine-grained poorly draining material was utilized as backfill. The experiments were conducted to investigate the influences of water retention characteristics of poorly draining materials utilized as backfills on the seepage response in MSE wall as subjected to rising of upstream water table. The flow response was examined in terms of effective saturation distribution, changes in phreatic surface as well. The calculated results show that the larger pore size yields the narrower zone of high saturation. The more uniform pore size yields narrower effective saturation profile in range of intermediate saturation zone. The moisture profile in reinforced soil mass is somewhat affected by flow properties of the soil placed next to reinforced part. The distribution of effective saturation at the interface between backfill and wall drainage composite is also governed by the capillary barrier which taken place at the interface between two materials having different pore size.