Combined Functioning of Geotextile as Barrier and Drainage Material in Unsaturated Earth Retaining Structures

Abstract

This article presents an insight into the effective functioning of geotextile as a barrier and drainage material when used in earth retaining structures under unsaturated conditions. A numerical model of the infiltration test on a one-dimensional soil column has been simulated and a finite element transient seepage analysis is conducted to determine the progression of saturated wetting front through the clay–geotextile interfaces. The barrier mechanism of a geotextile layer was highlighted in terms of the water accumulation over the soil–geotextile interface, and retardation of wetting front migration beneath the geotextile layer. It was observed that the barrier breakthrough time is substantially affected by the initial volumetric water content of the surrounding soil and the hydraulic characteristics of the geotextile. Rainwater infiltration analysis of a geotextile revealed that the barrier effect assures the geotextile to be functioning as horizontal drainage layer after exceeding the breakthrough suction of the geotextile. Provision of a facing drain channels the surface runoff, as well as the water emanated from the geotextile layers, to the toe drain. Such provisions resulting in an effective drainage system substantially lowers the lateral thrust and improves the stability of the soil wall, which inadvertently enhances the sustainability of the reinforced soil walls with marginal soil backfills.