Influence of evaporation on transient suction distribution in unsaturated soil

Abstract

This paper presents the results of numerical analysis on influence of evaporation process on the transient suction distribution induced by rainfall infiltration in unsaturated soil. Transient seepage and slope stability analyses were carried out using commercial software SEEP/W and SLOPE/W (Geo-Slope International, 2007a, b) on 1-year data representing a site at Johor Bahru, Malaysia. Soil samples were collected and relevant data, that is, soil water characteristics curve (SWCC), hydraulic conductivity curve, and shear strength parameters were gained through interpretation of laboratory test results. The study was performed for two typical periods: dry period and wet period, that is, March and June, and two conditions: Rainfall alone and combination of rainfall and evaporation. Residual water content was assigned at the beginning of all analyses. The results show that evaporation gives a positive effect on slope stability by reducing the effect of rainfall on suction distribution. Consideration of evaporation in transient seepage analysis gives a better prediction of suction distribution in soil and slope stability. Key words: Infiltration, evaporation, unsaturated soil, suction, transient seepage analyses.