Influence of Water Retention Curves Model Fitting Parameters on Unsaturated Seepage Modeling of Fly Ashes and Pond Ashes

Abstract

Water retention curves (WRC) and its fitting parameters are important inputs for conducting unsaturated seepage modeling study in any geotechnical and geo-environmental problems. This study investigated the effect of variation in WRC model fitting parameters on unsaturated seepage modeling behavior for different types of fly ashes and pond ash. A transient seepage analysis was carried out in a one-dimensional cylindrical column using a finite element method-based software SEEP/W, under a specified total head (H) boundary condition. The variation in pore water pressure (PWP) and volumetric water content (VWC) with time was studied for different conditions. It was found that both PWP and VWC variation with time got affected when WRC model fitting parameters of different fly ashes were used. The influence of suction measurement range on unsaturated seepage modeling result was also found to be considerable. It was established from this study that variation in PWP with time for different fly ashes was mainly due to the variation in the WRC model fitting parameters since the saturated hydraulic conductivity (ksat) value of all the fly ashes was comparable. Further, the sensitivity of Fredlund and Xing (Can Geotech J 31(3): 521–532, 1994) model parameters was studied in detail based on their standard deviations. The study showed that sensitivity on seepage modeling results drastically reduces beyond 20% variation from the reference mean value.