NUMERICAL MODELLING OF SEEPAGE BELOW HYDRAULIC STRUCTURES

Abstract

The floor thickness of the hydraulic structure is usually designed on the basis of steady state uplift pressure. Khosla's theory is widely used to estimate this uplift pressure at few key points below a hydraulic structure and exit gradient. The theory is based upon many assumptions, which may not always hold. Further, it permits estimation of only the steady state uplift pressure and exit gradient. In the present study a numerical model has been developed. The model permits estimation of transient piezometric head distribution in the flow domain. The model has been validated by comparing its results for steady state with Khosla's curves. Simulation runs were conducted to study the unsteady build-up of the piezometric head below a hydraulic structure. It was found that for relatively compressible and low hydraulic conductivity foundations, the steady state distribution may not be reached even after fifty years of the initiation of the flow. Dimensionless curves of the time to reach steady state are presented