Seepage Sensitivity Analysis through a Homogeneous Dam within the Unsaturated Soil Zone

Seepage through earth dams is affected by the soils characteristics that form them, which are characterized by the difference in time and place by the influence of various factors such as climatic factors and soil moisture variations because of changes in the storage level in the reservoir in front of the dam. Therefore, the possible randomness of these parameters that reflect the characteristics of the soils must be taken and their effect evaluated to ensure the survival of seepage is minimal. This research comes as a continuation of the study applied to several types of soils to find out the effect of the variation of some of their parameters on seepage through earth dams, and by following a new method that observes the unsaturated zone above the seepage line in earthen dams, which provides the best result to simulate the actual situation of any engineering facility (Where it is assumed with average constant values in previous researches to simplify the solution, but they are not constant in the actual case). The aim of the research is to analyze the sensitivity of the steady state seepage for the variation of the hydraulic conductivity, residual water content and saturated water content in a typical homogeneous earth dam, by building a mathematical model with the Seep/W program after writing a program code in c# for the used equations (van Genuchten model to determine the hydraulic conductivity parameter of unsaturated soil, and the van Genuchten to determine the water content). That allows generating random values for those parameters based on their statistical properties from previous research. The Monte Carlo technique was adopted to solve a very large number of simulations (5500 models), and a deterministic model for comparison was also built. The research showed that the variability of all parameters of the studied soil, gravely sand, did not affect the seepage, and the ability to rely on its fixed average values instead of random models, as the highest percentage of difference from the deterministic model was 0.1565%, which is a very small amount that can be neglected