ANALYSIS. OF UNSATURATED FLOW IN LAYERED SOILS

Abstract

Moisture movement through unsaturated zone is very important in many branches of engineering such as agricultural engineering, soil science, ground water engineering and hydro geological engineering. The unsaturated zone interacts with flow processes of soil surface as well as with ground water. Due to the complex nature of flow through unsaturated zone, it is difficult to get accurate and mass conserving solution for unsaturated flow problems. The present study comprises of developing a numerical model for analvsinn one-dimensional variably saturated flow in layered soils. This includes the study of the effect of the position of different layers and thickness over infiltration from topsoil layer and gravity drainage from bottom soil layer. In chapter 1 a brief description of water as the major source of energy, its utility and importance in different parts of human life, related engineering properties, the positional form of water in different type of soils and in different layer positions, different zones such as saturated and unsaturated zone is being presented. The chapter also briefly describes as to how water moves in unsaturated zone. The chapter 2 presents in brief the there is literature review related to unsaturated flow in layered soils, governing equations, boundary conditions and different types of solutions. The various forms of governing flow equations such as those moisture content based, pressure head based and their relationships have been discussed. In chapter 3 a numerical model is developed using implicit finite difference method. Formulae of various relationships, different boundary conditions that have been applied in the model for infiltration and for gravity drainage are also discussed. Solution of finite difference equations and solution algorithm is also presented. The model is validated by comparing model compute pressure heads with the Celia et al., (1990)'s results. In chapter 4, the model is applied to study the soil moisture movement in layered soils during gravity drainage and infiltration. The effects of position iillUktICSS or inaiviauai layers on tnese processes are studied. Chapter 5 presents the conclusions and recommendations drawn from the study.