Hydro-Mechanical Properties of an Unsaturated Frictional Material

4 CHAPTER 1. INTRODUCTION
- Model building and development of a simple suction-water content model, including
scanning process.
- Determination of soil-water characteristic curve, θ(ψ) and determination of the influence
of suction on the hydraulic conductivity, k(ψ) and on the oedometer stiffness modulus,
Eoed(ψ).
- Derivation of reliable experimental data for validation of constitutive equations.
- Determination of reliable model parameters for numerical simulations of geotechnical
problems. Only realistic soil parameters lead to realistic simulations and conclusions.
- Numerical simulations of experiments for parameter identification as well as improve-
ment and/ or development of underlying constitutive equations.
An example is used to underline the importance of investigation as well as implementation of
unsaturated soils to engineering practice. The change of mechanical behavior due to suction
in a soil is carried out using the classical problem of shallow foundation (i.e. the influence of
suction on bearing capacity, q(ψ) is investigated), that is a typical civil engineering problem.
Furthermore, the importance of the soil-water characteristic curve is given, which is used as
an important tool when dealing with unsaturated soils in combination with the saturated
shear strength for prediction of bearing capacity of unsaturated soils.
1.3 Organization of the Dissertation
The thesis contains eleven chapters. The first chapter (i.e. this chapter) outlines the back-
ground, the scope and objectives of the investigation as well as the organization of the dis-
sertation. The second chapter summarizes basic literature on unsaturated soils related to the
objectives of this study. Important hydraulic and mechanical functions as well as methods to
determine them are introduced. Sets of equations and models used in unsaturated soil me-
chanics are presented and discussed. Background, theory and the main variables of process
modeling are presented in the third chapter. Process modeling is used in this study for devel-
oping a model, that relates the suction to volumetric water content. Extended overview of the
developed and modified testing devices and the equipment used to study the hydro-mechancial
behavior of unsaturated sand are introduced in the fourth chapter. The material used and
the experimental program carried out are discussed in the fifth chapter. The experimental
program includes the investigation of hydraulic and mechanical unsaturated sand properties
under consideration of for instance several initial and loading conditions, or different boundary
conditions. This chapter also includes detailed explanations regarding to specimen prepara-
tion (preparation of homogenous, reproducible specimens) and the testing procedure. The
experimental results derived from the extensive laboratory program are presented in the sixth
chapter. The experimental results are analyzed and interpreted in the seventh chapter. The