Environmental Engineering Reference
In-Depth Information
Chapter 3
Instability of Soil Masses
3.1. Introduction
Among all natural dangers, phenomena connected with the movements of loose
soil are especially frequent and often spectacular, with consequences that are
sometimes dramatic for human beings and the environment, such as the destruction
of villages and of communication routes, and creation of temporary dams. The
analysis of these phenomena is very complex, and although there is abundant
literature on this subject, engineers are always led to drastically simplify the reality
in order to reduce it to a model for calculations. This chapter offers a brief overview
of the different modeling approaches in which material behavior plays a key role.
The kinematics of earth slides is quite varied and has led different authors to
propose classifications based on the geometry of the sliding mass and on the
velocities [HUT 88, VAR 78]. Very roughly, the three following categories will lead
to the development of specific calculation tools: creep, slide and flow (see Figure
3.1). The first category is characterized by movements noticeable in the long term,
appearing in internal deformations and surface movements in the order of a few mm
to a few cm per year. The modeling will have to call upon the laws of viscosity, or
more generally on elastoviscoplasticity.
The second category (slide) is characterized by the relatively abrupt movement
of two or more masses of soil along a shearing zone that is generally circumscribed.
