Master of Science theses supervised by staff of the Section Engineering Geology

1992. GIS in regional slope stability analysis / by Essa Nuru Alemu. - Delft : ITC, 1992. - 100 p. + 7 maps ; 30 cm. - ITC MSc-thesis ABSTRACT, supervisor: Hack, thesis availability: ITC Library

ABSTRACT

Planes of weakness (discontinuities) are very important in rock mass behaviour. The rock mass becomes anisotropic, weaker and more deformable, because the shear strength is reduced, permeability is higher parallel to discontinuities and compressibility is increased as well as tensile strength is reduced (essentially zero) perpendicular to planes of weakness (discontinuities).

Taking into account the role of discontinuities on the stability of rock slopes, this document discusses the approach to determine the stability of rock slopes on a regional level through the application of a Geographic Information System (GIS).

The research area is located in the north eastern part of Spain in the province of Taragaona around the town of Falset (location map). The area covered is 132 km2. 636 discontinuity sets from 237 observation sites have been recorded during general purpose engineering geological mapping and detailed rock slope evaluation. It has been conducted by engineering geology students of the ITC, Delft together with engineering geology students of the faculty of Mining and Petroleum Engineering of the TU, Delft as part of post graduate study in engineering geology in 1990 and '91.

The structural discontinuity data gathered during general purpose engineering geological mapping are processed and analyzed using statistics. The mean dip and dip direction of the discontinuity sets are assigned to the structural sub-areas which are classified mainly based on aerial photo interpretation.

Vector approach is made as an alternative (because the easy handling of large sets of data) to the stereographic projection techniques to determine the geometric parameters required in wedge failure analysis.

Using the Geographic Information System software, ILWIS (Integrated Land and Water Information System) developed at ITC (Goret et al ,1988), the stability of existing slopes and the maximum allowable safe cut angle based on plane and wedge sliding are evaluated. For the later case the slopes are assumed to be excavated along the existing terrain. This is often the case in road construction.