Abstract:
Soil nailing is a soil reinforcement technique which is used to stabilize
slopes by insertion of slender elements, called nails. When steep slopes are to be
stabilized by soil nailing, practical problems are encountered related to subsurface
investigations, as drilling machines cannot be placed on such slopes. Hence, bedrock
levels cannot be determined in advance, which is disadvantageous to produce cost
effective designs. This research was focused on studying the methods that can be
used for soil nail wall design optimization by applying geotechnical and
geophysical techniques. The study was based on an unstable slope situated near
Victoria dam. The physical properties of soil were determined by direct shear tests,
and stability analysis was done by means of “Slope-W” software. Determination of
the profile of weathered quartzite layer, inter-beded with Charnokite bands was the
major emphasis of this research. Three techniques were used: Ground Penetration
Radar (GPR), Earth Resistivity Measurements and Geological Mapping. This
investigation scientifically showed that the existing slope is unstable, and to be
protected. Further, it was identified in advance that the basement rock cannot be
encountered at designed depths of the soil nails, which was subcequently proven as
correct by the ongoing drilling for soil nail installations.
