Abstract
Rock slope failures are common issues on road cuts. Geological discontinuities are one of main causal factors for the occurrence of rock slope failures and most rocks exposed in road cuts show slope failures as rock falls. Most of the roads constructed across hilly areas have risk from such slope failures resulting in adverse effects on road uses. The aim of the present study is to model rock slope failures which can be used at the design stage to reduce the risk from structural geological features especially planer structures (foliation and joint planes). Two road traces which run across Sri Lankan mountain terrains (Avissawella – Hatton and Balangoda – Haputale roads) were used for the study. Field data on orientation of structural geological features and the type of rock involved in rock falls were collected from 44 locations along both road stretches. Dip Anlysist 2.0 was used for modelling the slope failures. Wedge failure, Toppling and Plane failure modes were considered. Wedge failure is the most common rock slope failure observed. When compared with field observations, the model shows 64% precision from 44 locations studied. The model revealed that the risk from road cut failures can be minimized by optimising existing road orientation and slope angle of the cut. The slope failures can be reduced by using this type of model analysis during the design stage of new roads.
Highlights
Rock falls and rock slope failures are common natural phenomena found in most of the road cuts and other rocky slopes
The aim of the present study is to model rock slope failures which can be used at the design stage to reduce the risk from structural geological features especially planer structures
Most of the rock falls have taken place along geological discontinuities such as foliation planes and joint/fracture planes of rocks (Figure 1). Both road stretches studied indicate that the rock exposures on the road cut comprised high grade hard crystalline metamorphic rocks such as charnockite, charnockitic gneisses, garnet biotite gneisses, garnet granulite and quartzite
Summary
Rock falls and rock slope failures are common natural phenomena found in most of the road cuts and other rocky slopes. In Sri Lanka, most of roads across hilly areas are constructed by using cut and fill method Very often these road cuts generate unstable condition of the ground leading to slope failures. This phenomenon is very common in hilly areas of Central. Central part of Sri Lanka is underlain by highly deformed metamorphic rocks subjected to various grades of weathering (Jayawardena and Eiji Izawa, 1994). These deformed metamorphic rocks are formed by multiple deformational events (Berger and Jayasinghe, 1976). Most of the road cuts with exposed rocks associated with such structures show rock falls as common slope failures
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