Shallow Modes of Slope Failure in Road Earth Cuttings in Sri Lanka

Road associated failures in Sri Lankan landslides that have been investigated to date were highly dependent on geological setting of the cut slope. Numbers of cut slopes and their failure modes were studied in order to understand the influence of factors: slope height and angle, bed rock geology, seepage, overburden geology and geometry of the cut slope on the slope failure. Shallow failure mode (height of failed mass less than 4 m) is a very common feature in these cut slopes when exposed to intense rainfall due to extensive saturation. Slope stability can be evaluated with the use of geometry, shear strength characteristics and geological setting. Importance of geological setting and characteristics of failure modes must be considered when designing structural measures to improve the stability. An understanding of combined effect of geomorphology and overburden geology, which sets stability of a road cutting, is an essential parameter and helps in understanding sliding potential of the immediate upper slope. This study emphasises importance of geological setting, which determines the characteristics of failure modes when designing structural measures to improve the stability. Combined effect of geomorphology and overburden geology, which sets stability of a road cutting, is an essential parameter for designing of remedial measures by reducing sliding potential of the immediate upper slope.