Geological investigation & landslide risk assessment of a section near kharpada village along mumbai-goa highway

Abstract

The rocks exposed in the area are compact Basalt belonging to the most famous basaltic lava flows known as Deccan Trap. These rocks are prone to weathering due to presence of cooling joints which are the discontinuities along which water penetrates and expose the fresh rock to alteration. Different degrees of alteration due to weathering, formation of soils and failure due to complex geological conditions together with high-intensity rain fall makes the Basalt prone to landslide. A section near Kharpada Village along the Mumbai- Goa Highway selected for Geological investigation and Landslide risk assessment, show presence of 3 set of joints. The joint set identified as J1, J2 and J3 are striking in the NE-SW, NW-SE and N-S direction respectively. The joint set J1 and J2 are near vertical whereas J3 is perfectly horizontal. These joints have divided the rock into blocks of varying size and altered it to varying degree depending upon the frequency and openness of joints. Kinematic analysis of the slope has revealed that the right-hand side slope of the road from spot no 1-7 and 17-10 is susceptible to wedge failure as the sliding surface daylight in the slope face. The vulnerability to slide along these spots have also increased due to highly weathered nature of the rock. The spot no 8-16 show stable slope as the sliding surface does not daylight in the slope face and the rock has not suffered weathering forming it a stable slope. This study reveals the importance of structural geology and kinematic analysis in slope stability analysis and if incorporated in designing of slope it can prevent loss of lives and property by slope failure.