Study of Stabilization of Unstable Area and Development of Mitigation Measures for Landslide at Peradeniya, due to Widening of Town Roads

Abstract

This paper investigates the current and future road traffic requirements around Peradeniya town, provides a summary of the detailed stud y of stability analysis of the adjoining slope area at Peradeniya town and finally a slope area re-shaping design solution is worked-out based on slope stability analysis for the unstable area in the town. The classified traffic movement data and road geometrical data were used to illustrate the present traffic conditions and future traffic requirements for a design period of 20 years. The required carriageway width for each road and the lateral distance toward s the slope that requires to be excavated from the centre of the existing road (i.e. land requirement for Colombo-Kandy road widening) was decided based on the outcome of the study. The slope area was analysed with the ground water levels, field and laboratory test data for its Stability using Morgenstern- Price finite slope stability method under three different scenarios: firstly considering actual observations, secondly for an adverse condition and thirdly for a situation after rearranging the shape of the slope to an angle of 35° with controlled ground water table. The results of the study indicate that the road towards Colombo has to be widened up to 25m from the center of the existing road towards slope area at Peradeniya. The stability of most parts of the area is in critical state and there is a higher percentage of probability for occurrence of landslide hazards during rainy seasons and the results of reshaping the slope area gives a remarkable level of stability.