Case History of Controlling a Major Landslide at Karandu, Turkey

Abstract

Landslides are the major geotechnical problems in highway projects. The trinity, consisting of water, discontinuity, and clay (WDC), is the major driving force behind any landslide. A detailed model study including geology, hydrogeology, engineering geology, and geotechnics, enables the geotechnical designer to alleviate a slide problem. The Karandu landslide with a mass of over 100 million m 3 forms a transportation bottleneck from Ankara and Istanbul to Sinop in Turkey. The artesian pressure in the slide mass is greater than 2 bars. Well-developed and outsloping discontinuities have conveyed infiltrating groundwater towards the slide area. High clay content of the slide mass derived from an underlying unit of claystone and siltstone reduced the shear strength considerably. In addition to surface drainage, a subsurface drainage system consisting of water wells and trenches have reduced the water table and piezometric level appreciably. They formed a comprehensive network to mitigate the adverse effect of the WDC. Thus, the minimum factor of safety increased 30% or more. This solution allowed the designer to cross the slide area and to follow the best alignment for the given corridor. Thus, construction costs have reduced to one third of rehabilitation costs for the existing road. Also, transportation time was reduced from 2.5 h to 50 min. (C) 2003 Elsevier B.V. All rights reserved.