A Geotechnical Investigation of 2017 Chattogram Landslides

In this study, an attempt is made to uncover and discuss the geo-environmental characteristics, triggers, and consequences of a landslide disaster in the Chattogram Hill Tracts (CHT) region of Bangladesh. The hilly areas are composed of Tertiary and Quaternary sediments which have been folded, faulted, uplifted and, then deeply dissected by rivers and other water bodies. This paper presents a case study on the geotechnical investigation and numerical modeling of the landslides of 13 June 2017. A field visit and soil sample collection, followed by laboratory testing were conducted at the landslide-afflicted areas. The study revealed that the soil type was an important factor behind landslides, while high precipitation, hill cutting, deforestation, and unplanned human settlements act as contributing factors behind the landslide disaster. Extensive analysis of the geotechnical facts has been carried out, and an attempt is made to pinpoint the cause. A finite element modeling was conducted using PLAXIS 2D to investigate the failure mechanism. The numerical modeling results have suggested that most of the hill slopes were susceptible to failure after heavy rainfall. A conclusion is drawn that the landslides were triggered by incessant rainfall infiltrating into the subsoil, which led to a notable increase in its degree of saturation and a simultaneous reduction in suction and shear strength of the soil.