Landslide Investigation at Phata Village on Rudraprayag-Kedarnath Road, Uttaranchal — A Case Study

Phata village on the Guptakashi-Gaurikund road in the Mandakini valley of Garhwal Himalaya was affected by a major landslide on 16th July 2001 due to heavy rainfall. The debris flow not only swept away several houses but it also claimed 15 lives. A detailed landslide investigation was carried out to assess the present stability condition. Geotechnical investigation was carried out to determine the soil properties. Seismic refraction survey to determine the overburden thickness was also carried out using Engineering Seismograph. Slope stability analysis was carried out to ascertain the existing stability of the slope. It was found that with rise in pore pressure the slope is marginally stable. The seismic stability analysis showed that seismicity of the order of 0.15g may trigger slips on the slope. The human settlement on the downhill slope may get effected in the eventuality of slide due to seismicity or rain. The paper presents the results of the geological and geotechnical studies which helped to assess the present stability condition