LANDSLIDE INVESTIGATION USING ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT), GEOTECHNICAL TECHNIQUES AND GIS MAPPING OF SARBALA LANDSLIDE, HATTIAN BALA, AZAD JAMMU & KASHMIR.

Abstract

Landslides are disastrous phenomena causll1g widespread destruction to landscape, infrastructure, and life throughout the world and mostly in mountainous terrain. The investigated mass movement Sarbala Landslide is located in district Hattian Bala Azad Jammu & Kashmir that was first activated in April 2018 after prolonged rainfalls. This mass movement caused extensive damage to the infrastructure and landscape of the area and still poses a threat to adjoining settlements. This study aims to investigate the slope failure mechanism of Sarbala Landslide using integrated geophysical and Geotechnical techniques. To characterize the Sarbala Landslide, techniques including geological field work, electrical resistivity tomography (ER T), geotechnical techniques, and GIS mapping were applied to evaluate the surface and subsurface dynamics of the Sarbala Landslide. Multiple field surveys were conducted in which soil samples were collected and six ERT profiles using the Wenner Schlumberger array were acquired in different parts of the Sarbala Landslide. ERT results reveal that the sliding mass of the Sarbala landslide mainly comprises saturated colluvium and debris that causes low resistivity in tomograms. Saturation of slope forming material is a major cause contributing to instability of Sarbala Landslide. A well-developed Slip surface is observed between unconsolidated landslide mass and underlying bedrock based upon resistivity contrast. The Atterberg limits of the landslide material indicated low to medium plastic behavior of Sarbala landslide. According to the study, soil is mostly sand with minor silt and clays and have high porosity and permeability, therefore more water entered the subsurface and decreases strength by increasing pore water pressure, causing the soil to break down and resulting in slope failure. In addition, tectonically this area is active and bounded by two active faults i.e., are Bagh Balakot fault and Jhelum fault. Distance to fault map reveals that these two faults are located within the diameter of 3-10 km from Sarbala landslide and play key role for the triggering of andSlide. WeI - eve ope scarps and large-scale tensional cracks in landslide depict the active nature of landslide. This study indicates that Sarbala Landslide is an active mass movement. Besides active tectonics of the study area, hydrogeology of the slope forming mass is a major factor reducing the stability of Sarbala Landslide. This study suggests the implication of more advanced research for monitoring of Sarbala landslide in future.