Comprehensive study on evaluation of Kaliasaur Landslide attributes in Garhwal Himalaya by the execution of geospatial, geotechnical and geophysical methods

Abstract

The devastating Kaliasaur Landslide of Garhwal Himalaya disrupted a significant part of the National route directing to Kedarnath-Badrinath originates from Kaliasaur fault of Srinagar thrust. This landslide event comprising mainly rocks as well as debris got provoked by the monsoonal precipitation overcasting the Himalayan region. The Tropical Rainfall Measuring Mission (TRMM) data evaluates this precipitation intensity. Further Rapid Mass Movement Simulation (RAMMS) modeling is employed (using ALOS PALSAR 12.5 m DEM data), that infers rockfall has 12.87 m maximum jump height, 41.52 ms−1 maximum velocities, and maximum kinetic rock energy of 1401.63 KJ just above as well as below the road. Whereas in the debris flow, the maximum height of flow is 5.3 m, the maximum velocity at its upper part is 13.04 ms−1, and maximum pressure at its upper-middle portion is 340.33 kPa. In this landslide zone, samples collected from four identified locations on which Attenberg test, as well as a direct shear test, are conducted to determine its moisture content and shear strength. Evaluation of these samples is done in terms of the grain size distribution (by sieve analysis), identification of the flaky structure of weathered minerals (by Field Emission Scanning Electron Microscope (FESEM) imaging), and measurement of reflectance (using ADS spectroscopy). All these evaluations ascertained the geology of this area is composed of weathered volcanic and metamorphic rocks. Now content with the surface investigation, the study is burrowed further into the subsurface. The concealed properties get revealed by the aid of Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) that identifies saturated, weathered as well as semi consolidated zone and inclined, horizontal bedding with discontinuity respectively. The saddles present in this landcover and impact loading of the river on the toe of the slope are the significant geomorphological findings. Finally, integrating all the methods, significant aspects of Kaliasaur landslide are sketched out, which shall help in the prevention of future fatal consequences.