Effect of moisture content in soil on mass flow during landslides

Abstract

Landslide constitute a major natural hazard, which causes considerable loss of life and damage to human settlements, communication routes, cultivation and forest lands. Landslide involves mass movement such as rock fall, mudflows or debris flows. Excessive rainfalls are a major cause for such mass movements. However, landslide can also be triggered by seismic events and human activities. Shear viscosity of soil play a major role in the governing flow behavior and failure in soil. Knowledge of shear viscosity is important to understand the post failure flow properties in landslide. In a developing country like India, the susceptibility of slopes to failure has not been well mapped and prediction and early warning systems for disaster are not in place. There are some mitigation methods such as
geometric method in which geometry of general slope is engineered, hydrological method in which soil moisture is controlled, chemical and mechanical method where shear strength of the soil is improved or piles or reinforced ground to counteract destabilizing forces. The present study focuses on water content due to excessive rains on shear viscosity of the soil. This in turn will affect the stability of foundations of many a structures. Tests were done using fall cone apparatus. The fall cone apparatus used in experimental study was connected to potentiometer and high speed data logger to record continuous data. Tests were conducted on clay sample thoroughly mixed with water and then kept overnight to ensure proper mixing. Cone was permitted to fall freely and time-penetration data recorded by logger is used to calculate viscosity. Obtained values of viscosity were observed decreasing with increase in liquidity
index.