EFFECTS OF INCREASING SOIL WATER CONTENT ON LIQUIDITY INDEX AND SLOPE FAILURE POTENTIAL THROUGH LABORATORY MODELLING

Abstract

This study investigates the influence of increasing soil moisture content on the Liquid Limit (LL), Liquidity Index (LI), and their subsequent effects on slope stability through controlled laboratory-scale physical modelling. Soil samples obtained from a landslide-prone area were initially characterized by index and consistency tests to determine their physical properties. The construction of slope models replicated the actual field condition at angles of 30°, 45°, and 60°, and was stimulated with a rainfall-induced failure scheme by progressive saturation. The main challenge found in the study was that changes in the Atterberg limits and Liquidity Index with rising moisture content in conventional slope stability assessment were frequently overlooked. Experimental results reveal that an increase in water content significantly elevates the Liquidity Index, with slope failures predominantly occurring when LI >1. Slopes with steeper angles, particularly those greater than 45°, indicates a significant reduction in shear strength and cohesion under the saturation stimulation, resulting in a high risk of instability. Furthermore, the results indicate that when water content exceeds the Liquid Limit, the soil structure rapidly degrades and transitions into a fluid-like state, causing it more vulnerable to flow-type failures. Also, the study provides empirical evidence encouraging the use of the Liquidity Index as a practical metric for assessing slope failure risk in fine-grained soils. By integrating Atterberg limit parameters with physical slope modeling, the study has managed to establish a simple, reliable, and cost-effective framework for evaluating rainfall-triggered landslide. In addition, the findings emphasize the critical importance of monitoring LI and LL values in steep, moisture-sensitive terrains as early warning indicators of slope instability.