RELATIONSHIP BETWEEN AIR PRESSURE AND VOLUMETRIC WATER CONTENT AT STEADY STATE IN RAINFALL-INDUCED LANDSLIDE BASED ON MODIFIED COLUMN TESTS

Abstract

The increasing frequency of localized heavy rainfall events exacerbates the problem of accurately predicting and mitigating rainfall-induced landslides. This study used a model test to clarify the relationship between air pressure and volumetric water content during quasi-saturation. A series of one-meter-high, 10-cm-diameter modified column tests were utilized to replicate slope conditions during rainfall. This study included five-column tests with different relative densities, all subjected to uniform rainfall intensity, to examine how air pressure variations influence the soil's quasi-saturated state. The test results revealed a correlation between the change in air pressure and the soil's quasi-saturated state. Specifically, increased volumetric water content at higher relative densities was accompanied by increased air pressure, reflecting a more complex interaction within the denser soil. Even after the water content reached a quasi-steady state, air pressure variations persisted, suggesting continuous adjustments within the soil structure. Entirely uniform saturation across all column heights was not achieved, with air entrapment contributing to persistent partial saturation. The conclusion drawn from this study is that air pressure dynamics play a pivotal role in the soil's response to hydrological stresses. By integrating air pressure measurements into the assessment of quasi-saturated soils, these findings can help predict the onset of landslides. This research contributes to a more comprehensive understanding of soil behaviour under unsaturated conditions, with significant implications for environmental management, particularly in regions prone to heavy rainfall-induced landslides.