Centrifuge Modelling of Extreme Rainfall Events on Reinforced Lateritic Soil Slopes

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4. Centrifuge Modelling of Extreme Rainfall Events on Reinforced Lateritic Soil Slopes

This paper presents the centrifuge results of rainwater infiltration tests on a soil nail reinforced slope. The slopes of lateritic soils were subjected to failure due to the induced stresses as the water infiltrated. The tests were performed on a 5V:1H slope, reinforced with a rectangular grid of 9 soil-nails. The length of each nail was 0.8 times the slope height. The effects of rainfall intensity, which varied from 10 mm per hour to 25 mm per hour, and duration were investigated. These moderate to very high rainfall intensities are typically observed in coastal regions of western Maharashtra during the monsoon season. Rainfall intensity and duration were found to have a significant impact on the stability of slope. It changed the interface shear stress and contact force between the nails and the surrounding soil. On the onset of rainfall, the tensile forces gradually increased in the nails, as the stresses got transferred from the soil to the nails. The stresses in the nails reduced when the rain stopped but some locked in stresses still remained, leading to accumulation and failure of the soil nails. The localised softening of soil caused saturation of the toe of the slope. The repeated rainfall episodes alter the stress state around soil nails, led to deformation through the development of tension cracks. Bottom most nails recorded the maximum force with 54% increase in tensile force and displacements. The depth of failed portion of soil at the end of test was found to be 1 m inside the slope for middle row nails and 1.4 m for bottom most nails equivalent in prototype condition which contributes to 22% of length of nail undergoing loss of contact of soil at the interface creating additional axial force mobilization around soil nails. With the increase in duration of heavy rainfall duration, the effective rainfall days for which the slope is stable without any deformation decreased by about 47%. The cracks subsequently evolved into preferential flow paths, ultimately triggering shallow slope failures.

4th Asia-Pacific Conference on Physical Modelling in Geotechnics (ACPMG2024)

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