Presentation Title

Effect of Soil Density and Wetting and Drying Cycle on Slope Instability

Start Date

November 2016

End Date

November 2016

Location

HUB 265

Type of Presentation

Oral Talk

Abstract

Landslides and associated hazards kill hundreds of people and cause a loss of tens of billions of dollar a year. Rainfall is considered as one among the major triggers of landslides. In order to fully understand how rainwater percolation through a slope cause landslides, it is important to understand the control parameters that play role on slope instability. Density of soil, slope inclination, intensity and duration of rainfall are among those parameters. In this study, soil slopes are prepared at an inclination of 40 degrees with different densities. Those slopes were subjected to a rainfall intensity of 3 cm/h until the slope got fully saturated. Eight inclinometers were installed in the slope at different locations to measure the variation in soil suction with rainfall duration. Eight flexible copper wires were installed to measure the deformation of the slope during rainfall. To measure seepage velocity of water, wetting front measurements immediately after the application of rainfall was marked in a regular interval. To evaluate the effect of rainfall after a natural drying, the slope was subjected to rainfall again after a week of natural drying. The result shows that infiltration of water into the slope causes soil settlement if the soil density is lower than a threshold value, whereas for larger densities that, soil swells upon infiltration of rain water and exhibits tension cracks. The results obtained from deformed copper wires were helpful to identify the weakest sliding surface. The study result shows that seepage velocity decreases with an increase in soil density. The experiments conducted in a smaller container (1 m x 1m x 1 m) exhibited lesser extents of cracks than the one at larger container (2.5 m x 1.5 m x 1.5 m), clearly showing a scale effect in experimental modeling. Moreover, the rainfall applied after the slope was naturally dried showed more deformation compared to the first application of rainfall.

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Nov 12th, 2:15 PM Nov 12th, 2:30 PM

Effect of Soil Density and Wetting and Drying Cycle on Slope Instability

HUB 265

Landslides and associated hazards kill hundreds of people and cause a loss of tens of billions of dollar a year. Rainfall is considered as one among the major triggers of landslides. In order to fully understand how rainwater percolation through a slope cause landslides, it is important to understand the control parameters that play role on slope instability. Density of soil, slope inclination, intensity and duration of rainfall are among those parameters. In this study, soil slopes are prepared at an inclination of 40 degrees with different densities. Those slopes were subjected to a rainfall intensity of 3 cm/h until the slope got fully saturated. Eight inclinometers were installed in the slope at different locations to measure the variation in soil suction with rainfall duration. Eight flexible copper wires were installed to measure the deformation of the slope during rainfall. To measure seepage velocity of water, wetting front measurements immediately after the application of rainfall was marked in a regular interval. To evaluate the effect of rainfall after a natural drying, the slope was subjected to rainfall again after a week of natural drying. The result shows that infiltration of water into the slope causes soil settlement if the soil density is lower than a threshold value, whereas for larger densities that, soil swells upon infiltration of rain water and exhibits tension cracks. The results obtained from deformed copper wires were helpful to identify the weakest sliding surface. The study result shows that seepage velocity decreases with an increase in soil density. The experiments conducted in a smaller container (1 m x 1m x 1 m) exhibited lesser extents of cracks than the one at larger container (2.5 m x 1.5 m x 1.5 m), clearly showing a scale effect in experimental modeling. Moreover, the rainfall applied after the slope was naturally dried showed more deformation compared to the first application of rainfall.