Experimental and Numerical Analysis on Failure of Soil Slopes Induced by Increasing Pore Water Pressure - SME Annual Meeting 2024

Slope failures very commonly occur during a long period of heavy rainfall and groundwater rise. The failures pose a substantial risk to people, infrastructure, and equipment downslope. In the recent past, the mining industry has faced an increase in tailings dam failure due to several reasons including pore pressure increases in the dams. Many failures have been observed to occur during times of water level fluctuations but the critical factors that influence the initiation of slope failures still need to be adequately clarified. To investigate these factors, laboratory experiments were conducted on model sandy slopes to determine pore pressure-induced slope failure initiation. This study also presents a method to examine water seepage through soil slopes using an ultraviolet (UV) dye and a UV flashlight. The small-scale model test simulation demonstrated failures induced by either water percolation from the upslope tank at a constant level or by raising the water level at intervals. A bottom chamber fully filled with water to replicate groundwater rise was also simulated. The soil slope was monitored at every stage to study the deformations and behavior until failure occurred. Results gathered from the controlled laboratory conditions were useful for the verification of the numerical modeling method created in the computer program Slide. The analysis showed that slope failure always occurred when the toe was fully saturated. High pore pressures and seepage forces reduce the shear force at the toe to almost zero causing it to slide. A comparison of slope height to water level also indicated an average of 96% water level to cause a failure. At this point, the soil slope is fully saturated and has no matric suction. The findings in this study show that, by monitoring the moisture content of slopes, failures can be predicted.