Centrifuge Modelling of Spatial Stress Variations in Soil-Nailed Slopes

Infrastructure projects on slopes that are exposed to changes in water levels face unique challenges. Fluctuations in water levels can significantly impact the stability and integrity of the slope. Stresses affecting soil nails are influenced by various factors, including changes in groundwater levels due to rainfall, temperature variations, or human activities. While studies have addressed the use of soil nails to enhance slope stability, there has been limited attention to the performance and serviceability of soil nails under cyclic changes in the groundwater table. Lateritic slopes are susceptible to instability due to factors such as extensive weathering, inadequate drainage, and steep cuts. Erosion and slope failure are exacerbated by insufficient vegetation cover, climate-induced degradation, and human activities. This highlights the importance of understanding the stress generated and the interaction between the soil and reinforcing material. In this study, centrifuge modelling was employed to simulate cyclic saturation and desaturation of a lateritic slope in response to fluctuations in groundwater levels. Four centrifuge tests were conducted on slopes with a 5V:1H ratio, both unreinforced and reinforced, at two different soil densities. The slopes were subjected to cycles of saturation and desaturation using a seepage simulator located behind them. Both unreinforced and reinforced slopes exhibited stability within a gravitational range from 1 to 40 g, showing no apparent cracks or settlements. Following the initiation of water flow through the slope, a gradual flow slide failure occurred in the unreinforced slope. When exposed to fluctuating water levels, the utilization of soil nails prevented the development of a continuous slip plane in higher-density slopes, while lower-density modelling revealed a failure slump and tensile cracks on the slope surface. Increased excess pore water pressure during ground saturation reduced effective stress on soil nails, reducing their tensile resistance. Conversely, lowering groundwater levels increased effective stress, mobilizing axial forces in the nails. This cyclic variation caused visible changes in settlements, strains, and tensile cracks in the slope following saturation and desaturation cycles.