Limit analysis approach for accessing stability of three-dimensional (3-D) slopes reinforced with piles

The stabilization of slopes by placing piles is one of the most innovative and effective slope reinforcement techniques in the coastal engineering in recent years. Due to the simplicity and efficiency, limit analysis method is the most common approach for assessing the stability of slopes. However, the majority of existing limit analysis methods is limited to slope without the presence of piles. In this technical note, a novel upper-bound limit analysis method was proposed to access the stability of three-dimensional slopes reinforced with piles incorporating the admissible rotational failure mechanism where toe failure, face failure, and base failure were taken into account. The effects of key designing parameters, e.g., pile location, pile spacing, slope angle, slope width on the stability of earth slopes, and geometry of critical slip surface were presented and discussed. The results demonstrate that the proposed approach is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of piles stabilizing the unstable slopes

Three-dimensional transient stability of slopes during pile driving using upper-bound limit analysis

A 3D rotational failure model for calculating the transient stability of a slope during pile driving was established based on the upper-bound limit analysis. The influences of the pile driving force and the lateral force between pile and soil on the slope stability were considered. The variation of the anti-slide safety factor of the slope during pile driving was analyzed in detail through examples. The parametric studies were carried out to explore the effects of pile diameter, pile location and slope angle on the anti-slide safety factor of the slope. The results demonstrate that the pile driving leads to a steady decrease of the safety factor during the earlier stage of pile driving and the safety factor increases significantly because of the anti-sliding effect of the pile body after the end of pile reaching the sliding surface. The greater the pile diameter is, the lower the safety factor is and the faster it drops during the earlier stage of pile driving. The closer to the top of the slope the pile location is, the faster the safety factor decreases and the lower the safety factor of the most dangerous depth is. The safety factor decreases dramatically with the increase of the slope angle during the whole process of pile driving