Effectiveness of a buttress wall in reducing retaining wall movement during dewatering before bulk excavation

Retaining wall movements are often estimated from a datum at the start of soil excavation. However, recent studies indicate that significant wall movements may occur during pre-excavation dewatering. In this study, the effectiveness of a buttress wall (that is, a short length of wall at 90° to the main wall) in limiting wall movement during pre-excavation dewatering is investigated numerically, focusing in particular on the buttress wall length (LB). Results indicate that wall movement decreases as LB increases. However, a smaller LB (less than 50% of the excavation width) may be sufficient if the drawdown or pumped depth is small (less than 30% of the total depth of retaining wall). With drawdowns greater than 60% of the total wall depth, a larger LB (greater than 75% of the excavation width) is needed to effectively control the deformation.