Effect of staged dewatering and excavation on the heave of soil beneath deep excavation

摘要

Deep excavation in soft ground can induce significant heave of soil beneath the bottomof excavation. Field measurement of a staged excavation project using top-down method was carried andshown that vertical displacement of uplift pile supporting permanent column is large. For staged dewateringand excavation, dewatering at each stage can increase the relief of effective stress of each stage ofexcavation compared with staged excavation without dewatering, so the effect of staged dewatering on thebehavior of soil need to be investigated. Triaxial tests were performed to simulate the process of stageddewatering and staged excavation. Test results show that dewatering can reduce the final amount of heaveof bottom of excavation. Soil located at different location relative to the excavation is subjected to differentstress path. This leads to that larger heave of bottom of excavation close to diaphragm wall comparedwith that close to center of excavation. The effect of dewatering must be taken into account when predictingheave induced by deep excavation in soft ground.