Ground surface settlement induced by diaphragm and buttress walls installation: numerical study

Abstract

In construction practices, diaphragm walls are a cast-in-situ reinforced concrete retaining wall that are constructed using a slurry supported trench method. The installation process includes slurry supported trench excavation, placing the reinforcement cage, concrete casting and curing. This installation process would modify the in-situ stress state in the soil close to the trench and generate ground surface settlements, which might be significant compared to those induced by the main excavation. Also, the construction of buttress walls, a concrete wall that perpendicular to diaphragm walls, might generate additional ground surface settlement, and this issue has not been investigated. For clarify this issue, a series of three-dimensional finite element analysis was performed to quantify the amount of ground surface settlement induced by the diaphragm and buttress walls installation process using the Wall Installation Modeling (WIM) method. Results show that the installation of buttress walls inside or outside the excavation zone did not yield significant additional ground surface settlement outside the excavation zone because the diaphragm wall was completed first before the construction of the buttress wall. But, the construction of outer buttress walls could widen the settlement zone.