Determining the portion of dewatering induced settlement in excavation pit projects

Abstract

Steady population growth has resulted in increasing the land prices which led to construction of deep excavation pits, necessary for tall buildings and underground spaces. One of the most important issues in the design of deep foundations and underground spaces is how to deal with the groundwater. Considering the difficulty of excavation and construction under wet condition, in most of the projects the groundwater level is preferred to be dropped under the construction level, the operation called ‘dewatering’. However, the dewatering operation has its own issues such as ground settlement and environmental impacts. In this research, the amounts of settlements due to excavation and dewatering were calculated separately using analytical and numerical models for Taklar 2 excavation pit located at the north-eastern part of Tehran city, as a case study. The analytical and numerical data were compared with some settlement data measured directly at the field. The results of this study confirmed that the numerical finite element method is appropriate for simulation of the settlement around excavation pits. The portion of settlement due to dewatering was estimated to be about 30 per cent of the total settlement during excavation operations.