Numerical 3D model supporting decision of waterproofing or installing a drainage system attenuating structures damage risks

ABSTRACT: The development of a new project is happening on a complex site. The overburden soil stratigraphy is heterogeneous and sensitive to settlement. Projected structures are an underground station, vertical shafts, main cavern and a tunnel. Associated transit structures are also planned to ensure connection with the Express Network Metropolitan of Montreal (REM). Shallower structures such as multi-level car parks and bus facilities are also planned. Authors have assessed the potential damages, and risks related to the lowering of water table. Such water level drop is caused by pumping operations. This paper presents the different phases of building the numerical 3D model. Then, it highlights main parameters that would impact the predictive hydrogeological results. After that, it describes the evolution of the infiltration rate during construction sequences. Moreover, it assesses the draw down of water table following a decision to waterproof or not. Finally, it expresses monitoring approaches to mitigate the risk of potential damage.