ABSTRACT
Line 9 TBM tunnel construction, at its arrival to Lesseps shaft, will be in interaction with several existing structures. In order to evaluate the impact between those structures and Line 9 TBM tunnel excavation (12 m diameter), a 3D Plaxis model has been developed. The model considers the geological conditions, soil & rock properties, and structural characteristics of the existing constructions and future Line 9 TBM tunnel excavation. The study’s main point is that the 3D model was calibrated using a back analysis. Fifteen years ago, in previous L9 construction stages at Lesseps area different excavations went through: 30m diameter shaft, its connection cavern and arrival of another 12 m diameter TBM excavating from city North side. Monitoring data from these construction works has been used for the back analysis. The adjustment of the numerical model based on the back analysis has allowed greater precision and reduced the uncertainty of the results. The analysis aims to assess the potential impacts of the Line 9 TBM tunnel construction on the stability and performance of the buildings and underground constructions and systems of the area. The model is used to evaluate the deformation, settlement/heave, and stress distribution in the surrounding soil and structures during the excavation and operation of the Line 9 TBM tunnel. The results of the analysis have helped to identify any potential issues and develop appropriate mitigation measures to minimize the impacts of the construction on the existing structures and ensure their safe and reliable operation. Having available data that enables back analysis and being able to introduce it into the design, results in optimized solutions.
