Time-Dependent Behavior of Saint-Martin-La-Porte Exploratory Galleries: Field Data Processing and Numerical Modeling of Excavation in Squeezing Rock Conditions
Résumé
Field monitoring programs (e.g., convergence measurements and stress measurements in the support system) play an important role in following the response of the ground and of the support system during and after excavation. They contribute to the adaptation of the excavation and support installation method and the prediction of the long-term behavior. In the context of the Lyon–Turin link project, an access gallery (SMP2) was excavated between 2003 and 2010, and a survey gallery (SMP4) has been excavated since 2017. Both tunnels are excavated in Saint-Martin-la-Porte (France) across a strongly tectonized Carboniferous formation, which is highly fractured and heterogeneous. Squeezing behavior has been observed and led to the instability of the support system and of the tunnel face in various locations. Based on the knowledge gained from field data processing and numerical modeling in SMP2, new field data are analyzed for SMP4, which is excavated at a much deeper depth, with a different orientation and with different excavation methods. Numerical modeling of the various profiles of SMP4 considering the excavation stages and the specific yielding support is presented, which predicts the time-dependent response of the tunnel.