Stabilité locale du front pour les tunneliers à pression de boue de grand diamètre dans les argiles molles

As the slurry shield tunnels of great dimension are widely used in recent years around the world , particular attention is paid to face stability of large or extra-large slurry shield driven-tunnels (Chapter 1). This thesis proposes to deal with the problem using three types of approaches, especially with the back ground of Shanghai Yangtze Tunnel. Firstly, experiments using a small scale laboratory mode to simulate the construction of a slurry shield driven-tunnel performed (Chapter 2). Then, upper-bound approach in limit analysis (Chapter 3) and three-dimensional numerical modeling (Chapter 4) are presented. Both the local failure and global failure in collapse and blow-out are studied when taking into account the characteristics of shield tunnels with large diameter. Finally, the parametric sensibility analysis of large slurry shield tunnel face stability is studied by numerical modeling (Chapter 5). A modified solution of local face stability taking into consideration different construction methods (represented mainly by the unit weight of support medium) is proposed and the partial failure mechanism especially for large slurry shield tunnels is firstly presented in this thesis. The failure mechanisms and critical slurry obtained from both the upper bound approaches and numerical simulations are compared with each other.