Maintaining the stability of the tunnel face is an essence to ensure safety during underground construction at any depth and through any ground condition. Specifically in the case of urban environments, where tunnels are typically shallow and often driven in increasingly difficult ground conditions. The objective of this dissertation is to assess face stability of conventional shallow tunnels in heterogeneous soil. The structure under examination is Tunnel Duphot, an urban tunnel commissioned to fulfil the role of connecting historical buildings in the heart of Paris. The research started from the theoretical study of the physical properties of the Parisian subsoil to understand the cause of face stability observed in situ that was apparently in contrast with the results provided by the analytical methods.