Numerical modeling of ground movements caused by tunneling

The construction of shallow tunnels causes movements that can affect existing structures, inducing unacceptable disorders. These disorders can not only result from settlements but also from horizontal displacements. In the case of tunneling with pressurized face shield boring machines, ground movements are found to be the result of complex interactions between soil, construction stages, and shield drive parameters. In this context, the direct prediction of final ground movements by empirical, or analytical, and numerical approaches has proven to be insufficient. It is therefore necessary to develop and to validate more accurate simulation tools to allow assessment of the magnitude and distribution of soil movements in relation to construction stages. By experimental results of two sections of the Lyons D line subway extension (1993-1995), the authors examine various numerical procedures, in this paper. A two-dimensional procedure, taking into consideration various stages of construction, is proposed. The confrontation of this approach to experimental results shows the necessity of corrections due to three-dimensional effects of various tunneling stages.