A simplified 3D model for tunnel construction using tunnel boring machines

This paper includes a presentation of a simplified three-dimensional numerical model for the prediction of soil movement induced during tunnel construction using tunnel boring machines (TBM). The model is based upon the generalization of the convergence-confinement concept to 3D tunnel construction. It uses two parameters (Ldec and αdec) which stand for the length of the unlined zone and the partial stress release, respectively. The value of the parameter Ldec can be taken equal to the tunnel diameter, while the value of αdec can be determined by fitting the model to empirical formula, and then adjusted based on settlement registered during tunnel construction.The capacity of the model is illustrated through an application to a shallow tunnel in soft soil. The comparison of the numerical results to those suggested by different authors shows good agreement.