Improved modeling of tunnel excavation with two-dimensional finite elements

摘要

While tunnel excavation is clearly a three-dimensional engineering process, a vast majority of design engineers usually rely on two-dimensional modeling. This fact is generally attributed to a number of complexities associated with preparation of geometrical and computational model, an accurate representation of material response and tedious representation of gradual advancement of tunnel heading. When simulating this process within the framework of the New Austrian Tunneling Method the universally appreciated convergence confinement method is often employed. Although capable of addressing a number of important facts, such as a supporting effect of the soil in the longitudinal direction of the tunnel and its inherent creep behavior, its accuracy is strongly affected by practical experiences of the designer. It is therefore still of considerable interest to improve the modeling phase whilst keeping its simplicity. Such a goal can be successfully achieved by combining the numerical analysis with in situ measurements. Particularly, taking advantage of convergence curves in the longitudinal direction constructed during excavation, both in front of and behind the tunnel heading, it is possible to extend the general formulation into 3D whilst maintaining the two dimensional format of the finite element mesh as demonstrated in this contribution.