Improved Design of Tunnel Supports. Volume I: Simplified Analysis for Ground-Structure Interaction in Tunneling

摘要

The purpose of this report is to provide the tunneling profession with improved practical tools in the technical or design area, which provide more accurate representations of the ground-structure interaction in tunneling. The design methods range from simple analytical and empirical methods to sophisticated finite element techniques as well as an evaluation of tunneling practices in Austria and Germany. Volume 1 describes a simplified analysis method for ground structure interaction in tunneling, which is necessary because of the indeterminate relationships which describe the realm of tunneling parameters. The method is geared toward hand calculations that incorporate the effects of three of the most significant factors influencing the ground structure behavior. The authors point out that it is doubtful that the complex interrelationships among the nearly countless variables in any real tunneling problem can ever be rigorously analyzed, even using the most sophisticated numerical techniques. As an alternative approach, the simplified method focuses on the essential elements of very complicated phenomena in order to isolate the three major factors that have an overriding influence on support loads. These factors are: (1) the relative stiffness of the support and ground mass; (2) the spatial lag or delay of support construction behind tunnel face; and (3) the yielding of ground mass as its shear strength is exceeded. Using these factors, the intent of Volume 1 is to provide an analysis in which accentuated computational ease, coupled with sufficient accuracy, makes the simplified method a valuable and effective design tool for use in preliminary design, for parametric studies in final design, and for updating the design during construction.