THE EFFECT OF TIME-DEPENDENT PROPERTIES OF ALTERED ROCK ON TUNNEL SUPPORT REQUIREMENTS

摘要

Squeezing ground conditions in hard-rock tunneling are associated with fault zones containing brecciated rock and gouge. The time-dependent nature of the deformation and support loads in squeezing ground conditions suggest that the creep behavior of fault gouge is the significant engineering property controlling the in situ behavior. An experimental and analytical study is presented that deals with soil creep and its application to the prediction of tunnel support requirements in squeezing ground. Support requirements given by the theoretical analysis are compared to numerous case histories obtained from the published literature. Finally, specific consideration is given to squeezing conditions at Straight Creek and Pacheco tunnels. The analysis provides a method for estimating steel support requirements for tunnels at different depths and in various squeezing ground conditions. (Modified author abstract)