ABSTRACT
A routing study should be performed as part of the early design process to confirm acceptable access to the project site or to identify upgrades, and new access tunnel construction that is required. This chapter shows an example of advanced site preparation of a tunnel portal. The preparation and construction of the tunnel portals or shaft access requirements may also be planned to be completed under advanced contracts if the properties of the various sites have been confirmed for use and designs prepared as part of the early design process. The implementation of a tunnel support design for a proposed tunnel should be based on the original design developed based on stability analyses using data from the geotechnical site investigation program and presented in the format of design drawings issued for construction. Geotechnical instrumentation is commonly utilized to provide verification of tunnel stability and support design as well as quality control for controlled drill and blast excavation.
