ABSTRACT
The Pinchat tunnel was completed in spring 2017. Its construction required to address numerous challenges created by:
– A 100 m2 cross-section with low overburden in an urban environment and loose ground;
– Access from a vertical shaft;
– Top-down construction of an underground station in an area occupied by numerous traffic routes;
– Excavation beneath a river;
Excavation of the 2 km long tunnel was carried out using conventional methods, with partial face excavation, forepoling and face bolts, and a steel braces and concrete support. The design was value-engineered by applying the observational method, what was made easier by a site supervision carried out by the same engineering team as the project. Value-engineering was also applied to adapt structures, techniques and phasing to the resources committed by the Contractor. The care taken to refine the design, combined with the improvements implemented during construction, allowed to finish the construction on time and on budget.
