ABSTRACT
Costanera Norte is an urban expressway concessionary in Santiago de Chile connecting its Western and Eastern sides. To enhance this connectivity several measures were necessary, including four new tunnels. The most singular one is ‘Tunnel Kennedy’, that has a length of 1,166 m with two sections (4 and 5 lanes), 17.45m and 20.95m wide, and 11.8m height. The tunnel was excavated in alluvial gravels, partially under the water table. The main challenges were: its section over 250m2, the ground conditions (requiring SEM), its urban environment and low overburden (10 to 16m). The support consists in a 3cm sealing, HEB steel arches spaced 1.0m and 27cm shotcrete. Systematically buttress and occasional canopy tubes have been used. A concrete lining (20cm to 40 cm, depending on the water column), was added, and a third layer 10cm with polypropylene fibers for fire protection. The excavation took place from October 2014 to February, 2017.
