Shotcrete applications and minimising the risk of damaging alkali-aggregate reaction in rock support for a subsea, geothermally active environment -Hvalfjoerdur Tunnel, Iceland

摘要

The Hvalfjoerdur Tunnel is a subsea road tunnel constructed through basalt in Iceland. The permanent rock support comprises predominantly mortar grouted rock bolts and sprayed concrete or shotcrete. Given the historical occurrence of alkali-silica reactivity identified in some Icelandic concrete the durability of the shotcrete used as permanent rock support at the Hvalfjoerdur Tunnel was of paramount importance. The prevailing conditions at the tunnel site of elevated water temperature and salinity provide a potentially highly aggressive environment for the shotcrete with damaging alkali-silica reactivity a major concern. This paper describes the measures taken to ensure that the potential for damaging alkali aggregate reaction in the shotcrete was minimised.