Abstract
It is highly possible that the concrete lining at the tunnel entrance will suffer from thermal cracks and drying shrinkage due to its exposure to external air and the scattering of snow melting agent. In this sense, in order to avoid thermal cracks, “localized pipe cooling” and “expansive concrete” were implemented. On the other hand, as an attempt to avoid drying shrinkage cracks and salt-attacks, the “water supply curing system with sheet suction” was implemented on the actual construction site. The effects of these measures on improving quality were quantitatively recorded on site and a three-dimensional FEM thermal stress analysis was modelled. The adoption of these countermeasures reduced the probability of occurrence of thermal cracks by about 30%, the drying shrinkage on the surface was reduced by 50～130×10-6 and the coefficient of permeability to air was improved by a factor of 1/15～1/4. Further, the effect of expansive concrete utilizing a conventional technology was compared, confirming that implementing the localized pipe cooling method was more effective.
