Spalling of railway tunnel concrete and its causes

A number of accidents of concrete block spalling from tunnel linings occurred recently in Japan. Although there were no personal injuries, trust of people in the safety and durability of tunnel was lost, because some accidents took place in Shinkansen ( high speed railroad ) tunnels. Investigations, model tests and numerical analyses were performed on the largest three accidents in particular to study the mechanisms and causes of spalling of concrete. This paper outlines the accident at the Fukuoka Tunnel out of these accidents and reports the causes of spalling through investigations, model tests and numerical analyses.