ABSTRACT
It was necessary to widen Kuradama Tunnel, while it was in use, in order to convert the road to two lanes. To do this, two protectors of different dimensions were used to achieve safe construction in the cutting of an additional lane for the tunnel road used for passage of ordinary vehicles. The construction method adopted for the tunnel work was chosen with consideration given to eliminating noise and dust that would affect residents in the area near the tunnel. The support structures of the left and right sides of the tunnel to be widened were asymmetrical, which meant measurements of convergence and stress on supports had to be conducted as the work was safely completed. This paper reports on the construction methods used in the widening work done on a tunnel in active use, and on the approach adopted with due consideration for residents in the surrounding area.
