| "In Japan, with upsizing of vehicle or increase of traffic volume, the number of tunnels in which passage of two vehicles and passage of pedestrians are difficult due to the narrow cross sections has been increased. To reconstruct existing tunnels rationally and economically, to arrange the right-sizing support structure by taking account of the existing tunnel characteristics is important. Field measurements at four existing road tunnels for enlargement were carried out to clarify the behavior of support structure during enlargement of existing tunnel’s cross section. From these results, the influence of enlarging existing tunnels was clarified and the effectiveness of rock bolting which was installed prior to enlargement of existing tunnels in restraining the ground movement was confirmed." |
