In Japan, some mountain tunnels are damaged by earthquakes and relative large-scale deformations such as the collapse of permanent lining and the deformation of supports have occurred. Although the earthquake resistant countermeasures for tunnels has been examined recently, some countermeasures for existing tunnels are performed on the result of tunnel inspection rather than the need against earthquake resistance. To clarify the effects and the mechanical behavior of countermeasures, the model experiment was conducted assuming the structure of actual road tunnels. The collapse mechanism was compared among the cases when various kinds of reinforcement to tunnel were performed, such as rockbolts, fiber sheet and rebar. Results showed that the improvement of load-bearing capacity of the tunnel was limited, however the prevention of falling concrete blocks from structure could be expected.
Mountain tunnel is considered to be a relatively strong structure against earthquake because it behaves in accordance with the surrounding ground. However, even mountain tunnels have suffered collapse of linings and deformation of supports in limited numbers due to large earthquakes such as the Niigata Chuetsu (2004) and the Kumamoto (2016) in Japan. An earthquake resistant measure for typical road tunnels in mountain areas newly constructed in Japan is empirically single reinforcement bar installed in the permanent lining, because the behavior of mountains is uncertain and seismic damage is not easy to predict. However, some countermeasures for existing tunnels are performed based on the result of tunnel inspection rather than the need against earthquake resistance. A tunnel with reinforcement and rehabilitation measures can keep health condition to some degree, however, the examination of their effects on the mechanical behavior of tunnel is limited. Therefore, this study aims to assess the earthquake resistance effect of the deformation countermeasures currently being implemented in mountain tunnels. A two-dimensional static loading test was conducted to simulate deformation countermeasures for rock tunnel, and effects of some countermeasures on the tunnel permanent lining during earthquakes was examined.
