ABSTRACT
Tunnels differ from on-ground structures, and the design conditions vary complicatedly case by case. Thus, it is not easy to rationally design and construct tunnels in all types of locations, and it is not unusual for deformation to occur after opening of the tunnels. For these reasons, it is important to conduct maintenance works, such as regular inspections, proper judgments as to the soundness of the tunnels, and the application of countermeasures, in order to maintain the function of each tunnel. This chapter introduces the history of tunneling technology and the existing tunnels in Japan, in addition to a state regarding maintenance. It examines deformation phenomena observed in actual tunnels and discusses the mechanisms of the occurrence of deformation. The chapter also reviews investigation and judgment techniques, as well as countermeasures against deformation and presents some typical examples.
