| Void above a tunnel lining is harmful to a tunnel structure in some cases especially inpoor ground conditions. The void often exists in old tunnels constructed with the steel rib andlagging method, and back-fill grouting is one of the most effective countermeasures against the void.Stiffness of the back-fill grouting material is an important factor and should be examinedappropriately to obtain enough ground reaction force to the lining. However, for many practical uses,the stiffness is not so seriously taken into account and is determined on the basis of our empiricalknowledge in many cases. In this study, a series of numerical analysis is performed to examine stresscircumstances of tunnel lining where a back-fill grout is applied. Major conclusions include: A highexpansion ratio material for back-fill grouting could be too soft to secure enough reaction force totunnel lining under external force acting conditions. |
