Abstract
At a shallow covered or a soft ground tunnel, the pre-lining method will be applied to excavation in order to improve face stability and to prevent ground surface settlement.
The authors are trying to clarify the mechanism of the pre-lining method by means of model experiments and to establish reasonable design methods for pre-linings. As a result of the experiments, it was confirmed that the effects of pre-linings such as improvement of face stability and less settlement mainly depend on the degree of restriction by pre-linings against vertical stress relief at the crown of the tunnel within the range of excavation. The authors also proposed that the efficiency of pre-linigs as the tunnel support should be evaluated by “compound stiffness”, which consists of the ground arch and pre-linigs around the tunnel, rather than by stiffness of the pre-lining itself.
