Internal strain measurement method of the extruded concrete lining

Abstract

The Sambongihara Tunnel on the Tohoku Shinkansen Line, located between Hachinohe and Shin-Aomori stations, is a double track tunnel 4,280m long. The geology of this tunnelling site mainly consists of alternating layers of un-consolidated sandy soil under high hydraulic pressure and cohesive soil. The lining concrete in the tunnel consists of primary and secondary lining layers. The primary lining, which is constructed by the Extruded Concrete Lining (ECL) method, has the same efficiency as that of shotcrete by NATM, while allowing small cracks and a little water leakage. On the other hand, the secondary lining is designed to maintain water tightness and install various facilities in the tunnel, and not to support external pressure. The concrete lining to be constructed by the ECL method is usually designed by using the segmental design method of a shield tunnelling. However, in-situ measurement to validate the design method has not been performed. Additionally, though it is necessary to measure the internal stress (strain) of the lining, the method for the purpose has not been established yet. Thus, we developed a method to measure the internal strain variation of cast-in-place concrete after pouring concrete into the inner formwork, and measured the internal stress (strain) of the lining. This paper describes an outline of the developed in-situ measurement method and results of its application. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.