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Development of a segment lining system subject to internal water pressure


Masayuki SAITOH and colleagues
Nippon Civic Consulting Engineers Co., Ltd.
5th International Conference on Pipelines, October 1997

Key words: shield tunnel, segment lining, segment joint, internal water pressure, underground reservoir, FEM analysis, beam-spring model

Background

Where vacant land is not available for conventional above-ground flood control reservoirs, as is commonly the case in Japanese cities, large diameter shield tunnels can be constructed to serve as underground regulating reservoirs. Such tunnels are subject to unusual loading conditions; most of the time they are empty, so external loads due to soil and groundwater pressure are dominant. But occasionally, when there is a flood, water pressure loading acts from within the tunnel, and tensile forces are generated on the RC segment linings and segment joints.

Research Summary
We proposed a segment lining structure with a new joint structure for shield tunnels subject to internal water pressure. A series of load tests on full scale model segment pieces was carried out, and the performance required for the linings of internal water pressure shield tunnels was confirmed. The joint structure of the newly proposed lining structure adopted a staggered joint. The locking mechanism of the new staggered jointing structure was verified by numerical analysis using the finite element method (FEM). Load tests were carried out with jacking loads on full scale test pieces. Internal water pressure tests were carried out on a 5 m external diameter segment ring model, and the performance of the new segments was verified. It was also demonstrated that the behavior of the segment ring model could be simulated with a beam-spring analysis model, so a method of designing shield tunnels using the new segment lining structure was proposed.

 
 




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