New Design Method for the Production Tolerances of Concrete Tunnel Segments

Some damages observed in tunnels constructed with tunnel-boring machines are caused by contact deficiencies between segments, which are the result of the sum and accumulation of several types of tolerances. Because the relation among the tolerances, the contact deficiencies, and the structural damage is not quite clear, the segmented lining is usually designed to meet very tight tolerances. The existing tolerance recommendations consist mostly of extrapolation of tolerances applied to other types of concrete structures with different characteristics. This explains the wide variation of production tolerances found in the literature, with different repercussions on the cost of molds and on the performance of the structure. The first part of this study shows the relation between structural damage and contact deficiencies. The second part of the study explains how the contact deficiencies found in practice are generated by the tolerances. Finally, a general design method is proposed for the estimation of the production tolerances. Based on this, general recommendations are derived for the maximum admissible production tolerance used to limit the incidence of structural damage. DOI: 10.1061/(ASCE)CF.1943-5509.0000291. (C) 2012 American Society of Civil Engineers.