Experimental and analytical study of concrete blocks subjected to concentrated loads with an application to TBM-constructed tunnels

To generate enough thrust for a Tunnel Boring Machine (TBM) to excavate a soil and advance, several jacks are typically used to apply force to the last installed ring that acts as a reaction frame. These loads generate bursting stresses that might cause cracks in the longitudinal direction of the segments. Many studies dedicated to evaluate this phenomenon focus mainly on elements with similar height-to-length ratios. To cover the wide variety of dimensions and load application patterns, additional experimental assessments are required. The objectives of the present paper are to extend the study of with different height-to-length ratios subjected to concentrated loads and to validate analytical formulations for the verification of concrete segments in SLS and ULS. To accomplish this, an experimental program was carried out using small-scale specimens with and without fibre reinforcement. The results obtained were used to validate the formulations derived from a struts-and-ties model. Finally, an application of the formulation proposed to the case study of Line 9 in Barcelona is presented. This study represents a contribution towards the development of engineered approaches for the design of segmented linings. (C) 2015 Elsevier Ltd. All rights reserved.