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

Abstract

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 evaluating 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 constructed 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 simplified tools for the design of segmented linings both in the SLS and in the ULS.

Development of Improved Models for Estimation of Bursting Stresses in Elements under High-Concentrated Load

“…These tests assessed the performance of fibre reinforced concrete as compared to steel reinforcement concrete and did not include assessment of the joint bursting capacity. Liao et al (2015) conducted an experimental program using small scale specimens with and without fibre reinforcement. The experimental results were compared with analytical expressions based on a parabolic distribution of tensile stress.…”

Design procedure for precast fibre‐reinforced concrete segments in tunnel lining construction

“…In order to define the envelopes simply, the strain related to the required maximum crack opening must be evaluated using Eq. (6) (section 4.1): (11) where l cs is the characteristic length.…”

“…Recently, the interest in using FRC for the production of precast segments in tunnel linings placed with tunnel boring machines (TBMs) has been growing steadily [5][6][7][8][9][10][11].…”

Sustainability based-approach to determine the concrete type and reinforcement configuration of TBM tunnels linings. Case study: Extension line to Barcelona Airport T1

“…Such cracks are usually caused by the localised effect of concentrated loads and specific states 16 of stresses that occur when segments are subject to jacks' thrust during installation ( Liao et al 2015b,). If the amount (Cf) and type 2 of fibre are correctly specified, it is possible to avoid spalling and to control the width of cracks that may 3 be caused by dynamic impacts and, more frequently, during the ram thrusts stage.…”