Numerical back analysis of Crossrail Bond Street Station sprayed concrete lined (SCL) concourse tunnel primary lining thickening layer longitudinal cracks

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4. Numerical back analysis of Crossrail Bond Street Station sprayed concrete lined (SCL) concourse tunnel primary lining thickening layer longitudinal cracks

The Crossrail Bond Street Station east end concourse tunnel comprises one layer of fibre-reinforced SCL primary lining and one layer of SCL thickening layer, in which steel reinforcement is installed locally around the 4no. cross-passage openings on both sides of the tunnel. After completing the thickening layer and the cross-passages, a deep longitudinal crack was observed at the crown of the thickening layer. The reason for this crack needed to be better understood. This paper aims to address this knowledge gap. This paper first introduces the tunnel layout, lining configuration and construction sequence. This is followed by a qualitative explanation of the reasons for the cracking. The main part of this paper is a presentation of lining stresses results from a numerical back analysis using the finite element package PLAXIS 3D. The analysis considers key influencing factors on the performance of the thickening layer, such as the sequential construction, early-age thermal and shrinkage-induced tensile stress and the impact of the multiple cross-passage constructions. Finally, recommendations are made for the numerical simulation of multi-layer tunnel lining with multiple cross-passage constructions.

10th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2023)

10. Tunnelling and mining applications