Geotechnical analysis of blinding struts in cut-and-cover excavations

Abstract

The term ‘blinding’ is used to describe the thin layer of unreinforced over-site concrete which is used to protect the base of excavations from construction traffic and to provide a clean surface for the construction of the base slab. Blinding is not generally seen or exploited as a structural element even though it clearly provides some temporary lateral support to the retaining walls of cut-and-cover excavations. The authors have previously shown that the axial resistance of blinding struts is typically governed by upheaval buckling as well as concrete crushing. This paper aims at quantifying the load likely to be transferred into blinding struts from the deflecting retaining walls in addition to the amount of heave to be expected after excavation. Numerical analyses are undertaken to assess the effect of blinding struts on a propped and cantilever retaining wall for various excavation sequences and excavation geometries.