Blinding struts under long-term loading

Abstract

The term ‘blinding' is used to describe the thin layer of unreinforced over-site concrete used to protect the base of excavations during construction. Blinding is not generally considered a structural element even though it clearly provides some temporary lateral support to the retaining walls of excavations. The authors have previously shown that enhanced blinding can be used to prop retaining walls in cut-and-cover excavations during construction prior to the completion of the base slab. This paper describes a series of laboratory tests carried out to investigate the effect of concrete creep on the axial resistance of blinding struts. The tests show that blinding can creep to failure if the sustained load exceeds a critical value that depends on the imperfection amplitude and profile as well as the strut thickness. The test results are used to validate a numerical model which is then used to carry out a series of parametric studies on full-scale blinding struts.