Blinding struts, Part 2: Towards a simplified design method

The companion paper described how concrete blinding can be used to prop retaining walls in cut and cover excavations prior to the completion of the base slab. In addition, it was demonstrated that the behaviour of blinding struts can be accurately predicted with nonlinear finite element analysis (NLFEA) if the strut properties and ground profile are known. This paper presents a simple design-oriented analytical model which can be used for blinding struts as an alternative to NLFEA. The simplified model is shown to give comparable results to NLFEA and is attractive for design since it allows the effect of variations in imperfection amplitude and length to be rapidly assessed. A case study is presented which illustrates the use of the method and demonstrates that relatively thin blinding struts can resist the maximum axial forces likely to be encountered in cut and cover excavations.