Design procedure for the modelling of jet-grout column slabs supporting deep excavations

Overlapping jet-grout columns are often used to form a grout slab at the bottom of deep excavations to support the retaining structures. Columnar geometrical imperfections, spatially varying strength and stiffness and the post-peak behaviour of the grout, render the simulation of the jet-grout column slab a very complex issue. In practice, these aspects are not taken into account and simplified models are commonly used, in conjunction with the application of a strength reduction factor. With the aim to improve the existing design process and extend its applicability to serviceability limit state analysis, a consistent design procedure is presented.