Rigorous Design Of Thinner Working Platforms Stabilised By Multi-Axial Geogrid

The design of working platforms typically involves the calculation of a two-layer bearing capacity. Existing calculation models are quite empirical with imprecise input parameters while other proposed methods have tended to involve multiple design charts and been suited to either strip or circular foundations only. It has also been difficult to incorporate the benefits of geogrid in an accurate way. The recently developed “T-Value Method” defines bearing capacity simply in terms of the shear strengths of the two layers and can be applied to both clay and sand subgrades. It also allows realistic incorporation of the benefit of multi-axial stabilising geogrid in terms of the enhanced shear strength of the upper granular layer. This is leading to significant cost savings due to thinner working platforms that are designed in a safe and scientifically rigorous way. This paper summarises the development of this new design method and proposes a new set of equations validated by physical testing for a mechanically stabilised granular layer on a sand subgrade.