Modelling deformation during the construction of wrapped geogrid reinforced structures

Although geogrids and geotextiles have been successfully used for over a quarter of a century to reinforce soil, there are currently no commonly agreed analytical methods to model their deformation behaviour. The Serviceability Limit State is becoming an ever more important design consideration, as structures are built with increasingly tighter tolerances. While there are many deformation databases and design charts available, providing information and guidance on the sensitivity to certain design variables, these are largely focused on facets such as height, shear strength and geogrid ultimate strength and do not consider construction method. Following a review of existing analytical and empirical guidance, this paper presents numerical modelling derived guidance for flexible faced Geogrid Reinforced Structures constructed using cohesionless fill that incorporates installation methods. The modelling approach is validated against measured results from three varied case studies, before analysing the changes in deformation distribution resulting from two different construction methods (layer by layer and full height construction). For the conditions analysed, including height of the structure, the lateral deformation resulting from layer by layer construction, was shown to be consistently greater, than for full height construction. In contrast, an analysis of post-construction deformation, for each of the construction methods, found full height construction to be more sensitive to post-construction loading, for the conditions considered. For low wall height structures constructed using the layer by layer method, <5 metres, this study indicates that horizontal face deformations are underestimated by current guidance.