Cross curves of stability for drystone retaining wall design

Drystone is an ancient, vernacular technique of construction consisting in interlocking rough or cut pieces of stones together, without mortar. This technique was extensively used in the XIXth and early XXth centuries in Europe for agriculture and development of transport networks. Although widespread, drystone structures remain largely unknown, and consequently, there are relatively few new constructions or even reconstructions of ancient structures in drystone. Over the past two decades, research studies in France and in the UK have been dedicated to a better understanding of the behaviour of drystone retaining walls. These studies have enabled the redaction of a good practice guide in 2008, including a first series of cross curves of stability. Ongoing on this project, the present work deals with the updating of the cross curves, based on recent research developments. The cross curves presented here rely on plain strain yield design modelling, enhanced with the information collected through full-scale experimental campaigns. The charts provide the minimum base thickness of the wall, given its height, its batter, the type of stones composing the wall, and the nature of the backfill. Cross curves of stability are intended to be incorporated into professional standards. The establishment of standards dedicated to drystone retaining walls should contribute to ensure a simple but reliable design, and thus support reconstructions and new constructions in drystone and enable the profession to develop.