Advances on structural, environmental and economical analysis of dry-stone retaining walls

9th International Conference on Structural Analysis of Historical Constructions, MEXICO, MEXIQUE, 14-/10/2014 - 17/10/2014Dry-stone technique is a vernacular but worldwide form of construction, appreciated for its simplicity, robustness, and permeability. It consists in interlocking rubble or square stones together without mortar, in order to build a wall or a vault. Dry-stone accounts for 18% of the retaining structures along the French national network, representing more than 1000 walls [1], and for 50% of the walls in Great Britain, stretching over 4500 km [2]. The recent renewal of interest for repair and construction of new dry-stone structures is yet slowed down by the lack of technical and economical knowledge proving their reliability and relevancy. This paper presents recent developments on design methods and sustainability analysis aiming at enhancing the use of dry-stone masonry in retaining wall construction. This study has been undertaken in the framework of the French programme for research PEDRA, which aims at developing analytical and numerical methods as well as decision support tools to assess the performance of vernacular masonry structures during their whole life cycle. First, a structural analysis model based on yield design is exposed. This model provides an analytical expression of the minimal thickness of the wall for a given geometry. Two approaches have been developed, and validated by full-scale experiments: a 2D model for upstream walls and a 3D approach for downstream walls subjected to traffic loading. The 2D approach has been implemented in cross curves of stability, and inserted in a good practice guide [3]. Then, a life cycle analysis and a life cycle cost have been undertaken in order to evaluate the ecological and economical impacts of drystone constructions. Studies on mortared masonry and concrete structures are also provided, as a comparison. As a case of study, the authors focus on the construction of a 50 m long dry-stone retaining wall in the district of Felletin (Creuse, France), built in 2012