This report summarises the results of surveys of the stock of masonry-faced earth retaining walls along the highway network in the UK, providing estimates of their replacement value and annual maintenance expenditure. The current level of expenditure shows that the stock is performing well and that much of it has a considerable residual life. Despite this satisfactory position, many walls would not have an adequate factor of safety as required by current design codes. The report goes on to review the factors that affect the stability of such walls, and the methods used to characterize safety. It then describes and discusses the results of numerical analyses undertaken using UDEC, a discrete element program, on four full-scale dry-stone retaining walls built by Burgoyne at Kingstown, now Dun Laoghaire, in Ireland in 1834. The results of these analyses show that a conventional wedge-type analysis can overestimate the overturning resistance of a block wall when it is treated as a monolith. This is because vertical joints running parallel to the face of a wall allow tension cracks to develop within it so that not all the weight of the wall contributes to its overturning resistance. Analysis also shows that conventional measures of overturning stability do not have unrestricted applicability and are rather arbitrary and so, therefore, are the minimum values prescribed for them. Recommendations for further applications of numerical methods to aid designers and assessors of retaining walls are provided in the report. (A)

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