In recent years considerable difficulty has been experienced in the development of limit state codes for geotechnical analysis. Much of the difficulty has been associated with providing clear and unambiguous statements concerning collapse and serviceability states, with the related problems of stress calculations for these states. This Report gives consideration to the stress analysis of earth retaining structures, with particular reference to bridge abutment walls. The approach adopted is to use equilibrium analysis to determine the mobilised strength in any region. Mobilised strength can then be compared with the maximum strength available, to assess safety against collapse. Given the appropriate relation between strength and strain for the soil, mobilised strength can also be used to estimate strains, to provide a serviceability check. Previous design approaches included arbitrary factors of safety for the assessment of both internal and external stability, together with nominal values of earth pressure or permissible bearing stresses. This approach did not consider aspects of real safety margins or the effect of in-service deformations. However, a limit state approach can be adopted for the evaluation of geotechnical designs by direct evaluation of both collapse and serviceability through the analysis of critical events. After the designation of load combinations, environmental or other conditions to be as hazardous as reason will allow, the calculation can then proceed by the methods set out in the report. The report describes methods of evaluating the stresses in the granular backfill for purposes of limit state design in both the retaining structure and in spread foundations. The methods presented consider the influence on the stresses of compaction, self weight and superimposed loads, as well as the effects induced by various modes of wall movement. The conditions pertaining to both collapse and unserviceability of the retaining walls are also considered, to enable the methods to be understood and readily adopted. A number of examples are fully described and non-dimensional charts presented.

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