Creeping large-scale landslides - Characterisation and assessment of safety

This article investigates to what extent a ”condition and safety assessment“ with a classically defined safety factor η (now partial safety factor or load factor) is useful or indeed possible for creeping slides of large masses as are often encountered in the Alps, or whether different quantities like the displacement rate and its change with time are more useful for the description of the condition of such large-scale slides. This discussion is held under the viewpoint that various procedures with different results are available for the determination of such a ”safety factor“ and consequently there are also justified discrepancies between experts in the assessment of such a ”safety factor for the current state“ of the moving slope. The authors are of the opinion that the partial safety factors required by standards or former ”safety factors“ are predominantly intended for engineering structures, earthworks and dams but not generally for creeping slopes. In this case, classification of creep rate and the geological engineering assessment are always preferred. This is illustrated with two examples.