Seismic performance of hillside fills

Permanent ground deformations in unsaturated, compacted hillside fills unde r seismic loading conditions are discussed, with emphasis given to fill per formance during the 1994 Northridge earthquake. These movements represent a significant yet often unrecognized hazard to developed hillside areas, as relatively modest deformations induced widespread damage totaling hundreds of millions of dollars during the Northridge event. The development of grad ing standards in the Los Angeles area is reviewed to place the seismic fill deformation problem in context with other issues that have shaped design a nd construction practices for hillside fills. Field observational data on f ill performance during the Northridge earthquake is presented, and typical ground distress patterns are found to include cracking near cut/fill contac ts, lateral extension and settlement of fill pads, and bulging of fill slop e faces. For most sites, the prevalent mechanism of permanent ground deform ation responsible for the fill movements is contractive volumetric strain a ccumulation within the unsaturated fill soils during strong earthquake shak ing (that is, seismic compression).