Slide in the Siburua Dam

A case study of a small slide in the downstream slope of a dam composed of shaley clay is presented. The slide started during steady seepage conditions under a full reservoir. Field pore water pressures and movements were recorded before, during, and after the slide. Extensive laboratory tests were run on undisturbed samples hand cut from the failure zone. Total stress analyses were made based on field water contents and a laboratory developed relationship of failure water content versus strength. Effective stress analyses were made based on field pore pressures and laboratory determined effective stress parameters. Both sets of analyses gave a computed factor of safety of about unity for the failure conditions.