Static Liquefaction of Soils and Tailings

Dr Mizanur Rahman

Seismically induced liquefaction failures of natural soils and mine tailings has been extensively covered in the literature. However, static liquefaction which occurs in the absence of seismic or dynamic loading is less known to the engineers but often led to devastating consequences including multiple fatalities, e.g. Samarco dam failure in Brazil (2015), Merriespruit failure in South Africa (1994). Static liquefaction may be triggered by many different static loading conditions, such as the rapid raising of perimeter embankments, reduction of mean effective stress due to a rising phreatic surface, or over steepening of the embankment slope, among many others. In this presentation, I will show simple elemental soil tests, such as triaxial and direct simple shear, for understanding the triggering mechanism of static liquefaction, to predict static liquefaction susceptibility and their remedial measure under the critical state soil mechanics framework. The use of field tests. e.g. SPT and CPT, to identify liquefaction susceptibility will be presented. The unknown and the limitation in the current state of knowledge and associate risk will be discussed.

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