Lessons learned from sampling and CPT in silt/sand soils

Abstract

Recent studies on the liquefaction behavior of sand and silt mixtures have covered a wide range of gradations. The term silt/sand or M/S is proposed as an inclusive abbreviation of soils that can span from clean sand, silty sand to pure silt. Earlier studies related to M/S soils have concentrated mostly on laboratory tests using reconstituted specimens. The author used Laval and gel-push sampler to retrieve high quality M/S samples at test sites in Central and Southern Taiwan. Piezo-cone penetration tests (CPTU) were conducted at the test sites concurrent with the field sampling. Results from natural undisturbed samples and field CPTU showed that the effects of fines are much less significant than what have been revealed from reconstituted soil specimens or field observations. CPTU in heterogeneous alluvial soil can be a drained test even with high fines contents. The age of natural soil deposit may reduce or nullify the effects of fines as we have learned from laboratory tests using freshly reconstituted specimens.