Evaluation and Mitigation of Membrane Compliance Effects in Soil Liquefaction Testing

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Liquefaction, a potentially destructive type of ground failure, is commonly associated with fine-grained soils. Yet evidence exists that liquefaction occurred in coarse-grained soils such as gravels in the following earthquakes: Fukui (1948), Japan; Alaska (1964); Tangshan (1976), China; Mt. Borah (1984), Idaho. In spite of this evidence, liquefaction in gravelly soils has never been observed in laboratory tests. Presumably, this is due in some way to the failure of laboratory tests to reproduce the in-situ performance of gravelly soils. The most probable reason for this failure is the "membrane compliance effect." Soil samples must be held within a compliant rubber membrane when loaded mechanically in laboratory tests. Due to its compliance, the membrane is able to penetrate into the surface voids between grains, and this penetration increases with the coarseness of the soil particles. The objective of this research program is to develop improved laboratory testing procedures to eliminate this membrane compliance effect in liquefaction testing. The P.I. is a young investigator with an outstanding track record. He has the facilities available to accomplish the research proposed. The liquefaction of gravels is of serious economic consequence for various large construction projects because decisions have to be made as to the necessity of remedial work: the liquefaction potential of gravelly soils was not recognized when these projects were designed and constructed. It is recommended that this request for support be approved.