Liquefaction Flow Failure of Silty Sand by Torsional Cyclic Testsby Ricardo Dobry,
Abstract: The use of undrained strain-controlled cyclic torsional loading of anisotropically consolidated triaxial specimens (CyT-CAU tests), is proposed for evaluating liquefaction flow failure of saturated sands in the field during earthquakes. Eighteen CyT-CAU tests and seven monotonic undrained CIU and CAU tests were conducted on contractive reconstituted specimens of three silty sands. All CAU and CyT-CAU tests were performed on specimens consolidated under a stress ratio, K//c equals sigma 1c ROOT sigma 3c equals 2, while in the CIU tests, K//c equals 1. The three soils tested, designated here as Sands A, B and C, were sampled from the same deposit but had different nonplastic silt contents of 13%, 32% and 63%, respectively. The steady-state lines obtained from these cyclic and monotonic tests were different for the three sands, with the slopes of the lines becoming flatter as the sand became siltier. When compared to the monotonic tests, the cyclic torsional CyT-CAU tests provide additional information on the rate of pore pressure buildup, number of cycles to flow failure and state of effective stresses at the time of triggering of the failure.
Subject Headings: Soil liquefaction | Soil stress | Soil pressure | Failure analysis | Load tests | Cyclic tests | Silt | Torsion
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