LIQUEFACTION AND FLOW FAILURE DURING SEISMIC EXPLORATION

A case history and analysis of a flow slide due to soil liquefaction is presented. The failure was triggered by vibratory tampers conducting a seismic reflection survey on a roadway embankment in Michigan's Upper Penninsula. Postfailure investigations included a survey of construction records, in situ and laboratory tests, and replication of the input ground vibrations to estimate the shearing strains and cyclic stress ratios at critical locations in the embankment. Construction records reveal that the embankment was essentially a loose, cohesionless hydraulic fill. Analysis shows that the maximum shearing strain was 5.5 x 10-2%, exceeding the known threshold value for generating excess pore pressures. The estimated cyclic stress ratio of 0.12 and corrected standard penetration test (SPT) W-values of 1-4 combined for a clear prescription for liquefaction. Stability analyses indicate that the residual shear strength of the liquefied soil mass was between 170 and 260 psf. © ASCE.