Recent large-scale slides occurring during the hydraulic placement of an artificial island berm in the Beaufort Sea resulted from the liquefaction of the berm sand. Subsequent laboratory tests and ...

The liquefaction of sands, a collapse surface approach

Liquefaction of loose, saturated sands may be caused by cyclic or static (monotonically increasing) undrained loading. Most previous studies of static liquefaction behavior have emphasized liquefaction susceptibility and the behavior of liquefied soils. An experimental investigation is undertaken to evaluate the stress conditions required to initiate liquefaction and the influence of various parameters on those stress conditions. The static liquefaction resistance, defined as the shear stress increase under undrained conditions required to initiate liquefaction, is observed to increase with increasing relative density and confining pressure, and to decrease dramatically with increasing initial shear stress level. At high initial shear stress levels, initiation of liquefaction is observed to result from increases in shear stress under undrained conditions of only a few percent of the initial shear stress. The distinction between the initiation and the effects of liquefaction is discussed, and an expression for a factor of safety against the initiation of liquefaction is proposed.

Initiation of Soil Liquefaction Under Static Loading Conditions

The differences in undrained stress-strain-strength behavior between undisturbed and reconstituted silt and silty sand specimens tested at the same void ratio and initial stress state may be dramat...

Strength of Undisturbed versus Reconstituted Silt and Silty Sand Specimens

The liquefaction behavior of a clean, fine, uniform sand designated F-70 Ottawa banding sand is examined Specifically, an investigation into the effects of loading systems and sample preparation methods on the stress-strain behavior is made A comparison between the results obtained with a dead-load apparatus and a hydraulic loading system on samples prepared by dry pluviation, moist tamping, and moist vibration indicates differences in the soil’s response during undrained shear The former loading system generates and maintains over a greater strain range lower residual deviator stresses and peak pore-water pressures during steady-state flow Furthermore, the steady-state velocities of the samples tested in the dead-load apparatus are two–three times higher than the velocities of those loaded hydraulically These differences can be attributed to the dead-load system’s ability to provide a constant driving force fast enough to achieve a sample’s maximum rate of strain once liquefaction commences The relative position of the steady-state curves is unaffected by the type of loading system However, the method of sample preparation dictates their position Samples prepared by dry pluviation exhibit residual effective minor principal stresses that are approximately one-quarter to one-half the value of samples prepared by either moist method

Loading systems, sample preparation, and liquefaction

A laboratory database of triaxial compression test results was collected to examine the use of strength ratios for liquefaction analysis. Specifically, the database was used to: (i) validate the yi...

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R.F. Tobin

Papers

Flow slides and the undrained brittleness index of some mine tailings