LIQUEFACTION OF SANDS DUE TO NON-SEISMIC LOADING (LANDSLIDE, TRIAXIAL, COMPLIANCE, MONTANA)

Liquefaction of loose, saturated sands may be initiated by cyclic or monotonically increasing loads. While the behavior of these sands under cyclic loading has received considerable attention from researchers, the phenomenon of liquefaction due to non-seismic has not been studied in the same detail.;A comprehensive laboratory testing program was performed to study the stress changes required to initiate liquefaction and the effects of relative density, confining pressure, and initial shear stress level on these stress changes. Load-controlled, undrained, isotropically- and anisotropically-consolidated triaxial tests were performed on samples of clean and silty fine sand. The laboratory investigation revealed that the undrained stress change required to initiate liquefaction, expressed as a ratio of shear stress/normal stress on a particular plane, increased with increasing relative density, decreased with increasing confining pressure, and decreased dramatically with increasing initial shear stress level. At high levels of initial shear stress, liquefaction was initiated by very small increases in shear stress under undrained conditions.;The results of the laboratory investigation were used to study the 1938 liquefaction failure of a portion of Fort Peck Dam. The foundation of the dam was underlain by a shale which contained numerous bentonite seams. Construction of the dam embankment was modeled by finite element analyses. The effect of creep deformation of the shale on the stress conditions within the dam and its foundation was studied. One of the effects of the creep deformation was to increase the initial shear stress level in certain zones of the dam and foundation. The occurrence of a small sudden slip, such as would be caused by creep rupture of the shale, was shown to be sufficient to cause a failure of magnitude similar to that observed at Fort Peck Dam.;The investigation described in this dissertation has shown that liquefaction of loose, saturated sands must be caused by an undrained increase in shear stress and that the magnitude of that increase may, under certain conditions of stress and density, be very small.;Detailed reviews of published reports of non-seismic liquefaction failures, and of the results of related previous research are presented. Previous research has focused on the conditions under which sands are and are not susceptible to liquefaction. The changes in stress required to initiate, or trigger, liquefaction have not been addressed to any significant extent.