Uplift Failure Mechanisms of Pipes Buried in Dense Sand

This study conducted finite-element (FE) modeling of uplift resistance from dense backfill sand. The prepeak hardening, postpeak softening, density, and confining-pressure-dependent soil behavior were implemented in FE analysis to simulate the progressive development of shear bands. The location of the shear bands was identified from soil failure mechanisms for a range of burial depths. For shallow buried pipelines, the inclination of the slip planes to the vertical was found to be approximately equal to the maximum dilation angle when the peak uplift resistance was mobilized and then decreased with an upward movement, resulting in a postpeak reduction of uplift resistance. For deeper conditions, in addition to two inclined slip planes, logarithmic spiral-type shear bands formed above the pipe. Based on mobilized shear strength parameters and inclination of slip planes, a method to calculate the peak and postpeak uplift resistances, using an equivalent angle of internal friction, is presented. (C) 2018 American Society of Civil Engineers.