Uplift resistance of buried pipelines in dry and unsaturated sands: Comparison of analytical and FE model results with large-scale test data

Pipelines are commonly buried underground to provide environmental stability, temperature insulation and mechanical protection. These pipelines are frequently subjected to earthquake induced upward displacements, which can cause significant social-economic loss to consumers and utility management. Further, high thermal and pressure of the conveying medium can induce differential stresses on the axial restrained pipe to result upward buckling of the pipeline that can disturb the serviceability conditions. The uplift resistance from soil cover protects the pipe against such unwanted movements, representing it as a vital design parameter, in that pipeline integrity under operating conditions relies on its value. The paper presents full-scale uplift results and finite-element parametric studies conducted to investigate the effects of dimensionless cover heights (soil cover height to diameter ratio), soil relative density and moisture content on the peak uplift resistance of pipes. The results showed that the available analytical models could predict realistic peak uplift resistance for pipes buried at shallower depths, however, they can substantially underpredict the pipe loads/uplift resistance especially when buried at deeper embedded depths and non-dry soil conditions. The results of the current study are useful for pipe designs against earthquakes and/or severe operating conditions induced uplift displacements in sandy soils.