An illustration of the importance of soil non-linearity in soil-structure interaction problems

Abstract

A comparison of the measured and predicted performance of a buried steel pipeline is presented. The cover depth to pipeline diameter ratio was only 0.25, and the pipeline was loaded through the application of a surface surcharge. Three different failure criteria were used to model the soil behaviour: the Mohr-Coulomb criterion and the corresponding inscribed and circumscribed surfaces defined by the Drucker-Prager criterion. Comparisons of measurements and predictions are limited to surcharge loads which were less than half that observed to cause failure in laboratory tests. Even at this relatively low value of the surcharge load, the constitutive law adopted to describe the confining soil behaviour was shown to have a very significant influence on pipeline hoop stresses and bending moments. It is concluded that neglecting the possibility of soil yield, and merely treating the soil continuum as an elastic medium, will result in an interaction mechanism between soil and structure which may produce invalid estimates of pipeline stresses.