E' and Its Variation With Depth

The modulus of soil reaction, E’, characterizes the stiffness of soil backfill placed at the sides of buried flexible pipelines for the purpose of evaluation deflection caused by the weight of backfill above the pipe. In this study, the nature of E’ is investigated in detail to determine whether its magnitude increases with increasing depth of embedment. The development of E’ in the literature is reviewed, and data from field installations are presented to establish that E’ can be shown to increase with depth on the basis of previous research. Analytical methods, based on elastic theory and finite element techniques, are also used to demonstrate the dependence of E’ on depth. Design values of E’, which vary with depth, are presented, together with recommendations regarding the use of E’ in the Iowa formula.