FELA Evaluation of uplift, lateral and inclined capacity of buried pipeline in layered clays

Abstract

The offshore buried pipelines are prone to upheaval and lateral buckling due to the high temperature and pressure of the materials being transported. The pipeline placed on marine soil or buried in layered soil can be subjected to drained and undrained loading conditions. An attempt has been made in the present study to evaluate the uplift and lateral capacity factor (N_u) of buried pipeline in layered clays using finite element limit analysis (FELA) considering the layered clay condition as soft clay over hard clay and hard clay over soft clay. The lateral and uplift capacity factors are evaluated corresponding to varying normalized C/D ratio, where C is the crown height and D is the diameter of the pipeline, h₁/D ratio, where h₁ is the height of upper layer of clay, and S_u1/S_u2, where S_u1 is undrained shear strength of upper clay layer and S_u2 is the undrained shear strength of bottom clay layer. The inclined capacity of buried pipeline in layered clays is also evaluated numerically and by interpolation using the vertical and lateral capacity factors. Then the assessment of the interpolated inclined capacity is also performed. The FELA results are compared with those solutions available in the literature and the present study outcomes are presented as design charts and tables. This study will be useful to the offshore foundation engineering practitioners.