What is upheaval buckling calculation in pipeline engineering?

Introduction

The expansion of pipelines due to high temperatures and pressures of fluid flow in pipelines is known as buckling. Such phenomena can be observed on both onshore and offshore pipelines in transporting products from one location to another.

Buckling may occur in pipelines downward in a free span, horizontally in lateral buckling on the seabed or vertically in upheaval buckling of buried pipelines. Operated at very high temperatures, buried pipelines may be susceptible to upheaval buckling caused by compressive loads.

Upheaval Buckling Calculation

Upheaval buckling calculations shall be performed for all buried lines with design temperatures above 82 C
Upheaval buckling can be prevented either by expansion offsets regularly spaced along the pipeline or a sufficient burial cover

There is several methodologies used for performing upheaval buckling calculations:

DEP 31.40.10.16-Gen
K Peter’s Technical Paper
OTC 6335 Technical Paper

Upheaval Buckling Calculation Based on OTC 6335

The first step is input data:

Input Data	Symbol	Value
Pipeline Nom Dia.	ND	–
Pipeline OD	D	–
Design Pressure	P	–
Design Temperature	T₂	–
Installation Temperature	T₁	21 C
Steel Expansion Coefficient		–
Youngs modulus of pipe	E	–
Selected wall thickness	t	–
Corrosion Allowance		–
Wall thickness (corroded)	t_n	–
Temperature derating factor	T	1
Poisson’s ratio		0.3
Steel density		–
Soil density		–
Cover to top of pipe	H	–
Contents density		–
Uplift coefficient	f	0.5 for dense/ 0.1 for loose

Second step is pipeline properties:

Pipeline Properties	Symbol	Formula
Pipe internal diameter (corroded)	d	–
Pipe cross section area	A_s
Pipe internal area	A_i
Pipe Moment of inertia	I
Pipe flexural rigidity	EI	–
Weight of pipe	W_s	–
Weight of contents	W_c