This document summarizes a study on the stiffness characteristics of buried and on-bottom pipelines under axial loading. The study aims to understand how soil conditions affect axial resistance and the risk of upheaval buckling. Key factors that determine the soil-pipeline interaction include soil type, pipeline roughness, rate of movement, and burial depth. The study will compare axial resistance for different soil conditions using governing equations, with the goal of proposing optimal burial depths to reduce the risk of upheaval buckling in subsea pipelines operating at high pressure and temperature.

1. SYNOPSIS
STIFFNESS CHARACTERISTICS OF BURIED AND ON-
BOTTOM PIPELINES LOADED AXIALLY
Under the Guidance of
Mr. Adarsh K.R. Arya
Assistant Professor Senior Scale
Submitted by:
Mintu Choudhury
SAP ID: 500024885
M.Tech: Pipeline Engineering

2. Problem
• Some pipelines operate in high temperature and pressure
upto 150 C.
• It leads to expansion in the pipeline which causes a
important phenomenon in the pipeline called Upheaval
Buckling due to the accumulation of compressive
stresses.

3. Background
• Buckling is a effect induced by a compressive force, which
distorts pipeline
• It is the same as buckling phenomenon in the column
loaded axially
• There is uneven distribution of restrain provided by soil
• This occurs due to difficult conditions of laying pipeline in
the seabed

4. Soil Resistance
• The movement of buried or on-bottom pipeline is
restricted by the soil
• The lateral movement is limited by the soil, which the
pipeline tries to push (Fig 1 and 2)
• The axial movement is limited by the soil-pipeline friction
(Fig 3)

6. The selection of appropriate pipeline/soil response
conditions is dependent on four factors:
Soil conditions
Pipeline roughness
Rate of pipeline movement
Degree of burial

7. Procedure
• Information to found out for different soil conditions
• Among the information:
 Assume pipeline roughness
 Consolidation Coefficient of Soil
 Subsea Temperature
 Drained and Undrained Conditions for Partially Embedded and Buried
Pipes
 Cohesive and Non-Cohesive Nature of Soil
 Governing Equations
• Interaction of the pipe material and the different soils will be
compared by finding out the Fa (soil axial resistance)
• A chart will be plotted for axial resistance vs. different soil conditions
to compare the results

8. Governing
Equations

9. Motivation
• The problem of UHB has become common now in
subsea pipelines in high pressure and temperature
conditions
• Research has been carried out to reduce the temperature
and pressure to avoid UHB
• But very less research has been carried out to solve the
problem geotechnically

10. Objectives
• To study the behavior of the pipe in different soil
conditions
• Check out the soil behavior in both on-bottom pipes and
partially embedded pipes
• To propose proper burial depth for subsea pipelines for
different soil condition