i
CERTIFICATION OF APPROVAL
AN EXPERIMENTAL STUDY ON THE WAVE INDUCED INSTABILITY OF PIPELINES: THE BREAKOUT OF PIPELINES
by
Ahmad Syahidi Bin Che Zainal
A project dissertation submitted to the Mechanical Engineering Programme
Universiti Teknologi PETRONAS in partial fulfilment of the requirement for the
BACHELOR OF ENGINEERING (Hons) (MECHANICAL ENGINEERING)
Approved by,
__________________________
(Mr. Rahmat Iskandar Khairul Shazi Shaarani)
UNIVERSITI TEKNOLOGI PETRONAS TRONOH, PERAK
January 2008
ii
CERTIFICATION OF ORIGINALITY
This is to certify that I am responsible for the work submitted in this project, that the original work is my own except as specified in the references and acknowledgements, and that the original work contained herein have not been undertaken or done by unspecified sources or persons.
___________________________________________
AHMAD SYAHIDI BIN CHE ZAINAL
iii
ABSTRACT
In this paper, a series of experiments have been conducted in a wave flume flow tunnel, which provides a more realistic simulation than the previous actuator loading methods. This experiment is carried out to investigate the lateral movement of underwater pipeline in laboratory. The breakout of pipeline from its original place is investigated under wave loading using wave flume generator in laboratory. The interaction between wave-pipe-seabed causes the pipeline to breakout from its places. Based on the experimental data of pipe displacement with two different constraint conditions (freely laid pipelines and anti-rolling pipelines), three characteristic times in the process of pipeline losing stability are identified. The effects of wave frequency on the pipeline lateral stability are also examined for freely laid pipelines and anti-rolling pipelines.
iv
ACKNOWLEDGEMENTS
First and foremost, I would like to express my gratitude to Mr. Rahmat Khairul Shazi. He had been very supportive during the entire of the project period.
He spent much time and energy to guide me throughout the 28 weeks despite their other commitments and packed schedule as lecturers in UTP. Under their constant supervision, I managed to start my project with proper planning and proceeded until completion of the project in the stipulated time frame.
I would also like to express my gratitude toward Mechanical Engineering Department of Universiti Teknologi PETRONAS (UTP) for providing the chance to undertake this remarkable final year project. My knowledge on mechanical engineering has been put to the test for the purpose of completing this project. This course has offered me a ood exposure to the applicants of wave mechanics and the opportunity to work with technologists and technician in the Mechanical and Civil Engineering Department.
A word of sincere gratitude goes to the Final Year Project Committee for arranging and managing the course throughout the two semesters, they have done a good job in keeping students well-informed of all the procedures and deadlines which are influential to the progress of the project.
I also extend my utmost gratitude to the UTP Resource Center Staffs and also the Mechanical Engineering Technologist, for allocating the much needed literature and their assistance in handling the equipment.
I wish to thank all fellow colleagues whose names were not mentioned here for providing assistance, support and cooperation in any form. Last but not least, I would like to thank my family especially my parents for their budget allocation for the project and their support for me to complete this project.
v
TABLE OF CONTENTS
PAGE
CERTIFICATION OF APPROVAL i
CERTIFICATION OF ORIGINALITY ii
ABSTRACT iii
ACKNOWLEDGEMENT iv
LIST OF TABLES AND FIGURES vii
CHAPTER 1: INTRODUCTION
1.1 Background 1
1.2 Problem statement 2
1.3 Objectives 3
1.4 Scope of work 3
CHAPTER 2: LITERATURE REVIEW
2.1 Loadings on an underwater pipeline 4 2.2 Principle of deep water condition 5 2.3 Principle of Similarity (Dimensionless Analysis) 6
CHAPTER 3: METHODOLOGY
3.1 Research Methodology 10
3.2 Project Activities 11
3.3 Project Phase for FYP I & FYP II 13
3.4 Experimental Setup 14
3.5 Experiment Procedure 18
3.5 Water Wave Flume 19
3.7 Pipeline Model 21
vi
3.7 Submerged Weight of Pipeline 22
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Qualitative Data 24
4.1.1 Free End Pipeline Model 24
4.1.2 Anti-Rolling Pipeline Model 24
4.2 Quantitative Data 26
4.2.1 Free-End Pipeline Model 26
4.2.2 Anti-Rolling Pipeline Model 27 4.2.3 Breakout time for different frequency 28 4.2.3.1 Free-End Pipeline Model 28 4.2.3.2 Anti-Rolling Pipeline Model 29
4.3 Discussion 31
4.3.1 Three characteristic times 31 4.3.2 Phases of pipeline instability process 32 4.3.3 Criterion for the on-bottom instability
of pipeline 32
4.3.4 Effect of different frequency to the pipeline
breakout 33
CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 34
5.2 Recommendations 35
REFERENCE 36
APPENDIX 37
vii
LIST OF FIGURES Figure 2.1: Loadings on pipeline
Figure 2.2: Pipeline is trenched into the seabed
Figure 2.3: The hydrodynamic force induced by wave Figure 3.1: Water Flume / wave tank for the experiment Figure 3.2: Test Section of the water wave flume
Figure 3.3: Test Section Box inserted into the water flume Figure 3.4: Pipeline Model is trenched in the sand / seabed Figure 3.5: The arrangement of the experimental setup Figure 3.6: Switch Panel for Water Wave Flume Figure 3.7: Dimension of the Wave Flume Tank Figure 3.8: Motor and the flap to generate water waves Figure 3.9: Method of restricting the rolling of pipeline Figure 3.10: Method of restricting the rolling of pipeline
Figure 4.1: Three characteristic states of pipe instability for free-end pipeline model (a) Onset of sand scour, (b) pipeline rocks, and (c) pipeline breakouts.
Figure 4.2: Three characteristic states of pipe instability for anti-rolling pipeline model (a) Onset of sand scour, (b) pipeline rocks, and (c) pipeline breakouts.
Figure 4.3: Graph Time (s) versus Displacement (cm) for Free-End Pipeline Model
Figure 4.4: Graph Time (s) versus Displacement (cm) for Anti-Rolling Pipeline Model.
viii
Figure 4.5: Graph Frequency (Hz) versus Time (s) for Free-End Pipeline Model.
Figure 4.6: Graph Frequency (Hz) versus Time (s) for Anti-rolling Pipeline Model.
Figure 4.7: Graph Frequency (Hz) versus Time (s) for Free-End and Anti-Rolling Pipeline Model.
ix
LIST OF TABLES
Table 4.0: Time and Displacement for the Free-End Pipeline Model (Frequency 2Hz)
Table 4.1: Time and Displacement for the Anti-Rolling Pipeline Model (Frequency 2Hz)
Table 4.2: Frequency and the Time for the pipeline model to breakout (free-end pipeline)
Table 4.3: Frequency and the Time for the pipeline model to breakout
