|Publisher||Offshore Technology Conference||Language||English|
|Content Type||Conference Paper|
|Title||Submarine Pipeline Support By Marine Sediments|
|Authors||Sam W. Small,Russell D. Tamburello and Peter J. Piaseckyj, Bechtel Inc.|
Offshore Technology Conference, 19-21 April , Houston, Texas
|Copyright||1971. Offshore Technology Conference|
This paper deals with the submarine pipeline installed on the bottom. Its summarizes the state of the art in submarine pipeline foundation design as extracted from publications available to the practicing engineer. In particular, it covers the quantitative evaluation of initial settlement. Various methods of analysis, using accepted theories of soil mechanics, are compared and evaluated.
Practical problems with which the practicing engineer is faced are identified and discussed. These include the major problems associated with soils sampling, soils analysis and development of an analytical approach.
A pragmatic approach to evaluating initial settlement of a pipeline is developed. Areas in which research and development might be of most immediate benefit are suggested.
When petroleum pipelines are laid under water, it is generally neither economical nor practical to prepare the bottom to receive the pipeline. The pipe must be laid on whatever soils are encountered. Because of this, the design engineer must evaluate soil-pipe interaction both during construction and after installation.
During construction by the lay barge method, initial settlement and lateral restraint due to soil friction and embedment must be evaluated. When using the bottom pull construction technique, longitudinal friction between the pipe and the soil must be evaluated along with initial settlement and lateral restraint. When a pipeline is to be buried, the jetability of the soil, or in some cases, the suitability for mechanical excavation, must be determined.
After installation, the positional stability of the pipeline is of major concern. Items to be evaluated depend upon whether the pipeline is buried or resting on the bottom. In the case of a buried pipeline, longitudinal restraint, long-term settlement and resistance to upward movement are the important ite-ms, whereas with the pipeline resting on the bottom, lateral restraint, longitudinal restraint and long-term settlement are of prime concern.
This paper deals only with the problem of evaluating initial settlement. Further, since initial settlement in sandy soils is not generally a problem, only initial settlement in cohesive marine soils is considered. The problem is additionally simplified by using two-dimensional, static analysis. A discussion of the state of the art with regard to soil theory, experimental work, and experience is followed by consideration of the practical problems of soils sampling, soils analysis, and development of an analytical approach. Finally, a pragmatic approach to the determination of initial settlement is outlined and areas are suggested for additional research and development.
STATE OF THE ART
Quantitative evaluation of initial settlement of a submarine pipeline to be laid on a soft marine sediment is a difficult foundation problem.. Text books provide a number of theories for calculating the ultimate bearing capacity of soils. These theories, however, were developed for use on land. Additionally, some technical papers have been published which deal with the various aspects of submarine pipeline foundation problems. Even so, the practicing engineer will be hard-put to find a comprehensive theoretical treatment of initial settlement of submarine pipelines, or any published works on experiments or experience in this area.
|File Size||805 KB||10|