Abstract
[Truncated] The current submarine pipeline on-bottom stability design method recommended by DNV RP-F109 is flawed because it neglects the seabed mobility. This research aims to improve the understanding of how seabed mobility, specifically local scour around a pipe, influences pipeline stability under realistic storm conditions.
To investigate the on-bottom stability of a submarine pipeline that is controlled by the ‘flow-pipeline-seabed’ tripartite interaction, an innovative large experimental facility, called the O-tube, was established at the University of Western Australia. The facility is capable of simulating cyclonic storm-induced hydrodynamic conditions at seabed level so that the responses of a model pipeline and a model seabed can be revealed at a relatively large scale to minimize the potential scaling effects associated with conducting physical model tests. The establishment of the O-tube facility forms a part of this thesis. The functionality and calibration of the facility are described herein.
A wide range of pipeline dynamic stability tests were conducted in the O-tube facility, with the pipe being actively controlled by an actuator system so that it can move freely in response to hydrodynamic load and soil resistance. Physical model test results of a model pipe installed on an erodible sediment bed demonstrated that local scour has a significant effect on pipeline stability. Based on the pipeline initial embedment, local scour affected pipeline stability in two different ways: (i) tunnel scour below a pipe with a shallow initial embedment appeared to be beneficial to pipeline stability because tunnel scour tended to cause the pipe sinking into the scour hole; whilst (ii) local scour at either side of a pipe with a deep embedment (without tunnel scouring) appeared to undermine the stability of the pipe because it reduced the pipe embedment depth.
To investigate the on-bottom stability of a submarine pipeline that is controlled by the ‘flow-pipeline-seabed’ tripartite interaction, an innovative large experimental facility, called the O-tube, was established at the University of Western Australia. The facility is capable of simulating cyclonic storm-induced hydrodynamic conditions at seabed level so that the responses of a model pipeline and a model seabed can be revealed at a relatively large scale to minimize the potential scaling effects associated with conducting physical model tests. The establishment of the O-tube facility forms a part of this thesis. The functionality and calibration of the facility are described herein.
A wide range of pipeline dynamic stability tests were conducted in the O-tube facility, with the pipe being actively controlled by an actuator system so that it can move freely in response to hydrodynamic load and soil resistance. Physical model test results of a model pipe installed on an erodible sediment bed demonstrated that local scour has a significant effect on pipeline stability. Based on the pipeline initial embedment, local scour affected pipeline stability in two different ways: (i) tunnel scour below a pipe with a shallow initial embedment appeared to be beneficial to pipeline stability because tunnel scour tended to cause the pipe sinking into the scour hole; whilst (ii) local scour at either side of a pipe with a deep embedment (without tunnel scouring) appeared to undermine the stability of the pipe because it reduced the pipe embedment depth.
| Original language | English |
|---|---|
| Qualification | Doctor of Philosophy |
| Publication status | Unpublished - 2012 |