Seismic risk assessment for oil and gas pipelines - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 704

networks due to their lower material, installation and maintenance costs,
corrosion resistance, lower friction at the interface, lightweight, and claimed
greater capacity to accommodate displacements than its counterpart, steel
pipes. The use of MDPE pipes takes advantage of having higher fl exibility
and fracture toughness while having comparable long-term strength and
stiffness to that of HDPE (Stewart et al. , 1999).
Over the years, numerous studies have been performed on steel pipes to
characterize the behavior when the pipes are subjected to ground move-
ment. However, reported experimental research on the response of buried
PE pipe systems subject to ground movement is very limited. Considering
the relatively smaller deformation stiffness and time-dependent and non-
linear stress-strain response (viscoelastic and creep behavior) of PE pipe
material in comparison to steel, there is likelihood for signifi cant limitations
to arise when methods developed for steel pipes are used in evaluating the
response of PE pipes. Clearly, data from controlled experimental work on
pipelines subject to axial movement, particularly at full-scale level, is needed
to advance the knowledge of the response of buried PE pipe systems
subject to ground movement. With this background, a number of research
programs have been already undertaken to investigate the response of PE
pipe systems under permanent ground movements and analytical methods
have been developed to account for the mobilization of soil loads in buried
PE pipes under such ground movements (Weerasekara and Wijewickreme,
2008).
25.11.3 Full-scale model testing
Modeling of chosen full-scale pipeline confi gurations in the laboratory
provides a very attractive way of capturing and understanding the com-
plexities associated with soil-pipe interaction. Due to the large number of
variables, full-scale testing provides a meaningful approach to characterize
soil-springs for pipe-soil interaction modeling (i.e., provides a meaningful
approach to estimate parameters of soil-springs in axial, lateral, and
upward directions to model the interaction between pipe and soil). Physi-
cal models simulating the fi eld situations also play a key role in calibrating
and validating the analytical approaches and numerical models. (Note:
tests in smaller scales, however, may be subjected to errors associated with
scaling.) Some of the large soil chambers for full-scale testing of pipe-soil
interaction problems are available at Cornell University (Trautmann and
O'Rourke, 1983), Center for Cold Oceans Resources Engineering (Paulin
et al. , 1997), Queen's University (Moore and Brachman, 1994), and Uni-
versity of British Columbia (Wijewickreme et al. , 2009; see Figs 25.6 and
25.7 for details related to the University of British Columbia (UBC) test
facility).