Permafrost

frost heave is one typical case of freezing damage to engineering projects in cold regions.
Designed depth of burial that must exceed local maximum depth of frost penetration might be a
solution, or the effect of frost heave shall be well considered during design process. Another
instance of defective design could be the stress originated by moving vehicles and transmitted
via soil to the pipeline when it run through transportation roads, this issue happens when
insufficient depth of burial exists. As to unregulated construction, criteria set forth for
construction are not duly observed, situation could be aggravated if people performing the task
are technically inadequately competent. With reference to management, lack of systematic and
austere rules and regulations as well as monitoring measures is another blamable factor. For the
purpose of above issues, this article recommends some ideas on design, management, and
construction processes.
Key words: gas pipeline, crack incident analysis, frost heave
Laboratory Observation of Dynamic Frost Bulb and Frost Heave
Development in Soil Surrounding Chilled Pipe Using Computerized
Ultrasonic Tomography
Hui Li and Gang Chen
(Department of Mining and Geological Engineering, University of Alaska Fairbanks,
Fairbanks, Alaska, USA)
Abstract: Buried and chilled gas pipelines have been used to transport pressurized gas through
permafrost regions to prevent thaw of permafrost through which the pipe traverses, as currently
planned for the proposed Alaska gas pipeline. In preventing thaw of frozen ground, freezing of
unfrozen frost susceptible soil creates a new problem – uneven frost heave along the buried
pipeline. As a chilled pipeline cross a transition zone from frozen to unfrozen ground, a
differential frost heave may develop and induce significant strains in the buried pipe causing
concerns on the integrity of the pipe structure. A good understanding of frost heave
development around chilled pipeline at various thermal and geotechnical conditions is essential
for a reliable design and construction of buried and chilled gas pipelines. Studies including field
and laboratory experimental studies have been conducted to investigate the behavioral
characteristics of chilled gas pipelines buried in frozen and unfrozen ground. Progresses have
been made to better understand the problems and address the concerns in dealing with chilled
pipelines. However, many questions are still unanswered and problems unsolved. Continued
studies are necessary for safe, reliable and economical development of buried and chilled gas
pipelines through permafrost regions.
A previous study on a two-dimensional laboratory frost heave model was conducted by
Akagawa (2006), in which the heave characteristics, thermal patterns and freezing front
growing surrounding a chilled pipe was investigated by placing pressure gauges and thermal
sensors in the soil. Following this 2-D laboratory model study, a multi-channel ultrasonic
scanning system (MUSS) is developed and applied in the current study to observe the dynamic
frost bulb and frost heave development surrounding a chilled pipe buried in soil. The MUSS
29