A Coupled Thermo-Hydro-Mechanical Model for Capturing Frost Heave Under Chilled Gas Pipelines

2021 ◽  
Author(s):  
SeonHong Na ◽  
Kshama Roy ◽  
Mahyar Malekzade Kebria
Keyword(s):  
Mechanical Model ◽  
Frost Heave ◽  
Gas Pipelines

Prediction of Long-Term Frost Heave of Chilled Gas Pipelines by Centrifuge Modeling

2004 ◽  
Author(s):  
Vincent Morgan ◽  
Jack Clark ◽  
Bipul Hawlader ◽  
Joe Zhou
Keyword(s):  
Climatic Conditions ◽  
Full Scale ◽  
Centrifuge Modeling ◽  
Frost Heave ◽  
Soil Types ◽  
Small Scale ◽  
Gravitational Acceleration ◽  
Gas Pipelines ◽  
Centrifuge Testing ◽  
Pipe Geometry

The use of chilled gas transmission for northern pipelines has been considered an effective solution to reduce potential problems relating to permafrost preservation, as well as to provide other benefits such as increased throughput. However, the potential for frost heave as the pipe crosses areas of unfrozen ground may have implications on induced strains and therefore pipeline integrity. C-CORE, under the sponsorship of Pipeline Research Council International (PRCI), has been investigating the effects of frost heave for different soil types and varying pipe geometry and temperature. Previous studies of the effects of frost heave of chilled gas pipelines involved the construction of full-scale test sites, operated over a number of years and small scale laboratory tests. Recent advances in centrifuge testing techniques have allowed small-scale models to be constructed and tested under increased gravitational acceleration to replicate full-scale conditions. The major advantages are the reduced scale and time effects used in the modeling of the frost heave. This allows a number of sequential tests to be performed to study a range of soil types, pipe temperatures, groundwater and climatic conditions in a relatively short time period and at significantly reduced cost. Centrifuge modelling also incorporates other forms of soil deformations with development of ice lenses which includes the consolidation of unfrozen soil and deformation of both frozen and unfrozen soil. The tests performed to date have focused on the determination of frost heave behaviour for a number of soil types covering the range of frost susceptibility. This paper discusses the interpretation of the test results, and provides a comparison with common methods of analysis for prediction of frost heave. A design methodology is also proposed, which makes use of centrifuge test and analytical methods.

scholarly journals Longitudinal Deformation Model and Parameter Analysis of Canal Lining under Nonuniform Frost Heave

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Pengfei He ◽  
Jianhua Dong ◽  
Xin Ren ◽  
Xiaolei Wu
Keyword(s):  
Normal Stress ◽  
Cross Section ◽  
Mechanical Model ◽  
Parameter Analysis ◽  
Frost Heave ◽  
Shear Rigidity ◽  
Frost Heaving ◽  
Transition Section ◽  
Maximum Normal Stress ◽  
Water Conveyance

Due to the unique hydrothermal environments, the frost heave failure of the concrete lining of water conveyance canals in cold regions is still frequent. The deformation of lining after frost heaving and the stress distribution calculated by the mechanical model can be the reference for the lining design. However, previous research mainly focused on the mechanical model of the cross-section while having little attention for the longitudinal nonuniform frost heave damage. In this study, a mechanical model of the bottom lining under the nonuniform frost heave deformation is built based on the Euler–Bernoulli beam and the Pasternak foundation model, and the analytical solution of the model is obtained. The internal stress of the lining is analyzed during the changes of subgrade coefficient, shear rigidity, transition section length, and frost heave amount inside the model. Also, the calculation process is proved to be correct. The result shows that dangerous cross-sections are at the start and the end of the transition sections. The maximum normal stress and the tangential stress increase when the subgrade coefficient and the frost heave amount increase and the shear modulus and transition section length decrease. The frost heave amount in the frozen ground subgrade increases constantly, while the temperature decreases, but at the same time, the shear rigidity of the subgrade increases with it. The former increases the stress of lining, and the latter decreases it. Therefore, during the frost heaving process, the internal force of lining is coupled with these two elements. By analyzing a water conveyance canal lining under the nonuniform frost heave in the Xinjiang Tarim irrigation district, the maximum normal stress of the dangerous lining cross-section is greater than its tensile strength when the transition section length smaller than 7 m at the frost heave amount is 0.031 m.

Centrifuge modelling of gas pipelines undergoing freeze–thaw cycles

2021 ◽  
Author(s):  
Rajith Sudilan Dayarathne ◽  
Bipul C. Hawlader ◽  
Ryan Phillips
Keyword(s):  
Vertical Displacement ◽  
Operating Conditions ◽  
Frost Heave ◽  
Seasonal Temperature ◽  
Test Results ◽  
Gas Pipelines ◽  
Freezing And Thawing ◽  
Geotechnical Centrifuge ◽  
Freeze Thaw ◽  
Cyclic Temperature

Frost heave and thaw settlement are two critical factors that need to be considered in the design of chilled gas pipelines in cold regions. Due to the variation in seasonal temperature and operating conditions (e.g., pressure and temperature at the compressor stations), the pipeline temperature in some segments might vary from subzero to above-zero during winter and summer. This study examines the freezing and thawing for cyclic and constant temperatures at the pipeline and ground surfaces based on the response of fourteen model pipes tested in a geotechnical centrifuge. The cyclic (temperature) operation reduces the frost heave rate per year and causes net settlement in some cases. When the thaw bulb resulting from an above-zero operating temperature is less than the previously developed frost bulb, upward water flow occurs through the thawed soil, which could alter the pipeline–soil interaction behaviour. Five types of freeze-thaw-induced vertical displacement of the pipe have been identified from the centrifuge test results.

Study on a Method Monitoring Oil and Gas Pipelines in Permafrost Regions

2012 ◽  
Author(s):  
Yunbin Ma ◽  
Dongjie Tan ◽  
Ning Song ◽  
Pengchao Chen ◽  
Tao Ma
Keyword(s):  
Temperature Field ◽  
Oil And Gas ◽  
Frost Heave ◽  
Fiber Grating ◽  
Test Results ◽  
Gas Pipelines ◽  
Monitoring Method ◽  
Oil And Gas Pipelines ◽  
The Impact ◽  
Permafrost Regions

Based on conditions of oil and gas pipelines in permafrost regions, this paper demonstrates a method for monitoring pipeline stress and displacement as well as permafrost temperature field. To measure pipeline displacement, Total Station measuring technique which calculates displacement by measuring the change of pipeline sign post was adopted; and to monitor pipeline stress and temperature field of permafrost, Fiber Grating Sensing technique was used. This method has been applied to Pipeline No. A for a year, according to the test results, during the year, displacements of different degrees have been occurred to the pipeline; this pipeline was not influenced by frost heave in winter but was influenced by thaw collapse in summer. Due to this monitoring method for oil and gas pipelines in permafrost regions, the condition of permafrost and the change of pipeline under the impact of permafrost were successfully monitored; therefore, this method is effective and feasible.

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