scholarly journals A Case Study of Pipeline Route Selection and Design Through Discontinuous Permafrost Terrain in Northwestern Alberta

1996 ◽  
Author(s):  
Cory Wiechnik ◽  
Raymond Boivin ◽  
Jim Henderson ◽  
Mark Bowman
Keyword(s):  
Life Cycle Cost ◽  
Field Data ◽  
Differential Settlement ◽  
Frozen Soil ◽  
Geophysical Data ◽  
Design Solution ◽  
Pipeline System ◽  
Permafrost Degradation ◽  
Discontinuous Permafrost ◽  
Pipeline Route

As the natural gas pipeline system in Western Canada expands northward, it traverses the discontinuous permafrost zone. As the ground temperature of the frozen soil in this zone is just below freezing, it can be expected that within the design life of a pipeline the permafrost adjacent to it will melt due to the disturbance of the insulating cover by construction activities. Differential settlement at the thawing frozen/unfrozen soil interfaces gives rise to pipeline strain. Based on the calculated settlement and resulting strain level, a cost effective mechanical or civil design solution can be selected to mitigate the differential settlement problem. Since these design solutions can be costly, it is desirable to combine them with a pipeline route that traverses the least amount of discontinuous permafrost terrain while minimizing the overall length of the pipeline. This paper will detail the framework utilized to select the routing for a package of pipeline projects in northwestern Alberta. The process began with a review of the state of the art in permafrost engineering in order to benefit from past experiences. Airphoto interpretation and terrain mapping were performed for potential pipeline corridors. Preliminary routing options through the corridors were chosen from this mapping information that minimized both pipeline length and amount of permafrost terrain traversed. The next step was to collect field data for each route that would determine the extent and characteristics of the permafrost. Essentially two sets of field data were collected: geophysical mapping of representative sections of each terrain type and physical sampling of the permafrost. Boreholes were located following field interpretation of the geophysical data to ensure they were optimally located to help in calibration of the geophysical data. Permafrost samples were tested in the laboratory for thaw settlement. Anticipated thaw settlements were used to estimate pipe strain levels. This information was then extrapolated for the entire proposed pipeline route and used to finalize both the pipeline route and the differential settlement design options. Monitoring sites will be instrumented to obtain data on the longer term performance of the pipeline, as well as for assessing permafrost degradation effects on the right-of-way such as settlement and impact on drainage patterns. It is believed that the increased front end effort will result in lower operating costs and an overall reduced life-cycle cost. This basic design methodology can be applied to any project that traverses discontinuous permafrost terrain.

Pipeline Integrity Design for Differential Settlement in Discontinuous Permafrost Areas

1996 ◽  
Author(s):  
Z. Joe Zhou ◽  
Raymond P. Boivin ◽  
Alan G. Glover ◽  
Phil J. Kormann
Keyword(s):  
Structural Integrity ◽  
Pipe Wall ◽  
Cost Effective ◽  
Differential Settlement ◽  
Pipeline System ◽  
Design Problems ◽  
Pipe Wall Thickness ◽  
Discontinuous Permafrost ◽  
Design Options ◽  
Effective Design

The NOVA Gas Transmission Ltd. (NGTL) gas pipeline system is expanding northwards as the producers search for and find new gas reserves. This growth has taken the system into the discontinuous permafrost zone, and also into new design problems. One such problem is the structural integrity of a pipeline subjected to the settlement differentials that occur between frozen and unfrozen soils. Adequate integrity design for differential settlement is required by design codes, such as CSA Z662, but the procedures and criteria must be established by the pipeline designers. This paper presents the methodology of pipeline integrity design for differential settlements used on a number of pipeline projects in Northwest Alberta. Outlined in the paper are the procedures, rationales and models used to: (a) locate discontinuous permafrost; (b) quantify the potential differential settlement; (c) predict pipeline stresses and strains; (d) establish strain limits; and (e) determine the pipe wall thickness to withstand those potential differential settlements. Several design options are available and are briefly discussed. For the projects mentioned, the heavy wall pipe option was identified as a cost effective design for medium to large differential settlements.

MONITORING OF THE THERMOABRASIONAL AND ACCUMULATIVE COASTS NEAR THE UNDERWATER GAS PIPELINE ROUTE ACROSS THE BAYDARATSKAYA BAY, KARA SEA

2017 ◽  
Author(s):  
Nataliya Belova ◽  
Nataliya Belova ◽  
Alisa Baranskaya ◽  
Alisa Baranskaya ◽  
Osip Kokin ◽  
...  
Keyword(s):  
Thermal Regime ◽  
Storm Surges ◽  
Gas Pipeline ◽  
The Arctic ◽  
Yamal Peninsula ◽  
Permafrost Degradation ◽  
Nearshore Zone ◽  
Barrier Beach ◽  
Energy Dissipater ◽  
Pipeline Route

The coasts of Baydaratskaya Bay are composed by loose frozen sediments. At Yamal Peninsula accumulative coasts are predominant at the site where pipeline crosses the coast, while thermoabrasional coast are prevail at the Ural coast crossing site. Coastal dynamics monitoring on both sites is conducted using field and remote methods starting from the end of 1980s. As a result of construction in the coastal zone the relief morphology was disturbed, both lithodynamics and thermal regime of the permafrost within the areas of several km around the sites where gas pipeline crosses coastline was changed. At Yamal coast massive removal of deposits from the beach and tideflat took place. The morphology of barrier beach, which previously was a natural wave energy dissipater, was disturbed. This promoted inland penetration of storm surges and permafrost degradation under the barrier beach. At Ural coast the topsoil was disrupted by construction trucks, which affected thermal regime of the upper part of permafrost and lead to active layer deepening. Thermoerosion and thermoabrasion processes have activated on coasts, especially at areas with icy sediments, ice wedges and massive ice beds. Construction of cofferdams resulted in overlapping of sediments transit on both coasts and caused sediment deficit on nearby nearshore zone areas. The result of technogenic disturbances was widespread coastal erosion activation, which catastrophic scale is facilitated by climate warming in the Arctic.

scholarly journals Experimental and analytical study of seismic site response of discontinuous permafrost

2016 ◽  
Vol 53 (9) ◽  
pp. 1363-1375 ◽  
Author(s):  
Behrang Dadfar ◽  
M. Hesham El Naggar ◽  
Miroslav Nastev
Keyword(s):  
Shear Wave ◽  
Site Response ◽  
Free Field ◽  
Frozen Soil ◽  
Shaking Table ◽  
Experimental Program ◽  
Small Scale ◽  
Seismic Site Response ◽  
Discontinuous Permafrost ◽  
Spectral Accelerations

Seismic site response of discontinuous permafrost is discussed. The presence of frozen ground in soil deposits can significantly affect their dynamic response due to stiffer conditions characterized by higher shear-wave velocities compared to unfrozen soils. Both experimental and numerical investigations were conducted to examine the problem. The experimental program included a series of 1g shaking table tests on small-scale models. Nonlinear numerical analyses were performed employing FLAC software. The numerical model was verified using the obtained experimental results. Parametric simulations were then conducted using the verified model to study variations of the free-field spectral accelerations (on top of the frozen and unfrozen soil blocks) with the scheme of frozen–unfrozen soil, and to determine the key parameters and their effects on seismic site response. Results show that spectral accelerations were generally higher in frozen soils than in unfrozen ones. It was found that the shear-wave velocity of the frozen soil as well as the assumed geometry of the blocks and their spacing have a significant impact on the site response.

Runoff generation processes in permafrost-influenced area of the Heihe River Headwater

2021 ◽  
Author(s):  
Fan Zhang ◽  
Xiong Xiao ◽  
Guanxing Wang
Keyword(s):  
Soil Water ◽  
Stream Water ◽  
Hydrological Regime ◽  
Summer Rainfall ◽  
Frozen Soil ◽  
Heihe River ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Runoff Generation ◽  
Spring Snowmelt

<p>Permafrost degradation under global warming may change the hydrological regime of the headwater catchments in alpine area such as the Tibetan Plateau (TP). In this study, he runoff generation processes in permafrost-influenced area of the Heihe River Headwater were investigated with the following results: 1) The observed stable isotope values of various water types on average was roughly in the order of snowfall and snowmelt < bulk soil water (BSW) < rainfall , stream water, mobile soil water (MSW) , and lateral subsurface flow. The depleted spring snowmelt and enriched summer rainfall formed tightly bound soil water and MSW, respectively. The dynamic mixing between tightly bound soil water and MSW resuted in BSW with more depleted and variable stable isotopic feature than MSW. 2) Along with the thawing of the frozen soil, surface runoff and shallowsubsurface flow (SSF) at 30−60 cm was the major flow pathway in the permafrost influenced alpine meadow hillslope during spring snowmelt and summer rainfall period, reapectively, with the frozen soil maintaining supra-permafrost water level. 3) Comparison between two neighouring catchments under similar precipitation conditions indicated that streamflow of the lower catchment with less permafrost proportion and earlier thawing time has larger SSF and higher based flow component, indicating the potential changes of hydrological regims subject to future warming.</p>

In situ creep of frozen soil, Fenghuo Shan, Tibet Plateau, China

1995 ◽  
Vol 32 (3) ◽  
pp. 545-552 ◽  
Author(s):  
B. Wang ◽  
Hugh M. French
Keyword(s):  
Key Words ◽  
Power Flow ◽  
Field Data ◽  
Field Measurements ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Soil Creep ◽  
Extreme Variability ◽  
The Mean

Field measurements of frozen soil creep in the upper 3.0 m of permafrost indicate that creep occurs in both winter and summer. Between 1992 and 1993, the mean rate of creep ranged from 0.44 cm at 1.6 m depth to 0.16 cm at 2.8 m depth but there was extreme variability. Creep parameters n and A, as defined by the power flow law, were calculated from field data. Parameter n ranged between 1.96 and 2.29 and increased with depth, while A decreased with depth. Comparisons of creep rates for different permafrost environments suggest that ground temperature largely controls the magnitude of permafrost creep. Key words : permafrost, creep parameters, Tibet Plateau.

Cryogenic cave carbonate formation during the Industrial Era in the Central Pyrenees (Iberian Peninsula)

2021 ◽  
Author(s):  
Miguel Bartolomé ◽  
Ana Moreno ◽  
Marc Luetscher ◽  
Christoph Spötl ◽  
Maria Leunda ◽  
...  
Keyword(s):  
Spring Water ◽  
Ice Formation ◽  
Cumulative Probability ◽  
Temperature Record ◽  
Permafrost Degradation ◽  
The North ◽  
Carbonate Formation ◽  
Discontinuous Permafrost ◽  
Ice Retreat ◽  
Instrumental Temperature

<p>Cryogenic cave carbonates (CCC) are rare speleothems that form when water freezes inside cave ice bodies. CCC have been used as an proxy for permafrost degradation, permafrost thickness, or subsurface ice formation. The presence of these minerals is usually attributed to warm periods of permafrost degradation. We found coarse crystalline CCC types within transparent, massive congelation ice in two Pyrenean ice caves in the Monte Perido Massif: Devaux, located on the north face at 2828 m a.s.l., and Sarrios 6, located in the south face at 2780 m a.s.l. The external mean annual air temperature (MAAT) at Devaux is ~ 0°C, while at Sarrios 6 is ~ 2.5°C. In the Monte Perdido massif discontinuous permafrost is currently present between 2750 and 2900 m a.s.l. and is more frequent above 2900 m a.s.l. in northern faces. In Devaux, air and rock temperatures, as well as the presence of hoarfrost and the absence of drip sites indicate a frozen host rock. Moreover, a river flows along the main gallery, and during winters the water freezes at the spring causing backflooding in the cave. In contrast, Sarrios 6 has several drip sites, although the gallery where CCC were collected is hydrologically inactive. This gallery opened in recent years due to ice retreat. During spring, water is present in the gallery due to the overflow of ponds forming beneath drips. CCC commonly formed as sub-millimeter-size spherulites, rhombohedrons and rafts. <sup>230</sup>Th ages of the same CCC morphotype indicate that their formation took place at 1953±7, 1959±14, 1957±14, 1958±15, 1974±16 CE in Devaux, while in Sarrios 6 they formed at 1964±5, 1992±2, 1996±1 CE. The cumulative probability density function indicates that the most probable formation occurred 1957-1965 and 1992-1997. The instrumental temperature record at 2860 m a.s.l. indicates positive MAAT in 1964 (0.2°C) and 1997 (0.8°C). CCC formation could thus correspond with those two anomalously warm years. The massive and transparent ice would indicate a sudden ingress of water and subsequent slow freezing inside both caves during those years. Probably, CCC formation took place at a seasonal scale during the annual cycle.</p>

Taliks: A Tipping Point in Discontinuous Permafrost Degradation in Peatlands

2019 ◽  
Vol 55 (11) ◽  
pp. 9838-9857 ◽  
Author(s):  
Élise G. Devoie ◽  
James R. Craig ◽  
Ryan F. Connon ◽  
William L. Quinton
Keyword(s):  
Tipping Point ◽  
Permafrost Degradation ◽  
Discontinuous Permafrost

An Integrated Engineering Model for Prediction of Strain Demands in Pipelines Subject to Frost Heave

2006 ◽  
Author(s):  
Joe Zhou ◽  
Gordon Craig ◽  
Beez Hazen ◽  
James D. Hart
Keyword(s):  
Life Cycle Cost ◽  
Cost Optimization ◽  
Axial Direction ◽  
Gas Pipeline ◽  
Frost Heave ◽  
Engineering Model ◽  
Long Distance ◽  
Demand Prediction ◽  
Discontinuous Permafrost ◽  
Differential Frost Heave

Long distance pipelines are actively pursued by the industry to transport natural gas from remote arctic regions to markets. A chilled gas pipeline is one of the options to minimize the environmental impact resulting from operation of such pipelines. When a chilled gas pipeline crosses discontinuous permafrost areas, differential frost heave can occur. The result is pipe being subjected to potentially high strains, primarily in the axial direction. Reliable prediction of strain demands is one of the key components for a strain-based design process and it is essential for both ensuring pipeline integrity and facilitating life-cycle cost optimization for the design and maintenance of pipelines. The prediction of strain demands resulting from frost heave of chilled gas pipelines involves three fundamental engineering analysis processes. They are gas hydraulic analysis, geothermal analysis and pipeline structural analysis. Not only are these three processes complex, they are also mutually interdependent. To reliably predict strain demands and fully capture the interactions among these processes, TransCanada Pipelines Ltd. (TransCanada) and its partners developed an integrated engineering model on the basis of three well established programs for the three individual engineering processes. This paper will briefly review the integrated model for strain demand prediction.

scholarly journals An Automated Procedure for Assessing Local Reliability Index and Life-Cycle Cost of Alternative Girder Bridge Design Solutions

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Ilaria Venanzi ◽  
Riccardo Castellani ◽  
Laura Ierimonti ◽  
Filippo Ubertini
Keyword(s):  
Life Cycle ◽  
Life Cycle Cost ◽  
Design Solution ◽  
Bridge Design ◽  
Limit States ◽  
Technical Standards ◽  
Local Character ◽  
Repair Costs ◽  
Design Solutions ◽  
Girder Bridge

Stakeholders of civil infrastructures have to usually choose among several design alternatives in order to select a final design representing the best trade-off between safety and economy, in a life-cycle perspective. In this framework, the paper proposes an automated procedure for the estimation of life-cycle repair costs of different bridge design solutions. The procedure provides the levels of safety locally guaranteed by the selected design solution and the related total life-cycle cost. The method is based on the finite element modeling of the bridge and uses design traffic models as suggested by international technical standards. Both the global behavior and the transversal cross section of the bridge are analyzed in order to provide local reliability indexes. Several parameters involved in the design, such as geometry and loads and materials’ characteristics, are considered as uncertain. Degradation models are adopted for steel carpentry and rebars. The application of the procedure to a road bridge case study shows its potential in providing local safety levels for different limit states over the entire lifetime of the bridge and the life-cycle cost of the infrastructure, highlighting the importance of the local character of the life-cycle cost analysis.

Impacts of permafrost degradation on a road embankment at Umiujaq in Nunavik (Quebec), Canada

2011 ◽  
Vol 48 (5) ◽  
pp. 720-740 ◽  
Author(s):  
Richard Fortier ◽  
Anne-Marie LeBlanc ◽  
Wenbing Yu
Keyword(s):  
Numerical Modeling ◽  
Permafrost Degradation ◽  
Sand Layer ◽  
Geophysical Investigation ◽  
The Road ◽  
Access Road ◽  
Discontinuous Permafrost ◽  
Snow Fence ◽  
On The Road ◽  
Ground Penetrating

Differential subsidence of as much as 0.85 m is affecting the access road to Umiujaq Airport in Nunavik (Quebec), Canada, located in the discontinuous permafrost zone. A geotechnical and geophysical investigation including piezocone test, ground-penetrating radar profiling, electrical resistivity tomography, and numerical modeling of the thermal regime of the road embankment and subgrade is presented to characterize the ground stratigraphy and permafrost conditions and to assess the exact causes and effects of permafrost degradation on the road embankment. The subsidence is due to thaw consolidation taking place in a layer of ice-rich silt underneath a superficial sand layer. While the seasonal freeze–thaw cycles were initially restricted to the sand layer, the thawing front has now reached the thaw-unstable ice-rich silt layer. According to our numerical modeling, the increase in air temperature recently observed in Nunavik cannot be the sole cause of the observed subsidence affecting this engineering structure. The thick embankment also acts as a snow fence favoring the accumulation of snow on the embankment shoulders. The permafrost degradation is also due to the thermal insulation of the snow cover reducing heat loss in the embankment shoulders and toes.

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