Numerical Simulation of Frost Heave in Soils around the Buried Oil Pipeline in Island Talik Permafrost Region

A systematic method to obtain the freezing characteristics and the amounts of frost heave in the soils around a buried oil pipeline in island talik permafrost region is presented on the basis of the simulation of soil temperature fields and a classic segregated potential frost heave model. The finite thermal effect domain and the equivalent heat capacity method were adopted to analyze the heat transfer process with phase change. The calculation parameters were derived from the China-Russia Crude Oil Pipeline engineering. The developments of the annual maximum freezing circles and frost penetrations emerging in typical years within the pipeline operation life cycle under different oil temperature, different thickness of thermal insulation layer, and different water content of soils were investigated. The maximum frost heaves in four typical sections of island talik were predicted. The results can be used to further mechanical calculation and can provide references for risk evaluation and site management of the buried pipelines in island talik permafrost regions.

Stochastic Prediction for Frost Heave Effect of a Subway Tunnel

Horizontal freezing induces ground frost heave and ground displacement happens. Excessive uneven displacement or deformation may be dangerous to the surrounding building. The stratum that a Nanjing subway tunnel will traverse through is the soft and silt clay. The artificial freezing construction method is proposed to help the tunnel to traverse through the worse stratum. To control the ground building deformation and displacement due to the ground frost heave, the frost heave effect for the artificial freezing construction should be predicted before the construction process. The stochastic media theory is proposed to predict the frost heave effect due to the artificial freezing construction in the paper. The basic analysis procedure for analyzing frost heave effect is introduced and ground deformations such as ground vertical displacement, ground curvature are analyzed. The analysis result shows that the ground deformation due to the frost heaves is in the limit of ground displacement control requirement.

Establishment and Instrumentation of a Full Scale Laboratory for Thermal and Hygroscopic Investigations of Soil Behavior in Cold Climates

This study presents the establishment and instrumentation of a laboratory for investigating how different soils behave under controlled conditions in cold climates. Ground conditions are extremely important in regards to the building sector. Establishing new infrastructure and buildings require high competence about the ground/soils in order to build robust and long lasting foundations and constructions. In cold climates, soils are frequently exposed to freezing and thawing cycles, and building projects often require additional resources compared to similar projects further south. During 2009-2010, a new laboratory was established in Narvik, Norway. The laboratory consists of 4 different 6x6m bins containing different homogenous soils down to a depth of 3m. A special designed measurement frame has been placed inside each bin, which facilitates instrumentation for thermal and hygroscopic measurements. The laboratory has many applications which may lead to advances within knowledge about thermal response of soils, artificial thawing for more efficient building in cold climates, faster dehydration and curing of concrete during winter, improved road foundations and preventing frost heaves and so on. This study describes the laboratory setup and presents test measurements on thermal responses of sand, silty sand and gravel during artificial thawing using a hydronic thawing system.

Actinobacterial Nitrate Reducers and Proteobacterial Denitrifiers Are Abundant in N2O-Metabolizing Palsa Peat

ABSTRACTPalsa peats are characterized by elevated, circular frost heaves (peat soil on top of a permanently frozen ice lens) and are strong to moderate sources or even temporary sinks for the greenhouse gas nitrous oxide (N2O). Palsa peats are predicted to react sensitively to global warming. The acidic palsa peat Skalluvaara (approximate pH 4.4) is located in the discontinuous permafrost zone in northwestern Finnish Lapland.In situN2O fluxes were spatially variable, ranging from 0.01 to −0.02 μmol of N2O m−2h−1. Fertilization with nitrate stimulatedin situN2O emissions and N2O production in anoxic microcosms without apparent delay. N2O was subsequently consumed in microcosms. Maximal reaction velocities (vmax) of nitrate-dependent denitrification approximated 3 and 1 nmol of N2O per h per gram (dry weight [gDW]) in soil from 0 to 20 cm and below 20 cm of depth, respectively.vmaxvalues of nitrite-dependent denitrification were 2- to 5-fold higher than thevmaxnitrate-dependent denitrification, andvmaxof N2O consumption was 1- to 6-fold higher than that of nitrite-dependent denitrification, highlighting a high N2O consumption potential. Up to 12 species-level operational taxonomic units (OTUs) ofnarG,nirKandnirS, andnosZwere retrieved. Detected OTUs suggested the presence of diverse uncultured soil denitrifiers and dissimilatory nitrate reducers, hitherto undetected species, as well asActino-,Alpha-, andBetaproteobacteria. Copy numbers ofnirSalways outnumbered those ofnirKby 2 orders of magnitude. Copy numbers ofnirStended to be higher, while copy numbers ofnarGandnosZtended to be lower in 0- to 20-cm soil than in soil below 20 cm. The collective data suggest that (i) the source and sink functions of palsa peat soils for N2O are associated with denitrification, (ii) actinobacterial nitrate reducers andnirS-type andnosZ-harboring proteobacterial denitrifiers are important players, and (iii) acidic soils like palsa peats represent reservoirs of diverse acid-tolerant denitrifiers associated with N2O fluxes.

Remedial Measures to Tame the Frost Heaves at Gas Distribution Stations in West-East Gas Pipeline

The first West-East Gas Pipeline, running from the Tarim Basin gas fields in Xinjiang to the Yangtze River Delta area in China, is an 1016-mm-dia, 3900-km-long pipeline, the design capacity and pressure of which are 12 billion cubic meters annually and 10 MPa respectively. The whole pipeline was put into commercial operation on Oct. 2004, and the distribution stations suffered from frost heaves due to subfreezing gas temperatures, with obvious uplifts of valves from the bases, upheavals of the ground, and cracks of the paved surfaces and fence walls, and deformations of gas pipelines. From the commission on, the demand on gas in the downstream market was booming, and the company strove to upgrade the throughput to 17 billion cubic meters annually by building new gas compressor stations, so the more serious frost heaves are expected at the regulator stations. As we know, gas-fueled heaters can effectively tackle the frost heaves, but the difficulty of land acquisition, and more expensive CAPEX and OPEX limit the installation of the gas-fueled heaters. In this paper, various types of measures to cope with the frost heaves are compared and analyzed. Based on the geotechnical survey of field soils, theoretical calculations and actual data, soil replacement schemes with a water migration control technique are developed and successfully applied at different gas distribution stations with different water tables. The schemes are simple to use, and are cost-effective. When the remedial actions with this scheme are conducted, no interruptions of service are required. Furthermore, a large sum of expense is saved in comparison with the gas-fueled heaters.