The Research For Rational Burying Depth Of Underground Water Pipeline In Cold Region

Permafrost is also known as the soil with ice, is a kind of composite soil,composed of porous medium soil skeleton, ice crystals and unfrozen water. Inaccordance with the freezing time length, permafrost can be divided into short-term,seasonal frozen soil and permafrost soil. Frozen soil is a soil medium that is verysensitive to the temperature, the long-term strength is much lower than theinstantaneous strength, therefore in the permafrost regions project will face two majorproblems, frost heaving and thaw settlement. The freezing damage of the buriedpipeline crossing in seasonal frozen soil and permafrost zone is the most commonsecurity problem. Due to the characteristics of the frozen soil environment with waterand heat sensitive, so the pipeline to the underlying permafrost damage has a certainlag, so that the permafrost daverse effect on pipeline are often in the production after acertain period of the pipeline, frost heave effect must be safe thawing permafrostengineering problems for further study, considering the temperature field of frozensoil, soil frost heave, thawing settlement control process, for accurate prediction offreeze-thaw damage, set against the science effective method has practicalsignificance.Water supply pipeline in the medium temperature of seasonal frozen soil layer ofsecurity is-4~-5℃,also need to consider the frost heave of soil,it should be noted inthe determination fo depth. Water supply pipeline in seasonal frozen soil in general isnot easy to freeze, even in the water temperature is0.4℃,many factors affect thewater temperature, water temperature decrease is the result of many factors.Determination of water supply pipeline in frozen area depth, should mainly considerthe relation between pipeline and frozen lines, pipelines and its properties, in thenetwork and the influence of external factors and several factors determine thepipeline and the frost line relationship. The buried pipeline in permafrost maximumfreezing depth0.5~0.6m is safe.Because the soil is a natural porous medium, the seepage mechanics and theprinciple of heat transfer, physical and mathematical model of permafrost pipeline,numerical calculation is carried out on the soil temperature field around undergroundpipeline in permafrost region.The main work of this paper:(1)factors affecting the depth of buried pipeline are analyzed, including thermalanalysis and calculation of buried pipeline in permafrost environment. Conclusionsare drawn as follows:The more close to the ground, the external effects of air temperature on soiltemperature is more obvious. The change of soil temperature lag behind the airtemperature. From the formula, there is significant correlation between soil freeze-thaw depth and surface negative accumulated temperature.(2)numerical calculation of temperature in economic field equation of buriedpipeline buried depth based on non steady control equations of soil temperature fieldaround the buried pipeline in cold region, focus on buried pipeline with initial andboundary conditions, namely soil periodic change of the initial temperature, thesurface of buried pipelines is simulated, analyzed the change trend of the same time,different buried depth of soil temperature field, in order to determine the depth ofburying pipeline more appropriate. Study on the changes of soil temperature field inthe unfrozen and frozen.(3)The technology of buried pipe is also discussed.Practice has proved when the temperature of the soil is about-4to-5,waterpipeline in seasonal frozen soil layer can be safe in the operation, but also need toconsider the factors such as soil frost heave, determining the depth of the pipelineshould be considered.In general the pipeline buried in the seasonal frozen soil is not easy to be frozen,as long as the guarantee that the flow of water, even when the temperature of water is0.5℃,but there are many factors that influence the changes of the pipelinetemperature. Various factors contribute to the reduction of the temperature.The depth of the pipeline is determined by the curve of the ground temperaturedistribution.The relationship between the position and the frozen pipeline is the mainconsideration to determine the depth of pipeline, but also consider the nature of thepipeline, the role of pipeline in the network and external factors, they are the factorsaffecting the relationship between the location of the pipeline and the frost line.