Engineering Geological Research On The Permafrost In High Latitudes Area And Its Impact On Pipeline Construction

The engineering geological character of permafrost and its coherent problems are the global difficult engineering problems which are suffered during the oil and gas pipeline construction. Therefore, this study takes the Russia-China oil pipeline project being planed now for example, starting from the engineering geological problems which might be met in the pipeline construction in the permafrost region of nigh latitude in China, on the basis of the generalization of the main character and distribution regulation of the permafrost region of high latitudes in China, and associated with the linear engineering project construction of railway and road, the essay explains some engineering geological problems of perma frost and its forming mechanics. The study makes testing systematically and makes statistic analysis or the engineering geological character of permafrost, and the essay also makes synthesis appraisal of the engineering geology condition of permafrost along the Russian-China Oil Pipelin Project, which is beneficial with high theoretical and practical significance.The analysis and research indicate that the permafrost distribution has close relation with the factors of latitude, elevation, tiny physiognomy, terrestrial heat and so on. On the whole, the distribution of permafrost is not continuous, which transfers from the north of large island area permafrost distributing to the south of sporadic area permafrost distributing. Owing to the globe getting warmer, the degradation trend of permafrost is apparent. According to the permafrost degradation of the research, the degradation in the north mainly represents a quantitative change, while in the south it represents a qualitative change.The field geological research indicates that the permafrost type is mainly of much ice- more ice - most ice, and there are ice layers containing soil distributing in the swampland area. This essay systemically expatiates the engineering geological character of permafrost in study area based on large quantity of experiment data, which include basic physical index, thermo-physical index, dynamics character, as well as the character of melt and compression. The study also statistically analyses the correlation relation among the factors of intensity and negative temperature of permafrost, lithology, water content, and the external force time.The simulating result of the interactivity between the frost and the pipeline indicates that the buried pipes can lower the soil temperature and form upward forces to the pipeline in winter, while in summer the buried pipes will cause the frozen soil melt, both the frost heave and the thaw collapse can make the pipeline distorted and bent. By analyzing the interactivity between the frost and basic foundation, the permanent load of the building which can not overcome the frost-heave force is the main cause of leading to foundation frost heave and damage, and the magnification of the compression coefficient during the frozen soil melting is the ultimate cause which leads the frozen soil thaw collapse.It's necessary to accumulate the engineering experience and experimental data of the perma frost region during the engineering practice. The basic testing data and the statistic analysis of the perma frost character obtained in this study along the Russia-China crude oil pipeline have high practicability and popularizing value for the frozen soil engineering geological synthesis appraisal of high latitude permafrost region and the solution of the frozen soil engineering geological problems.