The Statistical Analysis And Classification Study On Thawing Settlement Characteristics Of Permafrost

The thawing settlement of permafrost is overlaying soil happen settlement under the dead load and external pressure as result of increasing seasonal thawing depth and underground ice or permafrost layer's partial thawing caused by ground temperature which is related to nature and human being. Engineering examples have proved that uneven settlement of the foundation is the main reason of building damage in permafrost regions.This paper makes a research on thawing settlement experience of the permafrost along the pipeline based on china-russia oil pipeline. Under the development of economy, in spite of the continuous improvement of petroleum pipeline technology in permafrost region, thawing settlement still is a tough issue, especially in the situation of relative deficiency on engineering experiences in our country. So, it is very important to study the thawing settlement of permafrost in oil pipeline region.This paper is divided into five parts.The first part discusses the compositions of permafrost's effect on the quality of permafrost. The permafrost's composition soil particle,ice,water and gas, determines the permafrost's property ,and affects freezing and thawing of permafrost. In addition, background and significance of researching on permafrost thawing settlement is outlined. Finally, the research situation about thawing settlement characteristics at home and abroad, and the general contents and technical route in this paper are introduced.The second part starts with principle of thawing settlement, and introduces the basic principle of thawing settlement test, afterwards, and some basic works and some notices during the test. Finally, it generalizes the results of the thawing settlement test.The third part is the statistic analysis on the results of thawing settlement test. The thawing settlement characteristics is mostly affected by earthiness, water content, temperature, load and the like.The effects of water content and dry density to thawing settlement are discussed in this paper, such as the relation of water content with thawing settlement coefficient, the relation of dry density with thawing settlement coefficient, thawing settlement characteristics of different soil , comprehensive effect of water content and dry density to thawing settlement coefficient of different soil. The fourth part are classifications of thawing settlement results of permafrost on this test, which is based on the research on relation between water content and thawing settlement coefficient. The thawing settlement characteristics of permafrost are divided into five grades un-thawing settlement, weak thawing settlement, thawing settlement, strong thawing settlement, thawing collapse. This paper finds the limit water content under each thawing settlement grade of different soils using empirical formula between water content with thawing settlement coefficient. Finally, it takes a comparative analysis with criterion.It is the conclusion in the fifth part. Though statistic analysis on factors which affect thawing settlement coefficient of permafrost, it gets the rules that is approximate linear relationship between water content and thawing settlement coefficient, namely the thawing settlement coefficient's increase following the water content's, and approximate logarithmic relationship between dry density and thawing settlement coefficient, namely the thawing settlement coefficient's decrease following the dry density's. In addition, the effect of water content to thawing settlement coefficient is more than dry density of all the soils except the gravel soil containing fine grains. By making comparative analysis on thawing settlement coefficients of the different un-peat soils, it finds that the sensitivities'ranking of thawing settlement coefficient to water content from strong to weak is silt, clay, gravelly soil, weathered rock. By making comparative analysis to thawing settlement coefficients of the different peat soils, it finds that the sensitivities'ranking of thawing settlement coefficient to water content from strong to weak is peaty clay, peaty gravel soil containing fine-grain, peaty soil, turfy soil. By making classification of thawing settlement characteristics of different soils, it gets the results of this test are more than criterion value. Moreover,the thawing settlement characteristics of peat soil, turfy soil, weathered rock,peat clay and peaty gravel soil containing fine grain, peaty soil not mentioned in criterion that are classified in this paper.