| Due to the complexity of the permafrost structure in the Qinghai Tibet Plateau and the mutual thermal coupling between the existing structures and the frozen soil,the base pole of the frozen soil road is liable to produce heat and thawing subsidence,frost heave,pulp and subgrade cracks,and most of the diseases are caused by the frost heave and thawing deformation of the frozen soil.Based on the national "G109 Golmud Nagqu reconnaissance and design" project,the basic physical parameters of the survey and drilling in the permafrost section along the Qinghai Tibet highway are first determined.Secondly,the soil samples are tested in the laboratory to determine the amount of thawing settlement and the deformation of the thawing soil,and the frozen soil is calculated.The influence mechanism of the factors such as soil quality,water content,dry density and pressure on the melting compression coefficient is studied.Finally,the distribution of soil quality along the Qinghai Tibet highway and the spatial distribution of the melting compression characteristics along the Qinghai Tibet highway are studied by using the method of regional division and mathematical statistics,and the main conclusions are drawn.As follows:(1)When the same water content is in the range and the dry density is close,the influence regularity of the soil quality to the thawing coefficient is satisfied: the silty clay >silt soil > all weathered rock > Sand > gravel soil;the coefficient of soil thawing subsidence increases with the water content,and decreases with the increase of dry density,and the pressure is 50,100,200,400,and 600 KPa pressure.Under the action of loading,the melting compression coefficient increases with the increase of water content,and the higher the water content,the smaller the dry density,the more obvious.Under the same condition,the melting compression coefficient increases significantly with the increase of the vertical pressure.(2)The main soil quality in the Kunlun Mountains area is silty clay,sandy soil and gravel,and three accounts for more than 75%.The region of the Chu marar river is mainly powder clay,sandy soil and gravel,and three accounts for more than 90%;Beidaihe to Tanggula and Intermountain basins are dominated by silty clay,with a proportion of more than 50%.The order of the characteristics of soil thawing characteristics in different areas is:all weathered rock,gravel soil > gravel soil > sand soil > silt soil,the high plain area of the zumar River,all weathered rock > powder clay > Sand > gravel > gravel soil > Beidaihe to Tanggula Mountain Area and Intermountain basin area,sand soil is more than gravel.Soil is completely weathered rock,silty clay,silt.(3)On the soil type,the total weathering rock in three areas has high strength of melting and sinking,and the silty clay,sand and gravel soil are medium,and the silt is the lowest.Concretely,the thawing coefficient of silt,silty clay,fully weathered rock and gravel soil in Kunlun mountain area is higher,the high plain of the Chu marl River,the Beidaihe to the Tanggula Mountain and the Intermountain basin are lower,and the sand is higher in the mountainous area of Kunlun,the Beidaihe to the Tanggula Mountain and the Intermountain basin,and the thawing property is similar.In the high plains,chumar River thawing settlement coefficient is low.(4)From the Kunlun Mountains to the Tanggula Mountain Road of the Qinghai Tibet highway,the overall variation of the average compression coefficient of all kinds of soil under different pressure loads is first reduced and then increased.The compaction property of silt,sand and gravel soil is the strongest in Beidaihe to the Tanggula Mountain Road section.The Kunlun Mountains area is stronger and the zumar river is weak.The silty clay is the strongest in Kunlun Mountains area,the trumar River,Beidaihe to the Tanggula Mountain Road section is close,the range of change is not more than 1.11%,of which the pressure load is 50 KPa.The intensity regularity of the chemical compression characteristics is: the Kunlun Mountains area > the Chu marar River Area > from Beidaihe to the Tanggula Mountain Area;the fully weathered rock is the strongest in Kunlun Mountains area,the Beidaihe to the Tanggula Mountain Road is weak,and the Chu marar river is the weakest.(5)There are large thawing compression variables in the sections of K2879+980~K2880+258.8,K2881+333.5 and K2882+100~K2883+656.5 in the Kunlun Mountains area of the Qinghai Tibet highway.The maximum deformation of soil is more than 20 mm and belongs to the weak subgrade section.There is a larger thawing compression variable and the largest change of soil mass in the K2942+576.5 and K2944+057.5 sections of the zumar river.The shape is close to 9mm,and there is a large settlement deformation at K2952+885.0,and the K2957+182.5~K2958+137.5 section has alarge compression deformation under the action of 600 KPa load,and the shape variable is about 10 mm.The soil stability is better under the natural compression condition of the Beidaihe to the Tanggula Mountain Road section(K3046+637.5~K3307+150),and under the action of 600 KPa pressure load,the rock and soil composition of the K3136+020 and K3247+200~K3274+410 sections are mainly sand soil,the average water content is w >25%,which belongs to the ice rich frozen soil,and is compressed and deformed when it is subjected to the external load.It is obvious that the average shape variable is greater than 10 mm. |
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