| The G215 Liuyuan-Dunhuang Expressway is a convenient and fast passage for Xinjiang,Inner Mongolia,and the Liuyuan Station of the Lanxin High-speed Railway to reach Dunhuang.It is also a backbone supporting passage for the Dunhuang Cultural Tourism Economic Circle.It is important for further improving the regional road network structure and speeding up the construction of a comprehensive transportation system.It is of great significance to promote the economic and social development of Jiuquan.Based on the research background of the most severe saline soil disease section of Liudun Expressway,combined with local hydrogeological and meteorological conditions,this paper investigates and analyzes the freezing and thawing mechanism of saline soil foundation and its damage to subgrade As the research object,the basic characteristics of saline soil were studied,and on this basis,the saline soil freeze-thaw test was designed,and the influence of different factors on the frost heave and thaw settlement deformation of saline soil was analyzed,and finally combined with field monitoring The data analyzes the actual situation of the highway,and the main research contents are as follows:(1)The frost damage phenomenon of the foundations and roadbeds of the K88+558～K88+758 section of Liudun Expressway was investigated,and the frost damage phenomena such as salt whitening,salt swelling,swelling,swelling,and road frost cracking in the saline soil area were learned on the spot.Combined with the local hydrogeology and climatic conditions,the formation and distribution of saline soil in this area were studied.On this basis,the frost heave and thaw settlement mechanism and influencing factors of the foundation soil in the saline soil area are preliminary analyzed.(2)Through routine experiments on the foundation saline soil,the particle composition and gradation composition,natural density and natural moisture content of the saline soil in this section were studied,and on this basis,the largest dry density and optimal moisture content of soil sample was determined..Through the research and analysis of the soluble salt characteristics and content of saline soil,the composition and content of soluble salt in the top soil,middle soil and lower soil of the foundation are obtained,and the basic properties of saline soil are determined.(3)Through the freeze-thaw cycle test of saline soil,the deformation characteristics of different salt content,soil sample compactness,and soil sample moisture content in saline soil under different temperature changes and freeze-thaw cycles were studied.law.Including the frost heave deformation and thawing deformation of each soil sample as the number of freezethaw cycles increases,as well as the trend and size of the corresponding deformation;and the influence of salt content,degree of compaction,and moisture content on the cumulative deformation of freeze-thaw;On this basis,the study summarizes the influence of temperature changes and the number of freeze-thaw cycles on frost heave and deformation of saline soil.(4)one-year monitoring of temperature and humidity at different depths in the saline soil foundation,as well as observation of the freezing and thawing settlement of the saline soil section foundation and roadbed.By monitoring the temperature and humidity in the saline soil foundation,the changes of the temperature and humidity at different depths in the saline soil foundation over time and its causes are analyzed.On this basis,combined with the observation of freezing and thawing settlement of the saline soil section foundation and roadbed,the law of freezing and thawing settlement of the foundation and its influence on the settlement of the roadbed were studied,and a comparative analysis was carried out in combination with different waterproof measures of the roadbed. |
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