Study On The Mechanical Characteristics Of Subgrade Soil Of Zhang-cheng Expressway Under Freeze-thawing Cycle

As one of the trunk lines that constitute the layout of Hebei Province and Beijing-Tianjin-Hebei Expressway Network,Zhangcheng Expressway plays an extremely important role in promoting the integration of Beijing-Tianjin-Hebei,improving the traffic conditions in the northwestern part of Hebei Province,and realizing the "East to the West".The Zhangcheng Expressway is located in the northern part of Hebei Province and belongs to the seasonal frozen area.With the increasing traffic volume and the increase in road use requirements,the temperature changes,especially the roadbed pavement diseases caused by the freezing and thawing effect,have become more and more serious.The direct or indirect diseases caused by the freezing and melting of road genes have severely affected the service level of highways and increased the cost of maintenance and repair.Therefore,it is urgent to study the physical and mechanical characteristics of the subgrade fill soil under the freezing and thawing cycle of Zhang Cheng Expressway.Therefore,it provides data and theoretical support for the solution of freeze-thaw diseases in subgrade subgrade of highway in seasonal frozen area.Taking Zhangcheng high-speed roadbed filling as the main research object,this paper first selects roadbed filling soil in different areas on the main line for basic physical characteristics tests,including particle analysis,liquid plastic limit test and indoor compaction test.The engineering properties and classification of subgrade soil were determined,and the soil used for subsequent tests was initially allocated according to the principle of optimal water content.Then the static triaxial test of the test soil sample which is not consolidated or drained is carried out,and the static parameters of the soil sample including static strength,shear strength index and static elastic modulus under different pressure,number of freeze-thaw cycles,negative temperature in different environments,and compaction are explored.The variation curves of static parameters under different influencing factors are fitted,and the multiple nonlinear regression equations of static strength,static elastic modulus and shear strength index are proposed.Finally,the dynamic parameters including dynamic strength,dynamic elastic modulus,friction angle and cohesive force under different compressive conditions are studied in this paper.The regression formulas of dynamic cohesive force and maximum dynamic elastic modulus are pointed out according to the results of various influence factors.It is hoped to provide data reference for the follow-up construction and maintenance operation of Zhang Cheng Expressway and the expressway in the same frozen area.