Study On Static And Dynamic Mechanical Behavior Of Highway Subgrade Soil In Zhangjiakou Seasonally-frozen Area

China's highway construction has entered a new era with the implementation of the major national strategy on the integrated development of Beijing-Tianjin-Hebei and the successful application of the 2022 Winter Games in Zhangjiakou(city of Hebei province).Zhangjiakou locates at seasonally-frozen area.At the same time,with its increase of traffic density,road-using frequency,the damage caused by change of temperature become more serious.The freeze in winter and thaw settlement in spring become more and more obvious,affecting use of the road and increasing maintenance cost.On the basis of reasonable absorption and reference of previous studies,the thesis,taking the soil of highway subgrade in Zhangjiakou areas as research object,studies static and dynamic mechanical behavior of subgrade soil by static and dynamic triaxial compression test under freeze-thaw cycles.It aims to explore the influence of freeze-thaw cycles on subgrade strength and deformation property of highways in seasonally-frozen area in Zhangjiakou.The main contents are following:(1)The basic physical property of sample soil is analyzed,including grain size analysis test,liquid plastic combine test and compaction test,engineering classification results of soil can be gotten according to experimental results.Soil is shaped in the light of optimum water content.These samples are available to be tested on freeze-thaw cycles process and applied in triaxial compression test.(2)Indoor static triaxial compression test is operated under unconsolidated and undrained condition,so as to explore change laws of static strength,internal friction angle,cohesive strength and static elastic modulus of soil sample with different times of freeze-thaw cycles,compaction and environmental negative temperature.Furthermore,static parameters under different impacts are fitted to conclude multiple nonlinear regression formula for static strength,cohesion and static elastic modulus.At last,the significance of different impacts is estimated by means of orthogonal design.(3)Dynamic triaxial compression test is operated to investigate the change laws of dynamic strength,dynamic cohesion and dynamic internal friction angle,dynamicelastic modulus with different times of freeze-thaw cycles,compaction and vibration frequency.Furthermore,the change laws of dynamic parameters under different impacts are fitted to conclude multiple nonlinear regression formula for dynamic cohesion and maximum dynamic elastic modulus.At last,the significance of different impacts is estimated by means of orthogonal design.