Mechanical Properties Experimental Study And Numerical Analysis Of Reinforced Clay Structure In Seasonal Frozen Regions

Seasonal frozen soil accounts for about 53.5% of the total area in China.The freeze-thaw cycle(FTC)leaded to the destruction of the subgrade in the frozen soil area,mainly because the shear strength of the soil was decreased after FTC.The cohesion and internal friction angle were two important indicators of shear strength.Reinforcement could improve the strength of the soil after freeze-thaw(F-T),and effectively restrain its F-T deformation.Different conditions of initial reinforcement and F-T affected the soil strength after F-T differently.To comprehensively consider the influence of each main factor and their interactions on the shear strength index of the soil after F-T,this paper took the silty clay in Shenyang area as the research object,carried out 25 sets of indoor FTC orthogonal tests under conditions of different initial moisture content,compaction degree,reinforcement spacing,F-T times,freezing temperature and external load.Through the shear test and the moisture content test,the soil cohesion,internal friction angle,and moisture content of the soil after F-T were measured at the specified height of the soil under each F-T condition.The regression equations of cohesive force,internal friction angle and moisture content expressed by various influencing factors were fitted by SPSS software,and determined the importance of each factor on the soil cohesion,internal friction angle and moisture content after F-T.MATLAB software was used to optimize the regression equation,the optimal values of the soil cohesion,internal friction angle and moisture content after F-T and the corresponding combined values of various influencing factors were obtained.The main research results were as following:(1)The reinforced soil with a reinforced spacing of 15 cm had the largest cohesion after F-T when the initial moisture content was less than 24.6%.(2)The order of the influence of each factor on the cohesion of soil after F-T from high to low was the initial moisture content,reinforcement spacing,and compaction degree,and the order of the influence on the internal friction angle from high to low was reinforcement spacing,compaction degree,and initial moisture content.(3)The optimal combination values of the reinforced soil were: initial moisture content 12%,compaction degree 96%,reinforcement spacing 15 cm,and the corresponding upper,middle and lower cohesion were 6.56 k Pa,9.534 k Pa,and 7.062 k Pa,the internal friction angles were 25.11 °,26.28 °,and 26.02 °,and the moisture contents were 22.92%,23.74%,and 24.67%,respectively.ANSYS software was used to carry out finite element analysis on the given embankment model.The soil,geogrid and contact surface were adopted the D-P model,one-dimensional element model only allowed to withstand the tensile force,and the Goodman element model,respectively.The same mechanical performance parameters were inputted to the embankment model to obtain the corresponding contour maps of displacement and shear stress and analyze the extreme values.By comparing the effect of unreinforced and different reinforced methods on the displacement and shear stress of reinforced embankment,the 15 cm reinforcement spacing was determined as the optimal value,which provided a basis for reinforced structure design and construction in the seasonal frozen regions.