The Experiment Of Direct Shear Creep Of Clay Under Freeze-thaw Cycle

With the development of society and economy,the construction in the permafrost zone and resource development is increasing,and some disasters of geology and engineering often occur in the permafrost zone.The above-mentioned problems are closely linked with freeze-thaw effect and creep characteristics of rock and soil.Currently the study of freez-thaw and creep in geotechnical aspects of the research is still shallow.Based on the above results of previous studies,clay is chose for studying its creep characteristics under freeze-thaw cycles.(1)Experimental study is done for creep clay.The clay soil sample in the experiment is taken from Dayan Zhanihe River open pit.The remodeling clay specimens of initial moisture content of 15%,25% and 35% are made and respectively undertake 0,1,3,6,10,15 number of freeze-thaw cycles.The creep strain-time curve of clay specimens is drawn.The result shows that the creep deformation of clay specimens is proportional to freeze-thaw cycles and water content.The creep deformation change more obvious after the first freeze-thaw cycle.Creep curve increases gradually gather with the freeze-thaw cycles increasing.Creep deformation amount increases with increasing initial water content.The creep deformation is more impacted by the initial moisture content compared to freeze-thaw cycles.(2)The shear strain-stress curve analysis shows that creep is non-linear,is proportional to shear strain and shear loads.Nonlinearity becomes stronger with the increasing of shear loads and time.In this experiment,shear creep belongs to attenuated creep.Shear creep strain develops over time tends to a limit.Obvious inflection points don't appear on isochronous curve,therefore shear load does not exceed the long-term strength of clay.Shear strain increases with the increasing of shear loads and freeze-thaw cycles.The nonlinearity of shear creep is enhanced with increasing number of freeze-thaw cycles.(3)The analysis of the parameters of creep shows that the shear strain rate decreases with time,increases with the number of freeze-thaw cycles and with the moisture content.Viscosity increases with time,decreases with the shear stress and with the freeze-thaw cycles and decreases with the moisture content.(4)The creep equation of empirical model and theoretical model are applied for curve fitting.The empirical models of the type of power function and logarithmic function are chose.And the 5 element Kelvin model is chose as theoretical model.The result shows that the degree of fitting of the creep equation of theoretical model is better than the one of empirical model.