Experimental Research On Shear Strength Under Negative Temperatures For Silty Clay

Ranked third in the world,much of the Chinese land is covered by frozen soil.As the raise of One Belt,One Road and Jing-jin-ji,the Eastern Area of Inner Mongolia and the Three Provinces in Northeast China economic district,almost all of the frozen regions in China are included in it.On the premise of the rapid growth of economy,more resources will be required to build roads and other transportation infrastructure.However,the trend of multi axle and heavy load will also increase the road’s risk of disaster.As one kinds of complex geology,the frozen soil will be a great treat to the safety of the road.In this paper,the shear strength of the soil in the frozen subgrade and the silty clay are selected as the applied background and research object,respectively.Based on the static triaxial tests and theoretical analysis,the property of shear strength for frozen silty clay was studied.And a model for shear strength which taken the temperature and initial water content into consideration was constructed.The main works of this article are:1.The reason for the problems which are often encountered during the low temperature triaxial test,such as the control to temperature is difficult,the loading rod is easy to freeze and confining pressure supply is blocked,is analyzed.And the liquid cooling,water absorption by the desiccant,replacement of the confining pressure piping system and other measures were given to make the tests conduct smoothly.The defects exist in previous tests,such as the selection of consolidation confining pressure and freezing method were improved,and it makes the testing conditions are more accord with the practical engineering.Meanwhile the reliability of the results is guaranteed and the test period is shortened.2.The results of different temperature and initial water content showed: the stress-strain relationship of frozen silty clay under 50 k Pa tends to soften,and with the decrease of temperature the softening tends to weaken.There exists a criticalvalue for the influence of temperature and water content on the specimens’ axial failure strain,although there are some exceptions.Below the critical value,failure strain raises with the decrease of temperature and the increase of water content.And above the critical value,the results are opposite.The initial tangent modulus of the same moisture content samples increase with the decrease of temperature.However,the increasing trend gradually decreased.The failure strength increases nearly linear with decreasing temperature,and the water content has a critical value to the failure strength.3.By the regression of experimental data,a linear model used to describe the changes of shear strength with temperature was established.Fitting the formulas of model coefficients with water content,and put them into the model given above,then a shear strength model considering temperature and water content was obtained.The comparison shows that model results can reflect the shear strength of frozen silty clay under different temperature and initial water content reliably.The results of this paper will provide some reference for the practical engineering and related research.