Experimental Study On Mechanical Properties Of Frozen Clay In Ningdong Mining Area, China

In recent years,with the continuous implementation of China's western development strategy,Inner Mongolia,Gansu,Shanxi,Shanxi and other regions have set off a new wave of coal mine construction.The mechanical properties of frozen soil have an important impact on the construction of mines.A lot of research has been done on the physical and mechanical properties of frozen soil.Due to the special engineering hydrogeological conditions in Ningdong area,there are many uncertainties.The research on the mechanical properties of frozen soil in Ningdong area is relatively rare in China,so this paper makes a further study on the mechanical properties of frozen soil in Ningdong area.I hope to provide a certain reference for mine construction in Ningdong area.Based on the construction of the Hongdunzi mining area in Ningxia,this paper takes the frozen soil of the main and auxiliary mines of the Hongsi Mine as the research object,and uses the specific heat test device,thermal conductivity tester,and computer controlled frozen soil test machine to explore the frozen soil physics.Mechanical properties,including composition of frozen soil,thermophysical properties and influencing factors,uniaxial compression test,triaxial shear test and uniaxial creep test,and further explored the constitutive model of frozen soil,the results obtained are as follows:1.Frozen soil is a relatively complex system consisting mainly of solid(solid mineral particles),liquid(unfrozen water)gas and ice.The main thermal parameters are the freezing temperature of the soil,the specific heat capacity of the frozen soil,and the thermal conductivity of the frozen soil.The freezing temperature of soil is related to the grain thickness,water content and depth: the freezing temperature of the grain is low,and the freezing temperature is high when the grain is coarse.With the increase of water content,the freezing temperature shows an upward trend,and the freezing temperature increases with the depth.The specific heat capacity of the frozen soil is related to the mineral content of the soil layer and the water content: the higherthe mineral content in the soil layer,the higher the specific heat capacity of the soil skeleton,the higher the water content,the higher the specific heat capacity of the soil,and the thermal conductivity and moisture content of the frozen soil.,soil and temperature-related: the thermal conductivity increases with the increase of ice content,the thermal conductivity of coarse particles is larger than the thermal conductivity of fine particles,and the thermal conductivity of frozen soil increases slowly with the decrease of negative temperature;The frost heaving property of soil is related to the water content.The higher the water content,the greater the frost heave force.2.The uniaxial compression test was carried out under the three temperature gradients of-5 ?,-10 ? and-15 ? to obtain the stress-strain curve of the uniaxial compressive strength of the frozen soil and the elastic modulus of the frozen soil.Compared with Poisson's ratio,the experimental structure shows that the compressive strength of frozen soil increases with the decrease of frozen soil temperature,and the increasing trend tends to be slower;the uniaxial compressive strength increases with the increase of water moisture content.The trend of convex parabola changes;within a certain range,the uniaxial compressive strength of frozen soil becomes larger and larger with the increase of stress loading rate;the elastic modulus of frozen soil increases with the decrease of temperature,and this The increasing trend tends to be slow;with the increase of water content,the elastic modulus of frozen soil shows a trend of convex parabola;the Poisson's ratio of frozen soil decreases with the decrease of temperature and water content.3.The triaxial shear test results of frozen soil show that the lower the temperature,the larger the value of the cohesive force of frozen soil,the lower the internal friction angle of frozen soil decreases with the decrease of temperature;the cohesion and internal friction of frozen clay The angle decreases with increasing water content;as the confining pressure increases,the shear stress-axial strain curve softens after reaching the strength limit.4.The uniaxial creep test was carried out on the frozen clay in the Hongdunzi mining area in Ningxia.The basic parameters including m value,A value,? value and value were determined,and the constitutive equation of frozen soil under simple stress was determined.