Study On Deformation Characteristics And Ricrostructure Of Mauve Pisha Sandstone Under Freeze-thaw Cycle

Sediment of pisha sandstone area is.in non runoff dominated the formation of freeze-thaw and weathering erosion based runoff formation,as a kind of specific form of temperature change,the freezing and thawing cycles can be understood as a kind of special strong weathering.In the Inner Mongolia Autonomous Region Erdos Zhungeer County red pisha sandstone as the research object,and analysis the influence of moisture content and times of freezing and thawing undisturbed frozen pisha sandstone through laboratory experiments.The results show that:each freeze-thaw cycle of Pisha Sandstone generally experience five stages,such as:rapid cooling,constant freezing and rapid warming,thawing thermostatic and continue to heat up.Freezing and thawing cycle can be very clear response to the inter conversion of the interior heat changes of pisha sandstone solid and liquid phase in freezing and melting,it also reacts with volume change of pisha sandstone in freezing and thawing.frost heave were to follow the law of logarithmic function increases with time increase in the freezing process;times of freezing and thawing is closely related with the frost heaving ratio and water content;the moisture content is in a certain threshold range,and the thawing settlement is increasing with the regularily increase of the number of freeze-thaw cycles.The moisture content of original pisha-sandstone stratum was 12%to 13%,when the moisture content is less,thawing settlement coefficient increases with the increase of moisture content,when moisture content of pisha-sandstone stratum reaches a certain threshold,thawing settlement coefficient increases with the number of freeze-thaw cycles and tends to be gentle.The moisture content is the major factor that affects the total deformation of the freezing and thawing process,the moisture content of small undisturbed pisha-sandstone stratum occurred in compression deformation,on the contrary,the uplift deformation.No matter how other factors in the freezing and thawing cycles,the final thaw settlement will tend to be stable.Moisture content is low,the internal structure difference is relatively uniform,Moisture content increases,major changes have taken place in the elevation difference of ups and downs.With the increase of moisture content,>75 um aperture porosity shows the tendency of increase with the increase of moisture content.After freezing and thawing of the specimen under a state of large moisture content,total internal porosity is reduced compared with before freezing and thawing.With the increase of water content in pisha sandstone,the complexity of pore structure in reducing,Under the influence of freezing and thawing conditions,The influence of the self condition began to weaken,and the freezing thawing occupied the main factor of the pore structure complexity.