Experimental Research On The Thaw Settlement Characteristics Of Pisha-sandstone In Ordos

Pisha-sandstone in Ordos of Inner Mongolia belongs to continental clastic rock series, and most are white, gray, purple sandstones and siltstones. Since this area has a typical temperate continental climate with great temperature difference between day and night in early spring and late winter, Pisha sandstone shrinks and expands alternately with frequent changes between "water" and "ice" phase, making Pisha-sandstone structure more loose and the cementing force weak. Repeated alternation and conversion of freezing and thawing processes changes the structural connection and arrangement mode of the Pisha-sandstone soil, leading to changes in its physical and mechanical properties. In recent years, with the gradual increase of local water conservancy projects, water and soil erosion, slope stability and other issues in Pisha-sandstone region have brought great trouble to the construction there, so the study for the freeze-thaw characteristics of Pisha-sandstone is particularly important.In this paper, the author conducts freeze-thaw property experiment different dry density, moisture and freezing temperatures of Pisha-sandstone in Jungar Banner area, Ordos City and makes in-depth analysis of the thawing settlement characteristics of Pisha-sandstone under multiple factors in order to reveal the role of thawing settlement on structural changes of Pisha-sandstone and provide a reference for further research on freeze-thaw mechanism of Pisha-sandstone.The results show that:in freezing (thawing) process, the most significant factor influencing the frost heaving ratio(thawing settlement coefficient) of Pisha-sandstone is moisture content followed by cold junction temperature, while the weakest factor is the dry density; in thawing process, there is a starting thawing settlement moisture content of Pisha-sahdstone, and when the moisture content is greater than the starting moisture content, thawing settlement happens otherwise thawing expansion happens; thawing settlement coefficient of Pisha-sandstone is related to the dry density, and the smallest thawing settlement coefficient comes when the dry density is 1.80g/cm3; thawing settlement coefficient of Pisha-sandstone increases with decrease in the freezing temperature under the condition of the same moisture content and dry density. Furthermore, using SPSS statistical analysis software, the author gets the thawing settlement regression model of Pisha-sandstone under the combined action of the dry density, moisture content, and cold junction temperature, and this model can describe the laws of the thawing settlement of Pisha-sandstone.