Experimental Study On Compressive Deformation And Microscopic Properties Of Remolded Loess Under Coupling Effect Of Dry-wet And Freezing-thawing

With the accelerating of urbanization,the gully terrain in the loess area has limited the development of the city.Therefore,many cities carry out large-scale "excavating hill and filling gully" projects,which also brings about many loess engineering problems.Taking the project of Yan'an New District as the background,and remolding loess as the research object,based on experiments,macroscopic compression deformation analysis and microstructural studies were combined to study the coupling effects of remolded loess under the wet-dry and freeze-thaw cycles.Deformation characteristics and microstructure characteristics were obtained.The main research contents and research achievements are as follows:(1)By remodeling different dry density of loess,and imposing different cycle number tests and freeze-thaw cycle tests,combining with consolidation and compression test results,the stress-strain relationship and compressive modulus of the soil samples with different cycle times are related to the number of cycles and the sides are established.The fitting relationship between the limited compressive strain and the number of cycles reveals the deformation mechanism of remolded loess under the action of dry and wet cycles and freeze-thaw cycles.(2)By the coupled experiments of the wet and dry cycles of and freeze-thaw cycles of remodeled loess,the sensitive parameters affecting the compressive deformation of the soil samples are obtained,and their respective weights are obtained through multiple linear regression analysis;the superposition between the internal structure differences of the soil and the single factors is analyzed.The effect of the wet and dry cycle plays a leading role in the coupling,and the freeze-thaw cycle plays a certain role in promoting.Based on the existing constitutive model of compacted loess,a pressure constitutive model for compacted loess considering the number of cycles was established.(3)The microscopic structure of remolded loess was studied by electron microscopy scanning.The changes of microstructures of soil samples with different cycle times were studied by a combination of qualitative and quantitative methods.The microstructure of remolded loess was studied for its macroscopic deformation characteristics.Eleven representative microstructure parameters were selected for quantification,and the selected microstructure parameters were correlated with the macroscopic compressive deformationparameters of the remolded loess by the grey correlation analysis principle.Microstructures parameters closely related to macroscopic compression deformation characteristics were obtained.