干湿循环作用下易溶盐含量对伊犁黄土强度的影响OA

[Objective]The macroscopic and microscopic mechanisms of loess strength degradation under the coupled effects of wet-dry cycles and soluble salt content were analyzed in order to provide a basis for engineering construction and geologic disaster prevention and control in the Ili region.[Methods]The typical loess from the Ili region was taken as the research object.The influence of different numbers of wet-dry cycles and different soluble salt contents on the mechanical properties and microstructure of loess was analyzed through triaxial shear tests,scanning electron microscope(SEM)tests,and nuclear magnetic resonance(NMR)tests.[Results]① The cohesion decreased by approximately 17.5％after only 10 wet-dry cycles(η=0％).When the soluble salt content increased from 0％to 2％(N=0),cohesion decreased by about 3.5％.However,under their coupled effects(N=10,η=2％),cohesion decreased by 24.3％,demonstrating a significant synergistic deterioration effect.② Soluble salts exerted a highly significant influence on both cohesion and internal friction angle,while wet-dry cycles had a highly significant influence on cohesion and a significant influence on internal friction angle.③ Under low confining pressures,the failure mode of loess shifted from brittle to plastic failure.Under high confining pressures,although the strength remained relatively high,degradation continued.④ With increasing numbers of wet-dry cycles and soluble salt content,fracture development occurred,gradually increasing the pore fractal dimension and pore area ratio of loess.A reduction in micropores,along with a sharp expansion of mesopores and macropores,leading to increased porosity and enhanced connectivity within the pore system.[Conclusion]Under the coupled conditions of wet-dry cycles and soluble salts,the synergistic effects of repeated swelling and shrinkage driven by the wet-dry cycles and crystallization stresses generated by salt dissolution and recrystallization jointly disrupt soil structure.This process leads to strength degradation and structural degradation in Ili loess.