Title:macro-micro Evolution Law Of Structural Damag E Of Remolede Loess With Equal Matrix Suction

Loess has unique mechanical properties such as structural and water sensitivity.The change characteristics of loess microstructure under the action of water and force and its accompanying macroscopic mechanical change law are one of the focuses of current loess mechanics research.Therefore,taking two kinds of loess with different particle size distribution in Xi’an and Lanzhou as the research objects,the triaxial test,soil-water characteristic curve test and SEM scanning electron microscope test of unsaturated soil under the condition of controlled matric suction were carried out The microstructure change characteristics of remolded loess with different particle sizes under the condition of equal matric suction were analyzed.The evolution law of structural variability of unsaturated remolded loess under the condition of controlled matric suction was studied,and the internal mechanism of energy absorption and structural macro-micro evolution process of remolded loess with different particle sizes was revealed.The main research results are:(1)Taking Xi ’an loess with silt content and Lanzhou loess with sand content as the research objects,different matric suction balance tests were carried out by unsaturated soil consolidation instrument,and the soil-water characteristic curves of loess with two different particle sizes under dehydration conditions were obtained.Under the same volumetric water content,the matric suction of sandy loess is significantly smaller than that of silty loess.This is because the larger the particle size,the smaller the matric suction between soil particles.(2)Based on the triaxial shear test of unsaturated soil which controls the matric suction,through the method of saturated consolidation first and then different matric suction balance,the consolidation volume change of loess under different matric suction conditions before shear can be guaranteed(that is,the same density),so that the porosity of loess with different matric suction before shear is consistent,which lays a foundation for studying the structural evolution of loess under the same void ratio and different humidity conditions.(3)The particle size,shape,pore size and pore shape of two kinds of loess with different particle sizes were analyzed by SEM electron microscopy.The particles of Xi’an loess with silt content are round and flake,while the particles of Lanzhou loess with sand content are round and strip.Under the condition of equal matric suction shear,the large and medium pores of loess are transformed into small pores respectively,and the transformation amplitude increases with the increase of matric suction.The transformation amplitude of large and medium pores to small pores in loess with large particle size is small.(4)Based on the comprehensive structural potential theory,the evolution law of structural variability of loess under different humidity conditions with the same void ratio is analyzed.Under the action of different matric suctions,the evolution law of loess structural variability presents a monotonous attenuation form with equal spacing,and finally tends to be stable.The matric suction is the key factor of loess variability.Based on the energy absorption characteristics of loess,when the structural damage is in the attenuation stage,the energy absorbed by loess increases nonlinearly,and when the structural damage is in the stable stage,the energy increases linearly.From the perspective of structural damage,the structural variability of sandy loess is weaker than that of silty loess.From the perspective of energy absorption,the energy absorbed by sandy loess is significantly greater than that of silty loess,while the energy absorption efficiency of silty loess is higher than that of sandy loess.