ANALYSIS ON MICROSTRUCTURE OF ARTIFICIAL COLLAPSIBLE LOESS

Natural loess, possessing strong structural characteristic, will suffer inevitable disturbance in the process of sampling, transportation and sample preparation. Based on the principle of Carlo Monte, non-cohesive materials-quartz powder and sand and cohesive materials-bentonite, gypsum and industrial salt were chosen to prepare artificial collapsible loess with the air fall method. Vertical consolidation pressure was applied to the soil with 5kPa, 10kPa and 15kPa separately, and after 9months soil samples were taken to conduct geotechnical test and electron microscope scanning test. The geotechnical test results show that:with increase of consolidation pressure, shear strength parameters are improved, and the peak coefficient of collapsibility is reduced. Analysis on SEM microstructure shows that consolidation pressure has great effect on overhead pore, while inter-granular pore is influenced relatively slightly by the consolidation pressure; with the increase of consolidation pressure, particle anisotropy, area ratio and equivalent diameter increase, while particle oblate degree and fill ratio decrease. There is a good relationship between soil mechanical parameters such as internal friction angle, cohesion strength and coefficient of collapsibility and microstructure parameters such as area ratio, fill ratio, equivalent, anisotropy, and oblate degree. From the microscopic point of view, it is proved that the artificial collapsible loess is a relatively ideal similar material for the collapsible loess model test.