Study On Collapsibility Of Remolded Loess By Model Test And Evaluation Of Loess Collapsibility

Loessis widely distributed in northwestC hina;more and more projects have been started in the loess areas with the development of human society.The loess has water sensitivity because of its special properties, and collapsibility isthe typical manifestation of its water sensitivity, so the collapsibility of loess is one of the key issues need to be solved in the construction ofcollapsible loess areas. Many predecessors studiedthe assessment of loess collapsibility, but only a few people studied it fromtheviewpointofunsaturated soil mechanics.So, this paper study loess collapsibility based on a series of experiments of collapsible loess, including model test, numerical simulation, loess collapsibility test and microscopic test,with the self-developed model test device, and has achieved the following results:(1) The self-developed model test device can not only test the collapsesettlement of loess and soil water characteristics, but also observe its law ofinfiltratingcollapsing at the same time, with the simple operation and the reliable data, the device is an ideal test equipment forthe study of collapsibility loess.(2) Model test shows, the water immersion per hour decreased over time in the form of power function; The infiltration frontal displacement increased over time in the form of three polynomial, but its growth rate gradually decreased; The collapsibility process of loess divided intotwoparts, soaking period and stop-soaking period, collapsesettlementin soaking period is accounts for 77.6% of the total collapsesettlement, andthe total collapsesettlementincreased over timein the form of three polynomial.(3) From the numerical simulation based on model test, we got the seepage field,Y-displacement of different depth and the total collapsesettlement,and they are all consistent with the results of model test.(4) By CT and electron microscope scanning test and qualitative and quantitative analysis of loess microstructure parameter, we know that with the increased of collapsetimes, large pores and large gradually disappeared, soil densityuniformedgradually, soil grain abundance increased gradually, pore and grain’s area ratio decreased, grain orientation angle tended levelgradually;the main reason of collapsibility is the infiltration and leaching of water,which weaken the strength of the structure and made big soil grain disintegrated into small particles which then filled to the pores gradually,caused of soil consolidation.(5) A new collapsibility evaluation model is establishedbased on layer-wise summationmethod and the theory of unsaturated soil mechanics, it is reasonable through the validation, and it has a certain theoretical significance to the engineering construction in the loess areas.