LABORATORY STUDY ON SHEAR STRENGTH DETERIORATION OF LOESS WITH LONG-TERM FREEZING-THAWING CYCLES

By taking the loess of Yangling area in Shaanxi province as the research object,a direct shear test is conducted with different water contents,dry densities and times of freezing-thawing cycles. The tests are to explore the way and the criterion of long-term freezing-thawing cycles.Then the characteristic of loess deterioration with long-term freezing-thawing cycles is studied in a closed system.The test result show that: (1)in the condition of long-term freezing-thawing cycles,the surface of loess is destroyed greatly; (2)the cohesion of loess decreases firstly and increases later according to the suggestion.The freezing-thawing cycles and the minimum value are normally appeared in ten freezing-thawing cycles.The internal friction angle of loess keeps invariable basically. The strength of loess is affected greatly in three-five freezing-thawing cycles,which can lead to strength deterioration of loess.But with the time going,the influence of freezing-thawing cycles is reflected on the transmutation of loess surface.