Abstract:

A steaming humidifying method is proposed for humidifying unsaturated undisturbed loess sample; and the testing steps and testing parameters are given. The effectiveness of this method is verified by checking whether the distribution of moisture is uniform and whether the soil density has changed. The measured results of moisture content show that the results from microwave oven method meet the required precision; but the results from alcohol burning method have greater error at higher moisture contents. Strength index for unsaturated soil after freezing and thawing is measured on undisturbed soil samples with different moisture contents obtained by using the steaming humidifying method. The results reveal that the freezing and thawing effect has no influence on the cohesion of loess when the moisture content of unsaturated undisturbed loess sample is very low. However, when the moisture content is higher, the cohesion of loess decreases after freezing and thawing, the lower the freezing temperature and the more freezing-thawing cycles, the greater the decrease in cohesion. The internal friction angle of loess increases after freezing and thawing, the lower the freezing temperature, the greater the increase in internal friction angle. The internal friction angle has almost no change after freezing-thawing cycles when the moisture content is low. When the moisture content is higher, the more freezing-thawing cycles are, the greater the increase in internal friction angle is.

Key words: loess, moisture content, unsaturated soil, strength