Abstract:

The compression tests are conducted on Yangling and Qinghai structural loesses under different water contents. Based on the principle of equivalent deformation, the equivalent stress of structure fluid is defined by using compression stress difference between unsaturated and saturated loesses under the same consolidation void ratio . The effective stress principle of unsaturated structural loess is established under compression stress. Relations between equivalent stress of structure fluid and degree of saturation as well as stress are investigated. The relation between equivalent stress of structure fluid and stress is linear as the water content is lower. Based on the equivalent stress of structure fluid under lower water content, the formula of equivalent stress of structure fluid is proposed which can reflect coupling of stress and moisture. According to effective stress principle of unsaturated structural loess under compression stress and introducing equivalent stress of structure fluid reflecting the structure change, the formula of compression of structural loess is established. The compression curves of total stress and that of effective stress can be calculated under the coupling of stress and moisture by the formula. The calculating results are accord with the test results, so as to offer a new approach to evaluating unsaturated collapsibility.

Key words: structural loess, compression tests, equivalent stress of structure fluid, coupling of moisture and stress, effective stress