Overall volume change, water volume change, and yield associated with an unsaturated compacted loess

This paper presents the overall volume change, water volume change, and yield associated with an unsaturated, compacted, low-plasticity loess from China. Two types of tests were conducted using a modified triaxial apparatus, namely isotropic compression tests with controlled suction (ICT), and triaxial shrinkage tests (TST). In the triaxial shrinkage tests, the net cell pressure is controlled and suction is allowed to increase. The results show that the stress path has a significant effect on overall volume change and the water volume change. The soil parameters related to overall volume change and the water volume change for the isotropic compression tests vary significantly in the low suction range, whereas the same soil parameters related to the triaxial shrinkage tests exhibit gradual changes. The yield net mean stress for the loading-collapse yield curve increases with suction. The yield suction is not equal to the maximum suction experienced by the soil specimen for the suction increase yield locus. Based on the test data obtained from the low-plasticity loess, a modified criterion for yield associated with suction increase is proposed. The proposed modified yield criterion should be valid for loess and silts of similar densities and plasticities.