Abstract: To explore the relationship between the volume change characteristics of loess, pore pressure and liquefaction, Gulang Malan loess was selected as the research subject. Unsaturated consolidated undrained tests were conducted to study the shear volume characteristics of loess under different water contents and confining pressures. Saturated consolidated undrained tests were also conducted to examine the stress paths and pore pressure characteristics of loess. Based on these studies, the distribution pattern of the critical state lines under different water contents was analyzed. Critical state lines in saturated conditions were established and compared with those from saturated consolidated undrained tests for validation. This provided a basis for establishing a connection between the loess volume change and pore pressure, leading to the proposal of a liquefaction evaluation method based on unsaturated shear volume. The findings indicate that the stress-strain curves of unsaturated Malan loess generally exhibit strain hardening behavior, with shear deformation being contractive. Conversely, stress-strain curves of saturated Malan loess display strain softening behavior. The deviatoric stress initially increases to a peak value with increasing mean effective stress and then gradually decreases and stabilizes. Critical state lines under unsaturated conditions are approximately parallel. As water content increases, the distribution of the critical state lines shifts downward. Water content has a relatively minor effect on the slope of the critical state line but a significant impact on the intercept. The distance from the initial state of the soil to the saturated critical state line represents the change in pore pressure. The pore pressure calculated based on the saturated critical state line indicates that there is only a possibility of liquefaction in Gulang Malan loess. This research provides valuable exploration in the field of loess liquefaction evaluation.

Key words: Malan loess, shear volume characteristics, liquefaction critical state line, liquefaction evaluation, stress path, pore pressure testing