The behavior of undisturbed loess in the case of moistening or demoistening is investigated with single-line and double-line uniaxial compression test. According to the experimental results

the characteristics of collapsible deformation of loess changing with saturation level and pressure are presented. The collapsible deformation properties of loess during moistening or demoistening process and the influence of different stress-paths on collapse deformation characters of loess are analyzed. It is indicated that collapsibility coefficient curves can display different characteristics for different test method. The collapsibility of single-line method is larger than that of double-line method for lower initial moisture content

and is smaller than that of double-line method for higher initial moisture content. For certain value of initial moisture content in between

collapsibility coefficient curves of the two methods will intersect. This intersection phenomenon is caused by special structure of loess. Finally

the relation between collapsibility coefficient and initial moisture content is discussed.