Abstract: In the aim of investigating the relationship between elastic modulus and saturation of unsaturated loess,a testing method based on the suction stress theory and particle image velocimetry technique is employed to test the variation of elastic modulus with saturation of typical remolded Malan loess.The high-resolution digital images and moisture content data of flat cylindrical soil samples subjected to dessication from saturation to dry condition are obtained by this method using a self-made multi-function photogrammetric device.Meanwhile,the soil-water characteristic curve and Poisson’s ratio of the samples are measured by pressure plate instrument and uniaxial compression instrument,respectively.Furthermore,the elastic modulus of unsaturated soil with different water content are calculated based on the suction stress theory and the stress-strain relations in polar coordinates.The test data of samples with different dry densities during air drying process indicates that the elastic modulus of Malan loess samples increase exponentially with the decrease of saturation.A mathematical model for the relationship between the elastic modulus and saturation degree is proposed.

Key words: unsaturated loess, elastic modulus, saturation, particle image velocimetry, suction stress