Abstract: Expanded polystyrene (EPS) geofoam is a novel geosynthetic material with some prominent features, including light weight, good compressibility, water resistance and heat preservation. It can be used as a lining structural layer under the concrete lining slab of underwater slope of expansive soil canal to release the expansive pressure acting on the concrete slab and to maintain matrix suction of expansive soil, thus stabilizing the canal slope. In order to further explore the mechanical characteristics of EPS under compression in this application, one dimensional compression tests and compressive creep tests on EPS of different densities (14.7 kg/m 3, 17.05 kg/m 3 , 23.4 kg/m 3) were conducted. Results show that the uniaxial stress strain relationship of EPS is significantly nonlinear and the creep strain is significant even under longterm small loading. On the basis of the test results, a constitutive model describing the whole uniaxial compression process of EPS is proposed. It is further pointed out that the influences of EPS density on its deloading property, water resistance and heat preservation properties should be taken into account when selecting EPS for lining structure of canal slope in cold region. Meanwhile, the influence of compression creep of EPS on lining structure of canal slope should also be considered.

Key words: expansive soil canal slope, slope stability, expanded polystyrene (EPS), compression, creep