Abstract: In order to explore the basic engineering characteristics of loess modified by red mud, of which the optimum ratio is obtained based on unconfined compression test, direct shear test and seepage test; and then an empirical formula for shear strength, unconfined compression strength and resistivity is established. The cumulative plastic deformation, dynamic elasticity modulus and leaching toxicity of the modified loess under cyclic dynamic loading are analyzed by dynamic triaxial test. The results show that with the increase of red mud content, the unconfined compressive strength and cohesion of the modified loess first increased and then decreased; and when the amount of red mud is near 15%, the unconfined compression strength of 28 d reached 3.5 MPa, which is improved by about 34.7% than no red mud. The permeability coefficient decreased rapidly with the increase of red mud content, and reached the stability when the amount of red mud is 5%. There is a good linear relationship between the shear strength, unconfined compressive strength and resistivity. The critical dynamic stress of the modified loess reaches 600 kPa under cyclic dynamic loading, of which the maximum dynamic electricity modulus is 6 times ones of loess. The leaching solution of the modified soil does not have the toxicity of leaching.

Key words: loess modified by red mud, unconfined compression strength, shear strength, resistivity, dynamic elasticity modulus