Abstract: In order to study the friction angles between different soils and concrete surface in Guangzhou area, four soil samples and three different slurry-soil mixtures from different regions were put into the modified direct shear apparatus, and direct shear tests were carried out under different normal stresses to obtain the friction angles between soils, slurry-soil mixtures and concrete surfaces. Testing results show that: (1) the friction angle between granite residual remolded dry soil and concrete block surface is 25.2°. The friction angle between granite residual undisturbed soil and concrete block surface is 24.1°. Nansha silt soil and concrete block surface friction angle is 17.2°. Fujian standard dry sand and concrete block surface friction angle is 31.7°; (2) the friction angle between soil and concrete surface depends on the mineral composition of soil, normal pressure, the interlocking between particles, water content, and the interaction between soil and concrete surface. The degree of convexity and concavity changing on concrete surface, the content and gradation of sand particles in soil, the content of clay and mica, unsaturated state of soil, determine the cohesion of concrete and soil shear surface finally; and (3) as slurry weight ratio increasing, frictional coefficient and cohesion are both decreased between slurry-soil mixture and concrete surfaces.

Key words: granite residual soil, silty soil, Fujian standard sand, slurry-soil mixture, interface friction angle, interface cohesion