Abstract: In the aim of researching the shear strength properties of red clay under the condition of alkali pollution, laboratory simulation test with varying lye concentration and curing time was conducted to analyze the interaction between lye and red clay. Results showed that the shear strength, cohesion, and internal friction angle of the alkali-polluted red clay were higher than those of undisturbed red clay when the alkali concentration was high to some extent. The time when shear strength, cohesion and internal friction angle reached maximum was affected by lye concentration. On the contrary, in the presence of low lye concentration, the shear strength of alkali-polluted red clay decreased until a minimum value; while cohesion increased and then decreased, and internal friction angle decreased and then increased. Shear strength behaviors of red clay in the presence of alkali pollution is the result of hydration, ion adsorption, cation exchange, dissolution and external forces.

Key words: alkali contaminated, red clay, shear properties, action between alkali and red clay, laboratory tests