Abstract: In order to explore the influence of calcium chloride on the water holding capacity, mechanical properties and critical moisture content of Guilin Red Clay soils, the desiccation, unconsolidated undrained direct shear and critical moisture content tests were conducted by using adding 10% calcium chloride content of the soil mass by weight into the soil samples. The results show that the liquid limit of red clay decreases, the plastic limit slightly increases, and the plasticity index decreases; when calcium chloride is added to the red clay soil samples, the electric double layer on the surface of soil particles is compressed and the water film of the diffusion layer becomes thinner, which leads to the decrease of the liquid limit of red clay. At 25℃, CaCl₂·6H₂O is the main reaction product of CaCl₂. The CaCl₂·6H₂O solution has a specific heat capacity greater than the water, and the evaporation rate is lower than that of the pure water, which makes the fracture development of the calcium chloride red clay weaker than that of the red clay soil, and improves the water holding capacity of red clay soil samples. The addition of the calcium chloride weakens the mechanical properties of red clay soil samples. The cohesion of the red clay increases with the addition of the calcium chloride, and the internal friction angle decreases.

Key words: red clay, calcium chloride, water holding capacity, mechanical properties