Strength of unsaturated lime-treated expansive clay in Hefei

Lime-treated expansive clays in semiarid area are in typical unsaturated state. Consequently, to ensure the rational design of foundation treatment, and safe operation, research on shear strength is of great significance. Herein, Based on scanning electron microscope(SEM) technology, digital image processing technology, and unsaturated GDS triaxial stress path system, microstructures, soil-water characteristic curves (SWCC) and strength of improved expansive soil with 7% lime in Xinqiao airport of Hefei were discussed. And strength properties of unsaturated lime-treated expansive clay were also further investigated by means of macro-micro comprehensive methods. It is found that microstructure in lime-treated expansive soil appears obvious harsh granular texture. The diameters were mainly from 0.52to 7.80 μm, and pore area was less than 4 μm². The measured SWCC behaves hysteretic characteristics between drying test and wetting test, and the air-entry suction is bigger than that of undisturbed expansive clay. Under the same amount of cell pressure, the higher suction the larger the peak strength and residual shear strength were. Moreover, for tests with the constant suction, residual shear strength increased with increasing cell pressure. The volume strains in the procedures of suction balance and shearing appeared differently.