Experimental study on strength and water-stable behavior of unsaturated residual soils

Unsaturated granite residual soils are widely used as compacted soils in engineering structures such as slopes, embankments and backfills. Shear strength of soil are important in many geotechnical problems. A series of unconfined compression tests are carried out on unsaturated residual soils. Furthermore, since the residual soils are impaired in contact with water and have poor water-stable properties, slaking test of residual soil was conducted. Results of tests show effects of moisture content and cyclic wetting and drying on strength. Moisture content of soils is higher than the optimum moisture content of 2% for high strength and it is lower than optimum moisture content of 2% for good plasticity in Xiamen areas. Cyclic wetting and drying causes loss of unconfined compression strength and the maximum loss often occurs at the first cycle and then slowed down till the strength remains constant. In addition, wetting and drying cycles accelerate disintegration speed and shortened the whole disintegration. Soil in small dry density tends more easily to be disintegrated than one in high dry density.