ADVANCES IN RESEARCH ON UNSATURATED CHARACTERISTICS OF SHANGHAI SOFT SOIL

Based on the obtained water retention curves, the relative coefficients of permeability of Shanghai soft soil are predicted. At the same time, a series of tri-axial tests have been carried out for the analyzing of unsaturated strength of Shanghai soft soil. Results show that, the air-entry value for Shanghai soft soil (silty clay、clayey silt ) is about 110~250kPa, the residual suction value is about 10~20Mpa, and both of them decrease with the particle size increasing; the WRC for desorption process of Shanghai soft soil shows clearly in step-phase; for the lower suction range (0~1400 kPa), the water retention curves for Shanghai soft soil(layer 21) show significantly in hysteretic loop; coefficients of permeability of Shanghai soft soil changes nonlinearly with suction(water content), and it decreases with suction increasing(water content decreasing); for lower suction, the tri-axial strength for unsaturated Shanghai soft soil linearly increases with suction, and the tri-axial shear coefficient φb for Shanghai soft soil (layer 4)is 10.6°.