CONTRAST STUDY ON FORECAST OF SHEAR STRENGTH OF UNSATURATED SOIL USING SOIL WATER CHARACTERISTIC CURVE

At present, the engineering properties of unsaturated soil have become a hot topic in the geotechnical engineering field. The shear strength of unsaturated soil is particularly important for the engineering properties of soil. The authors have summarized four formulas which can forecast the shear strength of unsaturated soil using the soil water characteristic curve. The soil water characteristic curve of Majiagou Landslide Ⅰ is obtained with the five bar pressure plate instrument. The MATLAB software and Van Genuchten model are used to fit the test data. The international advanced GDS unsaturated back pressure shear apparatus(UBPS) is used to proceed the direct shear tests on the unsaturated soil. The matric suction is controlled to be 50kPa and 100kPa. The relevant shear strength is obtained. Besides, the four predicted values of soil water characteristic curve and the test result are compared. The veracity of the predictor formulas is verified. Their merits and demerits are summarized. Finally, the Fredlund's prediction formula is the most accurate one and the Huang-Runqiu's formula is the most simple and practicable.