Prediction of undrained shear strength in soft clays based on fall-cone tests

The fall-cone tests are used to determine the undrained shear strength of clays. However,owing to the uncertainty of K in the empirical formula cu=KW/d2,the calculated undrained shear strength is always different from the measured shear strength. For achieving a better application of fall-cone tests on the prediction of shear strength and the impacts on parameter K,six distinct types of cones are introduced on four different clays in fall-cone tests. The effect of cone mass and angle on cone penetration is discussed. And the results of fall-cone tests performed with cones of different angles and weights are correlated together with the results of unconfined shear strength tests for four different clays in order to determine the parameter K. The test results indicate that the effect of cone angles is much greater than that of the cone weights and the clay types. It is convenient to predict the undrained shear strength by a constant K with cone angles as K30°=0.69,K45°=0.39,K60°=0.17. The validity of the method in predicting the shear strength is verified by comparing the existing experimental results.