Fig. 15.27 Shear strength of soil
While analysing the stability of an embankment, the designer uses one of the two methods in vogue. These are: (i ) total stress method, and (ii) effective stress method. Laboratory tests (for determining shear strength parameters of a soil) for the total stress method are performed such that the experimental conditions with regard to pore pressure simulate the pore pressure conditions in the embankment at failure and the shear strength of the soil sample is measured in terms of total stress without pore pressure measurements. For the effective stress method, pore pressures on the potential failure surface are estimated and the shear strength is determined in terms of the effective stresses using Eq. (15.31). The total stress method is relatively simpler. But, the effective stress method is more fundamental in nature and, hence, is recommended (12) for the stability analysis of embankment dams.
