Abstract
Based on the analysis of the equilibrium of solid particles of an unsaturated
sample subject to a certain suction, it is possible to establish an analytical expression
for Bishop´s parameter X. With this parameter, the effective stress can be evaluated
and used to predict the shear strength and volumetric behavior of unsaturated soils.
For the determination of parameter X, three elements are required: the saturated
fraction, the unsaturated fraction, and the degree of saturation of the unsaturated
fraction of the sample. The equation established for parameter X clarifies some
features of the strength of unsaturated soils that, up to now, had no apparent
explanation. A drawback to this expression is that the three required parameters for
the determination of X cannot be obtained from current experimental procedures.