(3)

The assumption of seepage parallel to an infinite slope is realistic and indeed typical of most hillslope failures, to which one-dimensional infinite slope analysis may be applied. In this study, however, the general case of an ideal infinite slope of homogeneous isotropic saturated granular soil affected by uniform steady seepage with a vertical upward component was considered. Stability analysis was carried out in view of i) Mohr-Coulomb shear failure, the main result being the preparation of a stability chart for an infinite slope acted upon throughout by seepage in an arbitrary direction; ii) hydraulic instability in the guise of hydraulic heave failure. This occurs when the seepage gradient, at which the upward seepage forces transmitted to the soil exceed the gravitational forces, is the critical hydraulic gradient , for which a simple, albeit general, equation was derived. Subsequent comparison of these two types of failure showed that Mohr-Coulomb failure precedes hydraulic heave failure, except in one particular case, i.e. horizontal ground and vertical upward flow, where the failures are simultaneous. The study also considered iii) the phenomenon of static liquefaction resulting from undrained monotonic shear of saturated contractive loose soils, which generates a build-up of excess pore-water pressure triangle u. This leads to a sudden substantial or total loss of shear strength, i.e. the phenomenon of static liquefaction which, in turn, can produce catastrophic failures,even in gentle slopes. Lastly, in relation to the above mentioned excess pore-water pressure , an equation that enables us to estimate its value was easily obtained.

来源平台：ITALIAN GEOTECHNICAL JOURNAL-RIVISTA ITALIANA DI GEOTECNICA