Introduction

The development of excess pore-air pressure, although not often considered in practice, can be influential for a certain class of problem. For example, the relatively fast construction of earth fill dams or embankments can result in an undrained response of both the compacted material and foundation soil. The pore-air pressure in the unsaturated zone will equal atmospheric pressure or it could be positive and in excess of atmospheric conditions, while the pore-water pressure remains negative. The effective stress and therefore factor of safety of the earth structure is altered. SLOPE/W has been formulated to handle both saturated and unsaturated soil conditions, so the effect of both pore-water and pore-air pressures can be modeled.