<i>V–H–M</i> Capacity Envelopes for Well Foundations on Slopes under Gravity and Seismic Conditions

The foundations of a bridge in hilly terrain are usually supported on hill slopes. The piers of the bridge are subjected to combined vertical (V), horizontal (H), and moment (M) loading. The V–H–M interaction is considered in the design of piers. However, the capacity of the foundations of these piers is generally not considered under combined V–H–M loading. The behavior of foundations becomes even more complicated when these are on slopes. One of the commonly used deep foundations for bridges on slopes is the well foundation. In this study, the V–H–M capacity envelopes were developed for well foundations on the face of slopes. Three-dimensional (3D) finite-element limit analyses (FELA), incorporating material and interface nonlinearity, were used to simulate the response of well foundations that were subjected to gravity and seismic loading. Two typical slopes with characteristic c–ϕ material properties were considered to support the well foundation. In addition, the influence of factors, such as vertical load ratio (V/Vu), foundation embedment ratio (D/B), and horizontal seismic coefficient (αh), on the foundation capacity envelope was studied. The results for foundations on slopes were compared with their counterparts on flat ground. In addition, an analytical procedure was suggested for the estimation of foundation capacity, supported on frictional soil under combined loading.