Seismic Bearing Capacity of Strip Foundations Placed on Stable Slopes of Homogeneously Fractured Rock Mass

Abstract

Strip foundations are the most prevalently used shallow foundations in low-rise residential buildings in hilly regions. The strip foundations in many of these structures are often placed on rock slopes. In a seismic event, the behavior of the foundation–rock slope system is complex. It is characterized by a reduced bearing capacity in the strip foundation for low-intensity shaking and rock slope instability at higher seismic intensity. The quantification of this behavior is essential for the seismic design of these foundations. This work presents an analytical formulation to estimate the critical seismic loading for a given geometry and material properties of a rock slope that is represented by the Hoek–Brown (HB) failure criterion, up to which the stability of the slope is ensured. An extensive study that uses pseudo-static finite-element limit analysis (FELA) is carried out to parametrically analyze the effect of the slope angle and seismic acceleration on the seismic bearing capacity factor of a footing on rock slopes with a wide range of rock mass properties. The results of the FELA are utilized to develop a design tool (Rock-Bearing) to estimate the bearing capacity of strip foundations that are placed on rock slopes. The developed tool could be used instead of the computationally expensive numerical analysis for the preliminary design of foundations in seismically active hilly areas. The assessment of the seismic bearing capacity of a geomaterial that sustains a strip foundation is a crucial element in the design of strip foundations that rest on it. Using the code-based presumptive values for the bearing capacity for the seismic design might lead to unsafe designs where the strip foundation is near the edge of a slope in hilly areas. The seismic design of these foundations demands a comprehensive analysis, which preliminarily investigates the global stability of the slope and further incorporates the effect of horizontal seismic acceleration and vicinity of the slope in the reduction of the bearing capacity. The previously illustrated design requirements demand a sophisticated analysis of the design. This work develops a design aid tool that could be used instead of the computationally expensive numerical analysis for the preliminary design of foundations in seismically active hilly areas.