Innovative Soil Reinforcement Method to Control Static and Seismic Settlements

With increasing levels of seismic awareness and design-level earthquake accelerations, Geotechnical Engineers are challenged to find cost effective solutions to address both static and seismically induced settlement in high seismic areas. In Salinas, California a relatively heavy, one and two-story structure was recently constructed in an area of relatively deep, intermittent, layers of liquefiable soil resulting in the potential for excessive total and differential settlements. A traditional foundation system of driven piles with structural slab similar to the new surrounding buildings was initially considered. Although this option addressed static settlement control and the potential for excessive seismically induced differential settlements, the solution was not considered economically viable and posed a risk to adjacent historic, unreinforced masonry structures. Alternatively, an innovative soil reinforcement method consisting of a stiffened geo-grid reinforced engineered fill over reinforced soil utilizing an evenly spaced Rammed Aggregate Pier system was used to support the building. The reinforced soil mat was designed to control static settlement from the building loads and reduce seismically induced differential settlements to within allowable project tolerances.