In 1993, the Arizona-Mexico Commission and its sister organization, the Comisión Sonora-Arizona, initiated a binational strategic economic planning process to analyze how the two neighboring states could increase their regional competitiveness in the world economy and enhance the overall quality of life for their residents. One of the recommendations of the Strategic Economic Development Vision was to develop a set of indicators as a tool to monitor progress toward the goals of binational economic development. The purpose of the Regional Economic Indicators is to help policy and decision-makers understand and monitor economic changes in the Arizona-Sonora region and to support policies that promote economic transformation, investment and entrepreneurship in the region.

This report provides a simplified method to be used for evaluating the skin friction and tip resistance of axially loaded drilled shafts. A summary of literature and current practice was completed and then a comprehensive set of field and laboratory tests was performed. Several soil samples were collected from different sites from Arizona and surrounding states. Large scale direct shear apparatus was developed and used to determine the friction between soil and concrete. Finite element analyses were conducted on several prototype cases to determine effect of soil parameters such as dilation on the skin friction values. A step-by-step simplified approach was introduced to determine the skin and tip resistance of drilled shaft foundations in gravelly soils. An example application was presented to guide users in utilizing the simplified approach.