IMPROVED DESIGN ECONOMY FOR DRILLED SHAFTS IN ROCK - INTRODUCTION, LITERATURE REVIEW, SELECTION OF FIELD TEST SITES FOR FURTHER TESTING, AND HARDWARE

Published studies relating to the design of drilled shafts for axial loading in soft rock are reviewed, including previous load tests performed by the Texas Department of Transportation (TxDOT). A process whereby this information can be incorporated into improved design rules for drilled shafts in soft rock is described. This process involves the use of computer models that will be calibrated by existing load test and rock data as well as new data to be acquired later in the project, which will focus especially on borehole roughness as produced by augers and core barrels. A new series of load tests that will be conducted on drilled shafts in the Dallas, Texas, area is proposed, and candidate test sites in both clay-shale and limestone are identified. Initial rock strength and TxDOT penetrometer data from five sites in the Dallas area are summarized, and the design of test shafts at three of these sites is shown. The Osterberg Cell method of loading will be used at those sites. The shafts will be tested in clay-shale, clay-shale and soil overburden, and limestone. Data from the two Dallas area test sites not selected for new load tests will also be used later in the project. Documentation is provided for a laser profiling device that will be used to quantify borehole roughness at the test sites and for a simple penetrometer device that is proposed for the routine delineation of clay-shale from overlying soil.