Utilizing Site Investigation and Load Tests to Predict Drilled Shaft Design Parameters and Capacities for Various Geological Formations

Document Type

Conference Proceeding

Publication Date



An accurate prediction of design capacities of a drilled shaft on weak rock formations is vital for a better design of deep foundations. Irregularities in rock formations due to weathering cause high inconsistency in actual bearing capacities. The assessment of bearing capacity of these rocks typically requires frequent in situ field tests such as drilled shafts load test at smaller intervals (multiple gauges) that are time consuming and expensive. The current design charts that being used in few states such as Texas and Oklahoma do not distinguish between the various types of rock or degradable materials such as intermediate geomaterials (IGM) or shale formations. This study documents several load tests such as Statnamic and bi-directional (O-cell) load cell testing (Osterberg) that were performed across the United States. The principal goal of this research is to improve methods to predict drilled shaft design capacities by accounting for the geologic formations and learning from past projects. This research developed predictive equations to shaft capacities for various rock formations.