The following text will present the concept of rock socketed drilled shafts used to support electricalsubstation structures, and discuss the cost and schedule risks that traditional design responses to unforeseenshallow rock can pose to a project. Design considerations will be detailed, including rock characterization,shear strength of drilled shafts, and modeling lateral resistance of the shaft and surrounding rock. Thespecific case of drilled shafts installed for heavily loaded structures at the Moxie Freedom Substation willprovide an example of how close collaboration between the engineer and contractor to refine designs basedon site-specific feedback can provide tangible benefits to the project. In this example, value engineereddesigns resulted in an approximate 40% reduction in shaft/concrete volume and a 60% reduction in totalrock socket depth.
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