DESIGN METHOD FOR DRILLED SHAFTS IN SOFT ARGILLACEOUS ROCK

A simple, rational method for predicting load-movement behavior of axially loaded drilled shafts in argillaceous intermediate geomaterials (hard clays and soft rocks) is presented. The method is based on a parametric finite element study that is described in detail in a companion paper. The method emphasizes the importance of the value of initial concrete pressure and roughness of the borehole. A numerical example is presented, and four diverse case histories are summarized that illustrate applications of the method to realistic geological and construction situations. Parameters that are included in the method include geomaterial compressive strength and modulus, borehole roughness, borehole smear, concrete pressure in the socket, and angle of sliding friction at the interface. The method is applicable to cohesive intermediate geomaterials that exhibit drained (c= 0) interface behavior, which can be assumed to be nonporous, argillaceous (clay-based) hard soil and soft rock.