Interpreting the behavior of laterally loaded drilled shaft from measured deflection data

Abstract

SUMMARYThe drilled shafts have been widely used to support lateral loads (active load case) or as a means to stabilize an unstable slope (passive load case) due to their large lateral load resistance and structural capacity for shear and bending moments. However, there is a need to develop an analytical procedure that can use the actual measured deflection data of a drilled shaft subject to either active or passive load case to interpret the soil-drilled shaft interaction behavior. The mathematical formulation and the accompanied numerical procedure based on the principle of superposition were developed in this paper to allow for deducing the relevant soil-drilled shaft interaction behavior under the applied lateral load (i.e. net soil reaction force on the drilled shaft, the shear and bending moment in the shaft) from the measured deflection data. Both compatibility and force equilibrium conditions were utilized in formulating the mathematical equations for common single drilled shaft boundary conditions (free head and fixed bottom). The current application is limited to small deformation to meet the requirement that the drilled shaft responds in a linear elastic range. A total of three theoretical cases, along with two actual field cases, were used to demonstrate the validity of the proposed method and its engineering applications.