Axial Shaft Response from Seismic Piezocone Tests

The axial-load-displacement-capacity response of drilled shaft foundations can be analyzed efficiently using the results of seismic piezocone tests (SCPTu) which provide four independent readings in the ground: cone tip stress (q_t), sleeve friction (f_s), penetration porewater pressure (u_b), and downhole shear wave velocity (V_s). The penetration data are used in a direct CPT method to assess side resistance and end-bearing capacity components, while the shear wave provides the initial stiffness for an elastic continuum analysis of vertical displacements and axial load transfer distributions. Results from instrumented drilled shaft load tests conducted at the national geotechnical experimentation sites at College Station, Texas and Opelika, Alabama are utilized to illustrate the methodology.