Measured Lateral Response of Mass on Single Pile in Clay

The results of dynamic lateral load tests on a cantilevered mass supported by a single 10.75-in. (273-mm) diameter steel pipe pile embedded in stiff, overconsolidated clay are presented. These tests were conducted to provide a basis for evaluation of mathematical models that predict the relatively low-frequency dynamic pile response that is representative of systems in which the primary resonance frequency is controlled by the mass and stiffness of the superstructure. Frequency sweep shear forcing functions were applied at the top of the mass, which simulated a simple structure. The responses of the pile-supported mass, points on the embedded pile, and points in the supporting soil were recorded to determine frequency response functions. Frequency response functions between the applied load and pile cap-mass were then examined to aid in the identification of the pile–soil system parameters which most strongly influence response. The measured pile cap frequency response function peak amplitude was 0.0022 in./lb (0.0126 mm/N), or about ten times the static flexibility, and the resonance frequency was approximately 2.2 Hz.