Influence of soil-structure interaction on pile-supported machine foundations

Abstract

Influence of soil-structure interaction (SSI) on pile-supported machine foundation supporting low speed rotary machine is discussed. The importance of pile foundation in soft soil conditions in comparison with raft foundation is also discussed. An analytical model using lumped mass approach is developed to study the effect of the SSI on the dynamic response of pile-supported framed-foundation. Frequency-independent stiffness and damping coefficients are used to model the foundation-soil system. Newmark’s method is used to solve the governing equations of motion. It is found that, the SSI significantly reduces the natural frequency of the raft-supported framed-foundation resting on soft to very soft soil conditions.Though, the fundamental natural frequency is well separated from the operating frequency of the machine, there is possibility of resonance in higher modes in soft soil conditions and amplification in the peak amplitudes. The pile foundations are found to be a suitable system in soft to very soft soil conditions to control vibrations of framed-foundation. The damping in soft soil plays an important role to suppressthe amplitude of vibration.