VIBRATION ISOLATION OF MACHINE FOUNDATIONS BY PERIODIC TRENCHES

A unified method is proposed for screening the ground-transmitted vibr ations generated by machine foundations. The method is based on the so lid-state phenomenon of Bragg resonance, which leads to the fact that periodic shallow trenches are capable of reflecting a considerable amo unt of wave energy if they are carefully designed to have a tuned peri odicity with the propagating modes. The method of multiple scales is u sed to derive the coupled-mode equations, describing the interaction o f propagating waves with the tuned periodic trenches. Reflection coeff icients are calculated to evaluate the effectiveness of the trenches i n reducing wave amplitudes.