EXPERIMENTAL STUDY ON ACTIVE VIBRATION ISOLATION BY WIB IN LAYERED GROUND UNDER VERTICAL LOADING

Wave impedance block (WIB) had always been studied with numerical methods in present relative literatures. This paper presents an investigation on the actual active vibration isolation effect of WIB in multilayered ground under vertical excitation. It includes a series of field vibration isolation experiments. The experiments were conducted under 6 different working conditions. So, the influences of WIB plane size, shear modulus and embedded depth on the wave mitigation effect are examined. Fourier spectra are obtained by applying Fourier transformation to the time series response data. The RMS velocity amplitude value is taken as the maximum site response at each measuring point. The screening effectiveness is evaluated by the amplitude reduction ratios along the distance from the source and their average value within the range of measuring line. The results indicate that the WIB is efficient to reduce the ground vibration under vertical excitation. Better wave mitigation effect can be achieved by increasing WIB plane size and shear modulus or decreasing WIB embedded depth.