Abstract: An indirect boundary integration equation method (IBIEM) of high precision is used to analyze the vibration isolation effect of the two-dimensional discontinuous pile-group barriers on plane P and SV waves within a broad band of frequency. This method is based on the single layer potential theory, and the scattered field in vivo and vitro of the scatterer is constructed using the fictitious wave sources close to the surfaces of discontinuous barriers. The magnitude of the fictitious wave sources are determined by boundary conditions, while the total response can be obtained by the superposition of free field and scattered field. It is shown that the proposed method has excellent numerical accuracy in solving broadband isolation vibration problems related to arbitrary arranged piles. For the elastic cylindrical solid pile, the frequency spectrum is quantitatively analyzed, showing that different vibration isolation effects of elastic rowed piles are associated with different ranges of frequency with the incidence of P and SV waves. The vibration isolation effect for different wave velocity ratios, different distances of piles and different rows of piles are discussed, and it is shown that: 1) there exist optimal dimensionless frequencies for prominent vibration isolation effect; and thus it is necessary to carry out optimization design of pile diameter and pile spacing; 2) for softer soil, the isolation effect becomes better, and compared to P wave, SV waves is more sensitive to the pile spacing; 3) Multiple rows of piles should be adopted for low frequency waves, but for the high frequency wave, more than three rows of piles will not lead to significant improvement on the vibration isolation effect.

Key words: plane waves, indirect boundary integration equation method (IBIEM), vibration isolation by several rows of elastic piles, discontinuous barriers