Feasibility of vibration mitigation in unsaturated soil by periodic pile barriers

Abstract

Periodic wave barriers have been widely used to mitigate ambient vibration. However, almost all the studies on the performance of periodic wave barriers are conducted under the assumption that soil is a single-phase or saturated medium. In fact, soil often consists of three phases: solid, liquid and gas, and it is more reasonable to be considered as an unsaturated soil. Existing research demonstrates that the dynamic properties of unsaturated soil have been significantly changed by gas phase, or the dynamic performance of unsaturated soil is completely different from that of single-phase soil and saturated soil. Especially, the dynamic performances of unsaturated soil cannot be approximated by the two extremes (saturated soil and single-phase soil). In this paper, the feasibility of vibration mitigation in unsaturated soil by periodic pile barriers is numerically validated. Firstly, based on the periodic theory, the complex band structures of P-SV waves in the periodic pile-unsaturated soil system are calculated. The influence of the saturation on the complex band structures is also investigated. Secondly, a numerical model for analyzing ambient vibration isolation is established. The responses of the numerical model are carried out in both frequency and time domains. The results indicate that periodic wave barriers in unsaturated soil can be designed with a wide attenuation zone covering the dominant frequencies of P1 waves, which is just a dream in saturated soil. Furthermore, S waves can also be greatly shielded in the target band. The present study removes the obstacles for the vibration mitigation in unsaturated soil by periodic pile barriers.