Experimental study on wave isolation performance of periodic barriers

Abstract

A wave barrier—combining the advantages of trench-type wave barriers and metamaterials—is made by infilling the trench-type wave barrier with metamaterials. In this research, a series of full-scale field experiments are conducted to investigate the screening effectiveness of both empty trench and periodic barriers. The precast unit cells of periodic barriers are arranged to form one long barrier with a length of 2.44 m, one short barrier with a length of 1.22 m, or two short barriers with a length of 1.22 m to examine the influence of barrier length and the number of unit cells on the wave isolation performance. The state-of-the-art high-force triaxial (T-Rex) shaker truck is used to generate excitation in the vertical, horizontal inline, and horizontal crossline directions. Three excitation inputs are tested, including fix-frequency harmonic excitations, frequency sweeping excitations, and the earthquake excitation. For each test, a benchmark test is conducted prior to the barrier installation. The ground surface responses at each geophone location are recorded in all three directions. The normalized response of each point, the responses in front of the barrier and behind the barrier, and the frequency response function (FRF) are presented in detail. Test results show that the various excitation inputs lead to similar results. The performance of the periodic barrier is found to depend on the excitation directions due to the dominate wave form. By comparing the FRF between the benchmark case and the case with periodic barriers, the screening effectiveness of periodic barriers can be identified in some frequency ranges, which are expected to be the frequency band gaps of the periodic barriers.