Application Of Periodic Pile Barriers And Wave Barriers To Reduce Vibrations In Civil Engineering

ABSTRACT:This paper utilizes periodic theory of solid-state physics to study periodic pile barriers (such as periodic pile barriers with solid piles or hollow piles, periodic in-filled pile barriers and periodic fractal pile barriers) and periodic wave barriers in Civil Engineering. Periodic structures own the distinctive feature of wave forbidden characteristic of attenuation zones. When the frequencies of elastic waves are located on the attenuation zones, these waves cannot propagate through the periodic mediums. Moreover, even though the frequencies of elastic waves are out of the attenuation zones, periodic structures with a particular design can have the directional characteristics of elastic wave propagation. That means energy of waves just can flow in certain directions and other directions are called as "dead zones". We can design periodic structures with the capacity of vibration reduction or isolation by attenuation zones and the directional characteristics of wave propagation. Thus these periodic structures can be used to environmental vibration reduction and seismic isolation in Civil Engineering. The purpose of this paper is to find the new approaches on vibration reduction and seismic isolation in Civil Engineering by systematically studying the periodic structures. In this paper, the theoretical analysis and numerical simulation are conducted and the results are compared with others' experimental results. First, this paper uses series expansion technique and finite element method to study the dispersion curves of different periodic structures. Then, the scattering field of two-dimensional and three-dimensional periodic structures are studied by finite element method with reasonable models and boundary conditions. The correctness of the theoretical results and the existence of attenuation zones are validated by comparing with others' experimental results. The innovations can be drawn as follows.(1) Periodic theory of solid-state physics is firstly used to study the pile-soil interaction in pile barriers. The dispersion characteristics of periodic pile barriers for elastic waves are explained by the concept of attenuation zones. This paper proposes utilizing attenuation-zone characteristics of periodic pile barriers to environmental vibration reduction.(2) The attenuation zones of periodic pile barriers with solid piles and hollow piles are obtained. The influential factors on attenuation zones are studied comprehensively. The research reveals elastic modulus of soil, the pile radii and the periodic constant have an important influence on the attenuation zones of periodic pile barriers. It concludes that piles with the common size can easily help to middle-frequency vibration isolation.(3) The in-plane and out-of-plane attenuation zones of periodic in-filled pile barriers are investigated and the affecting factors on attenuation zones are analyzed. The locally resonant mechanism and Bragg scattering mechanism are used to explain the rationality of attenuation zones in periodic in-filled pile barriers. The periodic in-filled pile barriers based on locally resonant mechanism are expanded to low-frequency vibration reduction.(4) The attenuation zones and directional characteristics of periodic fractal pile barriers are discussed by theoretical analyses and numerical simulation. The influencing rule of generations and filling fraction on the attenuation zones of periodic fractal pile barriers are discovered.(5) Periodic wave barrier is designed to block the vibrations and seismic waves from three dimensional space. This new mentality is presented for the environmental vibration reduction and seismic isolation.Based on the study in this paper, the findings can help to deeply understand the scattering mechanism of periodic structures for elastic waves and the effectiveness of vibration reduction. Moreover, the findings have a guiding significance on understanding the mechanism of the pile-soil interaction in periodic pile barriers, the energy transfer and consumption of elastic waves between pile and soil. Theoretical model and design method of periodic pile barriers subjected to artificial vibrations can be found in this paper. This paper also provides the inspiration for designing new wave barriers.