Abstract:A large number of buildings and transportation facilities have been constructed in recent years. Residential areas, commercial centers, industrial areas, and highways have formed a three-dimensional transportation network, and artificial vibrations are generated with high frequency and large cycle numbers.Artificial vibration has become a new type of environmental pollution, and is listed as one of the world's seven major environmental hazards.All the various types of artificial vibrations involve the generation and dissemination of elastic waves.Setting up of barriers between vibration sources and protection zones can block the elastic wave propagation path, attenuate the vibration energy, and reduce the vibration amplitude;this has become one of the most effective vibration isolation measures.Based on the geometric structures, normally-used barriers can be divided into two types:(1)continuous barriers, which are integrated structures, such as open trench, concrete walls, and trenches filled with mud, sawdust, or foam;and (2)discontinuous barriers, which are composed of individual elements, such as one row of cylindrical cavities, solid piles, or hollow pipe piles.In this study, theoretical and experimental studies of these two types of isolation barriers are reviewed and some important conclusions are drawn;(1)the effectiveness of continuous isolation barriers is better, but the depth of the barriers is usually required to be more than ten meters for vibration sources with low frequencies, which approaches half the wavelength of a Rayleigh wave, and so high construction costs and large construction difficulties are caused when constructing in soft soils or regions with high groundwater levels;(2)discontinuous barriers can be easily constructed, are not limited to depth and space, do not need additional support and maintenance, and so several rows of discontinuous barriers have more application prospects.In the future, isolation studies should focus on three-dimensional theoretical analysis and experiments on new absorbing materials with several rows of discontinuous barriers.
