Influence of avenue trees on traffic pollutant dispersion in asymmetric street canyons: Numerical modeling with empirical analysis

The dispersion of traffic-related pollutants in urban street canyons is of importance for the health and quality of lives. To reveal the inherent principle, researchers have performed a lot of investigations; many dispersion phenomena have also been assessed during recent years. However, the presence of avenue trees in street canyons and their capacity for pollutant dispersion remains partly addressed. In this study, we investigated the effects of avenue trees in urban street canyons on traffic pollutant dispersion. The dispersion of CO concentration in asymmetric street canyons was simulated under varied situations. The computational results showed a good agreement with the experimental data, and the numerical model was validated to be adequate for investigating the pollutant dispersion in street canyons. Then, the numerical simulations were extended to explore the impacts of the effects of avenue trees on CO dispersion; the results indicated that avenue trees generally increase CO concentrations in asymmetric street canyons. When the wind direction is perpendicular to the street axis, a terraced building raises pollutant concentrations at the windward wall and reduces concentration at the leeward wall on the pedestrian levels. Findings of this study are expected to provide significant insight into urban road design and strategy making for avenue tree planting, particularly under the existing worldwide sustainable low-carbon urban development.     

深水峡谷库区高桩承台钢吊箱围堰设计与施工技术研究

针对太平湖特大桥主墩基础施工特点,且受外部施工环境影响较大,工期紧张,经过高桩承台钢吊箱围堰施工方案的比选(原位拼装下放和整体浮运到位下放),并结合钻孔桩钢平台施工需求,提出较为快捷的施工方案,即"钻孔桩施工平台与承台钢围堰合二为一";对工厂化作业、整体组装、下水浮运、定位以及搭建平台等施工策略予以探究,切实有效应对了高桩承台基础施工时间紧迫、作业难度高,同时提高工程质量,节约施工成本,最终取得了良好施工效果。