阳澄西湖围堰施工中悬浮物输移扩散数值模拟

Numerical simulation of suspended solids transport and diffusion in cofferdam construction of the West of Yangcheng Lake

为了探究涉水工程建设对湖泊系统的影响,基于二维非稳态水动力模型,对阳澄西湖水动力进行数值模拟,并在水动力模拟正确的基础上建立悬浮物预测模型,模拟了不同风向、施工工况下阳澄西湖隧道围堰施工扰动水体所引起的阳澄西湖悬浮物输移扩散,分析了围堰施工对水域环境的影响。模拟结果表明:围堰抽排水引起的悬浮物浓度增加对水生态影响最为严重,消散时间达到48 h;东北风条件下有利于阳澄西湖南湾悬浮物的消散,抽排水和围堰拆建时的消散时间分别为40 h和16 h且高浓度面积小,东南风和西北风为最不利条件,东南风条件下抽排水时的消散时间超过48 h且高浓度面积为0.07 km^(2),西北风条件下围堰拆建时的消散时间超过28 h且高浓度面积为0.1 km^(2),都将对水域产生较大影响。建议一期围堰抽排水在春夏季施工,围堰拆除在秋冬季施工,以减少对环境的不利影响。

In order to explore the impact of wading engineering construction on the lake system,based on the two-dimensional unsteady hydrodynamic model,numerical simulation of hydrodynamics of the West of Yangcheng Lake was carried out.Based on the correct hydrodynamic simulation,a suspended solids prediction model was established to simulate the transport and diffusion of suspended solids in the West of Yangcheng Lake caused by the water body disturbing from the cofferdam construction of the West of Yangcheng Lake tunnel under different wind directions and construction conditions,and to analyze the impact of cofferdam construction on the water area environment.The simulation results show that the increase of suspended solids concentration caused by water pumping and drainage in cofferdam had the most serious impact on aquatic ecology with the dissipation time reaching 48 h.Under the condition of northeast wind,it was favorable for the dissipation of suspended solids in the south Bay of the West of Yangcheng Lake.The dissipation time during water pumping and drainage and cofferdam demolition were 40 h and 16 h respectively with high concentration area being small.Southeast wind and northwest wind were the most unfavorable conditions.Under the condition of southeast wind,the dissipation time during water pumping and drainage exceeded 48 h and the high concentration area was 0.07 km^(2),while under the condition of northwest wind,the dissipation time during the cofferdam demolition exceeded 28 h and the high concentration area was 0.1 km^(2),which both had great impacts on the water area environment.It was recommended that the water pumping and drainage of cofferdam in the first phase should be constructed in spring and summer,and the cofferdam should be demolished in autumn and winter to reduce the adverse impact on the environment.