隧道围堰施工对湖泊水环境影响模拟研究

Simulation study on the influence of tunnel cofferdam construction on lake water environment

根据底泥再悬浮通量的概念,建立考虑底泥影响的二维水动力水质模型,结合再悬浮物理过程,确定底泥影响项中各参数的物理含义,采用独墅湖洪季和枯季的实测资料验证模型的适用性。利用模型预测独墅湖第二通道围堰施工排水过程中悬浮物、总磷与氨氮对流扩散过程,并分析施工对独墅湖湖泊富营养化的影响。结果表明:施工后湖流流速整体变小,围堰附近水域的流速变化较小,南部湖区湖流的流速受围堰影响较大且流速较小;围堰排水造成独墅湖水体悬浮物、总磷与氨氮浓度升高,但停止排水后,水体悬浮物浓度短时间内迅速下降;围堰排水对水体总磷与氨氮浓度影响范围有限,升高幅度不大;藻类生长的氮限制和磷限制在施工情景下的变化较小,围堰施工对水体营养盐的影响幅度十分有限。

According to the concept of sediment re-suspension flux,a two-dimensional hydrodynamic water quality model was established,which considered the influence of sediment.Combined with the physical process of re-suspension,the physical meaning of each parameter in the sediment influence term was determined.The applicability of the model was verified by the measured data of Dushu Lake in the flood season and the dry season.The convection diffusion process of suspended solids,total phosphorus and ammonia nitrogen during the construction of the second channel cofferdam in Dushu Lake was predicted by the model,and the influence of construction on the eutrophication of Dushu Lake was analyzed.The results show that the overall lake flow velocity becomes smaller after the construction,and the flow velocity in the waters near the cofferdam has a small change,and the flow velocity in the southern lake is greatly affected by the cofferdam.The concentration of suspended matter,total phosphorus and ammonia nitrogen in Dushu Lake increased due to cofferdam drainage,but the concentration of suspended matter in Dushu Lake decreased rapidly in a short time after stopping drainage.The influence of cofferdam drainage on the concentration of total phosphorus and ammonia nitrogen is limited,and the increase is not large.The nitrogen limit and phosphorus limit of algae growth change little under the construction scenario,and the influence of cofferdam construction on water nutrients is very limited.