城市分汊型河道环保疏浚深度设计关键要素

Key elements in depth design for environmental dredging of urban braided rivers

城市分汊型河道进行环保疏浚的边界条件较复杂,具有水质较差、流态复杂、淤积严重、过河建筑物较多的特点。提出环保疏浚深度应从污染层深度、河床演变、构筑物的安全等多角度考虑的设计理念:1)在单一河段复式断面以平滩高程控制疏浚深度。2)为了稳定河床,疏浚深度应控制过水面积的比例,并保持主河道与自然坡度一致。3)在堤防及构筑物处,疏浚深度应考虑与其安全距离及疏浚后冲刷深度的影响,从而在河床稳定和构筑物安全的前提下,最大限度挖除污染底泥。此理念已成功应用于某河段环保疏浚工程。

The boundary conditions for the environmental dredging of urban braided rivers are complex due to poor water quality, complex flow patterns, serious siltation, and large numbers of river-crossing buildings. This paper proposes a concept that the design of the environmental dredging depth should unfold from the perspectives of pollution layer depth, riverbed evolution, and structure safety, and the concept involves the following three aspects: 1)Controlling the dredging depth with the bankfull elevation is advisable at the compound section of a single river section. 2)for the stabilization of the riverbed, the design of the dredging depth presupposes controlling the proportion of the cross-sectional area and keeping the main channel consistent with the natural slope. 3)At dikes and structures, the design of the dredging depth should consider the influences of the safety distance from the dikes and structures and the scouring depth after dredging to excavate the polluted sediment to the maximum extent on the premise of stable riverbeds and safe structures. The proposed concept has achieved successful application to an environmental dredging project in a river section.