长江下游过江隧道河段最大冲深数值模拟

Mathematical model studies on maximum bed erosion depth near Shiyezhou river-crossing tunnel

隧道工程所在位置河床的最大冲刷深度是过江隧道方案设计的关键参数之一,合理确定最大冲刷深度能为保证工程安全和减少投资提供重要设计依据。在分析近年来河道演变特点和前人所做研究的基础上,以长江下游仪征水道世业洲河段拟建过江隧道为例,分析工程河段的来水来沙特点,采用二维水流泥沙数学模型对不同水文年条件下河段河床最大冲刷深度进行了研究。在验证模型水流和泥沙冲淤相似的前提下,确定了动床模拟的不利水沙系列为2007—2010年+1998年+300年一遇洪水流量过程,并结合地质勘测资料对模拟结果进行了合理预测。最终确定过江隧道断面河床左汊最大冲深为10.85 m,右汊最大冲深为8.87 m,该结果对拟建过江隧道工程而言偏于安全。

The maximum riverbed erosion depth near the crossing tunnel is a key parameter for the tunnel design. And its reasonable determination can provide a critical design basis for project safety and reduction of investment. Based on the analysis of previous studies, a two-dimensional flow and sediment mathematical model was developed to predict the bed erosion depth at the tunnel location, based on a case study of the Shiyezhou river-crossing tunnel that would be constructed in the Yizheng waterway. The Yizheng waterway is a critical river section of the lower reaches of the Yangtze River, and the river-bed evolution in the past century is as follows ： the head of Shiyezhou sandbar collapsed continually, the left branch developed slowly with the mainstream moving towards the right after the confluence, and the right inlet still played a dominant role. So it is very necessary to study the maximum bed erosion depth near the location of the river-crossing tunnel. After analyzing the incoming water and sediment conditions in the project reach, we verified the mathematical model based on the existing data of the river processes, the features of fiver flow movement and the law of sediment erosion and deposition. The calculated values agreed well with the actual measured values. After model calibration using hydrographic field data and data of the historical morphological changes the three-hundred-year return in the Yizheng waterway, the discharge processes in 2007--2010, 1998, and of period were determined as the adverse flow and sediment conditions with consideration of the incoming flow and sediment conditions. The simulated results are predicted with the survey data of river bed drilling, and eventually the predicted maximum erosion depths of the branch channel in the left and fight are 10. 85 m and 8.87 m respectively during different flow and sediment series. The results are sufficiently safe for the construction of the river-crossing tunnel project and will be a scientific basis for the engineering design.