Multi-approach analysis of maximum riverbed scour depth above a subway tunnel

Abstract: When subway tunnels are routed underneath rivers, riverbed scour may expose the structure with potentially severe consequences. Thus it is significant to research the maximum scouring depth to ensure the designed buried depth is adequate. There are a range of methods that may be applied to this problem, including fluvial process analysis, geological structure analysis, scouring formula, scouring model experiment and numerical simulation. However, the applicable range and forecasting precision of these methods vary considerably. In order to quantitatively analyze the characteristics of the different methods, a subway passing underneath a river is selected with the aforementioned five methods used to forecast the maximum scouring depth. The research results show that the fluvial process analysis method was used to characterise the river regime and evolution trend, which were the baseline for researching the scouring depth of the riverbed. The results obtained from the scouring model experiment and the numerical simulation method were reliable, these two methods were suitable to be applied to subways or tunnel projects passing under rivers. The scouring formula method was less accurate precision than the souring model experiment, so it was suitable to be applied to the “lower risk” projects as pipelines. The result of the geological structure analysis was of low precision, and it was suitable to be an assistant research method. To forecast the maximum scouring depth of the riverbed above the subway tunnel, a combination of methods was suggested, and the appropriate analysis method was chosen with respect to the local conditions.