雨、潮联合作用下防洪设计的不确定性分析

Uncertainty analysis of flood control design under combined effects of rainfall and tidal level

以北海铁山港入海明渠为例,基于北海站1967年—2008年实测连续42 a 24 h降雨量资料和与其相应石头埠潮位站潮位资料,采用G-H Copula函数构建以皮尔逊Ⅲ型分布为最优边缘分布的雨量、潮位联合分布模型,同时在传统的OR和AND重现期基础上,引用防洪重现期概念,发现防洪重现期与OR和AND重现期相比更能避免最可能设计组合值设计标准出现偏高或偏低的情况。此外,基于蒙特卡罗法对雨、潮组合进行不确定性分析。结果表明:雨、潮最可能组合联合设计值95%置信区间随着重现期水平的递减和样本容量的增加而逐渐减小。以防洪重现期为设计标准推求得到的明渠设计水深的95%置信区间宽度和标准差均小于OR重现期,说明防洪重现期可以有效减少明渠设计水深的不确定性。

The case of open channel to the sea in Tieshan Harbor was used as an example.At the same time,based on the 24 h rainfall data measured at Beihai rainfall Station from 1967 to 2008 for 42 consecutive years and the tidal level data of the corresponding Shibu tidal level station,the G-H Copula function was used to construct the Pearson III distribution as the combined distribution model of distributed rainfall and tidal level with the optimal edge,and based on the traditional OR and AND return periods,the concept of Flood-Control return period was introduced,and it is found that the Flood-Control return period can effectively avoid high or low conditions of the most likely design combination values,comparing with OR and AND return periods.In addition,the uncertainty analysis of the combination of rainfall and tidal level based on Monte Carlo Method shows that the 95%confidence interval of the joint design value of the most likely combination of rainfall and tidal level gradually decreases with the decrease of the return period level and the increase of the sample capacity.The 95%confidence interval width and standard deviation of the open channel design water depth derived from the Flood Control return period are both lower than the OR return period,indicating that the uncertainty of the open channel design water depth can be effectively reduced by the Flood Control return period.