城市化平原河网圩区缓冲式雨水系统失效风险评估的理论与方法研究

The buffering stormwater drainage system (BSDS) is a new mode of stormwater drainage systems, which has been adopted increasingly in low-lying river network areas. In preliminary studies, the applicant found that the BSDS is significantly affected by rainfall randomness because of the non-synchronization in hydrologic response of conduit system and channel system. So, the higher quality of rainfall probabilistic distribution theory and risk calculation method is needed in the failure risk assessment of the BSDS. However, the existed rainfall probabilistic theory is oversimplified and calculation method of model simulation is computationally expensive, which cannot be suitable for the BSDS. Therefore, the theory and methods should remain to be made better and further researched. For this reason, the overall hydrologic response and failure mechanisms of BSDS resulted from random rainfall events are investigated through model simulation tests. According to its hydrologic response rules and failure mechanisms, the random rainfall generalization theory and mathematical representations method are developed based on the consistency between the hydrological responses of BSDS before and after rainfall generalization. And then, a multivariate statistical analysis of rainfall events was studied to develop the multivariate probability distribution theory in order to describe the randomness of rainfall features. Moreover, the limiting status function of BSDS and its failure domain of arguments is researched and developed based on the response surface methods (RSM). The new risk assessment method is created through the limiting status function of BSDS instead of the massive simulation tests. Thereby the innovative theory and method are developed for the failure risk assessment of BSDS, which can improve the accuracy of assessment results and save computing costs. The proposed study has important theoretical significance and practical value for performance assessment and urban flooding management for the BSDS and other urban stormwater drainage systems.

缓冲式雨水系统是平原河网圩区城市化建设中应用较多的一种雨水排水模式，申请人在前期研究中发现该系统由于管道、河网对降雨水文响应的差异性，整体水文响应规律复杂，受降雨随机性影响显著，在失效风险评估中对降雨概率分布理论和风险计算方法的要求更高。目前过于简化的降雨概率分布理论和繁冗的模型仿真计算方法已无法适应缓冲式雨水系统失效风险评估的需要，而相关理论与方法的研究却相对滞后。因此，本课题通过缓冲式雨水系统管道?河网整体水文响应规律和失效机理的研究，提出基于系统水文响应一致性原则的降雨概化理论和数学表征方法，探索并完善失效风险评估的降雨概率分布理论；同时引入响应面原理研究并建立缓冲式雨水系统极限状态函数及对应的失效域，创新失效风险评估的计算途径，从而构建一套准确高效的缓冲式雨水系统失效风险评估新理论和新方法，为缓冲式雨水系统及其他排水系统的安全性评价、内涝灾害管理提供理论支持和技术保障。

城市内涝是由于强降水或是连续性降水超过了城镇排水能力而导致城市内产生积水的灾害现象。近年来，随着城市化的快速发展和全球气候的变化，城市暴雨内涝事件频繁发生而且强度不断变大，已经成为了影响城市安全和发展的主要自然灾害现象。本项目从降雨和排水管道沉积两方面出发，在总结前人对于降雨特征和洪涝灾害研究的基础上，借助排水系统计算机模型的模拟，考虑峰值雨强对于城市内涝的影响，采用阈值分析的方法对降雨事件进行了概率描述，并提出了一种用于城市区域尺度上内涝风险评估的新方法。在此基础上，鉴于缓冲式排水系统水流受阻，沉积严重导致排水系统失效的问题，对排水系统沉积情况进行了研究，考虑排水管道沉积物有机质含量较高的问题，首次将生物作用融入到排水管道沉积物冲蚀规律的研究中，建立了高有机沉积物的冲蚀启动规律，为缓冲式排水系统的沉积物管理提供了理论依据。通过本项目的研究,主要结论如下：.（1）通过对研究对象的流量调查，地下水的入渗和河道水抬升后的倒灌加剧了缓冲式系统发生CSO溢流和漫溢失效的主要原因。.（2）通过对降雨敏感性分析，发现30分钟降雨峰值强度和平均降雨强度对内涝具有很强的敏感性，在分析了平均雨强和峰值雨强的边缘分布和相关性结构的基础下，采用Frank Copula函数构建两变量的联合概率分布模型,为降雨事件的不确定性分析提供了理论基础，同时建立了基于Copula的缓冲式内涝风险分析技术和方法。.（3）考虑实际雨峰出现的位置可能对缓冲式排水系统的影响，增加峰前雨量比这一参数，联合平均雨强和峰值雨强建立降雨特征参数的三维联合概率分布，并构建了一种双矩形雨型用来描述降雨时程分配的不均匀性。.（4）生物作用对高有机性沉积物的冲蚀特性的影响可表现为两方面：一是影响沉积物堆积密度使其内部结构松散从而削弱其抗冲蚀能力；二是在沉积物表面形成生物膜层从而使其抗冲蚀能力得到增强。在常温(25℃)好氧工况下，由于生物作用较为活跃，沉积物不同深度处的堆积密度随培养时间的增加有不同程度的减小，而在低温(5℃)和厌氧条件下沉积物密度则随培养时间的增加而增大。.本项目共发表或录用SCI论文2篇，在投SCI论文2篇，发表EI论文1篇，授权发明专利4项，通过项目的研发，制定了我省《民用建筑雨水控制与利用设计导则》，课题部分成果在嘉兴海绵城市建设中得到示范应用，取得了取得了较好的社会效益。