洪水灾害下化工装置的脆弱性评估

Methodology for flood vulnerability analysis of hazardous material installations

针对洪水灾害下化工装置的脆弱性评估,提出了综合考虑洪水类型、装置结构特征和危险物质泄漏模式的脆弱性定量评估方法。该方法在厘定化工装置结构破坏模式、破坏等级和物质泄漏风险等级的前提下,构建洪水作用下装置的结构极限状态方程,获得结构极限状态曲线和结构失效控制参数阈值,进而得到结构破坏概率和危险物质泄漏频率,并将这两个参数作为洪水灾害脆弱性快速评估指标。以常压立式储罐为分析对象,对上述方法进行详细阐述,并结合实例验证了方法的适用性。结果表明,结构极限状态曲线可以用于快速区分结构安全状态和失效状态,临界装量系数是决定储罐洪水脆弱性的关键工艺参数,随罐壁高度和储液密度增加,洪水灾害脆弱性逐渐降低。

A short-cut quantitative assessment method for flood vulnerability of the chemical hazardous substances installations （CHSI） is proposed, which takes into account the severity of flood, the structure characteristic of CHSI and the leakage mode of hazardous materials. The methodology can be divided into three steps. At the first step, the damage state of CHSI and risk state of domino event need to be identified. The damage state is determined by the severity of leakage of hazardous materials, which is in accordance with the typical damage modes of CHSI in flooding disasters. With the help of Event Tree Analysis, the potential risk produced by the likely reaction between hazardous materials and floodwater is considered to obtain the modified risk state of domino event. At the second step, the structural or compositional maximum tolerance limit equation of CHSI under the load of flood is deduced. Base on the equation, the structural limit state function（SLSF） and the threshold of structural failure control parameter are derived. Finally, the damage probability of CHSI and the leakage frequency of hazardous materials are calculated, which are chosen as the indicative parameters of the flood vulnerability of CHSI. Taking the atmospheric storage tank as a case study sample, the above methodology is tested and illustrated in detail. The results show that for the damage mode of collapse of tank wall, the SLSF is a set of straight lines indicating the relation be- tween the square of the flood velocity and the flood depth. For the damage mode of displacement of the entire tank caused by buoy- ancy of floodwater, the SLSF can only be determined by the flood depth. Base on the deduced SLSF for atmospheric storage tank, another detailed case study of a tank farm close to a river is giv- en. It is found that the limit state function can be used to distin- guish between safe state and failure state of CHSI. The critical loading coefficient of the reaction serves as the critical operational parameter which can determine the flood vulnerability, of the atmospheric storage tank. What is more, the flood vulnerability has been proved decreasing with the increase of the height of the storage tank and the density of the hazardous chemicals.