森林城镇交界域内建筑受林火威胁风险的模型构建和应用举例

Modeling the Threats of Forest Fires to the Buildings in the Wildland-Urban Interface

【目的】开展森林城镇交界域内建筑受林火威胁风险的模型构建与风险等级划分,为合理规划城镇防火设计和灭火资源配置提供科学依据。【方法】以火行为为基础,分析森林火灾产生的热辐射强度和飞火颗粒数量。通过耦合火焰长度模型、火焰倾角模型、火焰辐射模型和飞火颗粒流量模型,提出以热辐射、飞火颗粒和建筑重要度为指标的交界域火灾威胁建筑的风险等级划分方法,采用赋值法将交界域火灾风险分为3个等级,并给出对应的形容词评级。利用局部参数敏感性分析对火焰辐射模型和飞火颗粒流量模型的输入参数进行重要度排序。将间距作为参照,定量划分热辐射和飞火颗粒的等级。以韩国蔚珍郡林火为例,分析社区内建筑的风险等级。【结果】依据归纳总结的文献资料和试验数据,将建筑暴露在热辐射中的等级分为3级,分别为0~9、9~30、≥30 kW·m^(-2);将建筑暴露在飞火颗粒中的等级分3级,分别为0~2、2~3、≥3个;从生命、经济、社会和环境影响力等因素,将建筑重要度分为4级。构建交界域火灾威胁建筑的风险模型,从危险严重程度将建筑所受风险分为高、中、低3级,并给出各等级对应特点。用新建的风险模型评估韩国蔚珍郡林火对面积400 m^(2)单层乙类厂房的破坏等级,在火线强度5000 kW·m^(-1)、风速2 m·s^(-1)和间距10 m的情况下,该厂房所受火灾风险为中等。【结论】通过局部参数敏感性分析,火焰辐射模型和飞火颗粒流量模型的参数重要度排序从高到低依次是火焰温度、间距、大气透射率、火焰发射率、火线强度和环境风速。交界域内建筑所受最大热流密度和飞火颗粒数量随火线与建筑间距增大而减小,随风速和火线强度增大而增大。

【Objective】This paper was aimed to model and grade the risks of forest fires threatening the buildings in the wildland-urban interface,in order to provide scientific evidences for rational planing of urban fire protection and appropriate allocation of firefighting resources in the WUI.【Method】Based on fire behavior analysis,the intensity of thermal radiation and the quantity of flying particles generated by fire.By coupling the flame length model,the flame tilt angle model,the thermal radiation model and the fire particle flux model,a method is proposed to grade the risks of fire threatening the WUI buildings using three indicators:thermal radiation,flying fire particles,and the importance of the buildings.The WUI fire risks are divided into three categories using an assignment method,each with corresponding adjective ratings.The importance of the input parameters in the thermal radiation model and the fire particle flux model are ranked by local sensitivity analysis.The level of thermal radiation and fire exposure is graded in terms of the spacing.Finally,a case study of Uljin County of Korea was conducted,the risk level of buildings is analyzed.【Result】By literature review on the available experimental data,the thermal radiation exposure of buildings are categorized into three levels:0-9,9-30,≥30 kW·m^(-2).The fire particle exposure of building is also divided into three levels:0-2,2-3,≥3 pieces.The importance of buildings is graded into four levels by its effects on human life,economy,society and environment.A risk model is developed for buildings threatened by forest fire.The risk levels are graded into high,moderate,and low levels based on the severity of the danger,and specific characteristics are provided for each risk level.Using the new model,the damage to a 400 m2 single-story Class B factory in Uljin County,by a fireline intensity of 5000 kW·m-1,under the wind speed of 2 m·s-1 and the spacing of 10 m,is graded as moderate.【Conclusion】By local sensitivity analysis,the importance of the parameters of the thermal radiation model and the fire particle flux model is ranked from high to low as the flame temperature,spacing between fireline and building,atmospheric transmissivity,flame emissivity,fireline intensity,and wind speed.The maximum radiant thermal flux and the quantity of fire particles,received by buildings in WUI,decrease with the increase of spacing,but increase with the increase of wind speed and fireline intensity.