基于GIS的城市地震次生火灾蔓延初步研究——以福州市区为例

PRELIMINARY STUDY OF EARTHQUAKE-INDUCED URBAN FIRE SPREADING- A CASE STUDY IN FUZHOU CITY, FUJIAN PROVINCE

以W Arcview/GIS为工具 ,结合传统的火焰蔓延数学模型 ,发展了复杂系统条件下城市地震次生火灾蔓延的计算机仿真模型 ,并结合福州市主要建筑物结构类型的具体情况 ,提出了根据建筑物类型来区分不同可燃物类型的划分方案。结合火源、风向风力、可燃物分布等因素 ,该模型在地震时可用以判定某一时段内可能的延烧区域 。

In the light of traditional fire spreading theory, we develop an Arcview/GIS based visual model to simulate the spreading process of urban earthquake induced fire. The basic constitutional law is from traditional equation: ρv 0 Δ H=Q , in which ρ = density of combustible material; v 0 = fire spreading velocity;Δ H = entropy increment from initial temperature T 0 to final temperature T i for unit mass; Q = fire thermal velocity. There are also three other factors involved in this model: 1) seasonal dominant wind direction; 2) possible explosive site; 3) results of seismic vulnerability evaluation. Basing on the previous studies of the relation between damage degree and induced fire probability, we calculate the possible number of fire events under different seismic hazards (seismic intensity of ⅩⅠ, ⅩⅡ, ⅩⅢ, and Ⅸ). If the hazard vulnerability analysis indicates that the buildings have 'no major damage', then the fire probability is taken as the annual average numbers of normal fire. The width of the fire lane is determined in accordance to the specific case of Fuzhou City as follows: 13m for distance between high storied buildings; 9m for distance between high storied building and 1 st class or 2 nd class private house; 11m for distance between high storied building and 3 rd class or 4 th class private house. Taking Fuzhou City as an example, we propose a method to classify the types of building combustibility based on different constructions of the buildings, and realize the visual and dynamic computer simulation under different damage conditions caused by earthquake. Under consideration of possible fire source, wind direction, wind speed, and spatial distribution of combustible materials, this model can be utilized to estimate the fire extent and damage degree at a specific time after induced fire caused by a strong earthquake, and is useful for economic loss assessment and hazard mitigation decision making. In normal times, this model can also be used as a tool to provide valuable information for the study of urban fire spreading, and for urban firefighting countermeasures.