不同恢复程度的长白山风灾区地下火阴燃特征和发生概率模拟

Simulation of the Smoldering Characteristics and Occurrence Probability of Sub-Surface Fires in the Typhoon-Caused Disaster Areas of Changbaishan Mountain with Different Recovery Degrees

【目的】基于室内模拟点烧试验分析长白山风灾区地下火阴燃特征并建立发生概率预测模型,为该地区地下火防控提供理论依据。【方法】以长白山风灾区不同恢复程度(恢复区、半恢复区、未恢复区)的地下可燃物为研究对象,设置不同地下可燃物含水率梯度(0%、5%、10%、15%),通过室内模拟点烧试验,分析不同恢复程度的地下火阴燃温度和蔓延速率变化特征;采用双因素分析方法,确定不同恢复程度和含水率对地下火阴燃峰值温度和蔓延速率的影响;使用含水率和深度2个因子,基于Logistic回归模型建立风灾区地下火阴燃发生概率预测模型。【结果】长白山风灾区恢复区和未恢复区地下火阴燃的极限含水率为10%,半恢复区地下火阴燃的极限含水率为15%。不同恢复程度的地下火阴燃温度较低,自我维持燃烧的时间随可燃物含水率升高而增加,高含水率条件下的熄灭时间最短;地下火阴燃蔓延速率缓慢,最快仅为3.25 cm·h^(-1)。恢复程度和含水率交互作用对地下火阴燃峰值温度的影响存在显著差异,含水率0%和5%条件下不同恢复程度的峰值温度之间存在显著差异,恢复区不同含水率之间的峰值温度存在显著差异;地下火阴燃的蔓延速率受恢复程度和含水率影响,二者交互作用对蔓延速率的影响不存在显著差异。地下火阴燃发生概率预测模型拟合效果较好,预测精度高(P<0.01,AUC=0.917)。【结论】长白山风灾区恢复区和半恢复区的地下火阴燃温度较高,最高温度分别为640.57℃和602.02℃,未恢复区的地下火阴燃蔓延速率最快(3.25 cm·h^(-1)),基于Logistic回归建立的地下火发生概率预测模型具有较高预测精度。

【Objective】Based on indoor simulation of ignition,the characteristics of smoldering of sub-surface fires in windcaused disaster area of Changbaishan Mountain were mastered,and a probability model was established to provide a theoretical basis for the prevention and control of sub-surface fires in this area.【Method】The sub-surface fuel in the Changbai Mountain wind disaster area with different recovery degrees(recovery area,semi recovery area and non restored area)was used as the research object,and different moisture content gradients(0%,5%,10%and 15%)of sub-surface fuel were set up.Through underground fire simulation ignition experiments,the characteristics of smoldering temperature and spreading rate of sub-surface fires with different recovery degrees were mastered.A two-factor analysis method was used to determine the influence of different recovery degrees and moisture contents on the smoldering peak temperature and spread rate of sub-surface fires.A probability prediction model of smoldering of sub-surface fires in wind disaster area was established based on logistic regression model by using two factors of moisture content and depth.【Result】The limit moisture content of smoldering of sub-surface fires in the recovery area and non restored area from wind disaster in Changbai Mountain was 10%,and the limit moisture content of smoldering of sub-surface fires in the semi recovery area was 15%.The smoldering temperature of sub-surface fires with different recovery degrees was lower,and the self-sustaining combustion time increased with the increase of moisture content of fuel,and the extinction time was the shortest under the condition of high moisture content.The smoldering spread rate of sub-surface fires was slow,with the fastest being only 3.25 cm·h^(–1).The interaction of different recovery degrees and moisture contents on the smoldering peak temperature of sub-surface fires was significantly different,among which there was a significant difference in the peak temperatures of different recovery degrees between the conditions of 0%and 5%moisture content,and there was a significant difference in the peak temperatures of different moisture contents among the differently restored area.The spread rate of smoldering of sub-surface fires was affected by the recovery degree and moisture content respectively,but there was no significant difference in the impact of their interaction on the spread rate.The established prediction model of smoldering probability of subsurface fires had good fitting effect and high prediction accuracy(P<0.01,AUC=0.917).【Conclusion】The smoldering temperature of sub-surface fires in the recovery area and the semi recovery area of Changbai Mountain wind disaster area is relatively high,with the highest temperature of 640.57℃and 602.02℃,respectively.The smoldering spread rate of sub-surface fires in the nonrestored area is the fastest(3.25 cm·h^(–1)).The probability prediction model of sub-surface fires based on logistic regression has high prediction accuracy.