Fire behavior of mining vehicles in underground hard rock mines

The results from a number of investigations and fire experiments are presented and analyzed in order to characterize the fire behavior of mining vehicles in underground hard rock mines. The analysis also includes fire safety and fire protection measures with respect to the mining vehicle fire behavior.Earlier studies on fires in underground hard rock mines have shown that vehicles or mobile equipment are the dominant sources of fire. A better knowledge about the fire behavior of vehicles in underground hard rock mines is therefore needed. During the analysis the direction and flow rate of the ventilation in a drift was found to have a significant impact on the fire behavior, causing for example flame tilt with rapid fire spread. The shielded sections of a vehicle will be less affected by the ventilation flow resulting in for example a decreased flame spread. It was also found that spray fires may result in considerable heat release rate but are generally of shorter duration and will not make any significant contributions to the overall heat release rate of the fully developed vehicle fire. The fire duration of a loader tire from a full-scale fire experiment was found to be at least 200 min and will largely determine the total fire duration of the vehicle. A different scenario with different conditions with for example a slower flame spread resulted in an even longer fire duration. The radiative and convective fraction will be a key factor when determining the heat transfer mechanisms involved in a fire and will vary from material to material.Calculations show that the radiative fraction of the tire fires on two mining vehicles is significantly lower than found in earlier experiments. The design and construction of the mining vehicle will have an important impact on the fire behavior and could possibly mitigate the consequences of a fire and allow fire personnel to extinguish a fire that otherwise would have had a too high heat release rate.

Study on the Fire Behavior of Sandwich Wall Panels with GFRP Skins and a Wood-Web Core

To investigate the temperature field and residual bearing capacity of the sandwich wall panels with GFRP skins and a wood-web core under a fire,three sandwich walls were tested.One of them was used for static load test and the other two for the one-side fire tests.Besides,temperature probe points were set on the sandwich walls to obtain the temperature distribution.Meanwhile,the model of the sandwich wall was established in the finite element software by the method of core material stiffness equivalent.The temperature distribution and performance reduction of materials were also considered.The residual bearing capacity of specimens after fire exposure were simulated considering the effects of web spacing,wall panel thickness and fire exposure time.Because the sandwich wall panels were stressed by eccentric compression after a fire,the residual compressive strength of the wall panel after the fire can be calculated through the eccentric loading analysis.Compared with the numerical results,it can be concluded that the effectiveness of calculation method of residual bearing capacity after fire exposure was proved.

Synergistic effects of expandable graphite and dimethyl methyl phosphonate on the mechanical properties, fire behavior, and thermal stability of a polyisocyanurate-polyurethane foam

In this study, a series of flame-retardant polyisocyanurate-polyurethane (PIR-PUR) foams were prepared using various concentrations (0-25% by weight) of expandable graphite (EG) and dimethyl methyl phosphonate (DMMP) (0-7% by weight). The effect of these additives on the properties of the PIR-PUR foams, including physico-mechanical, morphological, flame retardancy, and thermal stability, was studied. Increasing amounts of EG in the PIR-PUR foam caused a significant drop in the compression strength. However, DMMP caused the mechanical properties of PIR-PUR foam to improve compared to foam filled with EG alone. The flame retardancy of PIR-PUR foams containing both EG and DMMP was enhanced significantly compared to EG filled foams. Thermogravimetric analysis (TGA) indicated that EG enhances the thermal stability of PIR-PUR foams but that DMMP decreased it. The morphology of the residual char provided conclusive evidence for the weak thermal stability of foams filled with DMMP.

Review and discussion on fire behavior of bridge girders

This paper presents an overview on fire behavior of bridge girders mainly including prestressed concrete(PC) bridge girders and steel bridge girders. The typical fire accidents occurred on bridges are illustrated and, the seriousness of posing threats to bridge structures resulted from increasing traffic fires, specially intense hydrocarbon fires generated from petrol-chemicals, is highlighted. The current researches, embracing high-temperature properties of constituent materials, prestress state, measurement in fire tests, numerical methods, structural fire resistance, and so forth, taken on coping with problems existing in fire behavior and structural fire behavior in bridge girders are reviewed and discussed. Further, strategies for enhancing fire resistance of bridge girders followed with failure criterion and mode in types of bridge structures are provided. Future research area along with emerging trends in structural fire behavior of bridge girders is also recommended for mitigating fire hazards occurred on bridge girders. Herein, it can be attained a conclusion from review and discussion that prestressed concrete bridge girders with thin webs, specially T-shaped bridge girder, are prone to unstable under fire exposure conditions. High-strength concrete utilized in prestressed concrete bridge girders is vulnerable to spalling at elevated temperature. Steel-truss bridge girder present a more significant fragility to fire exposure compared than other steel bridge girders.

Generalized Blaze Flash,a“Flashover”Behavior for Forest Fires—Analysis from the Firefighter’s Point of View

The phenomenon called “flashover” or “eruptive fire” in forest fires is characterized by a sudden change in fire behavior: everything seems to burst into flames instantly and firefighters are overwhelmed by a sort of eruption, spreading at a speed at far several meters per second. Unfortunately it has cost several lives in the past. The reasons for such an accident always create controversy in the research field. Different theories are highlighted and especially two major axes are currently subject to discussion because they are very popular among people involved in fire-fighting. The one with regard to VOCs emissions is the best-known among firemen. Under great heat, during summer or with a fire approaching, plants emit VOCs and the more the temperature grows, the more the amount of VOCs emitted grows. Under specific conditions (essentially topographical, meteorological and atmospheric), the cloud of gas can accumulate in an appropriate zone. The concentration of VOCs may therefore reach the Lower Explosive Limit, triggering the burst of the cloud when in contact with the fire. The second theory depends on physical considerations. An example is based on a convective flow created by the fire itself. When a fire spreads on a slope, it creates an aspiration phenomenon in a way to supply the fire with oxygen. The more this phenomenon is important, the more the flames tilt and increase the rate of speed, needing even more oxygen and thus induced flow. This vicious circle can stabilize or have an erratic behavior to trigger off a fire eruption. This article presents these two theories, and especially the new advances on this research subject.

Post-fire cyclic behavior of reinforced concrete shear walls

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were investigated.Five RC shear walls were tested under low cyclic loading.Prior to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial load.Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated temperatures.While the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate load.However,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling.In addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

钢绞线热铸锚节点高温下抗拉性能试验研究

针对锌铜合金熔点较低(约460℃±10℃)、高温下热铸锚节点容易失效的问题,对预应力钢绞线热铸锚节点进行了高温抗拉性能试验,获得了高温下试件的破坏模式和抗拉承载力,提出了钢绞线热铸锚节点在高温下极限抗拉承载力计算公式,以及在各荷载比下的临界温度,可用于钢绞线热铸锚节点的抗火承载力验算与防火保护层厚度设计.试验研究表明,温度低于200℃时,破坏模式为钢绞线断裂;温度高于200℃时,破坏模式通常为钢绞线滑脱.温度为150~440℃时,钢绞线热铸锚节点的极限抗拉承载力随温度升高而降低,287℃、340℃、392℃和425℃时的极限承载力分别为常温时的77.3%、39%、35.2%和10.5%.

滇东地区海寨林场针叶林地表可燃物潜在火行为研究

在海寨林场针叶林内设置样地,开展外业调查,采集地表凋落物并进行室内燃烧模拟和实验室理化性质分析,采用SPSS 26.0软件分析数据,探究海寨林场针叶林地表可燃物的特征及潜在火行为。杉木的绝对含水率为(9.40±0.65)%,热值最低为(19 878.9±48.63) kJ/kg,并且杉木的火强度和蔓延速度最小,分别为(259.64±19.73) kW/m和(0.33±0.14) m/min,所以杉木的燃烧性最差;云南松纯林可燃物载量为(0.27±0.12)kg/m2,热值为(21390.88±73.39)kJ/kg,火强度较低,为(307.26±15.83) kW/m,实际烧损率仅为(55.32±15.02)%,云南松的热值最大,容易引燃,但载量太低,无法维持正常燃烧;华山松纯林的热值低于云南松,且火强度和烧损率低于云南松-华山松混交林;云南松-华山松混交林的蔓延速度和火强度为(0.82±0.31) m/min和(564.14±13.53) kW/m,远高于其他3种,潜在火灾风险等级最高。由上述潜在火行为可知,海寨林场4种针叶林引发火灾的风险等级由高到低依次为云南松-华山松混交林、华山松纯林、云南松纯林和杉木。

恐慌情绪和疏散行为交互影响的地铁站火灾疏散仿真方法

为提高地铁站火灾事故发生后的疏散效率,降低人员伤亡和财产损失,考虑到疏散过程中个体恐慌情绪的动态变化,基于元胞自动机模型分析恐慌情绪与疏散行为之间的交互影响,构建地铁站火灾疏散仿真模型,以双层岛式地铁站为例,讨论恐慌情绪对疏散效率和出口选择的影响。研究结果表明:恐慌情绪是人群疏散中的关键因素之一,轻度恐慌有助于缩短疏散时间,而过度恐慌会一定程度上减缓疏散效率;恐慌情绪对出口选择存在显著影响,恐慌人群在出口选择时表现出明显的从众行为。研究结果可为优化地铁站应急安全管理提供参考。

基于EN45545-2:2020+A1:2023的材料厚度对垂直燃烧试验影响的研究(下)

为了研究EN 45545-2:2020+A1:2023《铁路应用机车车辆防火第2部分:材料和零件的防火性能要求》中材料厚度对R26要求的垂直燃烧试验的影响,选用铁路车辆低功率电工电子产品使用的不同厚度的聚碳酸酯、聚酰胺和聚对苯二甲酸丁二醇酯3种非金属阻燃材料进行试验,采用UL94垂直燃烧试验(测试方法同R26要求的垂直燃烧试验)的判定方法确定试验结果。试验结果表明,随着样品厚度的增加,阻燃等级由V-2或V-1等级上升至V-0等级,厚度继续增加,维持V-0等级不变。原因有2种:一是材料的点燃时间随着厚度的增加而逐步增加;二是材料厚度越大,燃烧速率越慢。因此,若相同材料的部件在2个不同的厚度达到V-0阻燃等级,则更厚的部件也能达到V-0阻燃等级。此规律与EN 45545-2:2020+A1:2023中4.2(e)的规定不同,后者规定具有相同组成和密度的不同厚度的2个产品均满足防火要求时,则处于二者之间的所有厚度的产品视为满足要求。试验结果表明,当组成和密度相同但厚度不同的2个产品均满足R26要求的危害等级时,不仅2个厚度之间的产品满足4.2(e)规定,更厚的产品也能满足要求。此规律可用于判定产品是否符合R26要求。

基于EN 45545-2:2020+A1:2023的材料厚度对垂直燃烧试验影响的研究(上)

为了研究EN 45545-2:2020+A1:2023 《铁路应用机车车辆防火第2部分:材料和零件的防火性能要求》中材料厚度对R26要求的垂直燃烧试验的影响,选用铁路车辆低功率电工电子产品使用的不同厚度的聚碳酸酯、聚酰胺和聚对苯二甲酸丁二醇酯3种非金属阻燃材料进行试验,采用UL94垂直燃烧试验(测试方法同R26要求的垂直燃烧试验)的判定方法确定试验结果。试验结果表明,随着样品厚度的增加,阻燃等级由V-2或V-1等级上升至V-0等级,厚度继续增加,维持V-0等级不变。原因有2种:一是材料的点燃时间随着厚度的增加而逐步增加;二是材料厚度越大,燃烧速率越慢。因此,若相同材料的部件在2个不同的厚度达到V-0阻燃等级,则更厚的部件也能达到V-0阻燃等级。此规律与EN45545-2:2020+A1:2023中4.2 (e)的规定不同,后者规定具有相同组成和密度的不同厚度的2个产品均满足防火要求时,则处于二者之间的所有厚度的产品视为满足要求。试验结果表明,当组成和密度相同但厚度不同的2个产品均满足R26要求的危害等级时,不仅2个厚度之间的产品满足4.2 (e)规定,更厚的产品也能满足要求。此规律可用于判定产品是否符合R26要求。

浅析消防行政违法行为的构成要件

作为行政处罚领域的通用规范,行政处罚法为消防法律、法规设定行政处罚和消防救援机构实施行政处罚提供基本遵循。但现行法律法规在处罚法定原则的落实上偏重于法律效果,而对行政违法行为构成要件并未有明确规定,在确定是否构成行政违法认定上,执法人员存在认识上的混乱。消防违法行为的构成要件包括主体要素、主观要素、客体要素以及客观要素。明确的构成要件有助于调查取证的完整性,可以有效增强消防行政处罚的合法性和合理性。

基于“2-4”模型的高校火灾原因分析——以2000—2022年143起高校火灾事故为样本

为预防高校火灾,对2000—2022年143起高校火灾事故进行统计,通过行为安全“2-4”模型进行火灾原因分析,得出直接导致事故的是电器使用不当等19项不安全动作与线路故障等4项不安全物态,间接导致事故的是电器使用习惯不佳等20项习惯性不安全行为,根本上导致事故的是4项安全管理体系的欠缺,根源上导致事故的是9项安全文化元素欠缺和6项安全文化建设不足。根据分析结果,从加强消防安全知识教育培训、健全消防安全管理制度和多样化进行安全文化建设3方面提出高校火灾预防对策。

乙醇沸腾状态对抗醇泡沫灭火剂铺展特性的影响研究

乙醇沸点低、易挥发的特点使其在燃烧时易沸腾、状态易突变,会对抗醇泡沫灭火剂的灭火性能造成极大的影响。本文设计并构建温控操作平台和燃烧试验平台,对抗醇泡沫灭火剂的铺展特性进行试验,从灭火机理出发探究温度上升导致的沸腾状态变化对抗醇泡沫灭火剂铺展窒息效果的影响,进而探究乙醇沸腾状态对抗醇泡沫灭火剂灭火性能的影响规律,为消防救援队伍处置乙醇火灾提供相关数据和理论支持。

Review of state-of-the-art decision support systems (DSSs) for prevention and suppression of forest fires

Forest ecosystems are our priceless natural resource and are a key component of the global carbon budget. Forest fires can be a hazard to the viability and sustainable management of forests with consequences for natural and cultural environments, economies, and the life quality of local and regional populations. Thus, the selection of strategies to manage forest fires, while considering both functional and economic efficiency, is of primary importance. The use of decision support systems(DSSs) by managers of forest fires has rapidly increased. This has strengthened capacity to prevent and suppress forest fires while protecting human lives and property. DSSs are a tool that can benefit incident management and decision making and policy, especially for emergencies such as natural disasters. In this study we reviewed state-of-the-art DSSs that use: database management systems and mathematical/economic algorithms for spatial optimization of firefighting forces; forest fire simulators and satellite technology for immediate detection and prediction of evolution of forest fires; GIS platforms that incorporate several tools to manipulate, process and analyze geographic data and develop strategic and operational plans.

Impact of the red imported fire ant Solenopsis invicta Buren on biodiversity in South China: A review

The red imported fire ant, Solenopsis invicta, is a problematic invasive species in China since at least 2003. Over the past 15 years, a numerous studies were published on the impacts of this species on flora, fauna, and ecosystem function in natural and agricultural systems. We reviewed the literature on S. invicta invasion biology and impacts on biodiversity in South China. Both monogyne and polygyne colonies of S. invicta were introduced to China and polygyne colony is the dominant type. The range expansion rate of S. invicta may reach 26.5–48.1 km yr–1 in China. S. invicta forage activities occur year-round, peaking in the summer and fall in South China and show a preference for insects and plant seeds. We describe the ecological impacts of S. invicta on various habitats in South China, including arthropod community structure disruption and decreases in diversity and abundance of native ant species. S. invicta can replace the role of native ants in mutualisms between ants and honeydew-producing Hemiptera, which results in loss of important food resources for native ants and natural enemies of hemipterans. Further research is required to assess the complex ecosystem-level impacts of S. invicta in introduced areas.

不同烈度林火对油松林潜在地表火行为的影响

油松是我国华北地区代表性树种之一,含有丰富油脂,容易引发大面积高烈度森林火灾。阐明不同烈度林火对油松林地表可燃物负荷量和潜在地表火行为的影响,对于油松林林火管理具有重要意义。以辽河源自然保护区2014年不同烈度林火干扰后油松林分为研究对象,根据不同烈度(重度、中度、轻度)和对照(未过火)分别设置3块20 m×20 m样地,共12块样地,调查地表可燃物和林分结构指标,结合室内实验,利用BehavePlus 5.0软件进行潜在火行为模拟,探讨不同烈度林火5年后油松林地表可燃物负荷量和潜在地表火行为特点,并分析影响潜在地表火行为的主要因素。研究结果表明:(1)不同烈度林火之间,细小可燃物负荷量和地表可燃物总负荷量均不存在显著性差异(P>0.05)。(2)不同烈度林火后,在不同风速和可燃物含水率条件下,油松林潜在地表火蔓延速度、火线强度不存在显著性差异(P>0.05),单位面积发热量、火焰高度、反应强度存在显著性差异(P<0.05)。(3)不同烈度林火后油松林潜在地表火行为主要受油松更新幼苗基径、灌木负荷量、油松平均冠幅、上层枯叶负荷量、油松更新幼苗密度的影响。研究结果表明不同烈度林火均可以降低再次燃烧的火烈度和风险。

考虑心理潜变量的图书馆火灾疏散行为研究

为深入探究图书馆火灾下疏散行为的内在形成机理,综合考虑非适应性、适应性及显著影响疏散决策的6个心理潜变量,采用结构方程模型分析影响疏散过程中行为决策的各疏散心理潜变量之间的内在联系,并探讨个人属性对不同心理潜变量的影响。研究表明:非适应性的恐慌心理对从众、惯性非适应性疏散心理及利他适应性疏散心理均存在显著正影响;非适应性的惯性心理对从众非适应性疏散心理存在显著正影响,对利他适应性疏散心理存在显著负影响;风险感知对非适应性的惯性心理影响较大,环境熟悉度对从众、惯性非适应性疏散心理,利他适应性疏散心理均存在显著正影响;疏散人员的个人属性对部分心理潜变量产生不同程度影响,女性具有较高的风险感知、恐慌与利他心理。

基于云南松林计划烧除的可燃物调控效果评价研究

研究计划烧除效果,可以为森林可燃物调控机制提供科学依据。通过调查计划烧除和未计划烧除云南松林枝下高、地表可燃物载量、地表可燃物厚度、灌木高度及室内火行为对比分析,来评价云南松林计划烧除森林可燃物调控效果。结果表明,计划烧除后云南松林分枝下高得到显著提高,平均提高55.9%;地表可燃物载量显著降低,平均降低42.9%;地表可燃物厚度显著降低,平均降低40.8%;云南松林下灌木高度生长受到抑制,其高度和盖度都显著降低,分别降低59.1%和69.3%;草本植物高度和盖度得到提高,平均增幅20.3%和25.8%;计划烧除后云南松林分地表可燃物燃烧时的蔓延速度显著降低,平均降低50.6%,为0.15 m/s;地表可燃物燃烧时的火强度显著降低,平均降低69.3%,为33.3 kW/m/s;地表可燃物燃烧时火焰高度显著降低,平均降低42.3%,为0.29 m;云南松林分下枝高与火焰高度的距离明显增大,平均增幅91.2%,为1.77 m。通过计划烧除,降低了地表可燃物潜在火强度,减弱了地表火引发树冠火的潜在危险,达到了计划烧除森林可燃物调控的效果。