Extreme Heat Geotechnics

建筑物对火灾的敏感性是众所周知的，这在世贸中心的倒塌中得到了惊人的证明。地下建筑的火灾并不罕见，并导致了不可接受的生命损失。1996年英吉利海峡隧道大火；2001年霍华德街（巴尔的摩）隧道；和1999年勃朗峰公路隧道火灾是最近持续的大规模隧道火灾的例子。随着世界人口继续呈指数增长，并集中在城市地区，公共公路和铁路隧道将成为城市交通网络中越来越普遍和必不可少的环节。然而，火灾对这些关键交通部件和其他地下空间的影响却很少受到土木工程的关注。热负荷对土壤影响的研究主要局限于土壤在与气候变化相关的狭窄温度和热通量范围下的响应。相比之下，火灾的热负荷可能是太阳典型热负荷的50到100倍。这种强烈的热负荷会导致土壤内部剧烈的温度梯度、流体相变、水分迁移、土壤孔隙压力增加，以及土壤力学特性的临时和长期变化。我们建议通过实验确定在典型的浅埋隧道应力条件下，饱和和非饱和土壤对伴随严重隧道火灾条件的长时间、强烈温度梯度的整个系统响应，包括瞬态和永久响应。这种土壤反应预计将影响整个地下结构的稳定性，无论是在火灾发生期间还是之后。一个现实的土壤行为模型将被开发出来，反过来，可以联系到理解和预测火灾期间和之后土壤-隧道的相互作用。这项研究代表了马里兰大学土木工程系和消防工程系的学生和教师之间强有力的合作努力。这种跨学科的互动将产生创造性的方法和研究成果，否则可能无法想象。这项工作建立在2003年6月开始的美国国家科学基金会探索性研究小额赠款（SGER）调查的基础上。本研究是首次对三相多孔介质中非均匀热输运进行实验研究的科学工作。一个可信的一维热-水-力学模型将建立在实验测量和观察的基础上。该模型将用于了解和预测火灾期间和火灾后土-隧道相互作用。从教育的角度来看，这项研究将使研究生接触到一个新兴重要领域的跨学科研究环境，同时为关键土建工程的工程开发智力资本，应用更广泛的方法来解决问题。pi强调招募代表性不足的群体的学生成员，因为这为角色建模和指导提供了特殊的机会。

The sensitivity of structures to the insult of fire is well established and was stunningly demonstrated in the World Trade Center collapse. Fires in underground structures are not uncommon, and have led to unacceptable loss of life. The 1996 Channel Tunnel fire; the 2001 Howard St. (Baltimore) Tunnel; and the 1999 Mont Blanc road tunnel fire are recent examples of sustained, large-scale tunnel fires. As world populations continue to grow exponentially, and are concentrated in urban areas, public access highway and rail tunnels will become ever more common and essential links in urban transit networks. The impact of fire on these key transportation components and other underground spaces, however, has received relatively little civil engineering attention. The study of the effects of thermal loading on soil has been largely limited to soil response when subjected to the narrow temperature and heat flux ranges associated with climatic changes. Thermal loadings from a fire, in contrast, may be 50 to 100 times that of typical thermal loads from the sun. This intense thermal loading can result in dramatic temperature gradients within the soil, fluid phase change, moisture migration, increases in soil pore pressures, and both temporary and long term changes to mechanical properties of the soil. We propose to identify through experimentation, the whole system response, both transient and permanent, of saturated and unsaturated soil to prolonged, intense temperature gradients that accompany severe tunnel fire conditions, under stress conditions typical of shallow tunnels. That soil response is expected to impact the stability of the entire underground structure, both during and after a fire event. A realistic model of soil behavior will be developed that can be linked, in turn, to understanding and predicting soil-tunnel interaction during and after fires. This research represents a strong collaborative effort between students and faculty in the Civil Engineering and the Fire Protection Engineering Departments at the University of Maryland. This cross-disciplinary interaction will result in creative approaches and research findings that may not have been conceived otherwise. The work builds on an active NSF Small Grants for Exploratory Research (SGER) investigation, which began in June 2003. This research represents the first scientific work where non-uniform thermal transport has been experimentally investigated in three-phase porous media. A credible 1-D thermo-hydro-mechanical model will be developed based on the experimental measurements and observations. This model will be used to understand and predict soil-tunnel interaction during and after fires. From an education point of view, the research will expose graduate students to a cross-disciplinary research environment in an area of emerging importance, at the same time developing intellectual capital for engineering of key civil works, applying a broader approach to the problem. The PIs emphasis on recruiting student members of underrepresented groups because of the special opportunity this presents for role modeling and mentoring.