Extreme Heat Geotechnics

建筑物对火灾的敏感性是众所周知的，在世界贸易中心的倒塌中得到了惊人的证明。地下建筑火灾并不罕见，并已导致不可接受的生命损失。1996年的英吉利海峡隧道火灾; 2001年的霍华德圣（巴尔的摩）隧道火灾;和1999年的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级增长，并集中在城市地区，公共通道公路和铁路隧道将成为城市交通网络中越来越常见和必不可少的环节。然而，火灾对这些关键运输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限于土壤在与气候变化相关的狭窄温度和热通量范围内的反应。相比之下，来自火灾的热负荷可能是来自太阳的典型热负荷的50至100倍。这种强烈的热负荷会导致土壤内的剧烈温度梯度、流体相变、水分迁移、土壤孔隙压力的增加以及土壤机械性能的暂时和长期变化。我们建议通过实验，识别整个系统的响应，瞬态和永久性的，饱和和非饱和土壤的长期，强烈的温度梯度，伴随着严重的隧道火灾条件下，典型的浅隧道的应力条件。在火灾发生期间和之后，预计土壤反应将影响整个地下结构的稳定性。将开发一个现实的土壤行为模型，该模型可以反过来理解和预测火灾期间和之后的土壤-隧道相互作用。这项研究代表了马里兰州大学土木工程系和消防工程系的学生和教师之间的强烈合作。这种跨学科的互动将导致创造性的方法和研究成果，否则可能不会被设想。这项工作建立在一项积极的NSF探索性研究小额赠款（SGER）调查的基础上，该调查于2003年6月开始。这项研究代表了第一个科学工作，在三相多孔介质中的非均匀热传输进行了实验研究。一个可靠的一维热-水-力学模型将根据实验测量和观察。该模型将用于理解和预测火灾期间和之后的土壤-隧道相互作用。从教育的角度来看，这项研究将使研究生在一个新兴的重要领域接触到跨学科的研究环境，同时为关键土木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.