Limestone Cave Collapse Evolution As an Analog for Long-Term Rock Behavior

石灰岩洞穴塌陷演化作为长期岩石行为的模拟

• 批准号: 1332765
• 负责人: John Kemeny
• 金额: $ 36.81万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1332765&HistoricalAwards=false
• 关键词: Limestone; Cave; Collapse; Evolution; Analog

Long-term rock behavior is important for understanding the degradation and failure of rock slopes, underground excavations, dam and bridge foundations, national monuments, and other critical rock structures. Natural underground caverns are an ideal geologic analog for studying long-term rock behavior, because of the relatively constant climate and the preservation of rockfalls that accumulate on the floor of the cave over thousands of years. In this study, the evolution of rock degradation and failure in the Kartchner caverns in southern Arizona will be investigated, using a unique combination of radiometric dating and state-of-the-art geomechanics techniques. First of all, to date the evolution of rockfall that has occurred in the cave over the last 100,000 years, both U-TH and Carbon dating will be used. Because Kartchner is a live cave, speleothems occur on many of the rockfall blocks, and small cores will be taken at the base of these speleothems for dating. Secondly, a new generation ground-based LIDAR scanner will be used to obtain detailed three-dimensional point clouds of the cavern geometry and also of the rockfall fragments on the floor of the cave. The detailed point clouds along with the radiometric data will be used to reconstruct the cave geometry over the past 100,000 years. Finally, three-dimensional modeling will be conducted using the Abaqus finite element program. A time-dependent damage model based on subcritical crack growth will be implemented in Abaqus to simulate cave collapse evolution. Seismic loading of the cave will also be considered, since southern Arizona is susceptible to small to medium levels of seismic hazard.Kartchner caverns provides a unique opportunity to understand long-term rock behavior, and the results should be of great interest to rock mechanics scientists and engineers as well as karst and cave specialists. The results of this research will be used to develop and validate long-term strength models or subcritical crack growth models to correctly predict long-term rock behavior. Kartchner caverns is also an ideal platform to communicate geomechanics to the general public, with public access to 2.4 miles of passages and attracting over 150,000 visitors each year. As part of this research, an interactive geomechanics display case will be established in the Kartchner visitor center, and cave tour guides will provide geomechanics information on their daily tours. The results of this research will hopefully provide new findings in the areas of cave breakdown and sinkhole development. The results of this research might reveal the timing of past seismic events in southern Arizona, and therefore will be of interest to seismologists and also geologists studying Quaternary faulting.

长期的岩石行为对于了解岩坡、地下开挖、大坝和桥梁基础、国家纪念碑和其他关键岩石结构的退化和破坏非常重要。天然地下洞穴是研究长期岩石行为的理想地质模拟，因为相对恒定的气候和数千年来积累在洞穴底部的落石得以保存。在这项研究中，将利用放射性测年和最先进的地质力学技术相结合的独特方法，研究亚利桑那州南部Kartchner洞穴中岩石退化和破坏的演化。首先，为了确定过去10万年来洞穴中发生的落石的演化，将同时使用U-TH和碳测年。由于Kartchner是一个活的洞穴，许多落石区块上都会出现洞穴，因此会在这些洞穴的底部取下小岩芯进行测年。其次，新一代地面激光雷达扫描仪将用于获取洞穴几何形状的详细三维点云以及洞穴底部的落石碎片。详细的点云和辐射数据将用于重建过去10万年的洞穴几何图形。最后，利用ABAQUS有限元程序进行三维建模。基于亚临界裂纹扩展的时间相关损伤模型将在ABAQUS中实现，以模拟洞室坍塌演化过程。由于亚利桑那州南部容易受到中小地震危险的影响，洞穴的地震荷载也将被考虑在内。卡奇纳洞穴为了解岩石的长期行为提供了一个独特的机会，其结果应该引起岩石力学科学家和工程师以及岩溶和洞穴专家的极大兴趣。这项研究的结果将被用来开发和验证长期强度模型或亚临界裂纹扩展模型，以正确预测岩石的长期行为。Kartchner洞穴也是向公众交流地质力学的理想平台，公众可以进入2.4英里长的通道，每年吸引超过15万名游客。作为这项研究的一部分，将在Kartchner游客中心建立一个互动的地质力学展示柜，洞穴导游将提供他们日常旅游的地质力学信息。这项研究的结果有望为洞穴崩塌和天坑发育领域提供新的发现。这项研究的结果可能揭示亚利桑那州南部过去地震事件的时间，因此将引起地震学家和研究第四纪断裂的地质学家的兴趣。