Time-Dependent Instability in Rock Masses: Understanding, Prediction and Prevention

人类居住地区岩石结构的不稳定性很重要，在世界范围内造成了生命损失和巨大的经济损失。例子包括滑坡和落石、地下隧道和矿井塌方、大坝和桥梁基础破坏、天坑等。这个为期三年的项目将研究时间对岩石不稳定性的影响，特别是与时间相关的裂纹扩展（模式I， II和III）导致（或协助）现场规模的岩体变形和破坏。总的来说，拉伸和剪切裂缝的随时间增长是现场尺度岩石不稳定性的一个重要而鲜为人知的方面。研究将集中在岩体暴露于边坡或地下开挖时的随时间退化，并将考虑特定的触发岩石失稳的方法，如孔隙压力或冻融。此外，研究将侧重于“裂纹尖端”岩体的退化，而不是由于溶解和其他过程而可能发生的岩体的整体风化。本项目包括以下四个研究任务：1。高级非连续介质数值模拟。关键任务之一是将随时间变化的断裂力学应用到三维非连续介质代码中。这将是对先前研究的延伸，在之前的研究中，时间相关的断裂力学被实现为二维非连续介质代码（Kemeny, 2005）。随时间变化的断裂力学将允许随时间变化的岩石桥梁破坏和导致岩石块体破碎的渐进式裂纹扩展。总的来说，这将使实际野外规模岩体的随时间退化的真实模拟成为可能。地面激光雷达和高分辨率数字成像。将进行案例研究，利用激光雷达和数字成像进行详细的岩体表征。这还包括使用半自动软件来处理激光雷达和数字成像数据。详细的岩石特征数据将提供现场规模岩体的最先进的几何和参数信息，包括岩石桥的特征和可能导致岩石块体粉碎的小特征。新的成像技术可以用来描述原始岩体以及已经发生破坏的退化岩体。这些信息以及实验室测试将为任务1中描述的数值模拟提供基础。3. 制定预测和预防的工具和战略。任务1和任务2的结果，以及正在进行的理论破裂力学关系，将用于更好地理解和改进岩石结构的监测和监测结果的解释。现在正在开发许多技术来“感知”即将发生的岩石破坏，例如微地震监测、位移监测、地震层析成像和其他技术。所有这些技术的基础是对岩体中岩石破坏过程的时空性质的基本理解。通过这项工作，随着我们对随时间变化的岩石破坏的理解的增加，这些技术可以得到改进，新的技术可以开发出来。4. 传播研究成果。这一研究项目的成果将以几种方式传播，包括出版物和报告、远程授课课程以及与工业界、政府和学术机构的合作。这项工作非常符合DUSEL（深部地下科学与工程实验室）提出的岩石力学活动。该项目将与选定的DUSEL场地的设计、施工和运营活动进行合作。这种合作可能包括在选定的DUSEL站点进行案例研究（上面的任务1和2），与其他DUSEL项目和研究人员合作，特别是与地下监测和监测结果解释有关的项目（上面的任务3），以及发表与DUSEL项目和活动相关的研究（上面的任务4）。

The instability of rock structures in areas of human habitat is important and is responsible worldwide for the loss of lives and large financial damages. Examples include landslides and rockfall, the collapse of underground tunnels and mine drifts, dam and bridge foundation failure, sinkholes, etc. This three-year project will investigate the effects of time on rock instabilities, and in particular, time-dependent crack growth (modes I, II, and III) leading to (or assisting with) field-scale rock mass deformation and failure. In general the time-dependent growth of tensile and shear fractures is an important and poorly-understood aspect of field-scale rock instabilities. The research will focus on the time-dependent degradation of rock masses when exposed in slopes or underground excavations, and will consider specific triggering methods for rock instability such as pore pressure or freeze-thaw as necessary. Also, the research will focus on "crack tip" rock mass degradation as opposed to the overall weathering of rock masses that may occur due to dissolution and other processes. This project consists of the following four research tasks:1. Advanced discontinuum numerical modeling. One of the key tasks will be to implement time-dependent fracture mechanics into a three-dimensional discontinuum code. This will be an extension of previous research where time-dependent fracture mechanics was implemented into a two dimensional discontinuum code (Kemeny, 2005). The time-dependent fracture mechanics will allow for time-dependent rock bridge failure and the progressive crack growth that results in the comminution of rock blocks. Overall this will allow realistic simulations of the time-dependent degradation of actual field-scale rock masses.2. Ground-based LIDAR and high-resolution digital imaging. Case studies will be conducted where LIDAR and digital imaging are utilized for detailed rock mass characterization. This also includes the use of semi-automated software for processing the LIDAR and digital imaging data. The detailed rock characterization data will provide state-of-the-art geometric and parameter information on field scale rock masses, including the characterization of rock bridges and small features that may contribute to rock block comminution. The new imaging technologies can be used to characterize pristine rock masses as well as degraded rock masses where failure has taken place. This information, along with laboratory testing, will then provide the basis for the numerical modeling described in task 1. 3. Development of tools and strategies for prediction and prevention. The results from tasks 1 and 2, along with ongoing theoretical fracture mechanics relationships, will be used to better understand and improve the monitoring of rock structures and the interpretation of monitoring results. Many techniques are now being developed to "sense" impending rock failure, such as microseismic monitoring, displacement monitoring, seismic tomography, and other techniques. The basis for all of these techniques is a basic understanding of the spatial and temporal nature of the rock failure process in rock masses. As our understanding of time-dependent rock failure increases through this work, these techniques can be improved and new techniques can be developed. 4. Dissemination of research results. Results from this research project will be disseminated in several ways, including publications and presentations, distance-delivered courses, and collaborations with industry and government and academic institutions.This work fits in very well with the proposed rock mechanics activities for DUSEL (Deep Underground Science and Engineering Lab). Collaboration will take place between this project and design, construction and operation activities at the selected DUSEL site. This collaboration may include case studies at the selected DUSEL site (tasks 1 and 2 above), the collaboration with other DUSEL projects and researchers, particularly those projects having to do with underground monitoring and the interpretation of monitoring results (task 3 above), and publishing research related to DUSEL projects and activities (task 4 above).