Unstable Regions Around Underground Openings: A Model Based on Block Theory, Reliability, Stress Analysis and Linear Programming

CMS-9503855 Matthew Mauldon和Karen Chou，田纳西大学（诺克斯维尔）“地下开口周围的不稳定区域：基于块体理论、可靠性、应力分析和线性规划的模型” 不稳定区域的知识是至关重要的地下结构和设施的安全设计。 在低到中等的原地应力，不稳定区的位置和尺寸的强烈影响，开挖几何形状，在原地有效应力，岩体的不均匀性和不连续性。 合理的开挖设计方法，包括支护系统的设计，应基于对这些主要影响的综合效应的理解。 本研究解决了在块体理论模型适用的情况下确定地下开口周围不稳定区的大小和形状的问题，即，在低到中等应力水平下的坚硬、节理岩石。 不稳定的关键块体，占主导地位的故障机制，是有限的尺寸由两个主要因素，除了开挖尺寸：边界不连续的尺寸和形状，以及稳定的作用，在原地应力。 这项研究将完成1）的分析模型的关键块的大小分布的发展，2）的关键块大小的特征概率密度函数的发展，3）块理论与应力分析相结合，以确定不稳定的关键块的最大尺寸，和4）结合2）和3）开发支持系统的可靠性分析。 这项研究的结果将适用于隧道，采矿和地下空间的开发，以及基础设施的修复和安全评估。 所开发的方法可以扩展到岩石边坡和基础，根据客观，一致和合理的程序进行设计可以节省大量成本。

CMS-9503855 Matthew Mauldon and Karen Chou, The University of Tennessee (Knoxville) "Unstable Regions Around Underground Openings: A Model Based on Block Theory, Reliability, Stress Analysis and Linear Programming" Knowledge of unstable regions is crucial to the safe design of underground structures and facilities. At low to moderate in situ stress, the unstable zone location and dimensions are strongly influences by excavation geometry, in situ effective stresses, and rock mass inhomogeneities and discontinuities. A rational approach to excavation design, including design of support systems, should be based on an understanding of the combined effects of these major influences. This research addresses the problem of determining the size and shape of the unstable zone around underground openings in cases where the block theory model is appropriate, i.e., hard, jointed rock at low to moderate stress levels. Unstable keyblocks, the dominant failure mechanism, are limited in size by two main factors in addition to the excavation size: the sizes and shapes of the bounding discontinuities, and the stabilizing effect of in situ stress. This research will be completed with 1) development of an analytical model for keyblock size distribution, 2) development of characteristic probability density functions for keyblock size, 3) combining block theory with stress analysis to determine maximum size of unstable keyblocks, and 4) combining 2) and 3) to develop a reliability analysis for support systems. The results of this research will be applicable to tunneling, mining, and the development of underground space, as well as to infrastructure rehabilitation and safety assessments. The methods developed can be extended to rock slopes and foundations, with significant cost savings possible from designs based on objective, consistent and rational procedures.