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

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”不稳定区域的知识对地下结构和设施的安全设计至关重要。在低至中等地应力条件下，不稳定区位置和尺寸受开挖几何形状、原位有效应力、岩体非均质性和不连续面影响较大。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影响的理解。本研究解决了在块体理论模型适用的情况下，即在低至中等应力水平下的坚硬节理岩石中，确定地下开孔周围不稳定区大小和形状的问题。不稳定关键块体是主要的破坏机制，除开挖规模外，还受边界面大小和形状以及地应力的稳定作用两个主要因素的限制。本研究将完成以下工作：1)建立键块尺寸分布的分析模型；2)建立键块尺寸的特征概率密度函数；3)将块体理论与应力分析相结合，确定不稳定键块的最大尺寸；4)将2)和3)相结合，建立支撑系统的可靠性分析。本研究结果将适用于隧道掘进、采矿、地下空间开发，以及基础设施修复和安全评估。所开发的方法可以扩展到岩石边坡和基础，通过基于客观，一致和合理程序的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.