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

CMS-9503855田纳西大学(诺克斯维尔)的Matthew Mauldon和Karen Chou：“地下洞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。在中低地应力下，不稳定带的位置和大小受开挖几何形状、地应力以及岩体的不均匀和不连续性的影响很大。合理的开挖设计方法，包括支撑系统的设计，应该建立在对这些主要影响的综合影响的理解的基础上。研究了在块体理论模型适用的情况下，确定地下洞室周围不稳定带的大小和形状的问题，即在中低应力水平下的坚硬节理岩石。不稳定块体是主要的破坏机制，除了开挖大小外，还受到两个主要因素的限制：边界不连续面的大小和形状，以及地应力的稳定作用。这项研究将通过1)建立钥匙块尺寸分布的分析模型，2)建立钥匙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来确定不稳定的钥匙块的最大尺寸，以及4)结合2)和3)开展支撑系统的可靠性分析。这项研究的结果将适用于隧道挖掘、采矿和地下空间的开发，以及基础设施修复和安全评估。开发的方法可以推广到岩质斜坡和地基，根据客观、一致和合理的程序进行设计，可以显著节省成本。

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.