Scale Effects in Rock Failure

由于许多岩石工程涉及大型项目，尺度（包括空间和时间）对岩石可变形性和强度的影响是仍然没有很好理解的中心问题。节理和类似的大规模地质不连续被认为是降低强度的主要因素，但有证据表明，即使在“完整”的岩石中也存在显著的尺寸效应。数值模拟的最新发展使得裂缝之间的相互作用和它们之间完整岩石的桥梁能够比过去更真实地分析。位于南达科他州铅市的深部地下科学与工程实验室（DUSEL）为开展基础研究以评估和改进数值预测提供了绝佳的场所。在室内试验中，首先获得完整的荷载-变形曲线，以评估脆性破坏的可能性。利用合成岩体模型对矿柱开挖各阶段的荷载响应进行数值预测。预计测试样品的直径（或边宽，如果是正方形的）范围将从大约2米到5米，所有的最终高度与宽度比为2:1。知识转移将通过“大挑战”来完成，届时将邀请研究和咨询团队提交对实地研究关键阶段结果的盲目预测。这是为了建立最先进的预测模型，并刺激发展。教育任务将是创造和发展机制和技术，通过机器刚度效应来演示、调查和控制地下挖掘。

With much of rock engineering involving large scale projects, the effects of scale - both spatial and temporal - on rock deformability and strength are central issues that are still not well understood. Joints and similar large-scale geological discontinuities are assumed to be the primary factor in reducing strength, but there is evidence to support the existence of a significant size effect even in "intact" rock. Recent developments in numerical modeling allow the interaction of fractures and the bridges of intact rock between them to be analyzed more realistically than in the past. The deep underground science and engineering laboratory (DUSEL) in Lead, South Dakota provides an excellent location to carry out fundamental research to evaluate and improve the numerical predictions.Large-scale in situ compression tests, in which pillars will be loaded to failure, are proposed for DUSEL Complete load-deformation curves will first be obtained in laboratory tests to assess the potential for brittle failure. Numerical predictions will be made of the pillar response to loading - using the Synthetic Rock Mass model - for all stages of pillar excavation. It is anticipated that the test specimens will range in diameter (or side width, if square) from about 2 m to 5 m, all with a final height to width ratio of 2:1. Knowledge transfer will be accomplished through a Grand Challenge, whereby research and consulting teams will be invited to submit blind predictions of the outcome of key stages of the in situ studies. This is intended to establish the state-of-the-art of predictive modeling, and to stimulate development. The educational mission will be to create and develop mechanisms and technologies that demonstrate, investigate, and enable the control of subsurface excavations through machine stiffness effects.