Characterizing Rock Fractures from Borehole and Tunnel Data

这项研究将开发和测试新的方法，利用圆柱形样品中现成的数据来量化岩石破裂措施。来自钻孔、岩心、隧道和竖井的圆柱形数据广泛可用，但目前用于岩石断裂表征的数据尚未得到充分利用。钻孔和岩心是世界范围内岩土/地质环境现场调查和石油勘探的标准组成部分，钻孔成像技术（如BIPS）发展迅速。在更大的范围内，隧道、竖井和井为研究地下岩体结构提供了良好的窗口。钻孔图像、岩心和全外围隧道图将用于量化裂缝大小、密度（每单位体积岩体的裂缝中心数量）和强度（每单位体积岩体的裂缝面积）——这些都是裂缝丰度测量统一系统的主要组成部分。研究结果可以被工程师或地质学家用来帮助量化井眼、螺栓孔或油井等小直径圆柱体的裂缝特征，以及从隧道和竖井中获得直接、实时的定量裂缝数据。研究的方法包括：(1)通过骨折对圆柱体横截量与部分横截量的比值估算平均骨折尺寸；(2)利用相交、横断和部分横断的频率量化断裂密度和强度；(3)将垂直于柱面轴线的圆形扫描线与平行于柱面轴线的直线扫描线相结合，形成使取向偏差最小化的正交采样几何；(4)对零直径钻孔的Terzaghi校正进行修正，以考虑裂缝尺寸和筒体尺寸。这些方法是先前主要研究人员对暴露在平面上的线性断裂痕迹进行采样和解释的成果。拟议工作的一个关键方面是继续进行涉及土木工程和构造地质学的跨学科研究和教学。这次合作将来自两个领域的研究人员聚集在一起，他们在理解岩石断裂方面有着强烈但不同的兴趣。拟议研究的一个主要目标是将这两种观点融合在一起。该研究的关键成果将是两位共同指导的博士生，他们将在岩石工程和构造地质学方面进行交叉训练。

This research will develop and test new methods for using readily available data from cylindrical samples to quantify rock fracture measures. Cylindrical data from boreholes, rock core, tunnels and shafts are widely available but currently under-utilized for rock fracture characterization. Boreholes and core are standard components of geotechnical/geoenvironmental site investigations and petroleum exploration worldwide and borehole-imaging techniques (such as BIPS) are highly developed and rapidly progressing. On a larger scale, tunnels, shafts and wells provide excellent windows into the subsurface rock mass structure. Borehole images, rock core and full-periphery tunnel maps will be used to quantify fracture size, density (number of fracture centers per unit volume of rock mass) and intensity (area of fractures per unit volume of rock mass) - all major components of a unified system of fracture abundance measures. The research results could be used by engineers or geologists to help quantify fracture characteristics from small-diameter cylinders such as boreholes, bolt holes or oil wells, as well to obtaindirect, real-time quantitative fracture data from tunnels and shafts.Methods to be explored include: (1) estimating mean fracture size from the ratio of transections to partial transections of the cylinder by fractures; (2) using the frequencies of intersections, transections and partial transections to quantify fracture density and intensity; (3) combining circular scanlines normal to the cylinder axis with straight scanlines parallel to the axis to create an orthogonal sampling geometry that minimizes orientation bias; and (4) modification of the Terzaghi correction for zero-diameter boreholes to take into account fracture size and cylinder size. These approaches are outgrowths of previous work by the principal investigators on the sampling and interpretation of linear fracture traces exposed on planar surfaces.A key aspect of the proposed work is continued cross-disciplinary research and teaching involving civil engineering and structural geology. This collaboration brings together investigators from two fields that have strong but different interests in understanding rock fractures. A major goal of the proposed research is to meld the two viewpoints together. A key output of the research will the two co-supervised Ph.D. students, who will be cross-trained in rock engineering and structural geology.