In-situ rock deformation and micron-scale crack network evolution: a high-resolution time-resolved x-ray micro-tomography dataset (NERC Grant NE/R001693/1)

This collection comprises two time-series of 3D in-situ synchrotron x-ray microtomography (μCT) volumes showing two Ailsa Craig micro-granite samples (ACfresh02 and ACHT01) undergoing triaxial deformation. These data were collected in-situ at the PSICHE beamline at the SOLEIL synchrotron, Gif-sur-Yvette, France in December 2016 (standard proposal 20160434) and are fully explained in Cartwright-Taylor A., Main, I.G., Butler, I.B., Fusseis, F., Flynn M. and King, A. (in press), Catastrophic failure: how and when? Insights from 4D in-situ x-ray micro-tomography, J. Geophys. Res. Solid Earth. Together, these two time-series show the influence of heterogeneity on the micro-crack network evolution. Ailsa Craig micro-granite is known for being virtually crack-free. One sample (ACfresh02) remained as-received from the quarry until it was deformed, while the second (ACHT01) was slowly heated to 600 degC and then slowly cooled prior to deformation in order to introduce material disorder in the form of a network of nano-scale thermal cracks. Thus these two samples represent two extreme end-members: (i) ACfresh02 with the lowest possible (to our knowledge) natural pre-existing crack density, and so is a relatively homogeneous sample and (ii) ACHT01 with a thermally-induced nano-crack network imprinted over the nominally crack-free microstructure, and therefore has increased heterogeneity relative to ACfresh02. Each 3D μCT volume shows the sub-region of each sample in which the majority of damage was located and has three parts. Part one is reconstructed 16-bit greyscale data. Part two is 8-bit binary data showing individual voids (pores and micro-cracks) in the dataset after segmentation. Part three is 32-bit data showing the local thickness of each void, as in Cartwright-Taylor et al. (in press) Figures 4 and 5. Each part is a zip file containing a sequence of 2D image files (.tif), sequentially numbered according to the depth (in pixels, parallel to the loading axis) at which it lies within the sample volume. File dimensions are in pixels (2D), with an edge length of 2.7 microns. Each zip file is labelled with the sample name, the relevant letter for each 3D volume as given in Cartwright-Taylor et al. (in press) Tables 3 and 4, part 1, 2 or 3 (depending whether the data are greyscale, binary or local thickness respectively), the differential stress (MPa) on the sample, and the associated ram pressure (bar) to link with individual file names. The following convention is used: sample_letter_part_differentialstress_rampressure_datatype. Also included are (i) two spreadsheets (.xlsx), one for each sample, containing processing parameters and the mechanical stress and strain at which each volume was scanned, and (ii) zip files containing .csv files containing measurement data for the labelled voids in each volume. N.B. void label numbers are not consistent between volumes so they can only be used to obtain global statistics, not to track individual voids.本数据集包含两组三维原位同步辐射X射线显微断层扫描（microtomography，μCT）时间序列数据集，呈现了两块艾尔莎克雷（Ailsa Craig）微花岗岩样品（ACfresh02与ACHT01）受三轴变形的过程。这些数据于2016年12月在法国吉夫叙伊韦特（Gif-sur-Yvette）的SOLEIL同步辐射光源PSICHE光束线原位采集（标准提案编号20160434），详细说明见Cartwright-Taylor A.、Main I.G.、Butler I.B.、Fusseis F.、Flynn M.与King A.（即将刊印）的论文《灾难性失效：原理与时机？基于四维原位X射线显微断层扫描的洞察》，发表于《地球物理学研究杂志：固体地球》。 两组时间序列共同揭示了非均质性对微裂纹网络演化的影响。艾尔莎克雷微花岗岩以几乎无裂纹的特性著称。其中一块样品（ACfresh02）自采石场取出后保持初始状态直至变形实验，而另一块（ACHT01）则先缓慢加热至600摄氏度，随后缓慢冷却，以此引入纳米级热裂纹网络形式的材料无序性。因此，两块样品代表了两个极端端元：（1）ACfresh02：据我们所知，其自然预存裂纹密度达到最低水平，属于相对均质性样品；（2）ACHT01：在名义上无裂纹的微观结构上叠加了热诱导纳米裂纹网络，因此相较于ACfresh02具有更高的非均质性。 每个三维μCT体积数据集均展示了对应样品中损伤主要分布的子区域，且包含三部分内容：第一部分为重建的16位灰度数据；第二部分为经过图像分割后，表征数据集内单个孔隙与微裂纹的8位二值数据；第三部分为表征各孔隙局部厚度的32位数据，对应Cartwright-Taylor等人（即将刊印）的图4与图5。每一部分均为压缩包，内含一系列二维图像文件（.tif格式），文件按其在样品体积内与加载轴平行的深度（以像素为单位）依次编号。文件尺寸以像素为单位（二维），单边缘长度为2.7微米。 每个压缩包的命名遵循以下约定：sample_letter_part_differentialstress_rampressure_datatype，具体包含样品名称、Cartwright-Taylor等人（即将刊印）表3与表4中给出的每个三维数据集对应的相关字母、数据集类型（1、2或3，分别对应灰度数据、二值数据与局部厚度数据）、样品所受的差应力（单位：兆帕），以及用于关联单个文件名的活塞压力（单位：巴）。 此外，数据集还包含：（1）两份电子表格文件（.xlsx格式），分别对应两块样品，内含实验处理参数与各体积数据集扫描时的机械应力与应变数据；（2）若干压缩包，内含各体积数据集内标记孔隙的测量数据对应的.csv文件。注意：不同数据集间的孔隙标签编号不统一，因此仅可用于获取全局统计数据，无法用于追踪单个孔隙。