Abstract
Core discing often occurs in deep rocks under high-stress conditions and has been identified as an important characteristic for deep rock engineering. This paper presents the formation mechanism of core discing firstly. Then, the interaction between diamond drill bits and rock was analyzed based on numerical modeling. A novel drill bit with an inner conical crown for the mitigation of core discing was designed and verified by simulation experiments. The mitigation method was applied in the cavern B1 of CJPL-II and satisfactory results had been achieved. The percentage of core discing had been obviously decreased from 67.8% when drilling with a rectangular crown drill bit, to 26.5% when an inner conical crown drill bit had been adopted. This paper gives full insight into core discing characteristics and provides a new method for core discing mitigation; it will potentially contribute to stress measurement in deep rock engineering.
摘要
岩芯饼化是深部岩石在高应力条件下钻孔时经常发生的现象,是深部岩石工程的一个重要特征。 本文首先介绍了岩芯饼化的形成机理, 基于数值模拟分析了金刚石钻头与岩石之间的相互作用, 通过 数值模拟实验设计并验证了一种可以用于减轻岩芯饼化的新型内圆锥形冠状金刚石钻头。将该方法应 用于CJPL-II的B1 实验室中, 取得了满意的效果, 饼化岩芯所占的百分比从使用矩形冠状钻头钻进 时的67.8%明显降低到采用内圆锥形冠状钻头时的26.5%。本文全面介绍了深部岩石岩芯饼化特征, 并为缓解岩芯饼化现象提供了一种新方法, 这将有助于深部岩石工程中的应力测量。
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The general idea and method of this paper were developed by ZHENG Ming-zong and LI Shao-jun. ZHENG Min-zong was responsible for the full-text writing. YAO Zou and ZHANG Ao-dong provided drill bits and ZHOU Ji-fang provided a site for the field test in this paper. ZHENG Min-zong and XU Ding-ping carried out numerical simulation. LI Shao-jun and XU Ding-ping edited the draft of manuscript. All authors replied to reviewers’ comments and revised the final version.
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ZHENG Ming-zong, LI Shao-jun, YAO Zou, ZHANG Ao-dong, XU Ding-ping, and ZHOU Ji-fang declare that they have no conflict of interest.
Foundation item: Projects(U1765206, 51979268, 51621006) supported by the National Natural Science Foundation of China
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Zheng, Mz., Li, Sj., Yao, Z. et al. Core discing characteristics and mitigation approach by a novel developed drill bit in deep rocks. J. Cent. South Univ. Technol. 27, 2822–2833 (2020). https://doi.org/10.1007/s11771-020-4512-x
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DOI: https://doi.org/10.1007/s11771-020-4512-x