Shear sliding of rough-walled fracture surfaces under unloading normal stress

IF 9.4 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

Journal of Rock Mechanics and Geotechnical Engineering Pub Date : 2023-10-01 DOI:10.1016/j.jrmge.2023.02.005

Qian Yin , Chun Zhu , Jiangyu Wu , Hai Pu , Qi Wang , Yuanchao Zhang , Hongwen Jing , Tianci Deng

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引用次数: 2

Abstract

Through high-precision engraving, self-affine sandstone joint surfaces with various joint roughness coefficients (JRC = 3.21–12.16) were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses (1–7 MPa) and numbers of shearing cycles (1–5). The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies, while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure criterion. The joint friction angle of fractures exponentially increased by 62.22%–64.87% with JRC while decreased by 22.1%–24.85% with shearing cycles. After unloading normal stress, the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance capacity. The surface resistance index (SRI) of fractures decreased by 4.35%–32.02% with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress, but increased by a factor of 0.41–1.64 with JRC. After sliding initiation, the shear displacement of fractures showed an increase in power function. By defining a sliding rate threshold of 5 × 10⁻⁵ m/s, transition from “quasi-static” to “dynamic” sliding of fractures was identified, and the increase of sliding acceleration steepened with JRC while slowed down with shearing cycles. The normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded, and then enhanced shear dilation after sliding initiation due to climbing effects of surface asperities. Dilation was positively related to the shear sliding velocity of fractures. Wear characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation, indicating an increasing shear area ratio by 45.24%–91.02% with normal stress.

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卸载正应力作用下粗壁断口的剪切滑动

通过高精度雕刻，复制了不同节理粗糙度系数(JRC = 3.21 ~ 12.16)的自仿射砂岩节理面，进行了不同初始法向应力(1 ~ 7 MPa)和不同剪切循环次数(1 ~ 5)的卸载法向应力剪切滑动试验。由于表面形貌逐渐光滑，裂缝的峰值剪应力随剪切循环次数的增加而减小，而随JRC和初始法向应力的增加而增加，可以用非线性Barton-Bandis破坏准则进行验证。在JRC作用下，裂缝节理摩擦角呈指数级增大62.22% ~ 64.87%，而在剪切循环作用下，裂缝节理摩擦角减小22.1% ~ 24.85%。卸载法向应力后，由于裂缝形态更加弯曲，抗剪能力增强，裂缝起滑时间随JRC和初始法向应力的增加而增加。随着剪切循环次数的增加，裂缝的表面阻力指数(SRI)降低了4.35% ~ 32.02%，这是由于滑动起裂剪应力比滑动起裂正应力降低得更明显，而JRC则增加了0.41 ~ 1.64倍。滑移起裂后，裂缝剪切位移呈幂函数增大。通过将滑动速率阈值定义为5 × 10−5 m/s，确定了裂缝从“准静态”滑动到“动态”滑动的过渡，并且滑动加速度的增加随着JRC的增加而变陡，而随着剪切循环的增加而减慢。随着卸荷应力的解除，法向位移在剪切滑动前因变形恢复而略有增大，而在开始滑动后由于表面凹凸不平的爬升作用，法向位移增强。裂缝的剪切滑动速度与扩张率呈正相关。采用二元计算对断口剪切破坏后的磨损特性进行了评价，结果表明，在正常应力下，剪切面积比增加了45.24% ~ 91.02%。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Rock Mechanics and Geotechnical Engineering Earth and Planetary Sciences-Geotechnical Engineering and Engineering Geology

CiteScore

11.60

自引率

6.80%

发文量

227

审稿时长

48 days

期刊介绍： The Journal of Rock Mechanics and Geotechnical Engineering (JRMGE), overseen by the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, is dedicated to the latest advancements in rock mechanics and geotechnical engineering. It serves as a platform for global scholars to stay updated on developments in various related fields including soil mechanics, foundation engineering, civil engineering, mining engineering, hydraulic engineering, petroleum engineering, and engineering geology. With a focus on fostering international academic exchange, JRMGE acts as a conduit between theoretical advancements and practical applications. Topics covered include new theories, technologies, methods, experiences, in-situ and laboratory tests, developments, case studies, and timely reviews within the realm of rock mechanics and geotechnical engineering.