Failure characteristics and energy evolution process of delayed and instantaneous basalt rockburst under true triaxial conditions

IF 7 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL
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Abstract

Rockburst hazards exhibit different spatiotemporal characteristics in deep tunnel excavation. Failure characteristics and energy evolution process of delayed and instantaneous rockburst of basalt rock were investigated based on single-sided unloading experiments under true triaxial conditions. High-speed photography and acoustic emission (AE) monitoring were used, and computed tomography (CT) scanning, fractal theory, and crack classification were employed for failure analysis. A three-dimensional damage model considering variable stiffness of testing machine was established to calculate the energy evolution of rock-machine system during the entire process of rockbursts. Results show that delayed rockburst includes three stages of small particles ejection, rock slab buckling, and violent mixed ejection, while instantaneous rockburst is characterized by rock slab spalling accompanied with slight particles ejection. Delayed rockburst exhibits a progressive failure mode of large-scale expansion of tensile cracks (before failure) to small-scale penetration of shear cracks (upon failure), while instantaneous rockburst shows a large-scale shear failure and abrupt penetration of shear planes upon failure. Delayed rockburst consumes less energy, and most of dissipated energy is converted into kinetic energy of ejected rock fragments, causing a higher intensity level of rockburst; instantaneous rockburst consumes more energy, but almost all dissipated energy comes from internal friction energy of shear failure, causing a higher scale of rock damage. Before rockburst failure, elastic strain energy stored in rock remains basically unchanged, while the energy stored in testing machine continuously decreases, indicating that rockburst is triggered by energy release of loading system. Energy dissipation rate (EDR) can be used as a precursory index for rock failure induced by quasi-static loading such as delayed rockburst. High EDR means damage intensification, stress drop, active AE events, and acceleration of shear crack expansion inside the rock. The findings of this study can provide new perspectives for the mechanisms and early warning of rockbursts.

真三轴条件下延迟和瞬时玄武岩岩爆的破坏特征和能量演化过程
在深层隧道开挖过程中,岩爆危害表现出不同的时空特征。基于真实三轴条件下的单侧卸载实验,研究了玄武岩延迟岩爆和瞬时岩爆的破坏特征和能量演化过程。采用高速摄影和声发射(AE)监测,并利用计算机断层扫描(CT)、分形理论和裂缝分类进行破坏分析。建立了考虑试验机可变刚度的三维破坏模型,以计算岩爆全过程中岩石-机器系统的能量演化。结果表明,延迟岩爆包括小颗粒喷出、岩板屈曲和剧烈混合喷出三个阶段,而瞬时岩爆的特点是岩板剥落并伴随轻微颗粒喷出。延迟岩爆表现出从大规模拉伸裂缝扩展(破坏前)到小规模剪切裂缝穿透(破坏时)的渐进破坏模式,而瞬时岩爆则表现出大规模剪切破坏和剪切面突然穿透的破坏模式。延迟岩爆消耗的能量较少,大部分耗散能量转化为喷出岩石碎片的动能,导致岩爆强度较高;瞬时岩爆消耗的能量较多,但几乎所有耗散能量都来自剪切破坏的内摩擦能,导致岩石破坏规模较大。岩爆破坏前,岩石中储存的弹性应变能量基本保持不变,而试验机中储存的能量则不断减少,这表明岩爆是由加载系统的能量释放引发的。能量耗散率(EDR)可作为延迟岩爆等准静态加载诱发岩石破坏的前兆指标。高能量耗散率意味着破坏加剧、应力下降、主动 AE 事件以及岩石内部剪切裂缝扩展加速。这项研究的结果可为岩爆的机理和预警提供新的视角。
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来源期刊
CiteScore
14.00
自引率
5.60%
发文量
196
审稿时长
18 weeks
期刊介绍: The International Journal of Rock Mechanics and Mining Sciences focuses on original research, new developments, site measurements, and case studies within the fields of rock mechanics and rock engineering. Serving as an international platform, it showcases high-quality papers addressing rock mechanics and the application of its principles and techniques in mining and civil engineering projects situated on or within rock masses. These projects encompass a wide range, including slopes, open-pit mines, quarries, shafts, tunnels, caverns, underground mines, metro systems, dams, hydro-electric stations, geothermal energy, petroleum engineering, and radioactive waste disposal. The journal welcomes submissions on various topics, with particular interest in theoretical advancements, analytical and numerical methods, rock testing, site investigation, and case studies.
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