Accurate assessment of mechanical behaviour of rock is essential for safe and efficient design of structures on or within rock mass particularly under harsh in-situ stress conditions. Insights from rock engineering practices have revealed that rockbursts can occur at various scales and at any time during mining activities. These violent failure phenomena can be triggered by quasi-static stress redistribution resulting from mining activities as well as dynamically induced loads from seismic events. Moreover, the mechanical behaviour of rock has proven to differ under static and dynamic stress conditions, showing rate-dependent characteristics. Hence, this study aims to thoroughly investigate the triggers that can lead to rockburst events and provide insights into the brittle fracturing process under various stress conditions. To achieve this, a comprehensive set of static and dynamic laboratory tests was conducted on coal samples. The static experiments were conducted under uniaxial and triaxial conditions where the samples were tested at the confining pressures up to 20 MPa. For the dynamic tests, the samples were first pre-stressed uniaxially, biaxially and polyaxially at different ranges of static stresses up to 30 MPa hydrostatically and non-hydrostatically. Then, the high impact velocity up to 21.5 m/s was applied along the maximum stress direction to provide dynamic loading. The influences of loading condition, strain rate and confinement on the mechanical behaviour of coal were investigated. The fracturing process of samples based on their uniaxial, biaxial and polyaxial pre-stressing conditions and various strain rates were analysed to confirm the significant role of loss of confinement and strain rate in severe high-energy fragmentation of coal or so-called “rockburst” under both static and dynamic loadings.

中文翻译：

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多轴静动应力状态下完整岩石的力学特性


准确评估岩石的机械性能对于安全有效地设计岩体上或岩体内部的结构至关重要，尤其是在恶劣的原位应力条件下。来自岩石工程实践的见解表明，岩爆可能以各种规模在采矿活动期间的任何时间发生。这些剧烈的破坏现象可以由采矿活动产生的准静态应力重新分布以及地震事件引起的动态诱导载荷触发。此外，岩石的机械性能已被证明在静态和动态应力条件下有所不同，表现出与速率相关的特性。因此，本研究旨在彻底调查可能导致岩爆事件的触发因素，并提供对各种应力条件下脆性压裂过程的见解。为了实现这一目标，对煤样进行了一套全面的静态和动态实验室测试。静态实验在单轴和三轴条件下进行，样品在高达 20 MPa 的围压下进行测试。对于动态测试，首先在高达 30 MPa 的不同静应力范围内对样品进行单轴、双轴和多轴预应力静压和非静压。然后，沿最大应力方向施加高达 21.5 m/s 的高冲击速度以提供动态载荷。研究了装载条件、应变速率和约束对煤机械行为的影响。 根据样品的单轴、双轴和多轴预应力条件以及各种应变速率分析了样品的压裂过程，以确认在静态和动态载荷下，约束损失和应变速率在煤炭严重高能碎裂或所谓的“岩爆”中的重要作用。