基于能量耗散的深部大理岩剪胀特性研究

Mechanical response and dilatancy characteristics of deep marble under different stress paths: A sight from energy dissipation

摘要

剪胀是岩石在荷载作用下体积增长的一种普遍行为, 是理解岩石复杂非线性行为和构建本构方程的一个关键指标. 本文利用取自2400 m埋深锦屏地下实验室的锦屏大理岩, 进行不同准静态应变率单轴压缩、 三轴压缩试验以及不同围压下的加载、 卸荷试验, 分析了大理岩在四种应力路径下的力学响应和剪胀破坏特性, 提出了基于能量耗散法的新的经验剪胀系数. 结果表明, 随着应变速率的增加, 大理岩在单轴压缩条件下的脆性破坏特征更加明显, 而三轴压缩条件下的塑性破坏特征逐渐增强. 卸围压条件下的大理岩体积膨胀比恒围压条件下更小. 能量耗散与大理岩剪胀过程密切相关, 耗散能的迅速增加与大理岩剪胀的开始相吻合, 根据能量耗散率曲线的变化趋势, 定义了一个新的经验剪胀系数, 其变化趋势与大理岩在不同应力条件下的实际力学响应和剪胀破坏特征相一致. 对现有的 经验剪胀模型和理论剪胀模型进行了分析, 结果表明, 基于能量背景的经验剪胀系数更具有普遍性.

Abstract

Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock. This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m. Various uniaxial and triaxial tests at different strain rates, along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths. Subsequently, a new empirical dilatancy coefficient is proposed based on the energy dissipation method. The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing, and plastic failure characteristics of marble under triaxial compression are gradually strengthened. Furthermore, compared to the constant confining pressure, the volume expansion is relatively lower under unloading condition. The energy dissipation is closely linked to the process of dilatancy, with a rapid increase of dissipated energy coinciding with the beginning of dilatancy. A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve, of which change trend is consistent with the actual dilatancy response in marble under different stress paths. The existing empirical and theoretical dilatancy models are analyzed, which shows that the empirical dilatancy coefficient based on the energy background is more universal.

Keywords

deep marble / stress paths / dilatancy / energy dissipation / empirical dilatancy coefficient

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