空隙岩石非线性变形细观唯象分析及本构模型

三轴压缩条件下空隙岩石非线性变形分析方法及其变形全过程模拟方法是岩石变形力学特性研究的焦点之一。首先,在充分探讨三轴压缩条件下空隙岩石非线性变形机理与特征的基础上,采用细观唯象分析方法,将空隙岩石细观化为由基质材料和裂隙材料2部分串联组成,建立了空隙岩石非线性变形细观唯象分析模型。基于体积柔度与空隙岩石内部张开裂隙数量密切相关的特点,引入了体积柔度与弹性模量之间以及静水压力与裂隙纵横比之间的关系,建立了基质材料的弹性模量与围压之间的关系式。基于连续介质损伤力学理论,建立了三轴压缩条件下基质材料变形破坏过程的统计损伤本构模型。然后,在空隙岩石非线性变形细观唯象分析模型的基础上,建立了空隙岩石变形破坏全过程的统计损伤本构模型,并给出了模型参数的确定方法。最后,根据红砂岩和煤岩2类岩石三轴压缩试验资料对模型和方法的合理性与可行性进行了验证。结果表明:本模型不仅能够较好地反映三轴压缩条件下空隙岩石空隙压密非线性上凹变形特征,也能够反映出岩石弹性模量随围压增大而不断增大的变化特点,还能够较好地模拟出岩石峰值后区变形特征。空隙岩石非线性变形细观唯象分析模型和基质材料弹性模量分析模型的合理性得到了较好的验证,该模型和方法具有一定的可行性。

考虑空隙压密阶段特征的岩石应变软化统计损伤模拟方法

为建立能很好地反映岩石变形破坏全过程模拟方法,针对现有岩石统计损伤本构模型难以反映初始压密阶段变形非线性的局限性与不足,首先,在充分探讨空隙岩石变形机理基础上,采用宏观与微观相结合的分析方法,将空隙岩石抽象为岩石骨架和空隙两部分组成,建立空隙岩石变形分析模型;然后,在探讨空隙部分变形机理基础上,考虑空隙压密引起变形的不可恢复性特征,建立空隙部分变形分析方法,同时,引入统计损伤理论,建立岩石骨架变形分析方法,进而建立模拟空隙岩石变形破坏全过程的统计损伤本构模型,并给出了其参数确定方法。该模型不仅能反映空隙岩石的应变软化特征,而且,还能较好地反映空隙岩石在初始压密阶段的变形非线性特点。最后,通过试验曲线、本文及现有同类模型理论分析曲线的比较,表明了该模型与方法的合理性与优越性。

Influence of void space on microscopic behavior of fluid flow in rock joints

Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.