Micro-mechanical analysis of the effects of stress cycles on the dynamic and static mechanical properties of sandstone
Micro-mechanical analysis of the effects of stress cycles on the dynamic and static mechanical properties of sandstone
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DOI：
10.1016/j.ijrmms.2020.104431
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发表时间：
2020-10
影响因子：
7.2
通讯作者：
Yang Wang;Luanxiao Zhao;De‐hua Han;Xuan Qin;Jiali Ren;Q. Wei
中科院分区：
文献类型：
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作者：
Yang Wang;Luanxiao Zhao;De‐hua Han;Xuan Qin;Jiali Ren;Q. Wei
对于非均质多孔沉积岩，静态力学性质可以与动态弹性性质有很大差异，即使在极低的应力差内。通过设置一系列小应力循环，对一种多孔砂岩和一种致密砂岩进行了单轴加卸载试验，以探讨其静态性质与动态性质之间的关系。实验结果表明，动态杨氏模量的特征是高于静态杨氏模量在几乎任何应力水平，而静态泊松比表示一个较低的值在低应力水平和较高的值在高应力水平的动态泊松比。多孔砂岩的动、静态力学性质均比致密砂岩表现出更强的应力依赖性。分析了两种砂岩应力-应变曲线的非线性和滞后性，绘制了不同分段的广义曲线，并结合轴向颗粒接触模型和摩擦滑动模型，对比研究了其动静态行为背后隐藏的微观机制。从实验和细观力学的角度来看，由小应力循环确定的静态性能更接近于纯弹性，这比与动态弹性性能进行关联更有利。
For heterogeneous porous sedimentary rocks, the static mechanical properties can differ a lot from the dynamic elastic properties, even within an extremely low-stress difference. We perform uniaxial load-unload tests on one porous and one tight sandstone by setting a series of minor stress cycles to explore how the static properties are associated with their dynamic properties. The experimental results suggest that the dynamic Young's modulus is characteristically higher than the static Young's modulus at almost any stress level, whereas the static Poisson's ratio expresses a lower value at low-stress level and a higher value at high-stress level in contrast to the dynamic Poisson's ratio. Both dynamic and static properties of the porous sandstone exhibit more stress-dependences than those of the tight sandstone. We analyze the nonlinearity and hysteresis of the stress-strain curves of two sandstones and draw a generalized curve with different segments to comparatively investigate the hidden micro-mechanisms behind their dynamic-static behaviors, accompanied by an axial grain contact model and a frictional slip model. Form both experimental and micro-mechanical viewpoints, the static properties determined from minor stress cycles are closer to pure elasticity, which are preferable to making correlations with the dynamic elastic properties.