Abstract 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.

中文翻译：

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应力循环对砂岩动静态力学性能影响的微观力学分析

摘要 对于非均质多孔沉积岩，即使在极低的应力差异下，其静态力学特性与动态弹性特性也有很大差异。我们通过设置一系列较小的应力循环对一块多孔砂岩和一块致密砂岩进行单轴加载-卸载测试，以探索静态特性与其动态特性之间的关系。实验结果表明，在几乎任何应力水平下，动态杨氏模量的特征都高于静态杨氏模量，而静态泊松比在低应力水平下表现出较低的值，在高应力水平下表现出较高的值，与动态泊松比。多孔砂岩的动态和静态特性都比致密砂岩表现出更多的应力依赖性。我们分析了两种砂岩应力-应变曲线的非线性和滞后性，并绘制了不同段的广义曲线，以比较研究其动静行为背后隐藏的微观机制，并附有轴向颗粒接触模型和摩擦滑移模型. 从实验和微观力学的角度来看，由小应力循环确定的静态特性更接近纯弹性，这优于与动态弹性特性的相关性。