Experimental Observations of the Elastic and Inelastic Behaviour of Porous Sandstones
Experimental Observations of the Elastic and Inelastic Behaviour of Porous Sandstones
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DOI：
10.1111/j.1365-246x.1994.tb03940.x
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发表时间：
1994-05
影响因子：
2.8
通讯作者：
Y. Bernabé;D. Fryer;R. Shively
中科院分区：
文献类型：
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作者：
Y. Bernabé;D. Fryer;R. Shively
为了研究多孔砂岩的机械性能，在真空干燥和水饱和条件下，对孔隙率为17%至30%的八种砂岩进行了一些机械试验，包括蠕变试验。为了解释数据，必须将总应变的弹性和非弹性部分分开。小的应力偏移（岩石的弹性行为沿其沿着）沿主应力路径以离散的间隔沿着进行，这使我们能够估计应力/应变曲线上沿着不同点的弹性模量。我们观察到，弹性常数随平均应力的增加而显著增加，但弹性常数的大小和压力依赖性与目前提出的颗粒接触模型不一致。知道了弹性常数，我们就计算了变形的弹性部分，并通过差分计算了变形的非弹性部分。这项研究证实，塑性模型，如在土壤力学中使用的那些可以占，至少定性地说，多孔砂岩的非弹性行为的许多功能。特别是，我们观察到存在一个帽关闭的屈服面在静水压力方向。在这里使用的相对较低的应力范围内，非弹性行为似乎是由摩擦机制，而不是由晶粒断裂，通常观察到在较高的应力水平。非弹性似乎也与时间依赖密切相关。接近失效时，蠕变速率很高，而且在水的存在下加速。最后，比较弹性模量测量沿着不同的应力路径，使我们能够检测和量化的力学各向异性在一些岩石考虑。
SUMMARY In order to investigate the mechanical behaviour of porous sandstones, a number of mechanical tests, including creep tests, were run on eight sandstones ranging from 17 to 30 per cent porosity, in both vacuum-dry and water-saturated conditions. to interpret the data it is essential to separate the elastic and inelastic parts of the total strain. Small stress excursions, along which the rock behaved elastically, were performed at discrete intervals along the main stress path. This allowed us to estimate the elastic moduli at various points along the stress/strain curve. We observed that the elastic constants increased significantly with increasing mean stress, but the magnitudes and pressure-dependence of the elastic constants were not consistent with presently proposed grain contact models. Knowing the elastic constants, we computed the elastic and, by difference, the non-elastic parts of the deformation. This study confirms that plasticity models such as those used in soil mechanics can account, at least qualitatively, for many features of the inelastic behaviour of porous sandstones. In particular, we observed the existence of a cap closing the yield surface in the hydrostatic pressure direction. In the relatively low stress range used here, the inelastic behaviour appeared to be controlled by frictional mechanisms rather than by grain fracturing as is commonly observed at higher stress levels. Non-elasticity seemed also to be closely connected to time dependence. Near failure, the creep rates were high and, furthermore, accelerated in the presence of water. Finally, comparison of the elastic moduli measured along different stress paths allowed us to detect and quantify mechanical anisotropy in some of the rocks considered.