泥岩夹层对盐岩变形和破损特征的影响分析

INFLUENCE OF MUDSTONE INTERLAYER ON DEFORMATION AND FAILURE CHARACTERISTICS OF SALT ROCK

针对我国大多数盐矿的多层盐岩地质构造特征,对含泥岩夹层盐岩、纯泥岩和纯盐岩3种岩芯试样进行单轴压缩和不同围压下三轴压缩试验研究,对比分析3种试样的变形和破坏特性。试验结果表明:泥岩夹层对盐岩体的变形和破坏特性有明显的影响,强度高于盐岩的泥岩夹层却先于盐岩出现横向拉伸破坏;此外还观察到应力–应变曲线的“应力跌落”现象。针对试验结果,利用Cosserat介质扩展理论对泥岩夹层的影响进行理论分析。分析结果表明,泥岩和盐岩力学特性上的不匹配导致二者界面附近泥岩体等效受到横向拉伸应力作用,这很好地解释试验结果,这一分析结果可对进一步进行层状盐岩体内油(气)储库洞室稳定性分析提供理论基础。

Considering the geological formation characteristics of most salt mines in China, experimental studies of uniaxial and triaxial compression were carried out on three kinds of intedayered salt rock samples. The experiments indicated that the presence of mudstone interlayer affects the deformation and failure characteristics of samples remarkably. It was observed that the mudstone fractured prior to salt rock though its uniaxial peak strength is higher than that of the later, and a stress drop phenomenon was also observed in these tests. Motivated by the experimental phenomena, an analysis of the influence of interlayer based on the Cosserat medium expanding theory was presented. The theoretical results indicate it is the mismatch of mechanical properties of two adjacent layers that result in an equivalent tension stress are applied to the stiffer interlayer. The analytical results may provide a theoretical frame for further study on the stability of the oil/gas storage cavern in bedded salt rock formation.