冻融循环下云母石英片岩三轴力学特性与强度预测模型

为探究云母石英片岩物理力学特性受冻融循环作用的影响,对饱水云母石英片岩开展了0、25、50、75、100次冻融循环试验,并对试样分别进行了4级围压下的常规三轴压缩试验,研究了其动弹性参数、三轴压缩破坏形式及三轴抗压强度的变化规律,取得如下成果:①随着冻融循环次数的增加,三轴抗压强度、动弹性模量、动剪切模量及动体积模量呈指数衰减,黏聚力及内摩擦角则呈线性衰减趋势;②随着冻融循环的进行,围压对试样强度的增大作用逐渐削弱,冻融循环对试样强度的劣化作用逐渐凸显;③冻融作用使云母石英片岩三轴压缩破坏形态由张拉破坏逐步演化为顺片理剪切破坏;④基于Jaeger破坏准则建立了一种以冻融循环次数、片理面倾角及围压为控制参数的斜交片理云母石英片岩三轴抗压强度预测模型,预测结果与实测数据具有较好的一致性。研究成果可为研究云母石英片岩冻融损伤劣化规律提供参考。

Triaxial Mechanical Properties and Strength Prediction Model of Mica Quartz Schist under Freezing-thawing Cycles

The aim of this research is to explore the influence of freeze-thaw cycles on the physical-mechanical properties of mica quartz schist. Freezing-thawing test (0, 25, 50, 75, and 100 freezing-thawing cycles) was conducted on water-saturated mica quartz schist specimens and also conventional triaxial compression test was carried out under four levels of confining pressure. The dynamic elastic parameters, the failure mode caused by triaxial compression and the change rule of triaxial compressive strength were examined. Test results are presented as follows: 1) with the increase of freeze-thaw cycles, the triaxial compressive strength, dynamic elastic modulus, dynamic shear modulus and dynamic bulk modulus declined exponentially, while cohesion and internal friction angle decreased linearly. 2) Along with the proceeding of cyclic freezing and thawing, the boosting effect of confining pressure on the strength of samples were gradually weakened, whereas the deterioration effect of freezing-thawing cycles on the strength of samples became more prominent. 3) Under cyclic freezing and thawing, the triaxial compression failure pattern of mica quartz schist altered from tension failure to shear failure along schistose plane. 4) In addition, on the basis of the Jaeger failure criterion, a triaxial compressive strength prediction model for oblique schistosed mica quartz schist was established with the number of freezing-thawing cycle, the inclination of schistose plane, and confining pressure as control parameters. The prediction results were in good agreement with measured data.