脆性岩石循环加卸载试验及应变损伤参数分析

Experimental Test and Strain Damage Parameters Analysis of Brittle Rock Under Cyclic Loading-Unloading

为研究不同应力状态循环加卸载条件下脆性岩石的强度、变形和损伤力学特性,对马城铁矿辉绿岩开展了单轴压缩、三轴压缩以及单轴、三轴循环加卸载等不同应力路径岩石力学试验,得到了脆性岩石在单轴和三轴条件下的强度、变形特征以及循环加卸载应力-应变曲线变化规律。给出一种岩石循环加卸载过程中相对应变损伤参数,结合现有损伤力学理论,对脆性岩石破坏过程中的损伤演化规律进行了研究。试验结果表明：1UCS条件下,循环加卸载峰值强度比平均单轴压缩峰值强度低10%-20%;CTC条件下,峰值强度出现离散性。2循环加卸载过程中弹性常量变化趋势跟岩石内部微裂隙的闭合、张开、扩展等断裂损伤机制密切相关。3岩石内部的损伤积累程度随循环次数的增加而不断增大,绝对应变损伤参数几乎不受围压作用的影响,而相对应变损伤参数受到围压的约束作用。

To investigate the characteristics of strength, deformation and damage properties of brittle rocks under cyclicloading and unloading conditions of different stress,rock mechanical tests with various of stress paths corresponding as the uni-axial compression test, triaxial compressive test, nniaxial and triaxial cyclic loading and unloading test are carried out on the di-abase specimens from Macheng iron mine, to obtain the strength, deformation properties and the characteristics of completestress-strain curve of brittle rock under cyclic loading and unloading conditions. A kind of relative strain damage parameter inthe process of cyclic loading and unloading test, combined are presented. Combining with the existing damage mechanics theo-ry,the damage evolution of brittle rock are researched in the process of failure. The laboratory investigation shows that （1）Thepeak strength of cyclic loading and unloading test is 10% - 20% lower than the average uniaxial compressive strength, whilethe peak strength appears discreteness under triaxial conditions. （2）The variation trend of elastic constants is closely related tothe damage mechanism of mierocrack closed, open and expansion of rock under cyclic loading and unloading conditions. （3）Theextent of damage accumulation inside the rock increased with the increase of cycles and the absolute strain damage parameterare little affected by confining pressure ,while radial relative strain damage parameter is influenced much by confining pressure.