不同频率循环荷载作用下岩石阻尼比试验与变形破坏机制细观分析

通过对取自海南昌江核电厂一期工程主厂区的黑云母花岗岩，在RMT－150B多功能全自动刚性岩石伺服试验机进行单轴不同频率的循环加卸载试验，研究花岗岩动应变-应力滞回曲线、动弹性模量和阻尼比同循环频率之间的规律，然后对破坏断裂断口进行细观电镜扫描试验，分析了不同频率下花岗岩断口细观形貌与结构特征。结果表明，花岗岩在循环荷载作用下的加卸应力-应变曲线并不重合，而是形成一个封闭的滞回环；当循环频率在0.01～1.0 Hz范围内变化时，随着频率增大，花岗岩滞回环面积、动弹模和阻尼比都增大；通过细观数字图像试验分析发现，循环荷载作用下，随着频率的增大，岩石断口细观裂纹总的数目、面积、分形维数均变大。文中给出不同频率循环荷载作用下岩石破裂的细观损伤力学机制，研究成果对海南昌江核电厂的地震反应分析和场地安全性评价有着重要参考价值。

Damping ratio experiment and mesomechanical analysis of deformation failure mechanism on rock under different frequency cyclic loadings

The uniaxial different frequency cyclic loadings and unloading tests on biotite granite comes from the Changjiang of Hainan nuclear power first-stage construction major factory district are done on the RMT-150B multi-function automatic rigid rock servo material testing machine. The law between cyclic frequency and dynamic stress- dynamic strain hysteretic curve, dynamic elastic modulus and damping ratio are researched. Then the microtest (SEM) is carried out to study its fractography morphology and microstructure characteristics of failure surface under different frequency cyclic loadings. The results show that the curves of strain and stress for loading and unloading are not superposition under cyclic loading, but hysteretic loops. When cyclic frequency changes between 0.01 Hz and 1.0 Hz, the granite hysteretic loop area, dynamic elastic modulus and damping ratio are increased with frequency increaseing. Based on the testing analysis of microscopic digital image, there are more total number, larger area and fractal dimension of micro-cracks on rock fracture under higher frequency cyclic loading. Mesomechanical damgee mechanism of rock failure under different frequency cyclic loadings is given. The research result offers great reference value to seismic response analysis and site safety evaluation of the nuclear power factory in Changjiang.