循环荷载下花岗岩动力响应及本构模型

Dynamic Response Law of Granite and Its Constitutive Model with Cyclic Loading

利用真三轴试验机,对尺寸为100 mm×100 mm×100 mm的花岗岩试样进行了循环荷载下的试验研究,探究非破坏状态下不同围压、动载频率、动应力幅以及循环周次下花岗岩动弹性模量以及动阻尼比的变化规律,并将所得数据进行对比分析。试验结果表明:花岗岩动弹性模量随围压线性增长,动阻尼比随围压线性递减,动弹性模量增幅逐渐变大;花岗岩动弹性模量随动载频率指数增长,动阻尼比随动载频率幂函数增长,在20 Hz的动载频率下岩石内部活动较为剧烈,动载频率对岩石的影响程度较大;动弹性模量随动应力幅二次函数增长,动阻尼比随动应力幅幂函数减小,动阻尼比变化受到岩性影响;改进邓肯-张模型很好地反映了花岗岩在不同作用下岩石动态本构关系。该试验得到的模型可为后续动力特性的反演提供参考。

In this paper,the true triaxial testing machine was used to conduct experimental research on granite specimens with size of 100 mm×100 mm×100 mm with cyclic loading,and to explore the dynamic elastic modulus and dynamic damping ratio of granite under different confining pressure,dynamic loading frequency,dynamic stress amplitude,and number of cycle.The changing law of the data was compared and analyzed.The test found that the dynamic elastic modulus of granite increased linearly with the confining pressure,and the dynamic damping ratio decreased linearly with the confining pressure.The growth of dynamic elastic modulus gradually became larger.The dynamic elastic modulus of granite increased exponentially with the dynamic loading frequency,and the dynamic damping ratio increased as a power function with the dynamic loading frequency.At a dynamic load frequency of 20 Hz the internal activity of the rock was more intense,and the frequency had a greater impact on the rock.The dynamic elastic modulus increased as a quadratic function with the dynamic stress amplitude,and the dynamic damping ratio decreased as a power function with the dynamic stress amplitude.The composition of the rock had an influence on the dynamic damping ratio.The improved Duncan-Chang model reflected well the dynamic constitutive relationship of the granite under different actions of the rock.The model obtained in this test could be used as a reference for subsequent inversion of the dynamic properties.