三轴循环荷载下大理岩阻尼参数的试验研究

Experimental Study on Damping Parameters of Marble Under Triaxial Cyclic Loading

在MTS815 Flex Test GT岩石力学试验系统上对大理岩在4级不同围压下进行试验,每级围压下分3级动应力进行循环加卸载,得到三轴应力状态下大理岩阻尼比和阻尼系数与不同应力状态之间的变化规律。通过试验发现:在同一级应力状态下岩石塑性变形随着加载次数的增加逐渐增大,每次动循环岩石的能量耗散随着σmax/σc和围压σ3的增大而增大;同一级围压下,阻尼比和阻尼系数随着动应力振幅增大而递增,且随着围压的增大,递增的速率呈现出变快的趋势;在相同的σmax/σc下,阻尼比和阻尼系数随着围压的增大而递增,且随着σmax/σc的增大,递增的速率呈现出变快的趋势。岩石在高应力条件的循环荷载下,内部微裂纹扩展程度和新裂纹产生的数量和规模以及不可逆塑性变形更大,高应力水平下的每次循环荷载能量耗散也相应增加。

The damping parameters including damping ratio and damping coefficient of marble under triaxial cyclic loading were studied through experiments by MTS815 Flex Test GT rock mechanics testing system sets.For the marble under four grades of confining pressures,cyclic loading and unloading was carried out by three levels of dynamic stress under each confining pressure.The regularity in the changes of damping ratio and damping coefficient of marble under triaxial stress and different stress statuses was found as follows： with the increase of loading times,the plastic deformation of rock under the same stress status increased gradually,and the energy dissipation also increased with the rising of σmax/σc and confining pressure σ3.Meanwhile,under the same confining pressure,the damping ratio and damping coefficient increased progressively with the increment of dynamic stress amplitude,and accelerated along with the increase of confining pressure.Under the same σmax/σc,the damping ratio and damping coefficient increased progressively with the rising of confining pressure,and accelerated along with the increase of σmax/σc.Moreover,with the expansion of internal microcrack of the rock and the increase of the quantity and scale of new cracks as well as the irreversible plastic deformation under a cyclic loading of high level stress,the energy dissipation of each cycle increased accordingly.