循环荷载下岩石阻尼参数测试的试验研究

EXPERIMENTAL RESEARCH ON DAMPING PARAMETERS OF ROCK UNDER CYCLIC LOADING

对岩石阻尼参数测试进行理论分析,利用MTS815FlexTestGT岩石力学试验系统,对细砂岩和粉砂质泥岩进行单轴压缩循环荷载下的试验研究。试验加载波形为正弦波,频率3Hz,加卸载振动循环30次,动应力范围1.0～6.5MPa(即2～12kN)。利用循环加卸载试验方法对岩石阻尼参数进行测试,得到岩石密度与加卸载循环塑性变形、滞回环面积、阻尼比、阻尼系数等的变化特征。在相同测试条件下,岩石密度越大,循环加卸载得到滞回环间的塑性变形则越小,相互滞回环间距为紧密型;反之则塑性变形大,滞回环间距为稀疏型;岩石密度越大,滞回环面积则越小,岩石发生的能量耗散则越小,反之则滞回环面积大,能量耗散也大;阻尼比随密度增加而减小,阻尼系数则大致增加,故可通过岩石密度初步定性判断其阻尼参数特征。

Theoretical analysis of damping parameters of rocks is carried out;and the uniaxial cyclic loading tests for fine sandstone and silty mudstone are realized on MTS815 Flex Test GT rock mechanics test system. The sine wave is achieved in cyclic loading tests,and its frequency is 3 Hz. The cyclic number is 30 under dynamic stresses from 1.0 to 6.5 MPa. The method for testing damping parameters of rock by cyclic loading is provided;and some change characters between rock density and plastic deformation under cyclic loading and unloading are obtained together with the areas of hysteresis loops,damping ratios,damping coefficients,etc.. Under the same test conditions,it is found that the higher the rock density is,the smaller the plastic deformation between the hysteresis loops under cyclic loading and unloading tests is,and the denser the space of hysteresis loops is;conversely,the less the rock density is,the sparser the space of hysteresis loops is. With the rock density increasing,the area of hysteresis loops decreases,and the energy dissipation of rock is less;meanwhile,the area of hysteresis loops and the energy dissipation are larger. The results show that the damping ratio decreases,and the damping coefficient approximately increases with rock density increasing. Thus,it is possible to preliminarily estimate damping parameters according to rock density.