地震作用下岩石动态力学参数估算方法探讨

岩体在地震作用下的动态力学参数是对岩石工程准确地进行地震稳定性分析的基础。在探究地震作用下岩石材料合理应变速率基础上,利用动态力学试验与岩体力学参数的经验估算方法,讨论考虑地震作用的岩石动态力学参数估算问题。结果表明:(1)对于依托工程而言,相应的地震代表性应变速率为10^-2~5×10^-2/s。这一应变速率范围介于准静态和传统上的"中等应变速率"之间。(2)对动力学试验结果进行拟合时发现,强度包络线的形状并不随着应变率的增加而变化,仅有强度包络线截距变化。基于此提出考虑动态应变速率的地震动态强度参数估算经验公式,可在静态参数和应变速率的基础上估算考虑地震作用的动态强度参数。(3)基于Hoek&Diederichs经验公式,给出地震作用下岩体动态模量的估算方法。(4)最终,结合岩体的地震动态强度参数与模量参数的估算方法,提出考虑地震作用的岩石动态力学参数估算方法。并以白鹤滩水电站岩体为例,对这一方法进行了说明。

A discussion on estimating dynamic mechanical parameters of rocks considering earthquake actions

Dynamic mechanical parameters of rock mass under earthquake actions are the basis for accurate seismic stability analysis of rock engineering. In the present study,on the basis of exploring the reasonable strain rate of rock materials under earthquake actions,tests and empirical formulas were utilized to investigate the problem of determining the mechanical parameters for igneous rocks considering seismic effect. The results show that,for the relying projects,the corresponding representative strain rate is in the range of 10^-2 to 5×10^-2/s which is between the quasi-static rate and traditional "medium strain rate". Fitting analysis of dynamic test results reveals that the intercept of the strength envelope changes with the strain ratio while the shape of the envelope keeps changeless. Consequently,empirical formulas for evaluating dynamic strength parameters were proposed using static parameters and the strain ratio,and a estimating method of rock dynamic modulus under seismic actions was presented based on Hoek & Diederichs equation. The Baihetan hydropower plant project was taken as a study case to illustrate the proposed approach.