岩石非线性阻尼滞后响应特性研究

STUDY OF NONLINEAR DAMPING HYSTERESIS RESPONSE CHARACTER FOR ROCK SAMPLE

通过储层岩样的多重和多级循环加载试验,结合理论分析,研究岩石的非线性阻尼滞后特性。试验结果表明:(1)卸载阶段,应变相位滞后于应力相位;而在加载阶段,应变相位可能超前、相等或滞后于应力相位。(2)多级循环加载过程中,应力–应变曲线的外部循环双向弹性模量、内部小循环单向弹性模量以及动态弹性模量是不同的,并表现出较强的非线性。(3)不同应力条件下,波形尤其是尾波波形会发生变化,为采用尾波干涉进行波速检测提供基础。(4)多级循环加载下相同应力段的小循环具有较好的一致性,而阻尼效应的存在使小循环回到大循环处存在跳跃,小循环应力加、卸载转换点不能很好地记忆。通过分析弛豫机制、黏性阻尼机制以及塑性变形效应,并结合PM模型,研究不同机制对于PM空间密度分布的影响,表明理论分析能够给出与试验结果吻合较好的结果,较好地解释了试验结果。岩石准静态循环加载条件下非线性阻尼滞后响应特性的研究对研究地震波的动态响应特性和探索响应机制是有益的。

The multiple and multi-level cyclic loading tests for using the reservoir rock samples are carried out; and combining with theory analysis, the nonlinear damping hysteresis characteristics are studied. Experimental results show that： （1） At the unloading stage, the strain phase lags the stress phase; and at the loading stage, the strain phase response may lag, be equal to or be ahead of the stress phase. （2） Under multi-stage cyclic loading, exterior loop two-way elastic modulus, interior one-way elastic modulus and dynamic modulus of stress-strain curves are different. （3） Under different stress conditions, the waveform especially the coda waveform changes, that provides base for testing the wave velocity by code wave interference. （4） Small cycles in big cyclic have good consistency at the same stress level. As the existence of the sticky damping effect, the stress conversion point of small cycles can not be well memorized. The relaxation mechanism, the sticky damping mechanism and the plastic deformation mechanism are studied through theoretical analysis. All of them are phenomenological models, and can be used to describe the complex stress-strain properties of rock samples. Theoretical results can give good results qualitatively and quantitatively, comparing with experimental observations results. The study of nonlinear damping hysteresis characteristics under quasi-static cyclic loading is very useful.