单轴压缩下岩石能量演化的非线性特性研究

RESEARCH ON NONLINEAR CHARACTERISTICS OF ROCK ENERGY EVOLUTION UNDER UNIAXIAL COMPRESSION

岩石在变形直至破坏失稳中的能量转化是一个动态的过程,大致分为能量输入、能量积聚、能量耗散和能量释放4个过程。通过对不同能量转化机制的非线性关系分析,建立受载岩石能量转化随轴向应力的自我抑制演化模型,并由红砂岩能量演化试验对其进行验证,所建模型适用于岩石变形破坏峰前阶段。研究表明,随应力演化的能量密度值序列遵循标准Logistic映射,能量演化具有分叉和混沌特征,当轴向应力达到约92%峰值应力时,岩石系统进入倍周期分叉区,达到约97.5%峰值应力时,进入混沌区。定义能量迭代增长因子,其随应力单调递增,并初步提出岩石破坏预警判据=3。

Energy conversion during rock deformation and failure is a dynamic process,and it can be mainly divided into four subprocesses：energy input,energy accumulation,energy dissipation and energy release.Based on connection analysis of different energy conversion mechanisms,a self-repression model of energy transform with axial stress is founded;and the model is approved to be suited with the energy evolution in front of peak stress via experiments on red sandstone specimens.Energy density serials with axial stress follow standard Logistic mapping,and it is of the characteristics of bifurcation and chaos.When the axial stress reaches about 92% of peak stress,the rock system turns into period of doubling bifurcation region;and when 97.5% of peak stress,the rock system turns into chaos region.A parameter,called iterative growth factor,which is a monotonically increasing function of axial stress,is proposed;and a new warning criterion for rock failure,that is = 3,is brought out preliminarily.