三轴卸荷条件下大理岩扩容与能量特征分析

扩容现象是岩石变形破坏过程中的重要特征。基于MTS815 Flex Test GT岩石力学试验平台,采用室内三轴卸荷试验和塑性力学理论分析,揭示了大理岩在卸荷条件下的扩容特征及能量变化特征。结果表明,随着围压的增大,岩样的各特征应力随之增大,其扩容特征随之减弱；岩样的扩容参数——扩容指标以及剪胀角均具有围压效应,即扩容指标与围压呈良好的指数型分布,剪胀角与应力比呈线性分布；岩样的卸荷破坏过程中能量特征为初始时以可释放应变能为主到破坏时的耗散能为主,其间的转折点为初始损伤扩容点,同时卸荷条件下的特征能量值与围压具有良好的指数类型关系；在峰值点与残余点处,岩样的能量损伤值与剪胀角以及能量特征值与扩容指标均存在着较好的指数类型关系。

Dilatancy and energy properties of marble under triaxial unloading condition

Dilatancy is an important feature of rock during deformation and failure processes. By means of the MTS815 servo-controlled test machine, laboratory triaxial unloading experiments and plasticity theory analysis are made to obtain the characteristics of dilatancy and energy change of marble under unloading condition. The results show that the characteristic stress of rock samples increase and the dilatancy characteristics decrease with the increase of the confining pressure. The dilatancy parameters of rock samples, dilatancy index and dilatancy angle, have obvious effects of confining pressure. The dilatancy index and confining pressure have good exponential distribution, and the relationship between dilatancy angle and stress ratio is linearly distributed. The energy characteristics of rock samples under unloading destruction process are that the main energy is releasable strain energy at the initial stage and dissipation energy at the failure stage, and the turning point between these two stages is the initial damage dilatancy point. Meanwhile the characteristic energy value and confining pressure under unloading condition have a good exponential relationship. Both at the peak point and the residual point, the relationship both between the energy damage amount and the dilatancy angle and between the energy eigenvalues and the dilatancy index has a good exponential distribution.