Abstract: As welll known,the instability modes of rocks depend on quite a number of factors,such as rock type,fault gouge,temperature,confining pressure,strain rate and liquid media,etc.It is emphasized in the paper that all of them are associated with the plastic components contained in rocks to different extent.The plastic components of rocks are referred to those of minerals which can deform irreversibly under the given geological and physical environment.Triaxial compression tests of intact quartzite,granite,granodiorite,gabbro and basalt under room temperature and confining pressures up to 0.7 GPa indicate that the contents of plastic components in rocks have no obvious effect on the magnitudes of stress drop of sudden instability,but do influence the instability modes.The plastic components filled in the elastic framework of rock affect the elastic behavior of rock specimen on the whole in two aspects: (1)The effective bearing area of specimen and the effective height of reversible deformation part in specimen are reduced and higher stress level is necessary to accumulate enough reversible strain energy for sudden instability; (2) The plastic components,as damping elements,hinder the rebound of elastic framework and higher strain energy is necessary too.

摘要： 石英岩、花岗岩、花岗闪长岩、辉长岩和玄武岩在室温、固体围压(最大0.7GPa)下所进行的三轴压缩试验表明,岩石的塑性成分含量对突发失稳应力降没有明显影响,但影响岩石的失稳型式。塑性成分条件是突发失稳和强震的必要条件之一,只有当塑性成分不超过某种限度时,才可能发生突发失稳和强震。文中初步地建立了塑性成分条件的定量判据。