循环加载强化作用对花岗岩细观破坏影响的离散元研究

Discrete element study on effect of cyclic loading strengthening on meso-destruction of granite

基于室内单轴压缩试验结果,采用离散元方法建立等效晶质模型(GBM).根据室内循环加卸载试验结果改进GBM模型晶内、晶间接触模型,建立能够准确表征循环加载强化作用的GBM强化模型,借此GBM强化模型揭示循环加载强化作用对花岗岩单轴压缩过程细观破坏的影响机制.结果表明,在峰前应力阶段,自锁效应造成的应力分布不同,导致晶内/晶间接触出现以张拉为主的裂纹,石英、长石依次成为承载主体;在峰后应力阶段,前期强化作用所积蓄的剪切能量得到释放,导致长石出现密集的晶内裂纹,是试块失稳的主要标志;长石周边矿物差异性失效引起长石矿物破坏路径改变,造成试块峰值应力随强化系数增大呈现波动性增长.构建的GBM强化模型为研究循环加载强化作用对脆性岩石不同加载路径细观破坏机制提供新方法.

A grain-based model(GBM)was established based on the results of uniaxial compression test by discrete element method.The intragranular and intergranular contact model of GBM was improved according to the results of indoor cyclic loading and unloading tests.A grain-based reinforcement model was established,which accurately characterized the cyclic loading strengthening effect.The grain-based reinforcement model was used to reveal the influence mechanism of cyclic loading strengthening on the mesoscopic failure of granite during uniaxial compression.The results showed that the stress distribution by self-locking effect was different in the pre-peak stress stage,which led to tensile microcracks in intergranular and intragranular contact.The Quartz and feldspar became load-bearing bodies in turn.The shear energy by the earlier strengthening was released in the post-peak stress stage,leading to the intensive intergranular microcracks of feldspar.The phenomenon was the main sign of the instability of the specimen.The differential failure of the minerals around the feldspar caused the change of the feldspar destruction pathways and the peak stress of test block increased with the enlargement of strengthening factor.The grain-based reinforcement model provides a new method,which is used to study the mesoscopic failure mechanism of brittle rocks with different loading paths on cyclic loading strengthening.