摘要
为了获得单轴荷载下裂隙岩体的裂纹扩展过程及接触力变化的规律,以石膏为相似材料制作含有2种倾角组合的裂隙试样,在刚性试验机上进行单轴条件下的破坏试验,记录裂隙试样的破裂过程。采用离散元软件PFC2D建立数值分析模型,通过校核试验数据确定细观参数值,从宏观和细观两方面分析裂隙试样在压缩过程中微裂隙增长与轴向应力关系、接触力变化与裂纹的产生和扩展的关系,进行裂纹扩展的数值模拟和室内试验对比。结果表明:颗粒间接触力分布随压缩而变得不均匀,主要集中在裂隙的端部,进而产生微裂隙,微裂隙聚集形成宏观裂纹;微裂隙数量在峰值轴向应力之前增加较缓慢,在峰值轴向应力之后迅速增加,微裂隙的增长与应力增长有一定关系;峰值轴向应力之前,观察到轴向应力暂停增加或略微下降,但微裂隙数量持续增加现象,该现象与裂纹扩展有关;用颗粒流程序能较好地分析加载过程试样内细观变化和裂纹的扩展,与试验现象吻合较好。
The aim of this research is to obtain the crack propagation and contact force variation of fractured rock under uniaxial loading. Gypsum was considered as similar material and was used to prepare fractured samples containing two different inclination angles. Destructive tests in uniaxial compression were performed on these samples using rigid testing machine. Failure process of the fractured samples was recorded. Furthermore,numerical model was created by a distinct element method,particle flow code 2D,and micro-parameters for this model were obtained through calibrating laboratory data. The relations between micro-crack increment and axial stress,and contact force change and crack initiation and propagation during loading was analyzed from macro-and-mesoscopic views. The crack development in numerical model and real samples was compared. Results show that contact force distribution within numerical model during loading gradually changes from uniform distribution to that concentrating around flaw tips and then micro-crack develops at these locations. As contact force concentrates intensively,microcracks slowly form into macro-cracks. The number of micro-cracks prior to peak axial stress increases slowly but rapidly after peak axial stress. Increase in the number of micro-cracks is related to that in axial stress. Before axial stress reaches the peak,axial stress stops increasing or even decreases slightly,but the number of micro-cracks grows steadily,which is corresponding to the crack propagation. PFC model could well simulate the mesoscopic change and crack propagation within samples during loading,which matches well with laboratory phenomenon.
出处
《长江科学院院报》
CSCD
北大核心
2016年第4期71-77,共7页
Journal of Changjiang River Scientific Research Institute
基金
国家自然科学基金项目(51008309)
关键词
裂纹扩展
接触力
微裂隙
节理岩体
数值模拟
crack propagation
contact force
micro-crack
jointed rock
numerical simulation
