摘要
节理裂隙对岩石的强度破坏及裂纹扩展特征具有显著影响.为了进一步认识预制裂隙对断续裂隙岩石力学行为的影响,本文在一组经过室内试验标定的细观参数的基础上,进行了断续三裂隙砂岩试样单轴压缩颗粒流模拟.基于模拟结果,分析了岩桥倾角对裂隙砂岩试样应力-应变曲线、强度变形参数以及裂纹扩展特征的影响.研究结果表明:(1)峰值强度、弹性模量、峰值应变、裂纹起裂应力和贯通应力均随着岩桥倾角的增大呈先减小后增大再减小变化趋势,而裂纹损伤阈值与岩桥倾角之间无明显相关性;(2)岩桥倾角主要影响中间裂隙2的起裂模式,当岩桥倾角较小时裂隙2尖端不易萌生裂纹;(3)裂纹贯通模式和程度均与岩桥倾角密切相关.当岩桥倾角为0°、30°和60°时只有2处贯通,岩桥倾角为90°和120°时发生4处贯通,而岩桥倾角为150°时有5处贯通.裂纹贯通形式主要分为7类,而且断续三裂隙砂岩贯通模式是其中一类或多类贯通形式的组合.最后,从细观应力场和位移场角度讨论了岩桥倾角较小时中间裂隙2尖端裂纹较难起裂的原因.
The pre-existing fissures have a significant effect on the strength failure and cracking behavior of rock.To further investigate the effects of pre-fissures on fracture mechanical behavior,a series of PFC2 D numerical simulations for sandstone specimen containing three parallel fissures were carried out under uniaxial compression using the calibrated micromechanical parameters.On the basis of numerical results,the influences of ligament angle on stress-strain curves,strength and deformation parameters and crack evolution characteristics of sandstone containing three fissures were analyzed in detail.The investigation shows that:(1)The peak strength,elastic modulus,peak strain,crack initiation stress and crack coalescence stress of pre-fissured specimen all first decrease then increase and finally decrease with the increasing of ligament angle,while the crack damage threshold has no obvious relationship with the ligament angel.( 2) The crack initiation mode near fissure(2) is closely related to the ligament angle. When the ligament angle is low,cracks are hard to initiate from the tips of fissure(2).(3) The crack coalescence mode and extent of three-fissured specimens depend on the ligament angle. When the ligament angles are 0°,30° and 60°,only two crack coalescences between the two pre-existing fissures are observed. When the ligament angles are 90° and 120°,four crack coalescences occur. However,when the ligament angle is equal to 150°,five crack coalescences can be found in the specimen. Seven types of crack coalescence are identified according to the simulated results and crack coalescence mode of sandstone containing three fissures may be one of the seven types or combination of several types. Finally,the reason why hard to initiate from the tips of fissure(2) with low ligament angle was discussed based on the meso-stress field and displacement field.
出处
《应用基础与工程科学学报》
EI
CSCD
北大核心
2016年第6期1232-1247,共16页
Journal of Basic Science and Engineering
基金
江苏省杰出青年基金项目(BK20150005)
国家自然科学基金项目(41272344)
关键词
岩石力学
力学特性
裂纹演化
岩桥倾角
细观机制
rock mechanics
mechanical property
crack evolution
ligament angle
meso-mechanism
