单裂隙砂岩单轴压缩的中等应变率效应颗粒流模拟  

Influence of medium strain rate on sandstone with a single pre-crack under uniaxial compression using PFC simulation

作　　者：黄达[1,2,3] 岑夺丰[1] 黄润秋[2] 

机构地区：[1]重庆大学土木工程学院,重庆400045 [2]成都理工大学地质灾害防治与地质环境保护国家重点实验室,成都610059 [3]重庆大学教育部山地城市建设与新技术重点实验室,重庆400045

出　　处：《岩土力学》2013年第2期535-545,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金面上项目(No.41172243);国家自然科学基金青年科学基金项目(No.40902078);国家自然科学基金重点项目(No.41130745);中央高校基本科研业务费资助项目(No.CDJZR11 200007)

摘　　要：加载速率对裂隙岩体的力学性质及变形破坏均有重要影响。利用二维颗粒流程序PFC2D开展了不同倾角非贯通单裂隙砂岩试件的单轴压缩试验,研究了中等应变率对裂隙砂岩应力-应变曲线特征、裂隙尖端应力状态、特征应力状态、岩体损伤及裂隙扩展等力学响应的影响规律。裂隙岩体应力-应变曲线呈现明显的波动性,定义应力突变指标f对应力突变型波动剧烈程度进行了定量统计分析:随应变率的增加,曲线应力突变波动越剧烈,且峰后明显大于峰前;随裂隙倾角的增大,波动幅度峰前增大,而峰后减小。裂隙尖端破裂应力随应变率增大均有所提高,随裂隙倾角的增大,切向剪应力c总体上呈增加变化,而法向应力nc明显减小。尖端破裂时岩样加载应力j、岩样临界扩容应力d及峰值应力c均随应变率增大而增大。裂隙尖端的破裂可立即引起岩体扩容,一般应变率越低,岩体裂隙尖端破裂点j和扩容点d越接近峰值强度c。随着应变率的提高,损伤裂纹及宏观裂隙类型越多,岩体试件损伤破裂程度越强,特别是试件端部效应愈显著。裂隙首先以I型翼裂纹在其尖端起裂,而I型翼裂纹的扩展长度与加载速率与裂隙倾角具有较强的相关性。Strain rate has important influence on mechanical properties and failure of the fractured rock mass.The influences of medium strain rate on stress-strain,crack tip stress,characteristic stress and damage of rock mass,fracture expansion of crack of sandstone with a single fissure are researched under uniaxial compression using two-dimensional particle flow code（PFC2D）.The stress-strain curves of joint rock mass present obviously fluctuation and stress mutation.The stress mutation index is defined in order to quantitatively analyze the degree of stress mutation.The stress mutation fluctuation is more acute with the increase of strain rate;and after peak strength it is stronger than before.The fluctuation amplitude of stress is increased before peak strength but reduced after peak strength with the increase of the fissure angle.The fracture stress of crack is enhanced with the increase of strain rate;and the tangential shear stress is increased on the whole;but the normal stress obviously reduced with the increase of fissure angle.The loading stress when crack tip is fractured,the critical dilatancy stress σd and the peak strength are all increased with the increase of strain rate.The dilatancy of rock mass can be immediately triggered by the fracture of crack tip;and and are generally more close to when strain rate is lower.The more the cracks of damage and macroscopic fracture are,the stronger the degree of damage and fracture of rock mass are with the increase of strain rate;and especially the end effect of specimen is more significant.The initial fracture is begun in the way of I type wing crack;its length is related to the strain rate and the dip angle of fissure.

关 键 词：裂隙岩体 加载应变率 裂隙倾角 单轴压缩 颗粒流 

分 类 号：TU451[建筑科学—岩土工程]