摘要
研究了巷道内纯Ⅰ型及Ⅰ/Ⅱ复合型裂纹在冲击载荷作用下的动态扩展特征,预制裂纹位于巷道拱顶圆弧区域与巷道对称轴线平行,并与巷道对称轴线的间距不同。以中低速落锤冲击试验机对砂岩巷道模型试样进行动态冲击加载,巷道内裂纹的起裂时间与扩展特性采用粘贴在裂纹尖端的应变片进行相应的测试分析。采用AUTODYN模拟巷道内裂纹的扩展路径,总体上数值结果与试验结果比较吻合,采用ABAQUS计算裂纹的应力强度因子,结合试验-数值法确定巷道模型内预制裂纹的起裂韧度。研究结果表明:Ⅰ/Ⅱ复合型裂纹起裂过程中,既有Ⅰ型起裂韧度又有Ⅱ型起裂韧度,其比例大小与裂纹距离巷道对称轴的距离有关;纯Ⅰ型与Ⅰ/Ⅱ复合型裂纹的扩展行为有很大差别,纯Ⅰ型裂纹起裂沿着原裂纹方向竖直向上扩展,而Ⅰ/Ⅱ复合型裂纹与原裂纹成一定角度起裂,形成翼型裂纹,最后沿着最大主应力方向进行扩展,并且复合型裂纹在扩展过程中,存在明显的拐点特征。
Here,the dynamic propagation behavior of mode Ⅰ and multi-mode Ⅰ/Ⅱ cracks in a tunnel under impact loads was investigated.A pre-crack was placed in a tunnel arch arc region and parallel to the symmetrical axis line of the tunnel.The ratio of the distance between the pre-crack and the symmetrical axis to the radius of the tunnel arch arc was in the range of 0—1.The dynamic impact tests of a sandstone tunnel model with a pre-crack were conducted with a middle-low speed drop weight impact test system.The crack initiation time and the propagation characteristic of the precrack were measured with strain gauges stuck at tips of the pre-crack.The software AUTODYN was used to simulate the tunnel＇s crack propagation paths,and the numerical results agreed well with the test ones.The software ABAQUS was employed to calculate the crack＇s dynamic stress intensity factor.The test-numerical method was used to determine the initiation toughness of the pre-crack in the tunnel model.The study results showed that in multi-mode Ⅰ/Ⅱ crack initiation process,there exist both mode Ⅰ initiation toughness and mode Ⅱ one,and their proportion is related to the distance between the crack and the symmetrical axis of the tunnel; the propagation behaviors of mode Ⅰ and multi-mode Ⅰ/Ⅱ cracks are quite different,mode Ⅰ crack along the pre-crack direction vertically upward expands,while multi-mode Ⅰ/Ⅱ crack initiates at a certain angle to the original crack to form an airfoil crack,and finally it expands along the maximum principal stress direction; in the propagation process of multi-mode Ⅰ/Ⅱ crack,there are obvious features of an inflection point.
作者
周磊
朱哲明
应鹏
王雄
王蒙
ZHOU Lei;ZHU Zheming;YING Peng;WANG Xiong;WANG Meng(MOE Key Lab of Deep Underground Science an Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China)
出处
《振动与冲击》
EI
CSCD
北大核心
2018年第13期210-217,共8页
Journal of Vibration and Shock
基金
国家自然科学基金(11672194
11702181)
四川省安全监管局安全科技项目(aj20170515161307)
四川省科技计划项目(18SYXHZ0094)
关键词
巷道
裂纹扩展
冲击载荷
数值模拟
起裂韧度
tunnel
crack propagation
impact load
numerical simulation
initiation toughness
