脆性岩石试样断裂过程区及宏观疲劳裂纹行为研究  

Investigation of the fracture process zone and behavior of the macro-scalefatigue cracks in brittle rock specimens

作　　者：ERARSLAN Nazife ERARSLAN Nazife(Civil Engineering Department,Izmir Demokrasi University,Izmir 35140,Turkey;School of Civil Engineering,The University of Queensland,Brisbane,Queensland 4072,Australia)

机构地区：[1]伊兹密尔民主大学土木工程系,土耳其伊兹密尔35140 [2]昆士兰大学土木工程学院,澳大利亚昆士兰布里斯班4072

出　　处：《岩土力学》2023年第7期2041-2049,共9页Rock and Soil Mechanics

摘　　要：通过脆性岩石试样巴西圆盘试验研究了疲劳效应对脆性岩石断裂韧度KIC的影响,阐释了脆性岩石的疲劳损伤机制,首次展示了脆性岩石破坏前宏观裂纹的张开和闭合行为。巴西圆盘试验结果表明,循环荷载作用下,脆性岩样的KIC降低了35%,巴西劈裂拉伸强度降低了30%。通过高速相机数小时的观测并记录到了岩石力学领域从未观测到的过程,即脆性岩样破坏前,疲劳裂纹在正弦荷载作用下弹性张合。扫描电镜和计算机断层扫描结果显示,巴西圆盘和V形切槽巴西圆盘试样的破坏是由断裂过程区(fracture process zone,简称FPZ)引起的,FPZ中包含许多异于循环荷载作用下单条宏观裂纹的微裂纹,切槽裂纹尖端FPZ的形成导致未破坏脆性岩样中可视疲劳裂纹弹性张合。室内试验和数值计算结果表明,切槽裂纹倾角为60°时获得最大FPZ(即FPZmax),这表明最大FPZ的形成可能与Ⅰ-Ⅱ型(拉伸和剪切)组合加载模式有关。The importance of this study is to explain the fatigue damage mechanism while addressing the effect of fatigue on the fracture toughness(KIC)using the brittle Brazilian specimens and to show for the first time in the literature the behavior of macroscale cracks that open and close in brittle rock without leading to eventual failure.The KIC was reduced by 35%due to the cyclic loading,and the reduction of the indirect Brazilian strength was found to be reduced by 30%.The fatigue cracks were observed to open and close elastically without failure and have been recorded by a camera for hours in brittle rock specimens with sinusoidal loading for the first time in the rock mechanics field in this study.The findings of the scanning electron microscope(SEM)and computed tomography(CT)revealed that the failure of the Brazilian disc and chevron crack notched Brazilian disc(CCNBD)specimens was caused by the formation of the fracture process zone(FPZ),which included many microcracks rather than a single macrocrack propagation during the cyclic loading tests.Moreover,SEM and CT findings indicated the FPZ took place ahead of the kerf crack tip,leading to the visible fatigue crack opening and closing elastically in brittle rock specimens without any rupture.According to the experimental and numerical analysis results,the FPZmax could be obtained with the 60ºinclined notch crack.This demonstrates the maximum FPZ development possible with combined mode I-II(tensile and shear)loading.

关 键 词：V形切槽巴西圆盘岩石试样 岩石疲劳 FPZ和岩石疲劳 

分 类 号：TU451[建筑科学—岩土工程]