中文摘要：

岩石破坏时的临界断裂特征,如过程区长度,裂缝口张开位移是运用断裂力学解决岩石断裂问题的关键所在。传统测量方法,如应变片、直线位移传感器无法获得岩石破坏时的全场变形,因此,也无法准确地获得上述断裂特征。数字图像相关法是一种光学的变形测量方法,其通过试样表面的数字图像采集及相关计算,能够获得岩石破裂过程各个阶段的高精度全场变形特征。利用该试验手段,对两类岩石,即相对较硬的大理岩和相对较软的黄砂岩开展了一系列半圆盘三点弯曲断裂试验并获得了岩石断裂时的临界变形场,对变形场进行分析,从而确定了两类岩石破坏时临界特征、过程区长度及裂缝口张开位移。结果表明,大理岩的断裂过程区长度明显小于黄砂岩的断裂过程区长度,峰值时黄砂岩COD的值均大于相同裂纹长度的大理岩,而较软岩的力学行为更容易受边界效应的影响。上述研究有助于进一步了解不同类型岩石的断裂发展过程并采用相应的方法来解决岩石破裂问题。

英文摘要：

The critical fracture characteristics of rock,such as the length of process zone and crack mouth opening displacement（COD）,are the fundamentals to solve the fracture problems of rock by using fracture mechanics.Traditional measure methods,such as strain gauge and LVDT,etc.,cannot obtain the full-field displacement of rock specimen.In that case,it＇s difficult to achieve the above mentioned critical fracture characteristic of rock.Digital image correlation（DIC） method is a optical measure method which can obtain the accurate full-field displacement of the specimen by comparing the original image and deformed image.A series of three-point bending tests is performed on the semi-circular rock specimens（relatively hard marble and relatively soft yellow sandstone）,and the DIC method is used to measure the full-field displacements of the specimens.The obtained displacements are further analyzed,and the critical fracture characteristics of the specimens including the length of process zone and the crack mouth opening displacement are revealed.It is shown that the length of process zone in marble is obviously shorter than that in yellow sandstone,while the values of COD of yellow sandstone are higher than the ones of the marble with same crack length,which demonstrates that the soft yellow sandstone is prone to be affected by boundary effect.Those researches can help us to further understand the fracture process of rock,and to solve rock engineering problem using fracture mechanics.