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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。
Critical fracture characteristics during rock failure, such as the length of the process zone and the open displacement of the fracture opening, are the key points to solve the problem of rock fracture using fracture mechanics. Traditional measurement methods, such as strain gauges and linear displacement sensors, can not obtain the full field deformation when the rock is damaged, therefore, the above fault features can not be accurately obtained. The digital image correlation method is an optical deformation measurement method. Through the digital image acquisition and correlation calculation on the sample surface, the high-precision whole-field deformation features of various stages of the rock fracture process can be obtained. Using this test method, a series of semi-circular plate three-point bending fracture tests have been carried out on two types of rock, namely relatively hard marble and relatively soft yellow sandstone, and the critical deformation field during rock fracture has been obtained. For the deformation field The critical characteristics of the two types of rock failure, the length of the process area and the open displacement of the crack openings were determined. The results show that the length of the fracture zone of marble is obviously smaller than the length of the fracture zone of yellow sandstone. The value of COD of yellow sandstone is higher than that of marble with the same crack length at the peak, while the mechanical behavior of soft rock is more likely to be affected by the boundary effect . The above study will help to further understand the fracture development of different types of rocks and adopt corresponding methods to solve the problem of rock failure.