用人字形切槽巴西圆盘(CCNBD)确定岩石断裂韧度及其尺度律

国际岩石力学学会(ISRM)于1988年和1995年先后颁布了两种测试岩石断裂韧度的建议方法，其中1995年建议方法推荐的人字形切槽巴西圆盘(CCNBD)尚不够完善。有鉴于此，用两种大理岩制作成CCNBD和ISRM1988年建议方法推荐的人字形切槽三点弯曲圆棒(CB)试样，分别在MTS810型材料试验机进行试验。结果发现，CCNBD试样测出的断裂韧度值比CB试样测出的断裂韧度值小，而重新标定关于CCNBD计算公式中的关键系数Ymin*后得出的断裂韧度值有一定改善。此外，基于内聚裂纹模型，对CCNBD试样用于岩石断裂韧度测试的尺寸效应问题进行了初步探讨，提出CCNBD试样的几何形状函数gαm，很好地解决了Bazant的尺度律用于CCNBD试样结构的非相似性问题，从而减小了试样尺寸对材料断裂韧度的影响。

DETERMINATION OF MODE-I ROCK FRACTURE TOUGHNESS WITH CRACKED CHEVRON NOTCHED BRAZILIAN DISC (CCNBD) AND APPLICATION OF SIZE EFFECT LAW

International Society for Rock Mechanics (ISRM) proposed two suggested methods for determining rock fracture toughness in 1988 and 1995,respectively. Cracked chevron notched Brazilian disc (CCNBD) suggested by ISRM in 1995 still waits for being perfected. In view of it,two types of marbles are used to make CCNBD and chevron bend (CB) specimen suggested by ISRM in 1988. These specimens are tested on the test machine of MTS810 model. The results of the tests show that fracture toughness value calculated with ISRM suggested method in 1995 is lower than that in 1988,and that fracture toughness value calculated with ISRM suggested method in 1995 are distinctly better after dimensionless stress intensity factor of CCNBD is newly calibrated. The size effect of CCNBD specimens on fracture toughness is discussed based on the cohesive crack model. The geometric shape function mag is brought forward,which successfully resolve non-similarity problem of CCNBD when using the size effect law proposed by Bazant.