Effect of specimen thickness on ModeⅡfracture toughness of rock

来源期刊：中南大学学报(英文版)2001年第2期

论文作者：RAO Qiu-hua SUN Zong-qi WANG Gui-yao XU Ji-cheng ZHANG Jing-yi

文章页码：114 - 119

Key words：ModeⅡfracture toughness; rock; fracture; stress analysis; specimen thickness

Abstract: Anti-symmetric four-point bending specimens with different thickness, without and with guiding grooves, were used to conduct ModeⅡfracture test and study the effect of specimen thickness on ModeⅡfracture toughness of rock. Numerical calculations show that the occurrence of ModeⅡfracture in the specimens without guiding grooves (when the inner and outer loading points are moved close tothe notch plane) and with guiding grooves is attributed to a favorable stress condition created for ModeⅡfracture, i.e. tensile stress at the notch tip is depressed to be lowerthan the tensile strength orto be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of ModeⅡfracture toughness KⅡCdecreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness.