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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 11    No. 5    October 2001

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Effect of loading point position on
fracture mode of rock
RAO Qiu-hua(饶秋华)1, SUN Zong-qi(孙宗颀)1, WANG Gui-yao(王桂尧)2,
XU Ji-cheng(徐继成)3, ZHANG Jing-yi(张静宜)3

1. College of Resources, Environment and Civil Engineering,
Central South University, Changsha 410083, P.R.China;
2. River and Sea Department, Changsha Communications University,
Changsha 410076, P.R.China;
3. Open Laboratory of Mechanics, Central South University,
Changsha 410083, P.R.China

Abstract: Anti-symmetric fourpoint bending specimen with different loading point positions was used to study effect of loading point position on fracture mode of rock in order to explore a feasible method for achieving Mode Ⅱ fracture and determining Mode Ⅱ fracture toughness of rock, KC. Numerical and experimental results show that the distance between the inner and outer loading points, L1+ L2, has a great influence on stresses at notch tip and fracture mode. When  L1+L2>0.5L or 0.1L<L1+ L2<0.5L, maximum principal stress σ1 exceeds the tensile strength σt. The ratio of τmax/σ1 is relatively low or high and thus Mode Ⅰ or mixed mode fracture occurs. When  L1+L2<0.1L,σ1 is smaller than σand the ratio of τmax/σ1 is much higher, which facilitates the occurrence of Mode Ⅱ fracture.

 

Key words:  fracture mode; loading point position; stress analysis; rock

ISSN 1672-7029
CN 43-1423/U

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