中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 11 No. 5 October 2001 |
fracture mode of rock
（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 fourpoint 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, KⅡC. 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 σt and 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
