Fracture Analysis of Cracked Rock Masses under Compression-Shear Loading

Document Type : Research Paper


1 Assistant professor, Department of Mechanical Engineering, Faculty of engineering, Kharazmi University, Tehran, Iran

2 Ms. C student, Department of Mechanical Engineering, Faculty of engineering, Kharazmi University, Tehran, Iran


The rock masses have naturally a large number of cracks and discontinuities which cause to be prone to damage under dynamic loading. The earthquake as a kind of dynamic loading may propagate the inherent cracks in rock masses and leads to failure of the rock structures such as mines, oil and gas wells, tunnels, dams, etc. Therefore, the fracture of rock masses due to cracks under earthquake should be considered by civil, mining and even mechanical engineers and researchers. Fracture mechanics as a branch of mechanical engineering science has been frequently employed for investigating the fracture behaviour of cracked rock structures. According to the orientation of crack relative to applied load, the cracked parts may be subjected to pure or combined mode loading I, II and III. The underground rock masses are often subjected to a compressive loading due to the pressure of upper rock masses. In the first sight, the crack flanks under compression are pressured together and the geometry discontinuity is vanished. However, the crack faces may be subjected to sliding loading and the vulnerability of cracked rock masses is still remained. Therefore, the fracture analysis of cracked rock masses under compression-shear loading should be investigated. Similar to the mixed mode I/II loading, there are several studies in the literature investigated the fracture of cracked specimens under compression-shear loading both experimentally (Al-Shayea, 2005) and theoretically (Li et al., 2009). From the theoretical viewpoint, the compression is considered as a compressive stress in the stress field around the crack tip and then the fracture criteria based on new stress field is utilized for predicting the fracture resistance of cracked specimens. The aim of this paper is to present a new approach for predicting the fracture load of cracked rock samples under compression-shear loading. The new approach is based on the maximum tangential stress (MTS) criterion which is one of the classical fracture criteria in fracture mechanics.


[1]- Aliha, M. R. M., Ashtari, R., and Aystollshi, M. R., 2006, Mode I and mode II fracture toughness testing for a Coarse Grain Marble, Applied Mechanics and Materials, 5-6, pp.181-188.
[2]- Akbardoost, J., Ayatollahi, M. R., Aliha, M. R. M., Pavier, M. J. and Smith, D. J., 2014, Size-dependent fracture behavior of Guiting limestone under mixed mode loading, International journal of rock mechanics & mining sciences, pp.369-380
[3]- Tang, S. B., Bao, C. Y., and Liu, H. Y., 2017, Brittle fracture of rock under combined tensile and compressive loading conditions, Canadian Geotechnical Journal, 54, 1, pp.81-101
[4]- Al-Shayea, N. A., 2005, Crack propagation trajectories for rocks under mixed mode I–II fracture, Engineering Geology, 81, pp.84– 97.
[5]- Li, X. F., Liu, G. L., and Lee, K. Y., 2009, Effects of T-stresses on fracture initiation for a closed crack in compression with frictional crack faces, International Journal of Fracture, 160, pp.19–30.
[6]- Erdogan, F. and Sih, G. C., 1963, On the crack extension in plates under plane loading and transverse shear, Journal of Basic Engineering, Transactions of ASME, 85, pp.519-25.
[7]- Schmidt, R. A., 1980, A microcrack model and its significance to hydraulic fracturing and fracture toughness testing, Proc 21st US Symp On Rock Mech, pp.581-590.
[8]- Ayatollahi, M. R. and Aliha, M. R. M., 2007, Wide range data for crack tip parameters in two disc-type specimens under mixed mode loading, Computational Materials Science, 38, pp.660-70.