102 W. Yao et al. Conclusion The dynamic Mode II fracture toughness of rocks over various confining pressures was investigated through a dynamic punch-through shear method. The rock specimen was punched and broke into a short bar and a hollow cylinder. The wing cracks are vanishing and the “doughnut fractures” appear with the increment of confining pressure. Moreover, the main fracture is primarily a Mode II fracture. The KIIC of Fangshan marble at a specified confining pressure rises as the loading rate. Another important observation is that the KIIC at a given loading rate rises as the lateral confining pressure. Acknowledgment Funding was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Discovery Grant No. 72031326. References 1. Lukic´, B., Forquin, P.: Experimental characterization of the punch through shear strength of an ultra-high performance concrete. Int. J. Impact Eng. 91, 34–45 (2016) 2. Backers, T., Stephansson, O.: ISRM Suggested Method for the Determination of Mode II Fracture Toughness. In: Ulusay, R. (ed.) The ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 2007–2014 [S], pp. 45–56. Springer International, New York City (2015) 3. Yao, W., Xu, Y., Yu, C., Xia, K.: A dynamic punch-through shear method for determining dynamic Mode II fracture toughness of rocks. Eng. Fract. Mech. 176, 161–177 (2017) 4. Zhou, Y.X., Xia, K., Li, X.B., Li, H.B., Ma, G.W., Zhao, J., Zhou, Z.L., Dai, F.: Suggested methods for determining the dynamic strength parameters and mode-I fracture toughness of rock materials. Int. J. Rock Mech. Min. Sci. 49, 105–112 (2012)
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