ABSTRACT:

The fracture mechanical behavior of Dingziwan granite was investigated with two splitting loading methods. The granite was taken from Dingziwan zone of Hunan Province, a famous granite area in China. Model I fracture toughness tests were conducted with Cracked Straight Through Brazilian Disc specimen (CSTBD) by MTS Landmark testing machine. In the work, two splitting Brazilian loading methods according ISRM standard (method I) and China standard (method II) were employed. The difference between the fracture mechanical behavior of method I and II were very apparent. For fracture time or fracture displacement, the results of method I are large than that of method II. And the fracture toughness of method I is 1.01 MPa·m½, which is about 42% higher than that of the method II (0. 72 MPa · m½). Excluding the subtle effect of loading rate, the main reasons for above difference of two methods were also discussed. The linear relationship between fracture toughness and fracture displacement was obtained based on the actual measuring data, which provides a valuable understanding for the crack arresting problem.

I INTRODUCTION
1.1 Type area

Rock fracture mechanics can be used to identify and predict the imminent failure of rock mass structures thereby providing guidelines to improve the stability and the safety of these structures. Another application is for the exploitation of mineral resources by adopting techniques such as mechanical mining, blasting and hydraulic fracturing. In fracture processes which are not associated with high strain rates, the mode I plane-strain static fracture toughness gives the critical value of the stress intensity factor leading to the onset of crack growth in that mode. Some of the applications of fracture toughness include index of fragmentation processes like those used in tunnel boring, a modeling parameter in processes such as rock cutting and hydraulic fracturing and for the stability analysis of civil, mining and earthen structures.

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