Experimental Conditions Affecting Fracturing Research

The fracturing behavior and mechanical characterization of rocks are important for many applications in the fields of civil, mining, geothermal, and petroleum engineering. Laboratory testing of rocks plays a major role in understanding the underlying processes that occur on the larger scale and for predicting rock behavior. Fracturing research, such as producing multiple fractures that follow a particular pattern, requires well-defined and consistent boundary conditions. Consequently, the testing design and setup can greatly influence the results. In this study, a comprehensive experimental program using an artificial material was carried out to systematically evaluate the effects of different parameters in rock testing under uniaxial compression. The parameters include the compression platen type, centering of the specimen, loading control method and rate, specimen size, cross-sectional geometry, and boundary constraints. The results show that these parameters have a significant effect on the mechanical behavior of rocks. Using a fixed compression platen helped reduce bulging of the material. Centering of the specimen played a critical role to avoid buckling and unequal distribution of stress. Slower displacement rates can control the energy being released once failure occurs to prevent the specimen from exploding. Larger specimens generally fail at lower stresses compared to smaller specimens. Also, the frictional end effects were investigated by comparing lubricated and non-lubricated end conditions.