Abstract
The Split-Hopkinson pressure bar (SHPB) was used to determine the fracture characteristics of a long bar rock specimen with an elliptical cavity under different axial ratios and dip angles. A high speed camera was applied to record the fracturing process of the granite specimen around the cavity. The experimental results showed that the fracture characteristics around the elliptical cavity were closely related to the axial ratio and dip angle. A three-dimensional numerical model was established using LS-DYNA to quantitatively analyze the dynamic stress state around the cavity. The numerical results indicate that the dip angle and axial ratio of the elliptical cavity significantly affected the dynamic stress concentration factor (DSCF), then affected the rock failure. The location of higher DSCF led to a higher possibility of spalling failure. The maximum DSCF remarkably decreased with a decreasing dip angle and increased the axial ratio. In the dynamic loading propagate process, the stress concentration distribution around the cavity formed by a compression stress wave had a certain damaging effect on the destruction of rock around the cavity, and the stress concentration generated by the tensile stress wave was the main factor of the rock fracture, which was most notable in the peak area of the stress concentration.
Highlights
The construction of cavities widely exists in civil and mining engineering
The results indicate that the axial ratio was the main factor affecting the stress concentration distribution under the same dip angle, but that minimum stress occurred near = 0°
This study indicates that rock failure is affected by the dip angle and axial ratio of an elliptical hole
Summary
The construction of cavities widely exists in civil and mining engineering. Under external disturbances such as blasting and earthquakes, the stress waves that spread to cavities will produce a series of reflection and transmission phenomena. Regarding rock specimens with a cavity, Li et al [5] conducted an experimental study on the dynamic failure characteristics of a rock specimen containing an elliptic hole based on the Split-Hopkinson pressure bar (SHPB). In their experiment, the dynamic compressive strength, failure mode, and crack propagation characteristics of a rock specimen with a hole under different dynamic loads were analyzed
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