Mechanical properties of fractured media containing intermittent fractures at different strain rates

Aimed at the dynamic stability of fractured rock mass under earthquake and explosion loading,the mechanical properties of the fractured specimens were studied under uni-axial loading with strain rates 1.7×10-5 s-1,1.7×10-3 s-1,1.7× 10-1 s-1.The specimens used in this study were made of sandstone-like modeling material and contained two or three intermittent fractures with different geometric distributions.It was shown that the deformation properties of the specimens were correlative with the process of fractures coalescence,and presented localized and progressive damage.With the strain rate increasing,the moduli of specimens increased and the differences between fractured and non-fractured specimens diminished.The peak strengths were primarily dominated by its geometry,and the minimum for the specimens containing co-planar fractures appeaed at 35°inclination angle which was different with that for the specimens containing continuous fractures whose minimum appeared at about 60°.The peak strengths for specimens with three fractures depended on the coalescence modes,and its strengths were close to those for specimens with two-fractures whose were similar to coalescence modes.Moreover,the peak strengths increased with the strain rates,and the extent of strength increment for specimens with three fractures was more obvious than that for speeimens with two fractures and non-fractured specimens.Thus the conclusion that the weaken effect of the fractures might be lowered with the strain rate increasing could be obtained.