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Abstract The impact failure characteristics of rock subjected to one-dimensional coupled static and dynamic loads are conducted with a modified split Hopkinson pressure bar(SHPB). Firstly，the testing principle with axial precompression stress is re-examined based on one-dimensional wave theory. The axial precompression stress(in accordance with the static load strength of 20%，30%，40%，70%，80% and 90% in six series) is loaded on rock specimen before the axial impact loading is carried on，and the critical dynamic strength is obtained and studied respectively. The results show that in the case of critical damage，the total strain on all stress-strain curves (including the conventional impact testing and impact testing with coupled loads) will reduce finally. The reason for this phenomenon can be explained by the release of stored elastic energy of rock in the process of impact. When axial precompression stress is smaller，the stress-strain curves of impact testing are similar. When axial precompression stress is larger，there is no initial linear elastic part in the curves of impact testing with coupled loads. The dynamic strength increases with the increase of axial precompression stress and the maximum impact strength can be obtained when 60% static strength is precompressed. The absorption of energy increases slowly when the incident energy is smaller and will increase quickly when incident energy is larger. Rock specimen will break with shear failure model subjected to one-dimensional coupled static and dynamics loads，while failure mode will be splitting faulting for conventional impact testing.
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Received: 14 July 2009
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