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Abstract Impact compressive experiments on air-dried and water-saturated sandstone samples taken from Kaiyang Phosphate Mine with a constant length-diameter ratio of 0.5 are conducted with the modified f 75 mm split Hopkinson pressure bar(SHPB) apparatus. Compared with the static mechanical results tested by INSTRON material testing machine，the SHBP test results show that stress-strain relation of water-saturated sandstone under impact loads with intermediate strain rate is different from that under static loads；and its dynamic strength is close to that of air-dried sandstone，which is opposite to the decreased strength under static load condition. For air-dried sandstone，its dynamic yield stress under impact loads with intermediate strain rate is similar to its static yield stress. However，for water-saturated sandstone，the dynamic yield stress increases by two times compared with its static yield stress，which indicates that the sensitivity of water-saturated sandstone dynamic strength dependent on strain rate is more notable than that of air-dried sandstone. Water can influence the dynamic damage patterns of sandstone，thus the impact damage of air-dried sandstone becomes more serious than that of water-saturated sandstone. So the water-free viscosity and Stefan effect of water-saturated sandstone should be considered under impact loads with intermediate strain rate.
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Received: 21 November 2009
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