冲击荷载下玄武岩纤维水泥土吸能及分形特征

为研究玄武岩纤维对水泥土冲击破坏过程中能量吸收及碎块块度分布特征的影响，采用Φ50 mm变截面霍普金森压杆（split Hopkinson pressure bar，简称SHPB）试验装置对不同玄武岩纤维掺量的水泥土进行了冲击压缩和动态劈裂试验，分析了冲击荷载作用下玄武岩纤维掺量与水泥土吸收能、破坏形态和分形维数 的关系，试验结果表明：随着玄武岩纤维掺量的增加，水泥土吸收能呈先增大后减小的趋势，超过最佳掺量后，由于纤维-纤维薄弱面的存在，水泥土吸收能减少；冲击破坏后水泥土破碎块度分布是具有统计意义上的分形，冲击压缩试验中水泥土破碎块度平均粒径随玄武岩纤维掺量的增加而不断增大，对应的 值总体上呈现不断减小的趋势；在动态劈裂试验中，玄武岩纤维掺量在0～2.0%范围内，水泥土破碎块度平均粒径呈现上升趋势， 值不断减小，玄武岩纤维掺量超过2.0%后，平均粒径有所降低，对应 值增大。玄武岩纤维水泥土吸收能和 值之间有着密切的联系，冲击压缩试验中，吸收能在分形维数为2.20～2.26范围内呈先增大后减小的趋势，而在动态劈裂试验中，吸收能在分形维数为1.85～2.20范围内总体呈现下降趋势，两者具有一定的负相关性；合适掺量的玄武岩纤维对水泥土动态特性起着积极作用，通过试验得出玄武岩纤维的合适掺量为1.5%～2.0%。

Energy absorption and fractal characteristics of basalt fiber-reinforced cement- soil under impact loads

To study the effects of basalt fiber on energy absorption and fractal characteristics of cement-soil, a series of impact compressive tests and dynamic tensile tests was conducted on cement-soil with different basalt fiber contents by using a Φ50 mm Split Hopkinson Pressure Bar (SHPB) apparatus. The relationship between the basalt fiber content and three factors (i.e., energy absorption, failure mode and fractal dimension ( ) of cement-soil) was analyzed. The test results show that energy absorption firstly increased and then decreased with the inclusion of basalt fiber, and due to the existence of weak-surface made by excess basalt fiber, the energy absorption capacity was unresponsive to an increase of basalt fiber content when the basalt fiber content was more than the optimum content. The fragment-size distribution of cement-soil had a fractal property with statistical sense of self-similarity. In the impact compressive test, mean diameter of fragments increased with the increase of basalt fiber content but its appropriate had a decreasing trend. In the dynamic tensile test, when the basalt fiber content was from 0 to 2.0%, the mean diameter of fragments increased and the value of decreased. However, the mean diameter of fragments decreased and increased when more than 2.0% of basalt fiber was added. Also, there was a close relationship between the energy absorption and . In the impact compressive test, energy absorption firstly increased and then decreased when was from 2.20 to 2.26. When was from 1.85 to 2.20, the energy absorption continuously decreased in the dynamic tensile test, which shows a negative correlation between and energy absorption. The optimum content of basalt fiber plays a positive role in the dynamic properties of cement-soil, therefore, this study presents a suggestion that the optimum content of basalt fiber is 1.5% to 2.0%.