Experimental investigation of rigid confinement effects of radial strain on dynamic mechanical properties and failure modes of concrete

In this study,to confirm the effect of confining pressure on dynamic mechanical behavior and failure modes of concrete,a split Hopkinson pressure bar dynamic loading device was utilized to perform dynamic compressive experiments under confined and unconfined conditions.The confining pressure was achieved by applying a lateral metal sleeve on the testing specimen which was loaded in the axial direction.The experimental results prove that dynamic peak axial stress,dynamic peak lateral stress,and peak axial strain of concrete are strongly sensitive to the strain rate under confined conditions.Moreover,the failure patterns are significantly affected by the stress-loading rate and confining pressure.Concrete shows stronger strain rate effects under an unconfined condition than that under a confined condition.More cracks are created in concrete subjected to uniaxial dynamic compression at a higher strain rate,which can be explained by a thermal-activated mechanism.By contrast,crack generation is prevented by confinement.Fitting formulas of the dynamic peak stress and dynamic peak axial strain are established by considering strain rate effects(50–250 s-1)as well as the dynamic confining increase factor(DIFc).

切缝药包爆破机理分析与试验研究

通过理论和实验研究了切缝药包爆破机理和爆破参数，结果表明，切缝药包爆破有明显的聚能效应和护壁作用。其最佳装药不耦合系数为1．5～2．2。

灰岩和白云岩动态压缩力学性能的SHPB实验

为了得到爆破荷载作用下岩石的破坏特性及爆破振动波的传播特性,利用RMT-150C多功能实验机和改进后的ф50mm的分离式Hopkinson压杆装置,分别研究灰岩和白云岩试件的静态力学特性和在5种不同应变率等级下的动态力学性能。实验结果表明,随着平均应变率的增加,灰岩和白云岩试件的动态抗压强度、峰值应变、吸收能、比能量吸收值以及破碎程度都明显增加,表现出显著的应变率效应,而初始弹性模量对应变率的相关性不敏感。从岩石的动态抗压强度和能量吸收两个方面,对比分析灰岩和白云岩动态力学性能的共性和差异性,更合理地解释了岩石在动态冲击荷载下的破坏本质。