一维动静组合加载下岩石冲击破坏试验研究

 利用研制的岩石动静组合加载SHPB试验装置，系统研究岩石在一维动静组合加载下的冲击破坏特性。首先按照一维应力波传播理论，对动静组合加载的试验原理进行理论论证。试验过程中预先在轴向施加不同载荷，按照静载强度的20%，30%，40%，70%，80%和90%等6个系列进行，然后沿轴向进行冲击加载，考察岩石的临界破坏承载强度。研究结果表明：在临界破坏的情况下，动态冲击的应力–应变曲线(包括常规冲击和动静组合加载)最后都会出现总应变减小的现象，这是由于冲击过程中岩石内部储存弹性能释放所致。在轴向静压较小时，岩石的组合加载应力–应变曲线跟常规的冲击试验曲线类似；轴压较大时，岩石的组合加载应力–应变曲线没有初始的近似线弹性段，直接从非线性段开始。随着轴向静压的增大，岩石的抗冲击强度呈现出先增大后减小的趋势，大约在静载强度60%时，抗冲击强度达到最大值。在入射能较小时，岩石吸收的能量会缓慢增加，在入射能较高时，岩石吸能会快速增加。常规冲击下岩石的临界破坏模式为劈裂形式，动静组合加载下呈现压剪形式。

TEST STUDY OF IMPACT FAILURE OF ROCK SUBJECTED TO ONE- DIMENSIONAL COUPLED STATIC AND DYNAMIC LOADS

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.