真三轴动静组合加载饱水煤样动态强度特征研究

In order to investigate the mechanical and strength variation characteristics of coal specimens under dynamic and static combined loading conditions and to analyze the difference of dynamic strength performances between true triaxial and conventional triaxial conditions with static and dynamic combination loads. The natural and 7 d saturated coal specimens were compressed and impacted using the true triaxial Hopkinson bar systerm at Monash University. Experimental results show that, under the true triaxial dynamic and static combination loading, the dynamic strength of the saturated 7 d coal specimens in the X-axis direction is about 17.43% lower than that of the natural coal specimens, while the former is about 15.88% and 14.23% higher than the later respectively in Y- and Z-axis directions. With the variation of the intermediate principal stress, the dynamic triaxial strengths of two types of coal specimens show a initial increasing and then decreasing trend with a turning point corresponding to the intermediate principal stress of 6 MPa. The coal specimens exhibit a distinct confinement dependence, and the effect of water on the strength and deformation of coal is also significant. Besides, comparison between the test results of true triaxial and conventional triaxial static-dynamic combination loads indicates that the opposite trend of the coal strength is mainly attributed to the different propagation modes of the internal water bearing fractures.