三维动静组合加载下石灰岩力学特性研究

深部岩体处于“三高一扰动”的复杂环境中，为研究巷道掘进过程中冲击荷载对巷道围岩的影响，以石灰岩为研究对象，通过河南理工大学改进的SHPB动静组合加载试验装置，开展三维动静组合加载下的石灰岩力学特性研究。选取典型的轴压梯度（8、15、16、17 MPa）和围压梯度（1、2、3、5、7 MPa），开展冲击气压梯度（0.5、0.6、0.8、10 MPa）的三维组合加载试验。研究表明：在三维动静组合加载下，石灰岩峰值应变增大，吸收能也随之增大，峰值达到87.7 W/J时，约为入射能的60%，试件破碎程度最为明显，呈现实验室“岩爆”趋势；反射能、透射能、吸收能随入射能的增加呈线性增长，反射能、透射能、吸收能、入射能和单位体积吸收能随平均应变率的增加呈二次函数增长。此外，在轴压、围压不变时，随冲击气压的增加，应力—应变曲线分为4个阶段，在达到应变峰值时，出现回弹现象，即试件的变形达到峰值应变后应变又开始减小；围压与气压保持不变，轴压变化时试件应力—应变曲线的变化规律与轴压、围压不变时冲击气压的应力—应变曲线的变化规律基本吻合；不同围压下岩石的破坏形态主要为拉伸破坏和压剪破坏。

Study on the Mechanical Properties of Limestone under Three-dimensional Combined Dynamic and Static Loading

Deep rock mass is in the complex environment of " three high and one disturbance ".In order to study the influence of impact load on roadway surrounding rock during roadway excavation,limestone is taken as the research object,and the mechanical properties of limestone under three-dimensional dynamic and static combined loading are studied through the improved SHPB dynamic and static combined loading test device of Henan Polytechnic University.Typical axial pressure gradients (8,15,16 and 17 MPa) and circumferential pressure gradients (1,2,3,5 and 7 MPa) were selected,and three-dimensional combined loading tests with impact pressure gradients (0.5,0.6,0.8 and 1.0 MPa) were carried out.The results showed that the peak strain of limestone increased under the three-dimensional combined dynamic and static loading,and the absorbed energy also increased,with the peak value reaching 87.7 W/J,which was about 60% of the incident energy,and the fragmentation of the specimen was the most obvious,showing the trend of "rock burst" in the laboratory.The reflected energy,transmitted energy and absorbed energy increased linearly with the increase of incident energy,increased linearly with the increase of incident energy.The reflected energy,transmitted energy,absorbed energy,incident energy and absorbed energy per unit volume increased as a quadratic function with the increase of the average strain rate.In addition,when the axial pressure and confining pressure remain unchanged,the stress-strain curve is divided into four stages with the increase of the impact pressure.When the strain reaches the peak value,there is a rebound phenomenon,that is,the strain begins to decrease after the deformation of the sample reaches the peak strain.The variation law of the stress-strain curves when the confining pressure and the confining pressure remain unchanged is basically consistent with that of the impact pressure when the axial pressure and the confining pressure remain unchanged.The failure modes of rock under different confining pressures are mainly tensile failure and compressive shear failure.