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为研究深部地下工程围岩开挖卸载后又受到动力扰动的力学行为,利用动静组合加载SHPB试验系统对砂岩试件进行静载荷加卸载后再冲击试验。试验过程中,先对岩石试件施加不同的三轴载荷,围压按2,4,6,8 MPa加载,轴向载荷加载到对应三轴静载抗压强度的95%左右,再分别卸载至对应三轴静载抗压强度的20%,30%,60%,70%,80%和90%,然后沿轴向进行同一幅值的冲击载荷试验。试验结果表明:当岩石加卸载到对应三轴静载抗压强度的90%左右,岩石均匀化假设不太适用;动静组合载荷下岩石试件抗压强度随围压增大而增大,当围压不变时,随轴向静压增大出现先增大后减小的趋势;岩石破坏吸收的冲击能随轴向静压的增大逐渐减少,随围压增大而增加。
In order to study the mechanical behaviors of surrounding rock after deep excavation unloading and dynamic disturbances, SHPB test system was used to test the static load of sandstone after loading and unloading. During the test, different triaxial loads were applied to the rock specimens. The confining pressure was loaded at 2, 4, 6, 8 MPa. The axial loads were loaded to about 95% of the corresponding triaxial static compressive strength, To 20%, 30%, 60%, 70%, 80% and 90% of the corresponding triaxial static compressive strength, and then subjected to the same amplitude impact load test along the axial direction. The experimental results show that when rock loading and unloading is about 90% of the corresponding triaxial static compressive strength, the rock homogenization assumption is not suitable. The compressive strength of rock specimen increases with the increase of confining pressure under dynamic and static combined load. When the confining pressure is constant, the static pressure increases first and then decreases with the increase of axial static pressure. The impact energy of rock failure absorption decreases with the increase of axial static pressure and increases with the increase of confining pressure.