循环冲击荷载下含孔洞岩石损伤特性与能量耗散分析

Analysis on damage characteristics and energy dissipation of rock with a single hole under cyclic impact loads

为探究隧道工程开挖过程中外部荷载对隧道围岩多重扰动的影响,采用霍普金森压杆(SHPB)装置进行不同冲击荷载(0.6、0.7、0.8 MPa)和冲击方式(等幅与不等幅冲击气压)下的循环冲击试验,以此分析冲击载荷作用下含孔洞岩石试件的动力学特性、损伤特征、能量耗散和破坏形态。结果表明:基于一维应力波理论和界面连续条件得到适用于含竖向孔洞岩石试件计算的改良损伤计算公式;竖向孔洞的存在会影响岩石应力-应变曲线的变化趋势,并在经历数次冲击后尤为显著;花岗岩损伤积累随平均应变率增大呈幂函数增长,且随冲击荷载的增加呈现良好的规律性;积累比能量吸收值随循环冲击的进行逐渐增大,且试件的破坏模式经历了横向拉伸破坏、横向拉伸-轴向劈裂组合形式、轴向劈裂破坏的转变。

In order to explore influence of external load on multiple perturbations of surrounding rock during tunnel excavation,cyclic impact load tests of rock with a single hole were carried out by using Split Hopkinson Pressure Bar(SHPB)device under different impact loads(0.6,0.7,0.8 MPa)and impact methods(impact pressure of Equal-amplitude and Unequal-amplitude).Then,dynamic characteristics,damage characteristics,energy dissipation and failure modes of these rock specimens under impact loads were analyzed.The results show that based on one-dimensional stress wave theory and interface continuity conditions,an improved damage calculation formula is obtained suitable for rock specimen with a vertical hole which affects changing trend of rock stress-strain curves,especially after several shocks.Damage accumulation of granite increases in a power function along with increase of average strain rate,and shows a good regularity with increase of impact loads.Moreover,cumulative specific energy absorption value increases gradually with cyclic impact,and failure mode has undergone transformation from transverse tensile failure to transverse tensile failure-axial splitting failure and axial splitting failure.