高应力卸荷条件下硬岩能量演化研究

Study on Energy Evolution of Hard Rock Under High Confining Pressure and Unloading Condition

为探究引水隧洞在开挖过程中岩石破坏过程的能量演化规律,选取磁铁矿石开展了常规三轴及三轴峰前恒轴压卸围压试验。结果表明,在常规三轴试验中,岩石在峰值应力前以弹性应变能存储和耗散应变能消耗为主,在峰值应力后以弹性应变能释放和耗散应变能消耗为主;随着围压的增加,峰前剪切断裂能高于峰后;在卸围压试验中,耗散应变能均以指数函数趋势增加,卸荷速率越快,卸荷段经历时间较短,卸荷点与跌落点之间的耗散能在单位时间内能量增量变化速率越高;基于岩爆动力学M-C准则及卸荷路径下岩石内聚力丧失与岩石耗散应变能,新定义了岩石卸荷过程中的损伤变量,从能量角度揭示了岩石变形破坏的损伤程度。

In order to explore the energy evolution law of rock failure process in the excavation process of diversion tunnel,this paper selects magnetite ore and carries out conventional triaxial and triaxial pre-peak constant axial pressure unloading confining pressure tests.The results show that in the conventional triaxial test,the rock is dominated by elastic strain energy storage and dissipative strain energy consumption before the peak stress,and the elastic strain energy re-lease and dissipative strain energy consumption after the peak stress.With the increase of confining pressure,pre-peak shear fracture energy is higher than post-peak shear fracture energy.In the unloading confining pressure test,the dissipa-ted strain energy increases exponentially.The faster the unloading rate,the shorter the unloading period is,and the high-er the rate of energy increment per unit time between the unloading point and the drop point.Based on the M-C criterion of rockburst dynamics,the loss of rock cohesion and the dissipated strain energy of rock under unloading path,the dam-age variable in the process of rock unloading is defined,and the damage degree of rock deformation and failure is revealed from the perspective of energy.