基于最小能耗原理的花岗岩蠕变损伤分析

Analysis of Creep Damage of Granite Based on the Principle of Minimum Dissipative Energy

为了研究花岗岩蠕变损伤特性,采用MTS815.02岩石力学测试系统对花岗岩试样进行了三轴加载试验和分级加载蠕变试验,基于最小耗能原理、广义胡克定律和应变等效原理建立了弹性损伤方程和改进了非线性损伤蠕变模型,分析了花岗岩损伤变量与泊松比之间的变化规律和蠕变损伤过程.研究结果表明基于能量原理并结合任意阶段应力应变状态的损伤方程更合理地描述了岩石损伤发展过程.在耗能过程中损伤泊松比对岩石损伤起重要作用,损伤变量随着泊松比的增加而非线性增加,并逐渐趋于稳定,改进模型计算结果与试验曲线相吻合,较好地描述了岩石衰减蠕变、等速蠕变和加速蠕变的全过程;在岩石蠕变前期损伤速率较为平缓,进入加速蠕变阶段后随着微裂纹在强度弱化区汇聚,损伤速率直线升高且损伤变量突然增大.

To carry out the three axis load test and creep test with step loading axial stress ofgranite samples on the MTS815.02 rock mechanics test system.Based on the principle ofminimum dissipative enegry,generalized Hooke’s law and strain equivalence principle,the elastic damage equation and the nonlinear damage creep model are established,andthe variation law and creep damage process of granite damage variable and Poisson’sratio are studied.The results show that Damage Poisson’s ratio in the energy dissipationprocess plays an important role in the damage of rock,and the damage variable increaseswith the increase of Poisson’s ratio,and tends to be stable.The improved modelcalculation results are in great agreement with the experimental curves,and can greatlydescribe the whole process of rock creep that include the decelerated creep,steady creepand accelerate creep.In the early stage of creep damage,the damage rate is relativelyslow,and with the increase of micro cracks in the strength weakening region,the damagerate increases and the damage variable increases.Based on the energy principle and thedamage equation of the stress and strain state in any time,the damage evolution processof rock damage is more reasonable.