锦屏水电站大理岩卸荷条件下的流变试验及本构模型研究  

STUDY ON RHEOLOGICAL EXPERIMENT AND CONSTITUTIVE MODEL OF JINPING HYDROPOWER MARBLE UNDER UNLOADING CONDITION

作　　者：朱杰兵[1] 汪斌[1] 邬爱清[1] 胡建敏[1] 

机构地区：[1]长江科学院水利部岩土力学与工程重点实验室,武汉430010

出　　处：《固体力学学报》2008年第S1期99-106,共8页Chinese Journal of Solid Mechanics

基　　金：国家自然科学基金项目(40872192;50639090)资助助

摘　　要：以雅砻江锦屏二级水电站引水隧洞大理岩为研究对象,采用不同轴压方案下恒轴压、逐级卸围压的应力路径开展室内流变试验。试验表明,在由卸围压产生的偏差应力作用下,大理岩轴向及侧向均表现出一定的流变行为。在低偏应力水平下,主要表现为衰减蠕变阶段和稳定蠕变阶段,一旦围压卸荷至破坏级别时,变形突然加速,进入加速蠕变阶段而破坏。试验还表明,卸荷条件下的流变长期强度明显小于相应围压下的三轴压缩强度。在对流变试验数据进行深入分析基础上,以残差平方和为目标函数,利用嵌入Levenberg-Marquardt算法的最小二乘法(LM-NLSF法)对Burger’s流变模型参数进行了优化辨识。经比较,计算曲线与试验点拟合性较好,说明该流变本构模型能较好的反映出锦屏大理岩在卸荷条件下的衰减蠕变阶段和稳定流变特性,并验证了建立的Burger’s流变模型的正确性和合理性。通过模型参数与应力水平的相关性研究表明,瞬时弹性模量随着偏应力水平的增加总体上呈降低趋势且逐渐趋于一定值,而粘滞系数有一个先增加后突然跌落的过程。Taken marble sampled at Jinping Grade II hydropower water tunnels as research objective,the unloading rheological test scheme of keeping axial pressure stationary and unloading lateral stress gradually under different axial stress is performed in laboratory. The research reveals that marble specimens exhibit rheological property both in axial and lateral directions in some degree under condition of deviatoric stress as a result of confining pressure unloading. At lower comparably stress level, both behave attenuating creep stage and steady creep stage, and once the confining pressure unloading reaches the critical level, deformation would accelerate to turn into accelerating creep stage. The test results show that the long-term strength of marble specimens under unloading stress condition is a littler less than that of triaxial compressive condition at the same confining pressure. Based on the deep analysis of test data, the sum square of survival difference is taken as objective function, and the least square embedded in Levenberg-Marquardt algorithm is put forward to optimize the fitting parameters of Burger’s rheological model. By comparison with the primal data, the fitting curves are well fitted with test data, which indicates that this rheological model can preferably present attenuating creep and steady creep attribute of Jinping marble, and verifies the rationality and validity of the established Burger’s model. By research on the correlativity between the parameters and pressure level, it can be concluded that the instantaneous elastic modulus decrease with the deviatoric stress increasing as a whole, and the visco coefficients behave upward trend and decline suddenly once reaching some pressure level.

关 键 词：卸荷流变试验 Burger’s流变模型 LM-NLSF法 瞬时弹性模量 粘滞系数 

分 类 号：TV223.1[水利工程—水工结构工程]