基于成都黏土蠕变试验的非定常蠕变本构模型研究
Study on Unsteady Creep Constitutive Model Based on Creep Experiment of Chengdu Clay

针对黏土的蠕变特性对工程造成不利影响的问题，开展了成都黏土的常规三轴固结不排水试验和三轴固结不排水蠕变试验，分析其蠕变特性、应力-应变关系、弹性模量和黏滞系数的非定常性；同时，基于分数阶导数理论，利用软体元件替换常规黏性元件，并且考虑黏土弹性模量和黏滞系数的非定常性，构建了成都黏土的非定常蠕变本构模型，对本构模型进行了拟合和辨识分析，得到了成都黏土的长期强度值。结果表明：弹性模量和黏滞系数的非定常性包括时效特性和加载特性两方面，蠕变模型元件包括瞬时弹性元件、黏弹性元件和黏塑性元件；拟合的各项参数变化规律与室内试验规律一致，尤其是对加速蠕变阶段的拟合度极高，所构建的模型具有充分的合理性和可靠性。
Aiming at the problem of adverse effects of the creep characteristics of clay on engineering, the conventional three？？axis consolidation undrained test and three？？axis consolidation undrained creep test on Chengdu clay were studied. The unsteady performances of creep characteristics, isochronous stress？？strain relationship, elastic modulus and the viscosity coefficient of Chengdu clay were analyzed. Meanwhile, based on the fractional derivative theory, replacing the conventional viscous elements with software components, and considering the unsteady characteristics of the elastic modulus and viscosity coefficient of clay, the unsteady creep constitutive model of Chengdu clay was constructed, and the constitutive model was fitted and identified. Through the above analysis, the long？？term strength value of Chengdu clay was obtained. The results show that the unsteady performances of elastic modulus and viscosity coefficient of Chengdu clay include two aspects of timeliness and loading characteristics. The creep model elements include transient elastic elements, viscoelastic elements and viscoplastic elements. The variation rule of the fitting parameters is consistent with the indoor test rule, especially for the accelerated creep stage. The constructed model is reasonable and reliable