白垩系地层人工冻结软岩蠕变损伤耦合大变形本构模型及参数反演研究

The project uses the method of laboratory tests, field test and finite element numerical analysis to research the Cretaceous strata artificially frozen soft rock creep damage coupling large deformation constitutive model, the main contents are: (1) To get the frozen soft rock volume yield surface, the shear yield surface and loading and unloading criteria from the triaxial shear tests of the Cretaceous strata artificially frozen soft rock under the stress path. (2) Get the regular strength, nonlinear creep equation and the creep strength criterion from the triaxial creep tests of the Cretaceous strata artificially frozen soft rock under the stress path. (3)Through the micro-injury experimental study of the Cretaceous strata artificially frozen soft rock, obtain the frozen rock creep damage evolution and damage evolution equation. (4) Establish the creep damage coupled large deformation constitutive model of the Cretaceous strata artificially frozen soft rock, and embed the proposed constitutive model of the frozen soft rock into the finite element software program through the user subroutine; Based on the large deformation constitutive finite element and genetic algorithm theory to develop the parameter inversion procedure, and the establishment of the Cretaceous strata artificially frozen soft rock creep damage coupled large deformation constitutive model for parameter identification..The project research results are the basis of the Cretaceous strata artificially frozen soft rock frozen wall mechanics calculations, to provide scientific guidance for the stability analysis and engineering prediction of the frozen wall, and of great significance to promoting China's freezing sinking theory and technological progress.

项目采用室内试验、现场实测和有限元数值分析相结合的方法研究白垩系地层人工冻结软岩蠕变损伤耦合大变形本构模型，主要研究内容：（1）白垩系地层人工冻软岩应力路径下的三轴剪切试验，获得冻软岩体积屈服面、剪切屈服面和加载卸载准则。（2）白垩系地层人工冻软岩应力路径下的三轴蠕变试验，获得常时强度、非线性蠕变方程和蠕变强度准则。（3）白垩系地层人工冻软岩微观损伤试验，获得冻结岩蠕变损伤演化规律和损伤演化方程。（4）建立白垩系地层人工冻软岩蠕变损伤耦合大变形本构模型，将提出冻软岩本构模型通过用户子程序嵌入到有限元软件程序中；基于大变形本构有限元和遗传算法理论研发参数反演程序，并对建立的白垩系地层人工冻软岩蠕变损伤耦合大变形本构模型进行参数辨识。.项目研究成果是白垩系地层人工冻软岩冻结壁力学计算的基础，为冻结壁稳定性分析与工程预测提供科学指导，对推动我国冻结法凿井理论与技术进步具有重大意义。

项目采用室内试验、现场实测和有限元数值分析相结合的方法研究地层人工冻结软岩(土)蠕变损伤变形特征及本构模型，主要研究内容：.(1)深部人工冻结黏土三轴蠕变试验研究在较低的偏应力水平下，试样只发生前两个阶段的蠕变变形，且蠕变变形量超过总变形量的70%；当试样偏应力值高于某一临界值时会出现加速蠕变阶段，蠕变变形量超过总变形量的80%。可以用改进的Zienkiewicz-Pande抛物线型屈服准则来描述加速蠕变阶段的临界应力。.(2)深部软岩蠕变本构模型为描述非线性加速阶段蠕变规律，采用改进的元件模型，提出了软岩非线性的黏弹塑蠕变本构模型，通过有限元本构程序的二次开发，将提出的本构模型嵌入到ADINA非线性有限元程序中。.(3)应力路径下深部人工冻结黏土变形规律。偏应力较小时人工冻土的三轴剪切应力-应变曲线呈直线型，可以选用Mohr-Coulomb屈服函数来描述，若偏应力很大时人工冻土的三轴剪切应力-应变曲线为抛物线型分布，可以选用改进的Zienkiewicz-Pande抛物线型屈服准则来表达。.(4)白垩系软岩的一种增量型统计损伤本构模型。白垩系地层软岩的三轴应力-应变曲线具有显著的非线性分阶段特征，为准确模拟其损伤发展规律，从软岩变形机理出发，认为软岩存在初始损伤，并引入损伤恢复变量，以轴向应变为损伤演化控制量，并服从幂函数分布建立了裂隙压密阶段的损伤本构方程。.建立了白垩系软岩的一种增量型的统一损伤本构模型，通过三轴试验结果，对损伤参数进行反演，得到损伤参数与围压之间的关系。将模型导入ABAQUS有限元程序，对三轴压缩试验进行模拟，并将试验值和数值解进行比较，两者较为吻合，表明建立的损伤模型是合理、有效的,在矿井建设具有重要指导意义。