基于次加载面理论改进的ALPHA模型及其数值实施

基于次加载面理论对ALPHA模型进行了改进,并在模型中考虑了土体初始各向异性;提出了与模型相适应的半隐式本构积分算法,据此在通用有限元软件ABAQUS平台上开发了相应的用户材料子程序;利用建立的计算程序,对不同排水条件的三轴试验进行了数值模拟。与已有研究成果对比表明,提出的半隐式本构积分算法,可较好地实现复杂本构模型的数值实施。改进的本构模型克服了修正剑桥模型预测的超固结土峰值强度过高、初始屈服面内假定为弹性变形等缺点,能够较好地描述土体初始屈服面内的的非线性和不可恢复性变形特征;通过变化模型参数,可模拟变形特性较为复杂的土体。

A modified ALPHA model based on subloading surface theory and its numerical implementation

ALPHA model is modified based on subloading surface theory; and the initial anisotropy induced by settlement is also considered. Considering the characters of the modified model, a semi-implicit constitutive integration algorithm is proposed. In terms of the algorithm, a user material subroutine is developed in the framework of general-purpose finite element code ABAQUS. Using the subroutine, simulations for triaxial tests are performed; and the results have been compared with the published studies. The comparison shows that the presented algorithms are capable of the numerically implementing of complicated constitutive model; and the modified ALPHA model, which overcomes the deficiencies of modified Cam-Clay model, such as predicting higher peak strength for over consolidated clay and assuming elastic deformation inside the initial yield surface, can depict the nonlinear and nonrecoverable deformation before yielding. Through varying model parameters, more complicated deformation behaviors can be simulated by the modified model.