主应力轴旋转下黏土累积变形的分数阶元件模型

在长期交通载荷作用下土体塑性累积变形本构模型对路基沉降计算至为关键.元件组合模型可以计算岩土体循环累积应变,但现有的各类元件模型未能反映饱和软黏土的主应力轴循环旋转现象.在对饱和软黏土进行等向固结条件下的主应力轴循环旋转加载试验及非等向固结下的循环扭剪试验基础上,将Abel黏壶代替Burgers模型中的Newton黏壶,得到分数阶Burgers模型;利用遗传算法优化循环塑性累积应变的Burgers模型和分数阶Burgers模型的参数,通过对比两组模型的计算值与试验值,发现分数阶模型更适合模拟计算循环载荷下饱和软黏土的累积变形.

FRACTIONAL ORDER COMPONENT MODEL FOR ACCUMULATIVE DEFORMATION OF CLAY UNDER ROTATION OF PRINCIPAL STRESS AXES

A plastic accumulative deformation constitutive model of soils under a long term traffic load is very important in the foundation settlement calculation. The existing soil element model can be used to calculate the cumulative strain of the rock and soil body, but without consideration of the cyclic rotation of principal stress axes of the saturated soft clay. For the long-term settlement of subgrade caused by traffic loads, the cyclic principal stress rotation might be important. On the basis of the a series of loading tests with the principal stress rotating under the isotropic consolidation and a series of cyclic torsional tests with anisotropic consolidation, the Newton dashpot is replaced by the Abel dashpot and the fractional order derivative is established. The parameters of the Burgers model and the fractional order derivative Burgers model of the axial plastic cumulative strain are optimized by a genetic algorithm. By analyzing the correlation curve of the calculation value and the test value of the two models, the fractional order derivative Burgers model is found to be more appropriate for calculating the cumulative strain of the soft clay subjected to a cyclic rotation of principal stress axes.