两类剪切屈服面的非饱和土BBM模型对比研究

Comparison research of BBM models on adopting two shear yield surfaces to unsaturated soil

针对使用椭圆形剪切屈服面的非饱和土BBM弹塑性模型计算抗剪强度偏低的问题,提出了非饱和土水滴形剪切屈服面函数,对原模型进行了改进,将水滴形屈服面扩展到非饱和土中,提出了非饱和土水滴形剪切屈服面函数,采用相关联的流动法则改进了BBM模型。通过对同一组试验的数值模拟,对比研究了改进模型的合理性以及与原模型的差别,结果表明,在控制吸力条件的三轴压缩状态下采用水滴形屈服面的改进BBM模型对非饱和土强度及变形的计算更为合理。

The shear yield surface of ellipse is adopted to the elastic-plastic model of BBM so that the results of shear strength are low for unsaturated soil.To solve this problem,the drip type yield surface was extended to unsaturated soil,then the shear yield surface function of drip type for unsaturated soil was proposed,while the associated flow rule was also used to improve the BBM model.Through the numerical simulation to the same set of experiments,the shear yield surface of drip type and ellipse for BBM elasto-plastic model have significant difference on predicting of strength and deformation behaviors of unsaturated soil.The results show that improved model of drip type yield surface can more accurately predict the strength and deformation behaviors of unsaturated soil under suction-controlled triaxial compression stress states.