膨胀性非饱和土水力和力学性质的弹塑性模拟

Elastoplastic modelling of hydraulic and mechanical behaviour of unsaturated expansive soils

Alonso等人提出的非饱和土弹塑性本构模型(BBM),不能用于预测膨胀性非饱和土的力学性质。现有的膨胀性非饱和土的弹塑性模型(BExM),其微观参数及微宏观变形的转换关系确定非常困难。从宏观角度,在已有的非膨胀性非饱和土水力特性和力学性质耦合的弹塑性本构模型的基础上,发展和建立了一个可预测非饱和膨胀土的水力特性和力学特性的弹塑性本构模型。模型引入不同形状的等孔隙比线与屈服线,并考虑了变形对土水特性的影响。对已公开发表的非饱和膨胀土的试验结果进行预测,包括常净应力的吸湿试验,吸力不变的等向压缩试验及三轴剪切试验。预测结果表明该模型能够定量的描述膨胀性非饱和土的水力和力学特性。

The Barcelona basic model（BBM） proposed by Alonso et al.cannot predict the mechanical behaviour of unsaturated expansive soils,and the Barcelona expansive model（BExM） for unsaturated expansive soils is complicated,and the micro parameters and the coupling function from micro-structural strain to macro-structural strain are difficult to be determined.This paper presents an elastoplastic constitutive model from the macroscopic view for predicting the hydraulic and mechanical behaviour of unsaturated expansive soils based on an existing hydro-mechanical model for unsaturated non-expansive soils.The model takes into consideration the coupled effects of the saturation degree and void ratio.The concept of equivalent void ratio curve（EVRC）,which is different from the yield curve,is introduced in the model.The predictions are performed on the test results published in public,which include the swelling tests under constant net stresses,isotropic compression tests and triaxial shear tests under constant suctions.The comparisons between the measured and predicted results indicate that the proposed model can quantitatively predict the hydraulic and mechanical behaviour of unsaturated expansive soils.