The plastic potential surface of Lade-Duncan model was not rigorous because it was proposed by fitting test results. A new elasto-plastic model-the SMP-Lade model was established by taking the yield function of the SMP criterion as the plastic potential function in order to overcome the defect. The model can predict the essential aspects of sand behavior such as nonlinearity, stress-path dependency and shear-dilatancy effects. The plastic potential surface can cover the contribution of all the three stress tensor invariants. The true triaxial compression test results of loose and dense sands show that both the predicted results of the SMP-Lade model and Lade-Duncan model are close to test results under the condition of the inter-principal stress parameter b being zero. However, no matter whether the sand is loose or dense, the predicted results of the SMP-Lade model are more close to the test results than those of the Lade-Duncan model when b is greater than 0 and less than or equal to 1.%为了解决Lade-Duncan模型的塑性势面由试验结果拟合所得理论上不够严密的问题,采用SMP准则的屈服函数构建塑性势函数,建立一个砂土弹塑性本构模型(SMP-Lade模型).该模型可以反映砂土应力-应变关系的非线性、应力路径的相关性以及剪胀特性,且塑性势面考虑了3个应力张量不变量的影响.密砂和松砂真三轴试验结果表明:在中主应力参数b=0的条件下,SMP-Lade和Lade-Duncan模型的预测结果与试验结果基本一致；当0＜b≤1时,无论是松砂还是密砂,SMP-Lade模型的预测结果都更接近试验值.
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