砂土液化本构模型的试验研究

针对饱和砂土在动力作用下液化既有计算模型存在的问题,在汉丁-顿伊维奇(Handin-Drnevich)模型基础上,根据瞬态极限平衡理论的基本假设,按照应力状态不能逾越破坏条件等基本原则,借鉴增量非线性模型的计算思路,综合散粒体模型的优点,将整个振动液化过程划分成多个区域,并考虑液化过程中的剪胀、剪缩、刚度衰化和卸荷体缩等现象,推导出新的本构计算模型。该模型的参数少,且具有明确的物理意义,能够量化。通过室内动三轴试验对模型进行了验证。对比分析试验结果与计算结果可知,两者在孔隙水压力、应变发展初期是一致的,后期是有差异的;在应力路径方面两者的极限状态面几乎是一致的。因此,该模型可以较为完善地反映砂土液化过程中出现的各种现象。

Test Study on the Constitutive Model of Sand Liquefaction

According to the problems in the existing calculating models of saturated sand liquefaction under dynamic action,and on the basis of Handin-Drnevich model,a new calculating model of the dynamic constitutive relation of saturated sand is put forward.The model is based on the basic hypothesis of instantaneous limit balance according the basic principia of the stress estate not being overstepped and destroyed.It also uses for reference of the calculation method of increment nonlinear model combining with the excellences of the model of distributed particles.It divides the process of vibrating liquefaction of saturated sand into some areas,and it also considers the phenomena of shear dilatation,shear contraction,stiffness degradation and unloading shrinkage of saturated sand during liquefaction process.There are fewer parameters in the model.The physical meanings of the parameters are very evident and can be quantized.They can be obtained from the dynamic triaxial test in door.The model has been validated by indoor dynamic triaxial test.Test results are compared with the calculated ones,which indicate that the model can reflect more perfectly all sorts of phenomena appearing in the process of liquefaction of saturated sand.Especially,at the initial stage of development of pore water pressure and strain of saturated sand,the results of indoor dynamic triaxial test are very consistent with the calculating results of the model.But there is some difference between the results at the anaphase of development of pore water pressure and strain.On the calculating and experimenting path of stress,and the two limits state surfaces of stress paths are almost identical.