基于等效黏弹性模型获取土体最大动剪模量的计算方法

AN ALGORITHM FOR QUANTITATIVELY ACHIEVING MAXIMUM DYNAMIC SHEAR MODULUS(G_(MAX) ) OF SOIL BASED ON EQUIVALENT VISCO-ELASTIC MODEL

土动力特性参数中,最大动剪切模量Gmax是定量描述土动力学本构最重要的参量之一,现有研究方法通常需较多参量及工程经验方能对其进行半定量的计算,但天然状态条件下土体的Gmax真值是唯一且确定的。为此,结合对土体动力学特性广泛适用性的基于等效黏弹性理论的修正Davidenkov模型,基于土动三轴试验,提出对该模型中的3个参量多元回归和对Gmax自适应逼近迭代的反分析算法,用于求取Gmax并得到本构方程中所需系数。研究表明:该算法在同时满足Davidenkov模型曲线三参数对测试数据拟合以及反算Gmax残差最小的双重计算约束条件下,对3类土样的动三轴测试数据进行拟合,在规避直接获取Gmax存在困难的情况下,顺利得到各测试样本的动本构模型。

The maximum dynamic shear modulus(Gmax) is a very important parameter in describing the dynamic constitutive equation of soil. Gmax reflects the dynamic response of soil modulus and damping ratio directly,which changes with dynamic strain. Generally,Gmax is got by semi-quantitative formula in existed methods,and a lot of engineering experiences are needed. But in fact,Gmax is unique and constant. From this aspect,based on equivalent viscous elastic theory,the modified Davidenkov model is taken into account;and it is widely applicability for describing the dynamic behavior of soil. Based on dynamic triaxial test for three types of soil samples and according to the three parameters contain in modified Davidenkov model,the anti-analysis algorithm based on multiple regressions and self-adapting approximation is proposed to achieve Gmax and the factors required in Davidenkov model. The result shows that:with this algorithm,the dual constraints conditions above is carried out to fit test data. Under the premise of minimizing the residuals of Gmax,the fitting curve can describe the dynamic response behavior of soil very well within small strain condition. This algorithm is good at circumventing the difficulty of getting Gmax directly,and finally,the dynamic constitutive equation for three types of soil samples is achieved.