基于达维坚科夫骨架曲线的软土非线性动力本构模型研究

试验研究表明，上海地区软土的动力变形特性符合“应变软化”规律，可用达维坚科夫（Давидеков）模型描述。首先以达维坚科夫骨架曲线为基础，采用Masing法则，构造了土体加载、再卸载的动应力-应变关系滞回曲线，推导了达维坚科夫骨架曲线和卸载、再加载滞回曲线的增量剪切模量表达式。随后将土体动应力-应变关系曲线从一维推广到三维应变空间，基于FLAC3D提供的二次开发平台，编制了基于达维坚科夫骨架曲线和符合广义Masing法则的土体非线性动力本构模型计算程序，并且通过复杂加载路径验证了编制程序的正确性和合理性。以相关文献中的土体动剪切模量比 随剪应变幅值 变化，以及阻尼比 随剪应变幅值 变化的试验结果为依据，运用编制程序计算了不同剪应变幅值下的 - 和 - 曲线，并与文献试验结果进行了对比。研究结果表明，相比于工程上广泛应用的Hardin-Drnevich模型，基于达维坚科夫骨架曲线构造的本构模型所得到的软土 - 和 - 曲线能与试验结果更符合，进而验证了所建立的本构模型的合理性与实用性，其结果可用于上海地区软土场地的动力计算反应分析。

Study of nonlinear dynamic constitutive model of soft soils based on Davidenkov skeleton curve

Test data show that dynamic deformation characteristics of Shanghai soft soils are consistent with law of strain softening;and they can be described by Davidenkov model well.Firstly,based on Davidenkov skeleton curve,the dynamic shear stress-strain curves for loading and unloading are constituted by Masing rules;and the equations of incremental tangent shear modulus of skeleton curve and hysteresis curves are derived.Then the dynamic stress-strain relation is extended from one-dimensional to three-dimensional strain space.Using the development platform of FLAC3D,the nonlinear dynamic model of soils is programmed,which is based on Davidenkov skeleton curve and according with generalized Masing rules;and the validity and rationality of the program are validated by a complex stress-strain loading path.Finally,based on the soft soils test data of other related study,the calculated results by the program and test data results of related study,which contain the relation curves of dynamic shear modulus ratio vs.shear strain amplitude and damping ratio D vs.shear strain amplitude,are compared under series of different levels of shear strain amplitude.Study results show that compared with Hardin-Drnevich model which is widely used in engineering,the-curves and D-curves based on the Davidenkov skeleton curve are fitting to the soft soils test results better,so as to prove the rationality and practicability of the proposed constitutive model,and can be used for the dynamic response analysis of soft soils sites in Shanghai.