粗粒土非线性剪胀模型研究

Nonlinear dilatancy model for coarse-grained soils

粗粒土具有明显的剪胀剪缩性,为非虎克材料。对8种颗粒材料进行了11组三轴试验,将体应变分为球应力和偏应力引起的体应变两部分,并假定弹性变形泊松比为常数,对实测体应变两部分大小进行了分离。假定三轴试验的轴向应变和剪应力引起的体应变服从Rowe剪胀方程,分析表明,对任一种颗粒材料而言,Rowe剪胀方程参数Kf的归一性良好,即不同应力状态下参数Kf均近似为一个常数。在此基础上,基于邓肯–张模型和Rowe剪胀方程,建立了体变模量KP、剪胀模量Kq、剪切模量G三参量与应力状态的关系,初步提出了一种新的非线性剪胀模型。该模型可视为邓肯–张模型的改进型模型。经验证,该模型能比较准确地描述各种颗粒材料的体变过程,是一种物理概念明确,简单实用的非线性剪胀模型。

Coarse-grained soils exhibit evident dilatancy,and they do not obey the Hook’s law.Eleven groups of triaxial tests on eight kinds of particle materials are conducted.In order to separate the observed volumetric strain,the volumetric strain is viewed as two parts induced respectively by spherical stress and deviatoric stress,and the elastic Poisson’s ratio is assumed as constant.The axial strain and volumetric strain caused by the shear stress are assumed to obey the Rowe dilatancy law.The analysis shows that the parameter Kf is in good agreement with the normalization for any particle materials,which means the parameter Kf is approximately constant.The relationship between stress state and three parameters including volumetric strain modulus Kp,dilatancy modulus Kq,shear modulus G is established on the basis of the Duncan-Chang’s model and Rowe dilatancy law.A new nonlinear dilatancy model is initially proposed,and it can be seen as an improved Duncan-Chang’s model.The proposed model can well depict the processes of volumetric strains for different particle materials,and it is a simple and practical nonlinear dilatancy model with clear physical concept.