盐溶液饱和岩土的本构理论及在黏土中的应用

Constitutive theory of geomaterials saturated with salt solution and its application in clay

盐溶液中离子的化学活性会改变饱和岩土的力学性质,诱发其工程性能出现劣化甚至失效等岩土工程问题。为了研究化学活性对饱和岩土水力与变形特性的影响,基于混合物理论与热力学溶液理论,建立了盐溶液饱和岩土材料的本构理论框架。与以往研究不同,该理论将固相应变分解为孔隙率变化引起的骨架应变、固相材料变形引起的基质应变以及化学反应等物质交换引起的质量交换应变,用以凸显孔隙率在水-力-化学多场耦合机制中的关键作用;采用溶质的现时质量分数作为化学状态变量来反映化学活性的影响;利用自由能和耗散势分别建立弹性和塑性本构关系。根据该理论框架建立了NaCl溶液饱和黏土的固相、流相本构关系以及溶质的渗流-扩散方程,并得到了已有试验数据的验证,表明该框架可以指导盐溶液饱和岩土的本构建模工作。

The chemical activity of ions in salt solution will change the mechanical properties of saturated geomaterials,inducing geotechnical problems such as deterioration or even failure of engineering properties.In order to study the effects of chemical activity on the hydraulic and deformation properties of saturated geomaterials,a constitutive theory framework for geomaterials saturated with salt solution is established based on the mixture theory and thermodynamic solution theory.Different from the previous studies,the solid phase strain is decomposed into the skeleton one caused by porosity change,the matrix one caused by solid material deformation,and the mass exchange one caused by material exchange such as chemical reaction,to highlight the key role of porosity in the hydro-mechanical-chemo multi-field coupling mechanism.This theory adopts the current mass fraction of solute as the chemical state variable to reflect the effects of chemical activity.The free energy and dissipation potential are used to establish the elastic and plastic constitutive relations,respectively.Based on the above theoretical framework,the constitutive relations of solid and fluid phases for the clay saturated with NaCl solution and the seepage-diffusion equation for the solute are established.The constitutive model is validated by the experimental data,which proves that the framework can guide the establishment of the constitutive model for the geomaterials saturated with salt solution.