孔隙溶液对非饱和粘性土工程力学特性影响的物理化学机制

Many significant engineering issues, such as underground disposal of nuclear waste, land fill of buried contaminated soil and rainfall-induced landslide, are related to the unsaturated clayey soils. The research shows that when the water content, concentration and species of unsaturated soils are changed, there are complex physicochemical effects between the pore water and soil particles. These effects will strongly influence the macroscopic mechanical and hydraulic behavior of soils. However, these physicochemical mechanics have not been clarified and the accurate representation of these effects has not been given, which restrict severely the solution to the above engineering issues. This research focuses on the mechanical behavior of unsaturated soils under the effect of pore solution. Laboratory experiments (including the experiments of microstructure, mechanical and water retention properties) and theoretical analysis are conducted to reveal the mechanism of the physicochemical loading, such as the variation of water content, concentration and species, on the mechanical behavior and water retention characteristics. Based on the multi-field coupling continuum theory, the correlation between the potential and pressure of pore water is clarified within the whole range of water content. The change rule of the intergranular stress of unsaturated soils under the physicochemical effects is revealed. The chemo-hydro-mechanical coupling constitutive model of unsaturated soils is developed, which can be capable of describing the effect of water content, concentration and species variation. This research can lay bare a solid theoretical foundation and supply experimental support for analyzing the chemo-mechanical behavior of unsaturated soils underwent complex environmental loading conditions.

许多重大工程如高放废料地质处置、生活垃圾填埋、降雨诱发滑坡等均涉及非饱和粘性土问题。研究表明，在孔隙水的浓度、组份及含量变化下，非饱和粘性土中孔隙水与固体骨架之间存在着复杂的物理化学作用，这些作用对土介质的宏观水力学及力学特性产生重要影响。然而，目前尚未阐明这些物理化学作用机制并准确表征其效应，严重制约了上述工程的解决。本项目围绕着孔隙溶液作用下非饱和粘性土的工程力学特性，通过室内试验（包括微观结构、力学和持水特性试验）和理论分析，揭示含水量、浓度及组份变化对非饱和粘性土的力学和持水特性的影响机理；基于多场耦合连续介质理论，阐明在整个含水量变化范围内孔隙水势能与孔压之间的关联性，揭示物理化学作用下非饱和土粒间应力的变化规律，建立能够有效地描述含水量、浓度及组份变化下的非饱和粘性土的化学-水力-力学耦合本构模型。本研究将为模拟复杂环境荷载作用下非饱和土的化学力学特性提供重要的理论依据。

在孔隙水的浓度、组份及含量变化下，非饱和粘性土中孔隙水与固体骨架之间存在着复杂的物理化学作用，这些作用对土介质的宏观水力学及力学特性产生重要影响。然而，目前尚未阐明这些物理化学作用机制并准确表征其效应，严重制约了重大工程问题的解决。本项目围绕着孔隙溶液作用下非饱和粘性土的工程力学特性，通过室内试验（包括微观结构、力学和持水特性试验）和理论分析，揭示了含水量、浓度及组份变化对非饱和粘性土的力学和持水特性的影响机理；揭示了盐溶液对非饱和土的孔压、渗透压和基质势等变量的影响机理，探讨了上述变量的测定方法和技术；基于微观结构试验提出了毛细水和吸附水的分界点，得到了毛细水和吸附水的含量及其分布随着吸力的变化规律；开展了盐溶液浓度对膨胀力影响的试验研究，考虑了水化学作用对体积模量的影响，采用粒间应力的概念提出了预测膨胀力的宏观模型；采用粒间应力作为本构变量，建立了非饱和土化学-力学耦合的概念性本构模型，并将其成功应用于白垩岩水弱化效应的模拟。本研究将为模拟复杂环境荷载作用下非饱和土的化学力学特性提供重要的理论依据。