淋滤作用影响下黄土-古土壤接触带的剪切行为研究

Landslide disasters induced by irrigation frequently occurred in the loess region of China and it has been realized that loess-paleosoil contact zone has controlling influence on the stability of landslides. The leaching of loess stratum is enhanced under the long-term irrigation activities and thus the leaching in loess-paleosoil contact zone become more complex and more strong. The physical and chemical effect of leaching will change the shear behavior of loess-paleosoil contact zone and consequently influence the stability of soil. In this work, the influence of leaching on shear characteristic will be analyzed through triaxial shear tests performed on loess-paleosoil contact zone specimens leached by different solutions with various ion compositions, and under different leaching path. Then the change of composition and microstructure will be measured to research the physical and chemical effects of leaching, and the microstructure evolution during shear failure process will be studied to research the controlling effect of structure on shear behavior. Based on these research results, influence mechanism of leaching on shear characteristic will be discussed. Finally, based on the binary medium constitutive model, quantitative relationships between leaching parameter, structural parameter of loess-paleosoil contact zone, and breakage coefficient will be explored to established a structural constitutive model that can take account of leaching. These research results will enrich theories of loess mechanics and will provide basis for evaluation, prevention and control of geological disasters in loess region.

灌溉诱发的滑坡在我国黄土地区频繁发生，黄土-古土壤接触带这类土体结构面对滑坡稳定性的控制作用已受到关注。长期灌溉活动加剧了水对黄土地层的淋滤，黄土-古土壤接触带处的淋滤作用更加复杂而强烈，淋滤的物理化学效应影响土的剪切行为，进而影响土体稳定性。本项目拟考虑不同淋滤路径，选用不同成分淋滤液对原状试样进行淋滤，通过淋滤前后试样的剪切试验，研究淋滤作用对黄土-古土壤接触带剪切行为的影响。同时，分析淋滤后试样成分与结构变化，探讨淋滤作用的物理化学效应；观测试样剪切过程中微结构的发展演化，揭示结构对剪切行为的控制作用；从淋滤改变结构进而控制剪切行为的角度，阐明淋滤作用对剪切行为的影响机制。最后，基于二元介质模型和微结构观测，探索淋滤条件、微结构参数、破损率参数之间的量化关系，建立考虑淋滤作用的黄土-古土壤接触带结构性本构模型。研究成果能够丰富黄土力学相关理论，为黄土地区地质灾害评价及防治提供依据。

灌溉诱发的滑坡在黄土地区频繁发生，长期灌溉活动加剧了水对黄土地层的淋滤，黄土-古土壤接触带处的淋滤作用更加复杂而强烈，淋滤的物理化学效应影响土的剪切行为，进而影响斜坡土体稳定性，因此，研究淋滤作用影响下黄土-古土壤接触带的剪切行为具有重要的意义。本项目以灌溉诱发型黄土滑坡频发的陕西泾阳南塬地区为研究背景，综合采用剪切试验、微结构观测、理论分析和数值模拟的方法，开展了淋滤作用影响下黄土-古土壤接触带的剪切行为的研究工作。项目研究了试样的宏观剪切特性，揭示了剪切破坏力学模式、微结构发展演化及微结构对宏观剪切行为的控制作用，并探究了二元介质模型中的破损率函数形式；观测了试样纳米至微米级的微结构特征，建立了三维微结构模型并提出了定量化指标，测试分析了淋滤作用下黄土-古土壤接触带结构、成分和物理指标的规律；在此基础上研究了淋滤作用对黄土-古土壤接触带剪切行为的影响，深入阐明了影响机理。研究工作不但丰富了黄土结构面力学性质方面的相关成果，而且能够为黄土地区灌溉诱发型黄土滑坡的防控提供理论依据。