Irrigation has changed the original environment of loess.In the process of moistening and samrating after irrigation,engineering properties of loess such as microstructure,physical properties,mechanical properties and water-physical properties have more or less been changed,which become important factors inducing loess geo-hazards.Taking Heifangtai of Gansu Province as a study irrigation area,the authors carried out systematic studies of loess,from in-situ tests to laboratory tests,from traditional soil mechanics to mechanics for unsaturated soils,and from microstructures to macroscopic properties.On such a basis,the changes of engineering properties of loess caused by irrigation were revealed.The results show that irrigation has destroyed the original structures of loess with general decrease of both the total amount of voids and the porosity.Physical property indexes consisting of natural water content,natural density and dry density increase,while natural void ratio decreases.Compressibility and collapsibility of loess decrease.The shear strength decreases dramatically.In terms of soil mechanics for unsaturated soils,irrigation causes the increase of water content of loess and decrease of matrix suction.As a result,the strength parameters for unsaturated loess show decreasing trends.In terms of time-related deformation of loess,irrigation causes loess to creep and fail more easily.%引水灌溉改变了黄土的原生环境,使黄土在增湿乃至饱和的过程中,微结构、物理、力学及水理性质都不同程度地发生了变化,成为诱发黄土灾害的重要条件.以甘肃省黑方台灌区为研究区,开展从原位试验到室内测试、从传统土力学到非饱和土力学、从微观到宏观的多角度系统研究,揭示灌溉引起的黄土工程地质性质变化.研究结果表明,灌溉造成黄土原生结构破坏,孔隙总量和孔隙度普遍减小,造成天然含水量、天然密度、干密度等物理性质指标增高,天然孔隙比降低,黄土压缩性和湿陷性趋低,抗剪强度降幅尤为明显；从非饱和土力学角度看,灌溉使得黄土含水量增加,基质吸力降低,非饱和黄土强度参数也随之呈递减趋势；从黄土时效变形分析看,灌溉使得黄土更易发生蠕变变形和破坏.
展开▼
