灌溉淋滤对原状黄土物理力学性质的影响

甘肃黑方台地区因农业灌溉诱发了大量黄土滑坡，给当地群众生命财产安全构成了严重威胁。为探究灌溉诱发黄土滑坡的形成机理，以灌溉淋滤为出发点，对比分析了原状黄土在长期灌溉条件下物质组成、物理性质的变化规律，通过室内三轴试验研究了灌溉淋滤对原状黄土静态液化特性的影响。结果表明:长期灌溉造成原状黄土中可溶盐含量的大幅降低，胶结弱化，粗颗粒分散，黏粒增多，塑性指数增大，同时灌溉过程中发生的湿陷引起黄土干密度增大、孔隙比减小；淋滤前后饱和黄土均表现出强烈的应变软化特性，具有静态液化特征；与未淋滤黄土相比，淋滤后黄土脆性破坏特征有所减弱，表现为峰值应变增大、超孔隙水压力减小和稳态线上移。

Effect of Irrigation Leaching on Physical and Mechanical Properties of Undisturbed Loess

Agricultural irrigation in Heifangtai area of Gansu has induced a large number of landslides, which threaten the safety of the local residents. In order to investigate the mechanism of the irrigation-induced loess landslide, the variations of material composition and physical properties of undisturbed loess caused by long-term irrigation were analyzed; laboratory triaxial tests were performed to further study the effects of irrigation leaching on static liquefaction characteristics inherent in undisturbed loess. The results show that long-term irrigation leaching results in the decrease of contents of soluble salt in undisturbed loess, weakening in the cementation, the dispersion of coarse particles and the increase of clay particle and plasticity index; meanwhile, the wetting collapse in the process of irrigation causes the increase of dry density and the decrease of void ratio; all saturated loess before and after leaching are characterized by static liquefaction in isotropically consolidated undrained compression testing; compared with loess without leaching, the loess leached is characterized by smaller brittleness with the increase of peak strain, the decrease of excess pore water pressure and the upward of steady state line.