植被发育斜坡土体物理力学特性

Physicaland Mechanical Properties of Well Vegetated Slope Soils

头寨植被发育斜坡土体具有高含水率、大孔隙比、富含有机质等类似软土的基本物理性质。然而,与不同沉积相软土的压缩性对比,头寨土e-lgp曲线没有明显的结构屈服强度,e-p曲线不适用双曲线模型,也没有＂倒大＂的现象,压缩模量极小且有随深度递增的规律。头寨土剪应力-剪切位移曲线普遍无峰值,属于土样应变硬化的情况,年最低含水率〉100%、平均〉150%的超高含水率,使得土体具有极强的延性和变形性能。利用Image J对团聚体SEM照片分析表明,团粒的圆形度平均65%、复杂度平均42%、各向异性率平均25%,主定向角在0~360°之间变化,具有很好的＂支架＂结构,但团粒的＂支架＂作用并未体现。高含水率及团粒结构的特点,决定了头寨土压缩过程中孔隙水压力自始至终起到双重作用,即增大抗压性的同时也使得土中孔隙连通性增大,更容易压缩变形。

Ona well vegetated Slope of Touzhai in Zhuotong of Yunnan,China,the basic physical characteristics of the soil arehigh moisture content、largeporosity,rich organic matters,which is similarly to natural soft clays,butthecompression characteristicsis different thanvarious phasesoft clays,structural yield strength of the soil from Touzhai is not obvious,the hyperbola modelis not suitable for its stress-strain curve,and former coefficient of compressibility can＇t be less than the succeeding,its compressibility modulus is minimal and increasewith the increasing of depth. There is no peak on the curve of shear stress-shear displacement of Touzhai soils,the situationbelongs tosoil samples＇ strain hardening,Ultra-high moisture content makes the soils have a very strong ductile and deformation properties. Trough analyzing SEM photos by Image J,it is show that the circularity of soil aggregate is 65%,the complexity is 42%,the degrees of anisotropy is 25%,the main orientation angle is 0 ~ 360°,it has a good ＂skeleton＂structure,but the strength of soil ＂skeleton＂is not borne out. Annualminimummoisture content is greater than100% 、mean annualmoisture content is greater than 150%,the high moisture content and moisture contentproperties decide that the porewater pressure play a dual function role in compression process of soil from Touzhai that the pores connectivity of soil increase with press-resistance increasing,it iscompression easier with a larger load.