黄土高原西部黄土工程物理性质及其成因

Engineering Physics Property of Loess and its Causes in Western Loess Plateau

根据甘肃东部11个剖面黄土微结构、湿陷系数、凝聚力的测定和西安刘家坡剖面孔隙测定,研究了黄土孔隙度、湿陷性、抗剪强度及颗粒成分在垂向上的变化规律和成因。结果表明,孔隙度高、湿陷强和抗剪强度弱的层位是风化成壤弱的黄土层,孔隙度低、湿陷弱和抗剪强度大的层位是红色古土壤或风化成壤强的黄土层。黄土地层工程物理性质在垂向上具有波动变化特征。第四纪冷干与温湿气候的交替和由此产生的成壤过程变化,是造成黄土地层工程物理性质波动变化的根本原因。黄土湿陷性是在干旱与半干旱地区弱的成壤过程中产生的,是草原地带灰黄色土壤具有的特征。在不同地区,湿陷性黄土分布深度存在差别。干旱区分布深度比湿润区大。在干旱区,强湿陷黄土分布深度可达12m,中等湿陷黄土可达17m,弱湿陷黄土可达20m以上。

On the basis of measuration on loess microstructure, collapsing coefficient and cohesion in eleven sections in eastern Gansu province and porosity of loess strata in Xi'an, the vertical change law of porosity, collapsibility, shearing strength and particle size as well as the forming causes were studied. Result shows that the loessial layers which have high porosity, strong collapsibility and weak shearing strength underwent the weak weathering and soil-formation processes; the layers which have low porosity, weak collapsibility and strong shearing strength are the red paleosols or the loessial layers weathered strongly. The engineering physics property of loess strata changes fluctuantly in the vertical direction. The primary cause is the alternation of cold-arid climate and warm-moist climate in Quaternary period and the induced change of soil-formation processes. The loessial collapsibility came into being in the weak soil-forming processes of the arid and semiarid area, and it is the characteristic of several kinds of grey and yellow soils in steppe area. In different areas, there is difference in the distributing depth of loessial collapsibility. The depth of loess collapsibility the arid area is greater than that in moist area. In arid area, the depth of strong collapsibility can reach 12 m, that of middle collapsibility can reach 17 m and that of weak collapsibility can be more than 20 m.