紫色泥岩土壤<2mm岩屑及其对抗剪强度的作用机制  

The Rock Fragments(<2 mm) and Their Action Mechanism on the Shear Strength of Purple Mudstone-Developed Soils

作　　者：钟守琴[1] 刘波[1] 魏朝富[1] 胡斐南[1] 

机构地区：[1]西南大学资源环境学院/农业部西南耕地保育重点实验室,重庆400715

出　　处：《中国农业科学》2015年第23期4846-4858,共13页Scientia Agricultura Sinica

基　　金：国家科技支撑计划项目(2012BAD05B06)

摘　　要：【目的】土壤抗剪强度是反映土壤抗滑、抗侵蚀及抗倾覆稳定性的重要指标。而紫色土中大量岩石碎屑能够显著影响土壤抗剪强度。但过去的研究主要集中在>2 mm的岩石碎屑上,而<2 mm的岩石碎屑却被忽视。因此,研究<2 mm岩屑及其对抗剪强度的作用机制对紫色土区域土壤资源的可持续发展有非常重要的实践指导意义。【方法】以紫色泥岩发育的坡耕地土壤为研究对象,采用吸管法测定土壤颗粒组成,采用应变控制式直剪仪测定土样在不同含水率和垂向压力下的抗剪强度,通过对比分析研究<2 mm的岩石碎屑及其对抗剪强度的作用机制。【结果】从坡顶至坡谷,坡顶至坡脚旱地土壤与母岩的颗粒组成呈极显著性相关,而坡脚与坡谷水田土壤与母岩的颗粒组成的相关性则不显著,即紫色泥岩发育的旱地土壤的颗粒组成与其母岩的颗粒组成具有高度的一致性;土壤中<0.25 mm颗粒累积含量在99.84%—99.91%,其中,以>0.25 mm岩石碎屑存在的土壤颗粒的比例为0.96%—57.82%,以>0.25 mm团聚体存在的土壤颗粒的比例为6.33%—19.66%,随着位置高程的降低,土壤中岩石碎屑含量减少,且旱地土壤中岩石碎屑的含量显著高于水田土壤;而团聚体及黏粒含量则逐渐增加。在土壤含水率从7%增加到25%的过程中,土壤水分对旱地土壤黏聚力的影响要小于水田土壤;内摩擦角随着土壤含水率的降低而线性减小,且随着位置高程的降低,土壤水分对内摩擦角的影响逐渐增大;在相同垂直压力下,土壤水分对土壤抗剪强度的影响同样也随着位置高程的降低、岩石碎屑含量的减少而增大。【结论】在紫色泥岩发育的土壤中存在大量<2 mm的岩石碎屑。这些<2 mm岩石碎屑的存在改变了对传统土壤团聚体的认识,使得土壤团聚体可进一步细分为先天团聚体(<2 mm岩石碎屑)以及后天团聚体(水稳性团聚体)。同时,土壤中�[Objective] Soil shear strength is an indicator that reflects the ability of soil confronting sliding, water erosion, and overturning. The rock fragments in purple soil can significantly affect its shear strength. To date, most studies on the effects of rock fragments on shear strength often stress the role of rock fragments with sizes ;〉 2 ram. The effects of rock fragments 〈 2 mm in soil are often ignored. Thus, evaluating the mechanisms of 〈 2 mm rock fragments on soil shear strength can promote sustainable development of soil. [Method] This paper used the purple soils of the sloping land developed from the mudstone as the research objects. The soil particle composition was measured using a pipette method, and the soil shear strength was measured via the strain control direct shear test under different moisture contents and vertical pressure. The 〈 2 mm of rock fragments and their mechanisms on soil shear strength were studied by comparing the analysis. [Result] From the summit to the toeslope, the particle compositions of dryland soils from summit to footslope were highly significantly correlated with that of their parent rock, but the correlations between the particle compositions of paddy land soils from footslope to toeslope and their parent rock were not significant. Hence, the particle compositions of dryland soils were highly related to that of their parent rock. The content of soil particles 〈0.25 mm were about 99.84%-99.91%, in which the contents of particles presented as 〉0.25 mm rock fragments occupied a ratio of 0.96%-57.82%, particles presented as 〉0.25 nun aggregates occupied a ratio of 6.33%-19.66%. The content of 〈2 mm rock fragments reduced with the decreasing elevation, and the rock fragment content of dryland was much higher than that of paddy land; by contrast, the contents of aggregate and clay particles increased. When the soil water content was increased from 7% to 25%, the effects of soil water content on dryland soils cohesion were less than that of paddy soils. The int

关 键 词：〈2 mm岩石碎屑 土壤颗粒组成 抗剪强度 紫色土 作用机制 

分 类 号：S152[农业科学—土壤学]