干湿作用对紫色土坡耕地生物埂土壤抗剪强度衰减—恢复效应

发布时间：2018-03-06 00:05

  本文选题：生物埂　切入点：粘聚力　出处：《草业学报》2017年06期 　论文类型：期刊论文

【摘要】：在次降雨过程中,生物埂土壤内部经历了干燥-湿润-再干燥的干湿循环过程,对生物埂坎土壤抗剪强度和稳定性造成潜在影响;本文主要研究次降雨后干湿作用对桑树生物埂土壤抗剪强度衰减-恢复效应。采用根系挖掘法、室内直剪试验和土壤理化性质分析等综合性研究手段,全面研究了桑树生物埂根系分布、在次降雨前后(降雨第0~9天)干湿循环过程中生物埂土壤理化变化及抗剪强度响应特征、根系对土壤抗剪强度增强效应。结果表明:(1)不同径级根系随土层深度变化显著,根径级≤1mm的根系集中于土层深度较浅(0~20cm)位置,而2mm根径级≤5mm的根系在较深层次(20~40cm)土壤中穿插生长。(2)桑树生物埂土壤垂直层次土壤容重、土壤孔隙在次降雨前后均存在显著差异(P0.05)。除30~40cm土层外,土壤容重在经过一次干湿循环作用后有所增加,增加幅度为5.47%~5.88%,且在第5天时土壤容重达到最大值(各层次依次为1.39,1.37,1.44g/cm3);土壤总孔隙度、毛管孔隙度随干湿作用时间呈现先增大后减小的趋势,在第1天(峰值点)发生转折变化。(3)生物埂土壤粘聚力和内摩擦角随着含水率增加呈现出一阶指数衰减变化,各层次土壤粘聚力和内摩擦角在干湿作用过程呈现出先衰减后恢复的"V"型变化趋势;粘聚力与含水率的相关系数为0.68,内摩擦角与含水率的相关系数为0.73。(4)桑树生物埂不同根系径级土体的粘聚力、内摩擦角和抗剪强度与根长密度和根表面积密度呈正相关关系,相关系数在0.30~0.79之间。土壤粘聚力和内摩擦角随含水率增加呈线性衰减的趋势,在次降雨前后生物埂土壤容重、土壤孔隙特征表现为显著性变化;土壤粘聚力和内摩擦角的变化与根长密度、根表面积密度呈正相关关系。生物埂能够改善土壤结构及其土壤通气性,提高土壤养分含量,降低土壤容重,增加土壤孔隙度,为坡耕地耕层作物的生长发育、产量的提高创造有利的条件。
[Abstract]:In the process of rainfall, the soil of biological ridge experienced dry-wet-re-drying cycle, which had a potential impact on the shear strength and stability of the soil. In this paper, the effects of dry and wet effects on soil shear strength attenuation and recovery of mulberry biological ridges after rainfall were studied. The methods of root excavation, indoor direct shear test and physical and chemical properties analysis of mulberry soil were used to study the effects of drying and wetting on mulberry soil. The root distribution of mulberry biological ridge was studied comprehensively. The soil physical and chemical changes and shear strength response characteristics of the biological ridge during the dry and wet cycle before and after the second rainfall (the 9th day of rainfall) were studied. The effect of root system on soil shear strength was enhanced. The results showed that the root system of different diameter grade varied significantly with the depth of soil layer, and the root system with root diameter of 鈮，

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