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土壤含水率和干容重对不同植被类型边坡土壤抗剪强度的影响
王楠1, 赵友朋1, 郭晓平1,2, 张金池1, 刘胜龙1,3
1.南方现代林业协同创新中心 江苏省水土保持与生态修复重点实验室 南京林业大学 林学院, 江苏 南京 210037;2.环境保护部南京环境科学研究所, 江苏 南京 210042;3.浙江凤阳山-百山祖国家级自然保护区凤阳山管理处, 浙江 龙泉 323700
摘要:
[目的] 探究边坡土壤的含水率和干容重对土壤抗剪强度的影响,建立经验公式,为提高边坡稳定性提供理论依据。[方法] 以浙江省凤阳山国家级自然保护区内黄棕壤地带3种植被类型(常绿阔叶林、针阔混交林、灌草林地)边坡土壤为对象,进行重塑土直剪试验,分析不同含水率分级(25%,27%,29%,31%,33%)和干容重分级(0.8,0.9,1.0,1.1,1.2 g/cm3)对抗剪强度指标(内摩擦角φ和黏聚力c)的影响规律。[结果] ①黏聚力和干容重呈显著正相关,和含水率(mc)呈显著负相关。内摩擦角和干容重(ρd) 呈显著正相关。②土壤黏聚力随含水率的增加而减小,随干容重的增加而增加;随着干容重的增加,内摩擦角有明显增加的趋势,总是在高密实度的情况下,内摩擦角较大。相对于黏聚力,内摩擦角受含水率的影响较小,随含水率的增大,在灌草林地和针阔混交林表现出非线性减小的特征,在常绿阔叶林则呈现先增大后减小的趋势,考虑出现最优含水率。③在同一含水率下,干容重对土壤黏聚力具有增强作用,黏聚力的对数和干容重呈线性正相关。考虑含水率和干容重的综合影响,加入影响系数β,建立了经验公式。[结论] 黏聚力的对数与含水率呈显著负相关,与干容重呈显著正相关。土壤干容重对土壤内摩擦角影响显著,呈显著正相关。含水率对内摩擦角影响不明显。
关键词:  植被类型  含水率  干容重  抗剪强度  内摩擦角  黏聚力
DOI:10.13961/j.cnki.stbctb.2018.06.014
分类号:
基金项目:国家林业公益性行业科研专项(201504406);江苏省高校优势学科建设工程项目(PAPD)
Effects of Soil Moisture Content and Dry Bulk Density of Different Vegetation Types on Slope Soil Shear Strength
WANG Nan1, ZHAO Youpeng1, GUO Xiaoping1,2, ZHANG Jinchi1, LIU Shenglong1,3
1.Jiangsu Province Key Laboratory of Soil and Water Conservation and Ecological Restoration, Co-Innovation Center for the Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu 210037, China;2.Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing, Jiangsu 210042, China;3.The Fengyang Mountain Management Office of Fengyang Mountain-Baishanzu National Nature Reserve in Zhejiang Province, Longquan, Zhejiang 233700, China
Abstract:
[Objective] The influence of soil moisture content and dry bulk density on the shear strength of soil in the study area was explored and an empirical formula was established in order to provide a theoretical basis for improving the stability of the slope and protecting the soil and water environment.[Methods] Three typical forest stands (evergreen broadleaved forest, coniferous and broad-leaved mixed forest, shrub-grass forest)was sampled in Fengyang Mountain Nature Reserve, Zhejiang Province. Remolded soil direct shear experiment was conducted to analyze the effect of different classification of moisture content (25%, 27%, 29%, 31%, 33%) and dry bulk density (0.8, 0.9, 1.0, 1.1, 1.2 g/cm) on the shear strength parameters (the internal frictional angle φ and cohesive force c).[Results] ① There were a significant positive correlation between cohesive force and dry bulk density, and a significant negative correlation between cohesive force and moisture content. There was a significant positive correlation between the internal frictional angle and the dry bulk density. ② The soil cohesive force decreased with the increase of moisture content, and increased with the increase of dry bulk density, it had obvious regularity; with the increase of dry bulk density, the internal frictional angle had a tendency of obvious increase, which in the case of high compactness, the internal frictional angle was always large. In relate to the cohesive force, the internal frictional angle was less affected by the moisture content. With the increase of the moisture content, the characteristics of non-linear decrease in shrub-grassland forests and coniferous and broad-leaved mixed forest were showed. In the evergreen broad-leaved forest, there was a trend of increasing first and then decreasing, considering the occurrence of optimal moisture content. ③ At the same moisture content, the dry bulk density had an enhanced effect on the cohesive force of the three types of soils. The logarithm of cohesion and the dry density showed a positive linear correlation. We consider the combined effects of moisture content and dry bulk density, add the influence coefficient β, and establish an empirical formula, respectively.[Conclusion] The logarithm of cohesive force and moisture content were significantly negatively correlated with each other, and there was a significant positive correlation with dry bulk density and cohesive force. Soil dry bulk density had a significant effect on soil internal frictional angle, and moisture content had no significant effect on internal frictional angle.
Key words:  vegetation type  moisture content  dry density  shear strength  internal friction angle  cohesive force