紫色页岩发育土壤的颗粒特性及其对抗剪强度的作用机制
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摘要
土体发生破坏最开始往往是从内部的土壤颗粒破坏开始,而抗剪强度是反映土体抵抗剪切破坏能力的重要指标。本文以紫色页岩发育的坡耕地土壤为研究对象,通过测定土样颗粒组成以及不同含水率和垂向压力下的抗剪强度,研究页岩发育的土壤颗粒特性及其对抗剪强度的作用机制。结果表明从坡顶至坡脚,土壤颗粒组成与其母岩颗粒组成具有显著相关性;土壤中<0.25 mm颗粒累计含量在995.65～998.62 g/kg之间,其中以0.25～2 mm岩石碎屑存在的土壤颗粒含量为439.80～510.40 g/kg,以0.25～2 mm团聚体存在的土壤颗粒含量为6.01～80.50 g/kg,随着位置高程的降低,土壤中岩石碎屑和团聚体的含量并没有显著变化。在含水率从7%增加到25%的过程中,土壤水分与内摩擦角呈负相关关系且对内摩擦角的影响随着高程的降低缓慢减小,而对黏聚力的影响是随着含水率的增加单一坡位黏聚力呈现先增加后减少的趋势,但是随高程降低变化并不明显。因此,在紫色页岩发育的土壤颗粒组成中存在大量<2 mm的岩石碎屑,这些大量致密坚硬的岩石碎屑提高土壤抗剪强度同时减弱了抗剪强度的水敏性。
The beginning of soil destruction is often from the internal destruction of soil particles, and shear strength is an important indicator to reflect soil's resistance to shear failure. The paper takes shale-derived purple soils in sloping land as the research object and study particle characteristics of purple soil and their mechanism of shear strength by measuring soil particle compositions and shear strengths under different moisture contents and vertical pressures. The result showed that soil particle compositions from summit to footslope were significantly correlated with those of parent rocks. Soil particles <0.25 mm were about 995.65 – 998.62 g/kg, in which particles presented as 0.25 – 2 mm rock fragments were about 439.80 – 510.40 g/kg,however particles presented as 0.25 – 2 mm aggregates were about 6.01 – 80.50 g/kg. With the decrease of elevation, the contents of rock fragments and aggregates in soils did not change obviously. Within soil water content from 7% to 25%, soil water content was negatively correlated with internal friction angle and the influence of soil water content on internal friction angle decreased slowly with the decreased elevation, however cohesion was increased first and then decreased with soil water content increased on single slope, but cohesion did not change obviously with the decreased elevation. Therefore, there are a large amount of <2 mm rock fragments in soil particles in purple soil, and these rock fragments improve soil shear strength while weaken its water sensitivity.
The beginning of soil destruction is often from the internal destruction of soil particles, and shear strength is an important indicator to reflect soil's resistance to shear failure. The paper takes shale-derived purple soils in sloping land as the research object and study particle characteristics of purple soil and their mechanism of shear strength by measuring soil particle compositions and shear strengths under different moisture contents and vertical pressures. The result showed that soil particle compositions from summit to footslope were significantly correlated with those of parent rocks. Soil particles <0.25 mm were about 995.65 – 998.62 g/kg, in which particles presented as 0.25 – 2 mm rock fragments were about 439.80 – 510.40 g/kg,however particles presented as 0.25 – 2 mm aggregates were about 6.01 – 80.50 g/kg. With the decrease of elevation, the contents of rock fragments and aggregates in soils did not change obviously. Within soil water content from 7% to 25%, soil water content was negatively correlated with internal friction angle and the influence of soil water content on internal friction angle decreased slowly with the decreased elevation, however cohesion was increased first and then decreased with soil water content increased on single slope, but cohesion did not change obviously with the decreased elevation. Therefore, there are a large amount of <2 mm rock fragments in soil particles in purple soil, and these rock fragments improve soil shear strength while weaken its water sensitivity.
引文
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[19]王军光,李朝霞,蔡崇法,等.集中水流内红壤分离速率与团聚体特征及剪强度定量[J].土壤学报,2011,48(6):1133-1140
[20]周红艺,李辉霞.华南地区崩岗侵蚀区土壤水分含量对土体抗剪强度的影响[J].江苏农业科学,2014,42(12):347-350
[21]林鸿州,于玉贞,李广信,等.降雨特性对土质边坡失稳的影响[J].岩石力学与工程学报,2009,28(1):198-204
[22]倪九派,高明,魏朝富,等.干湿循环条件下重庆地区三种土壤抗剪强度的动态变化[J].土壤学报,2013,50(6):1090-1101
[23]钟茫.非饱和紫色土抗剪强度影响因素研究[D].重庆:西南大学,2014
[24]江浩浩,董希斌,王海飙.边坡土壤含水率对不同植被土壤抗剪强度的影响[J].森林工程,2009,25(3):77-80
[2]Cruse R M,Larson W E.Effect of soil shear-strength on soil detachment due to raindrop impact[J].J.Soil Sci.Soc.Am.,1977,41(4):777-781
[3]钟守琴,刘波,魏朝富,等.紫色泥岩土壤<2 mm岩屑及其对抗剪强度的作用机制[J].中国农业科学,2015,48(23):4846-4858
[4]蔡奕,施斌,刘志彬,等.团聚体大小对填筑土强度影响的试验研究[J].岩土工程学报,2005,27(12):1482-1486
[5]张爱国,李锐,杨勤科.中国水蚀土壤抗剪强度研究[J].水土保持通报,2001,21(3):5-9
[6]余宏明,胡艳欣,唐辉明.红色泥岩风化含砾粘土的抗剪强度参数与物理性质相关性研究[J].地质科技情报,2002,21(4):93-95
[7]Zhang W,Wei C,Li Y,et al.Effects of rock fragments on infiltration and evaporation in hilly purple soils of Sichuan Basin,China[J].Environmental Earth Sciences,2011,62(8):1655-1665
[8]刘波.重庆紫色土区坡耕地土壤抗剪强度特征[D].重庆:西南大学,2015
[9]中国科学院成都分院土壤研究室.中国紫色土上篇[M].北京:科学出版社,1991
[10]谢德体.土壤地理学[M].成都:成都科技大学出版社,1995
[11]李燕.紫色土砾石的分布及其对土壤水分性质的影响[D].重庆:西南大学,2006
[12]Amezketa E.Soil aggregate stability:A review[J].Journal of Sustainable Agriculture,1999,14(2):83-151
[13]赵澄林.沉积岩石学[M].北京:石油工业出版社,2001
[14]Rooij G H D.Methods of soil analysis:Part 4.physical methods[J].Vadose Zone Journal,2004,3(2):722-723
[15]洪波,吕艳兵.含砾石粘土抗剪强度分析[C].中国水利学会勘测专业委员会年会暨学术交流会,2011
[16]Kokusho T,Hara T,Hiraoka R.Undrained shear strength of granular soils with different particle gradations[J].Journal of Geotechnical&Geoenvironmental Engineering,2004,130(6):621-629
[17]王中文,洪宝宁,刘鑫,等.红粘土抗剪强度的水敏性研究[J].四川大学学报(工程科学版),2011,43(1):17-22
[18]张茂花,谢永利,刘保健.增湿时黄土的抗剪强度特性分析[J].岩土力学,2006,27(7):1195-1200
[19]王军光,李朝霞,蔡崇法,等.集中水流内红壤分离速率与团聚体特征及剪强度定量[J].土壤学报,2011,48(6):1133-1140
[20]周红艺,李辉霞.华南地区崩岗侵蚀区土壤水分含量对土体抗剪强度的影响[J].江苏农业科学,2014,42(12):347-350
[21]林鸿州,于玉贞,李广信,等.降雨特性对土质边坡失稳的影响[J].岩石力学与工程学报,2009,28(1):198-204
[22]倪九派,高明,魏朝富,等.干湿循环条件下重庆地区三种土壤抗剪强度的动态变化[J].土壤学报,2013,50(6):1090-1101
[23]钟茫.非饱和紫色土抗剪强度影响因素研究[D].重庆:西南大学,2014
[24]江浩浩,董希斌,王海飙.边坡土壤含水率对不同植被土壤抗剪强度的影响[J].森林工程,2009,25(3):77-80