引用本文:薛 乐,汪时机,李 贤,胡东旭,沈泰宇,江胜华.重庆紫色土抗侵蚀能力的粒组效应研究[J].土壤学报,2019,56(3):582-591. DOI:10.11766/trxb201807060329
XUE Le,WANG Shiji,LI Xian,HU Dongxu,SHEN Taiyu,JIANG Shenghua.Impact of Soil Particle Deletion on Erosion Resistance of Purple Soil in Chongqing Based on Strength Index[J].Acta Pedologica Sinica,2019,56(3):582-591. DOI:10.11766/trxb201807060329
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重庆紫色土抗侵蚀能力的粒组效应研究
薛 乐1, 汪时机1, 李 贤1, 胡东旭2, 沈泰宇1, 江胜华1
1.西南大学工程技术学院;2.金堂县城乡建设局
摘要:
严重的水土流失导致不同粒径的土壤颗粒流失,改变了土壤的抗侵蚀能力。为研究粒组缺失对土壤抗侵蚀能力的影响,以重庆地区紫色土为对象,采用去掉某一粒组颗粒后的土壤作为试验用土,重塑制样进行控制围压与吸力的三轴试验。基于试验所得黏聚力c、内摩擦角φ等强度指标,分析土壤侵蚀机理。结果表明:(1)相对于无粒组缺失的试样,缺失较大粒径(0.25 mm以上)的试样内部颗粒间表面摩擦力和咬合力更大,缺失较小粒径(0.25 mm以下)的土壤颗粒间表面摩擦力和咬合力较低;(2)随着围压的增大,土壤抗侵蚀能力均得到显著提高,缺失较大粒径(0.25 mm以上)的试样级配良好,压实性好,抗侵蚀能力提高的比例更大;缺失较小粒径(0.25 mm以下)的试样级配不良,不易被压实,抗侵蚀能力提高的比例相对较小;(3)颗粒级配不同的土体在固结剪切中会形成悬浮-密实结构、骨架-密实结构和骨架-孔隙结构,且抗侵蚀能力大小排序为骨架-密实结构>悬浮-密实结构>骨架-孔隙结构,且当黏聚力大于10 kPa时,影响土壤抗侵蚀能力的主要是土壤的内摩擦角;(4)通过灰色关联法分析发现,中值粒径d30与黏聚力c、内摩擦角φ值关联度较大,有效粒径d10cφ值关联度较小,并且不均匀系数Cu、曲率系数Cc、限定粒径d60d30d10均对土壤抗侵蚀能力有显著影响。研究结果可以为重庆紫色土地区浅层滑坡和水土流失发生机理的研究提供试验数据和科学依据。
关键词:  紫色土  粒组缺失  围压  抗剪强度  灰色关联分析
基金项目:国家自然科学基金项目 (11572262)、中央高校基本业务费专项资金项目(XDJK2018AB003)
Impact of Soil Particle Deletion on Erosion Resistance of Purple Soil in Chongqing Based on Strength Index
XUE Le1, WANG Shiji1, LI Xian1, HU Dongxu2, SHEN Taiyu1, JIANG Shenghua1
1.College of Engineering and Technology, Southwest University;2.Urban and Rural Construction Bureau of Jintang County
Abstract:
【Objective】Under a weather of plentiful rainfall, Chongqing is one of the most seriously eroded areas in China. The aggravating soil erosion causes depletion of soil particles of various sizes from the soil, weakening soil resistance to erosion, thus eventually leading to natural disasters, such as landslide and debris flow. So this paper aims mainly at exploring impacts of depletion of a certain fraction of soil particles on erosion resistance of the purple soil in Chongqing.【Method】 For this study, an indoor experiment was carried out on purple soil of loamy sands. of which soil samples, after being fully dispersed, passed through a standard soil sieve to remove a certain fraction of soil particles and then got blended uniformly again to simulate the soil that had lost a certain fraction of soil particle as a result of soil erosion. In this way, soil samples different in absence of a fraction of soil particles were prepared, and then made the same in water content and density. and reshaped for triaxial consolidation shear tests through controlling suction of the matrix and changing confining pressure. Based on the parameters of cohesion C and internal friction angle φ obtained from the test, analysis of soil erosion mechanism was performed.【Result】Results show: (1) Compared with the sample of original soil, the samples with the fraction (0.25 mm or more) of soil particles removed were higher in surface friction and snap-in force between soil particles, while the samples with the fraction (below 0.25 mm) of soil particles removed were lower; (2) With rising confining pressure, soil erosion resistance of the sample significantly improved. The soil samples with the fraction (0.25 mm or more) of soil particles removed were good in graduation and in compactibility, as well, and hence were enhanced in erosion resistance by a larger margin, while the soil samples with the fraction (less than 0.25 mm) of soil particles removed were poor in graduation and in compactibility and enhanced in erosion resistance by a relatively limited margin; (3) In the consolidation shearing test, soil samples different in graduation formed a suspension-compaction structure, a skeleton-compaction structure, and a skeleton-pore structure, separately, with erosion resistance following an order of skeleton-compaction structure > suspension-compaction structure > skeleton-pore structure. In soil samples with cohesive force being higher than 10 kPa, the main factor affecting soil erosion resistance was internal friction angle of the soil; and (4) Grey correlation analysis shows that soil particles of median size, d30, was quite closely correlated with cohesion c and internal friction angle φ is large, while soil particles of effective size, d10, were not so. Besides, nonuniformity coefficient Cu, curvature coefficient Cc, limited particle size d60, d30, and d10 of a soil sample all had significant impacts on its erosion resistance.【Conclusion】All the findings in the study are expected to be able to serve as experimental data and scientific basis for future studies on mechanisms of shallow landslide and soil erosion in the purple soil area of Chongqing.
Key words:  Purple soil  Missing of a certain fraction of soil particles  Confining pressure  Shear strength  Grey correlation analysis