Impact of Soil Particle Deletion on Erosion Resistance of Purple Soil in Chongqing Based on Strength Index
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National Natural Science Foundation of China (No.11572262),and Fundamental Research Funds for the Central Universities(No.XDJK2018AB003)

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    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.

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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.

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History
  • Received:June 19,2018
  • Revised:November 28,2018
  • Adopted:December 27,2018
  • Online: March 01,2019
  • Published: