Geomechanics and Engineering

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Effect of water distribution on shear strength of compacted loess

  • Kang-ze, Yuan (Department of Geological Engineering, College of Geological Engineering and Surveying and Mapping, Chang'An University) ;
  • Wan-kui, Ni (Department of Geological Engineering, College of Geological Engineering and Surveying and Mapping, Chang'An University) ;
  • Xiang-fei, Lu (Department of Geological Engineering, College of Geological Engineering and Surveying and Mapping, Chang'An University) ;
  • Hai-man, Wang (Department of Geological Engineering, College of Geological Engineering and Surveying and Mapping, Chang'An University)
  • Received : 2021.06.26
  • Accepted : 2022.12.05
  • Published : 2022.12.10
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Abstract

Shear failure in soil is the primary cause of most geotechnical structure failures or instability. Soil water content is a significant factor affecting soil shear strength. In this study, the shear strength of samples with different water contents was tested. The shear strength, cohesion, and internal friction angle decreased with increasing water content. Based on the variation of cohesion and internal friction angle, the water content zone was divided into a high-water content zone and low-water content zone with a threshold water content of 15.05%. Cohesion and internal friction angle have a good linear relationship with water content in both zones. Environmental Scanning Electron Microscopy (ESEM) test presented that the aggregates size of the compacted loess gradually increases with increasing water content. Meanwhile, the clay in the compacted loess forms a matric that envelops around the surface of the aggregates and fills the inter-aggregates pores. A quantitative analysis of bound water and free water under different water contents using a nuclear magnetic resonance (NMR) test was carried out. The threshold water content between bound water and free water was slightly below the plastic limit, which is consistent with the results of shear strength parameters. Combined with the T2 distributions obtained by NMR, one can define a T2 relaxation time of 1.58 ms as the boundary point for bound water distribution without free water. Finally, the effects of bound water and free water on shear strength parameters were analyzed using linear regression analysis.

Keywords

Acknowledgement

The authors gratefully acknowledge the China Postdoctoral Science Foundation (Grant no. 2019T120873 and Grant no. 2018M631117), Postdoctoral Research Project in Shaanxi Province (Grant no. 2018BSHGZZHQYXMZZ26), the Key Program of the National Natural Science Foundation of China (Grant no. 41931285), and the key research and development program of Shaanxi Province (Grant no. 2019ZDLSF05-07).

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