Geomechanics and Engineering

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Hydromechanical behavior and prediction of unsaturated loess over a wide suction range

  • Jiang, Tong (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power) ;
  • Zhao, Jindi (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power) ;
  • Zhang, Junran (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power) ;
  • Wang, Lijin (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power) ;
  • Song, Chenyu (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power) ;
  • Zhai, Tianya (Henan Province Key Laboratory of Geomechanics and Structural Engineering, North China University of Water Resources and Electric Power)
  • Received : 2021.03.29
  • Accepted : 2021.08.03
  • Published : 2021.08.10
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Abstract

Subgrade loess in arid and semi-arid regions subjected to high-suction conditions owing to low relative humidity and deep groundwater levels. Understanding the hydromechanical behavior of unsaturated compacted loess over a wide suction range is critical for resolving infrastructure problems in such areas. In this study, the water retention behavior of loess was investigated by imposing or measuring suction (s) using the axis translation technique, vapor equilibrium technique, and chilled mirror dew point technique. Triaxial tests were also performed to study the mechanical behavior of compacted loess under different net cell pressures (σ3n). The soil-water retention curves obtained using the different techniques are consistent. The degree of saturation and water content decreases significantly when s < 240 kPa, whereas the change of void ratio is relatively small. The water content versus s curves with different initial dry densities is coincident when s > 0.5 MPa, indicating that undrained triaxial tests can be considered as those under constant suction. For the same σ3n, specimens show strain-hardening, shrinkage, and drum-shaped shear failure under low-s conditions and strain-softening, dilatancy, and oblique section splitting under high-s conditions. The failure deviator stress and cohesion of the compacted loess specimens increase with increasing s over the full s range (0-299.37 MPa). An equation to predict the shear strength of unsaturated loess over a wide s range is proposed. The intersection of the capillary water retention curve and adsorption water retention curve is set as a reference point (sR), where capillary degree of saturation is applicable for s ≤ sR and adsorption degree of saturation is added for s > sR. The predicted and measured shear strengths of the compacted loess specimens are in good agreement.

Keywords

Acknowledgement

This study is financially supported by the National Natural Science Foundation of China (Grant No. 41602295), the Foundation for University Key Teacher by the Ministry of Education of Henan Province (Grant No. 2020GGJS-094), the Key Scientific Research Projects of Colleges and Universities in Henan Province (Grant No. 21A410002), the Natural Science Foundation of Guangxi (Grant No. 2019GXNSFAA245025), and the Doctoral Student Innovation Foundation of NCWU.

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