Granular Matter

, 22:1 | Cite as

The shear and tensile strength of unsaturated soils by a grain-scale investigation

  • Guoqing Cai
  • Xuzhen HeEmail author
  • Liang Dong
  • Shaopeng Liu
  • Zili Xu
  • Chenggang Zhao
  • Daichao Sheng
Original Paper


This paper presents a study of the tensile strength of unsaturated soil by a DEM model in a novel uniaxial tensile test device. For validation and comparison, traditional triaxial shear test of unsaturated soil are also conducted. In the DEM model, the capillary effects and some other cementation effects are modelled by a bond, whose strength is a function of the moisture content and void ratio in uniaxial tensile tests and also the confining pressure in triaxial tests. To compare the DEM simulations with experiments, the bond strength function is calibrated through a quantity measurable in both laboratory and DEM simulations such as the shear strength in triaxial tests or the uniaxial tensile strength in uniaxial tensile tests. The comparison shows that the proposed model is able to capture the phenomena observed in experiments. Most importantly, through investigation of the grain-scale data such as the motion, force chains and development of fractures, it is possible to explain some macroscopic observations such as the form of shear bands in the sample, the influence of the moisture content on the shear and tensile strength, etc.


Unsaturated soils Tensile strength Shear strength DEM Moisture content 

List of symbols


Bond strength


Void ratio


Elastic modulus of grains


Normal force between grains


Tangential force between grains


Normal stiffness


Tangential stiffness


Macroscopic friction coefficient, stress ratio


Atmospheric pressure


Normal displacement between grains


Tangential displacement between grains


Saturated moisture content


Macroscopic friction angle


Shear strength in triaxial tests


Largest principal stress in triaxial tests


Smallest principal stress in triaxial tests

\({{\upmu }}\)

Friction coefficient at contacts

\(A_{bond}\), \(B_{bond}\), \(A_{w}\), \(B_{w}\), \(C_{w}\)

Fitting parameters



The research is supported by the National Natural Science Foundation of China (51722802, U1834206, 51678041), Beijing Nova Program (Z181100006218005) and the Research Funds of Henan Provincial Department of Transportation (2017B4).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Human and animal participants statement

This article does not contain any studies involving animals performed by any of the authors. This article does not contain any studies involving human participants performed by any of the authors.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Key Laboratory of Urban Underground Engineering of Ministry of EducationBeijing Jiaotong UniversityBeijingChina
  2. 2.School of Civil EngineeringBeijing Jiaotong UniversityBeijingChina
  3. 3.School of Civil and Environmental EngineeringUniversity of Technology SydneySydneyAustralia
  4. 4.Railway Engineering Research InstituteChina Academy of Railway SciencesBeijingChina
  5. 5.CCCC Highway Consultants Co., Ltd.BeijingChina
  6. 6.School of Civil EngineeringGuilin University of TechnologyGuilinChina

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