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Geomechanics and Engineering
  Volume 25, Number 2, April25 2021 , pages 075-87

Modelling the hydraulic/mechanical behaviour of an unsaturated completely decomposed granite under various conditions
Xi Xiong, Yonglin Xiong and Feng Zhang

    Because the hydraulic/mechanical behaviour of unsaturated soil is more complicated than that of saturated soil, one of the most important issues in modelling unsaturated soil is to properly couple its stress-strain relationship with its water retention characteristics. Based on the results of a series of tests, the stress-strain relationship and the changes in suction and saturation of unsaturated completely decomposed granite (CDG, also called Masado) vary substantially under different loading/hydraulic conditions. To precisely model the hydraulic/mechanical behaviour of unsaturated Masado, in this study, the superloading concept was firstly introduced into an existing saturated/unsaturated constitutive model to consider the structural influences. Then a water retention curve (WRC) model considering the volumetric change in the soil, in which the skeleton and scanning curves of the water retention characteristics were assumed to shift in parallel in accordance with the change in the void ratio, was proposed. The proposed WRC model was incorporated into the constitutive model, and the validity of the newly proposed model was verified using the results of tests conducted on unsaturated Masado, including water retention, oedometer and triaxial tests. The accuracy of the proposed model in describing the stress-strain relationship and the variations in suction and saturation of unsaturated Masado is satisfactory.
Key Words
    unsaturated soil; completely decomposed granite; constitutive model; water retention curve model; water retention test; oedometer test; triaxial test
Xi Xiong: Institute of Science and Engineering, Faculty of Geoscience and Civil Engineering, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan

Yonglin Xiong:Institute of Geotechnical Engineering, Ningbo University, Ningbo 315211, China

Feng Zhang: Department of Civil Engineering, Nagoya Institute of Technology, Showa-ku, Gokiso-cho, Nagoya 466-8555, Japan


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