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Geomechanics and Engineering
  Volume 23, Number 4, November25 2020 , pages 301-311

Effect of grain size on the shear strength of unsaturated silty soils
Kurban Onturk, Ertan Bol, Aşkin Ozocak and Tuncer B. Edil

    In this study, shear strength behavior of fine-grained soils was investigated under unsaturated conditions. The samples in the unsaturated state were subjected to a net normal stress (σ-u_a) of 40 kPa and different matric suctions (u_a-u_w) of 50, 100 and 150 kPa. The matric suction values applied in the triaxial tests were selected according to the bubbling pressures determined from the SWC curves. The study was carried out on prepared re-constituted cylindrical samples by uniaxial consolidation of soil slurries. First, consolidated drained (CD) triaxial compression tests were performed on the saturated samples and the cohesion and angle of internal friction were determined. After that, drained triaxial compression tests under matric suctions were performed on the unsaturated samples. In order to obtain unsaturated test results, cohesion and internal friction angle values of saturated samples were used. The nonlinear surface representing the shear strength surface was approximated consisting of two planes (double planar surface). The reason for the nonlinear behavior of some soils is that the amount of sand content contained in it is relatively high and the bubbling pressure/permanent water content value is relatively low.
Key Words
    unsaturated soil; shear strength; soil behavior; suction; failure
Kurban Onturk: Institute of Natural Sciences, Sakarya University, Sakarya 54187, Turkey

Ertan Bol and Aşkin Ozocak: Department of Civil Engineering, Sakarya University, Sakarya 54187, Turkey

Tuncer B. Edil: Department of Civil & Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.

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