Stress and Deformation Characteristics of Nonwoven Geotextile Reinforced Sand Under Different Directions of Principal Stress

A series of drained torsional shear tests using a hollow cylinder apparatus HCA was performed to investigate the anisotropic characteristics of sand in terms of the stress–strain and volumetric changes of large scale sand samples reinforced with nonwoven geotextile under different directions of principal stress α. Results revealed that the inclusion of geotextile resulted in a significant increase in the peak deviator stress when α was 0°, 15° and 30°, corresponding with considerable restraint against the expansion strain of the samples. When α was rotated towards the horizontal, α = 60–90°, reinforced samples exhibited clear anisotropic behavior. Variations in the peak deviator stress between the maximum value occurred at α = 0° and minimum at α = 60° was about 30–47% (depending on the number of geotextile layers). This indicates that the ability of layers embedded horizontally resisting the shearing decreased as the principal stress rotated towards the bedding plane. Under the conditions of α = 60–90° tensile strength of the geotextile could not be mobilized to the same extent, compared to α = 0–30°. Larger values of α resulted in less expansion strain of the reinforced samples. © 2017, Springer International Publishing AG.