Rock and Soil Mechanics ›› 2021, Vol. 42 ›› Issue (6): 1485-1492.doi: 10.16285/j.rsm.2020.6692

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Experimental study on cyclic shear softening characteristics of gravel−geogrid interface

LIU Fei-yu1, JIANG Huai1, WANG Jun2   

  1. 1. Department of Civil Engineering, Shanghai University, Shanghai 200444, China 2. College of Architecture and Civil Engineering, Wenzhou University, Wenzhou, Zhejiang 325035, China
  • Online:2021-06-11 Published:2021-10-22
  • Contact: WANG Jun, male, born in 1980, PhD, Professor, research interests: ground treatment. E-mail:
  • About author: LIU Fei-yu, male, born in 1976, PhD, Professor, research interests: reinforced soil and soil dynamics.
  • Supported by:
    the National Natural Science Foundation of China(52078285, 51678352, 51878402)


In order to study the softening characteristics of gravel-geogrid interface during and after cyclic shearing, a series of displacement controlled monotonic direct shear tests, cyclic direct shear tests with 2 000 cycles and post cyclic direct shear tests were carried out on the gravel-geogrid interface using dynamic direct shear apparatus. The shear strength characteristics, volume change behavior, shear stiffness and damping ratio of the gravel-geogrid interface under four groups of normal stresses of 20, 40, 60 and 80 kPa were studied. The direct shear characteristics of the gravel-geogrid interface before and after cyclic shear were compared and analyzed. The results show that: in the cyclic direct shear test, the average peak shear stress of gravel-geogrid interface first increases and then decreases, and finally tends to be stable with the increase of number of cycles, and the interface shows shear softening characteristics; the vertical displacement increment of gravel-geogrid interface decreases gradually with the increase of number of cycles; the shear stiffness first increases and then decreases with the increase of number of cycles, and finally tends to be stable; the damping ratio first decreases and then increases with the increase of number of cycles, and finally tends to be stable; under the same normal stress, the peak shear stress increases and the residual shear stress decreases in the cyclic direct shear test compared with the monotonic direct shear test; the cyclic shear makes the interface cohesion increase significantly and the internal friction angle decrease.

Key words: direct shear test, shear stress, shear stiffness, damping ratio