Behavior of a Fiber-Reinforced Bentonite at Large Shear Displacements

The behavior of a polypropylene fiber-reinforced bentonite was evaluated at large shear displacements by a series of ring shear tests carried out at normal stresses varying between 20 and 400 kPa. Bentonite/polypropylene fiber composites were molded at an initial moisture content of 170%, with fiber lengths of 12 or 24 mm. The fiber thickness was 0.023 mm and the fiber content was either 1.5 or 3% by dry weight. The inclusion of randomly distributed fibers increased the peak shear strength of the bentonite, but the increase in strength deteriorated at large displacements and the residual strengths of both the nonreinforced and fiber-reinforced bentonite were similar. The peak shear strength was found to increase both with increasing fiber length and content. The fibers were exhumed after testing and it was found that the fibers had both extended and broken, with a predominance of broken fibers.