Soil reinforcement using natural fibers has been successfully employed in different projects. Among the natural fibers, the use of waste human hair fibers as a reinforcing material can be the solution for sustainable development. This study presents characterization of human hair fiber–reinforced sand using direct shear tests under dry and saturated conditions. Tests were conducted in three series: (i) Test Series-1: using unsorted human hair fibers (as collected from barber shops) under dry conditions, (ii) Test Series-2: using unsorted human hair fibers under saturated conditions, and (iii) Test Series-3: sorted fibers with lengths of 10, 15, and 20 mm to examine the effect of fiber length when under saturated conditions of sand. All test specimens were prepared at 80 % relative density. Initially, experiments were carried out on dry sand with fiber reinforcement up to 2.0 % by weight of sand. Under saturated conditions, the percentage of fiber content was restricted up to 1.0 %, as formation of fiber clusters was noticed beyond 1.0 %. Under saturated conditions, specimens were prepared with initial moisture content ranging from 1.0–3.0 % by weight of soil for easy homogeneous mixing and then saturated. It is found that the reinforcement using human hair fibers significantly affects the shear behavior of dry sand. However, under saturated conditions, the human hair fiber reinforcement is able to sustain shear strength parameters similar to unreinforced sand, even though these parameters are likely to reduce. The use of unsorted fibers as reinforcement is more beneficial than that the use of the sorted fibers of uniform length.
A series of drained cyclic triaxial tests was conducted to examine the behavior of sand reinforced with human hair fiber of random lengths subjected to cyclic loading. Experiments were conducted at two different relative densities (i.e., 50 and 80 %) with varying fiber content (0.25 to 1.0 %). Factors affecting the cyclic behavior, such as relative density, fiber content, load cycles, and shear strain amplitude, were examined and discussed in this article. Shear modulus and damping ratio evaluated for all the tests indicate that the maximum increase in shear modulus of reinforced sand is observed under medium shear strains and at 0.5 % fiber inclusion for 80 % relative density. However, the fiber inclusion seems ineffective with the sand at 50 % relative density. The damping ratio of reinforced and unreinforced sand did not show a marked variation except for fiber content more than optimum.
The possibilities of dielectric breakdown during the mechanical deformation of solids are studied. Equations are derived for the electric field produced during mechanical deformation of crystals. It is shown that the piezoelectrification, cleavage-electrification, and the movement of charged dislocations during the mechanical deformation of solids may give rise to sufficient fieId for the dielectric breakdown.
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