Investigation on the effect of relative density and grains shape on one-dimensional settlement of reinforced sandy soils by tire fibers

Waste tires can be used in shred or chips, whole tire, fiber or powder shapes for improvement of different soils. When a waste tire is used as fiber or powder, it should be used with a reinforcer material such as geotextile, geogrid or adhesive materials such as cement. It can behave extra cost. The engineering properties of sand-tire mixed depend on the percentage of added tire pieces and the geological properties of sand. This paper shows the effect of sand grains shape and the relative density on sand settlement while be mixed with tire fibers. To achieve this goal, a settlement test (Raw cell) was done. The used fibers had 4-5.5 mm length and 5%, 10%, 15% and 20% of fiber was mixed with two types of sandy soils. First type of soils had rounded grains and second type of soils had angular grains. The results show that the shape of grains and relative density (until 75%) of reinforced sand have a significant effect on settlement values and the settlement of angular grain sand is lower than rounded grains sand. Also, when the reinforced soil had dense state, a clear decrease trend of settlement value was observed, when reinforced soil had loose and medium state, similar behavior was observed. In these cases, it is necessary to use an adhesive material (i.e. cement) as the mixture of sand and tire fibers.