Reinforced sand shows larger dilatancy associated with a larger volume of shear zone in direct shear tests, compared to unreinforced sand. It is likely that multiple shear bands develop forming a thicken shear zone, resulting in larger dilatancy. Air-dried sand specimens reinforced with phosphor bronze strips installed perpendicularly to the shear direction were tested by using a medium scale direct shear test apparatus. The test results were analyzed with a new mechanical model using estimated thicknesses of shear zone as one on the major input parameters.