determination of some physical properties of four iranian improved rice cultivars

in this work, experimental studies of internal friction coefficient and porosity of four high productive rice varieties in iran (nemat, neda, pajouhesh and pardis) have been presented. moisture content varied in four different ranges between 8 and 20%. the obtained results indicated that the internal friction coefficient decreased with increasing the moisture content from 8 to 11%, then decreased with increasing the moisture content. the internal friction angles for nemat, neda, pajouhesh and pardis at the equilibrium moisture content, i.e., 11%, were 39.3, 37.5, 33.95 and 34.38° respectively. based on results obtained in this study, the apparent physical properties of the rice varieties, e.g., length of the grain, cross sectional diameter of the grain, relative roughness of the external surface of the grain, etc. have significant influence on the normal stress-shear stress relationship. meanwhile, porosity of the samples depends on the type of variety and moisture content. porosities of the samples at equilibrium moisture content were 70.8% for nemat, 63.9% for neda, 62.7% for pajouhesh and 66.5% for pardis