| In this paper the mensuration of angle of internal friction of wheat, paddy and maize, elastic modulus of wheat, bulk strain modulus of wheat were studied, those physical parameters were measured and analyzed. Angle of internal friction of wheat, paddy and maize were measured by direct shear apparatus. The factors influencing the angle of internal friction were discussed, such as moisture content, shear velocity, normal stress. Angle of internal friction of wheat, elastic modulus and bulk strain modulus of wheat were measured by triaxial apparatus. Several experiment conditions were determined by analyzing and comparing the result of pre-experiment of elastic modulus of wheat by triaxial apparatus, such as number of hysteresis loop, time interval of loading and unloading, vertical pressure. The relationship about confining pressure and the elastic modulus of wheat was discussed. The factors influencing bulk strain modulus of wheat were discussed, such as moisture content and confining pressure.The result of direct shear test showed that as the shear velocity (0.53~5.20mm/min) increase, the angle of internal friction of wheat(Nanjing production, moisture content is 10.96%) and the angle of internal friction of paddy(late rice 521, moisture content is 10.96%)decrease, the rang of the angle of internal friction is from 17.49°to 25.01°, 35.75°to 40.03°. As the shear velocity (1.33~5.20mm/min) increase, the angle of internal friction of maize (Nanjing production, moisture content is 11.05%) and the angle of internal friction of paddy(Nanjing production, moisture content is 13.77%) decrease, the rang of the angle of internal friction is from 22.21°to 28.93°, 28.95°to 33.19°. The shear velocity has little influence on the angle of internal friction of wheat(Nanjing production) and paddy(late rice 521). It could get that fitted equations about the relationships of shear velocity and the angle of internal friction of maize (Nanjing production) and paddy(Nanjing production), y = -0.2219x~2 + 0.2123x + 28.318, y = -0.0606x~2-0.2532x + 33.147, x is shear velocity, y is the angle of internal friction of grain. As the normal stress(25~100kpa) increase the angle of internal friction of wheat(moisture content is 18.14%), maize(moisture content is 14.93%), paddy(Nanjing production, moisture content is 17.57%) decrease. The rang of the angle of internal friction is from 23.75°to 40.03°, 26.57°to 35.73°, 28.37°to 39.04°. As the normal stress(25~200kpa) increase, the angle of internal friction of paddy(late rice 521, moisture content is 11.78%~18.45%) decrease, the rang of the angle of internal friction is from 26.57°to 41.35°. It could get that fitted equations about the relationships of normal stress and the angle of internal friction of grain, y=-2E-05x~2-0.0237x+32.42, y=0.0007x~2-0.1702x + 38.487, y=0.0003x~2-0.1286x + 40.074, y=-3.7072Ln(x)+32.073, x is normal stress, y is the angle of internal friction of grain. As moisture content increase, the angles of internal friction of wheat increase, the range of the angles of internal friction of wheat is from 19.19°to 32.62°when the moisture is from 10.96% to 18.14%. As moisture content increase, the angles of internal friction of maize increase, the range of the angles of internal friction of wheat is from 26.40°to 32.89°when the moisture is from 11.05% to 17.75%. It could get that fitted equations about the relationships of moisture content and the angle of internal friction of wheat, maize respectively, y = 0.1934x~2 - 4.4372x + 47.429,y = 0.0078x~2 + 0.7792x + 16.665, x is moisture, y is the angle of internal friction of grain. The moisture content has little influence on the angle of internal friction of paddy(Nanjing production, moisture is from 11.25% to 17.57%) and paddy (late rice 521, moisture content is from 11.78% to 18.45%). The difference of the angle of internal friction of paddy(late rice 521) and paddy(Nanjing production) is not significant. The angle of internal friction of paddy is bigger than maize, and bigger than wheat.The result of triaxial test showed that the angles of internal friction of wheat(moisture is 10.96% and 15.90%) was bigger than that measured by direct shear test. The angle of internal friction is 25.01°~27.46°, 27.8°~31.03°that measured by triaxial test. As confining pressure increase, the elastic modulus of wheat(moisture content is 12.91%) increase, the range is from 314.2kpa to 902.1kpa. It could get that fitted equations about the relationship of confining pressure and the elastic modulus of wheat, y = 418.92Ln(x) - 1325.2, x is confining pressure, y is the elastic modulus of wheat. As confining pressure(5kpa~30kpa) increase, the volume of wheat(moisture is 13.70%,16.4%,18%) decrease, the ratio of volume change is 2.9%~11.6%, 3.1%~12.5%, 3.3%~13.1%. As confining pressure(5kpa~30kpa) increase, bulk strain modulus of wheat(moisture content is 13.70%, 16.4%, 18%) increase, the range of bulk strain modulus is 173.5kpa~259.3kpa, 164kpa~240kpa, 151kpa~229.4kpa. As moisture content of wheat (13.7%~18%) increase, the bulk strain decrease, the range is 223.5kpa~270kpa.
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