EXPERIMENTAL DETERMINATION OF JANSSEN'S STRESS RATIO BY FOUR METHODS FOR SOYBEANS UNDER STATIC CONDITIONS

Abstract

ABSTRACT The stress ratio (K) used in Janssen's equation for calculating grain pressure was determined for soybeans by four different methods. Static stresses were measured in a 0.91 m diameter x 2.743 m high model galvanized smooth steel bin. The four methods were: 1) measure vertical loads on the floor and wall separately; 2) measure vertical and hoop strains in the bin walls with six, two-element, rosette gages evenly spaced around the bin circumference at 15.2 cm above floor, 3) measure horizontal and shear loads at the bin wall with three ring load cells placed at different heights on the model bin wall (15.2, 61.0, and 106.7 cm above the floor); and 4) directly measure vertical and horizontal stresses within the grain mass using in-mass transducers (IMTs) at four different heights at the bin center (15.2, 61.0, 106.7, and 152.4 cm above the floor). A total of 18 replications were performed. For grain depths less than H/D = 2.8, K-ratio decreased with increasing depth of soybeans. At depths about three times the bin diameter (U/D = 3.0), the K-ratio approached a constant value that may be approximated by KQ = 1 - sin p, where p is the angle of internal friction of grain to grain.