The Measurement of Shear Characteristics of Paddy Soil in Poyang Lake Area

Understanding the shear characteristics of paddy fields is of great significance for the design of high-trafficability paddy wheels and to improve the trafficability of the tiller in paddy fields. Taking the paddy soil in Poyang Lake area of Jiangxi Province as the research object, a simple, self-designed bevameter was constructed to measure the apparent cohesion c and apparent internal friction angle phi of paddy soil with water content of 37% by weight using an annular shear plate. The effects of different shear speeds, shear grouser heights, and shear plate diameters on the measured c and phi were investigated. The measured values of c and phi were 1.89-2.35 kPa and 10.2-11.4 degrees(deg), respectively. With the increase in shear speed, shear plate diameter, and grouser height, the value of c increased. Shear plate diameter and shear speed had small effect on c, whose change rate did not exceed 7.8%. However, shear grouser height had a greater influence on c, and the measured c increased by 24.5%. The influence of the three factors on phi followed the order: shear speed > shear plate diameter > shear grouser height, but the variation in phi did not exceed 1.2 degrees(deg). The optimal operational conditions were: shear plate diameter of 250 mm with inner diameter of 150 mm, shear grouser height of 10 mm, with a shear speed of pi/120 rad/s, and the apparent cohesion and apparent internal friction angle are 1887.8 pa and 11.06 degrees (deg), respectively.