Abstract:The pattern of soil disturbance by tillage tools is intimately linked with soil failure mechanisms and tilth quality, being a basis of tillage system optimization. Insitu videoassisted multiindex measurement is a pathway for the illustration on soil disturbance by tillage tools. The insitu composite tillage test rig was applied for measuring subsoiler performance in paddy soil. Videos from five viewports were taken, and meanwhile, soil microrelief, traction, EDEM simulation, CI of disturbed soil profile and theoretical analysis were also measured to investigate how the chisel blade angle α and tillage depth D affected the pattern of soil disturbance, soil failure and tilth quality. Results showed that three indices can be derived from videorecords, i.e., forward soil failure distance R, soil disturbance width W and lifting height H. All the three indices were significantly correlated with both α and D, and H was increased with α, while decreased with D, indicating that both design parameters and the working parameters of subsoiler can have its influence on soil lifting. R was linearly correlated with forward protruding length of the bent leg beneath soil surface, while W was increased with α. Both soil microrelief and soil disturbance width W reached the peak values at 20cm tillage depth. EDEM simulation provided microscopic illustration on the soil disturbance by the subsoiler, reaffirming the videorecorded evidence of nonbalanced soil failure, lateral compression failure and crescent failure patterns. Correspondence between EDEM simulation and videorecording also approved the scientific validness of the discrete models. EDEM simulation also revealed that stressconcentration region periodically shifted up and down along the bent leg. Downward compression effect also appeared beneath the chisel. The CI contour map of subsoiling trench profile not only affirmed the simulated compressing region, but also revealed the sideway rheological soil displacement and the resulted compact side walls at 30cm tillage depth. The results proved that videoassisted multiindex measurement was an important means for optimized subsoiler design for paddy soil.
