A NONLINEAR 3-DIMENSIONAL FINITE-ELEMENT ANALYSIS OF SUBSOILER CUTTING WITH PRESSURIZED AIR INJECTION

There are two different design objectives for sub-soilers with pressurized fluid injection for use as a pan-breaker and injector respectively: (i) to achieve a large soil failure when used as a pan-breaker and (ii) to achieve little soil failure when used as an injector. This paper reports experiments in a soil bin and analyses, theoretically, soil failure by a pan-breaker and an injector with and without air injection using a finite element method (FEM). Some work is also reported on plain tine shanks, in one case with a chisel point. The results showed that the shank rake angle had a considerable effect on soil failure. The regime of 45 to 90 deg in practical use was tested. When the rake angle was small, 45 to 60 deg, the plastic yield zone and tensile stress zone expanded and there was the greatest soil deformation and disturbance. Consequently, the optimum pan-breaker should have a rake angle of 45 to 60 deg and the optimum injector should have a rake angle of 90 deg which gave the smallest disturbance. Soil disturbance was increased by air injection both with the pan-breaker and injector. Consequently, air injection is advantageous to the pan-breakers.