Limitations of models used to predict soil failure in different soils

Soil failure geometry and corresponding theoretical geometrical models based on classical soil mechanics are still in use for studies on soil failure and deformation patterns, and for soil reaction prediction models useful for the design of tillage implements. However, the compatibility of these models when used in tillage applications under different conditions need to be studied. This paper assesses past research findings and compares results obtained under selected test conditions to reveal boundaries for the applicability of these models. Results obtained in laboratory soil-bin experiments on parameters like failure angle, rupture distance and wedge interface angle were used for comparison. Lateritic soil was selected with different soil gradations and compaction levels. The tine rake angle was changed to observe the limitations of the theoretical models. The results showed the limitations and trends of the models when applied under different test conditions. Poor correlations were obtained for coarser soils and different compaction levels, as well as for surcharge levels and for higher rake angles. Utilization of correction factors for soil surcharge, soil condition or type is recommended.