Research on Cutting Resistance Torque of Soil in Auger Drilling

Feeding and rotary motion's influence on real cutting thickness and real cutting angle was considered. A parameter m, which is called feeding-rotary speed ratio, was introduced. By employing McKyes-Ali's three-dimensional soil failure pattern and its limited equilibrium mechanics equations, a new formula of cutting resistance torque in auger drilling was deduced. Theoretical and experimental researches show that, the relationship between feeding-rotary speed ratio and cutting resistance torque is nonlinear. The existence of m makes the real cutting angle, real cutting thickness and real failure angle change, which leads to the differences between theoretical cutting resistance torque and the one without considering the influence of m. The differences between two theoretical values, that are related with mechanical parameters of soil, structural parameters of drill and pre-loaded pressure of upper soil, do not show a definite regular pattern as m changes. The distribution of test data shows a higher goodness of fit with theoretical value 1, whose correctness was thus proved. The research has important significance in determining the cutting resistance torque and drilling parameters in rotary drilling of soil.