Developing an excavation torque model for dense cohesionless soils

Torque encountered during the rotary excavation of soils (e.g., when using the DJM method for deep soft ground improvement) poses a serious detrimental effect not only to the excavating machines but also to the viability of a project as a whole. Consequently, this research investigates ways and means of realizing the reduction of torque encountered during the excavation of cohesionless soils. In this paper, the development of a torque model for a rotary excavation of cohesionless soils is proposed. Whereas in most of the soil tillage theories (i) the cutting tool is usually partially exposed at the surface, and (ii) excavation is generally longitudinal, this model is significant because; (i) the excavation process is radial, and (ii) the blade is completely immersed in the excavated medium. Various theories for the prediction of forces acting during the interaction of cutting tools and soils in conjunction with localized modeling of all the other forces, applied and adopted to suit this excavation geometry, have been applied in the development of the torque model. Experimental data was obtained from excavation experiments performed on compacted completely saturated sand samples. Within the experimental and theoretical limitations, the results showed that this model represented the excavation process. (C) 2004 Published by Elsevier Ltd on behalf of ISTVS.