ABSTRACT
The essence of the relationship between UCS and drilling parameters is mainly related to rock cutting theories. In previous studies, we had presented an analytical model based on the Nishimatsu model for drag bits in rotary drilling (Li and Itakura, 2012). According to this model, UCS has theoretically been proved to be proportional to the specific energy. However, there are several problems in this model. These problems and solutions are discussed in the following sections.
