Modeling for Predicting Thrust and Torque Requirement of Full-Face Blind Shaft Boring Machine with Conical Cutterhead

The power system selection and operating condition adaptability of the Full-face Blind Shaft Boring Machine (SBM) depend critically on the thrust and torque of its conical cutterhead. However, the complex forces acting on the conical cutterhead were not fully understood. This study analysed the shaft engineering conditions, including high ground stress, accumulated rock muck at the shaft bottom, and water presence at the shaft bottom. Based on this, the theoretical expressions for the thrust and torque were derived, considering the operational characteristics of rock breaking along the vertical conical surface and vertical excavation of conical cutterhead. Furthermore, theoretical load modeling for predicting thrust and torque requirement was established. The load modeling shows that the theoretical thrust accuracy of the conical cutterhead is 95.0 %, and the theoretical torque accuracy is 92.7 %, confirming its practical applicability. For the influence of shaft engineering conditions and cutterhead structural characteristics, the thrust required for rock-breaking increases with the cone angle. The resultant force of rock breaking influenced by the cone angle and the rotational resistance torque of the main bearing and the main seal need to be considered. Particularly, the passive earth pressure force and frictional resistance moment of the bottom panel need to be considered under the working condition of the large accumulation of muck at the bottom of the excavation face. The research results provide a reliable basis for the parameter selection of the power system during the SBM’s design phase.