Analytical Tunnel-boring Machine Pose Precision and Sensitivity Evaluation for Underground Tunnelling

Practical Tunnel-boring Machine (TBM) guidance systems usually use sophisticated instruments to obtain the orientation of the TBM. These systems require frequent calibration and work shutdown, making the procedure complex and time consuming. Besides, the majority of current TBM guidance solutions cannot provide the position of the invisible cutter head analytically including commonly used laser point tracking system. This makes it impossible to check the accuracy of the TBM positioning for ensuring the quality of the tunnel being installed in the ground. To address the problem, this research proposes an analytical approach to quantify the accuracy of the TBM position and orientation estimation based on a previously proposed survey-based TBM guidance system. The coordinates for the cutter head center are derived through error propagation based on defining geometric constraints and applying computing algorithms, such as the layout configuration of the prisms mounted on the TBM and the relative position of the cutter head center. The paper also provides a thorough analysis of the sensitivity of the solution with regards to certain configurations based on underlying formulas. To verify the results, a tunnelling experiment was also conducted based on a 1:20 scaled TBM model with its cutter head visible. The proposed method provides a valuable approach to evaluate the accuracy of the cutter head position estimation and potentially enable the operators to control and guide the tunnelling process in the field.