Abstract: Due to the impact of internal and external forces, tunnel drilling rig in the working could lead to instability, and affect the safety of the drilling rig work. Tunnel drilling rig could be kept its stability by loading a steady pressure on the base of the drilling rig when it was working. The steady pressure was decided by human experience at present, not be by a theoretical method. This method supported by a study of ZDY320 tunnel drilling rig can calculate the steady pressure of the drilling rig by finding the relationship of the steady pressure with the angle of drilling and the angle of support bar. In this method, the stability simulation analysis of drilling rig under the static and dynamic stimulations was made, and a variation law of drilling rig stability was obtained, which provided a theoretical support for the design of tunnel drilling rig.

Key words: tunnel drilling rig, stability, angle of drilling, steady pressure, stimulation