Abstract: During tunnel excavation, the digital drilling process monitoring (DPM) system can quickly obtain rock strength parameters in real time, and guide on-site excavation and support operations in a timely manner. In order to obtain the surrounding rock strength in front of the tunnel face in real time, this study carried out the in situ digital drilling tests based on the digital drilling process monitoring (DPM) system mounted on the pneumatic percussion rotary drilling rig. Through the real-time monitoring, recording and analysis of the drilling parameters such as thrust pressure, rotation pressure, percussion pressure and drill rod displacement in the whole drilling process, the characteristics of the drilling parameters in different drilling processes are obtained. On this basis, each drilling process is identified, and the drilling parameters of the pure drilling process are separated by using the DPM time series analysis method. The results show that the drilling depth of the pure drilling process changes linearly with the drilling time. The variation of working pressure of the drilling rig with the drilling time is relatively constant, and it has limited influence on the rate of penetration in different rate-of-penetration sections. Meanwhile, the rate of penetration decreases with the increase in rock strength, and an exponential relationship model between rock strength and rate of penetration is established to guide engineering practice.

Key words: percussive rotary drilling, drilling process monitoring, drilling parameters, saturated uniaxial compressive strength