Objective Operations in a narrow space pose a challenge to rescue in the case of the collapse of mine roadways or tunnels. To address this challenge, this study developed a modular rescue casing while drilling (CwD) rig system for horizontal boreholes. With the capacity for quick responses, this CwD rig was designed to enhance the rescue efficiency and safety under complex geological conditions.

Methods Following the modular design concept and compact layout principle, this study optimized core components such as the power heads, feed devices, and power system. The auxiliary operation vehicle was checked against overturning through multibody dynamics (MBD) simulations to ensure its stability under complex conditions. The structure of the ultra-thin foldable belt conveyor for drilling slag was optimized using the discrete element method (DEM)-MBD coupled simulation, thus significantly improving the conveying efficiency and spatial adaptability of the conveyor. A safety and risk assessment model for drilling sites was established by combining the analytic hierarchy process (AHP) method and the technique for order preference by similarity to ideal solution (TOPSIS). Furthermore, an intelligent early warning software was developed by integrating the autoregressive moving average (ARMA) and exponential smoothing algorithms. These contributed to the dynamic safety assessment and risk prediction of drilling sites. Finally, the performance of the developed CwD rig was verified through static loading tests, engineering trials in Shangluo, Shaanxi Province, and integrated tests in Yuxi, Yunnan Province.

Results and Conclusions The modular, remote-controlled rescue CwD rig for large-diameter boreholes, with a maximum module size of 4 000 mm × 1 700 mm × 1 450 mm, can be quickly assembled within three hours in a restricted space. The key components developed include dual rotary power heads, a feed system with independently driven inner and outer pipes, a top-opening variable-diameter clamping and centralizing system, and a remote-controlled monorail hoisting system. In combination with the electro-hydraulic dual-controlled, load-sensitive hydraulic control, remote-controlled explosion-proof techniques, and matched multi-stage casings, the drilling rig represents a set of rescue equipment integrating drilling, discharge, conveying, and protection. Static loading tests indicate that the maximum torque of casing reached up to 255 kN·m and the maximum propulsion force of the outer pipe measured up to 1 600 kN. During the engineering trials and integrated tests conducted in Shangluo, Shaanxi Province and Yuxi, Yunnan Province, respectively, three horizontal boreholes were drilled, with a maximum borehole length of 61.5 m and an evacuation passage diameter of 570 mm, verifying the performance of the drilling rig and the suitability of the multi-stage CwD process. The developed drilling equipment for underground rescue significantly improves the adaptability and rescue efficiency under narrow roadway environments, providing devices for emergency rescue in mines and tunnels.