Geological-Lithological Features of Namdok Coalmine and Directional Drilling Speed Modeling with Diamond Bits for Water-Inrush Detection

Water inrush is a critical geological hazard compromising safe coal mining, particularly in areas with complex hydrogeological conditions. The Namdok Coalmine, situated in a mountainous coal-bearing zone, experiences frequent water inrush events due to intricate lithological characteristics and extensive structural fractures. To address this challenge, we systematically characterized the mine's geological-lithological and hydrogeological properties using field surveys, drilling core analysis and scanning electron microscopy (SEM). We then conducted laboratory simulations of directional drilling with diamond bits to quantify the effects of lithological parameters, drilling conditions, and water content on the rate of penetration (ROP). A support vector regression (SVR) model optimized by the Gaussian radial basis function (RBF) was developed to predict drilling speed for waterinrush detection, validated with field drilling data. Results indicate the Namdok Coalmine is dominated by clastic and carbonate rocks, with faults and fractures acting as primary waterinrush pathways. ROP is significantly influenced by rock hardness, drilling pressure, rotational speed, and water content-rock strength decreases sharply when water content exceeds 3%, triggering abrupt ROP changes. The SVR model exhibits high prediction accuracy (R² = 0.968, MAE = 0.723, MAPE = 2.01%), enabling effective identification of ROP anomalies induced by water-bearing structures. This study integrates geological exploration, drilling engineering, and machine learning, offering a novel technical approach for water-inrush prevention in coalmines with complex geology.