Explainable Gradient-Boosting Framework for Robust Prediction and Geomechanical Interpretation of Drilling Rate Index (DRI) in Granitic Rocks
摘要
Predicting the Drilling Rate Index (DRI) with both high accuracy and physical interpretability remains a major challenge in rock excavation engineering, due to the nonlinear coupling of mechanical, petrographic, and abrasivity parameters. This study presents an Explainable Hybrid Gradient-Boosting Framework that integrates ensemble learning, Bayesian optimization, and explainable artificial intelligence (XAI) to deliver geomechanically interpretable DRI predictions for granitic rocks. A comprehensive experimental database of 41 granitic rock samples, encompassing 27 geotechnical variables, including uniaxial compressive strength (35–182 MPa), Brazilian tensile strength (5–20 MPa), brittleness index (S20) (25–60%), Schmidt rebound hardness (26–70), and Cerchar abrasivity index (1.3–3.9), formed the modeling foundation. Four gradient-boosting algorithms (XGBoost, LightGBM, CatBoost, and AdaBoost) were optimized via Bayesian hyperparameter tuning and validated under stratified fivefold cross-validation. A Shallow Neural Network (SNN) was additionally implemented as a benchmark for direct comparison on the same dataset. All optimized ensemble models achieved R2test > 0.994 and RMSE < 0.9 DRI units, with CatBoost delivering the highest accuracy (R2test = 0.9987, RMSEtest = 0.43). Bayesian posterior inference confirmed narrow uncertainty bounds (MAE95% CI ≤ ± 0.05), and Taylor diagram analyses verified near-perfect correlation and variance fidelity across all models. SHAP and Partial Dependence Plot analyses identified brittleness index (S20), Sievers’ J value (SJ), Brazilian tensile strength (BTS), and Cerchar abrasivity index (CAI) as the dominant DRI controls, collectively accounting for ≈ 65% of predictive variance, with physically consistent nonlinear threshold behavior confirmed across the full drillability spectrum. The optimal CatBoost model was operationalized in a graphical user interface (GUI) for real-time DRI estimation, supporting practical excavation decision-making.