Interpretable machine learning: a comparison of TabNet and XGBoost for axial pile capacity prediction using layered soil representations
摘要
Accurate estimation of axial pile bearing capacity remains challenging due to soil heterogeneity and the limitations of empirical design methods. This study compares TabNet, an interpretable deep learning architecture for tabular data, with XGBoost, a reference standard machine learning model for predicting axial pile capacity. Both models were trained on 440 load tests from Olson’s Axial Pile Capacity database with explicitly layered soil representations and tested using 184 load tests from the same database. Models were optimized using a consistent Bayesian framework and evaluated under strict site-separated training and testing to assess true generalization. While XGBoost achieved near-perfect training performance, its accuracy degraded on unseen sites, indicating overfitting. In contrast, TabNet showed weaker training fit but superior test performance. Feature-importance and stepwise mask analyses reveal that TabNet distributes importance more evenly across pile geometry and layered soil properties and provides intrinsic interpretability aligned with geotechnical reasoning. The results demonstrate that TabNet offers improved generalization and transparency compared to XGBoost for predicting axial pile capacity under realistic geotechnical uncertainty.