Effects of cognitive load and time-on-task on mental fatigue in real-world drilling operations

Mental fatigue is an important human factors issue affecting safety performance in high-risk operations. Previous studies have relied on short laboratory tasks and often examined the effects of time-on-task and cognitive load separately. This study investigated their joint effects on mental fatigue in a real drilling environment using EEG cross-frequency coupling (CFC) and a Transformer model. Cognitive load and time-on-task jointly influenced mental fatigue, as reflected in changes in local efficiency and global network reconfiguration. The Transformer framework achieved accuracies of 90.2% and 89.3%, while SHAP analysis identified efficiency entropy as the most important feature. Overall, CFC features effectively characterised mental fatigue in real operations and may support fatigue monitoring, human factors risk identification, and safety management in high-risk settings.