Forecasting and early warning of shield tunnelling-induced ground collapse in rock-soil interface mixed ground using multivariate data fusion and Catastrophe Theory

The high spatial variability of the rock-soil interface (RSI) in complex geological conditions introduces strong uncertainties in both subsurface stratigraphy and geotechnical properties. Inaccurate interpretation of such uncertainties during engineering geology investigations increases the geohazard risk of excessive surface settlement or even severe catastrophic ground collapse when shield machines are excavating in RSI mixed ground. Prediction and early warning of excessive surface settlement are necessary measures to address such a risk; however, unavoidable drawbacks such as overfitting, insufficient accuracy, and ineffectiveness remain in existing prediction models and early warning algorithms and have posed significant challenges. In this study, a novel framework using both a multivariate data fusion prediction model and a dynamic early warning algorithm was developed for forecasting and early warning of ground collapse during shield tunnelling in RSI mixed ground. The prediction model is the Differential Evolutionary Optimized Quadratic Taylor Series Extended Kalman Filter (DEQT-EKF); the early warning algorithm is based on Catastrophe Theory and uses the Gradient Ratio (GR) criterion to identify catastrophic singularities. The practicality and accuracy of the framework are well verified by a subway shield tunnelling-induced ground collapse incident in East China with complex RSI mixed ground conditions. The prediction results are compared with the surface settlement measurements and good agreement is obtained, indicating that the DEQT-EKF model can achieve satisfactory accuracy in predicting excessive settlement. The use of the GR criterion can trigger the early warning one time step before the ground collapse event, indicating that it is a competent and practical early warning strategy for shield tunnelling-induced ground collapse. The framework has the potential to significantly reduce the risk of ground collapse caused by geological uncertainties when constructing shield tunnels through complex ground conditions.