A prediction model for overlying rock thickness of subsea tunnel: A hybrid intelligent system

The overlying rock thickness of a subsea tunnel controls its vertical line. It not only ensures the safety and stability of tunnel construction period and operation period, but also ensures the economy of subsea tunnel. In the current research, few papers give full consideration to the complex indicators of prediction the overlying rock thickness. However, in this study, a hybrid intelligent system was established to predict the overlying rock thickness of a subsea tunnel based on Qingdao Kiaochow Bay Subsea Tunnel, China. The sea depth, basic quality index of rock mass, soft soil layer thickness, permeability coefficient, and construction management level were selected as the main factors influencing the overlying rock thickness. Using the data obtained from project site exploration, objective weight factors were calculated using rough set theory, and subjective weight factors were calculated using the analytic hierarchy process. Furthermore, the combination of weights was obtained for each factor. Finally, the weight of influencing factors was incorporated into the extension model, and the overlying rock thickness of pending section was calculated. The results of overlying rock thickness prediction model are consistent with the actual value, indicating that the model has good engineering applicability and application value.