A new method for risk assessment of water inrush in a subsea tunnel crossing faults

Abstract

The geological conditions of subsea tunnels are extremely complicated. When crossing faults, water inrush disasters are prone to occur under the combined action of seawater pressure, geological structure, and construction disturbance. An optimal combination weight-improved grey relational analysis (GRA) method is proposed here to evaluate the risk of water inrush in subsea tunnels through faults. Eight main factors are selected from fault zone properties, fault structure characteristics, engineering factors, and construction factors as risk assessment indexes, and the risk is divided into four levels. The subjective and objective weights are determined using the improved G1-method and entropy weight method, and the optimal combination weight is calculated based on the minimum discriminant information principle and the Lagrange multiplier method. The improved GRA considering the evaluation criteria interval is used to determine the correlation degree of the water inrush risk level, and the maximum correlation degree criterion is adopted to judge the risk level. The method is applied to the Qingdao Jiaozhou Bay subsea tunnel to assess the water inrush risk crossing faults, and the assessment results are basically consistent with the actual engineering situation. This study provides a practical reference for the risk assessment of water inrush in subsea tunnels.