A risk prediction method for water or mud inrush from water-bearing faults in subsea tunnel based on cusp catastrophe model

Abstract

Constructing a subsea tunnel is exceptionally difficult because of the complex geological conditions involved in the process. Water or mud inrush is a geological hazard that occurs suddenly during the construction of a cross-harbor tunnel, thereby causing major disasters and economic losses. The weak structural planes in a fault zone are the naturally preferred planes for water inrush. It is necessary to analyze the mechanism and to develop a risk prediction method for water or mud inrush from such faults. In order to effectively predict the risk of water or mud inrush during the construction of a subsea tunnel, this paper analyzes the mechanism of water or mud inrush from extensional faults, shear faults and compressive faults based on cusp catastrophe model. The potential function for the risk of water or mud inrush is built, and then the index of water inrush (IP) is obtained based on the equations of equilibrium for the fault surface. Water or mud inrush occurs only when IP > 1. The proposed method of risk prediction is successfully used in Qingdao Kiaochow Bay subsea tunnel to prove its applicability and feasibility.