Evacuating offshore working barges from a land reclamation site in storm emergencies

Abstract

This paper investigates a barge evacuation planning problem (BEPP) that can arise during land reclamation projects. The problem was motivated by the issue faced in actual practice by the Hong Kong International Airport (HKIA). In this problem, a fleet of heterogeneous barges working at an offshore land reclamation site needs to be evacuated to coastal shelters prior to the arrival of a storm. Having no propulsion power of their own, these barges must be towed by tug boats in order to be evacuated. The problem under consideration is very complicated since it involves a series of inter-correlated assignment and scheduling decisions at different planning levels. To solve the problem, this paper first formulates the problem as a nonlinear Mixed Integer Programming (MIP) model. The model is then linearized. We further proved that the BEPP is NP-hard in the strong sense. In view of the complexity of the problem, a tailored heuristic method is proposed. Extensive numerical experiments and a case study are performed, and the results demonstrate the effectiveness and efficiency of the solution method. Land reclamation projects have become increasingly popular in recent years, and the proposed method is applicable to solving BEPPs arising in similar scenarios.