Application of Large-Size Sandbag Cofferdam in Land Reclamation Engineering

Abstract

With the rapid economic and social development, land reclamation has been an increasingly urgent need to many countries. Land reclamation is indeed a preferential way to increase the land, but it may also result in some problems. Construction of cofferdam on coastal soft soil is one of the typical geotechnical problems in which many technical obstacles remain unsolved. A new technology of forming a cofferdam on soft soil by stacking super large sandbags has been developed in recent years. With its good integrity and strong adaption to ground deformation, the large-size sandbag cofferdam has been demonstrated an advanced technology. Although some reclamation engineering projects have adopted this new technology successively, we still saw accident cases where the cofferdam slope lost stability. It shows that the bearing capacity of soil bed and the slope stability of cofferdam cannot be estimated correctly in some situation. Under the action of super large bags, the theories about the critical stability and deformation limitation in design should be studied and developed. In this paper, two land reclamation projects completed in China are introduced. Among these two cases, one is totally successful but another has several slope failures during construction. Deformation and slope safety are analysed and compared to the actual behaviour of the cofferdams. Insights are summarized for better understanding of the large-size sandbag cofferdam technology.