Deepening of Port Facilities - Design and Installation of Toe Walls

Abstract

Deepening of port and waterfront facilities is a critical issue facing port authorities and waterfront facility operators around the world. Ships are becoming larger and require increased draft alongside the facilities. If the facilities are not deepened then in many cases ships either reduce the amount of cargo so that they are not fully laden and/or require tidal assistance to achieve adequate under-keel clearance. The response to this increase in ship size is a clear trend to deepen the navigation channels and approaches to port facilities around the world. To accommodate the larger ships and deeper channels, waterfront facilities must also be improved. The impacts associated with deepening waterfront facilities are numerous including impacts on the unbraced lengths of pile supported structures, reductions in stability of sheetpile bulkheads, and the potential for slope stability problems affecting the global stability of the waterfront structure. This paper focuses on the use of toe walls to allow waterfront facilities to be deepened without impacting existing pile supported structures. The objective of the toe wall is to retain the existing elevation of the mudline beneath the wharf while permitting the area in front of the toe wall to be dredged to the desired elevation. Three projects will be discussed with respect to the design and installation of toe walls. The discussion of each project will include a review of soil stratigraphy, design methodology and considerations including seismic affects, toe wall behavior, and construction equipment and methodologies. Each of the three toe wall installations is different and each has unique design and construction aspects. The three projects are located at Berths 3 through 8 at the North Carolina State Ports Authority in Wilmington, North Carolina, the Port Newark Container Terminal in Elizabeth, New Jersey and the North Charleston Terminal at the South Carolina State Ports Authority in Charleston, South Carolina.