Case Studies for the Beneficial Use of Lightweight Fill for Bulkhead Construction

Abstract: Bulkhead construction is a common construction method for the creation of new waterfront and shoreline protection for Ports and Terminals. The components and methods of construction for bulkheads can vary by material type, size, and method of restraint, but the general approach to bulkhead design comes down to the management of demands on the bulkhead both during construction and in the final design condition. One innovative method of reducing the demands is the use of lightweight fill (LWF) as backfill during construction. LWF comes in many different forms and can aid in the design process by providing a lower-density backfill material with reduced lateral earth pressures, increased soil friction angle, and reduced long-term settlement when used in locations with compressible soils.
In 2017, Port Canaveral was in the process of designing the new marine apron and bulkhead for their latest cruise terminal, Cruise Terminal 3 (CT-3). The layout for this new terminal required a new bulkhead in the existing channel with upland-filled submerged lands. This construction was to be performed while the channel remained open to cruise operations, placing a considerable demand on the bulkhead during construction. The design team determined that using LWF backfill could reduce the weight of the steel combination pipe pile wall bulkhead system by 40%. This smaller bulkhead system and reduced demand for the tie-back A-Frame system led to an overall savings of $3 million in construction cost. The use of LWF also reduced long-term settlement by 25% and improved the construction sequencing, allowing for the bulkhead to function in a cantilevered condition temporarily during construction until the A-Frame construction could be completed for the permanent tied-back condition.
In 2024, the Maritime Academy at Texas A&M University at Galveston was in the process of designing new marine facilities for their latest training vessel. The new bulkhead design was going to require an extensive bulkhead and tie-back system due to poor soils and high demand from heavy weather loading requirements. This was going to make construction for the project more challenging, as the new bulkhead had to be placed in a tight schedule between the dredging operations and upland construction. The use of LWF was considered to replace a considerable portion of the poor existing soils during the conceptual design for the project to determine if the bulkhead system size and complexity could be reduced to save cost and improve the construction schedule.
This paper explores the results of two case studies where lightweight fill was considered for the design of a new bulkhead at Port Canaveral and Texas A&M University at Galveston. This paper will navigate the reader through the evaluation process, describe the pros and cons for each project, and explain why LWF was selected for one project but not selected for the other project. These case studies will also cover some lessons learned during the design and construction of Cruise Terminal 3 at Port Canaveral, which should be taken into account when considering the use of LWF for waterfront projects.

How does this project / topic contribute to the advancement of the industry and profession?: This topic will provide marine and bulkhead designers with insights into the innovative approach to lightweight fill and provide lessons learned on when LWF may be used and what circumstances may not be beneficial for design considerations.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: This topic focuses on the innovative practice of using lightweight fill to improve bulkhead design and construction. This can lead to substantial savings to cost and construction schedule.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The most challenging aspect of the use of LWF for CT3 was managing the unexpected difficulties with keeping the lightweight fill in place when placing in water. The material was very fine and floated on the surface, there was a learning curve for the contractor to figure out how to properly place the material. Eventually, the placement was figured out and the lightweight fill performed as expected.

Who is the target audience for this paper?: The targeted audience for this paper includes Structural engineers, bulkhead designers, Cruise Terminal Designers, Port Authorities, and maritime engineers.