American Society of Civil Engineers

Bulkhead Design Using Recycled Materials as Backfill

by Dennis G. Grubb, M.ASCE, (Senior Associate, Schnabel Engineering, 510 E. Gay Street, West Chester, PA 19380 E-mail:, Wanxing Liu, (Project engineer, Schnabel Engineering, 510 E. Gay Street, West Chester, PA 19380), Allen W. Cadden, M.ASCE, (Principal, Schnabel Engineering, 510 E. Gay Street, West Chester, PA 19380), and Dana N. Humphrey, M.ASCE, (Malcolm G. Long Professor of Civil Engineering, University of Maine, 5711 Boardman Hall, Orono, ME 04469-5711)
Section: Bulkheads and Seawalls, pp. 1-11, (doi:

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Document type: Conference Proceeding Paper
Part of: Ports 2007: 30 Years of Sharing Ideas: 1977-2007
Abstract: This paper will present a conceptual analysis of a bulkhead design that instead of using conventional fill, stone or dredged sands, uses an alternative layered system based on re-used materials. The layered system is comprised of Tire Derived Aggregate (TDA; ASTM D6270) encapsulated by soil layers made from blends of curbside-collected, 9.5 mm (3/8")-minus crushed glass (CG) and dredged material (DM) fines, or CG-DM blends. TDA is a freely draining lightweight geotechnical fill (7.8 kN/m3 (∼50 lbs/ft3) which has been used in numerous civil engineering applications to improve slope stability, reduce surcharge pressures on soft compressible soils, and lower earth pressures on retaining walls. Pug-milled CG-DM blends can be prepared to meet DOT embankment and structural fill specifications while also enabling immediate fill construction by improving the workability, strength, drainage and settlement characteristics of DM fines without the need for curing or consolidation. Both materials have interesting geotechnical properties, and their application to maritime construction has the potential to revolutionize bulkhead design and construction while bolstering the efficiency of recycling programs. This paper compares the design of bulkheads with conventional backfills, versus a bulkhead leveraging recycled materials. The results clearly illustrate that recycled backfills introduce significant economical and technical advantages, such as simplified construction sequencing, improved backfill properties and reduction of backfill weight.

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