Source: Construction Equipment News
In recent years, geotextile tube technology has experienced growth, success, and acceptance. Several successful and highly visible projects have solidified the geotextile tube methodology as viable. One such project was a 1995 sand dune reconstruction project in Atlantic City, NJ using a Mud Cat™ type auger dredge.
Many experts would agree that this project was a turning point in the industry for the U.S., sparking confidence in and promoting the technology.
Between January 1993 and January 1994, Atlantic City lost more than 100 feet (30 m) of beach in some areas, a rate of eight-plus feet per month. During past storms and over time, sand dunes, which protect the city's boardwalk, as well as the homes, businesses, hotels and casinos along it, deteriorated, and in some cases, completely washed away. The problem was most severe when extreme high tides driven by offshore storms in the Atlantic Ocean slashed away the beach and sand dunes.
Conventional dune remediation measures include beach and dune re-nourishment, which sometimes cost millions of dollars per year. A more cost-effective, longer duration solution was needed. Representatives from a geosynthetics manufacturer and distributor, met with the city engineer in the fall of 1994 to introduce them to Geotubes®. Designers incorporated Geotubes® as the core of a replacement sand dune, acting as stable, sand filled, fabric tube. Although the tube may be uncovered during a storm event, the design limits erosion on the seaward side of the Geotube®, retaining the imported sand fill behind the tube. City engineers determined that a 30 foot (9 m) circumference tube would provide sufficient protection.
The protection was advertised for bid in February 1995 and a local contractor was awarded the project and began work that March 1995. The geotextile tubes stretch approximately 6,000 linear feet along Atlantic City's beach and create a more storm-resistant sand dune than conventional methods, preventing further dune deterioration.
The tubes used for this project were fabricated from high strength, woven, polypropylene geotextile designed specifically for use in tube fabrication. The tubes' circumference were all 30 feet (9 m), with the length ranging form 40 to 910 feet (12 m to 277 m). Injections ports for sand filling were attached along the top centerline of the tubes on 25-foot spacing. Upon completion of the geotextile tube installation, city workers covered them with sand and planted dune grass, resulting in a natural-looking dune.
In the summer of 1995, just three months after completion of the dune reconstruction, Hurricane Luis skirted the Eastern Seaboard, producing winds of 30 mph causing 10 to 12 foot (3 m to 3.6 m) waves along the Atlantic City shoreline. The three-day pounding caused dune erosion in front of the installed geotextile tubes (seaward side); however the landward side was virtually unscathed. Many dollars in reconstruction were saved by the timely installation of the geotextile tubes. The Atlantic City Press called it, "a line in the sand... there will be no more erosion past that line."
(Geotube® is a registered trademark of Ten Cate Nicolon)