Geotextile Tubes Used

To Combat Beach Erosion

Background

A series of strong coastal storms wreaked havoc on a South Jersey shoreline consuming a wide path of heavily vegetated dunes, and more than a dozen yards of beachfront separating a three-story condominium complex from the raging sea. The aftermath left this 18-unit complex in Sea isle City, New Jersey defenseless should another series of storms strike the shoreline. with several months of winter storms ahead, and no signs of El Nino relenting, City officials were gravely concerned with saving this beach front property and other surrounding real estate.

Introduction

Designed to protect shoreline beaches from the devastation caused by these coastal storms, high strength geotextile tubes are the latest in protection against the erosive forces of nature that occur every time waves, high tides and longshore currents collide with a vulnerable stretch of beach. These tubes are constructed of high strength polyester and filled with dredged material, or trucked-in sand (as in the case of Sea isle City). Once filled, the tubes are covered with sand, creating a resilient base for dunes to protect against erosion and storm damage.

Geotextile tubes are designed to resist abrasion, tearing, and puncturing, as well as endure pressure during filling and placement. Traditional materials, such as rock or concrete, can be ten times more expensive than the use of geotextile tubes. "The tubes are more easily removed, have a finite lifespan, and can have a far less permanent impact on the environment than conventional hard structures," stated Orrin Pilkey, director of Duke University's Study of Developed Shorelines.'

Construction

Albrecht & Heun, the General Contractor, kicked off the project to restore the shoreline between 91st and 93rd Streets only two weeks after the devastation to the Sea Isle City's shoreline occurred. With the aid of front-end loaders, backhoes, dump trucks, and hydraulic equipment, Heun's six-man crew began working to install 900 feet of Geotex® 12x12 tubing,

manufactured by Synthetic Industries (SI), with hopes of protecting the condominium complex from future storm damage.

 

 

During the first week, workers constructed a temporary road to the beach and began hauling in equipment for the replenishment and filling of the Geotex® 12x12 tubes. A crane lifted rocks and debris from the site so that the tubes could be placed on the beach without the possibility of puncture to the tubing.

The tube rests on a polypropylene scour apron that serves to inhibit undercutting of the tube's foundation if the sand layer is removed by future storms. In the Sea Isle City project, Geotex® 4x4 was specified in the construction of the scour apron.

The process began with a trapezoidal trench I foot below grade, onto which the apron was placed. The scour apron also serves to reduce local erosion caused by the flow of water during the filling process. Three tubes, 30 feet in circumference, were then set on the apron and a sand and water slurry was trucked and pumped into the tubing using an IMS submerged cutterhead dredge, through a 10" discharge line. The water percolates out through the fabric, leaving a dense sand-filled structure.

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