The Industrial Fabrics Association International (IFAI) International Achievement Awards (IAA) are an annual competition promoting awareness of the specialty fabrics used in thousands of products and applications ranging in size and shape. For more than 70 years, the awards have recognized innovation, technical skill and design excellence. Entries are judged by industry experts, editors, architects, educators and design professionals who were selected for their knowledge in a particular field of study or product area.
The association presented the awards in the Geosynthetics Products competition at IFAI Expo in New Orleans, La., in late September 2017. Categories included Roadways/Infrastructure, Mines/Landfills/Wastewater and Geosynthetic Miscellaneous.
This issue of Geosynthetics features the winners in the Roadways/Infrastructure category. The magazine will focus on winners in the other two categories in future issues.
IAA Award of Excellence
Sand-Filled Container Revetment
Completion Date: March 24, 2017
Fabric Name: Flintex™ OS160 w/ripstop and Flintex FL400C
Fabric Producer and Supplier: Flint Industries
The project involved the construction of a revetment in Ocean Isle Beach, N.C., to protect a home and associated infrastructure from erosion. Since conventional hardened structures, such as a seawall or sheet pile, were not permitted by the state regulatory agency, the only viable solution that could be permitted was the use of a soft structure utilizing modular and hydraulically filled sand containers with self-sealing fill ports proposed by the designer. The revetment consisted of installation of 2,317 TITANBags®, five feet wide and ranging in length from 10 to 15 feet. The sand-colored geotextile fabric utilized for the TITANBags featured an innovative ripstop weave that prevents a damaged area of the fabric from spreading. The container fabric also allowed a higher-than-normal water flow rate permitting substantially faster filling times, thereby reducing installation time.
Tubbs Inlet near Ocean Isle Beach is subject to natural migration to the east and west in response to the geomorphology of the flood and ebb tidal deltas. Since a channel relocation in the 1960s, a sand spit has steadily enlarged, growing from the shoreline in Sunset Beach to the east toward the town of Ocean Isle Beach. This enlarging sand spit allowed the flood tide delta to build in a manner whereby tidal flows into and out of the tidal prism were directed closer to the Ocean Isle Beach shoreline. As the area for tidal flow had narrowed, an increasingly deep tidal channel with high water velocities was formed, concentrated directly along the shoreline of the west end of Ocean Isle Beach, then approximately seven feet from homes, utilities and a street. The client requested an immediate solution for shoreline erosion protection, both to prevent the undercutting of a previously installed sand container revetment by the east side of the rapidly migrating tidal channel and to eliminate the risk of losing his home and critical infrastructure.
The specified erosion protection design was significantly different from that which is normally addressed with sand-filled geotextile containers. With the deep tidal channel having migrated onto the shoreline of the property, and with water depths of up to 22 feet adjacent to the previously installed revetment, the design had to address extreme erosive forces that were ongoing.
Anticipated construction methods could not be pursued since no work area existed beyond the toe of the previously installed sand container revetment that had eroded away by the time construction could be initiated. Nearly the entire area beyond this revetment was now part of the deep tidal channel. This necessitated a significant alteration of the design and construction methodology. An anti-scour apron had to be manufactured to larger-than-normal dimensions so that it could be carried beyond the bottom of the adjacent deep tidal channel. Methods for placement and securing the anti-scour apron at the bottom of the tidal channel had to be altered as well, enabling it to sink as designed and protect the sand container revetment from being undercut by the tidal channel as it continued to migrate inland and deepen.
Integral to a successful sand container revetment is an understanding of how the revetment will shift when subjected to the ongoing erosive effects of ocean waves and currents. The success of the revetment requires a design for the placement of properly sized sand containers in an arrangement that will resist random shifting of the containers within the revetment.
Several obstacles complicated the design and construction of the project. First, a permit by the state regulatory agency would only be issued if one could demonstrate that the property was under imminent threat, meaning that an erosion escarpment lies within 20 feet of the foundation of the structure to be protected. Second, state regulations only permitted sand container or sandbag structures of no more than six feet in height and a 20-foot base width. Eventually, a variance was issued permitting a base width of 58 feet and a not-to-exceed height of 12 feet North American Vertical Datum (NAVD).
Additionally, this project required the integration of the sand container revetment with an existing stone revetment. The erosion protection needed to be continuous, requiring the sand containers at the end of the revetment to be placed immediately adjacent to the stone. The challenge was to find a solution where the sand container geotextile material would not be compromised by contact with the stone as ocean forces caused both the containers and the stone to shift in place. This problem was addressed by the selection of a unique Flintex composite fabric to function as a cushioning layer at the interface.
Once the sand container revetment was completed, sand was spread on top of the structure to provide UV protection for the sand containers. Salt-tolerant vegetation will be planted to stabilize this sand cover, encourage sand accretion and improve the aesthetics of the site.
The design and construction of the TITANBag revetment proved to be a huge success by sufficiently stopping the migration of an ocean inlet. Infrastructure was protected and remains intact and functional. To our knowledge, this innovative technique had not been attempted in such an extreme environment and should have broader applications as an alternative to stone jetties and groins.
When considering the imminent loss of the client’s home, as well as adjacent structures and infrastructure that were at risk due to erosion, savings because of this project are estimated in excess of $10 million.
IAA Outstanding Achievement Award
Indiana Department of Transportation I-69 Section 5: Liberty Church Connector Road
Completion Date: September 1, 2017
Approximate Size: 600 feet
Fabric Name: Mirafi®
Fabric Producer: TenCate Geosynthetics
Interstate 69 Section 5 in Indiana is a portion of a new connector road circumventing a recently constructed interchange. The connector road is part of the Liberty Church Connector Road Interchange and was constructed through a cornfield. The water table was two feet below grade. The connector road construction required three to five feet of engineered fill to achieve the plan subgrade elevation, which would then be paved with a flexible pavement.
This project involved a single layer of Mirafi H2Ri geosynthetic with 16 inches of a silty sand (A-2) fill.
The earthwork contractor cut the topsoil along the proposed connector road route and began placing silty sand, engineered fill. Due to the high water table as well as compaction energy and trafficking, water was migrating up into the engineered fill, creating rutting and displacement of the fill. The contractor initially intended to utilize a geogrid or other reinforcing geotextile to stabilize and reinforce the fill. TenCate Geosynthetics instead suggested utilizing Mirafi H2Ri reinforcing geosynthetic. The initial 600 × 45 foot width was installed as a test section. The contractor sought a product that would stabilize the section, allowing the engineered fill to be placed to planned subgrade elevation and subsequently paved.
The challenging aspect of this application was the water. With the ground water table so close to existing grade (within two feet), a standard reinforcing geosynthetic would not be effective unless the water could be removed. Typical reinforcing geosynthetics would require temporarily lowering the water table via a dewatering system or installing some kind of drainage system (French drains, drainage composite, etc.) to remove the water as it migrates up into the fill. In addition to possessing separation, filtration, confinement and reinforcement functions, the Mirafi H2Ri also has a wicking capability. The technology, which works through a pressure differential mechanism, absorbs water into the specialized wicking fibers and carries the water (without releasing it back into the subgrade) to the outside edge, in this case released to an open ditch along the roadway. By preventing the water from migrating up into the engineered fill, the reinforcing and confinement functions of the geosynthetic perform as desired, stabilizing the engineered fill.
TenCate Mirafi H2Ri enabled installation of the engineered fill without having to utilize a dewatering system to temporarily lower the water table during placement of the fill nor install a French drain system or drainage composite—all of which would have cost more and taken more time off the schedule. The H2Ri continues to be used on the project where subgrade reinforcement and water are an issue.