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IFAI International Achievement Award 2010 winners demonstrate the versatility and value of geosynthetics in infrastructure projects.
Information compiled by Ron Bygness
Over land and sea
The Incheon Grand Bridge, an 11.4-mile, six-lane toll bridge constructed in the city of Incheon, connects Songdo City and Incheon International Airport located on Yeongjong Island. A major seaport city on Korea’s western coast, Incheon is also home to the country’s largest international airport.
The bridge’s construction was accomplished using barges in deep waters and the more cost-effective and time-efficient land-based construction in shallower waters. This decision, however, required creation of an artificial island platform to allow the use of land-based equipment. Reclamation dikes were constructed before fill was placed within the confines of the dikes to raise the platform to the design level. Geotextile tubes were used because it was more economical, and it satisfied the client’s technical requirements as well as construction time constraints.
The primary 7.6-mile center section of the bridge was constructed in an area of soft marine and estuarial deposits in waters of varying depth and a maximum tidal range exceeding 30 feet. The geotextile tube application allowed construction of the perimeter reclamation dike within a tight construction schedule as well as difficult tidal, wave, and foundation conditions. The sand-filled geotextile tube dikes adapted to the large foundation deformations and withstood wave onslaught from the sea during the entire bridge construction period.
A geotextile tube is a close-ended fabric tube with filling ports. Sand is hydraulically pumped in through the filling ports during site installation to effectively form a partially flattened “sand sausage” that acts as a reclamation dike unit. Reclamation dikes up to 10-feet high and 200-feet long were constructed within a few hours using geotextile tubes.
A total of more than 8.7 miles of geotextile tubes were supplied to the project to form a 1-mile-long artificial island strip that rises about 30 feet above the sloping seabed. The artificial island had to be functional and well-maintained during the entire construction period.
The $2 million geotextile tube supply contract is the largest of its kind in Korea in terms of quantity and project value and resulted in significant cost savings over conventional reclamation dike construction methods. The geotextile tube diameter (16.5 feet) used in this project also represents the largest dimension currently installed in Korea.
The fifth-longest cable-stayed bridge in the world, its design and construction was undertaken by Samsung Construction Joint Venture, which consisted of seven major Korean contractors. The complete project costs totalled more than $1.4 billion. TenCate Geosynthetics provided geosynthetics and fabrication of the Geotube® containment systems and earned an IAA Award of Excellence for the project.
The taxiway across the bay
Phase 1 of the Taxiway F-North extension at the La Crosse, Wis., Municipal Airport, located on French Island in the Mississippi River, needed to be fully operational in the fall of 2011 so that the ensuing taxiway construction project could be completed on schedule in 2011. Accomplishing this required creatively solving a number of construction issues.
The northward extension of Taxiway F was designed to run through a bay in the southeastern corner of Lake Onalaska (essentially a widening of the river). Placing fill at this site could not be accomplished until sediment up to four feet deep was removed from the floor of this corner of the bay. Removal of the sediment using hydraulic dredging was the most cost- and time-efficient method, while handling of the sediment remained a challenge. The engineering and design team chose to use geotextile tubes placed in a lined cell to allow for dewatering of the sediment and return of the effluent to the lake.
The engineering and design team ultimately used five geosynthetic materials to accomplish their client’s goals. Geo-Synthetics LLC (GSI), Waukesha, Wis., supplied geosynthetics and fabrication.
- Linear low-density polyethylene geomembrane to line the cell to manage effluent
- Geocomposite placed below the geotextile tubes to facilitate dewatering
- Geotextile tubes for dewatering the sediment. (An often overlooked benefit of using geotextile tubes to dewater sediment is the fact that this methodology is the most eco-friendly of all options.)
- Geogrid to allow for placement of an aggregate layer and sand layer. The geogrid panels were connected with “hog rings” to expedite deployment of the grid under water.
- Nonwoven fabric acted as a separator between the aggregate layer and sand layer.
About 20 acres of geosynthetic materials were used in this project. Approximately 16,500 cubic yards of sediment was dredged and dewatered to allow for placement of 160,000 tons of fill material during a narrow construction window. GSI earned an IAA Outstanding Achievement Award for the project.
Functional, safe, sustainable
ML Ingenieria, Mexico City, Mexico, provided engineering, design, project management and installation services for the construction of two vehicular bridge abutments near Veracruz City, Mexico. The location, important as a commercial seaport and railroad center, needed a bridge to cross over the railroad tracks of the Veracruz cargo train that travels from this port to all parts of the country. The bridge was also needed to connect a residential area with the Xalapa-Veracruz Highway.
The project plans required that area business operations remain unaffected during construction, so two bridge abutments were designed, one about 165 yards long and the other 173 yards, each 20 feet high. The clients also required that the abutments would harmoniously blend with the landscape to achieve a friendly integration with the surrounding environment and encourage future builders to be aware of the importance of construction with sustainable designs.
The design engineering had to first account for the low capacity of the soil and the short timeline for completion. Using geosynthetics meant time-saving construction without affecting safety or quality—and the use of these products does not require specialized skilled labor. The site required less preparation, and the installation of the reinforcement proceeded without interrupting the trains near the work site. Geosynthetic materials also brought a flexible structural element, allowing the absorption of soil deformations. This method also reduced the cost vs. a traditional mechanically stabilized earth (MSE) wall and reinforced slope.
According to the project plans, protection against erosion was required. Polyethylene geocells were placed on embankment surfaces for further vegetation using regional plants. The geocells were covered with vegetation, which provided protection against slope erosion, as well as aesthetic value.
This project demonstrates how soil can be reinforced through the application of geosynthetic materials, specifically for the construction of two vehicular bridge abutments. The versatility of geosynthetics played a significant role, from the efficiency of the reinforcement system of the geogrids, to the use of geocells on all the slopes for erosion control. The project, for which ML Ingenieria received an IAA Outstanding Achievement Award, combines engineering technique with environmental sustainability, resulting in a safe, high-quality structure.