Overview
American Consolidated Natural Resource, Inc. (ACNR) needed a cost-effective method to complete the closure of a coal slurry impoundment in Jefferson County, Alabama. Extremely low-strength Fine Coal Refuse (FCR) created significant access and constructability challenges, while the limited availability of coal combustion residuals (CCR) fill made material efficiency an important consideration.
Working with the project engineer, Solmax developed a reinforced construction platform using MIRAFI® CR440 and CCR fill. The resulting system provided safe access for equipment and personnel, allowing closure operations to proceed effectively over the extremely soft slurry material.
Challenge
The FCR within the impoundment had extremely low shear strength and could not safely support construction equipment or personnel. ACNR therefore needed a solution that would provide stable access across the impoundment while minimizing the amount of CCR fill required.
The selected system also needed to account for the weight of construction equipment and the overlying fill layer. The design had to provide adequate bearing capacity, manage stresses induced in the geosynthetic, and limit vertical displacement under applied loads.
Solution
To establish a stable working surface over the soft coal slurry, Solmax collaborated with the project engineer to design a reinforced construction platform incorporating MIRAFI CR440 and CCR fill. MIRAFI CR440 is a multifunctional, high-strength geosynthetic that provides reinforcement, separation, and filtration across the impoundment surface. When combined with the CCR fill, it created a stable platform capable of supporting equipment and personnel over the soft FCR.
MIRAFI CR440 was selected through an engineering analysis that accounted for the weight of the equipment and fill layer. The calculations evaluated bearing capacity requirements, stresses induced in the geosynthetic, and anticipated vertical displacement under the applied loads.
During construction, the MIRAFI CR440 panel was deployed directly over the FCR, with approximately 12 feet of runout extending around the perimeter onto firm ground. This runout was covered with approximately 1.5 to 2 feet of CCR to anchor the geotextile in place before fill was placed over the portion covering the FCR. Approximately 2 feet of CCR was then pushed over the CR440 panel, allowing closure operations to proceed safely.
The completed system provided safe and effective access across the FCR impoundment for equipment and personnel. As Solmax's strongest capping reinforcement product, MIRAFI CR440 is suited for applications involving extremely soft or saturated soils where high levels of reinforcement are required.
