Soil nail walls in residual soils

Construction of the Sandy Springs Subway Station of the Metropolitan Atlanta Rapid Transit Authority's (MARTA) North Line required temporary excavation support. The Station excavation was to be approximately 245 meters (880 feet) in length and varied from 15 to 46 meters (50 to 150 feet) in width, Excavation depths of up to 20 meters (70 feet) were required. Traditional construction practices in Atlanta would dictate that a soldier pile and lagging system be employed, Right-of-way easement limitations prohibited the use of the lengthy tiebacks, as required for a soldier pile and lagging system. An internally braced excavation was not considered feasible because of the width and depth requirements of the excavation. MARTA's design team elected to utilize a soil nail wall for temporary excavation support of the approximately 8300 square meter (89,000 square foot) excavation face. To date, this wall represents the largest and deepest known soil nail wall constructed in the Southeastern United States and represents a successful application of the soil nail technique in the Piedmont Physiographic Province.