Landscape Contractor / Design Build Maintain

MAR 2014

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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Bonnie Ellison Elementary School, San Antonio, TX Architect: Garza-Bomberger & Associates Civil Engineer: M.W. Cude Engineers, LLC Construction: 01/2013 – 5/2014 • Cost: $19.9 million (approx.) General Contractor: Joeris General Contractors, Ltd. Owner: Northside Independent School District, San Antonio, TX Wall Installer: Cribley Enterprises, Inc. dles, a series of retaining walls totaling 3,000 square feet became an es- sential part of the engineering and architectural design. With a focus on hardscapes, there was not enough room for conventional segmental walls with geosynthetic reinforcement. A Structural Solution The civil engineering firm working on the project, M.W. Cude, recommend- ed Pavestone's Anchorplex retaining wall system in tree preservation areas, because it requires little excavation and is designed to meet the engineering requirements of structural wall designs. The system uses a self-compacting structural backfill placed immediately behind the block to support retaining walls. The self-compacting structural backfill attaches itself to the wall facing, effectively extending the depth and mass of the wall. The structural backfill zone also serves as the required drainage zone directly behind the block facing. The unique system does not require a large geosynthetic reinforced stabilized earth zone behind the wall face, which means significantly less room is needed for excavation. Retaining walls with structural backfill zones are useful in cut wall appli- cations up to 10 feet high, particularly when lot lines, rock outcroppings or other obstructions limit the ability to excavate for geogrid reinforcement. Geo- synthetic reinforcement typically requires an excavation depth of at least 60 percent of a wall's height; structural backfill cuts the required excavation depth to 30-40 percent of the wall's height, depending on conditions. The struc- tural benefits combined with aesthetics, permeability and cost effectiveness to make the decision to install segmental retaining walls at Ellison Elementary an easy one. Segmental walls allow for diverse landscaping options and creativity within an installation, providing the flexibility to maintain a cohesive look while en- suring design parameters are met. This retaining wall system helped to create an attractive, functional, and value-engineered retaining wall for the Northside Independent School District's Bonnie Ellison Elementary School, which will open its doors to students in August 2014. Hardscapes PAVERS•MASONRY•BLOCKS•ROCKS (Continued from page 14) Installation of the structural backfill begins with placement of the backfill material behind the wall with a Bobcat S300 skid steer loader ( Above, Left ). Crewmembers tamp the material down in the backfill zone and work it into the voids and cores of the blocks ( Above, Right ). Finally, a worker sweeps off the top of the block units so the next row of blocks can be placed on top ( Left ). The backfill installation steps are repeated for each row of blocks until the wall is capped. Above: The Anchorplex system's structural backfill (Pavestone) is made with a mix of cementitious material, coarse aggregate and water. The cementitious material should be hydraulic cement (ASTM C 150 or C 1157), fly ash (ASTM C 618) or slag (ASTM C 989), and the stone should be coarse aggregate, size number 6, 8 or 57 (1/2 inch to 3/4 inch), type 3S (ASTM C 33). Stone size selection should be based on the application. 16 LC DBM DBM LC 014-017.indd 16 2/27/14 11:10 AM

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