Gravity Wall Construction
A gravity retaining wall relies on the weight and batter of the SRW units to resist the soil forces exerted on the wall. Geogrid soil reinforcement is not used with gravity walls. The allowable heights of gravity retaining walls are typically limited to 2 to 3 times the front-to-back depth of the SRW facing unit.
Geosynthetic-Reinforced Retaining Wall
Geosynthetic reinforced walls use soil reinforcement layers, typically geogrids, to stabilize the soil behind the SRW facing, creating a coherent mass large enough to resist the soil forces acting on the wall system. The SRW facing unit, the geosynthetic reinforcement and the reinforced soil together then form the retaining wall system.To resist more load, the reinforcement layers are lengthened and/or strengthened to provide the required resistance. Thus, reinforced wall systems can be designed for much taller earth retention heights and loading conditions than conventional gravity walls. Reinforced retaining walls should be designed by a qualified engineer and constructed by experienced contractors.
Occasionally in retaining wall applications, enough space does not exist behind the face units to allow excavation for placement of geosynthetic reinforcement. For these instances, an SRW can still be designed using specialized structural backfill to increase the depth and mass of the facing system.Using specialized structural backfill eliminates the use of geosynthetic reinforcement. The structural backfill also acts as the drainage zone for the retaining wall. This design approach also requires substantially less excavation than is required for geosynthetic reinforced retaining walls. Retaining walls using structural backfill should be designed by a qualified engineer and built by experienced contractors. Structural backfill is also referred to as “no-fines concrete”, “stabilized aggregate”, and “Anchorplex System®”.
Geosynthetic Reinforced Soil – Integrated Bridge System (GRS-IBS)
The Federal Highway Administration has developed GRS-IBS technology as an innovative and cost-effective bridge system that is an alternate option to conventional bridge construction. The system uses closely spaced geosynthetic reinforcement layers and compacted aggregate to directly support the bridge superstructure.Due to the simplicity of design, construction speed, use of readily available materials and the elimination of deep foundations, the GRS-IBS method can reduce costs by 25-60% compared to conventional methods. GRS-IBS should be designed by a qualified engineer and constructed by experienced contractors.