Design and performance of the facing column for geosynthetic reinforced segmental retaining walls

A unique feature of geosynthetic reinforced segmental retaining walls (SRW) is the use of mortarless dry-stacked modular concrete blocks to form the facing column. These materials act as a temporary form work during placement and compaction of backfill soils. They also perform a structural function by providing transverse rigidity and shear capacity over the height of the wall. In most systems the facing column is connected to the reinforced soil mass by passing the geosynthetic reinforcement between the facing units to the front of the wall. The dry-stacked facing column construction requires that unique analysis and performance testing of the connections and interface shear capacity be carried out that are not required for other types of reinforced soil retaining wall systems. The paper is focused on the analysis and design of facing stability modes of failure for geosynthetic reinforced segmental retaining walls. Selected data from two instrumented walls reported in the literature demonstrate that the facing column must be designed to transmit shear and to carry connection loads that are comparable in magnitude to values assumed for internal stability design. Performance test protocols developed by the authors and adopted by the National Concrete Masonry Association (NCMA) are described and the results of connection and interface shear tests presented. A set of parametric analyses are presented based on a range of connection and interface shear capacity data and the results used to examine the sensitivity of facing connection and interface shear capacity parameters on wall design.