Geosynthetic reinforcement of the base, or subbase, course of pavement structures is addressed. The value added with reinforcement, design criteria/protocols, and practices for design and for material specifications are presented. Base, or subbase, reinforcement is defined within as the use of geosynthetic reinforcement in flexible pavements to support vehicular traffic over the life of a pavement structure. Primary base reinforcement benefits are to improve the service life and/or obtain equivalent performance with a reduced structural section. Substantial life-cycle cost savings are possible with base reinforcement. Cost saving benefits should be quantified using life-cycle analyses, and on an agency specific basis due to the many input variables. Recommended design procedure and material specifications are presented. It is recommended that specification with an approved products list be utilized, as the mechanisms of reinforcement are not fully understood and the geosynthetic performance should be considered product, and test conditions, specific. Equivalent materials must demonstrate equivalent performance in test structures and/or possess equivalent material properties, as defined by the specifier.
The use of geosynthetic reinforcement to aid in construction over low strength subgrades, termed subgrade restraint within, is also addressed. Geosynthetic reinforcement is used to increase the support equipment during construction of a roadway. Subgrade restraint design procedures are based upon either (i) generic material properties, wherein a generic specification can be prepared based upon those design property requirements; or (ii) product-specific, empirically derived design methods, wherein an approved products list specification approach may be used.
Geogrid, geotextile, and geogrid-geotextile composite materials are addressed within.
This paper provides government agencies with current, logical recommended practice for the systematic use of geosynthetic reinforcement of pavement base courses. Refined guidance should be developed as the use of base reinforcement increases and additional long-term performance data becomes available.
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