TRANSPORTATION

Overview

GRS Walls are an adaptation of the GRS-IBS concept.  A limited number of small bridge projects have been constructed in other parts of the country using GRS abutments as a shallow foundation system. These projects were considered cost effective, are performing well, and the lessons learned during those projects led to the FHWA's GRS Guide.

Because GRS walls are not supporting the loads from a bridge superstructure, and may be in locations well away from rivers, streams and flood plains, portions of the standard details for GRS abutments may not be needed for GRS walls. Depending on the bearing capacity of the subsoil they may be constructed without the gravel filled Reinforced Soil Foundation (RSF) required for GRS abutments. Portions of GRS walls which are not part of the wrap-around GRS abutments and are not within 2 feet of the 500 Year Flood Elevation, may be constructed with material meeting the requirements Specification 548 in lieu of the gravel or GAB backfill required in Developmental Specification 549.

Temporary GRS walls may be designed for, and constructed with ASTM C-90 CMU blocks having a compressive strength lower than 4000 psi or using a wrapped face technique in lieu of CMU blocks.

Design Criteria

FDOT Design Requirements are provided in Structures Design Bulletin 12-06. Less restrictive design requirements for GRS walls are being developed and will be forthcoming.

Developmental Design Standard

Developmental Design Standard D6025 is available for presenting details in project plans. This Developmental Standard includes details for wrap-around abutments and details for the transition between the roadway guardrail and the bridge railing. Please review the Developmental Design Standards Policy prior to requesting D6025.

Specifications

Currently Developmental Specification 549 (Dev549) is written primarily for constructing wrap-around GRS abutments. Alternate versions for alternate design conditions will be forthcoming. Developmental Specification 549TW (Dev549TW) is written for temporary GRS walls.

Implementation Plan

With the exception of Interstate or major multi-lane highway applications, GRS walls may be utilized, when appropriate and cost effective, on all FDOT projects. Use of GRS walls on the Interstate or major multi-lane highways requires the approval of the State Structures Design Engineer.

GRS walls are limited to 40 feet in height. Use on the Interstate or major multi-lane highways requires the approval of the State Structures Design Engineer.