Upper Ouachita National Wildlife Refuge GRS Abutments for Replacement Bridges Michael Adams- FHWA Scott A. Saunders – FHWA/ EFLHD

Ouachita Bridge Replacement GRS Abutments l Introduction l BOF Program l Design and GRS Technology l Construction l Instrumentation l Performance/Conclusion

Ouachita Bridge Replacement Introduction l Replace 3 bridges in National Wildlife Refuge l Alternative foundation and abutment design l Evaluate cost, constructability and performance

Bridge of the Future l Develop new technologies to build better, more efficient bridge systems. l Cost-effective designs and efficient construction techniques for foot bridge systems. l Improved durability, maintenance, inspection accessibility and long-term performance. l Meet the growing demand for bridge replacement projects.

Upper Ouachita National Wildlife Refuge

Bridge Sites

Old Rail Car Bridges

Site Conditions Bottomland Bayous

Cecil Creek Subsurface Profile

GRS Technology l What is it? (MSE vs. GRS) l Design l FHWA GRS Research l An alternative to driven pile foundations

GRS Technology GRS Walls and Abutments l Built with readily available materials l Common construction equipment l Without highly skilled labor

GRS Technology Current GRS Projects

2 Factors for Internal Stability l Good compaction with quality fill l Close reinforcement spacing Bulging wall face indicates that the two factors were not practiced; It is not an excuse to use mechanical connection between blocks

GRS Design l Bearing Capacity (check) l Direct Sliding/Global Stability (check) l Eccentricity l Strength (check) l Connection l Pullout

Thrust on Facing Elements Assuming a “yielding” facing  h  h 7/10 S 3/10 S S Reinforcement Granular Backfill (  = 34°) (  lbs/ft 2   h =  S K a =  S tan 2 (45°- 34°/2) = 125 S (0.283) = 35.4 S F =  h (7/10 S) +  h (3/10 S) = 43/60  h S = 25.4 S 2 lbs/ft Wu, McMullen, and Ruckman

Reinforcement Spacing Controls Performance

Bridge Plan & Elevation

GRS Abutment

GRS Wrap Detail

GRS Abutment Materials l Geotextile Woven Polypropylene Type VIIA Contech C400 Type VIIB Contech C300 Wide Width Tensile Strength 4800 lb/ft & 2100 lb/ft l Aggregate Backfill Arkansas DOT - Aggregate Base Course Class 7: 1½ Maximum grain size

Abutment Construction

Spread Footing on GRS Abutment Cut Off Creek

Bridge Construction

Elastomeric Bearing Pad

Cutoff Creek Bridge

Cecil Creek Bridge

Big Lake No. 2 Bridge

Borehole Instrumentation

Instrumentation/Monitoring l Magnetic Extensometers l Inclinometer l Survey

Instrumentation 1C2C Magnetic Extensometer

Instrumentation 1A2A 2B 1B Inclinometer

Inclinometer South Abutment

Inclinometer North Abutment

Settlement Data settlementangular distortion averagedifferential(differential/L) BridgeL= 67 ft Cecil Creek Big Lake Cutoff Creek AASHTO Criteria = 0.005

Lab Testing l Comparison w/ field instrumentation results l Consolidation tests on Cecil Creek samples l South Abutment – Running Sands

Conclusions GRS vs. Pile Foundations l Cost: 40 % less than pile foundations (w/o footings) l Savings using shorter beams l Easy to deliver site materials l Less equipment required l Simplified QA/QC program l Less time to construct

Performance l Total settlement < 1.5 inches l Differential Settlement: 0.5 inches l No “bump” at the bridge/road interface l Continued Performance Monitoring