Upper Ouachita National Wildlife RefugeUpper Ouachita National Wildlife RefugeGRS Abutments for Replacement Bridges GRS Abutments for Replacement Bridges

Michael Adams- FHWA

Scott A. Saunders – FHWA/ EFLHD

Ouachita Bridge ReplacementOuachita Bridge ReplacementGRS AbutmentsGRS Abutments

Introduction BOF Program Design and GRS Technology Construction Instrumentation Performance/Conclusion

Ouachita Bridge ReplacementOuachita Bridge Replacement

Introduction

Replace 3 bridges in National Wildlife Refuge

Alternative foundation and abutment design Evaluate cost, constructability and

performance

Bridge of the FutureBridge of the Future

Develop new technologies to build better, more efficient bridge systems.

Cost-effective designs and efficient construction techniques for 70-90 foot bridge systems.

Improved durability, maintenance, inspection accessibility and long-term performance.

Meet the growing demand for bridge replacement projects.

Upper Ouachita Upper Ouachita National Wildlife Refuge National Wildlife Refuge

Bridge SitesBridge Sites

Old Rail Car BridgesOld Rail Car Bridges

Site Conditions Site Conditions Bottomland BayousBottomland Bayous

Cecil Creek Subsurface ProfileCecil Creek Subsurface Profile

GRS TechnologyGRS Technology

What is it? (MSE vs. GRS)

Design FHWA GRS Research An alternative to driven pile foundations

GRS TechnologyGRS Technology

GRS Walls and Abutments

Built with readily available materials

Common construction equipment

Without highly skilled labor

GRS TechnologyGRS Technology

Current GRS Projects

2 Factors for Internal Stability2 Factors for Internal Stability

Good compaction with quality fill 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 DesignGRS Design

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

Thrust on Facing ElementsThrust on Facing ElementsAssuming a “yielding” facingAssuming a “yielding” facing

h

h

7/10 S

3/10 SS

Reinforcement

Granular Backfill (= 34°) (lbs/ft2

h = S Ka = S tan2 (45°- 34°/2) = 125 S (0.283) = 35.4 S

F = h (7/10 S) + h (3/10 S) = 43/60h S = 25.4 S2 lbs/ft

Wu, McMullen, and Ruckman

Reinforcement Spacing Reinforcement Spacing Controls Performance Controls Performance

Bridge Plan & ElevationBridge Plan & Elevation

GRS AbutmentGRS Abutment

GRS Wrap DetailGRS Wrap Detail

GRS Abutment MaterialsGRS Abutment Materials GeotextileWoven Polypropylene

Type VIIA Contech C400

Type VIIB Contech C300

Wide Width Tensile Strength 4800 lb/ft & 2100 lb/ft

Aggregate BackfillArkansas DOT - Aggregate Base Course

Class 7: 1½ Maximum grain size

Abutment ConstructionAbutment Construction

Abutment ConstructionAbutment Construction

Abutment ConstructionAbutment Construction

Spread Footing on GRS Abutment Spread Footing on GRS Abutment Cut Off CreekCut Off Creek

Bridge ConstructionBridge Construction

Bridge ConstructionBridge Construction

Elastomeric Bearing Pad Elastomeric Bearing Pad

Cutoff Creek BridgeCutoff Creek Bridge

Cecil Creek BridgeCecil Creek Bridge

Big Lake No. 2 BridgeBig Lake No. 2 Bridge

Borehole InstrumentationBorehole Instrumentation

Instrumentation/MonitoringInstrumentation/Monitoring

Magnetic Extensometers Inclinometer Survey

InstrumentationInstrumentation

1C 2C

Magnetic ExtensometerMagnetic Extensometer

InstrumentationInstrumentation

1A 2A

2B1B

InclinometerInclinometer

InclinometerInclinometer

South AbutmentSouth Abutment

InclinometerInclinometer

North AbutmentNorth Abutment

Settlement DataSettlement Data

settlement angular distortion

average differential (differential/L)

Bridge L= 67 ft

Cecil Creek 0.78 0.27 0.00031.05

Big Lake 0.69 0.033 0.000410.36

Cutoff Creek 0.060.03 0.03 0.00004

AASHTO Criteria = 0.005AASHTO Criteria = 0.005

Lab Testing

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

ConclusionsConclusions

GRS vs. Pile Foundations

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

PerformancePerformance

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