Segmental Retaining Walls Theory & Design
This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
History of Mechanically Stabilized Earth (MSE) Structures
Ancient Structures
Natural Vegetation Reinforcement
The Great Wall of China
Modern Structures
Concrete Panel Systems
Steel Reinforcement
Traditional SRWs • boulders, timber, concrete masonry
Segmental Retaining Walls Mid 1980s
SRW Theory & Design
Examples of Facing Units
SRW Design Methodologies • NCMA – National Concrete and Masonry Association • AASHTO – American Association of State Highway and Transportation Officials
NCMA • • • • •
L/H ratio = 60% of wall height Variable reinforcement lengths Re-use of on-site soils Reduced block embedment depths Typically used on commercial/private projects
AASHTO • • • • • •
L/H ratio = 70% wall height with a min. length of 8 feet, which ever is greater. Uniform reinforcement lengths Select fill in reinforced Zone Minimum block embedment of 2 feet Creep/Durability reduction applied to the connection. Typically used on public projects
Introduction to Segmental Retaining Walls Gravity • No soil reinforcement • Height limitations • Relies on block weight, setback to resist soil forces • Requires less work area behind structure
Geosynthetic-Reinforced • Soil reinforcement used • No height limits • Used for larger applications • Requires larger work area behind • structure
Gravity Wall Weight of Block
Weight of Soil
Geosynthetic Reinforced Wall
Geosynthetic Reinforced Wall •
• • •
Wall is taller than maximum gravity height and has special conditions Contact a qualified engineer Your wall requires geosynthetic reinforcement You’ll need a cross-section to estimate the quantity of grid needed.
Soils and Geosynthetic Reinforcement
Soil
What Soils Do You Have On The Site? • Coarse Grained Soil: • Fine Grained Soils:
Sand/gravel Clay/silt
Which Soil Is Ideal?
Soil Zones Active Soil Zone
At Rest Soil Zone
Soils Up to 90% of a SRW system is soil Identify What You Have on Site: 1. 2. 3.
Soil Types and Friction Angle Soil Testing prior to construction QA/QC Testing during construction
Geosynthetic Reinforcement
Geogrids and Geotextiles • Geosynthetics
How Reinforcement Works
Without Reinforcement
Adding Reinforcement
Reinforced Soil Mass
Aesthetics Evolved
Aesthetics
x x replace with beveled product – Diamond gray/tan
Beveled Split
Straight Split
Non Split
Match Architectural Block
Color Bands – Custom Colors
Offset Split
Capitalize on Color Texture and Scale
Fact Texture
Rustic Face Texture
Blended Colors
Varying Block Dimensions
Vertical Unit
Applications
Residential Construction
Outdoor Courtyards
Creating Usable Space
Amphitheater Seating
Stadium Seating
Tree Save Area
Stairs and Railings
Free standing Walls and Columns
Commercial Courtyards
Golf Course Design
Elevated & Island Greens
Multi-Family & Town Homes
Entrance Ways and Signage
Retail Development
Value-Engineering
Water Applications
Channel Flow and Wave Action
Retention Ponds
Detention Ponds
Culvert and Utilities
Tunnels add hawcreek bike path
Rail Road Loading
Extreme Loading
Elevated Vehicle Ramp
60’ Tall – Back to Back Walls
Traffic Barrier
X B L OCK FA CED J ERS EY B A RRI ER WX (N OT TO S CA L E)
Land Bridge Applications
DOT Construction
Design Solutions for Unique Applications
• add finished hawcreek photo
X TRI PL E-S TA CK ED WA L L , 2 6 -D EG CL A Y WX (N O T TO S CA L E)
Direct Anchorage
Soil Nail Applications
Direct Anchor Existing Structures
Timber Wall Repair
Rock Bolt Applications
Frictional Connection
Why specify SRW’s?
Design Versatility
Ease of Installation
Extended Design Life
Benefits of Specifying SRWs • • • •
Aesthetics Performance Flexibility Economical
Summary