1. American Concrete Pipe Association Short Course
Superstructure Loads
What Precast Pipe and Box Designers Need to Know About Mechanically Stabilized Earth (MSE) Walls
American Concrete Pipe Association Short Course
Orlando Florida
Tuesday March 3rd, 2015
WAYNE HODGE, PE

2. Presentation Topics: Basic Understanding of MSE Walls
Culvert / MSE Interaction
Understanding and Addressing the Complexities of Designing Each System

3. Basic Understanding of MSE Walls

4. What Are MSE Walls?
MSE walls are earth retaining structures that are constructed by placing alternating layers of reinforcement and compacted soil behind a facing element to form a composite material which acts integrally to restrain lateral forces.

5. MSE Wall Components Facing Panels Reinforced Fill Reinforcement
Leveling Pad

6. What year was the modern method of soil reinforcement developed?
1895
1921
1957
1982

7. Historical Overview of MSE Walls
Henri Vidal develops reinforced soil concept.

8. Historical Overview of MSE Walls
Henri Vidal develops reinforced soil concept.
1963 – Vidal first publishes his research and files the patent for Reinforced Earth®

9. Historical Overview of MSE Walls
1971 – Vidal brought his technology to the US
1972 – First MSE wall constructed in US (California SH 32 near Los Angeles)
1974 – First Reinforced Earth structure in US to be used as bridge abutment (I-80 near Lovelock, NV)

10. Historical Overview of MSE Walls
1970’s – Introduction of competitive wall systems using welded wire grids.
1980’s – Introduction of geosynthetic reinforced walls.
1990’s – dramatic increase in the use of geosynthetic reinforced walls with the introduction of segmental retaining walls.

11. Historical Overview of MSE Walls
Currently over 60,000 MSE walls higher than 35 ft are in service along the US highway system.
Approximately 9 million ft2 are added annually, accounting for more than half of all types of retaining wall usage.

12. Sea-Tac Third Runway

13. MSE Wall Applications

14. Advantages of Using MSE Walls
Low Cost
Ease of Construction
Structural Tolerance to Foundation Settlement
Performance under seismic loading events
Wide range of possible facing types, colors, and textures.

15. Systems / Manufacturers
KeySystem I by Keystone Retaining Wall Systems, Inc.
Mesa HP System by Tensar Earth Technologies, Inc.
Reinforced Earth Classic Panel by The Reinforced Earth Company
EarthTrac HA by Earth Tec International, LLC
Sanders MSE Wall by Sanders Pre-Cast Concrete Systems Company
Strengthened Soil by Shaw Technologies
Sine Wall by Sine Wall, LLC
MSE Plus by SSL Construction Products
Vist-A-Wall by Vist-A-Wall Systems, LLC
Tricon Retained Soil by Tricon Precast

16. Facing Systems
Segmental Precast Concrete Panels
Dry Cast Modular Block Wall (MBW) Units
Welded Wire Mesh (WWM)
Gabion Facing
Geosynthetic Facing
Post-Construction Facing

17. Reinforcement Types Materials Configurations Metallic Geosynthetics
Strips
Straps
Grids
Mesh

18. Failure Modes of MSE Walls
External Stability
Internal Stability
Compound Stability

19. External Stability
Sliding
Bearing Capacity
Eccentricity
Overall Stability

20. Internal Stability
Reinforcement Rupture
Reinforcement Interaction with Reinforced Fill
Connection Strength

21. Compound Stability
Modes initiated outside the reinforced zone and exit through the reinforcement and facing.

22. Construction Sequence of MSE Walls with Precast Panel Facings
Preparation of subgrade.
Placement of a leveling pad for the erection of the facing elements.
Erection of the first row of facing panels on the prepared leveling pad.
Placement and compaction of reinforced wall fill on the subgrade to the level of the first layer of reinforcement and its compaction.
Placement of the first layer of reinforcing elements on the wall fill.
Placement of the wall fill over the reinforcing elements to the level of the next reinforcement layer and compaction of the wall fill.
Construction of traffic barriers and copings.

23. Culvert / MSE WALL Interaction

24. Questions
Loads – Factored or Unfactored
Load Type – Dead Load or Live Load (Traffic Surcharge)
Influence Zone of Load
Load Distribution Through Soil
Back-to-Back Walls
Culvert Placement and Orientation

25. Comparison of MSE Wall Project Data

26. Understanding and Addressing the Complexities WHEN Designing Each System

27. Involvement of Multiple Entities
Owner / Agency
Project Civil / Structural Design Engineer
Geotechnical Engineer
MSE Wall Design Engineer
MSE Wall Supplier
MSE Wall Installer
QA Testing Firm
Precast Pipe/Box Supplier

28. Division of Responsibility
External Stability – Owner / Geotech Consultant
Global stability of structure
Bearing capacity analysis
Settlement analysis
Internal Stability – MSE Wall System Supplier / Designer
Pullout and rupture of reinforcements
Design of all wall system components
Check sliding and overturning
Determine eccentricity of structure and applied bearing pressure at base of structure

29. Design Methods Coherent Gravity Method Tieback Wedge Design Method
AASHTO Simplified Method
FHWA Structure Stiffness Method
K-Stiffness Method
Ehrlich and Mitchell Model

30. MSE Wall Specifications
ASD / LRFD
US / Metric Units
FHWA Standard Specifications for Reinforced Earth (MSE Walls)
AASHTO Standard Specification for Highway Bridge
AASHTO LRFD Bridge Design Specification
State DOT Specifications

31. Questions and Comments