Post on 19-Feb-2021
transcript
Best Practices for
Design and Construction
of MSE Walls
Robert A. Gladstone, P.E.
Executive Director
Association for Mechanically Stabilized Earth
Geotechnical Consultant Workshop
Ohio Department of Transportation
June 7, 2017
Best Practices for Design and Construction
of MSE Walls
NOT a Best Geotechnical Practice
Best Practices for Design and Construction
of MSE Walls
Common MSE Wall Systems
Segmental Blocks, Steel
or Geosynthetic
Reinforcements
Welded Wire Facings, Steel
or Geosynthetic
Reinforcements
Precast Facing Panels,
Steel or Geosynthetic
Reinforcements
Best Practices for Design and Construction
of MSE Walls
Design Roles and Responsibilities
• MSE Designer
• Civil / Structural
• Geotech• Owner
Service Life Requirements
Aesthetic Requirements
Acceptable Wall Types
Global Stability
Bearing Capacity
Settlement
Acceptable Wall Types
Internal Stability
Detailed facing and
reinforcement design
Construction drawings
Site Grading
Wall Location
DRAINAGE DESIGN
Acceptable Wall Types
Loading
Best Practices for Design and Construction
of MSE Walls
Design Responsibility
• Internal Stability – MSE wall system supplier
• Simple check of sliding and overturning
• Determine eccentricity and applied bearing pressure
• Check reinforcement pullout and rupture
• Design of wall system components
• External Stability – Owner or Consultant
• Owner proposing to build the structure in the specified location
• Therefore, owner is responsible for investigating feasibility
• Includes: global stability, bearing capacity, settlement analysis
Best Practices for Design and Construction
of MSE Walls
Global Stability
Best Practices for Design and Construction
of MSE Walls
Options for Bearing Capacity and Settlement
Best Practices for Design and Construction
of MSE Walls
Specify Requirements in
Contract Drawings
Best Practices for Design and Construction
of MSE Walls
Contract Specifications
Best Practices for Design and Construction
of MSE Walls
Contract Drawings
Best Practices for Design and Construction
of MSE Walls
Design Parameters
• Design usually based on assumed parameters
• These parameters are actually a good choice:
• 34o is maximum value permitted by AASHTO without test data
• 34o is approximately the mobilized shear that will develop
• 34o has been assumed in design for 4 decades
* Foundation soil design parameters
should be clearly defined in the contract documents
Soil Type Unit WeightFriction
Angle
Select Granular fill 125 pcf 34°
Retained Fill 125 pcf 30°
Foundation Soil * ----- 30° *
Best Practices for Design and Construction
of MSE Walls
Coherent Gravity Design
W
Sliding Resistance
Vertical Pressure
E
Facing
Reinforced Soil
Best Practices for Design and
Construction of MSE Walls
Meyerhof Bearing Pressure Distribution
V = e=
V = BEARING PRESSURE
V = SUM OF VERTICAL LOADS
L = REINFORCING STRIP LENGTH
e = ECCENTRICITY OF STRUCTURE
DUE TO APPLIED LOADS
MC = SUM OF MOMENTS ABOUT
CENTER LINE DUE TO APPLIED
LOADS
V
L - 2e
MC
V
Best Practices for Design and Construction
of MSE Walls
Characteristics of the
Coherent Gravity Method
Best Practices for Design and Construction
of MSE Walls
Fabrication / QC and QA
Best Practices for Design and Construction
of MSE Walls
Pre-Construction Meeting
• Attendance
• MSE wall Rep, Resident Engineer, Inspector, Wall Foreman and Crew
• Presentation by MSE wall Rep
• Detailed MSE wall construction procedures
• Compaction of backfill and installation of soil reinforcements
• Project specific details – drainage structures, obstructions, etc
• Inspection
• What to look for, what will be required
• General discussion
• Discuss what's important to: Resident, Inspector, Contractor
Best Practices for Design and Construction
of MSE Walls
MSE Wall Construction
Best Practices for Design and Construction
of MSE Walls
Duties of MSE Wall Rep
• On site for start up of wall construction – 2 to 3 Days
• Instruct on installation of MSE wall components
• Instruct on backfilling within the MSE wall volume
• Answer questions of contractor and inspector
• MSE wall rep is NOT the Inspector
• The MSE wall Rep is employed by the Contractor
Best Practices for Design and Construction
of MSE Walls
Construction Inspection
Minimum 95%
Standard Proctor
Density Required
CONSIDER:
NHI training course # 132080:
Inspection of Mechanically Stabilized
Earth Walls and Reinforced Soil Slopes
Best Practices for Design and Construction
of MSE Walls
Backfill Selection is Critical
Clay backfill =
poor friction and
drainage
Good friction
and drainage
come from
granular
backfill
Best Practices for Design and Construction
of MSE Walls
Backfill Materials
Granular Fill
Expanded Shale
Crushed Stone
LWFC Fill
Best Practices for Design and Construction
of MSE Walls
Granular Backfill for MSE Walls
• Gradation limits per AASHTO
• Some states use different gradation limits and/or reduce fines
• FHWA allowed up to 25% fines in the early 1980s
• Backfills often exceeded this limit, up to 35% fines
• Facing panel alignment was difficult to achieve
• FHWA and AASHTO returned to 15% limit on fines
U.S. Sieve Size Percent Passing
4” 100
3” 75-100
#200 0-15
Best Practices for Design and Construction
of MSE Walls
Flat Plate Tamper
within 3 ft. of Wall Face
Compaction is Important
Minimum 95%
Standard Proctor
Density Required
Large Roller Stay 3 ft. Away
Best Practices for Design and Construction
of MSE Walls
Installation of Soil Reinforcements
Best Practices for Design and Construction
of MSE Walls
Reinforcement Connections are Critical
Best Practices for Design and
Construction of MSE Walls
Accommodating Differential Settlement
Perpendicular to the Face of Wall
2" Typical for
Normal
Construction
4" to 6" if
expect large
settlement
Best Practices for Design and Construction
of MSE Walls
Critical Bottom of Wall Details
• Adequate Foundation Soils
• Embedment
• Underdrain
Best Practices for Design and Construction
of MSE Walls
Drainage Within MSE Walls
Best Practices for Design and Construction
of MSE Walls
Angles Shift Reinforcements
at Inlets and Manholes
Best Practices for Design and Construction
of MSE Walls
Pipes Behind Walls
Best Practices for Design and Construction
of MSE Walls
Precast Traffic Barrier Design
4’-6”
Important: Coping Lip Required
Best Practices for Design and Construction
of MSE Walls
Membrane
with
Traffic
Barrier
Best Practices for Design and Construction
of MSE Walls
Locate Guiderail Posts - Skew Reinforcements
Best Practices for Design and Construction
of MSE Walls
Membrane with Guiderail Posts
Best Practices for Design and Construction
of MSE Walls
Precast Coping Detail
Best Practices for Design and Construction
of MSE Walls
There was a Reason for This!
• MSE Designer
• Civil / Structural
• Geotech• Owner
Service Life Requirements
Aesthetic Requirements
Acceptable Wall Types
Global Stability
Bearing Capacity
Settlement
Acceptable Wall Types
Internal Stability
Detailed facing and
reinforcement design
Construction drawings
Site Grading
Wall Location
DRAINAGE DESIGN
Acceptable Wall Types
Loading
Best Practices for Design and Construction
of MSE Walls
Implementing Best Practices
Produces
Beautiful Long-Performing Structures
That Reason Is …
Best Practices for Design and Construction
of MSE Walls
Some of Ohio's Best
I-90 Cleveland
(2015)
In Great
Condition!
(1984 – 33 yrs)
I-75 Dayton
(Wright
Brothers)
Best Practices for Design and Construction
of MSE Walls
Thanks for Listening
Front Street
City of Berea
Seneca-Jones Road over
CSX RR, Seneca County
US 23 & US 30 Interchange
Wyandot County