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Publication Number: FHWA-RD-03-048
Date: September 2003

Effects of Geosynthetic Reinforcement Spacing on The Behavior of Mechanically Stabilized Earth Walls

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Technical Report Documentation Page

1. Report No.
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle
Effects Of Geosynthetic Reinforcement Spacing On The Behavior Of Mechanically Stabilized Earth Walls
5. Report Date
September 2003
6. Performing Organization Code
7. Author(s)
Christina Vulova and Dov Leshchinsky
8. Performing Organization Report No.
9. Performing Organization Name and Address
Department of Civil and Environmental Engineering
University of Delaware
Newark, DE 19711
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
12. Sponsoring Agency Name and Address
Office of Infrastructure Research and Development
Federal Highway Administration (FHWA)
6300 Georgetown Pike
McLean, Virginia 22101-2296
13. Type of Report and Period Covered
Final Report, Feb. 1999-August 2000
14. Sponsoring Agency Code
15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): M. T. Adams, HRDI-06
16. Abstract
The behavior of mechanically stabilized earth walls (MSEW) with modular block facing and geosynthetic reinforcement was investigated with numerical models that simulate construction of the wall, layer by layer, until it fails under gravity loading. The two-dimensional finite difference program Fast Lagrangian Analysis of Continua (FLAC), version 3.4, Itasca 1998, was used to carry out the numerical analysis. The material properties were based on data reported in the literature, which represent typical values used in design practice. Failure mechanisms of MSEW's were identified as a function of geosynthetic spacing considering the effects of soil strength, reinforcement stiffness, connection strength, secondary reinforcement layers, and foundation stiffness. The effects of reinforcement length on reinfrocement stresses and wall stability were also investigated. FLAC predictions were compared with the American Association of State Highway and Transportation Officials (AASHTO) design method. Additional numerical experiments were carried out to investigate the effects of some modeling parameters on wall response.Four failure modes of MSEW were identified: external, deep-seated, compound, and connection. The reinforcement spacing was identified as a major factor controlling the behavior of MSEWs. Two types of spacing were considered in studying the effects of spacing: small (less than or eequal to 0.4 m) and large (larger than 0.4m). Increasing reinforcement spacing decreased the wall stability and changed the predominant failure mode from external or deep-seated to compound and connection mode. Similar effects were identified when the soil strength, reinforcement stiffness, or foundation stiffness were decreased. Connection strength appeared to affect only the behavior of walls with large reinforcement spacing, i.e., increased strength, decreased wall displacements, improved wall stability, and changed failure mode. Similar effects were identified when secondary reinforcement layers were introduced in a model with large reinforcement spacing. Increased reinforcement length improved wall stability and decreased wall displacements and reinforcement forces.A comparison between FLAC predictions and AASHTO calculations demonstrated a good agreement. The comparisons indicated that the existing design method could distinguish the modes of failure identified by FLAC analysis, especially those due to external stability. However, AASHTO disregards the effect of reinforcement spacing and thus, considers an external wedge always to develop internally.
17. Key Words
block walls, external stability, failure mechanism, FLAC, geosynthetic reinforcement, interface effects, internal stability, MSE walls
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
19. Security Classif. (of this report)
20. Security Classif. (of this page)
21. No. of Pages
22. Price

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