|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 PERFORMANCE OF MECHANICALLY STABILIZED EARTH WALLS
|5. Report Date
6. Performing Organization Code
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
Office of Infrastructure Research and Development
Federal Highway Administration (FHWA)
6300 Georgetown Pike
McLean, Virginia 22101-2296
|13. Type of Report and Period
Final Report, Feb. 1999-August 2000
|14. Sponsoring Agency Code
|15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): M. T. Adams, HRDI-06
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