Proposed AASHTO Specifications for the Seismic Design of Retaining Walls, Slopes and Embankments, and Buried Structures

The current AASHTO LRFD Bridge Design Specifications provide guidance for seismic design of retaining walls, but no guidance for seismic is provided for the design of slopes and buried structures. Guidance for retaining walls relies on the Mononobe-Okabe (M-O) equations for seismic active and passive earth pressure determination. Designers have found that the M-O equations have limitations. Specifically, the M-O equation for seismic active earth pressure results in unrealistically high pressures for some combinations of ground motion and wall geometry, as well as uncertainties where soils are not homogeneous and cohesionless. For passive earth pressures the M-O equation is based Coulomb failure theory which is believed to be inaccurate for some loading conditions. Realizing the limitations in the M-O equations and the absence of guidance for seismic design of slopes and buried structures, the National Cooperative Highway Research Program (NCHRP) Project 12-70 was conducted to update current design methods. The NCHRP 12-70 Project focused on free-standing retaining walls, cut and fill soil slopes, and small-diameter buried structures used for drainage and for pedestrian access. The products of the project included developing (1) recommendations on design ground motions, including effects of wave scattering, (2) an updated method for estimating permanent ground movement, (3) charts for including effects of cohesion in seismic earth pressure calculations, and (4) a generalized limit equilibrium approach for evaluating seismic active earth pressures for sites involving cohesive soils and complex site geometries. Draft specifications describing methods to follow during seismic design of retaining walls, slopes and embankments, and buried structures were also developed. This paper summarizes Project accomplishments.

• Corporate Authors:

  Multidisciplinary Center for Earthquake Engineering Research

  State University of New York, 107 Red Jacket Quadrangle, P.O. Box 610025
  Buffalo, NY  United States  14261-0025
• Authors:
  • Anderson, Donald G
  • Martin, Geoffrey R
  • Lam, I P
  • Wang, JN
• Conference:
  • Sixth National Seismic Conference on Bridges and Highways
  • Location: Charleston SC, United States
  • Date: 2008-7-28 to 2008-7-30
• Publication Date: 2008

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 12p
• Monograph Title: Sixth National Seismic Conference on Bridges and Highways: Seismic Technologies for Extreme Loads

Subject/Index Terms

• TRT Terms: Cohesive soils; Earthquake resistant design; Embankments; Granular soils; Retaining walls; Seismicity; Slopes
• Identifier Terms: AASHTO Guide Specifications for LRFD Seismic Bridge Design; Mononobe-Okabe (M-O) equation
• Uncontrolled Terms: Wave scattering
• Subject Areas: Bridges and other structures; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 01355101
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 25 2011 11:46AM