Seismic Pressures on Retaining Walls 

 

Introduction

 

The determination of seismic earth pressures acting against retaining walls is a complex soil-structure interaction (SSI) problem. Factors which affect these earth pressures include:

  1. The nature of the input motions which includes the amplitude, frequency, directivity and duration of the motion.
  2. The response of the soil behind, in front & underlying the wall.
  3. The characteristics of the wall, which includes the strength and bending stiffness of the wall.

 

The pseudo-static class of analysis is most commonly used in design and makes use of the free-field Peak Ground Acceleration (PGA ) expressed as a Seismic coefficient, C  (/g) typically obtained from national design standards (e.g., NZTA Bridge Manual, 2014).

 

Question:  Can Co  be optimized for New Zealand?

 

Project

 

  • Perform two-dimensional dynamic finite element analyses using OpenSees Consider 2 soil classes (Classes C &D) (NZS 1170.5:2004)
  • Use appropriate NZ acceleration-time histories for two zones in North Island & one for South Island, and allowance for magnitude scaling
  • Analyses for two embedded cantilever wall heights (2m and 3m) & one double propped wall height (3m, with two different prop stiffnesses)
  • Carried out 946 dynamic analyses run

 

Pseudo-static analyses 

 

Example results for Christchurch, Shallow Soils, Soil Class C

 

 

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Last updated: 24/09/15
 

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