SEISMIC DESIGN OF REINFORCED EARTH WALLS - DISCUSSION

The case history is described of vibration effects on a reinforced earth wall, the total height of which is 3.75 m and consists of concrete elements measuring 1.50 m x 1.50 m each with six ties of galvanized steel measuring 60 mm x 3 mm in section and 5 m in length. Ties are spaced at intervals of 75 cm vertically and 50 cm horizontally. Static compaction was applied in a zone of approx 2.5-m width adjacent to the wall in order to avoid the buildup of excessive earth pressures. Despite these precautions, outward deflections of the wall top of 8 cm - 10 cm occurred during construction and backfilling. Additional lateral deflections of the wall top of approx 10 cm occurred during the first 4 months after completion. Within the same period, the wall settled vertically approx 20 cm and the center of the embankment settled approx. 30 cm. The cause of the wall deflections during construction appear to have been caused by a partial pull out of the ties due to a superposition of factors related to reduction of soil tie friction resulting from vibrat ions (for compaction), and increase of the earth pressure above the active state. The discussers do not feel that the design of reinforced earth walls should generally be based on "at rest" earth pressures if vibrations occur. However, the effects of vibrating construction equipment should be evaluated in view of the backfill and equipment properties as well as the wall geometry. The risk of a pull out of the ties could be reduced by providing some sort of protrusions on the tie surface in order to increase the friction between the steel ties and the soil.

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Filing Info

  • Accession Number: 00134654
  • Record Type: Publication
  • Report/Paper Numbers: ASCE #11143
  • Files: TRIS
  • Created Date: Jun 23 1976 12:00AM