Liquefaction Induced Downdrag on Piles and Drilled Shafts

Sandy soil layers reduce in volume during and following liquefaction. The downward relative movement of the overlying soil layers around drilled shafts induces shear stress along the shaft and changes the axial load distribution. Depending on the site conditions, the change in the axial responses that result from liquefaction-induced settlement and the drag load can have a significant impact on the performance of drilled shafts in seismic regions. This study presents an analytical method to quantify the effects of liquefaction-induced downdrag on drilled shafts. The analytical method is based on the neutral plane method originally developed for clays but modified to account for liquefaction-induced effects. The neutral plane method is a simplification of soil-shaft interactions and is more representative of actual conditions compared to other methods. In this study, the neutral plane method was applied to an observed case of downdrag during the 8.8 magnitude earthquake in Maule, Chile and was able to predict the liquefaction-induced settlement that was the major cause of failure of the structure. The developed procedure is illustrated for two field cases of drilled shafts in liquefiable soils in Washington State.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Research Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 162p

Subject/Index Terms

Filing Info

  • Accession Number: 01644651
  • Record Type: Publication
  • Report/Paper Numbers: WA-RD 865.1
  • Contract Numbers: Agreement T4120, Task 26
  • Created Date: Aug 29 2017 10:09AM