POST GROUTING DRILLED SHAFT TIPS. PHASE II

This report presents results from a two-year study of the effects of post grouting drilled shaft tips. The objectives include reviewing construction sites where post grouted shafts may be a plausible alternative, instrumenting and monitoring grout tests and load tests of grouted and ungrouted shafts, developing design software for shafts with post grouted tips, and updating a database of post grouted shaft performances. Design curves generated from boring logs from 25 sites showed both the ungrouted and grouted capacity of drilled shafts. Predicted improvement from using post grouted over conventional shafts ranged from 195 to 1266% for sites with shafts tipped in sand and 3 to 91% for sites with shafts tipped in clay. The entire research project involved instrumentation, grouting and load testing of 8 full-scale test programs involving 26 test shafts tipped in sand, clay and silt. Improvements ranged from 40 to 743% in various soil types and consistencies. A software program capable of predicting the capacity of both conventional and post grouted shafts was developed and updated with new data sets made available by the Phase II efforts. Information obtained from post grouted shafts tipped in clay and silt provided rationale for capacity predictions in those soils. Likewise, information obtained from additional tests in sand was used to update the correlations developed in Phase I of the study. Given the variance in end bearing that can be observed for conventional shafts, it was recommended that the design approach developed in Phase I be updated to not only include the new data, but also to reevaluate the use of the control shaft data as the basis for the improvement ratio. The grouted shaft response which is relatively unaffected by construction variations would be compared to the predicted end bearing based on boring log information. This increases the breadth of the sandy soils encountered while also better representing various construction practices.

  • Corporate Authors:

    University of South Florida, Tampa

    Center for Urban Transportation Research, 4202 East Fowler Avenue
    Tampa, FL  USA  33620-5375

    Florida Department of Transportation

    605 Suwannee Street
    Tallahassee, FL  USA  32399-0450
  • Authors:
    • Mullins, G
    • Winters, D
  • Publication Date: 2004-6

Language

  • English

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: v.p.

Subject/Index Terms

Filing Info

  • Accession Number: 00980570
  • Record Type: Publication
  • Report/Paper Numbers: Final Report
  • Files: TRIS, STATEDOT
  • Created Date: Oct 24 2004 12:00AM