POST GROUTING DRILLED SHAFT TIPS. PHASE I

This report presents results from a two-year experimental study to evaluate the effects of post-grouting drilled shaft tips in and on the bearing capacity. Both model scale and full-scale tests were conducted on drilled shafts whose tip had been grouted using various grouting systems (flat jack, sleeve port (tube-a-manchette), and sleeve port systems with and without a backing plate). In the model tests, 24 shaft specimens were cast and tested in a Frustum Confining Vessel. This vessel provided the means to simulate soil pressure distributions similar to those expected in the field. Comparisons were made between shafts cast without post grouting (controls) and those grouted using a flat jack type grouting cell. Improvement was found to be somewhat proportional to grout take, but more closely proportionally to the maximum sustained grouting pressure. In the full-scale tests, a total of 12 Statnamic load tests were conducted on shafts constructed in three cohesionless soil types. At Sites 1 and 2, 24-in. diameter shafts were cast in shelly sand or silty sand. At Site 3, 48-in. diameter shafts were cast in sandy cemented coquina. Eight of the load tests were conducted on grouted shafts and four on ungrouted controls. The findings of these tests were similar to those found in the model scale tests in that the improvement was mostly closely proportional to maximum sustained grouting pressure. Based on the test results, design recommendations for the use of post grouted shafts have been prepared that use a grout pressure index (max sustained grout pressure/calculated bearing capacity) and the acceptable service limit displacement as expressed in percent shaft diameter. Construction, grout mix, and grouting guidelines have also been prepared using literature values as well as those found to be successful in this study.

• Corporate Authors:

  University of South Florida, Tampa

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

  Florida Department of Transportation

  605 Suwannee Street
  Tallahassee, FL  United States  32399-0450
• Authors:
  • Mullins, G
  • Dapp, S
  • Frederick, E
  • Wagner, R
• Publication Date: 2001-12

Language

• English

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 308 p.

Subject/Index Terms

• TRT Terms: Bearing capacity; Boreholes; Confining pressure; Granular soils; Grouting; Load tests; Prototype tests; Sand; Scale models; Silty sands; Specimens
• Uncontrolled Terms: Coquina; Drilled shafts
• Subject Areas: Bridges and other structures; Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00980569
• Record Type: Publication
• Report/Paper Numbers: Final Report
• Files: TRIS, STATEDOT
• Created Date: Oct 24 2004 12:00AM