Lateral Behavior of Post Grouted Drilled Shafts-Paper

Paper

Pdf Summary

The study evaluates the lateral behavior of post-grouted (base-grouted) drilled shafts, a technique primarily used to increase axial capacity and reduce settlement. Because little research has examined its effects on lateral response, researchers tested one grouted and one conventional 8.2-foot-diameter, 68.1-foot-deep shaft at the Wisconsin I-94 Zoo Interchange site.<br /><br />Axial tests showed that the grouted shaft had 47% greater base resistance and 30% greater total resistance at settlement equal to 1% of shaft diameter. Under lateral loading, it exhibited roughly half the movement of the conventional shaft, as well as less permanent deformation. The authors suggest that grout may have stiffened the soil–shaft interface and formed a bulb around the shaft base and lower sides.<br /><br />To interpret the results, the authors modeled the grouted shaft as having a hypothetical equivalent diameter about 20% larger. Lateral analyses using pressuremeter-based p-y curves and this increased diameter reproduced the measured response reasonably well. Analyses of the conventional shaft also generally agreed with test measurements.<br /><br />The findings indicate that base grouting may significantly increase lateral stiffness as well as axial resistance. However, the proposed equivalent-diameter approach is hypothetical, and results are based on a single tested shaft pair. The authors therefore advise against applying a lateral-design benefit for base grouting at this stage and recommend further field testing and research.

Keywords

post-grouted drilled shafts

base grouting

lateral response

axial resistance

soil-structure interaction

p-y curves

lateral stiffness

drilled shaft testing

equivalent diameter

Wisconsin I-94 Zoo Interchange