Micropile to Footing Connections- Findings of the CPF Research-Video

Video Transcription

Video Summary

The presentation discusses research on connections between micropiles and existing concrete footings, focusing on compression-loaded, grouted connections. Earlier U.S. and Portuguese tests showed that connection behavior depends on grout-annulus thickness, concrete and grout properties, confinement, reinforcement, edge distance, and surface texture.<br /><br />Failure is driven mainly by dilation and friction, not lasting adhesion: as a micropile moves, it pushes surrounding material outward, creating stresses and often cracking the concrete. Reinforcement and external confinement increase resistance. Smooth casings may lose capacity suddenly, especially in unreinforced concrete near a footing edge; shear rings are also less effective without adequate confinement.<br /><br />The presenter outlines methods for estimating resistance using cavity-expansion mechanics and the contribution of concrete and reinforcing steel, while emphasizing that predictions remain uncertain and may be conservative. Recommendations include minimizing grout thickness, avoiding connections within 24 inches of edges in unreinforced footings, and checking other failure modes separately. More testing and numerical modeling are needed to develop reliable design guidance.

Keywords

micropile connections

concrete footings

grouted compression

cavity expansion

reinforcement confinement

edge distance