PRELOADING AND HEAD CONNECTION METHOD FOR MICROPILE-Paper

Paper

Pdf Summary

The paper presents a new method for preloading micropiles installed through existing foundations and securing their connection to the footing. Preloading transfers part of the existing load to the micropiles before additional structural loads are applied, helping limit settlement and prevent overloading of the original foundation.<br /><br />The system uses a steel cone and split-threaded wedges. After installing the micropile, workers position the cone and wedges in the footing’s core hole, then use hydraulic jacks and reaction rods to engage the wedges with the concrete and preload the pile. Nuts lock the preload into the micropile, and the core hole is filled with non-shrink grout. Compared with conventional methods, the system avoids equipment such as reaction beams and tie-down anchors, potentially reducing installation time and cost.<br /><br />Displacement-controlled compression tests compared micropile-to-footing connections. The results indicated that interlocking between the wedges and existing concrete increases the connection’s total structural capacity.<br /><br />The authors conclude that the method offers an efficient, economical option for strengthening existing foundations, subject to project-specific needs. They note that further research is required, particularly on long-term prestress loss and wedge–concrete interlocking under different preload conditions.

Keywords

micropile

preloading

foundation strengthening

footing connection

structural capacity

hydraulic jacks

split-threaded wedges

non-shrink grout

settlement control

prestress loss