Strengthening of Existing Building Foundations by Micropiles-Paper

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The paper describes the use of micropiles to strengthen five existing column foundations in an operating process plant. The plant planned to replace a 20-tonne overhead travelling crane with a 25-tonne crane, increasing loads on some foundations. Conventional options—grouting beneath the footings or extending them within the building—were rejected because they would disrupt operations and require construction inside the shop.<br /><br />The selected solution installed micropiles outside the building and connected them to extensions of the existing foundations. Each strengthened foundation was designed with four 250 mm diameter, 18 m long micropiles. The piles had allowable capacities of 420 kN in compression and 310 kN in tension; their lateral capacity was 13 kN at a permitted 5 mm deflection. Hollow 73/56 Ischebeck TITAN bars served as both reinforcement and grout delivery channels, avoiding the need for separate temporary casing.<br /><br />New pile caps were integrated with the existing foundations using chemically anchored rebar dowels, designed to resist shear and tension. The approach was suited to the site’s limited access and space, and could be installed using lightweight drilling equipment with little noise, vibration, or spoil.<br /><br />The authors conclude that this arrangement provided the required foundation capacity for the heavier crane while minimizing interference with plant operations. Preparatory work, temporary restriction on crane use near the affected columns, and initial pile load testing were identified as important construction requirements.

Keywords

micropiles

foundation strengthening

existing foundations

crane upgrade

process plant

pile caps

chemical anchoring

Ischebeck TITAN bars

limited access construction

load testing