Method for underpinning an existing footing

摘要

A method for underpinning an existing footing of a building structure includes the steps of driving or drilling pile members into the ground on opposing sides of the footing, and forming concrete compression blocks on the opposing sides of the footing so that the concrete compression blocks are engaging relation with the footing and so that the concrete blocks are supported on the pile members. The method further includes the steps of drilling horizontal openings through the compression blocks and footing and extending post-tensioning strands through the openings. The post-tensioning strands are then tensioned to a predetermined load so that the compression blocks are urged into firm engaging and compressing relation with the footing. The earth beneath the footing and the compression blocks is then excavated wherein the footing and compression blocks are supported by the pile members. The load of the building is effectively transferred from the footing to the compression blocks by means of friction. A new foundation portion can then be formed directly beneath the existing footing while the footing is supported by the pile members.