Building pile foundation underpinning structure and underpinning method thereof

The invention relates to a building reinforcing device, in particular to a building pile foundation underpinning structure which comprises a bearing table, an underpinning pile and a high-strength supporting pipe, and the bottom end of the underpinning pile is fixed into a foundation through a fixing mechanism; the top end of the underpinning pile is detachably connected with a jack, and a piston rod of the jack abuts against the lower surface of the bearing table. The bottom end of the high-strength supporting pipe is fixedly connected with the top end of the underpinning pile, and the top end of the high-strength supporting pipe abuts against the lower surface of the bearing table. An old pile is fixedly arranged on the lower surface of the bearing table. The jack is convenient to disassemble. 本申请涉及建筑加固装置，尤其是涉及一种建筑物桩基托换结构，包括承重台、托换桩和高强度支撑管，所述托换桩的底端通过固定机构固定于地基内；所述托换桩的顶端可拆卸连接有千斤顶，所述千斤顶的活塞杆抵接于所述承重台的下表面；所述高强度支撑管的底端与所述托换桩的顶端固定连接，所述高强度支撑管的顶端抵接于承重台的下表面；所述承重台的下表面固定设置有旧桩。本申请便于将千斤顶拆卸下来。