Quality control supervision on metal structure installation of diversion bottom outlets

There are 22 joint crossing diversion bottom outlets in the dam of the Three Gorges Project Stage Ⅱ works. For each of these outlets, 4 gates are provided(i.e. stop log bulkhead gate with reverse hooks at the entrance, plane fixed wheel emergency gate, vertical framed radial working gate, stop log bulkhead with reverse hooks at the exit). The installation works of metal structures totals more than 20 000 t, including 88 sets of embedded parts for gate slots, 47 gate bodies. Before the installation works began, supervisory engineers had formulated controlling measures for quality supervision, signed and issued design documents,organized designers to tell contractors what their technical intentions are, examined and approved contractors construction plans and measures, inspected construction preparations, issued licences for starting construction, inspected arrival quality of construction equipment. After the installation works began, supervisory engineers conducted full process supervision of the installation works, taking an element project as basis and laying the stress on working procedure control. This paper presents the quality supervision of installation works, including manufacture and installation of steel dowels and first stage embedded parts, installation of second stage embedded parts for gate slots of plane gates and gate slots trial installation, installation of radial working gates and their embedded parts, installation and debugging of hydraulic hoists, etc.