WELLHEAD SYSTEM FOR VERTICAL SHAFT

PROBLEM TO BE SOLVED: To provide a safe wellhead system, using a concrete immersed shaft which does not need crushing of concrete of a pit mouth part or an expansible water stop packing such as a steel sheet pile shaft. SOLUTION: A concrete caisson 2 is bored in a pit mouth position, an annular water stop device 3 provided with a tenon part 3a is mounted on the inner circumference of an opening part 2a, an annular rubber-made first water stop packing 4 expansible to the inside is mounted on the tenon part 3a, an injection port 4a for injecting gas or liquid to the first water stop packing 4 is formed in the concrete caisson 2. A left steel plate 5 to be cut and removed after face cutting to pass an excavator therethrough is mounted on the outside of the opening part 2a for blocking, and a diversion steel plate 7 which forms a removable lid is mounted on the inside of the opening part 2a for blocking when the concrete caisson 2 is immersed. A second water stop packing 7 is mounted on the position where the diversion steel plate 7 is removed. When the excavator 8 reaches, the safety is enhanced by the double seal by the first water stop packing 4 and the second water packing 7. COPYRIGHT: (C)2010,JPO&INPIT