Cast-in-place pile by double dynamic drilling in complex formation

The common method used in construction of bored piles in complex formation, such as “three-large-stone” formation and rock, is the punching method. Sometimes, blasting, rotary drilling, DHD (down-hole hammer drilling), or their composite method are also used in the same formation. However, the pile-forming efficiency is lower due to the complex pile-forming process. The upper and lower rotary power devices, high pressure DHD, alloy boring crown and spiral drill pipe, produced by Korea, are integrated with Chinese domestic hydraulic walking or crawler pile machine, and the casing pipe is designed as the drill tool. Then a double dynamic drilling tool with high drilling ability in the complex formation is formed. Drilling cutting is discharged from the unearthed port by spiral drill pipe, so the defect of poor slag dumping in wet ground for DHD is overcome. The technology of fast plugging pipe is used to shorten the connect time and reduce the starting friction between the pipes and the soils in pipe sinking and pulling. The new method is a kind of environmental protection construction method due to the soil slag dry-dumping technique. Engineering practice shows that 5~7 piles are made by using the new method in 1 day. Compared with that of the punching method, the pile-forming efficiency is greatly improved by the new method.