Research of bored pile drilling technique under complicated geological condition

The foundation of super large bridge of Jinghu Express Railway over the Huaihe river is composed of eight bored piles whose diameter is 2.2m and the designed length of piles is 50m. The geological condition of bridge site is complicated and piles have to pass through six-meter thick granite. The drilling platform need to be built firstly at the position of the bored piles and then the air lifting reverse circulation drilling machine is used to the construction of bored piles. It was solved for the large diameter bored piles to be constructed in the deep water and complicated geological condition through the design and construction of deep water drilling platform, the drilling pressure and speed control under the different geological condition and so on. The research showed the bored piles could satisfy the technique request of express railway.