Proceedings - Fifth International Conference & Exhibition on Piling and Deep Foundations, 1994, Bruges, Belgium, (DFI)
Construction of piles of high bearing capacity in compacted sandy soil
T. Tsuchiya & M. Kakurai
A new piling method has shown promise with its demonstrated ability to efficiently mobilize shaft friction resistance and end bearing capacity in compacted and sandy soils with N-value in the range from 70 to 250. In this method, a high efficiency auger boring machine with casing is used for excavation. A cement past is then injected into the bottom of the borehole and a high strength steel H beam, supplementing the building’s foundation is inserted. In order to confirm the end bearing capacity of piles installed using this procedure, a vertical loading test up to a maximum load of 11 MN was conducted on a 22.7 m long pile in a 1000 mm diameter borehole. A 418 mm deep, 417 mm wide steel H beam was placed at the bottom of the borehole to insure a friction cut, except over a length of 4.5 m measured from the bottom of the pile. This piling method was employed in a top-down construction method of a structure with 13 stories above and 4 stories underground supported on a raft foundation. The excavation and the construction of the building frame from the first story to the third basement story were conducted concurrently. Steel H beams, 418 mm deep and 417 mm wide or 400 mm deep and 408 mm wide, with steel plates and stud connectors welded at the lower end were placed in boreholes 1000 mm in diameter. The bottom of the boreholes were located 7 to 9.5 m under the bottom of the raft foundation into a sandy layer. The piles withstood the maximum erection load of 6.3 MN and the excavation for the substructure was successfully completed.
|article #845; publication #36 (IC-1994)|