Abstract
In construction of artificial ground and other structures above railway tracks, foundation piles are placed in narrow spaces with small overhead clearance, that is, between tracks, below catenaries or under platform roofs. Aimed at providing an effective solution for such work, a technique was developed, which needs no auxiliary work such as hole wall protection, and employs steel pipe piling capable of reinforcing the pile foot (small-overhead-clearance foot-reinforced steel piling method), and its bearing properties were validated by means of vertical loading tests. In this technique, an improved small piling machine was used to bore a hole by placing short steel pipes (3.0 m or less, 700 mm in diameter) under pressure, and cement milk was jetted out through the end of the joined pipe pile to reinforce the pile foot. The vertical loading test verified that the steel pipe pile placed in this way had vertical bearing capacity equivalent to the foot-reinforced pile installed by inner excavation. In addition, it was demonstrated that cement milk filling around the steel pipe at the pile end increased the skin bearing capacity in the zone filled with cement milk. Furthermore, the authors confirmed that even if the calculation equation for cast-in place pile that has a skin bearing factor larger than that of inner-excavation leg-reinforced pile, the newly developed pile has an equivalent or superior skin bearing capacity.
