CENTER PRESTRESS TYPE PILE FOUNDATION

PURPOSE:To attain the resistance of a foundation structure against falling moments by a method in which a wire tension member is anchored to hard ground between piles driven into the foundation structure in such a way as to give a compressive force to each pile by the tension member. CONSTITUTION:A foundation structure 1 consisting of steel jackets having a threedimensional structure, built up by connecting three vertical tubular pillars 8 with a large number of concituous members 15, is installed on the upper layer 7 of hard stratum 3. Then, piles 2 are penetrated into each tubular pillar 8 until it reaches the hard stratum 3, and then cement mortar, etc., is injected into between the pile 2 and the tubular pillar 8. And, in the central part of the pile 2 group, small-diameter hole 4 is drilled in the hard stratum 3 by an excavator, a wire tension member 5 is inserted into the hole 4, and the lower end of the tension member 5 is anchored to the hard stratum 3. And, a compressive force is added to eah pile 2 by a nut 16 screwed with the tension member 5.