NOVELTY - The method involves pressure injecting a non-hardened concrete (4) from a front-tip portion of a rod and pulling up the rod of an excavator, after the rod of the excavator attains a target depth. The concrete is filled into a stake hole (2) with a non-hardened state. A reinforcement cage (3) in which a heat collection piping (5) is installed with respect to the stake hole, is inserted after extracting out the rod of the excavator from a stake hole and before non-hardened concrete hardens. The concrete is hardened and a foundation pillar (1) is generated.    USE - Heat-collection piping-installation method used for forming foundation pillar (claimed) using geothermal heat.    ADVANTAGE - The reinforcement cage in which heat-collection piping was installed with respect to the stake hole is inserted, so that even when it directly attaches to the support frame for reinforcement assemblies of a reinforcement cage, without providing a supporting segment and providing heat collection piping in a position far from the reinforcement of a reinforcement cage, it can avoid worsening the fillability of concrete. Thus a number of parts can be reduced, and the fillability of concrete is ensured. Since a foundation pillar can be constructed without pouring stabilizing liquid, the chipping operation of the defect concrete produced by pouring of stabilizing liquid becomes unnecessary. Thus the damage to heat-collection piping accompanying a chipping operation can be prevented suitably. Since a different builder especially from the connection of a reinforcement cage and the connection of heat-collection piping carries out in many cases, it can prevent that the builder which connects a reinforcement cage, and the builder which makes the connection of heat-collection piping mix in confusion by a construction site, and can greatly contribute to protraction prevention of a construction schedule. Thus the beam form and rigidity of reinforcement cage is improved by providing the circumference of the several main reinforcements with the hoop reinforcement. The reinforcement cage can be inserted easily when inserting a reinforcement cage into a stake hole, thus, when inserting a reinforcement cage in non-hardened concrete by forming the acute portion in the returning portion, the heat-collection piping attached to the reinforcement cage can be easily inserted in non-hardened concrete.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for foundation pillar.    DESCRIPTION OF DRAWING(S) - The drawing shows the side view of a foundation pillar constructed by heat collection piping-installation process. (Drawing includes non-English language text)    Foundation pillar (1)    Stack hole (2)    Reinforcement cage (3)    Non-hardened concrete (4)    Heat collection piping (5)