Concrete foundation structure and method for constructing same
Provided are a concrete foundation structure capable of firmly fixing a precast concrete foundation to a ground, and a method for constructing the concrete foundation structure. A concrete foundation structure 10 includes a precast concrete foundation 16 having a projecting portion 30 embedded in a ground G. An anchor plate 20 is placed inside an excavation hole 18 formed in the ground G, and the precast concrete foundation 16 and the anchor plate 20 are connected by a connecting member 22 . In the excavation hole 18 , a backfill portion 24 is formed of a backfill material 94 including a solidifying material and soil. A filler layer 26 is formed of a filler 96 containing a solidifying material between the precast concrete foundation 16 and the backfill portion 24 . The precast concrete foundation 16 has a through-hole 42 through which the connecting member 22 is inserted, and the filler 96 forming the filler layer 26 is filled through the through-hole 42.
1. A concrete foundation structure comprising:
a precast concrete foundation placed on a surface of a ground;
an excavation hole formed by excavating the ground below the precast concrete foundation;
a plate-shaped anchor plate placed inside the excavation hole;
a rod-shaped connecting member connecting the precast concrete foundation and the anchor plate;
a backfill portion formed by backfilling a backfill material including a first solidifying material in the excavation hole; and
a filler layer formed by filling a filler including a second solidifying material between the precast concrete foundation and the backfill portion, wherein
the precast concrete foundation comprises:
a foundation body formed to cover the backfill portion from above; and
a projecting portion provided to project downward from an outer periphery of the foundation body and embedded in the ground.
2. The concrete foundation structure according to claim 1 , wherein the projecting portion is formed annularly on the outer periphery of the foundation body.
3. The concrete foundation structure according to claim 1 or 2 , wherein
the foundation body is provided with a through-hole through which the rod-shaped connecting member is inserted, and
a portion of the rod-shaped connecting member projecting upward from the through-hole is provided with a movement preventing portion that contacts the foundation body and prevents the precast concrete foundation from moving upward.
4. The concrete foundation structure according to claim 3 , wherein
the filler is filled in the through-hole, and
the filler filled in the through-hole is continuously integrated with the filler forming the filler layer.
5. The concrete foundation structure according to claim 4 , wherein the through-hole is formed to have a cross-sectional area decreasing downward.
6. A method for constructing a concrete foundation structure, comprising:
a step (a) of excavating a ground to form an excavation hole;
a step (b) of attaching a plate-shaped anchor plate to a lower end of a rod-shaped connecting member, and placing the anchor plate and the rod-shaped connecting member inside the excavation hole;
a step (c) of backfilling a backfill material including a first solidifying material in the excavation hole to form a backfill portion, and projecting an upper end of the rod-shaped connecting member upward from an upper surface of the backfill portion;
a step (d) of preparing a precast concrete foundation having a foundation body provided with a through-hole through which the rod-shaped connecting member is inserted;
a step (e) of placing the precast concrete foundation on a surface of the ground and inserting the rod-shaped connecting member through the through-hole;
a step (f) of filling a filler including a second solidifying material between the precast concrete foundation and the backfill portion; and
a step (g) of attaching a movement preventing portion to a portion of the rod-shaped connecting member projecting upward from the through-hole, the movement preventing portion contacting the foundation body and preventing the precast concrete foundation from moving upward.
7. The method for constructing the concrete foundation structure according to claim 6 , wherein
in the step (f), the filler is also filled in the through-hole, and
the filler filled between the precast concrete foundation and the backfill portion and the filler filled in the through-hole are continuously integrated together.
8. The method for constructing the concrete foundation structure according to claim 6 , wherein in the step (f), the filler is filled between the precast concrete foundation and the backfill portion through the through-hole.
9. The method for constructing the concrete foundation structure according to claim 6 , wherein in the step (c), the backfill portion is compacted.
10. The method for constructing the concrete foundation structure according to claim 6 , wherein in the step (e), a height adjuster having a male screw extending in a vertical direction and a female screw screwed onto the male screw is attached to a side surface of the precast concrete foundation, and the male screw is rotated to adjust a length of a portion of the male screw projecting downward from the precast concrete foundation, so that a height of the precast concrete foundation is adjusted.