JPS6349765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a center prestress type pile foundation for a foundation structure.

Conventionally, in pile foundations for substructures such as steel jackets, it was difficult to drive the piles sufficiently due to hard ground such as rock in relatively shallow places, and it was difficult to drive the piles in to prevent the foundation structure from falling. If the pile cannot be expected to have sufficient pull-out resistance, a foundation structure 1 made of a steel jacket is installed on the upper ground 7 as shown in FIGS. After inserting an excavator from inside and making a vertical hole 9 in the hard ground below the pipe column 8, a hardening filler 11 such as mortar or concrete is injected into the vertical hole 9, and then the filler 11 (2) A method in which a pile 10 such as a steel pipe pile is inserted into the pipe column 8 and driven into the filler 11 in the pile hole 9 before the pile hardens, and the hardening of the filler provides pull-out resistance to the pile 10. As shown in FIG. 3, a pile 10 is inserted and driven into the pipe column 8 of the foundation structure 1, and then an excavator is inserted into the pile 10 to drive the pile into the hard ground 3 below the pile 10. A locking hole 12 with a smaller diameter than the inner diameter of the pile is drilled, and a steel pipe or steel rod with a smaller diameter than the pile 10 is drilled.
A locking member 13 such as a PS wire is inserted across the pile 10 and the vertical hole 12, and then the locking member 13
A hardening filler 1 is placed between the pile 10 and the vertical hole 12.
1 is injected and filled, and the pile 10 and the tube column 8 are integrated with a hardening filler 14 injected and filled between them to provide pull-out resistance.

However, in the case of the conventional method, it is necessary to drill the same number of vertical holes 9 and 12 in the hard ground 3 as the number of piles to be used, which increases the construction period and costs, and also reduces the cost of the foundation structure. If the area around which the piles are inserted is underwater, the actual construction would be extremely difficult because the construction would have to be done from underwater.

The object of the present invention is to provide a center prestress type pile foundation that advantageously solves the above-mentioned problems.

Next, the present invention will be explained in detail using illustrated examples.

4 and 5 show a first embodiment of the present invention, which is comprised of a three-dimensional steel jacket constructed by connecting three vertical pipe columns 8 with a number of connecting members 15. The foundation structure 1 is installed on the upper ground 7 on top of the hard ground 3, and then the piles 2 are inserted into each pipe column 8 in the foundation structure 1, and the piles 2 are driven into the hard ground 3. Then, a hardening filler 14 such as mortar or cement milk is injected and filled between the pile 2 and the pipe post 8, so that the pile 2 and the pipe post 8 are combined, and the center of the pile 2 group is A vertical small-diameter hole 4 is drilled by an excavator across the upper ground 7 and the hard ground 3 at or in the vicinity thereof, and a linear tension member 5 made of a steel rod, steel wire, steel cable, etc. is inserted into the small-diameter hole 4. When the lower part is inserted, a hardening filler 6 such as mortar or cement milk is injected, and the lower part of the linear tension member 5 is anchored to the hard ground 3 by the hardenable filler 6.

After the curable fillers 6 and 14 are completely cured, tension (approximately 50 to 150 tons) is applied to the tension member 5 by jacking or the like in the upper part of the foundation structure 1, and in this state, the upper end of the tension member 5 is is fixed to the foundation structure 1 by a wedge, or the upper end of the tension member 5 is secured to the upper surface of the foundation structure 1 by a nut 16 screwed thereto, and the tension of the tension member 5 causes each A compressive force is applied to the pile in advance, and the pile is configured to resist the overturning moment of the foundation structure 1.

6 and 7 show a second embodiment of the present invention, in which a foundation structure 1 consisting of piers supporting bridge girders is installed on an upper ground 7, and a footing 17 in the foundation structure 1 is installed. The piles 2 are inserted into four vertical steel pipes 18 provided around the area, and the piles 2 are driven into the hard ground 3, and there is no mortar between the piles 2 and the vertical pipes 18. Alternatively, a hardening filler 14 such as cement milk is injected and filled, but the other configurations are the same as in the first embodiment.

When carrying out this invention, either a steel pipe pile or a concrete pile may be used as the pile 2, and the foundation structure may be of any type other than those shown. Further, it is preferable to provide a vertical guide pipe (not shown) for inserting an excavating tool near the center of the foundation structure.

According to this invention, three or more piles 2 are driven through the periphery of the foundation structure 1 until reaching the hard ground 3, and each pile 2 and the foundation structure 1 are connected, and the foundation structure is Small diameter hole 4 from the center to hard ground 3
A lower part of a linear tension member 5 such as a steel rod or a steel wire rope is inserted into the small diameter hole 4, and the lower part of the tension member 5 is covered with a hardening filler 6 such as mortar or cement milk. The tension member 5 is pulled at the upper center of the foundation structure 1, and the upper part of the tension member 5 is attached to the foundation structure 1.
By anchoring at the upper center of the pile 2, compressive force is applied to each pile 2 in advance to resist the overturning moment of the foundation structure 1, so the overturning moment acting on the foundation structure 1 causes the pile 2 to By canceling the applied pulling force and the compressive force previously applied to the pile 2, it is possible to stabilize a foundation structure having a pile foundation, and it is also possible to stabilize a foundation structure with a pile foundation by canceling the applied pulling force and the compressive force applied to the pile 2 in advance. In this case, it was necessary to excavate the hard ground 3 for the number of piles, but in the case of this invention, the number of places to excavate the hard ground 3 is reduced, so the construction cost can be reduced and the construction period can be shortened. Further, since the excavation work for installing the tension member 5 can be performed at the upper center of the foundation structure 1 above the water surface, effects such as ease of construction can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view showing an example of a conventional foundation structure, FIG. 2 is a plan view thereof, and FIG. 3 is a longitudinal sectional view showing another example of a conventional foundation structure. FIG. 4 is a vertical sectional side view showing a jacket type foundation structure having a center prestress type pile foundation according to the present invention;
FIG. 5 is a front view thereof, FIG. 6 is a longitudinal sectional front view showing a pier having a center prestress type pile foundation of the present invention, and FIG. 7 is a plan view thereof. In the figure, 1 is the foundation structure, 2 is the pile, 3 is the hard ground, 4 is the small diameter hole, 5 is the linear tension member, 6 is the hardening filler, 7 is the upper ground, 8 is the pipe column, and 14 is hardening. 17 is a footing, and 18 is a vertical pipe.

Claims (1)

[Claims] 1 Drive three or more piles 2 around the foundation structure 1 until they reach the hard ground 3, and each pile 2
and a foundation structure 1, a small diameter hole 4 is bored in the hard ground 3 from the center of the foundation structure, and a lower part of a linear tension member 5 such as a steel rod or a steel wire rope is inserted into the small diameter hole 4. The lower part of the tensioning member 5 is anchored to the hard ground 3 using a hardening filler 6 such as mortar or cement milk, and the tensioning member 5 is stretched at the upper center of the foundation structure 1. The center is characterized in that by anchoring the upper part of the member 5 to the upper center of the foundation structure 1, compressive force is applied to each pile 2 in advance to resist the overturning moment of the foundation structure 1. Prestressed pile foundation.