JP3519375B2 - Cast-in-place pile construction method just below the existing foundation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to seismic reinforcement (including liquefaction countermeasures) or bearing capacity of existing foundations due to increased load of superstructures, bearing capacity (vertical and horizontal) of the foundation itself, and deformation during earthquakes. It relates to a construction method for constructing a new cast-in-place pile directly under the existing foundation when the performance is insufficient.

[0002]

2. Description of the Related Art FIGS. 21 and 22 are used to reinforce existing foundations.
As shown in Fig. 2, the additional footings 21 and the existing piles 22 are added to the outside of the existing piles 22, and the footing 21 is also added to improve the bearing capacity of the foundation, the proof strength and the deformation performance during an earthquake.
Alternatively, in both pile foundations and direct foundations, there is a method of improving the ground beneath and around the entire ground to improve the ground strength directly below the foundation or directly below the existing pile.

[0003]

[Problems to be Solved by the Invention] In the method of increasing piles,
The area within the plane of the existing foundation is not sufficient, and it cannot be used in places where there are restrictions on the site or restrictions on the empty head directly below the existing structure.

Further, in the reinforcement by the ground improvement method, the predetermined performance cannot be satisfied unless the entire area directly below the foundation or a wide area outside the foundation is improved, and the existing pile is not considered in the design, resulting in high cost. Become.

The object of the present invention is to eliminate the disadvantages of the above-mentioned conventional example, and to easily and surely improve the supporting force, proof stress and horizontal deformation performance of the foundation without widening the area or removing the existing foundation. The purpose is to provide a method for constructing cast-in-place piles directly under the existing foundation that can be used effectively if existing piles are available.

[0006]

In order to achieve the above-mentioned object, the present invention firstly forms a vertical through hole in an existing foundation, and uses this through hole directly below the existing foundation by a high-pressure injection replacement method. A cylindrical ground improvement body is constructed in, and a wire rod is spirally arranged near the peripheral surface inside the cylindrical ground improvement body using a through hole formed in the existing foundation, and the columnar ground improvement body is formed. The vertical steel material is arranged inside the spirally arranged wire rod inside the ground improvement body. Secondly, the vertical through hole is formed in the existing foundation, and the through hole is used for water Cut the ground with a jet to make it muddy, insert a rod through which synthetic resin fiber rope with weights attached at appropriate intervals is inserted into the muddy water cutting, and rotate it when pulling up the rod Centrifugal force is applied to the weight to spirally arrange the rope , Building a columnar soil improvement body by filling it with cement milk or mortar, and using a through hole drilled in the existing foundation inside the columnar soil improvement body inside the rope The gist of the present invention is to dispose a vertical steel material, and thirdly, to introduce prestress into the vertical steel material.

According to the first aspect of the present invention, in the columnar improved body constructed immediately below the existing foundation, a so-called support pile is provided directly below the existing foundation by disposing the spiral member and the steel material in the vertical direction. Demonstrates the same strength, vertical strength, proof strength against horizontal methods, and horizontal deformation performance as installed. Further, if there is an existing pile, this columnar improved body can be used effectively by combining it with the existing pile.

[0008] Further, since the piles can be formed directly under the existing foundation, new extra land is not required, and construction is possible if there is a space where boring can be performed.

Further, the cylindrical improved body which is covered with a bag and which is constructed directly below the existing foundation has the same strength as that when the support pile is constructed immediately below the existing foundation by arranging the steel material in the vertical direction inside. Demonstrates vertical and horizontal proof strength and horizontal deformation performance.

According to the second aspect of the present invention, which is the same as the above-mentioned action, the cemented milk or mortar constructed immediately below the existing foundation is filled and the columnar improved body is composed of weights attached at appropriate intervals. By arranging the resin fiber rope in a spiral shape, the same strength, vertical proof strength, horizontal proof strength, and horizontal deformation performance can be exhibited as if the support pile was installed directly under the existing foundation.

According to the third aspect of the present invention, by introducing prestress, the strength of the cylindrical ground improvement body can be further increased.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical sectional side view showing a first embodiment of a cast-in-place pile construction method immediately below an existing foundation of the present invention, FIG. 2 is a plan view of the same as above, wherein 1 is an existing foundation made of a reinforced concrete structure or the like, and 2 is this existing foundation. Precast piles that support the foundation. 4 to 7 are side views of each step.

As shown in FIG. 4, a vertical through hole 4a of about φ150 mm is bored in the existing foundation (footing) 1, and a rod 5 is inserted into the through hole 4a as shown in FIG. Existing foundation 1 by replacement method (jet grout method that cuts soil by the force of air and liquid to improve the ground)
A columnar ground improvement body 3 having a high strength (q _u = 150 to 200 kgf / cm ² ) is constructed immediately below

The jet grout method has two rods.
A JS that uses a heavy pipe to rotate and inject a liquid of ultra-high pressure hardening material with air into the ground to cut the ground and discharge slime to the surface of the ground, and at the same time to create a cylindrical solid body.
Using the G method and triple pipe, super high pressure water accompanied by air is rotated and jetted into the ground to cut the ground, the slime is discharged to the ground surface and the hardening material is simultaneously filled into a cylindrical shape. Although there is a column jet grouting method for forming a solidified body of the above, any one may be used in the present invention.

Further, a cross jet method (trade name) is used in which a high-speed jet is crossed, a form effect is obtained by using this crossing as a cutting limit, and a homogenous improved body is obtained by an earth crushed to a minimum size. It is also possible to construct the ground improvement body 3.

After this, a through hole 4b (φ50 to 100 mm) which is a vertical or obliquely cut hole by a diamond cutter or the like is bored in the existing foundation 1 and the guide pipe 6 made of a shape memory alloy is inserted into the through hole 4b. Wire rod made of steel wire, carbon fiber, glass fiber, vinylon, aramid fiber, or other high-performance resin fiber cable, etc., which is fitted and spirally processed using the same, and which has strength equal to or higher than that of rebar 7.
While being inserted, inside the cylindrical improvement body 3, a spiral shape is arranged near the peripheral surface from below. This wire 7 has a through hole 4
When passing b, the shape is straight, but after passing, the spiral state is reproduced.

Further, in the existing foundation 1, through holes 4c (φ50 arranged around the through hole 4a so as to surround the through hole 4a) are arranged.
.About.100 mm) is used to dispose the vertical steel material 8 inside the wire material 7 spirally arranged inside the cylindrical improvement body 3. As the steel material 8, different diameter reinforcing bars, PC steel wire, and PC stranded wire are preferable, and they are bundled and arranged as necessary.

Further, as a second embodiment, as shown in FIG. 3, a prestress may be introduced into the vertical steel material 8 as needed. In order to do this, boring holes are drilled deeper than the support layer 9 for the anchor fixing length, a casing 11 is arranged, and a bearing member 10 or the like is attached to the tip of the steel material 8 and is housed in the casing 11. 12 is filled, and after hardening, the steel material 8 is tensioned.

As a method of arranging the wire 7 in a spiral shape, as shown in FIGS. 9 and 10, the insertion guide 13 which opens like an umbrella is inserted through the through hole 4a in a closed state, and the wire is opened and closed at any time. It is also possible to install 7.

FIGS. 11 to 15 show a third embodiment of the present invention. As a first step, the existing foundation (footing) 1 has a φ shape.
The point of forming a vertical through hole 4a of about 150 mm is the same as in the first and second embodiments, but as a second step
As shown in FIG. 12, the through hole 4a is used to cut the ground with a water jet from the rod 14 to make it into a muddy state. In that case, mud water such as bentonite may be replaced.

As shown in FIG. 13, a bag 15 made of synthetic resin fiber such as polyester or vinylon is inserted together with the rod 16 in a closed state, and cement milk or mortar is poured into the bag 15 from the tip of the rod 16. Etc., the bag 15 is spread and the cylindrical ground improvement body 3 covered with the bag 15 is formed. 14 in FIG. 14 is a hole for removing muddy water.

A through hole 4c formed in the existing foundation 1
The steel material 8 in the vertical direction is arranged inside the cylindrical ground improvement body 3 by using. This steel material 8 is composed of different diameter reinforcing bars, PC steel wire, and PC stranded wire as in the case of the first embodiment,
Prestress may be introduced if desired.

FIGS. 16 to 20 show a fourth embodiment of the present invention. Like the third embodiment, as a first step, the existing foundation (footing) 1 is provided with a vertical through hole 4a of about φ150 mm. The points to be provided are the same as those in the first and second embodiments, but as a second step, as shown in FIG.
Is used to cut the ground with a water jet by the rod 14 to make it muddy. (See Figures 17 and 18)

A rod 20 through which a rope 19 made of synthetic resin fiber having weights 18 attached at appropriate intervals is inserted into the muddy water cutting, and the rope 19 is sequentially fed out from the tip of the rod 20 as shown in FIG. If the rod 20 is rotated when it is pulled up, centrifugal force is applied to the weight 18 of the rope 19 to press it against the natural ground surface, and the rod 20 can be arranged spirally.

Simultaneously with or after that, cement milk or mortar is filled to form a cylindrical ground improvement body 3, and a through hole 4 formed in the existing foundation 1 shown in FIGS. 19 and 20.
The steel material 8 in the vertical direction is disposed inside the rope 19 spirally disposed inside the cylindrical ground improvement body 3 by using c.

[0026]

As described above, the cast-in-place pile construction method directly below the existing foundation of the present invention is directly below the existing foundation without expanding the area and without removing the existing foundation.
It is possible to easily and surely improve the bearing capacity, proof stress, and horizontal deformation performance of the foundation, and increase the load on the existing structure (for example, using two layers of viaducts and the load accompanying the increase of various equipment).
Alternatively, it is possible to improve the seismic performance (the foundation can be reinforced according to the reinforcement level of the pier and the frame).

Further, even when the above-ground portion of the existing building is reconstructed, the existing foundation can be effectively utilized by adding the pile without removing the existing foundation.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a first embodiment of a cast-in-place pile construction method directly under an existing foundation of the present invention.

FIG. 2 is a plan view showing a first embodiment of a cast-in-place pile construction method directly below an existing foundation of the present invention.

FIG. 3 is a vertical cross-sectional side view showing a second embodiment of a cast-in-place pile construction method immediately below an existing foundation of the present invention.

FIG. 4 is a side view of the first step showing the first embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 5 is a side view of a second step showing the first embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 6 is a side view of a third step showing the first embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 7 is a side view of a fourth step showing the first embodiment of the cast-in-place pile construction method directly under the existing foundation of the present invention.

FIG. 8 is a perspective view showing a first embodiment of a cast-in-place pile construction method directly below an existing foundation of the present invention.

FIG. 9 is a perspective view showing an example of an insertion guide in a closed state.

FIG. 10 is a perspective view showing an example of an insertion guide in an open state.

FIG. 11 is a side view of the first step showing the third embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 12 is a side view of a second step showing the third embodiment of the cast-in-place pile construction method directly under the existing foundation of the present invention.

FIG. 13 is a side view of a third step showing the third embodiment of the cast-in-place pile construction method directly under the existing foundation of the present invention.

FIG. 14 is a side view of a fourth step showing the third embodiment of the cast-in-place pile construction method directly under the existing foundation of the present invention.

FIG. 15 is a side view of a fifth step showing the third embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 16 is a perspective view showing a fourth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 17 is a side view of the first step showing the fourth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 18 is a side view of a second step showing the fourth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 19 is a side view of the third step showing the fourth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 20 is a side view of the fourth step showing the fourth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 21 is a vertical sectional side view showing a conventional example.

FIG. 22 is a plan view showing a conventional example.

[Explanation of symbols]

1 ... Existing foundation 2 ... Existing pile 3 ... Cylindrical ground improvement body 4a, 4b, 4c ... Through hole 5 ... Rod 6 ... Guide pipe 7 ... Wire material 8 ... Steel material 9 ... Support layer 10 ... Pressure bearing body 11 ... Casing 12 … Mortar 13… Insertion guide 14… Rod 15… Bag 16… Rod 17… Hole 18… Weight 19… Rope 20… Rod 21… Existing footing 22… Existing pile 23… Additional pile

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) E02D 5/34 E02D 27/12 E02D 27/34

Claims (3)

(57) [Claims] 1. A vertical through hole is formed in an existing foundation,
By using this through-hole, a high-pressure injection replacement method was used to construct a cylindrical ground improvement body immediately below the existing foundation, and the through-hole drilled in the existing foundation was used to create a cylindrical ground improvement body near the peripheral surface inside. The cast-in-place pile directly under the existing foundation is characterized in that the wire rods are arranged in a spiral shape, and the steel members in the vertical direction are arranged inside the spirally arranged wire rods inside the columnar ground improvement body. Construction method. 2. A vertical through hole is formed in an existing foundation,
Cut the ground with a water jet using this through hole to make it into a muddy state, insert a rod through which synthetic resin fiber rope with weights attached at appropriate intervals is inserted into the muddy water cutting, and rotate it when pulling up the rod The rope weight that extends from the rod tip is centrifugally applied to the rope to arrange the rope in a spiral shape, and cement milk or mortar is filled to create a cylindrical ground improvement body, and a through hole drilled in the existing foundation. A method for constructing a cast-in-place pile directly under an existing foundation, characterized in that a steel material in a vertical direction is arranged inside a rope arranged spirally inside the cylindrical ground improvement body. 3. The method for constructing a cast-in-place pile directly under an existing foundation according to claim 1 or 2, wherein prestress is introduced into the vertical steel material.