JPH1025737A - Method of cast-in-place pile construction just under existing foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bearing power, yield strength and horizontal deformation performance of a foundation by effectively utilizing an existing pile without removing an existing foundation by boring a through-hole to the existing foundation and constructing a cast-in-place pile through the through-hole. SOLUTION: Through-holes 4a are bored to an existing foundation 1, a ground is cut by a water jet by a rod and brought to a muddy-water state, bags 15 made of high-strength resin fibers are inserted together with the rod, cement milk, mortar, etc., are poured in from the front end of the rod and the insides of the bags 15 are filled with cement milk, mortar, etc., and columnar soil improved bodies 3 are prepared. Reinforcing bars, steel bars, etc., are inserted into the through-holes 4a, and fixed onto the existing foundation 1 and the soil improved bodies 3, and the horizontal force is transmitted. Linear or spiral steel is arranged into the soil improved bodies 3 through separately bored through-holes, and the soil improved bodies 3 may also be created by a method of high-pressure infection replacement construction. Accordingly, a cast-in-place pile is constructed just under the existing foundation, and the bearing power, yield strength and horizontal deformation performance of the foundation can be improved simply and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an existing foundation for supporting seismic reinforcement (including liquefaction countermeasures) or increasing the load on a superstructure, supporting capacity, strength of the foundation itself (vertical and horizontal), and deformation during earthquake. This method relates to a method of constructing a new cast-in-place pile immediately below the existing foundation when performance is insufficient.

[0002]

2. Description of the Related Art As reinforcement of an existing foundation, FIGS.
As shown in the figure, the additional pile 23 is provided outside the existing footing 21 and the existing pile 22, and the footing 21 is also added to improve the bearing capacity of the foundation, the proof stress and the deformation performance at the time of the earthquake,
Alternatively, there is a method of improving the ground below and around the entire ground in any case of the pile foundation and the direct foundation to increase the ground strength immediately below the foundation or immediately below the existing pile.

[0003]

According to the method of increasing piles,
It is not sufficient in terms of area only within the plane of the existing foundation, and it cannot be used in places where there are restrictions on land or restrictions on the head below the existing structure.

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

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art and to simply and surely improve the foundation's bearing capacity, strength and horizontal deformation performance without increasing the area and without removing the existing foundation. It is to provide a cast-in-place pile construction method directly under the existing foundation that can be used effectively when existing piles are available.

[0006]

According to the present invention, in order to achieve the above object, first, a vertical through hole is formed in an existing foundation, and the ground is jetted with water or a stable liquid using the through hole. Is cut into muddy water, the bag is inserted with the rod in a state where the hole wall is stabilized, and the bag is filled with cement milk, mortar, concrete or the like, and spread.
Creating a cylindrical ground improvement body covered with bags, 2nd
The bag is made of high-strength fibers such as polyester, polyamide, vinylon, and aramid among the synthetic resin fibers, and the bag has the same function as the vertical and circumferential reinforcing bars, or The bag is made of synthetic resin fiber or natural fiber, filled with cement milk or mortar, spread, and after forming a columnar ground improvement body covered with the bag, using the through holes drilled in the existing foundation The gist of the invention is to dispose a vertical steel material inside the columnar ground improvement body.

Third, a vertical through-hole is formed in the existing foundation, and a columnar ground improvement body is constructed directly below the existing foundation by the high-pressure injection replacement method using the through-hole, and is drilled in the existing foundation. A spiral wire is arranged near the peripheral surface inside the cylindrical ground improvement body by using a through hole to make, and inside the wire rod spirally arranged inside the cylindrical ground improvement body, The point is to arrange a vertical steel material.

Fourthly, a vertical through-hole is formed in the existing foundation, and the ground is cut into a muddy state by using the through-hole with a water jet, and weights of synthetic resin fibers are attached at appropriate intervals. Insert the rod through which the rope is inserted into the muddy water cutting, rotate it when pulling up the rod, apply centrifugal force to the weight of the rope that is drawn out from the rod tip, arrange the rope spirally, and fill it with cement milk or mortar To form a columnar ground improvement body, and arrange a vertical steel material inside a rope spirally arranged inside the columnar ground improvement body by using a through hole drilled in the existing foundation. Fifth, the gist of the present invention is to introduce prestress into a vertical steel material.

According to the first aspect of the present invention, by constructing a columnar improvement body directly below the existing foundation, the same strength, vertical direction, and horizontal strength as those obtained when a so-called support pile is constructed immediately below the existing foundation. The columnar improvement exhibits the proof strength against the method and the horizontal deformation performance. Further, when the column-shaped improved body has an existing pile, the existing pile can be effectively used by combining it with the existing pile. When the bag is used as a mold as described above, the filled cement milk, mortar or concrete is replaced with muddy water.
High reinforcement of qu = 300 kgf / cm ^{2 to} 500 kgf / cm ² is possible.

[0010] In addition, since a pile can be formed immediately below an existing foundation, no extra land is required, and construction is possible if there is a space where boring holes can be drilled.

According to the second aspect of the present invention, in addition to the above-mentioned functions, high-strength fibers are used as the bag material, and the bag has the same function as the reinforcing bar in the vertical direction and the circumferential direction. It is possible to improve the bending strength of the pile without using a reinforcing bar or the like.

According to the third aspect of the present invention, the column-shaped improved body covered with the bag is provided with a vertical steel material inside, so that the support pile in a pile head fixed state is constructed immediately below the existing foundation. The same strength, proof stress in the vertical direction and horizontal direction, and horizontal deformation performance can be exhibited.

According to the fourth aspect of the present invention, the column-shaped improved body constructed immediately below the existing foundation is provided with a spiral member and a vertical steel material so that a so-called support pile is provided immediately below the existing foundation. Exhibits the same strength, proof strength against vertical and horizontal methods, and horizontal deformation performance as the construction. Further, when the column-shaped improved body has an existing pile, the existing pile can be effectively used by combining it with the existing pile.

According to the fifth aspect of the present invention, the operation is the same as that of the first embodiment, except that the cement-made milk or mortar constructed immediately below the existing foundation is filled and the column-shaped improved body is provided with weights attached at appropriate intervals. By arranging the resin fiber rope in a spiral shape, the same strength, vertical strength, horizontal strength, and horizontal deformation performance as when the support pile is installed immediately below the existing foundation are exhibited.

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

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a vertical sectional side view showing a first embodiment of a cast-in-place pile construction method immediately below an existing foundation according to the present invention, FIG. 2 is a plan view of the same, and FIG. 1 is an existing foundation made of a reinforced concrete structure or the like, and 2 is an existing foundation. It is a ready-made pile that supports the foundation. 3 to 7 are side views of each step.

As a first step, as shown in FIG. 3, a vertical through hole 4 of about 150 mm
In the second step, the ground is cut by a water jet using a rod 14 using the through-hole 4a as shown in FIG. In that case, muddy water such as bentonite may be replaced. The cut earth and sand is discharged upward from the gap of the double pipe or the triple pipe inserted into the through hole 4a.

As shown in FIG. 5, a bag 15 of high-strength resin fiber such as polyester, polyamide, vinylon, aramid or the like is inserted together with the rod 16 in a closed state, and as shown in FIG. The bag 15 is spread by filling it with cement milk or mortar or the like poured out from the tip of the bag, thereby forming a columnar ground improvement body 3 covered with the bag 15 as shown in FIG.

Since the bag 15 is made of a high-strength resin fiber as described above, the bag 15 can have the same function as the reinforcing bars in the vertical direction and the circumferential direction. When used, the filled cement milk or mortar is replaced with muddy water, so qu = 300 kgf / cm ²
High reinforcement of up to 500 kgf / cm ² is possible. In addition, the through hole 4
A horizontal force is transmitted by inserting a reinforcing bar or a steel rod into a and fixing it to an existing footing and a columnar ground improvement body.

As a second embodiment, the bag 15 is made of synthetic resin fiber or natural fiber which is not high in strength.
As shown in the figure, a through hole 4a is formed in the existing foundation (footing) 1.
The ground is cut by a water jet using a rod 14 by using the through hole 4a to make a muddy state, and the bag 15 is inserted together with the rod 16 in a closed state.
This is the same as the first embodiment in that the bag 15 is spread by filling with cement milk, mortar, concrete, or the like poured out from the tip of the container, and the columnar ground improvement body 3 covered with the bag 15 is formed. However, as shown in FIG. 8, a vertical steel material 8 is disposed inside the columnar ground improvement body 3 by using a through hole 4 c formed in the existing foundation 1.

The steel material 8 is made of a rebar of a different diameter, a PC steel wire or a PC stranded wire, and a prestress may be introduced as necessary.

FIGS. 9, 10, and 16 show a third embodiment of the present invention. As shown in FIG. 12, a vertical through hole 4a of about 150 mm in diameter is formed in the existing foundation (footing) 1. Then, as shown in FIG. 13, the rod 5 is inserted into the through-hole 4a and the existing foundation 1 is formed by a high-pressure injection replacement method (a jet grout method in which the soil is cut by the force of air and liquid to improve the ground).
A high-strength (qu = 150 to 200 kgf / cm ² ) columnar ground improvement body 3 is constructed immediately below the ground.

The jet grout method uses two rods.
Using a heavy pipe, a super-high pressure hardening material liquid with air is rotated into the ground and sprayed to cut the ground and discharge the slime to the ground, and at the same time to form a columnar consolidated body.
Using the G method and triple pipes, ultra-high pressure water with air is rotated into the ground and sprayed to cut the ground, the slime is discharged to the surface, and the hardening material is filled at the same time to form a cylinder. Although there is a column jet grouting method for forming a consolidated body of the present invention, either method may be used in the present invention.

Further, the high-speed jets are crossed, the crossing point is used as a cutting limit to give a form effect, and a columnar shape is obtained by a cross-jet method (trade name) in which a homogenized improved body can be obtained by a very small crushed earth mass. It is also possible to construct the ground improvement body 3.

After that, a through hole 4b (φ50 to 100 mm) which is a vertical or oblique hole made by a diamond cutter or the like is formed in the existing foundation 1, and a guide pipe 6 made of a shape memory alloy is inserted into the through hole 4b. Insert and insert a wire 7 made of a high-performance resin fiber cable such as steel wire, carbon fiber, polyester, vinylon, or aramid fiber, which has a strength approximately equal to or higher than that of a reinforcing bar, and is processed into a spiral shape using this. While spirally arranged from below in the interior of the cylindrical improvement body 3 near the peripheral surface. When the wire 7 passes through the through hole 4b, it becomes straight, but after passing, it reproduces a spiral state.

Also, in the existing foundation 1, the through holes 4c (φ50) are arranged around the through hole 4a so as to surround the same.
A vertical steel material 8 is disposed inside a wire 7 spirally disposed inside the column-shaped improved body 3 using a thickness of about 100 mm. The steel material 8 is preferably a rebar of a different diameter, a PC steel wire, or a PC stranded wire, and is bundled and arranged as necessary.

Further, as a fourth embodiment, as shown in FIG. 11, a prestress may be introduced into the vertical steel material 8 as required. To do this, a boring hole is drilled for the anchor anchoring depth deeper than the support layer 9, a casing 11 is provided, a supporting body 10 is attached to the tip of the steel material 8, and placed in the casing 11. 12 is filled, and after hardening, the steel material 8 is strained. The method of introducing the prestress is the same as in the case of the second embodiment.

As shown in FIGS. 17 and 18, the spirally arranged wire 7 is inserted through the through hole 4a with the insertion guide 13 opened like an umbrella closed, and opened and closed as needed. 7 may be provided.

FIGS. 19 to 23 show a fifth embodiment of the present invention. As in the fourth embodiment, as a first step, a vertical through hole 4a having a diameter of about 150 mm is formed in an existing foundation (footing) 1. FIG. The same point is provided, but as a second step, the ground is cut by a water jet using the rod 14 using the through hole 4a to make a muddy state. (See Figures 20 and 21)

A rod 20 through which a synthetic resin fiber rope 19 having weights 18 attached thereto at appropriate intervals is inserted is inserted into the above-mentioned 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 lifted, a centrifugal force is applied to the weight 18 of the rope 19 to press it against the ground surface, and the rope 19 can be spirally disposed.

Simultaneously or thereafter, a columnar ground improvement body 3 is formed by filling with cement milk or mortar, and the columnar ground is improved by using a through hole 4c formed in the existing foundation 1 shown in FIG. A vertical steel material 8 is arranged inside a rope 19 spirally arranged inside the improved body 3.

[0032]

As described above, the cast-in-place pile construction method under the existing foundation according to the present invention can be easily performed directly under the existing foundation without increasing the area of the foundation and without removing the existing foundation. In addition, it is possible to improve the bearing capacity, strength and horizontal deformation performance of the foundation reliably, and to increase the load on the existing structure (for example, two layers of viaducts, the load accompanying the increase of various facilities, etc.) or the seismic performance. It can be improved (the foundation can also be reinforced according to the reinforcement level of the pier and the skeleton).

Further, even when the existing building is reconstructed on the ground, the existing piles can be effectively used by expanding the piles without removing the existing foundation.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view showing a first embodiment of a cast-in-place pile construction method immediately below an existing foundation according to the present invention.

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

FIG. 3 is a side view of a first step showing a first embodiment of a cast-in-place pile construction method immediately below an existing foundation according to the present invention.

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

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

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

FIG. 8 is a side view of a final step showing a second embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 9 is a vertical sectional side view showing a third embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 10 is a plan view showing a third embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 11 is a vertical sectional side view showing a fourth embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 12 is a side view of a first step showing a third embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 13 is a side view of a second step showing a third embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 14 is a side view of a third step showing a third embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

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

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

FIG. 17 is a perspective view showing an example of an insertion guide in a closed state;

FIG. 18 is a perspective view showing an example of an insertion guide in an open state.

FIG. 19 is a perspective view showing a fifth embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

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

FIG. 21 is a side view of a second step showing the fifth embodiment of the cast-in-place pile construction method immediately below the existing foundation of the present invention.

FIG. 22 is a side view of a third step showing the fifth embodiment of the cast-in-place pile construction method immediately below the existing foundation according to the present invention.

FIG. 23 is a side view of a fourth step showing a fifth embodiment of the cast-in-place pile construction method immediately below an existing foundation according to the present invention.

FIG. 24 is a vertical sectional side view showing a conventional example.

FIG. 25 is a plan view showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Existing foundation 2 ... Existing pile 3 ... Columnar ground improvement body 4a, 4b, 4c ... Through-hole 5 ... Rod 6 ... Guide pipe 7 ... Wire rod 8 ... Steel material 9 ... Support layer 10 ... 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… increase pile

Claims (6)

[Claims] 1. A vertical through-hole is formed in an existing foundation,
Use this through hole to cut the ground with a water jet to make it muddy, insert the bag with the rod, fill it with cement milk, mortar, concrete, etc. and spread it out. Cast-in-place pile construction method immediately below the existing foundation, characterized by the creation of a ground improvement body. 2. The bag is made of a high-strength fiber such as polyester, polyamide, vinylon, or aramid among synthetic resin fibers, and the bag has a function similar to that of a reinforcing bar in the vertical and circumferential directions. Item 1. The cast-in-place pile construction method immediately below the existing foundation. 3. The bag is made of synthetic resin fiber or natural fiber. The bag is filled with cement milk or mortar and spread to form a columnar ground improvement body covered with the bag. The method of constructing a cast-in-place pile immediately below an existing foundation according to claim 1, wherein a vertical steel material is disposed inside the cylindrical ground improvement body using a through hole. 4. A vertical through-hole is formed in an existing foundation,
Using this through-hole, a columnar ground improvement body is constructed directly below the existing foundation by the high-pressure injection replacement method, and using the through-hole drilled in the existing foundation, near the peripheral surface inside this cylindrical ground improvement body A cast-in-place pile immediately below an existing foundation, wherein a wire is helically arranged, and a vertical steel material is arranged inside the helically arranged wire inside the columnar ground improvement body. Construction method. 5. A vertical through-hole is formed in an existing foundation,
Using this through hole, cut the ground with a water jet to make it muddy, insert a rod through which a synthetic resin fiber rope with weights attached at appropriate intervals into muddy cutting, rotate it when pulling up the rod A centrifugal force is applied to the weight of the rope that is drawn out from the rod end, and the rope is spirally arranged, filled with cement milk or mortar to form a columnar ground improvement body, and a through hole formed in the existing foundation. A method of constructing a cast-in-place pile immediately below an existing foundation, wherein a vertical steel material is disposed inside a rope spirally disposed inside the columnar ground improvement body using the method. 6. The cast-in-place pile construction method immediately below an existing foundation according to claim 3, wherein prestress is introduced into the vertical steel material.