JPH0137529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to a method for removing negative frictional force from cast-in-place piles.

``Conventional technology'' Foundation piles constructed on soft ground such as reclaimed land are subject to a negative frictional force that tries to pull the foundation piles together as the ground sinks due to soil consolidation. It causes unexpected subsidence in the foundations of buildings, causing slopes and cracks in buildings, and causes the destruction of piles.

Therefore, in such areas of ground subsidence, it is necessary to take some kind of edge cutting measures between the foundation piles and the strata. In the case of ready-made piles, it is necessary to attach a mantle steel pipe or cover the piles with asphalt, etc. A friction cutting material is applied and then hammered in.

However, in the case of cast-in-place piles, it is not possible to carry out edge cutting measures on the ground as described above, so a completely different method is taken.

For example, in the case of Japanese Patent Publication No. 58-58495, as shown in FIG.
The plurality of plates 12 are installed in the excavated hole 15 by the pressure of the poured concrete.
According to Japanese Patent Application No. 59-102736, the concrete pile is formed by pressing it against the wall of the building.
As shown in Figures 3 a to d, which are explanatory drawings showing the construction procedure of concrete piles and the state of ground subsidence, and Figure 4, which is an enlarged cutaway plan view of a concrete pile fitted with a steel pipe coated with a lubricant, After the concrete pile 2 is driven and the concrete hardens, a steel pipe 3 having a diameter larger than that of the concrete pile 2 and having a lubricant 5 attached to the outer peripheral wall 4 is fitted into the concrete pile 2 that has been driven. , special application 1987-
Regarding No. 108544, Figures 5 a to e of the explanatory diagram showing the concrete pile construction procedure and ground subsidence state
Also, as shown in Fig. 6, which is an enlarged cutaway plan view of a concrete pile into which a steel pipe with an injection pipe is fitted,
After the concrete pile 2' is driven into the ground 1' and the concrete hardens, a steel pipe 3' with an injection pipe 4' having a larger diameter than the concrete pile 2' is inserted into the concrete pile 2', and then the injection pipe 4 is inserted into the concrete pile 2'. While injecting the lubricant 7' into the ground 1' from the tip 6' of the lubricant 7', the steel pipe 3' with the injection pipe 4' is pulled up to form a permeation layer 8' of the lubricant 7' around the concrete pile 2'. I have to.

``Problems to be Solved by the Invention'' However, the first method requires the complicated work of movably attaching the plate to which the friction cutting material is attached to the reinforcing bar cage, and the plate is also buried together with the pile. In addition, since the plates are attached to a rebar cage, the diameter of the rebar cage must be smaller than conventional ones, which not only lacks strength against bending and shearing.
The most important thing is that concrete may enter between the plate and the wall of the excavation hole, which may prevent the frictional force from being cut.

In addition, the second method is to insert the steel pipe 3 as the jacket pipe to a predetermined depth using a drop hammer or vibrohammer, so this disposable steel pipe 3 is an expensive one with a predetermined strength. must be provided.

Furthermore, the third method not only has the disadvantage of requiring processing to attach the injection pipe 4' to the steel pipe 3', but also has the disadvantage that the injection pipe 4' cannot be fitted to a predetermined depth using a water jet or a vibro hammer. There is a drawback that it causes a large insertion resistance.

Note that both the second and third methods are undesirable because they require construction after waiting for hardening of the cast-in-place piles, which prolongs the construction process.

"Means for Solving Problems" and "Operation" The present invention was made in view of the above circumstances, and its gist is that a friction cutting material such as asphalt is attached to the outer peripheral surface, and the A cylindrical iron plate curtain body with a floating hollow ring section at the lower end is wrapped around a reinforcing bar cage at a predetermined position with strings, etc., and after the reinforcing bar cage is erected in the excavation hole, the hollow ring section is The ring part is injected and filled with drilling mud, etc. and kept in an expanded state, and under this condition, concrete is poured, and the gap between the wall of the excavation hole and the curtain body is filled with filler such as sand. The present invention provides a cast-in-place pile in which a friction force cutting material adhesion layer is simultaneously formed on the outer circumferential surface of the consolidation settlement layer, completely eliminating the problems of the conventional means described above.

"Example" This will be explained in detail below based on the drawings.

FIGS. 1a and 1b are explanatory diagrams of a cylindrical iron plate curtain body 16, which is a feature of the present invention. This is a long cylindrical iron plate, and its outer circumferential surface is coated with friction-cutting material such as asphalt. A material 17 is attached, and a floating ring-like hollow ring part 18 made of a resin sheet or the like is provided at the lowermost end thereof, and a water injection pipe 19 is attached to the hollow ring part 18. Since the steel plate provided for the curtain body 16 is not driven into the soil like the casing steel pipe, it may be an inexpensive one that has the strength to withstand concrete lateral pressure.

When water is injected into the hollow ring part 18 from the water injection pipe 19 and filled with water, it expands, imparts rigidity and becomes stable in a ring shape, and when inside an excavation hole, presses strongly against the hole wall. This becomes a weir, and a ring-shaped layer of the friction force cutting material 17 rises above it.

The present invention places this in advance at a predetermined position of the built-in reinforcing bar cage, that is, at a location corresponding to the consolidation settlement layer,
By subsequently pouring concrete, the piles can be used as cast-in-place piles that simultaneously form edge cutting measures.

That is, Figures 7a to 7c are construction procedure diagrams of the method of the present invention, and Figures 8a to 8c are diagrams of the middle part (top) of the iron plate curtain body and the hollow ring part (bottom) corresponding to Figures 7a to c. In a plan cross-sectional view, a reinforcing cage 21 is shown with a steel plate curtain body 16 wrapped around it using a fastening means such as a string fastener 20.
is built into the excavated hole 22 (a).

Next, the hollow ring part 1 is inserted from the water injection pipe 19.
When the hollow ring part 18 is expanded by injecting water (may be mud water for drilling) into the inside of the hollow ring part 18, the hollow ring part 18, which is given rigidity and enlarged in diameter in a ring shape, is formed in the drilling hole 22.
It is pressed against the wall of the
(b).

Therefore, concrete will not enter between the iron plate curtain body 16 and the wall surface of the excavation hole 22 even during concrete pouring, which will be described later.

After the hollow ring part 18 is maintained in expansion by taking measures such as plugging the water injection pipe 19, concrete 23 is poured, and sand is poured into the excavation hole 22 and the gap 24 of the iron plate curtain body 16. (c).

In the end, at the same time as the cast-in-place pile is completed by singulating the concrete 23, the edge cutting measures with the friction force cutting material 17 on the outer periphery of the concrete 23 in the area corresponding to the consolidation settlement layer are also completed.

In addition, in the method of the present invention, the smooth surface of the steel plate curtain body 16 in the expanded state under concrete side pressure (because of the steel plate) and the layer form of the friction force cutting material 17 completely match, so that the most desirable smooth surface can be obtained. Since the edge cutting layer is formed automatically, it is suitable for application to ground where the wall surface of the excavation hole 22 is difficult to finish smoothly.

Furthermore, as is clear from the above description, the iron plate curtain body 16 only needs to be maintained for a period of time until the cast-in-place pile hardens, and is unnecessary if a frictional force removal layer is formed, and its durability is within that range. That's good.

"Effects of the Invention" As is clear from the above, according to the present invention, there is no need to attach a large number of divided bodies to a reinforcing cage, and the frictional force of concrete that hinders frictional force cutting is eliminated. There is no invasion to the outside of the removal layer.

Further, there is no need to provide expensive materials as waste materials, and there is no difficulty in installing them.

Furthermore, the frictional force removal layer can be formed at the same time as the concrete solidifies, that is, at the same time as the conventional cast-in-place pile is completed, which does not cause any delay in the construction period and is extremely meaningful in practice.

[Brief explanation of drawings]

Figures 1a and 1b are overall bird's-eye views for explaining the cylindrical membrane used in the present invention, sectional views taken along the line bb in Figure a, Figures 2 to 4, and Figures 5 to 6, respectively. 7a to 7c are construction procedure diagrams of the method of the present invention, and FIGS. 8a to 8c are plan sectional views corresponding to FIG. 7. 1, 1'...Ground, 2, 2'...Concrete pile, 3, 3'...Steel pipe, 4...Outer wall, 4'...Injection pipe, 5...Lubricant, 6'...Tip, 7'...Lubricant, 8'...Penetration layer, 11...Asphalt, 1
2...Plate, 13...Rebar cage, 14...Wire,
15... Excavation hole, 16... Iron plate curtain body, 1
7...Friction force cutting material, 18...Hollow ring part, 1
9... Water injection pipe, 20... String stopper, 21...
Rebar cage, 22...Drilling hole, 23...Concrete, 24...Void, 25...Filling material.

Claims (1)

[Claims] 1 A cylindrical iron plate curtain body with a friction cutting material such as asphalt attached to the outer circumferential surface and a floating ring-like hollow ring section at the bottom end is wrapped in advance with strings, etc. at a predetermined position on the reinforcing cage. After erecting such a reinforcing bar cage in an excavation hole, the hollow ring portion is filled with drilling mud or the like to maintain it in an expanded state;
Under this condition, concrete is poured, and the gap between the wall of the excavation hole and the curtain body is filled with filler such as sand, and a layer of friction cutting material is applied to the outer peripheral surface in the consolidation settlement layer. A method for removing negative frictional force from cast-in-place piles, characterized by simultaneous encircling formation.