JPS61155511A - Removal of negative frictional force of in-situ pile - Google Patents

Abstract

PURPOSE:To remove negative frictional forces from in-situ piles by a method in which steel plates with frictional force-cutters and bags are alternately set, a reinforcing bar cage having a cylinder with a hollow ring on its lower end is built in the hole, the bag and the hollow ring are expanded, and concrete is placed. CONSTITUTION:Steel plates 17 and bags 18 made of water-stopping nylon sheets are alternately set circularly and a life-bouy shaped hollow ring 19 is provided to the lowest end portion to form a cylinder 16. A frictional force cutter 20 of asphalt, etc., is bonded to the outer surfaces of the steel plates 17 and the inner walls 18 of the bags 18, and a reinforcing bag cage 22 surrounded by the cylinder 16 is built in the excavated hole 23. When water is injected through the opening of the bags 18 to fill them with water, the bags 18 and the rings 19 are expanded and pressingly contacted with the wall of the hole 23. Concrete 24 is then placed and a filling material 25, e.g., sand, etc., is packed into the aperture between the hole 23 and the steel plates 17.

Description

[Detailed description of the invention] "Industrial application field" 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 negative frictional force that tries to pull the foundation piles together as the ground sinks due to the consolidation action of the ground, causing damage to buildings, etc. Unexpected subsidence in the foundations of buildings, etc., resulting in tilting, cracking, etc.
Or it may cause the pile to break.

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, and in the case of ready-made piles, either attach a mantle steel pipe or cover the piles with asphalt, etc. It is applied with a friction cutting material and then hammered in.

However, in the case of cast-in-place piles, it is not possible to perform edge cutting measures on the ground as described above, so different measures are taken.

For example, in Japanese Patent Publication No. 58-58495, as shown in FIG. A concrete pile is formed by pressing a plurality of plates 12 against the wall surface of the excavation hole 15 by the pressure of the concrete placed in the concrete.
In No. 736, Figures 3 fa) to (d) are explanatory diagrams showing the construction procedure of concrete piles and the state of ground subsidence, as well as an enlarged cutaway plan view of a concrete pile fitted with a steel pipe coated with a lubricant. As shown in Figure 4, after concrete piles 2 are driven into the ground 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 cast. As shown in Figures 5a to 5e, which are explanatory diagrams showing the construction procedure and ground subsidence state, and Figure 6, which is an enlarged cutaway plan view of a concrete pile into which a steel pipe with an injection pipe is inserted, the concrete pile is placed in the ground at 1°. After pouring 2° and solidifying the concrete, insert the steel pipe 3" with injection pipe 4', which has a larger diameter than the concrete pile 2", into the concrete pile 2", and then lubricate the 6° tip of the injection pipe 4". The steel pipe 3' with the injection pipe 4' is pulled up while injecting the lubricant 7° into the ground to form an 8° permeable layer of /I21 lubricant 7' around the concrete pile 2''.

``Problems to be solved by the invention'' However, the first method requires the complicated work of movably attaching the plate to which the frictional cutting material is attached to the reinforcing bar cage, and the plate is buried together with the pile. In addition, since the plates are attached to reinforcing bars, the diameter of the reinforcing bar cage must be smaller than conventional ones, which not only lacks strength against bending and shearing, but also The 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 the second method, the steel pipe 3 serving as the jacket pipe is inserted to a predetermined depth using a drop hammer or a vibrohammer, so this disposable steel pipe 3 is an expensive one with a predetermined strength. I have to give something.

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 requires a large amount of work when inserting the injection pipe 4 to a predetermined depth using a water jet or vibro hammer. However, there is a problem in that it results in resistance to insertion.

In addition, the second. The third method is undesirable because it requires construction after waiting for the casting-in-place table surface, which prolongs the construction process.

``Means for solving problems'' and ``effects'' The present invention was made in view of cost considerations, and its gist is that iron plates and bags made of water-stopping sheet material are alternately arranged in circles. It is arranged on the circumference and constitutes a cylinder with a hollow ring part in the form of a floating ring as a continuous body of the cough bag at the lowest end, and the frictional force of asphalt etc. is applied to the outer surface of the iron plate and the outer surface of the inner wall of the bag. After attaching the cut material and attaching it to the predetermined position of the reinforcing bar cage with strings, etc., and erecting the reinforcing bar cage in the excavation hole, the bag and hollow ring part are filled with drilling mud, etc. Under this condition, concrete is poured and the gap between the excavation hole wall and the steel plate is filled with filler such as sand, and friction is applied to the outer circumferential surface in the consolidation settlement layer. By providing a cast-in-place pile in which a force-cutting material adhesion layer is simultaneously formed, the problems of the conventional means described above are completely eliminated.

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

Figures 1a and 1b are explanatory diagrams of a cylindrical body 16, which is a feature of the present invention, in which iron plates 17 and bags 18 made of water-stopping sheet material such as nylon are arranged alternately on the circumference, and the lowermost end The bag 18 in the section
A floating ring-like hollow ring portion 19 is provided as a continuous body.

Since the iron plate 17 provided to the cylinder 16 is not driven into the soil like a separate casing steel pipe, it may be an inexpensive one that has the strength to withstand concrete side pressure.

Further, a friction cutting material 20 such as asphalt is attached to the outer surface of the iron plate 17 and the outer surface of the inner wall 18a of the bag 18.

When water is injected and filled from the opening of the bag 18, the bag 18 and the hollow ring part 19 expand, are given rigidity, enlarge in diameter, and become stable in columnar and ring shapes, so that they do not fit inside the borehole. It strongly presses against the hole wall (in the case of bag 18, the mode changes from the mode shown on the left in figure b to the mode shown on the right), and becomes a kind of vertical and horizontal weir, and above the hollow ring part there is a ring-shaped friction cutting material. A layer will rise.

The present invention is a cast-in-place pile that simultaneously forms edge cutting measures by placing the pile in advance at a predetermined position of a rebar cage, which corresponds to the consolidation settlement layer, and then pouring concrete. It is.

That is, FIGS. 7a to 7C are diagrams showing the construction procedure of the method of the present invention with a plan cross-section of the edge-cutting section, and show a reinforcing bar cage in which the cylinder 16 is wrapped once with a fastening means such as a string fastener 21. 22 is built into the excavated hole 23 (a).

Next, when the water injection pipe P is inserted into the opening of the bag 18 and the inside of the bag 18 and the hollow ring portion 19 are filled with water (mud from drilling may be used) and expanded, the water is imparted with aqueous properties and becomes large as described above. The bag 18 and the hollow ring part 19, which are increasing in diameter, are pressed against the wall surface of the excavation hole 23 and become stuck (
b).

However, due to the concrete pouring described later, the iron plate 17
Concrete will not enter between the hole 23 and the wall surface of the excavation hole 23.

The bag 18 and the hollow ring part 19 are kept inflated by taking measures such as plugging the opening of the bag 18, and then the concrete is poured.
, and at the same time, the gap between the excavated hole 23 and the iron plate I7 is filled with a filler 25 such as sand (C).

Eventually, the concrete 24 in the area corresponding to the consolidation settlement layer was completed at the same time as the cast-in-place pile was completed due to the solidification of the concrete 24.
The edge cutting tS position having the FlkM force cutting material 20 on the outer periphery is also completed.

In addition, in the method of the present invention, in the part of the steel plate 17, the smooth surface in the expanded state (because of the steel plate) subjected to concrete side pressure completely coincides with the layered reinforcement of the friction force cutting material 20, so that the excavation hole 23 The most desirable smooth edge cutting layer is automatically formed regardless of the wall surface condition, but in the bag 18 section, the friction cutting material 20 is pressed against the wall surface of the excavation hole 23.
Therefore, in order to form a cutting layer with a smooth surface, which is the best form, it is preferable that the wall surface of the excavation hole 23 is used in ground that is not very rough.

Furthermore, as is clear from the above description, the bag 18 only needs to be able to hold the cast-in-place pile for a period of time until it solidifies, and is unnecessary if a frictional force removing layer is formed, and the durability is good within that range. It is.

``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 the reinforcing bar cage, and there is no need to attach a large number of divided bodies to the reinforcing bar cage.Furthermore, the frictional force of the concrete, which hinders frictional force cutting, is eliminated. There is no invasion to the outside of the layer.

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

Furthermore, the friction 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, and it does not cause any delay in the construction period, which is extremely meaningful in practice.

[Brief explanation of drawings]

Figures 1a and 1b are overall overhead views for explaining the bag used in the present invention, a plane sectional view taken along line bb in figure a, and Figures 2 to 4 and 5 to 6 are conventional means, respectively. 7a-c
1 is a construction procedure diagram of the method of the present invention. 1.1"...ground, 2.2°...concrete pile,
3.3'...Steel pipe, 4...Outer peripheral wall, 4"...Injection pipe, 5...Lubricant, 6"...Tip, 7゛...Lubricant, 8°...・Permeation layer, 11... Asphalt, 12
...Plate, 13...Rebar cage, 14...Wire, 1
5...Drilling hole, 16...Cylinder, 17...Iron plate, 1
8... Bag, 19... Hollow ring part, 20... Friction force cutting material, 21... Strap stopper, 22... Rebar basket, 2
3...Drilling hole, 24...Concrete, 25...
Filling material. Zunshi θ

Claims (1)

[Claims] Iron plates and bags made of water-stopping sheet material are arranged alternately on the circumference, and a hollow ring in the form of a floating ring is provided at the lowest end as a continuation of the bags, forming a cylinder. A friction cutting material such as asphalt is attached to the surface and the outer surface of the inner wall of the bag, and this is wrapped in advance with a string or the like at a predetermined position of the reinforcing bar cage, and after the reinforcing bar cage is erected in the excavation hole, The bag and the hollow ring are filled with drilling mud, etc., and held in an expanded state. Concrete is poured under this condition, and a filler such as sand is filled into the gap between the borehole wall and the steel plate. A method for removing negative frictional force from a cast-in-place pile, characterized in that a layer of frictional cutting material attached to the outer circumferential surface is simultaneously formed surrounding the consolidation settlement layer.