JPS61151318A - Method of elimianting negative friction force of cast-in-place pile - Google Patents

Abstract

PURPOSE:To eliminate a negative friction force, by a method wherein, after a reinforcing cage, around which a bag body of a sheet material having a friction force cutting material attached to the surface of its inner wall, is erected in an excavated hole, muddy water is poured in the bag body, and concrete is placed in an expanded condition. CONSTITUTION:A reinforcing cage 19, around which a bag body 16, having a friction force cutting material 17, such as asphalt, attached to the surface of its inner wall and made of a cut off material formed in the shape of a life buoy in horizontal cross section, is wound by means of a wire 20 and the like, is erected in an excavated hole 21. When water is poured through a pipe 16a for pouring water in the bag body 1 for filling to expand the bag body 16, an outer wall 16c is firmly adhered to the surface of the excavated hole 21. Concrete is poured in a condition to hold expansion of the bag body 16. This prevents concrete from entering between the bag body 1 and the wall surface of the excavated hole 21, resulting in the possibility to eliminate a negative friction force.

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 carry out edge cutting measures on the ground as described above, so a completely different method is taken.

For example, in Japanese Patent Publication No. 5 B-58495, as shown in FIG. 2, a plurality of plates 12 to which asphalt 11 or the like is adhered are attached to the outer periphery of a reinforcing bar cage 13 with wires 14 and built into an excavated hole 15. It is assumed that 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 poured concrete.
In No. 2736, Figures 3 (a) to (dl) are explanatory diagrams showing the construction procedure of concrete piles and the state of ground subsidence, and Figure 3 (dl) is 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 were driven into the ground 1 and the concrete solidified, a steel pipe 3 with a diameter larger than the concrete piles 2 and having a lubricant 5 attached to the outer peripheral wall 4 was driven. In addition, in Japanese Patent Application No. 59-108544, a steel pipe with an injection pipe is inserted as shown in Figs. As shown in Fig. 6, which is an enlarged cutaway plan view of the concrete pile, after the concrete pile 2' is driven into the ground 1'' and the concrete hardens, a 4° injection pipe with a diameter larger than the concrete pile 2'' is inserted. Insert the steel pipe 3° with the injection pipe 4° into the concrete pile 2', then inject 7" of lubricant into the ground 1° from the tip 6" of the injection pipe 4°, and pull up the steel pipe 3' with the injection shaft 4", and attach it to the concrete pile. A permeation layer 8' of lubricant 7' is formed around the lubricant 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 bar cages, the diameter of the reinforcing bar cages 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 tube 4° to the steel pipe 3'', but also has the disadvantage that the injection tube 4'' takes a lot of effort when inserted 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 ``Operations'' The present invention was made in view of the above circumstances, and its gist is to provide a planar cross-section of a friction-cutting material such as asphalt attached to an inner wall surface. A bag body made of a floating ring-shaped water-stopping sheet material is wrapped in advance around a predetermined position on a reinforcing bar cage, and after the reinforcing bar cage is erected in an excavation hole, the bag body is inflated by injecting muddy water for drilling, etc. Assuming that concrete is placed under this condition, we will provide a cast-in-place pile with a layer of frictional cutting material attached to the outer circumferential surface simultaneously formed in the consolidation settlement layer. The problem lies in completely eliminating the problems of the conventional means mentioned above.

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

FIGS. 1a and 1b are explanatory diagrams of a bag 16, which is a feature of the present invention. This bag is made of a water-stopping sheet material with a flat cross-section floating ring shape, and the surface of the inner wall 16a is A friction force cutting material 17 such as asphalt is attached, and a water injection pipe 16b is attached to a predetermined location on the upper end.

When the water 18 is injected and filled into the bag from the water injection pipe 16b, it expands, imparts rigidity, and becomes stable in a cylindrical shape. A layer with a layer of water 18 interposed therein is formed.

The present invention is a cast-in-place pile that simultaneously forms edge cutting measures by placing these in advance at a predetermined position of a built-in reinforcing bar cage, that is, at a location corresponding to the consolidation settlement layer, and then placing concrete. be.

That is, FIGS. 7a, b, and c are diagrams showing the construction procedure of the method of the present invention in plan and longitudinal section, in which the reinforcing bar cage 19 with the bag body 16 wrapped around it with a fastening means such as a wire 20 is inserted into the excavated hole 21. Build on (a).

Next, when water is injected into the bag 1 from the water injection pipe 16a (mud for drilling may be used) and the bag 16 is expanded, rigidity is imparted and the bag 16, which has a larger diameter in a ring shape, has its outer wall 16
c is pressed against the surface of the excavation hole 21, and becomes stuck to the wall surface of the excavation hole 21 (b).

Therefore, even when concrete is poured to be described later, the concrete will not enter between the bag 1 and the wall surface of the excavation hole 21.

If the concrete 22 is poured after the bag l is maintained in expansion by taking measures such as plugging the water injection pipe 16b, the consolidation settlement layer will be formed at the same time as the concrete 22 hardens and the cast-in-place pile is completed. Concrete 22 in the area corresponding to
The edge cutting device with 17 layers of friction cutting material on the outer periphery is also completed (C).

In addition, in the method of the present invention, since the friction force cutting material 17 follows the manner in which the bag body 1 is pressed against the wall surface of the excavation hole 21,
In order to form the edge cutting layer on a smooth surface in the best form, it is best to apply it to the ground where the wall surface of the excavation hole 21 is finished smooth.

Further, the bag 16 may be provided with reinforcing hands at predetermined intervals to prevent bursting, and furthermore, as is clear from the above, the bag 16 can be maintained for a period of time until the cast-in-place pile hardens. If a frictional force removing layer is formed, it is unnecessary, and the durability is good within this range.

"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 would hinder 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 illustrating the bag used in the present invention, a plane sectional view taken along line bb in figure a, Figures 2 to 4, and 5 to 6 are conventional Explanatory diagram of the means, Figure 7a ”
-c 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... Excavation hole, 16... Bag body, 16a... Inner wall,
16b...Water injection pipe, 16c...Outer wall, 17.
...Friction force cutting material, 18...Water, 19...Reinforced cage, 20...Wire, 21...Drilled hole, 22...Concrete. Nrashi 7ri's trowel

Claims (1)

[Claims] A bag made of a water-stopping sheet material in the shape of a flat cross-section floating ring with a friction-cutting material such as asphalt attached to the inner wall surface is wrapped in advance at a predetermined position on a reinforcing bar cage, and after the reinforcing bar cage is erected in the excavation hole, The bag is filled with drilling mud, etc. and kept in an expanded state, and concrete is poured under this condition.At the same time, a layer of frictional cutting material is attached to the outer peripheral surface in the consolidation settlement layer. A method for removing negative frictional force from a cast-in-place pile, characterized by forming an encirclement.