JPS5978809A - Method of drawing steel material from cement group hardened material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for pulling out a steel material inserted into a cement-based hardened material, such as a method for pulling out a steel material inserted into a cast-in-place cement mortar pile without requiring a large force after the mortar has solidified and hardened. 1- Regarding the method of pulling out. The steel material here refers to all rod-shaped and linear materials such as H-shaped steel, ■-shaped steel, etc., but for convenience, the following explanation will be made using H-shaped steel as an example. Further, the cement-based cured product will also be explained using cement mortar as an example.

Until now, when pulling out an H-beam inserted into cement mortar after it has hardened, it has been difficult to pull it out because the cement mortar adheres to the surface of the H-beam, and it has been difficult to pull it out with excessive force. If so, the H-shaped steel will break,
There were disadvantages such as damage to the cement mortar or adverse effects on surrounding structures.

For this reason, conventionally, a sliding surface has been provided on the surface of the H-section steel, and the unnecessary I-■ section steel has been pulled out and collected after construction is completed. For this sliding surface, a method has been adopted in which grease, paraffin, asphalt, tar, sheet, cement setting inhibitor, etc. are applied or attached to the surface of the H-beam steel to reduce the sliding resistance. However, these methods have the following problems: 2- The materials used have high fluidity and are difficult to work with, are easy to peel off during insertion, and are insufficient to reduce sliding resistance;
There were drawbacks such as the sliding resistance increasing as time passed after insertion.

According to the present invention, as a method for solving the above-mentioned drawbacks and pulling out steel materials with less labor and mechanical force, the steel material is inserted into the cement-based hardened material at the portion where it comes into contact with the cement-based hardened material before inserting the steel material into the cement-based hardened material. , a resin coating that deteriorates due to the action of alkaline components in the cement-based cured product is applied in advance,
A method is provided in which the resin coating is deteriorated over time by the action of the alkaline component, thereby making it easier to draw out the steel material.

In general, resin compounds exhibit good resin strength (elongation, tension, compression, etc.) during del formation, but some resin compounds exhibit gel properties in a relatively short period of time when affected by water or alkaline components of cement mortar. change. The method of the present invention utilizes this fact to form a strong coating when the H-section steel is in contact with the cement F mortar, maintaining good workability, and
After the H-shaped steel comes into contact with cement mortar, the film deteriorates (becomes like grease) after a certain period of time, which reduces the resistance on the sliding surface.

In the present invention, any resin can be used as long as it is degraded by alkali. Examples of these are:
Examples include hydrophilic polyurethane-based, polyester-based, acrylamide-based, and urea-based resins. Of these,
Hydrophilic polyurethane resins are particularly suitable because of the ease of controlling the properties of the resin and the ease of gel formation. Deterioration of these resins due to alkaline components has traditionally been considered a drawback, but in the present invention, positive benefits are obtained by taking advantage of this drawback. These resins may contain additives such as calcium carbonate, asbestos, rock wool, bentonite, and
Preference is given to using it with water as solvent.

4- Next, a case in which the method of the present invention is applied to a column-type underground continuous wall construction method, which is an example of its implementation target, will be described with reference to the accompanying drawings.

As shown in Figures 1 to 3, mortar (
31) and a core material (H-shaped steel) (32) whose surface is covered with a coating (not shown for brevity) (32) are provided in succession, and the mortar piles (3) are surrounded by The excavated ground is dug up to a predetermined depth by applying 21) and struts (22).

The above mortar pile (3) is first made by digging a vertical hole (4) in the ground (1) as shown in Fig.
31), and then, before the mortar (31) has hardened, add the core material (H-beam steel) (32) as shown in Figure 5.
It is created by inserting . As shown in FIG. 8, a resin coating (33) is provided in advance on the surface of the H-shaped steel (32) that will be in contact with the mortar.

The coating may be formed by spraying, coating, or dipping in a resin solution bath. The thickness of the coating is approximately 0.4-1. OnHm.

5- After the role of the dug shaft (2) is completed, that is, after the structure inside the shaft is completed, remove the H-beam (32) that has completed its role from the mortar pile (3). During this time,
On the surface of 2), the coating gradually deteriorated and the slip resistance gradually decreased. For pulling out, for example, using a pulling device (5) as shown in Fig. 7, hold the H-shaped steel (32) from both sides with chucks (51), and repeat the operation of extending the jacks (52) and pulling it up. This is done by giving back. In addition to the pulling device (5) as shown, a vibrating pile pulling rock,
It is also possible to use equipment that is easily available at the construction site, such as a multiple pulley puller. According to the method of the present invention, the pull-out resistance can be reduced to about 2 tons/m2 or less, so in the case of an H-beam steel with 7 flange dimensions of 30 cm and a length of 15 m (surface area 27 m2), the required pull-out force is Each bottle weighs approximately 54 tons or less. Therefore, it can be easily pulled out using a commercially available vibrohammer or the like.

In addition, if an impact is applied to the head of the steel material (32) with a weight before the mortar (31) is sufficiently hardened, it will be easier to pull it out after hardening.

The table below shows the results of measuring the pull-out resistance of mortar piles made of H-beam steel with a seven-lung dimension of 30 cm and a length of 15 m, coated with various film-forming compositions.

In the present invention, the film-forming composition is not limited to a specific formulation as long as it is based on a resin that is degraded by alkali, and can bring about the desired effects of the present invention.

As mentioned above, the present invention has produced unexpected effects by reversing the deterioration caused by alkali, which was thought to be a drawback of resin compounds, and eliminates the drawbacks of conventional steel drawing methods. It is something. In other words,
When applied to steel materials, it has appropriate fluidity, so it does not drip or become sticky, and it is less likely to peel off when inserted into mortar, so the coating can be thin.
Furthermore, the resistance force when pulling out the steel material is significantly reduced.

[Brief explanation of drawings]

Figures 1 to 3 show the concept of the column-type underground continuous wall construction method using cast-in-place mortar piles, which is the subject of the present invention. Figure 1 is a plan view, and Figure 2 is a cross-sectional view. , Figure 3 is the second
This is a cross section taken along line A-A in the figure. FIGS. 9-4 to 7 are longitudinal cross-sectional views showing the implementation procedure using the cast-in-place mortar pile according to the present invention as an example. FIG. 8 is the B-1 side of FIG. 6. In the figure, 1 is the ground, 2 is the shaft, 21 is the upright, 22
3 is a strut beam, 3 is a mortar pile, 31 is mortar, 32 is a steel material, 33 is a resin coating, 4 is a vertical hole, 5 is a drawing device, 51
is a chuck, 52 is a jack, and 53 is a base. 10-

Claims (1)

[Claims] A method in which a steel material inserted into a cement-based hardened material is pulled out from the cement-based hardened material after the cement-based hardened material has solidified and hardened and achieved the intended purpose of the steel material and the cement-based hardened material. Before inserting the steel material into an object, a resin coating that is degraded by the alkaline components in the cement-based cured product is applied in advance to the part where the steel material comes into contact with the cement-based cured product. A method for pulling out steel material from a cement-based hardened material, characterized by facilitating the pulling out.