JPS6320309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an outer wall structure for an underground space that facilitates and completes soil corrosion prevention measures.

Piping buried underground, basements, underground tanks, etc. require measures against soil corrosion so that they can withstand long-term use. In the soil, corrosion factors such as oxygen, moisture, and soluble salts are involved in a complex manner and change over time.
It is difficult to unambiguously determine the corrosivity. Furthermore, the environment in which the same structures come into contact is non-uniform, and as a result, localized corrosion such as pitting corrosion is likely to occur after a long period of time. Moreover, because it is difficult to predict, pitting corrosion may progress unexpectedly and penetrate in a short period of time even in soil that is considered to have low corrosivity. Furthermore, it is difficult to test the degree of corrosion and repair techniques for underground structures, so underground structures that require particularly high safety require semi-permanent and maintenance-free anti-corrosion measures.

Conventionally, when constructing a steel structure underground, coating with paint or lining material and cathodic protection have been used as anti-corrosion measures. In case of painting,
If the paint film is damaged during civil engineering work, corrosion will concentrate in that area and cause pitting corrosion, so if cathodic protection is used in conjunction with this, even if a defect occurs, that area will be sufficiently protected. . When applying cathodic protection to underground structures, use a backing film 8 as shown in Figure 1.
The usual method is to bury a galvanic anode 3 wrapped in earth and sand 6 in soil 6 in close proximity to a panel 1 of a structure covered with a coating film 2, and to establish continuity with a wire 5. The backing film 8 is normally used for corrosion protection work in the soil to reduce the grounding resistance of the galvanic anode and facilitate the generation of anticorrosive current. Mixed proportions are common.

With the above method, the construction work for cathodic protection is added to the construction work for burying the structure, which increases the scale of the work, and when adding a small underground space, there is not enough land, making it difficult to bury the galvanic anode. It is.
Therefore, the current method is to harden the exterior of unpainted or lightly painted steel panels with concrete. By the way, concrete is a corrosion-proof construction method that suppresses the elution of base metal due to its inherent alkalinity, and also suppresses the buoyancy of steel structures. However, during long-term use, cracks may form, corrosive groundwater may penetrate, and pitting corrosion may occur, so it is not a perfect anti-corrosion measure.

The present invention simplifies the above-mentioned corrosion protection specifications, compensates for the above-mentioned drawbacks, and provides an underground space outer wall structure with extremely high corrosion protection effects. That is, the present invention involves attaching a galvanic anode made of a metal or alloy having a potential lower than steel to a part of a steel member while maintaining electrical continuity, and covering the member and the galvanic anode with mortar or concrete. This is an underground space exterior wall structure with excellent corrosion resistance.

The present invention will be explained in detail below based on the drawings.

Fig. 2 shows a galvanic anode 3 made of a metal or alloy having a potential less base than steel is attached to a steel panel 1 having an anticorrosive coating 2 using a connecting means 4 such as welding or bolts to establish electrical continuity with the steel panel 1. , which shows a structure in which the galvanic anode 3 is covered with a backing film 8 as already described, and all of these are further covered with mortar or concrete 7 to a desired thickness, and this figure shows a structure in which this is buried in earth and sand 6. It shows the state that has been applied. In this way, even if cracks occur in the mortar or concrete 7, local corrosion is suppressed by the action of the galvanic anode, so complete corrosion prevention measures can be provided.

FIG. 3 shows another embodiment of the present invention, in which a galvanic anode 3 made of a metal or alloy having a potential less base than steel is placed on one surface of a steel panel.
This shows a structure in which the mounting part is machined into a concave shape, the galvanic anode 3 is mounted therein by the same means as shown in FIG. hand,
The state in which this is buried in the earth and sand 6 is shown in the same manner as in FIG. 2. Compared to the structure shown in FIG. 2, the structure shown in FIG. 3 has a shape that is more suitable for transporting and assembling the panel. In the above embodiment, as shown in FIGS. 2 and 3, the galvanic anode 3 is of a structure confined in the mortar or concrete 7, but the galvanic anode 3 is directly connected to the mortar or concrete 7 without the backup film 8. Of course, it is also possible to use it by covering it with. That is, the mortar or concrete 7 acts as a backing film 8 to facilitate the generation of anticorrosion current. However, in some cases, as the galvanic anode wears out, its reaction products accumulate on the inner surface of the mortar or concrete, increasing the volume and causing cracks in the mortar or concrete. In such a case, if the backup film 8 is present between the galvanic anode 3 and the mortar or concrete 7, the volumetric expansion due to the reaction product of the galvanic anode 3 will be absorbed by the backup film 8, so the backup film 8 can be used. Also good.

Regarding the structures shown in Figures 2 and 3 above, it is possible to use the steel panels without coating in either case, but when using them in harsh environments such as coastal reclaimed land, it is recommended to apply anti-corrosion coating. A hardened steel panel is more suitable. Furthermore, part or all of the structure described above may be manufactured in advance at a factory, or the entire structure may be assembled on-site.

The type and size of the galvanic anode used in the structure of the present invention,
The quantity is determined according to conventional cathodic protection design, depending on the ground surface area and life of the buried structure and the resistivity of the soil. The shape of the galvanic anode can be either with a core for welding installation or with bolt holes for bolt-nut installation, but if the unit member is a panel, a flat plate is suitable for making it suitable for transportation. There is.

In addition, in the structure of the present invention, the galvanic anodes are not necessarily attached to all the members; the galvanic anodes are attached only to some of the members, and electrical continuity with other members is ensured using assembly bolts or the like. It is also possible to adopt a structure of

The coating thickness of mortar or concrete in the structure of the present invention is not particularly limited, but 50 to 200 mm is suitable based on the surface of the steel member. As mentioned above, the mortar or concrete coating in the present invention is provided for the purpose of corrosion prevention, but the mortar or concrete may be coated with reinforcing materials as long as it does not impair the corrosion prevention effect.
A swelling agent or the like may be added as necessary.

By adopting such a structure, the present invention brings about the following effects. That is, although the corrosion-preventing effect of galvanic anode installation is well known, the usual cathodic protection involves not only the aforementioned problem of increased construction costs, but also the following technical problems.

(1) Measurement of resistivity of buried soil and anode placement design based on this measurement.

(2) Design, construction, and management of current flow between the galvanic anode and target parts. On the other hand, in the structure of the present invention, the anticorrosion current is distributed well because the path for the anticorrosion current is made of mortar or concrete, which has a relatively lower resistivity than soil.

Therefore, the layout design of the galvanic anode can be easily done without the help of experts, since it is possible to apply a basic design with only the geometrical structure of the structure and the required life as the main prerequisites. Can be done.

Furthermore, since the calcium content in the mortar or concrete is precipitated onto the surface of the steel component to be protected against corrosion, the necessary corrosion protection can be achieved with a smaller current than in the case of a bare surface, making it possible to create an economical and reliable corrosion protection design. It is.

On the other hand, mortar or concrete is itself protective against external soil corrosive environments, and a coating thickness of 50 to 200 mm will usually prevent corrosion of the underlying steel. Even if cracks occur in the mortar or concrete, corrosion will be reliably prevented by the action of the galvanic anode.

Finally, the effects of the present invention will be explained in more detail with reference to Examples.

Example: A total surface area of approximately 60 m 2 was produced using 4 steel panels of 900 x 2700 mm on each side of the short side, 5 panels on both sides of the long side, and 5 panels of 900 x 3600 mm on the bottom ^. For the exterior wall structure of the underground space of ×
As shown in Figure 3, for the 3600mm bottom panel, welded a plate-like electrode of the same type to the concave pressed part in the center so that its surface was the same as the panel surface, and then A panel was used in which the void around the galvanic anode was filled with mortar. Next, the long side is 5m,
The above structure was installed on the concrete base of an underground hole with a short side of 4 m and a depth of 3 m, with a mortar layer for joining, and a formwork was installed on the side to form a 100 mm thick concrete covering layer. The invented structure was manufactured. As a result of backfilling the entire surface of this structure with earth and sand and burying it for two years, no rust was observed on the underlying steel surface, and judging from the change in steel surface potential over two years, a corrosion-protected life of more than 20 years can be expected. There was found.

As described above, the present invention has the advantage that corrosion protection work for underground structures can be carried out simply and completely without fear of unexpected local corrosion.
The service life of underground structures will also be extended and their reliability will be significantly improved. Particularly, in recent years, the use of basements has become more important due to housing conditions, and corrosion protection underground is of great significance for the future popularization.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional underground corrosion protection means, and FIGS. 2 and 3 are schematic views showing embodiments of the structure of the present invention. 1 is a steel panel for an underground structure, 2 is an anti-corrosion coating, 3 is a galvanic anode for cathodic protection, 4 is a galvanic anode connection means, 5 is a galvanic anode connection connection, 6 is earth and sand,
7 is mortar or concrete, 8 is backfill.

Claims (1)

[Claims] 1. A galvanic anode made of a metal or alloy with a potential lower than that of steel is attached to a part of a steel member while maintaining electrical continuity, and the member and the galvanic anode are covered with mortar or concrete. Features an underground space exterior wall structure with excellent corrosion resistance.