JPH0413513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reinforcing or repairing cement (mortar or concrete) structures, which are typically provided in contact with rock formations in tunnels.

Conventionally, as a method for repairing damaged or water leaking parts of existing cement structures, an epoxy adhesive consisting of a base agent and a hardening agent is applied to the damaged area, and then a cement composition consisting of water, cement, and aggregate is applied. Attempts have been made to firmly adhere the cement composition to the structure. However, in this case, the optimum leaving time between applying the adhesive and applying the cement composition differs slightly depending on the environmental temperature, the presence or absence of wind, strength, etc., but it is important to set and adhere to this optimum time on site. Therefore, the durability of cement structures repaired by this method varied greatly.

In addition, in recent years, water, cement,
It is also known to use polymer cement compositions containing cement polymers and, if necessary, aggregates, but these compositions provide sufficient adhesive strength to existing cement structures without the use of epoxy adhesives or the like. Although initial adhesive strength was achieved, over time there were many cases in which the layer provided by the repair peeled off from the underlying existing cement structure. In view of the above-mentioned conventional repair methods, the present invention eliminates the need to use epoxy adhesives, etc., and the polymer cement layer provided by the repair does not peel off from the existing cement structure for a long period of time. The purpose of this project is to provide a repair method for cement structures that can fully demonstrate performance such as strength and waterproofness even with a thin repair layer compared to other methods. installed in close contact with the inner wall surface of the cement structure of the tunnel, and the metal mesh is held down by a plurality of steel strips,
In addition, the steel band and metal mesh are fixed at multiple locations using fastening fittings consisting of bolts and nuts that are driven into the base of the existing cement structure, and at least the metal mesh, steel band, and fastening fitting are fixed with a polymer cement composition. The present invention relates to a method for repairing a tunnel, the method comprising coating the tunnel to form a polymer cement layer.

As the metal net in the present invention, iron is preferably used, and so-called metal lath (flat lath,
Flat laths are often used among re-plus, knobby laths, and corrugated laths), wire laths, welded wire meshes in which the intersection points of meshes are welded, etc. are widely used. In addition, the mesh roughness, material thickness, etc. are appropriately selected depending on the progress of cracks in the damaged part to be repaired, the dimensions of the steel strip used as necessary, and the type of fastening fittings, etc., but in general, the thickness The length is 0.4~2m/m, the width is 1
It is said to be about 3 m/m, and 0.8 for metal lath.
A mesh of approximately 1.5 m/m x 1.2 to 2.0 m/m is preferably used, and the mesh roughness is usually approximately 20 to 100 m/m.
Preferably it is about 20 to 40 m/m. In the present invention, these metal nets have a thickness of 0.5 to 6 m/
m, preferably 1 to 3 m/m, width 5 to 40 m/m,
Preferably, it is fixed via a flat steel plate of 10 to 30 m/m. That is, by stretching the steel band plate on the outside of the metal net and fixing the steel band plate to the existing cement structure using fastening fittings, the sandwiched metal net is indirectly fixed. The interval between the fastening fittings to be driven is not particularly limited, but is usually 10 to 50 cm.

Further, as the fastening fitting, a drive set anchor, a self-drilling anchor, a wedge, a construction fastener gun, etc., which will be described later, is used, which has an outer cylinder and a part of the embedded bolt can be screwed into the inside of the outer cylinder. Anchor bolts such as pin anchors are preferred, but concrete nails, barbed nails, wood screws, screws, etc. can also be used.

The polymer cement composition in the present invention is:
Conventionally known products containing water, cement, cement polymers, and aggregates if necessary are widely used, and depending on the presence or absence of aggregates, types, etc., polymer cement paste, polymer cement mortar,
It is called polymer cement concrete, etc. As the cement, Portland cement, alumina cement, mixed cement, etc. are often used, and these are used alone or in an appropriate mixture. Cement polymers are also called polymer admixtures, and they exist as polymers in cured polymer cement and are mixed in to improve the quality of the product, such as its impact resistance and adhesion to existing structures. Synthetic rubbers such as natural rubber, chloroprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber, polyvinyl acetate, ethylene-vinyl acetate copolymer, styrene-acrylic copolymer poly Examples include acrylic acid ester, polyvinyl chloride, polyvinylidene chloride, polyvinyl propionate, and the like. Most of these, except for natural rubber, are synthesized by emulsion polymerization, and then stabilizers, antifoaming agents, etc. are added as necessary, and they are usually used in the form of emulsion or latex.

Among the above polymers, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-vinyl acetate copolymer, and styrene-acrylic copolymer are selected from the viewpoints of adhesion to existing cement structures, flexibility, impact strength, economic efficiency, etc. Coalescing, etc. are preferred, and styrene-butadiene rubber and ethylene-vinyl acetate copolymers are particularly preferred. However, these polymers usually have a solid content of 10% per 100 parts by weight of cement.
~30 parts by weight is added. The type and amount of aggregate to be used as necessary is determined depending on the state of damage, scale, etc. of the existing cement structure to be repaired. Silica sand containing anhydrous silicic acid as a main component is preferably used, and is usually used at a concentration of 400 parts by weight per 100 parts by weight of cement in terms of workability, shrinkage properties during hardening of the polymer cement composition, various strengths after hardening, and economic efficiency. It is used in a range of parts by weight or less, and as the coarse aggregate, conventionally known chestnut stone and crushed stone for cement concrete are widely used.

As described below, the present inventors have confirmed that the polymer cement composition has greater waterproofing performance than conventional cement compositions, but in order to provide even better waterproofing properties, various waterproofing agents have been added. may be added to the polymer cement composition. Preferred examples of the waterproofing agent include amorphous aluminum silicate in which the molar ratio of aluminum oxide to silicon dioxide is 1:1 to 1:10, and synthetic amorphous aluminum silicate in which the molar ratio of aluminum oxide to silicon dioxide is approximately 1:9. Particularly preferred is aluminum silicate.

Furthermore, alkali-resistant glass fibers may be mixed into the polymer cement composition in order to increase the strength of the coating layer obtained by covering the metal mesh. Such glass fibers usually have a diameter of 2
~15μ, length 3-50m/m, preferably diameter 7
~13μ and a length of about 3 to 10m/m are used.

The present invention is characterized in that, compared to conventional cement compositions, the polymer cement composition has superior adhesion to cement structures such as concrete frames, has excellent adhesion to metals, particularly iron, and has excellent waterproof properties. This was done with a focus on

That is, according to the findings of the present inventors, polymer cement compositions generally have superior adhesion to metals, particularly iron, than to cement structures; for example, styrene-butadiene rubber or ethylene-vinyl acetate copolymer is used as the polymer. When comparing a polymer cement composition with a conventional cement composition in which the polymer-cement ratio, water-cement ratio, polymer specifications, etc. are within the range of normal use, the tensile adhesive strength of the former to steel plate is approximately the same as that of the latter. The waterproof (impermeable) performance of the former is about 40 to 60 times that of the latter (both adhesive strength and waterproof performance are the values when ordinary Boltland cement is used as cement, the water permeability test is based on JISA1404). (measured value). Next, the method of the present invention will be explained with reference to the drawings showing one embodiment thereof.

In Figures 1 to 4, 2 is an old reinforced concrete layer installed in contact with the rock layer 1 of the tunnel, 3 is a layer of 1 m/m thick, 1.5 m/m wide, and 30 m/m coarse mesh.
×30m/m extended metal lath made of mild steel plate,
A and B are steel strips each having a thickness of 2 m/m and a width of 20 m/m, and are arranged so as to cross each other perpendicularly. In addition, the drive set type anchor bolt 4 is
An outer cylinder 5 with a thread provided from the lower end to the center of the inner side wall in FIG. It consists of 8.

To repair the concrete layer 2, first, the metal lath 3 is brought into contact with the concrete layer 1 as shown in Fig.
cm) from below and tighten the steel strips A and B to the concrete layer 2 with anchor bolts 4, thereby tensioning the metal lath 3. To fix the steel bands A and B with anchor bolts 4, drill holes in the concrete layer 2, and bolts 6
Using an appropriate jig etc., drive the anchor bolt and 4 screwed into the hole, then rotate the bolt.
Steel strip A or B that is advanced and has small holes drilled in advance;
After attaching washers 7, tighten nuts 3.

Then, 100 parts by weight of ordinary Bolland cement,
A polymer consisting of 30 parts by weight of styrene/butadiene (55/45) copolymer emulsion (solid content 45%), 300 parts by weight of silica sand with a particle size of 1ⓓ or less, 30 parts by weight of on-site mixed water, and an appropriate amount of glass fiber. The cement composition is stirred and mixed to form a mortar, and sprayed using an air mortar gun to coat the surface of the concrete layer 2, metal lath 3, steel strips A, B,
The anchor bolt 6 is completely covered and pressed down with a plastering trowel to form a polymer cement layer 9 with a smooth surface and a thickness of about 11 m/m.

The thickness of the polymer cement layer depends on the degree of damage to the existing cement structure, but if it is too thin, the purpose of the repair will not be achieved, and if it is too thick, it will pose a problem for safe driving of vehicles, so it should be around 5 to 15 m/m. do.

Although the method of the present invention is suitable as a method for preventing tunnel deterioration and water leakage, it can also be used for cement structures with no damaged parts immediately after construction for the purpose of reinforcing waterproofness and durability. Preferably, a polymer cement composition containing high quality aluminum silicate is used.

The method of the present invention is constructed as described above and has good workability because it does not use a two-component curing epoxy adhesive.

In addition, the method of the present invention is such that a metal mesh, which is installed in close contact with the inner wall surface of the cement structure of an existing tunnel, is held down by a plurality of steel bands, and is fixed at a plurality of locations with fastening fittings, is attached to the cement structure. Since the surface is coated with the polymer cement composition, the coating layer becomes an integral structure with the metal mesh, effectively preventing cracks, etc. that have weakened and formed in the existing cement structure from further propagating and expanding from the surface. Can be prevented.

In particular, since the metal mesh mentioned above is directly or indirectly fixed to the existing cement structure using fastening fittings, it is highly effective in preventing damage and peeling off of weak parts in the event of an earthquake, etc. . Furthermore, according to the invention, the thickness of the polymer cement layer is between 5 and 15
Since it is possible to reduce the thickness to about m/m, it is possible to perform a repair method that is extremely unlikely to cause traffic problems such as vehicles.

[Brief explanation of drawings]

Figures 1 to 4 are explanatory diagrams of the repair method according to the present invention, where Figure 1 is a longitudinal cross-sectional view of the top of an existing tunnel, and Figure 2 is a state in which the metal lath is fixed to the concrete layer in Figure 1. Figure 3 is a top view of Figure 2 (however, the reduction magnification is different), Figure 4 is a top view of Figure 2.
FIG. 2 is a cross-sectional view of a state in which the polymer cement composition is coated in the figure. 2...Reinforced concrete layer, 3...Metal lath, 4...Drive set type anchor bolt, 9
...polymer cement layer.

Claims (1)

[Claims] 1. A metal net is installed in close contact with the inner wall surface of the cement structure of an existing tunnel, the metal net is held down by a plurality of steel bands, and the base is attached to the existing cement structure. The steel band and metal mesh are fixed at multiple locations using fastening fittings consisting of bolts and nuts, and the metal mesh, steel band and fastening fitting are coated with a polymer cement composition to form a polymer cement layer. A tunnel repair method characterized by: 2. The repair method according to item 1, wherein the polymer in the polymer cement composition is styrene-butadiene rubber. 3. The repair method according to item 1, wherein the polymer in the polymer cement composition is an ethylene-vinyl acetate copolymer.