EP0002216B1 - Reinforcing elements for reinforced earth structures - Google Patents

Description

For supporting structures in which metal strips are regularly and layered inserted in a non-cohesive floor, which absorb tensile forces and dissipate them into the ground through friction, the term "reinforced earth" has become established. The so-called filling floor becomes a load-bearing component of the building. In order to prevent the filling base from being bent off, an outer skin is necessary, which can consist of metallic half-shells or plate-shaped prefabricated concrete parts, the fastening of which is described, for example, in French Pat. No. 2,221,588. For example, "Reinforced Earth" is reported in "Straße und Autobahn" 5 (1976) 3/10, "Tiefbau" 8 and 9 (1976) or "Die Bautechnik" 53 (1976) 7, 217/226. Proposals are made in FR - PS 2 234 427 for anchoring mats or tapes in the ground.

For corrosion reasons, the metal reinforcement tapes used must have a zinc coating between 26 and 56 µ, whereby the imperfect cathodic edge protection for the tapes cut from galvanized sheet steel is particularly unfavorable. In addition, for safety reasons, a corrosion surcharge of up to 50% of the nominal thickness required for load transfer must be made. Another disadvantage is that despite these measures, additional requirements must be placed on the pH value and the electrical resistance of the filling floor in order to avoid critical conditions of use for the metallic reinforcement.

These measures limit the flat design of the strips with a high ratio of surface to cross-sectional area for reasons of the desired high frictional forces, as a result of which the transmission of the frictional forces can become too small. In order to improve the adhesive properties of steel strips, complex, rolled profiles with cross ribs of various types, such as curved ribs, oblique ribs or swept ribs, have been proposed.

Because of the particularly critical corrosion conditions in gaps, the proposed screw connections or bolt connections for the connection between the outer skin of the building and the reinforcement strips or between the reinforcement strips are also susceptible to failure. The use of corrosion-protected screws and washers, as prescribed by the provisional guidelines of the Federal Highway Research Institute for the use of the "reinforced earth" construction method, is particularly problematic in areas exposed to de-icing salt.

The invention has for its object to avoid the disadvantages and weak points mentioned above in the system "reinforced earth", in particular corrosion damage and to improve the friction in the earth structure. Other tasks include improving manageability and simple, secure connections between the reinforcement elements and the outer skin. The object is achieved in that the braided or woven tapes used are impregnated with a resin which cures only through the moisture in the filling floor.

According to the invention, it is proposed to use corrosion-resistant, high-strength woven or braided tapes as reinforcement elements. With predominantly warp-reinforced fabrics or braids made from stretched organic fibers, the strengths of the structural steels normally used can already be achieved, the fabrics or braids being able to be regarded as largely corrosion-resistant simply by selecting suitable base materials. Therefore, it is possible to use correspondingly wide and thin belts, which due to a high ratio of circumference to cross-section, due to their large surfaces alone, allow high frictional forces without special aids to increase the friction, e.g. Ribs to dig into the ground. Another advantage that enables the high tensile strength of the reinforcement tapes to generate even higher frictional forces than with smooth or wide tapes is the friction-increasing effect of the structure of the fabric or braided tapes, which can preferably be wide-meshed and through weave (e.g. Atlas , Twill or linen weave) can be influenced.

Because the tapes according to the invention are limp, there is an extremely good adaptability to the unevenness of the filling floor when laying on the construction site, and a low risk of injury when filling the individual floor layers. The tapes can be coiled in great lengths, and in contrast to conventional technology, the reinforcement elements are only cut to size on the construction site, which makes transportation and laying much cheaper.

In the case of the reinforcement tapes, the warp-reinforced fabric preferably consists of high-strength inorganic fibers, for example of glass fibers or of carbon fibers or of fiber mixtures of the fibers mentioned, which are impregnated with liquid reactive resins. These fabric tapes preferably have basis weights between 400 and 800 g / m ² . Suitable reaction resins are, for example, epoxy, polyurethane or isocyanate resins. The pre-impregnation of the fabric belts can be in impregnation baths between rollers, which can be attached directly in front of the take-off device by a suitable reel, respectively. The dosage of the reaction resin is not critical; the fabric tape only has to be completely wetted. The breaking load of the fabric tapes does not depend on the resin content of the impregnation. It may also be advantageous to lay the load-bearing fabric tapes dry and to spray or spray the liquid reaction resin onto the fabric tapes before filling them with the friction floor. The pre-impregnated tapes, which only need to be laid out on the construction site, are hardened after laying out by the moisture in the filling floor. The curing time can be set within wide limits; Advantageous settings allow for laying time between 15 minutes and 2 hours.

In contrast to steel belts, the installed belt adapts well to uneven floors due to its flexibility; the friction bond between the belt and the soil is further improved by the reaction resin as a result of the earth particles adhering to the fabric belt, thus achieving a strong load-bearing capacity for the soil surrounding the belt. After the reaction resin has hardened, the tape is dimensionally stable and has a considerable pull-out resistance. The use of suitable reactive resins leads to outstanding corrosion resistance; the already good per se resistance of the glass ^l and carbon fibers is increased even further by coating with reactive resins.

Especially when the fabric tapes are impregnated with isocyanate resins, the moisture in the filling floor can be used to harden these resins. The fabric tapes are perfectly hardened even in unfavorable weather conditions during installation. For construction site operation, it is also advantageous that the amount of resin used for impregnation is not critical, since the reinforcement fabric reaches its calculated breaking load regardless of the amount of resin impregnated.

The application of force in fabric or braid tapes is safe and easy to use. To apply force, the flexible bands can be laid in a hairpin-shaped manner, for example in the earthworks, the open ends of the band being directed into the earthworks and the loop being carried by a bracket which is attached to the outer skin of the structure and thus the non-positive connection between the outer skin and the reinforcement band manufactures. Another possibility for the non-positive connection of the fabric straps to the outer skin of the building is to place the straps in a loop around the strap on the outer skin and to secure the loop with a suitable closure, e.g. secure one or more clamps by friction. It is particularly expedient to provide a type of connection in such a way that one or more overlapping loops are formed over the bracket for the introduction of force in the outer skin of the earth structure, which form the load-bearing connection through the hardening of the reaction resin. An additional fixation of the individual layers of the fabric tapes by means of clip closures increases the handling security of this connection considerably and enables high tensile loads even before the reaction resin hardens.

• Figur 1 ein kettverstärktes Gewebeband in Leinenbindung;
• Figur 2 ein Geflecht mit Bändchen aus verstreckten organischen Werkstoffen;
• Figur 3 eine kraftschlüssige Verbindung über einen Reibungsverschluß;
• Figur 4 ein imprägniertes Gewebeband aus Glasseide;
• Figur 5 schematische Darstellung des Effektes der Reibungserhöhung.

The invention is illustrated by way of example in the figures and explained in more detail below. Show it:

• Figure 1 is a warp-reinforced fabric tape in linen weave;
• FIG. 2 shows a braid with ribbons made from stretched organic materials;
• Figure 3 shows a frictional connection via a friction lock;
• Figure 4 is an impregnated fabric tape made of glass silk;
• Figure 5 shows a schematic representation of the effect of increasing the friction.

Figure 1 shows warp-reinforced fabric tape in linen weave. It consists of 5 glass rovings as warp threads 1 and glass spun threads of the weft thread 2 with a load capacity of approximately 12 kN and a width of approximately 60 mm. Similar glass fabric tapes are commercially available, for example, as types RLS 304016 or RLS 4022 from A. Weng, Holzhausen or under the designation 94025 from Intergfas Textil GmbH, with which breaking loads between 6 and 15 kN can be achieved.

FIG. 2 shows a laboratory product made from a ribbon braid. The warp tape 3 is highly stretched polyethylene, the thickness is 100 ₁₁ , the width is about 5 mm. The weft tape 4 is made of polyethylene, has a width of 0.2 mm and is 50 u thick. The width of the finished braid of 5 tapes is 50 mm, the thickness about 0.8 mm. The breaking load of this band is 9.7 kN.

A possibility of anchoring the outer skin 9 is shown in FIG. In this case, the pre-impregnated band 10 consists of stretched organic fibers. It is laid out on the filling base 11, placed in a loop 12 around the plastic-coated support tube 13 and anchored non-positively by stretched combs 14.

In FIG. 4, a pre-impregnated fabric tape 15 made of glass silk is placed around the plastic-coated steel tube 17, which is encased in concrete in the outer skin 16; when pulling off a reel, the belt 15 is passed through an impregnation bath with a moisture-curing isocyanate resin with an NCO content of approx. 16% and a viscosity of approx. 5000 mPas and, after impregnation, is laid directly on the filling floor 18 in the manner shown, a provisional securing of the overlap of the strip end is carried out by U-shaped clamps made of ABS. Under normal conditions, the reaction resin is solid after 50 minutes and the connection to the outer skin of the earth structure is fully resilient.

In Figure 5, the increased load-bearing capacity of impregnated tapes is shown schematically. At Earth and sand particles 23 adhere to the impregnated fabric belt 22 and increase the friction in the loose soil 24.

Claims (3)

1. A reinforcement for armoured earthwork constructions comprising the positive connection of high strength, corrosion-resistant bands of netting or weaves, which are laid on the ground, to the outer skin of the building construction, characterised in that the bands of netting or weaves are impregnated with a resin which only hardens upon contact with the moisture of the ground filling.

2. A reinforcement for armoured earthwork constructions according to claim 1, characterised in that the reaction resins for the bands of netting or weaves are epoxide, polyurethane or isocyanate resins.

3. A reinforcement for armoured earthwork constructions according to claims 1 and 2, characterised in that the bands of netting or weaves are positively connected to the outer skin by being bent around bars fixed in the outer skin, the positive connection of the overlapping loop sections achieved by the hardening of the resin preventing the loops from pulling away from the bars.

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