A composite sheet for the reinforcement of earth supporting works for embankments, slopes and the like and production process of the same

Abstract

 The sheet comprises a cloth (14) made of polyester fabric, to one edge of which is attached a length of grating (16) made of polypropylene. The cloth is covered with a bituminous-elastomeric resin.
It is suitable for civil engineering works which require a high degree of durability, for example for supporting structures for embankments or slopes.

Description

[0001] The present invention concerns an article for use in civil engineering works as a ground reinforcement, for the anchorage of a wall in the earth, and other uses.

[0002] In this field, various types of sheet materials with different functions are already known and commonly used; in particular, woven or non -woven sheets, known as geo-textiles, usually made from synthetic fibres, are used to carry out draining, filtering, and separation of heterogeneous soils; net or grating type sheets, known respectively as "geo-nets" and "geo-gratings", are employed in civil engineering works to carry out draining and reinforcement. They have the drawback of being easily subject to warping when under load; in addition, they also tend to warp or deform under constant load as time passes (viscosity).

[0003] An earlier Italian patent, No. 1.228.478, by the same applicant, describes a panel, preferably for supporting embankments and slopes of earth, which comprises a reinforced concrete body, to which several anchoring elements, made of flexible material, are integral with an edge thereof.

[0004] The anchoring cloths or sheets for such uses mentioned in the patent consist of a fabric made of plastic material fibres.

[0005] Such sheets, however, show a certain degree of strain or deformation under load; in addition, they do not meet all the durability requirements foreseen for so-called definitive type works (that is, a durability of at least 100-120 years).

[0006] Therefore, the aim has been to avoid the drawbacks involved in the previous technique, and to realize a sheet material for civil engineering uses which will have sufficient durability qualities in order to comply with the requirements established by the regulations for "definitive type" works.

[0007] These and other aims have been achieved with an article as defined in claim 1. Further desired characteristics are defined in the subsequent claims.

[0008] Another part of the object of the present invention is a process for realizing the said material, as defined in claim 5.

[0009] In other words, an anchorage and/or reinforcement sheet is composed of a polyester fabric cloth, to one of whose edges, preferably an edge parallel with the weft, a length of a so-called geo-grating is made integral, this term being used to denote a flat, perforated structure made of polymeric material by means of an extrusion process followed by a stretching process.

[0010] The fabric part of the sheet is covered with a bituminous-elastomeric resin.

[0011] According to the process, the fabric cloth is fastened to the respective geo-grating by means of gluing. The intermediate product thus obtained is immersed with the fabric part only in tanks containing blow bitumens, preferably comprising gilsonite, dissolved in a solvent, preferably white spirit; then it is allow to drip and dried by means of ventilation.

[0012] The article achieves the above-mentioned aims: in particular from tests which have been carried out on samples (weathering with steam, rolling), data have resulted concerning durability, and resistance in general, which are better than data for previously known products, and to quite an unexpected extent.

[0013] A further advantage consists in the fact that the geo-grating allows each sheet to be pre-tensioned by means of stretching devices at installation, without tearing the sheet itself. As a whole, the sheet has a high tensile strength.

[0014] In addition, the geo-grating has a better adherence to the ground and therefore, at low stress levels (during the early phases), it is capable of improving the mobilization of tangential stresses at the interface with the ground.

[0015] The invention will be further described with reference to the single figure, in which the sheet material is shown applied to a vertical supporting panel made of concrete.

[0016] In the figure, the flexible sheet article for civil engineering uses according to the invention is indicated as a whole with 10, and is illustrated applied to a panel made of reinforced concrete, which is indicated with 12 and is only partially illustrated. It should be understood, however, that such article could also be used separately from the panel.

[0017] The flexible sheet 10 comprises a part 14 made of fabric and a grating part 16. The part 14 consists of a length of cloth woven from plastic material, preferably high modulus polyester (the term modulus being used to mean the ratio between a certain increase in load for a unitary width, and the corresponding increase in specific expansion).

[0018] The fabric is covered with a material indicated with 18 in the figure; this consists of a bituminous-elastomeric material, preferably comprising an asphalt known as gilsonite.

[0019] Along one edge of the cloth 14, at right angles to the warp, the length of grating 16 is fastened; the fastening is preferably realized by means of welding with a bonding agent, preferably a hot melt bonding agent; the end borders of the cloth and of the grating are overlapping.

[0020] A description follows of the manufaturing process, in a non-restrictive example.

[0021] Use is made of a polyester fabric with the following characteristics: mass for unitary area: 850 g/m², tensile strength when a longitudinal load is applied: 20000 N/5cm, tensile strength when a transverse load is applied: 2500 N/5cm, ultimate longitudinal elongation: 10%, ultimate transverse elongation: 20%

[0022] The fabric is made up into rolls of predetermined width. The rolls are cut with a thermal blade at a temperature of about 300°C, producing a weld on the cut borders.

[0023] The sheets obtained are transferred to the welding bench where to one end of the cloth a geo-grating is joined, made of polypropylene, measuring 100 X 100 cm. The characteristics of the geo-grating are preferably as follows: longitudinal tensile strength: about 60 kN/m; transverse tensile strength: about 43 kN/m, tensile strength at 2% of longitudinal elongation: about 12,6 kN/m, tensile strength at 5% of longitudinal elongation: about 29,3 kN/m; elongation at maximum longitudinal stress: about 17%, ultimate longitudinal elongation: about 24%.

[0024] The operation is effected by spreading the border of the sheet which is to be welded with a hot melt thermofusible bonding agent, checking at the same time that it is homogeneously impregnated, then spreading out the polypropylene geo-grating and covering the same with a strip of fabric 25 cm wide. The next phase is the pressing of the welded zone in order to render uniform the adhesion of the two layers of fabric.

[0025] The partly-finished product obtained is hung on a rail through its zone with the geo-grating, and transferred in treatment cells.

[0026] The cells are equipped with tanks containing blown bitumens having a high softening point and gilsonite, dissolved in a white spirit solvent.

[0027] The sheet is immersed with the whole of its part which consists of polyester fabric, and then it is raised, allowed to drip, and stretched out slightly. The sheet material is then subjected to forced ventilation at a temperature of about 30°C for drying.

[0028] Each sheet of material can be used by making it integral with a concrete panel for about 40 cm, and arranging it in a roll; after the panel is placed in position and the embankment is filled up to the height of the sheet, the said sheet is unrolled, and fixed in position by mechanical clamping of the geo-grating to the embankment.

Claims

1. A flexible sheet article for civil engineering works, characterized in that it comprises a cloth made of polyester fabric, and a geo-grating made of polypropylene coupled to the said cloth along one of its edges, the fabric cloth being covered and/or impregnated with a resin.

2. An article according to claim 1, characterized in that the said cloth is made of high modulus polyester; the said cloth and the said grating being coupled by means of overlapping along one of their edges and gluing their overlapping edges.

3. An article according to claim 1, characterized in that the said impregnating resin is a bituminous-elastomeric resin dispersed in a solvent.

4. An article according to claim 3, characterized in that the said impregnating resin comprises gilsonite.

5. A manufacturing process for producing an article according to claim 1, characterized in that:
a get-textile fabric cloth made of high modulus polyester is cut to size,
a polypropylene geo-grating is provided,
a border of the cloth is spread with a hot melt bonding agent,
the polypropylene grating is laid out and covered with a strip of fabric, then pressure is applied to the overlapped zone,
then the fabric part of the sheet thus obtained is immerged in a tank containing blown bitumens and gilsonite dissolved in white spirit solvent.

6. A process according to claim 5, characterized in that the strip of fabric and the strip of grating overlap for a width of about 25 cm.

7. A process according to claim 5, characterized in that a subsequent forced ventilation cycle at about 30°C is carried out.

Drawing