This invention refers to a procedure for the creation of artificial soil protection and lining structures in the form of mattress-type gabions made of double twist wire netting which are filled with soil to create a protective vegetable revetment.
It is known that revetments and other protective structures are employed to halt soil erosion caused by runoff or precipitation; these structures are constructed using so-called mattress gabions, i.e. rectangular containers filled with gravel, crushed stone and other material, fitted with a cover and consisting of galvanised or galvanised and plastic-coated double twist wire netting panels joined together with ties or wire stitches; these structures are corrosion-inhibiting and resistant to mechanical stresses.
One particular, well-known system for the creation of the above-mentioned structures consists in the construction and use of large, thin "mattress gabions" designed to cover, without any break, extensive tracts of land of the most disparate conformation, as if they were actual "mattresses". Preparation in the manufacturing plants consists of working the wire netting, the mattresses being divided into cells by means of vertical partition walls made with the netting of the bottom sheet.
Also known is the system which directly forms the transverse partitions, known as "ribs", obtaining them from the bottom sheet by transverse folds the same height as those of the "mattress", with similar folds for the long side walls and short end walls.
The connection together of the sides of each rib, obtained by bending the bottom sheet, with the cover sheet and with the side and end walls is accomplished using wire stitches, some of them fitted in the factory assemblea structure and some placed during installation.
When the container is filled with soil to act as ballast, there arises the problem of keeping the earth inside the structure ang preventing leaching and dispersion.
Attempts are made to overcome this problemi albeit with relatively unsatisfactory results, by using sheets of geotextile material extended under and around the gabion.
The Patent WO-A-90/12160 discloses a multiple-cell structure which is completely assembled in panels and covered with geotextile. This structure, being used for emergency operations, does not include a base and roof and the "accordion" type of folding makes total pre-assembly possible at the site.
The purpose of this invention is to permit the creation of a system designed to hold the soil inside each individual cell in a mattress gabion, having a continuous structure with a base and roof, after it has been filled with soil, in order to create a vegetale revetment to protect or consolidate the soil of the embankment to be treated.
The advantages are inherent in the formation of a layer measuring approximately 15-30 cm, which is reinforced (by the wire netting of the mattress) and also protective and stable, to achieve which the growth of vegetation is encouraged inside the mattress gabion in order to afford natural protection to the bank, escarpment, etc. of soil.
Geotextile material must completely line the inside of the cells of the mattress, covering the bottom, walls, ends and partitions over the entire length of the inside retaining surfaces of the mattress itself. When the mattress is installed on the ground prior to being filled, the geosynthetic lining is fastened with wire stitches (manually or automatically) attached to the inside frame of the galvanised or galvanised and plastic-coated double twist wire netting which comprime the mattress gabion.
The material of the wire stitches will have the same characteristics as the wire netting of the mattress.
Also required is an element or layer to retain fine material after the installed mattress has been filled with earth, to prevent leaching of the soil before the vegetation grows. Designed to answer this purpose is a geotextile which covers the whole of the top surface of the mattress and which is secured with wire stitches to the top edges and partition walls of the cells; the geocompound is introduced first, beneath the double twist wire netting cover, and it is fastened with wire stitches to the edges above the mattress to close the top of the gabion. For the sake of practical application, the invention is characterised by two alternatives: one entails forming the geotextile cover (inside lining) with panels fastened with wire stitches to the individual cells of the inside surface of the mattress, connected individually therefore to the hexagonal structure of the netting; the other takes the form of a continuous sheet (single panel) fixed beforehand to one end of the element during production with wire stitches, but in this case it follows the unbroken profile of the inside surface of the mattress gabion both on the bottom and the transverse "ribs" (partitions) and end walls of the gabion structure.
Particular care is taken with installation prior to filling to ensure that the geotextile material is resting on and adheres to the wire netting of the gabion without forming pockets that would impair the perfect functioning of the invention.
This invention achieves the purpose, as has been briefly described, of permitting the formation of a system of mattress gabions with an internal vegetable protective lining to hold in and collect the soil inside each single cell or box of the mattress, encouraging the growth of vegetation inside the gabion itself.
The geotextile fabric of the panels is generally composed of woven or non-woven material fibres, obtained using the technology of thermoplastics such as polyethylene or other appropriate materials, in individual panels or continuous sheets to be connected with wire stitches to the inside of the wire netting of the gabion.
Other aims and advantages will emerge from the description that follows and from the attached figures which show, in schematic form and by way of example, one form in which the invention can be realised.
With reference to these plates:
The mattress gabion element in FIG. 1 (in the drawing it is without the left side wall) is made up with the standard factory assembly process.
The galvanised or galvanised and plastic-coated hexagonal double twist wire netting, extending from the bottom sheet 1, with the end walls 2, the sides 3 and the partitions 4, acquires on the installation site its typical box-like structure.
The galvanised and plastic-coated wire stitches 10, placed between the ribs and between these and the sides and also between the sides and the ends, give the structure stability.
On site, the structure is covered by the series of geotextile panels 5 which adhere perfectly to the wire netting, to which they are fastened with the wire stitches 6.
When all the cells in the mattress have been filled with soil 7, the mattress is covered first by a geocompound 8 to retain the fine materials and lastly by the wire netting cover 9 which will close the full mattress gabion when it is in place.
Similar wire stitches 10 fasten the sides of the ribs or partitions together, the geocompound to the sides of the gabion and the cover sheet to the sides.
In FIG. 2, the lining of the inside surfaces of the gabion is accomplished with a continuous sheet 5' of geotextile material, previously connected with wire stitches to one end of the mattress at the production stage. When installing the lining on site, the sheet, in addition to adhering to the surface, will also fold over and cover the ribs of the partitions 11, thereby covering the entire mattress without a break.
The wire stitching 6' of the continuous geotextile sheet will follow, maximum adherence to the inside surface being ensured to prevent the formation of voids.
The filling with earth 7, the laying of the geocompound 8 and the cover 9, and the wire stitching will follow as in the example of FIG. 1.
This invention, illustrated and described in schematic form and by way of example, may be extended to all those secondary variations regarding shape, size and material which, as such, fall within its scope, while the technical details may be replaced by others of an equivalent technical nature, without stepping beyond the scope of protection afforded by the following claims.