IT201800005668A1 - Geocomposite, as well as the process for its manufacture - Google Patents

Description

DESCRIPTION of the industrial invention entitled: "Geocomposite, as well as the process for its manufacture"

Field of the invention

The present invention relates to a geocomposite. The invention was developed with particular regard to a geocomposite consisting of a plurality of layers, suitable for the consolidation and / or drainage of soils. The invention also relates to a process for the manufacture of such a geocomposite.

Technological background

Draining geocomposites consisting of layers of different materials are known. In general, these drainage geocomposites consist of two sheets of a geotextile, for example a non-woven fabric, fixed to an intermediate separation layer. The separation layer is generally a permeable material, for example a geomat, a geogrid or a geonet. A geomat suitable for this use is for example known from EP 1160367 and consists of an aggregate of extruded plastic filaments which are entangled and welded together in a hot forming process, to form a thin, low density, i.e. high void index.

A particular type of drainage geocomposite is known as “Terram Frost Blanket” and is produced by. This geocomposite consists of two layers of non-woven fabric separated by an extruded geogrid of plastic material. The lower non-woven fabric layer is water-repellent, to prevent or limit the passage of moisture from the ground into the geocomposite. This geocomposite is specifically designed to mitigate damage, for example to road pavements, due to the freezing / thawing cycles of the ground below the pavement. The purpose of this geocomposite is to limit the passage of moisture from the ground below the geocomposite to the upper ground or paving area by capillarity.

Geocomposites of the known type have been found to be effective and are currently adopted in many applications, but have some intrinsic limitations that in some cases prevent or advise against their use. When the intermediate separation layer is made using a geogrid, as in the case of the aforementioned "Terram Frost Blanket", there is a risk that a higher than expected pressure on the geocomposite, for example in one of its localized areas, brings the two sheets of geotextile in contact with each other, through the openings of the geogrid. This leads to the disappearance in that area of the insulating / draining effect of the geocomposite, which then ceases to perform its function. To overcome this drawback it is therefore necessary to use relatively rigid geotextile sheets, which can resist the localized bending caused by high pressure, which naturally increases the cost of the sheets themselves and therefore of the geocomposite in which they are used.

Another limitation of known geocomposites is given by the limited thickness which does not make them sufficiently soft for application, for example as a substrate for playing fields in order to ensure an adequate absorption effect of the impacts from trampling of athletes ("shock absorption "), thus failing to guarantee the prevention of damage to the athletes' joints.

Summary of the invention

One purpose of the invention is to provide a geocomposite which solves the drawbacks of the known technique, and in particular which reduces the risk of loss of effectiveness due to high localized pressures, and therefore guarantees adequate absorption of impacts ("shock absorption" ). Another purpose of the invention is to create a geocomposite that is simple and inexpensive to make, and that is effective, convenient and reliable in use. Another purpose of the invention is to provide a geocomposite manufacturing process that is flexible and can be used effectively to produce different geocomposites, having desired mechanical and filtering characteristics.

To achieve the aforementioned purposes, the invention relates to a geocomposite, as well as a process suitable for its manufacture, having the characteristics indicated in the attached claims.

According to a particular aspect, a basic geocomposite is described, suitable for the consolidation and / or drainage of soils. The base geocomposite can be composed of a plurality of geosynthetic layers. The base geocomposite can comprise at least two layers of geotextile, preferably a non-woven fabric, separated by a three-dimensional geomat. A geomat can be a kind of mat made with extruded filaments of plastic material that tangle with each other after extrusion, in order to create a structure of a certain thickness with a very low density and irregular voids inside. More precisely, a geocomposite is described which can comprise at least a first sheet of geotextile and at least a second sheet of geotextile, which can be heat-fixed to the sides of an intermediate separation layer. The intermediate separation layer can be made by means of at least one geomat of entangled plastic threads. The geomat can have a thickness of about 4-5 mm or more.

According to a particular aspect, the geotextile sheets can be relatively flexible, being made up of needled filaments and possibly thermo-fixed during the production process. According to a variant, at least one of the geotextile sheets can be water-repellent, that is, have a sufficiently small pore size to repel moisture that would tend to penetrate the sheet by capillarity.

According to another aspect, the base geocomposite can serve to form a multi-structure geocomposite. In the multiple geocomposite, at least one of the sheets of the base geocomposite can be heat-bonded to at least one further geosynthetic layer. The at least one further layer of geosynthetic can be selected from the group comprising geogrids, geonets, geomats, geotextiles, geomembranes or a combination or stratification thereof.

According to a particular aspect, the geocomposite can comprise a geomat and / or a geogrid coupled to one or both sheets of the base geotextile. A structure of this type has - in addition to the desired characteristics of soil drainage - a good capacity for absorbing impacts which make it particularly useful, for example, in the construction of tracks or playing fields and the like. The presence of an intermediate geotextile in a multilayer product represents a planar reinforcement which, by absorbing the impacts with its own tensile strength, transmits a lower load on the underlying geomat layer, thus increasing its resistance to crushing. In the event that the geocomposite has a geomat and a geogrid coupled together, for example by hot thermo-fixing, it appears to demonstrate a particularly high resistance compared to its thickness, without reducing its drainage capacities. This makes its use useful, for example, where the localized pressures exerted on the geocomposite become high, for example for use in landfill sites.

If the geocomposite has a further layer made with a geomat, a particular aspect is described according to which a waterproof geomembrane is applied to it, preferably by heat sealing.

In the production process of a geocomposite of the type indicated above, the basic type geocomposite is first made, with a geomat as a separator element between two layers of geotextile, preferably a non-woven fabric. Production takes place by making the geomat according to techniques known in the sector. The geomat is then passed through a pair of rollers that convey the two layers of geotextile, unwound by respective coils. The application of heat, for example by localized heaters or by heating the rollers themselves, determines the localized softening of the filaments of the geomat to which the two geotextiles adhere by heat sealing on both sides. The basic geocomposite thus produced is cooled and wound into reels for subsequent processing in order to manufacture the above mentioned variants of multilayer geocomposite. In particular, a coil of base geocomposite can be unwound and fed by one or more rollers under a geomat and / or geogrid, with local application of heat to allow the geomat and / or geogrid to heat-weld to one of the geotextiles of the base geocomposite. The application of local heat can also determine the heat sealing of the geomat and the geogrid between them, as well as the geotextile of the base geocomposite in a continuous process. Alternatively, the geogrid and the geomat can be heat-sealed upstream of their heat-sealing to the geotextile of the base geocomposite, to which they are then subsequently coupled by heat-sealing or by means of adhesive materials (glues).

In a variant, the basic geotextile unwound from the coil is fed under a geomat and a geomembrane. Also in this case, the local application of heat allows the geomat and the geomembrane to be heat-sealed to the base geocomposite.

In the geocomposite production plant, both the temperature and the pressure applied are regulated to heat-seal the various layers together, so as to ensure that they are adequate for fixing the layers together, without exceeding such values as to compact the geocomposite, and in particular the geomat (s) up to the point of compromising the drainage function of the geocomposite.

Brief description of the drawings

Further characteristics and advantages will emerge from the following detailed description of a preferred embodiment, with reference to the annexed drawings, given by way of non-limiting example, in which:

Figure 1 is a schematic perspective view of an example of a base geocomposite, incorporating aspects of the present invention, Figure 2 is a schematic view of a plant for manufacturing the base geocomposite of Figure 1,

- figure 3 is a schematic view in perspective of a first example of a multilayer geocomposite starting from the base geocomposite of figure 1, - figure 4 is a schematic view of a plant for manufacturing the multilayer geocomposite of figure 3,

- figure 5 is a schematic view in perspective of a second example of a multilayer geocomposite starting from the base geocomposite of figure 1, and - figure 6 is a schematic view of a plant for manufacturing the multilayer geocomposite of figure 5.

Detailed description

With reference now to Figure 1, a base geocomposite 10 comprises a lower sheet 12 of a geotextile, preferably but not limited to a non-woven fabric, for example of polypropylene. The base geocomposite 10 further comprises an upper sheet 14 of a geotextile, preferably but not limited to a non-woven fabric, for example of polypropylene. The lower web 12 and the upper web 14 can be the same or different from each other. In particular, for applications in which it is useful or necessary to provide protection from frost, the lower sheet 12 can be of the water-repellent type, in particular with a sufficiently small pore size and such as to prevent humidity from passing through the lower sheet 12 by capillarity. . The lower sheet 12 and the upper sheet 14 are fixed to the two sides of an intermediate separation layer 16, preferably made with a geomat. As known in the field, a geomat is a layer of material made with entangled filaments of plastic material welded together, so as to create a structure of a certain thickness having a very low density and irregular voids inside. Preferably, the intermediate separation layer 16 has a thickness of about 4-5 mm or more, so as to prevent any contact, even accidental, between the lower sheet 12 and the upper sheet 14 following, for example, a localized pressure or crushing of the base geocomposite 10 during operation on site.

The base geocomposite 10 is made in a plant and according to a generally known type of process, as schematized in Figure 2. Hot filaments 23 of a plastic material are emitted from an extruder 21, for example polypropylene, polyethylene polyamide, polyester, or a mixture of these polymers, and possibly with a part also with a natural base. Below the extruder 21 there is a cooling tank 22 containing a cooling liquid to cool the hot filaments 23. which, resting on the roller 24, intertwine with each other forming a three-dimensional material structure. The extrusion speed of the hot filaments 23 and the speed of the roller 24 are adjusted and synchronized to obtain a geomat 16 having a determined thickness, preferably of about 4-5 mm or more. The geomat 16 is then passed through a pair of rollers, a lower roller 29 and an upper roller 31, which preferably compress it slightly. On the upper roller 31 slides one of the two sheets which form the base geocomposite 10, for example the upper sheet 14, fed by a first reel 26. The other of the two sheets slides on the lower roller 29, for example the lower sheet 12, fed by a second reel 27. In the passage between the lower 29 and upper 31 rollers, the geomat 16 and the lower 12 and upper 14 sheets are locally heated in such a way as to heat-seal. Localized heating can take place by heating the lower 29 and upper 31 rollers themselves, or by separate heating means such as torches 30 or radiators or other functionally similar means.

In a variant not shown, the upper 12 and lower 14 sheets are both made to pass on the respective lower 29 and upper 31 rollers, while the roller 24 provides for the formation of only the geomat which forms the separation material 16 of the base geocomposite 10 The base geocomposite 10 described above can be advantageously used for making multilayer geocomposites. In this regard, the base geocomposite 10 can be sent to subsequent processing phases both on and off-line. In the first case, downstream of the base geocomposite 10 production plant, other processing stations synchronized with the base geocomposite 10 production station are arranged. Alternatively, the base geocomposite 10 is stored after being rolled up, for example. in base coils 32, as schematically indicated in Figure 2, which can subsequently be used for the manufacture of multilayer geocomposites.

This last method of use allows a considerable flexibility of use, being able to manufacture the base geocomposite 10 both for use alone as a traditional draining geocomposite, and for its use as a base material for the manufacture of more elaborate geocomposites, suitable from time to time to specific needs, in the quantities requested at the time.

With reference now to Figure 3, a first example of an elaborated geocomposite 20 comprises the base geocomposite 10 consisting of two sheets of geotextile 12 lower and 14 upper, welded to the intermediate separation layer 16 made for example with a geomat as indicated above, preferably having a thickness of 4-5 mm or more. On the upper sheet 14, on the opposite side to the intermediate separation layer 16, a second intermediate separation layer 19 is arranged, heat-sealed, also made for example with a geomat, preferably also having a thickness of 4-5 mm or more. An external sheet 25 of a geotextile, preferably but not limited to a non-woven fabric, for example of polypropylene or one of the materials indicated above with reference to the lower 12 and upper 14 sheets, is disposed, heat-sealed, on the second intermediate separation layer 19. . The external sheet 25 can be of the same type as the lower sheet 12 and / or the upper sheet 14, or of a different type from both the lower sheets 12 and the upper 14. According to a particular embodiment, the external sheet 2 5 can also be a waterproof or water repellent geosynthetic.

The multilayer geocomposite 20 described above and illustrated by way of example in Figure 3 can be made in a plant and according to a process schematized in Figure 4. The plant has similarities with that described schematically in Figure 2 for the construction of the base geocomposite 10 From an extruder 21 'hot filaments 23' of a plastic material are emitted, for example polypropylene, polyethylene polyamide, polyester, or a mixture of such polymers, and possibly with a part also having a natural base. Below the extruder 21 'there is a cooling tank 22' containing a cooling liquid to cool the hot filaments 23 '. which, resting on the roller 24 ', intertwine with each other forming a three-dimensional material structure. The extrusion speed of the hot filaments 23 'and the speed of the roller 24' are adjusted and synchronized to obtain a separation geomat 19 having a specific thickness, preferably of about 4-5 mm or more. The separation geomat 19 is then passed through a pair of two rollers, a lower roller 29 'and an upper roller 31', which preferably compress it slightly. The base geocomposite 10 passes over the lower roller 29 'and is unwound from the base coil 32.

The geotextile 25 is passed over the upper roller 31 ', which is unwound by a respective coil 26'.

In the passage between the lower 29 'and upper 31' rollers, the base geocomposite 10 is welded to the separation geomat 19 and coupled to the outer sheet 25, to form the multilayer geocomposite 20 which is wound on a collection reel 35. The geomat 19 and the base geocomposite 10 are heated locally in such a way as to heat-seal. Localized heating can take place by heating the lower 29 'and upper 31' rollers themselves, or by separate heating means such as 30 'torches or radiators or other functionally similar means.

With reference now to Figure 5, a second example of an elaborated geocomposite 40 comprises the base geocomposite 10 described above, consisting of two sheets of lower and 14 upper geotextile, welded to the intermediate separation layer 16 made for example with a geomat such as indicated above, preferably having a thickness of 4-5 mm or more. On the upper sheet 14, on the opposite side to the intermediate separation layer 16, a geomat 42 reinforced with a geogrid 44 is fixed, for example of the type consisting of strips of plastic filaments heat-sealed together in the form of weft and warp as previously indicated with reference to the elaborated geocomposite 20 of Figure 3. The geogrid 44 is mixed and / or interposed with twisted plastic filaments which form the geomat 42 during the extrusion process.

The multilayer geocomposite 40 described above and illustrated by way of example in Figure 5 can be made in a plant and according to a process schematized in Figure 6.

From an extruder 21 '' hot filaments 23 '' of a plastic material are emitted, for example polypropylene, polyethylene polyamide, polyester, or a mixture of these polymers, and possibly with a part also with a natural base. Below the extruder 21 'there is a cooling tank 22' containing a cooling liquid to cool the hot filaments 23 '. which, resting on the roller 24 '', intertwine with each other forming a three-dimensional material structure. The geogrid 44 is also passed on the roller 24 '', which is unwound from a coil 26 '' and passes on a tensioner 28 '', whose registration position affects the position of the geogrid 44 more or less centered with respect to the center line of the geomat 42 formed by the filaments 23 '' which are welded together and also to the geogrid 44. The extrusion speed of the hot filaments 23 '' and the speed of the roller 24 '' are regulated and synchronized to obtain a separation geomat 42 having a determined thickness, preferably about 4-5 mm or more. The separation geomat 42 reinforced by the geogrid 44 is then passed through a pair of two rollers, a lower roller 29 '' and an upper roller 31 '' to couple to the base geocomposite 10 in a similar manner to what was previously described with reference to figure 4, to which reference should be made.

Naturally, further variants of geocomposites elaborated starting from the base geocomposite 10 can be envisaged, using any combination of one or more geogrids, geonets, geomats, geotextiles and / or geomembranes stratified on one of the two sides, or on both sides of the geocomposite. base 10, according to manufacturing principles which will become evident to those skilled in the art upon reading the present description and the attached figures. The intermediate separation layer 16 can also comprise one or more geonets or geogrids of material and / or one or more reinforcing metal meshes, fixed or interposed or intertwined with the tangled plastic filaments that make up the geomat of the intermediate separation layer 16.

Naturally, without prejudice to the principle of the invention, the embodiments and construction details may vary widely with respect to what is described and illustrated, without thereby departing from the scope of the present invention.

Claims (8)

CLAIMS 1. Geocomposite suitable for the consolidation and / or drainage of soils, composed of a plurality of layers comprising at least a first sheet (12) of geotextile material and at least a second sheet (14) of geotextile material heat-fixed to the respective sides of a layer separation intermediate (16) made by at least one geomat of entangled plastic wires having a thickness of about 4-5 mm or more to form a base geocomposite (10), in which at least one of the first sheet (12) and the second sheet (14) of the base geocomposite (10) is thermo-fixed at least one further layer (19, 42, 44) of a geosynthetic selected from the group comprising geogrids, geonets, geomats, geotextiles, geomembranes or a combination or stratification thereof. 2. Geocomposite according to claim 1, wherein at least one of the first and second geotextile ply (12, 14) is a water-repellent non-woven fabric. Geocomposite according to claim 1 or claim 2, wherein the at least one further layer comprises at least one layer made by means of a geogrid (44) and / or a geomat (42) heat-bonded to one of the two geotextile sheets ( 12, 14) of the base geocomposite (10). Geocomposite according to any one of the preceding claims, wherein the at least one further layer comprises at least one geomat (42) reinforced by a geogrid (44), in which the plastic filaments of the geomat (42) are entangled in the geogrid (44 ), the geomat (42) reinforced by geogrid (44) being heat-fixed to one of the two geotextile sheets (12. 14) of the base geocomposite (10). 5. Geocomposite according to any one of the preceding claims, wherein the at least one further layer comprises at least one geomat (19) heat-fixed to one (12) of the two geotextile sheets (12, 14), an outer sheet (25) being heat-fixed to the geomat (19), on the opposite side to one (12) of the two geotextile sheets (12, 14). 6. Geocomposite according to claim 5, wherein the outer sheet (25) is a geomembrane. 7. Process for the preparation of a geocomposite according to any one of the preceding claims, comprising the step of making a base geocomposite (10) starting from a geomat (16) of entangled plastic threads obtained by hot extrusion (21), the geomat (16) having a thickness of about 4-5 mm or more and being subsequently heat-sealed on its sides to two sheets of geotextile (12, 14) by localized heating. 8. Process for the preparation of a composite according to claim 7, comprising the step of feeding the base geocomposite (10) to a thermoforming station to fix to at least one of the sheets (12, 14) of the base geocomposite (10) one or more layers (19, 42, 44) of a geosynthetic selected from the group comprising geogrids, geonet, geomats, geotextiles, geomembranes or a combination or stratification thereof.