PROCEDURE FOR THE PRODUCTION OF SUCH BODIES

The subject of the invention relates to a solid body, especially to an element for application in the construction industry, as well as to a procedure for the production of such solid bodies. The subject of the invention also relates to procedures for the production of tunnel drain structures, of the intermediate layers of tunnels deforming on the effect of a force, and of the granular filtration layer of perforated filtration pipe wells.

The world of engineering uses bulk, cohesion-free, solid granular materials in numerous fields for the most diverse of purposes. After being mixed with a post-hardening binding material, primarily cement or artificial resin, gravel, sand and gravel, crushed stone and material, granulates produced for this purpose, such as an agglomerate consisting of foamed glass or swollen clay pellets, etc. are used to make construction elements. Apart from using granular materials for the production of prefabricated concrete and reinforced concrete construction elements basically performing a load-bearing function, by appropriately selecting the solid granular material, it can be used for the production of elements for absorbing impacts; and elements with a large water permeability may be manufactured from granular material with the appropriate grain structure, which may be used for the construction of water drainage systems.

Drain structures are also made from loose, solid granular materials without a post-hardening binding material for the drainage of water and for obtaining water, for example, as the external filtration layer of pipe wells, by being filled into the space between the perforated water extraction pipe and the wall of the borehole accommodating it. Drain structures are usually made by tipping the loose granular material at the planned, delimited location of application, spreading it and dry-compacting it.

A solution is also known of in which a granulate is mixed with compressed air or a liquid and the mixture is then transported using a pump to the place where it is to be used, for example, behind a supporting wall.

In tunnel construction in certain cases prefabricated construction elements are used that deform on the effect of a force for tunnel walls to reduce the rock pressure exerted on the tunnel, as it is well known that the rock pressure drops as deformation increases. The prefabricated drainage elements mentioned above are used on the external side of tunnels and on the rear side of supporting walls in order to construct groundwater drainage systems.

According to the solution presented in patent document number GB 2 013 757 a compressible layer is formed between the ground and the tunnel lining, the material of which may be plastic foam, wood wool, cork, a loose granulate or a mixture of these. It is recommended that these materials be inserted behind the tunnel lining made from prefabricated reinforced concrete elements using tunnelling shield technology by injecting or pumping them. Reference is also made to the possibility of attaching the compressible layer to the prefabricated reinforced concrete elements; however, the specification does not contain a specific solution relating to this.

Beside being complex and requiring a great deal of time, the disadvantage of this solution is that neither pumping nor injecting operations are able to control whether the material has appropriately filled the space between the tunnel lining and the ground, or whether the degree of compaction and rigidity of the solidified material is suitable.

The method given in patent document number EP 1 108 855 relates to the production of a drainage layer from a solid granular material between a shotcrete shell and the tunnel lining. The task of this drainage layer is to prevent groundwater pressure being exerted on the tunnel lining. The essence of this method called the Valplast procedure is that using a curved grid made with concrete reinforcing and a concrete reinforcing mesh, a supporting structure is constructed in such a way that an intermediate space is provided between this curved grid and the tunnel wall, which is then filled with a water-draining granular material, for example, gravel. The curved grid is fixed to the tunnel wall with anchors, and so is capable of resisting the pressure of the water drainage layer. Patent document no EP 1 514 9988 relates to a further developed version of this method.

The disadvantage of this solution is that a curved supporting structure is required for filling the filtering material, and also that the material filling cannot be compacted, so the tunnel lining will not have sufficient rigidity, although from a structural point of view there is a need for packing providing the connection between the rock and the tunnel lining.

It is usually drilled wells that are used to obtain groundwater, in the case of which perforated pipes - filtration pipes - are inserted into the soil borehole, which is then surrounded with a solid granular material, mostly sand or sand and gravel, which may be a loose granular material or a prefabricated, artificial resin-bound filtration element as well. In the case of deep wells, apart from having good permeability, the filtration material must have suitable rigidity and must be available economically and in excellent quality; this may be achieved with the aforementioned prefabricated filtration elements that are either glued to the filtration pipe or fitted so as to surround it.

Patent document number DE 4 120 189 presents solutions for constructing the filtration layer around the filtration pipe from drain elements. These drain elements are thick-walled pipe elements with a circular ring cross-section, which are made from gravel with the appropriate grain structure and an artificial resin binding material. Prefabricated drainage sheets are also used for the creation of drainage systems, e.g. patent documents EP 0398023 and US 20110230598. However, these construction elements are extremely costly and their filtration ability does not always reach that of loose granular filtration layers.

The task to be solved with the invention is, by overcoming the deficiencies of the methods and construction elements detailed above, to provide a solution with which simple and safe deformable layers can be produced in a controllable way between the rock and the tunnel lining, and at other subsurface engineering structures, such as water drainage systems for supporting walls.

The invention is based on the recognition that if the loose, solid granular material agglomerate is enclosed in a sealed film envelope made of an airtight material, which may be formed into any shape within practical limits as a result of the grains rolling over one another in the loose granular agglomerate and then create and maintain a vacuum in the sealed film envelope a solid shaped body is created which may be stored, transported and installed as a traditional prefabricated construction element. Layers with the precisely planned parameters may be created from such elements that are deformed due to the effect of the pressure between the rock and the tunnel wall in the simplest and still in a safe way, and when the deformation is completed and the vacuum is terminated when the film breaks, the layer consisting of solid grains fulfils its task completely and due to its deformation it reduces the forces exerted on the tunnel wall.

We also recognised that if an airtight film envelope is used that decomposes when coming into contact with water for enclosing the granular material and subjecting it to a vacuum, to construct drainage structures the structure may be built at the location where the water is to be drained from solid bodies of the appropriate shape, which, after the film envelope has decomposed, operates as if the solid, granular material had been placed in the planned location in loose form. Finally we recognised that if film that decomposes in water is used as the airtight film envelope enclosing the solid granular material subjected to a vacuum, which is then used around the filtration pipe of filtration wells, the granular filtration layer may be made from such solid, porous pipe elements, which, after the decomposition of the film after a short period of time, operates perfectly as a loose granular filtration layer.

On the basis of the above recognitions, the set task was solved in accordance with the invention with a solid body, especially an element that may be used for construction technology applications, that contains a granular material, and it is characteristic of this element that the granular material is placed in a sealed, airtight film envelope in which there is a vacuum.

Depending on the current application, it may be preferable that the thickness of the airtight film according to an embodiment of the solid body is between 0.05-5.0 mm.

For specific construction technology applications it is preferable if the solid body has a film envelope that decomposes when coming into contact with water. According to another feature of the invention, there is a vacuum in the inside of the film envelope of from 0.01 to approx. 0.6 bar.

To make it possible and easier to position the solid body it is preferable if the film envelope has an outwardly protruding edge or tabs along its edges which may be used to affix the solid body, e.g. with rivets, to a surface, such as the rock surface surrounding a tunnel.

In the case of certain construction technology applications, it may be preferable if the solid body contains a fibrous material mixed with the granular material, especially steel fibre or plastic fibre.

The subject of the invention relates to a procedure for the production of a solid body, especially an element for construction technology applications, during which a solid granular material is used for the production of the body, and the procedure is characterised by that the granular material is filled into an airtight film envelope, which is then sealed, and a vacuum is created inside it, due to which the atmospheric pressure forces the grains up against one another to form a solid body.

It may be preferable if a friction-increasing material, such as a cement or artificial resin-based liquid is mixed with the granular materials before being formed in the film envelope to prevent the separation of the grain fractions. It is preferable if the solid granular material, before being subjected to a vacuum, is formed into a shaped body delimited with planar and/or curved surfaces, for example, into a plate-shaped or rectangular body, or a similar element, and this forming is preferably performed in a template.

The invention also relates to procedures based on the construction technology application of the solid body presented in detail above, through which a layer is created that is capable of being deformed due to the force effects between the rock and the tunnel wall, as defined by claims 13, 14, and 15. The subject of the invention also relates to the procedure defined in claim 16 based on the application of the solid body according to the invention for establishing a drain layer between rock and tunnel lining, supporting wall, basement wall and similar, and finally it also relates to the procedure included in claim 17 in which wells may be constructed using the elements according to the invention of the appropriate shape.

In the following the invention is presented in detail on the basis of the attached drawings, which contain a number of embodiments of the solid body and illustrate some possible methods of its application. In the drawings

figure 1 shows an agglomerate of solid, loose granular material; figure 2 shows a solid body made from a solid granular material sealed in a film envelope subjected to a vacuum;

figure 3 shows a curved element made with the procedure according to the invention in outline cross-section as well as the forces exerted on it;

figure 4 illustrates an example of the arrangement of the solid grains in outline;

figure 5 illustrates the compressive forces operating between the grains according to figure 4;

figures 6a and 6b illustrate a possible method of forming the still loose solid granular material into its desired final shape;

figure 7a shows a tunnel section in outline vertical cross-section in which the prefabricated elements according to the invention have been used to reduce the rock pressure;

figure 7b illustrates a details of the tunnel section according to figure 7a in larger scale;

figure 8a shows a circular cross-section tunnel made from prefabricated reinforced concrete tunnel wall elements where an external layer has been created from the prefabricated elements according to the invention outside of the prefabricated tunnel wall elements; figure 8a illustrates a detail of the tunnel wall according to figure 8a in outline perspective view;

figure 9 shows the cross-section of a tunnel in which a layer capable of deformation has been made from the prefabricated elements according to the invention underneath its invert;

figure 10 shows a detail of the tunnel section according to figure 9 in larger scale;

figure 11 shows the outline of the cross-section of a tunnel in which the drainage layer serving for draining the groundwater is formed from the prefabricated elements according to the invention;

figure 12 shows a detail of a filtration well in perspective view in which the filtration layer surrounding the perforated filtration pipe of the well is made from the prefabricated elements according to the invention.

In figure 1 the loose, solid granular material 1 used for the element according to the invention or rather for its production is illustrated as a material agglomerate tipped onto the ground surface t in the state before being formed into a solid body.

For this, the solid granular material 1 is filled into an airtight film envelope or film sack, which we have indicated in figure 2 with reference number 2. The film envelope 2, along with the granular material 1 inside it, is formed into the desired shape in, for example, a template, which shape in this case is a plate shape, the opening of the film envelope 2, or film sack, through which the granular material 1 is filled is sealed with, for example, a welded seam, and the interior space of the obtained shaped body 3 is subjected to a vacuum using a method known of in itself. As a consequence of this the external air pressure marked with the arrows a, which is exerted on every side of the shaped body 3, presses the grains 4 together with a force so that the shaped body 3 gains cohesion and has significant tensile strength. In this way a vaulted solid body 5 according to figure 3, for example, is created from the loose, completely cohesion-free granular material 1, which is able to take the load indicated with arrow series b, and the bending, pressing, stretching load, which may otherwise be present from its own weight, when resting on the ground surface t. Therefore, this solid body 5 may be stored, transported and installed as a prefabricated element where this function is required, for example, as a deformable element under the effect of a force, as a drain element, or a heat and sound insulating element, etc. As a result of the compression of the grains - on the effect of the pressure, e.g. 50 - 99 to/m ² , depending on the value of the vacuum in the body - the agglomerate is compacted to such an extent that provides the solid body 5 with the appropriate amount of rigidity for the above applications.

In figure 4 we have shown an agglomerate consisting of grains 4 of various diameters in the lose state before being subjected to a vacuum. In the state according to figure 5 mutually interacting compression forces occur between the grains in the space that is now subjected to a vacuum, which forces are shown with arrows c. These compression forces c occur as a result of the difference between the external atmospheric pressure and the reduced pressure maintained inside the sealed film envelope. As a consequence of the individual internal stabilising compression forces c between the individual grains 4 solid bodies of almost any desired shape may be produced, e.g. prefabricated elements suitable for construction technology applications. Such a solid body 5, such as the one shown in figure 3, an agglomerate "packaged" in airtight film, retains its formed shape and remains a rigid body after being subjected to a vacuum. With this procedure plates, rectangular bodies, beams, curved vault elements (figure 5), and hollow pipe elements may all be produced according to the current application.

Giving the solid body 5, e.g. a prefabricated element, its desired shape takes place in one of two ways. The first solution is to precisely select the shape of the film sack or envelope to comply with the shape of the solid body 5 we wish to make, and then to fill the loose granular material into this. After the granular material has been subjected to a vacuum in the sealed film envelope, the obtained solid body 5 stably retains the shape of the film sack.

An appropriately shaped template is used in the second shaping operation. The plastic film is inserted into the template so that it fits to the walls of the template taking on its shape, then it is filled with the solid granular material, and after sealing the film envelope the granular agglomerate is subjected to a vacuum. This operation has been illustrated in figures 6a and 6b. Figure 6a shows the top view of a film sack 2 with a circular cross-section which has been placed in a template 6 with a rectangular cross-section so that it takes on its shape, then after filling the film sack 2 with the agglomerate consisting of grains 4, the opening of the film sack 2 is sealed, the internal space is subjected to a vacuum, and with this the solid body 5, in other words the construction element is complete and after removal from the template it may be used immediately. Naturally, the circumference of the film sack 2 must exceed the internal circumference of the template to such an extent that it can be smoothed up against its side surfaces.

As it was stated in the introduction, it is known that the pressure exerted on tunnel walls is reduced as the rock surrounding the tunnel is deformed. To make the deformation of the rock possible, in spite of the construction of the tunnel wall and following this, a compressible material (intermediate layer) is installed between the tunnel wall and the rock. Figures 7a and 7b illustrate how this takes place using the solid bodies 5 according to the invention, in this case the elements 7 ("vacuum elements") pictured in cross-section in the larger scale figure 7b. These may be produced as rectangular bodies, or as shell-like elements, like "mattresses", as was described in reference to figures 6a and 6b.

The tunnel wall 9 of the tunnel 8 shown in cross-section in figure 7a is made from a shotcrete shell, which is not applied directly to the surface of the rock 10, instead an intermediate layer 11 capable of being deformed by a force - pressure - is constructed from elements 7 between the rock surface 10 and the shotcrete layer.

The elements are produced on the basis of the following recipe:

Granular material: foamed glass granulate 43 mass% 0 0.5-1.0 mm (spheres) 32 mass% 0 1.0-2.0 mm

25 mass% 0 2.0-4.0 mm Plastic fibre 20 kg/m ³

Plastic film 0.3 mm thick

The plastic film may be acquired commercially, for example, from the Swiss company blipak AG, and the plastic fibre known by the name "conrix" may be acquired from the Swiss company Brugg Contec AG.

The vacuum produced in the film envelope is 0.1 bar, therefore the pressure difference between the environment surrounding the granules and the environment outside of the film sack is 0.9 bar.

The fixing of the elements 7 onto the rock 10 surface takes place by forming an edge running around the film envelope of the element 7, or by forming tabs or bands protruding laterally at certain places, and when the elements 7 are placed on the rock 10 surface, these lie up against it and then may be stably fixed to the rock 10 with, for example, rivets to provide sufficient stability that is able to withstand the application of the shotcrete.

When pressure is exerted on the final tunnel structure 8 from the outside due to rock movements, the vacuum disappears from the split film, the grains of the agglomerate may roll over one another freely, and so the intermediate layer 11 completes its task of reducing the pressure exerted onto the tunnel wall 9 perfectly.

In figures 8a and 8b the possibility of using the elements 12 according to the invention has been illustrated when the tunnel wall 13a of a circular section tunnel 8 is made from known prefabricated reinforced concrete elements 13 ("tubbing") using a shield method. For this, using the technology detailed above, curved ("vacuum") elements 12 according to the invention are produced with a shape that complies with the shape of the elements 13, which are fixed using, for example, an adhesive to the external surface of the element 13, and then, with this, it is installed as a single piece; figure 8b shows a prefabricated reinforced concrete element 13 fitted or combined with such an element 12 according to the invention in larger scale. The fixing of the elements 12 to the prefabricated reinforced concrete elements 13 may take place at the site of installation or even outside of the tunnel, such as in an assembly plant, etc.

The tunnel 8 according to figures 9 and 10 has been constructed in rock 10 capable of intensive swelling containing clay and anhydrock, which rock 10 increases its volume when it comes into contact with groundwater. The wall 14 of such a tunnel 8 is closed off with an invert, or established as such, because without this the entire tunnel would rise when the rock swells. As a consequence of preventing the movement of the invert very large pressures are created, so-called "swelling pressures", which according to the invention may be significantly reduced if it is made possible for the rock 10 to rise a little when the swelling pressure occurs. This is achieved by creating a compressible layer 16 from the deformable elements 17 (figure 10) according to the invention under the invert 15, i.e. between the rock 10 and the invert 15, which may be made with the procedure described with reference to figures 6a and 6b on the basis of the following recipe:

Granular material:

Exfoliated vermiculite 43 mass% 0 0.4-1.2 mm

32 mass%0 0.7-2.0 mm 25 mass%0 2.0-4.0 mm plastic film 0.3 mm thick

(distributor: blipak ag, Switzerland)

The granular material is distributed by Isola Vermiculit AG, Bozen, Switzerland.

As was mentioned in the introduction, in the case of tunnels built in groundwater, there is a risk of the load transferred onto the wall of the tunnel from the water pressure in the case of high groundwater levels being too great, therefore the groundwater has to be drained away from its environment. This may be performed in accordance with the invention with the solution according to figure 11. In the case of this example the curved wall 18 of the tunnel 8 is made from shotcrete and the base plate 19 is made from monolithic concrete. After the tunnel 8 section is opened (not separately indicated) elements ("vacuum elements") according to the invention and made using the technology described in detail in connection with figures 6a and 6b are installed on the internal surface of the rock 10 in the regions delimiting the side of the tunnel wall 18, like the elements 7 according to figure 7b, for example, in the case of which elements the film sacks have a laterally protruding edge running around them. By riveting these edges to the rock 10, the elements are fixed next to each other, which then together form the drain layers 20a, 20b, which are then sealed off with sealing film. The horizontal drain layer 21 under the base plate 19 may be made in the same way. However, there is a fundamentally important difference as compared to that described in connection with figures 6a and 6b, namely that a film must be used for the production of the elements used to create the drain layer that is made from a material that decomposes when coming into contact with water, i.e. groundwater. After this the granular material takes up its planned location in a loose condition, therefore it is perfectly capable of fulfilling its water-draining function.

When the drain layers 20a, 20b and 21 have been constructed, the wall 18 may be constructed using shotcrete and the base plate 19 using monolithic reinforced concrete.

It is noted here that the solid granular material of the elements required to make the drain layers 20a-21 is the material usually used when constructing known, traditional drain systems, and 0.3-0.5 mm thick airtight plastic film may be used that, naturally, as stated above, decomposes when it comes into contact with water.

Such plastic film is distributed by the German company SOKUFOL FOLIEN GmbH, Limburg. It may be necessary to create a connection between the wall 18 of the tunnel 8 according to figure 11. For this a post-hardening material, such as cement mortar 22 is injected between this way and the rock 10 in the region of the top point of the tunnel wall 18.

The drain layers 20a and 20b may be established over a continuous surface in the longitudinal direction of the tunnel 8 or even as lateral bands perpendicular to the longitudinal direction of the tunnel 8 running at a distance from one another. The spaces between these drain bands may be filled in with, for example, shotcrete. The either continuous drain layers or the drain layers in bands, including the drain layer 21 under the base plate 19, are connected to the drain collection ducts indicated with reference number 23 in figure 11.

Apart from the tunnel drain system presented above, the elements according to the invention ("vacuum elements") may also be used for solving other water drainage or water collection tasks, for example tasks for which wells are used in civil engineering practices. Such known wells are usually made by placing a perforated steel pipe - filter pipe - into a bore driving into the ground, which is surrounded by a filtration layer made from a solid granular material capable of transmitting water at a great rate. This filtration layer is usually made by filling gravel, sand and gravel or an artificially produced granular material (foamed glass, expanded clay, etc.) between the filter pipe and the bore wall.

In the case of deep wells, beside good water-transmission ability, a requirement of the filtration layer is also satisfactory solidity. Beside this, for reasons of quality and economy, the filtration layer is assembled from prefabricated elements onsite. Such artificial resin bound prefabricated filter elements are used to an increasingly wide extent, with them being glued to the external surface of the perforated filter pipe, or thick-walled pipe elements are manufactured which create the filtration layer when fitted to the filter pipe.

This latter task may be easily solved using the elements ("vacuum elements") according to the invention, as was explained with reference to figure 12. As it can be seen in this figure, the elements 24 according to the invention have a circular ring-shaped cross-section, in other words thick-walled pipe elements, the granular material 26 of which is enclosed by an airtight film envelope 27, which in this case is the film product that decomposes on contact with water made by the company mentioned in connection with figure 11, and is used here at a thickness of 0.3 mm. The internal diameter d of the element 24is greater than the external diameter of the filter pipe 25, while the external diameter D of the element 24 is smaller than the diameter of the soil bore (not depicted). It is easy to realise that it is not a problem to produce a film sack with a shape complying with the element 24, i.e. internally and externally cylindrical, closed with a planar sheet at the bottom and top, fitted with an opening at the top for filling the granular material, and, in a given case, its filling with granular materials after being placed in a template formed by an internal pipe and external pipe, its sealing with an airtight seal, e.g. welding and it being subject to a vacuum may be simply performed. The materials usually used in the case of such filtration wells with the usual grain structure may be used as the solid granular material.

By using the element 24 according to figure 12 the construction of a filtration well takes place by inserting a perforated filter pipe 25 into the soil bore, and then the elements 24 are threaded onto it from above until the bore is filled with the elements 24, and the solid granular material filter layer 26 surrounding the filter pipe 25 is created along its entire length; when the film 27 decomposes, the filtration well may operate normally.

In the case of numerous engineering facilities and structures it becomes necessary to drain away the groundwater seeping along substantially planar, inclined or vertical surfaces. For this a sand, gravel or sand and gravel layer filled in next to the surface is made, or prefabricated drainage elements, such as filter sheets, shaped concrete filter bodies, etc. are installed; such elements are commonly used, for example, behind a retaining wall or on the external side of basement walls, etc. The prefabricated filter elements are concrete elements made from an aggregate with a special grain structure bound with cement or artificial resin.

The disadvantage of a filled gravel/ sand filter layer is that it must be made onsite and the characteristics demanded by its function, i.e. water transmission ability and rigidity, are difficult to control. However, the disadvantage of the prefabricated filter elements made popular because of this is that there is no need whatsoever for the binding material required for the provision of rigidity in order for them to perform their filtering function, but its make manufacture more difficult and more expensive.

It is obvious that the function of these known prefabricated concrete filter elements and filter plates may be perfectly performed with the elements containing airtight plastic film decomposing on contact with water according to the invention economically, quickly and in a wide field of application.

The advantage of the invention is that overcoming the necessity of any kind of post-hardening binding material it provides solid, storable, transportable prefabricated elements that have the appropriate degree of rigidity and that may be used in the construction industry using the usual structures and methods, which are suitable for solving many kinds of task and especially suitable for solving special construction technology tasks in connection with tunnel construction. Worthy of special mention is that characteristic of the solid bodies, shaped elements according to the invention that makes it possible to install loose, solid granular material in a simple way in places where such material may only be installed in a complex and costly way that provides an uncertain result. Such special areas of use include the creation of drainage systems in tunnels and other civil engineering facilities, e.g. retaining walls, the establishing of deformable intermediate layers between the tunnel wall and the surrounding rock, or the creation of a filter layer from a solid granular material around the filter pipe in a ground bore hole. An advantage of the invention is that these elements may be of any size or shape within the limits of practicality, and they are very economical as their production may take place from cheap materials with a production process requiring little physical labour.

Naturally the invention is not limited to the concrete embodiments of the solid body detailed above, its production is not limited to the described implementation methods, and the use of the elements is not limited to the application possibilities given as examples, instead it may be realised in numerous ways within the sphere of protection defined with the claims.