HK1177173B - Method and plant for producing a fiberglass profile to be used as reinforcing element for strengthening an excavation wall - Google Patents

Description

Method and device for producing a glass fibre profile for use as a reinforcing element for reinforcing a pit wall

Technical Field

The invention falls within the scope of producing a reinforcing element for reinforcing the pit surface of a tunnel. More precisely, the invention relates to a glass fiber profile having higher pullout strength properties than conventional profiles used for the same purpose. The invention also relates to a method for producing such a glass fiber profile at a lower cost by a smaller number of steps. The invention also relates to a device for carrying out the method, i.e. for producing the glass fiber profile according to the invention.

Background

As is known in the field of reinforcing tunnel walls, fiberglass elements have been in use for many years now, especially in the presence of clay and cohesive soil. These elements can be used both for reinforcing the pit surface and as radial fixing elements. It is also known to attach glass fibre profiles to the surrounding ground by cement casting. In other words, each profile is embedded in the cement mortar after having been inserted into a suitable preformed hole made in the wall to be reinforced. The arrangement of the profiles, their length and their density (i.e. number per square meter) vary according to the operating conditions. The fiberglass profiles typically have a solid cross section, or alternatively, an axial cavity for the insertion of cement mortar.

Fig. 1 to 3 relate to a conventionally used glass fiber profile (10). As shown, the profile has a circular cross section which is hollow inside, which in most cases has an outer diameter varying from 55 to 70 mm. The profile (10) is typically produced by a pultrusion process during which glass fibers previously impregnated with a polymer matrix are passed through a heated die having a circular shape. Referring to fig. 1, at the end of the pultrusion process, the outer surface (1A) of the profile (1) is machined to improve its adhesion to the cement mortar. In particular, the machining comprises the creation of a groove (2) by milling the profile to remove material, cutting away a portion of the longitudinal fibres forming the profile, so as to reduce the resistant section of the profile. As shown, the groove extends helically in a similar manner to a thread.

With reference to fig. 3, during the installation of the profile (10), cement mortar (5) is inserted between the outer surface (1A) of the profile (1) and the prefabricated hole through a valve or through other functionally equivalent elements. In the particular case of valves, these are arranged in the longitudinal position of the profile. The cement Mortar (MC) reaches the valve through a duct (not shown) arranged inside the longitudinal cavity (3) of the profile (1) to be subsequently distributed around the relative surface (1A) so as to occupy the helical groove (2) also as clearly shown in fig. 3. The cement Mortar (MC) arranged in the grooves (2) is subjected to a shearing action during any tensile stress (T) acting on the profile, providing a low resistance to the profile being pulled out. The geometry of the profile (1) actually causes a longitudinal interruption of the glass fibers arranged on the outside. These glass fibers are actually substantially cut and thus cannot contribute to the Tensile Strength (TS). It can also be seen that the glass fiber profiles currently used do not even provide acceptable tensile strength due to the reduction in the resistant cross section caused by the removal of material.

Also known are processes in which a wire or a metal mesh is wound around a profile made of glass fibres, which are subsequently polymerized. After polymerization, the metal mesh is removed from the profile, leaving a negative impression on the profile forming the corrugations of the profile. These processes are described, for example, in the prior art documents JP-57-18484, EP-0667228, EP-0733456. In these cases, the corrugation of the profile is not determined before the polymerization of the profile, but it results from the imprint left by the wires or the wire mesh that have to be removed after the polymerization process.

The main object of the present invention is therefore to provide a new fiberglass profile and a process for producing such a profile, which enable the aforementioned drawbacks to be overcome.

Within this aim, a first object of the invention is to provide a glass fibre profile having a pull-out strength greater than that which can be obtained by conventional solutions.

Another object of the present invention is to provide a method for producing such a glass fiber profile, which comprises a lower number of steps and is easy to produce at competitive costs.

A further object of the present invention is to provide a profile and a method that are reliable and easy to implement at competitive costs. It is a further object of the invention to provide an apparatus capable of carrying out the method according to the invention.

Disclosure of Invention

The invention thus relates to a glass fiber profile for use as a reinforcing element for reinforcing pit walls, for example in the field of producing underground tunnels and/or tunnels. The profile according to the invention comprises an axially extending body formed of glass fibres anchored in a polymer resin by a polymerisation process. Said profile is characterized in that the outer surface has a corrugated trend, which is intended to mean a substantially undulating trend in the axial sectional plane of said profile. In particular, such corrugations tend to be defined by different degrees of compression of the outermost glass fibers of the profile. In practice, according to the invention, the outermost glass fibers are compressed at axial intervals and maintain their integrity to maintain the resistant section of the profile. It has been observed that said corrugation of said outer surface of said profile tends to advantageously increase its pullout strength, since the cement mortar intended to surround said profile is mainly subjected to compression and no longer to shearing as is the case in conventional profiles.

The invention also relates to a method for producing a glass fiber profile according to the invention. The method provides for impregnating glass fibers with a polymer resin and subsequently orienting the glass fibers according to an axial direction, thereby arranging the glass fibers to construct an axially extending profile. The method according to the invention provides for compressing the outermost glass fibers at axial intervals so as to impart a corrugated trend to the outer surface of the profile, i.e. a trend of undulations in the considered axial section plane of the profile. The profile is then subjected to a polymerization process that anchors the profile's structure.

According to a possible embodiment, the outermost glass fibers are compressed by thread-like compression elements, which can be formed, for example, by threads made of polyester, glass fibers or other functionally equivalent materials. The thread-like compression element can be removed after completion of the polymerization process or, more preferably and advantageously, it can remain incorporated and encapsulated into the profile during the polymerization process.

According to the invention, the compression of the outermost glass fibers of the profile is such that the outer surface (15b) of the profile and the thread-like compression element together have an overall corrugated shape which substantially corresponds to the desired corrugated shape of the final profile. In other words, the definition of the corrugated profile of the final profile is already completed before the polymerization step and does not depend on the removal of the filiform element after polymerization. In this way, the entire production manufacturing process of the profile becomes much simpler and faster than the processes of the known art.

According to a first possible embodiment of the method, the thread-like compression element is formed by a thread having a circular section and is wound helically around the profile, preferably with a constant pitch, so that the outer surface has a regular trend, preferably sinusoidal, in an axial section plane. According to an alternative embodiment, the filiform compression element has a concave section and is wound around the glass fiber profile substantially at zero pitch (i.e. at a pitch substantially comparable to the thickness of the filiform element). After compression, the outermost glass fibers are partially disposed in a cavity defined by the cross-section of the filamentary element. In this way, the corrugation tends to be defined for the outer surface of the profile.

In the method of the invention, the corrugated profile is already fully defined before polymerization and is thus not dependent on the removal of the thread-like compression element after polymerization.

The invention also relates to a device for carrying out the method according to the invention. The apparatus according to the present invention comprises an impregnation tank containing a polymer resin through which glass fibers are impregnated. The apparatus further comprises means for orienting and arranging the glass fibers to allow orientation in the axial direction of the fibers and to construct an arrangement of axial profiles. The apparatus further comprises compression means to impart a corrugated trend to the surface. In particular, these compression means are operatively arranged upstream of a suitable polymerization device by which the polymerization process of anchoring the glass fibers in the polymer resin is activated.

Drawings

Further characteristics and advantages of the invention will be clear from the description of an embodiment of the profile according to the invention, illustrated as a non-limiting example in the accompanying drawings, and of the relative method and plant for producing said profile, in which:

figure 1 is a side view of a portion of a profile in a composite material currently in use;

figure 2 is a side view of the profile of figure 1;

figure 3 is a view relating to the application of the profile of figures 1 and 2;

figure 4 is a longitudinal section of a portion of a first embodiment of a profile according to the invention;

figure 5 is a further sectional view according to line IV-IV of figure 4;

figure 6 is a view relating to the application of the profile of figure 4;

figure 7 is a longitudinal section of a portion of a second embodiment of the profile according to the invention;

figure 8 is a cross-sectional view of the profile of figure 7;

figure 9 is a view of a further embodiment of a profile according to the invention;

figure 10 is a schematic view of a plant for producing a profile according to the invention.

Detailed Description

The profile according to the invention is designated hereinafter by the reference numeral 15. The profile 15 has an axially extending body formed by glass fibres 15A, 15B arranged according to an axial direction X. More precisely, the glass fibers 15A, 15B are anchored in the polymer resin (preferably polyester) by a polymerization process. According to the invention, the outer surface 15B of the body 15 is compressed at longitudinal intervals so as to have a corrugated trend (i.e. a substantially undulating trend) in the axial section plane of the profile 15 (i.e. in a section plane comprising the longitudinal axis). The waviness of the surface 15B tends to be defined by the varying degrees of compression of the outermost glass fibers 5B which are compressed substantially at the axial spacing. More precisely, "compressed" means pressing in a substantially radial direction of the external fiber 5B, so that the external surface 15B is formed by more compressed portions alternating with less compressed portions. The expression "radial direction" denotes a transverse direction substantially orthogonal to the axial direction X.

Figure 4 is a sectional view relating to a portion of a profile 15 according to the invention. While figure 5 is a section taken along an axial section plane and enables to observe the arrangement of the fibres 5A, 5B forming the profile 15. Obviously, the innermost fibres 5A of the profile 15 are arranged parallel to the axial direction X and have an integral and continuous tendency without longitudinal interruptions. While the outermost fibers 5B are compressed at axial intervals without longitudinal interruption. In particular, the compression of the outermost fibres 5B defines the portion of profile 15 having radial extension D1 and the other portion having radial extension D2. The continuity of the outermost fibers 15B advantageously increases the tensile strength of the profile relative to that provided by conventional profiles, such as the profile shown in fig. 1. In other words, unlike the conventional solution, the outermost fibres 5B of the profile 15 are not longitudinally interrupted or cut but are only compressed.

Fig. 6 is a view relating to a possible application of the profile 15. More precisely, this figure relates to a possible installation of the section bar 15, in which the section bar 15 is inserted into a prefabricated hole produced in the pit wall to be reinforced. The volume of the space between the profile 15 and the surface 19 of the prefabricated hole is filled with cement mortar MC. The external structure of the surface 15B ensures that during the application of tensile stress T to the profile 15, the cement mortar MC is mainly subjected to compressive stresses (indicated by the arrows marked C) rather than to shear stresses as occurs in the conventional solution (see figure 3). These compressive stresses are directly transmitted to the inner wall of the preformed hole by the cement mortar. The pullout strength of the profile 15 is thus advantageously increased, since the cement mortars MC have on the one hand excellent compressive strength properties and on the other hand they transmit compressive stresses to the surrounding ground. Laboratory tests have shown that, using the same cross-section and radial dimensions, the pull-out strength of the profile 15 according to the invention is more than 40% higher than that of a conventional profile having the structure shown in fig. 1 to 3. The pull-out strength means in practice the tensile stress T that must be applied to the profile in order to pull it out of the containment wall in which it was previously cemented.

Referring again to fig. 4, it can be observed that the outer surface 15B of the profile 15 has a very regular corrugated trend in the axial section plane and a precisely substantially sinusoidal trend. More precisely, the outer surface 15B preferably has concave portions 16 (in practice it is desirable to indicate more compressed portions) and convex portions 17 (i.e. less compressed portions) extending in a threaded alternating manner in the axial direction. As better specified hereinafter, such a structure can be obtained, for example, by helically winding the filiform compression element 8 at a constant pitch during the formation of the profile 15 and in particular before the polymerization process by which the glass fibers 5A, 5B are anchored to the polymer resin. Fig. 7 to 9 relate to a second embodiment of the profile 15 according to the invention, which differs from the embodiment of fig. 4 to 6 by virtue of the different transverse sections of the profile 15, wherein the term "transverse" denotes a section according to a plane substantially orthogonal to the axial direction X. In this second solution, the profile 15 has a cavity 27, the cavity 27 having a substantially circular cross section and preferably extending axially for the entire length of the profile. This cavity 27 has the function of allowing the passage of pipes (not shown) conveying cement mortar MC.

In this connection, fig. 9 shows a second part of the profile 15 in connection with this second embodiment. More precisely, the second portion comprises a first portion 21A and a second portion 21B having an outer surface 15B, the outer surface 15B corresponding to the outer surfaces shown in fig. 7 and 8. An intermediate portion 22 is defined between the two portions 21A, 21B for setting the inlet valves (not shown) of the cement mortar MC to which it is delivered through ducts (not shown) operatively arranged along the axial cavity 17. As shown, the intermediate portion 22 has a substantially cylindrical outer surface, i.e. it does not have the thread tending characteristics of the other portions of the profile 15. The radial channels 19 are arranged to allow cement mortar MC to travel from the inside of the axial cavity 27 to the outside of the profile 15.

The invention also relates to a method for producing a profile according to the invention. More precisely, the method can be used both for producing profiles with solid section, such as the one shown in fig. 4 to 6, and for producing profiles provided with axial cavities 27, such as the one described in connection with fig. 7 to 9.

The method according to the invention provides for impregnating the glass fibres 5A, 5B with a polymer resin, preferably polyester. The fibres 5A, 5B are preferably oriented according to an axial direction X under the effect of tensile stress and are mutually arranged to constitute a profile 15 extending substantially axially. The method according to the invention is thus arranged to compress the outermost glass fibers 5B of the profile 15 at axial intervals to impart a corrugated trend to the outer surface 15B, so that it is desired to obtain a substantially undulating trend in an axial section plane (for example the plane IV-IV represented in fig. 4). The axial sectional plane substantially represents a plane belonging to a cluster of planes having the axis X as center.

More precisely, the compression of the outer surface 15B is carried out during the traction and therefore the axial travel of the profile 15. Subsequently, the profile 15 is subjected to a polymerization process by which the glass fibers 5A, 5B of the compressed profile are anchored in place in the polymer resin and set.

Unlike conventional pultrusion processes, the final shape of the profile 15 is thus determined before the polymerization step, not after. In particular, the undulation shape of the outer surface 15B is imparted by compressing the outermost fibers 5B without any longitudinal interruption of the outermost fibers 5B. In other words, the external fiber 5B maintains a unitary and continuous structure for its entire associated longitudinal extension.

Thereby, the undulation shape of the outer surface 15B is independent of whether the compression element (which is used to compress the fibers before polymerization) is removed or not, so that the compression element can advantageously remain incorporated into the profile even after polymerization to constitute an integral part of the profile.

According to a possibly preferred embodiment of the invention, the outermost glass fibers 5B are radially compressed by a filiform compression element 8 (shown in fig. 7) wound helically around the outer surface 15B of the profile 15. The term "filamentous compression element" generally denotes the following elements: which can be wound around the profile in the same way as a wire, tape or other similar article to produce a compression action. The wire-like compression element can be made of metallic or non-metallic material. In the second case, the thread-like compression element can be made of, for example, polyester or glass fibers. But other types of materials can be used. Furthermore, the thread-like compression element can have a cross section shaped as a circle (as in the case of a thread) or alternatively also as a polygon.

According to a first embodiment of the method according to the invention, the filiform element 8 is in the form of a wire with a solid circular section and is wound with a substantially constant helical pitch P, so that the outer surface 15B has a regular trend along substantially the whole longitudinal extension, as can be seen in fig. 7. Such a wire remains wound around the profile 15 during the polymerization process of the profile 15 to maintain the relief structure imparted by the outer surface 15B. By the polymerization process, the glass fibers 5A, 5B are permanently anchored in the polymer resin, occupying in practice the attitude previously imposed by the tension of the filiform compression element 8. At the end of the polymerization process, the thread-like compression element 8 can be detached from the outer surface 15B, but more advantageously, the thread-like compression element 8 remains incorporated into the polymeric profile.

According to a further embodiment of the method according to the invention, the filiform compression element 8 has a concave cross section, for example semicircular, and is wound around the profile 15 with a substantially zero helical pitch (i.e. a pitch substantially comparable to the thickness of the filiform element). In particular, the filiform element 8 is wound so that a half circumference faces the external fibres of the profile 15. After this winding and subsequent polymerization, the outermost glass fibers 5B are partially arranged in the semi-circumferential recesses to define the undulation tendency of the outer surface 15B of the profile 15. At the end of the polymerization process, the filiform element 8 can be separated from the profile 15 to "free" the outer surface 15B, or more preferably, the filiform element 8 can remain incorporated into the polymerized profile, making the process even simpler and cheaper.

The method according to the invention thus also makes it possible to obtain a profile having a hollow axial section as shown in fig. 7 and 8. In this case, the method provides for the use of a cylindrical core around which the longitudinal glass fibers 5A, 5B are oriented and arranged before the compression of the outermost fibers 5B (i.e. before the polymerization process). The diameter of the cylindrical core determines in fact the diameter Di of the axial cavity 27 of the profile 15 (fig. 9).

From an operational point of view, once the glass fibers 5A, 5B are impregnated, they are oriented according to the axial direction X and arranged around a cylindrical core (not shown). Subsequently, the outermost fibres 5B are preferably compressed by helical winding of the filiform element 8 as described above. In this way, the profile 15 extends coaxially with the cylindrical core, which can also provide an advantageous support for the axial movement of the profile. After the polymerization process and any separation of the filiform extension element 8 from the profile 15, the profile 15 is removed from the cylindrical core to allow the subsequent use of the cylindrical core.

The method according to the invention can also be used to obtain the configuration of the profile shown in fig. 9, in which the central portion 22 is arranged between two portions 21A, 21B having an undulating outer surface 15B. In particular, the intermediate portion 22 has a cylindrical or in any case non-undulating outer surface 22B. To obtain such a surface, the method also allows the use of a thread-like compression element 8 in the form of a thread with a solid circular section, the thread-like compression element 8 being wound around the fibres 5A, 5B with a winding pitch of substantially zero (substantially comparable to the thickness of the thread-like element itself) for the length L1 of the intermediate portion 22.

The invention also relates to a device 100 for producing a profile 15 made of glass fibers 5A, 5B according to the invention. In this connection, fig. 10 is a schematic view relating to a plant 100 by means of which plant 100 the method for producing the profile 15 can be carried out according to the above.

The apparatus 100 according to the invention comprises an impregnation tank 5 containing a polymer resin with which the glass fibres 5A, 5B, the purpose of which is to form the profile 15, are impregnated. In particular, due to their diameter (of the order of a few tens of millimetres), the glass fibres 5A, 5B are gathered in the filaments 14 before reaching the impregnation tank 5. Each of these threads 14 actually comprises a set of glass fibers. The filaments are pre-set on a feed reel 50 feeding the apparatus 100.

Such a device comprises orienting and arranging means 51, 52 to orient the filaments 14 of the glass fibers 5A, 5B according to an axial direction X to construct an axially extending profile 15. The apparatus 100 further comprises pulling means 60 to pull the profile 15 along a pulling direction substantially parallel to the axial direction X. By means of the pulling device 60, the profile 15 made of glass fibres 5A, 5B is advantageously produced according to a "continuous" process.

The apparatus 100 also comprises pre-set polymerization means 66 to activate the polymerization process to anchor the structure of the profile 15. In particular, these polymerization devices 66, essentially formed by the polymerization oven 66B, are configured to heat the profile 15 to the correct polymerization temperature. This heating takes place by the profile 15 passing through the polymerization oven 66B due to the pulling action caused by the pulling device 60 arranged downstream of the polymerization oven.

The apparatus 100 according to the invention is characterized in that the apparatus 100 comprises means 80 for compressing the outermost fibres 5B of the profile 15. These means are arranged between the impregnation tank 5 and the polymerization furnace 66. The compression means 80 act on the outermost fibres 5B of the profile to shape the outer surface of the profile 15 according to the configuration and purpose described above. These compression means 80 preferably comprise a winding unit 70 by which the thread-like compression element 8 is wound around the surface 15B of the section bar 15. The winding unit 70 is adjusted so that the winding of the filiform element 8 occurs with a constant pitch P according to a substantially helical trend. The operation of the winding unit 70 is adjusted in terms of winding speed as a function of the speed at which the profile 15 is pulled by the pulling means 60. In practice, the extension of the helical pitch P is defined by the combination of the feeding speed of the profile 15 and the winding speed of the filiform extension element 8. By means of this adjustment it is possible, for example, to obtain the structure of the profile 15 shown in fig. 9. In this regard, to create the non-undulating surface 22B of the intermediate portion 22, the pulling speed is reduced and the winding speed of the thread-like compression element 8 is increased (or at most remains unchanged). In this way, the filaments can be wound with a substantially near zero helical pitch such that the outer fiber 5B is compressed to the diameter DC shown in fig. 9.

The drawing speed of the profile 15 is adjusted by means of an encoder 75 or functionally equivalent means. The pulling devices 60 can be those normally used in conventional pultrusion processes (for example a pair of pulling strips 60B arranged on opposite sides of the profile 15) to exert a combined and balanced pulling action on the profile 15.

With reference to the above, it is observed that in the case where a filiform compression element 8 with a concave cross section is used and wound with a substantially zero helical pitch, then the polymerization device 66 can also comprise a heated mould (or die) of the type commonly used in conventional pultrusion processes.

With reference to the schematic illustration of fig. 10, in a possible embodiment, the orienting and arranging devices 51, 52 of the glass fibers 5A, 5B comprise a first guide element 51 and a second guide element 52 arranged respectively downstream of the impregnation tank 5 and upstream of the polymerization furnace 66B. In particular, the first guide element 51 has the function of placing the thread 14, constituted by fiberglass fibres, under tension and orienting the thread 14 towards the second guide element 52. In a possible embodiment, the first guide element 51 is formed by a plate provided with holes through which the wires 14 are formed. In particular, the plate also performs a skimming function to eliminate any excess resin accumulated by the wires 14 in the impregnation tank 5.

As indicated above, the second guide element 52 is operatively arranged upstream of the polymerization oven 66B and immediately downstream of the compression device 80, wherein the thread-like compression element 8 is wound around the profile 15 by means of the compression device 80. In this connection, it is observed that the longitudinal distance L between the first guide element 51 and the second guide element 52 is chosen such that the wire 14 has been oriented substantially according to the axial direction X or according to the pulling direction. From a constructional point of view, the second guide element 52 can comprise a cylinder through which the profile 15 is formed to continue guiding the profile 15 towards the polymerization furnace 66B.

In order to obtain the fiberglass profile shown in fig. 7 to 9, the device according to the invention can be provided with a cylindrical core to support and pull the profile 15. According to what has been indicated above with respect to the method of embodiment, in the case where the wire 14 made of glass fibers 5A, 5B is arranged around a preferably metallic cylindrical core, the main function of the cylindrical core is to substantially define the axial cavity 27 of the profile 15. However, the cylindrical core also has the function of allowing the profile 15 to be pulled during the initial forming step of the profile 15. In practice, the pulling means 60 initially pull the cylindrical core in the axial direction X to subsequently perform a pulling action directly on the profile 15.

Referring again to the schematic view of fig. 10, a removal device 72 of the thread-like compression element 8 is operatively arranged downstream of the polymerization furnace 66B. These means are configured to continuously separate the thread-like element 8 during the drawing of the profile in the drawing direction.

In a preferred variant, the apparatus is devoid of the removal device 72, since the filiform element 8 can advantageously remain incorporated in the profile after its polymerization.

The technical solution adopted to the profile and to the method and plant for producing the same allow to fully achieve the aim and the aforementioned objects. In particular, the profile according to the invention has a greater pullout strength than the profile of the conventional solution. The method according to the invention enables the production of profiles with a reduced number of operations and at competitive costs with respect to the conventionally used processes. The profile, method and apparatus thus conceived are susceptible of numerous modifications and variations, all falling within the scope of the inventive concept; moreover, all the details can be replaced with other technically equivalent ones. In practice, the materials used, as well as the contingent dimensions and forms, can be any according to requirements and to the state of the art.

Claims (15)

1. A method for producing a profile (15) made of glass fibres (5A, 5B) for reinforcing an excavation wall, comprising the following steps:

-impregnating the glass fibres (5A, 5B) with a polymer resin;

-orienting the glass fibers (5A, 5B) according to a longitudinal direction and arranging them to configure an axially extending profile (15);

-compressing the outermost glass fibers (5B) of the profile (15) at axial intervals by a filiform compression element (8) to impart to the combination of the outer surface (15B) of the profile (15) and the filiform compression element a corrugated shape substantially corresponding to the corrugated shape of the final profile, the outer surface (15B) of the profile (15) having a substantially sinusoidal shape in an axial section plane;

-subjecting the profile (15) to a polymerization process.

2. The method according to claim 1, wherein the glass fibers (5A, 5B) are arranged around a cylindrical core to construct the axially extending profile (15), the profile (15) being removed from the cylindrical core after the polymerization process.

3. Method according to claim 1 or 2, wherein the thread-like compression element (8) is wound helically around the profile (15).

4. A method according to claim 3, wherein the thread-like compression element (8) is wound with a substantially constant helical pitch.

5. A method according to claim 3, wherein the thread-like compression element (8) is wound with a substantially constant helical pitch for a first predetermined axial length of the profile and with a substantially zero helical pitch for a second predetermined axial length.

6. The method according to claim 1, wherein the wire-like compression element (8) is a non-metallic wire.

7. Method according to claim 1, wherein the thread-like compression element (8) remains incorporated into the profile (15) after the polymerization process.

8. An apparatus (100) for producing a profile (15) made of glass fibres (5A, 5B) for use as a reinforcing element for reinforcing a pit wall, said apparatus (100) being characterized in that it comprises:

-at least one impregnation tank (5) for impregnating the glass fibers (5A, 5B) with a polymer resin;

-orientation and arrangement means (51, 52) of the glass fibers (5A, 5B) which orient them according to an axial direction X and arrange them in such a way as to constitute a profile (15) extending substantially axially;

-a compression device (80) comprising filiform compression elements (8) to compress the outermost glass fibers (5B) of the profile (15) at axial intervals to impart to the combination of the outer surface (15B) of the profile (15) and filiform compression elements a corrugated shape substantially corresponding to that of the final profile, the outer surface (15B) of the profile (15) having a substantially sinusoidal shape in an axial section plane;

-a polymerization device which polymerizes the profile.

9. Apparatus (100) according to claim 8, wherein it comprises pulling means (60) to pull said profile (15) in an axial direction.

10. Apparatus according to claim 8 or 9, wherein said compression means (80) comprise a winding unit (70) to wind a thread-like compression element (8) helically around said profile (15).

11. The apparatus (100) according to claim 10, wherein the winding unit (70) is adjusted such that the winding is performed with a constant helical pitch.

12. Apparatus (100) according to claim 11, wherein the winding speed of the thread-like compression element (8) around the profile (15) is adjusted as a function of the axial pulling speed determined by the pulling device.

13. Profile (15) made of glass fibres (5A, 5B) for reinforcing an excavation wall, the profile (15) comprising an axially extending body formed by the glass fibres (5A, 5B) anchored in a polymer resin by a polymerization process, the profile (15) being characterized in that the outer surface (15B) of the profile has a corrugated shape in an axial section plane of the profile (15), the corrugated shape being defined by different degrees of compression of the outermost glass fibres (5B) of the profile (15) obtained by means of filiform compression elements (8), the outer surface (15B) of the profile (15) having a substantially sinusoidal shape in the axial section plane.

14. Profile (15) according to claim 13, wherein the outer surface (15B) has a corrugated shape defined by concave portions (16) and convex portions (17) extending helically in axial direction alternately.

15. The profile (15) according to any one of claims 13 to 14, wherein the thread-like compression element (8) is incorporated into the profile (15).