EP3927898A1

EP3927898A1 - Sheath formed by at least one circular knit for producing a reinforced concrete pile

Info

Publication number: EP3927898A1
Application number: EP20710238.5A
Authority: EP
Inventors: Olivier BALAS; Alexandre SAUNIER; Loic ALIRAND
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-02-21
Filing date: 2020-02-18
Publication date: 2021-12-29
Also published as: CN113454289A; FR3093118B1; CA3127991A1; US20220145564A1; JP2022521524A; FR3093118A1; WO2020169916A1

Abstract

Disclosed is a sheath (15) for producing a reinforced concrete pile (100), characterized in that the sheath (15) is formed by at least one circular knit (10) comprising a succession of meshes (4) disposed in a helix so as to form a tube.

Description

Sheath formed by at least one circular knit for the realization of a reinforced concrete pile

The invention relates to the field of civil engineering and more particularly to a sheath for producing a reinforced concrete pile.

The construction of a structure, such as a building, an engineering structure, or a communication route, for example, requires that the structure rests on a stable basement, in order to support the weight of said structure. However, with more and more constructions, it is more and more common to have to build on a poor quality basement.

A poor-quality basement is called a basement that does not have the required stability qualities. A poor quality basement can present, for example:

- a layer containing a high proportion of compressible materials, such as peat, mud, a pocket of water or soft clay for example;

- a layer of altered limestone (karstic soil) and voids of solutions more or less filled by limestone scree, or alluvium for example;

- or a layer formed by a quarry void.

A poor quality basement can be reinforced by a rigid inclusion, that is to say a concrete column also called a pile, which allows the weight of the structure to be transferred to a deep layer with the required stability qualities. .

There is a known solution for producing a concrete pile, called a “cased bored pile technique”, in which a well is first produced by drilling. Next, a rigid tube, generally made of steel, is inserted over at least the entire height of the poor quality layer of the well. Then a metal reinforcing cage is introduced into the tube. The reinforcement cage allows reinforcement of the pile so as to obtain a reinforced concrete pile. Thus the reinforcing cage improves mechanical properties of the pile. Finally, a dip tube is installed in the reinforcing cage in order to pour the concrete.

The object of the tube is on the one hand to contain a hydrostatic pressure of the concrete during the pouring thereof, that is to say the force exerted by the weight of the concrete in equilibrium, and on the other hand to serve as a concrete formwork so as to keep said concrete in place while it becomes self-supporting by setting.

This technique has the disadvantage of using a rigid tube which is very expensive, difficult to transport because of its volume, requires significant handling means for its implementation such as a crane, and may require the realization of a welding of several tubes according to the height desired. In addition, the implementation of the rigid tube, depending on the weather conditions, can present a significant risk for the safety of personnel. Thus, it is known to replace the rigid tube with a flexible geotextile sheath formed by a substantially rectangular part, two opposite edges of which are connected together by means of a seam. In this way, the transport and the implementation of the sheath are facilitated. However, said sheath has a low resistance so that it is incapable of countering the hydrostatic pressure of the concrete on a borehole with a height greater than 5 meters. In addition, the sheath lets concrete escape at the level of the geotextile seam, which leads to overconsumption of concrete. Finally, the sheath does not allow sufficient evacuation of water from the concrete, resulting in poor setting of the concrete.

The object of the invention is to remedy all or part of the aforementioned drawbacks by proposing a sheath for producing a reinforced concrete pile, characterized in that the sheath is formed by at least one circular knit comprising a succession of positioned stitches helical so as to form a tube.

A knit is a fabric made of loops of threads called "stitches". Each stitch is made up of a head, two legs and two feet. In a horizontal direction, that is to say along an axis transverse to an axis of elongation of the legs of the mesh, a succession of meshes is called a row of meshes. In a vertical direction, that is to say along the axis of elongation of the legs of the stitch, a succession of stitches is called a column of stitches. In knitting, the stitches are interwoven in a defined pattern, which is called weave or tying. We distinguish knits having a pattern called plucked stitches, in which a yarn is associated with a row of stitches, and a pattern called "warp" knits or "chain" knits, in which a thread is associated with a needle, thus there will be as many needles as there are threads. Unlike weaving, that is to say a fabric in which two sets of threads are interwoven at right angles, knitting is a fabric which is extensible in the horizontal direction and in the vertical direction. The extensibility of the knit depends on the one hand on the pattern of interlacing of the stitches and on the other hand on the nature of the threads which compose it. In other words, a knit inherently exhibits a higher extensibility than the extensibility of the yarns which compose it.

A circular knit comprises at least one row of stitches of a determined length. More specifically, the length of the row of stitches is determined by a ratio between a length of threads used relative to a number of needles or to a number of turns. The stitches of the row of stitches are interlaced in a helix of so as to form a tube. The circular knit has a homogeneous structure, that is to say that there is no seam.

Thus, the sheath formed by the circular knit has homogeneous elasticity characteristics along an axis of elongation of the sheath, that is to say along the column of stitches, and along an axis radial to the axis of elongation of the sheath, that is to say along the row of meshes. The elasticity along the axis of elongation of the sheath may be different from the elasticity of the sheath along the radial axis.

Therefore, the sheath according to the invention is particularly suitable for extending along the radial axis so as to absorb an overpressure phenomenon which appears, when using the sheath, at the time of an injection of concrete. in a borehole.

In addition, the sheath according to the invention can, when using the sheath, easily adapt to the shapes of the subsoil and withstand hydrostatic pressure from the concrete. Finally, the sheath according to the invention does not have a zone of weakness thus making it possible to retain the concrete inside the sheath.

According to one characteristic of the invention, the sheath is formed by a plurality of tubular knits inserted into one another in a coaxial manner.

This reinforces the resistance of the sheath vis-à-vis tears.

According to one characteristic of the invention, the at least one circular knit has an elasticity allowing an elongation of between 10% and 400% of a flat diameter of said circular knit.

The flat diameter of the knit corresponds to a width of the sheath along an axis transverse to the axis of elongation of the sheath, when the sheath is folded on itself so as to extend in a plane.

In this way, the sheath has sufficient elasticity to absorb overpressure phenomena while controlling the maximum quantity of concrete that can be injected into it.

Preferably, the at least one circular knit has an elasticity allowing an elongation of between 25% and 75% of the flat diameter of said circular knit. According to one characteristic of the invention, the circular knit has an elasticity along the axis of elongation of the circular knit allowing an elongation of between 0% and 150%.

According to one characteristic of the invention, the at least one circular knit is permeable. Thus, when the sheath is filled with concrete, the circular knitting allows water, another liquid or a binding agent present in the concrete to be evacuated. Of this way, a setting, that is to say a crystallization or a hardening, of the concrete is carried out according to the rules of the art.

According to one characteristic of the invention, the stitches are interlaced according to a pattern chosen from: a pattern called "Jersey", a pattern called "ribs 1/1", a pattern called "ribs 2/2", or a pattern called " Interlock ”.

The pattern called "Jersey" is a pattern in which all stitches are threaded in the same way in the stitch of the row below.

The diagram called "rib 1/1" is a diagram in which there is an alternation of a stitch called "place" and a stitch called "reverse".

The pattern called “interlock” is a pattern in which two “1/1 rib” patterns are interlaced.

The diagram called “rib 2/2” is a diagram in which there is an alternation of two stitches called “places” and two stitches called “purl”.

According to one characteristic of the invention, the at least one circular knit comprises at least one loaded stitch.

A loaded mesh, also called a float mesh or double mesh, is a mesh on which a load loop is positioned.

Thus the resistance of the circular knitting is improved. In addition, the loaded stitches make it possible to block unraveling of the knit in the event of a tear.

According to one characteristic of the invention, the at least one circular knit comprises a plurality of loaded stitches.

According to one characteristic of the invention, the loaded stitches are regularly distributed in the circular knitting.

According to one characteristic of the invention, the at least one tubular knit is made with at least one yarn made from a material chosen from: a synthetic material, a cellulosic material, a plant material, an animal material, a mineral material, a metallic material.

The threads made from a synthetic material are fibers obtained from petroleum derivatives.

Yarns made from cellulose material include cellulose molecules.

The threads made from a plant material come from the environment, that is to say from plants.

The threads made from animal material come from animals.

The threads made from a mineral material are made from minerals such as rock, sand, natural stone ... The wires made of a metallic material involve a metallic bond. Thus, depending on the choice of the yarn or yarns of the knit, the at least one knit has improved mechanical resistance at a strongly basic pH (the pH of the concrete is 13) and against corrosion and UV resistance.

According to one characteristic of the invention, the synthetic yarn is made from a material chosen from: polyester, high tenacity polyester, high modulus polyethylene, high modulus polyester, high modulus para-aramid.

Polyester results from the condensation of two components derived from petroleum: an acid (terephthalic acid) and an alcohol (ethylene glycol). Polyester has high elasticity.

High tenacity polyester exhibits high resistance to breakage and abrasion. The high tenacity polyester is also particularly UV stable. High modulus polyethylene is a very high molecular weight polyethylene (UHMPE) fiber with excellent abrasion resistance.

High modulus polyester is a thermoplastic liquid crystal polymer (LCP) belonging to the family of aromatic polyesters.

High modulus para-aramid is an organic fiber belonging to the family of aramids or aromatic polyamides, the scientific name of which is poly-para-phenylene terephthalamide (PPDT).

According to one characteristic of the invention, the at least one tubular knit is made with at least one yarn having a tenacity of between 5 and 50cN / dtex.

The tenacity is expressed by the load in decanewtons (daN) necessary to break a wire of 1 mm ² in section.

Thus the at least one knit has improved mechanical strength.

According to one characteristic of the invention, the at least one tubular knit is produced with at least one yarn exhibiting a moisture uptake of less than 10%, preferably less than 5%.

According to one characteristic of the invention, the at least one tubular knit is made with at least one yarn with a density of less than 10, preferably less than 1.5.

Thus the sheath remains light to handle.

According to one characteristic of the invention, the at least one tubular knit is made with at least one thread which is inert with respect to the environment.

In this way, the sheath respects the environment in which it is placed.

According to one characteristic of the invention, the at least one tubular knit is made with at least one yarn having an elasticity of less than 50%. The invention also relates to a method for producing a reinforced concrete pile, said method comprising:

- an excavation step so as to form a well;

- a step of inserting one end of a reinforcing cage in a sheath according to any one of the preceding claims;

a step of positioning the sheath on a determined area of the reinforcing cage;

- a step of introducing the reinforcement cage into the well;

- a step of installing a dip tube inside the reinforcement cage;

- a step of filling the well with concrete using the dip tube. Thus the process makes it possible to easily produce a reinforced concrete pile.

In addition, the method makes it possible to position the sheath on a predetermined height of the well making it possible to cover or not the whole of the well.

According to one characteristic of the invention, the determined zone of the reinforcing cage is less than a zone corresponding to a total height of the reinforcing cage.

Thus, the determined zone has a lower height than the total height of the reinforcing cage. In this way, the sheath does not cover the whole of the reinforced concrete pile, but only part of it. The sheath protects the part of the reinforced concrete pile facing the poor quality subsoil while the rest of the reinforced concrete pile is in direct contact with the subsoil. The direct contact between the concrete and the subsoil makes it possible to ensure a transfer of force from the reinforced concrete pile in the traditional way and therefore to keep the technical data applicable to traditional reinforced concrete piles.

The invention will be better understood, thanks to the description below, which relates to an embodiment according to the present invention, given by way of non-limiting example and explained with reference to the attached schematic drawings, in which:

Figure 1 is a schematic representation of a mesh;

Figure 2 is a schematic representation of a knit;

Figure 3 is a schematic representation of a loaded mesh;

Figure 4 is a representation of several mesh interleaving schemes;

Figure 5 is a schematic representation of an excavation step;

FIG. 6 is a schematic representation of an insertion step;

FIG. 7 is a schematic representation of an introduction step;

FIG. 8 is a representation seen on a larger scale of the introduction step; FIG. 9 is a schematic representation of an installation step;

Figure 10 is a schematic representation of a filling step; FIG. 11 is a view on a larger scale of the filling step;

FIG. 12 is a schematic representation of a reinforced concrete pile produced with a method according to the invention;

Figure 13 is a representation view on a larger scale of the reinforced concrete pile of Figure 12.

A knit 10, as shown in Figure 2, is a fabric formed of loops of threads 5 called "stitches" 4. A stitch 4, as shown in Figure 1, is composed of a head 1, two legs 2 and two feet 3.

In a horizontal direction, that is to say along an axis X transverse to an axis of elongation Y of the legs 2 of the stitch 4, a succession of stitches 4 is called a row of stitches 4. In a vertical direction , that is to say along the axis of elongation Y of the legs 2 of the stitch 4, a succession of stitches 4 is called a column of stitches 4.

The knit 10 comprises a plurality of loaded stitches 7. Figure 3 shows a single loaded stitch 7. The loaded stitch 7 is a 4 stitch on which is positioned a load loop 6.

The loaded stitches 7 are regularly positioned in the knitting 10. Preferably, the loaded stitches 7 are positioned every 7 rows or every 17 rows.

In addition, the stitches 4 of the knit 10 can be interwoven according to different patterns as shown in Figure 4.

For example 4 stitches can be intertwined in a pattern called "Jersey" 11. In this pattern, all 4 stitches are threaded in the same way in stitch 4 of the row below.

For example, the stitches 4 can be interlaced according to a pattern called “rib 1/1” 12. In this pattern, there is an alternation of a stitch 4 called “place” and a stitch 4 called “reverse”.

For example, the stitches 4 can be interlaced according to a pattern called “interlock” 14. In this pattern, two “1/1 rib” patterns 12 are interlaced.

For example, the stitches 4 can be interlaced according to a pattern called “2/2 rib” 13. In this pattern, there is an alternation of two stitches 4 called “places” and two stitches 4 called “purl”.

Preferably, the stitches 4 of the knit 10 are interwoven according to the diagram called "rib 2/2" because the latter is more extensible along the X axis transverse to the axis of elongation Y of the legs 2 of the stitch 4 than the diagram called "rib 1/1", is disentangles less easily than the pattern called "Jersey" and is faster to produce.

Knit 10 is made with yarns 5 of synthetic material.

A sheath 15 according to the invention is formed by the circular knit 10 comprising a succession of stitches 4 positioned helically so as to form a tube. In other words, the circular knit 10 comprises a row of stitches 4 which winds on itself forming a helix. Each stitch 4 of the upper round being tied to a stitch 4 of the lower round.

The sheath 15, which is flexible, can be folded so as to be positioned in a plane. In the folded position, each point of an internal wall of the sheath 15 is in contact with a point of the diametrically opposed internal wall. In the folded position, the sheath 15 has two layers in contact with one another, interconnected by two opposite edges. A flat diameter of the circular knit 10 is a length between the two edges and measured transversely to them.

The sheath 15 is intended to allow the production of a reinforced concrete pile 100 in a basement 20.

The subsoil 20 considered is formed by a succession of layers. The upper layer, that is to say that which will be in contact with a construction, is called surface soil 21. It extends substantially between 0 meter and - 5 meters. The next layer extends between -5 meters and -15 meters, it is formed by a so-called soft layer 22, that is to say containing a high proportion of compressible materials. The layer below -15 meters is formed by a stable layer 23. It can serve as a base for the reinforced concrete pile 100.

A method of making a reinforced concrete pile 100 comprises an excavation step, as shown in FIG. 5. The excavation step consists in digging, generally by a drilling method, a subsoil 20 in such a manner. in forming a well 30 between the surface soil 21 and the stable layer 23. The well 30 has a diameter between 1 and 1600 millimeters In our example shown in FIG. 5, the well has a diameter of 100 millimeters and a length of 20 meters.

The method comprises, as shown in FIG. 6, a step of inserting one end of a reinforcing cage 40 into the sheath 15.

The reinforcement cage 40 is a hollow metal structure which is substantially parallelepiped or cylindrical having a length along an axis of elongation A of the reinforcement cage 40 substantially equal to a length of the well 30 and a width along a transverse axis B to l 'axis of elongation A of the reinforcement cage 40 less than the diameter of the well 30. In addition, the reinforcing cage 40 comprises spacers 41 regularly positioned along the length of the reinforcing cage 40. The spacers 41 are metal elements forming a shoulder on an outer part of the reinforcing cage 40.

The sheath 15 has a diameter at rest, that is to say when no force is exerted on the sheath 15, substantially less than the width of the reinforcing cage 40. In this way, the sheath 15 must be stretched radially, that is to say along an axis transverse to an axis of elongation of the sheath 15, to allow the reinforcement cage 40 to pass.

Further, the sheath 15 has a maximum diameter when stretched greater than the diameter of the well.

Finally, the sheath 15 has a length along its axis of elongation greater than a height of the soft layer 22.

To perform the insertion step, the sheath 15 is stretched radially and then one end of the reinforcing cage 40 is placed inside the sheath 15.

The method then comprises a step of positioning the sheath 15 on a determined area of the reinforcing cage 40. The determined area is that which will be in contact with the soft layer 22 of the subsoil 20 after carrying out a step. introduction of said reinforcing cage 40 into the well 30. When the sheath 15 is positioned on the determined zone of the reinforcing cage 30, no force stretching it radially, it seeks to return to its rest diameter . It thus sticks and hooks onto the reinforcement cage 40.

FIGS. 7 and 8 represent the reinforcing cage 40 on which the sheath 15 is positioned in the well 30 corresponding to an insertion step. The sheath 15 is opposite the soft layer 22 and pressed against the reinforcing cage 40. The reinforcing cage 40 is centered in the well 30 thanks to the spacers 41.

Next, a step is carried out for installing a dip tube 50 inside the reinforcing cage 40, as shown in FIG. 9. The dip tube 50 is lowered into the well 30.

Finally, a filling step is carried out as shown in FIGS. 10 and 11. During the filling step, concrete 51 is poured into the dip tube 50 so as to introduce it into the well 30. The speed concrete flow 51 is generally between 30 and 70 m ³ / h.

The concrete 51 exerts a radial force on the axis of elongation of the well 30. Thus, the concrete 51 pushes the sheath 15 radially. The sheath 15 deforms and extends. The concrete 51 is retained inside the sheath 15. The sheath 15 expands radially until it reaches its maximum expansion or until it comes into contact with the rocks forming the walls of the well 30. Its expansion is then retained by said rocks.

The radial expansion of the sheath 15 makes it possible to resist the hydrostatic pressure of the concrete.

The expansion of the sheath 15 also allows the concrete 51 to coat the reinforcing cage so as to protect it from oxidation phenomena.

When the well 30 is filled with concrete, the reinforced concrete pile 100 is produced as shown in FIGS. 12 and 13. The concrete forming the reinforced concrete pile 100 will then crystallize so as to become self-supporting. The sheath 15 is left in place.

By way of example, the invention also relates to a sheath made of a knit having a diameter of 800 mm, an extensibility in the horizontal direction, that is to say according to the diameter of the knitting, of 80%, and an extensibility. in the vertical direction, that is to say along the axis of elongation of the sheath, of 10%. The sheath has a weight of 450g / m ² and is made only with synthetic high tenacity polyester threads.

The above sheath is designed to be inserted over a determined area of a reinforcing cage having a substantially cylindrical hollow metal structure.

In order to ensure that the construction of the reinforced concrete pile is made secure, the process uses two identical and independent sheaths. The method of implementing the invention then comprises the step of inserting and the step of positioning a first sheath on the determined zone of the reinforcing cage then the step of inserting and the step positioning of a second sheath on the determined area so that the two sheaths overlap. The second sheath finally covers the first sheath. Thus, the construction of the pile is secured in the event of failure of one of the ducts.

The positioning step makes it possible to place the sheath on only part of the reinforcing cage which will be in contact with the soft layer of the subsoil after carrying out a step of introducing said reinforcing cage into the well. In this way, the sheath protects the part of the reinforced concrete pile facing the soft layer of the subsoil while the rest of the reinforced concrete pile is in direct contact with the subsoil. The direct contact between the concrete and the subsoil makes it possible to ensure a transfer of force from the reinforced concrete pile in the traditional way and therefore to keep the technical data applicable to traditional reinforced concrete piles. Of course, the invention is not limited to the embodiment described and shown in the appended figures. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.

Claims

1. Sheath (15) for making a reinforced concrete pile (100), characterized in that the sheath (15) is formed by at least one circular knit (10) comprising a succession of stitches (4) positioned in helix so as to form a tube.

2. Sheath (15) according to claim 1, wherein the at least one circular knit (10) has an elasticity allowing an elongation of between 10% and 400% of a flat diameter of said circular knit.

3. Sheath (15) according to any one of the preceding claims, in which the at least one circular knit (10) is permeable.

4. Sheath (15) according to any one of the preceding claims, in which the stitches (4) are interlaced according to a pattern chosen from: a pattern called "Jersey" (11), a pattern called "ribs 1/1" ( 12), a pattern called "2/2 ribs" (13), or a pattern called "Interlock" (14).

5. Sheath (15) according to any one of the preceding claims, in which the at least one circular knit (10) comprises at least one loaded stitch (7).

6. Sheath (15) according to any one of the preceding claims, wherein the at least one tubular knit (10) is made with at least one yarn (5) made of a material chosen from: a synthetic material, a material cellulosic, a plant material, an animal material, a mineral material, a metallic material.

7. Sheath (15) according to claim 6, in which the synthetic yarn (5) is made of a material chosen from: polyester, high tenacity polyester, high modulus polyethylene, high modulus polyester, para. high modulus aramid.

8. Sheath (15) according to any one of the preceding claims, in which the at least one tubular knit (10) is made with at least one yarn (5) having a tenacity of between 5 and 50cN / dtex.

9. A method of making a reinforced concrete pile (100), said method comprising:

- an excavation step so as to form a well (30);

- a step of inserting one end of a reinforcing cage (40) in a sheath (15) according to any one of the preceding claims;

- a step of positioning the sheath (15) on a determined zone of the reinforcing cage (40);

- a step of introducing the reinforcing cage (40) into the well (30);

- a step of installing a dip tube (50) inside the reinforcing cage (40);

- a concrete filling step (51) of the well (30) by means of the dip tube (50)

10. Production method according to claim 9, wherein the determined area of the reinforcing cage (40) is less than an area corresponding to a total height of the reinforcing cage (40).