TW202032058A - Modular prestressed concrete pressure tank - Google Patents

Abstract

A modular compressed gas storage tank comprising a plurality of prestressed preformed ring elements, each ring element comprising a concrete body and at least one tensioning tendon extending circumferentially within the concrete body.

Description

Modular pre-compressed concrete pressure tank

The present invention relates to compressed gas energy storage, and more specifically but not exclusively relates to compressed air energy storage (CAES).

Renewable energy sources (such as wind or solar energy) lead to energy surplus when electricity generation exceeds electricity consumption. In addition, since renewable energy is intermittent, the power demand can exceed the power generated.

In order to overcome these shortcomings, extensive research has been conducted to develop energy storage solutions.

Many solutions rely on batteries, which is not entirely satisfactory because battery manufacturing and recycling cause serious environmental problems.

CAES includes the use of residual energy in a compression stage to compress air for storage in a storage tank and the use of compressed air in a later stage to drive turbines to generate electricity.

The steel tank has been used as an overhead storage unit. However, the cost of these tanks is higher because they are made of complicated parts with higher transportation costs. As of now, this solution is limited to small capacity storage facilities.

Another solution is to use underground natural cavities as storage components. However, this means that certain geographical conditions are not always met and require long and costly preparations.

Pressure tanks made at least partly of pre-compressed concrete have been revealed as an alternative to pressure tanks made entirely of steel.

CN207316457U teaches a spherical or cylindrical shape pre-compressed concrete pressure tank assembled on site.

FR3055942 discloses a cylindrical pressure tank made of multiple concentric layers, which includes an innermost concrete inner layer, a steel layer, a concrete layer (with steel wire wound on it) and an outermost protective layer. The drawing of the steel wire requires a heavy equipment, which makes the operation on site relatively difficult. This technique also limits the diameter of the annular section due to the equipment used to wind and stretch the steel wire, and also results in a relatively high loss of preload. The monitoring and maintenance of steel wires are relatively difficult, if not impossible. The concrete layer inside the tank suffers from the risk of loss of adhesion and resistance over time, and may show cracks.

US3926134 discloses a tank adapted for cryogenic liquid placed in a conventional marine vessel. The groove is composed of a series of concrete and modular groove wall sections, which are pre-pressed circumferentially by steel tendons and have holes in them for allowing axially pre-compressed steel tendons to penetrate. The modular wall sections are separated by concrete or steel stiffening discs.

There is still a need for improved solutions for compressed gas energy storage and the purpose of the present invention is to meet this need.

Therefore, the exemplary embodiment of the present invention provides a modular compressed gas storage tank, which includes a plurality of pre-compressed pre-formed ring elements, each ring element includes a concrete body and at least one circumferentially extending inside the concrete body Stretch the tendons.

The preloaded ring elements can be positioned between the end elements.

The present invention provides an energy storage solution that is cheaper than a solution that relies on a container made entirely of steel. Concrete is a relatively cheap material available anywhere. A storage tank according to the present invention can be manufactured near the energy storage production site. The use of pre-formed elements increases the reliability of the groove. The storage tank can be easily made to withstand an internal pressure that varies in the range of 60 to 130 bar during the day.

In addition, the gas storage capacity can be easily adjusted by selecting the number of ring elements per groove and the number of grooves.

By "inside the concrete body", we should understand that the steel tendon includes at least one part extending along the circumference between the inner and outer diameters of the concrete body.

The end of the at least one steel tendon is preferably anchored against an outer surface of the concrete body.

Preferably, the at least one steel tendon extends circumferentially at least two or three turns around a longitudinal axis of the ring element. This realization separates the tendon anchoring areas and allows the concrete body to withstand high mechanical loads. Preferably, the at least one steel tendon extends spirally. Each ring element may include at least one radially outer tendon extending along the circumference and at least one radially inner tendon extending along the circumference coaxially with the first tendon. In this way, the tank can withstand higher internal pressures. Each ring element may include at least two radially outer tendons axially separated from each other by a gap, and at least one end of the at least one radially inner tendon extends through the gap. For example, each ring element includes at least two radially inner tendons. Preferably, each radially inner tendon extends circumferentially (for example, spirally) around a longitudinal axis of the ring element at least two or three turns.

Preferably, each ring element includes a channel extending longitudinally stretched tendon from one end element to the other end element.

The tendon anchors of each ring element can abut a shoulder that can be defined by at least one protruding rib section.

This rib section can be oriented downwards and connected to a base.

Preferably, the shoulders are defined by more than one protruding rib section. For example, the shoulders are defined by two opposed protruding ribs or by more than two protruding rib segments regularly spaced along the circumference of the ring element. The number of ribs can depend on the number of concentric steel tendons. The presence of multiple ribs allows the anchoring areas to be spaced apart and makes it easier for the tendons of layers of different depths to cross and reach their respective anchoring areas.

The groove may include more than two concentric steel tendon layers extending circumferentially within the concrete body. The number of concentric tendon layers can depend on the internal pressure that the groove will withstand.

The end of each tendon can be anchored to the shoulder defined by a respective rib section.

Preferably, each tendon extends within a corresponding catheter (also called "sheath").

Preferably, the groove includes a longitudinally stretched tendon for applying an axial load on the ring elements.

The end elements may each include a preformed concrete wall. Each end element may include an inner cover, which may be a liner that is impermeable to gas.

Each ring element may include an inner liner section that is impermeable to gas.

The inner liner section of each ring may include a radially inwardly extending end flange. These flanges are used to make one of the seals between two continuous ring elements.

The inner layer section and inner cover may include a metal layer (for example, such as steel). The flanges can be welded together.

The groove may include a screw pile fixed to the surface of the inner liner section and anchored in the concrete body. These bolts may be metal bolts welded to the liner section.

Two continuous ring elements can have complementary shear tenons on the facing surfaces. These shear tenon can be matched and cast. The groove may not include any stiffening discs between two consecutive ring elements. The interface between two continuous ring elements can be filled with a polymer adhesive (such as an epoxy resin).

Preferably, at least one of the end elements includes a tube (such as an intake tube) that is open inside the groove.

A further object of the present invention is a method of making a groove as defined above, the method comprising: -Continuously position at least two pre-formed ring elements, -Apply an axial compressive load on the ring elements.

The method can be performed near the energy production site where the tank will be used.

The method may include introducing a polymer adhesive at an interface between two continuous ring elements. The adhesive (for example) is an epoxy resin.

The method may include installing the ring elements in sequence, wherein temporary stretch rods are introduced through the ring elements to apply a temporary axial load to the ring elements during curing of the polymer adhesive. These temporary stretch rods can be replaced by steel tendons after all ring elements are in place.

Each ring element preferably includes one of the inner liner sections mentioned above, and the method may include continuously welding the inner liner sections. This welding is preferably performed automatically by a mechanical arm. Preferably the seal is also checked in an automatic manner.

The method may include assembling the inner cover to the adjacent inner liner section, and then assembling the concrete wall of the end element to the adjacent ring element. The welding of the cover to the inner liner section can be performed from the outside.

The method may include applying a temporary load between the wall and the adjacent ring element to fill a recess behind the cover positioned on the inner side of the concrete wall with cement grouting.

These ring elements can be matched and cast.

A further embodiment of the present invention relates to a pre-compressed concrete ring element for a groove as defined above, which comprises: a concrete body; at least one radially internally stretched steel tendon, which runs along the circumference of the concrete body Extension; and at least one radially outer tendon, which extends circumferentially in a concentric manner with the radially inner tendon, the end of each tendon is anchored against an outer surface of the concrete body, preferably set against On the shoulders on the outer surface.

The ring element may include some or all of the features defined above with respect to the groove.

A further object of the present invention is a method for manufacturing a ring element as defined above, the steel tendons extending in corresponding conduits, the method comprising: winding the steel tendons and the conduits around a removable forming tool ; According to the location of the conduit and the steel tendon in the concrete body, etc.; and preferably a reinforcement cage is formed around the conduit.

The circular or circumferential tendons of the ring element are preferably present in the ducts during the casting of the concrete. The steel tendons are preferably pre-threaded in the conduits before the steel cage surrounds the conduits and is installed by the cast concrete. The steel tendons are preferably individually sheathed with plastic materials (such as HDPE) and lubricated (lubricated) in the individual sheaths to ensure a low coefficient of friction. The friction coefficients mu and k are preferably lower than 0.06 and 0.015, respectively.

The method may include injecting a cement grout inside the ducts before stretching the tendons.

The ring element preferably includes a liner section, and the method may include casting the concrete in direct contact with a surface of the liner.

The ring element can be cast to match one of the adjacent ring elements previously made.

A further object of the invention relates to a method of temporarily storing energy, which comprises compressing a gas and storing the compressed gas in a tank according to the invention as defined above.

A further object of the present invention is an energy storage system comprising: at least one tank as defined above; at least one compressor unit for compressing a gas for storage under the pressure in the tank; and at least one turbine, which Used to generate energy through the expansion of the compressed gas.

The energy storage system 1 shown in Fig. 1 includes a compressed air storage tank 2 and one or more compressor units 3 for compressing incoming air and feeding the compressed air into the storage tank 2 and for generating electricity by the expansion of compressed air One or more turbines 4.

The storage tank 2 is made of one or more compressed air tanks 10, as shown in FIG. 2.

The tanks 10 can be connected in parallel and/or in series. Each tank 10 may be associated with a respective compressor group and/or turbine. In a variant, one compressor unit and/or turbine is associated with more than one tank 10.

Each groove 10 has a modular structure and includes two opposite end elements 11 and a plurality of intermediate ring elements 12 at least partially made of pre-compressed concrete. The system may include one or more heat exchangers (not shown) and/or a thermal insulator so that the temperature of the air inside the tank prevents the concrete from being exposed to more than 100°C.

The number of slots 10 and the number of intermediate ring elements 12 in each slot 10 depend on the required storage capacity. Each groove 10 may include between 1 and 50 ring elements, preferably between 2 and 50, more preferably between 10 and 30. The number of slots can range from 1 to 50.

The total storage capacity of a tank 10 can range from 50 to 3000 m ³ .

The range of the internal volume that can be used for compressed air storage brought about by each additional ring element 12 may be between 3 m ³ and 150 m ³ , and preferably between 15 m ³ and 60 m ³ .

In the described embodiment, each slot 10 extends horizontally along a straight longitudinal axis, but the present invention is not limited to a specific orientation of the longitudinal axis. In a variant (not shown), the groove is a ring body, for example, having a median diameter between 30 and 100 m, an inner diameter of a ring element of 2 to 4 m, each ring element having a diameter of 1.5 to 4.5 m A length and an oblique angle of about 5°.

The maximum nominal internal pressure of filling a tank with compressed air can range between 60 and 180 bar, preferably between 100 and 150 bar.

For example, as can be seen in FIGS. 2 and 4, each groove 10 may include a lower rib 20 extending longitudinally along the entire length of the groove.

The rib 20 protrudes downward and can rest on a base bottom plate 13 supported by the ground. Once backfilled, excavation 14 supports the lower part of the groove 10 on either side of the rib 20. The embankment provides greater mechanical stability and can reduce the risk of freezing the ground extending under the tank 10 in winter. The base bottom plate 13 can be replaced by a base that extends deeper into the ground.

The end element 11 and the ring element 12 each include a rib section 23 so that these sections 23 form a longitudinal rib 20 when aligned. Preferably, the rib 20 is continuous along the entire length of the groove 10.

In the example shown in FIGS. 2 to 4, the groove 10 includes only one longitudinal rib 20. In a preferred embodiment, the groove includes more than one rib protruding on its outer surface, as will be described in detail below.

Each ring element 12 is pre-formed and includes pre-compressed concrete. The end element 11 is also preformed.

5 to 7 show a ring element 12 according to an exemplary embodiment of the present invention.

The ring element 12 shown in these figures has two diametrically opposed rib sections 23 and 24. The lower rib section 23 can be oriented downward and rest on the aforementioned base bottom plate 13.

The ring element 12 includes a concrete body 25, which is preferably made of high performance concrete (HPC). The concrete used to make the concrete body 25 has a compressive strength of one of better than 30 MPa, preferably better than 60 MPa, and more preferably 90 MPa or better.

The ring element 12 includes a tensile steel tendon extending circumferentially in the corresponding ducts 30 and 31 within the concrete body 25.

These tendons extend in concentric paths within the concrete body 25. In the example shown, the duct 30 receives the radially outer tendon and the duct 31 receives the radially inner tendon.

As can be seen in FIGS. 6 and 7, the ring element 12 is provided with two radially outer ducts 30, each of which is spirally wound around the longitudinal axis of the groove 10. The coils made of the conduit 30 are spaced apart to define an annular gap 33 therebetween. Each coil may include at least two turns and preferably three turns, as shown.

The opposite end of each duct 30 is open on a respective shoulder 34 or 35 defined by the lower rib section 23, as best seen in FIG. 5.

The opposite end of each duct 31 is open on a respective shoulder 36 or 37 defined by the upper rib section 24.

To reach the shoulder 36 or 37, the end of a catheter 31 extends through the gap 33, as we can see in FIG.

The presence of the two rib sections 23 and 24 provides sufficient distance from the anchor of the corresponding tendon for the concrete body to carry the load.

FIG. 8 shows the end of a tendon 62 extending in a duct 31. This end is provided with an anchor 68 of known structure and shown schematically. A metal (for example, steel) plate 67 can be inserted between the anchor 68 and the shoulder 36 to better distribute the load to the concrete body 25. The plate can be replaced by a horn-shaped metal element (steel, cast iron or other) in other ways to better distribute the load behind the anchor. Depending on the tensile strength of the concrete used to cast the main body of the ring element, an explosion-proof specific stiffening element (several frames or spiral surfaces) can be arranged behind each anchor element and around the conduit.

Each ring element 12 also has a substantially axially oriented channel 100 for stretching the tendon 60 (only one of them is shown in dashed lines in FIG. 7), which extends from one end element 11 through the ring element 12 to The other.

These channels 100 can be provided between the ducts 30 and 31 and also in the upper rib section 24 as shown. The channels 100 may be evenly spaced around the longitudinal axis of the ring element 12 between the inner duct layer and the outer duct layer, as shown in FIG. 5.

Each ring element 12 is provided with a reinforcement cage 70 embedded in concrete, as shown schematically in FIG. 9.

Each ring element 12 also has an inner liner section 50, as shown in FIGS. 10 to 12, which defines an inner surface 51 of the ring element that is in contact with compressed air and is impermeable to compressed air.

The inner liner 50 is preferably made of a steel sheet (for example, stainless steel), and has a radially inwardly extending flange 52 at its axial end, as can be seen in FIG. 12.

For a better mechanical connection between the lining section 50 and the concrete main body 25, the lining 50 is preferably provided with screw piles 53 extending radially inside the concrete main body 25, as shown in FIG. 10.

As shown in FIG. 11, each end element 11 may include a concrete wall 14 (which may be stiffened using a cage (not shown)) and an inner cover 80 (which may be a liner).

The inner cover 80 is made of a material that is impermeable to compressed air and preferably has the same material as the inner liner section 50 of the ring element 12 (for example, steel).

The at least one end element 11 may be provided with at least one inlet pipe 90 for supplying compressed gas to the tank 10 during a compression phase as shown in FIG. 13. The same tube or another tube can be used to draw compressed air from the tank to power a turbine during an expansion phase. A corresponding recess 91 may be provided in the concrete wall 14 for the pipe 90 to pass through.

The tank 10 may be equipped with various pressure, strain, or temperature sensors and a thermal insulation or heat exchange system (not shown).

Each end element 11 is provided with a recess 86 behind the cover 80, which is filled with a hard filler 85, so that the force exerted by the compressed air on the cover is transmitted to the wall 14.

The flange 52 of the inner liner section 50 of the ring element 12 adjacent to the end element 11 is provided with an end collar 55 configured to overlap with a corresponding end collar 88 of the cover 80. The two collars can be fixed together by welding or welding.

The ring element 12 is pre-shaped and can be manufactured at a remote location. Their equal size is preferably compatible with conventional truck transportation. Alternatively, the ring element 12 is manufactured on site or nearby to reduce or avoid transportation costs. The same applies to the end element 11.

The inner liner section 50 can be manufactured at a remote location and brought to the site where the ring element 12 is made in its final shape. They can also be made in separate parts assembled after transportation. Each inner liner section 50 can therefore be a single piece or manufactured by assembling sub-sections. If sub-sections are assembled, these sub-sections are preferably made of sections assembled along longitudinal weld lines.

Before pouring the concrete of each ring element 12, the corresponding conduit and tendon are cut to the required length and the tendon is screwed into the conduit.

Then, the catheter and the steel tendon are shaped using a removable forming tool so that they extend along the circumference with a desired curvature, and the end of the catheter is positioned according to the contour of the concrete body.

The steel bars of the steel cage 70 are positioned in the template. The catheter section is positioned to form a channel 100 for the longitudinal tendon 60.

After positioning the conduit and rebar, the shaping tool can be removed. The inner liner section 50 serves as the inner wall of the template.

The bottom of the template for casting a ring element 12 may be horizontal and constituted by the top surface of another ring element 12 previously cast. In this way, the ring element 12 is matched cast, which allows an interlocking shape to be easily obtained at the interface of adjacent ring elements. Therefore, the facing surfaces of two adjacent ring elements can be provided with female and male complementary shear tenons 101 and 102, as shown in Figure 15, which facilitates the proper positioning of one ring element to the adjacent A ring element contacts, and also increases the shear resistance of each contact.

Next, the concrete is poured into the form and allowed to cure.

The conduits 30 and 31 are set before casting with the corresponding steel tendons. The steel tendons may be greased and plastic (for example, with HDPE), and have a low coefficient of friction after being individually sheathed. Before post-stretching the tendon, a cement grout is injected into the catheter. The coefficient of friction applied to this type of steel tendon can be given as coefficients mu (rad ^-1 ) and k (rad.m ^-1 ) in accordance with NF EN 1992-1-1, where the tensile (pre-compression) force is used along the cable The x position of the line layout and the cumulative angle change θ are given by a function of P(x)=P ₀ exp(-mu.(θ+kx)). For this type of tendon (lubricated with grease and with HDPE sheath), the typical values of mu and k are 0.05 rad ^-1 and 0.012 rad.m ^{-1 respectively} . These equivalent values are preferably lower than 0.06 rad ^-1 and 0.015 rad·m ^{-1, respectively} .

Tendon is a high tensile strength steel cable made of individual units called bundles. The tendon used for the pre-compression ring element 12 may have a type T15.7 bundle, where fGUTS=1860 MPa, with a cross-sectional area of 150 mm ² , which is a 279 kN FGUTS (guaranteed ultimate tensile strength).

Once the concrete has cured, the tendons present in the conduits 30 and 31 can be post-stretched to the required load. Generally, this type of tendon (also known as "bundle") can stretch up to 80% of fGUTS, which is as high as 1490 MPa.

The ring element 12 can be stored after the tendon is stretched until it is assembled for use in the groove 10.

In order to make the groove 10, the ring elements 12 are first assembled continuously along the longitudinal axis of the groove, as shown in FIG. 3. The two ring elements 12 to be assembled are coated with a polymer adhesive 105 (such as an epoxy resin) on their contact surfaces. The polymer adhesive 105 also acts as a lubricant when uncured, as shown in the figure Showed in 15.

Temporary stretching rods (not shown) are introduced into some of the channels 100 to apply a temporary load, thereby pressing the ring elements 12 against each other until the polymer adhesive 105 has cured.

These rods may have threaded ends to enable the rods to be coupled in series with each other to accommodate the increase in length as the number of assembled ring elements becomes higher.

Once the desired number of ring elements 12 has been assembled, the longitudinal tendons 60 can be installed in the remaining free channels 100 and post-stretched. These tendons can have type T15.7 bundles, where fGUTS=1860MPa, with a cross-sectional area of 150 mm ² which is a 279 kN FGUTS (guaranteed ultimate tensile strength).

After a sufficient number of tendons 60 have been installed and stretched, the temporary tension rods can be removed and additional tendons 60 can be installed in the remaining channel 100 previously occupied by the rods.

Adjacent flanges 52 of the inner liner section 50 are welded or welded at their peripheries 59, as shown in Figure 12, to provide a sealed connection between two consecutive liner sections. The welding or welding is preferably automatically preformed by a robotic arm.

The cover 80 of each end element 11 is also welded to the inner liner section 50 of the adjacent ring element 12 at its edge 89, as shown in FIG. 14, to achieve a sealed connection between the liner 50 and the cover 80.

Once the cover 80 is assembled to the adjacent inner liner section 50, the concrete wall 14 is assembled against the ring element 12 using a polymer adhesive in the same way as the adjacent ring element 12 is assembled.

After applying a temporary load to press the concrete wall 14 to the adjacent ring element 12, the recess 86 can be filled with a cement grout 85.

The final stretching of the trough 10 can only occur after the grout has solidified.

In a variant embodiment, each ring element 12 is provided with three concentric tendon layers, that is, at least one radially inner tendon layer, at least one middle tendon layer, and at least one radially outer tendon layer. All steel tendons in each layer are spirally wound. A given tendon layer may include coils of the same radius, the coils being axially spaced to form an annular gap for the through passage of one or more tendons located radially inside the given layer.

The concrete body 25 may be provided with three rib sections 110 for anchoring these tendons, as shown in FIG. 16. Each rib section 110 defines two opposing shoulders 111 for anchoring the respective ends of a corresponding steel tendon.

In the variant embodiment of Figure 17, there are four rib sections 110 anchoring at least four concentric tendon layers.

The invention is not limited to the disclosed embodiments.

For example, the inner liner section may be made of, for example, a non-metallic material that is impermeable to air, such as PVC or any hard airtight plastic. The profile of the cross section of a ring element is preferably circular as disclosed above, but other shapes are possible (for example, polygonal).

1: Energy storage system 2: compressed air storage tank 3: Compressor unit 4: turbine 10: Compressed air tank/slot 11: End element 12: Ring element 13: Base plate 14: Excavation by backfill/concrete wall 20: ribs 23: Rib section 24: Rib section 25: Concrete body 30: Catheter 31: Catheter 33: Annular gap 34: Shoulder 35: Shoulder 36: Shoulder 37: Shoulder 50: Internal lining section 51: inner surface 52: flange 53: Screw pile 55: End collar 59: Peripheral 60: Tendon 62: Tendon 67: metal plate 68: anchor 70: Steel cage 80: inner cover 85: hard filler/cement grouting 86: recess 88: End collar 89: Edge 90: intake pipe 91: recess 100: Channel 101: Shear Tenon 102: Shear Tenon 105: Shear Tenon 110: Rib section 111: Shoulder

The drawings show illustrative and non-limiting embodiments of the invention.

In the schema: -Figure 1 is a schematic diagram of an energy storage system according to the present invention, -Figure 2 is a perspective view of an exemplary embodiment of the storage tank of the system of Figure 1, -Figure 3 shows the assembly of a slot, -Figure 4 shows the cross section of the trough and supporting structure, -Figure 5 is a front view of a ring element, which transparently shows the tendon duct and channel for the axial tendon, -Figure 6 is a perspective view of the ring element of Figure 5, -Figure 7 is a side view of the ring element in Figure 5, -Figure 8 shows a part and schematic diagram of the anchoring of a tendon extending inside a ring element, -Figure 9 shows the cross section of a part of the concrete main body of a ring element of the reinforcement cage, -Figure 10 shows a partial cross-section of a lining section of anchor bolts extending inside the concrete body, -Figure 11 shows an axial section of an end element and adjacent ring elements, -Figure 12 shows the details XII of Figure 11, -Figure 13 shows a part of an end element of an intake pipe and a schematic axial section, -Figure 14 shows the detail XIV of Figure 11, -Figure 15 is a part of two adjacent ring elements of the groove and a schematic axial section, which shows an example of the interlocking shape between the elements (such as matching casting shapes), and -Figures 16 and 17 are schematic front views of variant embodiments of a ring element, which show the distribution of different rib sections.

12: Ring element

23: Rib section

24: Rib section

30: Catheter

31: Catheter

33: Annular gap

100: Channel

Claims (15)

A modular compressed gas storage tank (10), which includes a plurality of pre-compressed pre-formed ring elements (12), each ring element (12) includes a concrete body (25) and a circumferentially extending inside the concrete body At least one tensile steel tendon. Such as the storage groove of claim 1, the at least one steel tendon extends at least two turns around a longitudinal axis of the ring element along the circumference, and preferably three turns, the at least one steel tendon preferably extends spirally, and the steel tendons Preferably, a plastic material such as HDPE is individually sheathed and lubricated in each individual sheath to ensure a low coefficient of friction. Such as the storage groove of claim 1 or 2, each ring element (12) includes at least one radially outer tendon extending along the circumference and at least one radially inner tendon extending coaxially with the first tendon along the circumference. Such as the groove of claim 3, each ring element (12) includes at least two radially outer tendons axially separated from each other by an annular gap (33), and at least one end of the at least one radially inner tendon extends through Across the gap, each ring element (12) preferably includes at least two radially inner tendons, and each radially inner tendon preferably extends at least two turns around a longitudinal axis of the ring element (12) and Preferably three turns. For example, the groove of any one of claims 1 to 4, which includes end elements (11), the ring elements extend between the end elements (11), and each ring element (12) includes an end element (11) A channel (100) extending to the longitudinally stretched tendon (60) of the other end element (11). Such as the groove of any one of claims 1 to 5, the end of the tendon anchor abuts the shoulder defined by at least one protruding rib section (23; 23, 24; 110), at least one rib section ( 23) Preferably directed downwards. Such as the groove of any one of claims 1 to 6, which includes shoulders defined by more than one protruding rib section (23, 24; 110), these shoulders are preferably provided by two opposed protruding ribs The sections (23, 24) may be defined by more than two protruding rib sections (110) regularly spaced along the circumference of the ring element. Such as the groove of any one of claims 1 to 7, which includes more than two concentric steel tendon layers extending circumferentially in the concrete body (25), and the ends of each tendon are anchored by a respective rib area The segment defines the shoulders. Such as the groove of any one of claims 1 to 8, each tendon extends in a corresponding duct (30; 31). For example, the trough of any one of claims 1 to 10 includes end elements (11), each of the end elements (11) includes a preformed concrete wall (14) and an inner cover (80) impermeable to gas. Such as the groove of any one of claims 1 to 10, each ring element (12) includes an inner liner section (52) that is impermeable to the gas, and the inner liner section (50) of each ring element (12) ) Includes a radially inwardly extending end flange (52). Like the groove of any one of claims 1 to 11, two continuous ring elements (12) are provided with complementary shear tenons (101, 102) on the facing surfaces. A method of making a slot (10) as defined in any of the preceding claims, which includes: Position at least two pre-formed ring elements (12) consecutively, An axial compressive load is applied to the ring elements (12). A pre-compressed concrete ring element (12) for a groove (10) as defined in any one of claims 1 to 12, which comprises: a concrete body (25); at least one radially internally stretched tendon , Which extends circumferentially within the concrete body; and at least one radially outer steel tendon, which extends circumferentially in a concentric manner with the radially inner steel tendon, and the end of each steel tendon is anchored against one of the concrete bodies The outer surface preferably abuts a shoulder provided on the outer surface. A method for manufacturing a ring element (12) as defined in the preceding claims, the steel tendons extending in corresponding conduits (30, 31), the method comprising: winding the steel tendons around a removable forming tool And the ducts; according to the position of the ducts and the steel tendons in the concrete body (25); and preferably a steel cage (70) is formed around the ducts, the steel tendons are preferably in the steel The cage surrounds the ducts and is pre-threaded in the ducts before being installed by casting concrete. The ducts are preferably injected with grouting before stretching the tendons, which are preferably made of plastic materials such as HDPE Sheaths are added individually and lubricated in the individual sheaths to ensure a low friction coefficient. The friction coefficients mu and k are preferably lower than 0.06 and 0.015, respectively.

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