Composite pipes and composite pipe combinations

Abstract

This application provides a composite pipeline and a composite pipeline assembly. The composite pipeline includes a steel pipe and a concrete lining; the concrete lining is a hollow structure and is coaxially disposed inside the steel pipe; wherein, the inner surface of the steel pipe wall is in contact with the outer surface of the concrete lining wall, and the walls of the steel pipe and the concrete lining are pressed against each other. In this composite pipeline, the respective performance advantages of steel and concrete are utilized, achieving the characteristics of both withstanding internal pressure and unbalanced loads, making it suitable for applications in high-flow-rate pressure water transmission pipelines.

Description

Technical Field

[0001] This application belongs to the field of fluid transport pipeline technology, and particularly relates to a composite pipeline and a composite pipeline combination. Background Technology

[0002] Currently, the main types of pipes available on the market include steel pipes, cast iron pipes, concrete pipes (including box culverts of various shapes), prestressed concrete pipes with steel sleeves (PCCP), fiberglass pipes, and HDPE plastic pipes. In practical engineering applications, steel pipes and PCCP are the primary choices for large-diameter pressure pipelines.

[0003] Steel pipes are well-suited for applications with high internal water pressure. Due to the high tensile strength of steel, steel pipes generally do not require large wall thickness to withstand internal water pressure. However, due to unbalanced loads such as backfill, top moving loads, and the self-weight of the pipe and the internal and external liquids, the pipe needs to have a large ring stiffness. Therefore, steel pipes with larger diameters must meet certain wall thickness requirements (generally, the wall thickness should not be less than 1 / 100 to 1 / 150 of the pipe diameter; the larger the pipe diameter, the thicker the wall thickness). This characteristic allows steel pipes to meet economic requirements when used in applications with diameters below 1.2 meters. However, when the diameter exceeds 1.2 meters, the amount of steel used will surge, making steel pipes unsuitable for use in large-diameter pressure pipeline projects.

[0004] PCCP (Prestressed Concrete Pipeline) has been around for about a century, and its structural form has not changed fundamentally. This type of pipeline mainly utilizes the tensile strength of prestressed steel wires, which are wrapped around the outside of the concrete pipe to resist internal water pressure. The thicker pipe wall and prestressing provide greater ring stiffness. PCCP pipeline production involves many stages, with strict quality control requirements, resulting in higher production costs. In practical applications, the structural reliability of this type of pipeline is not high. The loose outer layer of shotcrete provides limited corrosion protection for the steel wires; if any prestressed steel wire breaks, the entire pipeline section will collapse. Furthermore, this type of pipeline has insufficient axial bending resistance and cannot adapt well to uneven foundation settlement. PCCP pipelines are facing obsolescence, but no better pipe type has yet filled the gap.

[0005] In the actual engineering selection of high-flow-rate and high-pressure water transmission, due to the low reliability of PCCP and the difficulty of installation and maintenance, steel pipes with larger wall thickness are generally preferred. When encountering pipeline projects with extra-large diameters, existing PCCP pipe types are directly selected.

[0006] The traditional types of pipes mentioned above cannot well coordinate the performance requirements of large pipe diameter, high internal water pressure, large unbalanced load and safety and reliability in terms of structure. As a result, the traditional types of pipes fail to make full use of the excellent performance of materials, resulting in material waste and high maintenance costs.

[0007] In the construction of high-flow-rate, high-pressure water transmission projects, there is an urgent need for pipelines that can reliably withstand internal water pressure and effectively resist unbalanced loads, while also being cost-effective. Addressing this need has become one of the most pressing issues in engineering applications. Utility Model Content

[0008] To address at least one shortcoming in the related technologies, this application provides a composite pipe and a composite pipe combination that allows the performance advantages of steel and concrete to be fully utilized, while achieving the characteristics of being able to withstand internal pressure and unbalanced loads, making it suitable for applications of high-flow-rate pressure water transmission pipelines.

[0009] The first aspect of this application provides a composite pipe, comprising: a steel pipe and a concrete lining; the concrete lining is a hollow structure, and the concrete lining and the steel pipe are coaxially disposed inside the steel pipe; wherein, the inner surface of the steel pipe wall is in contact with the outer surface of the concrete lining wall, and the steel pipe wall and the concrete lining wall are pressed against each other.

[0010] In some embodiments, the steel pipe is a pre-expanded steel pipe, which has a shape formed by the pre-expansion pressure acting radially outward along the steel pipe and has a tendency to shrink inward. The concrete lining can restrict the inward shrinkage of the pre-expanded steel pipe to form tangential pre-compression stress in the concrete lining and tangential pre-tension stress in the pre-expanded steel pipe.

[0011] In some embodiments, the inner surface of the steel pipe wall is inlaid with patterns, and a portion of the outer surface of the concrete lining pipe wall is embedded in the patterns.

[0012] In some embodiments, a reinforcing member is anchored within the concrete lining. The reinforcing member includes multiple axial reinforcing bars and circumferential reinforcing bars. The multiple axial reinforcing bars are spaced apart in the circumferential direction of the concrete lining, and the circumferential reinforcing bars are connected to the multiple axial reinforcing bars.

[0013] In some embodiments, the reinforcing member further includes a plurality of studs, which are spaced apart on the inner wall of the steel pipe. One end of each stud is fixedly connected to the inner surface of the pre-expanded steel pipe wall, and the other end is fixedly connected to an axial or circumferential reinforcing bar.

[0014] In some embodiments, end flanges are installed near both ends of the steel pipe, and the end flanges extend radially inward from the inner surface of the steel pipe wall; a concrete lining is located between the two end flanges.

[0015] A second aspect of this application provides a composite pipe assembly, comprising multiple sections of composite pipe connected in sequence as described above, wherein a distance is reserved between the end flange and the end of the steel pipe, the portion of the steel pipe protruding from the end flange is a pipe connection part, the ends of two adjacent composite pipe sections are opposite to each other, and a connection space is formed on the inner side of the two pipe connection parts of the two adjacent composite pipe sections and between the two end flanges.

[0016] In some embodiments, two water-stop pressure plates and an elastic water-stop ring are provided in each connection space; the two water-stop pressure plates are provided corresponding to two end flanges, each water-stop pressure plate includes a first pressure plate and a second pressure plate that are fixedly connected, the first pressure plate is opposite to and fastened to the corresponding end flange, and the second pressure plate is opposite to the pipe connection part; the elastic water-stop ring includes two oppositely arranged annular surfaces and a sidewall connecting the outer periphery of the two annular surfaces, the annular surfaces are sandwiched between the first pressure plate and the end flange, and the sidewall is sandwiched between the second pressure plate and the pipe connection part.

[0017] In some embodiments, a water-stop seat ring is provided within the connection space, the water-stop seat ring connects two adjacent pipe connection parts, and an annular sealing strip is installed between the water-stop seat ring and the pipe connection parts.

[0018] In some embodiments, the two opposite ends of two adjacent composite pipes are spaced apart.

[0019] In some embodiments, the ends of the pipe joints of every two adjacent composite pipes are connected by welding; and the joint space is filled with filler.

[0020] Compared with existing technologies, the advantages and positive effects of this application are as follows: By pressing the walls of the steel pipe and the concrete lining against each other, the outer steel pipe exerts tangential prestress on the inner concrete lining wall, while the inner concrete lining exerts tangential pretension on the outer steel pipe wall, forming a composite structure where the outer steel pipe tightly wraps the inner concrete lining. The aforementioned structure and mechanical characteristics of the composite pipeline allow the respective performance advantages of steel and concrete to be fully utilized, achieving the ability to withstand both internal pressure and unbalanced loads. It demonstrates advantages in performance, manufacturing, cost, safety, reliability, corrosion resistance, and connection, making it suitable for applications in high-flow-rate, high-pressure water transmission pipelines. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 This is a schematic diagram of the composite pipeline structure in an embodiment of this application;

[0023] Figure 2 This is a cross-sectional view of the composite pipe in an embodiment of this application;

[0024] Figure 3 for Figure 2 A magnified view of part A in the middle;

[0025] Figure 4 This is a longitudinal section view of the composite pipeline in an embodiment of this application;

[0026] Figure 5 for Figure 4 A magnified view of part B in the middle;

[0027] Figure 6 This is a schematic diagram of the first connection scheme of the composite pipe assembly in the embodiments of this application;

[0028] Figure 7 This is a schematic diagram of a second connection scheme for the composite pipe assembly in an embodiment of this application;

[0029] Figure 8 This is a schematic diagram of a third connection scheme for the composite pipe assembly in an embodiment of this application;

[0030] Figure 9 This is a flowchart of the forming process of the composite pipe in the embodiments of this application;

[0031] Figure 10 The state of the composite pipe forming process in the embodiments of this application. Figure 1 ;

[0032] Figure 11 The state of the composite pipe forming process in the embodiments of this application. Figure 2 ;

[0033] Figure 12a Simulation diagram of tangential tensile force on the wall of a concrete pipe with an existing steel lining;

[0034] Figure 12b The simulation diagram shows the first principal stress of the concrete lining in an existing steel-lined concrete pipe.

[0035] Figure 12c The simulation diagram shows the second principal stress of the concrete lining in an existing steel-lined concrete pipe.

[0036] Figure 13 This is a simulation diagram of the tangential tensile force on the pre-expanded steel pipe wall during the pouring of the concrete lining of the composite pipeline of this application.

[0037] Figure 14a Simulation diagram of tangential tensile force on the wall of the pre-expanded steel pipe after the concrete lining of the composite pipeline in this application has hardened and the pre-expanding pressure has been unloaded;

[0038] Figure 14b The simulation diagram of the first principal stress of the concrete lining of the composite pipeline of this application after hardening and unloading of pre-expansion pressure.

[0039] Figure 14c The simulation diagram of the second principal stress of the concrete lining of the composite pipeline of this application after hardening and unloading of pre-expansion pressure.

[0040] Figure 15a This is a simulation diagram of the tangential tensile force on the pre-expanded steel pipe wall under the action of internal water pressure in the composite pipeline of this application;

[0041] Figure 15b This is a simulation diagram of the first principal stress of the concrete lining of the composite pipeline under working internal water pressure.

[0042] Figure 15c This is a simulation diagram of the second principal stress of the concrete lining of the composite pipeline under working internal water pressure.

[0043] Figure 16a The simulation diagram shows the tangential tensile force of the pre-expanded steel pipe wall in the ring stiffness test simulation analysis of the composite pipeline in this application.

[0044] Figure 16b This is a simulation diagram of the first principal stress of the concrete lining in the ring stiffness test simulation analysis of the composite pipeline of this application.

[0045] Figure 16c The simulation diagram shows the second principal stress of the concrete lining in the ring stiffness test simulation analysis of the composite pipeline in this application.

[0046] Figure 17 This is a simulation diagram of the deformation of the composite pipeline in the ring stiffness test simulation analysis of this application;

[0047] Figure 18 The image shows the deformation simulation of a steel pipe model with an inner diameter of 2400 mm and a wall thickness of 24 mm in the ring stiffness test simulation analysis.

[0048] In the picture:

[0049] 1. Steel pipe; 11. Pre-expanded steel pipe; 12. Pressure chamber; 13. Pipe connection; 14. Connection space; 2. Concrete lining; 3. Reinforcing member; 31. Axial reinforcement; 32. Circumferential reinforcement; 4. End flange; 5. Cover plate; 61. Vent pipe; 62. Control valve; 71. Water-stop pressure plate; 711. First pressure plate; 712. Second pressure plate; 72. Elastic water-stop ring; 721. Ring surface; 722. Side wall; 81. Water-stop seat ring; 82. Annular sealing strip; 91. Annular weld; 92. Packing material. Detailed Implementation

[0050] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0051] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0052] In the description of this application, it should be understood that the terms "inner", "outer", "axial", "radial", "circumferential", "tangential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0053] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. The term "multiple" in this application refers to two or more.

[0054] It is to be understood that although the accompanying drawings may show a specific order of method steps, the order of steps may differ from the depicted order. Furthermore, two or more steps may be performed simultaneously or partially simultaneously. All such variations are within the scope of this disclosure.

[0055] For a long time, in the field of pipeline engineering applications, the selection of pipelines has mainly relied on the specific types of pipes supplied by manufacturers. This method of selecting pipelines has, to some extent, severed the close relationship between pipeline performance and application conditions, especially for large-diameter pressure-bearing pipelines.

[0056] Large-section reinforced concrete pressure pipelines typically have an inner steel lining. This lining is used solely for internal seepage prevention and as an internal formwork for concrete pouring, resulting in a significant waste of steel's properties. During pipeline manufacturing and construction, the inner steel lining undergoes numerous processes, including plate rolling, welding, internal reinforcement, pipe installation, rebar tying, and concrete pouring. These processing steps make it difficult to maintain a perfectly circular pipe wall, leading to cross-sectional profile defects.

[0057] For pressurized pipelines, such cross-sectional profile defects significantly weaken their pressure-bearing capacity. When a pipeline with cross-sectional profile defects is subjected to internal pressure, the cross-sectional profile will inevitably deform first, tending towards a standard circle to achieve an effective circular cross-section. Before the cross-sectional profile reaches an effective circle, the pipe wall cannot form effective tangential (circumferential) tension. At this time, the internal pressure is mainly balanced by the bending and tensile properties of the reinforced concrete. However, because the tensile properties of reinforced concrete are inherently weak, it is prone to cracking and damage under large internal pressure. Therefore, such pipelines cannot withstand large internal pressures and cannot meet the engineering requirements of high internal pressure scenarios.

[0058] To address the problems encountered in high-flow-rate, high-pressure water transmission projects, this application proposes a composite pipeline and a combination of composite pipelines that simultaneously achieve the characteristics of withstanding internal pressure and unbalanced loads. It demonstrates advantages in performance, manufacturing, cost, safety, reliability, corrosion resistance, and connection. It is understood that the pipeline provided in this application is also applicable to other transportation projects besides water transmission, such as oil or gas transportation.

[0059] The first aspect of this application provides a composite pipe, such as Figures 1-5 As shown, the composite pipeline includes: a steel pipe 1 and a concrete lining 2; the concrete lining is a hollow structure, and the concrete lining and the steel pipe are coaxially arranged inside the steel pipe; wherein, the inner surface of the steel pipe wall is in contact with the outer surface of the concrete lining wall, and the pipe walls of the steel pipe and the concrete lining wall are pressed against each other.

[0060] In the above-mentioned composite pipeline, since the pipe wall of the steel pipe 1 and the pipe wall of the concrete lining 2 are pressed against each other, a radial interaction force is formed between the steel pipe 1 and the concrete lining 2, thereby forming a tangential pre-compression stress in the concrete lining 2 and a tangential pre-tension stress in the steel pipe 1, forming a composite structure in which the outer steel pipe 1 tightly wraps the inner concrete lining 2.

[0061] In engineering applications, the aforementioned composite pipeline is buried underground. When there is no internal pressure or the internal pressure is low, the composite structure formed by the outer steel pipe 1 and the inner concrete liner 2 resists unbalanced loads using the characteristics of prestressed concrete, and the concrete generally does not experience tensile stress and cracking. After being subjected to internal pressure, the increase in internal pressure gradually reduces the prestress on the concrete liner 2, transferring the reduced prestress to the outer steel pipe 1, thus increasing the prestress of the outer steel pipe 1. As the internal pressure increases, the overall ring stiffness of the pipeline also continuously increases, and its ability to resist unbalanced loads is continuously enhanced. During the above-mentioned stress process, the performance advantages of the steel pipe and the concrete liner are brought into play, achieving the characteristics of simultaneously withstanding internal pressure and unbalanced loads. It demonstrates advantages in performance, manufacturing, cost, safety, reliability, corrosion resistance, and connection, making it suitable for applications of high-flow-rate pressure water transmission pipelines.

[0062] In the description of this application, "fitting" means that the surface shape of one component matches and is in contact with another component, and does not mean that a bonding medium such as an adhesive is used.

[0063] In some embodiments, the steel pipe 1 is a pre-expanded steel pipe 11, which has a shape formed by the pre-expansion pressure acting radially outward along the steel pipe and has a tendency to shrink inward. The concrete lining 2 can restrict the pre-expanded steel pipe 11 to shrink inward, so as to form tangential pre-compression stress in the concrete lining and tangential pre-tension stress in the pre-expanded steel pipe.

[0064] During the composite pipe forming process, a radially outward pre-expansion pressure is applied to the steel pipe 1. This pre-expansion pressure acts evenly across the pipe wall, causing the steel pipe 1 to expand outward, forming a pre-expanded steel pipe 11. The pre-expansion pressure eliminates contour defects in the cross-section of the steel pipe 1, achieving an effective circular shape. After the pre-expansion pressure is subsequently released, the retraction of the steel pipe 1 is restricted by the hardened concrete lining 2 inside, ensuring that the pre-expanded steel pipe 1 maintains an effective circular cross-section and exerts radial compression on the concrete lining 2, ultimately forming a composite structure where the outer steel pipe 1 tightly wraps the inner concrete lining 2. In this composite structure, as... Figure 2 As shown, the outer steel pipe 1 has tangential pre-tension stress on its wall and the inner concrete lining 2 has tangential pre-compression stress. This application refers to this type of pipe as a pre-expanding composite pipe (PSCP).

[0065] In some embodiments, the inner surface of the steel pipe wall is inlaid with patterns, and a portion of the outer surface of the concrete lining pipe wall is embedded in the patterns.

[0066] To increase the mutual restraint between the steel pipe 1 wall and the concrete lining 2, the steel pipe 1 can be processed using a patterned steel plate with an inner embossed surface. During the pouring of the concrete lining 2, some concrete will be embedded in the pattern, making the surface of the concrete lining 2 fixed to the pipe wall of the steel pipe 1, thereby increasing the shear resistance of the interface between the inner surface of the steel pipe 1 wall and the concrete lining 2. This application does not limit the shape of the pattern.

[0067] In some embodiments, a reinforcing member 3 is anchored within the concrete lining 2. The reinforcing member 3 includes multiple axial reinforcing bars 31 and circumferential reinforcing bars 32. The multiple axial reinforcing bars 31 are spaced apart in the circumferential direction of the concrete lining 2, and the circumferential reinforcing bars 32 are connected to the multiple axial reinforcing bars 31.

[0068] By setting axial reinforcement 31 and circumferential reinforcement 32, a reinforcement network structure is formed in the concrete lining 2, enabling the concrete lining 2 to have good ability to withstand external loads in both the axial and circumferential directions. Optionally, the circumferential reinforcement 32 can be multiple ring reinforcements, which are arranged axially in the inner cavity of the steel pipe and interconnected with multiple axial reinforcements 31; the circumferential reinforcement 32 can also be a continuous spiral reinforcement, which extends spirally along the axial direction of the steel pipe and is interconnected with multiple axial reinforcements 31.

[0069] In some embodiments, the reinforcing member 3 further includes a plurality of studs 33, which are spaced apart on the inner wall of the steel pipe 1. One end of the studs 33 is fixedly connected to the inner surface of the pipe wall of the steel pipe 1, and the other end is fixedly connected to the axial reinforcing bar 31 or the circumferential reinforcing bar 32.

[0070] The concrete lining 2 is anchored with reinforcing members 3 to form reinforced concrete. The reinforcing members 3 enhance the integrity and tensile strength of the concrete lining 2, preventing cracking due to excessive local stress. The reinforcing members 3 can be connected to each other and to the steel pipe 1 by welding.

[0071] In some embodiments, end flanges 4 are respectively installed near both ends of the steel pipe 1, and the end flanges 4 extend radially inward from the pipe wall of the steel pipe 1; the concrete lining 2 is located between the two end flanges 4. The width of the end flanges 4 can be equal to the thickness of the concrete lining 2. The end flanges 4 serve as the end boundaries of the concrete lining 2, and can be used to seal both ends of the steel pipe 1 during the pipe forming process, and can also be used to connect other pipe sections.

[0072] Existing PCCP joints typically use a socket-type connection method, sealed with rubber waterstop strips. However, when problems such as diameter deviation, ellipticity, and coaxiality exist in the pipes on both sides of the joint, this connection method becomes difficult to achieve, making connection and sealing challenging. Furthermore, once a sealing problem occurs after pipe installation, repair or replacement is extremely difficult. This socket-type joint can only accommodate axial deformation of the pipe, not misalignment deformation at the joint. In addition, existing steel pipe connections are generally made by welding, axially connecting multiple sections of steel pipe into a single unit. However, this method easily leads to the pipeline being unable to adapt to uneven foundation settlement or axial expansion and contraction caused by temperature changes.

[0073] A second aspect of this application also provides a composite pipe assembly, comprising multiple sections of composite pipe as described in any one of the claims of the second aspect, connected sequentially, wherein, as Figure 4 and Figure 5 As shown, a distance C is reserved between the end flange 4 and the end of the steel pipe 1. The part of the steel pipe 1 that protrudes from the end flange 4 is the pipe connection part 13. The ends of two adjacent composite pipe sections are opposite each other, and a connection space 14 is formed between the two pipe connection parts 13 of the two adjacent composite pipe sections and between the two end flanges 4.

[0074] The above-mentioned composite pipeline assembly, with the help of the pipeline connection part 13 and the end flange 4, can easily realize the connection of adjacent pipelines. The connection space 14 can accommodate various connection components required, protect the connection components from external damage, significantly improve the reliability of pipeline connection, and ensure that the composite pipeline assembly can work stably for a long time under complex working conditions.

[0075] Based on the structure of the pipe connection part 13 and the end flange 4, this application provides three pipe connection schemes.

[0076] In the first connection scheme, such as Figure 6 As shown, two water-stop pressure plates 71 and an elastic water-stop ring 72 are provided in each connection space 14; the two water-stop pressure plates 71 are respectively provided for the two end flanges 4, and the cross-section of each water-stop pressure plate 71 is L-shaped, including a first pressure plate 711 and a second pressure plate 712 that are fixedly connected. The first pressure plate 711 is opposite to and tightly connected to the corresponding end flange 4, and the second pressure plate 712 is opposite to the pipe connection part 13; the elastic water-stop ring 72 includes two oppositely arranged annular surfaces 721 and a side wall 722 connecting the outer periphery of the two annular surfaces 721. The annular surfaces 721 are sandwiched between the first pressure plate 711 and the end flange 4, and the side wall 722 is sandwiched between the second pressure plate 721 and the pipe connection part 13.

[0077] The connection scheme provided in the above embodiments can ensure flexible connection and sealing of pipe joints, ensure the independence of the force on each pipe section, adapt to various deformations, cope with changes in conditions such as uneven foundation settlement and axial expansion and contraction due to temperature, and facilitate connection with other structures or other types of pipes. It also brings convenience to the subsequent maintenance, repair, and pipeline upgrading and renovation of the water supply structure, and facilitates connection with water conveyance structures, other types of pipes and pipe equipment (such as control valves). In addition, the pipe connection part 13 protruding from the end flange 4 of the steel pipe 1 can also protect the inner elastic water-stop ring 72, preventing the water-stopping effect from being affected by damage to the water-stop ring.

[0078] The elastic water-stop ring 72 can be a U-shaped water-stop rubber ring; the water-stop pressure plate 71 and the end flange 4 can be fastened together with bolts.

[0079] In the first connection method mentioned above, the two adjacent composite pipe sections are flexibly connected, which can maintain a suitable connection gap between the adjacent pipes and adapt to uneven settlement of the foundation and axial expansion and contraction deformation of the pipes.

[0080] In the second connection scheme, such as Figure 7 As shown, a water-stop seat ring 81 is provided in the connection space 14. The water-stop seat ring 81 extends along the axial direction of the pipe and connects two adjacent pipe connection parts 13. An annular sealing strip 82 is installed between the water-stop seat ring 81 and the pipe connection part 13.

[0081] In the connection scheme provided in the above embodiment, the water-stop ring 81 and the annular sealing strip 82 are installed on the inner side of the ends of two adjacent composite pipe sections, and the annular sealing strip 82 is installed in the groove of the water-stop ring seat. This connection method is suitable for situations where the pipe foundation is relatively stable, and is also suitable for connection with pipes such as PCCP.

[0082] In the third connection scheme, such as Figure 8 As shown, the ends of the pipe connection 13 of every two adjacent composite pipes are connected by welding, achieving a rigid connection with a circumferential weld 91. The reserved distance C between the end flange 4 and the end of the steel pipe 1 can fully ensure that the welding temperature will not have an adverse effect on the concrete lining 2 during welding.

[0083] The connection space 14 between two adjacent composite pipe sections can be left untreated. For cases where the water flow velocity inside the pipe is high, flexible or rigid filler 92 can be selected to fill the connection space 14 as needed. This connection method is equivalent to the welding connection of ordinary steel pipes. This type of connection is suitable for situations where temperature differences do not cause significant axial expansion or contraction, or where the pipe needs to transmit axial force.

[0084] In some embodiments, the distance C reserved between the end flange 4 and the end of the steel pipe 1 is 50~200mm, which can be adjusted according to the characteristics of the water-stop structure. For example, the reserved distance C can be 100mm.

[0085] In addition, different anti-corrosion measures can be taken on the exposed surface of steel pipe 1 according to environmental conditions, such as coating with polymer coating, thermal spraying zinc anti-corrosion, cathodic protection, etc. The surface of concrete lining 2 may not be treated, or it may be sprayed with a highly elastic polymer sealing coating to enhance the protection of steel pipe 1, concrete and internal steel bars.

[0086] To aid in understanding the pre-expanded composite pipe in this application, a molding process for the pre-expanded composite pipe is provided below, such as... Figures 9-11 As shown, it includes the following steps:

[0087] S101 provides steel pipe 1; the diameter, wall thickness and material of steel pipe 1 meet the design specifications;

[0088] S102 Concrete pouring: Concrete is poured into the inner cavity of the steel pipe and distributed on the inner surface of the pipe wall of the steel pipe 1 to form a concrete lining layer 2.

[0089] S103 Apply pre-expansion pressure: Apply pre-expansion pressure to the inner cavity of the steel pipe. The pre-expansion pressure acts radially on the walls of the concrete lining 2 and the steel pipe 1. Under the action of the pre-expansion pressure, the steel pipe 1 expands radially to form a pre-expanded steel pipe 11.

[0090] S104 Concrete Hardening: During the hardening process of concrete lining 2, the pre-expansion pressure is maintained to keep the pre-expansion steel pipe 11 in a pre-expansion state and the concrete lining 2 presses against the pipe wall of the pre-expansion steel pipe 11.

[0091] S105 Unloading Pre-expansion Pressure: Unloading the pre-expansion pressure after the concrete lining 2 has hardened to form a pre-expansion composite pipe;

[0092] In the pre-expanded composite pipe, the pre-expanded steel pipe 11 tends to shrink inward and forms a radial interaction force between the pre-expanded steel pipe 11 and the concrete lining 2, so as to form tangential pre-compression stress in the concrete lining 2 and tangential pre-tension stress in the pre-expanded steel pipe 11.

[0093] like Figure 11 As shown, in the step of applying pre-expansion pressure, the openings at both ends of the steel pipe 1 are closed, forming a pressure chamber 12 inside the steel pipe 1. Pressurizing medium is injected into the pressure chamber 12. When the pressure in the pressure chamber 12 reaches the preset value, the injection of pressurizing medium is stopped and the pressure is maintained to form pre-expansion pressure. In the step of unloading pre-expansion pressure, after the concrete hardens, the pressurizing medium in the pressure chamber 12 is released to unload the pre-expansion pressure.

[0094] By sealing the openings at both ends of the steel pipe 1, a pressure chamber 12 is formed inside the pipe. By introducing a pressurizing medium into the pressure chamber 12, the pressure inside is gradually increased. This pressure acts on the concrete lining 2 and the pipe wall of the steel pipe 1, causing a radial outward expansion effect on the steel pipe 1. The internal pre-expansion pressure acts uniformly on the pipe wall of the steel pipe 1, causing it to overcome shape defects and tend towards a standard circle, thus achieving an effective circular cross-section. This allows for the formation of effective circumferential tension during subsequent use, enabling the steel to exert its tensile strength.

[0095] like Figure 11 As shown, by means of the design of the end flange 4, the cover plate 5 is used to close the openings at both ends of the steel pipe 1, so that the cover plate 5 abuts against the end flange 4 and is sealed to the end flange 4, thereby forming a pressure chamber 12 inside the steel pipe 1.

[0096] By monitoring the pressure in pressure chamber 12, when the pressure in pressure chamber 12 reaches a preset value, the pre-expansion pressure acting on the wall of steel pipe 1 causes the pre-tension stress inside steel pipe 1 to reach the design tensile strength, and the diameter of steel pipe 1 reaches its design maximum value under the action of pre-expansion pressure. During the use of the pre-expansion composite pipeline, its internal pressure is much lower than the pre-expansion pressure during the molding process, so the pre-compression stress of the concrete lining layer 2 will not decrease to zero, and the tangential stress of steel pipe 1 will not exceed the design tensile strength, thus improving the reliability of the pipeline in high internal pressure conditions.

[0097] Optionally, the pressurizing medium is compressed gas. For example... Figure 11 As shown, during the application of pre-expansion pressure, compressed gas is slowly introduced into the pressure chamber 12 through the vent pipe 61. As the compressed gas continuously enters the pressure chamber 12, pre-expansion pressure is generated within the pressure chamber 12. This pre-expansion pressure acts on the walls of the concrete lining 2 and the steel pipe 1, causing the steel pipe 1 to pre-expand from the inside out. The pressure is further increased by compressed gas until the pressure on the steel pipe 1 wall approaches the design tensile strength. Then, the control valve 62 on the vent pipe 61 is closed, stopping the continued injection of compressed gas. The pre-expansion pressure is maintained at a stable design value, allowing the concrete lining 2 to gradually harden. After the concrete lining 2 has completely hardened, the control valve 62 is slowly opened to release the gas in the pressure chamber 12. Due to the pressure release, the wall of the pre-expanded steel pipe 11 tends to retract inwards. The hardened concrete lining 2 can limit the retraction of the pre-expanded steel pipe 11 wall, resulting in tangential pre-compression stress in the concrete lining 2 and tangential pre-tension stress on the wall of the pre-expanded steel pipe 11.

[0098] It is understandable that, in addition to compressed gas, other media with similar functions can also be used as pressurizing media.

[0099] like Figure 9 and Figure 10As shown, before the concrete pouring step, there is also a step of S110 arranging the reinforcing member 3: the reinforcing member 3 is arranged in the space inside the steel pipe for pouring concrete; after the concrete pouring step and the concrete hardening step are performed, the reinforcing member 3 is anchored to the inside of the concrete lining 2.

[0100] The reinforcing member 3 includes multiple axial reinforcing bars 31 and circumferential reinforcing bars 32; the multiple axial reinforcing bars 31 are spaced apart and arranged circumferentially in the inner cavity of the steel pipe, and the circumferential reinforcing bars 32 are connected to the multiple axial reinforcing bars 31. The reinforcing mesh formed by the axial reinforcing bars 31 and the circumferential reinforcing bars 32 is arranged close to the inner side of the concrete lining 2.

[0101] By setting axial reinforcement 31 and circumferential reinforcement 32, a reinforcement network structure is formed in the concrete lining 2, enabling the concrete lining 2 to have good ability to withstand external loads in both the axial and circumferential directions. Optionally, the circumferential reinforcement 32 can be multiple ring reinforcements, which are arranged axially in the inner cavity of the steel pipe and interconnected with multiple axial reinforcements 31; the circumferential reinforcement 32 can also be a continuous spiral reinforcement, which extends spirally along the inner cavity of the steel pipe and interconnects with multiple axial reinforcements 31.

[0102] In some embodiments, the reinforcing member 3 further includes a plurality of studs 33, which are spaced apart on the inner wall of the steel pipe 1. One end of the studs 33 is fixedly connected to the inner surface of the pipe wall of the steel pipe 1, and the other end is fixedly connected to the axial reinforcing bar 31 or the circumferential reinforcing bar 32.

[0103] By arranging reinforcing members 3 within the space inside the steel pipe used for pouring concrete, the concrete lining 2 becomes reinforced concrete after pouring. The reinforcing members enhance the integrity and tensile strength of the concrete lining 2, preventing cracking due to excessive local stress. The reinforcing members 3 can be connected to each other and to the steel pipe 1 by welding.

[0104] Optionally, the concrete lining 2 can be cast using a centrifugal method. Specifically: after concrete is poured into the inner cavity of the steel pipe, centrifugal force is used to distribute the concrete on the inner surface of the steel pipe 1 wall. Once the concrete lining 2 reaches the predetermined thickness and is compacted, the centrifugal operation is stopped. The openings at both ends of the steel pipe 1 are sealed, and pressurizing medium is gradually introduced into the pressure chamber 12. The centrifugal operation is restarted, and pressurizing medium is continuously introduced until the pressure reaches the preset value. The concrete lining 2 will then be compacted again in the expanding inner cavity of the steel pipe. The centrifugal operation is stopped before the concrete lining 2 has fully set. The duration of the centrifugal operation can be determined based on the final setting time of the concrete and the casting process, generally ranging from 5 to 30 minutes.

[0105] The concrete lining 2 is cast using a centrifugal method. During the pressurization process, the centrifugal force compresses the inner concrete lining 2 onto the wall of the pre-expanded steel pipe 11. After hardening, the concrete lining 2 and the pre-expanded steel pipe 11 form a radial stress that compresses them together. During the use of the pipeline, the outer pre-expanded steel pipe 11 and the inner concrete lining 2 are tightly bonded and will not separate. They can act as a prestressed composite structure to jointly bear the load, and have a good stress state to ensure the safety and stability of the structure.

[0106] The compaction requirements in the centrifugal casting process described above are designed according to the centrifugal casting process and can be determined by a certain rotation speed and duration, which is common knowledge in this field.

[0107] Performance Analysis

[0108] Based on existing concrete pipes lined with steel pipes and the composite pipes provided in the embodiments of this application, pipe models were established for simulation analysis.

[0109] The concrete pipe model with a steel-lined inner pipe has an outer diameter of 2600 mm and an inner diameter of 2400 mm. The C40 concrete lining has a wall thickness of 96 mm, and the inner steel pipe has a wall thickness of 6 mm. Studs are installed on the outer wall of the steel pipe for anchoring to the concrete lining. The pipe cross-sectional profile defects are set within a standard roundness deviation of ±20 mm. The pipe model is 1 m long. The designed internal water pressure is 0.4 MPa, and the theoretical value of the tangential tensile force (axial force) on the pipe wall is 480 kN. Simulation results are as follows... Figure 12a and Figure 12b As shown.

[0110] like Figure 12a As shown, due to cross-sectional profile defects in the pipeline, simulation analysis reveals that the maximum tangential tensile force of the steel pipe is 202.29 kN, the minimum tangential tensile force is 18.42 kN, and the weighted average tangential tensile force is less than 80 kN. The concrete pipe wall at the corresponding cross-section needs to withstand tangential tensile forces of 480-202.29=277.71 kN, 480-18.42=461.58 kN, and 480-80=400 kN respectively. Figure 12b As shown, the maximum tensile stress in the concrete section is 8.26 MPa (far greater than the tensile strength of the concrete). Figure 12c As shown, the maximum compressive stress of the concrete on the cross-section is 1.75 MPa (which is much smaller than the compressive strength of the concrete).

[0111] The simulation results above show that the stress in the steel pipe in the model mainly comes from the joint bending resistance with the concrete. Due to the existence of cross-sectional profile defects, its cross-sectional profile has not yet reached an effective standard circle, and it cannot convert the internal water pressure into the tension of the pipe wall. The internal water pressure causes tensile force and bending moment to the annular cross-section of the concrete. The internal forces of the structure are obviously not suitable for the characteristics of steel and concrete.

[0112] Furthermore, the stress distribution of steel pipe structures with concrete linings that have not undergone pre-expansion treatment differs from that of the aforementioned steel-concrete lining pipes. When a steel pipe with a concrete lining is subjected to internal water pressure, the inner concrete lining bears the stress first. The concrete then transfers part of the load to the outer steel pipe through deformation. The internal force distribution in this case is different from that in steel pipe structures with concrete linings. Figure 12a and Figure 12b Similar. Over time, the inner lining concrete will become saturated with water, and the internal water pressure will eventually act directly on the inner wall of the outer steel pipe. At this point, the tangential tensile force of the steel pipe wall will fluctuate around the theoretical value (480KN). The inner lining concrete will have completely separated from the outer steel pipe and will no longer have the characteristics of a composite structure. As a result, the steel pipe cannot be used as a reinforcing bar for the concrete, and the concrete lining section will break due to the large tensile stress generated by the unbalanced load.

[0113] In reality, before the internal water pressure causes the steel pipe lined with concrete to detach from the concrete, the concrete's drying shrinkage has already caused it to separate from the inner wall of the steel pipe. This separation not only prevents the composite structure from bearing joint loads but also causes corrosion of the inner wall of the steel pipe. Therefore, steel pipes lined with concrete are not currently used in practice. At present, only steel pipes lined with mortar are available on the market, and these can only be used for low-pressure or unpressurized water transportation, where the mortar's main function is corrosion protection.

[0114] The composite pipe model in this application has an outer diameter of 2600 mm, an inner diameter of 2400 mm, a Q390 steel pipe wall thickness of 6 mm, a C40 concrete wall thickness of 94 mm, and a pipe model length of 1 m. The standard value of the concrete compressive strength is 26.8 MPa, and the standard value of the tensile strength is 2.39 MPa; the yield strength of the steel pipe is 390 MPa, and the design tensile strength is 350 MPa; the bearing capacity of the steel pipe wall at the yield strength is 2340 KN, and the design bearing capacity of the steel pipe wall is 2100 KN; the design working internal water pressure is 0.4 MPa, and the pre-expansion internal water pressure is controlled at 1.5 MPa; the theoretical value of the pre-expansion tangential tensile force of the steel pipe wall is 1950 KN; in the three-point ring stiffness test, the vertical load at the top of the pipe is taken as 100 KN, and the self-weight load is also considered.

[0115] like Figure 13 As shown in the simulation analysis, the above composite pipeline demonstrates that when the steel pipe is pre-expanded under air pressure, the concrete is poured and cured, ensuring that the steel pipe can achieve an effective standard circular cross-section. The tangential tensile force of the pipe wall is 1949.97 KN, which is consistent with the theoretical value.

[0116] like Figures 14a-14cAs shown, after the concrete hardens and the pre-expansion load is unloaded, the tangential tensile force of the pipe wall is 1443.70KN; the maximum value of the first principal stress (tensile stress) of the inner lining concrete is -1.04MPa, and the maximum value of the second principal stress (compressive stress) is -14.32MPa, that is, no tensile stress appears in the concrete.

[0117] like Figures 15a-15c As shown, under the working internal water pressure, the tangential tensile force of the pipe wall is 1578.73KN; the maximum value of the first principal stress (tensile stress) of the inner lining concrete is -0.77MPa, the maximum value of the second principal stress (compressive stress) is -10.51MPa, and no tensile stress is observed in the concrete.

[0118] like Figures 16a-16c As shown, in the ring stiffness test simulation analysis, the maximum tangential tensile force of the steel pipe wall is 1656.47KN, which is less than the yield strength tensile force (2340KN) and the design tensile capacity (2100KN); the first principal stress (maximum tensile stress) of the inner lining concrete is 2.55MPa, at which point the local concrete should just be in the crack initiation stage, and with the internal reinforcement, it fully meets the crack resistance requirements; the second principal stress (maximum compressive stress) of the inner lining concrete is -25.51MPa, that is, most of the concrete is under compression, and the compressive stress does not exceed the standard value of the concrete compressive strength.

[0119] For a steel pipe with a diameter of 2400mm, according to specifications and circumferential stability requirements, the wall thickness is generally taken as 24mm, and the above-mentioned steel pipe model is established. For example... Figure 17 and Figure 18 As shown, under the constraint conditions of the three-point method ring stiffness test, under the same vertical line load of 100KN / m, the vertical displacement of the top of the 24mm thick steel pipe is 123.10mm, while the vertical displacement of the top of the composite pipe of this application is 6.42mm, with a ring stiffness difference of approximately 19 times.

[0120] In practical engineering applications, the backfill and self-weight generally do not reach the limit state of the above-mentioned ring stiffness test. Therefore, the concrete and steel pipes of the pre-expanded composite pipe will work in a relatively ideal stress state. That is, the concrete works mostly under compression, with local tension but no cracking; the steel works mostly under tension, with large tensile stress, but the maximum tensile stress is less than the tensile strength, so the steel will not break.

[0121] The simulation analysis results above show that the composite pipeline of this application fully utilizes the characteristics of steel pipe in bearing internal water pressure and reinforced concrete pipe in resisting unbalanced loads. Compared with ordinary steel pipes, it can significantly save steel consumption; its circumferential stability far exceeds that of ordinary steel pipes. Compared with PCCP pipelines, it has significant advantages in terms of pipeline weight, material consumption, safety and reliability, axial stiffness and bending resistance, processing and manufacturing difficulty, pipeline installation and connection.

[0122] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0123] The above embodiments are only used to illustrate the technical solutions of this application and not to limit them; although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this application or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in this application.

Claims

1. A composite pipe, characterized in that, include: steel pipe; as well as A concrete lining, wherein the concrete lining is a hollow structure and is coaxially disposed inside the steel pipe; The inner surface of the steel pipe wall is in contact with the outer surface of the concrete lining wall, and the steel pipe wall and the concrete lining wall are pressed against each other.

2. The composite pipe according to claim 1, characterized in that, The steel pipe is a pre-expanded steel pipe, which has a shape formed by the pre-expansion pressure acting radially outward along the steel pipe and has a tendency to shrink inward. The concrete lining can restrict the pre-expanded steel pipe from shrinking inward, so as to form tangential pre-compression stress in the concrete lining and tangential pre-tension stress in the pre-expanded steel pipe.

3. The composite pipe according to claim 1, characterized in that, The inner surface of the steel pipe wall is inlaid with patterns, and part of the outer surface of the concrete lining pipe wall is embedded in the patterns.

4. The composite pipe according to claim 1, characterized in that, A reinforcing member is anchored within the concrete lining. The reinforcing member includes multiple axial reinforcing bars and circumferential reinforcing bars. The multiple axial reinforcing bars are spaced apart in the circumferential direction of the concrete lining, and the circumferential reinforcing bars are connected to the multiple axial reinforcing bars.

5. The composite pipe according to claim 4, characterized in that, The reinforcing member also includes a plurality of studs, which are spaced apart on the inner wall of the steel pipe. One end of each stud is fixedly connected to the inner surface of the steel pipe wall, and the other end is fixedly connected to the axial reinforcing bar or the circumferential reinforcing bar.

6. The composite pipe according to any one of claims 1-5, characterized in that, End flanges are installed near both ends of the steel pipe, and the end flanges extend radially inward from the inner surface of the steel pipe wall; the concrete lining is located between the two end flanges.

7. A composite pipe assembly, characterized in that, The system comprises multiple sections of the composite pipe as described in claim 6, connected in sequence, wherein a distance is reserved between the end flange and the end of the steel pipe, the portion of the steel pipe protruding from the end flange is a pipe connection part, the ends of two adjacent sections of the composite pipe are opposite each other, and a connection space is formed between the two pipe connection parts of the two adjacent sections of the composite pipe and between the two end flanges.

8. The composite pipe assembly according to claim 7, characterized in that, Two water-stop pressure plates and an elastic water-stop ring are provided in each of the connection spaces; Two water-stop pressure plates are provided corresponding to two end flanges. Each water-stop pressure plate includes a first pressure plate and a second pressure plate that are fixedly connected. The first pressure plate is opposite to and fastened to the corresponding end flange, and the second pressure plate is opposite to the pipe connection part. The elastic water-stop ring includes two opposing annular surfaces and a sidewall connecting the outer peripheries of the two annular surfaces. The annular surfaces are sandwiched between the first pressure plate and the end flange, and the sidewall is sandwiched between the second pressure plate and the pipe connection.

9. The composite pipe assembly according to claim 7, characterized in that, A water-stop seat ring is provided in the connection space, the water-stop seat ring connects two adjacent pipe connection parts, and an annular sealing strip is installed between the water-stop seat ring and the pipe connection part.

10. The composite pipe assembly according to claim 7, characterized in that, The ends of the pipe joints of every two adjacent composite pipes are connected by welding; the joint space is filled with filler.

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