Nodular cast iron jacking pipe and preparation method thereof

Abstract

The invention relates to the technical field of pipeline preparation, in particular to a preparation method of a nodular cast iron jacking pipe, which comprises the following steps of: a, pouring a spigot section, a socket connection section and a socket section of a concrete layer by using dry and hard concrete according to the model and size of the required nodular cast iron jacking pipe, and then naturally curing to obtain a nodular cast iron jacking pipe; after the concrete layer reaches the determined strength, the surface of the concrete layer is polished; b, the nodular cast iron pipe is stably placed on a horizontal base plane with the socket end facing downwards, then the nodular cast iron pipe is sequentially sleeved with the socket section, the socket connecting section and the spigot section from bottom to top, the positions of the socket section, the socket connecting section and the spigot section are adjusted, and the coaxiality of the concrete layer and the nodular cast iron pipe is guaranteed; c, mortar is poured into a gap between the nodular cast iron pipe and the concrete layer; and d, performing flaw detection operation after mortar curing, and finishing preparation after the mortar is qualified. According to the method, the high-temperature curing time of the concrete layer is shortened, meanwhile, assembling is more flexible, and the production efficiency is improved while the pouring quality is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline preparation, and in particular to a ductile iron jacking pipe and a preparation method thereof. Background Art

[0002] Pipe jacking construction is a trenchless laying technology for underground pipelines, which can complete the laying of pipelines without affecting ground buildings. Through the thrust generated by the jacking equipment, the prefabricated pipes are pushed from the working well into the underground soil layer section by section, while the soil is transported outward and the jacking direction is controlled, and finally the underground pipeline is laid under trenchless conditions. Pipe jacking construction technology is widely used in many fields such as municipal engineering, energy and communications.

[0003] Ductile iron pipe jacking is the preferred pipe material for pipe jacking construction. It has the advantages of long service life, short construction period, low comprehensive cost, convenient and quick installation, etc. The structure of ductile iron pipe jacking generally includes an internal cast iron pipe and a concrete layer outside the cast iron pipe. Existing pipe jacking mostly adopts wet concrete pouring, but the hardening speed of wet concrete is slow, and high-temperature steam curing is required to solidify the concrete layer, which greatly reduces the production efficiency of ductile iron pipe jacking.

[0004] For example, the Chinese patent document with the authorization announcement number CN103486349B discloses a method for preparing a ductile iron jacking pipe, which includes a jacking pipe flange, a ductile iron pipe, and a cement layer wrapped around the outer wall of the ductile iron pipe, a one-piece metal skeleton is arranged inside the cement layer, the lower end of the cement layer is flush with the socket surface of the ductile iron pipe, and the upper end is flush with the flange positioning block on the outer wall of the ductile iron pipe, there are more than 3 flange positioning blocks, and they are evenly distributed on the outer wall circumference of the ductile iron pipe at the same horizontal height, and the jacking pipe flange is arranged on the upper surface of the flange positioning block and welded to the ductile iron pipe. The jacking pipe has high strength and good tensile and jacking resistance.

[0005] When preparing ductile iron jacking pipes using the above preparation method, it is necessary to perform high-temperature curing treatment on the casting layer after the casting is completed to ensure that the strength of the concrete layer meets the use requirements, and the high-temperature curing process is often time-consuming, which will lead to a decrease in the production efficiency of ductile iron and an increase in production costs. In addition, this method uses a formwork to set up on the outside of the ductile iron pipe for integrated casting. Although it can ensure the close combination of the concrete layer and the ductile iron pipe, the erection and removal of the formwork will increase the production cost of the jacking pipe, and the difficulty of controlling the pouring quality of the concrete layer will also increase, and quality problems such as cracks and holes are prone to occur.

[0006] Therefore, a preparation method of a ductile iron jacking pipe is needed, which can not only shorten the curing time and improve the production efficiency of the ductile iron jacking pipe, but also reduce the production cost and quality control difficulty of the ductile iron jacking pipe. Summary of the invention

[0007] The present invention provides a ductile iron jacking pipe and a preparation method thereof, which can not only shorten the curing time, improve the production efficiency of the ductile iron jacking pipe, but also reduce the production cost and the difficulty of quality control of the ductile iron jacking pipe.

[0008] To solve the above problems, a ductile iron jacking pipe provided by the present invention adopts the following technical solutions: A ductile iron jacking pipe includes a ductile iron pipe and a concrete layer. The concrete layer is sleeved outside the ductile iron pipe. The ductile iron pipe includes a pipe body, a spigot end and a socket end. The concrete layer includes a spigot section, a socket connection section and a socket section. The spigot section, the socket connection section and the socket section are all cast with dry-hard concrete. The inner surface of the socket section is adapted to the outer shape of the socket end. The socket connection section is located between the spigot section and the socket section. The upper end surface of the socket connection section coincides with the lower end surface of the spigot section, and the lower end surface of the socket connection section coincides with the upper end surface of the socket section to ensure the sealing performance of the concrete layer; There is a mortar filling layer between the concrete layer and the ductile iron pipe. The mortar filling layer is used to support and fixedly connect the concrete layer and the ductile iron pipe.

[0009] The ductile iron jacking pipe of the present invention uses dry-hard concrete to make the concrete layer, so that the concrete layer can be quickly cured after pouring, without high-temperature curing, shortening the time of the curing process and improving the production efficiency of the ductile iron jacking pipe. In addition, by dividing the concrete layer into three parts: the spigot section, the socket connection section and the socket section, the spigot section, the socket connection section and the socket section can be cast separately, and then assembled up and down to form the concrete layer. Then, quick-drying mortar is poured into the gap between the concrete layer and the ductile iron pipe to make them an integral body. Compared with the traditional integral casting method, the split casting can reduce the casting difficulty, reduce the generation of cracks and pores, thereby improving the quality of the concrete layer. In addition, the split assembly method enables the ductile iron pipe and the concrete layer to be fabricated synchronously, improving the production efficiency. At the same time, large-scale prefabrication can also reduce the production cost of the concrete layer.

[0010] Further, the upper end of the socket section and the lower end of the socket connection section, and the upper end of the socket connection section and the lower end of the spigot section both have mortise and tenon structures that match the joint surfaces to improve the stability and sealing performance of the overall structure of the concrete layer.

[0011] The beneficial effect is that the setting of the mortise and tenon structure enables the spigot section, the socket connection section and the socket section to bite each other, which can improve the assembly accuracy between the spigot section, the socket connection section and the socket section, and also enhance the sealing performance of the concrete layer.

[0012] Further, an annular jacking flange is welded on the outer peripheral surface of the upper end of the ductile iron pipe. The jacking flange is used to transmit the jacking force and protect the end of the concrete layer.

[0013] Its beneficial effects are as follows: The jacking flange is used to disperse the jacking force to the pipe end section, avoiding the cracking of the pipe body caused by stress concentration and improving the end bearing capacity of the concrete layer.

[0014] Furthermore, the dry-hardened concrete is C60 high-strength dry-hardened concrete, and its components include water, Portland cement, granite / basalt gravel, and medium-coarse sand. Among them, the grade of Portland cement is greater than or equal to 525, and 15%-35% of fly ash is added. The mass ratio of water to Portland cement is 0.32-0.35; the particle size of granite / basalt gravel is less than or equal to 10 mm and the crushing value is less than or equal to 15%. The fineness modulus of medium-coarse sand is 2.8-3.2, and the sand ratio is 37%-39%.

[0015] Furthermore, lifting holes are provided in the middle of the socket section, the socket and spigot joint section, and the spigot section for the assembly of ductile iron jacking pipes.

[0016] The beneficial effects of a ductile iron jacking pipe provided by the present invention are as follows: 1. The ductile iron jacking pipe of the present invention uses dry-hardened concrete to make the concrete layer, so that the concrete layer can be quickly cured after pouring, without high-temperature curing, shortening the time of the curing process and improving the production efficiency of ductile iron jacking pipes. In addition, by dividing the concrete layer into three parts: the socket section, the socket and spigot joint section, and the spigot section, the socket section, the socket and spigot joint section, and the spigot section can be cast separately, and then assembled up and down to form the concrete layer. Then, quick-drying mortar is poured into the gap between the concrete layer and the ductile iron pipe to make them integrated. Compared with the traditional integral casting method, the split casting can reduce the casting difficulty, reduce the generation of cracks and pores, thereby improving the quality of the concrete layer. In addition, the split assembly method enables the ductile iron pipe and the concrete layer to be fabricated synchronously, improving the production efficiency. At the same time, large-scale prefabrication can also reduce the production cost of the concrete layer.

[0017] 2. The setting of the mortise and tenon structure enables the socket section, the socket and spigot joint section, and the spigot section to bite each other, improving the assembly accuracy between the socket section, the socket and spigot joint section, and the spigot section, and also enhancing the sealing performance of the concrete layer.

[0018] 3. The jacking flange is used to disperse the jacking force to the pipe end section, avoiding the cracking of the pipe body caused by stress concentration and improving the end bearing capacity of the concrete layer.

[0019] A preparation method of a ductile iron jacking pipe is as follows: a. Cast the socket section, socket and spigot connection section, and spigot section of the concrete layer using dry-hardened concrete according to the model size of the required ductile iron jacking pipe. After casting, perform natural curing. After the concrete layer reaches the determined strength, grind the surface of the concrete layer; b. Place the socket end of the ductile iron pipe downward and firmly on a horizontal base surface. Then, successively sleeve the socket section, socket and spigot connection section, and spigot section from bottom to top outside the ductile iron pipe, and adjust the positions of the socket section, socket and spigot connection section, and spigot section to ensure the coaxiality of the concrete layer and the ductile iron pipe; c. Pour mortar into the gap between the ductile iron pipe and the concrete layer to form a mortar filling layer; d. After the mortar cures, perform flaw detection operations. After passing, complete the preparation of the ductile iron jacking pipe.

[0020] The preparation method of the ductile iron pipe of the present invention uses dry-hardened concrete to cast the socket section, socket and spigot connection section, and spigot section of the concrete layer respectively, enabling the concrete layer to cure quickly. At the same time, high-temperature curing is not required, avoiding the reduction in production efficiency caused by long-term high-temperature curing; the method of assembling the socket section, socket and spigot connection section, and spigot section up and down enables the assembly operation of the ductile iron jacking pipe to be carried out inside or outside the factory area, improving the flexibility of the preparation of the ductile iron jacking pipe. At the same time, the reduction in the casting volume can reduce the casting difficulty, and the large-scale casting method can reduce the production cost of the concrete layer.

[0021] Further, step d further includes welding a jacking flange at the upper end of the outer peripheral surface of the ductile iron pipe.

[0022] Further, the mortar used for the mortar filling layer is quick-drying concrete mortar to improve the curing speed of the mortar filling layer.

[0023] Its beneficial effect is that: the quick-drying concrete mortar can make the mortar filling layer cure quickly, improving the preparation efficiency of the ductile iron jacking pipe.

[0024] Further, the number of the socket and spigot connection sections is one or more, and the connection method between the socket and spigot connection sections is mortise and tenon connection.

[0025] Its beneficial effect is that: the mortise and tenon connection method enables the socket section, socket and spigot connection section, and spigot section to bite each other, which can improve the assembly accuracy between the socket section, socket and spigot connection section, and spigot section, and can also enhance the sealing performance of the concrete layer.

[0026] Further, the concrete layer in step a contains steel fibers to improve the crack resistance of the concrete layer.

[0027] The beneficial effects are as follows: Steel fibers can form a three-dimensional random distribution in concrete, improving the tensile, flexural, and shear resistance of concrete, which is beneficial to extending the service life of ductile iron jacking pipes.

[0028] The beneficial effect of the preparation method of a ductile iron jacking pipe provided by the present invention is: 1. In the preparation method of the ductile iron pipe of the present invention, by using dry-hard concrete to cast the socket section, socket connection section, and spigot section of the concrete layer respectively, the concrete layer can be quickly cured, and at the same time, high-temperature curing is not required, avoiding the reduction of production efficiency caused by long-term high-temperature curing; the method of assembling the socket section, socket connection section, and spigot section up and down enables the assembly operation of the ductile iron jacking pipe to be carried out inside or outside the factory area, improving the flexibility of the preparation of the ductile iron jacking pipe. At the same time, the reduction of the casting volume can reduce the casting difficulty, and the large-scale casting method can reduce the production cost of the concrete layer.

[0029] 2. The quick-drying concrete mortar can quickly cure the mortar filling layer, improving the preparation efficiency of the ductile iron jacking pipe.

[0030] 3. The mortise and tenon connection method enables the socket section, socket connection section, and spigot section to bite each other, which can improve the assembly accuracy between the socket section, socket connection section, and spigot section, and also enhance the sealing performance of the concrete layer.

[0031] 4. Steel fibers can form a three-dimensional random distribution in concrete, improving the tensile, flexural, and shear resistance of concrete, which is beneficial to extending the service life of ductile iron jacking pipes. Description of the Drawings

[0032] Figure 1 is a schematic structural diagram of a ductile iron jacking pipe provided by the present invention; Figure 2 is a cross-sectional view of a ductile iron jacking pipe provided by the present invention; Figure 3 is Figure 1 a schematic structural diagram of the socket section shown; Figure 4 is Figure 1 a schematic structural diagram of the socket connection section shown; Figure 5 is Figure 1 a schematic structural diagram of the spigot section shown; Figure 6 is Figure 1 a schematic structural diagram of the jacking flange shown; Figure 7 is a schematic flow diagram of a preparation method of a ductile iron jacking pipe provided by the present invention.

[0033] Description of the Reference Numerals: 1. Ductile iron pipe; 11. Socket end; 12. Pipe body; 13. Spigot end; 14. Sealing groove; 2. Concrete layer; 21. Socket section; 22. Socket and spigot connection section; 23. Spigot section; 24. Mortise and tenon structure; 25. Lifting hole; 26. Thrust flange; 27. Reinforcing rib; 3. Mortar filling layer. Detailed implementation manners

[0034] Pipe jacking construction is a trenchless construction method. That is, by means of the jacking force generated by the jacking equipment in the working pit, the friction between the pipe and the surrounding soil is overcome, and the pipe is jacked into the soil according to the designed slope, and the soil is transported away. After one pipe is jacked into the soil layer, the second pipe is lowered and the jacking continues. Its principle is to use the thrust of the main jacking cylinder and between the pipes, relay jacks, etc. to push the tool pipe or tunneling machine from the working pit through the soil layer and into the receiving pit for hoisting. The pipe follows closely behind the tool pipe or tunneling machine and is buried between the two pits.

[0035] Ductile iron materials have mechanical properties similar to those of carbon steel, such as high mechanical strength and good toughness. At the same time, they have the unique corrosion resistance of cast iron and have gradually become the safest and most reliable pipe materials in the field of water supply and drainage in the world today. Ductile iron pipe jacking is the preferred pipe material for pipe jacking construction. It generally includes a ductile iron pipe and a concrete layer located outside the ductile iron pipe. The concrete layer of the existing pipe jacking is generally cast with wet concrete, and the hardening speed of wet concrete is relatively slow. It is necessary to cure and solidify the concrete layer through high-temperature steam curing, which greatly reduces the production efficiency of ductile iron pipe jacking. In addition, the concrete layer often adopts the form of integral casting, and the large-volume casting operation will undoubtedly increase the difficulty of controlling the casting quality, resulting in defects such as cracks and pores in the concrete layer.

[0036] In order to overcome the above defects, a preparation method of ductile iron pipe jacking is needed to improve the production efficiency of ductile iron pipe jacking while ensuring the quality.

[0037] Next, referring to several representative implementation manners of the present invention, the principles and spirits of the present invention will be explained in detail.

[0038] Example 1 of a ductile iron pipe jacking provided by the present invention: As Figures 1 to 6As shown in the figure, a ductile iron jacking pipe includes a ductile iron pipe 1, a mortar filling layer 3 and a concrete layer 2. The ductile iron pipe 1 is a circular pipe. It is defined that the ductile iron pipe 1 extends in the up and down direction and is a pressure-bearing structure for bearing soil pressure, external loads and the pressure of the internal conveying medium. The concrete layer 2 is a tubular structure extending up and down. It is coaxially sleeved outside the ductile iron pipe 1 to protect the ductile iron pipe 1 from damage during jacking and increase the anti-corrosion and durability of the ductile iron jacking pipe. The mortar filling layer 3 is located between the ductile iron pipe 1 and the concrete layer 2 and is used to support and fixedly connect the ductile iron pipe 1 and the concrete layer 2.

[0039] First, the ductile iron pipe 1 will be introduced. As Figure 1 and Figure 2 shown, the ductile iron pipe 1 includes a pipe body 12 extending up and down, a socket end 11 located at the upper end of the tank body, and a spigot end 13 located at the lower end of the pipe body 12. The socket end 11 is used to plug other ductile iron jacking pipes. A circumferentially extending jacking flange 26 is welded along the outer peripheral surface at the upper end of the socket end 11. The jacking flange 26 is used to transfer the jacking force to the contacted ductile iron jacking pipe when the pipe body 12 is jacked forward and evenly distribute the jacking force generated by the jack on the upper end surface of the concrete layer 2 to avoid cracking of the pipe body 12 due to stress concentration. There is a reinforcing rib 27 on the side of the jacking flange 26 close to the spigot. The reinforcing rib 27 is welded to the ductile iron pipe 1 to improve the bearing capacity of the jacking flange 26. The spigot end 13 is a bell-shaped structure with an outward expansion at the lower end and is used to be sleeved outside other ductile iron jacking pipes. A sealing groove 14 for installing a rubber sealing ring is provided on the inner surface at the lower end of the spigot section 23 to ensure the sealing performance of the connection between two ductile iron jacking pipes.

[0040] Next, the concrete layer 2 will be introduced. As Figures 1 to 5As shown, the concrete layer 2 includes a spigot section 21, a socket connection section 22, and a socket section 23. The spigot section 21 is located above the socket connection section 22, and the socket section 23 is located below the socket connection section 22. The spigot section 21, the socket connection section 22, and the socket section 23 are all formed by batch casting with a double-layer circumferential steel mesh and dry-hardened concrete through corresponding molds. Among them, the diameter of the circumferential steel bars is greater than 12 mm, the arrangement spacing is less than 50 mm, the diameter of the longitudinal steel bars is greater than 4 mm, and the arrangement spacing is less than 400 mm. The dry-hardened concrete is C60 high-strength dry-hardened concrete, and its components include water, Portland cement, granite / basalt gravel, and medium-coarse sand. Among them, the grade of Portland cement is greater than or equal to 525, and 15%-35% of fly ash is added. The mass ratio of water to Portland cement is 0.32-0.35, and a water reducer with a water reduction rate greater than or equal to 25% is added to reduce the water consumption. The particle size of the granite / basalt gravel is less than or equal to 10 mm and the crushing value is less than or equal to 15%. The fineness modulus of the medium-coarse sand is 2.8-3.2, and the sand ratio is 37%-39% to improve the curing speed and compressive strength of the concrete layer 2. The dry-hardened concrete also includes steel fibers with a diameter of 0.5 mm and a length of 25 mm to improve the crack resistance of the concrete layer 2. In addition, there are two lifting holes 25 in the middle of the spigot section 21, the socket section 23, and the socket connection section 22, which are used to complete the hoisting and assembly of the concrete layer 2.

[0041] There are mutually matching mortise and tenon structures 24 between the lower end of the spigot section 21 and the upper end of the socket connection section 22, and between the lower end of the socket connection section 22 and the upper end of the socket section 23. In this embodiment, the mortise and tenon structure 24 is a Z-shaped plug-in structure. The setting of the mortise and tenon structure 24 enables the spigot section 21 to be physically engaged with the socket connection section 22, and the socket connection section 22 and the socket section 23. While enhancing the connection strength, it can ensure the overall sealing performance of the concrete layer 2, and thus can prevent the internal ductile iron pipe 1 from rusting and extend the service life of the ductile iron jacking pipe. In addition, the inner surface of the lower end of the socket section 23 is adapted to the outer surface of the socket end 13 of the ductile iron pipe 1 to improve the overall stiffness and sealing performance of the ductile iron jacking pipe.

[0042] By setting the concrete layer 2 as an assembly composed of the spigot section 21, the socket connection section 22, and the socket section 23, different components of the concrete layer 2 can be independently cast and produced. By reducing the casting volume, the casting difficulty can be reduced. In addition, the form of the split structure also enables each component to be prefabricated in batches, improving production efficiency while reducing production costs.

[0043] Next, the mortar filling layer 3 is introduced, as Figure 2As shown, the mortar filling layer 3 is made of quick-drying concrete mortar. The ratio of water, cement, quartz sand, and silica fume in the quick-drying concrete mortar is 4:20:25:1 to improve the curing speed and support strength of the quick-drying concrete cement and maintain the integrity of the ductile iron jacking pipe.

[0044] Example 2 of a ductile iron jacking pipe provided by the present invention: The main difference from Example 1 is as follows: In Example 1, the dry-hardened concrete is C60 high-strength dry-hardened concrete.

[0045] In this example, the dry-hardened concrete is C25 high-strength dry-hardened concrete, and the ratio of water, portland cement, medium-coarse sand, and granite / basalt gravel is 0.5:1:1.82:3.68. The particle size of the granite / basalt gravel is 5 - 10 mm.

[0046] Example 3 of a ductile iron jacking pipe provided by the present invention: The main difference from Example 1 is as follows: In Example 1, the dry-hardened concrete is C60 high-strength dry-hardened concrete.

[0047] In this example, the dry-hardened concrete is C30 high-strength dry-hardened concrete, and the ratio of water, portland cement, medium-coarse sand, and granite / basalt gravel is 0.44:1:1.44:3.21. The particle size of the granite / basalt gravel is 3 - 6 mm.

[0048] Example 4 of a ductile iron jacking pipe provided by the present invention: The main difference from Example 1 is as follows: In Example 1, the dry-hardened concrete is C60 high-strength dry-hardened concrete.

[0049] In this example, the dry-hardened concrete is C40 high-strength dry-hardened concrete, and the ratio of water, portland cement, medium-coarse sand, and granite / basalt gravel is 0.38:1:1.11:2.76. The particle size of the granite / basalt gravel is 1 - 4 mm.

[0050] Example 5 of a ductile iron jacking pipe provided by the present invention: The main difference from Example 1 is as follows: In Example 1, the mortise and tenon structure between the lower end of the socket section and the upper end of the socket and spigot connecting section and between the lower end of the socket and spigot connecting section and the upper end of the bell section is a Z-shaped plug-in structure.

[0051] In this example, the mortise and tenon structure is a toothed structure that interlocks up and down in the circumferential direction.

[0052] Example 1 of the preparation method of a ductile iron jacking pipe provided by the present invention: As Figure 7 shown, the specific steps are as follows: a. According to the model size of the required ductile iron jacking pipe, use dry-hardened concrete with steel fibers added to pour the socket section 21, socket connection section 22, and spigot section 23 of the concrete layer 2. During pouring, use a high-frequency vibration device to vibrate the concrete evenly. After pouring, perform natural curing. After the concrete layer 2 reaches the determined strength, polish the surface of the concrete layer 2. At the same time, polish the installation positions of the jacking flange 26 and its lower reinforcing rib 27 at the upper end of the inner wall of the socket section 21; b. Place the spigot end 13 of the ductile iron pipe 1 downward and stably on a horizontal base surface. Then, sleeved the spigot section 23, one or more socket connection sections 22, and socket section 21 on the outside of the ductile iron pipe 1 from bottom to top in sequence. The socket section 21 and the adjacent socket connection section 22, between two adjacent socket connection sections 22, and between the spigot section 23 and the adjacent socket connection section 22 are all mortise and tenon connected. Adjust the positions of the spigot section 23, socket connection section 22, and socket section 21 to ensure the coaxiality of the concrete layer 2 and the ductile iron pipe 1; c. Pour quick-drying concrete mortar into the gap between the ductile iron pipe 1 and the concrete layer 2 to form a mortar filling layer 3; d. Weld the jacking flange 26 at the upper end of the outer peripheral surface of the ductile iron pipe 1. After the quick-drying concrete mortar cures, perform flaw detection operations to ensure the curing quality of the mortar filling layer 3 and the welding quality of the jacking flange 26.

[0053] e. Plug each lifting hole 25 of the concrete layer 2. After curing, complete the preparation of the ductile iron jacking pipe.

[0054] Example 2 of the preparation method of a ductile iron jacking pipe provided by the present invention: The main difference from Example 1 is: In Example 1, the dry-hardened concrete is enhanced by adding steel fibers with a diameter of 0.5 mm and a length of 25 mm to improve the crack resistance of the concrete layer.

[0055] In this example, the dry-hardened concrete is mixed with carbon fibers with a diameter of 10 μm and a length of 15 mm and steel fibers with a diameter of 0.5 mm and a length of 25 mm to improve the crack resistance of the concrete layer.

[0056] Based on the above description of this specification, those skilled in the art can also understand the terms used as follows. For example, terms indicating orientation or positional relationship such as "upper", "lower", "front", "rear", "left", "right", "width", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings of this specification. They are only for the purpose of facilitating the description of the solution of the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element involved must have the specific orientation, be constructed and operate in the specific orientation. Therefore, the above terms of orientation or positional relationship cannot be understood or interpreted as a limitation to the solution of the present invention.

[0057] In addition, in the description of this specification, the meaning of "a plurality of" is at least two, such as two, three or more, etc., unless otherwise specifically defined.

Claims

1. A ductile iron jacking pipe, comprising a ductile iron pipe and a concrete layer, wherein the concrete layer is sleeved on the outer side of the ductile iron pipe, and the ductile iron pipe comprises a pipe body, a spigot end and a socket end, characterized in that: The concrete layer includes a spigot section, a socket connection section and a socket section, the spigot section, the socket connection section and the socket section are all cast by dry hard concrete, the inner surface of the socket section is matched with the outer shape of the socket end, the socket connection section is located between the spigot section and the socket section, the upper end surface of the socket connection section is consistent with the lower end surface of the spigot section, and the lower end surface of the socket connection section is consistent with the upper end surface of the socket section, so as to ensure the sealing of the concrete layer; A mortar filling layer is provided between the concrete layer and the ductile iron pipe, and the mortar filling layer is used for supporting and fixing the concrete layer and the ductile iron pipe.

2. A ductile iron jacking pipe according to claim 1, characterized in that: The upper end of the socket section and the lower end of the socket-and-spigot connection section, as well as the upper end of the socket-and-spigot connection section and the lower end of the spigot section, all have mortise and tenon structures that match the joint surface to improve the stability and sealing of the overall structure of the concrete layer.

3. A ductile iron jacking pipe according to claim 1, characterized in that: An annular thrust flange is welded on the outer peripheral surface of the upper end of the ductile iron pipe, and the thrust flange is used to transmit the thrust force and protect the end of the concrete layer.

4. A ductile iron jacking pipe according to claim 1, characterized in that: The dry hard concrete is C60 high-strength dry hard concrete, and its components include water, silicate cement, granite / basalt crushed stone and medium-coarse sand, wherein the grade of silicate cement is greater than or equal to 525, and 15%-35% of fly ash is added, and the mass ratio of water to silicate cement is 0.32-0.35; the particle size of granite / basalt crushed stone is less than or equal to 10 mm and the crushing value is less than or equal to 15%, the fineness modulus of the medium-coarse sand is 2.8-3.2, and the sand ratio is 37%-39%.

5. A ductile iron jacking pipe according to claim 1, characterized in that: The middle parts of the spigot section, the spigot connection section and the socket section are all provided with lifting holes for assembling the ductile iron jacking pipe.

6. A method for preparing a ductile iron jacking pipe, characterized in that: The specific steps are as follows: a. Use dry hard concrete to pour the spigot section, spigot connection section and socket section of the concrete layer according to the required model and size of the ductile iron jacking pipe. After pouring, carry out natural curing. After the concrete layer reaches a certain strength, grind the surface of the concrete layer; b. Place the ductile iron pipe with the socket end facing downward firmly on the horizontal base surface, then sleeve the socket section, the socket connection section and the spigot section on the outside of the ductile iron pipe from bottom to top in sequence, and adjust the positions of the socket section, the socket connection section and the spigot section to ensure the coaxiality of the concrete layer and the ductile iron pipe; c. pouring mortar into the gap between the ductile iron pipe and the concrete layer to form a mortar filling layer; d. After the mortar solidifies, carry out nondestructive testing. After passing the test, the preparation of the ductile iron jacking pipe is completed.

7. The method for preparing a ductile iron jacking pipe according to claim 6, characterized in that: The step d also includes welding a thrust flange to the upper end of the outer peripheral surface of the ductile iron pipe.

8. The method for preparing a ductile iron jacking pipe according to claim 6, characterized in that: The mortar used in the mortar filling layer is quick-drying concrete mortar to increase the curing speed of the mortar filling layer.

9. The method for preparing a ductile iron jacking pipe according to claim 6, characterized in that: The number of the socket connection sections is one or more, and the connection method between the socket connection sections is mortise and tenon connection.

10. The method for preparing a ductile iron jacking pipe according to claim 6, characterized in that: In the step a, the concrete layer contains steel fibers to improve the crack resistance of the concrete layer.

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