Foam concrete type large-caliber shallow-buried pipeline assembly type thermal insulation layer and construction method thereof

Abstract

The invention relates to the technical field of road engineering, and discloses a foam concrete type large-diameter shallow-buried pipeline fabricated thermal insulation layer and a construction method thereof.The foam concrete type large-diameter shallow-buried pipeline fabricated thermal insulation layer comprises a layered structure including a gravel drainage bottom layer, a soft soil buffer layer, a waterproof isolation layer, a fiber thermal insulation board, a cement mixed gravelly sand bearing base layer and a foam concrete thermal insulation layer from bottom to top; according to the fabricated thermal insulation layer, industrial waste is compounded in foam concrete, and a multi-layer reinforcement design is combined, so that the thermal conductivity coefficient of the roadbed structure is remarkably reduced, the thermal insulation performance is improved, and the requirements of highway roadbed design specifications on strength and deformation are met; the use of traditional gravel materials can be reduced, resources are saved, the engineering cost is reduced, meanwhile, the reutilization rate of industrial waste is increased, and remarkable economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering, in particular to a foam concrete type large-diameter shallow buried pipeline assembled insulation layer and a construction method thereof. Background Art

[0002] The uneven distribution of water, oil, and gas resources is a widespread problem worldwide. Pipelines remain a highly efficient and cost-effective solution for transporting fluids. However, in cold regions, low winter temperatures and freeze-thaw cycles can cause frost heave damage to the roadbed, leading to cracking and subsidence in the pavement, thus impacting the service life of buried pipelines. Furthermore, buried pipelines are susceptible to damage from external forces during freeze-thaw conditions. Traditional pipeline insulation measures often fail to balance the load-bearing capacity of the roadbed with economic efficiency. Furthermore, due to on-site construction, pipelines are typically buried at depths of 2-3 meters, and in extremely cold regions, even more than 3 meters. This increases maintenance costs and makes repairs more difficult.

[0003] Prior art uses foamed concrete for geotechnical engineering, slope protection, and mine remediation due to its low density, high porosity, and excellent thermal insulation properties. However, single-use foamed concrete suffers from insufficient mechanical strength and poor long-term stability, making it unsuitable for direct use as a load-bearing roadbed material. Furthermore, traditional pipe insulation often utilizes insulating layers such as polyurethane or rock wool, but these materials are prone to aging and lack sufficient structural support.

[0004] At present, there are a lot of studies on the application of polymer materials in roadbed paving. The advantages of polymer materials are good waterproof performance, excellent thermal insulation and mechanical properties, and low cost. They are an ideal new type of surface roadbed material.

[0005] Therefore, in response to the special needs of road projects in cold regions, there is an urgent need for a new type of pipeline insulation project that integrates insulation, waterproofing, load-bearing and construction convenience functions to improve construction efficiency, increase the overall stability of the road, extend its service life, and reduce maintenance costs. Summary of the Invention

[0006] The object of the present invention is to provide a foam concrete type large-diameter shallow buried pipeline assembled insulation layer and a construction method thereof, so as to solve the problems raised in the above background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a foam concrete type large-diameter shallow buried pipeline assembled insulation layer, comprising a layered structure from bottom to top: The gravel drainage bottom layer is made of crushed stone or gravel, with a crushed stone particle size of 5-20mm, a thickness of 20-30cm, and a slope of 2%-3%; The soft soil buffer layer is composed of soft soil sieved through 20 mesh and 200 mesh, with a thickness of 10 cm; Waterproof isolation layer, using HDPE geomembrane to isolate surface water and improve the protection ability of the pipeline; Fiber insulation board, made of fiber materials such as glass fiber, carbon fiber or nanocellulose combined with cement or asphalt base, with a thickness of 5mm-10mm, and the seams are sealed with adhesive to prevent thermal bridge effect; Cement-mixed gravel-sand bearing base, using prefabricated concrete slabs; The foam concrete insulation layer has a thermal conductivity of less than 0.1W / (m·K) and can be prefabricated or poured on site in the geocell; The foamed concrete layer comprises the following components by weight percentage: composite foaming agent: volume expansion after dilution is 700-1000 times; fiber: 0.6%-1.2%; expanded perlite: 5%-8%; water reducer: ≤1%; antifreeze agent: 0.5%-2% of the total mass of concrete; the constituent materials of the foamed concrete are mixed to form a lightweight thermal insulation structural layer; The reinforced soil layer is composed of multiple layers of high-strength steel slag sand material, and the layers are connected by geosynthetics to form an overall structure, which improves the compressive strength and deformation resistance; The surface protection layer uses polymer-modified cement concrete to improve durability and resistance to frost heave.

[0008] According to the above technical solution, the concrete slab uses ordinary Portland cement with a strength grade ≥32.5, the sand material is medium sand or coarse sand with a mud content ≤3%; the gravel sand material is hard and clean, well-graded, and the maximum particle size is ≤2 / 3 of the thickness of the concrete slab; the admixtures are antifreeze agent and water reducer, which account for 0.5%-2% and 0.5%-1.5% of the total mass of the concrete respectively.

[0009] According to the above technical solution, the reinforced soil layer is composed of high-strength steel slag sand material with a particle size of 0.075-2mm and a mud content of no more than 5%. Each layer is reinforced and connected by geosynthetics geotextiles to form an integral structure.

[0010] The construction method of the assembled insulation layer of the foam concrete large-diameter shallow buried pipeline includes the following steps: S1, foundation preparation and gravel drainage base construction: lay gravel drainage base on the cleaned foundation, with a thickness of 20-30cm, and ensure uniform distribution and compaction; S2, construction of soft soil buffer layer: the soft soil excavated on site is sieved through 20 mesh and 200 mesh, and a soft soil buffer layer is laid with a thickness of 10 cm, and the density is ensured by wet compaction; S3, waterproof isolation layer and fiber insulation board construction: HDPE geomembrane is laid on the soft soil buffer layer, and fiber insulation board is laid on it, and sealed by hot air welding or compression process to ensure sealing; S4, cement mixed gravel sand bearing base construction: prefabricate cement mixed gravel sand bearing base, add appropriate amount of antifreeze and water reducer to enhance its frost resistance and impermeability, and cure for no less than 14 days, then alternately lay to ensure its uniformity and levelness; S5, construction of geocell and foam concrete insulation layer: multiple groups of geocells are placed alternately on the surface of the cement-mixed gravel-sand bearing base, and fixed to the underlying lateral geonet with anchor rods. Subsequently, the foam concrete with the correct mix ratio is injected to form the foam concrete insulation layer; S6, construction of reinforced soil layer and surface protection layer: laying lateral geonet on the surface of foam concrete insulation layer, and covering it with high-strength reinforced soil layer, and finally laying high-performance composite surface protection layer on top of the reinforced soil layer; S7, quality inspection and acceptance: conduct a comprehensive inspection of each layer, especially the stability, density and firmness of the structural connection of the foam concrete insulation layer and reinforced soil layer to ensure that the design standards are met.

[0011] According to the above technical solution, in step S1, for areas with weak foundations or high water content, the base is replaced and filled with sand with higher strength or soil with better stability, and compacted mechanically.

[0012] According to the above technical solution, in step S5, the foam concrete insulation layer can be prefabricated foam concrete blocks or poured in the geocell according to the construction site conditions. The foam concrete block adhesive used is lightweight concrete, and a no-aggregate or ultra-fine aggregate ratio is adopted. The foam concrete blocks are made by mixing with a foaming agent.

[0013] According to the above technical solution, in step S5, the geocells are prefabricated, and multiple groups of geocells are placed on the surface of the cement-mixed gravel-sand bearing base layer according to the designed position, and are fixed to the lower lateral geonet through anchor rods passing through the mounting plate and the geocells. A reinforced soil layer and a lateral geonet are laid on the outside of the geocells, and the head end of the geonet is hung on the anchor rods; the above process is repeated until the multiple groups of geocells reach the designed elevation.

[0014] According to the above technical solution, in step S6, the multi-layer reinforced soil layer is composed of high-strength steel slag sand material with a particle size of 0.075-2 mm, the layers are reinforced and connected by geosynthetics, and compacted by compacting machinery to ensure their density and stability. The density of each layer after compaction is ≥95%.

[0015] According to the above technical solution, in step S6, the geonet is laid on the flat surface of the foam concrete insulation layer, with the tail end reserved for the reverse wrapping length and reversely wrapped around the pressing block, and the reverse wrapping part is fixed by a connecting rod.

[0016] According to the above technical solution, in step S6, the thickness of the surface protection layer is controlled at 5 cm, and a steel mesh is used for reinforcement to prevent the surface protection layer from being broken by external forces.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Improve thermal insulation performance: Foam concrete combined with expanded perlite improves the overall thermal insulation effect and reduces the damage to the roadbed caused by freeze-thaw cycles.

[0018] (2) Enhance mechanical properties: Introduce industrial waste materials such as steel slag and fly ash to improve the compressive strength of foam concrete, and improve the overall stability through reinforcement measures.

[0019] (3) Optimize drainage function: The gravel drainage layer and the waterproof isolation layer work together to effectively reduce the impact of groundwater on the roadbed and prevent frost heave damage.

[0020] (4) Save material costs: Use industrial waste as filler to reduce the consumption of traditional sand and gravel materials, reduce project costs, and improve resource utilization.

[0021] (5) Easy to construct and maintain: The modular construction method is adopted, and the maintenance pipelines can be disassembled to improve the maintenance efficiency and reduce the maintenance cost.

[0022] (6) Adapt to cold regions: Specially designed for road projects in cold regions, it takes into account multiple functions such as insulation, waterproofing, and load-bearing, thereby improving the durability of the road. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 This invention Figure 1 Schematic diagram of the cross-section of the entire structure along the CC direction; Figure 3 It is a schematic diagram of the overall structure of the foam concrete insulation layer of the present invention; Figure 4 is a flow chart of a construction method of an assembled thermal insulation layer according to an embodiment of the present invention; In the figure: 1-gravel drainage base layer, 2-soft soil buffer layer, 3-waterproof isolation layer, 4-fiber insulation board, 5-cement mixed gravel and sand bearing base layer, 6-geocell, 7-foam concrete insulation layer, 8-reinforced soil layer, 9-surface protection layer. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] See also Figure 1-4 The present invention provides a technical solution: a foam concrete type large-diameter shallow buried pipeline assembled insulation layer, including a layered structure from bottom to top: Gravel drainage bottom layer 1, made of crushed stone or gravel, with a crushed stone particle size of 5-20mm, a thickness of 20-30cm, and a slope of 2%-3%; Soft soil buffer layer 2, composed of soft soil sieved through 20 mesh and 200 mesh, with a thickness of 10 cm; Waterproof isolation layer 3, using HDPE geomembrane to isolate surface water and improve the protection ability of the pipeline; Fiber insulation board 4, made of fiber materials such as glass fiber, carbon fiber or nanocellulose combined with cement or asphalt base material, with a thickness of 5mm-10mm, and the seams are sealed with adhesive to prevent thermal bridge effect; Cement mixed gravel sand bearing base 5, using prefabricated concrete slabs; The foamed concrete insulation layer 7 has a thermal conductivity of less than 0.1 W / (m·K) and can be prefabricated or poured on site in the geocell 6; The foamed concrete layer 7 comprises the following components by weight percentage: composite foaming agent: volume expansion after dilution is 700-1000 times; fiber: 0.6%-1.2%; accelerating agent and other materials: 4%-6%; expanded perlite: 5%-8%; water reducing agent: ≤1%; antifreeze agent: 0.5%-2% of the total mass of concrete; the components of the foamed concrete are mixed to form a lightweight thermal insulation structure layer; The reinforced soil layer 8 is composed of multiple layers of high-strength steel slag sand material, and the layers are connected by geosynthetics to form an integral structure, thereby improving the compressive strength and deformation resistance; Surface protection layer 9, using polymer modified cement concrete to improve durability and anti-frost heave ability; The present invention provides a foam concrete-type assembled insulation layer for large-diameter shallow-buried pipelines. This layer can quickly and evenly insulate pipelines through simple assembly during pipeline construction. The insulation layer also has better stability, greatly improving energy efficiency and the freeze-thaw resistance of roads in cold regions while enhancing the stability and durability of pipelines. The invention is particularly suitable for road construction in cold regions. Through reasonable material selection and layered design, the invention provides an efficient solution for balancing roadbed insulation and strength. Furthermore, the invention adopts a prefabricated base material and modularly assembles the insulation layer, thereby reducing construction difficulty and cost from a construction perspective, significantly optimizing costs and simplifying construction from the perspective of reducing pipeline burial depth, and significantly reducing labor and material costs associated with maintenance from a later maintenance perspective. The pipeline-roadbed integrated composite structure of the present invention includes the following components: a crushed stone drainage bottom layer 1: located at the bottom layer of the roadbed, using crushed stone or gravel materials to ensure good drainage performance, reduce the stress concentration effect caused by direct contact between the pipeline and the insulation layer, reduce the impact of groundwater on the roadbed, and reduce the risk of frost heave; a soft soil buffer layer 2: used to reduce the uneven impact of foundation settlement and improve overall stability; a waterproof isolation layer 3 and a fiber insulation board 4: a high-efficiency insulation board is laid around the pipeline, and a high-density polyethylene (HDPE) geomembrane is used to isolate surface water to improve the protection ability of the pipeline. The fiber insulation board 4 is made of the following materials: a fiber material selected from one or more of glass fiber, carbon fiber, and nanocellulose; a base material selected from one or more of cement and asphalt; a binder used to bind the fiber material to the base. Cement-mixed gravel-sand bearing base layer 5: used to provide the main load-bearing support, improve overall strength, and enhance the ability to resist traffic loads; foam concrete insulation layer 7: foam concrete is laid on the bearing base layer. This layer has an optimized ratio. Foam concrete provides excellent thermal insulation due to its low density and high porosity. The addition of expanded perlite further enhances its thermal insulation effect. The introduction of industrial waste such as discarded steel slag improves the mechanical properties and resource utilization of the material, and the addition of fiber materials further enhances the mechanical properties; reinforced soil layer 8: a reinforcement layer is laid on the foam concrete insulation layer 7 to improve compressive strength and deformation resistance; high-performance composite surface protection layer 9: polymer-modified cement concrete is used to enhance durability, improve freeze-thaw resistance, and improve the waterproof performance of the roadbed; Specifically, the concrete slab uses ordinary Portland cement with a strength grade of ≥32.5, and the sand material uses medium sand or coarse sand with a mud content of ≤3%. The gravel and sand material is hard and clean, well-graded, and has a maximum particle size of ≤2 / 3 of the thickness of the concrete slab. Antifreeze agent and water reducer are used as admixtures, accounting for 0.5%-2% and 0.5%-1.5% of the total mass of the concrete respectively. Specifically, the reinforced soil layer 8 is composed of high-strength steel slag sand material with a particle size of 0.075-2mm and a mud content of no more than 5%. Each layer is reinforced and connected by geosynthetics geotextiles to form an integral structure; The construction method of the assembled insulation layer of the foam concrete large-diameter shallow buried pipeline includes the following steps: S1, foundation preparation and construction of gravel drainage base layer 1: Gravel drainage base layer 1 is installed after pipeline construction is completed. Gravel drainage base layer 1 reduces the stress concentration effect caused by direct contact between pipeline and insulation layer. Gravel drainage base layer 1 thickness is controlled at 20-30cm, and ensures uniform distribution and compaction; S2, Construction of Soft Soil Buffer Layer 2: Soft soil buffer layer 2 is laid on the gravel drainage base layer 1 and leveled. Soft soil buffer layer 2 is made from soft soil excavated during on-site pipeline construction. The soft soil buffer layer 2 is sieved, first through a 20-mesh sieve and then through a 200-mesh sieve, to control the particle size within a certain range to provide a buffering effect. The laying thickness is 10 cm, and the density is ensured by wet compaction; S3, construction of waterproof isolation layer 3 and fiber insulation board 4: laying HDPE geomembrane on the soft soil buffer layer 2, and laying fiber insulation board 4 on it, and sealing it by hot air welding or pressing process to ensure sealing; S4. Construction of cement-mixed gravel-sand bearing base 5: The cement-mixed gravel-sand bearing base 5 uses prefabricated concrete slabs made of ordinary Portland cement with a strength grade of 32.5 or higher. Medium or coarse sand should be used, with a mud content of no more than 3%. The gravel and sand should be hard, clean, and well-graded, with a maximum particle size of no more than 2 / 3 of the concrete slab thickness. Antifreeze and water-reducing agents should also be added. The curing time after construction should be no less than 14 days, followed by alternating laying to ensure uniformity and levelness. S5, construction of geocells 6 and foam concrete insulation layer 7: multiple groups of alternating geocells 6 are placed on the surface of the cement-mixed gravel-sand bearing base 5 and fixed to the lower lateral geonet by anchor rods. Subsequently, foamed concrete with a complete mix is ​​injected to form a foamed concrete insulation layer 7. The production of foamed concrete requires precise control of the proportion of the foaming agent and the water-cement ratio of the concrete. A composite foaming agent can be used, which is diluted 30-50 times and then foamed to 700-1000 times the original volume. The water-cement ratio is in the range of 0.4-0.6 depending on the brand of concrete. The fiber content is in the range of 0.6%-1.2%, the accelerator and other materials are controlled in the range of 4%-6%, the water reducer does not exceed 1%, and the expanded perlite content is controlled in the range of 5%-8% to ensure its lightweight and loose structural characteristics while ensuring its excellent mechanical properties; S6, construction of reinforced soil layer 8 and surface protection layer 9: laying lateral geonet on the surface of foam concrete insulation layer 7, and covering it with high-strength reinforced soil layer 8, and finally laying high-performance composite surface protection layer 9 on top of reinforced soil layer 8; S7, Quality Inspection and Acceptance: Conduct a comprehensive inspection of all layers, especially the stability, density and structural connection of the foam concrete insulation layer 7 and the reinforced soil layer 8, to ensure that they meet the design standards; Specifically, in step S1, for areas with weak foundations or high water content, the base is replaced and filled with sand with higher strength or soil with better stability, and then compacted mechanically; Specifically, in step S5, the foam concrete insulation layer 7 can be prefabricated foam concrete blocks or poured in geocells according to the construction site conditions. The foam concrete block adhesive used is lightweight concrete, and a no-aggregate or ultra-fine aggregate ratio is adopted. The foam concrete blocks are made by mixing with a foaming agent. Specifically, in step S5, the geocells 6 are prefabricated, and multiple groups of geocells 6 are placed on the surface of the cement-mixed gravel-sand bearing base layer 5 according to the designed position. Anchor rods are passed through the mounting plate and the geocells 6 to be fixed to the lower lateral geonet. A reinforced soil layer and a lateral geonet are laid on the outside of the geocells 6, and the head end of the geonet is hung on the anchor rods. The above process is repeated until the multiple groups of geocells 6 reach the designed elevation. Specifically, in step S6, the multi-layer reinforced soil layer 8 is composed of high-strength steel slag sand material with a particle size of 0.075-2 mm, and the layers are reinforced and connected by geosynthetics and compacted by a compacting machine to ensure its density and stability. The density of each layer after compaction is ≥95%; Specifically, in step S6, the geonet is laid on the flat surface of the foam concrete insulation layer 7, with the tail end reserved for the reverse wrapping length and reverse wrapping the pressing block, and the reverse wrapping part is fixed by a connecting rod; Specifically, in step S6, the thickness of the surface protection layer 9 is controlled to be 5 cm, and a steel mesh is used for reinforcement to prevent the surface protection layer from being broken by external forces.

[0026] Example

[0027] This example describes in detail the structure and construction steps of a prefabricated pipe insulation layer, which is particularly suitable for the insulation construction of large-diameter shallow-buried pipes. This insulation layer has high thermal insulation performance and frost resistance, and can effectively improve soil stability. The construction process is carried out according to the following steps: Step 1: Foundation preparation and construction of gravel drainage base layer 1 1.1 Foundation cleaning After the pipeline construction is completed, the foundation around the pipeline is first cleaned to remove debris, plant roots and unstable soil on the original surface to ensure the stability of subsequent construction. For areas with weak foundations or high water content, the base can be replaced and filled with higher-strength sand or more stable soil, and compacted mechanically to improve the bearing capacity of the foundation.

[0028] 1.2 Construction of gravel drainage base layer 1 A gravel drainage base layer 1 is laid on the cleaned foundation. The gravel layer generally uses gravel with a particle size of 5-20mm and a thickness of 20-30cm. During the construction of the gravel layer, it should be evenly distributed and compacted by vibrating compaction equipment. The slope of the gravel layer should be set according to the buried depth of the pipeline and design requirements, generally with a slope of 2%-3% to ensure drainage effect. The function of this layer is to reduce the direct contact between the pipeline and the insulation layer, reduce stress concentration and provide drainage function.

[0029] Step 2: Construction of soft soil buffer layer 2 2.1 Material treatment of soft soil buffer layer 2 The soft soil buffer layer 2 is made from soft soil excavated during on-site construction. First, the soft soil is screened using 20-mesh and 200-mesh sieves to ensure that the particle size is within an appropriate range, avoiding excessive or insufficient particles that could affect the cushioning performance. The screened soft soil should exhibit good plasticity, capable of deforming without breaking under external pressure.

[0030] 2.2 Laying of soft soil buffer layer 2 The laying thickness of the soft soil buffer layer 2 is 10 cm. During construction, attention should be paid to the flatness of the surface, and the material needs to be compacted by wetting to ensure its density and stability. During the construction process, a combination of manual and mechanical methods is used to ensure that there are no gaps and loose areas in the soft soil layer.

[0031] Step 3: Construction of waterproof isolation layer 3 and fiber insulation board 4 3.1 HDPE geomembrane laying HDPE geomembrane is laid on the soft soil buffer layer 2. The main function of the geomembrane is waterproof isolation. During the laying process, the joints of the geomembrane should be sealed by hot air welding or pressing to ensure that the joints are tight to prevent moisture penetration. The membrane should be laid without damage and strictly in accordance with the slope required by the design to ensure that its drainage function is not affected.

[0032] 3.2 Installation of fiber insulation board 4 A fiber insulation board 4 is laid on the HDPE geomembrane. The insulation board is made of materials such as glass fiber, carbon fiber, nanocellulose, etc., and uses cement or asphalt as the base material. The thickness is 5-10mm. During construction, the joints between each insulation board need to be bonded to ensure its sealing. The insulation board should be laid to ensure that there are no gaps to avoid thermal bridges.

[0033] Step 4: Construction of cement mixed gravel sand bearing base 5 4.1 Concrete mix ratio of bearing base 5 The cement mixed gravel and sand bearing base layer 5 is prepared with ordinary Portland cement with a strength of not less than 32.5 grade, medium sand or coarse sand (mud content shall not be greater than 3%) and gravel and sand. The maximum particle size of the gravel and sand shall not exceed 2 / 3 of the thickness of the concrete slab, and the gravel and sand shall have good gradation to ensure the strength and durability of the concrete.

[0034] 4.2 Precast concrete slab construction During the prefabrication of concrete slabs, appropriate amounts of antifreeze and water reducers should be added to enhance their frost resistance and impermeability. The slabs should be cured for no less than 14 days after pouring to ensure that they reach the designed strength. During the laying of concrete slabs, uniformity and levelness should be maintained to avoid gaps or unevenness.

[0035] Step 5: Construction of geocell 6 and foam concrete insulation layer 7 5.1 Geocell 6 Installation Multiple groups of geocells 6 are placed on the surface of the cement-mixed gravel-sand bearing base layer 5 in the positions required by the design. The geocells are prefabricated to ensure their strength and stability. Each group of geocells is fixed to the underlying geonet by anchor rods. The anchor rods penetrate the bottom of the cells and are fixed in the base to ensure the stability of the cells.

[0036] 5.2 Laying of foam concrete insulation layer 7 After the installation of geocell 6 is completed, prefabricated foam concrete blocks or on-site cast foam concrete are selected according to the site conditions. The thermal conductivity of foam concrete is less than 0.1W / (m·K), and it has excellent thermal insulation performance. The production of foam concrete requires precise control of the proportion of foaming agent and the water-cement ratio of concrete. A composite foaming agent can be used, which is diluted 30-50 times and then foamed to 700-1000 times the original volume. The water-cement ratio is in the range of 0.4-0.6 according to different brands of concrete, the fiber content is in the range of 0.6%-1.2%, the accelerator and other materials are controlled in the range of 4%-6%, the water reducer does not exceed 1%, and the expanded perlite content is controlled in the range of 5%-8% to ensure its lightweight and loose structural characteristics while ensuring its excellent mechanical properties.

[0037] Step 6: Construction of reinforced soil layer 8 and surface protection layer 9 6.1 Laying of reinforced soil layer 8 A lateral geonet is laid on the surface of the foam concrete insulation layer 7 and covered with a high-strength reinforced soil layer 8. The reinforced soil layer is made of steel slag sand material with a particle size of 0.075-2mm and a mud content of no more than 5%. Each layer of reinforced soil material is reinforced and connected by geosynthetics. After each layer of reinforced material is laid, it is compacted by a compacting machine to ensure its density and stability.

[0038] 6.2 Construction of surface protection layer 9 A high-performance surface protection layer 9 is laid on top of the reinforced soil layer 8. The protection layer is made of polymer-modified cement concrete and high-molecular polymers are added to improve its frost resistance and durability. During construction, the thickness of the protection layer is controlled at 5 cm and reinforced with steel mesh to prevent the surface protection layer from being broken by external forces.

[0039] Step 7: Quality Inspection and Acceptance 7.1 Construction quality inspection at each level After construction is complete, a comprehensive inspection is conducted on all layers, focusing particularly on the stability, density, and structural connection strength of the foam concrete insulation layer and the reinforced soil layer. During the inspection, specialized instruments are used to measure parameters such as the thickness, strength, and thermal conductivity of the insulation layer to ensure it meets design standards.

[0040] 7.2 Final Inspection and Delivery After all construction is completed and passes inspection, a final inspection is conducted to ensure that the construction quality and functionality of each layer of material meet the design requirements. The foam concrete insulation layer is particularly inspected to ensure it provides the expected thermal insulation and frost protection properties. Ultimately, the construction quality and stability of the entire insulation layer are ensured and the unit is ready for commissioning.

[0041] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0042] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. Foam concrete type large diameter shallow buried pipeline assembled insulation layer, characterized by: It includes a bottom-up hierarchical structure: Gravel drainage bottom layer (1) is made of crushed stone or gravel, with a crushed stone particle size of 5-20 mm, a thickness of 20-30 cm, and a slope of 2%-3%; A soft soil buffer layer (2) is composed of soft soil sieved through 20 mesh and 200 mesh, with a thickness of 10 cm; A waterproof isolation layer (3) uses a HDPE geomembrane to isolate surface water and improve the protection capability of the pipeline; Fiber insulation board (4), made of fiber materials such as glass fiber, carbon fiber or nanocellulose combined with cement or asphalt base material, with a thickness of 5mm-10mm, and the joints are sealed with adhesive to prevent thermal bridge effect; Cement-mixed gravel-sand bearing base (5) using prefabricated concrete slabs; The foam concrete insulation layer (7) has a thermal conductivity of less than 0.1 W / (m·K) and can be prefabricated or poured on site in the geocell (6); The foamed concrete layer (7) comprises the following components in percentage by mass: a composite foaming agent: the volume expands 700-1000 times after dilution; Fiber: 0.6%-1.2%; expanded perlite: 5%-8%; water reducer: ≤1%; antifreeze agent: 0.5%-2% of the total mass of concrete; the constituent materials of the foam concrete are mixed to form a lightweight insulation structure layer; The reinforced soil layer (8) is composed of multiple layers of high-strength steel slag sand material, and the layers are connected by geosynthetics to form an integral structure, thereby improving the compressive strength and deformation resistance; The surface protection layer (9) uses polymer-modified cement concrete to improve durability and frost heave resistance.

2. The foam concrete type large-diameter shallow buried pipeline assembled insulation layer according to claim 1 is characterized by: The concrete slab adopts ordinary Portland cement with strength grade ≥32.5, and the sand material is medium sand or coarse sand with mud content ≤3%; the gravel sand material is hard and clean, well-graded, and the maximum particle size is ≤2 / 3 of the thickness of the concrete slab; the admixtures are antifreeze agent and water reducer, which account for 0.5%-2% and 0.5%-1.5% of the total mass of the concrete respectively.

3. The foam concrete type large-diameter shallow buried pipeline assembled insulation layer according to claim 1 is characterized by: The reinforced soil layer (8) is composed of high-strength steel slag sand material with a particle size of 0.075-2 mm and a mud content of no more than 5%. Each layer is reinforced and connected by geosynthetics geotextiles to form an integral structure.

4. The foam concrete type large diameter shallow buried pipeline assembled insulation layer construction method according to claim 1 is characterized in that: The following steps are involved: S1, foundation preparation and construction of gravel drainage base layer (1): laying gravel drainage base layer (1) on the cleaned foundation, with a thickness of 20-30cm, and ensuring uniform distribution and compaction; S2, construction of soft soil buffer layer (2): the soft soil excavated on site is sieved through 20 mesh and 200 mesh, and the soft soil buffer layer (2) is laid with a thickness of 10 cm and the density is ensured by wet compaction; S3, construction of waterproof isolation layer (3) and fiber insulation board (4): laying HDPE geomembrane on the soft soil buffer layer (2), and laying fiber insulation board (4) thereon, and sealing by hot air welding or pressing process to ensure sealing; S4, construction of cement mixed gravel sand bearing base (5): prefabricate cement mixed gravel sand bearing base (5), add appropriate amount of antifreeze agent and water reducer to enhance its frost resistance and impermeability, and cure for not less than 14 days, then lay alternately to ensure its uniformity and levelness; S5, construction of geocells (6) and foam concrete insulation layer (7): multiple groups of geocells (6) are placed alternately on the surface of the cement-mixed gravel-sand bearing base (5), and fixed to the lower lateral geonet through anchor rods, and then the foam concrete with the correct proportion is injected to form the foam concrete insulation layer (7); S6, construction of reinforced soil layer (8) and surface protection layer (9): laying lateral geonet on the surface of foam concrete insulation layer (7), and covering it with high-strength reinforced soil layer (8), and finally laying high-performance composite surface protection layer (9) on top of reinforced soil layer (8); S7, Quality Inspection and Acceptance: Conduct a comprehensive inspection of all layers, especially the stability, density and structural connection of the foam concrete insulation layer (7) and the reinforced soil layer (8), to ensure that they meet the design standards.

5. The method for constructing an assembled insulation layer of a foamed concrete large-diameter shallow-buried pipeline according to claim 4 is characterized in that: In step S1, for areas with weak foundations or high water content, the base is replaced and filled with sand with higher strength or soil with better stability, and then compacted mechanically.

6. The method for constructing an assembled insulation layer for a large-diameter shallow-buried foamed concrete pipeline according to claim 4, characterized in that: In step S5, the foam concrete insulation layer (7) can be prefabricated foam concrete blocks or poured in the geocell according to the construction site conditions. The foam concrete block adhesive used is lightweight concrete, and a non-aggregate or ultra-fine aggregate ratio is adopted. The foam concrete blocks are made by mixing with a foaming agent.

7. The method for constructing an assembled insulation layer for a large-diameter shallow-buried foamed concrete pipeline according to claim 4 is characterized by: In step S5, the geocells (6) are prefabricated, and multiple groups of geocells (6) are placed on the surface of the cement-mixed gravel-sand bearing base (5) according to the designed positions, and are fixed to the lower lateral geonet through anchor rods passing through the mounting plate and the geocells (6). A reinforced soil layer and a lateral geonet are laid on the outside of the geocells (6), and the head end of the geonet is hung on the anchor rods; the above process is repeated until the multiple groups of geocells (6) reach the designed elevation.

8. The method for constructing an assembled insulation layer for a large-diameter shallow-buried foamed concrete pipeline according to claim 4, characterized in that: In step S6, the multi-layer reinforced soil layer (8) is composed of high-strength steel slag sand material with a particle size of 0.075-2 mm, and the layers are reinforced and connected by geosynthetics and compacted by compacting machinery to ensure its density and stability. The density of each layer after compaction is ≥95%.

9. The method for constructing an assembled insulation layer for a large-diameter shallow-buried foamed concrete pipeline according to claim 4, characterized in that: In step S6, the geonet is laid on the flat surface of the foam concrete insulation layer (7), with the tail end reserved for the reverse wrapping length and reverse wrapping the pressing block, and the reverse wrapping part is fixed by a connecting rod.

10. The method for constructing an assembled insulation layer of a foamed concrete large-diameter shallowly buried pipeline according to claim 4, characterized in that: In step S6, the thickness of the surface protection layer (9) is controlled at 5 cm, and a steel mesh is used for reinforcement to prevent the surface protection layer from being broken by external forces.

Images