Foam concrete filling structure of large-diameter oil and gas pipeline tunnel and construction method of foam concrete filling structure

Abstract

The invention relates to the technical field of pipeline tunnel filling, and discloses a foam concrete filling structure of a large-diameter oil and gas pipeline tunnel and a construction method of the foam concrete filling structure. The filling structure comprises a tunnel, and a foam concrete filling layer, a foam concrete structure layer and a foam concrete reinforcing layer are sequentially arranged in the tunnel from bottom to top. A channel for separating the foam concrete reinforcing layer and exposing the foam concrete structural layer is arranged in the central area of the foam concrete reinforcing layer; a pipeline is arranged in the foam concrete filling layer, and pipelines are arranged on the two separated sides in the foam concrete reinforcing layer respectively. According to the filling structure, good filling protection can be conducted on the pipelines, by controlling distribution of the pipelines in the tunnel, the vibration influence between the pipelines can be reduced, the cracking risk of the filling structure is reduced, meanwhile, enough safe clear distances can be kept between the pipelines, and the safety of the pipelines is improved. And the influence of pipeline vibration, deformation and even explosion impact on adjacent pipelines is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of pipeline tunnel filling, and mainly to a foam concrete filling structure of a large-diameter oil and gas pipeline tunnel and a construction method thereof. Background Art

[0002] Oil and gas pipelines are the key link connecting the upstream and downstream of the oil and gas industry chain, and are an important part of my country's construction of a modern energy network. At present, oil and gas pipelines are responsible for the transportation of about 85% of crude oil, 30% of refined oil and 95% of natural gas in China, playing an irreplaceable role in ensuring national energy security. By the end of 2023, crude oil pipelines accounted for about 17% of my country's long-distance oil and gas pipelines, refined oil pipelines accounted for about 17%, and natural gas pipelines accounted for about 64%, ranking third in the world in total mileage.

[0003] After the installation of oil and gas pipelines, they usually need to be fully covered with filling protection to prevent deformation of the pipelines or even accidents such as gas leakage caused by external environmental factors such as temperature and pressure during the later operation. For a long time, the filling of newly built or abandoned oil and gas pipelines at home and abroad has mainly been based on water-sand filling. However, traditional water-sand filling has problems such as low strength and long construction period. In addition, once the pipeline is damaged during the later operation, the filling materials need to be repeatedly transported and refilled during the inspection and maintenance process. Huge amounts of water, sand and other filling materials need to be repeatedly transported back and forth, which is costly to repair and easily causes environmental pollution.

[0004] Foamed concrete is a new type of lightweight material with the characteristics of lightness and good fluidity. Its strength and dry density can be adjusted according to the needs of the project. At the same time, industrial solid waste such as slag and fly ash can be used as auxiliary admixtures to compound with cement, which has the advantages of high strength and low cost. Foamed concrete can be delivered to the filling area by pipeline pump or gravity flow. It is easy to construct and suitable for various complex construction environments. It can be used as a new type of filling material in oil and gas pipeline filling. At present, foamed concrete has been widely used in municipal pipeline backfilling and narrow foundation pit fertilizer tank backfilling projects, but there is no precedent for its use in filling large-diameter oil and gas pipeline tunnels. Therefore, it is necessary to propose a foamed concrete filling structure for large-diameter pipeline tunnels. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a foam concrete filling structure for a large-diameter oil and gas pipeline tunnel and a construction method thereof, aiming to solve the problems of low strength, long construction period, and difficult operation and maintenance existing in traditional oil and gas pipeline filling.

[0006] The technical solution of this application is as follows: In a first aspect, the present application provides a foam concrete filling structure for a large-diameter oil and gas pipeline tunnel, comprising a tunnel, wherein the tunnel comprises, from bottom to top, a foam concrete filling layer, a foam concrete structural layer, and a foam concrete strengthening layer; The central area of ​​the foamed concrete strengthening layer is provided with a channel which separates the foamed concrete strengthening layer and exposes the foamed concrete structural layer; The foamed concrete filling layer, the foamed concrete structural layer and the foamed concrete strengthening layer are made of foamed concrete; A pipe is arranged in the foam concrete filling layer, and a pipe is arranged on each of the two sides of the partition in the foam concrete strengthening layer. The present application adopts foam concrete to fill the large-diameter oil and gas pipeline tunnel. The good fluidity, density and strength adjustability of foam concrete can realize convenient construction in complex tunnel environments. Its light weight can reduce the load-bearing burden of the tunnel while providing good filling and protection for the pipeline, which is conducive to maintaining the stability of the tunnel.

[0007] Furthermore, the distance between the top surface of the foam concrete strengthening layer and the top of the tunnel is not less than 2m, and the partition distance of the channel is not less than 1.2 times the diameter of the pipeline and not less than 0.5m. The present application controls the clearance distance in the tunnel, reserves sufficient space and controls the filling degree to improve the stability of the filling structure. By controlling the partition distance, the superposition effect of pipeline vibration during the operation of parallel pipelines is weakened, and the adverse effects of parallel pipelines on each other are reduced.

[0008] Furthermore, the ratio of the diameter of the pipeline to the diameter of the tunnel is 0.3-0.42:1, the ratio of the thickness of the foamed concrete filling layer to the diameter of the pipeline is 1.15-1.4:1, and the ratio of the thickness of the foamed concrete strengthening layer to the diameter of the pipeline is 1.05-1.10:1. In the present application, the thickness of the foamed concrete filling layer and the foamed concrete strengthening layer is controlled to ensure the filling protection of the pipeline. By controlling the ratio of the diameter of the pipeline and the tunnel, the tunnel utilization efficiency is guaranteed while ensuring sufficient pipeline flux. Under this ratio, the amount of raw materials can be reduced while maintaining sufficient protection performance of the filling structure.

[0009] Furthermore, the thickness of the foamed concrete structure layer is 0.5-0.8 m. By controlling the foamed concrete structure layer to have a suitable thickness, the present application can ensure that the foamed concrete structure layer has sufficient vibration isolation effect, thereby preventing the vibration transmission of the upper and lower pipelines from affecting the normal use of the pipelines.

[0010] Furthermore, the compressive strength of the foamed concrete filling layer is 1.5~2MPa, the compressive strength of the foamed concrete structural layer is 2~3MPa, the compressive strength of the foamed concrete strengthening layer is 3~5MPa; the flexural strength of the foamed concrete strengthening layer is 1.2~2MPa. Through the gradient strength coordination between the foamed concrete filling layer, the foamed concrete structural layer and the foamed concrete strengthening layer of the present application, the overall lightweight of the filling structure can be maintained while meeting the requirements for filling protection, effectively improving the service life of the filling structure.

[0011] Furthermore, the foamed concrete reinforcement layer is provided with fibers, which are one of polypropylene fibers, basalt fibers, coconut shell fibers, and sisal fibers; the length of the fibers is 6-14 mm, the diameter of the fibers is 7-15 μm, and the aspect ratio of the fibers is 1000-3000: 1. The distribution of the fibers serves as a reinforcement, thereby improving the protective performance of the foamed concrete reinforcement layer.

[0012] Furthermore, a pipeline base is provided below the pipeline; the anti-floating stability coefficient of the tunnel K satisfy: =1.05~1.15; M 1 is the deadweight of the foamed concrete filling layer, M 2 is the deadweight of the foamed concrete structural layer, M 3 is the deadweight of the foamed concrete reinforcement layer, M p is the dead weight of the pipeline, M q is the deadweight of the pipeline base, V is the volume of the tunnel, ρ is the density of water, g is the acceleration due to gravity.

[0013] In a second aspect, the present application further provides a construction method of a foamed concrete filling structure of a large-diameter oil and gas pipeline tunnel as described in the first aspect, wherein the method comprises the following steps: Install pipes to fix the foam concrete filling layer and the foam concrete strengthening layer; Setting up a template for a foamed concrete filling layer and dividing a pouring area for the foamed concrete filling layer, arranging raw materials for the foamed concrete filling layer, and pouring the raw materials for the foamed concrete filling layer into the pouring area for the foamed concrete filling layer by a backward pouring method; After the compressive strength of the foamed concrete filling layer reaches 20%-30% of the design strength, a template for the foamed concrete structure layer is set up and a pouring area of ​​the foamed concrete structure layer is divided, raw materials for the foamed concrete structure layer are arranged, and the raw materials for the foamed concrete structure layer are poured into the pouring area of ​​the foamed concrete structure layer by a backward pouring method; After the compressive strength of the foam concrete structural layer reaches 50%-70% of the design strength, an installation groove is cut on the foam concrete structural layer, a lateral formwork is installed on the installation groove, a formwork for the foam concrete strengthening layer is set up and the pouring area of ​​the foam concrete strengthening layer is divided, raw materials for the foam concrete strengthening layer are arranged, and the raw materials for the foam concrete strengthening layer are poured into the pouring area of ​​the foam concrete strengthening layer by a backward pouring method.

[0014] Through the construction method provided in the present application, pouring can be carried out simply and quickly to prepare a foam concrete filling structure, shortening the construction period, and the prepared foam concrete filling structure can provide good protection for the pipeline.

[0015] Furthermore, the template is a polystyrene foam board, the thickness of the template is not less than 15 cm, and the lengths of the pouring areas of the foam concrete filling layer, the foam concrete structural layer and the foam concrete strengthening layer are all 20-25 m; The lateral template is a wooden template or a plastic steel template, the thickness of the lateral template is not less than 12 cm, the depth of the installation groove is 10-20 mm, and the groove width is the same as the thickness of the lateral template.

[0016] Furthermore, the single-layer pouring thickness of the foamed concrete filling layer is 0.3-0.8 m, the single-layer pouring thickness of the foamed concrete structural layer is 0.3-0.6 m, and the single-layer pouring thickness of the foamed concrete strengthening layer is 0.3-0.5 m.

[0017] Beneficial effects: Through the foam concrete filling structure of the large-diameter oil and gas pipeline tunnel provided by this application, the foam concrete filling layer can well protect the pipelines therein, and by setting a partitioned channel in the foam concrete reinforcement layer, the superposition effect of parallel pipeline vibration is reduced, the filling cost is reduced, and a maintenance channel is reserved for the operation period. The foam concrete structural layer can provide support for the channel and at the same time play a vibration isolation role to prevent the vibration transmission of the upper and lower pipelines from affecting the normal use of the pipelines. Through the setting of this application, the pipelines are distributed in an inverted T-shaped shape in the filling structure, which can reduce the vibration effect between the pipelines and reduce the risk of cracking of the filling structure. At the same time, it can maintain a sufficient safe clearance between the pipelines to avoid the impact of pipeline vibration, deformation and even explosion shock on adjacent pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a schematic diagram of the structure of the foam concrete filling structure of the large diameter oil and gas pipeline tunnel of this application.

[0019] Explanation of reference numerals: 1. Foam concrete filling layer; 2. Foam concrete structural layer; 3. Foam concrete strengthening layer; 31. Passageway. DETAILED DESCRIPTION

[0020] The present application provides a foam concrete filling structure for a large diameter oil and gas pipeline tunnel and a construction method thereof. To make the purpose, technical solution and effect of the present application clearer and more specific, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] At present, the largest diameter oil and gas pipelines in China are mainly 1016mm and 1219mm. If the diameter of the pipeline is further increased, it will bring technical challenges to long-distance pipeline transportation and long-term use, especially the traditional water-sand filling, which is difficult to provide adequate protection in addition to the construction difficulties.

[0022] Regarding this issue, Figure 1 As shown, the present application provides a foam concrete filling structure for a large-diameter oil and gas pipeline tunnel, including a tunnel, wherein the tunnel includes a foam concrete filling layer 1, a foam concrete structural layer 2 and a foam concrete strengthening layer 3 from bottom to top; A channel 31 is provided in the central area of ​​the foam concrete strengthening layer 3 to separate the foam concrete strengthening layer 3 and expose the foam concrete structural layer 2; The foamed concrete filling layer 1, the foamed concrete structural layer 2 and the foamed concrete strengthening layer 3 are made of foamed concrete; A pipe is arranged in the foam concrete filling layer 1, and a pipe is arranged on each of the two sides of the partition in the foam concrete strengthening layer 3. The present application adopts foam concrete to fill the large-diameter oil and gas pipeline tunnel. The good fluidity, density and strength adjustability of foam concrete can realize convenient construction in complex tunnel environments. Its lightweight characteristics can reduce the load-bearing burden of the tunnel while providing good filling and protection for the pipeline, which is conducive to maintaining the stability of the tunnel. By controlling the distribution of pipelines in the tunnel, the vibration effect between pipelines can be reduced, and the risk of cracking can be reduced.

[0023] Among them, the provided foam concrete filling structure can effectively protect large-diameter oil and gas pipelines. The diameter of the oil and gas pipeline can reach 1422mm, which is the largest diameter oil and gas pipeline in the country. It can ensure the long-term use of large-diameter oil and gas pipelines. Moreover, the filling structure is not only suitable for large-diameter, but also can meet the use requirements of small-diameter oil and gas pipelines.

[0024] In a specific embodiment of the present application, the distance between the top surface of the foam concrete reinforcement layer 3 and the top of the tunnel is not less than 2m, and the partition distance of the channel 31 is not less than 1.2 times the diameter of the pipe and not less than 0.5m.

[0025] Specifically, by controlling the clearance distance between the foam concrete strengthening layer 3 and the top of the tunnel, sufficient space is reserved for later maintenance and repair or installation of other devices. In addition, the filling degree in the tunnel can be controlled to reduce the impact of temperature changes on the combination of the filling structure and the tunnel, and improve the stability of the filling structure. By setting a partitioned channel 31 in the foam concrete strengthening layer 3, the foam concrete filling amount of the foam concrete strengthening layer 3 can be saved, the cost can be reduced, and a safety distance of not less than 0.5m can be maintained, and a manual maintenance channel can be reserved for pipeline operation. Moreover, by maintaining a partition distance of not less than 1.2 times the diameter of the pipeline, the superposition effect of pipeline vibration during the operation of parallel pipelines can be effectively weakened, while reducing the adverse effects of parallel pipelines on each other, reducing the risk of interlayer separation caused by resonance, and also helping to increase the service life of the filling structure.

[0026] Through the arrangement of the present application, the pipelines are distributed in an inverted T-shape in the filling structure, so that a sufficient safe clearance can be maintained between the pipelines to avoid the influence of pipeline vibration, deformation and even explosion impact on adjacent pipelines.

[0027] In a specific embodiment of the present application, the ratio of the diameter of the pipeline to the diameter of the tunnel is 0.3-0.42:1, the ratio of the thickness of the foamed concrete filling layer 1 to the diameter of the pipeline is 1.15-1.4:1, and the ratio of the thickness of the foamed concrete reinforcing layer 3 to the diameter of the pipeline is 1.05-1.10:1. By controlling the thickness of the foamed concrete filling layer 1 and the foamed concrete reinforcing layer 3, the pipeline is filled and protected. By controlling the ratio of the diameter of the pipeline and the tunnel, the tunnel utilization efficiency is guaranteed while ensuring sufficient pipeline flux. At this ratio, the amount of raw materials can be reduced while maintaining sufficient protection performance of the filling structure.

[0028] In a specific embodiment of the present application, the thickness of the foam concrete structural layer 2 is 0.5-0.8m. Specifically, if the thickness of the foam concrete structural layer 2 is too low, the vibration isolation effect of the foam concrete structural layer 2 is not obvious, and if the thickness is too high, the foam concrete structural layer 2 needs to be poured in layers to meet the required thickness, making it difficult to control the pouring uniformity in the vertical direction during the pouring process, and it is easy to have a layered phenomenon where the upper layer is light and the lower layer is heavy, affecting the integrity of the foam concrete structural layer 2 and reducing its vibration reduction effect. By controlling the foam concrete structural layer 2 to a suitable thickness, the present application can ensure that the foam concrete structural layer 2 plays a sufficient vibration isolation role and prevent the vibration transmission of the upper and lower pipes from affecting the normal use of the pipes. In addition, the provided foam concrete structural layer 2 can also facilitate the layered pouring construction needs of the filling structure, can be used as a temporary construction platform for the foam concrete strengthening layer 3, and provide support for the maintenance channel 31 during the operation period.

[0029] In the present application, the material of the foam concrete filling layer 1, the foam concrete structural layer 2 and the foam concrete strengthening layer 3 is foam concrete. The use of foam concrete for tunnel filling not only takes advantage of its good construction performance, but also reduces the filling cost. The filling cost and strength performance of foam concrete are directly related to its bubble volume rate. The higher the bubble volume rate, the lower the strength and the lower the filling cost, and vice versa. Therefore, when filling, it is necessary to make full use of the density and strength adjustability of foam concrete, and reasonably configure the strength and wet density according to the needs of each layer to minimize the filling cost and optimize the filling performance.

[0030] In a specific embodiment of the present application, the wet density of the foamed concrete of the foamed concrete filling layer 1 is 0.8-1.0 kN / m 3 The wet density of the foamed concrete of the foamed concrete structure layer 2 is 1.0~1.2kN / m 3 The wet density of the foamed concrete in the foamed concrete reinforcement layer 3 is 1.1~1.3kN / m 3 By controlling the foamed concrete filling layer 1, the foamed concrete structural layer 2 and the foamed concrete strengthening layer 3 at appropriate wet densities, the required strength requirements can be easily met.

[0031] More specifically, the compressive strength of the foamed concrete filling layer 1 is 1.5-2 MPa, the compressive strength of the foamed concrete structural layer 2 is 2-3 MPa, and the compressive strength of the foamed concrete reinforcing layer 3 is 3-5 MPa. Among them, since foamed concrete is used for filling, the compressive strength of each layer in the filling structure is mainly the compressive strength at 28 days of age.

[0032] In the present application, the foam concrete of the foam concrete filling layer 1 must have a certain strength to prevent the foam concrete from being damaged due to vibration or deformation of the pipeline; and the strength of the foam concrete of the foam concrete structural layer 2 is appropriately improved. On the one hand, it can serve as the function of the middle vibration insulation layer. On the other hand, the erection of the side formwork of the foam concrete reinforcing layer 3 is based on the hardening of the foam concrete of the foam concrete structural layer 2. The pipelines and formwork required for the construction of the foam concrete reinforcing layer 3 are all transported through the foam concrete structural layer 2 (also as the need to carry the operation and maintenance channel). Therefore, it is necessary to have higher strength performance to avoid damage to the foam concrete of the foam concrete structural layer 2 caused by vibration of the upper and lower pipelines or the traffic of vehicles during operation; the pipeline of the foam concrete reinforcing layer 3 has a lower coverage degree than that of the foam concrete filling layer 1, so it also requires higher compressive strength to ensure sufficient fixing effect.

[0033] Through the strength difference between the foam concrete filling layer 1, the foam concrete structural layer 2 and the foam concrete strengthening layer 3 provided in the present application, the filling structure can form a difference in properties and reduce the mutual influence of pipeline vibration. Through the gradient strength coordination between them, the overall lightweight of the filling structure can be maintained while meeting the requirements of filling protection, effectively improving the service life of the filling structure.

[0034] In the filling structure design of this application, the lower pipeline has been completely wrapped by the foam concrete filling layer 1. The pipeline, foam concrete, and tunnel segment support structure form an integral structure, which can fully offset the vibration or deformation caused by the operation of the pipeline; and the foam concrete strengthening layer 3 is limited by the design requirements of the tunnel clearance and the maintenance channel 31. The thickness of the foam concrete filling on the air-facing surface is limited, which is more likely to cause the foam concrete to crack under the long-term operation temperature and pressure of the pipeline, bringing the risk of oil and gas leakage. Therefore, it needs to be further strengthened in strength.

[0035] In view of the above problems, in a specific embodiment of the present application, fibers are provided in the foam concrete reinforcement layer 3, and the fibers are one of polypropylene fibers, basalt fibers, coconut shell fibers, and sisal fibers. In the present application, by adding a certain amount of fibers to the foam concrete reinforcement layer 3, a good reinforcement effect can be achieved, the tensile properties of the foam concrete can be effectively improved, and the deformation energy generated by the pipeline under long-term temperature and pressure during the operation period can be fully offset, so as to avoid cracking, shedding, and other defects of the foam concrete reinforcement layer 3 caused by vibration and deformation of the pipeline during the operation period.

[0036] The fiber content in the foamed concrete of the foamed concrete reinforcement layer 3 is 0.4%-0.8%.

[0037] Furthermore, the length of the fiber is 6-14 mm, the diameter of the fiber is 7-15 μm, and the aspect ratio of the fiber is 1000-3000: 1. In the present application, by using the fiber within the aspect ratio range, when mixed with the foamed concrete slurry, the fiber has good dispersibility and is not easy to form a mass; the evenly distributed fibers can be conducive to forming a three-dimensional staggered reinforcement system, improving the ductility and tensile strength of the foamed concrete, and improving the crack resistance and impact resistance of the foamed concrete under pipeline vibration, deformation or explosion impact.

[0038] In a specific embodiment of the present application, the flexural strength of the foamed concrete strengthening layer 3 is 1.2~2MPa. Under the action of long-term temperature and pressure, the oil and gas pipeline will vibrate and deform to a certain extent. When the foamed concrete strengthening layer 3 is wrapped and filled with the pipeline, the design requirements of the tunnel clearance and the channel 31 for maintenance are considered, and the top and side filling thickness is relatively thin. When the pipeline vibrates or deforms, static or dynamic relative displacement will occur between the pipeline and the foamed concrete. The foamed concrete itself is a brittle material and is very easy to crack under deformation. In order to reduce the risk of cracking of the foamed concrete strengthening layer 3, the strength, especially the tensile strength performance, of the foamed concrete strengthening layer 3 is improved by fiber reinforcement, and the toughness of the foamed concrete strengthening layer 3 structure is improved. For this reason, index requirements are put forward for its flexural strength.

[0039] In the present application, according to the filling technology requirements for different spatial distribution fillings in the tunnel, a foam concrete filling layer 1, a foam concrete structural layer 2 and a foam concrete reinforcement layer 3 with different strengths are gradiently set up. On the one hand, the construction efficiency is improved, and on the other hand, the anti-floating performance requirements of the foam concrete filling structure in the tunnel are met, avoiding the risk of floating of the foam concrete filling structure caused by leakage in the cross-river tunnel during operation, and reducing the risk of leakage due to pipe bending.

[0040] In a specific embodiment of the present application, a pipeline base is provided below the pipeline ( Figure 1 (not shown). In the present application, before filling, it is necessary to install and place the pipe through the pipe base to improve stability, and the pipe base will also be filled and protected, and will not affect the filling strength adjustment of the present application. Its structure can refer to the prior art and will not be repeated here.

[0041] In a specific embodiment of the present application, the anti-floating stability coefficient of the tunnel is K satisfy: =1.05~1.15; in, M 1——deadweight of foam concrete filling layer 1; M 2——deadweight of foamed concrete structure layer 2; M 3——deadweight of foam concrete reinforcement layer 3; M p - the dead weight of the pipeline; M q - the deadweight of the pipeline base; ρ - water density; g - acceleration due to gravity; V - volume of the tunnel; K ——The anti-floating stability coefficient of the tunnel.

[0042] Long-distance oil and gas pipeline tunnels generally need to be buried deep underground and may also need to pass under rivers. The tunnel may encounter groundwater or leakage nearby. This application controls the anti-floating stability coefficient of the tunnel, which is conducive to maintaining the stability of long-distance tunnels and effectively avoiding the risk of bending caused by floating.

[0043] This application provides a method of filling and protecting the pipeline with foam concrete with good fluidity, which is convenient for construction. According to the filling technology requirements of different spatial distribution fillings in the tunnel, a foam concrete filling layer 1, a foam concrete structural layer 2 and a foam concrete strengthening layer 3 with different strengths are gradiently set. On the one hand, the construction efficiency is improved, the risk of cracking caused by pipeline vibration can be reduced, which is conducive to maintaining the stability of the tunnel and extending its service life. On the other hand, the anti-floating performance requirements of the foam concrete filling structure in the tunnel are met, the risk of the foam concrete filling structure floating caused by leakage in the cross-river tunnel during operation is avoided, and the risk of leakage caused by pipeline bending is reduced, which is of great significance to my country's long-distance and large-diameter oil and gas pipeline transportation.

[0044] The present application also provides a construction method for the foam concrete filling structure of the large-diameter oil and gas pipeline tunnel as described above, which comprises the following steps: The pipes of the foamed concrete filling layer 1 and the foamed concrete strengthening layer 3 are installed and fixed; specifically, the pipes in the foamed concrete filling layer 1 and the foamed concrete strengthening layer 3 can be installed and fixed by the pipe installation device and installation method in the prior art, which will not be repeated here.

[0045] Setting up the template of the foam concrete filling layer 1 and dividing the pouring area of ​​the foam concrete filling layer 1, configuring the raw materials of the foam concrete filling layer 1, and pouring the raw materials of the foam concrete filling layer 1 into the pouring area of ​​the foam concrete filling layer 1 by a backward pouring method; After the compressive strength of the foam concrete filling layer 1 reaches 20%-30% of the design strength, the formwork of the foam concrete structure layer 2 is set up and the casting area of ​​the foam concrete structure layer 2 is divided, the raw materials of the foam concrete structure layer 2 are arranged, and the raw materials of the foam concrete structure layer 2 are cast into the casting area of ​​the foam concrete structure layer 2 by the backward casting method; wherein, the foam concrete filling layer 1 does not need to carry the transportation of construction materials, and the subsequent construction is carried out after the compressive strength of the foam concrete filling layer 1 reaches 20%-30% of the required design strength. At this appropriate strength, workers can stand without footprints, which can shorten the construction period.

[0046] After the compressive strength of the foam concrete structural layer 2 reaches 50%-70% of the design strength, a mounting groove is cut on the foam concrete structural layer 2, and the lateral formwork is installed on the mounting groove. The formwork of the foam concrete reinforcing layer 3 is set up and the pouring area of ​​the foam concrete reinforcing layer 3 is divided. The raw materials of the foam concrete reinforcing layer 3 are arranged, and the raw materials of the foam concrete reinforcing layer 3 are poured into the pouring area of ​​the foam concrete reinforcing layer 3 by the backward pouring method.

[0047] When pouring each layer in the filling structure, the pouring area can be divided by horizontally supporting templates along the extension direction of the tunnel. The backward pouring can be done by laying the conveying pipe to the middle section of the tunnel, with the pipe opening facing the inside of the tunnel. The conveying pipe retreats toward the tunnel opening while conveying the raw materials of the foam concrete for pouring, which is convenient for construction.

[0048] In the present application, since the foam concrete reinforcement layer 3 needs to be provided with a partition channel 31, which involves the transportation of construction materials during construction, and the foam concrete structural layer 2 serves as the support of the channel 31, in order to avoid damage to the apparent quality such as rutting caused by the transportation of materials, higher strength requirements are put forward for it, and it needs to reach 50%-70% of the design strength before construction can be carried out.

[0049] Specifically, the foam concrete filling layer 1 and the foam concrete structural layer 2 can also be cast in the next layer after they are completely cured, but the interface effect between the different layers is more obvious and easy to separate, and the pores in the foam concrete after complete curing are relatively large, and water can easily penetrate, which may also affect the curing performance of the next layer. In this application, by casting the next layer before complete curing, in addition to shortening the construction period, the foam concrete of the previous layer is relatively moist, and the penetration effect is not obvious, and the curing stages of the two layers of foam concrete will overlap, which weakens the interface effect between the layers and improves the overall bonding degree of the filling structure.

[0050] More specifically, since foamed concrete often changes in volume (especially in the early stage of hardening) in addition to increasing strength during the hardening process, and since it is poured in a tunnel, the overall pouring volume is also large, and the volume change is easily concentrated in the center. In this application, the foamed concrete filling layer 1 with the highest degree of contact with the tunnel reaches 20%-30% of the design strength, and the next layer is poured after the early stage of hardening where the volume change is most obvious. Even if the volume changes again, it is easy to maintain the flatness, and the slight degree of subsequent volume change does not affect the bonding effect between the layers. By controlling the foamed concrete structural layer 2 to reach 50%-70% of the design strength before pouring the next layer, the foamed concrete filling layer 1 has also increased to a sufficient compressive strength at this time. In addition to being able to ensure sufficient bearing capacity as a whole, it can also control the different bonding degrees between the foamed concrete structural layer 2 and the upper and lower layers, and can continue to maintain the gradient strength transition while improving the isolation between the foamed concrete filling layer 1 and the foamed concrete strengthening layer 3, so that the pipeline vibration is not easy to affect each other.

[0051] Through the construction method provided in the present application, pouring can be carried out simply and quickly to prepare a foam concrete filling structure, shortening the construction period, and the prepared foam concrete filling structure can provide good protection for the pipeline.

[0052] The conveying pipe can be fixed to the side of the track by a pipe clamp.

[0053] Among them, a circular advancement pouring method can be adopted during construction. The single pouring distance of the foam concrete filling layer 1 is not less than 200m. After the pouring length of the foam concrete filling layer 1 exceeds 400m and the compressive strength reaches 20%-30% of the design strength, the foam concrete structure layer 2 is poured. After the pouring length of the foam concrete structure layer 2 exceeds 200m and the compressive strength reaches 50%-70% of the design strength, the foam concrete strengthening layer 3 is poured. After the pouring of the foam concrete strengthening layer 3 is completed, the construction materials can be transported along the foam concrete structure layer 2 to the construction area of ​​the foam concrete filling layer 1, and the layers can be poured in a circular manner in sequence. After the overall pouring is completed, the construction materials can be transported to the outside of the tunnel by rail.

[0054] During the cyclic pouring, a certain distance must be maintained between the pouring of each layer to reserve sufficient space for operations and material transfer for the next layer of construction. Specifically, when the above-mentioned pouring conditions are met, the pouring interval between the foam concrete structure layer 2 and the foam concrete filling layer 1 is not greater than 100m. Among them, after the foam concrete filling layer 1 is poured for a certain distance (the design strength reaches 20%-30%), a certain distance of the foam concrete structure layer 2 is poured on the foam concrete filling layer 1, and the difference in the pouring distance between the two is not greater than 100m. Since the strength requirements of the foam concrete filling layer 1 are relatively low, and the contact area with the foam concrete structure layer 2 is also large, the construction period can be shortened by controlling the pouring interval, while reducing the degree of difference between the two during the hardening process, ensuring the degree of combination of the two, and providing sufficient bearing capacity together after the strength is increased.

[0055] Specifically, the raw materials of the foamed concrete filling layer 1, the foamed concrete structural layer 2 and the foamed concrete strengthening layer 3 can all be foamed concrete, and the preparation method of the foamed concrete may include the following steps: Mixing active cementitious material, pozzolanic auxiliary cementitious material and inert filler with water to obtain cementitious slurry; The cementitious slurry is then mixed with foam to obtain foamed concrete.

[0056] The component ratio, water-to-solid ratio or foam amount of the foamed concrete can be controlled to ensure that the strength of the foamed concrete is within the required range after hardening.

[0057] Specifically, when fibers are arranged in the foamed concrete reinforcement layer 3, the method for preparing the foamed concrete of the foamed concrete reinforcement layer 3 may include the following steps: Mixing active cementitious material, pozzolanic auxiliary cementitious material, fiber and inert filler with water to obtain cementitious slurry; Then, the cementitious slurry is mixed with foam to obtain the foamed concrete of the foamed concrete reinforcement layer 3 .

[0058] Furthermore, the template is a polystyrene foam board, the thickness of the template is not less than 15cm, and the length of the pouring area of ​​the foam concrete filling layer 1, the foam concrete structural layer 2 and the foam concrete strengthening layer 3 is 20-25m. Among them, the polystyrene foam board is mainly formed by extrusion, and can be filled in after being supported horizontally along the tunnel as a template, used as an expansion joint, to avoid shrinkage cracking in the later stage of large-volume pouring, and reduce the impact of temperature changes.

[0059] Furthermore, the lateral formwork is a wooden formwork or a plastic steel formwork, the thickness of the lateral formwork is not less than 12 cm, the groove depth of the installation groove is 10-20 mm, and the groove width is the same as the thickness of the lateral formwork. In the present application, the cutting direction of the installation groove is consistent with the erection direction of the lateral formwork. By controlling the groove width and groove depth, it is ensured that the lateral formwork can be embedded in the installation groove during erection. Specifically, it can be sealed in advance by spraying foam glue to avoid side leakage during pouring. By erecting the template of the foam concrete strengthening layer 3 and the lateral formwork, it is ensured that the foam concrete strengthening layer 3 is poured into the desired shape.

[0060] Among them, the lateral formwork is vertically supported along the extension direction of the tunnel, and the lateral casting area of ​​the foam concrete strengthening layer 3 is divided at a distance of 150-250m from the extension direction. In this application, the lateral formwork is used in rotation and is not used as part of the filling. The lateral wooden formwork is supported 150-250 meters laterally, considering the optimal operating efficiency and construction cost of the process flow of "foam concrete structural layer 2 casting - foam concrete strengthening layer 3 formwork - foam concrete strengthening layer 3 casting". If the lateral area is divided too long, the investment in the strengthening layer formwork is large, and the disassembly and turnover cycle of the lateral formwork is too long, the process flow cannot be connected, which leads to reduced efficiency and increased construction costs; if the lateral area is divided too short, the construction efficiency is low, resulting in increased construction period costs.

[0061] Furthermore, the single-layer pouring thickness of the foamed concrete filling layer 1 is 0.3-0.8 m, the single-layer pouring thickness of the foamed concrete structural layer 2 is 0.3-0.6 m, and the single-layer pouring thickness of the foamed concrete strengthening layer 3 is 0.3-0.5 m.

[0062] Specifically, in the filling structure of the present application, the thickness of a single layer of casting will affect the casting quality and later strength. Excessive thickness will cause quality risks such as foam defoaming and stratification in the foam concrete slurry. The present application performs gradient strength matching for the foam concrete filling layer 1, the foam concrete structural layer 2, and the foam concrete strengthening layer 3. The wet density of casting increases successively, and the foam content in the corresponding slurry will decrease successively. The higher the risk of stratification, therefore, the greater the casting wet density in the present application, the higher the control requirement for the single layer casting thickness is to ensure the casting quality.

[0063] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the scope of protection of the present application.

Claims

1. A foamed concrete filling structure for a large diameter oil and gas pipeline tunnel, comprising a tunnel, characterized in that: The tunnel comprises, from bottom to top, a foam concrete filling layer (1), a foam concrete structural layer (2) and a foam concrete strengthening layer (3); A channel (31) is provided in the central area of ​​the foamed concrete strengthening layer (3) for isolating the foamed concrete strengthening layer (3) and exposing the foamed concrete structural layer (2); A pipe is arranged in the foam concrete filling layer (1), and a pipe is arranged on each of the two partitioned sides in the foam concrete strengthening layer (3).

2. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 1 is characterized in that: The distance between the top surface of the foam concrete reinforcement layer (3) and the top of the tunnel is not less than 2 m, and the partition distance of the channel (31) is not less than 1.2 times the diameter of the pipeline and not less than 0.5 m.

3. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 2 is characterized in that: The ratio of the diameter of the pipeline to the diameter of the tunnel is 0.3-0.42:1, the ratio of the thickness of the foamed concrete filling layer (1) to the diameter of the pipeline is 1.15-1.4:1, and the ratio of the thickness of the foamed concrete strengthening layer (3) to the diameter of the pipeline is 1.05-1.10:

1.

4. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 3 is characterized in that: The thickness of the foamed concrete structure layer (2) is 0.5-0.8 m.

5. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 1 is characterized in that: The compressive strength of the foamed concrete filling layer (1) is 1.5-2 MPa, the compressive strength of the foamed concrete structural layer (2) is 2-3 MPa, and the compressive strength of the foamed concrete strengthening layer (3) is 3-5 MPa; The flexural strength of the foamed concrete reinforcement layer (3) is 1.2-2 MPa.

6. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 5, characterized in that: The foam concrete reinforcement layer (3) is provided with fibers, and the fibers are one of polypropylene fibers, basalt fibers, coconut shell fibers, and sisal fibers; The length of the fiber is 6-14 mm, the diameter of the fiber is 7-15 μm, and the aspect ratio of the fiber is 1000-3000:

1.

7. The foamed concrete filling structure for a large diameter oil and gas pipeline tunnel according to claim 1, characterized in that: A pipeline base is set under the pipeline; the anti-floating stability coefficient of the tunnel K satisfy: =1.05~1.15； M 1 is the deadweight of the foamed concrete filling layer (1), M 2 is the deadweight of the foamed concrete structure layer (2), M 3 is the deadweight of the foamed concrete reinforcement layer (3), M p is the dead weight of the pipeline, M q is the deadweight of the pipeline base, V is the volume of the tunnel, ρ is the density of water, g is the acceleration due to gravity.

8. A construction method for a foamed concrete filling structure of a large diameter oil and gas pipeline tunnel as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Installing and fixing the pipes for the foamed concrete filling layer (1) and the foamed concrete strengthening layer (3); Setting up a template for a foamed concrete filling layer (1) and dividing a pouring area of ​​the foamed concrete filling layer (1), arranging raw materials for the foamed concrete filling layer (1), and pouring the raw materials for the foamed concrete filling layer (1) into the pouring area of ​​the foamed concrete filling layer (1) using a backward pouring method; After the compressive strength of the foamed concrete filling layer (1) reaches 20%-30% of the design strength, a template for the foamed concrete structure layer (2) is set up and a casting area of ​​the foamed concrete structure layer (2) is divided, raw materials of the foamed concrete structure layer (2) are arranged, and the raw materials of the foamed concrete structure layer (2) are cast into the casting area of ​​the foamed concrete structure layer (2) using a backward casting method; After the compressive strength of the foamed concrete structural layer (2) reaches 50%-70% of the design strength, a mounting groove is cut on the foamed concrete structural layer (2), a lateral formwork is mounted on the mounting groove, a formwork for the foamed concrete strengthening layer (3) is set up and a pouring area for the foamed concrete strengthening layer (3) is divided, raw materials for the foamed concrete strengthening layer (3) are arranged, and the raw materials for the foamed concrete strengthening layer (3) are poured into the pouring area of ​​the foamed concrete strengthening layer (3) using a backward pouring method.

9. The construction method of the foamed concrete filling structure of a large diameter oil and gas pipeline tunnel according to claim 8 is characterized in that: The template is a polystyrene foam board, the thickness of the template is not less than 15 cm, and the lengths of the pouring areas of the foam concrete filling layer (1), the foam concrete structural layer (2) and the foam concrete strengthening layer (3) are all 20-25 m; The lateral template is a wooden template or a plastic steel template, the thickness of the lateral template is not less than 12 cm, the depth of the installation groove is 10-20 mm, and the groove width is the same as the thickness of the lateral template.

10. The construction method of the foamed concrete filling structure of a large diameter oil and gas pipeline tunnel according to claim 8, characterized in that: The single-layer pouring thickness of the foamed concrete filling layer (1) is 0.3-0.8 m, the single-layer pouring thickness of the foamed concrete structural layer (2) is 0.3-0.6 m, and the single-layer pouring thickness of the foamed concrete strengthening layer (3) is 0.3-0.5 m.

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