A double-layer protection structure and one-side asymmetric step grouting construction method for a water intake top pipe of an in-service oil and gas main pipe power plant

Abstract

The application relates to a double-layer protection structure and one-side asymmetric step grouting construction method for a top pipe of a power plant water taking pipe penetrating an in-service oil and gas main pipe, and belongs to the technical field of power plant water taking engineering construction. The double-layer protection structure comprises a coaxially sleeved outer concrete pipe, an inner steel pipe and a filling layer filled between the outer concrete pipe and the inner steel pipe. Two adjacent outer concrete pipes are spliced through a step socket structure, and the annular welding seam of two adjacent inner steel pipes is arranged in a staggered manner along the pipeline axial direction of the step socket splicing seam of the outer concrete pipe. A splicing assembly is arranged at the splicing position of the outer concrete pipe, and the splicing assembly is used for limiting the axis when the adjacent outer concrete pipes are docked. A positioning assembly is arranged on the inner steel pipe, and the positioning assembly is used for guiding and orienting when the inner steel pipe is installed. The application has the effects of improving the protection reliability of the top pipe structure and the grouting construction precision under the condition of the power plant water taking pipe penetrating the in-service oil and gas main pipe.

Description

Technical Field

[0001] This application relates to the technical field of power plant water intake engineering construction, and in particular to a double-layer protective structure for a power plant water intake jacking pipe that passes under an in-service oil and gas main pipeline and a single-sided asymmetric stepped grouting construction method. Background Technology

[0002] Pipe jacking for power plant water intake is a critical structure in the raw water transportation system of coastal and riverside power plants. It often traverses complex environments such as existing roads, embankments, and underground pipelines. The construction conditions are particularly complex when jacking under in-service oil and gas pipelines. Ground disturbance and soil deformation during pipe jacking can easily lead to pipeline settlement, displacement, or even rupture and leakage, causing major safety accidents. Therefore, precise control of the pipe jacking structure's protective strength and the surrounding soil reinforcement is a core technical key to ensuring the safety of construction under in-service oil and gas pipelines and the long-term operational safety of the pipelines. This technology is widely used in various underground pipeline crossing scenarios, such as power plant water intake projects, municipal water supply and drainage projects, and oil and gas pipeline intersection projects.

[0003] Currently, pipe jacking projects under in-service pipelines mostly adopt single-layer reinforced concrete pipe jacking structures. Pipe sections are mostly spliced ​​using flat butt joints or simple socket connections, with a single rubber sealing ring installed at the joints to achieve water stoppage. The surrounding soil reinforcement mostly adopts the conventional full-section symmetrical grouting method, with grouting holes evenly distributed on both sides of the jacking pipe, and grouting reinforcement is carried out according to a uniform grouting pressure and grouting volume. During the construction process, the monitoring of in-service pipelines mostly adopts simple surface settlement observation, and the construction progress is controlled by experience. After the construction is completed, the quality acceptance is mostly carried out by a single core drilling method.

[0004] Existing pipe jacking protection structures and grouting construction methods have significant shortcomings in the complex working conditions of tunneling under in-service oil and gas pipelines: First, the protection level of single-layer concrete pipe jacking structures is limited, relying solely on a single layer of pipe wall to resist external soil pressure and construction disturbances. Once local pipe wall cracks or leaks occur, the operational safety of the water intake pipeline will be directly affected. Second, pipe segment splicing is mostly flat-end or single-stage socket joint, with only a single seal at the joint, resulting in poor reliability of water-stopping seals. Under uneven settlement or stratum disturbance, misalignment and cracking are prone to occur at the joint. Third, grouting construction lacks scientific and precise termination criteria, relying mainly on grouting pressure or experience in grouting volume to control the timing of grouting termination. This results in poor uniformity of grouting reinforcement and a tendency for local under-grouting or over-grouting. Fourth, the monitoring methods during construction are limited. Relying solely on surface settlement observation cannot grasp the real deformation state of the oil and gas pipeline in real time, and the monitoring and early warning thresholds are set in a coarse manner, making it difficult to detect and control the disturbance impact of construction on the oil and gas pipeline in a timely manner. Summary of the Invention

[0005] To improve the protective reliability and grouting accuracy of pipe jacking structures under in-service oil and gas main pipelines, this application provides a double-layer protective structure and a single-sided asymmetric stepped grouting construction method for pipe jacking under in-service oil and gas main pipelines and power plant water intake pipes.

[0006] On the one hand, this application provides a double-layer protection structure for the water intake jacking pipe of an in-service oil and gas main power plant, which adopts the following technical solution: A double-layer protective structure for a water intake jacking pipe passing under an in-service oil and gas main power plant includes an outer concrete pipe, an inner steel pipe, and a filling layer between the outer concrete pipe and the inner steel pipe, all coaxially fitted together. Adjacent sections of the outer concrete pipe are spliced ​​together via a stepped socket structure. One end of each outer concrete pipe has an annular step, and the other end has an annular groove that matches the annular step. When adjacent outer concrete pipes are joined, the annular step fits into the annular groove to form a stepped splicing section. The annular weld seam of adjacent inner steel pipe sections is offset from the stepped socket splicing seam of the outer concrete pipe along the pipe axis. A splicing assembly is provided at the splice point of the outer concrete pipe, which is used for axial positioning when adjacent outer concrete pipes are joined. A positioning assembly is provided on the inner steel pipe, which is used for guidance and orientation during the installation of the inner steel pipe.

[0007] By adopting the above technical solutions, the outer concrete pipe and the inner steel pipe form a double-layer composite protection system. The stepped socket structure improves the rigidity and impermeability of the splicing nodes of the outer concrete pipe. The axial misalignment of the splicing joint avoids the concentration of weak sections and ensures uniform stress on the entire pipeline. The splicing components and positioning components respectively ensure the splicing accuracy of the outer concrete pipe and the coaxiality of the inner steel pipe installation, so that the double-layer pipes work together to meet the design expectations, greatly improving the overall deformation resistance of the jacking pipe and reducing the transmission impact of construction disturbances on the upper oil and gas main pipe.

[0008] Optionally, a first rubber water-stop ring is embedded in the inner wall of the annular groove, and a second rubber water-stop ring is embedded in the outer wall of the annular step. After the adjacent outer concrete pipes are spliced ​​together, the first rubber water-stop ring and the second rubber water-stop ring are pressed between the contact surface of the annular step and the annular groove to form two sets of sealing structures.

[0009] By adopting the above technical solution, the double water-stop rings form two radial sealing barriers on the stepped splicing surface, which significantly improves the water-stopping and seepage prevention performance of the external concrete pipe splicing joint, prevents groundwater from seeping in or pipeline leakage from eroding the strata, and ensures the stability of the strata around the oil and gas pipeline.

[0010] Optionally, the splicing assembly includes a first splicing ring and a second splicing ring pre-embedded in the inner wall of the joint end of two adjacent outer concrete pipes; the joint end face of the first splicing ring is provided with a guide positioning groove, and the joint end face of the second splicing ring is fixedly provided with a plug block. When adjacent outer concrete pipes are joined, the plug block is embedded in the guide positioning groove to achieve circumferential positioning.

[0011] By adopting the above technical solution, the pre-embedded splicing ring can be inserted and aligned synchronously with the splicing of the outer concrete pipe. This can not only limit the circumferential torsion of the pipe section and ensure the coaxial accuracy of the splicing, but also uniformly transmit the jacking force during the jacking process, reduce the local stress concentration at the splicing node, and improve the stability of the jacking construction.

[0012] Optionally, the circumferential weld of the adjacent inner steel pipe, the stepped socket splice of the outer concrete pipe, and the butt joint of the splicing component are arranged in a staggered manner along the pipe axis.

[0013] By adopting the above technical solution, the three structural joints are completely staggered, eliminating the problem of abrupt changes in stiffness on the same cross section, making the overall stiffness of the splicing node consistent with that of the normal pipe section, avoiding excessive local deformation from being transmitted upward to the oil and gas main pipe, and further ensuring the stress continuity of the protective structure.

[0014] Optionally, the positioning component includes a positioning ring and a positioning block; a first guide groove is formed on the inner wall of the outer concrete pipe, and multiple sets of positioning grooves are formed on one side of the first guide groove; a second guide groove is formed on the first splicing ring, and a third guide groove is formed on the second splicing ring; the first guide groove, the second guide groove, and the third guide groove are connected to form a continuous axial guide channel; the positioning ring is fixedly set at the innermost end of the outer concrete pipe, and a guide cone groove is formed on the positioning ring; a first guide cone and a second guide cone are respectively fixedly set at both ends of the inner steel pipe; the positioning block is fixedly set on the inner steel pipe and located in the positioning groove.

[0015] By adopting the above technical solution, the continuous guide channel provides axial guidance for the installation of the inner steel pipe. The guide cone groove of the positioning ring cooperates with the guide cone at the end of the steel pipe, which can automatically drive the inner steel pipe to circumferentially align, so that the positioning block is accurately inserted into the positioning groove. The coaxiality and circumferential position accuracy of the inner steel pipe can be guaranteed without repeated manual adjustment. It is suitable for the construction process of installing the inner steel pipe after the outer concrete pipe is passed through, improving installation efficiency and positioning reliability.

[0016] Optionally, a welding bevel is opened at the butt joint of the inner steel pipe, and a fully penetrated annular weld seam is formed by using a single-sided welding and double-sided forming process inside the pipe.

[0017] By adopting the above technical solution, the single-sided welding double-sided forming process can complete the butt welding of the inner steel pipe inside the outer concrete pipe without the need for operation on the outside of the outer concrete pipe. It is compatible with the construction process of installing and welding the inner steel pipe section by section. Moreover, the full penetration weld ensures the sealing performance and structural strength of the water pipeline and meets the anti-seepage requirements for long-term operation.

[0018] Optionally, the filling layer is C20 fine aggregate concrete.

[0019] By adopting the above technical solution, the fine stone concrete filling layer can uniformly transfer the load between the inner and outer pipes, so that the double-layer pipes form a whole structure that shares the load together, ensuring the effective implementation of the stress sharing mechanism of the thick-walled cylinder, and at the same time improving the overall impact resistance and deformation resistance of the pipeline.

[0020] On the other hand, the single-sided asymmetric stepped grouting construction method for a double-layer protective structure of the water intake pipe of an in-service oil and gas main power plant provided in this application adopts the following technical solution: A single-sided asymmetric stepped grouting construction method for a double-layer protective structure of a water intake pipe for an in-service oil and gas main power plant includes the following steps: S1 On-site survey and hole layout: Verify the plane coordinates and burial depth of the in-service oil and gas main pipe, complete the measurement and layout, and lay out 5 rows of grouting holes on one side of the pipe jacking near the river embankment. The depth of the grouting holes decreases by 1m from the first row of 25m to the last row of 21m, forming a stepped hole layout pattern. S2 outer concrete pipe (1) stepped socket jacking: the outer concrete pipe (1) is jacked section by section using the mud-water balance pipe jacking process. The stepped socket docking is completed by the fitting of the annular step (11) and the annular groove (12), and the splicing components (4) are aligned and fitted at the same time. S3 Inner steel pipe (2) guide installation and automatic alignment welding: Insert the inner steel pipe (2) into the outer concrete pipe (1) section by section. The positioning component (5) completes the guidance and orientation of the installation process. Adjust the axial position of the pipe section so that the circumferential weld of the inner steel pipe (2) and the stepped socket splice of the outer concrete pipe (1) are axially misaligned, and the welding of adjacent inner steel pipes (2) is completed. S4 Filling Layer (3) Grouting Construction: Fine stone concrete is poured into the annular gap between the outer concrete pipe (1) and the inner steel pipe (2). Micro-expansion steel fiber concrete mixed with polypropylene fiber is poured into the annular area corresponding to each joint to ensure that the filling layer (3) is dense and uniform, and to complete the construction of the double-layer protective structure. S5 Single-sided asymmetric stepped grouting reinforcement: The retreating segmented grouting process is adopted. The grouting operation is carried out in the order of first the outer holes and then the central holes, and skipping holes. The diffusion flow coefficient of single-sided asymmetric grouting is introduced to control the diffusion range. The grouting termination criterion is that the grouting flow rate of a single hole is ≤1L / min and lasts for 10min. The soil around the pipe jacking is reinforced. S6 Full-Process Monitoring and Triple Acceptance: Throughout the construction process, monitoring points for settlement and horizontal displacement of oil and gas main pipes are set up, and alarm control is implemented based on thresholds of 3mm daily settlement and 20mm cumulative settlement, 5mm daily horizontal displacement and 30mm cumulative horizontal displacement. After the construction is completed, triple quality acceptance is achieved through geophysical scanning comparison, borehole water injection test, and borehole core sampling.

[0021] By adopting the above technical solutions, using a single-sided stepped hole layout and segmented grouting process, the grouting diffusion range can be precisely controlled, forming a continuous soil reinforcement layer below the oil and gas main pipe. The construction of the double-layer pipe structure and the grouting reinforcement are connected in an orderly manner. With the full-process deformation monitoring and triple acceptance system, the deformation of the oil and gas pipeline can be controlled throughout the construction cycle, taking into account both construction efficiency and project safety and reliability.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. The double-layer pipe protection structure, which uses stepped socket splicing and multi-slit staggered design, effectively improves the rigidity and seepage prevention performance of splicing nodes and eliminates the problem of concentrated weak sections; 2. By using a unilateral asymmetric stepped grouting process, the grouting range can be controlled, avoiding problems such as over-grouting or insufficient reinforcement; 3. The positioning components enable automatic guidance and alignment of the inner steel pipe installation, which, combined with the whole-process monitoring and triple acceptance system, improves the construction accuracy and quality control level. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of an embodiment of this application; Figure 2 yes Figure 1 A magnified view of a section at point A in the middle; Figure 3 This is a cross-sectional view of an embodiment of this application after the fill layer has been hidden; Figure 4 yes Figure 3 A magnified view of a section at point B in the middle; Figure 5 This is a partial cross-sectional view of an embodiment of this application for showing the guide positioning groove.

[0024] Explanation of reference numerals in the attached drawings: 1. Outer concrete pipe; 11. Annular step; 12. Annular groove; 13. First rubber waterstop ring; 14. Second rubber waterstop ring; 15. First guide groove; 16. Positioning groove; 2. Inner steel pipe; 21. First guide cone; 22. Second guide cone; 3. Filling layer; 4. Splicing assembly; 41. First splicing ring; 411. Guide positioning groove; 412. Second guide groove; 42. Second splicing ring; 421. Insertion block; 422. Third guide groove; 5. Positioning assembly; 51. Positioning ring; 511. Guide cone groove; 52. Positioning block. Detailed Implementation

[0025] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0026] This application discloses a double-layer protective structure for a water intake jacking pipe that passes under an in-service oil and gas main pipeline and power plant. (Refer to...) Figure 1 A double-layer protective structure for a water intake jacking pipe passing under an in-service oil and gas main pipeline power plant includes an outer concrete pipe 1, an inner steel pipe 2, and a filling layer 3 between the outer concrete pipe 1 and the inner steel pipe 2, all coaxially fitted together. The outer concrete pipe 1 serves as the main pipe section for pipe jacking construction, bearing the jacking force and external ground loads. The inner steel pipe 2 serves as a permanent water conveyance channel, responsible for transporting raw water to the power plant. The filling layer 3 fills the annular gap between the inner and outer pipes, achieving uniform load transfer and creating a composite structure where the inner and outer pipes work together to bear the load.

[0027] Two adjacent sections of outer concrete pipe 1 are spliced ​​together using a stepped socket structure. One end of the outer concrete pipe 1 has an annular step 11, and the other end has an annular groove 12 that matches the annular step 11. When adjacent outer concrete pipes 1 are joined, the annular step 11 fits into the annular groove 12 to form a stepped splicing section. Compared with the traditional flat-end joint, the stepped splicing section increases the contact area of ​​the joint, improves the overall rigidity and bending resistance of the splicing node, and extends the seepage path, thereby improving the seepage prevention performance.

[0028] Reference Figure 2 The inner wall of the annular groove 12 is fitted with a first rubber water-stop ring 13, and the outer wall of the annular step 11 is fitted with a second rubber water-stop ring 14. After the adjacent outer concrete pipes 1 are spliced ​​together, the two rubber water-stop rings are squeezed between the contact surfaces of the annular step 11 and the annular groove 12, forming two independent radial sealing structures. The double water-stop rings, combined with the stepped seepage path, can effectively resist the infiltration of external groundwater, while preventing internal water from leaking outward, ensuring the stability of the surrounding strata, and reducing the impact of seepage scouring on the upper oil and gas main pipe. The two ends of the inner steel pipe 2 are respectively fixed with a first guide cone 21 and a second guide cone 22. Reference Figure 1 and Figure 2 A splicing component 4 is provided at the joint of the outer concrete pipe 1. The splicing component 4 is used to limit the circumferential axis when adjacent outer concrete pipes 1 are joined. Specifically, the splicing component 4 includes a first splicing ring 41 and a second splicing ring 42, which are respectively pre-embedded in the inner wall of the joint end of the two adjacent outer concrete pipes 1.

[0029] Reference Figure 3 and Figure 4The inner wall of the outer concrete pipe 1 is provided with a first guide groove 15, and multiple positioning grooves 16 are provided on one side of the first guide groove 15. A second guide groove 412 is provided on the first splicing ring 41, and a third guide groove 422 is provided on the second splicing ring 42. The first guide groove 15, the second guide groove 412, the third guide groove 422, and the multiple positioning grooves 16 are arranged in multiple sets at intervals along the circumference of the outer concrete pipe 1. After adjacent outer concrete pipes 1 are spliced ​​into place, the first guide groove 15, the second guide groove 412, and the third guide groove 422 are aligned and connected to each other to form a continuous axial guide channel.

[0030] Reference Figure 2 and Figure 5 The first splicing ring 41 has a guide positioning groove 411 on its mating end face, and the second splicing ring 42 has a plug-in block 421 fixedly installed on its mating end face. When adjacent outer concrete pipes 1 are connected by a stepped socket, the plug-in block 421 is simultaneously embedded into the guide positioning groove 411. On the one hand, this can achieve circumferential positioning when the pipe sections are connected, avoid twisting and misalignment of the pipe sections, and ensure the coaxiality of the splicing. On the other hand, it can evenly transmit the jacking force during the jacking construction process, reduce local stress concentration at the joint, and avoid problems such as pipe section misalignment and cracking during the jacking process.

[0031] In this embodiment, the circumferential weld of the adjacent inner steel pipe 2, the stepped socket splice of the outer concrete pipe 1, and the butt joint of the splicing component 4 are staggered along the pipeline axis. The three structurally weak sections are staggered along the axis, avoiding the problem of sudden drop in stiffness at the same cross section, making the overall stiffness of the splicing node consistent with that of the normal pipe section, ensuring uniform stress on the entire pipeline, and preventing excessive local deformation from transmitting upward disturbance to the upstream in-service oil and gas main pipe.

[0032] Reference Figure 1 and Figure 3 A positioning component 5 is provided on the inner steel pipe 2. The positioning component 5 is used to guide and orient the inner steel pipe 2 during installation, ensuring the coaxiality of the inner and outer pipes. Specifically, the positioning component 5 includes a positioning ring 51 and multiple positioning blocks 52. The positioning ring 51 is fixedly installed on the inner wall of the innermost end of the outer concrete pipe 1, and a guide cone groove 511 is opened on the side of the positioning ring 51 facing the inner steel pipe 2. Multiple sets of positioning blocks 52 are arranged along the axial direction of the inner steel pipe 2, and each set of positioning blocks 52 has multiple blocks, which correspond to multiple sets of first guide grooves 15. The positioning blocks 52 are fixedly installed on the outer wall of the inner steel pipe 2, and one end is located in the positioning groove 16.

[0033] During the installation of the inner steel pipe 2, the positioning block 52 is embedded in the axial guide channel and slides axially to provide radial limit for the inner steel pipe 2, preventing the inner steel pipe 2 from deviating during the installation process. When the front end of the inner steel pipe 2 is pushed to the innermost end of the outer concrete pipe 1, the first guide cone 21 is embedded in the guide cone groove 511 of the positioning ring 51. The cone surfaces fit together, driving the inner steel pipe 2 to rotate slightly circumferentially, causing the positioning block 52 to slide into the corresponding positioning groove 16, realizing the circumferential locking and axial positioning of the inner steel pipe 2, automatically completing the coaxial alignment of the inner and outer pipes, eliminating the need for repeated manual adjustments, and adapting to the construction procedure of installing the inner steel pipe 2 after the outer concrete pipe 1 has been passed through.

[0034] The inner steel pipe 2 has a welding bevel at the butt joint, and is processed into a fully penetrated circumferential weld using a single-sided welding and double-sided forming process inside the pipe. This welding process can be completed only inside the steel pipe, without the need for work in the gap between the outer concrete pipe 1 and the inner steel pipe 2.

[0035] In this embodiment, the filling layer 3 is formed by pouring C20 fine aggregate concrete. The fine aggregate concrete filling layer 3 can uniformly transfer the internal pressure borne by the inner steel pipe 2 to the outer concrete pipe 1, and at the same time uniformly transfer the external ground load to the inner steel pipe 2, so that the double-layer pipe as a whole conforms to the stress sharing mechanism of a thick-walled cylinder.

[0036] The implementation principle of the double-layer protective structure for a water intake pipe jacking under an in-service oil and gas main pipeline and power plant in this application embodiment is as follows: During construction, the outer concrete pipe 1 is jacked in section by section and spliced ​​through a stepped socket structure. The splicing components 4 are simultaneously connected to achieve circumferential limiting, ensuring the splicing accuracy of the outer concrete pipe 1 and the uniformity of the jacking force. After the outer concrete pipe 1 is fully penetrated, the inner steel pipe 2 is installed section by section. The installation is guided by an axial guide channel. The inner steel pipe 2 is circumferentially aligned by the cooperation of the guide cone and the guide cone groove 511, so that the positioning block 52 is inserted into the positioning groove 16 to complete automatic positioning. At the same time, it ensures that the weld of the inner steel pipe 2 and the splicing joint of the outer concrete pipe 1 are axially misaligned. Then, the filling layer 3 is poured to make the inner and outer pipes form a whole that shares the force. Through the stepped splicing, multi-joint misalignment and automatic positioning design, the rigidity, seepage prevention performance and installation accuracy of the double-layer pipe splicing node are greatly improved, the problem of concentrated weak sections is eliminated, and the uniformity of the overall pipeline force is ensured.

[0037] This application discloses a single-sided asymmetric stepped grouting construction method for a double-layer protective structure of a water intake pipe for an in-service oil and gas main pipeline power plant.

[0038] S1 Site Survey and Hole Layout Positioning: Prior to construction, a site geological survey was conducted, employing a combination of geophysical exploration and manual verification to accurately locate the plane coordinates and burial depth of the existing oil and gas main pipe, clarifying the relative positional relationship between the pipe jacking and the main pipe. After completing the survey and layout, five rows of grouting holes were laid out on one side of the pipe jacking closest to the riverbank. The depth of the grouting holes decreased by 1 meter from the first row of 25m to the last row of 21m, forming a stepped hole layout pattern, ensuring that the grouting reinforcement area accurately covered the target strata below the main oil and gas main pipe.

[0039] S2 external concrete pipe 1-step socket jacking: The outer concrete pipe 1 is jacked up section by section using a slurry-balanced pipe jacking process. A positioning ring 51 with a guide cone groove 511 is pre-installed at the innermost end of the outer concrete pipe 1. During jacking, the jacking speed and soil pressure are controlled to minimize disturbance to the surrounding strata. When each pipe section is jacked and connected, a stepped socket connection is achieved by the interlocking of the annular step 11 and the annular groove 12. Simultaneously, the insertion block 421 of the splicing component 4 is embedded into the guide positioning groove 411, achieving circumferential positioning and coaxial connection of the pipe section. This ensures that the guide grooves of each section of the outer concrete pipe 1 are aligned and connected, providing a continuous guiding channel for the subsequent installation of the inner steel pipe 2.

[0040] S3 Inner Steel Pipe 2 Guide Installation and Automatic Alignment Welding: After the outer concrete pipe 1 is pushed into place as a whole, the inner steel pipe 2 is inserted segment by segment from the starting end. The positioning block 52 on the outer wall of the inner steel pipe 2 is aligned with the axial guide channel and pushed in, and the radial displacement of the inner steel pipe 2 is restricted by the guide channel. When the first segment of the inner steel pipe 2 is pushed to the end, the first guide cone 21 at the front end is embedded in the guide cone groove 511. The inner steel pipe 2 is driven to rotate circumferentially through the cone surface cooperation, which drives the positioning block 52 to be inserted into the positioning groove 16 to complete the automatic positioning.

[0041] The inner steel pipes 2 are then inserted sequentially. The alignment is completed by the guide cone at the end, and the axial position of the pipe section is adjusted so that the circumferential weld of the inner steel pipe 2 and the stepped socket splice of the outer concrete pipe 1 are axially misaligned. The bevel welding of adjacent inner steel pipes 2 is completed by using the single-sided welding and double-sided forming process inside the pipe. After the weld is qualified by flaw detection, the installation of the inner steel pipes 2 is completed.

[0042] S4 Filler Layer 3 Grouting Construction: After all the inner steel pipes 2 are installed, C20 fine stone concrete is poured into the annular gap between the outer concrete pipe 1 and the inner steel pipe 2. The filling layer 3 is uniform and dense by using a layered pouring and vibration compaction process.

[0043] S5 unilateral asymmetric stepped grouting reinforcement: A retreating, segmented grouting process was employed for soil reinforcement. The grouting sequence followed the principle of grouting the outer holes first, then the central holes, and skipping holes. The outer holes were grouted first to form boundary sealing, and then the internal areas were gradually reinforced to avoid disorderly diffusion of the grout. A grouting termination criterion was set at a single hole grout flow rate of ≤1L / min for 10 minutes to ensure uniform and full reinforcement of the formation, forming a continuous and stable rigid reinforcement layer below the main oil and gas pipeline, further isolating the pipeline from the impact of pipe jacking construction and operation.

[0044] S6 Full-Process Monitoring and Triple Acceptance: Throughout the construction process, settlement and horizontal displacement monitoring points were deployed at the corresponding locations of the oil and gas mains, establishing a multi-party joint monitoring mechanism to share monitoring data in real time. A tiered alarm system was set with thresholds of 3mm daily settlement and 20mm cumulative settlement, and 5mm daily horizontal displacement and 30mm cumulative horizontal displacement. Once an alarm was triggered, construction was immediately suspended and control measures were implemented. After construction, a triple acceptance system was used to verify the project quality: First, geophysical scanning was used to compare the geological properties before and after grouting to verify the reinforcement range and uniformity; second, borehole water injection tests were conducted to verify that the water absorption of the strata after grouting was no more than 3%~5% of the water before grouting, confirming the seepage prevention and reinforcement effect; third, inspection boreholes were set up at a ratio of no less than 3% of the total number of boreholes for core sampling to visually verify the soil reinforcement strength and integrity, ensuring that the project quality met standards.

[0045] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A double-layer protective structure for a water intake jacking pipe passing under an in-service oil and gas main pipeline and power plant, characterized in that: The system includes an outer concrete pipe (1) and an inner steel pipe (2) coaxially mounted, and a filling layer (3) between the outer concrete pipe (1) and the inner steel pipe (2); two adjacent sections of the outer concrete pipe (1) are spliced ​​together by a stepped socket structure. One end of the outer concrete pipe (1) is provided with an annular step (11), and the other end is provided with an annular groove (12) that matches the annular step (11). When adjacent outer concrete pipes (1) are joined, the annular step (11) fits into the inner steel pipe. A stepped splicing section is formed in the annular groove (12); the annular weld seam of the two adjacent sections of the inner steel pipe (2) and the stepped socket splicing seam of the outer concrete pipe (1) are staggered along the pipe axis; a splicing component (4) is provided at the splicing point of the outer concrete pipe (1), and the splicing component (4) is used to limit the axis when the adjacent outer concrete pipes (1) are connected; a positioning component (5) is provided on the inner steel pipe (2), and the positioning component (5) is used to guide and orient the inner steel pipe (2) during installation.

2. The double-layer protective structure for a water intake jacking pipe under an in-service oil and gas main pipeline power plant as described in claim 1, characterized in that: The inner wall of the annular groove (12) is fitted with a first rubber water-stop ring (13), and the outer wall of the annular step (11) is fitted with a second rubber water-stop ring (14). After the adjacent outer concrete pipes (1) are spliced ​​together, the first rubber water-stop ring (13) and the second rubber water-stop ring (14) are pressed between the contact surface of the annular step (11) and the annular groove (12) to form two sets of sealing structures.

3. The double-layer protective structure for a water intake jacking pipe under an in-service oil and gas main pipeline power plant as described in claim 1, characterized in that: The splicing assembly (4) includes a first splicing ring (41) and a second splicing ring (42) pre-embedded in the inner wall of the docking end of two adjacent outer concrete pipes (1); the docking end face of the first splicing ring (41) is provided with a guide positioning groove (411), and the docking end face of the second splicing ring (42) is fixedly provided with a plug block (421). When the adjacent outer concrete pipes (1) are docked, the plug block (421) is embedded in the guide positioning groove (411) to achieve circumferential positioning.

4. The double-layer protective structure for jacking water intake pipes of power plants under in-service oil and gas main pipelines as described in claim 3, characterized in that: The circumferential weld of the adjacent inner steel pipe (2), the stepped socket splice of the outer concrete pipe (1), and the butt joint of the splicing component (4) are arranged in a staggered manner along the pipeline axis.

5. The double-layer protective structure for a water intake jacking pipe under an in-service oil and gas main pipeline power plant as described in claim 3, characterized in that: The positioning component (5) includes a positioning ring (51) and a positioning block (52); the inner wall of the outer concrete pipe (1) is provided with a first guide groove (15), and a plurality of positioning grooves (16) are provided on one side of the first guide groove (15); a second guide groove (412) is provided on the first splicing ring (41), and a third guide groove (422) is provided on the second splicing ring (42); the first guide groove (15), the second guide groove (412) and the third guide groove (422) are connected to form a continuous axial guide channel; the positioning ring (51) is fixedly installed at the innermost end of the outer concrete pipe (1), and a guide cone groove (511) is provided on the positioning ring (51); a first guide cone (21) and a second guide cone (22) are fixedly installed at both ends of the inner steel pipe (2); the positioning block (52) is fixedly installed on the inner steel pipe (2) and located in the positioning groove (16).

6. The double-layer protective structure for a water intake jacking pipe under an in-service oil and gas main pipeline power plant as described in claim 5, characterized in that: The inner steel pipe (2) has a welding bevel at the butt joint and is processed into a fully penetrated annular weld seam using a single-sided welding and double-sided forming process inside the pipe.

7. The double-layer protective structure for a water intake jacking pipe under an in-service oil and gas main pipeline power plant as described in claim 1, characterized in that: The filling layer (3) is C20 fine aggregate concrete.

8. A method for single-sided asymmetric stepped grouting construction of a double-layer protective structure for water intake pipes of an in-service oil and gas main power plant, based on any one of claims 1-7, characterized in that... include: S1 On-site survey and hole layout: Verify the plane coordinates and burial depth of the in-service oil and gas main pipe, complete the measurement and layout, and lay out 5 rows of grouting holes on one side of the pipe jacking near the river embankment. The depth of the grouting holes decreases by 1m from the first row of 25m to the last row of 21m, forming a stepped hole layout pattern. S2 outer concrete pipe (1) stepped socket jacking: the outer concrete pipe (1) is jacked section by section using the mud-water balance pipe jacking process. The stepped socket docking is completed by the fitting of the annular step (11) and the annular groove (12), and the splicing components (4) are aligned and fitted at the same time. S3 Inner steel pipe (2) guide installation and automatic alignment welding: Insert the inner steel pipe (2) into the outer concrete pipe (1) section by section. The positioning component (5) completes the guidance and orientation of the installation process. Adjust the axial position of the pipe section so that the circumferential weld of the inner steel pipe (2) and the stepped socket splice of the outer concrete pipe (1) are axially misaligned, and the welding of adjacent inner steel pipes (2) is completed. S4 Filling Layer (3) Grouting Construction: Fine stone concrete is poured into the annular gap between the outer concrete pipe (1) and the inner steel pipe (2). Micro-expansion steel fiber concrete mixed with polypropylene fiber is poured into the annular area corresponding to each joint to ensure that the filling layer (3) is dense and uniform, and to complete the construction of the double-layer protective structure. S5 Single-sided asymmetric stepped grouting reinforcement: The retreating segmented grouting process is adopted. The grouting operation is carried out in the order of first the outer holes and then the central holes, and skipping holes. The diffusion flow coefficient of single-sided asymmetric grouting is introduced to control the diffusion range. The grouting termination criterion is that the grouting flow rate of a single hole is ≤1L / min and lasts for 10min. The soil around the pipe jacking is reinforced. S6 Full-Process Monitoring and Triple Acceptance: Throughout the construction process, monitoring points for settlement and horizontal displacement of oil and gas main pipes are set up, and alarm control is implemented based on thresholds of 3mm daily settlement and 20mm cumulative settlement, 5mm daily horizontal displacement and 30mm cumulative horizontal displacement. After the construction is completed, triple quality acceptance is achieved through geophysical scanning comparison, borehole water injection test, and borehole core sampling.

Images