Rapid installation and transformation construction method for deep-buried pipeline in saturated water silt stratum near water area

Abstract

The invention relates to the technical field of pipeline construction, in particular to a near-water-area saturated water silt stratum deep-buried pipeline rapid installation and transformation construction method which comprises the following steps that S1, the size of a working pit, the size of a platform, the size of a steel jacket box and the model of a Larsen steel sheet pile are determined; s2, carrying out descending treatment on the shallow earth surface soil; s3, carrying out closed support by adopting a first-stage Larsen steel sheet pile; s4, first-stage tube wells are arranged around the first-stage Larsen steel sheet piles for dewatering and pressure reduction; s5, a first-stage working pit is excavated; s6, secondary Larsen steel sheet pile construction is conducted; s7, the operation platform is subjected to hardening treatment through C20 concrete; s8, a secondary tube well is constructed for dewatering; s9, a plurality of steel tube wells are evenly constructed in the second-stage working pit; s10, the second-stage working pit is lowered to the bottom elevation of the accident pipeline, the steel jacket box is hoisted into the second-stage working pit, and the accident pipeline is embedded into a notch of the steel jacket box; and S11, hoisting and welding the pipeline. The method has the technical effects of rapid excavation at the pipeline accident position and high construction speed.

Description

Technical Field

[0001] This invention relates to the technical field of pipeline construction, and in particular to a rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata. Background Technology

[0002] With the acceleration of urbanization in my country, the demand for energy transmission continues to grow. Numerous long-distance pipelines traverse complex areas such as cities, villages, mountains, and rivers. Directional drilling, as a commonly used construction method for crossing these areas, is highly favored. However, when geological and hydrological conditions are unfavorable, external disturbances occur, or improper construction operations are performed, pipeline pullback often results in accidents such as borehole collapse, hook detachment, and pipeline or drill rod breakage. This is particularly true in saturated silty sand strata near water sources, where thick layers of silt and fine sand are buried underground, often interspersed between impermeable layers and containing large amounts of saturated groundwater, forming quicksand layers. These strata exhibit strong thixotropy and permeability. Combined with pipeline depths of tens of meters, the possibility of pipeline excavation and repair is virtually zero, posing significant difficulties and challenges to pipeline modification and repair work. There are two conventional methods: one is to abandon the affected section and re-drill and pull the pipeline at another location; the other is to modify the pipeline route and perform open-cut construction, which requires substantial economic costs.

[0003] In summary, the existing methods have the following problems: they are limited in scope, costly, expensive, slow, and time-consuming. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a construction method for rapid excavation, pipeline modification, and repair at pipeline accident sites.

[0005] This invention provides a rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata, employing the following technical solution: A rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata includes the following steps: S1. Based on the engineering and hydrogeological conditions, the location and depth of the accident pipeline, and the requirements of the working face, determine the size of the working pit, the platform size, the steel casing size, and the Larssen sheet pile model step by step from the inside out. Use computer software technology to simulate the working conditions of the working pit, perform stress analysis and calculation, and verify the local and overall stability of the structure. S2. Based on the soil conditions and surrounding environment, the shallow surface soil is reduced in depth. After determining the depth, a backhoe excavator is used for slope excavation. S3. Based on the engineering geology and hydrology, the excavation depth of the first-level working pit is determined by calculation, and first-level Larssen steel sheet piles are used for closed support; S4. Install a primary manhole around the primary Larssen sheet piles for dewatering and pressure reduction; S5. Excavate the first-level working pit, and simultaneously install the walers and steel supports with sheet piles as the excavation progresses; S6. After the first-level working pit is excavated to the predetermined elevation, it is moved back four meters inward from the first-level Larssen sheet pile to serve as an operating platform for the construction of the second-level Larssen sheet pile. S7. The operating platform is hardened with C20 concrete, and the hardened zone also serves as the concrete support zone for the primary steel sheet piles. At the same time, a pre-formed mold is used to reserve the position of the secondary pipe well. S8. Construct secondary wells for dewatering, with the bottom depth of the secondary wells extending at least two meters beyond the weakly permeable silty clay layer beneath the quicksand layer; S9. After the concrete in the concrete support strip reaches a certain strength, several steel pipe wells are evenly constructed in the secondary working pit. The bottom of the steel pipe well is buried in the quicksand layer, and the bottom of the well is one meter away from the bottom of the quicksand layer. The quicksand layer is discharged by suction. The upper silty clay layer sinks by its own weight until it is lowered to the elevation of the accident pipeline. During the process, the steel pipe well is dismantled as it is lowered. At the same time, the walers and steel supports of the secondary steel sheet piles are erected. S10. Lower the secondary working pit to the bottom elevation of the accident pipeline, hoist the steel casing into the secondary working pit, embed the accident pipeline into the gap of the steel casing, use a vibratory hammer to evenly press the four corners of the steel casing, so that the bottom of the steel casing cuts into the weakly permeable silty clay layer for no less than 1.5 meters, the top of the accident pipeline must be tightly pressed against the gap, at the same time use manual labor to remove the soil within 0.5 meters of the bottom of the accident pipeline, and use sandbags and cotton cloth to seal the gap, and use additional water pumps to continuously pump groundwater from inside and outside to ensure that the water level is controlled below 0.5 meters from the bottom of the pipe; S11. Weld one end of the connecting pipe to the elbow on the ground, set a lifting point at the other end, and use a truck crane to vertically lift the connecting pipe into the steel casing for butt welding with the accident pipe. During the process, the crane should always maintain the adjustment posture and not loosen the hook. S12. After the pipe welding, testing and repair are completed, the working pit is backfilled. Only after the backfill reaches the upper end of the connecting pipe can the crane hook be removed and the upper bend of the connecting pipe be constructed.

[0006] Optionally, the bottom depth of the primary well shall exceed the weakly permeable silty clay layer below the quicksand layer by no less than two meters.

[0007] Optionally, the top of the secondary Larssen sheet pile is completed at an elevation 700mm above the working platform surface.

[0008] Optionally, the steel casing is made of welded steel plates and shaped steel, without a bottom or cover. The steel casing is embedded in the middle of one side of the emergency pipeline and cut into a semi-circular door-shaped notch.

[0009] Optionally, the centerline of the waler and steel support of the first-grade Larssen sheet piles should coincide with the centerline of the concrete support thickness. Compared with the prior art, the present invention has the following technical effects: The working pit adopts a closed "nested" structure system, with modules nested at different levels and progressive control, which improves space utilization. At the same time, the "coupling" effect between modules is obvious, making dewatering more effective and support safety higher.

[0010] Using a method of blocking small-scale suction of flowing sand and reverse excavation for the working pit at the end of the system can greatly improve excavation efficiency and avoid impacting the surrounding environment.

[0011] The steel casing can further block the lateral seepage of saturated groundwater in the working pit. At the same time, by cutting into the weakly permeable soil layer, it can extend the seepage path and time at the bottom, providing a relatively safe working environment for personnel. This enables the segmented prefabrication and installation of pipelines to be carried out quickly and orderly. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of the excavation stage in an embodiment of the present invention; Figure 2 This is a plan view of the excavation stage in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the pipeline modification stage in an embodiment of the present invention; Figure 4 This is a plan view of the pipeline modification stage in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the emergency pipeline and connecting pipe according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the steel casing and emergency pipeline according to an embodiment of the present invention; Figure 7 A schematic diagram of the steel casing structure according to an embodiment of the present invention.

[0013] Explanation of reference numerals in the attached drawings: 1. Primary Larssen sheet pile; 2. Secondary Larssen sheet pile; 3. Steel casing; 4. Waler and steel support; 5. Primary manhole; 6. Secondary manhole; 7. Water pump; 8. Steel manhole; 9. Concrete support strip; 10. Sump; 11. Connecting pipe; 12. Emergency pipe; 13. Water pump drain pipe; 14. Gap. Detailed Implementation

[0014] The following is in conjunction with the appendix Figure 1 - Appendix Figure 7 The present invention will be described in further detail below.

[0015] Reference Figures 1-7 This invention discloses a method for the installation and renovation of large-diameter deep-buried pipelines in near-water saturated silty sand strata, comprising the following steps: S1. Based on the engineering and hydrogeological conditions, the location and depth of the accident pipeline 12, and the requirements of the working face, the dimensions of the working pit, platform, steel casing 3, and Larssen sheet piles were determined step by step from the inside out. Computer software was used to simulate the working conditions, perform stress analysis and calculations, verify the local and overall stability of the structure, and then implement targeted reinforcement measures. The computer software used was Lizheng Deep Foundation Pit.

[0016] S2. Based on the soil conditions and surrounding environment, the shallow surface soil is reduced in depth. After determining the depth, a backhoe excavator is used for slope excavation.

[0017] S3. Based on the engineering geology and hydrology, the excavation depth of the first-level working pit is determined by calculation, and Larssen steel sheet piles are used for closed support.

[0018] S4. At regular intervals around the first-level Larssen sheet pile 1, first-level manholes 5 are set up for dewatering and pressure reduction. The bottom depth of the first-level manholes 5 shall exceed the weakly permeable silty clay layer below the quicksand layer by no less than two meters.

[0019] S5. Excavate the first-level working pit, and simultaneously install the waler and steel support 4 of the first-level Larssen steel sheet pile 1.

[0020] S6. After the primary working pit is excavated to the predetermined elevation, it is moved back four meters inward from the primary Larssen sheet pile 1 to serve as an operating platform for the construction of the secondary Larssen sheet pile 2. The top of the secondary Larssen sheet pile 2 is completed at an elevation 700mm above the operating platform surface.

[0021] S7. The operating platform is hardened with C20 concrete with a thickness of 500mm. The hardened strip also serves as the concrete support strip 9 for the primary steel sheet pile 1. At the same time, a pre-formed mold is used to reserve the position of the secondary pipe well 6.

[0022] S8. Construct secondary well 6 for dewatering. The bottom depth of well 6 shall exceed the weakly permeable silty clay layer below the quicksand layer by no less than two meters.

[0023] S9. After the concrete of the concrete support strip 9 reaches a certain strength, several steel pipe wells 8 are evenly constructed in the secondary working pit. The bottom of the steel pipe wells 8 is buried in the quicksand layer, with the bottom of the well one meter away from the bottom of the quicksand layer. The quicksand layer is discharged by suction, and the upper silty clay layer sinks under its own weight until it is lowered to the elevation of the accident pipeline 12. During the process, the steel pipe wells are dismantled as they are lowered, and the walers and steel supports 4 of the secondary steel sheet piles 2 are erected at the same time. To ensure the force transmission effect, the center axis of the walers and steel supports 4 of the primary Larssen steel sheet piles 1 should coincide with the center line of the thickness of the concrete support strip 9.

[0024] S10. The secondary working pit is lowered to the bottom elevation of pipe 12. The steel casing 3 is hoisted into the secondary working pit, and the emergency pipe 12 is embedded in the notch 14 of the steel casing 3. A vibratory hammer is used to evenly press the four corners of the steel casing 3 so that the bottom of the steel casing 3 cuts into the weakly permeable silty clay layer by at least 1.5 meters. The top of the emergency pipe 12 must be firmly pressed against the notch 14. At the same time, the soil within 0.5 meters of the bottom of the emergency pipe 12 is manually removed, and the notch 14 is sealed with sandbags and cotton cloth. The additional water pump 7 continuously pumps groundwater from inside and outside to ensure that the water level is controlled below 0.5 meters from the bottom of the pipe. A sump 10 is set up on the silty clay layer, and the water in the working pit and the sump 10 is discharged through the water pump drain pipe 13.

[0025] Furthermore, the steel casing 3 is made of steel plates and shaped steel welded together. It has no bottom or cover. The steel casing 3 is embedded in the middle of one side of the accident pipeline 12 and cut into a semi-circular door-shaped notch 14. The height of the notch 14 is the pipeline diameter + 0.5 meters working surface + 1.5 meters burial depth. The semi-circular diameter is 5 mm larger than the outer diameter of the accident pipeline 12.

[0026] S11. On the ground, weld one end of the connecting pipe 11 to the elbow, set a lifting point at the other end, and use a truck crane to vertically lift the connecting pipe 11 into the steel casing 3 for butt welding with the accident pipe 12. During the process, the crane always maintains the adjustment posture and does not loosen the hook.

[0027] S12. After the pipe welding, testing and repair are completed, the working pit is backfilled. Only after the backfilling reaches the upper end of the connecting pipe 11 can the crane hook be removed and the upper bend of the connecting pipe 11 be constructed.

[0028] Similarly, the present invention is not limited to two stages, and can be used to "overlap" multiple working pits according to pipeline depth, geological conditions and site conditions.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

[0030] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for rapid installation and renovation of deeply buried pipelines in near-water saturated silty sand strata, characterized in that: Includes the following steps: S1. Based on the engineering and hydrogeology, the location, depth, and working face requirements of the accident pipeline (12), determine the working pit size, platform size, steel casing (3) size and Larssen steel sheet pile model from the inside out. Use computer software technology to simulate the working conditions, analyze the stress and calculate the structure to verify the local and overall stability of the structure. S2. Based on the soil conditions and surrounding environment, the shallow surface soil is reduced in depth. After determining the depth, a backhoe excavator is used for slope excavation. S3. Based on the engineering geology and hydrology, the excavation depth of the first-level working pit is determined by calculation, and the first-level Larssen steel sheet piles (1) are used for closed support; S4. Set up a first-level pipe well (5) around the first-level Larssen steel sheet pile (1) for dewatering and pressure reduction; S5. Excavate the first-level working pit, and at the same time install the waler and steel support of sheet piles (4). S6. After the first-level working pit is excavated to the predetermined elevation, it is moved back four meters inward from the first-level Larssen sheet pile (1) to serve as an operating platform for the construction of the second-level Larssen sheet pile (2); S7. The operating platform is hardened with C20 concrete. The hardened strip also serves as the concrete support strip (9) for the first-level steel sheet pile (1). At the same time, a fixed mold is used to reserve the position of the second-level pipe well (6). S8. Construct a secondary well (6) for dewatering. The bottom depth of the secondary well (6) shall exceed the weakly permeable silty clay layer below the quicksand layer by no less than two meters. S9. After the concrete of the concrete support strip (9) reaches a certain strength, several steel pipe wells (8) are uniformly constructed in the secondary working pit. The bottom of the steel pipe well (8) is buried in the quicksand layer. The bottom of the well is one meter away from the bottom of the quicksand layer. The quicksand layer is discharged by suction. The upper silty clay layer sinks by its own weight until it is lowered to the elevation of the accident pipeline (12). During the process, the steel pipe well is dismantled as it is lowered. At the same time, the walers of the secondary steel sheet piles (2) and steel supports (4) are erected. S10. The secondary working pit is lowered to the bottom elevation of the accident pipeline (12). The steel casing (3) is hoisted into the secondary working pit. The accident pipeline (12) is embedded in the gap (14) of the steel casing (3). The four corners of the steel casing (3) are pressed evenly with a vibratory hammer so that the bottom of the steel casing (3) is cut into the weakly permeable silty clay layer for no less than 1.5 meters. The top of the accident pipeline (12) must be tightly pressed against the gap (14). At the same time, the soil within 0.5 meters of the bottom of the accident pipeline (12) is removed manually. The gap (14) is sealed with sandbags and cotton cloth. The additional water pump (7) continuously pumps groundwater from inside and outside to ensure that the water level is controlled below 0.5 meters from the bottom of the pipe. S11. On the ground, weld one end of the connecting pipe (11) to the elbow and set a lifting point at the other end. Use a truck crane to vertically lift the connecting pipe (11) into the steel casing (3) and weld it to the accident pipe (12). During the process, the crane always maintains the adjustment posture and does not loosen the hook. S12. After the pipe welding, testing and repair are completed, the working pit is filled. Only after the filling reaches the upper end of the connecting pipe (11) can the crane hook be removed and the upper bend of the connecting pipe (11) be constructed.

2. The rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata according to claim 1, characterized in that: The bottom depth of a first-level well (5) shall exceed the weakly permeable silty clay layer below the quicksand layer by at least two meters.

3. The rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata according to claim 1, characterized in that: The top of the secondary Larssen sheet pile (2) is 700mm above the operating platform surface.

4. The rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata according to claim 1, characterized in that: The steel casing (3) is made of steel plates and steel sections welded together. It has no bottom or cover. The steel casing (3) is embedded in the middle of one side of the accident pipeline (12) and cut into a semi-circular door-shaped notch (14).

5. The rapid installation and renovation method for deep-buried pipelines in near-water saturated silty sand strata according to claim 1, characterized in that: The centerline of the waler and steel support (4) of the first-level Larssen sheet pile (1) should coincide with the centerline of the thickness of the concrete support strip (9).

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