Uninterrupted drainage pipeline replacement construction method for deeply-buried large-flow sewage pipeline above metro section

Abstract

The invention discloses a replacement construction method for a large-flow sewage pipeline deeply buried above a metro section and an uninterrupted drainage pipeline, and relates to the technical field of buildings, which comprises the following steps: measuring and determining the excavation depth of a foundation pit, selecting a Larsen steel sheet pile to support the foundation pit, adopting a double-pipe high-pressure jet grouting pile to carry out full reinforcement on a soil layer at the bottom of the pit, and carrying out construction. Daily monitoring the normal water level in an upstream sewage inspection well, excavating a foundation pit, excavating earthwork to the top of a current sewage pipe, installing a tongue-and-groove pipe as a downstream diversion well, installing a first section of L-shaped diversion steel pipe, installing a second section of L-shaped diversion steel pipe, extending into an open caisson hole which is chiseled away in advance, and connecting the first section of L-shaped diversion steel pipe and the second section of L-shaped diversion steel pipe; a chute is built between an open caisson and an inspection well, two corrugated pipes are temporarily blocked, after drainage is conducted through a temporary flow guide pipe, underwater building and plastering are conducted, foundation pit earthwork is excavated in a layered and segmented mode, the corrugated pipes are dismantled for drainage, a tongue-and-groove pipeline is installed, a DN1500 reinforced concrete pipeline is replaced in situ, and finally upstream and downstream temporary blocking parts are dismantled to restore smoothness of the pipeline.

Description

Technical Field

[0001] The present invention relates to the field of engineering construction technology, and in particular to the field of underground pipeline construction, and specifically to an uninterrupted drainage pipeline replacement construction method for a deep-buried large-flow sewage pipeline above a subway section. Background Art

[0002] With the rapid construction of urban rail transit, the subway network has gradually taken shape and continued to improve. Most of the operating subway tunnels are located under the main roads of the city, and the pipelines under the roads are crisscrossed. There are many problems such as poor operation and use in the later stage due to pipeline elevation conflicts.

[0003] In the existing technology, the elevation of the sewage pipe conflicts with the elevation of the intersection of the plane position of the heating pipe, and the original sewage pipe is temporarily connected under the thermal pipe using two pipes. However, due to the large discharge volume of the sewage pipe, the diameter of the pipe temporarily connected at the intersection node cannot meet the surrounding sewage discharge needs, causing the sewage pipe upstream to be blocked all year round. If the existing sewage pipe is abolished and the jacking is re-implemented, all kinds of surrounding municipal pipes need to cooperate in the relocation, which requires the cooperation of multiple departments, complicated approval, increased construction costs, longer construction period, and many uncontrollable factors, increasing the risk of subway operation. Summary of the invention

[0004] In order to solve the problems that the current urban drainage pipes are located above the shield section of rail transit, and the drainage is poor due to disrepair or long-term clogging of the pipes, which cannot meet the original usage needs, and further line changes require the involvement of various surrounding pipe networks for auxiliary cooperation, involving many departments, increasing construction costs, and extending the construction period, the present invention provides an uninterrupted drainage pipe replacement construction method for deeply buried large-flow sewage pipes above the subway section.

[0005] The present invention is implemented by the following technologies: The present invention provides a construction method for replacing an uninterrupted drainage pipe of a deep-buried large-flow sewage pipe above a subway section, which specifically includes the following steps: a. Construction preparation Actual measurements are taken of the sewage pipes, asphalt pavement and top of shield tunnel segments in the upstream and downstream sewage inspection wells. The elevations of the outer bottom of the pipes and top of the shield tunnel segments are calculated based on the measurement data to determine the excavation depth of the foundation pit, base reinforcement and thickness.

[0006] b. Foundation pit support PU400×170×15.5 (Q295P) type Larsen steel sheet piles are selected for foundation pit support. The Larsen steel sheet piles are exposed 1.2m above the ground. During the steel sheet pile insertion process, the pile top elevation and exposed length are strictly controlled to ensure the safety of the shield section.

[0007] c. High-pressure jet grouting pile reinforcement According to the measurement and calculation, the minimum vertical clearance between the bottom of the foundation pit and the operating area is 5.26m. Before the excavation of the foundation pit, double-tube high-pressure rotary jet piles are used to fully reinforce the soil layer at the bottom of the pit. The length of the pile body is 3m below the bottom of the foundation pit.

[0008] d. Excavation of foundation pit and support erection in diversion area In order to effectively control the floating deformation of the operating tunnel caused by earth unloading and ensure the safety of the tunnel structure, the foundation pit excavation adopts zoned, layered and segmented excavation. The foundation pit includes two sections: the diversion area and the pipeline replacement area. The length of each section is 5m and the thickness of each layer does not exceed 2m.

[0009] Based on the daily monitoring of the water level in the upstream sewage inspection well, in order to cooperate with the sewage pipe replacement construction, buried U-shaped diversion steel pipes are used for diversion; Specifically, the foundation pit is excavated in the diversion area, and the excavation depth of the foundation pit in the diversion area is 3.7m, which is the normal water level upstream. The foundation pit is excavated in two layers, the first layer of earthwork excavation depth is 1.7m, and the second layer of earthwork excavation depth is 2m; the foundation pit is excavated in the pipeline replacement area, and the foundation pit is excavated in four layers, the first layer of excavation depth is 1.7m, the second layer of excavation depth is 2m, the third layer of excavation depth is 1.95m, and the fourth layer of excavation depth is 2m; After the excavation of the first foundation pit is completed, the first wall and support are erected; Specifically, a mechanical working platform is reserved at one end of the foundation pit, and a backhoe is arranged to excavate the first layer of earthwork below the first steel support elevation from the end farthest from the mechanical working platform and gradually approach the end of the mechanical working platform, and the dump truck is used to load the earth and transport it out; After the first layer of earth excavation is completed, the first layer of steel perimeter purlins will be installed. After the first steel perimeter purlin is installed and two steel supports are erected, the excavation will be withdrawn from the end farthest from the mechanical working platform to the end close to the mechanical working platform. Every 5m of excavation, two steel supports will be erected, and another excavator will be added to excavate the next layer of earth and continue to withdraw.

[0010] e. Construction of upstream and downstream diversion wells and installation of diversion pipes According to the center line of the existing sewage pipe downstream in the foundation pit, excavate earth to the top of the existing sewage pipe, install a tongue-and-groove pipe as the downstream diversion well, install the first section of the L-shaped diversion steel pipe, and backfill the earth within 3m around the diversion well; The drainage pipe hole is chiseled out on the caisson wall, and the second section of the L-shaped diversion steel pipe is installed and extended into the caisson hole chiseled out in advance; the first section of the L-shaped diversion steel pipe is connected to the second section of the L-shaped diversion steel pipe; the pipe joints and caisson joints are sealed, and a chute is built between the caisson and the inspection well; First, remove the downspout, C20 bottom concrete and existing sewage pipe wall in the downstream diversion well, and remove the inspection well shaft in the upstream caisson.

[0011] The specific steps include: ea, downstream diversion well and diversion pipe construction According to the center line of the existing sewage pipe downstream in the foundation pit, manual labor and mechanical excavation are used to reach the top of the existing sewage pipe, and a tongue-and-groove pipe is installed as a downstream diversion well. The axis of the tongue-and-groove pipe is perpendicular to the axis of the existing sewage pipe. The elevation of the downstream water surface is determined according to the elevation of the upstream water surface and the 1% longitudinal slope of the water flow, and a hole with a diameter of 0.85m is chiseled out. The first section of the L-shaped diversion steel pipe with a total length of 10.3m and a diameter of DN800mm is installed in the hole, using water-tight internal and external grouting.

[0012] After the first section of the L-shaped diversion steel pipe is installed, backfill the soil within 3m around the diversion well to the bottom of the pavement structure layer and compact it to ensure that the compaction degree is not less than 0.95 to prevent rainwater from soaking the backfill soil and causing the tongue-and-groove pipe to slide and become unstable; After the backfill is completed, in order to ensure the stability of the soil around the inspection well during the subsequent diversion process, the inside of the tongue-and-groove pipe is manually cleaned and filled to 30 cm below the outer top of the sewage pipe, and C20 bottom sealing concrete is poured inside the tongue-and-groove pipe to 20 cm above the inner bottom of the tongue-and-groove pipe.

[0013] eb, upstream diversion well and diversion pipe construction The upstream sewage well adopts the form of an inspection well inside a caisson. The space between the caisson and the inspection well is filled with 37 lime soil. The 37 lime soil filled in the caisson is manually chiseled vertically with a pneumatic pick and discarded outside. After manual excavation to the normal sewage water level, the drainage pipe hole is chiseled out of the caisson wall. According to the angle of the installed downstream diversion pipe, the diameter of the chiseled hole is determined to be 0.95m; the second section of the L-shaped diversion steel pipe with a total length of 8.8m and a diameter of DN800mm is installed and extended into the caisson hole chiseled in advance; the first section of the L-shaped diversion steel pipe and the second section of the L-shaped diversion steel pipe Connection: The joints of the first section of the L-shaped diversion steel pipe and the second section of the L-shaped diversion steel pipe are connected by spot welding of steel plates and wrapped 360° with 1mm iron sheets; C20 concrete is used to seal the pipe joints and caisson joints to ensure the overall stability of the diversion steel pipe after sewage diversion; the chute is built between the caisson and the inspection well. In order to improve the construction efficiency, 600mm long × 240mm wide × 200mm high concrete aerated blocks are used to build the flow channel. The building height is 0.8m, and the bottom of the chute is sealed with manually mixed concrete.

[0014] ec, upstream and downstream diversion well connection construction The connection operation is carried out during the low-peak water usage period. First, the downspout in the downstream diversion well is chiseled out, and the C20 bottom sealing concrete and the existing sewage pipe wall are manually chiseled out with a pneumatic pick. The chiseling thickness is 0.35m and the downspout diameter is 1m. The inspection well shaft in the upstream caisson is chiseled out, and the diameter of the hole is 0.8m.

[0015] f. Seal the upstream sewage inspection well The upstream inspection well is sealed by professional divers who dive into the inspection well. They first use two steel plates with a length of 1m, a width of 0.8m and a thickness of 1cm to seal the two DN600mm corrugated pipes using water pressure adsorption force. After the water level rises and drains through the temporary diversion pipe, professional divers carry standard bricks and pre-mixed leak-proof king to dive into the inspection well to carry out underwater construction and plastering of 24 sealing walls in the upstream inspection well.

[0016] g, airbag plugging in the downstream pipeline When the water flow in the upstream sewage inspection well rises and is diverted through the diversion pipe, a 1.5m diameter high-pressure airbag is placed in the sewage pipe on one side of the downstream diversion well. To ensure the smooth removal of the subsequent airbag, U-shaped clips are used at both ends of the high-pressure airbag to tie it to the steel support through a 15m long steel wire rope. The high-pressure airbag is pushed into the sewage pipe to inflate and seal it.

[0017] h, backfilling of foundation pit at diversion pipe After the sewage diversion is completed, the foundation pit at the diversion pipe is backfilled to the bottom of the road structure layer in time. The backfill material is backfilled with the soil excavated from the foundation pit, and the backfill soil within 1m above the top of the pipe is compacted with a manual rammer.

[0018] i. Excavation of foundation pit in pipeline replacement area Excavate the foundation pit in sections, layers and segments. The length of each segment is consistent with step d, that is, the length of each segment is 5m and the thickness of each layer does not exceed 2m.

[0019] j. Pipeline removal An excavator is used to dismantle the existing pipeline, namely the DN600mm corrugated pipe, with a dismantling length of 5m. After the dismantling work is completed, a water pump is lowered to drain the accumulated water in the foundation pit.

[0020] k. Concrete pipe installation Use 15cm thick C20 cushion concrete for pouring. After the concrete strength reaches 5Mpa, install the tongue-and-groove pipes one by one from downstream to upstream. The pipe foundation is a 180°C20 concrete foundation. When pouring concrete, pour and vibrate symmetrically on both sides. The pipe interface is wrapped 360° with wire mesh and M10 cement mortar. After the cement mortar reaches 2.5Mpa, use C20 anti-seepage concrete for 360° full wrapping to avoid water seepage.

[0021] l. Upstream and downstream blockage removal After the sewage pipe connection construction is completed, professional divers dive into the upstream sewage inspection well and use a jackhammer to manually dismantle the upstream blocking wall. The removed brick residue is put into a barrel and lifted and discarded by the workers on the well. After the upstream blocking wall is completely dismantled, the high-pressure airbag in the downstream pipeline is deflated and lifted out. Specifically, a 25t truck crane is used to pull a long steel wire rope to lift the high-pressure airbag out of the downstream diversion well.

[0022] m, upstream and downstream diversion wells plugged A circular steel plate with a thickness of 1cm and a diameter of 1.1m of Q235b is used to cover and seal the upper water outlet of the pipe in the downstream diversion well. The diameter of the upper water outlet of the pipe in the downstream diversion well is 1m, and 30cm thick C20 concrete is poured on the upper part of the circular steel plate. Standard bricks and water-tight materials are used to restore the inspection well shaft in the upstream diversion well. After dismantling the brick chute in the caisson, medium and coarse sand is backfilled to the bottom of the road structure layer.

[0023] n. Backfilling of foundation pit in pipeline replacement area The soil excavated from the foundation pit is used for backfilling. The backfill soil within 1m above the top of the pipeline is made of clay with poor permeability, which is compacted using a manual rammer.

[0024] o, support structure removal After the foundation pit is backfilled and compacted, remove the steel sheet piles. Specifically, first use a pile driver to clamp the head of the steel sheet pile and vibrate it for 1 to 2 minutes to loosen the soil around the steel sheet pile, produce "liquefaction", reduce the friction of the soil on the pile, and then slowly vibrate and pull it upwards. When pulling out the pile, pay attention to the load of the pile driver. If it is difficult or impossible to pull it up, stop pulling out the pile. You can first inject a little downwards and then push it up. Repeat this process until the pile is pulled out.

[0025] p, fill the gaps in the soil layer with sand After the steel sheet piles of the supporting structure are removed, sandy soil with a fineness modulus of 2.5~3.0 is used to backfill the gaps in the soil layer. Before backfilling, a sand filling construction platform and a sand filling bucket are set at the hole mouth, and the sandy soil is poured into the sand filling bucket, and the sand filling speed is controlled; after the sand filling is completed, it is compacted and compacted using a manual rammer.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The uninterrupted drainage pipe replacement construction method for deeply buried large-flow sewage pipes above subway sections designed by the present invention solves the problems of narrow site and tight construction period by proposing partial relocation of thermal pipes at pipe intersection nodes and temporary diversion of sewage pipes, and replacing the deeply buried large-flow sewage pipes in situ while ensuring uninterrupted drainage. It forms an uninterrupted drainage pipe replacement construction method for deeply buried large-flow sewage pipes above subway sections, which is largely suitable for pipe replacement construction of deeply buried, large-flow sewage pipes located above urban main roads and rail transit shield sections.

[0027] This method has high construction efficiency and short construction period. It can temporarily divert the sewage pipe while ensuring uninterrupted drainage. The open-cut pipe replacement construction period is short. After the support system and base reinforcement work are completed, it only takes one day to complete the pipe replacement and restore the drainage pipeline, which can greatly save the overall construction period.

[0028] This method requires less work for pipeline relocation and occupies less temporary construction area, which is conducive to controlling the settlement and deformation of surrounding buildings and roads. If the sewage pipe is replaced by jacking, all kinds of surrounding municipal pipe networks need to cooperate in the relocation, which requires a lot of external coordination and occupies too much area of ​​the city's main roads, which is not conducive to vehicle traffic. With this method, only the sewage pipes that cause siltation need to be replaced, which greatly reduces the workload, and only some lanes of the city's main roads need to be closed during construction, which is conducive to vehicle traffic and settlement and deformation control.

[0029] This method is beneficial to controlling soil erosion and has little impact on urban rail shield sections. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in detail below.

[0031] The construction method for replacing the uninterrupted drainage pipe of the deeply buried large-flow sewage pipe above the subway section, this embodiment takes a street station of the first phase of a certain line as an example, the elevation of the sewage pipe parallel to the east-west direction of the north end of the station conflicts with the elevation of the intersection of the plane position of the DN1000mm heating pipe in the north-south direction of the road. The original DN1500mm sewage pipe is temporarily connected with two DN600mm corrugated pipes under the thermal pipe. Since the diameter of the pipe temporarily connected at the intersection node cannot meet the surrounding sewage discharge needs, it causes the sewage pipe upstream to be blocked all year round. The corrugated pipe temporarily connected at the intersection node needs to be replaced. Since there are many municipal pipe networks under the main roads in the city and the traffic volume is large, this method is used for replacement construction; specifically including the following steps: a. Construction preparation Actual measurements were taken of the sewage pipes, asphalt pavements and tops of the shield tunnel segments in the upstream and downstream sewage inspection wells. The elevations of the outer bottom of the pipes and the tops of the shield tunnel segments were calculated based on the measurement data. The excavation depth of the foundation pit was determined to be 7.65m below the existing road surface, and the burial depth of the top covering soil of the Jinnan left line shield tunnel segment was determined to be 12.91m below the existing road surface.

[0032] b. Foundation pit support PU400×170×15.5 (Q295P) type Larsen steel sheet piles with a length of 12m are selected for foundation pit support. The Larsen steel sheet piles are 1.2m above the ground. During the steel sheet pile insertion process, the pile top elevation and exposed length are strictly controlled to ensure the safety of the shield section.

[0033] c. High-pressure jet grouting pile reinforcement According to the measurement and calculation, the minimum vertical clearance between the bottom of the foundation pit and the operating area is 5.26m. Before the excavation of the foundation pit, Φ600mm@400mm double-tube high-pressure rotary jet piles are used to fully reinforce the soil layer at the bottom of the pit. The length of the pile body is 3m below the bottom of the foundation pit. The high-pressure rotary jet piles use 42.5 grade ordinary Portland cement, the water-cement ratio of cement slurry is 0.45~0.55, and the cement content should be 20% of the natural mass of the soil.

[0034] Before starting the construction of high-pressure jet jet piles every day, technical personnel will review the existing ground elevation and calculate the depth from the ground to the pile bottom. During the construction process, the drill rod length and lifting speed are strictly controlled to ensure the safety of the shield section and the effective pile length.

[0035] d. Excavation of foundation pit and support erection in diversion area In order to effectively control the floating deformation of the operating tunnel caused by earth unloading and ensure the safety of the tunnel structure, the foundation pit excavation adopts zoned, layered and segmented excavation. The foundation pit includes two sections: the diversion area and the pipeline replacement area. The length of each section is 5m and the thickness of each layer does not exceed 2m.

[0036] Based on the daily monitoring of the water level in the upstream sewage inspection well, in order to cooperate with the sewage pipe replacement construction, buried U-shaped diversion steel pipes are used for diversion; Specifically, the foundation pit is excavated in the diversion area, and the excavation depth of the foundation pit in the diversion area is 3.7m, which is the normal water level upstream. The foundation pit is excavated in two layers, the first layer of earthwork excavation depth is 1.7m, and the second layer of earthwork excavation depth is 2m; the foundation pit is excavated in the pipeline replacement area, and the foundation pit is excavated in four layers, the first layer of excavation depth is 1.7m, the second layer of excavation depth is 2m, the third layer of excavation depth is 1.95m, and the fourth layer of excavation depth is 2m; After the excavation of the first foundation pit is completed, the first wall and support are erected; Specifically, a mechanical working platform is reserved at one end of the foundation pit, and a backhoe is arranged to excavate the first layer of earthwork below the first steel support elevation from the end farthest from the mechanical working platform and gradually approach the end of the mechanical working platform, and the dump truck is used to load the earth and transport it out; After the first layer of earth excavation is completed, the first layer of steel perimeter purlins will be installed. After the first steel perimeter purlin is installed and two steel supports are erected, the excavation will be withdrawn from the end farthest from the mechanical working platform to the end close to the mechanical working platform. Every 5m of excavation, two steel supports will be erected, and another excavator will be added to excavate the next layer of earth and continue to withdraw.

[0037] e. Construction of upstream and downstream diversion wells and installation of diversion pipes ea, downstream diversion well and diversion pipe construction According to the center line of the existing sewage pipe downstream in the foundation pit, earth is excavated to the top of the existing sewage pipe using manual labor and machinery, and a tongue-and-groove pipe with an inner diameter of 1200mm is installed as a downstream diversion well. The axis of the tongue-and-groove pipe is perpendicular to the axis of the existing sewage pipe. The elevation of the downstream water surface is determined according to the elevation of the upstream water surface and the 1% longitudinal slope of the water flow, and a hole with a diameter of 0.85m is chiseled out. The first section of the L-shaped diversion steel pipe with a total length of 10.3m and a diameter of DN800mm is installed in the hole, using water-tight internal and external joints.

[0038] After the first section of the L-shaped diversion steel pipe is installed, backfill the soil within 3m around the diversion well to the bottom of the pavement structure layer and compact it to ensure that the compaction degree is not less than 0.95 to prevent rainwater from soaking the backfill soil and causing the tongue-and-groove pipe to slide and become unstable; After the backfill is completed, in order to ensure the stability of the soil around the inspection well during the subsequent diversion process, the inside of the tongue-and-groove pipe is manually cleaned and filled to 30 cm below the outer top of the sewage pipe, and C20 bottom sealing concrete is poured inside the tongue-and-groove pipe to 20 cm above the inner bottom of the tongue-and-groove pipe.

[0039] eb, upstream diversion well and diversion pipe construction The upstream sewage well adopts the form of an inspection well inside a caisson. The space between the caisson and the inspection well is filled with 37 lime soil. The 37 lime soil filled in the caisson is manually chiseled vertically with a pneumatic pick and discarded outside. After manual excavation to the normal sewage water level, the drainage pipe hole is chiseled out of the caisson wall. According to the angle of the installed downstream diversion pipe, the diameter of the chiseled hole is determined to be 0.95m; the second section of the L-shaped diversion steel pipe with a total length of 8.8m and a diameter of DN800mm is installed and extended into the caisson hole chiseled in advance; the first section of the L-shaped diversion steel pipe and the second section of the L-shaped diversion steel pipe Connection: The joints of the first section of the L-shaped diversion steel pipe and the second section of the L-shaped diversion steel pipe are connected by spot welding of steel plates and wrapped 360° with 1mm iron sheets; C20 concrete is used to seal the pipe joints and caisson joints to ensure the overall stability of the diversion steel pipe after sewage diversion; the chute is built between the caisson and the inspection well. In order to improve the construction efficiency, 600mm long × 240mm wide × 200mm high concrete aerated blocks are used to build the flow channel. The building height is 0.8m, and the bottom of the chute is sealed with manually mixed concrete.

[0040] ec, upstream and downstream diversion well connection construction The connection operation is carried out during the low-peak water usage period. First, the downspout in the downstream diversion well is chiseled out, and the C20 bottom sealing concrete and the existing sewage pipe wall are manually chiseled out with a pneumatic pick. The chiseling thickness is 0.35m and the downspout diameter is 1m. The inspection well shaft in the upstream caisson is chiseled out, and the diameter of the hole is 0.8m.

[0041] f. Seal the upstream sewage inspection well The upstream inspection well is sealed by combining sealing steel plates with 24 sealing walls. Since the upstream sewage inspection well is silted all year round, the water level is high and the water pressure adsorption force is large. In order to ensure the safety of divers and the quality of brick-built sealing walls, two steel plates with a length of 1m, a width of 0.8m and a thickness of 1cm are first used to use the water pressure adsorption force to seal the two DN600mm corrugated pipes. After the water level rises and drains through the temporary diversion pipe, professional divers carry standard bricks and pre-mixed leak-proof king to carry out underwater sealing, masonry and plastering in the upstream inspection well. Before sealing, technical briefings, safety briefings, pre-job training and other work must be done well. A diving test must be carried out before going into the water, and the oxygen supply must be checked to ensure the safety of various tools and equipment to ensure the safety of divers.

[0042] g, airbag plugging in the downstream pipeline When the water flow in the upstream sewage inspection well rises and is diverted through the diversion pipe, a high-pressure airbag with a diameter of 1.5m is placed in the sewage pipe on one side of the diversion well. To ensure the smooth removal of the subsequent airbag, both ends of the high-pressure airbag are tied to the steel support with a 15m long steel wire rope using U-shaped buckles. The high-pressure airbag is pushed into the sewage pipe to be inflated and sealed; the high-pressure airbag is pushed by an excavator in cooperation with professional divers. Safety work must be done well in the sealing work to ensure the oxygen supply of the divers, the installation of safety ropes, and the wearing of protective equipment.

[0043] h, backfilling of foundation pit at diversion pipe After the sewage diversion is completed, the foundation pit of the diversion pipe shall be backfilled to the road structure layer in time. The backfill material shall be backfilled with the soil excavated from the foundation pit, and the backfill soil within 1m above the top of the pipe shall be compacted with a manual tamping machine. The backfilling of soil shall be carried out synchronously, evenly and symmetrically, and the backfill shall be compacted layer by layer, with each layer no thicker than 30cm and the compaction degree of the backfill no less than 95%.

[0044] i. Excavation of foundation pit in pipeline replacement area The foundation pit earthwork is excavated in zones, layers and sections, and the length of each section is consistent with step d, that is, the length of each section is 5m. In this embodiment, the excavation depth of the foundation pit earthwork is 7.65m, and the thickness of each layer does not exceed 2m. The excavation depth of the first layer is 1.7m, the second layer is 2m, the third layer is 1.95m, and the fourth layer is 2m.

[0045] j. Pipeline removal An excavator was used to dismantle the existing pipeline, with a demolition length of 5m. After the demolition work was completed, a water pump was lowered to drain the accumulated water in the foundation pit.

[0046] k. Concrete pipe installation Use 15cm thick C20 cushion concrete for pouring, and install the tongue-and-groove pipe after the concrete strength reaches 5Mpa. Use Grade III DN1500 tongue-and-groove pipe to replace the sewage pipe with a replacement length of 4m. The pipe is hoisted manually with a 25t truck crane. During installation, the pipe is fastened by manual lifting belts and the truck crane is used to lift the pipe. During the installation, the central axis and elevation of the pipe are strictly controlled. The pipes are installed one by one from downstream to upstream. The pipe foundation is a 180°C20 concrete foundation. When pouring concrete, the two sides are poured and vibrated symmetrically. The pipe interface is wrapped 360° with wire mesh and M10 cement mortar. After the cement mortar reaches 2.5Mpa, C20 anti-seepage concrete is used for 360° full wrapping to avoid water seepage.

[0047] l. Upstream and downstream blockage removal After the sewage pipe connection construction is completed, professional divers dive into the upstream sewage inspection well and use a jackhammer to manually dismantle the upstream blocking wall. The removed brick residue is put into a barrel and lifted and discarded by the workers on the well. After the upstream blocking wall is completely dismantled, the high-pressure airbag in the downstream pipeline is deflated and lifted out. Specifically, a 25t truck crane is used to pull a long steel wire rope to lift the high-pressure airbag out of the downstream diversion well.

[0048] m, upstream and downstream diversion wells plugged A circular steel plate with a thickness of 1cm and a diameter of 1.1m of Q235b is used to cover and seal the upper water outlet of the pipe in the downstream diversion well. The diameter of the upper water outlet of the pipe in the downstream diversion well is 1m, and 30cm thick C20 concrete is poured on the upper part of the circular steel plate. Standard bricks and water-tight materials are used to restore the inspection well shaft in the upstream diversion well. After dismantling the brick chute in the caisson, medium and coarse sand is backfilled to the bottom of the road structure layer.

[0049] n. Backfilling of foundation pit in pipeline replacement area Use the earth excavated from the foundation pit for backfilling. The backfill soil within 1m above the top of the pipeline shall be clay with poor permeability and compacted with a manual rammer. The backfilling of earth shall be carried out synchronously, evenly and symmetrically. The backfill shall be compacted layer by layer. The thickness of each layer shall not exceed 30cm and the compaction degree of the backfill shall not be less than 95%.

[0050] o, support structure removal After the foundation pit is backfilled and compacted, remove the steel sheet piles. Specifically, first use a pile driver to clamp the head of the steel sheet pile and vibrate it for 1 to 2 minutes to loosen the soil around the steel sheet pile, produce "liquefaction", reduce the friction of the soil on the pile, and then slowly vibrate and pull it upwards. When pulling out the pile, pay attention to the load of the pile driver. If it is difficult or impossible to pull it up, stop pulling out the pile. You can first inject a little downwards and then push it up. Repeat this process until the pile is pulled out.

[0051] p, fill the gaps in the soil layer with sand After the steel sheet piles of the supporting structure are removed, sandy soil with a fineness modulus between 2.5 and 3.0 is used to backfill the gaps in the soil layer. Before backfilling, a sand filling construction platform and a sand filling bucket are set at the hole mouth, and the sandy soil is poured into the sand filling bucket. The sand filling speed is controlled. After the sand filling is completed, it is compacted and compacted using a manual rammer.

[0052] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various deformations and changes. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The construction method for replacing the uninterrupted drainage pipe of the deep buried large-flow sewage pipe above the subway section is characterized by: The following steps are involved: a. Construction preparation Conduct actual measurements of sewage pipes, asphalt pavement and shield section segment tops in upstream and downstream sewage inspection wells, calculate the elevation of the outer bottom of the pipe and shield section segment tops based on the measurement data, and determine the excavation depth of the foundation pit, base reinforcement and thickness; b. Foundation pit support Larsen steel sheet piles are used for foundation pit support, and the Larsen steel sheet piles are exposed 1.2m above the ground; c. High-pressure jet grouting pile reinforcement According to the measured and calculated minimum vertical clearance between the bottom of the foundation pit and the operating area, double-tube high-pressure jet grouting piles are used to fully reinforce the soil layer at the bottom of the pit, with the length of the pile body being 3m below the bottom of the foundation pit; d. Excavation of foundation pit and support erection in diversion area The excavation of foundation pit is carried out in zones, layers and sections. The foundation pit includes two sections: diversion area and pipeline replacement area. The length of each section is 5m and the thickness of each layer does not exceed 2m. According to the daily monitoring of the normal water level in the upstream sewage inspection well, the diversion is carried out by burying U-shaped diversion steel pipes. The excavation depth of the foundation pit in the diversion area is the normal water level upstream. After the excavation of the first layer of foundation pit is completed, the first enclosure and support are erected; e. Construction of upstream and downstream diversion wells and installation of diversion pipes According to the center line of the existing sewage pipe downstream in the foundation pit, excavate earth to the top of the existing sewage pipe, install a tongue-and-groove pipe as the downstream diversion well, install the first section of the L-shaped diversion steel pipe, and backfill the earth; The drainage pipe hole is chiseled out on the caisson wall, and the second section of the L-shaped diversion steel pipe is installed and extended into the caisson hole chiseled out in advance; the first section of the L-shaped diversion steel pipe is connected to the second section of the L-shaped diversion steel pipe; the pipe joints and caisson joints are sealed, and a chute is built between the caisson and the inspection well; First, remove the downspout and C20 bottom sealing concrete in the downstream diversion well and the existing sewage pipe wall, and remove the inspection well shaft in the upstream caisson; f. Seal the upstream sewage inspection well First, use two steel plates to block the two corrugated pipes by water pressure adsorption. After the water level rises and drains through the temporary diversion pipe, build and plaster the underwater 24 blocking wall. g, airbag plugging in the downstream pipeline When the water flow in the upstream sewage inspection well rises and is diverted through the diversion pipe, a high-pressure airbag is placed in the sewage pipe on one side of the downstream diversion well. Both ends of the high-pressure airbag are tied to the steel support through a long steel wire rope with a U-shaped buckle, and the high-pressure airbag is pushed into the sewage pipe to inflate and seal; h, backfilling of foundation pit at diversion pipe After the sewage is diverted, the foundation pit at the diversion pipe is backfilled to under the road structure layer; i. Excavation of foundation pit in pipeline replacement area Excavate the foundation pit in sections, layers and segments. The length of each segment is consistent with step d, and the thickness of each layer does not exceed 2m; j. Pipeline removal Excavators were used to dismantle the existing pipelines, and after the dismantling work was completed, the water in the foundation pit was pumped out; k. Concrete pipe installation Use C20 cushion concrete pouring, and install the tongue-and-groove pipes after the concrete strength reaches 5Mpa. Install one by one from downstream to upstream. The pipeline foundation is 180°C20 concrete foundation. The pipeline interface is wrapped with 360° steel mesh and M10 cement mortar tape. After the cement mortar tape reaches 2.5Mpa, C20 impermeable concrete is used for 360° full wrapping. l. Upstream and downstream blockage removal The upstream blocking wall is manually dismantled, and the dismantled brick slag is put into a bucket and lifted out for disposal; after the upstream blocking wall is completely dismantled, the high-pressure airbag in the downstream pipeline is deflated and lifted out; m, upstream and downstream diversion wells plugged A circular steel plate is used to cover and seal the upper water outlet of the pipe in the downstream diversion well. A 30cm thick C20 concrete is poured on the upper part of the circular steel plate. A manhole shaft is built in the upstream diversion well to restore the inspection well. After removing the brick chute in the caisson, medium-coarse sand is backfilled to the bottom of the road structure layer. n. Backfilling of foundation pit in pipeline replacement area The excavated earth in the foundation pit is used for backfilling. The backfill soil within 1m above the top of the pipeline is made of poorly permeable clay soil and compacted; o, support structure removal After the foundation pit is backfilled and compacted, remove the steel sheet piles; p, fill the gaps in the soil layer with sand After the steel sheet piles of the supporting structure are removed, sandy soil with a fineness modulus of 2.5~3.0 is used to backfill the gaps in the soil layer.

2. The uninterrupted drainage pipe replacement construction method for a deep-buried high-flow sewage pipe above a subway section according to claim 1 is characterized by: Step e specifically includes the following steps: ea, downstream diversion well and diversion pipe construction According to the center line of the existing sewage pipe downstream in the foundation pit, use manual and mechanical excavation to the top of the existing sewage pipe, and install a tongue-and-groove pipe as a downstream diversion well. The axis of the tongue-and-groove pipe is perpendicular to the axis of the existing sewage pipe. According to the elevation of the upstream water surface and the 1% longitudinal slope of the water flow, the elevation of the downstream water surface is determined, and a hole is chiseled out. The first section of the L-shaped diversion steel pipe is installed in the hole, and watertight internal and external joints are used; After the first section of the L-shaped diversion steel pipe is installed, fill the diversion well with earth within 3m around it to the bottom of the pavement structure layer and compact it to ensure that the compaction degree is not less than 0.95; After the backfill is completed, the stability of the soil around the well is checked. The inside of the tongue-and-groove pipe is manually cleaned and filled with soil to 30 cm below the top of the sewage pipe, and C20 bottom sealing concrete is poured inside the tongue-and-groove pipe to 20 cm above the inner bottom of the tongue-and-groove pipe; eb, upstream diversion well and diversion pipe construction Manually chisel out the Sanqi lime soil filled in the caisson vertically and discard it. After manually excavating to the normal sewage water level, the drainage pipe hole is chiseled out on the caisson wall. The diameter of the chiseled hole is determined according to the angle of the installed downstream diversion pipe; the second section of the L-shaped diversion steel pipe is installed and extended into the caisson hole chiseled out in advance; the first section of the L-shaped diversion steel pipe is connected to the second section of the L-shaped diversion steel pipe; C20 concrete is used to seal the pipe joints and caisson joints; a chute is built between the caisson and the inspection well, and the bottom of the chute is sealed with manually mixed concrete; ec, upstream and downstream diversion well connection construction During the low-peak water usage period, the connection operation is carried out by first chiseling out the downspout in the downstream diversion well, and manually chiseling out the C20 bottom concrete and the existing sewage pipe wall. The chiseling thickness is 0.35m and the downspout diameter is 1m; the inspection well shaft in the upstream caisson is chiseled out, and the diameter of the hole is 0.8m.

3. The uninterrupted drainage pipe replacement construction method for a deep-buried high-flow sewage pipe above a subway section according to claim 1 is characterized by: In step c, according to the actual measurement data, the minimum vertical clearance between the bottom of the foundation pit and the rail transit shield section is 5.26m. Before the excavation of the foundation pit, Φ600mm@400mm double-tube high-pressure rotary jet piles are used to fully reinforce the soil layer at the bottom of the pit, and the length of the pile body is 3m below the bottom of the foundation pit.

4. The uninterrupted drainage pipe replacement construction method for a deep-buried high-flow sewage pipe above a subway section according to claim 1 is characterized by: In step d, a mechanical working platform is reserved at one end of the foundation pit, and a backhoe is arranged to excavate the first layer of earthwork below the first steel support elevation from the end away from the mechanical working platform and gradually approach the end of the mechanical working platform, and a dump truck is used to load the earth and transport it out; After the first layer of earth excavation is completed, the first layer of steel perimeter purlins will be installed. After the first steel perimeter purlin is installed and two steel supports are erected, the excavation will be withdrawn from the end farthest from the mechanical working platform to the end close to the mechanical working platform. Every 5m of excavation, two steel supports will be erected, and another excavator will be added to excavate the next layer of earth and continue to withdraw.

5. The uninterrupted drainage pipe replacement construction method for a deep-buried high-flow sewage pipe above a subway section according to claim 1 is characterized by: In steps d and i, the diversion area excavates a foundation pit in two layers, the first layer of earthwork excavation depth is 1.7m, and the second layer of earthwork excavation depth is 2m; The foundation pit is excavated in the pipeline replacement area, and the foundation pit is excavated in four layers. The excavation depth of the first layer is 1.7 meters, the second layer is 2 meters, the third layer is 1.95 meters, and the fourth layer is 2 meters.

6. The uninterrupted drainage pipe replacement construction method for a deep-buried high-flow sewage pipe above a subway section according to claim 2 is characterized by: In step eb, the connection between the first section of the L-shaped guide steel pipe and the second section of the L-shaped guide steel pipe is connected by spot welding of steel plates, and is wrapped 360° with 1mm iron sheets, and then the pipe joints and caisson joints are sealed with C20 concrete.