Double-small-pipe water stop structure for blocking deep well of deep foundation pit and construction technology

Abstract

The invention relates to the technical field of deep foundation pit deep well plugging, and discloses a double-small-pipe water stop structure for deep foundation pit deep well plugging and a construction technology, the deep foundation pit deep well comprises a well pipe and a cushion layer located on the periphery of the well pipe, and the double-small-pipe water stop structure is arranged on the well pipe. According to the double-small-pipe water stopping structure for blocking the deep well of the deep foundation pit and the construction technology, a multiple waterproof sealing system of waterproof structural layer water stopping, double water stopping wing ring water stopping and fire-fighting plug terminal sealing is constructed; an underground water channeling channel at the joint of the cushion layer and the well casing is completely blocked, and root water prevention is achieved; the double water stop wing rings extend the underground water seepage path, increase the water seepage resistance, form a structural water-resisting layer and achieve middle water blocking. The double-sealing structure of the fire-fighting plug realizes tight plugging of a terminal in a water-carrying state, and is matched with basic sealing of the sealing steel plate, so that leakage paths are cut off from outside fluid channeling and inside leakage.

Description

Technical Field

[0001] This invention relates to the field of deep foundation pit and deep well sealing technology, specifically to a double-small-pipe water-stopping structure and construction process for sealing deep foundation pits and deep wells. Background Technology

[0002] Basement water seepage is a long-standing quality problem in the construction industry, with complex and diverse causes. Poor sealing of deep wells is one of the important factors contributing to water seepage in basement floors. In deep foundation pit engineering, deep well dewatering is widely used for groundwater control operations. However, when stopping pumping and sealing deep wells, the traditional sealing process of "grouting and filling + welding pipe sealing" commonly used in the industry is prone to leakage risks.

[0003] The existing deep foundation pit and deep well plugging technology, taking a 700mm drainage well and a 273mm pressure relief well as examples, has the following structural design and construction process: Structural design: A single large-diameter well pipe 11 is used as the dewatering and sealing carrier. An annular waterstop plate 12 is welded on the outside of the well pipe 11. The outer diameter of the annular waterstop plate 12 is 650mm and it is 550mm away from the bottom excavation surface of the traditional cushion layer 13. This is used to increase the length of groundwater bypass and prevent groundwater from flowing along the outer wall of the well pipe 11 to the basement floor slab 14.

[0004] Construction Process: Step 1: After dewatering, lower a 1-inch grouting pipe 15 into the well pipe 11, down to the bottom of the well pipe 11; Step 2: Fill the well pipe 11 with layers of gravel 16, simultaneously injecting cement grout 17 with a water-cement ratio of 0.8-1.0 through the grouting pipe 15. Pull up the grouting pipe 15 by 0.5-1.0m every 0.5-1.0m of grouting, and remove the grouting pipe 15 after grouting to the top surface of the gravel 16; Step 3: After observing for 2-4 hours and finding no significant rise in water level, pour concrete 18 into the well pipe 11, pouring the concrete 18 to a height of 100mm above the top surface of the basement floor slab 14; Step 4: After the concrete 18 has set, cut off the exposed well pipe 11 above the top surface of the floor slab 14, weld a steel plate 19 100mm below the top surface of the floor slab 14, and finally smooth the well opening with cement mortar 20 to complete the sealing.

[0005] The structural design and construction process based on the above technical features have inherent defects such as structural damage and susceptibility to leakage, as detailed below: Structural design defects: 1. The filling and sealing relies on the dual bonding of the concrete 18 of the base slab 14 with the outer wall of the well pipe 11, and the concrete 18 inside the well pipe 11 with the inner wall of the well pipe 11. The large diameter of the deep well pipe 11 results in a wide contact surface, making it easy for groundwater to flow along the bonding surface between the outer wall of the well pipe 11 and the surrounding concrete 18, forming a leakage channel; 2. The shrinkage of the concrete 18 is an inherent property of the material. At the same time, it is difficult for the concrete 18 to form a tight bond with the smooth inner pipe wall, which easily forms small gaps or even cracks, becoming a path for groundwater to seep from inside the well pipe 11; 3. The large-diameter well pipe 11 penetrates the base slab 14, causing the double-layer bidirectional reinforcement of the base slab 14 to be cut off at the well pipe 11, which cannot form a continuous stress system, weakening the integrity and stability of the base slab 14 structure and leaving potential quality hazards.

[0006] Construction process defects: The bonding between the melon seed chips 16 and the cement slurry 17 is unreliable, and the construction of concrete 18 inside the manhole is unreliable. Due to the difficulty of operation in the manhole space, the vibrating equipment cannot penetrate deeply, resulting in insufficient compaction. During construction, honeycomb pitting is very likely to occur, and voids are also easily formed at the bottom, making it impossible to form a continuous water barrier. In step 4, the welding of the steel plate 19 requires internal welding. The already poured base plate 14 concrete 18 must first be excavated and damaged around the manhole. At the same time, the welding quality depends on the worker's operation, and there is a risk of incomplete sealing.

[0007] Defects in adapting to working conditions: Under normal circumstances, deep foundation pits contain a certain amount of pressurized water. After the pumping stops, the water level will rise rapidly. Underwater grouting or concrete pouring is prone to segregation, which exacerbates the problem of incomplete sealing. Therefore, it cannot be adapted to working conditions with abundant groundwater and rapid replenishment. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a double-small-pipe water-stopping structure and construction process for sealing deep foundation pits and deep wells, thus solving the problems mentioned in the background.

[0009] This invention provides the following technical solution: a double-small-tube water-stopping structure and construction process for sealing deep foundation pits and deep wells, comprising a deep foundation pit and deep well including a well pipe body and a cushion layer located around the well pipe body, characterized in that the well pipe body is provided with a double-small-tube water-stopping structure, the double-small-tube water-stopping structure comprising: A dual-tube assembly includes a first steel pipe and a second steel pipe arranged in parallel, the first steel pipe and the second steel pipe being used to pass through the basement floor slab; Two sets of water-stop wing ring assemblies are respectively fixedly installed on the outer walls of the first steel pipe and the second steel pipe; A sealing steel plate is horizontally installed on the well casing body, and the sealing steel plate is sealed to the well casing body. The first steel pipe and the second steel pipe pass through the sealing steel plate and are sealed to the sealing steel plate. A waterproof structural layer is provided on the upper surface of the pad layer and folds upward to cover the inner wall of the well casing body and the outer walls of the first steel pipe and the second steel pipe. The sealing plug is detachably and sealingly connected to the first and second steel pipes.

[0010] Preferably, the first steel pipe is a pressure drain pipe for connecting to a pumping device, and the second steel pipe is a pressure inlet pipe for connecting to a pressure air source.

[0011] Preferably, both the first steel pipe and the second steel pipe are hot-dip galvanized seamless steel pipes, the diameter of the first steel pipe is 40mm, the diameter of the second steel pipe is 25mm, and the center distance between the two steel pipes is 70mm to 90mm.

[0012] Preferably, each set of water-stop wing ring assemblies includes an upper water-stop wing ring and a lower water-stop wing ring, which are arranged vertically at intervals. The upper water-stop wing ring is located 130mm to 170mm below the top surface of the basement floor slab, and the lower water-stop wing ring is located 130mm to 170mm above the bottom surface of the basement floor slab. The distance between the upper and lower water-stop wing rings is 280mm to 320mm. Both the upper and lower water-stop wing rings are circular steel plates with a thickness of 4mm to 6mm and a width of 90mm to 110mm. During installation, both the upper and lower water-stop wing rings are fully welded together.

[0013] Preferably, the sealing steel plate is a circular steel plate with a diameter that matches the inner diameter of the well casing body. The sealing steel plate has two through holes that match the outer diameters of the first steel pipe and the second steel pipe, respectively. The center-to-center distance between the two through holes is the same as the center-to-center distance between the first steel pipe and the second steel pipe. The outer edge of the sealing steel plate is fully welded to the inner wall of the well casing body. The first steel pipe and the second steel pipe pass through the through holes and are fully welded to the sealing steel plate.

[0014] Preferably, the waterproof structural layer includes a non-curing rubber asphalt waterproof coating layer and a polymer self-adhesive waterproof membrane layer arranged sequentially from bottom to top. The thickness of the waterproof coating layer is ≥2mm, the thickness of the waterproof membrane layer is ≥1.5mm, and the height of the waterproof structural layer folded upward from the upper surface of the padding layer is ≥80mm.

[0015] Preferably, the sealing plug includes a threaded plug and a sealing element. The top ends of the first steel pipe and the second steel pipe are provided with internal threads. The threaded plug is connected to the internal threads, and the sealing element is disposed between the threaded plug and the top end of the steel pipe to form a seal. The threaded plug is a brass internal thread plug with a built-in nitrile rubber sealing ring; the sealing element also includes PTFE tape wrapped around the internal thread.

[0016] A construction process for a double-small-pipe water-stop structure for sealing deep foundation pits and deep wells, comprising the following steps: Step S1, Scheme Optimization and Refinement: Conduct on-site research and optimize the construction scheme based on the research results; based on the optimized scheme, carry out drawing refinement design and economic analysis in parallel; when the results of drawing refinement or economic analysis do not meet the preset requirements, the problem is fed back to the scheme optimization step for iterative adjustment until a final scheme that meets the requirements is obtained; Step S2, Material Preparation and Inspection: Based on the final plan, select materials, prefabricate double small pipe components, water-stop wing rings and sealing steel plates, and conduct performance inspections on the incoming components, waterproof materials and sealing components; Step S3, On-site construction: After the materials have passed inspection, on-site construction is carried out, including constructing a waterproof structural layer on the subbase, installing sealing steel plates, installing double small pipe assemblies, and pouring concrete for the basement floor slab. Step S4, sealing operation: After the on-site construction is completed and the sealing conditions are met, stop the deep well dewatering and install the sealing plug at the top of the double small pipes for sealing; Step S5, Effect Check: Check the effect of the sealing operation.

[0017] Preferably, step S3, on-site construction specifically includes: Waterproof structural layer construction: A waterproof structural layer is constructed on the bedding layer around the deep well, so that the waterproof structural layer covers the upper surface of the bedding layer and folds upward to the inner wall of the well casing; Sealing steel plate installation: Install a sealing steel plate inside the well casing body, and seal and fix the outer edge of the sealing steel plate to the inner wall of the well casing body; Installation of double tubes and water-stop rings: Pass the double tube assembly with pre-welded water-stop rings through the sealing steel plate, and seal and fix the double tubes to the sealing steel plate; The basement floor slab is poured, allowing the two small pipes to pass through the slab with their tops flush with the top surface of the slab. Step S4: During the sealing operation, after stopping the deep well dewatering, first observe the rise of the water level in the well. After the water level stabilizes, install the sealing plug. When installing the sealing plug, use a torque wrench to tighten it in stages. After installation, verify the effect and observe whether there is any leakage in the base plate. After the effect verification is qualified, use cement mortar to smooth the surface of the plug and the surrounding base plate.

[0018] Preferably, in step S2, material preparation and inspection, if the material inspection fails, the process returns to the drawing refinement step for design review and adjustment. Step S4: If the sealing effect is not good during the sealing operation, return to the on-site construction steps for rectification.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs a multi-layer waterproof sealing system consisting of a waterproof structural layer for water stoppage, a double-layer water-stopping ring for water blocking, and a fire-resistant plug for terminal sealing. Non-curing rubber asphalt waterproof coating and polymer self-adhesive waterproof membrane are applied from the padding layer upwards, completely sealing the groundwater flow channels at the connection between the padding layer and the well pipe, achieving root waterproofing. The double-layer water-stopping rings extend the groundwater seepage path and increase seepage resistance, forming a structural waterproof layer to achieve mid-section water blocking. The fire-resistant plug's double-sealing structure ensures a tight terminal seal even when wet, and combined with the base seal of the sealing steel plate, it cuts off the seepage path from both external flow and internal leakage.

[0020] 2. This invention abandons the complex process of traditional "grouting + concrete pouring + internal welding" and adopts a dry construction mode of on-site assembly of prefabricated components: the double small pipe assembly, water-stop ring, and sealing steel plate are all prefabricated in the factory, and only the waterproof structural layer construction, component installation and fixing, and bottom slab concrete pouring are required on site; in the sealing stage, fire-fighting special sealing plugs are used for one-time screw sealing in a water-filled state, without waiting for concrete curing, achieving immediate sealing and inspection. This process mode brings multiple technical benefits: First, by using the construction sequence of "installing double small pipes first, then binding bottom slab reinforcement", and controlling the distance between the reinforcement and the steel pipe ≥50mm, the structural damage problem of forced cutting of reinforcement due to large-diameter well pipes penetrating the bottom slab in traditional processes is avoided, and the original bottom slab stress system is completely preserved; Second, the destructive excavation and internal welding operations in traditional processes are eliminated, eliminating the hidden dangers of unstable quality caused by human operation; Third, the single well sealing construction time is shortened by more than 50% compared with traditional solutions, greatly improving construction efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the existing technology structure; Figure 2 This is a schematic diagram of the double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to the present invention; Figure 3 For the present invention Figure 2 Enlarged structural diagram at position A in the middle; Figure 4 This is a schematic diagram of the construction process of the double-small-pipe water-stop structure for sealing deep foundation pits and deep wells according to the present invention; Figure 5 This is a schematic diagram of the structure of an embodiment of the pressure relief well plugging of the present invention.

[0022] In the diagram: 1. Well casing body; 2. Bedding layer; 3. Double small pipe assembly; 31. First steel pipe; 32. Second steel pipe; 4. Water-stop wing ring assembly; 41. Upper water-stop wing ring; 42. Lower water-stop wing ring; 5. Sealing steel plate; 6. Waterproof structural layer; 61. Waterproof coating layer; 62. Waterproof membrane layer; 7. Sealing plug; 71. Threaded plug; 72. Sealing element; 8. Basement floor slab; 11. Well casing; 12. Circular waterstop plate; 13. Traditional bedding layer; 14. Base plate; 15. Grouting pipe; 16. Grouting material; 17. Cement grout; 18. Concrete; 19. Steel plate; 20. Cement mortar. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 2-3 A double-tube water-stopping structure for sealing deep foundation pits and deep wells includes a well pipe body 1 and a cushion layer 2 surrounding the well pipe body 1. The well pipe is vertically buried at the bottom of the foundation pit. The well pipe body 1 is provided with a double-tube water-stopping structure, which includes a double-tube assembly 3, two sets of water-stopping wing ring assemblies 4, a sealing steel plate 5, a waterproof structural layer 6, and a sealing plug 7. The dual-pipe assembly 3 includes a first steel pipe 31 and a second steel pipe 32 arranged in parallel. The first steel pipe 31 and the second steel pipe 32 pass through the basement floor slab 8. The first steel pipe 31 is a hot-dip galvanized seamless steel pipe with a diameter of Φ40mm and a length of 10m, made of Q235B, and is used to connect to the pressure drainage pipe of the pumping equipment. The second steel pipe 32 is a hot-dip galvanized seamless steel pipe with a diameter of Φ25mm and a length of 1m, also made of Q235B, and serves as a pressure air inlet pipe to maintain anti-buoyancy. The center-to-center distance between the first steel pipe 31 and the second steel pipe 32 is adjustable within the range of 70mm to 90mm, preferably 80mm, with a verticality deviation controlled to ≤1%. After installation, the tops of both steel pipes are flush with the structural surface of the basement floor slab 8, with a deviation ≤±2mm. Two sets of water-stop wing ring assemblies 4 are respectively fixed on the outer walls of the first steel pipe 31 and the second steel pipe 32. Each set of water-stop wing ring assemblies 4 includes an upper water-stop wing ring 41 and a lower water-stop wing ring 42. The thickness of a single water-stop wing ring is 4mm to 6mm, preferably 5mm; the width is 90mm to 110mm, preferably 100mm; the upper water-stop wing ring 41 is located 130mm to 170mm from the top surface of the basement floor slab 8, preferably 150mm; the lower water-stop wing ring 42... The distance from the bottom surface of the base plate is 130mm to 170mm, preferably 150mm; the distance between the upper water-stop ring 41 and the lower water-stop ring 42 is 280mm to 320mm, preferably 300mm; the installation position deviation is ≤ ±5mm; the upper water-stop ring 41 and the lower water-stop ring 42 are fixed by full welding, the weld height is consistent with the thickness of the water-stop ring, the weld is continuously arranged along the inner circumferential direction of the water-stop ring, and the weld slag is removed after welding and two coats of anti-rust paint are applied. A sealing steel plate 5 is horizontally mounted on the well casing body 1, and is sealed to the well casing body 1. The first steel pipe 31 and the second steel pipe 32 pass through the sealing steel plate 5 and are sealed to it. The sealing steel plate 5 is a circular steel plate with a diameter matching the inner diameter of the well casing body 1. Two through holes, each matching the outer diameter of the first steel pipe 31 and the second steel pipe 32, are opened on the sealing steel plate 5. The center-to-center distance between the two through holes is the same as the center-to-center distance between the first steel pipe 31 and the second steel pipe 32. The outer edge of the sealing steel plate 5 is fully welded to the inner wall of the well casing body 1. The first steel pipe 31 and the second steel pipe 32 pass through the through holes and are fully welded to the sealing steel plate 5. Plate 5 is made of 10mm thick Q235B round steel plate with a diameter of 690mm, which is suitable for Φ700mm drainage wells. The center of the sealing steel plate 5 has two round through holes with diameters of 42mm, which are suitable for Φ40mm first steel pipe 31 and 27mm, which are suitable for Φ25mm second steel pipe 32. The center distance between the two holes is 80mm, which is consistent with the center distance between the two small pipes of the second steel pipe 32 and the second steel pipe 32. It is 50mm away from the top surface of the pad layer 2. The outer ring of the sealing steel plate 5 is fully welded to the inner wall of the original deep well. After the two small pipes pass through the openings of the sealing steel plate 5, they are fully welded to the sealing steel plate 5 to form a basic sealing and fixing structure. Waterproof structural layer 6 is set on the upper surface of the pad layer 2 and folds upward to cover the inner wall of the well body 1 and the outer walls of the first steel pipe 31 and the second steel pipe 32. Waterproof structural layer 6 is composed of a non-curing rubber asphalt waterproof coating layer 61 and a polymer self-adhesive waterproof membrane layer 62 arranged sequentially from bottom to top. The thickness of the waterproof coating layer 61 is ≥2mm and the thickness of the waterproof membrane layer 62 is ≥1.5mm. Waterproof structural layer 6 is constructed starting from the upper surface of the pad layer 2 and folds upward along the pad layer 2 to the inner wall of the original large pipe well and the outer wall of the double small pipes. The total upward height is ≥80mm. The sealing plug 7 is detachably and sealingly connected to the first steel pipe 31 and the second steel pipe 32. The sealing plug 7 includes a threaded plug 71 and a sealing element 72. The top ends of the first steel pipe 31 and the second steel pipe 32 are provided with internal threads. The threaded plug 71 is connected to the internal threads. The sealing element 72 is disposed between the threaded plug 71 and the top end of the steel pipe to form a seal. The threaded plug 71 is a brass internal thread plug with a built-in nitrile rubber sealing ring. The sealing element 72 also includes PTFE tape wrapped around the internal threads.

[0025] A multi-layer waterproof sealing structure was constructed, consisting of a waterproof structural layer 6 for water sealing, double-layer water-stopping wing rings for water blocking, and a fire-resistant plug for terminal sealing. The waterproof structural layer 6 folds upward from the upper surface of the pad layer 2, covering the well pipe and the outer wall of the double small pipe assembly 3, completely sealing the groundwater flow channel at the connection between the pad layer 2 and the well pipe, achieving root-level external protection. The double-layer water-stopping wing rings are arranged vertically at intervals on the outer wall of the double small pipe assembly 3, extending the groundwater seepage path and increasing seepage resistance, forming a central water blocking. The sealing steel plate 5 is fully welded to the inner wall of the well pipe and the double small pipes to form a basic seal. In conjunction with the detachable sealing plug 7, it is connected to the internal threaded seal at the top of the double small pipes to achieve a tight terminal seal under water conditions, completing the top internal seal. This triple waterproof system works synergistically to cut off the seepage path from both external flow and internal leakage, avoiding leakage problems.

[0026] Please see Figure 4 A construction process for a double-small-pipe water-stop structure for sealing deep foundation pits and deep wells includes the following steps: Step S1, Scheme Optimization and Refinement: Conduct on-site research, collecting geological data of the foundation pit, groundwater data, deep well layout drawings, and bottom slab structural drawings. Based on the research results, optimize the construction scheme, clarifying key technical parameters such as the location of the double small pipes, the installation height of the water-stop ring, and the fixing method of the sealing steel plate 5. Based on the optimized scheme, conduct parallel detailed design and economic analysis. Detailed design includes: the positional relationship between the double small pipes and the bottom slab reinforcement, detailed node treatment of the waterproof structural layer 6, and detailed welding drawings of the sealing steel plate 5 and the well pipe. Economic analysis includes: material cost accounting, labor cost accounting, and assessment of the impact on the construction period. When the results of the drawing refinement or economic analysis do not meet the preset requirements, such as the inability to guarantee the spacing of the reinforcing bars or the cost exceeding the budget, the problem is fed back to the scheme optimization step for iterative adjustment until a final scheme that meets the requirements is obtained. Step S2, Material Preparation and Inspection: Based on the final scheme, material selection is carried out, and prefabrication is performed on the double small pipe assembly 3, two sets of water-stop wing ring assemblies 4, and sealing steel plate 5. Specific prefabrication requirements are as follows: Double small tube assembly 3: The first steel pipe 31 is made of Φ40mm hot-dip galvanized seamless steel pipe, and the second steel pipe 32 is made of Φ25mm hot-dip galvanized seamless steel pipe. The two steel pipes are arranged in parallel with a center distance of 80mm, and two water-stop wing rings are welded and fixed to the outside of the double small tubes according to the design height. Sealing steel plate 5: A circular steel plate is machined according to the diameter of the well pipe, and through holes corresponding to the two small pipes are opened. The diameter of the holes is 2mm larger than the diameter of the steel pipe. Two sets of water-stop wing ring assemblies 4: made of 5mm thick Q235 steel plate cut into rings, the inner diameter of which is adapted to the outer diameter of the double small tube assembly 3.

[0027] After the components arrive on site, they are inspected for appearance, dimensions, and performance. Three sets of double small pipe and plug assemblies are randomly selected for a water pressure test. The test pressure is 1.5 times the working pressure, and the pressure holding time is not less than 30 minutes. No leakage is considered qualified. Waterproof coatings and waterproof membranes are tested for physical properties according to specifications. The sealing plugs are checked for the integrity of the sealing rings and the precision of the thread processing. They can only be used after all inspections are qualified.

[0028] If the material inspection fails, return to the drawing refinement step for design review and adjustment, and reselect or optimize the design scheme; Step S3, On-site Construction: After the materials have passed inspection, on-site construction will commence, including: I. Construction of Waterproofing Layer 6: Clean the surface of the subbase 2 of loose debris and accumulated water to ensure the base layer is flat, dry, and free of sharp objects. Starting from the upper surface of the subbase 2, apply a 2mm thick layer of non-curing rubber asphalt waterproofing coating evenly, without any missed areas or accumulation. Before the waterproofing coating cures, immediately lay a 1.5mm thick polymer self-adhesive waterproof membrane upwards from the outer side of the large manhole to the double small pipes, with an upward extension height consistent with the waterproofing coating (≥80mm). The membrane and waterproofing coating layer 61 should be tightly bonded, without any hollow areas or air bubbles. Treat the membrane overlaps with a special sealant and seal the edges with sealant to ensure the continuity and integrity of the waterproofing layer.

[0029] II. Installation of Sealing Steel Plate 5: Place the processed sealing steel plate 5 horizontally inside the large manhole, adjust its position so that the steel plate is 50mm from the top surface of the padding layer 2, and ensure that the horizontal deviation of the steel plate is ≤±3mm. Fully weld the outer ring of the steel plate to the inner wall of the large manhole. The weld should be continuous, uniform, free of slag inclusions, porosity, incomplete penetration, and other defects to ensure a tight seal and secure fixation.

[0030] 3. Installation of the double-pipe assembly and water-stop ring: Insert the double-pipe assembly 3, with the pre-welded water-stop ring, vertically through the corresponding opening in the sealing steel plate 5. Adjust the verticality of the double-pipe assembly to a deviation of ≤1‰, i.e., a deviation of ≤1mm per meter. After adjustment, fully weld the double-pipe assembly to the opening in the sealing steel plate 5, forming a continuous ring around the circumference of the steel pipe. After welding, remove the weld slag and perform a penetration test to ensure no leakage.

[0031] IV. Coordinated Construction of the Base Slab and Main Structure: Reinforcement binding of the basement base slab (8 sections). During binding, ensure the spacing between the reinforcement bars and the sealing steel plate (5 sections) and the double small pipes is ≥50mm. Cutting or bending the reinforcement bars to accommodate the steel pipe positions is strictly prohibited; the original load-bearing system of the base slab must be completely preserved. Before pouring the base slab concrete, verify the positions of the steel pipes and plates. Concrete will be poured only after confirmation. During pouring, a designated person will monitor the steel pipes and plates to prevent displacement due to concrete impact or vibration. Vibration should avoid the area within 50mm of the steel pipe roots; manual tamping should be used to ensure the concrete in this area is dense. Concrete should be poured to the design elevation, ensuring the top of the double small pipes is flush with the top surface of the base slab, with a deviation ≤±2mm. Step S4, Sealing Operation: After the on-site construction is completed and the sealing conditions are met, the sealing operation is carried out, including: I. Preparations before sealing: Stop pumping water from the deep well 3 days before sealing, observe the rise of the water level in the well, and record the water level changes daily. Once the water level stabilizes and the change is ≤50mm for 24 consecutive hours, prepare for the sealing operation. Check the integrity of the sealing ring of the sealing plug 7 and clean the debris from the top of the double small pipes.

[0032] II. Water Sealing: Use a torque wrench to tighten the sealing plug in 7 stages to the top of the first steel pipe 31 and the second steel pipe 32. Tighten initially to 60% of the set torque, check for any abnormalities, and then tighten again to 100% of the set torque. The set torque is determined according to the plug specifications, generally 30–50 N·m. Immediately after tightening, wipe the area around the plug and observe for any water leakage. If leakage is found, remove the plug, rewrap it with Teflon tape, and tighten again.

[0033] If the sealing effect is not good and water continues to seep, return to the on-site construction steps for rectification, check for defects in the welds of the waterproof structural layer 6 and the sealing steel plate 5, or at the connection between the double small pipes and the steel plate, repair them, and then re-seal the work.

[0034] The double-tube water-stop structure of this invention can flexibly adjust its size parameters according to the type of deep well. Please refer to [link / reference]. Figure 5 In another embodiment: Example of a Φ273mm pressure relief well adaptation: For the pressure relief well with a diameter of Φ273mm, the diameter of the sealing steel plate 5 is adjusted to 263mm, while the plate thickness remains at 10mm. The double small pipe assembly 3 still uses Φ40mm and Φ25mm hot-dip galvanized seamless steel pipes with a center-to-center spacing of 80mm. The installation height and spacing of the two water-stopping rings remain unchanged: the upper ring is 150mm below the top surface of the base plate, and the lower ring is 150mm above the bottom surface of the base plate, with a spacing of 300mm. The construction requirements for the waterproof structural layer 6 are the same as those for sealing the drainage well, with an upward turning height ≥80mm. The specifications of the sealing plug 7 remain unchanged.

[0035] For deep wells with a burial depth exceeding 10m, the length of the first steel pipe 31 can be customized according to the actual well depth, while the length of the second steel pipe 32 remains unchanged at 1m. The verticality control standard for the double small pipe assembly 3 remains ≤1‰ to ensure installation accuracy. The installation position of the water-stop ring assembly 4 is adjusted based on the structural surface of the basement floor slab 8, always maintaining a relative positional relationship of the upper ring being 150mm below the top surface of the floor slab and the lower ring being 150mm above the bottom surface of the floor slab.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A double-pipe water-stopping structure for sealing deep foundation pits and deep wells, comprising a well casing body (1) and a cushion layer (2) surrounding the well casing body (1), characterized in that, The well casing body (1) is provided with a double-small-tube water-stop structure, which includes: The dual-tube assembly (3) includes a first steel pipe (31) and a second steel pipe (32) arranged in parallel, the first steel pipe (31) and the second steel pipe (32) being used to pass through the basement floor slab (8); Two sets of water-stop wing ring assemblies (4) are respectively fixed on the outer walls of the first steel pipe (31) and the second steel pipe (32); A sealing steel plate (5) is horizontally set on the well casing body (1). The sealing steel plate (5) is sealed to the well casing body (1). The first steel pipe (31) and the second steel pipe (32) pass through the sealing steel plate (5) and are sealed to the sealing steel plate (5). A waterproof structural layer (6) is provided on the upper surface of the pad layer (2) and is folded upward to cover the inner wall of the well body (1) and the outer walls of the first steel pipe (31) and the second steel pipe (32); The sealing plug (7) is detachably and sealingly connected to the first steel pipe (31) and the second steel pipe (32).

2. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 1, characterized in that, The first steel pipe (31) is a pressure drain pipe for connecting to a pumping equipment, and the second steel pipe (32) is a pressure inlet pipe for connecting to a pressure air source.

3. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 2, characterized in that, The first steel pipe (31) and the second steel pipe (32) are both hot-dip galvanized seamless steel pipes. The diameter of the first steel pipe (31) is 40mm, the diameter of the second steel pipe (32) is 25mm, and the center distance between the two steel pipes is 70mm to 90mm.

4. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 1, characterized in that, Each set of water-stop wing ring assemblies (4) includes an upper water-stop wing ring (41) and a lower water-stop wing ring (42). The upper water-stop wing ring (41) and the lower water-stop wing ring (42) are arranged vertically at intervals. The upper water-stop wing ring (41) is located 130mm to 170mm below the top surface of the basement floor slab (8), and the lower water-stop wing ring (42) is located 130mm to 170mm above the bottom surface of the basement floor slab (8). The distance between the upper water-stop wing ring (41) and the lower water-stop wing ring (42) is 280mm to 320mm. The upper water-stop wing ring (41) and the lower water-stop wing ring (42) are both circular steel plates with a thickness of 4mm to 6mm and a width of 90mm to 110mm. During installation, the upper water-stop wing ring (41) and the lower water-stop wing ring (42) are both installed by full welding.

5. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 1, characterized in that, The sealing steel plate (5) is a circular steel plate with a diameter that matches the inner diameter of the well pipe body (1). The sealing steel plate (5) has two through holes that match the outer diameters of the first steel pipe (31) and the second steel pipe (32), respectively. The center distance between the two through holes is the same as the center distance between the first steel pipe (31) and the second steel pipe (32). The outer edge of the sealing steel plate (5) is fully welded to the inner wall of the well pipe body (1). The first steel pipe (31) and the second steel pipe (32) pass through the through holes and are fully welded to the sealing steel plate (5).

6. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 1, characterized in that, The waterproof structural layer (6) includes a non-curing rubber asphalt waterproof coating layer (61) and a polymer self-adhesive waterproof membrane layer (62) arranged sequentially from bottom to top. The thickness of the waterproof coating layer (61) is ≥2mm, the thickness of the waterproof membrane layer (62) is ≥1.5mm, and the height of the waterproof structural layer (6) folded upward from the upper surface of the padding layer (2) is ≥80mm.

7. The double-small-pipe water-stopping structure for sealing deep foundation pits and deep wells according to claim 1, characterized in that, The sealing plug (7) includes a threaded plug (71) and a sealing element (72). The top ends of the first steel pipe (31) and the second steel pipe (32) are provided with internal threads. The threaded plug (71) is connected to the internal threads. The sealing element (72) is disposed between the threaded plug (71) and the top end of the steel pipe to form a seal. The threaded plug (71) is a brass internal thread plug with a built-in nitrile rubber sealing ring; the sealing element (72) also includes PTFE tape wrapped around the internal thread.

8. A construction process for a double-small-pipe water-stopping structure for sealing deep foundation pits and wells according to any one of claims 1 to 8, characterized in that, The process includes the following steps: Step S1, Scheme Optimization and Refinement: Conduct on-site research and optimize the construction scheme based on the research results; based on the optimized scheme, carry out drawing refinement design and economic analysis in parallel; when the results of drawing refinement or economic analysis do not meet the preset requirements, the problem is fed back to the scheme optimization step for iterative adjustment until a final scheme that meets the requirements is obtained; Step S2, Material preparation and inspection: Based on the final scheme, select materials, prefabricate double small pipe components (3), water-stop wing rings and sealing steel plates (5), and conduct performance inspections on the incoming components, waterproof materials and sealing components; Step S3, on-site construction: After the materials have passed inspection, on-site construction is carried out, including constructing a waterproof structural layer (6) on the cushion layer (2), installing a sealing steel plate (5), installing a double small pipe assembly (3), and pouring concrete for the basement floor slab (8). Step S4, sealing operation: After the on-site construction is completed and the sealing conditions are met, stop the deep well dewatering and install the sealing plug (7) to the top of the double small pipe for sealing; Step S5, Effect Check: Check the effect of the sealing operation.

9. The construction process of the double-small-pipe water-stop structure for sealing deep foundation pits and deep wells as described in claim 8, characterized in that, Step S3, on-site construction specifically includes: Waterproof structural layer (6) construction: Waterproof structural layer (6) is constructed on the cushion layer (2) around the deep well, so that the waterproof structural layer (6) covers the upper surface of the cushion layer (2) and folds upward to the inner wall of the well casing (1); Sealing steel plate (5) installation: Install sealing steel plate (5) inside well casing (1) and seal and fix the outer edge of sealing steel plate (5) to the inner wall of well casing (1); Installation of double tubes and water-stop wing ring: Pass the double tube assembly (3) with the water-stop wing ring pre-welded through the sealing steel plate (5), and seal and fix the double tubes to the sealing steel plate (5); The basement slab is poured with concrete (8) so that the two small pipes pass through the basement slab and their tops are flush with the top surface of the basement slab. Step S4: During the sealing operation, after stopping the deep well dewatering, first observe the rise of the water level in the well, and then install the sealing plug (7) after the water level stabilizes; when installing the sealing plug (7), use a torque wrench to tighten it in stages; after installation, verify the effect and observe whether there is any leakage in the bottom plate; after the effect verification is qualified, use cement mortar to smooth the surface of the plug and the surrounding bottom plate.

10. The construction process of the double-small-pipe water-stop structure for sealing deep foundation pits and deep wells according to claim 9, characterized in that, In step S2, material preparation and inspection, if the material inspection fails, the process returns to the drawing refinement step for design review and adjustment. Step S4: If the sealing effect is not good during the sealing operation, return to the on-site construction steps for rectification.

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