Implementation method for plugging joint by lengthening steel casing in pile foundation construction

Abstract

The invention discloses an implementation method for plugging a joint by lengthening a steel casing in pile foundation construction. The implementation process comprises the following steps: step 1, building an overwater working platform; step 2, machining a lengthened section steel casing; 3, the state of a top opening of the underwater section pile casing is checked; 4, the lengthened section pile casing is lifted to enter water for butt joint; 5, underwater butt joint and fixation of the pile casing are carried out; step 6, reinforcing the joint and blocking the gap; and 7, plugging is conducted in the mode that outer wrapping hoop concrete is poured at the joint through an underwater method. A set of complete and efficient construction process is formed from processing, butt joint, reinforcement and plugging of the pile casing, the construction quality and efficiency of plugging the joint by lengthening the steel pile casing in pile foundation construction are greatly improved, rework and delay in the construction process are reduced, the construction cost is reduced, and remarkable economic benefits and social benefits are achieved. The method adopts an underwater method to cast the externally-wrapped hoop concrete, the leaking stoppage success rate is high, and operation is easy and convenient.

Description

Technical Field

[0001] The invention relates to the field of underwater pile foundation construction, and in particular to a method for implementing a pile foundation construction extending steel casing to seal joints. Background Art

[0002] In the field of underwater pile foundation construction, steel casings have a series of vital functions. They not only store drilling wall mud and provide a stable environment for drilling operations, but also need to maintain the overpressure head in the hole, effectively support the hole wall, ensure the safety and stability of the drilling process, play a drilling guide role, and bear the load of the drilling rig and platform in certain circumstances. However, this field is currently facing many severe challenges. On the one hand, natural environmental factors bring great troubles to the construction. Rapid changes in water levels are a common problem, which often leads to the steel casing being submerged in water after being buried because it cannot be extended to above the construction water level in time, seriously affecting the construction progress and quality. On the other hand, the uneven processing quality of the casing makes it very easy for the casing joints to leak. Once the joint leaks, the mud in the hole will leak out in large quantities, and the water head in the hole will be difficult to maintain, which will make it impossible for the pile foundation construction to proceed normally. What is even more difficult is that traditional technical means are not effective in plugging leaks in steel casing butt joints. Practical experience shows that underwater welding is difficult to ensure due to the complex underwater environment; the bonding performance of adhesives is greatly reduced in underwater environments, and both are extremely difficult to achieve successful plugging. Although there are certain conventional operating methods for the existing water work platform construction, steel casing processing and docking processes, there is a lack of efficient and reliable solutions for key links such as casing tilt, docking gaps and plugging leaks. For example, the traditional casing docking guide method is not accurate enough, which makes docking difficult; for the plugging of casing joint gaps, previous methods cannot effectively prevent underwater concrete leakage. In this context, there is an urgent need for a new, efficient and reliable implementation method for extending steel casings in pile foundation construction to plug joints, so as to overcome the many difficulties in existing technologies, promote the advancement of underwater pile foundation construction technology, and ensure the smooth implementation of construction projects.

[0003] Steel casing is an important device that is indispensable for pile foundation construction using the underwater drilling method. It plays an important role in storing drilling wall mud, maintaining overpressure head in the hole, supporting the hole wall, guiding the drilling, and bearing the load of the drilling rig and platform when necessary. During the construction of underwater pile foundation, the steel casing may be submerged due to rapid changes in water level, resulting in the failure to extend it above the construction water level in time after being buried; or due to processing quality reasons, the casing joint leaks, resulting in the leakage of mud in the hole, making it impossible to maintain the water head in the hole and thus making it impossible to construct the pile foundation. In response to such situations, this method provides a method for extending steel casing underwater and reliably sealing the joints to prevent water leakage. Summary of the invention

[0004] Therefore, in order to solve the above-mentioned shortcomings, the present invention provides a method for implementing the plugging of seams by extending steel casings in pile foundation construction. From the processing, docking, reinforcement to plugging of casings, a complete and efficient construction process is formed, which greatly improves the construction quality and efficiency of plugging seams by extending steel casings in pile foundation construction, reduces rework and delays in the construction process, reduces construction costs, and has significant economic and social benefits. This method adopts the underwater method of casting the outer hoop concrete, has a high plugging success rate, and is easy to operate.

[0005] The present invention is implemented by constructing a method for extending steel casing for sealing joints in pile foundation construction, which is characterized by the following implementation process: Step 1: Set up the water working platform: set up the beams and lay the panels by driving steel pipe piles, or use the hull, pontoon, etc. to set up the water working platform; Step 2, processing the extended steel casing: Process the steel casing according to the required length and diameter; weld 4 to 8 external guide positioning blocks at the lower end of the casing to be extended; Step 3: Divers check the top status of the underwater casing: Professional divers check the top status of the long casing to be connected, clean up the debris, and measure whether the top is level and round; Step 4: Lift the extended length casing and place it in water for docking: Use reliable lifting equipment and lifting methods to lift the extended length casing into water; the entry point is determined according to the theoretical center position of the casing; Step 5: Underwater docking and fixing of the casing: Under the guidance of the diving operators who have entered the water in advance, align the bottom of the extended casing with the top of the long casing to be connected, and use the guide block to guide the casing mouth to dock until it is in contact; Step 6: Reinforce the joints and seal the gaps: (6.1) Divers shall clean the outer wall of the casing within 0.5m above and below the joint to remove sludge, debris, and blocky and layered rust; (6.2) Perform underwater welding on the contact area of ​​the casing mouths at both ends of the joint to reinforce the joint; Step 7: Seal the leak by pouring outer hoop concrete at the joint underwater.

[0006] According to the method for implementing the extension of steel casing and sealing joints in pile foundation construction of the present invention, the characteristics are as follows: in step 2, the guide positioning block is trapezoidal, the slope is 1:3~1:5, and the length is 20~40cm; and 4~8 extension plate bolt connection holes are pre-made.

[0007] According to the method for implementing the plugging of joints by extending steel casing in pile foundation construction of the present invention, the feature is that: Step 3 also includes the following operations: if the casing is tilted but the enlarged inner diameter of the casing does not affect the passage of the drill bit, no treatment is performed. If the tilt causes a gap of more than 10 cm when the extended section of the casing is kept in a vertical state, underwater cutting and leveling should be performed; if the gap is within 10 cm, no cutting is performed, and thin iron sheet or steel mesh is used for external treatment during the extension.

[0008] According to the method for implementing the plugging of joints by extending steel casing in pile foundation construction of the present invention, the feature is that: Step 5 also includes the following operations: keep the lifting point partially stressed. The diver cuts and opens bolt connection holes at the top of the lower casing corresponding to the pre-made upper casing connection bolt positions, installs the connection plate, tightens the bolts, and after the connection is completed, the lifting point can be removed. And the external guide wedge is cut off.

[0009] According to the implementation method of the pile foundation construction extension steel casing plugging joints described in the present invention, it is characterized in that: in step 6.2, it also includes the following operations: plugging the gap that is difficult to avoid in the joint, the plugging method is to wrap the joint with 0.5mm thin iron sheet, or wrap it with multiple layers of dense wire mesh; the wrapped joint is ensured to be firmly overlapped, tensioned and fixed by pre-welding screws and screwing nuts on the outer wall of the casing. Note that the width of the wrapping material is only about 10cm wider than the two sides of the gap. Too wide will affect the subsequent plugging effect; the purpose of the plugging here is not to prevent the casing joint from leaking, but to prevent the underwater concrete to be poured for plugging in the subsequent links from leaking from the joints.

[0010] According to the method for implementing the extension of steel casing for sealing joints in pile foundation construction of the present invention, the method is characterized in that the specific decomposition process of step 7 is as follows: Step 7.1, a diver welds 4 to 6 positioning steel bars on the outer wall of the lower casing at a position about 0.5 to 0.8 m below the top of the casing. This device is used to accurately position the L-shaped trough plate in height during the subsequent underwater concrete pouring. Step 7.2, make the bottom side formwork of the joint plugging concrete ring: the skeleton can be made of thick steel bars, small angle steels and other materials, and covered with thin iron sheets; the iron sheets and the skeleton are tied and positioned firmly with fine iron wires; the inner ring diameter is about 3cm larger than the outer diameter of the casing; the outer ring diameter is determined by the thickness of the proposed plugging concrete block; the thickness is determined according to the internal head pressure difference borne by the joint when the casing is actually drilled. For example, if the hole needs to maintain a 5m overpressure head, the thickness is 40cm; the side form height is about 1m; Step 7.3, install hoop concrete reinforcement: arrange 2 circles of 4 steel bars with a diameter of φ12 or above in the L-shaped template, and sparsely arrange the frame reinforcement to form a skeleton; the gap between the steel bars should not affect the insertion of the bottom of the pouring conduit; Step 7.4, install the annular bottom side formwork: set at least 3 hanging ropes evenly arranged along the circumference on the ring formwork (the diameter of the hanging ropes shall be based on the ability to safely bear the total weight of the concrete to be poured for plugging), put the ring formwork on the upper and lower parts of the casing and put it into water, and lower it to the joint under the action of its own weight; if there is difficulty in the lowering process, heavy objects such as stones and iron blocks can be hung at the bottom of the ring side formwork to assist in lowering; the lower height positioning position should be h / 2 (h is the height of the side formwork) from the bottom formwork to the joint; use the positioning steel bars described in step 7.1 to assist in positioning; after positioning, the diver checks the gap between the template and the outer wall of the casing, and blocks and seals the gap greater than 3 cm; Step 7.5, pouring underwater concrete: install underwater concrete pouring conduit; the conduit diameter should not be greater than φ250mm so that it can be inserted into the L-shaped template groove; symmetrically install 3 sets of pouring conduits; according to the underwater pile foundation pouring process, fill the L-shaped template groove with underwater concrete of C30 or above by the method of simultaneous opening; after static curing to more than 90% strength, the casing can be put into use.

[0011] The present invention has the following advantages: (1) Efficient construction of working platform: The implementation method of the present invention provides a variety of ways to build working platforms on water. Whether it is to drive steel pipe piles, set beams and lay panels, or use hulls, pontoons, etc., it can be flexibly selected according to the actual construction environment, greatly improving the efficiency of working platform construction and laying a solid foundation for the smooth development of subsequent construction links. (2) Accurate guidance and docking of casing: When processing the extended steel casing, the welded 4-8 external trapezoidal guide positioning blocks, with a slope of 1:3-1:5 and a length of 20-40cm, can accurately guide the bottom of the extended casing to the top of the long casing to be connected during the underwater docking of the casing, significantly improving the accuracy and convenience of docking, effectively shortening the docking time, and reducing the difficulty of construction. (3) Reasonable handling of casing tilt: Through the careful inspection of the top of the underwater casing by professional divers, a reasonable treatment plan for the casing tilt problem has been formulated. When the enlarged inner diameter does not affect the drill bit, no treatment is done, thus reducing unnecessary construction operations. For the gap exceeding 10 cm due to the inclination, underwater cutting and leveling are carried out. For the gap within 10 cm, thin iron sheets and wire mesh are used for external treatment, thus ensuring the quality of the casing docking while taking into account the construction cost and efficiency. (4) Safe and reliable lifting and docking: Reliable lifting equipment and lifting methods are used, such as crane, gantry or floating crane, and the entry point is determined according to the theoretical center position of the casing. For waters with high flow rate, horizontal steel ropes are set at the root of the casing. These measures ensure the safety and stability of the lifting and entry into the water docking process of the extended casing, thus reducing the construction risk. (5) Firm casing docking and fixing: Under the guidance of the diving workers, the casing docking is completed using the guide block, and the diving workers cut and open the connection hole at the top of the casing corresponding to the bolt position, install the connection plate and tighten the bolts. This method makes the casing docking firm and reliable. After the docking is completed, the lifting point is removed and the external guide wedge is cut out, further optimizing the construction process. (6) Effective reinforcement and sealing of joints: Divers clean the outer wall of the casing within 0.5 m above and below the joints, creating good conditions for subsequent underwater welding and plugging work, and improving welding quality and plugging effect. The joints are wrapped with 0.5mm thin iron sheets or multiple layers of dense wire mesh, and the joints are firmly overlapped, tensioned and fixed by pre-welding screws and screwing nuts, which effectively prevents the subsequent underwater concrete from leaking from the joints. Compared with the traditional underwater welding and adhesive plugging methods, the innovative underwater method of pouring outer hoop concrete plugging has a high success rate and is easy to operate. A series of steps such as setting the positioning steel bar to assist the L-shaped groove plate in place, reasonably designing the annular bottom side mold, scientifically arranging the hoop concrete steel bars, accurately installing the annular bottom side mold, and using a suitable diameter of the pouring conduit to symmetrically pour underwater concrete are ensured to ensure the plugging effect, the sealing and stability of the steel casing, so that the overpressure head in the hole can be effectively maintained to ensure the normal progress of the pile foundation construction. (7) Improve construction quality and efficiency: The overall patent implementation method forms a complete and efficient construction process through optimization and innovation of each link, from casing processing, docking, reinforcement to plugging, which greatly improves the construction quality and efficiency of pile foundation construction to extend the steel casing to seal the joints, reduces rework and delays during construction, reduces construction costs, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of welding 4 to 8 external guide and positioning blocks at the lower end of the casing to be connected; Figure 2 It is a schematic diagram of underwater docking and fixing of casing; Figure 3 It is a schematic diagram of the installation of an annular bottom side mold on the casing; Figure 4 It is a schematic diagram of the installation of an annular bottom side mold on the casing; Figure 5 This is a schematic diagram of pouring underwater concrete. DETAILED DESCRIPTION

[0013] The following will be combined with the attached Figure 1-Figure 5 The present invention is described in detail, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] The present invention provides a method for underwater extension of steel casings and reliable sealing of joints to prevent water leakage. Basic principle: utilizing the characteristics of concrete that is easy to shape, has good fluidity and filling properties, and can be cast underwater, a hoop-shaped concrete block is cast outside the casing interface to seal the leak.

[0015] The implementation process of the present invention is as follows: Step 1, build a water working platform: set up beams and lay panels by driving steel pipe piles, or use hulls, pontoons, etc. to set up a water working platform.

[0016] Step 2, process the extended steel casing: process the steel casing according to the required length and diameter at a suitable work site on the shore. Weld 4 to 8 external guide positioning blocks to the lower end of the casing to be extended. (Depending on the casing diameter, use a decimal within d1.5, and a larger number for larger diameters). The guide block is trapezoidal, with a slope of 1:3~1:5 and a length of 20~40cm; and pre-make 4 to 8 bolt connection holes for the extension plate. (Use M24~M32 bolts), such as Figure 1 shown.

[0017] Step 3, divers check the top status of the underwater section of the casing: professional divers check the top status of the casing to be extended and clean up the debris. Measure whether the top is level and round. If the casing is tilted but the enlarged inner diameter of the casing does not affect the passage of the drill bit, no treatment is required. If the tilt causes a gap of more than 10cm when the extended section of the casing is kept vertical, underwater cutting and leveling should be performed; if the gap is within 10cm, no cutting is required, and thin iron sheet or wire mesh should be used for external treatment during the extension.

[0018] Step 4, hoist the extended casing into the water for docking: Use reliable hoisting equipment and hoisting methods (such as hoisting with a crane, gantry, etc. on a water working platform, or hoisting with a floating crane) to hoist the extended casing into the water. The entry point is determined according to the theoretical center position of the casing. For waters with a large flow rate, a horizontal steel rope is set at the root of the casing.

[0019] Step 5, underwater docking and fixing of the casing: Under the guidance of the diving workers who have entered the water in advance, align the bottom of the extended casing with the top of the long casing to be connected, and use the guide block to guide the casing mouth to dock until it is in contact. Keep the lifting point partially stressed. The diver cuts the bolt connection hole on the top of the lower casing corresponding to the pre-made upper casing connection bolt position, installs the connecting plate, tightens the bolts, and removes the lifting point after the docking is completed. And cut off the external guide wedge. If Figure 2 shown.

[0020] Step 6, reinforce the joints and seal the gaps: (1) Have divers clean the outer wall of the casing within 0.5m above and below the joints to remove sludge, debris, and blocky and layered rust; (2) Perform underwater welding on the parts where the casing mouths at both ends of the joint touch to reinforce the joint. Seal the gaps that are difficult to avoid at the joints. The sealing method is to wrap the joints with 0.5mm thin iron sheets, or wrap them with multiple layers of dense wire mesh. The wrapped joints are firmly overlapped, tensioned, and fixed by pre-welding screws and screwing nuts on the outer wall of the casing. Note that the width of the wrapping should be about 10cm wider than the gap on both sides. Too wide will affect the subsequent plugging effect.

[0021] The purpose of the sealing here is not to prevent leakage from the casing joints, but only to prevent the underwater concrete to be poured for plugging in the subsequent stages from leaking from the joints.

[0022] Step 7: Pour the outer hoop concrete underwater at the joint to seal the leak. Practice has shown that it is extremely difficult to successfully seal the steel casing butt joint with underwater welding, adhesives and other sealing methods. This method uses the method of pouring the outer hoop concrete underwater, which has a high sealing success rate and is easy to operate.

[0023] The specific process of step 7 is as follows: Step 7.1 Divers weld 4 to 6 positioning steel bars on the outer wall of the lower casing at a position about 0.5 to 0.8 m below the top of the casing. This device is used to accurately position the height of the L-shaped trough plate for subsequent underwater concrete pouring; Step 7.2 Make a ring-shaped bottom side form for plugging joints: Coarse steel bars, small angle steels and other materials can be used to make a skeleton, and a thin iron sheet can be covered inside. The iron sheet and the skeleton are drilled and tied with fine wire to firmly position them. The inner diameter is about 3cm larger than the outer diameter of the casing; the outer diameter is determined by the thickness of the planned plugging concrete block. The thickness is determined by the internal head pressure difference at the joint when the casing is actually drilled. Taking the example of maintaining a 5m overpressure head in the hole, the thickness is 40cm. The side form height is about 1m. If Figure 3 As shown; Step 7.3 Install hoop concrete reinforcement: Arrange 2 circles of 4 steel bars with a diameter of φ12 or above in the L-shaped template, and sparsely arrange the frame reinforcement to form a skeleton. The gap between the steel bars should not affect the insertion of the bottom of the pouring conduit; Step 7.4 Install the annular bottom side formwork: Set at least 3 lifting ropes evenly arranged along the circumference of the ring formwork (the diameter of the lifting ropes should be based on the ability to safely bear the total weight of the concrete to be poured to plug leaks), put the ring formwork over the casing and put it into the water, and lower it to the joint under the action of its own weight. If there is difficulty in the lowering process, heavy objects such as stones and iron blocks can be hung on the bottom of the ring side formwork to assist in the lowering. The lower height positioning position should be h / 2 (h is the side formwork height) from the bottom formwork to the joint. The positioning steel bars described in (7.1) above can be used to assist in positioning. After positioning, the diver checks the gap between the formwork and the outer wall of the casing, and blocks and seals any gap greater than 3 cm; if Figure 4 shown.

[0024] Step 7.5: Pouring underwater concrete: Install underwater concrete pouring conduits. The conduit diameter should not be larger than φ250mm so that it can be inserted into the L-shaped template groove. Install three sets of pouring conduits symmetrically. According to the underwater pile foundation pouring process, pour underwater concrete with a grade of C30 or higher in the L-shaped template groove by the method of simultaneous opening. After static curing to a strength of more than 90%, the casing can be put into use. Figure 5 shown.

[0025] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for extending steel casing and sealing joints in pile foundation construction, characterized in that; The implementation process is as follows: Step 1: Set up the water working platform: set up the beams and lay the panels by driving steel pipe piles, or use the hull, pontoon, etc. to set up the water working platform; Step 2, processing the extended steel casing: Process the steel casing according to the required length and diameter; weld 4 to 8 external guide positioning blocks at the lower end of the casing to be extended; Step 3: Divers check the top status of the underwater casing: Professional divers check the top status of the long casing to be connected, clean up the debris, and measure whether the top is level and round; Step 4: Lift the extended casing into the water for docking: Use reliable lifting equipment and lifting methods to lift the extended casing into the water; The water entry point is determined based on the theoretical center position of the casing; Step 5: Underwater docking and fixing of the casing: Under the guidance of the diving operators who have entered the water in advance, align the bottom of the extended casing with the top of the long casing to be connected, and use the guide block to guide the casing mouth to dock until it is in contact; Step 6: Reinforce the joints and seal the gaps: (6.1) Divers shall clean the outer wall of the casing within 0.5m above and below the joint to remove sludge, debris, and blocky and layered rust; (6.2) Perform underwater welding on the contact area of ​​the casing mouths at both ends of the joint to reinforce the joint; Step 7: Seal the leak by pouring outer hoop concrete at the joint underwater.

2. According to claim 1, a method for extending steel casing and sealing joints in pile foundation construction, characterized in that; In step 2, the guide positioning block is trapezoidal, with a slope of 1:3~1:5 and a length of 20~40cm; and 4~8 bolt connection holes for the extended plate are pre-made.

3. According to claim 1, a method for implementing a pile foundation construction extending steel casing to seal joints, characterized in that; Step 3 also includes the following operations: if the casing is tilted but the enlarged inner diameter of the casing does not affect the passage of the drill bit, no processing is performed; If the inclination causes a gap of more than 10cm when the extended section of the casing is kept in a vertical state, underwater cutting and leveling should be carried out; if the gap is within 10cm, no cutting is required and the extension can be covered with thin iron sheet or wire mesh.

4. According to claim 1, a method for implementing a pile foundation construction extending steel casing to seal joints, characterized in that; Step 5 also includes the following operations, keeping the suspension point partially stressed; The diver cuts and opens bolt connection holes on the top of the lower casing according to the pre-made upper casing connection bolt positions, installs the connection plates, tightens the bolts, and after the connection is completed, the lifting points can be removed; and the external guide wedges can be cut out.

5. According to claim 1, a method for implementing a pile foundation construction extending steel casing to seal joints, characterized in that; Step 6.2 also includes the following operations: plugging the gap that is difficult to avoid in the joint, the plugging method is to wrap the joint with a 0.5 mm thin iron sheet, or wrap it with multiple layers of dense wire mesh; the wrapped joint is ensured to be firmly overlapped, tensioned and fixed by pre-welding screws and screwing nuts on the outer wall of the casing; The width of the wrapping material only needs to be about 10 cm wider than the two sides of the gap. If it is too wide, it will affect the subsequent plugging effect. The purpose of the plugging here is not to prevent leakage from the casing joints, but to prevent the underwater concrete to be poured for plugging in the subsequent links from leaking from the joints.

6. A method for implementing a pile foundation construction extension steel casing plugging joints according to claim 1, characterized in that; The specific decomposition process of step 7 is as follows: Step 7.1, a diver welds 4 to 6 positioning steel bars on the outer wall of the lower casing at a position about 0.5 to 0.8 m below the top of the casing. This device is used to accurately position the L-shaped trough plate in height during the subsequent underwater concrete pouring. Step 7.2, make the bottom side formwork of the joint plugging concrete ring: the skeleton can be made of thick steel bars, small angle steels and other materials, and covered with thin iron sheets; the iron sheets and the skeleton are tied and positioned firmly with fine iron wires; the inner ring diameter is about 3cm larger than the outer diameter of the casing; the outer ring diameter is determined by the thickness of the proposed plugging concrete block; the thickness is determined according to the internal head pressure difference borne by the joint when the casing is actually drilled. For example, if the hole needs to maintain a 5m overpressure head, the thickness is 40cm; the side form height is about 1m; Step 7.3, install hoop concrete reinforcement: arrange 2 circles of 4 steel bars with a diameter of φ12 or above in the L-shaped template, and sparsely arrange the frame reinforcement to form a skeleton; the gap between the steel bars should not affect the insertion of the bottom of the pouring conduit; Step 7.4, install the annular bottom side mold: set at least 3 hanging ropes evenly arranged along the circumference on the ring mold, put the ring mold on the upper and lower parts of the casing into the water, and lower it to the joint under the action of its own weight; if there is difficulty in the lowering process, heavy objects such as stones and iron blocks can be hung on the bottom of the ring side mold to assist in lowering; the lower height positioning position should be h / 2 (h is the side mold height) from the bottom mold to the joint; use the positioning steel bars described in step 7.1 to assist in positioning; after positioning, the diver checks the gap between the template and the outer wall of the casing, and blocks and seals the gap greater than 3 cm; Step 7.5, pouring underwater concrete: install underwater concrete pouring conduit; the conduit diameter should not be greater than φ250mm so that it can be inserted into the L-shaped template groove; symmetrically install 3 sets of pouring conduits; according to the underwater pile foundation pouring process, fill the L-shaped template groove with underwater concrete of C30 or above by the method of simultaneous opening; after static curing to more than 90% strength, the casing can be put into use.

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