A caisson underwater bottom sealing device and method for in-situ pouring concrete

Abstract

The application discloses a caisson underwater bottom sealing device and method for in-capsule cast concrete, and belongs to the technical field of caisson construction. The method solves the problems of the existing caisson underwater bottom sealing technology, such as easy mixing of bottom sealing concrete with mud water, uneven quality, and poor waterproof reliability. The technical scheme comprises the following steps: underwater laying a waterproof capsule at the bottom of the caisson, pouring concrete into the capsule through a conduit; setting a grid cover plate, a counterweight block and a detection rope on the top surface of the capsule to control the net pressure of the concrete in the capsule; the concrete in the capsule expands after being poured, and the capsule wall is pressed against the inclined surface of the caisson blade foot and the sealing groove to realize sealing. The method realizes complete isolation of the bottom sealing concrete and mud water in the caisson, improves the construction quality of the bottom sealing concrete and the waterproof reliability of the caisson, forms a double sealing effect of 'rigid bearing + flexible sealing', simultaneously reduces special requirements for underwater pouring concrete materials, and improves the economy and reliability of the caisson bottom sealing.

Description

Technical Field

[0001] This invention relates to the field of caisson construction technology, and in particular to an underwater sealing device and method for caissons with concrete poured inside the caisson. Background Technology

[0002] Underwater sealing of a caisson typically requires two stages. The first stage involves pouring plain concrete underwater to initially seal the bottom of the caisson. The second stage involves pouring a reinforced concrete slab on top of the plain concrete layer, serving as the structural layer at the bottom of the caisson. This reinforced concrete slab is integral with the caisson and provides structural support for the bottom. (In other words, the primary function of the plain concrete layer in the first stage is sealing and waterproofing, while the primary function of the reinforced concrete slab in the second stage is structural support.) The structural layering of the underwater caisson bottom sealing is illustrated below. Figure 17 As shown.

[0003] Plain concrete bottom sealing construction is generally divided into two methods: drainage and non-drainage. When the site's hydrogeological conditions permit, the drainage method is used, and the sealing concrete is poured directly on the waterless base, making quality control easier. However, in conditions such as high groundwater levels, the presence of quicksand layers, or underwater conditions (such as river channels), the non-drainage method must be used, and the final underwater bottom sealing process becomes crucial to the quality and safety of the caisson.

[0004] Currently, the main method for constructing non-drained caissons is the tremie pipe method for underwater concrete sealing, such as... Figure 18 As shown. Although this method is widely used, it has inherent drawbacks: concrete is delivered to the bottom of the well via a tremie pipe, and to cover the entire base, the tremie pipe needs to be moved within the plane. This movement disturbs the interface between the already poured concrete and the surrounding mud and water, causing them to mix. More importantly, when the bottom sealing thickness is thin, the bottom end of the tremie pipe is very likely to detach from the already poured concrete surface during the movement, causing the newly poured concrete to come into direct contact with the mud and water, resulting in mud and water inclusions within the concrete, forming a weak layer with low strength and poor impermeability.

[0005] Due to the aforementioned technological defects, the quality of underwater-cast concrete is difficult to guarantee, exhibiting significant strength dispersion and a tendency to crack. To meet basic performance requirements, measures such as increasing the design strength grade of concrete and adding various admixtures are often necessary, which not only increases costs but also fails to fundamentally solve the problem. This quality hazard directly increases the risks of the traditional "secondary sealing" model: the initial underwater-cast plain concrete sealing layer, due to uneven quality and susceptibility to cracking, has poor waterproofing and sealing effects; during the secondary reinforced concrete slab construction after dewatering, external groundwater can easily seep in through cracks in the initial sealing concrete, interfering with the secondary sealing construction and leaving long-term leakage risks.

[0006] Therefore, the core problem with existing underwater sealing technologies for caissons lies in the inability to reliably isolate the concrete pouring process from the mud and water inside the caisson, resulting in poor quality of the sealing concrete and a lack of effective active sealing mechanisms, making it difficult to guarantee the reliability of the waterproof seal at the bottom of the caisson. There is an urgent need for a new underwater sealing technology for caissons that can isolate mud and water from the technological principles, ensure the quality of concrete pouring, and enhance the overall sealing effect of the caisson. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for underwater sealing of caissons using a bladder-type concrete pouring system. During underwater sealing of a caisson, a waterproof bladder is first placed underwater within the caisson. Concrete is then poured into the bladder via a conduit, and after solidification, the concrete is encased by the waterproof bladder. On one hand, pouring concrete into the bladder prevents mud and water from mixing with the concrete, ensuring the quality of the sealing concrete. On the other hand, the waterproof bladder ensures the waterproof effect of the caisson bottom sealing even if cracks occur. Furthermore, the bladder's enclosure and close fit with the caisson's cutting edge slope and base constitute a double sealing system, significantly improving the reliability, waterproofness, and overall construction quality of the underwater caisson bottom sealing.

[0008] To achieve the aforementioned objectives, the present invention employs the following technical solution: an underwater sealing device for a caisson with concrete poured inside, comprising a waterproof bladder, a cover plate, a counterweight, a grouting assembly, and a cutting edge inclined surface and a support platform arranged sequentially from bottom to top on the inner side of the caisson bottom. A sealing groove is provided on the cutting edge inclined surface, forming a ring around the cutting edge inclined surface. The cutting edge inclined surface at the bottom of the caisson encloses and forms a frustum-shaped structure, smaller at the top and larger at the bottom. The waterproof bladder is adapted to be laid at the bottom of the caisson, its sides meeting the cutting edge... The inclined surface fits snugly, and the bottom surface fits snugly with the caisson base. A grouting port is located at the center of the top surface. A sealing ring that matches the sealing groove is located in the middle of the side of the waterproof bladder. The grouting assembly includes a guide pipe and a grouting pipe. The lower end of the grouting pipe is sealed and installed at the grouting port, and the upper end is threadedly connected to the end of the guide pipe. A one-way valve is installed inside the grouting pipe. The cover plate is a grid-shaped perforated plate, placed on the support platform and located above the waterproof bladder. The counterweight is laid on the top surface of the cover plate to control the net pressure of the concrete inside the waterproof bladder.

[0009] Furthermore, the waterproof bladder is made of elastic sealing rubber, formed by hot-pressing the top, bottom, and side surfaces together. After filling, its shape is a combination of an upper frustum and a lower spherical cap. This frustum structure is consistent with the frustum shape enclosed by the beveled edge of the cutting edge, and the height of the side surface is 0.9-0.95 times the height of the beveled edge. The angle between the beveled edge and the vertical plane is preferably 20-30 degrees. This design allows the waterproof bladder to fit tightly against the beveled edge and the base after inflation, forming a continuous and complete wrapping surface. This ensures the morphological stability of the bladder under concrete pressure and guarantees geometric compatibility with the caisson structure, thereby improving the overall sealing reliability and the uniformity of concrete forming.

[0010] Furthermore, an elastic ring is wrapped around the junction of the side and bottom surfaces of the waterproof bladder. This elastic ring is made of high-carbon steel wire and can be folded and deformed. After being released from restraint, it automatically extends due to its own elasticity, allowing the waterproof bladder to be laid flat on the caisson base. This design solves the problems of difficulty in unfolding and easy folding and jamming when laying waterproof bladders underwater. Relying on the automatic unfolding function of the elastic ring, the bladder can be quickly and flatly laid on the base, reducing manual intervention and improving the efficiency and quality of underwater construction.

[0011] Furthermore, the sealing ring has a rectangular and semi-circular cross-sectional shape. The rectangular portion is heat-pressed and fused to the side of the waterproof bladder, while the semi-circular portion protrudes from the side of the waterproof bladder. The sealing groove has an isosceles right triangle cross-sectional shape, and its depth matches the height of the sealing ring. Through this cross-sectional fit design, under the pressure of the concrete inside the bladder, the semi-circular head can be squeezed and embedded into the triangular groove, forming a "mold wedge effect." This achieves adaptive enhancement of contact pressure, significantly improving the dynamic sealing performance at the cutting edge and effectively preventing external water from seeping in.

[0012] Furthermore, the grouting pipe is made of metal or plastic. Its bottom end is sealed to the grouting port on the top surface of the waterproof bladder via a flange and sealing gasket, and its top end is threaded to the end of the conduit. The outer wall of the grouting pipe is provided with a wing plate, and a circular hole is opened on the wing plate. The wing plate is used to fix the grouting pipe to prevent it from rotating with the conduit. This structure not only ensures a reliable seal between the grouting pipe, the waterproof bladder, and the conduit, preventing leakage during concrete pouring, but also facilitates the removal of the conduit through the wing plate, preventing the grouting pipe from rotating with the conduit when it is rotated, thus avoiding removal difficulties.

[0013] Furthermore, a mesh is provided on the lower surface of the cover plate, the mesh having a length and width not exceeding 50mm, and the diameter of the cover plate being 100mm~200mm smaller than the diameter of the caisson. The mesh prevents the waterproof bladder from partially bulging out of the mesh holes under pressure and being damaged, while allowing mud and water to pass smoothly, avoiding water resistance. The cover plate diameter is slightly smaller than the inner diameter of the caisson, facilitating hoisting and providing adequate space for lateral expansion of the bladder, thus balancing construction convenience with the need for bladder shape control.

[0014] Furthermore, the top surface of the counterweight is equipped with a lifting ring. The counterweight is evenly and symmetrically arranged on the top surface of the cover plate during installation to ensure uniform stress on the top surface of the waterproof bladder. The standardized and modular design of the counterweight facilitates lifting and placement, and the symmetrical and uniform laying prevents excessive or insufficient local pressure on the top of the bladder, thus ensuring uniform shape and consistent sealing performance of the waterproof bladder during pressurization, improving construction efficiency and quality control.

[0015] The present invention also provides a method for underwater sealing of a caisson by pouring concrete inside the caisson, comprising the following steps:

[0016] S1. Precast caisson, with the inner side of the bottom of the caisson machined with the beveled cutting edge, sealing groove and bearing platform;

[0017] S2. The caisson will be lowered to the design elevation using the non-drainage method;

[0018] S3. Fabricate the waterproof bladder, cover plate, counterweight, and grouting components, and seal the lower end of the grouting pipe at the grouting port of the waterproof bladder.

[0019] S4. First, thread the guide pipe to the upper end of the grouting pipe, then fold the waterproof bladder and tie it with ropes to restrain it. At the same time, set a rope release rod at the end of the rope.

[0020] S5. Place the folded waterproof bladder at the bottom of the caisson, pull out the rope release rod and loosen the rope. The waterproof bladder will automatically extend under the action of the elastic ring. Then, the staff will use a long pole to adjust the underwater position of the waterproof bladder so that it fits the caisson base and the slope of the cutting edge.

[0021] S6. Hoist the cover plate to the top of the caisson, arrange the inspection ropes around the cover plate, and then slowly lower the cover plate. After the center hole of the cover plate passes through the guide pipe, it falls onto the bearing platform. Then tighten the inspection ropes and fix the upper end of the inspection ropes to the top of the caisson.

[0022] S7. Pour concrete into the waterproof bladder through the conduit until the waterproof bladder expands and lifts the cover plate. Stop pouring concrete when the test rope is observed to be loose. Lay a counterweight on the cover plate and the cover plate will press the waterproof bladder flat again.

[0023] S8. Re-tension the test rope, continue pouring concrete until the test rope loosens again, stop pouring and remove the guide pipe;

[0024] S9. After the concrete inside the waterproof bladder has solidified, remove the counterweight and cover plate in sequence, and pump out the mud and water from the caisson.

[0025] S10. Remove the grouting pipe and clean up any remaining concrete. Pour a reinforced concrete base slab on the top surface of the waterproof bladder to complete the bottom sealing. This method achieves complete isolation between the concrete and the mud and water inside the caisson through pouring inside the bladder, eliminating the problem of concrete and mud mixing from a technological perspective. Combined with the control of the net pressure of the concrete inside the bladder and the sealing structure, it forms a dual guarantee of "rigid load-bearing + flexible sealing," improving the overall quality of the bottom sealing and the reliability of waterproofing.

[0026] Furthermore, in steps S7 and S8, the net pressure of the concrete inside the waterproof bladder is controlled to be 10 kPa to 30 kPa.

[0027] When the depth of mud and water on the top surface of the waterproof bladder inside the caisson is less than 10 meters, the net pressure is taken as 10 kPa.

[0028] When the mud and water depth at the top surface of the waterproof bladder inside the caisson is between 10 meters and 30 meters, the net pressure of the concrete inside the waterproof bladder is determined by linear interpolation between 10 kPa and 30 kPa.

[0029] When the depth of mud and water on the top surface of the waterproof bladder inside the caisson exceeds 30 meters, the net pressure is set at 30 kPa. By setting a reasonable range of net pressure according to different water depths, it is possible to ensure that the waterproof bladder fully expands and fits tightly against the surrounding structure to squeeze out the mud and water, while also preventing the bladder from rupturing due to excessive pressure. This achieves the best balance between safety control during construction and sealing effect.

[0030] Further, in step S7, the effective weight of the counterweight is calculated and determined using the following formula: ;

[0031] in, The effective weight of the cover plate. This is the effective weight of the counterweight. The cross-sectional area of ​​the caisson To control the net pressure inside the waterproof bladder, 0.9 is the ratio of the contact area between the top surface of the waterproof bladder and the cover plate to the cross-sectional area of ​​the caisson. The effective weight of the counterweight refers to the self-weight of the counterweight minus the buoyancy of the mud and water acting on the counterweight; the effective weight of the cover plate refers to the self-weight of the cover plate minus the buoyancy of the mud and water acting on the cover plate. This formula provides a quantitative basis for counterweight setting, making the pressure control inside the bladder more precise, avoiding reliance on experience-based judgment, and facilitating stable and repeatable construction quality control under different engineering conditions.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. This method completely confines the concrete pouring process within a pre-laid waterproof bladder, creating a molding space that is entirely isolated from the external mud and water environment. In traditional underwater duct pouring, the concrete is directly exposed to the mud and water, making it highly susceptible to mixing due to water flow disturbance and duct movement, resulting in weak areas or through-holes. Pouring within the waterproof bladder fundamentally eliminates this risk. The concrete smoothly fills the bladder from bottom to top, remaining under the pressure of the external mud and water until it hardens. This not only prevents the introduction of harmful substances, but the combined effect of its own weight and external water pressure also promotes a denser concrete structure and significantly improves the uniformity of the internal structure. Therefore, the formed bottom sealing concrete core achieves strength and durability similar to that of land-based pouring, providing a solid and reliable foundation for the overall caisson structure.

[0034] 2. The waterproof bladder completely encapsulates the bottom concrete, essentially adding a continuous, complete, and flexible external waterproof layer to the bottom of the caisson. Traditional waterproofing relies on the concrete's own impermeability; once cracks appear due to temperature stress, shrinkage, or uneven foundation settlement, the waterproofing function is compromised. In this method, even if microscopic cracks appear inside the concrete, the dense and elastic bladder material effectively blocks the migration of moisture along the cracks. This composite waterproofing mode of "rigid concrete bearing capacity + flexible bladder sealing" greatly improves the reliability and fault tolerance of the waterproofing system. Furthermore, the bladder material is corrosion-resistant and aging-resistant, maintaining its sealing performance for a long time, thus ensuring the waterproof sealing effect at the bottom of the caisson throughout its service life and eliminating subsequent maintenance problems caused by leakage.

[0035] 3. The specially designed beveled cutting edge, annular sealing groove, and sealing ring on the side of the bladder together form an active compression sealing mechanical sealing system. When concrete is poured and internal pressure is generated, the side of the bladder expands outward, forcing the base of the rectangular sealing ring to compress and deform, and its semi-circular head to be tightly squeezed into the right-angled triangular sealing groove. This "mold wedge effect" is enhanced as the internal pressure increases, achieving adaptive adjustment of the sealing pressure at the contact surface. At the same time, the beveled cutting edge structure, which is smaller at the top and larger at the bottom, makes the bottom sealing concrete tend to move into the caisson when subjected to the reaction force of the base, thus continuously compressing the side of the bladder. This multi-stage, dynamic sealing mechanism far surpasses the traditional sealing methods that rely on static contact or post-grouting, maintaining excellent sealing stability even under complex water and soil pressure changes, and significantly improving the long-term seepage prevention performance at the joint.

[0036] 4. In terms of economic benefits and construction convenience, this method, by isolating the water environment, relaxes the special performance requirements for concrete materials. Traditional underwater casting requires the use of special concrete with high fluidity and high anti-dispersion properties, often necessitating higher cement grades, the addition of expensive admixtures (such as flocculants and thickeners), and strict mix proportioning and production control, significantly increasing material costs. This method, however, allows the direct use of ordinary concrete of conventional strength grades. Its mix design, mixing, and transportation processes can all be carried out according to standard surface procedures, eliminating the need for additional material and technical costs to adapt to underwater casting. This not only directly reduces the unit material cost of the sealing project but also simplifies the complexity of construction organization, reduces dependence on the special material supply chain, and makes the technology more universally applicable. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0038] Figure 1 This is a schematic diagram of the cross-section of the bottom of the caisson.

[0039] Figure 2 Figure 1 shows a schematic diagram of the sealing groove on the inclined surface of the caisson cutting edge and the side sealing ring of the waterproof bladder. Figure 2 shows the sealing ring and sealing groove in a separated state, and Figure 3 shows the sealing ring and sealing groove in a fitted state.

[0040] Figure 3 This is a top view of the inflated waterproof bladder.

[0041] Figure 4 This is a cross-sectional schematic diagram of the waterproof bladder in its inflated state.

[0042] Figure 5 This is a cross-sectional schematic diagram of the connection between the waterproof bladder, the grouting pipe, and the guide pipe.

[0043] Figure 6 This is a top view of the grouting pipe.

[0044] Figure 7 This is a top view of the cover plate.

[0045] Figure 8 This is a schematic diagram of the cross-sectional structure at the center hole of the cover plate.

[0046] Figure 9 This is a top view of the counterweight.

[0047] Figure 10 This is a schematic diagram of the counterweight block from the front.

[0048] Figure 11 This is a schematic diagram showing the caisson being lowered to the designed elevation.

[0049] Figure 12 A schematic diagram showing the waterproof bladder being laid out on the surface of the caisson base after the connecting tubes are installed.

[0050] Figure 13 This is a schematic diagram showing the cover plate after it has been installed on the bearing platform.

[0051] Figure 14 This is a schematic diagram showing the installation of counterweights on the cover plate after it has been lifted.

[0052] Figure 15 This diagram illustrates the process of draining the mud and water from the caisson after removing the counterweight and cover plate.

[0053] Figure 16 A schematic diagram of pouring a reinforced concrete base slab on the bottom concrete of a caisson.

[0054] Figure 17 This is a schematic diagram of the layered structure of underwater sealing of caissons in existing technologies.

[0055] Figure 18 This is a schematic diagram of underwater concrete sealing of a non-drained caisson using the guide pipe method in the prior art.

[0056] The attached diagram is labeled as follows: 1. Waterproof bladder; 2. Cover plate; 3. Counterweight block; 4. Caisson; 5. Cutting edge slope; 6. Sealing groove; 7. Foundation; 8. Sealing ring; 9. Guide pipe; 10. Grouting pipe; 11. Elastic ring; 12. Sealing gasket; 13. Wing plate; 14. Mesh plate; 15. Detection rope; 16. Center hole; 17. Reinforced concrete base plate; 18. Lifting ring; 19. One-way valve; 20. Limiting ring; 21. Flange; 22. Water surface; 23. Ground surface; 24. Base plate groove; 25. Sealing concrete. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0058] refer to Figure 1 and Figure 14This invention proposes an underwater sealing device for a caisson with in-situ concrete pouring, comprising a waterproof bladder 1, a cover plate 2, a counterweight block 3, a grouting assembly, and a cutting edge slope 5 and a support platform 7 arranged sequentially from bottom to top on the inner side of the bottom of the caisson 4. The cutting edge slope 5 has a sealing groove 6, and the cutting edge slope 5 forms a frustum-shaped structure that is smaller at the top and larger at the bottom. The waterproof bladder 1 is fitted to the bottom of the caisson 4, its side surface fitting against the cutting edge slope 5, and a sealing ring 8, which matches the sealing groove 6, is provided in the center of its side surface, providing waterproofing. An elastic ring 11 is installed inside the connection between the side and bottom of the waterproof bladder 1. The bottom of the waterproof bladder 1 is in contact with the base of the caisson 4, and a grouting port is provided at the center of the top surface. The grouting assembly includes a conduit 9 and a grouting pipe 10. The grouting pipe 10 is sealed and installed at the grouting port. A one-way valve 19 is provided inside, and the top end is threadedly connected to the conduit 9. The cover plate 2 is a grid-shaped perforated plate, placed on the foundation 7 and located above the waterproof bladder 1. The counterweight 3 can be detachably laid on the top surface of the cover plate 2 to control the net pressure of the concrete inside the waterproof bladder 1.

[0059] refer to Figure 1 The inclined surface 5 is an sloping surface located on the inner side of the bottom of the caisson 4. The inclined surface 5 makes the opening size at the bottom of the caisson 4 larger, gradually decreasing as it extends upwards into the caisson 4. The angle between the inclined surface 5 and the vertical surface is preferably 20 to 30 degrees. The height of the inclined surface 5 is equal to the thickness of the edge of the sealing concrete 25, and slightly greater than the lateral height of the waterproof bladder 1 in its expanded state. The inclined surface 5 encloses a frustum shape, smaller at the top and larger at the bottom, giving the inner side of the bottom of the caisson 4 a frustum shape with a large opening at the bottom and gradually decreasing in size upwards. This allows the sealing concrete 25 to be fixed at the bottom of the caisson 4, preventing it from being squeezed upwards into the caisson 4. Simultaneously, under normal operating conditions, the sealing concrete 25, under the upward reaction force of the base, tends to be squeezed into the caisson 4, enhancing the sealing effect of the caisson 4 (similar to the sealing effect of a conical cork in a thermos).

[0060] refer to Figure 1 and Figure 2 The sealing groove 6 is located in the middle of the inclined surface 5 of the cutting edge, and is arranged in a ring around the inclined surface 5 of the cutting edge. The cross-sectional shape of the sealing groove 6 is an isosceles right triangle, with the right angle of the triangle at the bottom of the groove and the hypotenuse at the opening of the groove. The depth of the sealing groove 6 (i.e., the distance from the right angle vertex of the isosceles right triangle to the hypotenuse) is equal to the cross-sectional height of the sealing ring 8 on the side of the waterproof bladder 1. After concrete is poured into the waterproof bladder 1, the sealing ring 8 on the side of the waterproof bladder 1 will be squeezed and embedded into the sealing groove 6. The sealing ring 8 is deformed by the pressure of the concrete in the waterproof bladder 1 and fits tightly with the sealing groove 6, further strengthening the sealing effect between the bottom sealing concrete 25 and the inclined surface 5 of the cutting edge of the caisson 4.

[0061] refer to Figure 1The support platform 7 is located on the upper side of the inclined surface 5 of the cutting edge. The cross-sectional shape of the support platform 7 is a right triangle, and the bottom surface of the support platform 7 is the top of the inclined surface 5 of the cutting edge. The support platform 7 protrudes from the inner wall of the caisson 4 towards the inner side of the caisson 4. The function of the support platform 7 is to provide a support for the cover plate 2, so as to facilitate the installation and fixing of the cover plate 2.

[0062] refer to Figure 1 The bottom slab groove 24 is a horizontal groove along the inner wall of the caisson 4, designed for connecting, fixing, and waterproofing the cast-in-place reinforced concrete bottom slab 17 of the caisson 4. Multiple bottom slab grooves 24 can be provided as needed, or designed with different cross-sectional shapes. The bottom slab groove 24 is a conventional feature in existing caisson technology and will not be elaborated upon here.

[0063] refer to Figure 3 and Figure 4 The waterproof bladder 1 is made of an elastic, sealing, and waterproof material, such as a rubber sheet that has been cut and hot-pressed together. After being pressurized, the waterproof bladder 1 takes the shape of a combination of an upper frustum and a lower spherical cap. The top surface of the frustum is small, and the bottom surface is large. The spherical cap is connected to the bottom surface of the frustum and protrudes downwards. The shape of the frustum is consistent with the shape of the frustum enclosed by the inclined surface 5 of the cutting edge of the caisson 4. The height of the side of the frustum of the waterproof bladder 1 is slightly less than the height of the inclined surface 5. The waterproof bladder 1 expands after being pressurized. To prevent the top surface of the waterproof bladder 1 from protruding excessively upwards beyond the inclined surface 5, the side height of the waterproof bladder 1 is made slightly less than the height of the inclined surface 5 during manufacturing. After the waterproof bladder 1 expands under pressure, its side height is approximately the same as the height of the inclined surface 5. The shape of the spherical cap at the bottom of the waterproof bladder 1 is consistent with the shape of the base of the caisson 4, ensuring a tight fit between the bottom of the waterproof bladder 1 and the base of the caisson 4.

[0064] The waterproof bladder 1 consists of four parts: top surface, bottom surface, side surface, and grouting port. The shape of the top surface of the waterproof bladder 1 is consistent with the internal cross-sectional shape of the foundation 7 of the caisson 4. The shape of the bottom surface of the waterproof bladder 1 is consistent with the shape of the base of the caisson 4. The side surface of the waterproof bladder 1 is frustum-shaped, and the shape of the frustum is consistent with the shape of the frustum enclosed by the bottom cutting edge slope 5 of the caisson 4. The height of the side surface of the waterproof bladder 1 is slightly less than the height of the cutting edge slope 5. According to the expansion data of the rubber waterproof bladder 1 after being inflated, the height of the side surface of the waterproof bladder 1 is preferably 0.95 times the height of the cutting edge slope 5.

[0065] The contact between the side of the waterproof bladder 1 and the inclined surface 5 of the cutting edge of the caisson 4 is crucial to the sealing performance of the caisson 4. To prevent water from outside the caisson 4 from seeping into the caisson 4 through the gap between the side of the waterproof bladder 1 and the inclined surface 5 of the cutting edge, the side of the waterproof bladder 1 should be made of a material with good elasticity and sealing performance, preferably elastic sealing rubber. The thickness of the rubber sheet on the side of the waterproof bladder 1 should not be less than 10mm. To further enhance the sealing between the side of the waterproof bladder 1 and the inclined surface 5 of the cutting edge of the caisson 4, a sealing ring 8 is set in the middle of the side of the waterproof bladder 1, protruding beyond the side of the waterproof bladder 1. The cross-sectional shape of the sealing ring 8 is a rectangle plus a semi-circle. The rectangle is connected to the side of the waterproof bladder 1, and the semi-circle is outside the rectangle. The width of the rectangle is equal to the diameter of the semi-circle, and the height of the rectangle is equal to the radius of the semi-circle. The sealing ring 8 and the side of the waterproof bladder 1 are connected by heat pressing. (See details...) Figure 2 .

[0066] refer to Figure 3 and Figure 4 An elastic ring 11 is located inside the junction of the side and bottom surfaces of the waterproof bladder 1. The elastic ring 11 is made of a highly elastic material, preferably high-carbon steel wire. The two ends of the high-carbon steel wire are connected to form a closed elastic ring 11. The elastic ring 11 is embedded inside the junction of the side and bottom surfaces of the waterproof bladder 1, and the waterproof bladder 1 encloses the elastic ring 11 to prevent it from being exposed and rusting. The elastic ring 11 can be folded, twisted, and deformed after external force is applied (such as by binding or restraining with ropes) to reduce the volume of the waterproof bladder 1, facilitating storage, transportation, and installation. After the external force is released, the elastic ring 11 can automatically extend and open based on its own elasticity (similar to the unfolding of a folding mosquito net with a wire frame). The function of the elastic ring 11 is to allow the waterproof bladder 1 to automatically extend at the bottom of the caisson 4 after it sinks underwater, so that the bottom surface of the waterproof bladder 1 lies flat on the base surface of the caisson 4.

[0067] refer to Figure 5 and Figure 6The grouting assembly includes a conduit 9 and a grouting pipe 10. The grouting pipe 10 is located at the center of the top surface of the waterproof bladder 1. The grouting pipe 10 is made of metal or plastic. The bottom end of the grouting pipe 10 is sealed to the waterproof bladder 1, and the top end of the grouting pipe 10 is threaded to the conduit 9. A one-way valve is installed inside the grouting pipe 10, allowing concrete to flow only from the grouting pipe 10 into the waterproof bladder 1, and preventing concrete from flowing out of the grouting pipe 10 from the waterproof bladder 1. The outer side of the top end of the grouting pipe 10 has threads that match the inner thread of the bottom end of the conduit 9. A sealing ring and a limiting ring are located below the threads of the grouting pipe 10. The limiting ring is used to limit the depth to which the conduit 9 is screwed into the grouting pipe 10, and the sealing ring is located between the bottom end of the conduit 9 and the limiting ring, and provides a sealing effect when compressed. The grouting pipe 10 is connected to the top surface of the waterproof bladder 1 via a flange 21 and a sealing gasket 12. The bottom end of the grouting pipe 10 has a lower flange 21, and a sealing gasket 12 is placed on the lower flange. The top surface of the waterproof bladder 1 is connected to the sealing gasket 12. A sealing gasket 12 is also placed on the top surface of the waterproof bladder 1, and an upper flange is placed on the sealing gasket 12. The upper flange is threaded to the outside of the grouting pipe 10. By rotating the upper flange, the top surface of the waterproof bladder 1 can be clamped between the upper and lower flanges 21, forming a sealed connection. Concrete can be injected into the waterproof bladder 1 through the guide pipe 9 and the grouting pipe 10. When the concrete pressure inside the waterproof bladder 1 is higher than the external mud and water pressure, even after the guide pipe 9 is removed, the concrete inside the waterproof bladder 1 will not flow out of the top surface of the waterproof bladder 1. A wing plate 13 is provided at the middle of the height of the grouting pipe 10. The wing plate 13 is a rectangular flat plate with a round hole in the middle. The wing plate 13 is fixedly connected to the outside of the grouting pipe 10 and extends horizontally to both sides of the grouting pipe 10. The wing plate 13 is used to fix the grouting pipe 10 when installing and removing the guide pipe 9, and to prevent the grouting pipe 10 from rotating with the guide pipe 9 when the guide pipe 9 is rotated.

[0068] Reference 7 and Figure 8The cover plate 2 is a grid-shaped perforated plate. During the sealing process, the cover plate 2 is placed on the foundation 7, above the waterproof bladder 1. Its main function is to limit the excessive upward expansion of the waterproof bladder 1 after it is filled with concrete. When the waterproof bladder 1 is filled with concrete, it will gradually fill and expand from a flattened state. After the waterproof bladder 1 expands, it will gradually squeeze the mud and water on its upper part upward. Since the cover plate 2 is designed as a perforated plate, the mud and water flowing upward can easily pass through the cover plate 2. The cover plate 2 allows the top surface of the waterproof bladder 1 to be basically flat after it is filled with concrete. Therefore, the cover plate 2 can prevent the top surface of the waterproof bladder 1 from bulging excessively upward under the pressure of the internal concrete. Since the cover plate 2 restricts the upward displacement of the top surface of the waterproof bladder 1, the waterproof bladder 1 can fully extend and expand downward and outward under the pressure of the internal concrete, so that the waterproof bladder 1 can be in close contact with the base of the caisson 4 and the inner wall of the caisson 4, and fully squeeze out the mud and water between them to achieve a sealing effect. Therefore, the cover plate 2, the inclined surface of the cutting edge 5, and the base of the caisson 4 form a closed space around the waterproof bladder 1, which restricts the excessive expansion of the waterproof bladder 1 outward, and makes the waterproof bladder 1 in close contact with the external restraint object under the action of internal pressure.

[0069] The cover plate 2 is manufactured according to the cross-sectional shape of the caisson 4. The planar dimensions of the cover plate 2 are slightly smaller than the cross-sectional dimensions of the inner wall of the caisson 4. Preferably, the dimensions of the cover plate 2 are 200mm less than the cross-sectional dimensions of the inner wall of the caisson 4, so that the cover plate 2 can be smoothly lowered and installed within the caisson 4. The cover plate 2 can be made of metal materials such as rectangular steel pipes or reinforced concrete. The grid holes of the cover plate 2 are relatively large. To prevent the waterproof bladder 1 from bulging out and being damaged through the holes in the grid of the cover plate 2 under internal pressure, a layer of finely meshed plate mesh 14 is provided on the lower surface of the cover plate 2. The plate mesh can be steel plate mesh or plastic mesh, and the maximum size of the mesh holes in the steel plate mesh or plastic mesh should not exceed 50mm. The combined use of the cover plate 2 and the steel plate mesh 14 or plastic mesh can limit the upward displacement of the top surface of the waterproof bladder 1, protecting the waterproof bladder 1 from damage under pressure, while allowing mud and water to pass through.

[0070] When concrete is poured into the waterproof bladder 1, it simultaneously bears the outward pressure of the internal concrete and the inward pressure of the mud and water outside. When the concrete pressure inside the waterproof bladder 1 is less than the mud and water pressure outside, the mud and water will flatten the waterproof bladder 1, preventing concrete from entering. When the concrete pressure inside the waterproof bladder 1 is greater than the mud and water pressure outside, concrete can enter, causing the waterproof bladder 1 to expand outward. Once the waterproof bladder 1 is fully expanded, its walls will be stretched due to the expansion, generating inward pressure. At this point, the sum of the inward pressure generated by the tensile force of the waterproof bladder wall and the inward pressure generated by the mud and water outside balances the outward pressure of the concrete inside. The net pressure inside the waterproof bladder 1 is the concrete pressure minus the mud and water pressure outside, balanced by the inward pressure generated by the tensile force of the waterproof bladder wall.

[0071] The net pressure inside the waterproof bladder 1 is the driving force for its outward expansion and also the driving force for the one-way valve of the grouting pipe 10 to close. Controlling the net pressure inside the waterproof bladder 1 is a key technology in the construction method of pouring concrete inside the waterproof bladder 1. If the net pressure inside the waterproof bladder 1 is too low, it cannot expand fully, resulting in insufficient pressure between the waterproof bladder 1 and the base of the caisson 4 and the inclined surface 5 of the caisson 4's cutting edge. This prevents the mud and water between the waterproof bladder 1 and the base of the caisson 4 and the inclined surface 5 of the caisson 4's cutting edge from being fully squeezed out and drained. This will affect the sealing and waterproofing effect of the caisson 4's bottom sealing and also affect the bearing capacity of the caisson 4's base. The closing effect of the one-way valve 19 will also be weak, potentially allowing external mud and water to enter the waterproof bladder 1 after the conduit 9 is removed. If the net pressure inside the waterproof bladder 1 is too high, it will over-expand, potentially causing the waterproof bladder 1 to burst or causing the top surface of the waterproof bladder 1 to bulge excessively upwards, affecting the construction of the reinforced concrete base slab 17 structure during the secondary sealing of the caisson 4. Therefore, the net pressure inside the waterproof bladder 1 during the pouring of concrete should be precisely controlled.

[0072] In this application, the net pressure inside the waterproof bladder 1 during concrete pouring is controlled by a combination of cover plate 2 and counterweight 3.

[0073] Driven by the net pressure inside the waterproof bladder 1, the top surface of the waterproof bladder 1 will expand, causing it to bulge upwards. When the waterproof bladder 1 is fully expanded, its top surface will contact the cover plate 2, and the net pressure inside the waterproof bladder 1 will lift the cover plate 2. The net pressure inside the waterproof bladder 1 can be controlled by controlling the total weight of the cover plate 2 and the counterweight 3 on the cover plate 2. When the waterproof bladder 1 lifts the cover plate 2 and the counterweight 3, the pouring of concrete into the waterproof bladder 1 is stopped. At this time, the total effective weight of the cover plate 2 and the counterweight 3 (effective weight equals the self-weight of the cover plate and the counterweight minus the buoyancy generated by the mud and water) divided by the contact area between the top surface of the waterproof bladder 1 and the cover plate 2 is the net pressure inside the waterproof bladder 1.

[0074] Whether the waterproof bladder 1 has lifted the cover plate 2 can be determined using the detection ropes 15 installed on the cover plate 2. Several flexible detection ropes 15 are arranged around the cover plate 2, with their bottom ends connected to the cover plate 2. After the cover plate 2 is installed on the foundation 7, the top ends of the detection ropes 15 are connected to a fixed point on the top surface of the caisson 4, ensuring the detection ropes 15 are taut. At this time, the waterproof bladder 1 is under the pressure of mud and water, and its top surface is not in contact with the cover plate 2; the detection ropes 15 are taut. As concrete is poured into the waterproof bladder 1, it expands continuously, and its top surface rises. When the waterproof bladder 1 is fully expanded, its top surface will contact the cover plate 2, gradually lifting it; at this point, the detection ropes 15 are slack. Therefore, by checking the tension or slack of the detection ropes 15, it can be determined whether the top surface of the waterproof bladder 1 has lifted the cover plate 2.

[0075] Because the cover plate 2 is relatively lightweight, the waterproof bladder 1 can lift the cover plate 2 with a small net pressure. At this time, a counterweight 3 should be installed on the cover plate 2 to ensure that the pressure inside the waterproof bladder 1 reaches the designed net pressure control pressure inside the waterproof bladder 1.

[0076] The counterweight 3 needs to be determined through calculation. The principle for setting the counterweight 3 is: the effective pressure generated by the total effective weight of the cover plate 2 and the counterweight 3 on the top surface of the waterproof bladder 1 is equal to the net pressure controlled inside the waterproof bladder 1.

[0077] Based on engineering experience in underwater concrete pouring, the pressure requirements for the full extension of the waterproof bladder 1, the pressure requirements for the closure of the one-way valve of the grouting pipe 10, and the safe pressure bearing range of the rubber waterproof bladder 1, the preferred net pressure control inside the waterproof bladder 1 in this embodiment is 10 kPa to 30 kPa. When the water level in the caisson 4 is shallow (the mud and water depth at the top surface of the waterproof bladder 1 in the caisson 4 is less than 10 meters), a lower value of 10 kPa can be used. When the mud and water depth at the top surface of the waterproof bladder 1 in the caisson 4 is between 10 meters and 30 meters, the net pressure control of the concrete inside the bladder can be determined by linear interpolation between 10 kPa and 30 kPa. When the water level in the caisson 4 is deep (the mud and water depth at the top surface of the waterproof bladder 1 in the caisson 4 exceeds 30 meters), a higher value of 30 kPa can be used.

[0078] The formulas for calculating the weight of the cover plate and counterweight are as follows: ;

[0079] In the formula, The effective weight of the cover plate is equal to the weight of the cover plate minus the buoyancy force (kN) on the cover plate in the mud and water. The effective weight of the counterweight is equal to the weight of the counterweight minus the buoyancy force exerted on the counterweight in the muddy water. ; The cross-sectional area of ​​the caisson ; To control the net pressure inside the waterproof bladder Depending on the depth of the mud and water inside the caisson, it is recommended to take... ; 0.9 is the ratio of the contact area between the top surface of the waterproof bladder and the cover plate to the cross-sectional area of ​​the caisson, and 0.9 is recommended.

[0080] refer to Figure 9 and Figure 10 The counterweight 3 can be made of concrete. For easy installation and positioning, the counterweight 3 is preferably a prism-shaped block with a standard cross-sectional size (1m x 1m). The height of the counterweight 3 can be determined by calculation. The top surface of the counterweight 3 is equipped with a lifting ring 18 for hoisting.

[0081] After the waterproof bladder 1 fully expands and lifts the cover plate 2, the calculated counterweight 3 is installed on the cover plate 2. At this time, the counterweight 3 may press the cover plate 2 back down onto the support platform 7. After the counterweight 3 is installed, the detection rope 15 of the cover plate 2 is readjusted, tensioned, and fixed.

[0082] Continue pouring concrete into the waterproof bladder 1 until the test rope 15 loosens again, then stop pouring concrete into the waterproof bladder 1. At this point, the net pressure inside the waterproof bladder 1 has been controlled.

[0083] After the concrete inside the waterproof bladder 1 is poured, the guide pipe 9 can be removed from the grouting pipe 10. The removal method is to first use a long rod to fix the wing plate 13, and then rotate the guide pipe 9 to remove it from the top of the grouting pipe 10. At this time, because the concrete pressure inside the waterproof bladder 1 is greater than the mud and water pressure outside the waterproof bladder 1, and due to the setting of the one-way valve 19, the concrete inside the waterproof bladder 1 will not flow out.

[0084] After the concrete inside the waterproof bladder 1 has fully solidified, remove the counterweight 3 and the cover plate 2.

[0085] At this point, the underwater sealing construction of caisson 4, in which concrete was poured inside the waterproof bladder 1, has been completed.

[0086] The next step is to drain the mud and water from the caisson 4, remove the grouting pipe 10 on the waterproof bladder 1, and clean up any remaining concrete on the grouting pipe 10. The reinforced concrete base slab 17 of the caisson 4 can be poured directly onto the top surface of the waterproof bladder 1, or the top surface of the waterproof bladder 1 can be cut off along the inner wall of the caisson 4 with a utility knife, and after cleaning the top surface of the waterproof bladder 1, the reinforced concrete base slab 17 can be poured onto the sealing concrete 25.

[0087] The following example uses a specific underwater sealing project of a caisson to illustrate the specific implementation steps of the underwater sealing method of caisson 4 by pouring concrete inside the waterproof bladder 1.

[0088] 1) Caisson design parameters

[0089] Caisson 4 has an outer diameter of 12m, an inner diameter of 10m, a wall thickness of 1m, a total height of 13.5m, a height of 1m above ground level 23, a height of 12.5m below ground level 23, and a water level 22 2m below ground level 23 within caisson 4. The cutting edge thickness of caisson 4 is 500mm, the cutting edge height is 1500mm, the thickness of the bottom sealing concrete edge is 1500mm, the center thickness is 3110mm, and the bottom slab thickness is 1000mm. The density of the slurry inside caisson 4 is... Concrete density Concrete was poured inside the waterproof bladder 1, and the net pressure inside the waterproof bladder 1 was controlled. .

[0090] 2) Construction preparation

[0091] (1) Construction of caissons

[0092] The caisson 4 is precast with reinforced concrete on the ground surface 23. The caisson 4 has an outer diameter of 12m, an inner diameter of 10m, a wall thickness of 1m, a total height of 13.5m, a cutting edge thickness of 500mm, and a cutting edge height of 1500mm. The angle between the cutting edge slope 5 and the vertical plane is 25 degrees. A support platform 7 is provided on the cutting edge slope 5, protruding 200mm into the inner wall of the caisson 4, forming a circumferential horizontal support platform 7 for placing the cover plate 2. A horizontal sealing groove 6 is provided at the middle of the cutting edge slope 5 (750mm from the bottom of the cutting edge). The sealing groove 6 has an isosceles right triangle cross-section, a width of 80mm (the length of the hypotenuse of the isosceles right triangle), and a depth of 40mm. The bottom plate groove 24 is rectangular, with a height of 400mm and a depth of 200mm.

[0093] (2) Making waterproof bags

[0094] Waterproof bladder 1 is made of rubber sheet. Waterproof bladder 1 is formed into a frustum shape by its top, bottom, and sides. The top surface of waterproof bladder 1 is a circular sheet, 8mm thick, with a diameter of 9600mm. The bottom surface of waterproof bladder 1 is a spherical cap-shaped sheet, 8mm thick, with a cap diameter of 11000mm and a cap height of 1610mm. The sides of waterproof bladder 1 are made of 12mm thick elastic rubber sheet, forming a frustum shape with a top diameter of 9600mm, a bottom diameter of 11000mm, and a height of 1425mm. The sides of waterproof bladder 1 are cut according to the unfolded shape of the frustum side, taking into account the allowance for the overlap during hot pressing and fusion of the rubber sheets.

[0095] The top, sides, and bottom of the waterproof bladder 1 are made into a whole by hot-pressing fusion process. When the bottom and sides of the waterproof bladder 1 are hot-pressed together, an elastic ring 11 is embedded inside the waterproof bladder 1 at the junction of the bottom and sides. The elastic ring 11 is made of 5mm diameter high carbon steel wire, and the ends are connected and closed. The elastic ring 11 is embedded into the bottom and side walls of the waterproof bladder 1 by hot-pressing fusion process.

[0096] A sealing ring 8, made of elastic rubber strip, is installed at the midpoint of the side of the waterproof bladder 1. The cross-sectional shape of the sealing ring 8 is a rectangle with a semi-circle. The rectangle is connected to the side of the waterproof bladder 1, and the semi-circle is outside the rectangle. The width of the rectangle is 40mm, the height of the rectangle is 20mm, and the diameter of the semi-circle is 40mm. The sealing ring 8 is heat-pressed and fused to the side of the waterproof bladder 1 to form a single unit.

[0097] A circular opening with a diameter of 380 mm is made at the center of the top surface of the waterproof bladder 1. A grouting pipe 10, made of steel pipe, is installed in the opening. The grouting pipe 10 has an outer diameter of 380 mm and a height of 400 mm. The bottom of the grouting pipe 10 is sealed to the opening at the center of the top surface of the waterproof bladder 1 using a flange 21 and a rubber sealing gasket 12. The top of the grouting pipe 10 is equipped with threads, a rubber ring, and a limiting ring. It is connected to the bottom end of the guide pipe 9 via threads, and the connection and sealing between the guide pipe 9 and the grouting pipe 10 are achieved through the rubber ring and the limiting ring. A one-way valve 19 is installed inside the grouting pipe 10, which only allows concrete to flow from the guide pipe 9 into the waterproof bladder 1, and does not allow concrete to flow from the waterproof bladder 1 into the guide pipe 9. When the pressure inside the waterproof bladder 1 is higher than the external mud and water pressure, the concrete inside the waterproof bladder 1 will not flow out of the top surface of the waterproof bladder 1 even after the guide pipe 9 is removed from the grouting pipe 10.

[0098] (3) Making the cover plate

[0099] Cover plate 2 is a circular grid plate composed of multiple circumferential and radial beams, with a diameter of 9800 mm. Both the circumferential and radial beams of cover plate 2 are made by bending and welding 150x150x10 mm square steel tubing. (See cover plate 2 planar shape for reference.) Figure 7 The cover plate 2 has a central hole with a diameter of 1000mm, through which the conduit 9 passes.

[0100] A steel mesh 14 with a thickness of 5mm is installed below the cover plate 2. The steel mesh 14 has evenly distributed round holes with a diameter of 30mm. The ratio of the area of ​​the round holes to the area of ​​the steel mesh 14, i.e., the opening rate, is 50%.

[0101] (4) Making counterweights

[0102] Calculations show that the total mass of cover plate 2 and steel mesh 14 is 8200 kg, and after deducting the buoyancy of mud and water, the effective weight is 69.4 kN.

[0103] Calculate the weight of counterweight 3 required to achieve a net pressure of 10 kPa inside waterproof bladder 1 using the following formula:

[0104] Depend on ;have to ,

[0105] Right now: ;

[0106] The effective weight of the required counterweight 3 is 637.1 kN.

[0107] Make counterweight 3. The plane dimensions of counterweight 3 are 1m x 1m, and the height of counterweight 3 is 2m. The weight of a single counterweight 3 is 4800kg.

[0108] The effective weight that a single counterweight 3 can provide is: ;

[0109] Calculations show that 27 counterweights are needed.

[0110] The total effective weight of the 27 counterweights is 648 kN.

[0111] The effective pressure exerted by cover plate 2 and counterweight 3 on the top surface of waterproof bladder 1 is:

[0112] ;

[0113] The effective pressure exerted by the cover plate 2 and the counterweight 3 on the top surface of the waterproof bladder 1 is close to the net pressure controlled inside the waterproof bladder 1, which is 10 kPa.

[0114] 3) Construction steps

[0115] refer to Figures 11-16 The construction process for underwater sealing of the caisson 4 by pouring concrete inside the waterproof bladder 1 is as follows:

[0116] (1) Construct a reinforced concrete caisson 4 on the ground according to the above-mentioned construction preparation requirements.

[0117] (2) The caisson 4 was constructed using the non-drainage method, and the caisson 4 was sunk to the design elevation using the mud-water circulation method.

[0118] (3) In accordance with the above construction preparation requirements, manufacture waterproof bladder 1, cover plate 2, counterweight 3 in the factory, and process or purchase components such as conduit 9 and funnel.

[0119] (4) Transport the waterproof bladder 1, cover plate 2, counterweight block 3, guide tube 9 and funnel to the construction site of caisson 4.

[0120] (5) Install the conduit 9 onto the grouting pipe 10 of the waterproof bladder 1. Rotate the conduit 9 to achieve a sealed connection between the conduit 9 and the grouting pipe 10 on the waterproof bladder 1 using threads and rubber rings.

[0121] (6) Tie and fold the waterproof bag 1 with a rope. Set a rope release lever at the end of the rope. After pulling out the rope release lever, the tying rope will loosen, and the waterproof bag 1 will automatically unfold due to the rebound of the elastic ring 11 on the bottom surface (similar to unfolding a folded mosquito net). Place the waterproof bag 1 in the folded state into the caisson 4 and sink it to the bottom of the caisson 4. Pull out the rope release lever on the waterproof bag 1 by pulling the rope, so that the waterproof bag 1 unfolds underwater. The staff at the top of the caisson use a long pole to adjust the position of the waterproof bag 1 underwater, so that the elastic ring 11 of the waterproof bag 1 is fully extended and extends into the bottom of the inclined surface 5 of the cutting edge of the caisson 4. The waterproof bag 1 is laid flat on the base surface of the caisson 4. Due to the presence of mud and water pressure, the air inside the waterproof bag 1 will be expelled at this time. In addition, for particularly important caissons 4, divers can also use underwater to adjust the position of the waterproof bag 1. Under normal circumstances, the outer edge of the waterproof bag 1 is pressed down to the bottom of the caisson 4 using a long pole, and the waterproof bag 1 will automatically adjust to the correct position due to the unfolding action of the elastic ring 11.

[0122] (7) Using a crane, hoist the cover plate 2, with the steel mesh 14 connected to the bottom, to the top surface of the caisson 4. Attach a detection rope 15 at each of the four positions around the cover plate 2 at 0 degrees, 90 degrees, 180 degrees, and 270 degrees. The detection ropes 15 are made of soft rope. Pass the top of the conduit 9 connected to the waterproof bladder 1 through the central hole 16 of the cover plate 2 and slowly lower the cover plate 2 until it lands on the bottom support 7 of the caisson 4. However, do not install the counterweight 3 on the cover plate 2 at this time, because the waterproof bladder 1 is in a compressed state and located at the bottom of the caisson 4, and has not yet contacted the cover plate 2. If the counterweight 3 is installed on the cover plate 2 at this time, the effective weight of the counterweight 3 will be entirely borne by the cover plate 2, which will put excessive pressure on the cover plate 2 and may damage it. After the cover plate 2 lands on the bottom support 7 of the caisson 4, tighten the four detection ropes 15 connected to the cover plate 2, and fix the top of the detection ropes 15 to the corresponding vertical positions on the top surface of the caisson 4.

[0123] (8) Connect a concrete pouring funnel to the top of the guide pipe 9. Pour concrete into the waterproof bladder 1 through the funnel, guide pipe 9, and grouting pipe 10. To ensure sufficient net stress inside the waterproof bladder 1 and allow it to fully expand, the free surface of the concrete pouring should be at least 2 meters higher than the mud-water surface inside the caisson 4. Since the density of concrete is greater than that of the mud-water slurry inside the caisson 4, and there is no air inside the waterproof bladder 1, the concrete will automatically sink to the bottom inside the caisson 4 after being poured into the waterproof bladder 1. The poured concrete will gradually fill the interior of the waterproof bladder 1 from the base of the caisson 4 upwards, and under the pressure of the mud-water, it will squeeze out the air inside the waterproof bladder 1 and the guide pipe 9. As the concrete is continuously poured in, the top surface of the waterproof bladder 1 gradually rises, squeezing the mud-water inside the caisson 4 upwards until the top surface of the waterproof bladder 1 contacts the cover plate 2.

[0124] (9) After the top surface of the waterproof bladder 1 contacts the cover plate 2, the top surface of the waterproof bladder 1 will expand upwards and lift the cover plate 2 due to the small weight of the cover plate 2. At this time, the slackness of the detection rope 15 connected to the cover plate 2 can be used to determine whether the cover plate 2 has been lifted. When the detection rope 15 is found to be slack, the pouring of concrete into the waterproof bladder 1 should be stopped, and the counterweight 3 should be hoisted to the top surface of the cover plate 2 according to the calculation requirements. Note that the counterweight 3 should be placed evenly and symmetrically on the top surface of the cover plate 2 so that the top surface of the waterproof bladder 1 is evenly compressed. Since the top surface of the waterproof bladder 1 is in contact with the cover plate 2 at this time, it forms an upward supporting force on the cover plate 2. The effective weight of the counterweight 3 placed on the cover plate 2 will be mainly borne by the top surface of the waterproof bladder 1. The pressure of the counterweight 3 on the cover plate 2 is not large and will not damage the cover plate 2.

[0125] (10) Under the effective pressure of the counterweight 3, the waterproof bladder 1 will be squeezed further downward and outward, which helps to fully squeeze out and drain the mud and water between the waterproof bladder 1 and the base and between the waterproof bladder 1 and the inclined surface 5 of the cutting foot of the caisson 4.

[0126] (11) After the counterweight 3 is installed, readjust the four detection ropes 15 of the cover plate 2 to make the detection ropes 15 taut, and fix the upper end of the detection ropes 15 to the corresponding vertical position on the top surface of the caisson 4. Continue to pour concrete into the waterproof bladder 1 to increase the concrete pressure inside the waterproof bladder 1 and make the waterproof bladder 1 fully expand. The top surface of the waterproof bladder 1 will gradually rise, lifting the cover plate 2 again and loosening the detection ropes 15. When the detection ropes 15 are found to be loose, it means that the net pressure inside the waterproof bladder 1 has reached the control net pressure inside the waterproof bladder 1. At this time, stop pouring concrete into the waterproof bladder 1.

[0127] (12) After the concrete in the waterproof bladder 1 is poured, the guide pipe 9 can be removed. By rotating the guide pipe 9 and simultaneously inserting a long rod into the round hole of the fixing wing plate 13 to fix it, the grouting pipe 10 is prevented from rotating with the guide pipe 9. The guide pipe 9 is then removed from the grouting pipe 10. Since the grouting pipe 10 is equipped with a one-way valve 19, even if the concrete pressure inside the waterproof bladder 1 is higher than the mud and water pressure outside the waterproof bladder 1, the concrete will not flow out of the waterproof bladder 1.

[0128] (13) After the concrete inside the waterproof bladder 1 has solidified, use a crane to remove the counterweight 3 and the cover plate 2.

[0129] (14) Use a mud pump to drain the mud and water from the caisson 4. Note that the buoyancy stability of the caisson 4 should be verified before pumping water out. If the caisson 4 cannot meet the buoyancy requirements by its own weight, a counterweight needs to be placed on the top of the caisson 4 to ensure its buoyancy stability. The buoyancy verification of the caisson 4 and the placement of a counterweight on the top of the caisson 4 to maintain its buoyancy stability are standard techniques for the caisson 4 and will not be elaborated here.

[0130] (15) After draining the mud and water from the caisson 4, construct the reinforced concrete base slab 17 of the caisson on the sealing concrete 25 inside the caisson 4. Before pouring the reinforced concrete base slab 17, remove the grouting pipe 10 on the waterproof bladder 1 and clean the residual concrete on the grouting pipe 10 on the waterproof bladder 1. Since the bottom and sides of the sealing concrete are completely wrapped by the waterproof bladder 1, the waterproof bladder 1 on the upper surface of the sealing concrete does not have a waterproofing function. Therefore, no special treatment is needed for the grouting pipe 10 and its surrounding area of ​​the waterproof bladder 1. Only the grouting pipe 10 needs to be removed and the residual concrete at the grouting pipe 10 needs to be cleaned. The reinforced concrete base slab 17 can be poured directly on the top surface of the waterproof bladder 1. When the design requires the reinforced concrete base slab 17 to be directly connected to the sealing concrete, the top surface of the waterproof bladder 1 can be cut off and removed along the perimeter of the caisson 4 with a utility knife. Rebar installation, roughening and other connection measures can be taken on the surface of the sealing concrete to make the sealing concrete and the reinforced concrete base slab 17 a whole.

[0131] (16) After the reinforced concrete base slab 17 solidifies, the bottom sealing construction of caisson 4 is completed.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A caisson underwater sealing device for pouring concrete inside a bladder, characterized in that, It includes a waterproof bladder (1), a cover plate (2), a counterweight (3), a grouting assembly, and a cutting edge slope (5) and a support platform (7) arranged sequentially from bottom to top on the inner side of the bottom of the caisson (4). A sealing groove (6) is provided on the cutting edge slope (5). The sealing groove (6) is arranged in a ring around the cutting edge slope (5). The cutting edge slope (5) at the bottom of the caisson (4) forms a frustum-shaped structure with a smaller top and a larger bottom. The waterproof bladder (1) is adapted to be laid at the bottom of the caisson (4), its side is in contact with the inclined surface (5) of the cutting edge, its bottom surface is in contact with the base of the caisson (4), and a grouting port is provided at the center of the top surface. A sealing ring (8) adapted to the sealing groove (6) is provided in the middle of the side of the waterproof bladder (1). The grouting assembly includes a conduit (9) and a grouting pipe (10). The lower end of the grouting pipe (10) is sealed and installed at the grouting port, and the upper end is connected to the end of the conduit (9). A one-way valve (19) is provided inside the grouting pipe (10). The cover plate (2) is a grid-shaped perforated plate, placed on the support (7) and located above the waterproof bladder (1); The counterweight (3) is laid on the top surface of the cover plate (2) to control the net pressure of the concrete inside the waterproof bladder (1); The waterproof bladder (1) is made of elastic sealing rubber and includes a top surface, a bottom surface and a side surface. After filling, its shape is a combination of an upper frustum shape and a lower spherical cap shape. The frustum shape structure is consistent with the frustum shape enclosed by the cutting edge slope (5), and the side height is 0.9-0.95 times the height of the cutting edge slope (5). The angle between the inclined surface (5) of the cutting edge and the vertical surface is 20 degrees to 30 degrees.

2. The underwater sealing device for caissons with in-bag concrete pouring according to claim 1, characterized in that, The waterproof bladder (1) is wrapped with an elastic ring (11) at the junction of its side and bottom surfaces. The elastic ring (11) is made of high carbon steel wire. The elastic ring (11) can be folded and deformed. After the constraint is released, it can automatically extend by its own elasticity, so that the waterproof bladder (1) can be laid flat on the base of the caisson (4).

3. The underwater sealing device for caissons with in-bag concrete pouring according to claim 2, characterized in that, The sealing ring (8) has a rectangular shape plus a semi-circular shape. The rectangular part is heat-pressed and fused to the side of the waterproof bag (1), and the semi-circular part protrudes from the side of the waterproof bag (1). The sealing groove (6) has an isosceles right triangle shape, and its depth is adapted to the cross-sectional height of the sealing ring (8).

4. The underwater sealing device for caissons with in-bag concrete pouring according to claim 3, characterized in that, The grouting pipe (10) is made of metal or plastic. Its bottom end is sealed to the grouting port on the top surface of the waterproof bag (1) through a flange and a sealing gasket (12). Its top end is threaded to the end of the guide pipe (9). The outer wall of the grouting pipe (10) is provided with a wing plate (13). The wing plate (13) has a round hole. The wing plate (13) is used to fix the grouting pipe (10) to prevent the grouting pipe (10) from rotating with the guide pipe (9).

5. The underwater sealing device for caissons with in-bag concrete pouring according to claim 4, characterized in that, The cover plate (2) has a layer of mesh (14) on its lower surface. The mesh length and width of the mesh (14) are no more than 50 mm. The diameter of the cover plate (2) is 100 mm to 200 mm smaller than the diameter of the caisson (4).

6. The underwater sealing device for caissons with in-bag concrete pouring according to claim 5, characterized in that, The counterweight (3) is provided with a lifting ring (18) on its top surface. When the counterweight (3) is laid, it is evenly and symmetrically arranged on the top surface of the cover plate (2) to ensure that the top surface of the waterproof bag (1) is subjected to uniform force.

7. A method for underwater sealing of a caisson by pouring concrete inside the caisson, wherein the sealing method employs the sealing device described in claim 6, characterized in that, Includes the following steps: S1. Precast caisson (4), with a cutting edge bevel (5), sealing groove (6) and bearing platform (7) machined on the inner side of the bottom of the caisson (4); S2. The caisson (4) is lowered to the design elevation using the non-drainage method; S3. Make a waterproof bladder (1), a cover plate (2), a counterweight (3) and a grouting assembly, and seal the lower end of the grouting pipe (10) at the grouting port of the waterproof bladder (1); S4. First, thread the grouting pipe (10) to the guide pipe (9) at the upper end, then fold the waterproof bladder (1) and tie it with a rope. At the same time, set a rope release rod at the end of the rope. S5. Place the folded waterproof bag (1) into the bottom of the caisson (4), pull out the rope release rod and loosen the rope. The waterproof bag (1) will automatically extend under the action of the elastic ring (11). Then the staff will use the long rod to adjust the underwater position of the waterproof bag (1) so that it fits the base of the caisson (4) and the slope of the cutting edge (5). S6. Hoist the cover plate (2) to the top of the caisson (4), arrange the detection rope (15) around the cover plate (2), and then slowly lower the cover plate (2). The center hole (16) of the cover plate (2) falls onto the support platform (7) through the guide tube (9). Then tighten the detection rope (15) and fix the upper end of the detection rope (15) to the top of the caisson (4). S7. Pour concrete into the waterproof bladder (1) through the conduit (9) until the waterproof bladder (1) expands and lifts the cover plate (2). Stop pouring concrete when the test rope (15) is observed to be loose. Lay a counterweight (3) on the cover plate (2) and the cover plate (2) will press the waterproof bladder (1) flat again. S8. Re-tighten the test rope (15), continue pouring concrete until the test rope (15) loosens again, stop pouring and remove the guide pipe (9); S9. After the concrete inside the waterproof bladder (1) has solidified, remove the counterweight (3) and cover plate (2) in sequence, and pump out the mud and water in the caisson (4). S10. Remove the grouting pipe (10) and clean up the residual concrete. Pour a reinforced concrete base plate (17) on the top surface of the waterproof bladder (1) to complete the bottom sealing.

8. The bottom sealing method according to claim 7, characterized in that, In steps S7 and S8, the net pressure of the concrete inside the waterproof bladder (1) is controlled to be 10 kPa to 30 kPa. When the depth of mud and water on the top surface of the waterproof bladder (1) inside the caisson (4) is less than 10 meters, the net pressure is taken as 10 kPa. When the mud and water depth at the top surface of the waterproof bladder (1) inside the caisson (4) is between 10 meters and 30 meters, the net pressure of the concrete inside the waterproof bladder (1) is determined by linear interpolation between 10 kPa and 30 kPa. When the depth of mud and water on the top surface of the waterproof bladder (1) inside the caisson (4) exceeds 30 meters, the net pressure is taken as 30 kPa.

9. The bottom sealing method according to claim 7, characterized in that, In step S7, the effective weight of the counterweight (3) is calculated and determined by the following formula: ; in, For the effective weight of the cover plate (2), The effective weight of the counterweight (3) is... The cross-sectional area of ​​the caisson (4) is... To control the net pressure inside the waterproof bladder (1), 0.9 is the ratio of the contact area between the top surface of the waterproof bladder (1) and the cover plate (2) to the cross-sectional area of ​​the caisson (4); The effective weight of the cover plate (2) is the weight of the cover plate (2) minus the buoyancy of the mud and water acting on the cover plate (2); The effective weight of the counterweight (3) is the weight of the counterweight (3) minus the buoyancy of the mud and water acting on the counterweight (3).

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