Method for dismantling a steel sheet pile cofferdam in water

Abstract

The present application relates to a kind of steel sheet pile cofferdam dismantling method in water, belong to cofferdam construction technical field.The steel sheet pile cofferdam dismantling method in water, it includes the following steps: first support is arranged in cofferdam bottom, to provide upward support force to bottom layer cofferdam;Second support is installed on each layer cofferdam except top layer cofferdam, to provide upward support force to its adjacent upper layer cofferdam;Hoisting steel wire rope is installed on cofferdam, and the free end of hoisting steel wire rope is lifted to the height above the water level in outside;Reserved steel sheet pile is selected in the steel sheet pile of each side of cofferdam, water is backfilled to cofferdam to be flush with the water level in outside, and other each steel sheet pile except reserved steel sheet pile is pulled out;Each layer cofferdam is hoisted out in whole from top to bottom using crane in sequence;Reserved steel sheet pile is pulled out, to complete cofferdam dismantling.The steel sheet pile cofferdam dismantling method in water does not need to disassemble each layer cofferdam, simplifies the dismantling procedure, reduces high-risk operation, and reduces construction risk.

Description

Technical Field

[0001] The invention belongs to the technical field of cofferdam construction, and in particular relates to a method for dismantling an underwater steel sheet pile cofferdam. Background Art

[0002] During underwater construction, such as bridge pier casting, steel sheet pile cofferdams are often required to create a dry working environment. These cofferdams are constructed from multiple steel sheet piles connected by interlocking joints. Multiple layers of cofferdam walls are installed inside the piles, providing internal support and strengthening the cofferdam's structure. After the cofferdam is closed, a concrete seal layer is poured, and the water inside is then pumped out to create a dry working environment.

[0003] After the dry construction of the buildings within the cofferdam is completed, the steel sheet pile cofferdam needs to be dismantled to restore the surrounding environment. The conventional dismantling method for a steel sheet pile cofferdam involves dismantling and removing the lowest level of cofferdam walls, then refilling the cofferdam with water until it reaches the upper level, dismantling and removing that level of cofferdam walls. This process continues from bottom to top, with water being refilled and cofferdam walls being removed layer by layer, before finally removing the steel sheet piles. Patents CN102409688A, CN112962641A, CN111764417A, and CN101289867A all disclose dismantling procedures similar to the conventional steel sheet pile cofferdam dismantling method described above.

[0004] However, the conventional steel sheet pile cofferdam dismantling method has the following shortcomings: (1) The dismantling and removal of the cofferdam is carried out in a narrow working space, which makes the dismantling construction inconvenient; (2) The cofferdam must be dismantled in a bottom-up order, and the cofferdam must be dismantled. The process is complicated, and there are many high-risk operations such as lifting, electric welding, high-altitude operations, and water-side operations. The dismantling construction risk is high, and each cofferdam dismantling and removal takes 2 to 3 days, which is a long dismantling period. At the same time, when the dismantled cofferdam is reused, an additional 2 to 3 days of cofferdam assembly time is required, resulting in a certain amount of construction time waste; (3) When dismantling the cofferdam, the water return method is adopted layer by layer, and the internal and external water pressures are unbalanced. The cofferdam is dismantled and removed under stress, which poses a great risk. Summary of the Invention

[0005] In response to the above-mentioned shortcomings of conventional steel sheet pile cofferdam dismantling methods, the present invention provides a method for dismantling underwater steel sheet pile cofferdams, which does not require dismantling each layer of the cofferdam, simplifies the dismantling process, improves the dismantling efficiency, shortens the dismantling period, and at the same time, reduces high-risk operations and reduces the risk of dismantling construction.

[0006] The present invention provides a method for dismantling an underwater steel sheet pile cofferdam, comprising the following steps:

[0007] Temporary support installation steps: Install a first support member on the top surface of the bottom concrete layer at the bottom of the cofferdam or on the structure constructed inside the cofferdam to provide upward support for the bottom cofferdam at the bottom; Install a second support member on each cofferdam layer except the top cofferdam at the top to provide upward support for the adjacent upper cofferdam layers;

[0008] Preparation steps for hoisting the enclosure: Install the hoisting wire rope on the enclosure and lift the free end of the hoisting wire rope to a height above the external water level;

[0009] Step of removing steel sheet piles: Select reserved steel sheet piles from the steel sheet piles on each side of the cofferdam, refill water into the cofferdam until it is flush with the external water level, and remove all other steel sheet piles except the reserved steel sheet piles, so that the cofferdam can be supported by the reserved steel sheet piles, the first support member and the second support member;

[0010] Steps for dismantling enclosures layer by layer: Connect the hoisting wire ropes connected to the enclosures to the crane, and use the crane to hoist out each layer of enclosures from top to bottom. During the process of hoisting out each layer of enclosures, use the reserved steel sheet piles to prevent the remaining layers of enclosures from shifting.

[0011] Steps for removing reserved steel sheet piles: Remove the reserved steel sheet piles to complete the cofferdam demolition.

[0012] In some embodiments, during the temporary support installation step, first support members are installed correspondingly below the inner support at each corner of the bottom enclosure, so that the inner support at each corner of the bottom enclosure is supported on the first support members.

[0013] In some embodiments, in the step of installing the temporary support, the first support member is a support block.

[0014] In some embodiments, in the temporary support installation step, second support members are installed on the frames of the enclosure located on each side of the cofferdam, so that the frames of the adjacent upper enclosure are supported on the second support members.

[0015] In some embodiments, in the temporary support installation step, the second support member is a support column fixedly connected to the enclosure, and the height of the support column is equal to the distance between two adjacent layers of enclosures, so that the adjacent upper layer of enclosure is placed on the top of the support column.

[0016] In some embodiments, during the cofferdam lifting preparation step, the free end of the lifting wire rope is temporarily fixed to the part of the building constructed inside the cofferdam that is above the external water level, so that the free end of the lifting wire rope is maintained at a height above the external water level.

[0017] In some of the embodiments, when the cavity is formed in the enclosure and is connected to the outside, the hoisting preparation step further comprises: forming a plurality of through holes in the enclosure, which are connected to the cavity; and in the step of removing the enclosure layer by layer, the hoisting is paused when the enclosure is just lifted out of the water, and the hoisting is continued after the water in the cavity is discharged through the through holes.

[0018] In some of the embodiments, in the step of removing the steel sheet piles, the specific step of selecting the reserved steel sheet piles from the steel sheet piles on each side of the cofferdam is: selecting at least two positions on each side of the cofferdam as selected positions, and selecting the steel sheet piles at the selected positions as the reserved steel sheet piles.

[0019] In some of the embodiments, in the step of removing the steel sheet piles, 2-3 adjacent steel sheet piles at each selected position are selected as the reserved steel sheet piles.

[0020] In some of the embodiments, in the step of removing the steel sheet piles, during the process of backfilling water into the cofferdam, the backfilling of water is stopped when the water level rises to the level of the enclosure layers located below the water level of the outside, the connection between the current enclosure layer and all the steel sheet piles is released, and then the backfilling of water is continued; after the water is backfilled to the level of the water level of the outside, before the removal of the steel sheet piles other than the reserved steel sheet piles, the connection between the enclosure layers located above the water level of the outside and the steel sheet piles other than the reserved steel sheet piles is released; and in the step of removing the enclosure layer by layer, before the enclosure layers located above the water level of the outside are lifted out by the crane, the connection between the enclosure layer and the reserved steel sheet piles is released.

[0021] Compared with the prior art, the advantages and beneficial effects of the present application are:

[0022] 1. The method for removing the steel sheet pile cofferdam in water provided by the present application, first installs first and second support members as temporary supports in the cofferdam in a dry working environment to realize vertical support of the enclosure, installs a hoisting steel wire rope on the enclosure to facilitate subsequent hoisting of the enclosure, removes the steel sheet piles other than the reserved steel sheet piles in a water-filled state of the cofferdam, at this time the support system of the enclosure is converted into a support system composed of the temporary supports and the reserved steel sheet piles, then the enclosure layers are sequentially lifted off from top to bottom in whole through the pre-installed hoisting steel wire rope, and finally the reserved steel sheet piles are removed, thereby completing the removal of the cofferdam. The conversion of the support system of the enclosure is realized by the cooperation of the temporary support system and the reserved steel sheet piles, the steel sheet piles are removed in advance, the enclosure layers can be sequentially lifted and removed in whole from top to bottom, the enclosure layers do not need to be disassembled, the construction process is simplified, the removal efficiency is improved, and the removal period is shortened. At the same time, the construction process in the narrow space of the cofferdam is less, the high-risk operation is less, and the risk of removal construction is reduced.

[0023] 2. In the method for dismantling underwater steel sheet pile cofferdams provided by the present invention, water is first refilled into the cofferdam until the internal and external water pressures are balanced, and then the cofferdam is dismantled. This avoids dismantling the cofferdam under stress and maintains the integrity of the internal cofferdam structure when dismantling the steel sheet piles, thereby improving structural safety and reducing construction risks.

[0024] 3. The method for dismantling underwater steel sheet pile cofferdams provided by the present invention does not require the dismantling of each layer of cofferdams, facilitating the reuse of the cofferdams. For pre-supported cofferdams, this saves the work of reassembling and installing the cofferdams during the construction of the next cofferdam during the flow operation, greatly improving construction efficiency and saving construction costs.

[0025] 4. In the underwater steel sheet pile cofferdam dismantling method provided by the present invention, some reserved steel sheet piles are retained, which can ensure the overall stability and safety of the cofferdam from the time the steel sheet piles are removed to the time the cofferdam is dismantled, so that the cofferdam will not be displaced or even collapsed when affected by waves and water flow after the steel sheet piles are removed. At the same time, during the cofferdam dismantling process, the reserved steel sheet piles can ensure the stability of the cofferdam hoisting operation within the sheet pile range, avoid displacement or violent shaking of the cofferdam during hoisting, and reduce the risk of hoisting construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 A flowchart of a method for dismantling an underwater steel sheet pile cofferdam provided by one embodiment of the present invention;

[0028] Figure 2 A top view of an underwater steel sheet pile cofferdam provided in one embodiment of the present invention;

[0029] Figure 3 A schematic diagram of the steps for installing temporary supports;

[0030] Figure 4 Schematic diagram of the installation arrangement of the second support member on the enclosure in the temporary support installation step;

[0031] Figure 5 This is a schematic diagram of the installation of lifting wire ropes on each level of the enclosure during the preparation steps for enclosure lifting;

[0032] Figure 6 A schematic diagram of opening a through hole in the enclosure in preparation for hoisting the enclosure;

[0033] Figure 7 It is a schematic diagram after all steel sheet piles except the reserved steel sheet piles are removed in the steel sheet pile removal step;

[0034] Figure 8This is a schematic diagram of the top enclosure after it is hoisted out as a whole during the step of dismantling the enclosure layer by layer;

[0035] Figure 9 This is a schematic diagram of the second layer of enclosure after it is hoisted out as a whole during the step of dismantling the enclosure layer by layer;

[0036] Figure 10 This is a schematic diagram of the bottom enclosure after it is hoisted out as a whole during the step of dismantling the enclosure layer by layer;

[0037] Figure 11 This is a schematic diagram after the reserved steel sheet piles are removed.

[0038] In the picture:

[0039] 1. Cofferdam; 2. Building; 3. Bottom concrete layer; 4. First support member; 5. Second support member; 6. Lifting wire rope;

[0040] 11. Steel sheet piles; 11a. Reserved steel sheet piles;

[0041] 12. Enclosure; 12a. Bottom enclosure; 12b. Second enclosure; 12c. Top enclosure; 121. Frame; 1211. I-beam; 122. Internal support;

[0042] 21. Bridge pier; 22. Bridge pier cap;

[0043] a. Cavity; b. Through hole. DETAILED DESCRIPTION

[0044] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0046] The terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the quantity of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0047] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0048] As attached Figure 1-Figure 5 、 Figure 7-11 As shown, in an exemplary embodiment of the method for dismantling a steel sheet pile cofferdam in water according to the present invention, the method for dismantling a steel sheet pile cofferdam in water comprises the following steps:

[0049] S1: Install temporary supports: Install first supports 4 on the top surface of the bottom concrete layer 3 at the bottom of the cofferdam 1 or on the structure 2 constructed within the cofferdam 1 to provide upward support for the bottom cofferdam 12a at the bottom layer; install second supports 5 on each cofferdam 12 except the top cofferdam 12c at the top layer to provide upward support for the adjacent upper cofferdam 12;

[0050] S2: Preparation step for hoisting the enclosure: Install the hoisting wire rope 6 on the enclosure 12, and lift the free end of the hoisting wire rope 6 to a height above the external water level;

[0051] S3: Step of removing steel sheet piles: Select reserved steel sheet piles 11a from the steel sheet piles 11 on each side of the cofferdam 1, refill water into the cofferdam 1 until the water level is flush with the external water level, and remove all other steel sheet piles 11 except the reserved steel sheet piles 11a, so that the cofferdam 12 can be supported by the reserved steel sheet piles 11a, the first support members 4, and the second support members 5;

[0052] S4: dismantling the enclosure layer by layer: connect the lifting wire rope 6 connected to the enclosure 12 to a crane, and use the crane to lift out the enclosures 12 from top to bottom in their entirety. During the process of lifting out the enclosures 12 in each layer, use the reserved steel sheet piles 11a to prevent the remaining layers of enclosures 12 from shifting.

[0053] S5: Step of removing the reserved steel sheet piles: removing the reserved steel sheet piles 11a to complete the dismantling of the cofferdam 1.

[0054] The above-mentioned method for dismantling the underwater steel sheet pile cofferdam is to first install the first support member 4 and the second support member 5 as temporary supports inside the cofferdam 1 in a dry working environment to realize the vertical support of the cofferdam 12, and install the lifting wire rope 6 on the cofferdam 12 to facilitate the subsequent lifting of the cofferdam 12, and then remove the other steel sheet piles 11 except the reserved steel sheet piles 11a in the water-filled state in the cofferdam 1. At this time, the support system of the cofferdam 12 is converted to the support of the temporary support system and the reserved steel sheet piles 11a. Then, the pre-installed lifting wire rope 6 can be used to lift each layer of the cofferdam from top to bottom. The cofferdam 1 is dismantled by lifting the cofferdam 12 as a whole and finally removing the reserved steel sheet piles 11a. The cofferdam 1 is dismantled in this way. The cofferdam 1 support system is converted by coordinating the temporary support system and the reserved steel sheet piles 11a. The steel sheet piles 11 can be dismantled first, so that each layer of cofferdam 12 can be hoisted and dismantled as a whole from top to bottom. There is no need to dismantle each layer of cofferdam 12, which simplifies the construction process, improves the dismantling efficiency, and shortens the dismantling period. At the same time, there are fewer construction work processes and fewer high-risk operations in the narrow space of the cofferdam 1, which reduces the risk of dismantling construction. At the same time, in the above-mentioned underwater steel sheet pile cofferdam dismantling method, water is first refilled into the cofferdam 1 until the internal and external water pressures are balanced, and then the cofferdam 12 is dismantled, which avoids the cofferdam 12 being dismantled under stress, and the overall structure of the internal cofferdam is kept intact when the steel sheet piles 11 are dismantled, which improves structural safety and reduces construction risks. Furthermore, the above-mentioned method for dismantling the underwater steel sheet pile cofferdam does not require the dismantling of each layer of the cofferdam 12, which facilitates the reuse of the cofferdam 12. For the pre-support cofferdam 1, it saves the work of reassembling and installing the cofferdam 12 when constructing the next cofferdam 1 during the flow operation, greatly improving construction efficiency and saving construction costs. In addition, in the above-mentioned method for dismantling the underwater steel sheet pile cofferdam, some reserved steel sheet piles 11a are retained, which can ensure the overall stability and safety of the cofferdam 12 from the removal of the steel sheet piles 11 to the removal of the cofferdam 12, so that the cofferdam 12 will not be displaced or even collapsed when affected by waves and water flow after the steel sheet piles 11 are removed. At the same time, during the removal of the cofferdam 12, the reserved steel sheet piles 11a can ensure the stability of the hoisting operation of the cofferdam 12 within the sheet pile range, avoid displacement or violent shaking of the cofferdam 12 during hoisting, and reduce the risk of hoisting construction.

[0055] Regarding the steps for installing temporary support for S1, it should be noted that if Figure 3 As shown, the steel sheet pile cofferdam 1 of this embodiment is specifically used for the casting construction of bridge piers 21, wherein the first support member 4 is installed on the pier cap 22 cast within the cofferdam 1. It will be appreciated that when the structure 2 cast within the cofferdam 1 does not have a flat surface and its area is relatively small relative to the bottom concrete layer 3, the first support member 4 can be installed on the bottom concrete layer 3 to provide stable vertical support for the bottom enclosure 12a.

[0056] It should also be noted that if Figure 3As shown, a first support member 4 is mounted below the inner supports 122 at each corner of the bottom enclosure 12a, so that the inner supports 122 at each corner of the bottom enclosure 12a are supported on the first support members 4. Having the first support members 4 supported on the inner supports 122 at each corner of the bottom enclosure 12a places the first support members 4 closer to the center of the enclosure 12, improving support stability and facilitating installation of the first support members 4. Preferably, the first support members 4 are support blocks.

[0057] It is further necessary to explain that if Figure 3 and Figure 4 As shown, the second support members 5 are installed on the frame 121 of the enclosure 12 located on each side of the cofferdam 1, so that the frame 121 of the adjacent upper enclosure 12 is supported on the second support members 5. The second support members 5 are installed on the frame 121 of the enclosure 12 to improve the supporting force at the frame 121 of the upper enclosure 12, which can more evenly distribute the load of the upper enclosure 12 and avoid deformation or damage of the enclosure 12 due to excessive local force. It is understandable that, if Figure 4 As shown, multiple second support members 5 can be installed on each frame 121 of the enclosure 12. The multiple second support members 5 are evenly distributed on the frame 121 along the extension direction of the frame 121, which is beneficial to distributing the load of the upper enclosure 12 and improving the stability of the support. Figure 3 As shown, the second support member 5 is a support column fixedly connected to the enclosure 12. The height of the support column is equal to the distance between two adjacent enclosures 12, so that the upper enclosure 12 can be placed on the top of the support column. This arrangement of the second support member 5 ensures that the upper enclosure 12 and the lower enclosure 12 only have a supporting relationship, not a fixed connection, which facilitates the subsequent lifting of the enclosures 12 layer by layer. It should be noted that the support column can be installed on the enclosure 12 by welding.

[0058] Regarding the enclosure lifting preparation step S2, it should be noted that this step involves pre-installing the lifting wire rope 6 on the enclosure 12 and raising the free end of the lifting wire rope 6 to a height above the external water level. This is to avoid the need for underwater connection operations when subsequently lifting the enclosure 12 using a crane. It is understood that in this step, the lifting wire rope 6 can be pre-installed only for enclosures 12 located below the external water level. For enclosures 12 located above the external water level (e.g., the top enclosure 12c), the lifting wire rope 6 can be installed and connected to the crane before lifting. Furthermore, to facilitate lifting of the enclosure 12, lifting points are provided at the four corners of the enclosure 12 for connecting the lifting wire rope 6.

[0059] It should also be noted that in order to keep the free end of the lifting wire rope 6 at a height above the external water level, Figure 5As shown, the free end of the lifting wire rope 6 is temporarily secured to a portion of the structure 2 constructed within the cofferdam 1 that is above the external water level (in this embodiment, specifically, the free end of the lifting wire rope 6 is temporarily secured to the top surface of the cast pier 21). This maintains the free end of the lifting wire rope 6 above the external water level. Furthermore, by temporarily securing the lifting wire rope 6 to the structure 2 constructed within the cofferdam 1, the lifting wire rope 6 can also provide tension to the cofferdam 12 after the steel sheet piles 11 are removed, thereby maintaining the stability of the cofferdam 12.

[0060] In addition, if Figure 6 As shown, the cofferdam 12 used in this embodiment is assembled from two parallel I-beams 1211 arranged in a vertical direction. A cavity a is formed between the two I-beams 1211, which is connected to the outside world. After water is subsequently refilled into the cofferdam 1, water can enter the cavity a of the cofferdam 12. When the cofferdam 12 is subsequently lifted and removed, the water in the cavity a cannot be quickly drained, which increases the lifting weight. In order to quickly drain the water in the cavity a, the cofferdam lifting preparation step S2 also includes: opening multiple through holes b in the cofferdam 12 that are connected to the cavity a; in the cofferdam removal step S4, when the cofferdam 12 is lifted just out of the water, the lifting is suspended, and the cofferdam 12 is resumed after the water in the cavity a is drained through the through holes b. When a cavity a is formed within the enclosure 12 that is communicable with the outside world, a through hole b is pre-formed in the enclosure 12. This allows water in the cavity a of the enclosure 12 to be quickly drained through the through hole b during the lifting and removal of the enclosure 12, thereby reducing the total lifting weight of the enclosure 12 and ensuring operational safety. It should be noted that if the crane's lifting capacity is sufficient to meet the total lifting weight requirements of the enclosure 12 steel structure and the water within it, the steps of forming the through hole b in the enclosure 12 and draining water through the through hole b are not required.

[0061] Regarding the S3 steel sheet pile removal steps, it should be noted that if Figure 7 As shown, the specific steps for selecting the reserved steel sheet piles 11a from the steel sheet piles 11 on each side of the cofferdam 1 are as follows: at least two spaced locations are selected on each side of the cofferdam 1 as selected locations, and the steel sheet piles 11 at the selected locations are used as the reserved steel sheet piles 11a. This method of selecting the reserved steel sheet piles 11a enables the reserved steel sheet piles 11a to be distributed at intervals on each side of the cofferdam 1, which is more conducive to providing support and protection for the cofferdam 12. Preferably, as Figure 7 As shown, the selected positions on each side of the cofferdam 1 are evenly distributed on the side of the cofferdam 1, so that the reserved steel sheet piles 11a are more evenly distributed. Figure 7 As shown, at each selected location, 2 to 3 adjacent steel sheet piles 11 are used as reserved steel sheet piles 11 a to further improve stability.

[0062] Regarding the step S3 of removing the steel sheet piles and the step S5 of removing the reserved steel sheet piles, it should be further explained that the specific steps of removing the steel sheet piles 11 or the reserved steel sheet piles 11a are as follows: using a vibrating hammer to clamp the steel sheet piles 11 or the reserved steel sheet piles 11a, and vibrating the steel sheet piles 11 or the reserved steel sheet piles 11a by the vibrating hammer. Clamping the steel sheet piles 11 and vibrating them with the vibrating hammer can quickly remove the steel sheet piles 11.

[0063] Regarding the step of removing the enclosure layer by layer in S4, it should be noted that Figures 8-10 As shown, in this embodiment, specifically: first lift and remove the top enclosure 12c, then lift and remove the second enclosure 12b, and finally lift and remove the bottom enclosure 12a.

[0064] In addition, if Figure 3 As shown, when designing a steel sheet pile cofferdam 1, its top cofferdam 12c is typically located above the external water level, while the second cofferdam 12b and the bottom cofferdam 12a are typically located below the external water level. Furthermore, before removing the steel sheet piles 11, the connections between the steel sheet piles 11 and each layer of cofferdam 12 must be released. Before lifting and removing the cofferdam 12, the connections between the cofferdam 12 and the reserved steel sheet piles 11a must also be released. To avoid underwater operations when releasing the connections between the cofferdam 12 and the steel sheet piles 11 or the reserved steel sheet piles 11a, the following solution is preferred:

[0065] In the step of removing the steel sheet piles S3, during the process of refilling water into the cofferdam 1, the process also includes: when the water level of the refilled water rises close to the layers of cofferdams 12 located below the external water level, the refilling is stopped, the connection between the current layer of cofferdams 12 and all the steel sheet piles 11 is released, and then the refilling of water is continued; after the refilled water reaches the same level as the external water level and before the steel sheet piles 11 other than the reserved steel sheet piles 11a are removed, the process also includes releasing the connection between the layers of cofferdams 12 located above the external water level and the steel sheet piles 11 other than the reserved steel sheet piles 11a; in the step of dismantling the cofferdams layer by layer S4, before using a crane to lift out the layers of cofferdams 12 located above the external water level, the process also includes releasing the connection between the layers of cofferdams and the reserved steel sheet piles 11a.

[0066] It should be noted that releasing the connection between the enclosure 12 and the steel sheet piles 11 specifically refers to removing the steel pad located in the gap between the enclosure 12 and the steel sheet piles 11 and unwelding the steel sheet piles 11 and the enclosure 12 .

[0067] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, persons skilled in the art should understand that the specific implementation methods of the present invention may still be modified or some technical features may be replaced by equivalents without departing from the spirit of the technical solutions of the present invention, and all of these should fall within the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A method for dismantling a steel sheet pile cofferdam in water, characterized in that: The steps include: Temporary support installation steps: Install a first support member on the top surface of the bottom concrete layer at the bottom of the cofferdam or on the structure constructed inside the cofferdam to provide upward support for the bottom cofferdam at the bottom; Install a second support member on each cofferdam layer except the top cofferdam at the top to provide upward support for the adjacent upper cofferdam layers; Preparation steps for hoisting the enclosure: Install the hoisting wire rope on the enclosure and lift the free end of the hoisting wire rope to a height above the external water level; Step of removing steel sheet piles: Select reserved steel sheet piles from the steel sheet piles on each side of the cofferdam, refill water into the cofferdam until it is flush with the external water level, and remove all other steel sheet piles except the reserved steel sheet piles, so that the cofferdam can be supported by the reserved steel sheet piles, the first support member and the second support member; Steps for dismantling enclosures layer by layer: Connect the hoisting wire ropes connected to the enclosures to the crane, and use the crane to hoist out each layer of enclosures from top to bottom. During the process of hoisting out each layer of enclosures, use the reserved steel sheet piles to prevent the remaining layers of enclosures from shifting. Steps for removing reserved steel sheet piles: Remove the reserved steel sheet piles to complete the cofferdam demolition.

2. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: In the temporary support installation step, the first support members are installed correspondingly below the inner supports at each corner of the bottom enclosure, so that the inner supports at each corner of the bottom enclosure are supported on the first support members.

3. The method for dismantling underwater steel sheet pile cofferdam according to claim 1 or 2, characterized in that: In the step of installing a temporary support, the first support member is a support block.

4. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: In the temporary support installation step, the second support member is installed on the frame of the enclosure located on each side of the cofferdam, so that the frame of the adjacent upper enclosure is supported on the second support member.

5. The method for dismantling underwater steel sheet pile cofferdam according to claim 1 or 4, characterized in that: In the temporary support installation step, the second support member is a support column fixedly connected to the enclosure, and the height of the support column is equal to the distance between two adjacent layers of the enclosure, so that the adjacent upper layer of the enclosure is placed on the top of the support column.

6. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: In the cofferdam lifting preparation step, the free end of the lifting wire rope is temporarily fixed to the part of the building constructed in the cofferdam that is above the external water level, so that the free end of the lifting wire rope is maintained at a height above the external water level.

7. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: When a cavity that can communicate with the outside world is formed inside the enclosure, the enclosure lifting preparation step also includes: opening a plurality of through holes connected to the cavity on the enclosure; in the step of dismantling the enclosure layer by layer, the lifting is suspended when the enclosure is just lifted out of the water surface, and the lifting of the enclosure is continued after the water in the cavity is discharged through the through holes.

8. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: In the step of removing the steel sheet piles, the specific steps of selecting reserved steel sheet piles from the steel sheet piles on each side of the cofferdam are: selecting at least two spaced positions on each side of the cofferdam as selected positions, and using the steel sheet piles at the selected positions as reserved steel sheet piles.

9. The method for dismantling underwater steel sheet pile cofferdams according to claim 8, characterized in that: In the step of removing the steel sheet piles, at each selected location, 2 to 3 adjacent steel sheet piles are used as reserved steel sheet piles.

10. The method for dismantling underwater steel sheet pile cofferdams according to claim 1, characterized in that: In the step of removing the steel sheet piles, during the process of refilling water into the cofferdam, the following steps are further included: when the water level of the refilled water rises close to the layers of cofferdams located below the external water level, the refilling is stopped, the connection between the current layer of cofferdams and all the steel sheet piles is disconnected, and then the refilling is continued; after the refilled water reaches the same level as the external water level and before the steel sheet piles other than the reserved steel sheet piles are removed, the connection between the layers of cofferdams located above the external water level and the steel sheet piles other than the reserved steel sheet piles is disconnected; in the step of dismantling the cofferdams layer by layer, before the layers of cofferdams located above the external water level are lifted out by a crane, the connection between the layers of cofferdams located above the external water level and the reserved steel sheet piles is disconnected.

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