Non-enclosed cofferdam structure and construction method thereof

Abstract

The application discloses a non-closed cofferdam structure and a construction method thereof. The non-closed cofferdam structure is provided with an arc-shaped cofferdam axis protruding towards a water side on a plane, and the cofferdam structure is fixed to the slopes at both ends. The embedded depth of the cofferdam structure gradually increases from the maximum water retaining section to both ends along the length direction of the cofferdam structure, and a double-row steel sheet pile concrete thin-wall water retaining structure is formed by combining the inner and outer double-row steel sheet piles and the intermediate concrete core wall. Meanwhile, the cofferdam body is integrally constrained by a fixing device, a crown beam and a rigid arch support, so that the first steel sheet pile, the concrete core wall, the second steel sheet pile, the rigid arch supports at both ends, the crown beam and the fixing device form a cooperative force whole in space. The cofferdam structure of the application transmits water pressure through arch effect, reduces construction cost and shortens construction time on the basis of realizing stable water retaining, and does not need to rely on large-scale earth and rock filling and internal support, and conforms to the green construction concept.

Description

Technical Field

[0001] This application relates to the field of water conservancy and hydropower engineering technology, and in particular to a non-enclosed cofferdam structure and its construction method. Background Technology

[0002] In the construction of water conservancy and hydropower projects, water intakes, pumping stations and similar hydraulic structures are usually built in rivers or reservoirs. In order to ensure the construction quality and safety of the main structure, temporary dry conditions must be created in the construction area. Therefore, cofferdam structures have become a key temporary water-retaining engineering measure.

[0003] In existing technologies, the most commonly used type of cofferdam is the earth-rock cofferdam, which forms a gravity-type water-retaining structure by filling a large amount of earth and rock. Although the construction technology is mature and highly adaptable, it has significant shortcomings in deep water conditions (exceeding 10m): Firstly, as the water depth increases, the cross-sectional dimensions of the cofferdam increase significantly, with the bottom width reaching tens or even hundreds of meters. This results in a huge volume of earthwork (tens of thousands to hundreds of thousands of cubic meters), a large demand for earthwork, high costs, and significant environmental impact from soil extraction and transportation.

[0004] Secondly, an excessively large cofferdam cross-section can severely narrow the original river channel's flow cross-section. In reservoir tail or narrow river conditions, it may even include upstream channels within the cofferdam's scope, thereby increasing the risk of flood backflow during construction and seriously affecting flood control safety during the foundation pit construction period.

[0005] Third, in areas with steep terrain or large differences in riverbed elevation, the toe of the cofferdam on the water-facing side often needs to be extended into a deeper part of the riverbed, which further increases the height of the cofferdam and the amount of engineering work, making the traditional earth-rock cofferdam less economical to construct under complex terrain conditions.

[0006] For water depths of 3m to 6m, single-row sheet pile cofferdams are often used in engineering projects. They provide cantilever stability through the embedment depth of the sheet piles. However, when the water depth exceeds 10m to 15m, due to the limitations of the conventional sheet pile length (maximum length is 18m) and geological conditions, single-row sheet piles are difficult to meet the requirements for overturning resistance and stability.

[0007] On the other hand, the closed steel cofferdam structures commonly used in existing bridge engineering (such as circular or rectangular cofferdams) are typically used for pier and abutment construction. These structures are enclosed systems on all four sides, allowing water pressure to balance within the cofferdam, with compressive stress being the dominant stress mode. However, cofferdams in water conservancy and hydropower projects are mostly open structures, subjected to long-term unilateral water pressure, which is fundamentally different from closed cofferdams. Therefore, the mature closed cofferdam structures used in bridge engineering are difficult to directly apply to the open cofferdam scenarios in water conservancy and hydropower projects. Summary of the Invention

[0008] This application aims to address at least one of the technical problems existing in the prior art. This application provides a non-enclosed cofferdam structure and its construction method, which can reduce construction costs and shorten construction time while achieving stable water retention, eliminating the need for large-scale earth and rock filling and internal support, and conforming to the concept of green construction.

[0009] According to the first aspect of the present application, the non-enclosed cofferdam structure has an arc-shaped structure protruding towards the water-facing side in the plane, and the two ends of the cofferdam structure are respectively fixed to the bank slopes at both ends; along the length direction of the cofferdam structure, the embedment depth of the cofferdam structure gradually increases from the position of the maximum water-blocking section towards both ends.

[0010] The non-enclosed cofferdam structure according to the embodiments of this application has at least the following beneficial effects: This application describes a non-enclosed cofferdam structure that, in plan view, presents an arc-shaped structure bulging towards the water-facing side. The entire cofferdam axis is an open arc-shaped structure, with both ends fixed to the bank slopes. This creates a spatially formed arch-shaped load-bearing structure with fixed bank slopes at both ends and an outward-protruding central section. Along the length of the cofferdam structure, the embedment depth gradually increases from the location of the maximum water-retaining section towards both ends, allowing the cofferdam structure to gradually embed into the bank slope soil. The deeply embedded areas at both ends, together with the bank slope soil, form a stable arch-shaped support structure, enhancing the constraint between the cofferdam and the bank slope foundation. During water retention, the cofferdam structure of this application can generate an arch effect, converting the water pressure at the bulging arc apex into axial compressive stress transmitted along the length of the cofferdam structure. This compressive stress is borne by the arch-shaped support structure formed by the deeply embedded areas at both ends and the bank slopes. Because the cofferdam structure of this application transmits water pressure through the arch effect, the embedment depth in the middle can be greatly reduced. The maximum water-retaining section in the middle only needs to be shallowly embedded to meet the seepage prevention requirements. This not only solves the stability risk caused by insufficient embedment depth of traditional steel sheet piles, but also solves the problem that earth-rock cofferdams cannot be constructed due to site limitations.

[0011] According to some embodiments of this application, including The cofferdam body includes a first sheet pile, a second sheet pile, and a concrete core wall. The first sheet pile and the second sheet pile are arranged in parallel, and the concrete core wall is arranged between the first sheet pile and the second sheet pile. A fixing mechanism is provided on the cofferdam body for fixing the first sheet pile, the concrete core wall, and the second sheet pile together.

[0012] According to some embodiments of this application, the fixing mechanism includes at least one fixing device, each of which is arranged along the length direction of the cofferdam body.

[0013] According to some embodiments of this application, each of the fixing devices includes a plurality of tie rods and two fixing components. Each tie rod is spaced apart along the length direction of the cofferdam body. The tie rod passes through the first sheet pile, the concrete core wall, and the second sheet pile. The two fixing components are respectively disposed on the outside of the first sheet pile and the second sheet pile and are connected to each tie rod.

[0014] According to some embodiments of this application, each of the fixing components includes two channel steels, a steel pad, and a fixing member. The two channel steels are respectively arranged along the length direction of the cofferdam body and connected to the side of the tie rod. One end of the channel steel is connected to the cofferdam body, one side of the steel pad is connected to the other end of the two channel steels, one end of the fixing member is connected to the tie rod, and the other end of the fixing member is connected to the other side of the steel pad.

[0015] According to some embodiments of this application, the fastener includes at least three fasteners, each of which is evenly distributed along the circumference of the pull rod; and / or Each of the fixing components further includes a plurality of fixing plates, each fixing plate being spaced apart along the length of the channel steel, the fixing plate being located between two adjacent tie rods and being connected to the other end of the two channel steels.

[0016] According to some embodiments of this application, the cofferdam structure is provided with rigid arch seats at both ends, and the rigid arch seats are embedded in the weakly weathered rock layer deep in the bank slope.

[0017] A construction method for a non-enclosed cofferdam structure according to a second aspect embodiment of this application, the construction method comprising the steps of... The cofferdam curve is determined based on the topographic conditions of the water-retaining area, and the cofferdam curve is arranged as an arc-shaped structure protruding towards the water-facing side. The height of the cofferdam body and the embedment depth are determined based on the water-retaining height of each water-retaining section. Pre-construction of steel sheet piles was carried out on the bank slope section located above the construction water level, and the driving of steel sheet piles on the bank slope section was completed under dry conditions; The construction of the first sheet pile and the second sheet pile is completed in sequence, and the second sheet pile and the first sheet pile are arranged in parallel with a preset distance. A fixing mechanism is installed on the cofferdam body to form an overall load-bearing frame structure; Concrete was poured between the first and second sheet piles to form a concrete core wall, completing the construction of the non-enclosed cofferdam structure.

[0018] According to some embodiments of this application, in the step of sequentially completing the construction of the first sheet pile and the second sheet pile, and the second sheet pile maintaining a preset distance and being arranged in parallel with the first sheet pile, the following steps are included: S1. Float the water positioning device to the designated construction area; S2. Measure and calibrate the water positioning device to make the installation channel coincide with the curve of the cofferdam to be constructed, so as to form a guide reference for the steel sheet piles; S3. The positioning steel pipe pile is driven through the positioning pipe sleeve and into the soil of the water-retaining area to fix the water positioning device. S4. Using the installation channel of the water positioning device, steel sheet piles are driven sequentially from the opening end and engaged with the already constructed steel sheet piles to complete the construction of this section of steel sheet piles; S5. Pull out the positioning sheet piles and move the water positioning device to the next construction section; S6. Repeat steps S2 to S5 until the continuous arc construction of the first sheet pile is completed, and proceed to step S370. S7. Repeat steps S2 to S5 until the continuous arc construction of the second sheet pile is completed, so that the second sheet pile and the first sheet pile are kept at a preset distance and arranged in parallel to form a double-row arc sheet pile system.

[0019] According to some embodiments of this application, lubricating oil is applied to the surface of the sheet pile before installation. Attached Figure Description

[0020] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is one of the structural schematic diagrams of a non-enclosed cofferdam structure according to an embodiment of this application; Figure 2 This is a second schematic diagram of a non-enclosed cofferdam structure according to an embodiment of this application; Figure 3 for Figure 2 A schematic diagram of the slope of surface AA; Figure 4 for Figure 2 A schematic diagram of the slope of the BB surface; Figure 5 This is a schematic diagram of the structure of a fixing device according to an embodiment of this application; Figure 6 for Figure 5 A schematic diagram of the slope of the CC surface; Figure 7 This is a schematic diagram of the structure of a water positioning device according to an embodiment of this application; Figure 8 for Figure 7 A schematic diagram of the slope of the DD surface.

[0021] Figure label: Cofferdam structure 100; Cofferdam body 200; First cofferdam body 201; Second cofferdam body 202; Third cofferdam body 203; Fourth cofferdam body 204; First sheet pile 210; Second sheet pile 220; Concrete core wall 230; Rigid arch seat 240; Crown beam 250; Fixing mechanism 300; Fixing device 310; Pull rod 400; Fixing component 500; channel steel 510; steel pad 520; fastener 530; fastener 531; first fixing part 532; second fixing part 533; fixing plate 540; 600; first frame 610; cross brace 611; second frame 620; connector 630; movable positioning component 640; positioning steel pipe pile 641; positioning sleeve 642; floating component 650; installation channel 660; Water-facing side: 1000mm; Water-repellent side: 2000mm; Excavation pit: 2100mm; Left bank slope: 3000mm; Right bank slope: 4000mm; Topographic contour line 10000; construction water level 20000; design water level 30000. Detailed Implementation

[0022] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] In the description of this application, it should be understood that the use of terms such as "center," "middle," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" to indicate orientation or positional relationships is based on the orientation or positional relationships shown in the accompanying drawings and is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] The following reference Figures 1 to 8 This application describes the non-enclosed cofferdam structure and its construction method in the embodiments of this application.

[0026] according to Figure 1 As shown, an embodiment of this application describes a non-enclosed cofferdam structure 100 used to temporarily block water in a river or reservoir during a water conservancy and hydropower project, so as to form a construction pit 2100 on the backwater side 2000.

[0027] The cofferdam structure 100 has an arc-shaped structure protruding towards the water-facing side 1000 in plan view. The overall axis of the cofferdam is a non-closed arc-shaped structure, with both ends fixed to the left bank slope 3000 and the right bank slope 4000 respectively. This results in the cofferdam structure 100 forming an arch-shaped load-bearing structure with fixed banks at both ends and an outward convex center. The backwater side 2000 of the cofferdam structure 100 forms an open pit area 2100. (Continue to see...) Figure 2 Along the length of the cofferdam structure 100, the embedment depth of the cofferdam structure 100 gradually increases from the position of the maximum water-retaining section towards both ends. The gradual increase can be either incremental or gradient. The embedment depth of the cofferdam structure 100 is the smallest at the position of the maximum water-retaining section (i.e., the position of the maximum water depth), and gradually increases along the direction of the cofferdam structure 100 towards both ends of the bank slope, so that the cofferdam structure 100 is gradually embedded into the bank slope soil. The deeply embedded areas at both ends and the bank slope soil together form a stable arch structure, which enhances the constraint effect between the cofferdam structure 100 and the bank slope foundation.

[0028] The cofferdam structure 100 of this application can form an arch effect during water retention, converting the water pressure at the convex apex into axial compressive stress transmitted along the length of the arched cofferdam structure 100. This compressive stress is borne by the arch-shaped abutment structure formed by the deep-embedded areas at both ends and the bank slope. Because the cofferdam structure 100 of this application transmits water pressure through the arch effect, the embedment depth in the middle can be significantly reduced. The maximum water-retaining section in the middle only needs to be shallowly embedded to meet the seepage prevention requirements, without relying on deep embedment to provide the main anti-overturning force. The cofferdam structure 100 of this application not only solves the stability risk caused by insufficient embedment depth of traditional steel sheet piles, but also solves the problem of earth-rock cofferdams being unable to be constructed due to site constraints, reducing unnecessary embedment construction costs.

[0029] The cofferdam structure 100 of this application bears compressive stress through an arch structure formed by the deeply embedded areas at both ends and the bank slopes. However, when the bank slopes at both ends are soft foundations such as overburden or weathered layers, the conventional embedment depth of steel sheet piles is insufficient to provide adequate reaction force, which may lead to instability or excessive deformation of the arch abutment. Therefore, according to Figure 1 and Figure 2 As shown, in one embodiment of this application, rigid arch seats 240 are provided at both ends of the cofferdam structure 100. The rigid arch seats 240 are embedded in the weakly weathered rock layer deep in the bank slope, which can further enhance the bearing capacity of the arch seats and ensure the arch effect of the arc-shaped cofferdam structure 100.

[0030] according to Figure 3 and Figure 4 As shown, in one embodiment of this application, the cofferdam structure 100 includes a cofferdam body 200 and a fixing mechanism 300.

[0031] The cofferdam body 200 includes first sheet piles 210, second sheet piles 220, and a concrete core wall 230. The first sheet piles 210 and second sheet piles 220 are arranged in parallel and extend along the length of the cofferdam structure 100. The spacing between the first sheet piles 210 and second sheet piles 220 is approximately 0.3m to 2m, forming a continuous filling space. The concrete core wall 230 fills the filling space between the first sheet piles 210 and second sheet piles 220. The (first or second) sheet piles serve as a tensile force transmission skeleton, and the concrete core wall 230 provides compressive strength and overall structural rigidity. The three work together to form a rigid-flexible, arc-shaped, thin-walled water-retaining structure.

[0032] The fixing mechanism 300 is fixedly installed on the cofferdam body 200 to fix the first steel sheet pile 210, the concrete core wall 230 and the second steel sheet pile 220 together, so that the first steel sheet pile 210, the concrete core wall 230 and the second steel sheet pile 220 deform together under stress to form a double-row pile concrete structure under overall stress.

[0033] The cofferdam structure 100 of this application, through the synergistic effect of the double-row pile concrete structure and the arch effect of the arc structure, enables the inner side of the cofferdam structure 100 to safely block water without internal support, providing a more open space for the operation of large mechanical equipment and the construction of the main structure within the foundation pit 2100. Secondly, the spacing between the double-row steel sheet piles of the cofferdam body 200 of this application is only 0.3m to 2m, and the total thickness of the thin-walled structure formed after combining with the concrete core wall 230 is much smaller than the bottom width of the earth-rock cofferdam (ten meters, or even hundreds of meters). Compared with the traditional trapezoidal cross-section, the rectangular, narrow-section cofferdam body 200 of this application can significantly reduce the occupation of the riverbed and bank slope, reduce the riverbed narrowing rate, and thus mitigate the impact on the original river channel flood passage cross-section. At the same time, the cofferdam layout is more flexible, effectively avoiding upstream channels and preventing them from being enclosed and causing floodwater to enter the foundation pit 2100, thereby significantly improving the flood control safety of the foundation pit 2100 during construction and reducing the pressure of frequent drainage.

[0034] In some embodiments, the rigid arch 240 may be connected to the ends of the first sheet pile 210 and the second sheet pile 220 simultaneously.

[0035] In some embodiments, see Figure 3 and Figure 4 The top of the double-row pile concrete structure, which consists of the first sheet pile 210, the concrete core wall 230, and the second sheet pile 220, is provided with a capping beam 250. The capping beam 250 can be made of reinforced concrete. The capping beam 250 further enhances the integrity of the cofferdam structure 100 by forming an integral structure together with the first sheet pile 210, the concrete core wall 230, the second sheet pile 220, and the rigid arch seats 240 at both ends.

[0036] according to Figures 1 to 4 As shown, in one embodiment of this application, the fixing mechanism 300 includes at least one fixing device 310, each fixing device 310 is arranged along the length direction of the cofferdam body 200, and the fixing devices 310 are spaced apart along the height direction of the cofferdam body 200.

[0037] according to Figures 3 to 6 As shown, in one embodiment of this application, each fixing device 310 includes multiple tie rods 400 and two fixing components 500. The tie rods 400 are spaced apart along the length of the cofferdam body 200, and horizontally pass through the first sheet pile 210, the concrete core wall 230, and the second sheet pile 220, forming a multi-point through-force distribution. The two fixing components 500 are respectively disposed on the outside of the first sheet pile 210 and the second sheet pile 220, and are fixedly connected to each tie rod 400, enabling the tie rods 400 to cooperate in bearing force and improving their resistance to deformation.

[0038] according to Figure 5 and Figure 6As shown in one embodiment of this application, each fixing component 500 includes two channel steels 510, a steel pad 520, and a fixing member 530. The two channel steels 510 extend along the length of the cofferdam body 200 and abut against the upper and lower sides of the tie rod 400. One end of each channel steel 510 is fixedly connected to the cofferdam body 200, one side of the steel pad 520 is fixedly connected to the other end of each channel steel 510, one end of the fixing member 530 is fixedly connected to the tie rod 400, and the other end of the fixing member 530 is fixedly connected to the other side of the steel pad 520. When the cofferdam structure 100 is subjected to water pressure, the tie rod 400 is subjected to axial tensile force, which is transmitted to the steel pad 520 through the fixing member 530, and then distributed by the steel pad 520 to the channel steel 510 structures on both sides. Since the two channel steels 510 are continuously arranged along the length of the cofferdam, the tensile force can be transmitted along the length of the channel steel 510 (i.e., the length of the cofferdam body 200), thereby avoiding local stress concentration and improving the overall rigidity of the cofferdam structure 100.

[0039] according to Figure 5 and Figure 6 As shown, in one embodiment of this application, the fixing member 530 includes at least three fasteners 531, each fastener 531 being evenly distributed along the circumference of the pull rod 400 to form a locking structure with uniform force. By evenly distributing multiple fasteners 531 and cooperating with the steel pad 520 and the two channel steels 510, the torsional resistance of the pull rod 400 can be improved. Specifically, the fastener 531 includes a first fixing part 532 and a second fixing part 533, the first fixing part 532 and the second fixing part 533 being perpendicularly arranged, the first fixing part 532 being fixedly connected to the steel pad 520, and the second fixing part 533 being fixedly connected to the pull rod 400.

[0040] Each fixing component 500 also includes multiple fixing plates 540, each fixing plate 540 being spaced apart along the length of the channel steel 510. The fixing plates 540 are located between two adjacent tie rods 400 and are fixedly connected to the other end of the two channel steels 510, thereby improving the overall integrity of the fixing component 500.

[0041] The fixed connection method can be an integral connection, a welded connection, etc.

[0042] The non-enclosed cofferdam structure 100 of this application can be constructed using the following construction methods.

[0043] according to Figures 1 to 8 As shown, a construction method for a non-enclosed cofferdam structure 100 according to an embodiment of this application is used to construct the non-enclosed cofferdam structure 100 of the above embodiment. The construction method includes the following steps.

[0044] S100. Determine the cofferdam curve based on the topographic conditions of the water-retaining area, and arrange the cofferdam curve as an arc-shaped structure protruding 1000 to the water-facing side. Determine the height of the cofferdam body 200 and the embedment depth based on the water-retaining height of each water-retaining section.

[0045] S200. For the bank slope section located above the construction water level of 20,000 meters, pre-construction of steel sheet piles shall be carried out, and the driving of steel sheet piles for the bank slope section shall be completed under dry conditions.

[0046] S300. The construction of the first sheet pile 210 and the second sheet pile 220 is completed in sequence, and the second sheet pile 220 and the first sheet pile 210 are arranged in parallel with a preset distance.

[0047] S400. Fixing mechanism 300 is installed on the first sheet pile 210 and the second sheet pile 220 to form an integral load-bearing frame structure.

[0048] S500. Concrete is poured between the first sheet pile 210 and the second sheet pile 220 to form a concrete core wall 230, thus completing the construction of the non-enclosed cofferdam structure 100.

[0049] See Figures 1 to 8 The following is a specific construction method for a non-enclosed cofferdam structure 100 according to an embodiment of this application, including the following steps.

[0050] S100. Determine the cofferdam curve based on the topographic conditions of the water-retaining area, and arrange the cofferdam curve as an arc-shaped structure protruding 1000 to the water-facing side. Determine the height of the cofferdam body 200 and the embedment depth based on the water-retaining height of each water-retaining section.

[0051] S200. At the designed positions at both ends of the cofferdam structure 100, a rotary drilling rig is used to construct a rigid arch seat 240, and a steel sheet pile lock is reserved at the end of the rigid arch seat 240 to facilitate subsequent connection with (the first or second) steel sheet piles.

[0052] S300. Steel sheet pile pre-construction is carried out on the left bank slope 3000 and right bank slope 4000 sections located above the construction water level of 20000 (under dry conditions). After precise positioning using measuring instruments, steel sheet piles are applied using a pile driver. One end of the steel sheet pile overlaps with the arch seat, and the embedment depth of the steel sheet piles on the bank slope section is not less than the predetermined depth.

[0053] S400. The construction of the first sheet pile 210 and the second sheet pile 220 is completed sequentially, with the second sheet pile 220 maintaining a preset distance from the first sheet pile 210 and arranged in parallel. Specifically, this includes the following sub-steps.

[0054] S410. Float the waterborne positioning device 600 to the designated construction area. The waterborne positioning device 600 includes a first frame 610, a second frame 620, a floating component 650, a connecting component 630, and multiple movable positioning components 640. The first frame 610 and the second frame 620 are arranged side-by-side at intervals to form an installation channel 660. The sidewalls of the first frame 610 and the second frame 620 facing the installation channel 660 are parallel to each other, and the arc curvature of the installation channel 660 matches the arc curvature of the cofferdam curve. The floating component 650 is disposed within the first frame 610 and the second frame 620, and the first frame 610 is fixedly connected to the second frame 620 via the connecting component 630. The movable positioning component 640 includes a positioning steel pipe pile 641 and a positioning sleeve 642. Each positioning sleeve 642 is disposed on the first frame 610 and / or the second frame 620, and the positioning steel pipe pile 641 passes through the positioning sleeve 642.

[0055] S420. The water positioning device 600 is measured, calibrated and its position is adjusted by a total station so that the installation channel 660 coincides with the curve of the cofferdam to be constructed, so as to form a guide reference for the steel sheet piles.

[0056] S430. The positioning steel pipe pile 641 is inserted through the positioning pipe sleeve and into the soil of the water-retaining area to fix the water positioning device 600.

[0057] S440. Using the installation channel 660 of the waterborne positioning device 600, steel sheet piles are driven one by one from the open end. The steel sheet piles are driven vertically along the installation channel 660, and the verticality and planar position accuracy of the pile body are ensured by the guiding effect of the installation channel 660. After driving is completed, the newly driven steel sheet piles are engaged with the already constructed steel sheet piles to complete the construction of this segment of steel sheet piles.

[0058] S450. Pull out the positioning steel pipe pile 641 and move the water positioning device 600 to the next construction section.

[0059] S460. Repeat steps S420 to S450 until the continuous arc construction of the first sheet pile 210 is completed, and proceed to step S470.

[0060] S470. Repeat steps S420 to S450 until the continuous arc construction of the second sheet pile 220 is completed, so that the second sheet pile 220 and the first sheet pile 210 are kept at a preset distance and arranged in parallel to form a double-row arc sheet pile system.

[0061] S500. Install the fixing mechanism 300 on the cofferdam body 200 to form an integral load-bearing frame structure. This includes the following steps.

[0062] S510. Install at least one layer of fixing device 310 according to the height of the sheet piles in each section.

[0063] S520. In each fixing device 310, each tie rod 400 is interspersed with the first sheet pile 210 and the second sheet pile 220 at preset distances.

[0064] S530. In each side fixing assembly 500, two channel steels 510 are abutted against the upper and lower sides of the tie rod 400. One end of the channel steel 510 is fixedly connected to the cofferdam body 200. A steel pad 520 is provided at the exposed end of the tie rod 400. One side of the steel pad 520 is fixedly connected to the other end of the two channel steels 510. Fasteners 531 are distributed circumferentially along the tie rod 400, and the first fixing part 532 is connected to the other side of the steel pad 520, and the second fixing part 533 is fixedly connected to the tie rod 400.

[0065] S540. Fix the fixing plate 540 between adjacent tie rods 400.

[0066] S600. Using the tremie method or pumping method, underwater concrete is continuously poured from bottom to top between the first sheet pile 210 and the second sheet pile 220 to form a concrete core wall 230, thus completing the construction of the non-enclosed cofferdam structure 100.

[0067] S700. A reinforced concrete cap beam 250 is installed along the entire top of the cofferdam body 200. The cap beam 250 contains longitudinal steel bars and stirrups. The steel bars are welded to the sheet piles, so that the first sheet pile 210, the concrete core wall 230, the second sheet pile 220, and the rigid arch seats 240 at both ends form an integral structure.

[0068] S800. After the concrete of the capping beam 250 reaches its design strength, dewatering of the foundation pit 2100 can continue. In this step, traditional earth-rock cofferdams require a water level drop rate of less than 1 m / s to ensure slope stability, while the present application has no such restriction, which can significantly accelerate the dewatering progress. Under water pressure, the cofferdam structure 100 of the present application can convert water pressure into axial pressure through the arch effect and transmit it to the deeply embedded arch abutment structures on both banks, and the cofferdam body 200 of the present application can form a stable water-retaining structure without internal support.

[0069] S900. After the main structure of the water intake is completed, water is pumped into the foundation pit at 2100mm (backwater side 2000mm). Once the water level at 2000mm on the backwater side is level with the water level at 1000mm on the water-facing side, the fixing components 500mm and the capping beam 250mm are cut and removed sequentially. Then, the sheet piles are extracted using a pile driver operating on water. Because lubricating oil was pre-coated onto the surface of the sheet piles before installation, the extraction resistance is significantly reduced, allowing the sheet piles to be recycled and reused.

[0070] In one embodiment of this application, before the (first or second) sheet pile is installed, the surface of the sheet pile is coated with lubricating oil to reduce the resistance to subsequent removal, improve the recycling rate of the sheet pile, and reduce the project cost.

[0071] The following is an embodiment of a non-enclosed cofferdam structure 100 and its specific construction method according to this application. A water intake is established at the tail of the reservoir, located in a low-lying area at the tail, with a water depth of approximately 14m. The banks are covered by a layer of overburden and a completely weathered layer. The cofferdam's axial length is approximately 130m, the water depth at the maximum water-retaining section is approximately 14m, the construction water level (20000) is approximately 8m, and the design water-retaining level (30000) is approximately 14m. An open foundation pit 2100 is formed on the backwater side (2000) for the construction of the main structure of the water intake. As shown in the topographic map (contour line 10000), the reservoir tail where the cofferdam structure 100 is located has a U-shaped topographic feature, with the ridges on both banks above the water surface and the valley in the middle below the water level. Setting the water intake in a low-lying area reduces the amount of excavation required for the main project. See also... Figures 1 to 8 The construction method includes the following steps.

[0072] S100. The cofferdam curve is determined based on the topographic conditions of the water-retaining area, and the cofferdam curve is arranged as an arc-shaped structure bulging towards the reservoir side (water-facing side 1000), with an arc radius of approximately 50m. The height and embedment depth of the cofferdam body 200 are determined based on the water-retaining height of each water-retaining section, and a gradient configuration is adopted for each construction section. Specifically, the topographic contour line 10000 shows that the terrain of the two bank slopes is higher, while the middle reservoir bottom is lower. The water depth at the largest water-retaining section in the middle is 14m, and a fourth cofferdam body 204 with a height of 18m is adopted, with 1m exposed above the water surface as a safety freeboard and an embedment depth of 3m. The steel sheet piles transitioning to both banks successively adopt a third cofferdam body 203 with a height of 12m, a second cofferdam body 202 with a height of 9m, and a first cofferdam body 201 with a height of 6m. Although the sheet piles on the bank slope section use the first cofferdam body 201 (or the second cofferdam body 202), due to the higher ground elevation of the bank slope section, the sheet piles can be embedded in the soil to a depth of 4m to 7m. The sheet piles in the deeply embedded areas at both ends, together with the bank slope soil, form an arch structure. Before subsequent construction steps, grease or a special release lubricant is applied to the surface of each sheet pile.

[0073] S200. At the designed locations at both ends of the cofferdam structure 100, rotary drilling rigs will be used to construct underground continuous wall trench sections. Each continuous wall trench section will be 5m long and 1.2m thick, with the trench bottom penetrating at least 4m into the weakly weathered rock layer. After cleaning the trench, a reinforcing cage will be hoisted and C30 concrete will be poured into the trench to form a rigid arch seat 240. Steel sheet pile interlocking openings will be reserved at the ends of the rigid arch seat 240 to facilitate subsequent connection with (the first or second) steel sheet piles.

[0074] S300. Steel sheet pile pre-construction is carried out on the left bank slope 3000 and right bank slope 4000 sections located above the construction water level of 20000 (under dry conditions). After precise positioning using surveying instruments, steel sheet piles are applied using a pile driver. One end of the steel sheet pile overlaps with the arched arch seat, and the embedment depth of the steel sheet piles on the bank slope section is not less than 4m.

[0075] S400. The construction of the first sheet pile 210 and the second sheet pile 220 is completed sequentially, with the second sheet pile 220 maintaining a preset distance from the first sheet pile 210 and arranged in parallel. Specifically, this includes the following sub-steps.

[0076] S410. Float the water positioning device 600 to the designated construction area. See details. Figure 7 and Figure 8 The water positioning device 600 includes a first frame 610, a second frame 620, a floating component 650, a connector 630, and multiple movable positioning components 640. The first frame 610, second frame 620, and connector 630 are made of 20a channel steel. Multiple cross braces 611 are embedded within the first frame 610 and second frame 620. The first frame 610 and second frame 620 are arranged side-by-side at intervals to form an installation channel 660 (350mm wide, slightly larger than the width of the (first or second) sheet pile, 340mm). The sidewalls of the first frame 610 and second frame 620 facing the installation channel 660 are parallel to each other, and the curvature of the sidewalls matches the curvature of the cofferdam curve (radius 50m). The floating component 650 is disposed within the first frame 610 and second frame 620, and the first frame 610 is fixedly connected to the second frame 620 via the connector 630. The movable positioning component 640 includes a positioning steel pipe pile 641 and a positioning sleeve 642. Each positioning sleeve 642 is set on the first frame 610 and the second frame 620, and the positioning steel pipe pile 641 is inserted into the positioning sleeve 642.

[0077] S420. The water positioning device 600 is measured, calibrated and its position is adjusted by a total station so that the installation channel 660 coincides with the curve of the cofferdam to be constructed, so as to form a guide reference for the steel sheet piles.

[0078] S430. Four positioning steel pipe piles 641 are inserted into corresponding positioning sleeves 642 and penetrate into the soil of the water-retaining area to fix the water-based positioning device 600. The positioning steel pipe piles 641 have a diameter of 159mm and a conical bottom for easy insertion; the positioning sleeves 642 have an inner diameter of 180mm.

[0079] S440. Using the installation channel 660 of the waterborne positioning device 600, steel sheet piles are driven one by one from the open end. The steel sheet piles are driven vertically along the installation channel 660, and the verticality and planar position accuracy of the pile body are ensured by the guiding effect of the installation channel 660. After driving is completed, the newly driven steel sheet piles are engaged with the already constructed steel sheet piles to complete the construction of this segment of steel sheet piles.

[0080] S450. Pull out the positioning steel pipe pile 641 and move the water positioning device 600 to the next construction section. Each construction section is approximately 6m to 8m long, and 15 to 20 steel sheet piles are driven in each section.

[0081] S460. Repeat steps S420 to S450 until the continuous arc construction of the first sheet pile 210 is completed, and proceed to step S470.

[0082] S470. Repeat steps S420 to S450 until the continuous arc construction of the second sheet pile 220 is completed, so that the second sheet pile 220 and the first sheet pile 210 are kept 1m apart and arranged in parallel to each other to form a double-row arc sheet pile system.

[0083] S500. Install the fixing mechanism 300 on the cofferdam body 200 to form an integral load-bearing frame structure. This includes the following steps.

[0084] S510. Install at least one layer of fixing device 310 according to the height of the sheet piles in each section. For larger water-retaining sections, see [reference needed]. Figure 3 Two layers of fixing devices 310 are installed on the fourth cofferdam body 204. The first layer of fixing devices 310 is located 0.5m above the construction water level of 20000 meters, and the second layer of fixing devices 310 is located 1m below the top of the sheet piles. For smaller water-retaining sections, see [reference needed]. Figure 4 The first cofferdam body 201 has a water-blocking height of about 1m, and only one layer of fixing device 310 needs to be installed. S520. In each fixing device 310, each tie rod 400 is interspersed with the first steel sheet pile 210 and the second steel sheet pile 220 at preset intervals.

[0085] S520. In each fixing device 310, each tie rod 400 (with a diameter of 40mm) is inserted at intervals of 5m, with the first steel sheet pile 210 and the second steel sheet pile 220 inserted at intervals.

[0086] S530. In each side fixing assembly 500, two channel steels 510 (specifically 20a channel steel) abut against the upper and lower sides of the tie rod 400. One end of the channel steel 510 is welded and fixed to the first sheet pile 210 or the second sheet pile 220. A steel pad 520 is provided at the exposed end of the tie rod 400. One side of the steel pad 520 is welded and fixed to the other end of the two channel steels 510. Fasteners 531 are distributed circumferentially along the tie rod 400, and the first fixing part 532 is welded and fixed to the other side of the steel pad 520, and the second fixing part 533 is welded and fixed to the tie rod 400.

[0087] S540. Fix each fixing plate 540 between adjacent tie rods 400.

[0088] S600. Underwater non-dispersible concrete is continuously poured from bottom to top between the first sheet pile 210 and the second sheet pile 220 using either the tremie pipe method or the pumping method. During the concrete pouring process, as the concrete surface rises, the tremie pipe is gradually raised, keeping the bottom of the tremie pipe always buried 1m to 2m below the concrete surface, and pouring is continued until the design elevation of the top of the cofferdam is reached, forming the concrete core wall 230, thus completing the construction of the non-enclosed cofferdam structure 100.

[0089] S700. A reinforced concrete cap beam 250 is installed along the entire top of the cofferdam body 200. The cap beam 250 is 1m high and 1.34m wide, which is the same as the width of the double-row steel sheet pile concrete structure. The concrete strength grade is C30. The cap beam 250 contains longitudinal steel bars and stirrups. The steel bars are welded to the steel sheet piles, so that the first steel sheet pile 210, the concrete core wall 230, the second steel sheet pile 220, and the rigid arch seats 240 at both ends form an integral structure. This allows the cofferdam structure 100 to deform in a coordinated manner as a whole when subjected to water pressure, avoiding local stress concentration.

[0090] S800. After the concrete of the capping beam 250 reaches its design strength, dewatering of the foundation pit 2100 can continue. In this step, traditional earth-rock cofferdams require a water level drop rate of less than 1 m / s to ensure slope stability, but this application has no such restriction, which can significantly accelerate the dewatering progress. Under water pressure, the cofferdam structure 100 of this application can convert water pressure into axial pressure through the arch effect and transmit it to the deeply embedded arch abutment structures on both banks, and the cofferdam body 200 of this application can form a stable water-retaining structure without internal support.

[0091] S900. After the main structure of the water intake is completed, water is pumped into the foundation pit at 2100mm (backwater side 2000mm). Once the water level at 2000mm on the backwater side is level with the water level at 1000mm on the water-facing side, the fixing components 500mm and the capping beam 250mm are cut and removed sequentially. Then, the sheet piles are extracted using a pile driver operating on water. Because lubricating oil was pre-coated onto the surface of the sheet piles before installation, the extraction resistance is significantly reduced, allowing the sheet piles to be recycled and reused.

[0092] Traditional earth-rock cofferdam schemes: The maximum cofferdam height is approximately 18m (including safety freeboard, which increases due to the large cross-section and the cofferdam toe extending into the reservoir area). This requires filling a large amount of earth and rock, laying impermeable geomembranes and slope protection riprap, and constructing a floating dam to intercept turbid wastewater. The cofferdam body is large, requiring the pumping of a significant amount of water from the 2100m deep pit during construction, resulting in high project investment. It is estimated that the total investment for the traditional earth-rock cofferdam scheme is approximately 12 million yuan. Compared to the traditional earth-rock cofferdam scheme, this embodiment of the application: Sheet piles: approximately 260 tons; Underwater concrete core wall 230: approximately 500 m³; 250mm concrete capping beam: approximately 200m³; Rigid arch abutment for diaphragm wall 240: approximately 180m³; 250mm diameter cap beam and diaphragm wall reinforcement: approximately 50t; Steel consumption for the fixed mechanism 300: approximately 20 tons; 600 Water Positioning Device: A temporary facility that can be used multiple times; Furthermore, sheet piles can be repeatedly recycled, further reducing overall costs. Calculations show that the total investment for this embodiment is approximately 5.8 million yuan. Therefore, the cofferdam structure 100 of this application saves more than 50% in investment compared to the earth-rock cofferdam scheme, demonstrating significant economic advantages. Simultaneously, the construction period is shortened by approximately 40 days, and environmental pollution caused by earthwork mining and transportation is avoided.

[0093] The non-enclosed cofferdam structure 100 and its construction method of this application firstly establish a non-enclosed arc-shaped cofferdam axis protruding towards the water-facing side 1000 on the plane. The two ends of the cofferdam structure 100 are fixed to the bank slopes at both ends. Along the length of the cofferdam structure 100, the embedment depth of the cofferdam structure 100 gradually increases from the maximum water-retaining section to both ends. It is combined with the inner and outer double rows of steel sheet piles and the middle concrete core wall 230 to form a double row of steel sheet pile concrete thin-walled water-retaining structure. At the same time, the cofferdam body 200 is constrained as a whole by the fixing device 310, the cap beam 250 and the rigid arch seat 240, so that the first steel sheet pile 210, the concrete core wall 230, the second steel sheet pile 220, the rigid arch seats 240 at both ends, the cap beam 250 and the fixing device 310 form a coordinated force-bearing whole in space. The cofferdam structure 100 and its construction method described in this application do not rely on large-scale earth and rock filling or complex internal supports. Furthermore, they utilize the arch effect to achieve a stable, non-enclosed cofferdam structure 100 that effectively blocks water. This significantly reduces the cofferdam's cross-sectional dimensions and its impact on the river's flood discharge capacity, while simultaneously improving the overall stability and economy of the cofferdam structure 100. Secondly, the cofferdam structure 100 of this application uses physically driven steel sheet piles, with underwater concrete poured within the closed cavity formed by the steel sheet piles. This minimizes contact with external water, avoiding the large-scale water turbidity problems caused by earth and rock cofferdam construction, and aligns with the concept of green construction.

[0094] In the description of this specification, the use of terms such as "an embodiment," "some examples," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0095] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A non-enclosed cofferdam structure, characterized in that: The cofferdam structure has an arc-shaped structure that bulges towards the water-facing side in plan view. The two ends of the cofferdam structure are fixed to the bank slopes at both ends. Along the length of the cofferdam structure, the embedment depth of the cofferdam structure gradually increases from the position of the maximum water-blocking section towards both ends.

2. The non-enclosed cofferdam structure according to claim 1, characterized in that: include The cofferdam body includes a first sheet pile, a second sheet pile, and a concrete core wall. The first sheet pile and the second sheet pile are arranged in parallel, and the concrete core wall is arranged between the first sheet pile and the second sheet pile. A fixing mechanism is provided on the cofferdam body for fixing the first sheet pile, the concrete core wall, and the second sheet pile together.

3. The non-enclosed cofferdam structure according to claim 2, characterized in that: The fixing mechanism includes at least one fixing device, and each fixing device is arranged along the length direction of the cofferdam body.

4. The non-enclosed cofferdam structure according to claim 3, characterized in that: Each of the fixing devices includes multiple tie rods and two fixing components. The tie rods are spaced apart along the length of the cofferdam body. The tie rods pass through the first sheet pile, the concrete core wall, and the second sheet pile. The two fixing components are respectively located on the outside of the first sheet pile and the second sheet pile and are connected to each tie rod.

5. The non-enclosed cofferdam structure according to claim 4, characterized in that: Each of the fixing components includes two channel steels, a steel pad, and a fixing member. The two channel steels are respectively arranged along the length direction of the cofferdam body and connected to the side of the tie rod. One end of the channel steel is connected to the cofferdam body, one side of the steel pad is connected to the other end of the two channel steels, one end of the fixing member is connected to the tie rod, and the other end of the fixing member is connected to the other side of the steel pad.

6. The non-enclosed cofferdam structure according to claim 5, characterized in that: The fastener includes at least three fasteners, each of which is evenly distributed along the circumference of the pull rod; and / or Each of the fixing components further includes a plurality of fixing plates, each fixing plate being spaced apart along the length of the channel steel, the fixing plate being located between two adjacent tie rods and being connected to the other end of the two channel steels.

7. The non-enclosed cofferdam structure according to claim 1, characterized in that: The cofferdam structure is provided with rigid arch seats at both ends, and the rigid arch seats are embedded in the weakly weathered rock layer deep in the bank slope.

8. A construction method for a non-enclosed cofferdam structure, characterized in that: The construction method includes the following steps. The cofferdam curve is determined based on the topographic conditions of the water-retaining area, and the cofferdam curve is arranged as an arc-shaped structure protruding towards the water-facing side. The height of the cofferdam body and the embedment depth are determined based on the water-retaining height of each water-retaining section. Pre-construction of steel sheet piles was carried out on the bank slope section located above the construction water level, and the driving of steel sheet piles on the bank slope section was completed under dry conditions; The construction of the first sheet pile and the second sheet pile is completed in sequence, and the second sheet pile and the first sheet pile are arranged in parallel with a preset distance. A fixing mechanism is installed on the cofferdam body to form an overall load-bearing frame structure; Concrete was poured between the first and second sheet piles to form a concrete core wall, completing the construction of the non-enclosed cofferdam structure.

9. The construction method of the non-enclosed cofferdam structure according to claim 8, characterized in that: In the step of sequentially completing the construction of the first and second sheet piles, with the second sheet piles maintaining a preset distance and arranged parallel to the first sheet piles, the following steps are included: S1. Float the water positioning device to the designated construction area; S2. Measure and calibrate the water positioning device to make the installation channel coincide with the curve of the cofferdam to be constructed, so as to form a guide reference for the steel sheet piles; S3. The positioning steel pipe pile is driven through the positioning pipe sleeve and into the soil of the water-retaining area to fix the water positioning device. S4. Using the installation channel of the water positioning device, steel sheet piles are driven sequentially from the opening end and engaged with the already constructed steel sheet piles to complete the construction of this section of steel sheet piles; S5. Pull out the positioning sheet piles and move the water positioning device to the next construction section; S6. Repeat steps S2 to S5 until the continuous arc construction of the first sheet pile is completed, and proceed to step S370. S7. Repeat steps S2 to S5 until the continuous arc construction of the second sheet pile is completed, so that the second sheet pile and the first sheet pile are kept at a preset distance and arranged in parallel to form a double-row arc sheet pile system.

10. The construction method of the non-enclosed cofferdam structure according to claim 8 or 9, characterized in that: Apply lubricating oil to the surface of the sheet pile before installation.

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