A cofferdam structure for long and narrow waterways

Abstract

This utility model relates to a cofferdam structure for narrow river channels, comprising: a sheet pile assembly, which is a double-layered structure with both ends fixedly installed on the riverbank, forming a closed rectangular structure with the riverbank; walers are fixedly installed on the upstream and downstream sides of the sheet pile assembly; several tie rods horizontally penetrating the sheet pile assembly and located in the middle of the walers; several partition piles fixedly installed at intervals between the double-layered structure of the sheet pile assembly, perpendicular to the sheet pile assembly, dividing the internal space of the sheet pile assembly into several closed compartments; and reinforcing components spaced at intervals on the downstream side of the sheet pile assembly. This cofferdam structure adopts a combination of outer sheet piles, inner sheet piles, and core backfill of the compartments, providing both water-stopping and soil-retaining functions. Furthermore, the adjacent sheet piles use a socket-locking combination structure, resulting in higher stability and stronger deformation resistance for both the outer and inner sheet piles.

Description

Technical Field

[0001] This utility model belongs to the field of cofferdam construction technology, and relates to cofferdams for water-related projects, especially a cofferdam structure for narrow river channels. Background Technology

[0002] In water-related engineering construction, different cofferdam structures are required for different river widths. For wide rivers, mature methods such as earth-rock cofferdams, sandbag cofferdams, sheet pile cofferdams, composite steel pipe pile cofferdams, and river diversion are commonly used, and their structural stability and seepage prevention performance meet construction requirements. However, in narrow river construction, traditional cofferdam technology has the following problems:

[0003] 1. Due to their large size and high permeability coefficient, earth-rock cofferdams are difficult to meet the requirements for flood discharge cross-sections and are not suitable for narrow river channels.

[0004] 2. Due to the large and narrow shape of the river-facing cofferdam, Larssen sheet pile cofferdams are difficult to form an effective support system under this structure. The overall stiffness is poor, and the lateral displacement in the cantilever state often exceeds the limit. During use, deformation is likely to occur, which can lead to problems such as water seepage, soil erosion, and instability of the cofferdam. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a cofferdam structure with stable structure and high seepage resistance for narrow river channels.

[0006] To solve the above problems, the technical solution of this utility model is as follows:

[0007] A cofferdam structure for narrow river channels, comprising:

[0008] Sheet pile assembly: The sheet pile assembly has a double-layer structure, with both ends fixedly installed on the riverbank. The sheet pile assembly and the riverbank enclose a closed rectangular structure. Walers are fixedly installed on the water-facing side and the back side of the sheet pile assembly, respectively.

[0009] Several pairs of tension reinforcing bars horizontally penetrate the sheet pile assembly and are located in the middle of the waler;

[0010] Several partitioned piles are fixedly installed at intervals between the double-layer structure of the sheet pile assembly. The partitioned piles are perpendicular to the sheet pile assembly and divide the internal space of the sheet pile assembly into several closed compartments.

[0011] The reinforcing components are spaced apart on the backwater side of the sheet pile assembly.

[0012] In a further embodiment, the sheet pile assembly includes a plurality of outer sheet piles and a plurality of inner sheet piles, wherein the plurality of outer sheet piles and the plurality of inner sheet piles are connected together in sequence, and the outer sheet piles and the inner sheet piles are arranged at intervals.

[0013] In a further embodiment, the shapes of the outer sheet piles and the inner sheet piles are corresponding.

[0014] In a further embodiment, the reinforcing component includes a plurality of steel pipe piles, which are fixedly installed at intervals on the walers of the outer and inner sheet piles, and the plurality of steel pipe piles are all located on the backwater side of the outer and inner sheet piles.

[0015] In a further embodiment, the reinforcing assembly also includes a plurality of reinforcing piles, which are fixedly installed at intervals in the recesses on the backwater side of the outer sheet pile and the inner sheet pile.

[0016] In a further embodiment, the tie rod includes a plurality of first pairs of tie rods, which are spaced apart and inserted through the side of the sheet pile assembly, and the first pairs of tie rods penetrate the double-layer structure of the sheet pile assembly.

[0017] In a further embodiment, the tie rod also includes a plurality of second pairs of tie rods, which are respectively spaced apart and installed at the corner positions of the sheet pile assembly, and the plurality of second pairs of tie rods are all inclined.

[0018] In a further embodiment, the dividing piles include a number of closely connected I-beams, which are arranged alternately in the longitudinal and transverse directions.

[0019] In a further embodiment, the cell is filled with soil.

[0020] In a further embodiment, two sheet pile assemblies located at the corner are fastened together by a socket lock.

[0021] Compared with the prior art, the beneficial effects of this utility model are:

[0022] 1. This cofferdam structure combines outer and inner steel sheet piles with core backfill in a grid structure, providing both water-stopping and soil-retaining functions. The adjacent steel sheet piles utilize a socket-locking composite structure, enhancing their stability and deformation resistance. This avoids problems such as cracking and soil erosion causing water pollution due to deformation of the outer and inner steel sheet piles. It also solves the risks of instability caused by prolonged water immersion in traditional earthen cofferdams, as well as the safety hazards of deep-seated slippage. Furthermore, this cofferdam structure is recyclable and reusable, making it green, low-carbon, and environmentally friendly. It greatly simplifies the construction process in water-related projects, while also reducing project costs and construction time.

[0023] 2. The reinforcing piles, outer steel sheet piles, inner steel sheet piles, walers, and tie rods of this cofferdam structure combine to form a composite support system of "internal support and external tension," which enhances the overall rigidity of the cofferdam and solves the problems of poor overall integrity, weak rigidity, and easy deformation of conventional steel sheet pile cofferdams. It has good stability and high efficiency, and strengthens the cofferdam's resistance to water flow impact, seepage resistance, overall structural rigidity, and self-stability, making it suitable for narrow and long cofferdam structures along riverbanks.

[0024] 3. The outer and inner sheet piles of this cofferdam structure are connected to each other by interlocking joints to form a whole, forming a double-row sheet pile structure. The space between the outer and inner sheet piles is divided into multiple independent compartments by the partition piles, which enhances the overall rigidity of the cofferdam. At the same time, the partition piles provide support for the outer sheet piles, reduce the span of the outer sheet piles of the cofferdam, and transfer the load to the inner sheet piles, so that the outer and inner sheet piles share the load, which enhances the integrity and self-stability of the cofferdam.

[0025] 4. After the soil filling and compaction of the previous independent cell is completed, this cofferdam structure can be used as a construction platform for the next cell. It can be used for the construction of the cofferdam by the advance method or the demolition of the cofferdam by the retreat method. This simplifies the construction process of conventional water-related projects that require the prior construction of temporary steel trestle bridges or other forms of temporary work platforms, and greatly reduces the project cost and saves the construction period. Attached Figure Description

[0026] Figure 1 A top view of a cofferdam structure used in narrow river channels;

[0027] Figure 2 An enlarged view of a cofferdam structure used in narrow river channels;

[0028] Figure 3 This is a schematic diagram of a steel sheet pile connection for a cofferdam structure used in narrow river channels;

[0029] Figure 4 This is a schematic diagram of a cofferdam structure used in narrow river channels.

[0030] In the diagram: 1. River embankment; 2. Outer sheet pile; 21. Socketed locking mechanism; 3. Inner sheet pile; 4. Dividing pile; 41. Grid cell; 5. Tie rod; 51. First pair of tie rods; 52. Second pair of tie rods; 6. Waler; 61. Connecting plate; 7. Steel pipe pile; 8. Reinforcing pile. Detailed Implementation

[0031] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do 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 utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0032] Example 1:

[0033] A type of cofferdam structure for narrow river channels, such as Figures 1 to 4 As shown, the structure includes several outer sheet piles 2 and several inner sheet piles 3. The outer sheet piles 2 are vertically arranged and are arranged in close proximity, with adjacent outer sheet piles 2 connected by interlocking joints to form a whole. The inner sheet piles 3 are also vertically arranged and are arranged in close proximity, with adjacent inner sheet piles 3 connected by interlocking joints to form a whole. The tops of the outer sheet piles 2 and the inner sheet piles 3 are flush. The inner sheet piles 3 are spaced apart, and the outer sheet piles 2 and inner sheet piles 3 have corresponding shapes. The inner sheet piles 3 are located inside the outer sheet piles 2. The outer sheet piles 2 are positioned on the upstream side of the cofferdam, and the inner sheet piles 3 are positioned on the downstream side. Both the outer sheet piles 2 and inner sheet piles 3 are U-shaped structures. Both ends of the outer sheet piles 2 and inner sheet piles 3 are fixedly installed on the riverbank 1, so that the riverbank 1, the outer sheet piles 2 and the inner sheet piles 3 respectively enclose a closed rectangular structure, forming a cofferdam. Preferably, the outer sheet piles 2 and inner sheet piles 3 are Larssen sheet piles, and the orientation of several outer sheet piles 2 and inner sheet piles 3 is alternately arranged inward and outward. According to actual construction needs, several additional sheet piles can be added between the outer sheet piles 2 and the inner sheet piles 3. The structure of the additional sheet piles is the same as that of the outer sheet piles 2 and the inner sheet piles 3. Figure 3As shown, a socket lock 21 is fixedly installed on one end of one of the outer sheet piles 2 located at the corner. The shape of the socket lock 21 corresponds to the shape of one end of the outer sheet pile 2 and both are near-spiral structures, allowing the socket lock 21 to be connected to the outer sheet pile 2 via positive and negative hooks. It should be noted that the positive and negative hook connection here refers to a socket connection, which can be flexibly disassembled. One end of the other outer sheet pile 2 located at the corner can be fixedly installed on the socket lock 21, and the connection part of the two is flat, which can more firmly connect the outer sheet piles 2 on both sides of the corner, ensuring that the outer sheet piles 2 form a whole. Preferably, the outer sheet pile 2 and the inner sheet pile 3 located at the corner should be standardized products, and their bending radius should meet the design requirements. The driving speed should be slowed down to ensure a tight lock connection.

[0034] Several rows of dividing piles 4 are set at intervals between the outer sheet piles 2 and the inner sheet piles 3. These dividing piles 4 are vertically set along the extension direction of the outer sheet piles 2 and the inner sheet piles 3, dividing the space between the outer sheet piles 2 and the inner sheet piles 3 into several independent compartments 41. Each compartment 41 is a rectangular structure, and each compartment 41 is filled with compacted core fill. During construction, the previous compartment 41 is filled with core fill first, with the top surface of the fill flush with the tops of the outer sheet piles 2 and the inner sheet piles 3. After the previous compartment 41 is filled with core fill, it can serve as a construction platform for the next compartment 41 and the dividing piles 4, facilitating the filling of the next compartment 41 and other construction work. This simplifies the construction process, eliminating the need for temporary steel trestle bridges or other work platforms, and significantly reduces project costs and construction time. The core filling adopts a layered filling and compaction construction process. The preferred filling material is cohesive soil or silty clay with low permeability. When using permeable materials such as sand, a geomembrane must be laid inside the grid cell 41. The geomembrane should extend to the interlocking points of the outer sheet piles 2 or inner sheet piles 3, and be sealed with sealant to prevent water seepage. During the filling process, mechanical collisions with the outer sheet piles 2, inner sheet piles 3, and tie rods 5 should be avoided to prevent deformation. Preferably, the dividing piles 4 are made of several I-beams connected together, with the I-beams spaced longitudinally and laterally, and interlocking to increase the rigidity of the piles. The spacing between adjacent dividing piles 4 is determined based on the dimensions of the grid cell 41 and stress calculations to ensure the structural integrity of each grid cell 41 and the lateral restraint force after filling.

[0035] like Figure 2As shown, transverse walers 6 are fixedly installed on both the upstream and downstream sides of the outer sheet piles 2, and transverse walers 6 are fixedly installed on the downstream side of the inner sheet piles 3. This allows for the connection of several outer sheet piles 2 and several inner sheet piles 3 into a single unit. The walers 6 of the outer sheet piles 2 and the inner sheet piles 3 are located on the same horizontal plane. The walers 6 are made of double-unit I-beams, meaning each waler 6 consists of a pair of spaced-apart I-beams of the same specifications and length. Figure 4 As shown, several connecting plates 61 are fixedly installed at equal intervals on the outer surfaces of a pair of I-beams. The connecting plates 61 are rectangular structures, which can connect the pair of I-beams into a whole, increasing the integrity, rigidity, and strength of the waler 6, while also facilitating the installation and fixing of the tie rods 5. Preferably, the model of the waler 6 is selected according to the magnitude of the force on the outer sheet piles 2 and the inner sheet piles 3, and its length should cover the entire lateral range of the cofferdam structure. When installing the waler 6, it should fit tightly with the outer sheet piles 2 and the inner sheet piles 3. If there are gaps, wedge-shaped steel plates should be used to fill them to ensure effective force transmission.

[0036] Several horizontally arranged tie rods 5 are also installed at intervals between the outer sheet piles 2 and the inner sheet piles 3. These tie rods 5 are located within several cell 41s, increasing the inner rigidity and overall integrity of the cell 41s. The tie rods 5 are installed between a pair of I-beams of the walers 6, and pass through several walers 6 on the outer sheet piles 2 and inner sheet piles 3 respectively. Steel washers and nuts are installed on the tie rods 5, which are then fixed to the water-facing walers 6 of the outer sheet piles 2 and the backwater walers 6 of the inner sheet piles 3, facilitating flexible installation of the tie rods. The installation position of the reinforcing rod 5 serves to increase the overall rigidity of the cofferdam structure and balance the horizontal earth pressure exerted by the backfill on the outer sheet piles 2 and inner sheet piles 3. The reinforcing rod 5 includes several first pairs of tie rods 51 and several second pairs of tie rods 52. The first pairs of tie rods 51 are spaced apart on the sides of the outer sheet piles 2 and inner sheet piles 3, and are arranged through each other. The second pairs of tie rods 52 are spaced apart at the corner positions of the outer sheet piles 2, with their ends respectively threaded onto the outer sheet piles 2 located on both sides of the corner. All second pairs of tie rods 52 are inclined. Preferably, the diameter of the reinforcing rod 5 is determined based on calculations of the lateral earth pressure and water pressure of the cofferdam. The reinforcing rod 5 should be installed horizontally, and the pre-tightening force should meet the design requirements. After pre-tightening, its stress condition should be monitored, and any loosening should be promptly re-tightened. The second pairs of tie rods 52 should be appropriately densified and diagonal supports should be provided to enhance the structural rigidity of the corner areas.

[0037] like Figure 2As shown, after the core of the dam is filled, several steel pipe piles 7 are fixedly installed at equal intervals on the backwater side of the outer steel sheet pile 2 and the backwater side of the inner steel sheet pile 3. If a tie rod 5 is encountered, the installation position of the steel pipe pile 7 is locally adjusted to ensure that the force is reasonable, which can enhance the integrity, rigidity and stability of the outer steel sheet pile 2 and the inner steel sheet pile 3, balance the horizontal earth pressure and horizontal water pressure of the core fill, and reduce the lateral displacement of the cofferdam. Several steel pipe piles 7 are all close to the outside of the waler 6. The steel pipe piles 7 are made of steel pipes and are driven vertically along the extension direction of the outer steel sheet pile 2 and the inner steel sheet pile 3. Several outer sheet piles 2 and several inner sheet piles 3 are fixedly installed in the depression on the backwater side with reinforcing piles 8. The reinforcing piles 8 are close to the outer sheet piles 2 or the inner sheet piles 3. The reinforcing piles 8 are made of I-beams and are driven vertically along the extension direction of the outer sheet piles 2 and the inner sheet piles 3. The reinforcing piles 8 are made of I-beams and are perpendicular to the outer sheet piles 2 and the inner sheet piles 3 in the horizontal direction. The reinforcing piles 8 can be driven at the same time as the outer sheet piles 2 and the inner sheet piles 3, or they can be driven at the same time when the dam core is filled, so as to enhance the overall rigidity and stability of the sheet pile group. Preferably, the embedment depth of the outer sheet piles 2, inner sheet piles 3, and steel pipe piles 7 is determined by calculation based on geological conditions, hydrological conditions, and the height of the cofferdam. Before driving the outer sheet piles 2, inner sheet piles 3, and steel pipe piles 7, precise layout should be carried out using surveying instruments to ensure that the axial deviation and verticality deviation of the outer sheet piles 2, inner sheet piles 3, and steel pipe piles 7 meet the specifications. The tops of the outer sheet piles 2, inner sheet piles 3, and steel pipe piles 7 are flush, and the top elevation of the dividing piles 4 and reinforcing piles 8 is flush with the bottom elevation of the waler 6.

[0038] The structure combining the outer sheet piles 2, inner sheet piles 3, and the core backfill of the grid 41 serves a dual function of water stopping and soil retention. The use of a socket-locking composite steel structure enhances the stability and deformation resistance of the outer sheet piles 2 and inner sheet piles 3, thus avoiding problems such as cracking and soil pollution caused by deformation of the outer sheet piles 2 and inner sheet piles 3. It also solves the danger of instability caused by long-term water immersion in traditional earthen cofferdams, as well as the safety hazard of deep slippage. Furthermore, this cofferdam structure is recyclable and reusable, making it green, low-carbon, and environmentally friendly. It greatly simplifies the construction process in water-related projects, while also reducing project costs and construction time. The removal of the outer sheet piles 2 and inner sheet piles 3 should be carried out after the completion of the construction within the cofferdam. Before removal, water should be injected into the cofferdam pit to maintain a relatively level water level on both sides of the cofferdam, and then the core backfill should be removed. The removal sequence should follow the principle of "top to bottom, inside to outside". After removal, the outer sheet pile 2 and the inner sheet pile 3 should be cleaned, repaired, and maintained for reuse.

[0039] The construction method of this utility model is as follows:

[0040] The socket locking buckle 21 is welded to the side ends of the outer sheet pile 2 and the inner sheet pile 3 located at the corner position; several sheet piles are interlocked with each other through the socket locking buckle 21 according to the position and size of the cofferdam to form the outer sheet pile 2 and the inner sheet pile 3.

[0041] Several dividing piles 4 are driven at intervals between the outer sheet piles 2 and the inner sheet piles 3 to divide the space between the outer sheet piles 2 and the inner sheet piles 3 into several independent and closed compartments 41. Horizontal walers 6 are installed at a certain height below the top of the outer sheet piles 2 on the water-facing and back-facing sides, and the inner sheet piles 3 on the back-facing side. Holes are drilled at corresponding locations on the outer sheet piles 2 and the inner sheet piles 3, through which tie rods 5 are passed to connect the outer sheet piles 2 and the inner sheet piles 3. Steel pipe piles 7 are driven at equal intervals along the back-facing side of the inner sheet piles 3, close to the walers 6. If a tie rod 5 is encountered, the position of the steel pipe piles 7 can be locally adjusted. The first cell 41 is filled with core soil and compacted, thus completing the filling of one cell 41. After the core soil of the previous cell 41 is filled, steel pipe piles 7 are driven at equal intervals on the backwater side of the outer sheet piles 2. If tie rods 5 are encountered, the position of the steel pipe piles 7 can be adjusted locally. This step is repeated until the construction of all cell 41 is completed, thus forming the overall cofferdam structure.

[0042] The adjacent sheet piles of the cofferdam structure are connected by socket-locking couplings 21, forming outer sheet piles 2 and inner sheet piles 3 respectively. Then, the middle section of the outer sheet piles 2 and inner sheet piles 3 is reinforced to form multiple independent compartments 41, enhancing the overall rigidity of the cofferdam. After the construction of the previous independent compartment 41 is completed, it can be backfilled and compacted, serving as a construction platform for the next compartment 41. This allows for the construction of the cofferdam using the advance method or the dismantling of the cofferdam using the retreat method, simplifying the construction process that typically requires the prior construction of temporary steel trestle bridges or other forms of temporary work platforms in water-related projects. This significantly reduces project costs and saves time. The use of walers 6 and tie rods 5 increases the internal rigidity and integrity of each compartment 41, and can also be used according to the needs of the cofferdam construction. The cofferdam height can be flexibly adjusted by modifying parameters such as the pile length of the outer sheet piles 2, inner sheet piles 3, steel pipe piles 7, and reinforcing piles 8, as well as the cofferdam width and the spacing of the grid cells 41. This cofferdam structure serves both as a water stop and a soil retainer. The "internal support and external tension" structural system enhances the cofferdam's stability and resistance to deformation, preventing problems such as cracking and soil erosion causing water pollution due to cofferdam deformation. Furthermore, a combined reinforcing structure of reinforcing piles 8 and steel pipe piles 7 is added to the backwater side of the outer sheet piles 2 and inner sheet piles 3. This strengthens the cofferdam's integrity and rigidity, reduces local deformation, improves its safety reserve and stability, balances the horizontal earth pressure and horizontal water pressure of the core fill, and reduces lateral displacement. All components of this cofferdam structure are recyclable and reusable, making it environmentally friendly and low-carbon. The components are all standard parts, facilitating construction and making it widely applicable in water conservancy and municipal engineering projects.

[0043] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A cofferdam structure for narrow river channels, characterized in that, include: The sheet pile assembly is a double-layer structure with both ends fixedly installed on the river embankment (1). The sheet pile assembly and the river embankment (1) enclose a closed rectangular structure. The walers (6) are fixedly installed on the water-facing side and the water-repellent side of the sheet pile assembly, respectively. Several pairs of tie rods (5) are horizontally inserted through the sheet pile assembly and located in the middle of the waler (6); Several partition piles (4) are fixedly installed at intervals between the double-layer structure of the sheet pile assembly. The partition piles (4) are perpendicular to the sheet pile assembly and divide the internal space of the sheet pile assembly into several closed compartments (41). Reinforcing components are spaced apart on the backwater side of the sheet pile assembly.

2. The cofferdam structure for narrow river channels according to claim 1, characterized in that, The sheet pile assembly includes a number of outer sheet piles (2) and a number of inner sheet piles (3). The number of outer sheet piles (2) and the number of inner sheet piles (3) are connected together in sequence, and the outer sheet piles (2) and the inner sheet piles (3) are spaced apart.

3. The cofferdam structure for narrow river channels according to claim 2, characterized in that, The shapes of the outer sheet piles (2) and the inner sheet piles (3) are corresponding.

4. The cofferdam structure for narrow river channels according to claim 3, characterized in that, The reinforcing component includes a plurality of steel pipe piles (7), which are fixedly installed at intervals on the walers (6) of the outer sheet piles (2) and the inner sheet piles (3), and the plurality of steel pipe piles (7) are all located on the backwater side of the outer sheet piles (2) and the inner sheet piles (3).

5. The cofferdam structure for narrow river channels according to claim 3, characterized in that, The reinforcing assembly also includes a number of reinforcing piles (8), which are fixedly installed at intervals in the recesses on the backwater side of the outer sheet pile (2) and the inner sheet pile (3).

6. The cofferdam structure for a narrow river channel according to any one of claims 1 to 5, characterized in that, The tension reinforcement bar (5) includes a plurality of first tie rods (51), which are spaced apart and inserted on the side of the sheet pile assembly, and the first tie rods (51) penetrate the double-layer structure of the sheet pile assembly.

7. The cofferdam structure for narrow river channels according to claim 6, characterized in that, The tie rod (5) further includes a plurality of second tie rods (52), which are respectively installed at intervals at the corner positions of the sheet pile assembly, and the plurality of second tie rods (52) are all inclined.

8. The cofferdam structure for a narrow river channel according to any one of claims 1 to 5, characterized in that, The dividing pile (4) includes several closely connected I-beams, which are arranged alternately in the longitudinal and transverse directions.

9. The cofferdam structure for a narrow river channel according to any one of claims 1 to 5, characterized in that, The compartment (41) is filled with soil.

10. The cofferdam structure for a narrow river channel according to any one of claims 1 to 5, characterized in that, The two sheet pile assemblies located at the corner are fastened together by a socket lock (21).

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