A dam-approaching eccentric load cofferdam anchor pile support system and construction method

Abstract

The present application belongs to the technical field of cofferdam support, and particularly relates to a dam bias cofferdam anchor pile support system and a construction method, aiming to solve the problem of insufficient support reliability of the existing cofferdam anchor pile support system when facing the bias working condition. The dam bias cofferdam anchor pile support system provided by the present application comprises a cofferdam body, a first inner support rod, a first anchor pile, a connecting frame and an inclined support pile. The two ends of the first inner support rod are respectively connected with the inner wall of the cofferdam body. The first anchor pile is vertically arranged on the free side and connected with the cofferdam body through the connecting frame. The inclined support pile is obliquely arranged on the free side and connected with the side of the first anchor pile away from the cofferdam body. The present application strengthens the support effect by arranging the combination of the first anchor pile and the inclined support pile on the free side. The elastic member is introduced into the first inner support rod to change the traditional rigid force transmission into the elastic force transmission with buffering capacity, thereby reducing the impact borne by the first anchor pile and the inclined support pile and significantly enhancing the reliability of the support system.

Description

Technical Field

[0001] This invention belongs to the field of cofferdam support technology, specifically relating to a cofferdam anchor pile support system and construction method for eccentrically loaded cofferdams near dams. Background Technology

[0002] A cofferdam is a temporary structure used in the construction of hydraulic engineering projects such as bridges and wharves, or structures involving water, to protect the construction area of ​​the foundation in water or on soft soil. Its functions include water isolation, soil retention, and support of the foundation pit sidewalls, providing a dry and stable working environment for the concrete pouring of the foundation. When the foundation is located on a riverbank at a considerable depth, the bank-facing side of the cofferdam experiences significant soil pressure, while the river-facing side is adjacent to the river channel, resulting in substantial uneven loads on both sides. With excavation, the cofferdam may experience risks such as leakage and pile top displacement. The bank-facing side of the cofferdam, also known as the dam-facing side, must withstand a large combined eccentric load, including the dam's own weight, construction loads, and additional soil pressure, generating a strong overturning moment and horizontal thrust pointing towards the foundation pit or river channel. The open side (the side of the foundation pit or river-facing side, i.e., the side of the cofferdam furthest from the dam-facing side) only bears conventional soil and water pressure, exhibiting weaker constraint stiffness. Traditional support systems, such as internal bracing and anchor bolts, can only passively withstand eccentric loads. In soft soil and under high eccentric load conditions, they are prone to risks such as excessive horizontal displacement of the cofferdam, local instability, and deep sliding.

[0003] While traditional rigid internal bracing can transfer loads, it cannot release the additional stresses caused by sudden changes in eccentric loading and temperature variations, making it prone to brittle cracking and ultimately leading to bracing failure. In other words, existing cofferdam anchor pile support systems suffer from insufficient reliability when facing eccentric loading conditions. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a cofferdam anchor pile support system and construction method for eccentrically loaded dams.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: An anchor pile support system for a cofferdam under eccentric load near a dam includes the cofferdam body, a first inner support rod, a first anchor pile, a connecting frame, and inclined bracing piles; The first inner support rod is horizontally set and extends along the direction from the side adjacent to the dam to the side exposed to the air. Both ends of the first inner support rod are connected to the inner wall of the cofferdam body. The first inner support rod includes a first connecting rod, a second connecting rod, and a first elastic element. The first connecting rod and the second connecting rod are capable of moving towards each other along their own length direction. The first elastic element is disposed between the first connecting rod and the second connecting rod and is used to apply a thrust to the first connecting rod and the second connecting rod. The first anchor pile is vertically installed on the free side and connected to the cofferdam body through the connecting frame; The inclined support pile is inclinedly installed on the free side, and its upper end is connected to the side of the first anchor pile away from the cofferdam body.

[0006] Furthermore, a first flange and a second flange are respectively provided at the ends of the first connecting rod and the second connecting rod that are close to each other, and the first elastic element is disposed between the first flange and the second flange; The first flange and the second flange are connected by bolts.

[0007] Furthermore, the first elastic element is configured as a butterfly spring, and a plurality of the butterfly springs are arranged along the length direction of the first inner support rod.

[0008] Furthermore, the inclined bracing pile is hinged to the first anchor pile or ball-jointed.

[0009] Furthermore, the anchor pile support system of the eccentric load cofferdam near the dam also includes an anti-pull-out cone, and the anti-pull-out cone is provided at one end of the first anchor pile and the inclined support pile inserted into the soil layer; Along the direction of insertion into the soil layer, the outer diameter of the pull-out cone gradually decreases, and the maximum outer diameter of the pull-out cone is greater than the outer diameter of the first anchor pile or the inclined support pile connected to it.

[0010] Furthermore, the eccentric load cofferdam anchor pile support system also includes a countermeasure plate, which is connected to the outer wall of the first anchor pile and the inclined support pile, and is inclined upward in a direction away from the outer wall.

[0011] Furthermore, the anchor pile support system of the eccentric load cofferdam near the dam also includes auxiliary limiting piles, which are vertically set and connected to the connecting frame; The auxiliary limiting pile is set between two adjacent inclined support piles.

[0012] Furthermore, it also includes a bridge unit, which is disposed above the connecting frame and connected to the upper end of the first anchor pile.

[0013] Furthermore, the anchor pile support system of the eccentrically loaded cofferdam near the dam also includes a second inner support rod, which is horizontally set and connected at both ends to the two side walls adjacent to the cofferdam body respectively; The second inner support rod includes a third link, a fourth link, and a second elastic element. The third link and the fourth link are capable of moving towards each other along their own length direction. The second elastic element is disposed between the third link and the fourth link and is used to apply a thrust to the third link and the fourth link.

[0014] In another aspect, the present invention proposes a construction method for an anchor pile support system for a dam-side cofferdam under eccentric loading, which is used in the aforementioned dam-side cofferdam anchor pile support system, comprising the following steps: Anchor pile construction: Using the working face of the dam and the temporary trestle bridge, the retaining piles of the cofferdam body are driven into the dam slope and in the water respectively. Then, the first anchor pile and the corresponding inclined support pile are driven into the open side of the cofferdam. Anchor pile connection: The connecting frame is constructed by welding, and the cofferdam body, the first anchor pile, and the inclined brace pile are connected into a whole through the connecting frame; Laying bridge units: The bridge units are fixed above the connecting frame using bolts; Installation of the first inner support rod: Excavate downwards layer by layer. After installing the first inner support rod at each layer, continue to excavate downwards and install the first inner support rod until the cofferdam is excavated to the bottom and a complete pier construction surface is formed. Dismantling of the support system: After the pier cap construction is completed, the support system is dismantled in the following order: bridge unit, first inner support rod, connecting frame, inclined brace pile, and first anchor pile.

[0015] In summary, the technical effects achieved by this invention are as follows: The eccentric load cofferdam anchor pile support system provided by the present invention includes a cofferdam body, a first inner support rod, a first anchor pile, a connecting frame, and inclined bracing piles; the first inner support rod is horizontally arranged and extends along the direction from the side adjacent to the dam to the side exposed to the open space, and both ends of the first inner support rod are respectively connected to the inner wall of the cofferdam body; the first inner support rod includes a first connecting rod, a second connecting rod, and a first elastic element, and the first connecting rod and the second connecting rod can move towards each other along their own length direction; the first elastic element is arranged between the first connecting rod and the second connecting rod and is used to apply thrust to the first connecting rod and the second connecting rod; the first anchor pile is vertically arranged on the side exposed to the open space and connected to the cofferdam body through the connecting frame; the inclined bracing pile is inclinedly arranged on the side exposed to the open space, and its upper end is connected to the side of the first anchor pile away from the cofferdam body.

[0016] The anchor pile support system for eccentrically loaded cofferdams provided by this invention enhances the support effect by combining a first anchor pile and inclined bracing piles on the free side. The inclined bracing piles utilize their tilting support to convert part of the horizontal eccentric load into downward pressure, actively balancing the enormous thrust on the free side and effectively suppressing the displacement and overturning tendency of the cofferdam body towards the free side. In particular, the introduction of an elastic element into the first inner support rod transforms the traditional rigid force transmission into an elastic force transmission with buffering capabilities. This elastic element can absorb and release the impact energy generated by sudden changes in eccentric load and temperature stress, preventing brittle cracking or instability of the first inner support rod due to stress concentration. This reduces the impact borne by the first anchor pile and inclined bracing pile, significantly improving the stability and durability of the support system under complex dynamic loads, and significantly enhancing the reliability of the support system.

[0017] Furthermore, the first inner support rod can vary its length within a certain range, both absorbing and dissipating some of the impact through the first elastic element and ensuring the structural stability of the cofferdam body. It possesses both rigidity and impact resistance, making it particularly suitable for cyclic load conditions. It should be noted that, in the installed state, the first elastic element is under compression and can continue to be compressed and deformed. That is, it will only continue to be compressed and deformed to absorb impact when the load exceeds the preset pressure, thus ensuring the safety of the cofferdam. When the load does not exceed the preset pressure, the first elastic element remains in its initial compressed state and will not be compressed; the first inner support rod functions as a conventional rigid rod. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the anchor pile support system for the eccentrically loaded cofferdam provided in an embodiment of the present invention; Figure 2 This is a top view schematic diagram of the anchor pile support system of the eccentrically loaded cofferdam near the dam. Figure 3 This is a schematic diagram of a temporary pier; Figure 4 This is another structural schematic diagram of the anchor pile support system for the eccentrically loaded cofferdam near the dam. Figure 5 This is a schematic diagram of the anti-pull cone and counterweight plate. Figure 6 This is a structural schematic diagram of a bridge unit; Figure 7 This is a schematic diagram of the structure of the first inner support rod; Figure 8 This is a schematic diagram showing the location of the anchor pile support system for the eccentrically loaded cofferdam near the dam. Figure 9 This is a construction schematic diagram of the anchor pile support system for the eccentrically loaded cofferdam near the dam.

[0020] Icons: 100, Cofferdam body; 110, Retaining pile; 120, Waler; 200, First inner support rod; 210, First connecting rod; 220, Second connecting rod; 230, First elastic element; 240, Connecting bolt; 211, First flange; 221, Second flange; 300, First anchor pile; 400, Connecting frame; 500, Diagonal bracing pile; 600, Anti-uplift cone; 610, Cone body; 620, Connecting stiffening plate; 700, Countermeasure plate; 800, Auxiliary limiting pile; 900, Bridge unit; 910, Load-bearing beam; 920, Longitudinal beam; 930, Bridge deck steel plate; 1000, Second inner support rod; 1100, Sheath; 10, Temporary trestle. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The following combination Figures 1-9 The structure and shape of the anchor pile support system for the eccentrically loaded cofferdam provided in this embodiment are described in detail: In this embodiment, the eccentrically loaded cofferdam anchor pile support system includes the cofferdam body 100, the first inner support rod 200, the first anchor pile 300, the connecting frame 400, and the inclined bracing pile 500, as follows: Figure 1 , Figure 2As shown. The cofferdam body 100 is a ring-shaped closed structure formed by sequentially connecting steel sheet piles or steel pipe piles, used to isolate the soil and water inside and outside the foundation pit. The first inner support rod 200 is set horizontally, and its overall extension direction is from the side adjacent to the dam to the side free of soil. The two ends of the first inner support rod 200 are rigidly connected to the inner walls of the opposite sides of the cofferdam body 100 by welding or high-strength bolts, which plays a supporting role to resist the soil pressure on the side adjacent to the dam. The first anchor pile 300 is set vertically on the free side and is rigidly connected to the cofferdam body 100 through the connecting frame 400. Multiple first anchor piles 300 are formed as a whole through the connecting frame 400. The connecting frame 400 can be a steel truss or a steel plate beam. The inclined bracing pile 500 is set inclined on the free side. The upper end is connected to the side of the first anchor pile 300 away from the cofferdam body 100 through a hinge seat. The lower end is inserted obliquely into the stable soil layer. The inclined support of the inclined bracing pile 500 converts part of the horizontal load into downward pressure, actively balancing the huge thrust on the side adjacent to the dam.

[0025] In this embodiment, multiple first anchor piles 300 form an anchor pile group. In the high eccentric load zone near the dam, steel pipe piles with an outer diameter of 630mm and a wall thickness of 10mm are used, with the pile spacing increased to 1.2m. In the low load zone, steel pipe piles with an outer diameter of 630mm and a wall thickness of 10mm are used, with the pile spacing maintained at 2.0m, arranged in a variable-spacing manner in a designated area outside the foundation pit. The pile length is determined according to the foundation pit depth and soil layer distribution. The tops of the piles are connected by connecting rods with an outer diameter of 273mm and a wall thickness of 8mm to form a whole. The connecting rods form a connecting frame 400, enhancing the collaborative working ability of the pile group, connecting the dispersed piles into a whole, and ensuring that the eccentric load is evenly distributed throughout the cofferdam, preventing single pile overload or local instability. It should be noted that since multiple first anchor piles 300 are formed into a whole through the connecting frame 400, only the row of first anchor piles 300 furthest from the cofferdam body 100 needs to be equipped with inclined bracing piles 500, such as... Figure 1 , Figure 2 As shown.

[0026] In this embodiment, the cofferdam body 100 includes retaining piles 110 and walers 120. The retaining piles 110 are formed by sequentially connecting steel sheet piles or steel pipe piles to form a closed annular structure. The walers 120 are arranged in an annular structure along the inner wall of the retaining piles 110. The cofferdam body 100 has a rectangular ring structure, and the two ends of the first inner support rod 200 are connected to the two parallel sides of the rectangle. Multiple walers 120 are arranged along the height direction of the cofferdam body 100. The walers 120 are located inside the retaining piles 110, and water-swellable sealing rubber strips are installed at the joints between them, and grouting pipes are pre-embedded. After the walers 120 are installed, grouting is immediately performed at the joints to stop water leakage caused by eccentric load deformation.

[0027] In this embodiment, the first inner support rod 200 includes a first connecting rod 210, a second connecting rod 220, and a first elastic element 230, such as... Figure 7As shown. The first connecting rod 210 and the second connecting rod 220 are both high-strength seamless steel pipes, coaxially arranged with their ends facing each other, allowing them to move in opposite or opposite directions along their length. The first elastic element 230 is disposed between the first connecting rod 210 and the second connecting rod 220. When subjected to external pressure, it is compressed, thereby absorbing energy and generating a reverse thrust to balance external eccentric load impacts and simultaneously release stress. In this embodiment, the use of the first elastic element 230 increases the buffering of rigid force transmission, effectively coping with the impact of changing eccentric loads, preventing frequent force changes from causing displacement of the support rods, and preventing loosening between the cofferdam body 100, the first anchor pile 300, the inclined bracing pile 500, and the soil layer, effectively reducing eccentric load impacts and improving the overall impact resistance. Simultaneously, the inclined bracing pile 500 enhances the ability to resist eccentric loads, thus significantly improving the overall support stability of the support system.

[0028] In this embodiment, a first flange 211 and a second flange 221 are welded and fixed to the ends of the first connecting rod 210 and the second connecting rod 220 respectively, with multiple bolt holes evenly distributed on the two flanges. A first elastic element 230 is clamped between the first flange 211 and the second flange 221. The two flanges are fixedly connected by multiple high-strength connecting bolts 240 passing through the bolt holes and tightening nuts. During assembly, the first elastic element 230 is pre-compressed by tightening the connecting bolts 240, causing a certain amount of pre-deformation while still retaining deformation allowance. That is, in the default state, the first connecting rod 210 and the second connecting rod 220 compress the first elastic element 230, causing a certain amount of deformation, but still maintaining deformation allowance. At this time, the first elastic element 230 ensures the pre-tightening force of the bolt connection, making the bolt connection reliable. The connecting bolts 240 are inserted into the bolt holes of the first flange 211 and the second flange 221, guiding the relative movement of the first connecting rod 210 and the second connecting rod 220 and preventing deflection. Multiple connecting bolts 240 are arranged circumferentially along the flange, which can limit the first elastic element 230. In this embodiment, the pre-compressed elastic element can apply a continuous axial preload to the connecting bolts 240, effectively preventing the bolts from loosening under vibration load, ensuring the reliability of the flange connection, and at the same time, the guiding effect of the bolts ensures the coaxiality of the elastic element when it is compressed.

[0029] In this embodiment, the bolted connection limits the maximum length of the first inner support rod 200, and the first elastic element 230 limits the minimum length of the first inner support rod 200, making the first inner support rod 200 an elastic support rod with a limited range of extension and contraction, thus ensuring its stability under impact loads. This structure not only ensures stable support for the cofferdam body 100 but also buffers the impact of loads.

[0030] In an optional embodiment, the first elastic element 230 is specifically configured as a disc spring. To improve load-bearing capacity and deformation, multiple disc springs are arranged along the length of the first inner support rod 200. Specifically, a guide shaft is provided on the first flange 211 or the second flange 221, and the guide shaft is inserted into the central through hole of the disc spring to limit its movement. Furthermore, eight standard disc springs are used, with a total deformation of 12mm and a rated load capacity of 4800kN. Disc springs have the advantages of high stiffness, strong damping and vibration absorption capacity, short stroke, and large load capacity. They can provide a huge elastic restoring force in the steel pipe support with limited installation space, and the guide shaft further prevents radial instability of the disc spring assembly. At the same time, the contact between the disc springs generates friction, making the actual stiffness greater than the theoretical calculation value and bringing a damping effect, which helps to dissipate impact energy.

[0031] Specifically, the flange is made of 20mm thick steel plate, with 26 evenly spaced bolt holes of 22mm diameter. The disc spring has an outer diameter of 600mm, an inner diameter of 300mm, a thickness of 12mm, and a single-piece deformation of 3mm.

[0032] In this embodiment, the inclined bracing pile 500 and the first anchor pile 300 are connected by a hinge. Specifically, an ear plate with a pin hole is welded to the outer wall of the first anchor pile 300, and a corresponding ear plate is welded to the upper end of the inclined bracing pile 500. The two are hinged by a high-strength pin. Optionally, to adapt to more complex water flow and foundation deformation, the inclined bracing pile 500 and the first anchor pile 300 are connected by a ball joint. That is, a hemispherical groove is provided on the first anchor pile 300, and a hemispherical protrusion is provided at the end of the inclined bracing pile 500. The two cooperate to form a universal ball joint. A fixed-angle inclined bracing pile 500 cannot adapt to complex soil inclination angles and water scouring conditions. After long-term use, the root is prone to detachment. The hinge or ball joint method allows the inclined bracing pile 500 to make small angle adaptive adjustments according to the actual stress and foundation deformation, avoiding the additional bending moment generated by the rigid connection. This keeps the inclined bracing pile 500 in the optimal axial compression state, making installation more flexible and convenient, and preventing root detachment.

[0033] Specifically, the inclined support pile 500 uses a steel pipe with an outer diameter of 630mm and a wall thickness of 10mm. One end is connected to the first anchor pile 300 through a ball joint, which can achieve an angle adjustment of 15°-45° to adapt to different soil inclination angles and water flow directions. The other end is inserted obliquely into the stable soil layer of the riverbed to form an inclined compression member.

[0034] In this embodiment, to enhance the pull-out and compressive strength of the first anchor pile 300 and the inclined bracing pile 500 in soft soil foundations, a pull-out cone 600 is also provided, such as... Figure 5As shown. The pull-out cone 600 is welded and fixed to the lowest end of the first anchor pile 300 and the inclined support pile 500 inserted into the soil layer. Along the direction of insertion into the soil layer, the outer diameter of the pull-out cone 600 gradually decreases, and its maximum outer diameter is greater than the outer diameter of the pile body to which it is connected. Specifically, the pull-out cone 600 includes a cone body 610 and a connecting stiffener 620. The cone body 610 is a hollow frustum structure. One end of the inclined support pile 500 is inserted into the cone body 610 and welded and fixed. The connecting stiffener 620 is welded circumferentially between the outer walls of the cone body 610 and the inclined support pile 500 to form a reinforcing rib, as shown. Figure 5 As shown. When the pile is subjected to tension, the enlarged end of the inverted umbrella-shaped tension cone 600 will compress the soil above, generating huge end bearing resistance and greatly improving the tension resistance. At the same time, when subjected to compression, it can better penetrate the soil layer and spread the load to the deeper layers, achieving the triple function of tension resistance, compression resistance and locking.

[0035] Specifically, the 600 anti-extraction cone has a maximum outer diameter of 1.2m and is made of steel plate with a wall thickness of 16mm. It is embedded in the stable soil layer to a depth of not less than 1.5m. Through the triple action of pile side friction resistance, pile end bearing, and anti-extraction locking, it greatly improves the anti-sliding and anti-overturning capacity in soft soil foundations.

[0036] In this embodiment, the anchor pile support system of the eccentrically loaded cofferdam near the dam also includes a counter-dam plate 700, such as... Figure 5 As shown, the counterweight plate 700 is connected to the outer wall of the first anchor pile 300 and the inclined bracing pile 500, and is inclined upward in a direction away from the outer wall, forming an acute angle with the pile axis. Multiple counterweight plates 700 can be arranged in layers along the length of the pile or radially along the circumference. When the pile is subjected to horizontal thrust and tends to move, the upwardly inclined counterweight plate 700 cuts into the surrounding soil like barbs, using passive earth pressure to generate a reverse restraint force, effectively resisting the horizontal displacement of the pile top and enhancing the overall overturning resistance of the anchor pile group.

[0037] In this embodiment, the anchor pile support system of the eccentrically loaded cofferdam near the dam also includes auxiliary limiting piles 800, such as... Figure 1 , Figure 4As shown. The auxiliary limiting pile 800 is vertically installed, its bottom inserted into the soil layer, and its top rigidly connected to the connecting frame 400. The auxiliary limiting pile 800 is arranged between two adjacent inclined support piles 500, forming a staggered planar arrangement to increase overall rigidity. When on-site construction space is limited and it is impossible to directly drive densely packed inclined support piles 500, the auxiliary limiting pile 800 can assist the inclined support piles 500. Specifically, the connecting frame 400 is a truss structure; the upper end of the inclined support pile 500 is connected to the first anchor pile 300, with the connection point being the upper chord of the connecting frame 400; the top of the auxiliary limiting pile 800 is connected to the lower chord of the connecting frame 400. The auxiliary limiting pile 800 mainly serves as an independent safety redundancy. Even if the bearing capacity of the main anchor pile decreases due to unexpected situations such as pile corrosion or soil liquefaction, the auxiliary limiting pile 800 can still maintain the basic stability of the system, buying time for emergency rescue. When soil conditions are favorable, the auxiliary restraining pile 800 can be omitted. By appropriately lengthening the first anchor pile 300 and the inclined bracing pile 500, the overall rigidity requirement can be met, thus simplifying the structure. Similarly, an anti-pull-out cone 600 is also provided at the end of the auxiliary restraining pile 800 that is inserted into the soil.

[0038] Specifically, the auxiliary limiting pile 800 is a steel pipe pile with an outer diameter of 300mm and a wall thickness of 8mm. The top of the pile is rigidly connected to the connecting frame 400. The auxiliary first anchor pile 300 forms a double lateral constraint to limit lateral displacement.

[0039] In this embodiment, the eccentrically loaded cofferdam anchor pile support system also includes a bridge unit 900. The bridge unit 900 is positioned above the connecting frame 400 and connected to the upper end of the first anchor pile 300. Specifically, the bridge unit 900 includes a load-bearing beam 910, a longitudinal beam 920, and a bridge deck steel plate 930, as shown below. Figure 4 , Figure 6As shown. The load-bearing beam 910 is made of I-beams, positioned on the top of the first anchor pile 300 and extending along the direction from the dam side to the open side. Both ends of the load-bearing beam 910 are rigidly connected to the flanges on the top of the first anchor pile 300 and the flanges on the top of the cofferdam body 100 via high-strength bolts. Simultaneously, limiting blocks are installed at the ends of the load-bearing beam 910 to prevent slippage of the bridge unit 900 under horizontal loads. The longitudinal beams 920 are made of H-beams, extending along the length of the bridge unit 900 and positioned on the load-bearing beam 910 at 600mm intervals. They are connected to the load-bearing beam 910 via high-strength bolts, evenly distributing the bridge deck load to the load-bearing beam 910. That is, the longitudinal beams 920 and the load-bearing beam 910 are horizontally positioned and perpendicular to each other. The bridge deck steel plate 930 is made of 10mm thick checkered steel plate, fully laid and fixed on the longitudinal beams 920, directly bearing the vertical loads of vehicles, construction equipment, etc., forming a flat working and passage surface. Bridge unit 900 integrates and reuses the foundations of the cofferdam body 100 and the temporary trestle bridge 10, eliminating the need for separate foundation piles for bridge unit 900 and significantly reducing the workload. Simultaneously, the vertical load of bridge unit 900 is converted into downward compressive stress on the anchor piles, enhancing pile-soil interlocking and improving the system's resistance to horizontal eccentric loads, thus achieving coordinated stress distribution between the support and the construction access. The vertical load of bridge unit 900 includes its own weight and the load-bearing weight, which includes the weight of vehicles, construction equipment, etc.

[0040] In this embodiment, the anchor pile support system of the eccentrically loaded cofferdam also includes a second inner support rod 1000. The second inner support rod 1000 is horizontally positioned, with its two ends connected to the two adjacent side walls of the cofferdam body 100, respectively, to enhance the rigidity of the cofferdam body 100 itself. Specifically, the second inner support rod 1000 includes a third connecting rod, a fourth connecting rod, and a second elastic element. The third and fourth connecting rods can move towards each other along their length, and the second elastic element is positioned between them to apply thrust. The specific structure of the second inner support rod 1000 is exactly the same as that of the first inner support rod 200, also including a flange, a disc spring assembly, and a guide shaft. The second inner support rod 1000, through the second elastic element, increases the buffering of rigid force transmission, effectively coping with the impact of changing eccentric loads and preventing frequent force changes from causing loosening or slippage of the piles of the cofferdam body 100, thus improving the stability of the cofferdam body 100.

[0041] In this embodiment, the anchor pile support system of the eccentrically loaded cofferdam near the dam also includes a sheath 1100, which is installed in the soil section of the inclined support pile 500, i.e., within 2m below the riverbed line. Specifically, the sheath 1100 is fitted onto the inclined support pile 500 and is made of high-density polyethylene. The space between the sheath 1100 and the inclined support pile 500 is filled with graded sand and gravel to prevent water erosion from causing the soil at the root of the inclined support pile 500 to become hollow, thus ensuring stability even under a 50-year flood.

[0042] In this embodiment, the cofferdam body 100 is equipped with multiple layers of internal support rods to effectively control the deformation of the cofferdam body 100 at different depths, uniformly transferring the eccentric load to the deep stable soil, and ensuring the safety and stability of the cofferdam during the entire foundation pit excavation process. Figure 1 , Figure 4 As shown. Each layer of internal support rods includes a first internal support rod 200 and a second internal support rod 1000, as... Figure 2 As shown.

[0043] In this embodiment, the waler 120 and the inner support rod efficiently collect the eccentric load borne by the cofferdam and directionally transfer it to the first anchor pile 300, avoiding excessive deformation of the cofferdam itself. The first anchor pile 300 and the inclined support pile 500 diffuse the concentrated eccentric load to the deep soil, using the bearing capacity of the deep soil layer to dissipate the eccentric load energy and avoid cofferdam failure caused by local stress concentration. This forms a triple force transmission path of the first anchor pile 300, the auxiliary limiting pile 800, and the inclined support pile 500. The eccentric load can be transferred to the deep soil through three paths at the same time, greatly improving the resistance to eccentric load.

[0044] The anchor pile support system for the cofferdam under eccentric load provided in this embodiment breaks through the limitations of traditional passive bearing support. Its resistance to eccentric load is 4-5 times higher than that of a single system. It can withstand composite eccentric loads of more than 150 kPa for the cofferdam. The horizontal displacement of the cofferdam in soft soil foundation is controlled within 20 mm. The cracking rate of the support is reduced to 0, the leakage rate of the pile joint is reduced to 0, the construction period of the modular trestle bridge is shortened by 30%, the materials can be 100% dismantled and reused, and the overall cost is reduced by more than 25%. It completely solves the problems of easy instability, easy leakage, and easy cracking of the support of the cofferdam under eccentric load conditions.

[0045] This embodiment provides a construction method for an anchor pile support system for a dam under eccentric loading, which is used in the above-mentioned dam under eccentric loading cofferdam anchor pile support system, and includes the following steps: S100 anchor pile construction: With the help of the dam working face and the temporary trestle bridge 10, the retaining piles 110 of the cofferdam body 100 are driven into the dam slope and in the water respectively. Then, the first anchor pile 300 and the corresponding inclined support pile 500 are driven into the open side of the cofferdam.

[0046] Specifically, the working face of the dam is Figure 8 The temporary trestle bridge 10 is located on both sides of the cofferdam, as indicated by the location on the side of the dam.

[0047] During construction, the displacement of the pile top is monitored simultaneously, and the angle of the diagonal bracing is adjusted when the displacement exceeds 5mm.

[0048] Finally, insert the auxiliary limit stake 800.

[0049] S200 anchor pile connection: The connecting frame 400 is constructed by welding, and the cofferdam body 100, the first anchor pile 300, the inclined bracing pile 500, and the auxiliary limiting pile 800 are connected into a whole through the connecting frame 400.

[0050] S300 bridge unit 900: The bridge unit 900 is fixed above the connecting frame 400 by bolts to form a complete bridge deck structure.

[0051] Specifically, the prefabricated load-bearing beams 910 and longitudinal beams 920 are hoisted and fixed by high-strength bolts. Finally, the bridge deck steel plate 930 is laid and the limiting baffle is installed to form a complete bridge deck structure.

[0052] Repeat the above steps, using the already completed parts to advance and drive the first anchor pile 300, the inclined bracing pile 500, and the auxiliary limiting pile 800.

[0053] S400 foundation construction: excavate layer by layer downwards and install internal support rods. Each layer of internal support rods includes a first internal support rod 200 and a second internal support rod 1000.

[0054] S410: Dewatering and excavation to the elevation of the first layer of inner support rods. Triangular support plates are welded to the corresponding elevation position on the inner side of the cofferdam body 100. The walers 120 are then assembled on top of the triangular support plates. Before installation, water-swellable rubber strips are pasted at the joints of the walers 120. The walers 120 are arranged in a closed loop around the inner wall of the cofferdam. Immediately after installation, grouting is performed at the joints through pre-embedded grouting pipes to stop the water seepage.

[0055] S420: The first inner support rod 200 and the second inner support rod 1000 are pre-assembled on the ground and hoisted and fixed as a whole to the inside of the waler 120, completing the installation of the first layer of inner support rods.

[0056] S430: Dewater and excavate to the elevation of the second layer of inner support rods. Repeat S410 and S420 to complete the installation of the second layer of inner support rods. Excavate layer by layer until the eccentric load cofferdam anchor pile support system is completed and a complete pier cap construction surface is formed.

[0057] S500 support system dismantling: After the pier cap construction is completed, the system will be dismantled in layers in the following order: bridge unit 900, internal support rod, connecting frame 400, inclined brace pile 500, and first anchor pile 300. After each layer is dismantled, the cofferdam will be left to stand for 24 hours to monitor the rebound displacement. If the displacement exceeds 10mm, the dismantling will be suspended and reinforcement measures will be taken, such as adding support rods.

[0058] Among them, bridge unit 900 is dismantled in the order of bridge deck steel plate 930, longitudinal beam 920, and load-bearing beam 910. The internal support rods are dismantled layer by layer from the top to the bottom.

[0059] The construction method provided in this embodiment ensures the safety and controllability of the support system throughout the entire process from construction to dismantling, achieving efficient material reuse and precise deformation control. The layered unloading protection process can control the rebound displacement of the cofferdam within 10mm, avoiding structural damage caused by traditional one-time unloading.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cofferdam anchor pile support system for eccentrically loaded dams, characterized in that, It includes the cofferdam body (100), the first inner support rod (200), the first anchor pile (300), the connecting frame (400), and the inclined support pile (500). The first inner support rod (200) is horizontally set and extends along the direction from the side adjacent to the dam to the side exposed to the air. Both ends of the first inner support rod (200) are respectively connected to the inner wall of the cofferdam body (100). The first inner support rod (200) includes a first connecting rod (210), a second connecting rod (220), and a first elastic element (230). The first connecting rod (210) and the second connecting rod (220) are capable of moving towards each other along their own length direction. The first elastic element (230) is disposed between the first connecting rod (210) and the second connecting rod (220) and is used to apply a thrust to the first connecting rod (210) and the second connecting rod (220). The first anchor pile (300) is vertically installed on the free side and connected to the cofferdam body (100) through the connecting frame (400); The inclined support pile (500) is inclined on the free side, and its upper end is connected to the side of the first anchor pile (300) away from the cofferdam body (100).

2. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, The first connecting rod (210) and the second connecting rod (220) are respectively provided with a first flange (211) and a second flange (221) at their respective ends close to each other, and the first elastic element (230) is provided between the first flange (211) and the second flange (221); The first flange (211) and the second flange (221) are connected by bolts.

3. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 2, characterized in that, The first elastic element (230) is configured as a butterfly spring, and a plurality of the butterfly springs are arranged along the length direction of the first inner support rod (200).

4. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, The inclined support pile (500) is hinged or ball-jointed to the first anchor pile (300).

5. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, It also includes an anti-pull cone (600), and the first anchor pile (300) and the inclined support pile (500) are both provided with the anti-pull cone (600) at one end of the soil layer. Along the direction of insertion into the soil layer, the outer diameter of the pull-out cone (600) gradually decreases and the maximum outer diameter of the pull-out cone (600) is greater than the outer diameter of the first anchor pile (300) or the inclined support pile (500) connected to it.

6. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, It also includes a countermeasure plate (700), which is connected to the outer wall of the first anchor pile (300) and the inclined support pile (500) and is inclined upward in a direction away from the outer wall.

7. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 6, characterized in that, It also includes an auxiliary limiting post (800), which is vertically arranged and connected to the connecting frame (400); The auxiliary limiting stake (800) is set between two adjacent inclined support stakes (500).

8. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, It also includes a bridge unit (900), which is disposed above the connecting frame (400) and connected to the upper end of the first anchor pile (300).

9. The anchor pile support system for eccentrically loaded cofferdams near dams according to claim 1, characterized in that, It also includes a second inner support rod (1000), which is horizontally arranged and its two ends are respectively connected to the two side walls adjacent to the cofferdam body (100); The second inner support rod (1000) includes a third link, a fourth link, and a second elastic element. The third link and the fourth link are capable of moving towards each other along their own length direction. The second elastic element is disposed between the third link and the fourth link and is used to apply a thrust to the third link and the fourth link.

10. A construction method for a cofferdam anchor pile support system for eccentric load on a dam, used in the cofferdam anchor pile support system for eccentric load on a dam as described in any one of claims 1-9, characterized in that, Includes the following steps: Anchor pile construction: Using the working face of the dam and the temporary trestle (10), the retaining piles (110) of the cofferdam body (100) are driven into the dam slope and the water respectively. Then, the first anchor pile (300) and the corresponding inclined support pile (500) are driven into the open side of the cofferdam. Anchor pile connection: The connecting frame (400) is constructed by welding, and the cofferdam body (100), the first anchor pile (300), and the inclined support pile (500) are connected into a whole through the connecting frame (400); Laying bridge units: The bridge units (900) are fixed above the connecting frame (400) by bolts; Installation of the first inner support rod: excavate downwards layer by layer, and after installing the first inner support rod (200) at each layer, continue to excavate downwards and install the first inner support rod (200) until the cofferdam is excavated to the bottom and a complete pier construction surface is formed; Dismantling of the support system: After the pier cap construction is completed, the support system is dismantled in the following order: bridge unit (900), first inner support rod (200), connecting frame (400), inclined support pile (500), and first anchor pile (300).

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