A cable type settlement restraint structure for a deep overburden layer connecting plate and a construction method thereof

Abstract

A cable-stayed settlement constraint structure for a connecting plate in a deep overburden layer and its construction method are disclosed, belonging to the field of high dam seepage control system design and construction technology. The structure includes a concrete cutoff wall, a connecting plate, a top fixing device for the cutoff wall, cables, upstream counterweights, bolt sets, and an asphalt cushion layer. The steps are as follows: 1) Complete the construction of the main body of the cutoff wall, the lower reinforcement of the connecting plate, and the asphalt cushion layer; 2) Construct the top tower column of the cutoff wall as a single unit and install the tower top fixing device on it; 3) Construct the connecting plate and the upstream counterweight, and pre-embed bolt sets respectively; 4) Erect and tension the upstream and downstream cables connecting the tower top fixing device and each bolt set; 5) Complete the joint sealing construction before water impoundment and verify the pre-tension of the locking cables. This invention uses the cutoff wall as a rigid support and transfers and balances the settlement load of the connecting plate through cables and counterweights, realizing a transition from "passive adaptation" to "active constraint" of excessive settlement of the connecting plate; it can reduce the tensile stress on the downstream side of the cutoff wall during water impoundment, improving the reliability and safety of the high dam seepage control system in a deep overburden layer.

Description

Technical Field

[0001] This invention belongs to the field of high dam seepage prevention system design and construction technology, specifically relating to a novel structure for controlling differential settlement of the connecting plate in a concrete-faced rockfill dam constructed on an ultra-deep overburden layer. The structure directly transfers the load of the connecting plate to the top tower structure of the cutoff wall via cables, achieving active constraint on excessive settlement of the connecting plate and solving the problem of excessive settlement of the connecting plate on a deep overburden layer. It also helps to alleviate the tensile stress problem downstream of the cutoff wall caused by water impoundment. Background Technology

[0002] Against the backdrop of the ongoing new energy revolution, hydropower development in Southwest China has become a hot topic in the industry. However, due to long-term plate tectonics, river erosion, and frequent earthquakes, many watersheds in this region exhibit significant erosion-deposition geology, with riverbeds widely covered by extremely deep overburden layers, typically hundreds or even thousands of meters deep, making traditional excavation-backfilling methods impractical. Given the complex geological conditions and poor transportation in this region, earth-rock dams, especially face-faced rockfill dams, which are adaptable to deformation and utilize locally sourced materials, have become the preferred dam type selection. In the practical construction of high face-faced rockfill dams on deep overburden layers in Southwest China, the settlement difference of the anti-seepage system has become a core challenge restricting project safety. In traditional anti-seepage structures, the concrete anti-seepage wall is embedded in the deep foundation, possessing high rigidity and minimal settlement. However, the connecting plate located downstream of the anti-seepage wall, under the coupled effect of reservoir water pressure and the settlement of the deep overburden layer, is prone to settlement far exceeding the design threshold, resulting in a large displacement difference with the anti-seepage wall. Taking a certain project as an example, numerical simulation revealed that under the traditional scheme, the settlement difference between the connecting plate and the cutoff wall exceeded 30 cm. This deformation is several times the allowable deformation threshold. Such a settlement difference can cause the joint's seepage prevention function to fail, threatening the safety and stability of the dam. At the same time, under the pressure of the upstream reservoir water and the action of the downstream cover layer, tensile stress is prone to occur in local locations of the cutoff wall.

[0003] To address the aforementioned problems, the existing technology, "A Design and Application Method for Inclined Joints to Improve Deformation of Waterstop Joints on the Upper Panel of a Dam with Overburden Layer," addresses these issues. The "Construction Method" proposes an inclined joint design scheme, but compared with the traditional parallel arrangement scheme, this scheme is prone to compression and misalignment of the connecting plates, which can easily affect structural stability, and the force transmission technology needs improvement. Therefore, there is an urgent need to develop a new type of structure that can actively bear the settlement load of the connecting plates and can be adjusted. From the perspective of load transfer, the settlement load of the connecting plates is balanced with the counterweight, and the load is rationally transferred to the low-settlement seepage barrier structure, thus achieving active control of settlement. At the same time, improving the structural design also helps to improve the reliability of the seepage prevention system. Summary of the Invention

[0004] To address the inability to effectively and actively constrain excessive settlement of the connecting plate of a deep overburden dam relative to the cutoff wall, this invention provides a cable-stayed settlement constraint structure and construction method for the connecting plate in deep overburden dams. Drawing inspiration from the design and structural scheme of cable-stayed bridges, the cutoff wall serves as a supporting tower. The vertical load of the connecting plate is transferred to the cutoff wall via cables, and balanced by a concrete counterweight device located upstream. This actively constrains the settlement load of the connecting plate, keeping its settlement within a safe threshold. Simultaneously, the bending moment and vertical compressive stress generated on the cutoff wall during the force transfer process alleviate the tensile stress problem downstream of the cutoff wall. Furthermore, the addition of an asphalt cushion layer beneath the connecting plate helps improve the reliability of the seepage control system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A cable-stayed settlement restraint structure for connecting plates in a deep overburden layer is disclosed. A typical cable-stayed settlement restraint structure includes a concrete cutoff wall 1, a first connecting plate 2, a second connecting plate 3, a third connecting plate 4, a bolt set 11 for the connecting plates, a counterweight 16, a tower top fixing device 17, and an asphalt cushion layer 21. Each connecting plate is provided with at least two cables, and the counterweight is provided with at least two cables.

[0006] The concrete cutoff wall 1 is embedded in bedrock at the bottom and extends upwards beyond the elevation h2 of the connecting plate to form a tower column, serving as the supporting foundation for the entire cable-stayed load transfer system. Referring to relevant bridge specifications, the minimum inclination angle of the outer cable is 22°. In hydraulic engineering applications, the design can be based on the number of connecting plates, the length h4 of the connecting plates, and the bolt positions, comprehensively determining the elevation h2 of the cutoff wall beyond the connecting plate.

[0007] The concrete cutoff wall 1 is provided with a top cable fixing device 17 for anchoring the top of the upstream and downstream cables, distributing the tension to the concrete cutoff wall 1, and avoiding local stress concentration at the top of the tower.

[0008] The first connecting plate 2, the second connecting plate 3, and the third connecting plate 4 are located on the downstream side of the concrete anti-seepage wall 1. The upstream end face of the first connecting plate 2 is in close contact with the downstream face of the concrete anti-seepage wall 1 and an anti-seepage joint is provided, which has little impact on the load-bearing structure. The lower part of the first connecting plate 2, the second connecting plate 3, and the third connecting plate 4 is respectively provided with an asphalt cushion layer 21 and a downstream reinforcement 20 of the anti-seepage wall, which are used to bear part of the vertical load and serve as a safety barrier for the anti-seepage system.

[0009] The connecting plate bolts 11 are high-rigidity cable fixing devices, pre-embedded inside the first connecting plate 2, the second connecting plate 3, and the third connecting plate 4. The connecting plates are connected to the cable fixing device 17 at the top of the cutoff wall via the connecting plate bolts 11 and downstream cables. The connecting plate bolts 11 are used to concentrate the load of the three connecting plates to each cable, and the bolts facilitate maintenance and replacement. That is, the lower ends of multiple downstream cables are anchored to the first connecting plate 2, the second connecting plate 3, and the third connecting plate 4 via the connecting plate bolts 11, and the upper ends extend upward to the cable fixing device 17 at the top of the cutoff wall for load transfer. The downstream cables can convert the vertical loads such as the self-weight and water pressure borne by the connecting plates 2, 3, and 4 into oblique tensile forces, which act directly on the top of the cutoff wall 1. Together with the upstream cables, they apply vertical pressure and bending moment to the entire cutoff wall 1, forming a closed-loop force transmission system of "connecting plate - cable - cutoff wall - cable - counterweight".

[0010] An upstream counterweight 16 is provided on the upstream side of the concrete anti-seepage wall 1. An upstream counterweight bolt set 15 is provided inside the upstream counterweight 16. The counterweight 16 is connected to the top of the anti-seepage wall top cable fixing device 17 through multiple upstream cables to transfer the load.

[0011] Furthermore, the upstream and downstream tensions are not completely balanced. Due to the functional limitations of the seepage prevention system, the connecting plate bears a larger water pressure load, resulting in a greater downstream tension. For example, in a water depth of 100m, the downstream connecting plate bears a water pressure of 1000 kcal / kg. The tension in the downstream cable can be decomposed into a vertically downward pressure component and a horizontal force component pointing downstream. The vertically downward pressure increases the axial compression of the cutoff wall 1, while the bending moment generated by the horizontal force on the cutoff wall 1 is opposite to the tensile stress generated on the downstream side of the cutoff wall under the action of high reservoir water, which can effectively alleviate the tensile stress level on the downstream side of the cutoff wall.

[0012] Furthermore, the downstream cables are arranged at an angle. According to the current Chinese design code for cable-stayed bridges (JTG / T3365-01—2020), the inclination angle of the outermost cable of a cable-stayed bridge should not be less than 22°. Based on the positions of connecting plates 2, 3, and 4, and considering the characteristics of water conservancy projects, the range of cable inclination angles is determined to ensure reasonable cable stress. Based on this, the height h2 of the anti-seepage wall 1 exceeding the top of the connecting plates is further determined, ultimately taking into account both engineering characteristics and cable load-bearing efficiency.

[0013] Furthermore, unlike traditional marine engineering applications where mooring cables are often hundreds or even thousands of meters long, the cable length described in this invention is limited by the number and length of the connecting plates, and is mostly less than 20m. Moreover, the design cable force is much greater than the self-weight, and the sag effect caused by the self-weight can be ignored. All cables are analyzed as straight cables without considering sag.

[0014] Furthermore, the cable described in this invention is modeled after the mooring cables of offshore floating platforms, using high-strength mooring steel strands. The steel strand specifications are initially selected based on tensile stress calculations and relevant standards, and can be verified according to the allowable stress requirements of operational conditions. The steel strand surface is galvanized and coated with an anti-corrosion coating, possessing sufficient tensile strength and adaptability to long-term underwater operating environments; the scope of protection of this invention is not limited to this type of cable material.

[0015] Furthermore, the bolt sets 11 arranged on the connecting plates 2, 3, and 4, and the bolt sets 15 on the counterweight 16, all have sufficient anchorage length, stiffness, and bearing capacity, and their specifications and layout density can be selected based on the cable tension determined by manual calculation.

[0016] Furthermore, in addition to the three connecting plates, the cable-stayed settlement restraint structure can also have more connecting plates added according to the actual situation. The connecting plates are a typical structure for high concrete-faced rockfill dams with thick overburden layers.

[0017] A construction method for a cable-stayed settlement restraint structure for a deep overburden layer connecting plate includes the following steps: S1, complete the construction of the seepage barrier 1 and connecting plates 2, 3, and 4, the lower reinforcement 20 of the toe plate 22, and the asphalt cushion layer 21. Specifically: Step 1.1: Using trenching machinery, excavate trenches in the deep overburden layer down to the bedrock surface, and then pour concrete after using mud slurry to form a seepage barrier wall 1 with its bottom embedded in the bedrock and its top extending above the overburden layer.

[0018] Step 1.2: At the designed locations of connecting plates 2, 3, and 4 downstream of the seepage barrier wall 1, the lower cover layer is reinforced with foundation treatment. Reinforcing bodies 20 are filled and compacted to the designed density to provide the foundation bearing capacity of the connecting plates. An asphalt cushion layer 21 is then added on top.

[0019] S2, the construction layout of the fixing device 17 at the top of the seepage barrier and the tower top, specifically: Step 2.1: Continue pouring on top of the cutoff wall 1, with the two being constructed as a single unit. The top elevation of the cutoff wall 1 is determined based on the top surface elevations of connecting plates 2, 3, and 4, as well as the preset upward tension angle of the cables 10, ensuring that the cable force can generate a reasonable vertical constraint component while also taking into account the stress stability of the tower column.

[0020] Step 2.2: Install the tower top fixing device 17 on the top of the seepage barrier wall 1 as an anchoring node and stress dispersion component at the upper end of the upstream and downstream cables.

[0021] S3, construction connecting plates 2, 3, and 4, with pre-embedded connecting plate bolt set 11, construction upstream counterweight 16, and upstream counterweight bolt set 15. Specifically: Step 3.1: Tie the reinforcing bars of connecting plates 2, 3, and 4 on the upper part of the asphalt subbase, and pre-embed bolt sets 11 at the designed positions on the upper part of each connecting plate, with 2 bolts arranged along the river direction for each connecting plate. Then pour concrete for the connecting plates so that the bolt sets 11 and each connecting plate form an integral load-bearing structure.

[0022] Step 3.2: The upstream end face of connecting plate 2 is in close contact with the downstream end face of the anti-seepage wall 1, and the same applies to the joints between connecting plates. The joints between the connecting plates are fitted with water-stop structures according to the anti-seepage requirements of relevant specifications.

[0023] Step 3.3 involves pouring concrete for the upstream counterweight 16, and installing three rows of bolts at the designed location, i.e., bolt set 15. The construction method is the same as that for the connecting plate.

[0024] S4, install and tension downstream cables 5, 6, 7, 8, 9, and 10; and upstream cables 12, 13, and 14. Taking cable 5 as an example, specifically: Step 4.1: Lead the upper end of the cable 5 upward to the top of the seepage barrier wall 1 and anchor it to the top fixing device 17.

[0025] Step 4.2 involves erecting cable 5 and connecting it downwards to the upstream bolts of connecting plate 2. A certain amount of prestress can be applied to prevent excessive elongation during subsequent water storage and load-bearing processes. The erection of the remaining cables follows the same principle.

[0026] S5. Before water storage operation, complete the installation of the joint sealing structure and perform final verification and locking of the pretension of the cables. During operation, compensation tension can be performed based on the actual settlement monitoring data of connecting plates 2, 3, and 4.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The cable-stayed settlement constraint structure provided by the present invention uses a low-settlement cutoff wall as a rigid support. The settlement load of the connecting plate is directly transferred to the top of the cutoff wall through the inclined cable. A counterweight is set up upstream to balance the load. A balanced force transmission system of "connecting plate - cutoff wall - counterweight" is constructed, realizing a fundamental leap from "passive adaptation" to "active constraint" of the settlement of the connecting plate. It can effectively transfer the vertical load of the connecting plate to the cutoff wall and avoid large settlement.

[0028] (2) While constraining the settlement of the connecting plate, the vertical pressure and bending moment exerted by the cable tension on the top of the seepage barrier are exactly opposite to the tensile stress on the downstream side of the seepage barrier caused by water storage. This structure can significantly reduce the tensile stress amplitude in this area and improve the overall stress deformation characteristics of the seepage barrier. The structure solves two technical problems at the same time: the settlement constraint of the connecting plate and the tensile stress control of the seepage barrier.

[0029] (3) This structure is equipped with upstream counterweight and upstream cable, and uses the rigidity of the seepage barrier wall itself as the closing point of the unbalanced tension. It is easy to construct and has little interference with the existing construction process. The constraint force can be adjusted by adjusting the tension of the cable in the later stage. It is flexible in operation and maintenance and is especially suitable for the reinforcement and new construction of seepage prevention systems under the condition of large settlement in deep overburden.

[0030] (4) By adding an asphalt pad layer under the connecting plate, the present invention effectively ensures the safety and stability of the seepage prevention system. It can not only adapt to uneven deformation of the connecting plate, but also provide a final safety guarantee in the event of damage to the connecting plate or failure of the water stop.

[0031] (5) The cable structure of the present invention can be modified based on the existing seepage prevention structure, and can be used for both new construction projects and reinforcement and renovation of existing dams. There is no need to make significant adjustments to the original structural design. At the same time, the cable is easy to maintain in the later stage. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall layout of the cable-stayed settlement constraint structure in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the cable-stayed settlement constraint structure in an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram showing the dimensions of the cable-stayed settlement constraint structure in an embodiment of the present invention.

[0035] In the diagram: 1. Concrete cutoff wall; 2. First connecting plate; 3. Second connecting plate; 4. Third connecting plate; 5. Downstream first cable; 6. Downstream second cable; 7. Downstream third cable; 8. Downstream fourth cable; 9. Downstream fifth cable; 10. Downstream sixth cable; 11. Connecting plate bolt set; 12. Upstream first cable; 13. Upstream second cable; 14. Upstream third cable; 15. Upstream counterweight bolt set; 16. Upstream counterweight; 17. Cutoff wall top cable fixing device; 18. Upstream reinforcement of cutoff wall; 19. Cutoff wall transition material; 20. Downstream reinforcement of cutoff wall; 21. Asphalt cushion layer; 22. Toe plate; 23. Face plate; 24. Face plate cushion layer; 25. Dam transition layer. h1 Thickness of the cutoff wall; h2 Height difference between the top of the cutoff wall and the top of the connecting plate; h3 Thickness of the connecting plate; h4 Length of the connecting plate along the river; h5 Thickness of the counterweight; h6 Length of the counterweight along the river; α1 Inclination angle of the first cable; α2 Inclination angle of the second cable; α3 Inclination angle of the third cable; α4 Inclination angle of the fourth cable; α5 Inclination angle of the fifth cable; α6 Inclination angle of the sixth cable. Detailed Implementation

[0036] To make the technical solutions, objectives, and advantages of the embodiments of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific engineering examples, but the scope of protection of the present invention is not limited thereto.

[0037] This invention provides a cable-stayed settlement restraint structure for a deep overburden layer connecting plate and its construction method, such as... Figure 1 and Figure 2 As shown, the settlement constraint structure includes a concrete cutoff wall 1, connecting plate 2, connecting plate 3, connecting plate 4, cable 5, cable 6, cable 7, cable 8, cable 9, cable 10, downstream bolt set 11, upstream cable 12, upstream cable 13, upstream cable 14, upstream bolt set 15, upstream counterweight 16, and cutoff wall top fixing device 17. The remaining auxiliary structures include an upstream reinforcement of the cutoff wall 18, a cutoff wall transition material 19, a downstream reinforcement of the cutoff wall 20, an asphalt cushion layer 21, a toe plate 22, a face plate 23, a face plate cushion layer 24, and a dam transition layer 25.

[0038] like Figure 3 As shown, the dimensions and angle markings include the thickness h1 of the seepage barrier wall 1, the height difference h2 between the top of the seepage barrier wall 1 and the connecting plate 2, the thickness h3 of the connecting plate, the length h4 of the connecting plate along the river, the thickness h5 of the counterweight, the length h6 of the counterweight along the river, the angle α1 between the cable 5 and the horizontal plane, the angle α2 between the cable 6 and the horizontal plane, the angle α3 between the cable 7 and the horizontal plane, the angle α4 between the cable 8 and the horizontal plane, the angle α5 between the cable 9 and the horizontal plane, and the angle α6 between the cable 10 and the horizontal plane.

[0039] In this embodiment, a specific engineering project is used as an example. The overburden layer thickness exceeds 400m, and the concrete dam is designed as a 100-meter-class high dam. The concrete cutoff wall 1 has the same depth as the overburden layer thickness, penetrates the overburden layer, and is embedded in the bedrock. The thickness h1 of the cutoff wall 1 is 1.5m, and the top of the cutoff wall 1 exceeds the top elevation h2 of the connecting plate by 3.0m. Connecting plates 2, 3, and 4 are located downstream of the cutoff wall 1, with a river-direction length h4 of 4.0m and a thickness h3 of 1.2m. The concrete strength grade used is C40. The lower part of the connecting plate 2 consists of a reinforcement 20 and an overburden layer from top to bottom. The reinforcement 20 is compacted to the designed density.

[0040] like Figure 1 , Figure 2 and Figure 3 As shown, in this embodiment, the height h2 of the top of the seepage barrier wall 1 exceeding the top of the connecting plate 2 is 3.0m, which serves as the force transmission tower column for anchoring the upper end of the cable.

[0041] like Figure 1 , Figure 2 and Figure 3As shown, in this embodiment, connecting plates 2, 3, and 4 are each equipped with two bolts, spaced 2.0m apart. A single row is considered along the dam axis (unit thickness is 1m for two-dimensional analysis). The bolts are anchored to the connecting plates, with the anchoring depth and specifications designed to withstand stresses not less than those of the corresponding cables.

[0042] like Figure 1 , Figure 2 and Figure 3 As shown, in this embodiment, the lower end of the first cable 5 is connected to the connecting plate bolt 1.0m upstream of the connecting plate 2, and the upper end extends upward to the top of the seepage barrier wall 1, is anchored to the top fixing device 17 of the seepage barrier wall, and is connected to the counterweight 16 through the upstream cable and the upstream counterweight bolt set 15. The other cables are connected in the same way.

[0043] Referring to the current Chinese design code for cable-stayed bridges (JTG / T 3365-01—2020): the inclination angle of the outermost stay cable of a cable-stayed bridge should not be less than 22°. However, since the cable system in hydraulic engineering serves only as a settlement mitigation device, this requirement can be appropriately relaxed. Special attention should be paid to the first connecting plate 2 downstream of the cutoff wall; the constraint requirements for the second connecting plate 3 and the third connecting plate 4 are relatively low. Therefore, the design height of the supporting tower on the cutoff wall is 3m. The cables provide the vertical constraint component; because the cable length is relatively short and the cable force is much greater than its own weight, the sag effect is not considered.

[0044] The minimum tilt angle of cable 10 on the third connecting plate is designed to be 15.3°, and the minimum tilt angle of cable 8 on the second connecting plate is 23.2°.

[0045] like Figure 3 As shown, in this embodiment, the height difference h2 from the top of the seepage barrier wall 1 to the top surface of the connecting plate 2 is 3.0m. The inclination angle of the first cable 5 is α1≈71.6°, the inclination angle of the second cable 6 is α2=45.0°, the inclination angle of the third cable 7 is α3≈31.0°, the inclination angle of the fourth cable 8 is α4≈23.2°, the inclination angle of the fifth cable 9 is α5≈18.4°, and the inclination angle of the sixth cable 10 is α6≈15.3°.

[0046] Regarding the cable specifications, calculations were performed manually based on the water pressure at a water depth of 100m acting on the third connecting plate and the self-weight load of the connecting plate. The vertical stress borne by the connecting plate per unit length in the dam axis is approximately 1.02 MPa, and the vertical load per unit length in the dam axis of a single connecting plate is 4080 kN. The design vertical tensile force component borne by a single cable is approximately 2040 kN. Based on the requirements of standards such as high-strength steel strand for structural engineering (GB / T 33026-2017), 61 high-strength galvanized mooring steel strand cables were selected and bundled together to bear the load. The steel strand specifications are Φ21.6mm and strength 1860 MPa. Calculations show that the total stress borne by each cable during the full storage period is approximately 445 MPa, which is lower than the long-term allowable stress of 744 MPa specified in the standard, meeting the design requirements. An anti-corrosion coating is applied to the surface, providing sufficient durability.

[0047] like Figure 1 and Figure 2 As shown, in this embodiment, the upstream end face of the connecting plate 2 is in close contact with the downstream end face of the concrete anti-seepage wall 1, and a joint water-stop structure is set between the two. The joint water-stop structure adopts a three-layer water-stop system consisting of a bottom copper water-stop, a middle rubber water-stop strip, and a top flexible caulking material. The water-stop material is selected as a high-quality product that meets the requirements of current specifications, ensuring that it still has sufficient water-stopping performance redundancy after differential settlement is constrained.

[0048] The above structure forms a direct force transmission closed loop of "connecting plate - cable - cutoff wall - cable - counterweight": the self-weight and water pressure load borne by connecting plates 2, 3, and 4 are transmitted to the downstream cables through the connecting plate bolt assembly 11. The cable tension is then applied to the upstream cables and counterweight via the tower top fixing device 17. The mechanical effect of the unbalanced cable force on the top of the cutoff wall 1 can be decomposed into a vertical pressure component and a horizontal force component pointing downstream. The vertical pressure increases the axial pressure reserve of the cutoff wall 1, while the additional bending moment generated by the horizontal force on the cutoff wall 1 is opposite to the direction of the downstream tensile stress caused by water storage, thereby effectively reducing the amplitude of the downstream tensile stress.

[0049] The construction process in this embodiment includes the following steps: The first step involves completing the construction of the concrete anti-seepage wall 1, the reinforcement treatment of the lower cover layer of the connecting plate, and the laying of the asphalt cushion layer. Specifically: Step 1.1: Using trenching machinery, excavate trenches down to the bedrock surface in the deep overburden layer. The trench width is 1.5m. After using mud slurry to protect the wall, pour concrete to form a concrete anti-seepage wall 1 with the bottom embedded in the bedrock and the top extending above the overburden layer.

[0050] Step 1.2: At the design location of the connecting plate on the downstream side of the seepage barrier wall 1, the lower cover layer is reinforced with foundation treatment, and the reinforcement body 20 is filled and compacted to the design density to provide the foundation bearing capacity of the connecting plate.

[0051] Step 1.3: Add an asphalt cushion layer on top of the reinforcement, and compact it to meet the design requirements and design bearing capacity.

[0052] The second step is to continue construction on the top of the seepage barrier wall 1, specifically: Step 2.1: Erect formwork on the top of the seepage barrier wall 1, and pour the top part of the seepage barrier wall to form an integral part of the seepage barrier wall 1. The top exceeds the design height h2=3.0m of the connecting plate.

[0053] Step 2.2: Pre-embed cable fixing devices at the top of the seepage barrier wall 1, with sufficient anchoring depth and strength, for connection of upstream and downstream cables and stress distribution.

[0054] The third step involves constructing connecting plates 2, 3, and 4, and pre-embedding connecting plate bolt set 11. Specifically: Step 3.1: Tie the connecting plate reinforcement on the asphalt subbase 21, and pre-set bolts at corresponding positions at the upstream end of the connecting plate. The anchorage depth of the bolts is determined according to the design tension of the cable. Then, pour C40 concrete to make the bolt set 11 and the connecting plate form an integral load-bearing structure.

[0055] Step 3.2: The upstream end face of the connecting plate 2 is in close contact with the downstream end face of the anti-seepage wall 1. The same applies between the connecting plates. Their joints are set with a three-layer water-stop structure consisting of copper waterstop, rubber waterstop and flexible caulking material as required by the design.

[0056] The fourth step is to install and appropriately tension the upstream and downstream cables. Taking the first cable, 5, as an example, the specific steps are as follows: Step 4.1: Connect the upper and lower ends of the first cable 5 to the top fixing device 17 of the anti-seepage wall and the bolt set 11 of the connecting plate, respectively. The remaining cables are connected in the same way.

[0057] Step 4.2: Perform graded synchronous tensioning on the cables. The tensioning control force can be determined based on the settlement load that the connecting plate needs to offset after water storage. Lock the cables after the design pretension is reached.

[0058] The fifth step is to complete the final inspection of the joint sealing structure before water storage operation, and to check and lock the preload of the cables. During operation, compensation tension can be performed based on the settlement monitoring data of the connecting plates to maintain the restraint effect.

[0059] In summary, this invention uses the cutoff wall as a rigid support and transfers and balances the settlement load of the connecting plate through cables and counterweights, realizing a transition from "passive adaptation" to "active constraint" of excessive settlement of the connecting plate; by using unbalanced cable forces to apply vertical pressure and additional bending moment to the cutoff wall, the tensile stress on the downstream side of the cutoff wall during the water storage period is significantly reduced, and combined with the asphalt cushion layer to adapt to deformation, the reliability and safety of the high dam seepage prevention system on the deep overburden layer are comprehensively improved.

[0060] The above-described embodiments are merely implementation methods of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate, characterized in that, The typical cable-stayed settlement restraint structure includes a concrete cutoff wall (1), a first connecting plate (2), a second connecting plate (3), a third connecting plate (4), a connecting plate bolt set (11), a counterweight (16), a tower top fixing device (17), and an asphalt cushion layer (21); wherein, each connecting plate is provided with no less than 2 cables and the counterweight is provided with no less than 2 cables; The concrete anti-seepage wall (1) is embedded in the bedrock at the bottom and extends upward beyond the elevation of the connecting plate to form a tower column, which serves as the supporting foundation for the entire cable-stayed power transmission system. The concrete cutoff wall (1) is provided with a top cable fixing device (17) for anchoring the top of the upstream and downstream cables and distributing the tension to the concrete cutoff wall (1). The first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) are located on the downstream side of the concrete anti-seepage wall (1). The upstream end face of the first connecting plate (2) is in close contact with the downstream face of the concrete anti-seepage wall (1) and an anti-seepage joint is provided. The lower part of the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) are respectively provided with an asphalt cushion layer (21) and a downstream reinforcement 20 of the anti-seepage wall, which are used to bear part of the vertical load and serve as a safety barrier for the anti-seepage system. The connecting plate bolt (11) is a high-rigidity cable fixing device, which is embedded in the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4). The connecting plate is connected to the cable fixing device (17) at the top of the seepage barrier wall through the downstream cable based on the connecting plate bolt (11); finally forming a closed loop of force transmission of "connecting plate - cable - seepage barrier wall - cable - counterweight". An upstream counterweight (16) is provided on the upstream side of the concrete anti-seepage wall (1). An upstream counterweight bolt set (15) is provided inside the upstream counterweight (16). The counterweight (16) is connected to the top of the anti-seepage wall top cable fixing device (17) through multiple upstream cables to transfer the load.

2. The cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, Referring to bridge specifications, the downstream cables are arranged at an angle, with a minimum inclination angle of 22° for the outer cables. In water conservancy engineering applications, the design is based on the number of connecting plates, the length of the connecting plates, and the position of the bolts, and the elevation of the anti-seepage wall above the connecting plates is determined comprehensively.

3. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, The connecting plate bolts (11) concentrate the load of the three connecting plates to each cable; The lower ends of multiple downstream cables are anchored to the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) through the connecting plate bolt set (11), and the upper ends extend upward to the cable fixing device (17) at the top of the seepage barrier wall to transfer the load. The downstream cables convert the vertical load borne by the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) into oblique tension, which acts directly on the top of the concrete seepage barrier wall (1). Together with the upstream cables, they apply vertical pressure and bending moment to the concrete seepage barrier wall (1) as a whole, and finally form a closed loop of force transmission of "connecting plate - cable - seepage barrier wall - cable - counterweight".

4. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, The cable length is less than 20m, and the designed cable force is much greater than its own weight.

5. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, The cable layout is based on the mooring cables of offshore floating platforms, using high-strength mooring steel strands. The specifications of the steel strands are selected based on the tensile stress calculation results, and the results are checked according to the allowable stress requirements under operating conditions.

6. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, The cable surface is galvanized and coated with an anti-corrosion coating.

7. A cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 1, characterized in that, In addition to the three connecting plates, the cable-stayed settlement restraint structure can also have more connecting plates added according to the actual situation. The connecting plates are a typical structure for high concrete-faced rockfill dams with thick overburden.

8. A construction method for a cable-stayed settlement restraint structure for a deep overburden layer connecting plate as described in any one of claims 1-7, characterized in that, Includes the following steps: S1, complete the construction of the concrete anti-seepage wall (1), the first connecting plate (2), the second connecting plate (3), the third connecting plate (4), the lower reinforcement (20) of the toe plate (22), and the asphalt cushion layer (21). Specifically: Step 1.1: Using trenching machinery, excavate trenches to the bedrock surface in the deep overburden layer, and then pour concrete after using mud slurry to form a concrete anti-seepage wall with the bottom embedded in the bedrock and the top extending above the overburden layer (1). Step 1.2: At the designed locations of the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) on the downstream side of the concrete anti-seepage wall (1), the foundation reinforcement treatment of the lower cover layer is carried out, the reinforcement body (20) is filled and compacted to the designed density; an asphalt cushion layer (21) is added on top of it. S2, Construction layout of the fixing device (17) at the top of the seepage barrier and the top of the tower, specifically: Step 2.1, continue pouring on top of the concrete anti-seepage wall (1), the two are constructed as one piece; the top elevation of the concrete anti-seepage wall (1) is determined according to the top surface elevation of the first connecting plate (2), the second connecting plate (3), the third connecting plate (4) and the preset angle of the upward tension of the cable (10); Step 2.2, install the tower top fixing device (17) on the top of the concrete seepage barrier (1) as the anchoring node and stress dispersion component at the upper end of the upstream and downstream cables; S3, construct the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) and pre-embed the connecting plate bolt set (11), construct the upstream counterweight (16) and the upstream counterweight bolt set (15); specifically: Step 3.1: Tie the reinforcing bars of the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4) on the upper part of the asphalt cushion layer, and pre-embed the connecting plate bolt set (11) at the designed position on the upper part of each connecting plate. Arrange 2 bolts along the river direction for each connecting plate; then pour the connecting plate concrete so that the connecting plate bolt set (11) and each connecting plate form an integral load-bearing structure. Step 3.2, the upstream end face of the first connecting plate (2) is in close contact with the downstream face of the concrete anti-seepage wall (1), and the joints between the connecting plates are in the same manner; the joints between them are equipped with water-stop structures in accordance with the anti-seepage requirements of relevant specifications; Step 3.3: Cast the upstream counterweight (16) and lay three rows of bolts at the designed position, i.e., bolt set (15); the construction method is the same as that of the connecting plate. S4, Install and tension the cables, specifically: Step 4.1: Lead the upper end of the cable upward to the top of the concrete anti-seepage wall (1) and anchor it to the top fixing device (17); Step 4.2: Install the cable and connect it downwards to the upstream bolt of the first connecting plate (2); S5. Before water storage operation, the joint sealing structure is installed, and the pretension of the cable is checked and locked.

9. A construction method for a cable-stayed settlement restraint structure for a deep overburden layer connecting plate according to claim 8, characterized in that, During operation, compensation tension is performed based on the actual settlement monitoring data of the first connecting plate (2), the second connecting plate (3), and the third connecting plate (4).

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