Design method for adjusting water stop position to reduce concrete tensile stress

Abstract

The invention discloses a design method for reducing concrete tensile stress by adjusting a water stop position, and particularly relates to a design method for effectively reducing the tensile stress in a flow channel of a concrete gravity dam by reasonably adjusting water stop arrangement. Comprising the following steps that a concrete gravity dam discharge dam section and foundation model is established, finite element software is imported, and numerical simulation parameters are set; grid division is carried out on the model, and grids in the runner are encrypted; constraint and load are applied to the target analysis dam section, the water stop position of the side face of the target analysis dam section is adjusted, hydrostatic pressure is applied, and a reasonable water stop arrangement type is achieved through repeated adjustment; and solving the model by using finite element software, and evaluating a stress result in the flow channel of the discharge dam section. The hydrostatic pressure is applied to the side surface of the dam section to simulate the influence on the stress of the dam section after the water stop position is adjusted. The design method shows that the tensile stress in the concrete gravity dam flow channel can be reduced by adjusting the water stop position, and therefore the use amount of steel bars is reduced.

Description

Technical Field

[0001] This invention relates to the field of concrete gravity dam technology, and is particularly applicable to design methods for adjusting the waterstop position to reduce tensile stress in concrete. Background Technology

[0002] A concrete gravity dam is a type of dam that is divided into several sections by transverse joints. Each section relies on its own weight to resist water pressure and other external forces in order to maintain the stability of the dam.

[0003] Transverse joints allow each dam section to better adapt to uneven foundation settlement, temperature changes, and construction pouring capacity. However, as artificially created seepage channels, transverse joints generally lack grooves and are not grouted. Therefore, waterstops are needed at these joints to prevent seepage. Typically, one or two waterstops are installed 1m from the upstream and downstream surfaces of the dam, with the top of the waterstops above the highest water level and the bottom extending 0.5m into the dam foundation rock. However, the presence of transverse joints and waterstops on the dam body creates an imbalance of internal and external pressure in the flow channels, leading to significant tensile stress in the concrete within these channels. Concrete is a material resistant to compression but not to tension, making it prone to cracking under tensile stress. To resist the tensile stress caused by this pressure imbalance, multiple layers of large-diameter steel reinforcement are often required within the flow channels, causing considerable inconvenience during construction. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for adjusting the water-stop position to reduce the tensile stress of concrete, which is used to reduce the tensile stress of concrete in the channel dam section under the condition of unbalanced internal and external pressure by adjusting the water-stop position.

[0005] To achieve the above objectives, the design method for adjusting the water-stopping position to reduce concrete tensile stress according to the present invention includes the following steps: S1. Establish a concrete spillway dam section and foundation model. The model is divided into the side surface of the dam section according to the flow channel characteristics and a water stop position adjustment area is set. S2, import the spillway section and foundation model into the finite element software and set the numerical simulation parameters; S3, divide the spillway section and foundation model into meshes, and refine the mesh inside the flow channel; S4, apply boundary conditions to the spillway section and foundation model; the boundary conditions include constraints and loads, as well as apply hydrostatic pressure to the water-stopping position on the side of the spillway section; S5. Use finite element software to analyze and solve the static structure of the spillway section and foundation model; S6. Examine and evaluate the stress results of the inlet section, gate slot section, and breast wall section of the spillway section; repeatedly adjust the water-stop position to obtain the most reasonable water-stop arrangement.

[0006] Furthermore, the flow channel features include either a long pressurized section or a short pressurized section.

[0007] Furthermore, the water-stopping position adjustment area covers areas of excessive concrete tensile stress within the flow channel, including the inlet section, maintenance door slot section, breast wall section, and emergency door slot section, and satisfies the requirement of having the fewest bending sections.

[0008] Furthermore, for long pressurized channels, at 10m above the highest point of the channel top surface or at the bend point, the side surface of the dam section is divided, and the horizontal upper boundary of the water-stopping adjustment area is set; at 10m below the lowest point of the channel bottom surface, the side surface of the dam section is divided, and the horizontal lower boundary of the water-stopping adjustment area is set; at 10m downstream of the emergency gate slot in the channel, the vertical right boundary of the water-stopping adjustment area is set; the upstream surface of the dam is offset downstream by 1m as the vertical left boundary of the water-stopping adjustment area.

[0009] Furthermore, for short pressurized channels, at 10m above the highest point of the channel top surface or at the bend point, the side surface of the dam section is divided, and the horizontal upper boundary of the water-stopping adjustment area is set; at 10m below the lowest point of the channel bottom surface, the side surface of the dam section is divided, and the horizontal lower boundary of the water-stopping adjustment area is set; at the end of the pressurized section in the channel, the vertical right boundary of the water-stopping adjustment area is set; the upstream surface of the dam is offset downstream by 1m as the vertical left boundary of the water-stopping adjustment area.

[0010] Furthermore, the constraints mentioned in step S4 include full constraints on the foundation surface and normal displacement constraints on the foundation side; the loads include self-weight, hydrostatic pressure, uplift pressure, silt pressure, and seismic load; the distribution and magnitude of the hydrostatic pressure applied in the area after the water stop position is adjusted are the same as the hydrostatic pressure acting on the upstream face of the dam.

[0011] The advantages of this invention lie in its ability to segment the side surfaces of the dam section based on the flow channel characteristics, import the data into finite element analysis software for material assignment and mesh generation, and set boundary conditions. In particular, by applying hydrostatic pressure to the side surfaces of the dam section, the stress impact of adjusting the waterstop position on the dam section is simulated. By solving the model and reviewing and evaluating the calculation results, the most reasonable waterstop arrangement is obtained. The calculation results of this invention show that adjusting the waterstop position can balance the internal and external water pressure of the flow channel, improve the stress state of the concrete, reduce the tensile stress in the concrete within the flow channel, thereby reducing the amount of steel reinforcement used in the flow channel. This approach is safe, economical, and convenient for construction, and provides a scientific method and basis for the rational design of waterstop arrangements. Attached Figure Description

[0012] The technical solutions in 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 a part of the embodiments of the present invention and are used to explain the present invention.

[0013] Figure 1This is a flowchart of the method described in this invention.

[0014] Figure 2 This is a schematic diagram of the water-stopping adjustment area in the long pressurized flow channel dam section of the method described in this invention.

[0015] Figure 3 This is a schematic diagram of the water-stopping adjustment area in the short pressurized channel dam section of the method described in this invention.

[0016] Figure 4 The stress profiles of the inlet section of the long pressurized flow channel before (a) and after (b) water stop position adjustment are compared using the method described in this invention.

[0017] Figure 5 The stress comparison diagrams of the long pressurized flow channel gate groove before (a) and after (b) water stop position adjustment are obtained by comparing the cross-sectional stress of the gate groove using the method described in this invention.

[0018] Figure 6 The stress comparison diagrams of the breast wall cross section of the long pressurized flow channel before (a) and after (b) water stop position adjustment are obtained by comparing the water stop position adjustment using the method described in this invention.

[0019] Figure 7 The stress comparison diagrams of the inlet profile of the short pressurized flow channel before (a) and after (b) water stop position adjustment are obtained by comparing the water stop position adjustment using the method described in this invention.

[0020] Figure 8 The stress comparison diagrams of the short pressurized flow channel gate groove cross sections before (a) and after (b) water stop position adjustment are obtained by comparing the water stop position adjustment using the method described in this invention.

[0021] Figure 9 The stress comparison diagrams of the short pressurized flow channel breast wall sections before (a) and after (b) water stop position adjustment are obtained by comparing the stress of the breast wall sections before (a) and after (b) water stop position adjustment using the method described in this invention. Detailed Implementation

[0022] The design method for reducing concrete tensile stress by adjusting the water-stopping position as described in this invention, such as... Figure 1 As shown, it includes the following steps: S1. Establish a concrete spillway dam section and foundation model. The model is divided into the side surface of the dam section according to the flow channel characteristics and a water-stop position adjustment area is set.

[0023] The flow channel characteristics of concrete gravity dams are generally divided into two types: long pressurized and short pressurized. The water-stopping adjustment area varies depending on the flow channel characteristics of the dam section, but the general adjustment principle is: the water-stopping adjustment area should cover the area of ​​excessive tensile stress in the concrete within the flow channel, usually the inlet section, maintenance gate slot section, breast wall section, emergency gate slot section, and the arc section after the emergency gate slot; the water-stopping adjustment area should minimize bends to facilitate construction.

[0024] Specifically, for concrete gravity dams with long pressurized flow channels, the adjustment area for the water-stop position is set as follows: 10m above the highest point of the flow channel top surface or at the bend point, the side surface of the dam section is divided as the upper horizontal boundary of the water-stop adjustment area; 10m below the lowest point of the flow channel bottom surface, the side surface of the dam section is divided as the lower horizontal boundary of the water-stop adjustment area; 10m downstream of the emergency gate slots within the flow channel (usually the first is a maintenance gate, and the second is an emergency gate) is designated as the right vertical boundary of the water-stop adjustment area; the water-stopping at other locations is not adjusted, and the left vertical boundary of the water-stop area is set 1m downstream from the upstream surface of the dam. For example... Figure 2 The diagram shown is a schematic of the water-stop adjustment area of ​​a long pressurized flow channel.

[0025] For short, pressurized concrete gravity dams, the adjustment area for the water-stop position is set as follows: 10m above the highest point of the channel top surface or at the bend point, the side surface of the dam section is divided as the upper horizontal boundary of the water-stop adjustment area; 10m below the lowest point of the channel bottom surface, the side surface of the dam section is divided as the lower horizontal boundary of the water-stop adjustment area; the end of the pressurized section within the channel is used as the right vertical boundary of the water-stop adjustment area; the water-stop for other parts is not adjusted, and the vertical left boundary of the water-stop area is offset 1m downstream from the upstream surface of the dam. Figure 3 The diagram shows the water-stop adjustment area of ​​a short pressurized flow channel.

[0026] S2. Import the concrete spillway section and foundation model established in step S1 into the finite element software and set the numerical simulation parameters.

[0027] S3 involves meshing the concrete spillway section and foundation model, and refining the mesh inside the flow channel.

[0028] S4 applies boundary conditions to the concrete spillway section and foundation model. Boundary conditions include applying constraints and loads to the target dam section, and applying hydrostatic pressure at the waterstop locations on the sides of the target dam section.

[0029] Constraints are applied to the target dam section, including full constraints on the foundation surface and normal displacement constraints on the foundation sides, while no constraints are applied to the dam body.

[0030] The loads applied to the target dam section include its own weight, hydrostatic pressure, uplift pressure, silt pressure, and seismic loads.

[0031] Hydrostatic pressure is applied to the water-stopping position on the side of the target dam section. The distribution and magnitude of this hydrostatic pressure are the same as the hydrostatic pressure acting on the upper surface of the dam. By continuously and repeatedly adjusting the water-stopping position, the impact of the adjustment on the deformation and stress of the dam section can be simulated. Through trial calculations and repeated adjustments, a reasonable water-stopping arrangement can be achieved.

[0032] S5. The static structure of the spillway section and foundation model is analyzed and solved using finite element software.

[0033] S6. Review and evaluate the stress results of the inlet section, gate slot section, and breast wall section of the spillway. Repeatedly adjust the target analysis of the hydrostatic pressure at the side stop locations of the dam section to obtain a reasonable stop arrangement.

[0034] To verify the reliability of the design method for reducing concrete tensile stress by adjusting the water-stopping position as described in this invention, numerical simulations were performed on both long and short pressurized dam sections, and the following results were obtained: like Figure 4 As shown, taking a long pressurized dam section as an example, under conventional constraints and loads, and with a certain head, the stress along the dam axis at the inlet profile within the flow channel is as follows: The maximum tensile stress is 9.82 MPa, greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 10m high. After adjusting the waterstop position, the stress in the same direction on the same cross-section is entirely compressive stress.

[0035] like Figure 5 As shown, taking a long pressurized dam section as an example, under conventional constraints and loads, and with a certain water head, the stress along the dam axis of the portal groove section within the flow channel is as follows: The maximum tensile stress is 5.97 MPa, greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 8m high. After adjusting the waterstop position, the stress in the same direction on the same cross-section is entirely compressive stress.

[0036] like Figure 6 As shown, taking a long pressurized dam section as an example, under conventional constraints and loads, and with a certain water head, the stress along the dam axis of the breast wall section inside the flow channel is as follows: The maximum tensile stress is 7.24 MPa, which is greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 12m high. After adjusting the waterstop position, the stress in the same direction on the same cross-section is entirely compressive stress.

[0037] like Figure 7 As shown, taking a short pressurized dam section as an example, under conventional constraints and loads, and with a certain head, the stress along the dam axis at the inlet profile within the flow channel is as follows: The maximum tensile stress is 5.71 MPa, greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 10m high. After the water position is adjusted, the stress in the same direction on the same cross-section is entirely compressive stress.

[0038] like Figure 8As shown, taking a short pressurized dam section as an example, under conventional constraints and loads, and with a certain head, the stress along the dam axis in the portal section of the flow channel is as follows: The maximum tensile stress is 2.86 MPa, which is greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 8m high. After the water position is adjusted, the stress in the same direction on the same cross-section is entirely compressive stress.

[0039] like Figure 9 As shown, taking a short pressurized dam section as an example, under conventional constraints and loads, and with a certain head, the stress along the dam axis of the breast wall section inside the flow channel is as follows: The maximum tensile stress is 3.38 MPa, which is greater than 0.45 MPa. ( The tensile stress zone (design value of concrete tensile strength) is approximately 12m high. After the water position is adjusted, the stress in the same direction on the same cross-section is entirely compressive stress.

[0040] Finite element analysis has verified that by applying hydrostatic pressure to the side surface of the dam section to simulate the stress effect of adjusting the water stop position, the internal and external water pressure of the flow channel can be balanced, the stress state of the concrete can be improved, the tensile stress of the concrete in the flow channel can be reduced, thereby reducing the amount of steel reinforcement used in the flow channel, facilitating construction, and ensuring safety and economy.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for adjusting the waterstop position to reduce tensile stress in concrete, characterized in that, Includes the following steps: S1. Establish a concrete spillway dam section and foundation model. The model is divided into the side surface of the dam section according to the flow channel characteristics and a water stop position adjustment area is set. S2, import the spillway section and foundation model into the finite element software and set the numerical simulation parameters; S3, divide the spillway section and foundation model into meshes, and refine the mesh inside the flow channel; S4, apply boundary conditions to the spillway section and foundation model; the boundary conditions include constraints and loads, as well as apply hydrostatic pressure to the area after the side water stop adjustment of the spillway section; S5. Use finite element software to analyze and solve the static structure of the spillway section and foundation model; S6. Examine and evaluate the stress results of the inlet section, gate slot section, and breast wall section of the spillway section; repeatedly adjust the water-stop position to obtain the most reasonable water-stop arrangement.

2. The design method for adjusting the waterstop position to reduce concrete tensile stress according to claim 1, characterized in that: The flow channel features include either long pressurized or short pressurized channels.

3. The design method for adjusting the waterstop position to reduce concrete tensile stress according to claim 1, characterized in that: The water-stop position adjustment area covers the area of ​​excessive concrete tensile stress in the flow channel, including the inlet section, maintenance door slot section, breast wall section, and emergency door slot section, and meets the requirement of having the fewest bending sections.

4. The design method for adjusting the waterstop position to reduce concrete tensile stress according to claim 2, characterized in that: For long pressurized channels, at 10m above the highest point of the channel top surface or at the bend point, the horizontal upper boundary of the water-stopping adjustment area is set on the side surface of the dam section; at 10m below the lowest point of the channel bottom surface, the horizontal lower boundary of the water-stopping adjustment area is set on the side surface of the dam section; at 10m downstream of the emergency gate slot in the channel, the vertical right boundary of the water-stopping adjustment area is set; the vertical left boundary of the water-stopping adjustment area is offset 1m downstream from the upstream surface of the dam.

5. The design method for adjusting the waterstop position to reduce concrete tensile stress according to claim 2, characterized in that: For short pressurized channels, at 10m above the highest point of the channel top surface or at the bend point, the side surface of the dam section is divided, and the horizontal upper boundary of the water-stopping adjustment area is set; at 10m below the lowest point of the channel bottom surface, the side surface of the dam section is divided, and the horizontal lower boundary of the water-stopping adjustment area is set; at the end of the pressurized section in the channel, the vertical right boundary of the water-stopping adjustment area is set; the upstream surface of the dam is offset downstream by 1m as the vertical left boundary of the water-stopping adjustment area.

6. The design method for adjusting the waterstop position to reduce concrete tensile stress according to claim 1, characterized in that: The constraints mentioned in step S4 include full constraints on the foundation surface and normal displacement constraints on the foundation side; the loads include self-weight, hydrostatic pressure, uplift pressure, silt pressure, and seismic load; the distribution and magnitude of the hydrostatic pressure applied in the area after the water stop position is adjusted are the same as the hydrostatic pressure acting on the upstream face of the dam.

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