Design method of concrete gravity dam on semi-covering layer and semi-bedrock complex foundation

Abstract

The application discloses a design method of a concrete gravity dam on a semi-covering layer and semi-bedrock complex foundation, which comprises the following steps: determining control conditions and standards suitable for the foundation conditions according to different covering layer and bedrock foundation conditions, and adopting different structural types and partitioned integral joint design ideas suitable for different foundation conditions; expanding the platform integral type at the bottom of the gravity dam, so as to facilitate the integral anti-sliding stability; adopting the structural wide-slot partition during the operation period of the upper structure, the joint integral stress during the construction period and the temperature control; adopting the solid structure on the upper part of the bedrock on the two sides of the structural wide-slot, and adopting the cavity structure on the upper part of the covering layer to reduce the weight and resist the lateral overturning stability; adopting the anti-seepage wall and the curtain for the covering layer foundation and the bedrock foundation respectively to control the seepage; and finally, adopting the three-dimensional finite element numerical calculation to assist in verifying the structure type. The application provides a new design idea and scheme for solving the gravity dam structure design under the semi-covering layer and semi-bedrock complex geological conditions, and is strong in operability and convenient for engineers to use.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering design technology, specifically to a design method for concrete gravity dams on complex foundations with semi-overburden and semi-bedrock. Background Technology

[0002] Concrete gravity dams are generally situated on bedrock, relying on their own weight for stability. They are highly adaptable to various terrain and geological conditions, and their design theories and methods are mature. When the river valley is open, the dam axis is long, the riverbed cover is shallow, and the bank slope cover is deep, a combination of riverbed gravity dams and bank slope earth-rock dams is typically used, connected by a spiked wall insertion joint, as seen in the Guanyinyan Hydropower Station Dam and the Danjiangkou Water Control Project Dam. When the river valley is narrow, and the steep sections of the bank slope have developed overburden, the conditions for arranging earth-rock dams on the bank slope are limited, leading to the challenge of arranging concrete gravity dams on semi-overburden, semi-bedrock foundations. The design of concrete gravity dams in complex semi-overburden, semi-bedrock foundation conditions is extremely complex, facing challenges such as longitudinal sliding stability, lateral overturning stability, coordination of stress and deformation of ultra-wide bank slope structures, temperature control during construction, insufficient bearing capacity of the bank slope overburden, settlement deformation, and seepage control. Currently, there are no successful design cases or experiences available for reference, both domestically and internationally. Conventional concrete gravity dam design methods lack specificity and comprehensive control criteria, making them unsuitable for such complex foundation conditions. Therefore, in order to rationally utilize complex foundations and scientifically determine the design of concrete gravity dams on such foundations, it is necessary to innovate and propose new design methods. Summary of the Invention

[0003] The purpose of this invention is to provide a design method for gravity dams on complex foundations with semi-overburden and semi-bedrock, revealing the design principles and methods for concrete gravity dams on such foundations, providing a quantitative method for the utilization of complex soil and rock foundations, and solving the structural design problems of concrete gravity dams under complex geological conditions.

[0004] To achieve the above objectives, the technical method of the present invention includes:

[0005] A design method for concrete gravity dams on complex foundations with semi-overburden and semi-bedrock includes the following steps:

[0006] Analyze the characteristics of the overburden and bedrock foundation to clarify the design principles and control standards for gravity dam structures;

[0007] Based on the aforementioned structural design principles and control standards, the design of the enlarged foundation platform at the bottom of the gravity dam is carried out. The design of the enlarged foundation platform includes the anti-sliding stability design of the overall structure of the gravity dam.

[0008] A wide-groove structure is designed for the upper part of the gravity dam;

[0009] The upper part of the cover layer is designed with a weight-reducing cavity structure. The wide groove of the structure divides the upper part of the gravity dam into two parts, one of which is a cavity structure. The two parts are B1 area and B2 area, respectively.

[0010] Design seepage prevention measures for the overburden foundation.

[0011] Furthermore, the anti-slip stability of the overall structure is calculated using the following formula:

[0012] (1),

[0013] Where: K' is the anti-sliding stability safety factor calculated based on shear strength, and f' is the shear friction coefficient of the contact surface between the gravity dam structure and the foundation. N B1 For the structural self-weight of area B1, N B2 For the structural self-weight of area B2, N A The self-weight of the A section structure below sections B1 and B2, U S1 The uplift pressure at the base section of the gravity dam at elevation Z1. U S2 Let c1′ be the uplift pressure at the base section of the gravity dam at elevation Z2, c2′ be the shear cohesion at the foundation contact surface at elevation Z1, and c2′ be the shear cohesion at the foundation contact surface at elevation Z2. S 1 represents the cross-sectional area of ​​the foundation contact surface at elevation Z1 of the gravity dam structure. S 2 represents the cross-sectional area of ​​the foundation contact surface at the elevation Z2 of the gravity dam structure, and P represents the downstream water pressure acting on the gravity dam structure.

[0014] Furthermore, the design of the weight-reducing cavity structure on the upper part of the cover layer includes: the excavation line of the gravity dam foundation design intersects with the foundation cover line at point F; the horizontal plane where point F is located is used as the horizontal structural boundary line of the gravity dam structure; the horizontal structural boundary line divides the gravity dam into upper and lower structures, the lower structure is the enlarged foundation area A, and the upper structure is the structure area B; the structure area B is divided into structural area B1 and structural area B2 by a structural wide groove, and structural area B1 is designed as a cavity structure.

[0015] Furthermore, the expanded foundation area A is a horizontal section of the foundation surface designed along the axial direction of the foundation, and the minimum length of the foundation surface is designed to be 1 / 3 to 1 / 2 of the width of the dam crest.

[0016] Furthermore, a vertical structural trench is constructed to the right of the boundary point F between the overburden and the underlying bedrock; the structural trench extends from the dam crest to the horizontal structural boundary line; the structural trench divides structural B into structural zone B1 and structural zone B2 located on both sides of the structural trench; the center of gravity of zone B1 on the left side of the structural trench is to the right of point F; the structural trench is later reinforced with concrete to unite zone B1 and zone B2 into a whole.

[0017] Furthermore, the B1 region is designed as a hollow structure, and the center of the B1 region structure does not coincide with the center of its bottom cross-section, resulting in an eccentricity. e Assuming the stress is linearly distributed along the dam axis, the base stress and eccentricity... e The following formula is used for calculation:

[0018]

[0019] In the formula: The stress at the left edge of the dam axis at the bottom of the structure in zone B1 is the stress. The stress is located at the right edge of the dam axis at the bottom of the structure in area B1. M The transverse moment of the structure's self-weight about the bottom center in zone B1. T The length of the base axis of the structure in region B1. N B1 The self-weight of the B1 zone structure;

[0020] To ensure that the entire cross-section of the B1 zone structural base is subjected to eccentric compression, i.e. >0, the eccentricity can be obtained from formulas (3) and (4). e When the eccentricity e < T / 6, the entire cross-section of the B1 zone structural base is subjected to eccentric compression.

[0021] Furthermore, the foundation seepage prevention measures are designed to include a concrete seepage prevention wall as the cover layer and curtain grouting for seepage prevention in the bedrock.

[0022] This invention discloses a design method for concrete gravity dams on complex foundations in semi-overburden and semi-bedrock formations. It adapts to different geological conditions through zoning with different structural types. The enlarged foundation at the bottom ensures anti-sliding stability, while the ultra-wide upper structure with wide-groove zoning satisfies overall stress distribution during operation and construction temperature control. Simultaneously, a hollow structure is designed above the overburden layer, and the center of gravity of the cavity is adjusted to ensure minimal eccentric compression of the foundation. Based on this, the structural shape of the gravity dam is determined. The beneficial effects include:

[0023] 1. This invention proposes a zoning control standard and zoning structural shape for the design of concrete gravity dams on complex soil and rock foundations, which can provide new ideas and solutions for the structural design of gravity dams under complex geological conditions of semi-overburden and semi-bedrock.

[0024] 2. This invention establishes a design concept for concrete gravity dams on complex foundations with semi-overburden and semi-bedrock, breaking through the limitations of traditional gravity dam design regarding the utilization of complex foundations.

[0025] 3. This invention provides a complete design process for concrete gravity dams on complex foundations with semi-overburden and semi-bedrock layers. It is highly operable and easy for designers of similar projects to refer to and use. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the integrated gravity dam section on a complex foundation of semi-overburden and semi-rock as described in this invention.

[0027] Figure 2 This is a flowchart of the design method of the present invention.

[0028] Figure 3 This is a plan view of the left bank gravity dam of a hydropower station according to a specific embodiment of the present invention.

[0029] Figure 4 This is an elevation view of the upstream of a gravity dam in a hydropower station, according to a specific embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram illustrating the adjustment of the center of gravity of the hollow structure of a hydropower station gravity dam, according to a specific embodiment of the present invention.

[0031] Figure 6 This is a cross-sectional view of the cavity structure in the B1 section of the gravity dam of a hydropower station according to a specific embodiment of the present invention.

[0032] Figure 7 This is a cross-sectional view of the physical structure of the gravity dam B2 section of a hydropower station in a specific embodiment of the present invention, along the flow direction.

[0033] Among them: 1. Excavation line of foundation surface design; 2. Foundation cover line; 3. Horizontal structural boundary line; 4. Structural wide trench; 41. Center line of structural wide trench; 5. Centroid point of structure in area B1; 6. Cover to form anti-seepage wall; 7. Bedrock; 8. Gallery; 81. Foundation gallery; 82. Downstream traffic gallery; 9. Dam axis; 10. Left bank dam abutment platform; 11. Horizontal joint; 12. Concrete gravity dam; 13. Drainage steel pipe; 14. Inserted reinforcement; 15. Rib plate; 16. Vertical line; 17. Monitoring house; 18. Drainage hole; 19. Bottom area S1 of horizontal foundation elevation Z1 of gravity dam structure; 20. Bottom area S2 of horizontal foundation surface 1 elevation Z2 of gravity dam structure; 3. Boundary elevation Z3 between enlarged foundation area A and its superstructure area B; 4. Crest elevation Z4 of gravity dam. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only some, not all, of the embodiments of this invention, and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0035] The core of this invention lies in the design concept of adopting different structural forms and combining zoning and overall design to adapt to different foundations; the bottom adopts an enlarged platform overall form to facilitate overall anti-sliding stability; the upper structure combines overall stress during operation and disperses stress and temperature control during construction, adopting wide-groove zoning; according to the different bedrock foundation conditions of the overburden layer, different structural forms are adopted to adapt to the geological conditions, the upper part of the bedrock adopts a solid structure, and the upper part of the overburden layer adopts a cavity structure to reduce weight and resist lateral overturning stability; at the same time, the overburden foundation adopts an anti-seepage wall for seepage control; finally, three-dimensional finite element numerical calculation is used to assist in verifying the structural shape.

[0036] The basic principle of this invention is as follows: adopting control conditions and standards adapted to the foundation conditions, taking into account different zoning structural types for different foundation conditions, enlarging the foundation at the bottom, adopting a cavity structure on the upper part of the overburden layer, adopting a solid structure on the upper part of the bedrock, combining the overall stress of the operational zones, and dispersing the stress during the construction period. Based on this idea, gravity dam structures can be designed.

[0037] This invention discloses a design method for concrete gravity dams on complex foundations consisting of a semi-overburden and semi-bedrock layer. The implementation process includes six steps: 1. Analyzing the characteristics of the overburden and bedrock foundations to clarify structural design principles and control standards; 2. Designing the enlarged foundation at the bottom of the gravity dam; 3. Designing the wide-groove structure of the gravity dam's superstructure; 4. Designing the weight-reducing cavity structure above the overburden; 5. Designing seepage prevention measures for the overburden foundation; 6. Performing three-dimensional finite element numerical analysis to verify the structural form.

[0038] Step 1: Analyze the characteristics of the overburden and bedrock foundation to clarify the structural design principles and control standards;

[0039] The zoning design control standards mentioned in this step mainly include the anti-sliding stability, bearing capacity, deformation, uneven settlement, and seepage control of the overburden, while the bedrock includes anti-sliding stability, stress, and seepage control. The structural design control standards for the overburden and bedrock are given by geologists based on geological conditions.

[0040] Step 2: Design of the enlarged foundation platform at the bottom of the gravity dam;

[0041] This step addresses the anti-sliding stability of the bedrock portion of the gravity dam structure in Step 1 by employing an enlarged foundation design to increase the cohesion of the base contact surface. The enlarged foundation design involves designing a horizontal foundation section along the base axis, with the minimum length of the foundation surface rock mass designed to be 1 / 3 to 1 / 2 of the dam crest width L, maximizing the proportion of the horizontal foundation section. To make full use of the foundation rock mass, the foundation platform structure is enlarged, and a horizontal structural boundary line 3 is drawn at point F, the boundary between the overburden and bedrock, dividing the gravity dam into upper and lower structures. The lower section forms enlarged foundation area A, and the upper section forms structural area B.

[0042] Figure 1 A schematic diagram of the integrated zoning of a gravity dam on a complex foundation consisting of a semi-overburden layer and semi-bedrock (upstream elevation view). Figure 1 In the diagram, 6 is the overburden seepage barrier, 7 is the bedrock, and there is a bedrock line 2 at the junction of the overburden and the bedrock 7. The intersection of the design excavation line 1 and the bedrock line 2 on the foundation surface is point F. The area on one side of the design excavation line 1 on the foundation surface is the overburden, and the lower area is the bedrock.

[0043] In this step, the overall structural anti-slip stability is calculated using the following formula:

[0044] (1),

[0045] In the above formula (1): K 'This is the safety factor for anti-sliding stability calculated based on shear strength.' f ' is the shear friction coefficient of the contact surface between the gravity dam structure and the foundation. N B1 for Figure 1 The structural self-weight of section B1, N B2 for Figure 1 The structural self-weight of section B2, N A for Figure 1 The structural self-weight of section A, U S1 The uplift pressure at the base section at elevation Z1 in area A. U S2 The uplift pressure at the base section at elevation Z2 in area A. c 1′ represents the shear cohesion at the foundation contact surface at elevation Z1 in area A of the gravity dam structure. c 2′ represents the shear cohesion at the foundation contact surface at elevation Z2 in area A of the gravity dam structure. S 1 represents the cross-sectional area of ​​the foundation at elevation Z1 in area A of the gravity dam structure. S 2 represents the cross-sectional area of ​​the foundation at elevation Z2 in area A of the gravity dam structure, and P represents the downstream water pressure acting on the gravity dam structure.

[0046] Step 3: Wide-slot design for the upper structure of the gravity dam;

[0047] The structural wide trench design described in this step takes into account the overall stress and deformation coordination during operation, construction temperature control, and ensuring simultaneous construction and ascent from both sides. A vertical structural wide trench 4 is set at a certain distance to the right of the boundary between the overburden and the lower bedrock. The structural wide trench 4 extends from the dam crest to the horizontal structural interface. The upper structure B area is subdivided into structural area B1 and structural area B2. In this step, the specific location of the wide trench must ensure that the center of gravity of the B1 area on the left side of the wide trench is to the right of point F.

[0048] The concrete poured into the wide groove 4 of the structure later united area B1 and area B2 into a whole.

[0049] Step 4: Design of weight-reducing cavity structure above the overburden foundation;

[0050] The B1 area above the overburden foundation described in this step adopts a cavity structure to reduce the structural weight and meet the allowable bearing capacity of the overburden foundation. In order to meet the lateral overturning stability of the B1 area during construction, a reasonable cavity structure shape is designed using a three-dimensional BIM platform. When the B1 area structure is designed to be hollowed out, its structural center of gravity falls within the core of the bottom horizontal section of the B1 area. At this time, the B1 area structural base is eccentrically compressed across the entire cross section, which is the reasonable cavity shape of the B1 area.

[0051] Because the center of the structure in section B1 does not coincide with the center of its bottom section, there is an eccentricity. e The structure in region B1 is subjected to eccentric compression, such as Figure 1 As shown. Draw a vertical line upwards from the center of the bottom section of region B1. The perpendicular distance between the centroid point 5 of region B1 and the vertical line is the eccentricity. e .

[0052] Assuming the stress is linearly distributed along the dam axis, the base stress and eccentricity... e The following formula is used for calculation:

[0053]

[0054] In the formula: The stress at the left edge of the dam axis at the bottom of the structure in zone B1 is the stress. The stress is located at the right edge of the dam axis at the bottom of the structure in area B1. M The transverse moment of the structure's self-weight about the bottom center in zone B1. T The length of the base axis of the structure in region B1. N B1 for Figure 1 The structural self-weight of the middle B1 zone.

[0055] To ensure that the entire cross-section of the B1 zone structural base is subjected to eccentric compression, i.e. >0, the eccentricity can be calculated from formulas (3) and (4). e < T / 6.

[0056] In this step, the volume, weight, and center position of the cavity structure in area B1 can be easily measured and obtained directly on the 3D BIM platform. The cavity structure in area B1 is designed to achieve an eccentricity... e < T / 6, the B1 area structural base is subjected to full-section eccentric compression.

[0057] Step 5: Design of seepage prevention measures for the overburden foundation;

[0058] The seepage prevention measures described in this step are designed with a concrete cutoff wall structure for the upper left overburden foundation and curtain grouting for the bedrock. The overburden and bedrock adopt the seepage control standards described in step 1.

[0059] Step 6: Three-dimensional finite element numerical analysis to verify the structural shape;

[0060] This step involves using three-dimensional finite element numerical analysis to assist in verifying the rationality of the structural design, taking into account the complexity of the semi-overburden, semi-bedrock gravity dam structure.

[0061] Steps 3 through 6 can determine the structural shape of the concrete gravity dam.

[0062] The following examples, combined with Figures 3-5 The technical solution of the present invention will be further described in detail below. Figure 3 In the diagram, number 8 represents the gallery, number 9 represents the dam axis, number 10 represents the left bank abutment platform, and number 11 represents the transverse joint. Figure 4 Designation 12 indicates a concrete gravity dam; designation 41 indicates the centerline of the structural wide channel; designation 13 indicates a drainage steel pipe; designation 14 indicates reinforcing bars; and designation 15 indicates a rib plate. Figure 5 The number 16 in the diagram represents a vertical line drawn upwards from the center of the bottom section of region B1. Figure 5 In the diagram, the yellow area represents structural area B1, and the blue area represents expanded foundation area A.

[0063] Figure 4 for Figure 3 CC-plane cross-section, Figure 6 for Figure 3 DD section view, Figure 7 for Figure 3 EE section view, Figure 6 , Figure 7 The arrows in the diagram indicate the direction of water flow.

[0064] Example: A hydropower station adopts a diversion-type development scheme. The normal water level of the reservoir is 2815m, and the total reservoir capacity is 9.14 million m³. 3The installed capacity is 1015MW, and the project is a second-class large (2) type. The main structures of the hub consist of the head hub concrete gravity dam, the right bank fishway, the shore ecological power station, the right bank long water diversion tunnel and the ground power plant. The maximum height of the concrete gravity dam is 70m. The left bank has a high elevation with a layer of boulders covering it, and the left bank has a low elevation, the riverbed and the right bank have sandy slate. The left bank has a soil and rock foundation and a slope concrete gravity dam structure design problem. In order to make reasonable use of the dam site overburden and bedrock, determine the slope gravity dam structure, adopt the zonal adaptation to the foundation conditions and the overall stress structure, and propose a concrete gravity dam structure design method on a complex foundation of half overburden and half bedrock. Its implementation process includes:

[0065] Step 1: Analyze the characteristics of the overburden and bedrock foundation to clarify the structural design principles and control standards;

[0066] In this specific embodiment, the upper part of the left bank foundation of the gravity dam of the hydropower station is covered by a boulder cover layer, and the lower part is weakly weathered sandy slate. The design principle and control standards of the zonal structure are adapted to the foundation conditions. The zonal control standards mainly include the anti-sliding stability, bearing capacity, deformation, uneven settlement and seepage control of the upper left boulder cover layer structure, and the anti-sliding stability, stress and seepage control of the lower weakly weathered sandy slate structure. The design control standards of the boulder cover layer and the weakly weathered sandy slate structure are given by geologists according to the geological conditions.

[0067] Step 2: Design of the enlarged foundation platform at the bottom of the gravity dam;

[0068] To address the anti-sliding stability of the bedrock portion of the gravity dam structure in step 1, an enlarged foundation design is adopted to increase the cohesion of the base contact surface. This enlarged foundation design involves a horizontal section of the foundation surface along the base axis. The foundation surface is composed of weakly weathered sandy slate rock mass, with its minimum length designed to be 1 / 3 to 1 / 2 of the dam crest width. The horizontal section of the foundation surface is maximized; in this embodiment, the widths of the horizontal sections at foundation surface elevations of 2794m and 2787m are 8.4m and 9.2m, respectively. After enlarging the overall platform at the bottom, the horizontal structural boundaries are divided in the height direction, separating the gravity dam into upper and lower structures. To maximize the utilization of the weakly weathered sandy slate foundation, the foundation platform structure is enlarged, as shown below. Figure 4 As shown, in this embodiment, the boundary between the overburden and the bedrock is F (Z1 elevation 2802m), forming an enlarged foundation area A below and a structural area B above.

[0069] In this embodiment, the overall structural anti-slip stability is calculated using the following formula:

[0070] , (1)

[0071] In the above formula (1): K 'This is the safety factor for anti-sliding stability calculated based on shear strength.'f ' is the shear friction coefficient of the interface between the structure and the foundation. N B1 For the structural self-weight of area B1, N B2 For the structural self-weight of area B2, N A For the structural self-weight of area A, U S1 Let A be the uplift pressure at the base section at an elevation of 2794m in area A. U S2 The uplift pressure at the base section of area A, at an elevation of 2787m. c 1′ represents the shear cohesion of the foundation at an elevation of 2794m in area A. c 2′ represents the shear cohesion of the foundation at an elevation of 2787m in area A. S 1 represents the area of ​​the foundation surface at an elevation of 2794m in Area A. S 2 represents the area of ​​the foundation surface at an elevation of 2787m in area A, and P represents the downstream water pressure acting on the structure.

[0072] Step 3: Wide-slot design for the upper structure of the gravity dam;

[0073] The structural trench design described in this step takes into account the overall stress and deformation coordination during operation, construction temperature control, and ensuring simultaneous construction and ascent from both sides. A vertical structural trench 4 is set at a certain distance to the right of the boundary between the overburden and the lower bedrock, subdividing the upper structure B zone into structural zone B1 and structural zone B2. The structural trench is designed to be 1.8m wide, with reinforcing bars installed. Waterstops are installed on the vertical surfaces on both upstream sides. Concrete will be poured later to connect zones B1 and B2. The specific location of the structural trench is approximately 1 / 3 to 1 / 2 of the width of the dam crest in zone B1. L 1. Location: In this embodiment, the specific location of the wide groove is 13.56m to the right of point F.

[0074] Step 4: Design of weight-reducing cavity structure above the overburden foundation;

[0075] In this step, a hollow structure is adopted for the upper part of the B1 zone of the overburden foundation to reduce structural weight while meeting the allowable bearing capacity of the overburden foundation. To ensure lateral overturning stability during the construction period of the B1 zone, a reasonable hollow structure shape is designed using a 3D BIM platform. Figure 5 As shown, when the structure of area B1 is designed with an open excavation, its center of gravity falls within the core of the horizontal section (elevation 2802m) at the bottom of area B1, as follows. Figure 5 As shown, the vertical joint distance between the platform at elevation 2794m and the bedrock design excavation line is d=3.24m. At this time, the entire cross-section of the B1 area structure foundation is eccentrically compressed, which is the reasonable shape of the cavity in the B1 area.

[0076] Because the center of the structure in section B1 does not coincide with the centroid of the bottom section, there is an eccentricity.e The structure in zone B1 is subjected to eccentric compression. Assuming that the stress is linearly distributed along the dam axis, the base stress is calculated using the following formula:

[0077]

[0078] In the formula: The stress at the left edge of the dam axis at the bottom of the structure in zone B1 is the stress. The stress is located at the right edge of the dam axis at the bottom of the structure in zone B1. M is The transverse moment of the structure's self-weight about the bottom center in zone B1. T is B1 zone structural base axis length.

[0079] To ensure that the entire cross-section of the B1 zone structural base is subjected to eccentric compression, i.e. >0, the eccentricity can be calculated from formulas (3) and (4). e < T / 6.

[0080] In this step, the volume, weight, and center position of the cavity structure in area B1 can be easily measured and obtained directly in the 3D BIM platform (3DEXPERIENCER2024x). The cavity structure in area B1 is designed to achieve an eccentricity... e < T / 6=2.11, and the structural base of area B1 is subjected to full-section eccentric compression.

[0081] Step 5: Design of seepage prevention measures for the overburden foundation;

[0082] The seepage prevention measures described in this step are designed as follows: the foundation of the upper left pebble cover layer adopts a 1m thick fully enclosed concrete seepage prevention wall structure, and the bedrock adopts curtain grouting; the structure on the foundation surface of the cover layer slope adopts an integral connecting plate, and the top of the seepage prevention wall and the slope slope plate adopt asphalt flexible connection and copper water stop seepage prevention.

[0083] Step 6: Three-dimensional finite element numerical analysis to verify the structural shape;

[0084] Step 6 describes the use of three-dimensional finite element numerical analysis to assist in verifying the rationality of the structural design, taking into account the complexity of the semi-overburden and semi-bedrock gravity dam structure.

[0085] Through steps 2-4 above, the gravity dam body shape on the semi-overburden and semi-bedrock foundation was designed, and step 6, with finite element numerical verification, was used to determine the final left bank gravity dam structure of the hydropower station. Figure 6 and Figure 7 As shown, Figure 7 In the diagram, number 17 is the monitoring room, number 81 is the basic corridor, number 82 is the downstream traffic corridor, and number 18 is the drainage hole.

[0086] The above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for designing a concrete gravity dam on a semi-covering layer and semi-bedrock complex foundation, characterized in that: The method comprises the following steps: Analyzing the characteristics of the covering layer and the bedrock foundation, and determining the structural design principles and control standards of the gravity dam; Designing the expanded foundation platform of the gravity dam on the bedrock according to the structural design principles and control standards, wherein the expanded foundation platform design comprises the anti-sliding stability design of the overall structure of the gravity dam; Designing the structural wide slot on the upper part of the gravity dam, wherein the structural wide slot divides the upper structure of the gravity dam into two parts, i.e., the B1 area and the B2 area; Designing the weight-reducing cavity structure on the upper part of the covering layer, and designing the B1 area of the gravity dam on the upper part of the covering layer as a cavity structure; Designing the anti-seepage measures of the covering layer and the bedrock foundation; The upper cover layer weight-reducing cavity structure design comprises: intersection F between the gravity dam foundation surface design excavation line (1) and the base cover line (2); the horizontal plane where the F point is located is used as the horizontal structure boundary line (3) of the gravity dam structure; the horizontal structure boundary line (3) divides the gravity dam into upper and lower structures, the lower structure is the enlarged foundation A area, and the upper structure is the structure B area; a vertical structure wide groove (4) is arranged on the right side of the cover layer and the lower rock boundary point F; the structure wide groove (4) extends from the dam top to the horizontal structure boundary line (3); the structure wide groove (4) divides the structure B area into structure areas B1 and B2 located on the two sides of the structure wide groove (4); the gravity center of the B1 area on the left side of the structure wide groove (4) is on the right side of the F point; the structure wide groove (4) is poured with concrete in the later stage to make the B1 area and the B2 area into a whole; the B1 area is designed as a cavity structure, the structure center of the B1 area is not coincident with the bottom section center, and there is an eccentricity e , it is assumed that the stress is linearly distributed along the dam axis direction, the base stress, the eccentricity e The following formula is used for calculation: wherein: is the stress at the left edge of the B1 zone structure bottom dam axis direction, is the stress at the right edge of the B1 zone structure bottom dam axis direction; M is the transverse river force moment of the B1 zone structure self weight on the bottom center, T is the length of the B1 zone structure base axis, N B1 is the B1 zone structure self weight; To ensure the whole section of the B1 area structure base is eccentric compression, that is > 0, the eccentricity is calculated by formula (3), (4) e , the eccentricity is calculated by formula (3), (4) e , T / 6, the whole section of the B1 area structure base is eccentric compression.

2. The method for designing a concrete gravity dam on a semi-covering layer and semi-bedrock complex foundation according to claim 1, characterized in that: The anti-sliding stability of the overall structure is calculated by using the following formula: （1）， Wherein: Wherein: K' is the anti-sliding stability safety factor calculated by shear strength, f' is the shear friction coefficient of the gravity dam structure and foundation contact surface, N B1 is the self-weight of the B1 area structure, N B2 is the self-weight of the B2 area structure, N A is the self-weight of the A area structure under the B1 area and the B2 area, U S1 is the uplift pressure of the gravity dam elevation Z1 base section, U S2 is the uplift pressure of the gravity dam elevation Z2 base section, c1' is the shear cohesion of the gravity dam structure elevation Z1 foundation contact surface, c2' is the shear cohesion of the gravity dam structure elevation Z2 foundation contact surface, S 1 is the gravity dam structure elevation Z1 foundation contact surface sectional area, S 2 is the gravity dam structure elevation Z2 foundation contact surface sectional area, P is the water pressure acting on the gravity dam structure in the flow direction.

3. The method for designing a concrete gravity dam on a semi-covering layer and semi-bedrock complex foundation according to claim 1, characterized in that: The expanded foundation A area is the horizontal base surface of the axial design of the base, and the minimum length of the base surface is designed as 1 / 3-1 / 2 of the width of the dam top.

4. The method for designing a concrete gravity dam on a semi-covering layer and semi-bedrock complex foundation according to claim 1, characterized in that: The anti-seepage measure design of the foundation comprises the concrete anti-seepage wall of the covering layer and the curtain grouting anti-seepage of the bedrock.

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