Simulation rehearsal method for structural state of gate dam under earthquake action

Abstract

The invention belongs to the technical field of gate dam structural state analysis, and particularly provides a gate dam structural state simulation rehearsal method under the earthquake action, which comprises the following steps: constructing a gate dam and foundation overall three-dimensional finite element model, and reflecting the shape of a gate dam, engineering geological conditions, an anti-seepage curtain, a structural parting and the interaction between the gate dam and a foundation; operation period working conditions, operation period loads, earthquake action and extreme weather conditions are analyzed; analyzing and evaluating the overall stability of the gate dam and the foundation under the normal operation condition; and analyzing and evaluating the overall stability of the gate dam under the earthquake action and extreme weather conditions: adopting a nonlinear finite element time-history analysis method to carry out the earthquake response analysis of the gate dam and the foundation, and evaluating the overall stability of the gate dam according to the earthquake response. According to the method, the influence of earthquake action and extreme weather conditions on the overall stability of the gate dam is considered, and the bearing capacity of the foundation and the overall stability of the gate dam are analyzed and evaluated from multiple angles and multiple aspects.

Description

Technical Field

[0001] The invention belongs to the technical field of dam structure performance analysis, and in particular, relates to a simulation preview method for dam structure performance under earthquake action. Background Art

[0002] At present, most of the simulation and pre-performance research on the structural behavior of dams under earthquakes is aimed at the structural behavior simulation and pre-performance of dams under specific earthquakes and specific water levels. There are few studies on the structural behavior simulation and pre-performance of dams under different earthquakes, different operating water levels and extreme weather conditions, and no reasonable and effective analysis method has been proposed. Therefore, it is of great significance to propose reasonable and effective simulation and pre-performance of the structural behavior of dams under different conditions, study the seismic response characteristics of dams under different earthquakes, different operating water levels and extreme weather conditions, conduct stability analysis and safety assessment, and propose corresponding seismic measures to scientifically estimate the safety margin of dams when encountering earthquakes under different conditions and ensure the safety and quality of engineering construction. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a simulation preview method for the structural behavior of a dam under earthquake action, which takes into account different earthquake actions, different operating water level conditions and extreme weather conditions, and analyzes and evaluates the foundation bearing capacity and the overall stability of the dam from multiple angles and aspects.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a simulation preview method of the structural behavior of a dam under earthquake action, comprising the following steps: Step 1: Construct an overall three-dimensional finite element model of the dam and foundation to reflect the shape of the dam, engineering geological conditions, anti-seepage curtain, structural joints, and the interaction between the dam and foundation; Step 2: Analysis of operating conditions, operating loads, earthquake effects and extreme weather conditions; Step 3: Analysis and evaluation of the overall stability of the dam and foundation under normal operating conditions; Step 4: Analysis and evaluation of the overall stability of the dam under earthquake and extreme weather conditions: Use nonlinear finite element time-history analysis method to conduct seismic response analysis of the dam and foundation, and evaluate the overall stability of the dam based on the seismic response.

[0005] In the preferred solution, in step one, the numerical analysis model of the overall three-dimensional finite element model of the dam and foundation includes a material constitutive model, a contact surface between the dam structure and the foundation, a structural joint simulation, a dynamic water pressure simulation, and a structural damping simulation.

[0006] In a preferred solution, in the material constitutive model, for the dam concrete material, the elastic-plastic damage model is used for simulation; for the foundation cover layer and rock mass material, the Mohr-Coulomb elastic-plastic constitutive model is used for simulation, and the expression of the Mohr-Coulomb yield criterion is: (1); Where: For the cohesion of the material; is the internal friction angle of the material; are shear stress and normal stress respectively; The yield function is expressed as: (2); Where: are the first and third principal stresses respectively; Formula (1) represents shear failure. For rock and concrete materials with low tensile strength, tensile cracks occur when the shear stress is far from reaching the shear strength. Therefore, the tensile strength criterion is increased, that is: (3); Where: is the tensile strength of the material.

[0007] In a preferred solution, the contact surface between the structure of the dam and the foundation and the structural joint simulation are simulated using a constraint function contact algorithm to meet the following contact constraint conditions: The normal contact constraint is: (4); Where: is the normal contact force between the contact surfaces, is the normal distance between the contact surfaces; ,and When , it indicates that the contact surface is open; when ,and When , it indicates that the contact surface is closed ; The tangential friction between the contact surfaces satisfies Coulomb's friction law, so the tangential contact force The size cannot exceed its limit ,Right now: (5); Where: , are the components of the tangential contact force in the directions of the two coordinate axes respectively; Introducing a dimensionless variable , ; The relative sliding speed between the contact surfaces is , defined as: (6); Where: is the tangential velocity of object A on the contact surface, is the tangential velocity of object B on the contact surface; The tangential friction contact condition is expressed as: (7); when When , there is no relative slip between the contact surfaces. ;when When the relative slip occurs between the contact surfaces, the relative slip velocity between the contact surfaces is , its direction is Consistent direction; The constraint function contact algorithm used introduces the normal constraint function and friction constraint function To describe the above contact constraints, when When , the normal contact constraint condition described by equation (8) is satisfied; when When , the tangential contact constraint condition described by equation (9) is satisfied, and the constraint function and The expression is as follows: (8); (9); in, is a very small constant, which makes the mathematical representation of the normal contact condition smoother and is conducive to the convergence of the calculation; is a parameter that controls the closeness between the regularized friction model and the Coulomb friction model. The smaller, the closer; is the related quantity of relative sliding velocity between contact surfaces, is an auxiliary variable related to the friction contact process.

[0008] In a preferred solution, the dynamic water pressure simulation is to consider the dynamic water pressure in the form of additional mass in the seismic calculation of the hydraulic structure. The additional mass is calculated using the Westergaard additional mass formula, which is expressed as: (10); In the formula, is the reservoir water depth, which is the water level under common working conditions or the water level under extreme working conditions; is the water depth at the calculation point; is the water density.

[0009] In a preferred solution, the structural damping simulation uses Rayleigh damping to characterize the total damping matrix of the system, that is, assuming that the damping matrix of the structure is expressed as a linear combination of the mass matrix and the stiffness matrix: (11); in, , The value of is calculated using the following formula: ; ; Where: Respectively represent Damping ratio of the order vibration mode; Respectively represent The frequency of the order vibration mode.

[0010] In a preferred solution, in step 2, the operating conditions, operating loads and possible earthquake analysis during operation include the following: 1) Operation conditions include the following: Normal water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Normal water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Design flood level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure + dynamic water pressure; Dead water level: dead weight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; 2) The loads during operation include self-weight load, hydrostatic pressure and seepage load, which are as follows: a) Self-weight load: (12); In the formula, For structural quality; is the acceleration due to gravity; b) Hydrostatic Pressure: (13); Where: is the density of water; is the acceleration due to gravity; The depth of the reservoir water; c) Seepage load: The three-dimensional finite element method is used to calculate the three-dimensional constant seepage field of the dam and foundation. When performing static and dynamic calculations of the dam, the seepage pressure at the bottom of the dam is integrated into the node force as uplift pressure and applied to the bottom of the dam structure. 3) Earthquake effects include: Design basic earthquake acceleration DBE; Operation basic earthquake acceleration OBE; Maximum credible earthquake acceleration MCE; Also consider: a) Probability of exceeding within 50 years P 50 The earthquake action is 0.05; b) Probability of exceeding within 100 years P 100 The earthquake action is 0.02; c) When the reservoir is empty, if earthquake effects need to be considered, the representative value of the design earthquake acceleration shall be halved for seismic design; d) Short-term conditions during the construction period may not be combined with earthquake effects; e) Typical earthquake actions in historical data; The seismic fortification level of various hydraulic structures is characterized by the design intensity on flat surface and the representative value of the horizontal design seismic peak acceleration.

[0011] 4) Extreme weather conditions include: a) Flood; b) The temperature drops suddenly.

[0012] In the preferred solution, in step 3, the overall stability analysis and assessment of the dam and foundation under normal operating conditions includes overall deformation analysis of the dam, foundation bearing capacity analysis and overall stability assessment of the dam and foundation, which are as follows: 1) Overall deformation analysis of the dam: Summarize the deformation of each part along the river, across the river and vertically, and analyze the deformation position and deformation of each part with the maximum deformation in each direction; 2) Foundation bearing capacity analysis: Analyze the interface pressure to determine whether it is less than the allowable bearing capacity; 3) Overall stability assessment of the dam and foundation: Based on the overall deformation of the dam and the contact state of the interface between the dam and the foundation, the overall stability of the dam and foundation is comprehensively assessed, specifically: Determine whether the overall deformation law of the dam-foundation is normal under normal operating conditions, whether the deformation value is controllable, whether serious uneven settlement occurs on both sides of the structural joint, whether the vertical compressive stress at the dam-foundation interface exceeds the allowable bearing capacity, and whether the dam produces shear sliding along the interface between the dam and the foundation, and then analyze the overall stability of the dam and foundation.

[0013] In the preferred solution, in step 4, a nonlinear finite element time history analysis method is used to carry out seismic response analysis of the dam and foundation, and the overall stability of the dam is evaluated according to the seismic response, including: The calculated load combination is: normal operating condition + earthquake action; The earthquake took into account three types of earthquake motion: earthquake motion along the river, earthquake motion across the river, and vertical earthquake motion, as follows: 1) Earthquake time course According to the seismic motion selection and target response spectrum matching work, a seismic motion time history curve that can reflect the seismic characteristics of the project site is generated, and then the overall stability of the dam under the earthquake is analyzed; 2) Earthquake situation ① Downstream earthquake: The propagation direction of the seismic wave is basically consistent with the flow direction of the river; ② Transverse river earthquake: The propagation direction of the seismic wave is roughly perpendicular to the flow direction of the river; ③ Vertical earthquake: Vertical earthquake refers to the vibration component of seismic waves in the vertical direction; 3) Analysis and evaluation of overall stability of dams and gates a) Analysis of dynamic displacement of dams Take the key points on the dam and apron structures and the points with the maximum static settlement to analyze the reciprocating changes in the displacement of the dam and apron during an earthquake. By summarizing the displacements of various parts in various directions, analyze the displacement change rules of key points during an earthquake, and judge the dynamic stability of the dam from the displacement time history. b) Foundation bearing capacity analysis Determine whether the interface pressure exceeds the allowable bearing capacity, and determine whether the state of the continuous reciprocating changes during the earthquake is in a bonding state, an open state, or a sliding state. If no through sliding area is formed, no sliding instability damage will occur along the bottom contact surface, that is, the bottom contact surface will not be in a sliding state when the earthquake ends; c) Overall stability assessment of dam and foundation During an earthquake, the displacements of the dam and the apron change with the action of the earthquake. After the earthquake, the displacements of the dam in various directions are summarized to determine whether the stress on the contact surface between the dam and the foundation meets the bearing capacity requirements. During the earthquake, it is determined whether the contact surface between the dam and the foundation is in a bonding state, or changes back and forth between a bonding state, an open state, and a sliding state. If only the contact surface of the dam foundation is in a sliding state at a certain moment, but no continuous sliding area is formed, the dam will not suffer from overall sliding instability damage. Based on the above, it is determined whether the overall stability of the dam is guaranteed.

[0014] The present invention provides a simulation preview method for the structural behavior of a dam under earthquake action, which has the following beneficial effects: 1. The present invention constructs a three-dimensional finite element model of the dam and uses a three-dimensional nonlinear finite element method to calculate the deformation and stress of the dam under static conditions and earthquakes, analyzes whether the deformation and base stress of the dam meet the control standards, and analyzes and evaluates the bearing capacity of the foundation and the overall stability of the dam.

[0015] 2. The present invention takes into account different earthquake effects, different operating water level conditions and extreme weather conditions, and analyzes and evaluates the bearing capacity of the foundation and the overall stability of the dam from multiple angles and aspects, filling the gaps beyond the general conditions considered by the existing technical solutions, and improving the complex and changeable condition system of the dam under earthquake action, so that the structural state simulation preview of the dam under earthquake action is closer to the actual real situation. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is a flow chart of the present invention; Figure 2 is the normal contact constraint function curve; Figure 3 is the friction contact constraint function curve; Figure 4 It is a three-dimensional finite element model of a dam-foundation; Figure 5 is the overall total water head distribution cloud diagram of a dam-foundation (unit: m); Figure 6 is the overall seepage pressure distribution cloud diagram of a dam-foundation (unit: m); Figure 7 It is a comparison chart of deterministic and consistent disaster response spectra; Figure 8 It is a schematic diagram of the position of key points in the displacement time history; Fig. 9 is the deformation of a sluice body along the river (unit: m); Fig.10 is the transverse river deformation of a gate body (unit: m); Fig.11 is the vertical deformation of a gate body (unit: m). DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Reference Figure 1 A simulation preview method for the structural behavior of a dam under earthquake action comprises the following steps: Step 1: Construct finite element calculation model Construct the overall three-dimensional finite element model of the dam and foundation, such as Figure 4As shown in the figure, the model should truly reflect the shape of the dam, engineering geological conditions, anti-seepage curtain, structural joints, and the interaction between the dam and the foundation. It includes material constitutive model, the contact surface between the dam's structure and foundation, structural joint simulation, dynamic water pressure simulation, and structural damping simulation.

[0018] In the numerical analysis model, the dam concrete material is simulated by the elastic-plastic damage model, the foundation cover and rock material are simulated by the Mohr-Coulomb elastic-plastic constitutive model, the interface between the dam bottom and the foundation is simulated by the contact unit without thickness, and the interface between the dam side and the foundation is simulated by the thin layer unit; the dynamic water pressure is simulated by applying additional mass to the dam surface nodes; the massless foundation uniform input model is used to analyze the seismic response of the dam structure.

[0019] 1) Material constitutive model For the dam concrete material, the elastic-plastic damage model is used for simulation.

[0020] The concrete elastoplastic damage model is based on the elastoplastic mechanics theory and the damage mechanics theory. The elastoplastic mechanics theory describes the elastic deformation and plastic deformation behavior of materials during loading and unloading, and is characterized by introducing parameters such as elastic modulus, plastic modulus, and yield stress. The damage mechanics theory is used to describe the damage accumulation caused by the expansion and evolution of microcracks and microvoids in the process of stress on the material, and describes the degree of damage by introducing damage variables, which are usually associated with mechanical properties parameters such as stiffness and strength of the material.

[0021] The concrete elastoplastic damage model can simulate the deformation and damage of concrete materials after being subjected to stress, predict the failure point, residual strength and fatigue life of concrete structures, and analyze the influence of external factors such as water pressure and seismic force on concrete.

[0022] For foundation cover and rock materials, the Mohr-Coulomb yield criterion is used for simulation, that is, (1); Where: For the cohesion of the material; is the internal friction angle of the material; , are shear stress and normal stress respectively.

[0023] The yield function is expressed as: (2); Where: , are the first and third principal stresses respectively.

[0024] The above formula is shear failure. For rock and concrete materials with low tensile strength, cracks often occur when the shear stress is far from reaching the shear strength. Therefore, the tensile strength criterion is increased, that is: (3); Where: is the tensile strength of the material.

[0025] (2) Simulation of structure-foundation interface and structural joints The constraint function contact algorithm is used to simulate the contact surface between the dam structure and the foundation as well as the structural joint. The contact process of the joint surface is a complex mechanical behavior. When it is abstracted into a mechanical model, the following three contact constraints should be met: (1) normal non-penetration condition; (2) normal contact force is a compressive stress condition; (3) tangential friction condition.

[0026] The mathematical expressions of the above three constraints are given below.

[0027] The normal contact constraint is: (4); Where: is the normal contact force between the contact surfaces, is the normal distance between the contact surfaces. ,and When , it indicates that the contact surface is open; when ,and When , it indicates that the contact surface is closed .

[0028] The tangential friction between the contact surfaces satisfies Coulomb's friction law, so the tangential contact force The size cannot exceed its limit .Right now: (5); Where: , are the components of the tangential contact force in the directions of the two coordinate axes, is the friction coefficient.

[0029] Introducing a dimensionless variable , The relative sliding speed between the contact surfaces is , defined as: (6); The tangential friction contact condition can be expressed as: (7); when When , there is no relative slip between the contact surfaces. ;when When the relative slip occurs between the contact surfaces, the relative slip velocity between the contact surfaces is , its direction is The direction is consistent.

[0030] The constraint function contact algorithm used introduces the normal constraint function and friction constraint function To describe the above contact constraints, such as Figure 2 , Figure 3 As shown. When , the normal contact constraint condition described by equation (8) is satisfied; when When , the tangential contact constraint condition described by equation (9) is satisfied. Constraint function and The expression is as follows: (8); (9); in, is a very small constant, which makes the mathematical representation of the normal contact condition smoother and is conducive to the convergence of the calculation; It is an important parameter that controls the closeness between the regularized friction model and the Coulomb friction model. The smaller the closer.

[0031] Where: is the related quantity of relative sliding velocity between contact surfaces, is an auxiliary variable related to the friction contact process.

[0032] (3) Dynamic water pressure simulation When a structure vibrates, it will drive the surrounding water to move, and this part of the water can be added to the surface of the structure in the form of mass. However, dynamic water pressure is not equivalent to additional mass. Additional mass is only an approximate consideration of the effect of dynamic water pressure. Under dynamic conditions, water also has effects on stiffness and damping of the structure. In the seismic calculation of hydraulic structures, dynamic water pressure is considered in the form of additional mass in order to approximately reflect the effect of dynamic water pressure on the structure. Additional mass can be calculated using the Westergaard additional mass formula: (10); In the formula, is the reservoir water depth; is the water depth at the calculation point; is the water density.

[0033] In the present invention, a simulation preview of the structural properties of the dam under earthquake action under different possible operating water levels can be carried out to observe the influence of possible earthquake action on the structural form of the dam under possible operating water level conditions, and then a simulation preview of the structural properties of the dam under possible operating water level conditions can be carried out to study the overall stability of the dam and the dam foundation under possible earthquake action and possible operating water level conditions, analyze the rationality of the structural type, and provide a scientific basis for structural design.

[0034] like: The value of: Water level under common working conditions; The water level under extreme conditions, i.e. the highest and lowest water levels, can be compared with historical data.

[0035] (4) Structural damping simulation Rayleigh damping is used to characterize the total damping matrix of the system, that is, it is assumed that the damping matrix of the structure can be expressed as a linear combination of the mass matrix and the stiffness matrix: (11); , The value of is calculated using the following formula: ; ; Where: ——No. Damping ratio of the order vibration mode; ——No. The frequency of the order vibration mode.

[0036] The actual structural type, structural joints, backfill materials, different rock layers of the foundation (cover layer, soft rock, hard rock) and the contact surface between the dam and the foundation are simulated to establish an overall three-dimensional finite element model of the dam and the foundation.

[0037] Step 2: Operation conditions, operation loads and possible earthquake analysis (1) Operating conditions Normal water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Normal water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Design flood level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure + dynamic water pressure; Dead water level: dead weight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; (2) Load during operation Self-weight load: (12); In the formula, For structural quality; is the acceleration due to gravity, take 9.81m / s 2 .

[0038] Hydrostatic Pressure: (13); Where: is the density of water; is the acceleration due to gravity, take 9.81m / s 2 ; For water depth.

[0039] Seepage load: The three-dimensional finite element method is used to calculate the three-dimensional constant seepage field of the dam and foundation. When performing static and dynamic calculations of the dam, the seepage pressure at the bottom of the dam is integrated into the node force as the uplift pressure applied to the bottom of the dam structure. Figure 5 , Figure 6 shown.

[0040] (3) Earthquake effects Design basic earthquake acceleration DBE, generally the exceedance probability P within 50 years 50 is 0.10; Operational basic earthquake acceleration OBE; Maximum credible earthquake acceleration MCE, generally the probability of exceeding within 100 years P 100 is 0.01; Also consider: The probability of exceeding within 50 years is P 50 The earthquake action is 0.05 The probability of exceeding within 100 years is P 100 The earthquake action is 0.02 When the reservoir is empty, if earthquake effects need to be considered, the representative value of the design earthquake acceleration can be halved for earthquake-resistant design. The temporary conditions during the construction period may not be combined with earthquake effects. Typical earthquake actions in historical data The seismic protection level of various hydraulic structures shall be characterized by the design intensity of flat surface and the representative value of horizontal design earthquake peak acceleration, and shall be determined according to the following provisions: For hydraulic structures whose fortification levels are determined based on GB 18306 "China Seismic Parameter Zoning Map", for general projects, the zoning value of the seismic peak acceleration in the area where the site is located in the map should be taken, and after adjustment according to the site category, it should be used as the representative value of the design horizontal seismic peak acceleration, and the corresponding basic earthquake intensity should be used as the design intensity; for hydraulic structures whose engineering seismic fortification category is Class A, the design intensity should be increased by 1 degree on the basis of the basic intensity, and the representative value of the design horizontal seismic peak acceleration should be increased by 1 times accordingly.

[0041] For projects whose fortification is determined based on a special site seismic safety assessment, the probability level of the representative value of the horizontal design seismic peak acceleration of the bedrock of the building is flat. For the backwater and important drainage buildings of the project with seismic fortification category A, the probability of exceeding within 100 years should be P 100 is 0.02; for Class B non-water-blocking buildings, the probability of exceeding within 50 years should be P 50 0.05; for hydraulic structures other than Class A in the seismic fortification category, the probability of exceeding within 50 years should be P 50 It is 0.10, but should not be lower than the corresponding seismic horizontal acceleration zoning value on the zoning map.

[0042] For hydraulic structures with seismic fortification category A that are subject to special site seismic safety evaluation, in addition to seismic design according to the designed peak acceleration of seismic motion, a special demonstration should be conducted on the safety margin to prevent uncontrolled discharge of reservoir water when the site is subjected to the maximum credible earthquake, and a special seismic safety report based on it should be submitted. Among them, the representative value of the horizontal peak acceleration of the "maximum credible earthquake" should be calculated based on the seismic geological conditions of the site, according to the deterministic method or the probability of exceedance within 100 years P 100 The results were determined by the probability method with a probability of 0.01.

[0043] When the water-blocking structure is upgraded from level 2 to level 1 due to the dam height and earthquake geological conditions, in addition to the exceedance probability P within 50 years, 50 In addition to the seismic design based on the horizontal design ground motion peak acceleration of 0.10, the design should also be based on the probability of exceeding P within 100 years. 100 The peak acceleration of horizontal seismic motion is 0.05, and the safety margin to prevent uncontrolled discharge of reservoir water is specially demonstrated.

[0044] In the special report on seismic safety, the site-related design response spectrum should be determined according to the set earthquake corresponding to the horizontal design seismic peak acceleration, and the artificial simulated seismic acceleration time history should be generated based on it; for the strong nonlinear analysis of the seismic effects of the structure, the influence of the frequency non-stationarity of the seismic motion should be studied.

[0045] (4) Extreme weather conditions flood Floods can cause a sharp increase in the amount of water in the basin upstream of the dam, leading to a rapid rise in the reservoir water level. Excessively high water levels can increase the water pressure on the dam, which may cause changes in the stress state inside the dam structure.

[0046] At the same time, floods will increase the moisture content of the foundation, leading to increased uplift pressure.

[0047] Temperature drops A sudden drop in temperature will cause the surface temperature of the dam to drop rapidly, while the internal temperature will drop relatively slowly, resulting in a large temperature gradient inside the dam, which will cause shrinkage deformation of the concrete. Since the deformation of the surface and the interior is inconsistent, the surface concrete will be subjected to tensile stress. If the temperature stress exceeds the tensile strength of the concrete, cracks will appear on the surface of the dam.

[0048] The specific effects of extreme weather conditions on dams are analyzed based on forecast data.

[0049] Step 3: Analysis and evaluation of the overall stability of the dam-foundation under normal operating conditions (1) Analysis of overall deformation of dam Summarize the deformation of each part along the river, across the river and vertically, and analyze the deformation position and deformation of each part in each direction with the maximum deformation, such as Figures 9-11 shown.

[0050] (2) Analysis of foundation bearing capacity Analyze the interface pressure to determine whether it is less than the allowable bearing capacity.

[0051] (3) Overall stability assessment of dam-foundation Based on the overall deformation of the dam and the contact state of the dam-foundation interface, the overall stability of the dam-foundation is comprehensively evaluated.

[0052] Determine whether the overall deformation law of the dam-foundation is normal under normal operating conditions, whether the deformation value is controllable, whether serious uneven settlement occurs on both sides of the structural joint, whether the vertical compressive stress at the dam-foundation interface exceeds the allowable bearing capacity, and whether the dam produces shear sliding along the interface between the dam and the foundation, and then analyze the overall stability of the dam-foundation.

[0053] Step 4: Analysis and evaluation of the overall stability of the dam under earthquake action The nonlinear finite element time history analysis method is used to carry out the seismic response analysis of the dam and foundation, and the overall stability of the dam is evaluated based on the seismic response. This includes generating seismic time history, setting earthquake conditions, and analyzing and evaluating the overall stability of the dam.

[0054] In this embodiment, the calculated load combination is: normal operating conditions (self-weight + water weight + hydrostatic pressure + earth pressure + uplift pressure + arc gate load) + earthquake action. The earthquake takes into account three situations: earthquake motion along the river, earthquake motion across the river, and vertical earthquake motion.

[0055] (1) Earthquake time course According to the seismic motion selection and target response spectrum matching work, the seismic motion time history curve that can reflect the seismic characteristics of the engineering site is generated, such as Figure 7 As shown in the figure, the overall stability of the dam under earthquake action is analyzed.

[0056] (2) Earthquake situation Earthquake along the river: The propagation direction of the seismic wave is basically consistent with the flow direction of the river. Earthquake along the river may cause axial deformation of the structure, scour of the foundation, etc.

[0057] Cross-river earthquake: The propagation direction of seismic waves is roughly perpendicular to the flow direction of the river. Cross-river earthquakes may cause large displacement and stress in the structure in the horizontal direction, which may affect the stability of the dam body and the rock stability of the dam shoulder.

[0058] Vertical earthquake: Vertical earthquake refers to the vibration component of seismic waves in the vertical direction. Vertical earthquake may cause vertical vibration of the structure, increase in tension or pressure of components, etc.

[0059] (3) Analysis and evaluation of overall stability of dams and gates Analysis of dynamic displacement of dams and gates Take the key points on the dam and apron structures and the points with the maximum static settlement to analyze the reciprocating changes in the displacement of the dam and apron during an earthquake. By summarizing the displacements of various parts in various directions, analyze the displacement change rules of key points during an earthquake, and judge the dynamic stability of the dam from the displacement time history. The position of the key points in the displacement time history is shown in the figure. Figure 8 Shown Foundation bearing capacity analysis Determine whether the interface pressure exceeds the allowable bearing capacity, and determine whether the state of continuous reciprocating changes during the earthquake is in a bonding state, an open state, or a sliding state. If no through sliding area is formed, no sliding instability damage will occur along the bottom contact surface, that is, there will be no sliding state on the bottom contact surface at the end of the earthquake.

[0060] Dam-sluice foundation overall stability assessment.

[0061] During an earthquake, the displacement of the dam and the apron changes back and forth with the earthquake. After the earthquake, the displacement of the dam in various directions is summarized to determine whether the stress of the dam-foundation contact surface meets the bearing capacity requirements. During the earthquake, it is determined whether the dam-foundation contact surface is in a bonding state, or changes back and forth between the bonding state, the open state, and the sliding state. If only the dam foundation contact surface is in a sliding state at a certain moment, but no through sliding area is formed, the dam will not produce overall sliding instability damage. Based on the above, it is determined whether the overall stability of the dam is guaranteed.

[0062] The present invention constructs a three-dimensional finite element model of the dam, uses a three-dimensional nonlinear finite element method, calculates the deformation and stress of the dam under static conditions and earthquakes, analyzes whether the deformation and base stress of the dam meet the control standards, and analyzes and evaluates the bearing capacity of the foundation and the overall stability of the dam. The present invention takes into account different possible earthquake effects and different possible operating water level conditions, analyzes and evaluates the bearing capacity of the foundation and the overall stability of the dam from multiple angles and aspects, fills the gap beyond the general conditions considered by the existing technical solutions, and improves the complex and changeable condition system of the dam under earthquakes, so that the structural state simulation preview of the dam under earthquakes is closer to the actual real situation.

[0063] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A simulation preview method for the structural behavior of a dam under earthquake action, characterized in that: The following steps are involved: Step 1: Construct an overall three-dimensional finite element model of the dam and foundation to reflect the shape of the dam, engineering geological conditions, anti-seepage curtain, structural joints, and the interaction between the dam and foundation; Step 2: Analysis of operating conditions, operating loads, earthquake effects and extreme weather conditions; Step 3: Analysis and evaluation of the overall stability of the dam and foundation under normal operating conditions; Step 4: Analysis and evaluation of the overall stability of the dam under earthquake action: Use nonlinear finite element time-history analysis method to conduct seismic response analysis of the dam and foundation, and evaluate the overall stability of the dam based on the seismic response.

2. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 1 is characterized in that: In the step 1, the numerical analysis model of the overall three-dimensional finite element model of the dam and foundation includes a material constitutive model, a contact surface between the dam structure and the foundation, a structural joint simulation, a dynamic water pressure simulation, and a structural damping simulation.

3. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 2 is characterized in that: In the material constitutive model, the elastic-plastic damage model is used to simulate the dam concrete material; the Mohr-Coulomb elastic-plastic constitutive model is used to simulate the foundation cover layer and rock mass material. The expression of the Mohr-Coulomb yield criterion is: （1）； Where: For the cohesion of the material; is the internal friction angle of the material; are shear stress and normal stress respectively; The yield function is expressed as: （2）； Where: are the first and third principal stresses respectively; Formula (1) represents shear failure. For rock and concrete materials with low tensile strength, tensile cracks occur when the shear stress is far from reaching the shear strength. Therefore, the tensile strength criterion is increased, that is: （3）； Where: is the tensile strength of the material.

4. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 2 is characterized in that: The contact surface between the structure and foundation of the dam and the simulation of the structural joints are simulated using the constraint function contact algorithm to meet the following contact constraint conditions: The normal contact constraint is: （4）； Where: is the normal contact force between the contact surfaces, is the normal distance between the contact surfaces; ,and When , it indicates that the contact surface is open; when ,and When , it indicates that the contact surface is closed ; The tangential friction between the contact surfaces satisfies Coulomb's friction law, so the tangential contact force The size cannot exceed its limit ,Right now: （5）； Where: , are the components of the tangential contact force in the directions of the two coordinate axes respectively; Introducing a dimensionless variable , ; The relative sliding speed between the contact surfaces is , defined as: （6）； Where: is the tangential velocity of object A on the contact surface, is the tangential velocity of object B on the contact surface; The tangential friction contact condition is expressed as: （7）； when When , there is no relative slip between the contact surfaces. ;when When the relative slip occurs between the contact surfaces, the relative slip velocity between the contact surfaces is , its direction is Consistent direction; The constraint function contact algorithm used introduces the normal constraint function and friction constraint function To describe the above contact constraints, when When , the normal contact constraint condition described by equation (8) is satisfied; when When , the tangential contact constraint condition described by equation (9) is satisfied, and the constraint function and The expression is as follows: （8）； （9）； in, is a very small constant, which makes the mathematical representation of the normal contact condition smoother and is conducive to the convergence of the calculation; is a parameter that controls the closeness between the regularized friction model and the Coulomb friction model. The smaller, the closer; is the related quantity of relative sliding velocity between contact surfaces, is an auxiliary variable related to the friction contact process.

5. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 2 is characterized in that: The dynamic water pressure simulation is to consider the dynamic water pressure in the form of additional mass in the seismic calculation of hydraulic structures. The additional mass is calculated using the Westergaard additional mass formula, which is expressed as: （10）； In the formula, is the reservoir water depth, which is the water level under common working conditions or the water level under extreme working conditions; is the water depth at the calculation point; is the water density.

6. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 2 is characterized in that: The structural damping simulation adopts Rayleigh damping to characterize the total damping matrix of the system, that is, it is assumed that the damping matrix of the structure is expressed as a linear combination of the mass matrix and the stiffness matrix: （11）； in, , The value of is calculated using the following formula: ； ； Where: Respectively represent Damping ratio of the order vibration mode; Respectively represent The frequency of the order vibration mode.

7. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 1 is characterized in that: In step 2, the analysis of operating conditions, operating loads, earthquake effects and extreme weather conditions during operation includes the following: 1) Operation conditions include the following: normal Water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Normal water storage level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; Design flood level: deadweight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure + dynamic water pressure; Dead water level: dead weight + hydrostatic pressure + uplift pressure + sediment pressure + wave pressure; 2) The loads during operation include self-weight load, hydrostatic pressure and seepage load, which are as follows: a) Self-weight load: （12）； In the formula, For structural quality; is the acceleration due to gravity; b) Hydrostatic Pressure: （13）； Where: is the density of water; is the acceleration due to gravity; The depth of the reservoir water; c) Seepage load: The three-dimensional finite element method is used to calculate the three-dimensional constant seepage field of the dam and foundation. When performing static and dynamic calculations of the dam, the seepage pressure at the bottom of the dam is integrated into the node force as uplift pressure and applied to the bottom of the dam structure. 3) Earthquake effects include: Design basic earthquake acceleration DBE; Operation basic earthquake acceleration OBE; Maximum credible earthquake acceleration MCE; Also consider: a) Probability of exceeding within 50 years P 50 The earthquake action is 0.05; b) Probability of exceeding within 100 years P 100 The earthquake action is 0.02; c) When the reservoir is empty, if earthquake effects need to be considered, the representative value of the design earthquake acceleration shall be halved for seismic design; d) Short-term conditions during the construction period may not be combined with earthquake effects; e) Typical earthquake actions in historical data; The seismic protection level of various hydraulic structures is represented by the design intensity on flat surface and the representative value of the horizontal design seismic peak acceleration; 4) Extreme weather conditions include: a) Flood; b) The temperature drops suddenly.

8. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 1 is characterized in that: In the step 3, the overall stability analysis and assessment of the dam and foundation under normal operating conditions includes overall deformation analysis of the dam, foundation bearing capacity analysis and overall stability assessment of the dam and foundation, which are as follows: 1) Overall deformation analysis of the dam: Summarize the deformation of each part along the river, across the river and vertically, and analyze the deformation position and deformation of each part with the maximum deformation in each direction; 2) Foundation bearing capacity analysis: Analyze the interface pressure to determine whether it is less than the allowable bearing capacity; 3) Overall stability assessment of the dam and foundation: Based on the overall deformation of the dam and the contact state of the interface between the dam and the foundation, the overall stability of the dam and foundation is comprehensively assessed, specifically: Determine whether the overall deformation law of the dam-foundation is normal under normal operating conditions, whether the deformation value is controllable, whether serious uneven settlement occurs on both sides of the structural joint, whether the vertical compressive stress at the dam-foundation interface exceeds the allowable bearing capacity, and whether the dam produces shear sliding along the interface between the dam and the foundation, and then analyze the overall stability of the dam and foundation.

9. The method for simulation preview of the structural behavior of a dam under earthquake action according to claim 1, characterized in that: In step 4, a nonlinear finite element time-history analysis method is used to carry out seismic response analysis of the dam and foundation, and the overall stability of the dam is evaluated based on the seismic response, including: The calculated load combination is: normal operating condition + earthquake action The earthquake took into account three types of earthquake motion: earthquake motion along the river, earthquake motion across the river, and vertical earthquake motion, as follows: 1) Earthquake time course According to the seismic motion selection and target response spectrum matching work, a seismic motion time history curve that can reflect the seismic characteristics of the project site is generated, and then the overall stability of the dam under the earthquake is analyzed; 2) Earthquake situation ① Downstream earthquake: The propagation direction of the seismic wave is basically consistent with the flow direction of the river; ② Transverse river earthquake: The propagation direction of the seismic wave is roughly perpendicular to the flow direction of the river; ③ Vertical earthquake: Vertical earthquake refers to the vibration component of seismic waves in the vertical direction; 3) Analysis and evaluation of overall stability of dams and gates a) Analysis of dynamic displacement of dams Take the key points on the dam and apron structures and the points with the maximum static settlement to analyze the reciprocating changes in the displacement of the dam and apron during an earthquake. By summarizing the displacements of various parts in various directions, analyze the displacement change rules of key points during an earthquake, and judge the dynamic stability of the dam from the displacement time history. b) Foundation bearing capacity analysis Determine whether the interface pressure exceeds the allowable bearing capacity, and determine whether the state of the continuous reciprocating changes during the earthquake is in a bonding state, an open state, or a sliding state. If no through sliding area is formed, no sliding instability damage will occur along the bottom contact surface, that is, the bottom contact surface will not be in a sliding state when the earthquake ends; c) Overall stability assessment of dam and foundation During an earthquake, the displacements of the dam and the apron change with the action of the earthquake. After the earthquake, the displacements of the dam in various directions are summarized to determine whether the stress on the contact surface between the dam and the foundation meets the bearing capacity requirements. During the earthquake, it is determined whether the contact surface between the dam and the foundation is in a bonding state, or changes back and forth between a bonding state, an open state, and a sliding state. If only the contact surface of the dam foundation is in a sliding state at a certain moment, but no continuous sliding area is formed, the dam will not suffer from overall sliding instability damage. Based on the above, it is determined whether the overall stability of the dam is guaranteed.

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