Optimization design method for diversion engineering of extra-high core-wall rock-fill dam

Abstract

The invention relates to the technical field of water conservancy and hydropower engineering construction, discloses an optimal design method for a diversion project of an extra-high core wall rock-fill dam, and provides a scientific theoretical basis and technical support for reducing the investment of the diversion project, ensuring the flood safety of hydropower engineering construction and the like. The optimization design method comprises the following steps: S1, establishing a mathematical model for the optimization design of the diversion engineering of the extra-high core-wall rockfill dam; s2, building a flood-fighting water retaining elevation calculation model in the initial-middle stage of construction of the extra-high core-wall rockfill dam; s3, constructing a risk mathematical model of the construction flood control of the extra-high core-wall rockfill dam; s4, systematic analysis is conducted on the dam filling rising randomness, and distribution parameters of all random factors are determined; s5, parameter analysis is conducted on random factors of the construction flood process and the drainage capacity of the diversion tunnel, and distribution parameters of the random factors are determined; and S6, the deep optimization design of the flow guide engineering of the extra-high core wall rock-fill dam is carried out.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy and hydropower engineering construction, and in particular to an optimization design method for a diversion project of an ultra-high core wall rockfill dam. Background Art

[0002] A number of ultra-high core rockfill dams above 300m in Southwest China, such as Shuangjiangkou, Lianghekou, and Rumei, are under construction and in planning and design. Most of these ultra-high rockfill dams are built in the high mountain canyon areas of Southwest China. Their construction diversion generally adopts a tunnel diversion method in which the cofferdam is used to cut off the flow once and the foundation pit is constructed throughout the year. According to relevant specifications, the stage of using the upstream cofferdam to block water is the initial diversion stage; when the dam is filled beyond the cofferdam, the dam body is used to temporarily block water until the last batch of diversion buildings are closed, which is the mid-term diversion stage. The construction period of ultra-high core rockfill dams is long, the construction difficulty is high, the construction environment is harsh, the construction flood changes significantly, and the flood safety issues during the entire construction process are very prominent.

[0003] According to relevant engineering experience, the investment in diversion projects of ultra-high core rockfill dams accounts for a large proportion, mainly including diversion tunnels and upstream and downstream cofferdam projects. How to use scientific and reasonable optimization design methods to reduce the investment in diversion projects has always been an area of ​​focus for designers. However, the construction period of ultra-high core rockfill dams is long and the quality requirements are high. The construction process is affected by various uncertain factors. Its diversion system is a typical risk system. Once an overtopping event occurs, the harm to itself and the downstream is huge. In the process of optimizing the design of diversion projects, it is necessary to use risk theory-based methods to scientifically and reasonably consider the impact of these random factors.

[0004] In recent years, diversion optimization design technology has been applied in engineering projects. For example, Patent ZL201810833311.4 proposed a method for optimizing the size of diversion tunnels in high arch dams. However, this method is mainly aimed at the construction characteristics of high arch dams and is difficult to adapt to other dam types.

[0005] In summary, during the engineering planning and design stage, studying the design optimization method of ultra-high core rockfill dam diversion engineering based on risk analysis theory has important theoretical value and engineering application prospects. Summary of the invention

[0006] The technical problems to be solved by the present invention are:

[0007] An optimization design method for diversion engineering of ultra-high core rockfill dam is proposed, which provides a scientific theoretical basis and technical support for reducing the investment in diversion engineering and ensuring the safety of hydropower project construction during flood season.

[0008] The technical solution adopted by the present invention to solve the above technical problems is:

[0009] The optimization design method of the diversion project of the ultra-high core rockfill dam includes the following steps:

[0010] S1. Establish a mathematical model for the optimal design of diversion engineering of ultra-high core rockfill dam;

[0011] S2. Establish a calculation model for the flood retaining elevation of the super-high core rockfill dam during the initial and intermediate stages of construction;

[0012] S3. Construct a mathematical model for the risk of super-high core rockfill dam construction during flood season;

[0013] S4. Conduct a systematic analysis of the randomness of the dam filling rise and determine the distribution parameters of each random factor;

[0014] S5. Analyze the parameters of the random factors of the construction flood process and the discharge capacity of the diversion tunnel to determine the distribution parameters of each random factor;

[0015] S6. Conduct in-depth optimization design of the diversion project of the ultra-high core rockfill dam.

[0016] Furthermore, in step S1, the mathematical model for optimizing the design of the diversion project of the ultra-high core rockfill dam is established, including:

[0017] According to the principle of minimizing the total direct investment of diversion tunnel and cofferdam engineering, the mathematical model for the size optimization design of the diversion engineering of ultra-high core rockfill dam is:

[0018]

[0019] Among them, S T is the design parameter of the diversion tunnel, Z W is the design elevation of the upstream cofferdam, f(S T ,Z W ) is the objective function of the total investment of diversion project; H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through;

[0020] is the diversion risk rate in the initial construction period of the ultra-high core rockfill dam, T IB is the flood return period corresponding to the initial diversion standard;

[0021] is the initial diversion risk rate during the construction of the ultra-high core rockfill dam, T MB is the flood return period corresponding to the medium-term diversion standard.

[0022] Furthermore, in step S2, the establishment of a calculation model for the flood-proof water retaining elevation during the initial and intermediate stages of construction of an ultra-high core rockfill dam includes:

[0023] The diversion period from the initial to the middle stage of facility construction is t d Years, of which the initial diversion period is t c The mid-term diversion period is 1 year, which is the tth year of the mid-term diversion. d If the dam filling elevation exceeds the cofferdam elevation before the main flood season of that year, then the diversion t in the early and middle stages of construction is d In the year, the water retaining elevation Z of the core rockfill dam during the initial and intermediate flood seasons before the main flood season in the jth year dj The calculation model is:

[0024] where j = 1, 2, ..., t d

[0025] Among them, Z W Z is the initial flood retaining elevation, i.e. the elevation of the top of the upstream cofferdam; sj It is the water retaining elevation for the mid-term flood season.

[0026] Furthermore, in step S3, the risk mathematical model for super-high core rockfill dam construction during flood season is constructed, including:

[0027] The initial diversion risk of construction is defined as the probability that the highest flood level in the main flood season exceeds the elevation of the upstream cofferdam top within the initial diversion period of construction, which represents the ability of the upstream cofferdam to resist the construction flood process during the main flood season within the initial diversion period. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the initial diversion risk R of ultra-high core rockfill dam construction is established. W The mathematical model is:

[0028] R W =P(max(Z Hj (t))>Z W |[S T ,Z W ]), where j = 1, 2, ..., t c

[0029] Among them, Z Hj (t) is the dynamic change process of the water level of the reservoir in front of the dam for flood control in the jth year; S T is the design parameter of the diversion tunnel, Z W is the design elevation of the upstream cofferdam; P() is the probability calculation; [S T ,Z W ] is S T and Z W The relationship matrix of

[0030] The mid-term diversion risk of construction is defined as the probability that the highest flood level during the main flood season exceeds the flood retaining elevation of the dam within the mid-term diversion period of construction. It represents the ability of the temporary dam with fill rising above the cofferdam elevation during the mid-term diversion period to resist the construction flood process during the main flood season. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the mid-term diversion risk R of ultra-high core rockfill dam construction is established. D The mathematical model is:

[0031]

[0032] in, For the tth d Dynamic changes in water level of the reservoir in front of the dam for flood control in 2017.

[0033] Furthermore, in step S4, the randomness of the dam filling rise is systematically analyzed to determine the distribution parameters of each random factor, including:

[0034] The calculation model of the dam core wall filling elevation in the kth month of the initial and intermediate construction period

[0035] where k = 1, 2, ..., t d ×12

[0036] The daily average rise speed H of the core wall of the core rockfill dam vi and the dam filling suspension days index T si The impact of the dam filling suspension days index T si Follows normal distribution;

[0037] The average daily rise speed of the dam core wall is H vi It obeys the triangular distribution, and its probability density function is:

[0038]

[0039] Among them, h d is the lower limit, i.e. the slowest daily average rising speed; h m is the median value, i.e. the most likely daily average rising speed; h u is the upper limit, i.e. the fastest daily average rising speed.

[0040] Furthermore, in step S5, the parameter analysis of the random factors of the construction flood process and the discharge capacity of the diversion tunnel is performed to determine the distribution parameters of each random factor, including:

[0041] The random factors of the construction flood process and the discharge capacity of the diversion tunnel need to consider the randomness of the peak flow of the construction flood, the randomness of the water level-reservoir capacity relationship, and the randomness of the discharge capacity flow coefficient. The peak flow of the construction flood is set to satisfy the P-III distribution, and the reservoir capacity relationship coefficient and the discharge capacity coefficient are assumed to obey the triangular distribution.

[0042] Furthermore, in step S6, the in-depth optimization design of the diversion project of the ultra-high core rockfill dam includes:

[0043] S61. Conduct preliminary optimization of the design scheme for diversion engineering of super-high core rockfill dam construction;

[0044] S62: Risk assessment is performed on the preliminary optimal scheme. If the scheme meets the flood control requirements, the process proceeds to S63. Otherwise, the diversion project design is adjusted until the scheme meets the requirements, and then the process proceeds to S63.

[0045] S63, design optimization adjustment: give the step size of the optimization design, and set the optimization adjustment termination condition number ε, with the inequality condition 0≤|R W -R IB |≤εor0≤|R D -R MB |≤ε is used as the convergence condition of the deep optimization design to determine whether the iterative convergence is satisfied. If so, the process proceeds to S64. Otherwise, the design dimensions of the diversion project are continuously adjusted until the convergence condition is satisfied, and the process proceeds to S64.

[0046] S64. Output the optimized design results of the diversion project, and the calculation process ends.

[0047] Further, in step S61, the preliminary optimization of the design scheme for the construction diversion project of the ultra-high core rockfill dam specifically includes:

[0048] S611. Comprehensively consider the project scale, construction arrangement, interception difficulty and hydrological conditions, and combine engineering experience to make preliminary design of diversion project dimensions;

[0049] S612, Design cofferdam size: H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through;

[0050] S613. Analyze the trend of direct investment in diversion projects: The corresponding relationship matrix between the diversion hole size and the cofferdam size is determined by hydraulic method [S T ,Z W ], initially drafting several diversion engineering design schemes, and obtaining the variation law of direct investment of diversion engineering and cofferdam height and diversion tunnel size under the conditions of satisfying relevant design constraints;

[0051] S614. Based on the direct investment of diversion projects and the changing patterns of cofferdam height and diversion tunnel size, and taking the lowest direct investment of diversion projects as the criterion, the optimal diversion project design scheme is recommended.

[0052] Furthermore, in step S62, the risk identification of the preliminary optimal solution specifically includes:

[0053] Based on the optimal diversion engineering design scheme initially selected, the diversion risk rate is estimated to obtain R W , R D , and make risk identification according to the constraints of the optimization design mathematical model;

[0054] Among them, the methods for estimating the diversion risk rate include:

[0055] a. Input model-related calculation parameters;

[0056] b. Determine the total number of simulation calculations N required to meet the accuracy requirements C ;

[0057] c. Conduct a series of random simulations of flood retaining elevations during the initial and mid-term construction period:

[0058] ① Generate random numbers of the average daily rise speed of the dam core wall in each month during the construction period to simulate the average daily rise speed of the dam core wall;

[0059] ② Generate a random number of days for dam filling suspension in each month during the construction period, simulate the number of days for dam filling suspension in each month, and calculate the effective construction days in each month;

[0060] ③According to the simulated calculation of the dam filling elevation series, the total diversion years t in the early and middle stages of construction are obtained. d , the number of years of diversion period at the beginning of construction t c According to the simulation model, the annual flood water retaining elevation matrix [Z d1 , Z d2 ,……,Z td ];

[0061] d. Conduct random simulation of the highest flood level in front of the dam for flood control:

[0062] ①Generate diversion period t d Random numbers of construction flood peaks in each year to simulate the construction flood process;

[0063] ②Generate diversion period t d The random number of the reservoir capacity relationship coefficient in each year is used to simulate and fit the water level capacity relationship curve;

[0064] ③Generate diversion period t d The random number of the discharge capacity coefficient of each year in the year is used to simulate and fit the diversion and discharge capacity curve;

[0065] ④ Obtain the diversion period t through simulation of flood control calculation d Matrix of the highest flood levels in front of the dams in each year

[0066] e. Estimation of diversion risk rate based on random simulation results:

[0067] ① After N C Sampling simulation calculations and statistical analysis of the diversion period t in the early and middle stages of construction d The highest flood level in front of the dam in each year (max(Z Hj (t)), where j = 1, 2, …, t d The elevation of the dam before the main flood season is not more than Z dj , where j = 1, 2, ..., t d The number of times is recorded as N D , then the dynamic risk rate estimation formula of the initial-mid-term diversion of the ultra-high core rockfill dam is:

[0068]

[0069] ②After N C Sampling simulation calculations were performed to statistically analyze the initial diversion period t c The highest flood level in front of the dam during the year max(Z Hj (t)), where j = 1, 2, …, t c Exceeding the flood retaining elevation Z of the dam construction before the main flood season W The number of times is recorded as N W , then the initial diversion risk rate estimation formula of the ultra-high core rockfill dam is:

[0070]

[0071] ③After N C The sampling simulation calculation is performed to statistically analyze the tth time of the mid-term diversion period. d The highest flood level before the dam Exceeding the flood-proof elevation during the mid-term construction of the dam The number of times is recorded as N G , then the mid-term diversion risk rate estimation formula is:

[0072]

[0073] The beneficial effects of the present invention are:

[0074] (1) The present invention constructs a mathematical model for the optimal design of diversion tunnels for ultra-high core rockfill dams, which comprehensively considers the characteristic that the diversion tunnels of ultra-high core rockfill dams operate throughout the early and middle flood seasons of construction, and is suitable for the optimal design of diversion projects for ultra-high core rockfill dams.

[0075] (2) The calculation of the filling rise of the ultra-high core rockfill dam in the present invention fully considers the randomness of the dam filling rise, which is more in line with the objective reality of the project.

[0076] (3) The present invention adopts a risk analysis method based on probability theory in the optimization design of diversion projects, scientifically, reasonably and comprehensively considering the influence of dam filling rise, hydrology and hydraulic randomness, thereby improving the scientificity and accuracy of risk rate estimation.

[0077] (4) The optimized design scheme of the present invention can reduce the investment in diversion projects, shorten the construction period, and ensure the safety of the construction of ultra-high core wall rockfill dam projects during flood seasons, thus having good social and economic safety benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 The present invention is a flowchart of the optimization design method for the diversion project of the ultra-high core rockfill dam. DETAILED DESCRIPTION

[0079] The present invention aims to propose an optimization design method for diversion engineering of ultra-high core rockfill dam, so as to provide a scientific theoretical basis and technical support for reducing the investment in diversion engineering and ensuring the safety of hydropower engineering construction during flood season.

[0080] In specific implementation, the optimization design method process of the present invention is as follows Figure 1 As shown, it includes the following implementation steps:

[0081] S1. Establishment of mathematical model for optimization design of diversion project of ultra-high core rockfill dam:

[0082] 1. Risk identification method:

[0083] The extra-high core rockfill dam in the southwest canyon area has a large dam height and reservoir, and the operation of the diversion tunnel runs through the early and middle diversion stages of construction. The scale of different diversion tunnels and upstream cofferdams will affect the diversion risk rate. Assume S T is the design parameter of the diversion tunnel, and the design elevation of the upstream cofferdam is Z W , then the design parameters of the diversion project are mainly [S T ,Z W ].

[0084] The present invention uses the risk theory method to identify the risk of diversion tunnel engineering design schemes:

[0085] Assume that the flood return period corresponding to the initial diversion standard is T IB , the flood return period corresponding to the medium-term flood control standard is T MB , and at the same time converted to obtain the initial diversion design risk rate R IB and mid-term diversion design risk rate R MB , the calculation expression is:

[0086]

[0087] According to the requirements of the current regulations and specifications in my country, when the dam is filled beyond the cofferdam, the medium-term diversion standard is suddenly and significantly higher than the initial diversion standard at a certain point in time, which brings difficulties to the construction diversion planning and design and risk decision-making. In the planning and design stage, the diversion engineering design needs to meet the requirements of both the initial diversion and the medium-term diversion for flood control. Therefore, the risk judgment criteria for the diversion design scheme of the ultra-high core wall rockfill dam to meet the requirements of the specification are:

[0088]

[0089] 2. Design optimization mathematical model:

[0090] The ultra-high core rockfill dam in the canyon area basically adopts the method of year-round cut-off cofferdam and tunnel diversion. Usually, after the layout of the diversion tunnel is determined, the diversion engineering design scheme is compared and optimized. Therefore, according to the principle of minimizing the total direct investment of the diversion tunnel and cofferdam project, the mathematical model for the optimization design of the size of the diversion project of the ultra-high core rockfill dam is:

[0091]

[0092] Where: f(S T ,Z W ) is the objective function of the total investment of diversion project; H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through.

[0093] S2. Establish a calculation model for the flood retaining elevation of the super-high core rockfill dam during the initial and intermediate stages of construction:

[0094] In the engineering design stage, since the ultra-high core rockfill dam has extremely stringent requirements on filling quality, in order to reduce the uneven settlement of the dam body and ensure the filling quality of the ultra-high dam and facilitate construction, the dam generally requires the whole section to be leveled and balanced, and its rising speed is mainly controlled by the rising speed of the core wall. At the same time, without necessary special protection measures, water is not allowed to flow through the dam. When the dam filling elevation exceeds the cofferdam, the dam water retention is mainly controlled by the core wall elevation.

[0095] Therefore, the construction of the initial and middle diversion stages of the ultra-high core rockfill dam during the flood season is a process of transition from cofferdam water retention to dam water retention, which includes two stages:

[0096] ① The first stage: before the main flood season, the elevation of the core wall of the dam body does not exceed the elevation of the top of the upstream cofferdam. At this time, the upstream cofferdam is relied on to retain water during the flood season, and the water retaining elevation during the flood season is the elevation of the upstream cofferdam.

[0097] ②The second stage: before the main flood season, the elevation of the dam core wall exceeds the elevation of the upstream cofferdam crest. At this time, the dam is relied upon to retain water during the flood season, and the water-retaining elevation during the flood season is the filling elevation of the dam core wall.

[0098] According to domestic and foreign engineering experience and relevant specifications, the filling rise of the core wall rockfill dam is mainly affected by the daily average rising speed of the core wall and the number of days of suspension of dam filling. Therefore, during the project planning and design stage, the monthly average daily rising speed of the dam core wall and the number of days of suspension of dam filling are important technical indicators for construction planning and design. The diversion period from the initial to the middle stage of the facility construction is t d The calculation model for the dam core wall filling elevation in the kth month of the initial and middle stages of construction is:

[0099] where k = 1, 2, ..., t d ×12 (4)

[0100] Where, T i is the number of construction days in the ith month; T si is the number of days that work needs to be stopped in the i-th month; H vi is the average daily rising speed of the dam core wall in the i-th month.

[0101] Diversion during the early and mid-term construction d During the year, the filling elevation Z of the dam core wall before the main flood season of each year is extracted from the filling elevation series of each month. sn The calculation model of the series is:

[0102] Where n=1,2,…,t d (5)

[0103] In the formula, f D () Simplified functional expression of the core wall filling elevation series of the dam body before the main flood season.

[0104] According to the design experience of similar ultra-high dam projects, the mid-term diversion period is generally 1 to 2 years, and the dam body filling in the second year exceeds the design water level, which can basically meet the design requirements of flood control and flood prevention. Therefore, combined with the focus of this study, the mid-term diversion can only consider the flood prevention situation in the first year. Assume that the initial diversion period is t c Years, the mid-term diversion period is 1 year, then the tth d (t d =t c +1) is the year when the dam filling elevation exceeds the cofferdam elevation before the main flood season of that year. The diversion time t in the early and middle stages of construction is d In the year, the water retaining elevation Z of the core rockfill dam during the initial and intermediate flood seasons before the main flood season in the jth year dj The calculation model is:

[0105] where j = 1, 2, ..., td (6)

[0106] In the formula, Z W It is the initial flood retaining elevation, and also the elevation of the top of the upstream cofferdam; Z sj It is the water retaining elevation for the mid-term flood season.

[0107] S3. Constructing a mathematical model for the risk of super-high core rockfill dam construction during flood season:

[0108] The extra-high core rockfill dam has a large dam height and reservoir, and is mostly built in the high mountain canyon areas of the southwest. The construction period is long and the construction is difficult. The regulation and storage function of the construction flood process during the main flood season is obvious. Its construction diversion is subject to the comprehensive influence of random factors such as hydrology, hydraulics, and dam filling rise, which contains risks. Once the highest flood level during the main flood season during the construction diversion period exceeds the construction flood retaining elevation, it will cause huge economic and social losses to the cofferdam or dam body itself and the downstream. In addition, the extra-high core rockfill dam in the southwest canyon area has a large dam height and reservoir, and the operation of the diversion tunnel runs through the initial and middle diversion stages of construction. Different diversion tunnel diameters and upstream cofferdam scales will affect the diversion risk rate.

[0109] Let S T is the design parameter of the diversion tunnel, and the design elevation of the upstream cofferdam is Z W , then the design parameters of the diversion project are mainly [S T ,Z W Therefore, assuming that the highest flood level matrix of each year during the construction diversion period is [Z d1 , Z d2 ,……,Z td ]. Considering the randomness of the dam filling rise, there is a certain randomness in the time when the dam exceeds the cofferdam before the main flood season, so the diversion period t c and t d There is randomness.

[0110] The initial diversion risk of construction is defined as the probability that the highest flood level during the main flood season exceeds the elevation of the upstream cofferdam top within the initial diversion period of construction. It mainly represents the ability of the upstream cofferdam to resist the construction flood process during the main flood season within the initial diversion period. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the initial diversion risk R of ultra-high core rockfill dam construction is established. W The mathematical model is:

[0111] R W =P(max(Z Hj (t))>Z W |[S T ,Z W ]), where j = 1, 2, ..., t c (7)

[0112] In the formula, Z Hj(t) is the dynamic change process of the water level of the reservoir in front of the dam during flood control in the jth year.

[0113] The mid-term diversion risk of construction is defined as the probability that the highest flood level during the main flood season exceeds the flood retaining elevation of the dam during the mid-term diversion period. It mainly represents the ability of the temporary dam with fill rising above the cofferdam elevation during the mid-term diversion period to resist the construction flood process during the main flood season. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the mid-term diversion risk R of ultra-high core rockfill dam construction is established. D The mathematical model is:

[0114]

[0115] S4. Conduct a systematic analysis of the randomness of the dam filling rise and determine the distribution parameters of each random factor:

[0116] The construction of the super-high core rockfill dam is affected by many complex factors such as site conditions, soil characteristics, construction management, construction machinery, material field mining, transportation, rainfall, temperature, etc. The average daily rise speed of the core wall of the dam in each month and the number of days of suspension of dam filling are obviously random. According to relevant research, the number of days of suspension of dam filling in each month is T si A normal distribution can be assumed.

[0117] In addition, according to the experience of similar projects at home and abroad and the statistical data of dam filling, under the necessary constraints, the number of daily filling layers of the dam core wall in each month generally varies within a certain range. In the engineering design stage, considering the characteristics that the daily average filling rise speed of the dam core wall in each month varies within a certain range, there is a slowest daily average rise speed, a fastest daily average rise speed, and a most likely daily average rise speed, indicating that its random characteristics are relatively close to the characteristics of triangular distribution. The present invention assumes that the daily average rise speed of the dam core wall in the i-th month H vi It obeys the triangular distribution, and its probability density function is:

[0118]

[0119] In the formula, h d is the lower limit, i.e. the slowest daily average ascent speed, also used as the daily minimum control ascent speed; h m is the median value, i.e. the most likely daily average rising speed; h u is the upper limit, i.e. the fastest daily average rising speed.

[0120] S5. Perform parameter analysis on the random factors of the construction flood process and the discharge capacity of the diversion tunnel to determine the distribution parameters of each random factor:

[0121] Hydrological and hydraulic random factors mainly consider the randomness of construction flood peak flow, the randomness of water level-reservoir relationship, and the randomness of discharge capacity flow coefficient. The flood process in the main flood season in the southwestern mountainous area is characterized by steep rise and fall. The construction flood process mainly considers the randomness of the construction flood peak. According to the characteristics of my country's floods, the P-III distribution can better describe its randomness.

[0122] In addition, based on similar engineering experience and related research results, the reservoir capacity relationship coefficient and discharge capacity coefficient are assumed to obey a triangular distribution.

[0123] S6. Conduct in-depth optimization design of diversion project for ultra-high core rockfill dam:

[0124] This step is to carry out in-depth optimization design of the diversion project of the ultra-high core rockfill dam. The specific implementation steps are as follows:

[0125] S61. Conduct preliminary optimization of the design scheme for diversion engineering of super-high core rockfill dam construction;

[0126] The optimization process is as follows:

[0127] a. Comprehensively consider the project scale, construction arrangement, interception difficulty and hydrological conditions, and combine engineering experience to make preliminary design of diversion project dimensions;

[0128] b. Design cofferdam size: H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through;

[0129] c. Analyze the trend of direct investment in diversion projects: The size of diversion tunnel and cofferdam is determined by hydraulic method, and the corresponding relationship matrix [S T ,Z W ], initially drafting several diversion engineering design schemes, and obtaining the variation law of direct investment of diversion engineering and cofferdam height and diversion tunnel size under the conditions of satisfying relevant design constraints;

[0130] d. Based on the changing patterns of direct investment in diversion projects, cofferdam height and diversion hole size, and taking the lowest direct investment in diversion projects as the criterion, the optimal diversion project design scheme is recommended.

[0131] S62: Risk assessment is performed on the preliminary optimal scheme. If the scheme meets the flood control requirements, the process proceeds to S63. Otherwise, the diversion project design is adjusted until the scheme meets the requirements, and then the process proceeds to S63.

[0132] In this step, based on the optimal diversion engineering design scheme initially selected, the diversion risk rate is estimated to obtain R W , R D, and make risk identification according to the constraints of the optimization design mathematical model;

[0133] Among them, the methods for estimating the diversion risk rate include:

[0134] a. Input model-related calculation parameters;

[0135] b. Determine the total number of simulation calculations N required to meet the accuracy requirements C ;

[0136] c. Conduct a series of random simulations of flood retaining elevations during the initial and mid-term construction period:

[0137] ① Generate random numbers of the average daily rising speed of the dam core wall in each month during the construction period to simulate the average daily rising speed of the dam core wall;

[0138] ② Generate a random number of days for dam filling suspension in each month during the construction period, simulate the number of days for dam filling suspension in each month, and calculate the effective construction days in each month;

[0139] ③According to the simulated calculation of the dam filling elevation series, the total diversion years t in the early and middle stages of construction are obtained. d , the number of years of diversion period at the beginning of construction t c According to the simulation model, the annual flood water retaining elevation matrix [Z d1 , Z d2 ,……,Z td ];

[0140] d. Conduct random simulation of the highest flood level in front of the dam for flood control:

[0141] ①Generate diversion period t d Random numbers of construction flood peaks in each year to simulate the construction flood process;

[0142] ②Generate diversion period t d The random number of the reservoir capacity relationship coefficient in each year is used to simulate and fit the water level capacity relationship curve;

[0143] ③Generate diversion period t d The random number of the discharge capacity coefficient of each year in the year is used to simulate and fit the diversion and discharge capacity curve;

[0144] ④ Obtain the diversion period t through simulation of flood control calculation d Matrix of the highest flood levels in front of the dams in each year

[0145] e. Estimation of diversion risk rate based on random simulation results:

[0146] ① After N C Sampling simulation calculations and statistical analysis of the diversion period t in the early and middle stages of constructiond The highest flood level in front of the dam in each year (max(Z Hj (t)), where j = 1, 2, …, t d The elevation of the dam before the main flood season is not more than Z dj , where j = 1, 2, ..., t d The number of times is recorded as N D , then the dynamic risk rate estimation formula of the initial-mid-term diversion of the ultra-high core rockfill dam is:

[0147]

[0148] ②After N C Sampling simulation calculations were performed to statistically analyze the initial diversion period t c The highest flood level in front of the dam during the year max(Z Hj (t)), where j = 1, 2, …, t c Exceeding the flood-proof water retaining elevation Z of the dam construction before the main flood season W The number of times is recorded as N W , then the initial diversion risk rate estimation formula of the ultra-high core rockfill dam is:

[0149]

[0150] ③After N C The sampling simulation calculation is performed to statistically analyze the tth time of the mid-term diversion period. d The highest flood level before the dam Exceeding the flood-proof elevation during the mid-term construction of the dam The number of times is recorded as N G , then the mid-term diversion risk rate estimation formula is:

[0151]

[0152] S63, design optimization adjustment: Given the step size of the optimization design, and set the optimization adjustment termination condition number ε, which is a very small positive number, based on the inequality condition 0≤|R W -R IB |≤εor0≤|R D -R MB |≤ε is used as the convergence condition of the deep optimization design to determine whether the iterative convergence is satisfied. If so, the process proceeds to S64. Otherwise, the design dimensions of the diversion project are continuously adjusted until the convergence condition is satisfied, and the process proceeds to S64.

[0153] S64. Output the optimized design results of the diversion project, and the calculation process ends.

[0154] Example:

[0155] Taking the implementation of the SJK Hydropower Station, a controlling reservoir in the upper reaches of the Dadu River Basin in China, as an example, the barrage dam is a core wall rockfill dam with a height of 315.00m, which is currently the highest dam in the world. The project is a first-class large (1) type project, and the hub project consists of a barrage dam, flood discharge structures, and a water diversion and power generation system. The valley slope of this project is steep and the bedrock is exposed. The project adopts a tunnel diversion method in which the cofferdam is used to cut off the flow once and the foundation pit is constructed throughout the year. According to the construction diversion plan, the initial diversion tunnel will operate throughout the initial to mid-term diversion stages of construction, and the mid-term diversion period is considered to be 1 year for analysis. According to the relevant specifications, the initial diversion standard of this project adopts the 20-year flood standard, and the design flow is 4790m 3 / s; the medium-term diversion standard adopts the 100-year flood standard, and the design flow is 5300m 3 / s.

[0156] Conduct in-depth optimization design of the diversion project of the ultra-high core rockfill dam. The specific implementation steps are as follows:

[0157] (1) Preliminary optimization of diversion engineering design scheme:

[0158] According to the hub layout, topographic and geological conditions, based on the experience of domestic cofferdam filling projects, combined with the current construction level, considering that the upstream cofferdam needs to meet the requirements of completion within a dry season, the upper limit of the upstream cofferdam height is 70m, the lower limit is 50m, and the minimum hole width required for construction and transportation vehicles is 2.5m. Under the standard diversion conditions of once in 20 years, the hydraulic method is used to establish the relationship between the design scale of the diversion tunnel and the investment of the diversion project corresponding to different upstream cofferdam heights as shown in Table 1.

[0159] Table 1 Design parameters of diversion project

[0160] project Diversion tunnel section <![CDATA[Diversion tunnel area / m 2 > Cofferdam top elevation / m Cofferdam height / m Civil construction investment of diversion project / 10,000 yuan Solution 1 14×17.2 224.47 2322 70 41422 Solution 2 14×18.0 235.67 2317 65 42666 Solution 3 14×18.9 248.27 2312 60 44065 Solution 4 15×18.4 258.19 2307 55 44828 Solution 5 16×18.2 271.93 2302 50 46056

[0161] According to the changing rules, taking the lowest direct investment in diversion engineering as the optimization criterion, the optimal diversion engineering design scheme 1 is preliminarily selected.

[0162] (2) According to the dam construction plan, carry out random parameter analysis of dam filling rise:

[0163] According to the SJK project dam construction plan, the foundation concrete will be poured from December of the fourth year to January of the fifth year, the foundation consolidation grouting construction will be carried out in February, and the dam filling construction will begin in March.

[0164] The SJK project dam is 315m high, and the dam filling quality requirements are extremely high. In order to ensure the quality of the dam filling, the design requires that the entire section of the dam be filled and raised flat. According to the research results of dam construction planning and combined with the experience of similar projects, under various relevant constraints, the number of daily filling layers of the dam core wall material is about 0.5 to 1.5 layers, and the daily average rising speed is about 0.1 to 0.3 m / d. The daily average rising speed given by the design is 0.21 m / d. Considering that the daily average rising speed of the dam core wall follows a triangular distribution, its distribution parameters are h d =0.1m / d (lower limit), h m =0.21m / d (median), h u =0.3m / d (upper limit).

[0165] According to the analysis of the effective construction days for the gravel-soil core wall filling of the dam, the influence of natural conditions such as rainfall and temperature is taken into account, and appropriate suspension standards are formulated in combination with the natural conditions of the construction area. Considering that the dam body filling adopts the method of daytime construction and night suspension in December to February in winter, there is no rainfall from November to March, and from June to September, the rainy season is appropriately reduced by 0.6 based on relevant engineering experience. The normal distribution parameters of the effective construction days and suspension days in each month (this project mainly considers the influence of rainfall) are shown in Table 2.

[0166] Table 2 Construction time parameters

[0167] project January February March April May June July August September October November December <![CDATA[T i ]]> 12 6 31 30 31 30 31 31 30 31 30 15 <![CDATA[T si ]]> 0 0 0 N(1.4,0.5) N(3.8,0.5) N(6.4,1.3) N(5.7,1.2) N(4.8,0.5) N(5.5,1.5) N(2,0.5) 0 0

[0168] (3) Conduct hydrological and hydraulic random parameter analysis:

[0169] ① Hydrological random parameters:

[0170] Based on the measured annual maximum flow series of the hydrological station, the investigated annual historical floods are added to form a discontinuous series for frequency calculation. The empirical frequencies of historical floods and measured series are calculated according to the expectation formula, the moment method is used to calculate the initial estimated parameters, and the hydrological random parameter is determined as μ by the eye estimate fit line. Q =2540m 3 / s,C v =0.33,C s / C v =5.0.

[0171] ②Hydraulic random parameters:

[0172] The discharge capacity coefficient of the initial diversion and discharge building follows a triangular distribution, generally ranging from 0.97 to 1.05. Based on the experience of similar projects, the distribution parameters are 0.97 (lower limit), 1.00 (median value), and 1.05 (upper limit). Considering that the water level-reservoir capacity relationship coefficient of this project follows a triangular distribution, the distribution parameters are 0.99 (lower limit), 1.00 (median value), and 1.01 (upper limit).

[0173] (4) Risk assessment of the preliminary optimization plan:

[0174] Taking into account the random factors of hydrology, hydraulics and dam filling rise, combined with the random parameter values ​​of this project, the number of simulations was set at 100,000 times. According to the preliminary optimized diversion project design scheme, the corresponding diversion risks in the early and middle stages of construction were obtained, and the risk identification results are shown in Table 3.

[0175] Table 3 Results of diversion risk rate under the condition of randomness of dam filling rise

[0176] project Section(m×m) Cofferdam elevation / m <![CDATA[R W ]]> <![CDATA[R D ]]> Initial risk identification IMN risk assessment Scheme 1 (preliminary optimization) 14×17.2 2322.0 1.666％ 0.582％ satisfy satisfy

[0177] Based on the above analysis, the optimal diversion engineering design scheme preliminarily selected for this project meets the risk identification requirements and can be further optimized.

[0178] (5) Design optimization and adjustment:

[0179] Since this project is located in a high mountain canyon area, the diversion tunnel project accounts for a large proportion of the direct investment, so it is preferred to dynamically optimize and adjust the diversion tunnel size with a step size of 0.1m.

[0180] Given the optimization termination condition data ε is 0.05%, comprehensive consideration of the hydrological, hydraulic, and dam filling rise random factors, combined with the random parameter values ​​of this project, the number of simulations is 100,000 times. Based on the preliminary optimal diversion engineering design scheme, the diversion tunnel diameter is continuously optimized until the optimal diversion engineering design scheme is obtained. The design optimization process is shown in Table 4.

[0181] Table 4. Diversion tunnel optimization design process table

[0182] Optimization times Section(m×m) Initial guide height / m <![CDATA[R W ]]> <![CDATA[R D ]]> Initial risk identification IMN risk assessment 1 14×17.2 2322.0 1.666％ 0.582％ satisfy satisfy 2 14×17.1 2322.0 1.752％ 0.588％ satisfy satisfy 3 14×17.0 2322.0 1.812％ 0.613％ satisfy satisfy 4 14×16.9 2322.0 1.887％ 0.649％ satisfy satisfy 5 14×16.8 (final selection) 2322.0 1.954％ 0.688％ satisfy satisfy 6 14×16.7 2322.0 2.046％ 0.677％ Dissatisfied satisfy

[0183] (6) Output the optimization design results of diversion project:

[0184] According to the diversion tunnel optimization design adjustment process, the final result of deep optimization is a diversion tunnel size of 14m×16.8m and a cofferdam design elevation of 2322m. Compared with the preliminary diversion engineering design scheme, the final optimal design scheme further saves about 6.2545 million yuan in engineering investment, with significant economic benefits.

[0185] Finally, it should be noted that the above embodiments are only preferred implementations and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, several modifications, equivalent replacements, improvements, etc. can be made without departing from the scope of the present invention and the scope of protection of the claims, and all of these should be included in the protection scope of the present invention.

Claims

1. Optimization design method for the diversion project of an extra-high core wall rockfill dam, characterized in that, it includes the following steps: S1. Establish a mathematical model for the optimization design of the diversion project of an extra-high core wall rockfill dam; S2. Establish a calculation model for the flood control water retaining elevation during the initial to mid-stage of the construction of an extra-high core wall rockfill dam; S3. Construct a risk mathematical model for flood control during the construction of an extra-high core wall rockfill dam; S4. Conduct a systematic analysis of the randomness of the dam filling and rising, and determine the distribution parameters of each random factor; S5. Conduct a parameter analysis of the random factors such as the construction flood process and the discharge capacity of the diversion tunnel, and determine the distribution parameters of each random factor; S6. Conduct a deep optimization design of the diversion project of an extra-high core wall rockfill dam.

2. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 1, characterized in that, in step S1, the establishment of the mathematical model for the optimization design of the diversion project of an extra-high core wall rockfill dam includes: According to the principle of minimizing the total direct investment of the diversion tunnel and the cofferdam project, the mathematical model for the optimization design of the dimensions of the diversion project of an extra-high core wall rockfill dam is: Among them, S T is the design parameter of the diversion tunnel, Z W is the design elevation of the upstream cofferdam, f(S T ,Z W ) is the objective function of the total investment of diversion project; H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through; is the diversion risk rate in the initial construction period of the ultra-high core rockfill dam, T IB is the flood return period corresponding to the initial diversion standard; is the initial diversion risk rate during the construction of the ultra-high core rockfill dam, T MB is the flood return period corresponding to the medium-term diversion standard.

3. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 2, characterized in that, in step S2, the establishment of the calculation model for the flood control water retaining elevation during the initial to mid-stage of the construction of an extra-high core wall rockfill dam includes: The diversion period from the initial to the middle stage of facility construction is t d Years, of which the initial diversion period is t c The mid-term diversion period is 1 year, which is the tth year of the mid-term diversion. d If the dam filling elevation exceeds the cofferdam elevation before the main flood season of that year, then the diversion t in the early and middle stages of construction is d In the year, the water retaining elevation Z of the core rockfill dam during the initial and intermediate flood seasons before the main flood season in the jth year dj The calculation model is: where j = 1, 2, ..., t d Among them, Z W Z is the initial flood retaining elevation, i.e. the elevation of the top of the upstream cofferdam; sj It is the water retaining elevation for the mid-term flood season.

4. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 2, characterized in that, in step S3, the construction of the risk mathematical model for flood control during the construction of an extra-high core wall rockfill dam includes: The initial diversion risk of construction is defined as the probability that the highest flood level in the main flood season exceeds the elevation of the upstream cofferdam top within the initial diversion period of construction, which represents the ability of the upstream cofferdam to resist the construction flood process during the main flood season within the initial diversion period. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the initial diversion risk R of ultra-high core rockfill dam construction is established. W The mathematical model is: R W = P(max(Z Hj (t)) > Z W |[S T , Z W ), where j = 1, 2, …, t c Among them, Z Hj (t) is the dynamic change process of the water level of the reservoir in front of the dam for flood control in the jth year; S T is the design parameter of the diversion tunnel, Z W is the design elevation of the upstream cofferdam; P() is the probability calculation; [S T ,Z W ] is S T and Z W The relationship matrix of The mid-term diversion risk of construction is defined as the probability that the highest flood level during the main flood season exceeds the flood retaining elevation of the dam within the mid-term diversion period of construction. It represents the ability of the temporary dam with fill rising above the cofferdam elevation during the mid-term diversion period to resist the construction flood process during the main flood season. Taking into account the randomness of hydrology, hydraulics, and dam filling rise, the mid-term diversion risk R of ultra-high core rockfill dam construction is established. D The mathematical model is: in, For the tth d Dynamic changes in water level of the reservoir in front of the dam for flood control in 2017.

5. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 2, characterized in that, in step S4, the systematic analysis of the randomness of the dam filling and rising and the determination of the distribution parameters of each random factor include: According to the calculation model of the elevation of the core wall filling of the dam in the k-th month during the initial to mid-stage of the construction where k = 1, 2, ..., t d ×12 The daily average rise speed H of the core wall of the core rockfill dam vi and the dam filling suspension days index T si The impact of the dam filling suspension days index T si Follows normal distribution; The average daily rise speed of the dam core wall is H vi It obeys the triangular distribution, and its probability density function is: Among them, h d is the lower limit, i.e. the slowest daily average rising speed; h m is the median value, i.e. the most likely daily average rising speed; h u is the upper limit, i.e. the fastest daily average rising speed.

6. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 1, characterized in that, in step S5, the parameter analysis of the random factors such as the construction flood process and the discharge capacity of the diversion tunnel, and the determination of the distribution parameters of each random factor include: For the random factors of the construction flood process and the discharge capacity of the diversion tunnel, the randomness of the peak flood flow of the construction flood, the randomness of the water level-storage relationship, and the randomness of the discharge coefficient of the discharge capacity need to be considered. It is assumed that the peak flood flow of the construction flood satisfies the P-III type distribution, and both the reservoir storage relationship coefficient and the discharge capacity coefficient are assumed to follow the triangular distribution.

7. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 2, characterized in that, in step S6, the conduct of the deep optimization design of the diversion project of an extra-high core wall rockfill dam includes: S61. Conduct a preliminary optimization of the design scheme for the construction diversion project of an extra-high core wall rockfill dam; S62. Conduct a risk discrimination on the preliminary optimized scheme. If it meets the flood control and flood season requirements, enter S63; otherwise, adjust the diversion project design until the design scheme meets the requirements, and then enter S63; S63, design optimization adjustment: give the step size of the optimization design, and set the optimization adjustment termination condition number ε, with the inequality condition 0≤|R W -R IB |≤εor0≤|R D -R MB |≤ε is used as the convergence condition of the deep optimization design to determine whether the iterative convergence is satisfied. If so, the process proceeds to S64. Otherwise, the design dimensions of the diversion project are continuously adjusted until the convergence condition is satisfied, and the process proceeds to S64. S64. Output the optimized design results of the diversion project, and the calculation process ends.

8. The optimization design method for the diversion project of an extra-high core wall rockfill dam according to claim 7, characterized in that, In step S61, the preliminary optimization of the design scheme for the diversion project for the ultra-high core rockfill dam construction specifically includes: S611. Comprehensively consider the project scale, construction arrangement, interception difficulty and hydrological conditions, and combine engineering experience to make preliminary design of diversion project dimensions; S612, Design cofferdam size: H max The maximum height of the upstream cofferdam that can be completed in a dry season or the maximum height under anti-seepage requirements; B min The minimum hole width required for construction and transportation vehicles to pass through; S613. Analyze the trend of direct investment in diversion projects: The corresponding relationship matrix between the diversion hole size and the cofferdam size is determined by hydraulic method [S T ,Z W ], initially drafting several diversion engineering design schemes, and obtaining the variation law of direct investment of diversion engineering and cofferdam height and diversion tunnel size under the conditions of satisfying relevant design constraints; S614. Based on the direct investment of diversion projects and the changing patterns of cofferdam height and diversion tunnel size, and taking the lowest direct investment of diversion projects as the criterion, the optimal diversion project design scheme is recommended.

9. The method for optimizing the design of diversion engineering for a super-high core rockfill dam according to claim 7, It is characterized in that In step S62, the risk identification of the preliminary optimal solution specifically includes: Based on the optimal diversion engineering design scheme initially selected, the diversion risk rate is estimated to obtain R W , R D , and make risk identification according to the constraints of the optimization design mathematical model; Among them, the methods for estimating the diversion risk rate include: a. Input model-related calculation parameters; b. Determine the total number of simulation calculations N required to meet the accuracy requirements C ; c. Conduct a series of random simulations of flood retaining elevations during the initial and mid-term construction period: ① Generate random numbers of the average daily rise speed of the dam core wall in each month during the construction period to simulate the average daily rise speed of the dam core wall; ② Generate a random number of days for dam filling suspension in each month during the construction period, simulate the number of days for dam filling suspension in each month, and calculate the effective construction days in each month; ③According to the simulated calculation of the dam filling elevation series, the total diversion years t in the early and middle stages of construction are obtained. d , the number of years of diversion period at the beginning of construction t c According to the simulation model, the annual flood water retaining elevation matrix [Z d1 , Z d2 ,……,Z td ]; d. Conduct random simulation of the highest flood level in front of the dam for flood control: ①Generate diversion period t d Random numbers of construction flood peaks in each year to simulate the construction flood process; ②Generate diversion period t d The random number of the reservoir capacity relationship coefficient in each year is used to simulate and fit the water level capacity relationship curve; ③Generate diversion period t d The random number of the discharge capacity coefficient of each year in the year is used to simulate and fit the diversion and discharge capacity curve; ④ Obtain the diversion period t through simulation of flood control calculation d Matrix of the highest flood levels in front of the dams in each year e. Estimation of diversion risk rate based on random simulation results: ① After N C Sampling simulation calculations and statistical analysis of the diversion period t in the early and middle stages of construction d The highest flood level in front of the dam in each year (max(Z Hj (t)), where j = 1, 2, …, t d The elevation of the dam before the main flood season is not more than Z dj , where j = 1, 2, ..., t d The number of times is recorded as N D ; The dynamic risk rate estimation formula of the initial-mid-term diversion of the ultra-high core rockfill dam is: ②After N C Sampling simulation calculations were performed to statistically analyze the initial diversion period t c The highest flood level in front of the dam during the year max(Z Hj (t)), where j = 1, 2, …, t c Exceeding the flood retaining elevation Z of the dam construction before the main flood season W The number of times is recorded as N W , then the initial diversion risk rate estimation formula of the ultra-high core rockfill dam is: ③After N C The sampling simulation calculation is performed to statistically analyze the tth time of the mid-term diversion period. d The highest flood level before the dam Exceeding the flood-proof elevation during the mid-term construction of the dam The number of times is recorded as N G , then the mid-term diversion risk rate estimation formula is:

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