CN117973163B - Dam flood discharge energy dissipation structure safety risk assessment method based on Bayesian network - Google Patents
Dam flood discharge energy dissipation structure safety risk assessment method based on Bayesian network Download PDFInfo
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Abstract
The invention discloses a dam flood discharge energy dissipation structure safety risk assessment method based on a Bayesian network, which comprises the steps of constructing a finite element simulation model of a dam and a Bayesian network of the dam flood discharge energy dissipation structure; searching a damage path in the finite element simulation model by adopting a flood discharge energy dissipation structure damage criterion; calculating the damage probability p o of each structural damage mode by adopting a Monte Carlo method according to the risk agent model, the mechanical parameters of the dam and foundation materials and the hydraulic parameters of the overflow surface; calculating the structural system damage probability p α of the flood discharge energy dissipation structure; when any damaged path o is assumed to be absent, calculating damage probability of flood discharge energy dissipation structure when disaster factors of damaged path o are not damaged based on the rest damaged paths and Bayesian network; According to p α andCalculating the importance of disaster factors of the damaged path o; and selecting a failure path corresponding to the disaster causing factor with the highest importance as a main control path for destroying the flood discharging and energy dissipating structure.
Description
Technical Field
The invention relates to a dam risk assessment technology, in particular to a dam flood discharge energy dissipation structure safety risk assessment method based on a Bayesian network.
Background
With the deep advancement of hydropower development in China, a large number of high concrete dams have been put into construction and operation, such as a Dragon beach gravity dam (dam height 216.5 m), a land gravity dam (dam height 168 m), a brocade primary arch dam (dam height 305 m) and a white crane beach arch dam (dam height 289 m). The high dam junction dam has large high-warehouse, large flood discharge flow, high water head, high flow speed, large power and long duration, and the phenomenon of damage to the flood discharge energy dissipation structure caused by erosion of high-speed water flow is frequent, so that the normal operation and long-term service safety of the dam junction engineering are seriously affected.
The flood discharge and energy dissipation structure of the high concrete dam generally comprises a dam body water discharge hole, a flood discharge hole, a stilling pool/plunge pool and the like. The flood discharge energy dissipation structure is influenced by multiple factors such as earthquake, temperature, wind, turbulent water flow and the like to generate erosion, strength and the like. At present, the safety evaluation of the concrete dam flood discharge energy dissipation structure system in engineering is still limited to the deterministic analysis of a single component, so that the accuracy of the analysis and evaluation is poor, but the research of the safety risk analysis method of the multi-path multi-mode flood discharge energy dissipation structure system has not been reported yet. Therefore, how to reasonably evaluate the safety risk of the flood discharge energy dissipation structure system, identify the safety risk main control path and key factors, and have important theoretical significance and application value for dam design, construction and operation safety.
Disclosure of Invention
Aiming at the defects in the prior art, the dam flood discharge energy dissipation structure safety risk assessment method based on the Bayesian network solves the problem that the accuracy of dam risk assessment by adopting single construction is low in the prior art.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
The dam flood discharge energy dissipation structure safety risk assessment method based on the Bayesian network comprises the following steps:
S1, constructing a finite element simulation model of a dam, and constructing a safety risk Bayesian network of a dam flood discharge energy dissipation structure according to a damage mode of the dam and a reason for causing the damage mode;
s2, searching for damage paths of different failure modes in the finite element simulation model by adopting damage criteria corresponding to the different failure modes according to the safety risk Bayesian network;
S3, calculating the damage probability p o of each structural damage mode by adopting a Monte Carlo method according to the risk agent model of each damage mode, the mechanical parameters of the dam and foundation materials and the hydraulic parameters of the overflow surface;
s4, calculating the structural system damage probability p α of the flood discharge energy dissipation structure according to the damage probability of all the structural damage modes and the safety risk Bayesian network;
s5, when any damaged path o is assumed to be absent, calculating damage probability of flood discharge energy dissipation structures when disaster factors of the damaged path o are not damaged based on the rest damaged paths and the safety risk Bayesian network ；
S6, according to the damage probability p α and the damage probabilityCalculating importance beta o of the disaster causing factors of the damaged path o:
；
and S7, selecting a failure path corresponding to the disaster causing factor with the highest importance degree beta o as a main control path for destroying the flood discharging energy dissipation structure.
Further, the dam failure modes include scour failure, strength failure, structural instability failure, and cavitation failure, each failure mode including multiple structural failure modes; the flood discharge energy dissipation structure damage criterion comprises a scour damage criterion, an intensity damage criterion, a structure instability damage criterion and a cavitation damage criterion;
The expression of the flushing failure criterion is:
，/>
wherein a and k are constants; c is cohesive force; phi is the internal friction angle; i 1、J2 is a first invariant of stress tensor and a second invariant of stress tensor respectively; A break criterion function for flushing;
The intensity disruption criterion is expressed as:
Wherein, As a function of intensity disruption criteria; f t is the material allowable tensile strength; σ 3 is the small principal stress of the structure;
The structural instability damage criterion comprises a stilling pool guide wall anti-slip stability damage criterion and stilling pool bottom plate anti-floating stability damage criterion, and the expressions are respectively as follows:
Wherein, And/>Respectively a stilling pool guide wall anti-slip stable damage criterion function and a stilling pool bottom plate anti-floating stable side damage criterion function; sigma i and tau i are respectively the positive stress and the shear stress of the i unit in the failure path searched by the finite element model; n is the total number of units; f is the coefficient of friction of the material; l i is the length of the i unit along the sliding surface; G. p tr, F, U and P fr are respectively representative values of self weight, time average pressure, effective weight of an anchoring foundation, lifting pressure and pulsating pressure of the bottom plate of the stilling pool; k f is an anti-floating stable safety coefficient allowable value;
The cavitation damage criterion is expressed as:
Wherein, As a cavitation damage criterion function; /(I)The primary cavitation number of the structural water flow; and theta is the cavitation number of the water flow.
Further, the method for searching the damaged path comprises the following steps:
searching a damage path of the damage mode in the finite element simulation model by adopting a load increment method based on a damage criterion corresponding to strength damage, structural instability damage and scour damage;
Searching a failure path of the concrete lining strength damage caused by surrounding rock deformation in the finite element simulation model by adopting a strength folding and subtracting method based on a strength damage criterion;
And simulating flow field distribution characteristics of the flood discharge and dissipation structure under the single wide flow of the constant flood by adopting Fluent software, and searching potential damage points in the finite element simulation model by adopting cavitation damage criteria to form a cavitation damage path.
Further, the step S3 further includes:
substituting a plurality of groups of random variables corresponding to the g-th structural damage into a risk agent model corresponding to the g-th structural damage to obtain a plurality of risk analysis model values;
Calculating the damage probability of the g-th structural damage mode according to a plurality of risk analysis model values ：
Wherein,Is the total sampling number; /(I)A risk analysis model value for the mth sampling; d f is the disruption domain; /(I)As an indication function.
Further, the expression of the risk agent model is:
Wherein, Analyzing a response surface equation for the risk of the g-th structural failure mode; x gh is the h random variable of the g structural failure mode, and the random variable is the foundation material mechanical parameter and the overflow surface hydraulic parameter; n g is the total number of random variables in the g-th structural failure mode; a gh and b gh are response surface equation coefficients corresponding to a random variable h of a g-th structural failure mode; c g is a constant corresponding to the g-th structural failure mode; g is the total number of all failure modes.
Further, the method comprises the steps of,
The method for obtaining a gh、bgh corresponding to the random variable h of the g-th structural failure mode and a constant c g corresponding to the g-th structural failure mode comprises the following steps:
acquiring a plurality of groups of random variables of a destruction mode of a g-th structure, and obtaining a functional function of the destruction mode corresponding to the destruction of the g-th structure;
Inputting a plurality of groups of random variables of the g-th structural failure mode into a finite element simulation model, and calculating to obtain a plurality of function values;
Substituting the function values and a group of random variables corresponding to the function values into the risk agent model respectively, and solving to obtain a gh、bgh corresponding to the random variable h of the g-th structural failure mode and a constant c g corresponding to the g-th structural failure mode.
Further, the expressions of the functional functions corresponding to the scouring damage, the strength damage, the structural instability damage and the cavitation damage are respectively as follows:
wherein g= {1,2,3}, corresponds to The functions of flushing and destroying the structures of the dam body spillway hole, the spillway tunnel and the stilling pool/plunge pool are respectively performed; x is a random variable;
Wherein g= {4,5,6}, corresponds to The dam body water discharge hole, the flood discharge channel and the stilling pool/plunge pool structure damage function are respectively provided; /(I)The stress is small corresponding to X;
where g= {7,8}, corresponds to The function is a destabilization and destruction function of a stilling pool bottom plate and a guide wall structure respectively;
wherein g= {9,10,11}, respectively The cavitation erosion damage function functions of a dam body spillway hole, a spillway tunnel and a stilling pool/plunge pool are respectively provided; /(I)Destroying a corresponding random variable for cavitation; /(I)The primary cavitation number of the structure when g= {9,10,11 }; /(I)The cavitation number of the structure at g= {9,10,11} was calculated.
The beneficial effects of the invention are as follows: the method and the system are used for constructing the Bayesian network model through the damage modes and the causes of the dams, and comprise that all possible paths are damaged by all dams, and then the damage paths can be accurately searched by combining the damage criteria of each damage mode, so that a foundation is laid for the follow-up main key factors and the active paths.
In the scheme, when the damage probability of each damage path is calculated, the damage modes corresponding to the multiple structures in each damage mode are fully considered, so that the damage probability of the searched damage path can be accurately calculated through the damage probability of the multiple structure damage modes.
Finally, by combining disaster factors and importance of each damage path, the method can accurately identify key risk factors and main control paths, is convenient for relevant departments to purposefully adjust materials and construction processes of corresponding structures of the main control paths when the dam is constructed or operated, achieves reinforcement of the corresponding structures, improves damage resistance of the dam, and ensures long-term safe and efficient operation of the dam; the application of the scheme has very important significance for actively controlling and eliminating structural risk.
Drawings
Fig. 1 is a flowchart of one embodiment of a method for evaluating the security risk of a dam flood discharge energy dissipation structure based on a bayesian network.
Fig. 2 shows the damage ratio and the mode statistics of the flood discharge and energy dissipation structures of the dam, wherein (a) is the damage ratio of the flood discharge and energy dissipation structures, and (b) is the damage mode statistics of the flood discharge and energy dissipation structures.
Fig. 3 is a network architecture of a security risk bayesian network.
Fig. 4 is a schematic diagram of finite element mesh and material partition of an overflow dam-stilling pool, (a) is a schematic diagram of mesh of a finite element model, and (b) is a concrete structure material partition.
Fig. 5 is a main cavitation damage path of a concrete gravity dam overflow dam-stilling pool structure.
Fig. 6 shows the strength and scouring damage primary path (overflow surface-bottom plate) of a concrete gravity dam overflow dam-stilling pool structure.
Fig. 7 shows the principal path (side wall) of the strength failure of a concrete gravity dam overflow dam-stilling pool structure.
FIG. 8 is a diagram illustrating the importance of disaster factors according to an embodiment.
Fig. 9 is a security risk and path evolution bayesian network.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.
Referring to fig. 1, fig. 1 illustrates a flowchart of one embodiment of a bayesian network-based dam flood discharge energy dissipation structure security risk assessment method; as shown in FIG. 1, the method S includes steps S1 to S7.
In the step S1, a finite element simulation model of a dam is built, and a safe risk Bayesian network of a dam flood discharge energy dissipation structure is built according to a damage mode of the dam and a reason for causing the damage mode; the finite element simulation model is constructed according to the design parameters of the dam.
According to the scheme, statistical analysis of damage reasons of flood discharge and energy dissipation structures of 84 reservoirs (see fig. 2, wherein in fig. 2, (a) is the damage proportion of the flood discharge and energy dissipation structures, and (b) is the damage mode statistics of the flood discharge and energy dissipation structures), the maximum damage proportion of spillways in a flood discharge and energy dissipation structure system of a land-rock dam and a concrete dam is 30.9%, and then the dam body water discharge holes, flood discharge holes, a stilling pool/plunge pool are sequentially arranged, and the ratio is 25.5%, 24.5% and 19.1% respectively. In the flood discharge and energy dissipation structure of the concrete dam, the overflow surface and the guide wall are cracked, the anti-arc section is cavitation eroded, the bottom plate of the stilling pool is eroded, and the bottom plate is unstable, wherein cavitation erosion and erosion damage account for up to 72.53 percent; the present approach designs dam failure modes to include scour failure, strength failure, structural instability failure, and cavitation failure, each failure mode including multiple structural failure modes. The reasons for the damage mode mainly include insufficient strength of concrete materials, freezing and thawing, too high groundwater level, too large pressure difference between the upstream and downstream of a chute bottom plate, uneven deformation, design and construction quality defects and the like.
In the scheme, by combining the structural characteristics, the working principle and the statistical analysis of a large number of damage cases of the flood discharging and energy dissipating structure of the high concrete dam, according to main modes such as dam body water discharging hole damage, flood discharging tunnel damage, stilling pool/plunge pool damage and other damage, a result event (the damage of the flood discharging and energy dissipating structure system) in each risk evolution path is taken as a target layer; taking initial events (insufficient intensity, excessive flow rate, uneven surface and the like) as index layers; and (3) the events in the risk evolution path process are collectively called a criterion layer, a high concrete dam flood discharge energy dissipation structure system safety risk accident tree structure is constructed, and the flood discharge energy dissipation structure system safety risk accident tree structure is converted into a corresponding Bayesian network structure based on a conversion principle between the accident tree structure and the Bayesian network, as shown in fig. 3.
In step S2, searching for failure paths of different failure modes in the finite element simulation model by adopting failure criteria corresponding to the different failure modes according to the safety risk Bayesian network; the flood discharge energy dissipation structure damage criteria include a scour damage criterion, a strength damage criterion, a structure instability damage criterion and a cavitation damage criterion.
In one embodiment of the invention, the flush destruction criterion is expressed as:
，/>
wherein a and k are constants; c is cohesive force; phi is the internal friction angle; i 1、J2 is a first invariant of stress tensor and a second invariant of stress tensor respectively; A break criterion function for flushing;
The intensity disruption criterion is expressed as:
Wherein, As a function of intensity disruption criteria; f t is the material allowable tensile strength; σ 3 is the small principal stress of the structure;
The structural instability damage criterion comprises a stilling pool guide wall anti-slip stability damage criterion and stilling pool bottom plate anti-floating stability damage criterion, and the expressions are respectively as follows:
Wherein, And/>Respectively a stilling pool guide wall anti-slip stable damage criterion function and a stilling pool bottom plate anti-floating stable side damage criterion function; sigma i and tau i are respectively the positive stress and the shear stress of the i unit in the failure path searched by the finite element model; n is the total number of units; f is the coefficient of friction of the material; l i is the length of the i unit along the sliding surface; G. p tr, F, U and P fr are respectively representative values of self weight, time average pressure, effective weight of an anchoring foundation, lifting pressure and pulsating pressure of the bottom plate of the stilling pool; k f is an anti-floating stable safety coefficient allowable value;
The cavitation damage criterion is expressed as:
Wherein, As a cavitation damage criterion function; /(I)The primary cavitation number of the structural water flow; and theta is the cavitation number of the water flow.
In implementation, the method for searching the damaged path preferably comprises the following steps:
searching a damage path of the damage mode in the finite element simulation model by adopting a load increment method based on a damage criterion corresponding to strength damage, structural instability damage and scour damage;
Searching a failure path of the concrete lining strength damage caused by surrounding rock deformation in the finite element simulation model by adopting a strength folding and subtracting method based on a strength damage criterion;
And simulating flow field distribution characteristics of the flood discharge and dissipation structure under the single wide flow of the constant flood by adopting Fluent software, and searching potential damage points in the finite element simulation model by adopting cavitation damage criteria to form a cavitation damage path.
In step S3, calculating the damage probability p o of each structural damage mode by adopting a Monte Carlo method according to the risk agent model of each damage mode, the mechanical parameters of the dam and foundation materials and the hydraulic parameters of the overflow surface;
in one embodiment of the invention, substituting a plurality of groups of random variables corresponding to the g-th structural damage into a risk agent model corresponding to the g-th structural damage to obtain a plurality of risk analysis model values;
Calculating the damage probability of the g-th structural damage mode according to a plurality of risk analysis model values ：
Wherein,Is the total sampling number; /(I)A risk analysis model value for the mth sampling; d f is the disruption domain; /(I)As an indication function.
The expression of the risk agent model is as follows:
Wherein, Analyzing a response surface equation for the risk of the g-th structural failure mode; x gh is the h random variable of the g structural failure mode, and the random variable is the foundation material mechanical parameter and the overflow surface hydraulic parameter; n g is the total number of random variables in the g-th structural failure mode; a gh and b gh are response surface equation coefficients corresponding to a random variable h of a g-th structural failure mode; c g is a constant corresponding to the g-th structural failure mode; g is the total number of all failure modes.
In implementation, the method for obtaining a gh、bgh corresponding to the random variable h of the g-th structural failure mode and the constant c g corresponding to the g-th structural failure mode includes:
acquiring a plurality of groups of random variables of a destruction mode of a g-th structure, and obtaining a functional function of the destruction mode corresponding to the destruction of the g-th structure;
Inputting a plurality of groups of random variables of the g-th structural failure mode into a finite element simulation model, and calculating to obtain a plurality of function values;
Substituting the function values and a group of random variables corresponding to the function values into the risk agent model respectively, and solving to obtain a gh、bgh corresponding to the random variable h of the g-th structural failure mode and a constant c g corresponding to the g-th structural failure mode.
Here, it should be noted that, in this embodiment, the constant c g of each failure mode does not change with the increase of the number of random variables, for example, there are only two random variables in failure mode 1, and then two sets a gh、bgh（a11 and b 11 and a 12、b12 are corresponding to this time), but there is only one constant c g corresponding to failure mode 1.
The expressions of the corresponding function functions of the scouring damage, the strength damage, the structural instability damage and the cavitation damage are respectively as follows:
wherein g= {1,2,3}, corresponds to The functions of flushing and destroying the structures of the dam body spillway hole, the spillway tunnel and the stilling pool/plunge pool are respectively performed; x is a random variable, and comprises cohesive force, friction angle, elastic modulus of concrete and foundation materials, time average pressure of a flow surface under the action of water flow and the like.
Wherein g= {4,5,6}, corresponds toThe dam body water discharge hole, the flood discharge channel and the stilling pool/plunge pool structure damage function are respectively provided; /(I)The stress is small corresponding to X;
where g= {7,8}, corresponds to The function is a destabilization and destruction function of a stilling pool bottom plate and a guide wall structure respectively;
wherein g= {9,10,11}, respectively The cavitation erosion damage function functions of a dam body spillway hole, a spillway tunnel and a stilling pool/plunge pool are respectively provided; /(I)The corresponding random variables are cavitation damage, and at the moment, the random variables corresponding to X comprise single-width flow and structural surface roughness; /(I)The primary cavitation number of the structure when g= {9,10,11 }; /(I)The cavitation number of the structure at g= {9,10,11} was calculated.
In step S4, calculating a structural system failure probability p α of the flood discharge energy dissipation structure according to the failure probabilities of all the structural failure modes and the safety risk bayesian network;
In this scheme, when all the failure paths belong to the parallel system, the failure probability p α =the failure probability of the parallel system When all the failure paths belong to a series system, the failure probability p α =series system failure probability/>；
(1) Probability of parallel system destructionExpressed as:
Constructing an indication function ：
The probability of destruction of the flood discharge and energy dissipation structure can be expressed as
Wherein,The total sampling times; /(I)In the parallel system, the corresponding indication function value is sampled for the mth time; a 1、A2…Aq is an event formed by the damage of the flood discharge energy dissipation structure along the 1 st path and the 2 nd path … q path respectively; a r is an event formed by the damage of the flood discharge energy dissipation structure along the r-th path, and r is more than or equal to 1 and less than or equal to q;
(2) Probability of series system failure The method comprises the following steps:
Constructing an indication function ：
The probability of destruction of the flood discharge energy dissipation structure system can be expressed as:
wherein, A s、At is the event formed by the damage of the flood discharging and energy dissipating structure along the 1 st path and the t path respectively; In the case of a series system, the corresponding value of the display function is sampled for the mth time.
In step S5, assuming that any damaged path o does not exist, calculating damage probability of flood discharge energy dissipation structure when disaster factor of damaged path o does not damage based on the rest damaged path and safety risk Bayesian network; Probability of destruction/>The calculation process of (1) is similar to the destroy probability p α, and will not be described in detail here.
In step S6, the method is performed according to the destruction probability p α and the destruction probabilityCalculating importance beta o of the disaster causing factors of the damaged path o:
；
In step S7, a failure path corresponding to the disaster-causing factor with the highest importance β o is selected as the main control path for destroying the flood discharging and energy dissipating structure.
In order to facilitate understanding of the present solution, the following describes a security risk assessment method of the present solution in conjunction with specific examples:
The finite element model and material partition of the overflow dam-stilling pool dam section of a gravity dam are shown in fig. 4, in which (a) is a grid schematic diagram of the finite element model, and (b) is a concrete structure material partition. Finite element simulation range: along the river, the dam heel and the dam toe extend upwards and downwards for 2 times of dam height respectively, and the vertical direction extends downwards from the building base surface for 2 times of dam height. The finite element model is split into 42508 units, 51984 nodes. The dam height of the overflow dam is 168m, the dam top width is 25m, the elevation of a building base surface is 1166.00m, the normal water storage level of the reservoir is 1330.00m, the design flood level is 1330.18m, and the check flood level is 1330.44m. The normal flood single-width flow is 77.3m 3/s, the design flood single-width flow is 125.3m 3/s, and the check flood single-width flow is 163.2m 3/s. The volume weights of roller compacted concrete (RII) and normal Concrete (CII) are 2520kg/m 3、2500kg/m3 respectively, and the Poisson's ratio is 0.2. The foundation is basalt, the volume weight is 2850kg/m 3, and the poisson ratio is 0.22. Referring to similar engineering, the surface roughness delta of the overflow surface and the concrete surface of the stilling pool is 0.6mm.
According to the concrete dam flood discharge energy dissipation structure system safety risk accident tree and the Bayesian network framework, the working characteristics of each flood discharge energy dissipation structure of the gravity dam are combined, disaster factors, damage paths and damage modes which are difficult to quantify are not considered, wherein the disaster factors, damage paths and damage modes are listed, and the overflow dam-stilling pool structure system safety risk Bayesian network (the network framework is shown in figure 3) comprising 10 damage paths of two damage modes, namely, a water discharge hole damage mode and a stilling pool damage mode. The simulation analysis considers that the cohesive force, the friction coefficient, the elastic modulus, the time average pressure, the roughness and the single-width flow are random variables.
According to the searching method of main damage paths of different damage modes of the flood discharge and energy dissipation structure system of the concrete dam and the corresponding damage criteria, the load increment method is adopted to obtain the structural strength, stability and scouring damage main damage paths of the overflow dam and the absorption basin. The flow field distribution characteristics of the overflow dam-stilling pool structure under the single wide flow of the constant flood are simulated by adopting Fluent software, potential damage points of cavitation damage are further determined, main damage paths of the potential damage points are obtained through searching, and the potential cavitation damage points of the overflow surface, the potential cavitation damage points of the stilling pool, the strength and scouring damage points of the overflow surface and the guide wall, the strength and scouring damage points of the bottom plate of the stilling pool and the guide wall, the strength damage points of the tail ridge and the like are shown in fig. 5-7, and in fig. 5 and 6. In fig. 7, the stability of the stilling pool guide wall and the stability of the bottom plate in the stilling pool structure meet the standard requirements, so that the instability damage of the stilling pool bottom plate and the guide wall is not considered in the damage path of the stilling pool structure.
According to the judging criteria of the main damage mode of the flood discharge energy dissipation structure, in the structural strength and scouring damage risk analysis of the overflow dam-stilling pool, the random variables are considered as the cohesive force, friction angle and elastic modulus of concrete and foundation materials and the time-average pressure of the overflow dam face-stilling pool floor; in cavitation damage risk analysis, the single wide flow and roughness are considered as random variables. Therefore, based on the safety risk analysis model of the flood discharge energy dissipation structure system in the step S3, a main damage mode risk analysis proxy model of the overflow dam-stilling pool structure system can be constructed:
In the method, in the process of the invention, Respectively representing the scouring, strength damage and cavitation damage of the overflow dam-stilling pool structure, wherein p1 and p2 respectively represent an overflow surface hole and a stilling pool; a p1h and b p1h are respectively response surface equation coefficients corresponding to the h random variable of the p1 st structural failure mode; a p2h and b p2h are respectively response surface equation coefficients corresponding to the h random variable of the p2 structural failure mode; a qh and b qh are respectively the response surface equation coefficients corresponding to the h random variable of the q-th structural failure mode; c p1、cp2 and c q are constants corresponding to the p1 st, p2 nd and q th structural failure modes respectively; a p1 is a data matrix consisting of a p1h、bp1h and c p1; a p2 is a data matrix consisting of a p2h、bp2h and c p2; a q is a data matrix consisting of a qh、bqh and c q; n p1、np2 and n q are the total number of random variables of the p1 st, p2 nd and q th structural failure modes respectively; /(I)、/>And/>Respectively/>Is a transpose of (2); is a random variable matrix; /(I) And analyzing random variables for structural strength and scouring damage risk of the overflow dam-stilling pool, wherein Q is single-width flow, and delta is concrete surface roughness.
According to the safety risk Bayesian network framework of the overflow dam-stilling pool structure system, analysis is carried out aiming at the situation that the structure system is not damaged due to static and dynamic loads before the damage such as flood discharge and energy dissipation hydraulic erosion and the like. The damage probability of the flood discharge efficiency structure system is obtained by constructing a multi-mode multi-path security risk analysis agent model of the overflow dam-stilling pool structure system shown in formulas (1) - (6), a Monte-Carlo random perturbation of the series-parallel system and the like (see table 1).
TABLE 1 calculation of failure probability of overflow dam-stilling pool structural System
As can be seen from Table 1, the 7 paths of the overflow dam-stilling pool structure system have a failure probability of 2.06×10 -8~3.29×10-6, and the corresponding reliability index is 4.51-5.49; the damage probability of the structural system is 6.52 multiplied by 10 -6, the corresponding reliability index is 4.36, and the reliability index is greater than the target reliability index 4.2 specified in the unified design standard of the reliability of the structure of the hydraulic and hydroelectric engineering (GB 50199-94). Wherein, the cavitation damage probability of the arc section with the overflow surface is the maximum and is 3.29 multiplied by 10 -6; the minimum probability of damage to the strength of the stilling pool is 2.06 multiplied by 10 -8.
The importance analysis is an effective method for rapidly judging the influence degree of each disaster causing factor on the damage risk of the structural system, and meanwhile, the comparison analysis of the importance of each disaster causing factor is also an important means for identifying a main control path and key factors. The importance of the damage disaster-causing factors of the overflow dam-stilling pool structure system can be calculated through the step S6.
As can be seen from fig. 8, in the 7 main damage paths of the overflow dam-stilling pool structure system, the factor importance of cavitation damage by the anti-arc section of the overflow surface is the highest, which is 0.51, and the factor importance is 0.26.
Therefore, cavitation erosion damage of the anti-arc section of the overflow surface is a key factor of the safety risk of the structural system, and the path of structural damage of the overflow dam and the stilling pool caused by the cavitation erosion damage is a main control path, namely, cavitation erosion damage of the anti-arc section of the overflow surface, damage of an overflow surface hole and structural system damage, and the method can be particularly referred to as shown in fig. 9.
In summary, the method provided by the scheme can accurately identify the key factors and path evolution of the security risk of the main control structure system, and is very important for actively regulating and eliminating the hidden danger of the structure risk and ensuring long-term safe and efficient operation of the dam.
Claims (6)
1. The dam flood discharge energy dissipation structure safety risk assessment method based on the Bayesian network is characterized by comprising the following steps:
S1, constructing a finite element simulation model of a dam, and constructing a safety risk Bayesian network of a dam flood discharge energy dissipation structure according to a damage mode of the dam and a reason for causing the damage mode;
s2, searching for damage paths of different failure modes in the finite element simulation model by adopting damage criteria corresponding to the different failure modes according to the safety risk Bayesian network;
S3, calculating the damage probability p o of each structural damage mode by adopting a Monte Carlo method according to the risk agent model of each damage mode, the mechanical parameters of the dam and foundation materials and the hydraulic parameters of the overflow surface;
s4, calculating the structural system damage probability p α of the flood discharge energy dissipation structure according to the damage probability of all the structural damage modes and the safety risk Bayesian network;
s5, when any damaged path o is assumed to be absent, calculating damage probability of flood discharge energy dissipation structures when disaster factors of the damaged path o are not damaged based on the rest damaged paths and the safety risk Bayesian network ；
S6, according to the damage probability p α and the damage probabilityCalculating importance beta o of the disaster causing factors of the damaged path o:
；
S7, selecting a failure path corresponding to a disaster-causing factor with the highest importance degree beta o as a main control path for damaging the flood discharge energy dissipation structure;
The dam failure modes include scour failure, strength failure, structural instability failure, and cavitation failure, each failure mode including multiple structural failure modes; the flood discharge energy dissipation structure damage criterion comprises a scour damage criterion, an intensity damage criterion, a structure instability damage criterion and a cavitation damage criterion;
The expression of the flushing failure criterion is:
，/>
Wherein a and k are constants; phi is the internal friction angle; i 1、J2 is a first invariant of stress tensor and a second invariant of stress tensor respectively; A break criterion function for flushing;
The intensity disruption criterion is expressed as:
Wherein, As a function of intensity disruption criteria; f t is the material allowable tensile strength; σ 3 is the small principal stress of the structure;
The structural instability damage criterion comprises a stilling pool guide wall anti-slip stability damage criterion and stilling pool bottom plate anti-floating stability damage criterion, and the expressions are respectively as follows:
Wherein, And/>Respectively a stilling pool guide wall anti-slip stable damage criterion function and a stilling pool bottom plate anti-floating stable side damage criterion function; sigma i and tau i are respectively the positive stress and the shear stress of the i unit in the failure path searched by the finite element model; n is the total number of units; f is the coefficient of friction of the material; l i is the length of the i unit along the sliding surface; G. p tr, F, U and P fr are respectively representative values of self weight, time average pressure, effective weight of an anchoring foundation, lifting pressure and pulsating pressure of the bottom plate of the stilling pool; k f is an anti-floating stable safety coefficient allowable value; c is cohesive force;
The cavitation damage criterion is expressed as:
Wherein, As a cavitation damage criterion function; /(I)The primary cavitation number of the structural water flow; and theta is the cavitation number of the water flow.
2. The bayesian network-based dam flood discharge energy dissipation structure safety risk assessment method according to claim 1, wherein the method for searching for the damaged path comprises:
searching a damage path of the damage mode in the finite element simulation model by adopting a load increment method based on a damage criterion corresponding to strength damage, structural instability damage and scour damage;
Searching a failure path of the concrete lining strength damage caused by surrounding rock deformation in the finite element simulation model by adopting a strength folding and subtracting method based on a strength damage criterion;
And simulating flow field distribution characteristics of the flood discharge and dissipation structure under the single wide flow of the constant flood by adopting Fluent software, and searching potential damage points in the finite element simulation model by adopting cavitation damage criteria to form a cavitation damage path.
3. The bayesian network-based dam flood discharge energy dissipation structure safety risk assessment method according to claim 1, wherein the step S3 further comprises:
substituting a plurality of groups of random variables corresponding to the g-th structural damage into a risk agent model corresponding to the g-th structural damage to obtain a plurality of risk analysis model values;
Calculating the damage probability of the g-th structural damage mode according to a plurality of risk analysis model values ：
Wherein,Is the total sampling number; /(I)A risk analysis model value for the mth sampling; d f is the disruption domain; /(I)As an indication function.
4. A bayesian network-based dam flood discharge energy dissipation structure security risk assessment method according to claim 1 or 3, wherein the expression of the risk agent model is:
Wherein, Analyzing a response surface equation for the risk of the g-th structural failure mode; x gh is the h random variable of the g structural failure mode, and the random variable is the foundation material mechanical parameter and the overflow surface hydraulic parameter; n g is the total number of random variables in the g-th structural failure mode; a gh and b gh are response surface equation coefficients corresponding to a random variable h of a g-th structural failure mode; c g is a constant corresponding to the g-th structural failure mode; g is the total number of all failure modes.
5. The bayesian network-based dam flood discharge energy dissipation structure safety risk assessment method according to claim 4, wherein the method for obtaining a gh、bgh corresponding to the random variable h of the g-th structural failure mode and a constant c g corresponding to the g-th structural failure mode comprises the steps of:
acquiring a plurality of groups of random variables of a destruction mode of a g-th structure, and obtaining a functional function of the destruction mode corresponding to the destruction of the g-th structure;
Inputting a plurality of groups of random variables of the g-th structural failure mode into a finite element simulation model, and calculating to obtain a plurality of function values;
Substituting the function values and a group of random variables corresponding to the function values into the risk agent model respectively, and solving to obtain a gh、bgh corresponding to the random variable h of the g-th structural failure mode and a constant c g corresponding to the g-th structural failure mode.
6. The bayesian network-based dam flood discharge energy dissipation structure safety risk assessment method according to claim 5, wherein expressions of the functional functions corresponding to the scouring damage, the strength damage, the structural instability damage and the cavitation damage are respectively:
wherein g= {1,2,3}, corresponds to The functions of flushing and destroying the structures of the dam body spillway hole, the spillway tunnel and the stilling pool/plunge pool are respectively performed; x is a random variable;
Wherein g= {4,5,6}, corresponds to The dam body water discharge hole, the flood discharge channel and the stilling pool/plunge pool structure damage function are respectively provided; /(I)The stress is small corresponding to X;
where g= {7,8}, corresponds to The function is a destabilization and destruction function of a stilling pool bottom plate and a guide wall structure respectively;
wherein g= {9,10,11}, respectively The cavitation erosion damage function functions of a dam body spillway hole, a spillway tunnel and a stilling pool/plunge pool are respectively provided; /(I)Destroying a corresponding random variable for cavitation; /(I)The primary cavitation number of the structure when g= {9,10,11 }; /(I)The cavitation number of the structure at g= {9,10,11} was calculated.
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