Chinese Standard: 'DL50771997'
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Specifications for load design of hydraulic structures
 
DL 50771997

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Standard ID  DL 50771997 (DL50771997)  Description (Translated English)  Specifications for load design of hydraulic structures  Sector / Industry  Electricity & Power Industry Standard  Classification of Chinese Standard  P55  Word Count Estimation  102,119  Date of Issue  1997/10/22  Date of Implementation  1998/2/1  Quoted Standard  GB 501991994; GBJ 91987; GBJ 1451990; DL 50731997; DL/T 50581996  Drafting Organization  Ministry of Power Industry Investigation Design and Research Institute, Central South  Administrative Organization  Ministry of Water Resources and Hydropower Planning and Design of Power Industry  Summary  This standard applies to all types of structural design of hydraulic structures. 
DL 50771997
Specifications for load design of hydraulic structures
Foreword
1 Scope
2 Reference standards
3 General
4 Main symbols
5 Action classification and combination of action effects
6 Building weight and permanent equipment weight
7 Hydrostatic pressure
8 Lifting pressure
9 Dynamic water pressure
10 Insitu stress and surrounding rock pressure
11 Earth pressure and silt pressure
12 Wind load and snow load
13 Ice pressure and frost heave
14 Wave pressure
15 Floor and platform live load
16 Bridge crane and door crane load
17 Temperature effect
18 Earthquake action
19 Grouting pressure
Appendix A (Standard Appendix) The main functions of hydraulic structure are classified according to time variation
Appendix B (Standard Appendix) The material weight of hydraulic structures
Appendix C (Standard Appendix) External Water Pressure Reduction Factor of Concrete Lining Pressure Tunnel
Appendix D (standard appendix) improved drag coefficient method
Appendix E (Standard Appendix) Simple Pipeline Water Hammer Pressure Calculation Formula
Appendix F (Standard Appendix) Calculation of Active Earth Pressure Coefficient Ka and Static Earth Pressure Coefficient K0
Appendix G (Standard Appendix) Wave Elements and Climbing Calculation
Appendix H (standard appendix) calculation of water temperature in front of the dam
Appendix J (Standard Appendix) Standard values of temperature effects during arch dam operation
Appendix K (Standard Appendix) Terms used in this specification
1 Scope
This code is applicable to the structural design of various hydraulic structures.
2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard by quotation in this standard. When this standard was published, the editions shown were
effect. All standards will be revised, all parties using this standard should explore the possibility of using the latest version of the following standards.
GB 5019994 Unified Standard for Structural Reliability Design of Water Conservancy and Hydropower Projects
GB J 987 Building Structural Load Specification
GB J 14590 soil classification standards
DL/T 50581996 Design Specification for Surge Chamber of Hydropower Station
3 General
3.0.1 In order to unify the function value standards of hydraulic structure design, and make the design meet the requirements of safety and application, economical rationality, and advanced technology, this specification is specially formulated.
3.0.2 This specification is based on the principles stipulated in GB 5019994 "Unified Standards for Structural Reliability Design of Water Conservancy and Hydropower Engineering".
3.0.3 Other functions not specified in this code shall be determined in accordance with the provisions of various hydraulic structure design codes.
3.0.4 When the hydraulic structure design refers to the functions related to highway, shipping and port engineering, it shall be determined after specific analysis in accordance with the provisions of the design codes of various departments.
The relevant provisions of Chapter 4 and Chapter 7, and the subsequent chapters have made specific provisions on the value of various functions and their subcoefficients.
The role of structure usually refers to the general name of various causes of effects (internal force, deformation, etc.) on the structure, and can be classified as direct action and
Indirect effect. Direct action refers to the concentrated or distributed force directly applied to the structure, which can also be called "load"; indirect action refers to the effect
Causes of external deformation or constrained deformation of the structure, such as earthquakes and temperature effects. For a long time, the engineering community has been accustomed to making no distinction between the two types of roles,
Both are called "loads". In order to simplify the name of the code and take care of idioms, this code is still named "Code for Design of Loads on Hydraulic Structures".
But in fact, it includes direct and indirect roles.
3.0.3 There are many functions on hydraulic structures, and subject to objective conditions, it is impossible for this code to conduct a comprehensive study of all functions
The corresponding regulations only deal with some of the main functions commonly encountered in the design of hydraulic structures. As for the special role of certain buildings (structures), or this regulation
Other functions not included in Fan, such as structural prestress, soil pore water pressure and welding deformation of steel structure, etc., can be determined by the corresponding hydraulic structure
The design specifications make provisions as needed.
3.0.4 The design rules of the departments of highway, shipping and port engineering, the principles and methods of their value (load) may not be consistent with this code, so
When quoting the value of the action (load), the characteristics of the hydraulic structure should be analyzed in detail to determine the value of the related action and its partial coefficient.
To be used in conjunction with this specification.
5 Action classification and combination of action effects
5.1 Function classification and representative value
5.1.1 Various functions in structure, when they are independent in time and space, then each function can be considered as a separate function. "Hydraulics
"Standard Standard" adopts three classification methods for action, namely, the variation with time of action, the variation with space position (fixed or movable) and the effect on structure
The response characteristics (static or dynamic) are classified. Among them, the classification according to the variability of action over time is the most important classification, because it is directly related to
To the choice of probability models of action variables, the value of some actions is also related to the length of their duration. This specification will be based on the "Hydraulic Standards"
The variation with time is divided into the following three categories.
(1) Permanent effect. the value does not change with time during the design reference period, or its change is negligible compared with the average value;
(2) Variable effect. the value changes with time during the design reference period, and its change cannot be ignored compared with the average value
(3) Accidental effect. The probability of occurrence in the design reference period is very small, and once it appears, its value is large and the duration is very short.
Appendix A "Classification of main functions of hydraulic structure according to time variation" is listed in principle according to Appendix D of "Hydraulic Standards".
5.1.2 When using the partial coefficient limit state design method, the value used in the acting variable in the design expression is called the acting representative value. "Hydraulics
The "Standard Standard" stipulates that. the representative values of permanent action and variable action shall adopt the standard value of action, and the representative value of accidental action shall be determined according to the relevant specifications. "water
The "Standard of Engineering Standards" specifies specific principles and methods for determining the value of the function standard. When determining the standard values of various permanent and variable actions in this specification,
Followed these rules. As for the two main accidental effects in the design of hydraulic structuresthe representative values of the hydrostatic pressure and earthquake action when checking the flood level,
This specification makes provisions in the relevant chapters.
5.2 Combination of effects
5.2.1 When the entire structure (including foundation and surrounding rock) or a part of the structure exceeds a certain state and cannot meet the functional requirements specified in the design
At this time, the specific state is called the limit state of the structure corresponding to the function. Starting from the actual needs of engineering structure design, the limit state can be divided into
There are two types of "bearing capacity limit state" and "normal use limit state". The limit state of the bearing capacity of the structure is generally based on the structure or structure
The structural member reaches the maximum loadcarrying capacity or is unsuitable for continued loadbearing deformation; it is based on the structure or structural structure for the normal use limit state
Based on a certain functional limit for normal use or durability requirements. The internal force and deformation caused by the action on the structure, such as axial force, bending moment,
Shear forces, displacements, deflections and cracks are collectively called "action effects" and should be determined by structural analysis.
According to the different structures, action systems and environmental conditions that may appear in different stages of construction, installation, operation and maintenance, the structure
The design status can be divided into the following three types.
(1) Enduring condition. It must appear during the normal use of the structure and the duration is very long, generally the same order of magnitude as the structural design benchmark period
Design status
(2) Transient conditions. design conditions that appear briefly during structural construction (installation), maintenance, or use;
(3) Accidental situation. a design situation with a low probability and a short duration during the use of the structure.
The above three design conditions, not only the size and duration of the action may be different, but also the structure, type and supporting force transmission conditions of the structure
And structural material properties may also be different. Therefore, the design must first distinguish the design status of the structure, and then according to two different limit states
Respectively combine the various effects that may occur at the same time to obtain the total effect of the structure. Due to the combination of effects (effects) possible
There are many cases, so in all possible combinations, the most unfavorable combination should be taken as the basis of the limit state design.
5.2.2 The "Hydraulic Standards" stipulates that the permanent, transient and accidental conditions should be designed according to the limit state of the carrying capacity. among them,
The combination of effects under permanent and transient conditions is called the basic combination, which only considers the combination of permanent effects and variable effects;
The combination of action and effect under the condition is called accidental combination, which is a combination of permanent effect, variable effect and a kind of accidental effect. Due to accidental action
The probability of occurrence in the design reference period is very small, and the probability of simultaneous occurrence of two accidental effects must be smaller, so only one kind of accidental combination is considered
Accidental effect. For example, the hydrostatic pressure when checking the flood level should not be combined with the earthquake action.
5.2.3 In the design expression of the limit state of the partial coefficients, "Hydraulic Standards" adopts the safety level, design status, operation
There are five types of subcoefficients that are related to the variability of material properties and the uncertainty of the calculation model, and are related to the target reliability index, namely.
(1) Structural importance coefficient γ0. hydraulic structures or components used to consider different safety levels should have different reliability levels, corresponding to Ⅰ,
The three structural safety levels of Ⅱ and Ⅲ adopt 1.1, 1.0 and 0.9 respectively;
(2) Design condition factor ψ. used to consider that the structure should have different reliability levels under different design conditions, corresponding to durable conditions, short
Different values are used for temporary and accidental conditions;
(3) Action subcoefficients γG and γQ. used to consider the adverse variation of the action on its standard value, but does not reflect the change of the action imposed on the structure
The calculation uncertainty calculated as the effect effect;
(4) Material performance partial coefficient γm. used to consider the adverse variation of material performance to its standard value;
(5) Structure coefficient γd. It is used to consider the uncertainty of the calculation of the action effect, the uncertainty of the calculation model of the structural resistance and the failure of the above partial coefficients
Other uncertainties reflected.
Among the above five subitem coefficients, the structural importance factor γ0 has been prescribed by the “Hydraulic Standards”; the action subfactors γG and γQ are determined by this regulation
Fan is given separately for various functions; the remaining three subitem coefficients are specified by various hydraulic structure design codes.
In the occasional combination, the variable value of the participating combination generally adopts its standard value. But considering some variable effects and accidental effects
At the same time, the probability of occurrence is small, so this article makes "variable effects that occur at the same
The standard value shall be appropriately reduced ". For example, for checking the wave pressure under the flood level, this code stipulates that the calculation of wind speed shall use the multiyear average
The annual maximum wind speed is a reduction in the calculated wind speed for a 50year recurrence period under a durable, shortterm design condition.
5.2.4 According to the length of the total duration of the variable effect on the structure, the combination of longterm and shortterm effects should be considered for the normal service limit state
Happening. The combination of the shortterm and permanent effects of variable action is called the combination of shortterm effects; the longterm and permanent effects of variable action
The combination of longterm effects is called the combination of longterm effects. The variable effect in the combination of shortterm effects can directly adopt its standard value; the combination of longterm effects
The variable effect in the should be multiplied by its standard value by a longterm combination coefficient ρ less than 1.0 as a frequently occurring variable effect value to participate in the longterm effect
combination. The determination method of the longterm combination coefficient ρ has been given in Appendix F of the “Hydraulic Standards”, and specific regulations are made by various hydraulic structural design codes.
For the normal use limit state, the “Hydraulic Standards” still stipulates that generally the longterm and shortterm combinations corresponding to the permanent design status should be used.
For design, shortterm combinations corresponding to shortterm design conditions can also be considered as needed. When the two effects are combined, each permanent effect and variable
The subcoefficients of the functions can be 1.0.
6 Building weight and permanent equipment weight
6.1 Building weight
6.1.1 Appendix Table B1 refers to the relevant material weights in GB J987 "Code for Loads of Building Structures" and "Technical Specifications for Port Engineering" (1987)
Degree, and amended and supplemented according to relevant data of water conservancy and hydropower projects.
6.1.2 In the process of compiling this specification, a total of 52 largescale normal concrete, water conservancy and hydropower projects at home and abroad (including 25 domestic projects),
The actual measured data of roller compacted concrete and asphalt concrete. Normal part of the concrete is measured by the core sample of the drill hole, and the other is measured by the machine port.
Gravity measurement; roller compacted concrete is the gravity measured on site by the nuclear density meter; asphalt concrete is the gravity measured by the laboratory. Extensive mathematical statistical analysis
The results show that normal concrete and RCC with the same grade and qualified construction can use the same weight value. Heavy clothing for bulky concrete
From the normal distribution, for 80% of the projects, the coefficient of variation is 0.005 to 0.01. According to the statistical analysis results, and refer to some comparison
As a result of familiarity, the specification lists Appendix Table B2 for design selection. When determining the gravity of concrete by testing, refer to 5.2.2 of "Hydraulic Standards"
According to regulations, the value can be taken according to the 0.2 quantile of its probability distribution.
6.1.3 During the compilation of this specification, a total of more than 100 domestic and international (including more than 30 domestic) earthrock dam compaction dry weight data were collected and carried out
A lot of mathematical statistics work. The results show that the compacted dry weight of earthrock dams follows a normal distribution, and the coefficient of variation of 80% engineering is 0.02 ～ 0.08.
According to the statistical analysis results and referring to the design and construction experience of earth and rock dams at home and abroad, the table B3 is listed for design selection. Due to impact
There are many factors for the weight of the dam, and the damming materials for each specific project are everchanging. The attached table B3 only gives a rough range. Engineering design
Among them, the compacted dry weight of the earthrock dam should be determined mainly on the basis of the roller compaction test. With reference to the provisions of 5.2.2 of the “Hydraulic Standards”, its severity can be adjusted according to
The value of 0.1 quantile of the probability distribution. The classification of soil in Appendix Table B3 follows GB J14590 "Classification Standard of Soil".
6.1.4 The weight of hydraulic mass concrete (including normal concrete and RCC) is mainly used to resist overturning and slipping.
It is favorable, and the variability of its geometric size is relatively small, and the construction quality control also provides a certain guarantee for the weight of the concrete, so its subitem is taken
The coefficient is 1.0.
For ordinary concrete structures, the compilation team of GB J6884 "Uniform Standards for Building Structure Design" has tested 17 provinces, municipalities and autonomous regions.
The selfweight of 2,667 largescale industrial and civil construction reinforced concrete prefabricated members, and about 10,000 leveling layers, cushion layers, insulation layers, waterproof layers, etc. above 20,000m2
The thickness and partial gravity of each measuring point were counted, and the results showed that the measured average value was 1.060 times the standard value. "Port Engineering Structure Reliability Design
The "Unified Standards" compilation team has conducted statistics on 322 samples of concrete and reinforced concrete in port construction throughout the country, and the results show that the average weight
The ratio to the standard value is 1.03. Annex 2 of "Hydraulic Standards" (Draft for Review) "Reliability Analysis of Hydraulic Reinforced Concrete Structure and Determination of Subitem Coefficients"
A study was carried out on the permanent effect (mainly the selfweight of hydraulic reinforced concrete), and the results show that the effect of the selfweight of ordinary hydraulic concrete structures is divided into items
A coefficient of 1.05 is appropriate.
In the stability analysis of earthrock dams, the different parts of the soil or rockfill have different roles. The weight of the upper part of the sliding arc promotes its sliding, and
The weight of the lower part tends to prevent it from sliding. Therefore, it is difficult to distinguish the earthrock dam's own weight as a whole from its beneficial or unfavorable structure. But for the same soil
The greater the weight of the body or rockfill, the higher the degree of compaction and the better the shear resistance, which is beneficial to the stability of the dam. Therefore, the subfactor is 1.0.
7 Hydrostatic pressure
7.1 General
7.1.2 According to the requirements of the "Hydraulic Standards", the structural design should be based on the specific conditions of the structure during construction and operation.
Three design situations, short and accidental. The construction and operation conditions of hydraulic structures (structures) are complex, so when calculating the hydrostatic pressure, the
Make sure that it is compatible with certain design conditions. The hydrostatic pressure corresponding to the lasting design condition or the temporary design condition during construction and maintenance is variable
Function; under the accidental design situation when the check flood occurs, the hydrostatic pressure is an accidental effect. For the sake of conciseness, the general
Hydrostatic pressure is regarded as the standard value during variable action and as the representative value during accidental action, collectively referred to as the representative value of hydrostatic pressure.
7.1.3 The calculated water level of the representative value of the hydrostatic pressure of the hub building and the gate structure under different design conditions is generally the characteristic water level of the reservoir.
The water level can be artificially controlled during the operation of the building, so the partial coefficient of effect on the hydrostatic pressure is 1.0. Affect the pipeline and underground structure in the dam
The factors for the standard value of external water pressure are more complicated. This code basically follows the principles and methods determined in the current hydraulic structure design code, and
It is stipulated that its function subfactor coefficient is 1.0.
7.2 Hydrostatic pressure of hub buildings
7.2.1 The provisions of 4.3.3 of the Hydraulic Standards, "For those who have traditional values or have distinctive characteristics, and it is difficult to rely on statistical data according to probability
The quantile value of the distribution determines the variable effect of its standard value, and its standard value can be defined in a defined form. "The hydrostatic pressure of a hub building belongs to
This situation. The current design specifications for hydraulic structures are based on the characteristic water level of the reservoir when considering the hydrostatic pressure of the building. Therefore, this regulation
Fan is also based on the characteristic water level of the reservoir in principle to determine the representative value of the hydrostatic pressure of the hub building under the corresponding design conditions.
This specification clearly specifies the normal water storage level (or high flood control water level) as the calculated water level of the standard value of hydrostatic pressure under a permanent design condition. Normal storage
Water level refers to the highest water level that should be stored at the beginning of the water supply period in order to meet the design's profitable requirements under normal operation of the reservoir; flood control and high water
Position refers to the highest water level reached before the dam when the reservoir encounters the design flood of the downstream protection object. In view of the general flood control standards of the downstream protection objects of the dam
They are all within the range of 100year floods, and can be considered to be in the category of frequent floods. Therefore, for reservoirs with flood control, the
(Or equal to) the high flood control water level of the normal water storage level is treated as the water level under persistent conditions.
Reservoir check flood level refers to the highest water level reached before the dam when the reservoir encounters the check flood of the dam. The probability of checking floods is very low,
It is a rare event and should be considered as an accidental design situation. The corresponding check flood level is the calculated water level of the representative value of the hydrostatic pressure under the accidental design situation.
Reservoir design flood level refers to the highest water level reached before the dam when the reservoir encounters the design flood of the dam, which is between the normal water storage level (or high flood control level)
Water level) and the check flood level are mainly used to calculate the discharge flow during normal operation and determine the discharge capacity of the discharge structure. For waterretaining buildings
As far as the stability of the object and the structural strength are concerned, the design flood level generally has no control effect. In SDJ2178 "Specifications for Design of Concrete Gravity Dams (Trial)
In the Supplementary Provisions and SDJ14585 "Specifications for Design of Concrete Arch Dams", the design flood level is generally not considered as a load combination. Ginseng
Examining the dam engineering design codes or design guidelines in the United States, Japan and other countries, the dam design only considers the normal storage level and the check flood level.
condition. Therefore, this code does not consider the design flood situation.
This specification is to determine the value of the representative value of the role under various design conditions, some buildings (such as arch dams, earthrock dams) also need to consider the calculation of water
The combination of hydrostatic pressure and corresponding effect when the water level is lower than the normal storage level. Such a combination should be specified by the relevant professional design specifications. River
The bedtype hydropower plant is part of the waterretaining structure, so the calculated water level of the representative value of the hydrostatic pressure should be the same as that of the waterretaining structure such as gates and dams.
7.2.3 The effect of the hydrostatic pressure on the powerhouse behind the dam and the shore type hydropower station, the calculated water level depends on the downstream characteristic water level.
The flood control design flood level and the check flood level of the plant in accordance with the design standards; in the shortterm design conditions of the plant construction period, unit maintenance, etc., its still water
The calculated water level of the representative value of pressure shall be determined in accordance with the relevant provisions of SD33589 "Code for Design of Hydropower Plant Buildings".
7.2.5 Temporary hydraulic structures (such as diversion structures, construction cofferdams, temporary pumping stations, etc.) and various types of dams are designed for
The design flood standard used in SDJ1278, SDJ21787 "Water Conservancy and Hydropower Project Grade Classification and Design Standard", SDJ33889
The "Water Conservancy and Hydropower Construction Organization Design Code" clearly states that the calculated water level of the representative value of hydrostatic pressure can be determined by calculation.
7.3 Hydrostatic pressure of hydraulic gate
7.3.1 There are many types of hydraulic gates, which can be divided into working gates, accident gates, maintenance gates and construction gates according to their uses.
The specific operating conditions vary. This article points out the general principles that should be considered when determining the representative value of the gate hydrostatic pressure.
7.3.2 Working gates or accident gates installed at the water inlets of buildings such as power generation, water supply, and discharge are groups of waterblocking structures such as dams and sluices.
As a part, the gate acts as a water stop when it is closed. Therefore, the calculated water level of the representative value of the hydrostatic pressure of the working gate or accident gate should be in accordance with the
7.2.1 The same water level standard, that is, the calculated water level under the permanent design condition can use the normal water storage level or the high water level for flood control.
The calculation of the water level uses the check flood level.
7.3.3 According to domestic engineering data, the maximum navigable water level upstream of most ship locks is consistent with the normal water storage level, and the maximum water blocking level is consistent with the check flood level.
7.3.4 The hydraulic structures listed in this article are generally provided with an overhaul gate on the upstream or downstream side for blocking water during the overhaul of the structure. In addition to riverbed water
It is possible to arrange the power station outside the flood season for maintenance, and generally arrange it for the dry season. The water levels of the upstream and downstream of each building are different during maintenance. therefore,
The calculated water level of the representative value of the hydrostatic pressure of the maintenance gate under the shortterm design condition shall be determined according to the water level at which the building is scheduled to be overhauled by design.
7.3.5 The gates of diversion bottom holes and other temporary waterretaining buildings have complicated application conditions and different conditions. Therefore, the hydrostatic pressure of the gate represents
The calculated water level of the value can refer to the relevant flood standards specified in 7.2.5, combined with the designed water retention level, and determined by comprehensive analysis.
7.4 External water pressure of pipes and underground structures
7.4.1 The external water pressure of the steel pipe in the dam is mainly formed by the seepage of the reservoir through the concrete of the dam and the infiltration along the outer wall of the steel pipe. This article refers to SD144
85 the relevant provisions of the "Code for Design of Pressure Steel Pipes for Hydropower Stations", and refer to the 17 domestic projects and the waters of Japan's Tian Zi Cang, South Africa's Mochirok, etc.
Prepared by the design experience of the power station and the design standards of the US Bureau of Reclamation Steel Pipe. At present, the value of reduction factor α in engineering design is mostly 1.0.
7.4.2 The measured groundwater level is the basic basis for determining the external water pressure of a building. Due to the heavy workload of groundwater level measurement, the general measurement period
It is shorter and the data obtained is limited, so the higher groundwater level measured can be considered as the basis for determining the design groundwater level. In addition,
In some cases, it is difficult or almost impossible to measure the groundwater level. In this case, it can be considered to be given by a geological expert based on experience. For land near the reservoir
Section, the changes in groundwater level that may occur after the reservoir is impounded should be considered. For diversion tunnels with high internal water pressure, internal water leakage may elevate underground
Water level, especially at the junction of concrete lining and steel pipe, should pay more attention to this situation.
7.4.3 This article follows SD13484 "Code for Design of Hydraulic Tunnels" regarding the calculation method and external water pressure of concrete lining pressure tunnels
The value of the force reduction factor. Considering that even in the rock layer with good integrity, there may still be water leakage through the crack, so this specification
The external water pressure reduction coefficients of the middle and first grade rock masses were adjusted appropriately.
7.4.4 Pressureless tunnels and underground powerhouses can be drained directly through lining to greatly reduce external water pressure. The valve chamber of Yunfeng Hydropower Station is coagulating
Drainage channels are set between the soillined side wall and the surrounding rock to reduce the external water pressure to almost zero; Gongzui and Nanshui Hydropower Stations are set around the underground powerhouse
The drainage corridor is set up, and the drainage groove is set between the lining and the rock body. The external water pressure is not considered in the side wall of the factory building, and the top arch is tested according to the external pressure of 0.3 to 0.5 times.
consider. In view of the practical experience of domestic hydropower projects, the relevant provisions in the provisions are proposed.
7.4.5 This article stipulates that the external water pressure of steel plate lining pressure tunnels is divided into three situations.
(1) For steel lining tunnels with a shallow burial depth, the thickness of the steel plate is usually calculated according to the calculation of the internal water pressure, and the external stabilization can be satisfied with appropriate stiffening measures
It is required that in this case, drainage measures are generally not required. In view of the experience and lessons of the failure of the steel pipe buckling due to external water pressure, the external
The water pressure should be calculated according to the full head below the design groundwater level.
(2) There are many examples of projects to set up drainage tunnels on the upper or side of steel lined tunnels to reduce the groundwater level.
Water ditch, Lubuge hydropower station, foreign countries such as Basconti in the United States, Gangdou in Sweden, etc. The effect of drainage pressure reduction of drainage tunnel and its engineering geological conditions,
Groundwater recharge conditions are closely related. For example, Huamuqiao Hydropower Station, after excavating the drainage hole 16m above the top of the lower horizontal section, make the drainage hole
The above groundwater level is reduced from the original 37.5m to below 10m; and the lower flat section of the highpressure pipeline of the Bascondi Pumped Storage Power Station
Two drainage holes were excavated at 46m above the pipeline, and a large number of drainage holes were drilled to cover the range of 6 highpressure pipes.
The leakage of reinforced concrete lining and steel pipe joints only reduced the external pressure head from 124m to 90m. Engineering practice shows that the use of drainage
Drilling holes and drilling deep holes for drainage can achieve better drainage results, but it is necessary to determine the longterm effectiveness of drainage in combination with engineering geological conditions.
(3) There are also some domestic and foreign engineering examples of setting up drainage pipes between steel pipes and concrete or between concrete and surrounding rocks, such as Japan ’s Shin Takase
The highpressure pipelines of pumped storage power stations in Sichuan and Jinshi are equipped with drainage pipes between the steel pipe and the concrete and between the concrete and the surrounding rock, and the external water pressure
The head of the steel pipe is covered with 0.3 times the vertical thickness of the rock layer, and the highpressure pipeline of Xizhuanshan Pumped Storage Power Station, although between the steel pipe and the concrete
Drainage was installed in the room, but the external water pressure head was not reduced. The Huamuqiao Hydropower Station in China is equipped with a drainage pipe in the highpressure pipeline, and the external water pressure
The head reduction factor is 0.20, the Tianshengqiao II Hydropower Station uses a drainage pipe at the periphery of the steel pipe, and the head reduction factor for external water pressure is 0.5.
It is good to install a drain pipe on the outside of the steel pipe, but it is difficult to maintain and repair. When the groundwater contains segregated minerals, the drain pipe may be blocked.
Therefore, the longterm effectiveness of the drainage pipe must be considered when estimating the drainage effect.
8 Lifting pressure
8.1 General
8.1.1 Concrete dams, sluices and other hydraulic structures are usually constructed by layered pouring concrete.
It is a channel that may seep. Due to the small amount of observation data, the estimated area or contact surface may be part of the total area as a percentage of the total area.
It is difficult, in order to bias the safety plan, the current design specifications of concrete dams, sluices, and hydropower plants in our country all assume the calculation of the rising pressure of the section.
The area factor is 1.0. This is related to the design codes of the United States and Japan that “the uplift pressure inside the dam body and on the dam base surface all act on the calculation
The "crosssectional area" is the same for all sections.
8.1.2 Practical experience and prototype observation data show that concrete solid gravity dams, wideslot dams, openweb dams, bighead dams and arch dams on rock foundations
The distribution pattern of uplift pressure on the base surface is different; the uplift pressure of the same dam type under different foundation geological conditions and antiseepage drainage measures
The force distribution pattern is very different. Therefore, the lifting pressure should be determined according to different hydraulic structure types, foundation geological conditions and antiseepage drainage measures.
Distribution graph of force.
The uplift pressure of the waterretaining structure is generated by the seepage field formed by the upstream and downstream static water heads, and is the load derived from the static water pressure.
Therefore, the calculated water level should be consistent with the calculated water level of the hydrostatic pressure.
8.1.3 In the uplift pressure distribution graph, in the past, it was customary to call the resultant force of the rectangular part depending on the calculated head downstream as the buoyancy force, and the rest
The combined force is called osmotic pressure. For the case where a drainage system is installed at the dam foundation, the main drainage hole is used as the boundary line to calculate the lifting pressure before and after it respectively.
8.2 Uplift pressure of concrete dam
8.2.1 The influence of the geological conditions of the foundation of the concrete dam and the antiseepage drainage measures on its uplift pressure distribution pattern is very complicated, so it is usually based on
According to the measured data of the construction project, statistically analyze the relationship between the pressure head at the drainage hole and the upstream and downstream water levels. According to different seepage and drainage conditions,
Can be divided into the following three situations.
(1) When the dam foundation is provided with antiseepage curtains and drainage holes, statistically analyze the infiltration pressure intensity coefficient α at the drainage holes and define as.
9.3.4 The pressure distribution of centrifugal force in the reverse arc section varies greatly, and the calculation formulas have been simplified to a certain extent, combined with the analysis of experimental research results to determine
The partial factor of its effect is 1.1.
9.4 Impact of water flow on the tail sill
9.4.1 In the current design code, the calculation formula of the impact force of water flow on the tail sill is evolved from the hydrodynamic resistance formula. Due to fatigue
The water flow in the pool is a water jump that changes from a rapid flow to a slow flow. There may be a large water level difference between the upstream and downstream of the tail threshold, which is a semilimited space overflow.
The general flow is very different, so it is unreasonable to use the resistance coefficient of the general flow.
There are many factors that affect the impact of water flow on the tail sill, of which the flow pattern in the stilling tank is the most significant. Canada, Japan, United Kingdom and
Indian scholars have studied this much. Although the experimental conditions, experimental methods, and set standards discussed in different literatures are not consistent, the impact threshold
The flow pattern of the water flow is generally consistent, and the resistance coefficient Kd can be determined according to the following three different flow patterns.
Flow pattern I. No water jump is formed in the stilling tank, and the water flow directly hits the tail sill;
Flow pattern II. A water jump is formed in the stilling tank, and the downstream water depth does not affect the position of the jump head;
Flow pattern III. A water jump is formed in the stilling tank, and the downstream water depth affects the position of the jump head.
Regarding the flow resistance coefficient Kd of flow state I, the measurement result of Rand is about 0.6, and the result of Karki is 0.324.
The result of Rajaratnam is 0.5, and the result of Narayanan is 0.45. Otthur gives the empirical formula and its calculation
The result is 0.57 ~ 0.63.
The flow state II is a transition from the flow state I, and the upper limit value of the drag coefficient is 0.5, and decreases with the increase of the Fr value. Corresponds to Fr
= 10, calculated according to Rajaranan ’s formula, the resistance coefficient gradually decreases to 0.09; calculated according to the experience formula of Outsourcing, Kd = 0.39 ～ 0.14,
The larger the Fr, the smaller the value.
Regarding the flow state III, due to the increase of the downstream water depth, the drag coefficient is smaller than that of the flow state II, and the calculation result according to the Rajaranan formula is 0.07 ～ 0.42
The larger the Fr, the smaller the value.
In summary, for the case where no water jump is formed in the stilling tank and the water flow directly hits the tail sill, the resistance coefficient may be 0.6; for the stilling tank
In the case where a water jump is formed and 3≤Fr≤10, the drag coefficient may be 0.1 to 0.5, and the larger the Fr, the smaller the value.
9.5 Pulsating pressure
9.5.1 The pulsating load encountered in engineering design involves "point" pulsating pressure and "surface" pulsating pressure and their relationship. This specification is based on domestic and foreign
Existing research results have made appropriate regulations.
(1) For the turbulent boundary layer type pulsating pressure at the top, steep groove and sill of the overflow type factory building, according to the research results of Pan Dejia and others in China
And the timespace correlation function derived from the observation of the prototype of Japan's Xinchengyu project according to the law of exponential decay, and the "pointsurface" conversion coefficient is derived
The value of βm is. when the length of the structural block in the downstream direction Lm ≤ 5m, βm = 0.133, this specification takes 0.14; when Lm> 5m, part of the pulsating pressure is not
In the phase synchronization range, βm = 0.1. The above provisions only consider vertical correlation, and horizontal correlation is generally vertical correlation
Therefore, the value taken in this specification has sufficient safety margin.
(2) With regard to the "pointplane" relationship of the water jump acting on the pulsating pressure of the bottom plate in the flatbottomed stilling pool, this specification refers to the 11th International Dam Conference
The results of the trial on βm published at the meeting. However, this research is not enough at present, and important projects should be determined through appropriate special tests.
The pulsating pressure of water flow is an alternating load, so it can be considered as a positive or negative value according to different conditions according to different design requirements.
9.5.2, 9.5.4 The pulsating pressure is random for space or time (random field or random process), and its statistical characteristics include amplitude of pulsating pressure
Value (intensity), timespatial correlation characteristics and spectrum (power spectrum, energy spectrum) density and spatial correlation scale and other aspects.
According to the method of defining "pressure coefficient" in hydraulics, the pulsating pressure coefficient Kp is defined as.
The statistical analysis results of a large number of prototype observations and model test data show that the amplitude of the pulsating pressure of the water flow is approximately normally distributed. This specification
Take 2.31 times the mean square deviation as the representative value of pulsating pressure, take 3 times the mean square deviation as the design value, and the corresponding subfactor of action is 1.3.
9.5.3 The pulsating pressure coefficient of water flow can be determined according to the characteristics of the water flow according to the smooth flow boundary and sudden flow boundary of the rapid area (Fr >> 1). former
It belongs to the turbulent boundary layer type, such as the top of the overflow type factory building, the bottom plate of the discharge steep groove and the spur flow sill surface; the latter belongs to the strong separation flow type,
Such as the bottom of the water jump energy dissipation pool and the sudden expansion and contraction of the side walls.
(1) Theoretical analysis shows that the theoretical value of the pulsating pressure coefficient Kp on the inner wall of the turbulent boundary layer is about 3%. Fluctuating pressure of smooth boundary layer in jet stream
The force amplitude is not large, which has been confirmed by a large number of prototype observation data and model test results.
Regarding the pulsating pressure coefficient Kp on the roof of the overflowtype factory building, the existing prototype observation data of Xiuwen, Chitan, Wujiangdu, Japan's Xinchengyu, etc.,
The change range is 0.20% ～ 1.59%, among which the revision is 1.6%; Chitan is 0.2% ～ 0.77%; Xin'an River is 0.36% ～ 1.04%; Wujiang Duzuo
The top of the auxiliary plant of the shore ski slope is 0.81% to 1.59%; the fullness (horizontal protection tank, analogy to the top of the flat overflow plant) is 0.45% to 1.58%; Japan's Xincheng
The plume is 0.2% to 0.77% (based on the head of the flow field outside the boundary layer). In addition, we can still refer to the model test data of two projects. Ertan is
0.45% to 1.1%; the top of the main building of the Three Gorges is 0.8% to 1.84% (when a ventilation slot is provided at the end of the reverse arc, it can be increased to 2.08% to 2.82%).
Regarding the water flow pulsation pressure coefficients of the drainage trough trough body, nasal ridge, etc., there are also prototype observations and models of the model mouth, Wujiangdu and other projects
Test data is available for reference. The steep trough body of the mode entrance is 1.6%; the arch aqueduct body of the downstream of the Wujiangdu right bank spillway tunnel is 0.72% ～ 2.00%, counter arc
The central part is 0.69%; the lowest point of the antiarc of Wujiangdu left spillway tunnel is 0.45% ～ 0.63%, and 0.86% ～ 1.46% above the sill; Wujiangdu left bank slips
The lowest point of the antiarc of the snow road is 1.38% to 1.68%, and the top of the nose is 1.01% to 1.34%; the overflow surface is 0.23% to 1.52%; Wujiangdu No. 2 overflow hole
The lowest point of antiarc is 0.2% ～ 1.2%, 0.3% ～ 1.0% on the nasal ridge; the chute body of the flat bridge test is less than 1%, and 0.74% ～ 1.16% on the nasal ridge.
Based on the above research results, this code specifies the pulsating pressure on the roof, chute and nasal of the overflow type plant. Due to its nature
All belong to the pressure fluctuation of the turbulent boundary layer, so the lower limit can be taken as 0.010. Regarding the upper limit, considering the short flow of the top of the overflow plant, the boundary layer
Generally, it does not develop to the water surface, and the influence of aeration is small, so 0.015 is adopted; for the drain channel, the boundary layer usually develops to the surface due to its long process.
It is usually necessary to set an aeration groove, and the pulsating pressure on the bottom plate of the downstream of the groove increases exponentially, so 0.025 is taken; for the pulsating pressure of the water flow on the nasal barrier, the actual measurement
The result shows that it is generally not large, but considering that this part generally has the effect of aeration and has a backpressure gradient, the boundary layer is relatively unstable, so 0.020 is taken.
(2) The water jump in the stilling pool, the water flow changes from the rapid flow to the slow flow, and its water flow movement has strong separation, diffusion and mixing effects. therefore,
The pressure pulsation of the water flow on the bottom of the stilling tank is more complicated, and there are many influencing factors, such as the Fresnel number, Reynolds number, submergence degree, and the length along the water jump.
Changes in the face. This specification only stipulates the value of Kp according to the difference between the inflow (at the contraction crosssection) Fres number Fr1 and the distance along the length of the water jump.
The impact of Fr1 can only be considered by distinguishing between more than 3.5 and less than 3.5. Considering that the water jumps in the stilling pool are common in general projects
A certain degree of submergence, so this specification specifies different Kp values for different parts of the stilling tank, and its lower Kpmax value is taken.
9.6 Water hammer pressure
9.6.1 The current commonly used calculation methods for water hammer pressure in pressure pipes of hydropower stations are analytical method, characteristic line method and numerical integration method. For large
For engineering and complex pipelines, numerical integration method is mostly used, and it can be jointly calculated with surge in surge chamber. For small and medium projects and simple pipelines (including
It can be simplified into a complex pipeline with a simple pipeline.) It can be calculated according to the formula listed in Appendix E, and its calculation result has a certain degree of accuracy and safety after correction.
The analytical formulas listed in Appendix E are derived according to the straightline change based on the process of pipe orifice outflow and guide vane opening (closing).
Indirect water hammer pressure calculation. When used in counterturbine turbines, the error is large and should be multiplied by a correction factor greater than 1.0. Refer to "Hydropower Station Machine
"Electrical Design Manual (Hydraulic Machinery)", the correction factor Ky is related to the specific speed of the impact turbine, which needs to be determined through tests;
1.2 for Francis turbines and 1.4 for axial turbines.
9.6.2 After the arrangement and structural dimensions of the pressure water channel are determined, the representative value of the water hammer pressure in the calculated pressure water channel should first be distinguished from different designs
Status and unit operating conditions; the design status should take into account the permanent status and occasional status. This article refers to DL/T 50581996 "Hydraulic Power Station Pressure Regulation
"Specifications for the Design of the Office" make specific provisions.
The control conditions for the calculation of the representative value of the water hammer pressure of the upstream and downstream pressure water channels of conventional hydropower stations are that the unit suddenly discards the entire load or the unit
From partial load to full load. The calculation condition of the upstream pressure water channel of the pumped storage power station is the same as that of the conventional hydropower station, but the downstream pressure water channel 1
Generally controlled by the pump working conditions, the minimum head is determined by the conditions when the high water level under the corresponding design conditions of the reservoir and the lowest storage level of the upper reservoir are pressed.
9.6.3 The calculation formula given in this article is based on the assumption that the product of the water hammer pressure and the length of each section of the pipeline along the pipeline is linear with the flow rate.
Fixed. The ΔHi and ΔHj calculated according to the formula are the water hammer pressure increase values of the calculated sections of the pipeline, that is, the calculated values of
Representative value of water hammer pressure.
