NB 35047-2015 English PDF (NB35047-2015)
NB 35047-2015 English PDF (NB35047-2015)
NB 35047-2015: Code for seismic design of hydraulic structures of hydropower project
ENERGY INDUSTRY STANDARD OF
THE PEOPLE REPUBLIC OF CHINA
Registration number. J2042-2015
P NB 35047-2015
Replacing DL 5073-2000
Code for seismic design of
hydraulic structures of hydropower project
ISSUED ON. APRIL 02, 2015
IMPLEMENTED ON. SEPTEMBER 01, 2015
Issued by. National Energy Administration
Table of Contents
Foreword ... 4
1 General ... 9
2 Terms and symbols ... 11
2.1 Terms ... 11
2.2 Symbols ... 14
3 Basic requirements ... 16
4 Site, foundation and slope ... 19
4.1 Site ... 19
4.2 Foundation ... 21
4.3 Slope ... 22
5 General in earthquake action and seismic analysis ... 24
5.1 Seismic action components and its combination ... 24
5.2 Seismic action types ... 25
5.3 Design seismic acceleration and standard design response spectrum ... 25 5.4 Earthquake action and combination with other actions ... 26
5.5 Structural modeling and calculation method ... 27
5.6 Dynamic properties of concrete and foundation rock for hydraulic structures ... 29
5.7 Seismic design ultimate limit state with partial factors ... 30
5.8 Seismic calculation for subsidiary structure ... 31
5.9 Seismic earth pressure ... 32
6 Embankment dam ... 33
6.1 Seismic calculation ... 33
6.2 Seismic measure ... 36
7 Gravity dam ... 39
7.1 Seismic calculation ... 39
7.2 Seismic measure ... 43
8 Arch dam ... 44
8.1 Seismic calculation ... 44
8.2 Seismic measure ... 47
9 Sluice ... 49
9.1 Seismic calculation ... 49
9.2 Seismic measure ... 51
10 Underground hydraulic structure ... 53
10.1 Seismic calculation ... 53
10.2 Seismic measure ... 55
11 Intake tower ... 56
11.1 Seismic calculation ... 56
11.2 Seismic measure ... 61
12 Penstock of hydropower station and ground powerhouse ... 63
12.1 Penstock... 63
12.2 Ground powerhouse ... 64
13 Aqueduct ... 65
13.1 Seismic calculation ... 65
13.2 Seismic measure ... 66
14 Shiplift ... 67
14.1 Seismic calculation ... 67
14.2 Seismic measure ... 67
Appendix A Seismic stability calculation of embankment dam with quasi-static method ... 69
Appendix B Calculation of aqueduct dynamic water pressure ... 72
Explanation of wording in the Code ... 76
List of normative standards ... 77
2 Terms and symbols
2.1.1 Seismic design
Special design for the engineering structure of the strong earthquake zone. It generally includes two aspects. seismic calculation and seismic measure. 2.1.2 Basic intensity
Within the 50-year period, under general site conditions, it may encounter the seismic intensity of which the exceeding probability P50 is 0.10. Generally, the corresponding seismic intensity value is determined in accordance with the Appendix [in GB 18306], in accordance with the seismic peak acceleration value as indicated in GB 18306 for the site.
2.1.3 Design intensity
The seismic intensity determined as the basis for engineering fortification based on the basic intensity.
2.1.4 Reservoir earthquake
Earthquakes associated with reservoir impoundment that generally occur within 10 km of the reservoir bank.
2.1.5 Maximum credible earthquake
Earthquakes with the greatest ground motion that may occur at sites which are evaluated in accordance with the seismic geological conditions of the project site.
2.1.6 Scenario earthquake
Among the potential sources that may generate peak acceleration of ground motion at the site, the earthquake with the magnitude and epicentral distance that is determined along the main fault location in accordance with the principle of the maximum probability of occurrence.
2.1.7 Seismic ground motion
Geotechnical movement caused by earthquakes.
2.1.8 Seismic action
The dynamic action of ground motion on the structure.
2.1.18 Mode decomposition method
The method of firstly solving the seismic effect of the structure corresponding to its various modes at each stage and then combining them into the structure total seismic effect. The direct superimposing of the mode effects of each stage obtained by time-history analytical method is called mode decomposition time- history analytical method, whilst the combination of those obtained by reaction spectrum is called mode decomposition reaction spectrum method.
2.1.19 Square root of the sum of the squares (SRSS) method
The mode combination method of taking the square root of the sum of squared seismic effects of various modes as the total seismic action.
2.1.20 Complete quadratic combination (CQC) method
The mode combination method of taking the square of the seismic effect of each mode and the square root of the sum of the coupling items of different vibration modes as total seismic effect.
2.1.21 Seismic hydrodynamic pressure
The dynamic pressure exerted by the water body on the structure due to
2.1.22 Seismic earth pressure
The dynamic pressure exerted by the soil on the structure caused by the earthquake.
2.1.23 Quasi static method
The static analytical method of using the product of gravity action, the ratio of design seismic acceleration to gravity acceleration, and the given dynamic distribution factor as the designed seismic force.
2.1.24 Seismic effect reduction factor
A factor that is introduced to reduce the seismic effects due to the simplification of the calculation method of the seismic effect.
2.1.25 Natural vibration period
The time required for the structure to complete a free vibration in accordance with a certain mode. The natural vibration period corresponding to the first mode is called the basic natural vibration period.
years is 0.10 for the hydraulic structures of categories other than
category A, but it shall also not be less than the corresponding
seismic horizontal acceleration divisional value in the divisional map. 3 For the hydraulic structures, of which the engineering seismic
fortification is category A, which requires specific site seismic safety evaluation, in addition to performing seismic design based on the
design seismic peak acceleration, it shall make specific
demonstration for the safety margin of avoiding uncontrolled
drainage catastrophe of reservoir water when it is subject to the
maximum credible earthquake of the site, and propose the seismic
safety theme report it is based on, wherein. the horizontal peak
acceleration representative value of the ?€?maximum credible
earthquake?€? shall be determined in accordance with the seismic
geological conditions of the site, using the deterministic method or
the result of the probability method of which the exceeding
probability P100 within 100 years is 0.01.
4 When the backwater structure is upgraded from grade 2 to grade 1 due to dam height and seismic geological conditions, in addition to performing seismic design based on the horizontal design seismic peak acceleration of which the exceeding probability P50 within 50 years is 0.10, it shall also be based on the horizontal design seismic peak acceleration of which the exceeding probability P100 within 100 years is 0.05 to perform specific demonstration for the safety margin of avoiding uncontrolled drainage
catastrophe of reservoir water.
5 In the special report on seismic safety, the site-related design response spectrum should be determined in accordance with the scenario
earthquake corresponding to the horizontal design seismic peak
acceleration, and produce the manually simulated seismic acceleration
time-history based on this; for the strong nonlinearity analysis of the structural seismic effect, it should study the influence of the non-stationary frequency of ground motion; when the seismic fault is less than 30 km
from the site and the inclination angle is less than 70??, it should be
included in the influence of the hanging wall effect; when the distance from the site is less than 10 km and the magnitude is greater than 7.0, it should study the process that, in the near-field large earthquake, the seismogenic fault acts as the surface source rupturing, to directly generate the random seismic acceleration time-history of the site, and take-use the time-history of which the asymptotic spectrum peak period is most approaching to the basic period of the structure.
6 The short-term condition during the construction period can be exempted from combining with the seismic action.
4.2.1 The seismic design of the foundation of a hydraulic structure shall take into account the type, load, hydraulic and operating conditions of the upper structures, as well as the engineering geological and hydrogeological
conditions of the foundation and bank slope.
4.2.2 For foundations and bank slopes of dams, sluices, and other backwater structures, it shall meet the requirements for no failure of strength instability (including sand liquefaction, soft cohesive soil subsidence, etc.) and seepage deformation under the seismic action of design intensity, to avoid harmful deformation that affects the use of the structures.
4.2.3 The weak structural planes such as ruptures, fracture zones and interlayer displacements in the foundations and bank slopes of hydraulic structures, especially the gently inclined angled mud layers and rock layers that may be muddy, shall be subject to demonstration that it does not cause instability or unallowed deformation under the seismic action based on their occurrence and burial depth, boundary conditions, seepage conditions, physical and
mechanical properties, and it shall take seismic measures if necessary. 4.2.4 The anti-seepage structure of the foundation and bank slope of the hydraulic structure and its connection parts, as well as the drainage filtration structure shall take effective measures to prevent harmful cracks or osmotic damage during the earthquake.
4.2.5 For the uneven foundations with large changes in the horizontal direction such as geotechnical properties and thicknesses, it shall take measures to avoid large uneven settlement, slippage and concentrated leakage during earthquakes, and take measures to improve the upper structure?€?s ability to adapt to the uneven settlement of the foundation.
4.2.6 The determination of soil liquefaction category in the foundation shall be carried out in accordance with the relevant provisions of GB 50287 Code for hydropower engineering geological investigation.
4.2.7 For the liquefiable soil layer in the foundation, it can be based on the project type and actual conditions to select the following seismic measures. 1 Excavate the liquefied soil layer and replace it with non-liquefied soil; 2 Artificial densification such as vibrating densification and strong blow compaction;
3 Ballasting and drainage;
5 General in earthquake action and seismic analysis
5.1 Seismic action components and its combination
5.1.1 In general, hydraulic structures other than aqueducts may only consider horizontal seismic action.
5.1.2 The following grade 1 and 2 hydraulic structures of which the design intensity is VIII and IX. the backwater structures such as embankment dams and gravity dams, long cantilever, large-span or towering hydraulic concrete structures shall take into account the horizontal and vertical seismic action simultaneously. The representative value of the vertical design seismic acceleration can generally take 2/3 of the representative value of the horizontal design seismic acceleration. For the near-site earthquake, it shall take the representative value of the horizontal design seismic acceleration.
5.1.3 For special types of arch dams with severe asymmetry and void, as well as the grade 1 and 2 double-curved arch dam of which the design intensity is VIII and IX, it should perform specific study for its vertical seismic effect. 5.1.4 For horizontal seismic action, in general, in the seismic design of embankment dams and concrete gravity dams, it may only take into account of the horizontal seismic action along the river flowing direction. For the gravity dam section on the steep slope of the two banks, it should take into account of the horizontal seismic action perpendicular to the river flowing direction; for important embankment dams, it should make special study for the horizontal seismic action perpendicular to the river flowing direction.
5.1.5 For the concrete arch dam and sluice, it shall consider the horizontal seismic action along the river flowing direction and that perpendicular to the river flowing direction.
5.1.6 For the hydraulic concrete structure with the similar lateral stiffness along the two main axial directions, such as the intake tower and the sluice top frame, it shall consider the horizontal seismic action of the structure along the two main axial directions.
5.1.7 When the mode decomposition method is used to simultaneously
calculate the seismic effects in mutually orthogonal directions, the total seismic effect may take the square root value of the sum of the squares of the seismic effects in mutually orthogonal directions.
6 Embankment dam
6.1 Seismic calculation
6.1.1 Seismic calculation shall include seismic stability calculation, permanent deformation calculation, anti-seepage safety evaluation and liquefaction determination, etc., the comprehensive evaluation of seismic safety is
performed combined with seismic measures.
6.1.2 For the seismic stability calculation of embankment dams, the quasi-static method is generally used to calculate the seismic effects. When one of the following conditions is met, the finite element method shall be used
simultaneously to perform the dynamic analysis for the seismic effect of the dam body and the dam foundation, to judge comprehensively its seismic
1 Design intensity VII and dam height of 150 m or more;
2 Design intensity VIII, IX and dam height of 70 m or more;
3 When the thickness of the cover layer exceeds 40 m or there is a liquefiable soil layer in the dam foundation.
6.1.3 When the quasi-static method is used to calculate the seismic effect and the seismic stability calculation is carried out for the embankment dam, it should be based on the slip-arc method based on the force between the strips to make verification in accordance with clause 5.7.1 of this Code, the calculation formula is as shown in Appendix A. For foundations with thin soft clay interlayers, as well as thin inclined wall dams and thin core wall dams, it may use the slip wedge method for calculation.
6.1.4 When the quasi-static method is used to calculate the seismic effect and the seismic stability calculation is carried out for the embankment dam, the dynamic distribution factor of the seismic inertia force of the particle i shall be adopted in accordance with the provisions of Table 6.1.4. In the table, the ??m is taken as 3.0, 2.5, and 2.0 when the design intensity is VII, VIII, and IX. 6.1.5 When the embankment dam uses the quasi-static method to calculate the seismic effect and the seismic stability calculation is carried out, for the grade 1 and 2 embankment dam, it should use the dynamic test to determine the dynamic shear strength of the soil body. When the dynamic strength given by the dynamic test is higher than the corresponding static strength, it shall take the static strength value.
For non-liquefied soils such as cohesive soil and compact sand gravel, when 6.2 Seismic measure
6.2.1 For the construction of embankment dams in strong earthquake areas, it should use the dam axis that is curved straight or upstream. It should not adopt a dam axis that is curved downstream, folded or S-shaped.
6.2.2 When the design intensity is VIlI and IX, it should select the rockfill dam, the anti-seepage body should not adopt the type of rigid core wall. When using a homogeneous dam, it shall set an internal drainage system to lower the immersion line.
6.2.3 The safety freeboard of embankment dams in strong earthquake areas shall include earthquake surge height and earthquake subsidence, which can be determined in accordance with the following principles.
1 In accordance with the design intensity and the water depth in front of the dam, the earthquake surge height is taken as 0.5 m ~ 1.5 m.
2 When the design intensity is VII, VIII, IX, the safety freeboard shall take into account of the seismic subsidence of the dam and foundation.
3 For the surges that may be formed by large-scale collapse and landslides in the reservoir area due to earthquakes, it shall perform special research. 6.2.4 When the design intensity is VIII or IX, it should widen the dam crest and slow down the upper dam slope. The foot of the slope can be covered or
ballasted, the upper dam slope can be protected by a masonry block stone, the upper dam slope can be reinforced with reinforcing steel, geosynthetic
materials or concrete frame.
6.2.5 It shall appropriately improve the seismic indicators of the embankment dam anti-seepage body in the strong earthquake area, especially the top of the dam which may crack during earthquake and the connection part between the dam body and the bank slope or concrete structure. The joint surface of the anti-seepage body and the bank slope or concrete structure shall not be too steep, the slope changing angle should not be too large, there shall be no anti- slope and sudden slope change; it shall appropriately thicken the anti-seepage body and its anti-filter layer and transition layer upstream and downstream of it. 6.2.6 It shall select the earth and rock materials with good seismic performance and permeability stability and good grading for dam construction. Uniform medium sand, fine sand, grit and silt should not be used as dam materials in strong earthquake areas.
6.2.7 For the compaction function and compaction of cohesive soils and the filling dry density or porosity of the rockfill, it shall be carried out in accordance 7 Gravity dam
7.1 Seismic calculation
7.1.1 For the seismic calculation of gravity dams, it shall perform the dam strength and the overall anti-sliding stability analysis along the construction base plane. For roller compacted concrete gravity dams, it shall also perform the anti-sliding stability analysis along the rolling layer.
7.1.2 For the seismic analysis of gravity dams, generally the highest dam section of different types of dam sections can be taken, which is carried out in accordance with a single dam section. For gravity dams with significant overall actions, it should perform the comprehensive analysis for the entire dam section. 7.1.3 The seismic calculation of gravity dam can be performed by dynamic method or quasi-static method. the seismic effects of the gravity dam of the engineering seismic fortification category A, or that of the engineering seismic fortification category B and C but the design intensity VIII and above or the dam height higher above 70 m shall be calculated by the dynamic method.
7.1.4 The overall anti-sliding stability analysis of the gravity dam along the foundation base plane and the anti-sliding stability analysis along the rolling compaction layer shall be calculated in accordance with the shear strength formula in the rigid body limit equilibrium method. For the deep anti-sliding stability problem, the rigid body limit equilibrium method based on the equal safety factor method (also known as the equal-K method) shall be taken as the basic anal...