NB 35047-2015 PDF in English
NB 35047-2015 (NB35047-2015) PDF English
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Code for seismic design of hydraulic structures of hydropower project
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NB 35047-2015: PDF in English NB 35047-2015
NB
ENERGY INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 27.140
P 59
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 Terms
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.
time history.
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
seismic effect.
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 Foundation
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
stability.
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 αm 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 analysis method. For gravity dams with complex geological conditions, it
should supplement nonlinear finite element analysis.
7.1.5 For gravity dams with a dam height greater than 70 m, the strength safety
shall subject to the finite element method analysis in addition to the material
mechanical calculation of dynamic and static force. For the gravity dam of the
engineering seismic fortification category A or with complex structure or with
complex geological conditions, it shall consider the nonlinear influence such as
materials when performing finite element analysis. For gravity dams that shall
be subjected to seismic calculation under the maximum credible earthquake,
special studies shall be carried out using the finite element method that
accounts for the nonlinear characteristics of the dam and foundation.
7.1.6 The dynamic analysis method of gravity dam shall adopt the mode
decomposition method. For the gravity dam of which the seismic fortification
category A, it shall increase the calculation evaluation of nonlinear finite
element method.
7.1.7 Under the design earthquake, the dynamic method is used to check the
the rock mass shall take the static mean value, the partial factor shall be 1.0,
the structural factor of anti-sliding stability shall not be less than 1.40; or
otherwise it shall use the time-history analysis method to perform
comprehensive analysis judgement of the seismic stability of the potential
sliding rock mass of the abutment.
8.1.10 When using the time-history analysis method to comprehensively
analyze and evaluate the seismic stability of the potential sliding rock of the
abutment, the following steps shall be taken.
1 Under the action of the three components of the design ground motion, the
time-history analysis method is used to calculate the combined time-
history of static and dynamic integration of the arch end, and it acts on the
potential sliding rock mass together with the inertial force of the rock mass
without the power amplification effect.
2 In each time step, the structural factor of the stability of the abutment rock
mass is calculated in accordance with the rigid body limit equilibrium
method, to provide the time-history of the structural factor changes with
time in the whole seismic process, and the minimum value of the structural
factor in the time-history is used to evaluate the abutment seismic stability.
3 If the minimum value of the structural factor time-history does not meet the
requirements specified in clause 8.1.9, it shall be based on the duration
and extent of the stability index overrun, to comprehensively evaluate the
anti-sliding stability of the potential sliding rock of the abutment as well as
its impact onto the integral safety of the dam.
8.1.11 In the seismic calculation analysis of important arch dams fortified with
the maximum credible earthquakes, it shall take into account of the impacts of
dam transverse joint and the contact nonlinearities forming the controlled
slipping plane in the dam foundation, the material nonlinearities of the main
weak belts in the near-site bedrock, and the radiation damping effect of the far-
site foundation. For important arch dams within the scope of clause 3.0.6, it
shall be based on the calculation analysis and model test, combined with the
engineering comparison, in accordance with the fortification requirements of the
catastrophic failure of the reservoir water out of control, to perform the
comprehensive evaluation.
8.1.12 When the seismic analysis and evaluation of the dam is carried out in
accordance with the provisions of clause 8.1.11, the inflection point on the curve
of the typical deformation of the dam or bedrock changed with the increase of
the seismic action may be used as the evaluation index for the overall safety of
the dam foundation system, at this time, the ratio of the seismic acceleration
value to the design seismic acceleration is used as the safety margin for the
dam to avoid uncontrolled drainage catastrophe of reservoir water.
by the formula (7.1.14) can be converted into the waterfront additional mass
corresponding to the unit seismic acceleration for consideration.
9.1.8 The representative value of the seismic active earth pressure acting on
the sluice side pier or side wall and wing wall may be calculated in accordance
with the provisions of clause 5.9.1.
9.1.9 The structural strength of each component of the sluice structure shall be
subject to seismic verification in accordance with clause 5.7.4 and comply with
other relevant provisions of the SL 265 Design specification for sluice. It shall
check the influence of the structural deformation of each part of the sluice during
earthquake on the operation of the hoisting equipment.
9.1.10 The anti-sliding stability along the bottom surface of the sluice foundation
shall determine the seismic effect in accordance with this Code and comply with
other relevant provisions of SL 265. When the dynamic method is used to
calculate the seismic stability of the sluice, it shall use the seismic effect
consistent with the strength verification.
9.1.11 For the sluice on the rock foundation, when using the dynamic method
or quasi-static method to check the anti-sliding stability along the foundation
bottom surface or the shallow layer of sluice foundation, it can make reference
to the provisions of 7.1.7 or 7.1.15, respectively; for the sluice on the soil
foundation, when using the quasi-static method to verify the anti-sliding stability
along the foundation bottom surface or the shallow layer of sluice foundation,
the structural factor shall be taken as 1.2.
9.2 Seismic measure
9.2.1 When the pile foundation is used for the sluice foundation, the connection
between the pile foundation and the sluice bottom plate and the anti-seepage
measures shall be taken. The bottom plate may be provided with measures
such as anti-seepage wall, tooth wall and tail sill, to prevent the foundation from
being separated from the sluice bottom plate due to seismic action, thus
causing piping or concentrated seepage.
9.2.2 The arrangement of the sluice chamber structure shall be symmetrical
and enhance the integrity. The sluice chamber shall adopt a reinforced concrete
integral structure. The water-stop structure of the split joint shall be of a type
and material that is durable and adaptable to large deformations, and the water-
stop measures for the split joint of key parts shall be strengthened.
9.2.3 It should reduce the height of the rack bridge and reduce the weight of the
top of the rack from the selection and arrangement of the sluice and hoist.
9.2.4 The frame bridge should adopt the frame structure, it shall strengthen the
11 Intake tower
11.1 Seismic calculation
11.1.1 The seismic calculation of the intake tower shall include the verification
of the tower body stress or internal force, the overall anti-sliding and anti-
overturning stability, and the bearing capacity of the foundation at the bottom of
the tower. The non-structural components, the auxiliary electromechanical
equipment and the joints with the structural body shall be subject to seismic
design.
11.1.2 The dynamic method or quasi-static method shall be used to calculate
the seismic effect of the intake tower. For the non-reinforced concrete structure
intake tower of which the engineering seismic fortificat......
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Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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