Dams and Earthquake: Design of Dams to Resist Earthquake - Conference Proceedings

319 Pages·1981·51.21 MB·English

by  Civil Engineers

Dams
and
earthquake

2 -6 -<r~c
Dams
and
earthquake
Proceedings of a conference held at the Institution
of Civil Engineers, London, on 1-2 October 1980
Thomas Telford Limited, London, 1981
Organized by the Institution of Civil Engineers in association with the British
Section of the International Commission on Large Dams and the Society for
Earthquake and Civil Engineering Dynamics—the British Section of the
International Association for Earthquake Engineering: also sponsored by UNESCO
Organizing Committee: Mr R. G. T. Lane (Chairman); Mr D. A. Howells;
Professor J. K. T. L. Nash; Mr F. F. Poskitt
Cover photograph by courtesy of Sir Alexander Gibb and Partners,
Consulting Engineers
Published for the Institution of Civil Engineers by Thomas Telford Limited,
PO Box 101, 26-34 Old Street, London EC1P 1JH
First published 1981
ISBN: 0 7277 0123 1
© The Institution of Civil Engineers, 1981
All rights, including translation, reserved. Except for fair copying, no part of this
publication may be reproduced, stored in a retrieval system, or transmitted in any
form or by any means electronic, mechanical, photocopying, recording or otherwise
without the prior written permission of the publisher. Requests should be directed
to the Managing Editor, Publications Division, Institution of Civil Engineers,
PO Box 101, 26-34 Old Street, London EC1P 1JH
The Institution of Civil Engineers as a body does not accept responsibility for the
statements made or for the opinions expressed in the following pages
Printed in Great Britain by Burlington Press (Cambridge) Ltd, Foxton, Cambridge
CONTENTS
Opening address. Marcus Fox, MP 1
SESSION 1: SEISMICITY
1. Optimum seismic input in the design of large structures. R E. Long 3
7 2. The definition of seismic risk at dam sites. R Chaplow 9
3. Substitute short duration earthquake accelerograms for non-linear analysis.
O. C Zienkiewicz, N. Bicanic and R Fejzo 17
4. Seismic risk studies for large dam projects in northern Iraq. M. B. Tosic 23
/ 5. Design earthquake recurrence analysis. E. R Ries, N. R Vaidya and
A. P. Michalopoulos 31
6. Aseismic design considerations for a large arch dam. R Dungar 37
Discussion on Papers 1-6 45
SESSION 2: MATERIALS BEHAVIOUR WHEN SUBJECTED TO EARTHQUAKE
7. Materials behaviour under earthquake loading. P. Bertacchi 57
8. Liquefaction potential of Wash sands. T. D. Ruxton 61
9. Dynamic behaviour of rockfill dams. M. Nose and K. Baba 69
10. Friction parameters for the design of rock slopes to withstand earthquake
loading. S. R Hencher 79
11. Peculiarities of the seismic-resistant analysis of earth dams with pervious
gravelly shells. A. J. L. Bolognesi 89
f 12. Lessons from the performance of earth dams during earthquake. H. Bolton
Seed 97
13. Seismic stability analysis of Kokubo dam. K. Mori, K. Ishihara, K. Takeya
and K. Kanazashi 105
14. The response of concrete to short term loading. J. W. Dougill 113
15. Failure and damage: earth and rock fill. D. A. Howells 125
16. Thirty years of research work on earthquake resistance of hydraulic
structures in China C Shen and H. Chen 129
17. Soil amplified earthquake ground motions. J. N. Protonotarios 137
Discussion on Papers 7-17 145
SESSION 3: STRUCTURE BEHAVIOUR WHEN SUBJECTED TO EARTHQUAKE
18. A simplified method for the earthquake resistant design of earth dams.
S. K. Sarma 155
19. Seismic analysis and design consideration for concrete dams. K. J. Dreher 161
20. Computational models for the transient dynamic analysis of concrete dams.
O. C. Zienkiewicz, E. Hinton, N. Bicanic and P. Fejzo 171
21. Earth dam analysis for earthquakes: numerical solution and constitutive
relations for non-linear (damage) analysis. O. C Zienkiewicz, K. H. Leung,
E. Hinton and C T. Chang
22. Seismic studies in relation to the design of Alicura dam and appurtenant
works. B. Gilg
23. Natural frequencies and response characteristics of gravity dams. D. Altinisik
and R T. Severn
24. Aseismic design of arch dams: particularly the contribution from the reservoir,
and multiple-support excitation of the base. D. Altinisik, P. A A Back,
S. R Ledbetter, R T. Severn and C A Taylor
25. The use of models in assessing the behaviour of concrete dams. G. Oberti and
A Castoldi
26. Theoretical assessment of the behaviour of arch dams for seismic loading.
G. L. Hutchinson and T. G. Tsicnias
27. Criteria for the earthquake resistant design of concrete dams. J. Laginha
Serafim
Discussion on Papers 18-27
SESSION 4: ENVIRONMENT AND RISK INCLUDING INDUCED SEISMICITY
28. Dams, natural and induced earthquakes and the environment E. T. Haws
and N. Reilly
29. Hazards of natural and induced seismicity in the vicinity of large dams.
P. L. Willmore
30. Computed and observed deformation of two embankment dams under
seismic loading. M. P. Romo and D. Resendiz
31. Full-scale forced vibration studies and mathematical model formation of
arch concrete dams. T. A Paskalov, J. T. Petrovski and D. V. Jurukovski
32. The potential for induced seismicity—geological approaches. B. O. Skipp
and M. Higgins
33. Probable risk estimation due to reservoir induced seismicity. S. K. Guha,
J. G. Padale and P. D. Gosavi
Discussion on Papers 28-33
Closing address. R G. T. Lane and H. Bolton Seed
Opening address
MARCUS FOX, MP (Parliamentary Under Secretary of State,
Department of the Environment)
The consequences of failure of a large dam are and the damage extended to at least 150km from
many times greater than those of any other type the epicentre.
of structure. Civil engineers have recognized
this themselves, and I am most impressed by We think of severe earthquakes occurring
the world-wide co-operation and exchange of primarily in known seismic zones, but I am told
information that takes place through the that these are virtually impossible to predict
International Commission on Large Dams. and earthquakes have occured outside those
zones in areas considered to be geologically
This Conference, which brings together both stable.
seismologists and civil engineers, has been
convened to consider just one aspect of dam Another phenomenon is the fact that earthquakes
safety - their ability to resist earthquake. have been observed following the impounding of
Nevertheless, the subject matter is very wide water in large reservoirs, indicating that large
starting with the study of seismicity, moving reservoirs can induce their own earthquakes.
on to the behaviour of materials and structures
when subjected to earthquake, and ending with The engineer is faced with many unknown factors,
a study of the environment and risks, including and the object must be to achieve greater
induced seismicity. understanding of seismic activity, to improve
designs to allow for these movements and to
A study of an atlas indicating the localities acquire greater knowledge of the characteristics
of the most severe earthquakes reveals that the of the materials used. All these are essent­
UK is relatively stable, although not completely ials for the improvement of the earthquake
stable because occasional tremors do occur and resistance of dams.
some occasional slight damage to dams is report­
ed. There was an earthquake near Carlisle in Engineers must always bear in mind the dev­
December last year, and there have been recent astation that a community can suffer on the
tremors in the Stoke-on-Trent area. Scotland, failure of a large dam. Their design decisions
too, has had tremors around the villages of must always be of the highest order. I trust
Comrie and Menstrie. But the majority of prob­ that this Conference helps them to achieve this
lems arise in other parts of the world. If high standard and it gives me great pleasure,
British consulting engineers are to compete therefore, that the Institution of Civil
with engineers from other countries in obtain­ Engineers has organized the Conference in
ing commissions to design and supervise the association with the British Section of the
construction of large dams in those parts of International Commission on Large Dams and the
the world which are physically less stable, Society for Earthquake and Civil Engineering
they must ensure that they are familiar with Dynamics, the British Section of the Inter­
the problems encountered and also practised in national Association for Earthquake Engineering
all the modern techniques available to combat and UNESCO.
the effects of earthquake.
I am most impressed that some 140 delegates
We all know how devastating earthquake can be. are here from over 20 countries. I welcome
The disaster in Tangshan in north-east China, you on behalf of Her Majesty's Government and
which occurred on 27 July 1976, is reported our people.
to have killed no less than 650 000 people
Dams and earthquake, TTL, London, 1981
1

1 Optimum seismic input in the design of large structures
R. E. LONG, BSc, PhD, FRAS, MBCS, University of Durham
From a consideration of the nature and characteristics of seismic waves, a model for testing
design for earthquake failure is proposed. The model, referred to as an integrated model,
considers an earthquake as a fault slip and places this within the geology. Direct calculation
of energy entering the dam is made by modelling source, geology and dam as one complete unit.
The problems of implementation of this model are discussed and its potential value estimated.
INTRODUCTION both P and S. This illustration shows in a
1. This paper aims to place the design of simple way the waves generated by a moving
dams (and particularly earth dams) in their source. To this simple model can be added
true seismological context. The seismologist plausible variants which can account for
has a growing understanding of motions in the the wide range of near field motions found in
near field of a large earthquake. The dam practice.
designer, however, generally approximates
these motions to give a simple model on which These waves propagate through the geology
to test a design. It is not apparent that from the fault source to the dam. That the
such simple models necessarily test a design geology modifies the motions is well known.
with all the types of motion that could cause What is less well known is that the trans­
failure. Thus this paper seeks a closer mission function varies with the angle 6f
fusion of seismology and design methods. incidence of the input motion onto the geology.
This problem was studied in detail by Haskell
2. The aim is not to present a complete new (2). In engineering terms the peaks of
design method but to investigate the possib­ amplification of a layer occur at frequencies
ility of a method where seismological data can which are angle of incidence dependent.
form an integral part of design. Normally
seismic motions are assessed on one model by 5- The effects of a layered geological
the seismologists, and then transferred to foundation can be expressed either as a
another model for engineering design. In the frequency dependent transmission function or as
ideal situation these two models should be a series of separate wavelets emerging at the
combined. Thus we investigate an integrated surface for a particular input. This latter
design method where earthquake source, found­ approach reveals the basic mechanism. A series
ation geology and dam are considered as one of multiply reflected and refracted arrivals
overall single unit. are generated by each of the input wavelets.
These reflections and refractions will be
The Seismological Problem accompanied by changes of wave type, P to S and
3. The basic reason for proposing such an S to P. Thus a simple P input gives rise to
approach to design is that it allows full a mixture of P and S energy at the surface of
account to be taken of the nature and charac­ a layered geology, and similarly for an S input.
teristics of seismic motions. The need for
this becomes evident by considering such 6. The input waveform therefore becomes
motions in general terms. Motions from an extended in time with each input wavelet trans­
earthquake are generated by relative displace­ formed into a series of (interfering) P and S
ments of the sides of a fault. The waves wavelets which are input to the dam itself.
propagated from such a moving source can be These several P and S arrivals interfere to
considered as a set of individual wavelets. give a complex particle motion which is rarely
The multiplicity of wavelets received at rectilinear, but more ellipsoidal. Thus the
points in the near field is well demonstrated dam is subjected to motion which contains
by considering simple models. Fig. 1 shows virtually all possible motion in a generally
accelerations generated at the surface by a random sequence.
slip propagating over a finite area of a fault
(1). The particular source parameters are 7. This refers specifically to the motions,
here chosen to show the structure of the motion but the direction of propagation is not random
The several impulses of acceleration corres­ and is predominantly directed away from the
pond to the start and stop of the slip, each source. The source is not static but extended
of which generate an acceleration pulse in over the slip zone of the faulting starting at
Dams and earthquake, TTL, London, 1981 3
SEISMICITY
one point on the fault and propagating outward
clusions. Firstly the type of energy incident
from that point. Thus the effective angle of
is not restricted to any particular wave type.
incidence of this energy through the geology
Secondly the response to a particular wave
and into the dam varies with time during the
type cannot be considered separately from 'any
earthquake. For a large, close event the
other wave type. The word type here not only
change in angle can be considerable. The effect
refers to P or S but also the several separate
of the layered geology changes with angle and
arrivals of P and S. Thirdly, since the
therefore effectively with time.
several wave types have differing velocities
and differing angles of approach into the
8. Thus we may summarise the incident motion
structure, the composite motion cannot be
as a time variant multiplicity of interfering
considered as a single input time history over
wavelets generated by a moving source and
any one surface that might be drawn in the
travelling into the dam via a geology which
structure. This implies that application of
acts as a time dependent filter. This pattern
a single time history, say to the base of a
of input motion is of totally different
model, is not realistic, nor is it a realistic
character to motions applied in a quasi-static
approximation.
environment where the travelling nature of the
wave and the effective time dependence of the
The model for design
geological filter is ignored. The result is
13. These observations suggest that if input
to widen the total range of input motions. An
motions are to be totally realistic the test
integrated model with the source modelled in
model should not only include the dam and
the geology automatically includes a solution
foundations, but also the fault with earth­
of the attenuation problem and the problem of
quake placed in the foundation geology.
assessing motion from specific events.
Checks for failure would then be made by
allowing an appropriate slip on the fault and
The inclusion of a dam
observing resultant stress conditions. Such a
9. Into this environment we may now place a
design method is clearly capable of providing
dam. A structure whose dimensions are much
a close approximation to the real problem.
smaller than a wavelength would tend to move
as a unit with acceleration and deceleration
14. The implication of this method however
forces providing the major hazard. For such a
presents a number of problems. Firstly the
case the application of a specific motion to
elastic properties of the geology must be
the foundations or to the whole structure
known sufficiently accurately with accurate
would be appropriate.
location of faults at depth. Secondly the
source parameter (area of slip, distribution
10. Such an approach is not applicable to a
of the amplitude of slip motion over the
large dam whose dimensions are of the same
slipped region, etc.) need to be known or
order as the wavelength of the seismic energy
assessed. Thirdly the mathematical technique
input. For such large structures the waves
required to calculate the motion generated by
are propagated into the dam so as to form a
a fault slipping in a layered geology have yet
pattern of motion over the dam. This pattern
to be developed. Fourthly the integrated
is the result of the interference of waves
method would normally be implemented using
from the multiplicity of ray paths from source
finite element or different techniques, when
through the intervening geology to the struct­
the size of the model in comparison with the
ure.
seismic wavelength would require a large number
of nodes with appropriate computer problems of
11. The surface motions resulting from a
handling large arrays.
plane wave incident on an earth dam can be cal­
culated by considering the earth dam as a
15. Consider these problems in order:
simple hill in a homogeneous geology. Fig. 2,
The geology is normally investigated by a
based on Bouchon (3), shows how surface motions
borehole. These are of limited depth and
vary with position on the surface and angle of
therefore give data of only the upper few
incidence. These studies explaining the
metres normally restricted to the site itself.
amplification of motion by topography also
To- gain accurate knowledge of deeper layers
show in essence the problem of inputting seis­
would require deeper boreholes than normal and
mic energy into an earth dam. The complexity
then -bhese would not show up lateral variation
of motions arise from a scattering of energy
in sufficient detail. Such investigations
by the surface discontinuity formed by the
would be required over an area much larger
dam. The implication for dam design is that
than the site. The solution in an earthquake
motion and the implied stress distribution are
environment is to measure the transmission
assymetric and clearly very different from
function from fault to dam directly. Small
results obtained from applying non-travelling
earthquakes occurring on the fault can be
waves to the structures. In the real environ­
recorded at site. These records can be
ment several such input waves, each with a
decomposed to remove the source function
different angle of approach and therefore
when the transmission function in the time
different stress patterns within the dam,
domain remains. This analysis can be done for
would interfere to form a continuously changing
a variety of events distributed over the fault
pattern of stress with time.
to give the changing transmission function
with position. A generalised function for a
12. This approach leads to a number of con­
station in Iran is shown in fig. 3- This
4