1423
Seismic slope stability of earthen levees
La stabilité sismique de pente de digues en terre
Athanasopoulos-Zekkos A.
University of Michigan, Ann Arbor
Seed R.B.
University of California, Berkeley
ABSTRACT: This study focuses on systematically studying the seismically induced deviatoric-type displacements for earthen levees.
The study was based on levee sites representative of select California Central Valley regions. A wide range of input ground motions
were used in an effort to capture and assess the variability in response and performance due to multiple possible earthquake scenarios.
Dynamic, 2D, equivalent linear, finite element numerical analyses were performed using QUAD4M, to obtain accelerations and shear
stresses for the three levee profiles. Four critical sliding surfaces were selected for the evaluation of permanent seismic deviatoric type
displacements for each levee cross section: a shallow and a deeper sliding surface on both the landside and waterside. Seismic
displacements were calculated using a decoupled equivalent-linear, Newmark-type approach. The observed variability in the
computed seismic displacements due to the different input ground motions was significant and was greater than the variability
observed due to differences in site conditions. Results from this study are compared to the Makdisi and Seed (1975) displacements vs
k
y
/k
max
ratio, and recommendations are made on evaluating seismically-induced deviatoric displacements for levees.
RÉSUMÉ : Cette étude se fixe sur étudiant systématiquement les déplacements de deviatoric-type sismiquement induits pour les
digues en terre. L'étude était fondée sur le représentant de sites de digue de Californie privilégiée régions de Vallée Centrales. Une
grande variété de données fonde des mouvements ont été utilisés dans un effort pour capturer et évaluer la variabilité dans la réponse
et l'exécution en raison des scénarios de tremblement de terre possibles multiples. Dynamique, 2D, l'équivalent élément linéaire et fini
numérique analyse a été exécuté utilisant QUAD4M, pour obtenir des accélérations et des tensions de cisailles pour les trois profils de
digue. Quatre surfaces coulissantes critiques ont été choisies pour l'évaluation de déplacements de type de deviatoric sismiques
permanents pour chaque coupe transversale de digue : un peu profond et une surface coulissante plus profonde sur le landside et le
bord de l'eau. Les déplacements sismiques ont été calculés utiliser une détaché équivalent-linéaire, l'approche de Newmark-Type. La
variabilité observée dans les déplacements sismiques calculés en raison des mouvements de sol d'entrée différents était significative et
était plus grand que la variabilité a observé en raison des différences dans les conditions de site. Les résultats de cette étude sont
comparés au Makdisi et Seed (1975) les déplacements contre la proportion de k
y
/k
max
, et les recommandations sont faites sur évaluer
les déplacements de deviatoric sismiquement-induits pour les digues.
KEYWORDS: levees, seismic slope stability, dynamic analysis, ground motions.
1 INTRODUCTION
Flooding is one of the most dangerous and costly natural
hazards. Flood-protection systems are therefore important
engineering systems for handling water resources, but also
protecting urban areas, important civil infrastructure elements
and agricultural land properties that lie in or cross potential
floodplains. An important part of these systems are earthen
levees, often originally created by the river’s own overbank
deposits, and then further improved by humans in an effort to
use the rich land of the river floodplains and to provide flood
protection for growing populations. The vast majority of river
cities, now growing at increasing rates, are also protected from
flooding by earthen levees, that can be viewed as series systems,
where failure at one location or failure of one component can
result in catastrophic failure of the entire protection system
leading to tragic loss of life, substantial damage to buildings,
homes and civil infrastructure, and significant impact on the
economy of the surrounding areas.
Levees are very challenging engineering structures to study,
in part because they are not typically well-engineered structures.
Robust estimates as to the seismic vulnerability of earthen
levees are needed as the government is moving towards
reassessing the condition of our nation’s flood protection
systems. Unfortunately, there is little to no guidance as to how
to evaluate the seismic vulnerability of levees with respect to
seismically-induced permanent displacements. Since in seismic
slope stability analyses the input acceleration time-history is the
most important parameter (Bray, 2007) a systematic study of the
dynamic response of earthen levees of varying soil stratigraphy
and for a wide range of ground motions is needed.
As part of this study, three typical levee cross-sections were
analyzed that are representative of the Stockton area, the West
Sacramento area, and the Marysville area, in California. These
are denoted by Levee types A, B, and C respectively, and are
among the sites under study as part of the Urban Levee Project
of the California Department of Water Resources.
2 DYNAMIC ANALYSIS
The geometry and soil stratigraphy of the three characteristic
levee cross-sections and the criteria used for the selection of the
input ground motion recordings and a list of these seismic
motions are presented in detail by Athanasopoulos-Zekkos
(2008 and 2010) and Athanasopoulos-Zekkos and Saadi (2012)
and due to space limitations will only be summarized in this
paper. Figure 1 shows the three levee cross-sections together
with the Vs profile that was used in the analyses. A 2D, finite
element, equivalent linear program called QUAD4M (Hudson et
al., 1994 and Idriss et al., 1973) was used for performing the
dynamic analyses. A wide range of ground motions (~1,500)
was used in the present study to develop statistically stable
estimates of dynamic response of levees for the three different
levee sites and to also provide insight towards the effect of
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Seismic slope stability of earthen levees.
La stabilité sismique de pente de digues en terre
A. Athanasopoulos-Zekkos
University of Michigan, Ann Arbor
R. B. Seed
University of California, Berkeley
ABSTRACT: This study focuses o sy t matically studying th seismically induced d viatoric-type dis lacem nts for e rthen levee .
The study was based o leve sites r presenta ive of select California Central Valley re ions. A wide range of input gr und motions
were u ed in an effort to ca ture and assess he var ability in respons and p rformanc due to multi le possible arthquake scenarios.
Dynamic, 2D, equiv lent lin ar, finite lement numerical alyses w e performed using QUAD4M, to obtain ccelerations and shear
stresses for the thre levee profiles. Four criti al sliding s rf c s wer selected fo the evaluati n of permanent seismic dev a oric typ
displacements for each levee cross section: a shallow and a deeper slid ng surface on both the landside nd w terside. Seismic
displac ments were cal ulated using a decoupled equivalent-linear, New ark-type approach. The observed variability i the
computed seismic displac ments due to th different i put ground motions was significant nd was greater than the variability
observed due to differences in site conditions. Results from this study are compared to the Makdisi and Seed (1975) displacements vs
k
y
/k
max
ratio, and recomm ndations are made on evaluating s ismically-induced deviatoric displacem nts for leve s.
RÉSUMÉ : Cett étude e fixe sur étudiant systématiquement les déplacements de deviatoric-type sismiquemen induits pour les
digu s en terr . L'étude était fondée sur l représ tant d sites de digue de Califor ie privilégiée r gions de Vallé Ce tr l s. Une
grande variété de donn es fonde des mouvements ont été utilisés dan un effort pour capturer et évaluer la variabilité dans la épons
et l'exécution en raison des scén rio de remblement de terre possibles multiples. Dynamiqu , 2D, l'équival nt élémen linéaire et fini
numérique analyse a été exécuté utili ant QUAD4M, po r obtenir des accélérations et des ten io s de cisailles pour les trois profils d
digue. Quatre surfaces oulissante critiques ont été choisies pour l'évaluation de déplacements de type de deviatoric sismiques
permanents pou chaque coupe tr nsv rsale de digue : un peu profond et une surface couli sante plus pro onde sur le la dside et l
bord de l'eau. Les dépl cements sismiqu s ont été calculés ut liser un détaché équivalent-linéaire, l'approche de N wmark-Type. La
variabilité observée dans l s éplacem nts sismiqu s calculés en raison des mouvements de ol d'entrée ifférent était significative t
était plus grand qu la v riabilité a observé e rai on des différences dans les conditions de site. Les résultats de cette étude sont
comparés au Makdisi et Seed (1975) les déplacements contre la proportion de k
y
/k
max
, et les recommandations sont faites sur évaluer
les déplacements de deviatoric sismiquement-induits pour les digues.
KEYWORDS: levees, seismic slope stability, dynamic analysis, ground motions.
1 INTRODUCTION
Flooding is one of the most dangerous and costly natural
hazards. Flood-protection systems are therefore important
e ginee ng systems fo handling wat r resource , but also
pr tecting urba areas, important civil infra tructure l ments
and agricultural la d prop rti s that lie n or cross potential
floodplains. An important part of these systems re earthen
lev es, often originally created by the river’s own ov rbank
deposi s, and then further improved by humans in an effo t to
use the rich land of the riv r floodplains and to provid flo d
pr tection for growing popul ions. The vast majo ty of river
citi s, now growing at increasing r tes, are also protected from
flooding by e r hen levees, that can b view d as s ries sy tems,
where failure at one location or failure of one component can
result in catastrophic failure of the entire protection system
l ading to tragic loss of life, substantial damage to buildings,
homes and civil infrastructure, a d significant impac on the
economy of th surrounding areas.
Levees are v ry challenging engineering structures to study,
in part becaus th y are not typically w ll-engineered structures.
Robust estimat s as to the seismic vul erabi ity of earthe
leve s are needed as
government is moving towards
reassessing
cond tion of our nation’s flood protection
yste s. Unfort nately, ther is l ttle to no guida as to how
to evaluate the seismic vulnerability of levees with respect to
seismically-induc d p rmanent displacements. Since in seismic
slope stability analyses the i put acceleration time-history is the
most importan parameter (Bray, 2007) a systematic study of th
dynamic respons of earthen levees of varying soil stra igraphy
and for a wide r nge of ground motions is needed.
As part of this study, three typic l levee cross-sections we
nalyzed that are repre entative of the Stockton area, the W st
Sacramento are , and the Marysvill area, in California. These
are denoted by Levee types A, B, and C respectively, and are
among the sites under study as part of the Urban Levee Project
of the California Department of Water Resources.
2 DYNAMIC ANALYSIS
The geometry and soil stratigraphy of the three characteristic
levee cross-sections and the criteria u ed for the selection of the
input ground motion rec rdings and a list of thes seismic
motions are pre ented in detail by Athana opoulos-Zekkos
(2008 and 2010) and A hanasopoulos-Z kkos and Saadi (2012)
and due to sp c limitations will on y be summarized in this
paper. Figure 1 shows the three levee cross-sections together
with the Vs profile that was used in the a alyses. A 2D, finite
element, equival nt lin ar program called QUAD4M (Hudson et
al., 1994 and Idriss et al., 1973) was u ed for performing the
dynamic an lyses. A wide range of round motions (~1,500)
was used in the present study to develop statistically stable
