liquefaction evidence for strong earthquakes of holocene and latest pleistocene ages in the states of indiana and illinois usa abstract sand and gravel filled clastic dikes of seismic liquefaction origin occur throughout much of southern indiana and illinois nearly all of these dikes originated from prehistoric earthquakes centered in the study area in this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the holocene and at least one during the latest pleistocene the recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects but some have been recognized only by geotechnical testing at sites of liquefaction most paleo earthquakes presently recognized lie in indiana but equally as many may have occurred in illinois studies in illinois have not yet narrowly bracketed the age of clastic dikes at many sites which sometimes causes uncertainty in defining the causative earthquake but even in illinois the largest paleo earthquakes probably have been identified prehistoric magnitudes were probably as high as about moment magnitude m 7 5 this greatly exceeds the largest historic earthquake of m 5 5 centered in indiana or illinois the strongest paleo earthquakes struck in the vicinity of the concentration of strongest historic seismicity elsewhere paleo earthquakes on the order of m 6 7 have occurred even where there has been little or no historic seismicity both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back calculating prehistoric magnitudes methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere

liquefaction failure and remediation king harbor redondo beach california liquefaction failure including large lateral displacements and associated settlement severely damaged marina facilities at redondo beach king harbor during the northridge earthquake of january 17 1994 although minor ground deformation apparently occurred in several areas of the harbor severe damage was restricted to the central portion of mole b one of four offshore fills constructed as a part of marina improvements in 1960 61 local ground conditions and methods used to remediate liquefaction are presented and discussed two ground modification techniques were used to mitigate the liquefaction potential of the reconstructed mole b facilities the major portion of the failure area was treated with vibroreplacement stone columns vibratory displacement and installation of the gravel columns not only densified the foundation soils but also provide additional strength and drainage capacity compaction grouting was used to densify foundation soils in the vicinity of existing improvements that were considered sensitive to construction induced ground vibrations these ground improvement techniques effectively reduced the liquefaction potential and allowed the marina improvements to be reconstructed on shallow foundations similar to the original design

numerical modeling of liquefaction and comparison with centrifuge tests the prediction of liquefaction and resulting displacements is a major concern for earth structures located in regions of moderate to high seismicity conventional procedures used to assess liquefac

influence of bearing pressure on liquefaction induced settlement of shallow foundations earthquake induced soil liquefaction continues to pose problems for structures on shallow foundations one particular problem is the excessive settlement that such structures undergo as a consequence of earthquake shaking for design and insurance purposes it is therefore necessary to be able to estimate the magnitude of these settlements current procedures relate the potential settlement to foundation size and liquefiable depth however the influence of foundation bearing pressure is also a significant factor in particular experimental results have indicated that large bearing pressures may inhibit liquefaction underneath a shallow foundation resulting in lower induced settlement by collecting new data from 23 buildings that suffered settlement and tilting as a consequence of soil liquefaction during the 27 february 2010 maule earthquake in chile the existing method of estimating liquefaction induced settlement is reassessed and shown to require bearing pressure information based on both the new

seismic response of shallow foundation on liquefiable sand investigators conducted eight centrifuge model experiments to study the mechanism of liquefaction induced settlement of a shallow foundation as well as the effectiveness of sand densification by vibrocompaction under the footing two series of model tests were conducted with a surface circular footing placed on a medium dense saturated sand layer overlying an impervious rigid base horizontal shaking simulating an earthquake was used to excite the base of each model in flight in all cases this shaking liquefied the sand in the free field the first series of tests concentrated on the effect of the depth of soil compacted under the foundation on the footing acceleration and settlement investigators discovered that as the compaction depth increased and approached the total thickness of the soil deposit the footing acceleration during shaking increased and its settlement decreased the soil was not densified in the second series of tests this series focused on the effect of soil permeability on pore pressure buildup and footing settlement investigators learned that as the soil becomes more impervious significant negative excess pore pressures develop under the footing during shaking and the contribution of postshaking foundation settlement increases while the total foundation settlement does not change significantly building settlements observed after two earthquakes in liquefied areas of niigata japan in 1964 and dagupan philippines in 1990 are discussed comparisons are made between the field observations and the centrifuge results

time dependent ground motion amplification characteristics at reclaimed land after the 1995 hyogoken nambu earthquake two sets of borehole array records obtained from the great hanshin earthquake as well as its fore and after shocks are investigated one of the stations is located at port island in kobe city where severe liquefaction occurred and the records from the main event include the typical phenomena of liquefaction the other station is located at rokko island in kobe city where the liquefaction phenomenon was not predominant as it was at port island the non linear ground motion amplification depending on the level of input ground motion as well as its spectral characteristics is carefully investigated two numerical techniques for seismic response ground analysis are applied for these stations one is the frequency dependent equivalent linearization technique for frequency domain analysis and the other is the effective stress based liquefaction analysis the discussion is focused on the amplification characteristics of these two reclaimed lands depending on their reclamation history the time dependent amplification ratio for peak ground motion and spectral contents is demonstrated caused by the recovery of soil rigidity due to the decrease in excess pore water pressure after the main event

the densification of granular soils using vibro methods the method of densifying in situ sandy soils using deep vibration vibro was first developed in germany over 60 years ago since then the technique has been extended to improve a wide range of soil types for structures of up to 30 storeys in height a major development in the vibro market worldwide over the last 25 years has been the treatment of soils to resist the effects of liquefaction during seismic events it is well known that the presence of silt and clay fines inhibits the physical in situ densification of sandy soils experience has shown that a maximum fines content of about 15 would normally permit the performance of vibro compaction methods without the addition of stone aggregate however the development of new vibrators and modified construction techniques has enabled sands with significantly higher fines content to be treated the paper describes how densification of granular soils has progressed with the development of new equipment the greater appreciation in the manner in which soils

mapping submarine sand waves with multiband imaging radar 2 experimental results and model comparison on august 16 1989 and on july 12 1991 experiments were performed to study the mapping of submarine sand waves with the airborne imaging radar a polarimetric and in 1991 interferometric airborne p l and c band synthetic aperture radar system the experiments took place in an area 30 km off the coast of the netherlands where the bottom topography is dominated by sand waves with a height between 2 and 6 m and a crest to crest distance of about 400 m at an average depth of 22 m ground measurements were recorded on a nearby platform and on a ship in the test area which also acted as a position fix on august 16 1989 the wind was 5 m s directed toward the northeast while the surface current velocity was around 0 5 m s directed toward the southwest one overflight was made with the flight direction parallel to the sand wave crests and the radar looking upwind at p band the sand waves are clearly visible as dark bands as predicted by theory while at l band the sand waves show up as sawtooth shaped modulations on july 12 1991 wind and surface current had the same opposite directions as in 1989 though the wind was much higher 10 m s three flights were made with the radar pointing upwind cross wind and downwind the upwind and downwind images are very similar despite the high wind speed the sand waves are clearly visible as sawtooth shaped modulations at p band and vaguely visible at l band at c band only wind streaks can be seen all cross wind images show the sand waves as dark bands now with the highest modulations at c band the wind streaks that dominated the upwind and downwind images at c band are much less pronounced in the cross wind images the images are compared with predictions from a new model of the imaging mechanism which includes contribution to the radar cross section of waves moving both from and to the radar wave blocking or wave reflection is treated in an approximate manner for the radar looking upwind or downwind the predicted modulations at p and l band agree well with the observations while those at c band are too high for the radar looking cross wind the model severely underestimates the modulations it is questioned whether a local relaxation source term can describe such a situation the interferogram shows some structure caused by bottom induced surface current variations

equivalent number of uniform cycles versus earthquake magnitude relationships for fine grained soils in current geotechnical seismic design practice the empirical correlation between equivalent number of uniform cycles neq of shaking and earthquake magnitude mw forms an integral part of lique

development of pervious concrete pile ground improvement alternative and behavior under vertical loading permeable granular columns are used to increase the time rate of consolidation reduce liquefaction potential improve bearing capacity and reduce settlement however their behavior depends on the confinement provided by surrounding soil which limits their use in very soft clays and silts and organic and peat soils this research effort aims to develop a new ground improvement method using pervious concrete piles pervious concrete piles provide higher stiffness and strength that are independent of surrounding soil confinement while offering permeability comparable to granular columns this proposed ground improvement method can improve the performance of different structures supported on poor soils to achieve the goal of the research project four vertical load tests were performed on one granular column and three pervious concrete piles in this paper the material properties of pervious concrete the developed installation method and the vertical load response of pervious concrete and aggregate piles are presented and the variation of soil stresses and displacement during pile installation are briefly discussed the experimental test results show that the ultimate load capacity of the pervious concrete pile was 4 4 times greater than that of an identical granular column in addition the ultimate load capacity of a pervious concrete pile installed using the developed technique was 2 6 times greater than a precast pervious concrete pile the used installation method created nonuniform lateral soil displacement and increased vertical and horizontal soil stresses

modeling the stone column behavior in soft ground with special emphasis on lateral deformation abstractamong various ground improvement techniques soft soil reinforcement by stone columns is one of the most common and convenient methods with numerous benefits including increased bearing cap

liquefaction resistance of undisturbed and reconstituted samples of a natural coarse sand from undrained cyclic triaxial tests the paper deals with an experimental study of the undrained cyclic behavior of a natural coarse sand and gravel deposit located in gioia tauro a town situated on the continental side of the messina strait in italy the study was conducted through cyclic undrained triaxial tests carried out on both undisturbed and reconstituted samples undisturbed samples were recovered by an in situ freezing technique and the sample quality was carefully assessed reconstituted samples were prepared by using two different reconstitution methods namely air pluviation ap and water sedimentation ws and tested under the same in situ initial relative density and effective overburden stress tests were carried out on both isotropically and anisotropically consolidated specimens the results obtained from this study provide direct evidence that cyclic liquefaction resistance obtained from water sedimented samples closely approximates that exhibited by undisturbed samples in both isotropically and anisotropically consolidated tests conversely ap leads to a marked underestimation since the investigated deposit is considered to have been formed by the marine water environment these results can be regarded as proof that ws closely replicates the in situ fabric of the investigated deposit allowing the substitution of the expensive undisturbed samples with their reconstituted counterparts anisotropically consolidated specimens respectively exhibit cyclic liquefaction or cyclic mobility depending on whether or not they are loaded under the shear stress reversal mode

dilatancy induced p waves as evidence for nonlinear soil behavior a much discussed topic in seismology deals with how and under which loading conditions soil shows nonlinear behavior and how this can be verified from seismograms seismologists have been seriously searching for signatures of nonlinear soil response to earthquakes for about two decades a mechanism explaining the dispersion in the p wave spectra due to the interaction between compressional p and shear s waves is presented shear waves in granular materials induce longitudinal dilatancy waves so called waves with approximately double frequency this can be explained with dilatancy and contractancy which is characteristic of granulates under shear deformations the predicted dispersion is observed in laboratory experiments and verified by comparing accelerograms from hard rock and soil stations from the vrancea region romania the arrival time difference between waves and s waves may theoretically be indicative of the thickness of nonsaturated granular layers these results modeled with nonlinear constitutive relations of the rate type show a specific type of nonlinearity in granular sediments also for earthquakes of moderate magnitudes

assessment of liquefaction potential during earthquakes by arias intensity an arias intensity approach to assess the liquefaction potential of soil deposits during earthquakes is proposed using an energy based measure of the severity of earthquake shaking recorded on seismograms of the two horizontal components of ground motion values representing the severity of strong motion at depth in the soil column are associated with the liquefaction resistance of that layer as measured by in situ penetration testing spt cpt this association results in a magnitude independent boundary that envelopes initial liquefaction of soil in arias intensity normalized penetration resistance space the arias intensity approach is simple to apply and has proven to be highly reliable in assessing liquefaction potential the advantages of using arias intensity as a measure of earthquake shaking severity in liquefaction assessment are arias intensity is derived from integration of the entire seismogram wave form incorporating both the amplitude and duration elements of ground motion all frequen

instability and liquefaction of granular soils under undrained and partially drained states an experimental investigation of the initiation of instability liquefaction in saturated sand under partially drained conditions is presented the domain of stress space in which this instability develops is identified under various degrees of drainage and its relationship to the zone of instability observed under undrained shear is explored it is shown that partially drained conditions may render sand unstable that would otherwise be stable in a completely undrained state extremely small void ratio increases that cannot be regarded as physical loosening of sand if sand is partially drained contribute to instability implications of the findings are discussed in practical problems of liquefaction key words sand liquefaction undrained partially drained instability triaxial test

comparison of 2 d and 3 d models of the steady wind driven circulation in shallow waters abstract the classical theory of the steady wind driven circulation in shallow waters described by the linear three dimensional equations is generalized to include arbitrary variations of the vertical eddy viscosity the stream function equation is compared to the corresponding equation of a two dimensional model the influence on the solution of various eddy viscosity profiles and or bottom boundary conditions is discussed from the comparison of the equations a parameterization of the bottom stress in terms of transport and wind stress is derived such that the two dimensional model can yield results identical to those of the three dimensional model

numerical model verification and calibration of george massey tunnel using centrifuge models dynamic soil structure interaction analyses were carried out for the seismic retrofit design of the immersed george massey tunnel both to predict and study soil liquefaction and related tunnel mov

cyclic loading response of loose air pluviated fraser river sand for validation of numerical models simulating centrifuge tests cyclic loading response of loose fraser river sand was investigated as input to numerical simulation of centrifuge physical models using constant volume direct simple shear tests conducted with a

performance of embankments on liquefiable soils improved with dense granular columns observations from case histories and centrifuge experiments abstractdense granular columns dgcs are generally known to mitigate the liquefaction hazard through a combination of 1 installation induced ground densification 2 enhanced drainage and 3

cyclic shear response of fine grained mine tailings the mechanical response of three different types of fine grained mine tailings is examined using data from constant volume cyclic direct simple shear dss tests under cyclic dss loading fine grained tailings typically exhibit a cumulative decrease in effective stress along with progressive degradation of shear stiffness the observed shear strain development due to cyclic mobility is similar in form to that of the previously observed cyclic shear response for natural silts the cyclic resistance ratio crr of laterite tailings is observed to increase with an increase in the initial effective confining stress vc for this material the dilative tendency due to stress densification seems to have overridden the contractive tendency due to the increase in confining stress in contrast the crr of copper gold zinc tailings is insensitive to the initial effective confining stress suggesting a response similar to that of normally consolidated clay the postcyclic maximum shear strength ratio su pc v

laboratory investigation on assessing liquefaction resistance of sandy soils by shear wave velocity shear wave velocity vs offers engineers a promising alternative tool to evaluate liquefaction resistance of sandy soils and the lack of sufficient in situ databases makes controlled laboratory study very important in this study semitheoretical considerations were first given based on review of previous liquefaction studies which predicted a possible relationship between laboratory cyclic resistance ratio crrtx and vs normalized with respect to the minimum void ratio confining stress and exponent n of hardin equation undrained cyclic triaxial tests were then performed on three reconstituted sands with vs measured by bender elements which verified this soil type dependent relationship further investigation on similar laboratory studies resulted in a database of 291 sets of data from 34 types of sandy soils based on which the correlation between liquefaction resistance and vs was established statistically and further converted to equivalent field conditions with well defined parameters reve

geotechnical site characterization in the greater memphis area using cone penetration tests abstract the determination of seismic ground hazards in memphis and shelby county tennessee is facilitated by the use of electronic cone penetration tests that can provide up to four independent readings with depth from a single sounding one series of soundings is being performed for site specific mapping to determine the presence and extent of potentially liquefiable sediments in situ soil resistance to liquefaction and initial soil stiffness for ground motion amplification studies another series of soundings is being conducted in conjunction with field paleoliquefaction mapping in the new madrid seismic zone to better define the intensity magnitude and geographic extent of ground failures caused by large past earthquake events as well as information about the source sands in this paper an overview is given on the types of multi channeled penetrometer data that are being collected including vertical profiles of cone tip stress qt sleeve friction fs penetration porewater pressure u1 or u2 downhole shear wave velocity vs and or electrical conductivity ke representative soundings are presented from select sites to illustrate repeatability data post processing methods and that derived downhole vs profiles are generally in good agreement with non invasive surface techniques at two memphis test sites cyclic stress based procedures for liquefaction are discussed with relation to data from a paleoliquefaction site in germantown tennessee and estimates of the minimum magnitude of the historic event are discussed while estimates of the earthquake magnitude are preliminary pending additional study on attenuation relationships and site response in the deep soils of the mississippi embayment it is inferred from evaluation of in situ test data using cyclic stress based techniques that the december 1811 new madrid earthquake was likely larger than a mw 7 5 event

fault rupture propagation through previously ruptured soil abstractsurface fault rupture during recent earthquakes has significantly damaged structures although several researchers have studied surface fault rupture the effects of fault rupture propagating through soil that has been ruptured previously have not been investigated yet faults rupture multiple times so that native soil deposits will have likely undergone previous ruptures that would have developed shear bands within the soil and the stress state of the soil will have evolved because of these events in addition the predominant modes of soil shearing during the fault rupture process have not been characterized fully numerical simulations are performed to analyze the mechanics of dip slip surface fault rupture and to explore the effects of previously ruptured soil the numerical results demonstrate that the soil rupture process occurs in two distinct stages first broad deformation occurs before strain localization which is followed by more localized deformation after shear band formation str

mitigation of liquefaction and associated ground deformations by stone columns soil liquefaction and associated ground failures have been a major source of damage during the past earthquakes the risk of liquefaction and associated ground deformation can be reduced by various ground improvement methods including the stone column gravel drain technique this paper presents the current state of the stone column technologies as a liquefaction countermeasure a comprehensive review is provided aiming to a identify key considerations for the general use of stone columns as a liquefaction countermeasure b provide insights for design and construction c compile the latest research developments and d identify sources of useful information case histories of field applications and observed field performance are cited to portray different stone column applications and observed effectiveness the paper identifies areas where more research is needed and includes recommendations for future research and development

centrifuge modeling of prefabricated vertical drains for liquefaction remediation drainage methods for liquefaction remediation have been in use since the 1970s and have traditionally included stone columns gravel drains and more recently prefabricated vertical drains this paper presents the results from a dynamic centrifuge test designed to evaluate the performance of a liquefiable site treated with prefabricated vertical drains the centrifuge model consisted of gently sloping untreated and treated liquefiable soil deposits overlain by a clay crust the model was subjected to multiple shaking events that included both recorded earthquake acceleration time histories and sinusoidal input motions comparisons of deformations and excess pore water pressures in the untreated and treated areas showed that drains were effective in expediting the dissipation of excess pore water pressures and reducing deformations however depending on the characteristics of the input ground motion the peak excess pore pressures in the treated area were not always substantially smaller than in the untr

liquefaction during the 1977 san juan province argentina earthquake ms 7 4 liquefaction effects generated by the 1977 san juan province argentina earthquake ms 7 4 are described the larger and more abundant effects were concentrated in the 60 km long band of the lowlands in the valle del bermejo and in an equally long band along the rio san juan in the valle de tulum fissures in the valle del bermejo were up to several hundred meters long and up to several meters wide sand deposits from boils that erupted through the fissures covered areas up to tens of square meters fissures generally parallelled nearby stream channels because the valle del bermejo is undeveloped these large features caused no damage liquefaction in the valle del tulum caused important or unusual damage at several localities including the following five sites 1 at the barrio justo p castro a subdivision of caucete liquefaction of subsurface sediments decoupled overlying unliquefied stiff sediments producing a form of ground failure called ground oscillation the associated differential ground movements pulled apart houses and pavements in extension while shearing curbs and buckling canal linings in compression at the same locality 2 at the escuela normal in caucete the roof of a 30 m long single story classroom building shifted westward relative to the foundation that displacement fractured and tilted columns supporting the roof the foundation was fractured at several places leaving open cracks as wide as 15 mm the cumulative width of the open cracks was 48 mm an amount roughly equivalent to the 63 mm of offset between the roof and foundation at the east end of the building the ground and foundation beneath the building extended or spread laterally opening cracks and lengthening the foundation while the roof remained in place 3 the most spectacular damage to structures at the community of san martin was the tilting of a 6 m high water tower and the toppling of a nearby pump house into a 1 m deep crater similarly a small crater developed beneath a hand pump in an open area and a large 6 m diameter crater formed nearby the following sequence of events created the craters and toppled the pump structures during the earthquake ground shaking generated excess pore pressures which were dissipated by upward flow of groundwater free drainage was restricted by an impermeable plastic silt layer water apparently accumulated below the plastic silt layer and then burst to the surface through several holes and cracks including holes around well casings 4 at the san isidro winery nine storage tanks tilted 2 to 5 five reinforced concrete tanks were dismantled but four steel tanks were repaired by placing new footings and jacking the structures into an upright position 5 at escuela j j pasos differential settlement beneath building fractured several columns and walls the largest settlements were about 60 mm and the maximum settlement of footings supporting columns was about 40 mm in spite of the damage the buildings were in no danger of collapse

dynamics characteristic of red clay in a deep seated landslide northwest china an experiment study abstract the red mudstone sediments are widely encountered in earthquake region northwestern china which is vulnerable to the occurrence of landslides previous studies focused on rain induced shallow landslides some deep seated landslides in red clay with a gentle inclination are still not well understood a fatal landslide named as zhengjiamo landslide located in tianshui china was investigated the aim of this study was to study mechanism of shear surface development under earthquake using a series of cyclic triaxial tests the test results of the red clay from the zhengjiamo landslide revealed that the undrained shear strength and excess pore pressure increase with increasing confining stresses 3 and ocr it is also observed that those stress strain behaviors on the deviatoric stress axial strain and pore water pressure subsequent to the initial contractive response the saturated clay exhibited dilation upon continued shearing the dilated tendency of the clay becomes more prevalent with increasing confining stresses 3 and ocr during the dynamic response the reduction of shear strength of the red clay is substantially caused by the increasing number of cycles n under earthquakes the sliding zone may behave in a brittle ductile pattern

a depth consistent spt based empirical equation for evaluating sand liquefaction abstract focusing on the deficiencies of the current liquefaction evaluation methods typically on deep sandy layers of 10 m to 20 m a new liquefaction evaluation formula which is based on the 156 spt data from liquefaction investigation in china mainland is proposed the formula is plausible for wide depth range up to 20 m the formula which takes a hyperbolic function form fits the liquefaction data at shallow depth and predicts satisfactorily deep liquefaction the liquefaction dataset available from china earthquakes and foreign earthquakes i e kobe earthquake and chichi earthquake are statistically summarized the deficiencies of prevailing liquefaction evaluation methods and the csr method by seed are pinpointed to validate the proposed formula a liquefaction dataset consist of 312 liquefaction data from china mainland and foreign countries is used for re evaluation the results indicate that the new formula is quite feasible for wide sandy layer buried depth different seismic intensities and varying groundwater tables comparing with the current chinese code methods and the csr method the new formula which approaches to an asymptote eliminates the abnormality of the csr method that decreases inversely when the depth exceeds a certain value the new formulae solve the deficiency of chinese codified liquefaction evaluation methods that are conservative for intensity vii at shallow depth

numerical and centrifuge modeling of seismic soil foundation structure interaction on liquefiable ground abstractthe effective mitigation of the liquefaction hazard requires an improved understanding of the consequences of liquefaction in terms of ground shaking permanent displacement and building performance in this paper results from centrifuge experiments of a shallow founded structure on liquefiable sand are used to evaluate the predictive capabilities of a state of the art numerical tool solid fluid fully coupled 3d nonlinear numerical simulations were performed using the pdmy02 soil model implemented in a software modeling domain the numerical model captured excess pore pressures and accelerations well in the free field but largely underestimated volumetric settlements due to loss of water during shaking this was associated with the drastic increase in soil hydraulic conductivity when approaching liquefaction which was not taken into account numerically as well as the underestimation of soil volumetric compressibility the contribution of volumetric strains to total building settlement was

effect of fabric anisotropy on liquefaction of sand abstractliquefaction of sand is the main cause of failure for earth structures during earthquakes some past research showed that the fabric anisotropy of soils in the ground can cause different responses to both static and dynamic loading the inherent fabric anisotropy of sand due to the deposition history and pattern may also affect the liquefaction potential of the ground in this study a group of earthquake centrifuge tests was performed on models of a level ground to investigate its seismic response with the soil deposited by different angles a special rigid container was designed and used to prepare the models it was found that the fabric anisotropy greatly influenced the response of the ground in displacement acceleration and excess pore pressure the models with larger deposition angles had higher liquefaction potential the results show that liquefaction evaluation of a sand layer should take into account the influence of fabric anisotropy caused by its deposition history and pattern

infragravity velocity profiles in the surf zone we present a theoretical solution for the vertical structure of the velocity profiles in infragravity waves the solution predicts that while the velocity without local forcing of the infragravity waves does not vary significantly with the vertical coordinate the velocity with local forcing of the infragravity waves has a substantial vertical structure

seismic response of liquefaction sites the authors of this technical paper focus on the seismic response of liquefaction sites by evaluating the transient shear strains and strong motion characteristics at treasure island during the 1989 loma prieta earthquake the strain levels are used to model soil and buried pipeline deformations observed in the marina district of san francisco during the same earthquake the authors found that transient strains play a critical role in lifeline performance based on the favorable comparisons of predicted and observed pipeline damage a simple model for liquefaction sites reveals that shear modulus reduction caused by increased pore pressure can amplify either acceleration or transient displacement depending on soil properties and deposit thickness liquefaction of thick loose sand deposits can attenuate accelerations while amplifying long period displacements the model offers a quantitative means of characterizing the phenomenon of ground oscillation that has been noted at liquefaction sites

the loma prieta earthquake ground motion and damage in oakland treasure island and san francisco abstract the basis of this study is the acceleration velocity and displacement wave forms of the loma prieta earthquake 18 october 1989 m 7 0 at two rock sites in san francisco a rock site on yerba buena island an artificial fill site on treasure island and three sites in oakland underlain by thick sections of poorly consolidated pleistocene sediments the waveforms at the three rock sites display a strong coherence as do the three sedimentary sites in oakland the duration of strong motion at the rock sites is very brief suggestive of an unusually short source duration for an earthquake of this size while the records in oakland show strong amplification effects due to site geology the s wave group at treasure island is phase coherent with the oakland records but at somewhat diminished amplitudes until the steps in acceleration at approximately 15 sec apparently signaling the onset of liquefaction all seven records clearly show shear wave first motion opposite to that expected for the mainshock radiation pattern and peak amplitudes greater than expected for sites at these distances 95 3 km from an earthquake of this magnitude while the association between these ground motion records and related damage patterns in nearby areas has been easily and eagerly accepted by seismological and engineering observers of them we have had some difficulty in making such relationships quantitative or even just clear the three oakland records from sites that form a nearly equilateral triangle about the cypress street viaduct collapse are dominated by a long period resonance 1 1 2 sec period far removed from the natural frequency of the structure to transverse motion 2 5 hz or from high frequency amplification bands observed in aftershock studies a spectral ratio arbiter of this discrepancy confuses it further the failure of the east bay crossing of the san francisco oakland bay bridge cannot be attributed to relative displacements of the abutments in oakland and yerba buena island but the motions of the bay bridge causing failure remain unknown the steps in acceleration at treasure island present unusual strong motion accelerogram processing problems and modeling suggests that the velocity and displacement waveforms are contaminated by a spurious response of the filtering operations to the acceleration steps a variety of coincidences suggests that the treasure island accelerogram is the most likely strong motion surrogate for the filled areas of the marina district for which no mainshock records are available but the relative contributions of bad ground poor construction and truly strong ground motion to damage in the marina district will never by known in any quantitative way the principal lesson of all of this is that until a concerted effort is mounted to instrument ground and structures that are likely to fail during earthquakes our understanding of the very complex relationships between strong ground motion and earthquake damage will in general remain rudimentary imprecise and vague

quasi 3d modelling of nearshore currents abstract existing concepts of wave induced nearshore current models in the cross shore vertical plane 2dv and depth integrated 2dh are combined to a quasi 3d mathematical model this combination is tested for reproducing correct results in 2dv and 2dh situations the importance of the various contributions to the wave induced secondary circulation in the vertical plane is investigated for realistic parameter ranges which leads to the conclusion that both the non breaking and the breaking fraction of a random wave field in the surf zone generate important secondary currents additional computations show the relevance of a 3d approach of nearshore currents even in seemingly simple situations like a plane sloping beach with obliquely incident waves

coastal ocean current response to storm winds design of offshore structures requires knowledge of the appropriate current profile to be used in conjunction with the design wave accurate determination of the current profile will depend on reliable current models vertical transfer of momentum in storm driven current models is commonly treated either by using eddy viscosity or by assuming slab like mixed layer flow these two fundamentally different approaches predict different current speeds and profiles during severe storms the existing data base is inadequate to determine which approach is better but most existing data sets are subject to one or more of four limitations that can lead one improperly to interpret the data as supporting the existence of current velocity shear in otherwise uniform mixed layers one dimensional slab models are found to compare favorably with observed wind driven currents at the ocean test structure in the gulf of mexico deployed in 20 m deep water by using some reasonably simple assumptions these slab models are able to replicate many of the significant features of a wide range of different responses the character of the response appears to depend on an interaction of stratification and topography barotropic responses are characteristic of typical coastal responses currents are oriented longshore and are in phase with the wind baroclinic responses are dominantly inertial as might be expected in the deep sea but with an additional near bottom cross shore counter flow the structure of one observed barotropic response is compared in detail to predictions of both slab and eddy viscosity models and found consistent with a slab model and inconsistent with eddy viscosity models shear observed during this event was not significantly different from zero but was significantly below estimated shear predictions of four eddy viscosity models given the peak 0 4 n m2 wind stress

on extracting tidal current profiles from vertically integrated two dimensional hydrodynamic models a numerically accurate and computationally efficient method is developed for extracting tidal current profiles from vertically integrated two dimensional models the method can incorporate an arbitrary profile of eddy viscosity and determines tidal current profiles satisfying a no slip condition at the sea bed comparisons with observations and current profiles computed with full three dimensional models confirm the accuracy of the method bottom boundary layer thicknesses determined from these current profiles clearly show regions of the european continental shelf where the bottom boundary layer extends to the sea surface the boundary between these regions and other areas where the bottom layer is less than the water depth corresponds quite closely to the known position of tidal fronts

cyclic shear strain needed for liquefaction triggering and assessment of overburden pressure factor kσ abstractthis paper has two objectives the first is to evaluate the cyclic shear strain needed to trigger liquefaction cl in clean and silty sands in the field during earthquakes as an alternative to the currently used cyclic resistance ratio crr the second objective is to explore the effect of a high effective overburden pressure v0 on the value of crr the first objective is accomplished mainly by using an equation relating cl and crr valid for shear wave velocity based liquefaction charts this equation is supplemented with laboratory results from undrained cyclic strain controlled tests as well as large scale and centrifuge model shaking experiments it is shown that for recent uncompacted clean and silty sand deposits and earthquake magnitude mw 7 5 cl 0 03 with this value increasing to cl 0 3 in some cases to 0 6 in denser and overconsolidated preshaken and compacted sands these small values of cl in the field are controlled by two factors excess pore pressure buildup in the

empirical methodology to estimate seismically induced settlement of partially saturated sand abstractsettlement of soil layers during and after earthquake shaking is a major cause of damage to buildings and geotechnical structures the available empirical design methods to consider seismically induced settlement focus on sands in dry or water saturated conditions and there is currently a gap in the basic understanding of the mechanisms of seismically induced settlements of partially saturated sands an effective stress based empirical methodology is proposed to estimate the seismically induced settlement of a free field layer of sand in partially saturated conditions this approach estimates the settlement by separately considering the volumetric strains caused by compression of void space during strong shaking seismic compression and dissipation of excess pore water pressures generated during earthquake shaking postcyclic reconsolidation a parametric evaluation of the methodology indicates that the small strain shear modulus the parameters of the modulus reduction curve the approach to e

dynamic centrifuge tests to evaluate reinforcing mechanisms of soil cement columns in liquefiable sand abstractfour centrifuge tests were performed to investigate the reinforcing mechanisms of soil cement columns in liquefiable sand two unimproved baseline models and two models improved with soil cement columns were subjected to sine sweep and earthquake base motions of varying intensities to observe acceleration pore pressure lateral displacement and settlement responses the dynamic records were processed to derive the effective natural frequency of the profiles and to obtain the dynamic stress strain responses for unimproved and improved soil it was found that the shear reinforcement mechanisms of columns was not effective in reducing cyclic stress ratios in the treated soil liquefaction triggering occurred nearly at same time for both unimproved and improved soil cases and the magnitude of the resulting soil settlement was not significantly reduced when the bases of the columns were free to rotate the columns rocked within the soil and produced negligible shear stiffening of the soil profile w

stress densification and its evaluation stress densification occurs in natural soils as well as manmade embankments and physical model tests such densification can increase stability and liquefaction resistance one dimensional compress

on improving the bed stress formulation in storm surge models a method of improving the representation of bottom stress in storm surge models an enhanced bed stress model is tested using a fine mesh model of the celtic and irish seas and is compared with results from a conventional two dimensional model the approach uses a convolution method to determine the bed stress rather than relating it directly to the depth mean current as in a conventional storm surge model for the region considered comparisons of surge elevations computed with both models and observations show only a slight improvement of surge elevation in the near coastal region with the enhanced bed stress model however spatial distributions of bed stresses from the two models do exhibit significant differences which are important in considering sediment movement paths during major storms the magnitude and direction of the bed stress vectors computed from the enhanced bed stress model are in excellent agreement with calculations using a full three dimensional model of the area this suggests that the enhanced bed stress model can compute a bed stress that is not significantly different from that in a full three dimensional model at a fraction of the computational cost

experimental observations on the response of loose sand under simultaneous increase in stress ratio and rotation of principal stresses the drained response of loose sand relative density of 30 under simultaneous increase in principal stress ra tio r 1 3 and the inclination of major principal stress to the vertical is examined using data from hollow cylin der torsional shear testing the study specifically pertains to the behaviour of loose sand subject to monotonic linear stress path loadings in the r space within the domain of r 2 4 58 while intermediate principal stress parameter b and effective mean normal stress m are held constant the relationship between horizontal shear stress zt and hori zontal shear strain zt of loose sand under such loadings is shown to be unique and stress path independent at any stress state the horizontal shear stiffness dzt dzt for a given m depends only on the current value ofzt and not on the value of individual components of normal effective stress or their increments when r and are increased simultaneously in a linear manner loose sand initially exhibits linear strain paths suggesting no significant changes to the inherent anisotropy during the early stages of such loading the directions of principal stress increment and principal strain increment 3 are found coincident when 4 58 an approach to predict the response of loose sand under simultaneous in crease in r and with constant b and m has been developed based on these findings

influence of prefabricated vertical drains on the seismic performance of similar neighbouring structures founded on liquefiable deposits increasing the resilience of structures to seismically induced soil liquefaction is a major objective for the earthquake engineering community increasingly soil drains are being used to mitigate

on extracting current profiles from vertically integrated numerical models abstract a transformation method is presented by which current profiles of tidal or wind induced origin can be extracted at any horizontal position and moment in time from a vertically integrated two dimensional hydrodynamic numerical model an arbitrary vertical variation of eddy viscosity can be included in the method which can incorporate a no slip bottom boundary condition the technique assumes that the sea is homogeneous the method is used to improve the representation of bottom stress within the two dimensional model whereby the bottom stress is no longer related simply to the depth mean current as in the conventional two dimensional vertically integrated model idealized calculations for a range of eddy viscosity profiles show that elevations current profiles and time series of current extracted from this enhanced two dimensional numerical model are in good agreement with currents obtained from a full three dimensional model

seismic demand of the liquefaction potential with equivalent number of cycles for probabilistic seismic hazard analysis abstractequivalent number of cycles ncyc is a significant factor in assessing liquefaction potential during earthquakes however the effects of ncyc are considered a deterministic value by using a magnitude scaling factor and the uncertainties of these effects have not been included in the current design practice this paper calculates ncyc within the soil mass by deconvolution analysis as a function of the period of soil layer from the ground surface ts and the soil property b using a wide range of acceleration time histories the predictive model of ncyc is developed as variable dependent on earthquake magnitude peak ground acceleration pga and ratio of spectral acceleration ts and b then the ncyc model is combined with the ground motion prediction equation of pga and the prediction equation of seismic shear stress reduction coefficient rd to obtain the prediction equation of the seismic demand of the liquefaction potential k1cyc the standard deviation of k1cyc is also modeled on the

dynamic analyses of two buildings founded on liquefiable soils during the canterbury earthquake sequence abstracta series of major earthquakes near christchurch new zealand produced different levels of liquefaction induced ground failure and damage to multistory buildings in the city s central busin

vacuum preloading consolidation of yaoqiang airport runway yaoqiang airport is an international airport serving the city of jinan china the soil on the site consists of alternate layers of silty sand silty clay silt and clay an under consolidated soft clay layer approximately 4 m thick is located at between 7 5 m and 11 5 m depth above a silty clay layer soil improvement was proposed to consolidate the site prior to the construction of a runway to eliminate excessive settlement under static and dynamic loads on the runway the results from field pilot tests for both surcharge preloading and vacuum preloading under the same consolidation pressure of 80 kpa are presented soil settlement in the range 20 30 cm was achieved in 80 90 days for the vacuum treatment in situ deep mixing slurry cut off walls were installed to control vacuum loss in a shallow silty sand layer data from the successful full scale vacuum treatment of the site are also presented

equivalent linear computation of response spectra for liquefiable sites the spectral envelope method abstracta simplified methodology is proposed for the computation of elastic response spectra at liquefiable sites based on the widely used equivalent linear frequency domain site response analysis method the actual response spectrum is obtained as the upper bound envelope of the thus calculated response spectra corresponding to the preliquefaction and the postliquefaction segments of the seismic excitation the former computed for the natural soil properties and the latter for the properties of the liquefied soil the time of liquefaction onset which separates the two seismic excitation segments is defined in terms of the minimum factor of safety against liquefaction within the liquefiable layer additional guidelines are provided for the estimation of the excess pore pressure buildup and the associated soil softening during the preliquefaction segment of the seismic excitation as well as for the definition of the liquefied soil stiffness and the hysteretic damping ratio the proposed methodology h

centrifuge tests of adjacent mat supported buildings affected by liquefaction abstractgeotechnical centrifuge tests can provide valuable insights into the mechanisms governing the performance of buildings affected by liquefaction an area particularly lacking knowledge is the effect of liquefaction on adjacent structures which is a common possibility in urban areas two well instrumented centrifuge tests were performed to investigate the response of isolated and adjacent structures founded on ground that underwent varying degrees of liquefaction three types of single degree of freedom model structures were used in the experiments acceleration pore water pressure and settlement measurements illustrated that liquefaction induced settlement of structures depends on a complex interaction of ground motion soil and structural characteristics for the cases examined in this study adjacent structures experienced moderately lower foundation accelerations than isolated structures of the same type adjacent structures tended to tilt away from one another and settled less than isolated

effect of shaking strength on the seismic response of liquefiable level ground abstract shaking strength is one of the most important parameters that characterize earthquake events in the past it was common to apply shaking of different strengths consecutively on a soil model to investigate the effect of shaking level on seismic ground response without considering the effect of loading history in this study a series of dynamic centrifuge tests under different shaking levels was performed on fresh saturated sand models with the same initial conditions to investigate the effect of shaking strength on the seismic response of liquefiable level ground the experimental observations indicate the following effects 1 shaking strength has pronounced effect on the excess pore pressure buildup in the saturated sand deposit the maximum excess pore pressure at the deep part of the deposit increased by 184 and 109 as the peak input acceleration along the x direction increased from approximately 0 064 g to 0 098 g and from 0 098 g to 0 189 g respectively 2 shaking strength has significant effect on the development of shear strain in soil however the permanent settlement is sensitive to the shaking strength at low shaking level but the increment rate tends to slow down as the shaking strength becomes stronger 3 the peak acceleration along the x direction at the ground surface was 0 126 0 079 and 0 087 g at peak input accelerations of 0 064 0 098 and 0 189 g respectively the peak acceleration at the ground surface under slight shaking was greater than that under strong shaking 4 the amplification pattern of acceleration varied continuously during shaking the amplification factor decreased quickly as the excess pore pressure accumulated under strong shaking but continued to increase at an early stage under low strength earthquake the natural frequency of the soil column also evolved with the development of the shaking induced excess pore pressure which had adversely affected the wave propagation and ground response the data presented in this paper enrich the ground response database and can be used to validate the current site response analysis methods

static and cyclic liquefaction potential of fraser delta sand in simple shear and triaxial tests the potential for static and cyclic liquefaction of the sand that underlies the highly seismic fraser delta is assessed under simple shear test conditions typical of an earthquake shaking a comparison of liquefaction potential is also made between simple shear and conventional triaxial stress conditions it is shown that the liquefaction potential of sand is profoundly influenced by the stress path the reduction factors currently applied to the cyclic triaxial resistance for representing simple shear response may involve a large degree of conservatism in design a direct measurement of soil behaviour under stress conditions typical of earthquake loading may thus have large economic benefits key words sand liquefaction static cyclic triaxial simple shear

cyclic characterization of wave induced oscillatory and residual response of liquefiable seabed the paper presents a robust modeling method for a fully coupled effective stress analysis of the wave induced liquefaction scenarios based on the biot consolidation theory in this context emphasis is placed on the implementation of a well calibrated cyclic soil model and an empirical shear volume coupling equation which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle unlike most of the previous investigations using the amplitude of shear stress over the wave period or the phase resolved oscillatory shear stresses as the source term for calculating the residual pore pressure in this study the source term is related to the rate of plastic volumetric deformation and implemented into the biot consolidation equation to consider both generation and partial dissipation of excess pore pressure during wave propagation then the proposed modeling method is incorporated into a dynamic finite difference analysis procedure model calibrations are carried out in terms of individual soil element behavior and seabed response under progressive waves respectively overall good agreement demonstrates the reliability of the modeling method for the prediction of wave induced seabed response finally the paper highlights the potentials of proposed modeling framework to simulate the basic features of wave induced seabed response i e the coupling of progressive buildup of pore pressure and cyclic softening of soil skeleton by means of numerical examples the obtained results show that the cyclic behavior of liquefiable seabed under wave actions can be well captured by the proposed model

earthquake prediction by animals evolution and sensory perception animals living within seismically active regions are subjected episod ically to intense ground shaking that can kill individuals through burrow collapse egg destruction and tsunami action although anecdotal and retrospective reports of animal behavior suggest that although many organisms may be able to detect an impending seismic event no plausible scenario has been presented yet through which accounts for the evolution of such behaviors the evolutionary mechanism of ex aptation can do this in a two step process the first step is to evolve a vibration triggered early warning response which would act in the short time interval between the arrival of p and s waves anecdotal evidence suggests this response already exists then if precursory stimuli also exist similar evolutionary processes can link an animal s perception of these stimuli to its p wave triggered response yielding an earthquake predictive behavior a population genetic model indicates that such a seismic escape response system can be maintained against random mutations as a result of episodic selection that operates with time scales comparable to that of strong seismic events hence additional understanding of possible earthquake precursors that are presently outside the realm of seismology might be gleaned from the study of animal behavior sensory physiology and genetics a brief review of possible seismic precursors suggests that tilt hygroreception humidity electric and mag netic sensory systems in animals could be linked into a seismic escape behavioral system several testable predictions of this analysis are discussed and it is recom mended that additional magnetic electrical tilt and hygro sensors be incorporated into dense monitoring networks in seismically active regions

precompression design for secondary settlement reduction a large water treatment plant is to be built on soft deltaic deposits precompression has been selected as the method for achieving the required ground improvement an instrumented preload test has been carried out to obtain reliable information on precompression performance distributions of displacements throughout the foundation depth obtained using sliding micrometer extensometers have proved extremely useful for identifying the mechanisms of behaviour controlling ground deformation the magnitudes of displacements are largely dependent on the overconsolidation state of the soil as primary consolidation settlements take place rather quickly they can be largely controlled by applying a preload over a limited period the main design criterion therefore concerns secondary settlements laboratory and field data indicate clearly that overconsolidating the soil even in moderate amounts significantly reduces the secondary compression rate the performance of an unloading stage in the preload test provi

seismically induced settlement of ground experiencing undrained shaking and laterally constrained compression a method is proposed for estimating seismically induced settlement of saturated sands experiencing undrained shaking and laterally constrained compression an empirical relationship is developed between the seismic coefficient of vertical compression mvs and standard penetration test blow count n60 as a function of factor of safety against liquefaction fl based on data interpreted from 18 sets of laboratory cyclic direct simple shear tests and 23 cases of field observations of seismic liquefaction the proposed method is compared with seismic settlement observed at 78 sites subjected to 7 1 8 0 magnitude earthquakes and with predictions by the previous well known methods of settlement analysis for undrained shaking for silty clayey sands the significant effect of the plasticity of fines on seismic settlement is illustrated the use of pre or post earthquake penetration resistance for back analyses of field seismic settlement observations is examined a tentative correction factor is suggested fo

study on liquefaction mechanism of saturated sand considering stress redistribution abstract most of the saturated soil in actual condition is anisotropically consolidated and can liquefy during minor earthquake based on the analysis of stress state in actual soil the present paper considers that the stress redistributed during loading process which result in the liquefaction however in present conventional element tests the liquefaction in anisotropically consolidated saturated sands acs cannot be induced under dynamic cyclic loading without stress reversal it contributes to the uncertainty about the liquefaction resistance of soil and the development model of excess pore water pressure pwp a brief theoretical interpretation within the theory of limit state of soils is given to explain why the liquefaction in acs could not be induced using the conventional element test under dynamic cyclic load with low or moderate amplitude and the validity of the theoretical analysis is verified by experiments the stress redistribution is realized by confining the lateral deformation based on the conventional test and the liquefaction in acs under minor cyclic load is realized furthermore a new concept called continued liquefaction is proposed apart from transient liquefaction the pwp the total confining pressure and the total vertical stress are always at the same level and the mean effective stress of sands is always zero in the continued liquefaction stage finally a suggestion that the development model of pwp should be established on the basis of the ratio of the pwp to the initial vertical stress is recommended

geotechnical mitigation strategies for earthquake surface fault rupture abstractsurface fault rupture can be damaging to structures built on or near active faults if the hazard is not addressed properly fault induced angular distortion and lateral ground strain can cause beams to yield and eventually lead to structural collapse when avoidance is not possible geotechnical mitigation strategies can be used these strategies include spreading fault displacement over a large area causing the structure to respond with rigid body movement and diverting the fault rupture around the structure the effectiveness of these strategies can vary from protecting life safety to preventing significant damage and can be effective for a range of dip slip fault displacements earth fills should be sufficiently thick and ductile to prevent the underlying fault dislocation from developing at the ground surface thick rc mat foundations proved to be especially effective in shielding the superstructure from the damaging effects of the underlying ground movements although more challenging to im

numerical simulation of building response on liquefiable sand abstractthe effective design of earthquake resistant structures and liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction in this paper the results from centrifuge experiments of structures with shallow foundations on liquefiable sand were used to evaluate the predictive capabilities of a state of the practice numerical tool fully coupled numerical simulations with the ubcsand model implemented in flac 2d captured building settlements measured in these experiments reasonably well for one scaled input motion mostly within factors of 0 7 and 1 8 the soil model captured the overall contribution of deviatoric displacement mechanisms and localized volumetric strains during partially drained cyclic loading the primary limitation of the model became evident for slower rates of earthquake energy buildup when the extent of soil softening and building displacement was overestimated by up to a factor of 4 the observations from recent case hi

equivalent number of uniform stress cycles for soil liquefaction analysis the seismic demand on potentially liquefiable soils can be approximated by a series of uniform shear stress cycles procedures are reviewed for converting an arbitrary acceleration time history to a series of uniform cycles with amplitude 0 65 of the peak the number of cycles n at this amplitude is evaluated so as to represent a seismic demand for liquefaction triggering equivalent to that of the accelerogram an assumed relationship between n and magnitude m underlies so called magnitude scaling factors used to adjust the liquefaction resistance of soil for the effects of duration magnitude scaling factors can alternatively be related directly to n which enables the effects of factors other than m for example site source distance r to be quantified we develop empirical models for n that are applicable to active tectonic regions and find a strong dependence on m and r and a weaker dependence on site condition and near fault rupture directivity effects the model for n is used to develop new s

three dimensional modal model of wind induced flow in a sea region abstract the solution of the linear three dimensional hydrodynamic equations describing wind induced flow in a sea region is developed using the galerkin method through the vertical a basis set of b splines is shown to have some computational advantages over a set of eigenfunctions vertical modes however a basis set of modes leads to a system of essentially uncoupled equations and current profiles can be interpreted in terms of vertical modes the influence of wind induced surface turbulence and turbulence at depth due to tidal motion upon current profiles in both deep 260 m and shallow 35 m sea regions is examined the variation in the angle between surface current and surface wind for different viscosity profiles and the effect of bottom friction upon it is considered the magnitude and direction of the surface current is significantly influenced by surface eddy viscosity however viscosity at depth due to tidal motion also has an important effect upon the surface current the time evolution of current structure following the sudden onset of a wind is examined using the modal model calculations show that the rate of damping of the internal modes is inversely proportional to the square of the depth consequently wind induced current structure takes longer to reach a steady state in a deep sea region than a shallow area the influence of sea surface elevation gradients in determining the direction of surface current is also considered

shear wave velocity based probabilistic and deterministic assessment of seismic soil liquefaction potential abstractshear wave velocity vs offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property this paper presents the results of an 11 year international project to gather new vs site data and develop probabilistic correlations for seismic soil liquefaction occurrence toward that objective shear wave velocity test sites were identified and measurements made for 301 new liquefaction field case histories in china japan taiwan greece and the united states over a decade the majority of these new case histories reoccupy those previously investigated by penetration testing these new data are combined with previously published case histories to build a global catalog of 422 case histories of vs liquefaction performance bayesian regression and structural reliability methods facilitate a probabilistic treatment of the vs catalog for performance based engineering applications where possible uncertainties of the variables comprising both the seismic demand an

behavior of a fine grained soil during the loma prieta earthquake results of an investigation into the behavior of a fine grained clayey soil at moss landing during the 1989 loma prieta earthquake are presented a deposit of this soil underlies portions of the mo

liquefaction and soil failure during 1994 northridge earthquake the 1994 northridge california earthquake caused widespread permanent ground deformation on the gently sloping alluvial fan surface of the san fernando valley the ground cracks and distributed deformation damaged both pipelines and surface structures to evaluate the mechanism of soil failure detailed subsurface investigations were conducted at four sites three sites are underlain by saturated sandy silts with low standard penetration test and cone penetration test values these soils are similar to those that liquefied during the 1971 san fernando earthquake and are shown by widely used empirical relationships to be susceptible to liquefaction the remaining site is underlain by saturated clay whose undrained shear strength is approximately half the value of the earthquake induced shear stress at this location this study demonstrates that the heterogeneous nature of alluvial fan sediments in combination with variations in the groundwater table can be responsible for complex patterns of permanent ground deformation it may also help to explain some of the spatial variability of strong ground motion observed during the 1994 earthquake

effect of waste rock inclusions on the seismic stability of an upstream raised tailings impoundment a numerical investigation over the years seismic activity has been a relatively common cause of tailings impoundment failure the flow of liquefied tailings from such ruptures can result in very severe consequences includ

seismic compression of two compacted earth fills shaken by the 1994 northridge earthquake seismic compression is defined as the accrual of contractive volumetric strain in unsaturated soil during strong shaking by earthquakes we document and analyze two case histories denoted school site and site a of ground deformation from seismic compression in canyon fills strongly shaken by the northridge earthquake site a had ground settlements up to about 18 cm which damaged a structure while the school site had settlements up to about 6 cm for each site we perform decoupled analyses of shear and volumetric strain shear strain is calculated using one dimensional and two dimensional ground response analyses while volumetric strain is evaluated from shear strain using material specific models derived from simple shear laboratory testing that incorporates important effects of fines content and as compacted density and saturation analyses are repeated using a logic tree approach in which weights are assigned to multiple possible realizations of uncertain model parameters at the school site predicted settlements appear to be unbiased at site a the analyses successfully predict the shape of the settlement profile along a section but the weighted average predictions are biased slightly too low we speculate that the apparent site a bias can be explained by limited resolution of the site stratigraphy bias in laboratory derived volumetric strain models and or uncertainty in the estimated earthquake induced settlements

insight into the seismic liquefaction performance of shallow foundations the mechanisms that control the seismic liquefaction performance of shallow foundations are identified for the special still com mon case of a clay crust separating the foundation from the liquefied ground for that purpose foundation response is first analyzed with the nonlinear dynamic finite difference method and consequently evaluated in connection with published field and experimental evidence insight is given into the excess pore pressure buildup under the foundation the seismic settlement accumulation the static bearing capacity degrada tion and the inertia induced interaction with the superstructure it is thus shown that a naturally or artificially created nonliquefiable soil crust may effectively mitigate the detrimental effects of liquefaction and allow for a performance based design of surface foundations without

water film in liquefied sand and its effect on lateral spread a one dimensional 1d saturated sand layer of 2 m in thickness in which a silt seam is sandwiched is liquefied by an instant shock it is found that a water film is easily formed beneath the silt seam with a thickness as thin as a few millimeters just after liquefaction in loose sand and that the film lasts longer than the postliquefaction settlement the effect of the water film on pore pressure distribution and sand settlement is intensively studied one gram shake table tests are then carried out for 2d models with or without seams of silt within a saturated sand layer in the former case water films formed beneath silt seams just after liquefaction enable the soil mass above them to glide because of an unbalanced force along the water films not only during but also after shaking in the latter case the soil deforms continuously mostly during shaking and stops afterward thus a significnat effect of water films formed beneath thin low permeability sublayers in a liquefied loose sand on the failure mode and timing in lateral spread is clearly demonstrated by these simple model tests

the bhuj india earthquake lessons learned for earthquake safety of dams on alluvium abstract the bhuj india earthquake of 26 january 2001 m s 7 9 caused dams built on alluvium to sustain damage ranging from cosmetic to severe major damage was caused almost entirely by soil liquefaction in the alluvium the critical factor was the level of earthquake ground motion the bhuj earthquake showed that peak horizontal accelerations phas 0 2 g were generally safe phas 0 2 g were hazardous when unconsolidated granular foundation soils were water saturated n values of 0 2 g must be evaluated over the full area beneath a new dam and all soils deemed susceptible to liquefaction must be either removed or treated for remediating an old dam reliable options are removal and replacement of liquefiable alluvium beneath upstream and downstream portions of the dam combined with building berms designed to provide stability for the dam should there be a strength loss in soils beneath the dam

analysis of canlex liquefaction embankments prototype and centrifuge models un objectif principal du projet canadien d etude de la liquefaction canadian liquefaction experiment canlex etait de verifier les procedures d analyse pour la prediction des phenomenes de liquefaction a cette fin deux cas de chargement ont ete realises un chargement sur le terrain comprenant un remblai construit sur une couche de fondation de sable l che et un essai au centrifuge realise sur un modele de la structure prototype tant l essai sur le terrain que l essai au centrifuge ont ete planifies de facon a induire une rupture par liquefaction statique les caracteristiques mecaniques fondamentales de la couche de fondation ont ete determinees dans des essais en laboratoire sur des elements triaxiaux et cisaillement simple ces caracteristiques ont ete d abord obtenues sur un element en utilisant un modele de comportement contrainte deformation elasto plastique le prototype et les structures a l echelle ont alors ete modelises comme un ensemble de tels elements le drainage etait un facteur tres important durant le chargement et etait directement incorpore dans la procedure de l analyse les resultats predits concordent bien tant avec l essai au centrifuge qu avec les mesures sur le terrain

mechanisms of seismically induced settlement of buildings with shallow foundations on liquefiable soil seismically induced settlement of buildings with shallow foundations on liquefiable soils has resulted in significant damage in recent earthquakes engineers still largely estimate seismic building settlement using procedures developed to calculate postliquefaction reconsolidation settlement in the free field a series of centrifuge experiments involving buildings situated atop a layered soil deposit have been performed to identify the mechanisms involved in liquefaction induced building settlement previous studies of this problem have identified important factors including shaking intensity the liquefiable soil s relative density and thickness and the building s weight and width centrifuge test results indicate that building settlement is not proportional to the thickness of the liquefiable layer and that most of this settlement occurs during earthquake strong shaking building induced shear deformations combined with localized volumetric strains during partially drained cyclic loading are the dominant mechanisms the development of high excess pore pressures localized drainage in response to the high transient hydraulic gradients and earthquake induced ratcheting of the buildings into the softened soil are important effects that should be captured in design procedures that estimate liquefaction induced building settlement

seismic deformation analysis of tuttle creek dam to facilitate the design of seismic remediation for tuttle creek dam in east central kansas a seismic finite difference analysis of the dam was performed using the software flac and the ubcsand and ubctot soil constitutive models the flac software has a key advantage because it can use calibrated site specific constitutive models earlier deformation analyses using a hyperbolic constitutive model for the foundation fine grained materials did not properly represent the modulus and strength reduction and predicted extremely large permanent deformations cyclic triaxial laboratory tests using high quality samples and in situ vane shear tests were used to calibrate the flac constitutive model herein the resulting flac analysis of the unremediated dam predicted an upstream slope toe deformation of about 0 6 m a crest settlement of about 0 6 m and a downstream slope toe deformation of about 1 5 m using the design ground motion based on the estimated permanent deformations and other factors it was decided

seismic liquefaction lateral spreading and flow slides a numerical investigation into void redistribution experience from past earthquakes indicates that seismically induced large lateral spreads and flow slides in alluvial sand deposits have taken place in coastal and river areas in many parts of the world the ground slope in these slides was often not very steep gentler than a few percent recent research indicates that the presence of low permeability silt or clay sublayers within the sand deposits is responsible for this behaviour such layers form a barrier to upward flow of water associated with earthquake generated pore pressures this causes an accumulation of pore water at the base of the layers resulting in greatly reduced strength and possible slope instability this paper uses an effective stress coupled stress flow dynamic analyses procedure to demonstrate the effects of a low permeability barrier layer on ground deformations from an earthquake event the analyses show that an expansion zone develops at the base of barrier layers in stratified soil deposits under seismic loading which can grea