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

structural and lithostratigraphic controls of earth flow evolution montaguto earth flow southern italy this paper aims to define the control exerted by geological setting on the evolution and segmentation of the montaguto earth flow in southern italy a detailed geological survey and multi temporal maps were used to reconstruct the geological model of la montagna mt and to quantify the evolution of the flow in terms of sediment pulse formation movement direction and spatial change in earth flow area the spatial distribution of structural fabric of the mountainside was compared with 1 planar geometry of earth flow source area 2 orientation of strike slip faults bounding the earth flow moving core i e movement direction and 3 kinematic zone position and extent we infer that the evolution of the earth flow is controlled by geological structures and lithology moreover the entire basal slip surface is composed of newly formed basal slip surface in the source area and corresponds to pre earth flow topography downslope from the neck implications of our work are that 1 a detailed geological model of an unstable mountainside combined with information about earth flow spatial evolution might be considered as a tool that allows the localization of areas of possible earth flow enlargement and 2 geological structures constrain earth flow movement inducing a predictable seasonal behaviour in terms of movement direction

alpine faunas from the white mountains california adaptive change in the late prehistoric great basin abstract high elevation archaeological sites in the white mountains of eastern california document the establishment of small villages at elevations above 3100 m at about ad 800 replacing occupations that lacked substantial structures storage facilities and abundant plant processing equipment previllage faunas are far more tightly focused on large artiodactyls than on smaller mammals but do not differ significantly from village faunas in richness or diversity these differences do not provide strong support for the bettinger baumhoff 1982 model of late prehistoric adaptive change in the great basin but adequate testing of more subtle versions of such hypotheses may require a massive research effort

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

the 22 march 2014 oso landslide washington usa abstract the oso washington usa landslide occurred on the morning of saturday 22 march 2014 and claimed the lives of 43 people the landslide began within an 200 m high hillslope comprised of unconsolidated glacial and previous landslide colluvial deposits it continued as a debris avalanche debris flow that rapidly inundated a neighborhood of 35 single family residences an intense three week rainfall that immediately preceded the event most likely played a role in triggering the landslide and other factors that likely contributed to destabilization of the landslide mass include alteration of the local groundwater recharge and hydrogeological regime from previous landsliding weakening and alteration of the landslide mass caused by previous landsliding and changes in stress distribution resulting from removal and deposition of material from earlier landsliding field reconnaissance following the event revealed six distinctive zones and several subzones that are characterized on the basis of geomorphic expression styles of deformation geologic materials and the types size and orientation of vegetation seismic recording of the landslide indicate that the event was marked by several vibration generating episodes of mass movement we hypothesize that the landslide occurred in two stages with the first being a sequential remobilization of existing slide masses from the most recent 2006 landslide and from an ancient slide that triggered a devastating debris avalanche debris flow the second stage involved headward extension into previously unfailed material that occurred in response to unloading and redirection of stresses

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

soil parameters for deformation analysis of sand masses meaningful stress and deformation analysis of soil structures requires an adequate stress strain law herein are presented guidelines for selection of parameters for a simple incremental hyperbolic stress strain law for sand based upon a tangent stiffness that varies with stress level the parameters are obtained from an examination of laboratory and field measurements available in the literature and are presented in terms of both penetration value and relative density the laboratory results indicate the importance of first time or primary loading versus repeated loading on modulus values back analysis of field observations for monotonic loading conditions indicates that primary loading modulus values obtained from triaxial tests are appropriate at low relative density whereas perhaps higher values in the repeated loading range are appropriate at high relative densities key words sand deformation analysis hyperbolic tangent stiffness modulus relative density monotonic loading repeated loading

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

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

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

the sequence of sediment behaviour during wave induced liquefaction this paper presents the results of an experimental investigation of the complete sequence of sediment behaviour beneath progressive waves the sediment was silty with d50 0 060 mm two kinds of measurements were carried out pore water pressure measurements across the sediment depth and water surface elevation measurements the process of liquefaction compaction was videotaped from the side simultaneously with the pressure and water surface elevation measurements the video records were then analysed to measure i the time development of the mudline ii the time development of liquefaction and compaction fronts in the sediment and iii the characteristics of the orbital motion of the liquefied sediment including the motion of the interface between the water body and the sediment the ranges of the various quantities in the tests were wave height h 9 17 cm wave period t 1 6 sec water depth 42 cm and the shields parameter 0 34 0 59 the experiments reveal that with the introduction of waves excess pore pressure builds up which is followed by liquefaction during which internal waves are experienced at the interface of the water body and the liquefied sediment the sequence of processes known from a previous investigation this sequence of processes is followed by dissipation of the accumulated excess pore pressure and compaction of the sediment which is followed by the formation of bed ripples the present results regarding the dissipation and compaction appear to be in agreement with recent centrifuge wave tank experiments as for the final stage of the sequence of processes formation of ripples the ripple steepness normalized with the angle of repose for sediment with liquefaction history is found to be the same as that in sediment with no liquefaction history

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

influence of slip surface geometry on earth flow deformation montaguto earth flow southern italy we investigated relations between slip surface geometry and deformational structures and hydrologic features at the montaguto earth flow in southern italy between 1954 and 2010 we used 25 boreholes 15 static cone penetration tests and 22 shallow seismic profiles to define the geometry of basal and lateral slip surfaces and 9 multitemporal maps to quantify the spatial and temporal distribution of normal faults thrust faults back tilted surfaces strike slip faults flank ridges folds ponds and springs we infer that the slip surface is a repeating series of steeply sloping surfaces risers and gently sloping surfaces treads stretching of earth flow material created normal faults at risers and shortening of earth flow material created thrust faults back tilted surfaces and ponds at treads individual pairs of risers and treads formed quasi discrete kinematic zones within the earth flow that operated in unison to transmit pulses of sediment along the length of the flow the locations of strike slip faults flank ridges and folds were not controlled by basal slip surface topography but were instead dependent on earth flow volume and lateral changes in the direction of the earth flow travel path the earth flow travel path was strongly influenced by inactive earth flow deposits and pre earth flow drainages whose positions were determined by tectonic structures the implications of our results that may be applicable to other earth flows are that structures with strikes normal to the direction of earth flow motion e g normal faults and thrust faults can be used as a guide to the geometry of basal slip surfaces but that depths to the slip surface i e the thickness of an earth flow will vary as sediment pulses are transmitted through a flow

instrumented laboratory flowslides flowslides have been induced in small instrumented coking coal stockpiles by slowly raising the water table these strongly resembled field cases showing sudden collapse rapid fluid like motion and very flat final slopes failure initiated under essentially static drained conditions and with a mobilized secant effective strength parameter d much less than the steady state value highspeed measurements showed that excess pore pressures were generated during rather than before movement and liquefaction was therefore a result of shear failure rather than the cause des glissements par liquefaction furent provogues dans de petites reserves de charbon cokeflant a instrumentation par elevations lentes de la nappe aquifere ils ressemblaient beaucoup a des cas sur chantier avec affaissement abrupt un mouvement rapide quasi fluide et des pentes finales tres plates la rupture commenca dans des conditions drainees essentiellement statiques et avec un parametre o de resistance effective secante mobilisee

viscous type sliding laws for landslides sliding of a moving soil mass along a basal surface is analyzed and viscous type sliding laws are presented they relate the relative sliding velocity at the base or at an interface to the state of stress at this surface examples of practical parameter determination illustrate the suitability of this approach two landslides in switzerland and in france provide the data for this purpose a third site la frasse switzerland serves as an example of three dimensional analysis of creeping slopes using the proposed formulation comparison of computed and measured velocity distributions shows the method to be promising key words landslides creep sliding law time dependence interface

cyclic resistance ratio of pleistocene age sands from the south carolina coastal plain abstract field and laboratory tests were performed on sandy soils from three pleistocene age sites in the south carolina coastal plain to investigate the age related resistance to liquefaction reported research indicates that liquefaction resistance of sands increases with the age of the deposit and that liquefaction may reset the aging clock the stress controlled cyclic triaxial test was used to determine the cyclic strength of soil deposits with geologic ages of approximately 200 000 450 000 and 1 400 000 years and evidence of sand blows that are 467 to 4185 years old specimens were obtained using a fixed piston sampler frozen ex situ and include naturally occurring differences in fabric cyclic stress ratios ranging from 0 135 to 0 225 were used to determine the peak deviator stress applied during the cyclic triaxial test and were initially estimated from two age based methods which were found to over estimate the laboratory cyclic stress ratio estimates of the at rest earth pressure coefficient were applied to the laboratory cyclic resistance ratio which resulted in field cyclic resistance ratios that ranged from 0 100 for the oldest deposit 1 400 000 years to 0 131 for the mid aged deposit 450 000 years for initial liquefaction occurring when the generated excess pore pressure was equal to the effective confining stress of 100 kpa ru 1 0 at n equal to 15 cycles the carbon dated age of the sand blow events correlated with the field cyclic resistance ratios the geologic ages of the soil deposits did not a correlation between the clay content not the fines content was observed

modelling tailings dams and mine waste dumps failures this paper presents a depth integrated model that can be used to simulate the flowslides mudflows and debris flows that are caused by the failure of tailing dams mining waste dumps and other similar structures the sliding mass is first determined using a coupled elastoplastic finite element code and a suitable constitutive equation once failure has been triggered propagation of the mobilised material is analysed considering flow properties averaged over depth a simple law of pore pressure dissipation is postulated for cases in which the consolidation and propagation times are of the same order of magnitude

canlex full scale experiment and modelling a major aim of the canadian liquefaction experiment canlex was to verify analysis procedures for pre dicting liquefaction phenomena towards this purpose two loading events were carried out a field event comprising a clay embankment built over a loose sand foundation layer and a centrifuge test performed on a model of a sand em bankment structure both the field event and the centrifuge model were planned so as to induce a static liquefaction failure and were instrumented to observe their response in terms of displacement and pore pressure the fundamental mechanical characteristics of the foundation layer were determined from laboratory element tests triaxial and simple shear these tests formed the basis for the stress strain modelling used in the numerical analyses two fundamentally different modelling techniques were used one involved a fully coupled plasticity model and the other involved a model based on a collapse surface approach the model and prototype structures were then analyzed and the predicted results in terms of displacements and pore pressures were compared with the measured values the results from both approaches were found to be in reasonable agreement with the measurements provided allowance was made for direc tion of loading and drainage effects were accounted for resume un but principal du canadian liquefaction experiment canlex etait de verifier les procedures d analyse pour predire les phenomenes de liquefaction a cette fin deux cas de chargement ont ete realises un chargement sur le terrain comprenant la construction d un remblai d argile sur une couche de fondation de sable meuble et un essai au centrifuge realise sur un modele d une structure de remblai de sable tant le remblai sur le terrain que le modele dans le centrifuge ont ete planifies de facon a induire une rupture par liquefaction statique et ont ete instrumentes pour ob server leurs reponses en termes de deplacement et de pression interstitielle les caracteristiques mecaniques

electrical resistivity imaging for the characterization of the montaguto landslide southern italy abstract electrical resistivity tomography surveys were carried out for the characterization of the montaguto earth flow located in the southern apennines chain campania region southern italy the earth flow investigated is one of the largest and most complex landslides in europe with a length of 3 1 103 m a width ranging between 45 and 420 m and an area of about 6 6 105 m2 in the spring of 2010 a large reactivation of the earth flow heavily damaged some strategic infrastructures in order to mitigate the effects of the mass movement considerable efforts were carried out by the italian national civil protection department dpc to tackle the emergency the aim of the study was to contribute to a more accurate geometric reconstruction of the landslide body and to improve the knowledge of the geological setting due to the lithological characteristic of the outcropping lithotypes i e faeto flysch calcarenite clay and marl and villamaina unit sand and silty clay the electrical resistivity contrasts were not very pronounced however the high resolution of the electrical tomographies was the key to observe the presence of both lateral and vertical discontinuities that were associated with lithological boundaries structural features and sliding surfaces the results of the geoelectrical surveys could be considered for planning additional and more appropriate actions aimed at the stabilization of different portions of the montaguto landslide

liquefaction flow of submarine slopes under partially undrained conditions an effective stress approach the stability of submarine slopes is commonly assessed based on undrained soil response liquefaction flow may occur when pore pressure rise in soil elements under constant shear stress causes a reduction in effective stresses recent experimental studies have shown that a small net flow of water into an element results in additional pore pressure generation and further reduces its strength as a result soil elements can liquefy due to expansive volumetric strains that cannot be predicted by undrained analysis submarine deposits of the fraser river delta are known to contain high concentrations of methane gas tidal variations can cause unequal pore pressure generation with depth and time in these soils such changes reduce the effective stresses during low tides and may induce liquefaction flow of slopes due to partial drainage conditions an effective stress approach based on an elastic plastic stress strain relationship is presented to model liquefaction flow of sand a fully coupled analysis is carr

morphological and kinematic evolution of a large earthflow the montaguto landslide southern italy article ml ong earthflow in the southern apennines of italy following an analysis of th ed ifferent methods and techniques available to measure surface modifications caused by a large earthflow we selected a combination of monitoring techniques com patible with the montaguto case study we exploited i visual interpretation of aerial and satellite imagery ii quantitative analysis of six digital elevation model s dems covering the landslide area and iii al arge set of high accuracy three dimensional topographic measurements captured by three robotised total stations rtss in tegration of the results obtained from the different monitoring techniques allowed us to investigate the long multi decadal and short seasonal term evolution of the montaguto earthflow in the 58 year period 1954 2011 the examination of the available aerial satellit ea nd hill shade images revealed ac yclic long term behaviour of mass movements of different types in the rio nocelle catchment occupied by the recent montaguto earthflow the combined analysis of the six dems allowed measuring the material eroded from the landslide crown area v 1 4 10 6

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

the montaguto earthflow a back analysis of the process of landslide propagation abstract earthflow and mudflow processes represent a class of landslides that owing to their typical long run out may generally induce huge damages to infrastructure lines with negative economic impacts therefore the analysis of the landslide propagation with time in such cases can provide useful information to mitigate landslide risk the present paper discusses the case history of a huge earthflow developed in 2005 2006 in the area of montaguto town southern apennines italy that produced significant damages to a national road and a national railway at the slope toe the average displacement rate during the first critical stage of propagation was of some m day the aim of this contribution is the reconstruction of the propagation stage of this landslide during the first high mobility stage a detailed geomorphological analysis aimed at defining the main features of the in situ landslide propagation is firstly described later on a back analysis of the kinematical features of the same landslide process based on a simple infinite slope sliding consolidation model is presented to investigate the role of different factors in the process of landslide propagation the application of this analytical solution suggests that the development of high excess pore water pressures due to undrained loading processes and the consequent consolidation process can represent a reasonable way to explain the earthflow mobility the application of the analytical model to the specific case study is also supported by the field evidence of the existence of excess pore water pressures in the landslide mass which have been measured in situ during the recent monitoring campaign and the corresponding data are also discussed in the work

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

a landslide forecasting model using ground based sar data the portalet case study this paper presents a kinematic study of the portalet landslide sallent de gallego central spanish pyrenees which was triggered by the construction of a big parking area at the toe of the slope a description of the landslide from a geomorphological point of view is first introduced the measurements of displacement performed by conventional total station inclinometers and differential gps and advanced gb sar ground monitoring techniques are presented and gb sar and dgps datasets are compared the correlation between measured displacements and rainfall series indicates that the landslide is very sensitive to rainfall the continuous gb sar measurements from the 5th of october 2006 to the 21st of november 2006 at a rate of 1 h were used to calibrate a simple 1d infinite model by back analysis the model includes a viscoplastic behaviour and takes into account directly the known daily rainfall intensity and the dissipation of the excess pore fluid through a simple consolidation equation prediction was made in an extended period of time from may 2006 to july 2007 and compared to the dgps measurements

communal hunting along the continental divide of northern colorado results from the olson game drive 5bl147 usa abstract the olson site 5bl147 is a multi component rock walled game drive located in the james peak wilderness area of northern colorado usa it is one part of a much larger game drive complex located at rollins pass situated above modern tree limit and along the continental divide at approximately 3600 m above sea level byron olson and james benedict conducted work at the site in the late 1960s we combined their efforts with our recent field and lab work to produce a synthetic overview of the site at least 45 blinds and 1307 m of rock walls are present to funnel game upslope to waiting hunters radiocarbon and lichenometric dates suggest occupations spanning the last 3200 years with diagnostic tools suggesting even older use lithic analysis of the debitage and tools from both excavated blinds and surface contexts intercept and processing areas provides possible scenarios for the use of the site large game drives of the colorado alpine zone represent accumulated landscapes of artifacts and features the byproduct of many years of construction use and re use and built for a variety of reasons

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

problems in predicting the mobility of slow moving landslides abstract this paper discusses problems in predicting the mobility of slow moving landslides three case studies are presented here where research has been carried out by the utrecht university the la valette landslide complex in the french alps the la mure landslide in the french pre alps near grenoble and the hau landslide in switzerland to predict field velocities of these slow moving landslides the viscosity parameters of the material of these landslides were determined by strain controlled tests in a ring shear apparatus based on bishop s design at utrecht university the viscosity parameters from the laboratory proved to be 10 to 1000 times lower than viscosities obtained from back analyses on the observed velocities in the field this discrepancy may be explained by the development of negative pore pressures when the plastic material slides over a rigid wavy slip surface and or by convergent flow effects the associated gain in strength results in a higher apparent viscosity a more detailed analysis is made for the movements of the la valette landslide observed velocities at the la valette landslide are difficult to describe by one parameter set as the response to a change in groundwater level is not the same during a rise or fall in the piezometric level this deviation may be explained by rapid changes in total stresses and consequently changes in pore pressure under partly undrained conditions the emerging hysteresis with local and temporal variations in pore pressure makes it difficult to predict in detail the moving pattern of landslides

a sliding consolidation model for flow slides a model is proposed for the behaviour of flow slides in loose cohesionless materials in which the debris spreads out as a uniform sheet excess pore fluid pressures are assumed to be generated for example by undrained loading arising from the collapse of metastable structure in the source area of the flow slide under the influence of these the leading element of the debris moves downslope by basal sliding consolidating as it does so by single upward drainage as a result the pore pressure at the base of the element eventually decays to a value that brings the element to rest hence defining the run out of the flow slide the model is applicable in principle to subaqueous and subaerial flow slides and to pore fluids consisting of water gas or both of these the predictions of the model are tested against the observed behaviour and measured properties of the 1966 flow slide at aberfan south wales the results show that a sliding consolidation model provides a possible mechanism for that event

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

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

theoretical investigation of the undrained stability of shallow submerged slopes the problem of the criteria of stability of the equilibrium state of an infinitely long slope with constant inclination is tackled and the conditions of spontaneous collapse of the slope are proposed an experimental programme is described to define the stability locus for loose hostun rf sand the validity of the instability line concept introduced by lade for isotropically consolidated virgin specimens is corroborated it is further shown that this instability line can still be defined when specimens are anisotropically consolidated although then the slope of the line is greater it is shown that an instability line cannot be defined for specimens pre loaded in drained conditions and subsequently reloaded undrained as the level at which peak occurs in undrained conditions is dependent on the pre loading history the results are examined in the light of elastoplastic strain hardening theory by using a model to allow for mixed isotropic kinematic hardening all the experimental phenomena observed can

analysis of wave induced liquefaction of sand beds this paper describes finite element analyses of wave induced liquefaction of sand beds the authors were motivated by previous experimental results in which a series of centrifuge wave tank tests were performed on loosely packed fresh deposits of sand with viscous scaling introduced the principal finding was that the resistance to liquefaction under progressive waves was considerably smaller than the resistance exhibited under standing waves an important factor for this marked difference was suggested to be the rotation of the principal stress axes that occurs under progressive wave loading the present study extends an existing cyclic plasticity constitutive model to account for the effect of stress axis rotation of sands this model was incorporated into a finite element analysis procedure which was applied to soil responses to progressive wave and standing wave loading the predicted results compare well with observed soil behaviour the predicted effective stress paths and associated stress strain

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

a comparison between theoretical and measured creep profiles of landslides abstract continuous creep contributes to the movements of a landslide in varved clays the creep models developed in this paper are based on the bingham rheological behaviour of the soil in this bingham model the yield strength value and the viscosity coefficient can be defined in different ways as was done by ter stepanian 1963 and yen 1969 the yield strength can be defined as a residual strength value for overconsolidated clays yen or as a fixed fraction of the peak strength parameters cp and p ter stepanian and the viscosity coefficient can be considered as a constant yen or as a flow factor which depends on the effective normal stress ter stepanian creep tests reversal direct shear tests and triaxial tests were carried out on varved clay samples in order to determine yield strength values and the viscosity parameter according to different definitions four creep models have been evaluated these are based on four possible combinations of the different definitions of yield strength and the viscosity parameter yen s definition of the yield strength in combination with a flow factor which depends on the effective stress ter stepanian is found to give the best prediction of the creep velocity data that were measured in the field

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

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

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

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

behaviour of sands under generalized drainage boundary conditions an experimental study of the behaviour of sands under generalized drainage boundary conditions is presented the influence of partially drained conditions which generally is a reflection of the loading rate and the permeability of the soil has been studied by limiting the volumetric deformation between drained and undrained states the effect of potential pore pressure variations in situ has been assessed by simulating various levels of volumetric deformation during shear conventional drained and undrained tests were also carried out on the same sands to enable a direct evaluation of the effect of drainage a triaxial device with the ability to control strain paths was used to carry out the tests and all tests were performed under compression loading with no change in total lateral stress a systematic change in the stress strain response was noted as the drainage conditions gradually change from drained to undrained the maximum excess pore pressure generated owing to inhibition of drainage is almost

some aspects of the initiation of debris avalanches in the campania region the role of morphological slope discontinuities and the development of failure abstract in may 1998 a prolonged period of rainfall caused disastrous landslides in the sarno quindici area campania southern italy the landslides initiated as small debris slides and developed into debris avalanches and debris flows involving the shallow pyroclastic deposits that lie on the steep vegetated slopes of this area in view of the potential for such events to occur again in this area an understanding of the initial failure mechanism is crucial if assessments are to be made of the hazard levels in this paper the results of detailed surveys of the morphological characteristics of the source areas are presented statistical analyses and parametrical relationships have been performed on key parameters demonstrating that the initial failures were associated with the presence of morphological discontinuities such as limestone scarps and road cuts notably the presence of man made cuts appears to have been responsible for about the 60 of the initial debris slides morphometric analysis has shown that the debris avalanches are characterised by a typical triangular shape statistical analyses have been used to try to relate the apex angles to relevant geomorphological parameters allowing for differences in local morphology the findings show some significant correlation

human responses to middle holocene altithermal climates on the north american great plains abstract the climate of the great plains during the middle holocene varied considerably but overall it was marked by a north south gradient of increasingly warmer and drier conditions with a reduction in effective moisture surface water and resource abundance and an increase in resource patchiness sediment weathering erosion and aeolian activity pronounced drought conditions were most evident on the southern high plains understanding the human responses to middle holocene climates is complicated by a lack of archaeological data which is partly a result of geomorphic processes that removed or deeply buried sites of this age and by the varying adaptive responses of hunter gatherers during this period on the southern high plains where drought was most severe surface and groundwater sources dried and bison populations were diminished prompting substantial adaptive changes including local abandonment well digging to tap underground water and a widening of the diet breadth to incorporate higher cost lower return seed and plant resources sites of this age on the central and northern plains also show a possible increase in diet breadth with the incorporation of plant foods in the diet and perhaps changes in settlement mobility including possible shift into higher elevation areas or mapping on to extant rivers and springs but linking those changes to middle holocene drought is less straightforward

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

dilation angle and liquefaction potential its proposed that the dilation angle or expansion rate of the sand during shear is a measurement describing the initial state of the sand which could be obtained in both the laboratory and the field and which could give a measure of liquefaction resistance the dilation angle can be readily obtained in the laboratory from drained triaxial or simple shear tests and in the field it can be obtained from self boring pressuremeter tests a liquefaction resistance chart based on dilation angle rather than on corrected blow count is presented from this chart an estimate of the field liquefaction resistance of saturated sands can be obtained from dilation angles from self boring pressuremeter tests details are given of the analysis procedure in which the dilation angle was obtained as a function of relative density by performing drained static simple shear tests on the same sand over a range of relative densities and observing volume change characteristics the relations between liquefaction resistance relative density and dilation angle are discussed liquefaction resistance can be correlated with relative density corrected dilation angle or corrected blow count and a chart showing liquefaction resistance in terms of these three parameters is shown the latter indicates that liquefaction is not likely to occur regardless of the stress level provided the relative density is in excess of 75 the corrected dilation angle is greater than 16 degress or the corrected blow count exceeds 20