a field experiment for calibrating landslide time of failure prediction functions over the last decades time of failure semi empirical prediction functions have been developed and applied to different landslides with mixed results in this study a field experiment was carried out to calibrate these functions with the simultaneous consideration of small size landslides and landslides that occur on slopes modified by human activities four years of continuous monitoring using an integrated platform consisting of both traditional sensors i e inclinometers piezometers load cells topographic measurement and innovative remote sensing equipment i e terrestrial sar interferometer resulted in the collection of a notably large amount of data several landslides affecting different slopes i e cut slopes cut slopes covered by spritz beton and slopes stabilised by anchored bulkheads were observed as part of the experiment thus facilitating the inference of detailed information for the pre failure behaviour nine landslides were back analysed thus allowing for calibration of the failure prediction functions for different types of slopes from these observations it was found that events occurring on slopes modified by human interventions could be effectively predicted using the voight function if suitable parameters are used as a general remark the landslides that originate from cut slopes in natural terrain behave similar to large landslides reported in the literature similar values of a and while landslides that originate from cut slopes covered by spritz beton and slopes stabilised by anchored bulkheads show values that are significantly lower and a values that are significantly higher than those of landslides on natural terrains

integration of ground based radar and satellite insar data for the analysis of an unexpected slope failure in an open pit mine abstract on 17 november 2016 an unexpected slope failure occurred in an undisclosed copper open pit mine the nature of the event urged for a thorough back analysis of slope monitoring data in order to assess its size and temporal evolution and to determine whether precursors potentially able to anticipate the failure were present to this aim satellite insar data spanning over the final 9 months before the event were in retrospect acquired and coupled with measurements from a ground based radar that was in use at the time of the failure although progressive deformation was detected by the ground based radar in correspondence of the two uppermost benches in the pit the satellite insar data revealed that the vast majority of the instability actually involved a large part of natural slope above the mine crest this sector was not visible by the ground based radar thanks to the short revisit time of the sentinel 1 mission clear slope accelerating creep was observed for the first time in satellite insar measurements over an open pit mine the delimitation of the area featuring accelerating creep behavior matched remarkably the source area of the failure as mapped in the field after the event considerations on the volume of the instability and on the development of the failure process both in space and time were consequently derived the results provided a clear example of the value of jointly using ground based and satellite interferometry to reduce the uncertainties inherent to the identification and characterization of impending catastrophic slope failures

simulation of a long runout rock avalanche triggered by the lushan earthquake in the tangjia valley tianquan sichuan china abstract only one long runout rock avalanche was triggered by the 2013 lushan earthquake in the tangjia valley tianquan sichuan china the rock avalanche involved the failure of 530 000 m3 of sandstone from the source area the displaced material travelled a horizontal distance of 1600 m with an elevation descent of 480 m equivalent to a fahrboschung of 16 7 based on a detailed field investigation we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in one run up in the chunwojian valley a superelevation in the gangoutou valley and increase in volume due to the entrainment of path materials a numerical model dan3d was used to simulate the post failure behavior of the rock avalanche by means of trial and error a combination of the frictional model and voellmy model is found to provide the best performance in simulating this rock avalanche the simulation results reveal that of the rock avalanche lasted approximately 160 s and an average velocity of 10 m s

the distinction between geomagnetic excursions and reversals summary two recent studies of the geomagnetic eld in the last 1 myr have found 14 excursions large changes in direction lasting 5 10 kyr each six of which are established as global phenomena by correlation between diierent sites the older picture of the geomagnetic eld enjoying long periods of stable polarity may not therefore be correct instead the eld appears to suier many dramatic changes in direction and concomitant reduction in intensity for 10 20 per cent of the time during excursions the eld may reverse in the liquid outer core which has timescales of 500 yr or less but not in the solid inner core where the eld must change by diiusion with a timescale of 3 kyr this timescale is consistent with the remarkably uniform duration of well dated excursions the disparity of dynamical timescales between the inner and outer cores a factor of 10 is consistent with the 10 excursions between full reversals

terrestrial laser scanning of rock slope instabilities this manuscript presents a review on the application of a remote sensing technique terrestrial laser scanning tls to a well known topic rock slope characterization and monitoring although the number of publications on the use of tls in rock slope studies has rapidly increased in the last 5 10 years little effort has been made to review the key developments establish a code of best practice and unify future research approaches the acquisition of dense 3d terrain information with high accuracy high data acquisition speed and increasingly efficient post processing workflows is helping to better quantify key parameters of rock slope instabilities across spatial and temporal scales ranging from cubic decimetres to millions of cubic metres and from hours to years respectively key insights into the use of tls in rock slope investigations include a the capability of remotely obtaining the orientation of slope discontinuities which constitutes a great step forward in rock mechanics b the possibility to monitor rock slopes which allows not only the accurate quantification of rockfall rates across wide areas but also the spatio temporal modelling of rock slope deformation with an unprecedented level of detail studying rock slopes using tls presents a series of key challenges from accounting for the fractal character of rock surface to detecting the precursory deformation that may help in the future prediction of rock failures further investigation on the development of new algorithms for point cloud filtering segmentation feature extraction deformation tracking and change detection will significantly improve our understanding on how rock slopes behave and evolve perspectives include the use of new 3d sensing devices and the adaptation of techniques and methods recently developed in other disciplines as robotics and 3d computer vision to rock slope instabilities research

the khazzan gas accumulation a giant combination trap in the cambrian barik sandstone member sultanate of oman implications for cambrian petroleum systems and reservoirs khazzan is a giant tight gas accumulation located in northern oman the accumulation is associated with cambrian barik sandstone member reservoirs in a semiregional combination stratigraphic structural trap this article outlines the background to the discovery of khazzan and describes our understanding of its geology and petroleum systems and the study work used to support screening appraisal and development strategies for the khazzan accumulation the stratigraphic element of the trap is associated with a northerly thinning and transition of continental fluvial braid plain and shoreface sandstones into offshore mud rocks the structural element of the trap formed as a result of the compactional drape of these reservoir units and the later structuring associated with an underlying long lived intrabasin high the integration of multiple correlation techniques well log correlation recognition of changes in core facies and ichnofacies and magnetostratigraphy has helped to define an intrareservoir correlation framework for the barik sandstone member with a resolution of approximately less than or equal to 1 m y allowing detailed insights into stratigraphic and areal controls on hydrocarbon compositional variations trapping mechanisms reservoirs and reservoir connectivity fluvial sandstones within the khazzan stratigraphic pinch out form better reservoirs the stratigraphic framework developed indicates that these fluvial units are associated with discrete geographically extensive progradation events the association of production with discrete reservoir levels and areas allows a robust semipredictive regional model for targeting better reservoirs and highlights a scope for an additional intra barik stratigraphic trapping potential regionally enhanced reservoir quality within the more productive reservoirs is attributed to depositional and possibly hydrocarbon charge controls on secondary porosity and it is complex subtle crest to flank compositional variations in hydrocarbon type across the gas accumulation hint at complex hydrocarbon charge and mixing between two structural domains and petroleum systems before and during barik deposition john millson holds a b sc honors geology degree and a ph d from aston university in birmingham united kingdom and the university of wales abersytwyth joining the oil industry as a petroleum geologist in 1985 he has worked in the united kingdom nigeria netherlands and oman with some 11 years of working on various aspects of the geology of oman his main interests include tectonostratigraphy and unconventional hydrocarbon resources jamie quin is a geologist for statoil hydro since joining the oil industry in 2001 he has worked on assets in oman for badley ashton and associates libya for repsol ypf and norway statoil he holds a b sc degree from the university of glasgow an m sc degree from royal holloway university of london and a ph d from trinity college dublin erdem idiz is currently a global exploration adviser for exploration new ventures with shell international exploration and production in the netherlands he received his m sc degree in geology 1981 and ph d in geochemistry 1987 from the university of california los angeles ucla after a postdoctorate at the institut francais du petrole he joined shell in 1988 working in research and applications as a geochemist and basin modeler in the netherlands germany and canada his research interests are petroleum systems analysis biomarkers and stable isotopes peter turner holds degrees from cardiff and leicester universities and was a reader in earth sciences at the university of birmingham in the united kingdom from 1988 to 2006 where he was head of the petroleum geoscience group his research includes paleomagnetism sedimentology and hydrocarbon reservoirs and since retiring from university life he has worked as a full time consultant focusing on exploration in north and west africa and china no details available

a new practical method for prediction of geomechanical failure time abstract predicting the failure time of geo hazards is an important rock mechanics problem we first evaluated the validity of the inverse velocity inv method to predict failure time of rock mass and landslides this method utilizes rates of displacement or strain to predict the actual failure time tf so the value of total displacement or strain before failure is not crucial second we developed a new method for computing failure time predictions based on the slope gradient to predict tf termed the slo method finally a simple conceptualised model representing safe and unsafe predictions was proposed to validate these hypotheses prediction of rock mass failure in the asamushi and vaiont landslides in situ studies was conducted furthermore laboratory conditions were incorporated into the research which include predictions using circumferential strain and axial strain from uniaxial compression creep test on shikotsu welded tuff swt and predictions of failure time for inada granite under brazilian creep tests it was found that the slo method is better than the inv method slo gave safe predictions in all the cases in contrast inv tends to give unsafe predictions predicted failure time tfp tf our findings reveal that predictions using circumferential strain are better than those made using axial strain for swt and notably given failure with very short tertiary creep the methods tend to show limited reliability however the slo method could find extensive application in predicting failure time of geo hazards for instance roof wall failure in mines etc

longitudinally confined geomagnetic reversal paths from non dipolar transition fields it has long been thought that conditions at the boundary between the core and mantle influence the earth s magnetic field but the supporting evidence is rather indirect1 3 recent palaeomagnetic results suggesting that there are persistent preferred longitudinal paths for the virtual geomagnetic pole vgp during reversals4 would provide the first direct evidence of the solid mantle s influence on the core although their statistical significance has been disputed5 6 the results are potentially exciting because the preferred paths lie close to the pacific rim where the present geomagnetic secular variation changes character2 7 here we present a simple model based on an extension of a previous theory8 that produces reversals with vgp paths confined within relatively narrow longitude bands despite the transition field having a substantially non dipolar structure thus although longitude bias of the vgp paths is definitive evidence for core mantle interaction simple vgp paths are not evidence of near dipolar transition fields

timing of quaternary geomagnetic reversals and excursions in volcanic and sedimentary archives abstract we review the ages of quaternary magnetic polarity reversals and magnetic excursions improvements in radioisotopic 40ar 39ar dating of reversals and excursions reflect the use of multi collector mass spectrometers along with ultra low backgrounds laser based incremental heating methods and adoption of 28 201 ma for the fish canyon sanidine fcs standard age kuiper et al 2008 these improvements have brought 40ar 39ar ages of reversals and excursions into close correspondence with astrochronological ages based on the correlation of 18o data to lr04 lisiecki and raymo 2005 and in a few cases correlation to ice core chronologies ages of two polarity reversals the matuyama brunhes boundary and base olduvai are at odds with ages given in popular geomagnetic polarity timescales sedimentary records of the laschamp and iceland basin excursion are numerous and widespread and attest to global manifestation and global synchronicity of these excursions records of other quaternary excursions are less numerous the blake excursion 115 ka has been recorded in north atlantic sediments chinese loess indian ocean volcanics and spanish speleothems the santa rosa excursion 932 ka has been recorded in north atlantic and phillipine basin sediments as well as in volcanic rocks from new mexico and galapagos the punaruu excursion 1115 ka has been observed in sediments from the north atlantic and california margin as well as in volcanic rocks on tahiti uniformity of individual excursion ages using astrochronological 40ar 39ar and u th methods argues for synchronous global manifestation of excursions strengthening the usefulness of magnetic excursions and reversals in quaternary stratigraphy

identifying rock slope failure precursors using lidar for transportation corridor hazard management abstract in the thompson and fraser river valleys rockfall and rockslides are a hazard for railway traffic in the region in june 2013 a 2600 m 3 rockslide occurred in the white canyon causing damage to infrastructure and interruption to service in the year preceding this failure the slope was monitored using terrestrial light detection and ranging lidar as part of the railway ground hazards research program initiative the purpose of this study is to evaluate a hazard management strategy for transportation corridors exposed to steep slopes involving the identification of rockfall precursors prior to significant slope failures for this failure deformation was observed in the seven months preceding collapse with an accelerating period occurring in the final 28 days a distinct pattern of smaller rockfalls was observed around the perimeter of the deforming rock block as well as loss of surficial material over the slides tension crack this study shows that with lidar monitoring precursors to rock slope failures can be identified allowing for better rock slope hazard management by focusing attention on areas with the highest probability of failure

integration of advanced monitoring and numerical modeling techniques for the complete risk scenario analysis of rockslides the case of mt beni florence italy on december 28 2002 a landslide occurred on the eastern flank of mt beni florence italy on a slope where jointed basalts and ophiolitic breccias overlie mesozoic limestones calcari a calpionelle formation the collapse was preceded by several forewarning signals the evolution of the slope deformation was the most important of them and its analysis was the starting point for a risk scenario assessment in fact during the management of the emergency period which began on april 13 2002 in effort to evaluate the actual extension of the landslide the distribution of the displacements within the mass its kinematical characteristics and its spatial and temporal evolution data obtained by means of geomechanical surveys laboratory analyses geotechnical investigations geophysical surveys seismic and gbinsar monitoring systems distometric and automatic and distinct element numerical modeling were integrated thus it has been possible to provide public authorities with all necessary information to plan suitable measures for risk management and reduction after the event the study was completed with a runout back analysis that highlighted successes and failures of the predictive investigations

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

development and application of a pseudo 3d pit slope displacement map derived from ground based radar slope monitoring plays an important role in the risk management of large open pit slopes historically displacement data derived from measuring geodetic prisms have been relied upon to delineate the boundaries of potential slope hazards however that data can be limited by its point measurement nature localized displacements at each prism may be misinterpreted when extended to the behavior of the entire slope and important displacements between prisms may be overlooked new technologies like ground based radar can provide high resolution full area coverage of a slope in combination with near real time acquisition and millimeter precision as a line of sight instrument these tools provide data on displacement magnitudes and rates but not true direction hence limiting their use in gaining understanding of the kinematics and behavior of the moving slope this paper describes a novel experiment in which two ground based synthetic aperture radar systems were simultaneously deployed to record continuous line of sight displacements of an open pit slope in stereo the displacement vectors were combined to create a pseudo 3 d displacement map for the slope which was subsequently used to interpret the influence of a major fault and the rock mass fabric in promoting different kinematic responses the data collected demonstrates that an improved understanding of the 3 d kinematics of a large rock slope can be achieved using advanced state of the art monitoring techniques to aid mine design

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

classification of large scale landslides induced by the 2008 wenchuan earthquake china over 30 000 landslides were triggered by the 2008 wenchuan earthquake the deformation and failure mechanisms of these landslides have been found distinct from those of general landslides self weight induced under gravity typical sliding in rock slope commonly occurs along a gentle tension crack in some depth at the rear part which connects to a shear plane at the lower part of the slope to form a complete failure surface however due to seismic shaking a much deeper and steeper tension crack tends to develop at the rear part which promotes the shearing at the far lower part of the slope in this paper the failure modes of earthquake induced landslides have been classified into four scenarios in terms of failure mechanisms characteristics of geological structures and development of the sliding surface i e tension strike slipping tension dip layering tension shattering and tension shearing failures this is evidenced by field investigations detailed field investigations were performed on the deformation and failure characteristics of large scale and deep seated landslides induced by the wenchuan earthquake among which five typical landslides are introduced in this paper in order to illustrate the classification

twenty ninth canadian geotechnical colloquium the role of advanced numerical methods and geotechnical field measurements in understanding complex deep seated rock slope failure mechanisms the underlying complexity associated with deep seated rock slope stability problems usually restricts their treatment to phenomenological studies that are largely descriptive and qualitative quant

use of an integrated finite discrete element method discrete fracture network approach to characterize surface subsidence associated with sub level caving abstract the lkab kiruna sub level cave mine located in kiruna sweden is one of the most well studied sub level cave mines due to proximity of the city to the hanging wall the mine has developed a comprehensive surface deformation monitoring program which is perhaps unparalleled in the mining industry this surface monitoring scheme provides an excellent data source with which to constrain numerical modelling in this study a finite discrete element modelling approach coupled with a discrete fracture network fdem dfn is utilized to analyse the kiruna hanging wall surface subsidence with an emphasis on investigating the influence of discontinuity persistence and spacing the fdem dfn data interpretation uses a variety of novel approaches including time displacement hanging wall deformation characterization numerical inverse velocity analysis and virtual hanging wall inclinometer simulation to improve our understanding of the extent and mechanism of hanging wall failure with mine advance the simulated displacements correspond closely to the actual field data illustrating the ability of the proposed approach to reproduce sub level cave behaviour three distinct time displacement phases namely regressive progressive and steady state are observed in the fdem dfn models the paper also reviews the potential application of the inverse velocity method and virtual inclinometers in characterizing sub surface brittle failure associated with sub level caving

deep seated failure propagation in a fractured rock slope over 10 000 years the la clapiere slope the south eastern french alps abstract the la clapiere area tinee valley alpes maritimes france is a typical large complex unstable rock slope affected by deep seated gravitational slope deformations dgsd with tension cracks scarps and a 60 106 m3 rock slide at the slope foot that is currently active the slope surface displacements since 10 ka were estimated from 10be ages of slope gravitational features and from morpho structural analyses it appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre existing tectonic faults in the slope a progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope by comparing apertures variations and changes in direction between cracks of different ages three phases of slope surface displacement were identified 1 an initial slow slope deformation spreading from the foot to the top characterized by an average displacement rate of 4 mm yr 1 from 10 5 6 ka bp 2 an increase in the average displacement rate from 13 to 30 mm yr 1 from the foot to the middle of the slope until 3 6 ka bp and 3 development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr 1 for the last 50 years the main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration the results obtained agree with several previous studies indicating that in situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure

evidence for a very long term trend in geomagnetic secular variation reconstructions of palaeosecular variation suggest that the earth s magnetic field reversed less frequently 2 82 to 2 45 billion years ago relative to the cenozoic era this suggests a long term trend of decreasing geodynamo stability since the archaean eon the earth s inner core is believed to inhibit rapid fluctuations in the geomagnetic field from developing into full polarity reversals1 2 consequently during the precambrian the smaller size of the inner core might suggest that polarity reversals could occur more readily it is therefore surprising that there are indications that reversals were rare during this period3 4 here we use new and existing palaeomagnetic data from three continents to examine the stability of the earth s magnetic field from 2 82 to 2 45 billion years ago we show that on average geomagnetic secular variation the field variations produced by normal geodynamo action during the late archaean and early proterozoic was different from that of the past 200 million years specifically the apparent variability of the geomagnetic pole as viewed at low and mid latitudes was reduced relative to the past 200 million years according to both dynamo simulations4 and more recent palaeomagnetic field observations5 the observed pattern of secular variation suggests a lower frequency of polarity reversals 2 5 billion years ago this may imply that the geodynamo is becoming progressively less stable over long timescales consistent with some numerical simulations6 7 possibly as a result of changing outer core geometry that has accompanied inner core growth

mono lake excursion recorded in sediment of the santa clara valley california 1 two intervals recording anomalous paleomagnetic inclinations were encountered in the top 40 meters of research drill hole ccoc in the santa clara valley california the younger of these two intervals has an age of 28 090 330 radiocarbon years b p calibrated age 32 8 ka this age is in excellent agreement with the latest estimate for the mono lake excursion at the type locality and confirms that the excursion has been recorded by sediment in the san francisco bay region the age of an anomalous inclination change below the mono lake excursion was not directly determined but estimates of sedimentation rates indicate that the geomagnetic behavior it represents most likely occurred during the mono lake laschamp time interval 45 28 ka if true it may represent one of several recurring fluctuations of magnetic inclination during an interval of a weak geomagnetic dipole behavior noted in other studies in the region

seismic fragility functions for slope stability analysis with multiple vulnerability states the seismic performance and stability analysis of slopes are important in predicating damage and mitigating potential losses in landslide prone areas fragility functions can give results of slope performance assessment that are more comprehensive and richer this study presents a procedure of constructing seismic fragility functions for slope stability analysis with various vulnerability states based on incremental dynamic analysis ida ida is a performance based earthquake engineering analysis based on a series of dynamic time history analyses conducted for suitable multiple scaled seismic records ida not only estimates the seismic demand and capacity of systems but also provides basic data for the estimation of fragility functions firstly an ensemble of seismic records meeting the requirements of specific site conditions of a slope is selected to consider the randomness of ground motion a series of seismic stability analyses of the slope are performed to obtain the dynamic safety factor time history of the slope each minimum safety factor and corresponding seismic intensity measure is then extracted to develop a set of ida curves on the basis of ida results analytical seismic fragility functions of a slope are developed considering the prescribed various vulnerability states of the slope in terms of the safety factor the failure probabilities of exceeding different specific vulnerability states for a given intensity measure of the earthquake are finally obtained

does vertical seismic force play an important role for the failure mechanism of rock avalanches a case study of rock avalanches triggered by the wenchuan earthquake of may 12 2008 sichuan china the wenchuan earthquake triggered 15 000 rock avalanches rockfalls and debris flows causing a large number of causalities and widespread damage similar to many rock avalanches field investigations showed that tensile failure often occurred at the back edge some soil and rock masses were moved so violently that material became airborne the investigation indicates that this phenomenon was due to the effect of a large vertical seismic motion that occurred in the meizoseismal area during the earthquake this paper analyses the effect of vertical earthquake force on the failure mechanism of a large rock avalanche using the donghekou rock avalanche as an example this deadly avalanche which killed 780 people initiated at an altitude of 1 300 m and had a total run out distance of 2 400 m the slide mass is mainly composed of sinian limestone and dolomite limestone together with cambrian slate and phyllite static and dynamic stability analysis on the donghekou rock avalanche has been performed using flac finite difference method software under the actual seismic wave conditions as recorded on may 12 2008 the results show that the combined horizontal and vertical peak acceleration caused a higher reduction in slope stability factor than horizontal peak acceleration alone in addition a larger area of tensile failure at the back edge of the avalanche was generated when horizontal and vertical peak acceleration were combined than when only horizontal acceleration was considered the force of the large vertical component of acceleration was the main reason rock and soil masses became airborne during the earthquake

new quantitative displacement criteria for slope deformation process from the onset of the accelerating creep to brittle rupture and final failure abstract two quantitative displacement criteria for slope deformation were deduced through the combination of a one dimensional renormalization group model and the strain softening constitutive model of geological materials the criteria can be used to understand the mechanical process from the onset of the accelerating creep on a slope through brittle rupture to the final failure and landslides the study showed that according to the first criterion the displacement ratio between the brittle rupture and the onset of the accelerating creep is approximately 1 48 which can be used to predict the brittle rupture of a slope with continuous progressive deformation the second displacement criterion shows that the displacement ratio between the final failure and the onset of the accelerating creep is approximately 2 59 which can be used to predict the occurrence of the ultimate disaster thus the critical displacement prior to the failure of the slope can be predicted using a time series of monitoring displacement data the methodology proposed in this study was validated using data from two well known landslides the vajont landslide in italy and the xintan landslide in china the results verify the applicability of this method

understanding the kinematic behavior of the active gascons rockslide from in situ and satellite monitoring data abstract the monitoring of the 410 000 m3 coastal gascons rockslide began in 2009 this paper presents and analyzes combined in situ and satellite based monitoring data to interpret the kinematic behavior of the slide and the evolution of the rockslide and the possible mechanisms that can lead to an accelerating phase of movement the available data are 1 relative displacements measured by thirteen crackmeters and manually with an extensometer tape 2 absolute displacements obtained from inclinometers and vertical shape accelerometer arrays in boreholes total station surveys and satellite based point target analysis insar pta 3 the settlement of the railway ballast monitored by two horizontal shape accelerometer arrays 4 groundwater pressures from nine vibrating wire piezometers and 5 weather conditions the study indicates that the role of water on displacements varies spatially within the rockslide the rockslide s kinematic behavior enables us to develop evolution scenarios of the rockslide which could be useful to conduct a risk analysis this leads to the identification of critical zones for railroad safety the unique set of monitoring data helps to elucidate the complexity of the rockslide s behavior

anomalous concentrations of seismically triggered rock falls in pacoima canyon are they caused by highly susceptible slopes or local amplification of seismic shaking anomalously high concentrations of rock falls were triggered in pacoima canyon los angeles california during the 1994 northridge earthquake similar concentrations were also documented from the 1971 san fernando earthquake using an engineering rock mass classification that evaluates the susceptibility of rock slopes to seismic failure based on the fracture properties of a rock mass in terms of a numerical q value that describes rock quality the rock slopes in pacoima canyon were compared with rock slopes in surrounding areas where topography and lithology are similar but rock fall concentrations from the earthquakes were much lower a statistical comparison of q values from five sites surrounding pacoima canyon indicates that seismic susceptibilities are similar to those within pacoima canyon differences in the characteristics of rock slopes between these sites are not sufficient to account for the relatively high concentrations of rock falls within pacoima canyon as compared to low concentrations elsewhere by eliminating susceptibility differences as a cause the most likely explanation for the differences in rock fall concentrations is anomalously high shaking levels in pacoima canyon possibly resulting from topographic amplification within the canyon manuscript received 21 may 2001

on characteristics and dynamic analysis of the niumian valley rock avalanche triggered by the 2008 wenchuan earthquake sichuan china on may 12 2008 a large catastrophic rock avalanche was triggered by the wenchuan earthquake on niumian valley in yingxiu town wenchuan county china the displaced landslide materials traveled about 2 640 m with a descent of about 850 m and buried several houses and caused nearly 20 casualties based on detailed field investigation some basic characteristics of this landslide are introduced field investigation showed that the displaced landslide materials experienced three times of run up and twice of superelevation along the run out path and downslope enlargement due to the entrainment of run out path materials a numerical model dan3d is used to simulate the landsliding process by means of trial and error it can be seen that the voellmy model and values of friction coefficient f 0 19 dimensionless and turbulent coefficient xi 2 000 m s2 can provide the best performance in the prediction of sliding and depositing areas the simulated results show that the duration of the rock avalanche is about 120 s with an average velocity of 22 m s

detection and spatial prediction of rockfalls by means of terrestrial laser scanner monitoring abstract a rock face affected by small rockfalls has been monitored using a ground based remote sensing apparatus terrestrial laser scanner tls the pilot study area corresponds to the main scarp of the 1881 puigcercos landslide pallars jussa catalonia spain four datasets of the slope were acquired from september 2007 to july 2008 in an ongoing project the geomorphological evolution of the rock face in terms of volume and frequency of rockfall was studied by the comparison of sequential datasets in addition to the detection of past events this study deals with the spatial prediction of rockfalls through the detection of pre failure deformation as a precursory indicator the high resolution and accuracy and the maximum range of the tls offer interesting prospects for both spatial location and prediction of rockfall

a modified inverse velocity method for predicting the failure time of landslides abstract prediction of the failure time of landslides is always an important issue based on fukuzono s theory which suggests that the logarithm of the surface displacement velocity is proportional to the logarithm of the surface displacement acceleration in the final stage of the slope movement just before failure a modified inverse velocity method was proposed by introducing a controllable variable one landslide was detected in the certain open pit coal mine and four landslides were detected in the certain open pit iron mine by using ground based radar in the four landslides in the certain open pit iron mine the acceleration obviously decreased a few hours before failure which is inconsistent with the existing creep theory the traditional inverse velocity method and the modified inverse velocity method were employed to analyze the five landslides the analysis results show that the modified inverse velocity method can improve the effectiveness of prediction by reducing the prediction error caused by the acceleration decrease before failure the modified inverse velocity method proposed in this paper not only improves the prediction accuracy but also provides a study direction to improve the inverse velocity method that is it introduces controllable variables to improve the prediction accuracy

kinematics and geological constraints of the slow moving pisciotta rock slide southern italy abstract the pisciotta landslide is a slow moving deep seated rock slide in the campania region of southern italy which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide the landslide involves an oligocene turbidite series which is composed of intercalated calcarenites marls and mudrocks the principal objectives of this study were to investigate the morphological evolution of the unstable slope quantitatively analyse ground deformations and construct an engineering geological model that is consistent with the spatial features of the landslide the long term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006 kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road as evident from the topographic maps and orthophotos 1955 2006 and the bi weekly displacement survey of 50 targets distributed across the landslide area september 2006 march 2009 the engineering geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological structural and geophysical surveys the analysis of the aerial photographs revealed an early stage of deformation in 1943 which has been gradually widening since then in addition to the main scarp and the landslide flanks other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years these studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot long term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009 which revealed a cumulative horizontal displacement of up to 53 m and an average velocity of 0 98 m year 1 which has increased in the recent decades in addition the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities the engineering geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints the landslide involves a stratigraphic interval of the saraceno formation nord calabrese tectonic unit with a largely marly argillaceous composition whose structural setting displays complex folding at the mesoscale and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale the left flank of the landslide rests on a normal fault

simulation of the sliding process of donghekou landslide triggered by the wenchuan earthquake using a distinct element method in the village of donghekou in qingchuan county sichuan province china a major landslide was triggered by the wenchuan earthquake in 2008 with more than 10 106 m3 of rock displaced the kinematic behavior of this landslide is simulated using a 2d discrete element model the numerical model used in this work is composed of discs bonded together the initial boundary conditions are applied along the ball wall contacts by using an initial velocity estimated from the strong motion data the constraints are mainly issued from the final geometry of the landslide including its capacity to dam the river the modeling thus indicates that a low friction coefficient about 0 1 is required to account for the actual landslide characteristics the runout behaviors are analyzed and some useful conclusions are drawn

failure forecast for large rock slides by surface displacement measurements forecasting the failure of large rock slides is difficult because of nonlinear time dependency and seasonal effects which affect the displacements starting from the accelerating creep theory prop

determination of minimum detectable deformation of terrestrial laser scanning based on error entropy model terrestrial laser scanning tls is a widely used remote sensing technique which can produce very dense point cloud data very promptly and is particularly suited for surface deformation monitoring deformation magnitude is typically estimated by comparing tls scans over the same area but at different time epochs of interest however there is an issue related to such a method which is not clear that whether the difference between two successive surveys results from the surface deformation hence it is vital to determine the minimum detectable deformation mdd by a tls device with a given registration and point cloud error level in this paper the mdd is determined based on the computation of the point cloud error entropy the performance of the proposed method is extensively evaluated numerically using simulated plane board deformation point clouds under a range of distances and incidence angles this proposed method was also successfully applied to deformation monitoring of one landslide test site located in the wuhan university of technology the experimental results demonstrate that the theoretical mdd has a good match with the actual deformation and the deformation greater than mdd can be accurately detected by the tls device

retrieval of historical surface displacements of the baige landslide from time series sar observations for retrospective analysis of the collapse event abstract landslides and resultant barrier lakes are significant threats to human lives and infrastructures three dimensional 3d surface displacements can give vital clues to the exploration of internal structure of landslides but they are difficult to be retrieved from spaceborne synthetic aperture radar sar observations due to the intrinsic limitation of sar imaging geometry meanwhile studies on predicting slope failure based on sar measured displacements are rarely seen here we used sar pixel offset tracking to investigate the baige landslide before the collapse on 10 october 2018 3d surface displacements retrieved by combining satellite sar and optical observations revealed heterogeneous spatial patterns within the landslide complex we observed linear secondary creep and accelerating tertiary creep prior to the failure from multi sensor sar data the possibility of forecasting the failure was demonstrated by applying an inverse velocity method to the time series displacements measured by sentinel 1 during the tertiary creep which is valuable for risk evaluation and disaster early warning

on the monitoring and early warning of brittle slope failures in hard rock masses examples from an open pit mine abstract the management of unstable slopes is one of the most critical issues when dealing with safety in open pit mines suitable notice of impending failure events must be provided and at the same time the number of false alarms must be kept to a minimum to avoid financial losses deriving from unnecessary outages of the production works comprehensive slope monitoring programs and early warning systems are usually implemented to this aim however systematic procedures for their tuning are lacking and several key factors are often overlooked therefore the mitigation of slope failure risk is still a topic of great concern especially in open pit mines excavated through hard rock masses featuring markedly brittle behavior which supposedly provide little or no measurable precursors to failure in this paper 9 instabilities occurred at an undisclosed open pit mine and monitored by ground based radar devices were reviewed with the goal of characterizing the typical slope deformation behavior and defining the appropriate strategy for the setup of alarms the estimated mass of the case studies ranged from 1500 t to 750 000 t 5 instabilities culminated to failure whereas the other 4 although showing considerable amounts and rates of movement ultimately did not fail the analysis provided critical insights into the deformation of hard rock masses of high geomechanical quality and allowed the identification of signature parameters of the failure events general operative recommendations for effective slope monitoring and early warning were consequently derived

a physical model predicting instability of rock slopes with locked segments along a potential slip surface abstract better understanding the evolutionary mechanism of landslides is very important to predict their occurrence based on firm scientific grounds the stability of a rock slope is often dominated by one or more locked segments along a potential slip surface with a large bearing capacity to resist instability we propose three preliminary categories for locked segments and develop a physical model for predicting the instability of rock slopes with locked segments by coupling a one dimensional renormalization group model with a strain softening constitutive model based on the weibull distribution we found that the ratio of the strain at the peak strength point of a locked segment to the strain at its volume dilation point is exclusively dependent on the weibull shape parameter m and is approximately constant at 1 48 the accelerating displacement of the slope can be observed from the volume dilation point of the locked segment due to unstable fracture propagation the physical model for slopes with multiple locked segments is only related to the displacement corresponding to the volume dilation point of the first locked segment and the number of locked segments applying this model to two typical cases the yanchihe rockslide in china and the wedge rockslide in libby dam usa the results are in agreement with field records this work will help to better understand the failure mechanism of slopes with locked segments and may provide guidelines for disaster mitigation and prevention

paleomagnetism of quaternary sediments from lomonosov ridge and yermak plateau implications for age models in the arctic ocean abstract inclination patterns of natural remanent magnetization nrm in quaternary sediment cores from the arctic ocean have been widely used for stratigraphic correlation and the construction of age models however shallow and negative nrm inclinations in sediments deposited during the brunhes chron in the arctic ocean appear to have a partly diagenetic origin rock magnetic and mineralogical studies demonstrate the presence of titanomagnetite and titanomaghemite thermal demagnetization of the nrm indicates that shallow and negative inclination components are largely unblocked below 300 c consistent with a titanomaghemite remanence carrier following earlier studies on the mendeleev alpha ridge shallow and negative nrm inclination intervals in cores from the lomonosov ridge and yermak plateau are attributed to partial self reversed chemical remanent magnetization crm carried by titanomaghemite formed during seafloor oxidation of host detrital titanomagnetite grains distortion of paleomagnetic records due to seafloor maghemitization appears to be especially important in the perennially ice covered western mendeleev alpha ridge and central arctic ocean lomonosov ridge and to a lesser extent near the ice edge yermak plateau on the yermak plateau magnetic grain size parameters mimic the global benthic oxygen isotope record back to at least marine isotope stage 6 implying that magnetic grain size is sensitive to glacial interglacial changes in bottom current velocity and or detrital provenance

seven thousand year duration for a geomagnetic excursion constrained by 230thxs 1 the duration of geomagnetic excursions may provide important information about the geodynamo it has proven difficult however to assess the exact duration of both excursions and reversals we combine high resolution paleomagnetic records from marine sediments with measurements of the 230thxs flux to the seafloor in order to better constrain the duration of the iceland basin excursion ibe we find the duration of the ibe to be 7 8 kyr implying that it is considerably longer than previous estimates for the laschamp excursion 2 kyr and more similar in duration to that of full polarity reversals there may not be therefore a characteristic timescale for transitional field configurations that distinguishes excursions from reversals

analysis of baishuihe landslide influenced by the effects of reservoir water and rainfall since the impoundment of the three gorges reservoir in june 2003 a number of new landslides have occurred and existing landslides have been made worse the 1 260 104 m3 baishuihe landslide located at 56 km west of the three gorges dam began to deform more noticeably after the first impoundment in early july 2003 the sliding of the two blocks comprising the landslide one an active block and the other a relatively stable block became apparent after approximately 5 years of monitoring field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir these effects have been investigated in the present paper including the deformation characteristics movement pattern direction displacement and velocity earmarking the temporal evolution of the active block based on a practical creep model of a large rock slide alert velocity thresholds for pre alert alert and emergency phases have been computed corresponding to the imminence of failure the alert velocity thresholds are being proposed to be included as a part of an early warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure the emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the three gorges reservoir in the near future

vertical acceleration effect on landsides triggered by the wenchuan earthquake china the 2008 wenchuan earthquake with ms8 0 triggered extensive throwing pattern landslides in the area within or near the seismic faults the resultant landslides from this earthquake brought to the fore the effect of vertical earthquake acceleration on landslide occurrence the pseudostatic analysis and the dynamic response on landslide stability due to the wenchuan earthquake are studied with the chengxi west town catastrophic landslide used as a case study the results show that the epicenter distance is an important factor which affects the vertical acceleration and thus the stability of landslide also the vertical acceleration was found to have a significant impact on the fos of landslide if the earthquake magnitude is quite large within the seismic fault the amplitude effect of vertical acceleration is very dominant with the fos of landslide for vertical acceleration ranging from positive to negative having a variation of 25 the variation of fos of landslide for vertical acceleration ranging from positive to negative are 15 and 5 for landslides near seismic fault and outside seismic fault respectively for landslide with a slope angle 45 the fos of landslide with both horizontal and vertical accelerations is significantly greater than the one without vertical acceleration further the results computed from both the pseudostatic method and dynamic analysis reveal that the fos during the earthquake varied significantly whether vertical acceleration is considered or not the results from this study explain why lots of throwing pattern catastrophic landslides occurred within 10 km of the seismic fault in the wenchuan earthquake

longitudinal confinement of geomagnetic reversal paths as a possible sedimentary artefact the positions of the virtual geomagnetic pole vgp during a large number of reversals of the earth s magnetic field seem to show a remarkable confinement to longitudes over the americas or to antipodal longitudes1 2 although it has been argued that this confinement is statistically insufficiently constrained3 it has also been pointed out4 that the same bands of longitude appear in other geophysical observations such as the pattern of fluid motion in the outer core and regions of higher seismic velocities in the lower mantle suggesting a causal relationship here we show that longitudinal confinement of vgps can arise from the smoothing of non antipodal stable directions just before and after a geomagnetic reversal because of the filtering effect of the remanence acquisition process in sediments the origin of this non antipodality is still uncertain and must remain speculative until more reversal records become available that include sufficiently long pre and post transitional intervals

measurement and interpretation of long term deformation of a rock slope at the ikura limestone quarry japan abstract more than 10 years of displacement measurements at the ikura limestone quarry in japan have clarified aspects of rock slope deformation arising from excavation in the quarry although the cause of most deformations can be explained theoretically those occurring in a rock slope just behind the tarumi working face proved perplexing contraction continued to occur on the rock slope although excavation of limestone had ceased at this face the cause of this continuous deformation was evaluated through numerical analysis employed to assess the stability of the rock slope an automatic 3d mesh generation technique was used to model the complex topography of the quarry resulting from the excavation and a finite element mesh model was rendered for each of the successive excavation stages elastic analysis then allowed the resulting rock slope deformation to be predicted the calculated results reveal that the rock slope continued to deform elastically after excavation had ceased on the tarumi face and that the on going excavation at the kawamukai working face located 400 m away from the rock slope was the probable cause the calculated results using appropriate elastic moduli were in good agreement with measured results the rock slopes are assessed as stable and the continuous deformation is believed to be elastic

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part ii three dimensional deformation patterns the monitoring of slope displacements over time provides the basis for most rockslide early warning systems yet the prediction of catastrophic failure from these records is highly problematic and tenuous especially if the underlying kinematics and instability mechanism are poorly understood an example is the moving slope above the town of randa in the swiss alps this slope is considered typical of those in crystalline rock that lacks a natural highly persistent weakness plane dipping towards the valley that can serve as a through going detachment surface for kinematic release in part i the companion paper to this the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented in this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures both on surface and at depth the displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements borehole inclinometer and extensometer measurements up to 120 m depth and microseismicity the results showed that the displacement field is highly heterogeneous internal deformation is accommodated by both shear and opening mode dislocation of faults and fracture zones which dip moderately to steeply into the slope microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures the small displacement rates at the study site of up to 2 cm year coupled with a modest deviation of up to 15 from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data we describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block kinematic processes whose evolution governs the long term progressive failure of unstable rock slopes