new insights into the 1963 vajont slide using 2d and 3d distinct element method analyses the 1963 vajont rock slide is studied using the distinct element method dem two dimensional 2d and three dimensional 3d dem models were constructed based on information published in the literature in this study a strength reduction approach was used to calculate the slide surface friction angles required for stability the influence of several parameters was investigated in 2d namely the reservoir water level the shear stiffness of the slide surface the rock mass strength the rock mass deformability and rock joint patterns of the parameters which have been investigated the most important parameter was found to be the reservoir water level the rock mass deformability which is neglected by other investigators is also found to be important from the 3d analyses the failure friction angle was found to be sensitive to the assumptions made on the eastern boundary and could affect the failure friction angle by approximately 3 the slope was found to exhibit signs of failure beginning from s

landslide hazard assessment in the three gorges area china using aster imagery wushan badong abstract the objectives of this study are to develop a methodology for regional scale assessment of landslide hazard using remotely sensed data and to produce a landslide hazard map of the wushan badong area in the three gorges china from advanced spaceborne thermal emission and reflection radiometer aster images the area is undergoing rapid urban development with slope instability causing a widespread natural hazard landslide related parameters were largely estimated through image processing and visual interpretation of aster multi spectral and topographic data we used field measurements to define the quantification for three parameters a slope angle in relation to lithology b distance to drainage network in relation to stream order and c distance to tectonic lineament in relation to lineament length we employed a multi parameter elimination and characterization model based on estimation of the geometric mean to remove areas where landslides are not expected to occur and classify the remaining areas into landslide hazard categories our results show increased landslide hazard in and around wushan and badong towns as well as other populated areas along the yangtze and its tributaries we used field data on landslide distribution to identify typical geomorphological settings for different landslide types and to provide ground control for the hazard assessment the results indicate good correlation between classified high hazard areas and field confirmed slope failures and show the usefulness of aster imagery for landslide hazard assessment at a regional scale

kinematic behaviour and velocity characteristics of a complex deep seated crystalline rockslide system in relation to its interaction with a dam reservoir abstract this paper presents the geometry kinematics and temporal deformation characteristics of a deep seated rockslide system the hochmais atemkopf situated above the gepatsch dam reservoir in northern tyrol austria results from surface and subsurface geological investigations and deformation monitoring indicate that the hochmais atemkopf rockslide system involves several sliding masses one on top of the other characterized by different velocity characteristics with displacements being greater for the shallower slide bodies during the initial impounding phases of the gepatsch reservoir uplift forces beneath the foot of the slope led to the activation of one of these shallower slide bodies moving it more than 10 m downslope in 2 years after continuous deceleration of the sliding mass the deformation rates reduced to about 2 to 4 cm per year these were found to show seasonal fluctuations that correlated with reservoir levels and drawdown conditions with induced slope accelerations peaking when reservoir levels were at their lowest this suggests in part a controlling mechanism based on seepage forces where reservoir drawdown drives the episodic rockslide deformation behaviour together the data and analyses presented demonstrate the importance of integrating detailed geology and monitoring data to derive a basic understanding of the kinematics and controlling mechanisms of a deep seated rockslide system in advance of undertaking comprehensive numerical modelling

simulating the process of reservoir impoundment induced landslide using the extended dda method abstract in this work three extensions to the traditional discontinuous deformation analysis dda method are tested to simulate the entire process describing the behavior of landslides induced by reservoir impoundment these extensions include the discretization of the area of interest block gluing and the hm hydro mechanical coupling approach several hydraulic boundary conditions are introduced based on the water level during the dry and rainfall seasons as verification the entire processes for two practical landslides the qianjiangping and the majiagou landslides which occurred in the three gorges reservoir tgr of china are simulated the simulation results agree well with the observed failure modes indicating that the proposed methodology can intuitively reproduce the entire reservoir impoundment induced landslide process

landslide hazard assessment in the three gorges area of the yangtze river using aster imagery zigui badong this paper reports a regional assessment of landslide hazard in the three gorges area china based on terra 1 satellite advanced spaceborne thermal emission radiometer aster imagery data including a stereo image derived digital elevation model dem and multi spectral reflective and thermal imagery in combination with limited field investigation the three gorges dam and reservoir project has gained international attention not only for its great potential for hydro electrical power generation and flood control but also for its potentially harmful effects on the environment and socio economy the most significant and widespread natural hazard in the region is slope instability a simple multi variable elimination and characterisation model employing geometric mean and boolean decision rules has been applied to a multi criterion image dataset to categorise the area into a series of potential landslide hazard levels which are presented in map form the results presented here show high levels of hazard in and around all the main inhabited areas along the river limited fieldwork has been conducted to provide reliable ground control and the results of this paper show good correlation with this field evidence

parameter inversion and deformation mechanism of sanmendong landslide in the three gorges reservoir region under the combined effect of reservoir water level fluctuation and rainfall abstract previous studies suggested that the qianjiangping landslide was caused by the combined effect of rainfall and reservoir water after the first water storage of the three gorges reservoir the sanmendong landslide with a length of 830 m an area of 2 49 105 m2 an average thickness of 22 m and a volume of 5 48 105 m3 which is located by the qinggan river a tributary of the yangtze river is only 4 km away from another famous landslide along the same river the qianjiangping landslide based on the experimental data of mechanical parameters of the landslide and displacement monitoring a nonlinear mapping relationship between mechanical parameters of the failure mass and the displacement of landslide were established by using genetic algorithms by means of uniform design numerical calculation and artificial neural networks the mechanical parameters of the failure mass are obtained by the global minimization of the deviation between the calculated displacements and the monitored displacements on this basis the deformation mechanism of the sanmendong landslide under the combined effect of rainfall and reservoir water level fluctuations was analyzed in detail the results indicated that the increase of displacement of sanmendong landslide can be primarily attributed to the combined result of reservoir water level fluctuation and rainfall

kinematics triggers and mechanism of majiagou landslide based on fbg real time monitoring reservoir landslide as one of the most serious geohazards is worldwide distributed to investigate its triggering factors and mechanisms that underlie its propagations a real time monitoring system based on fiber bragg grating fbg technology was designed for the majiagou landslide in the three gorges reservoir tgr region through analyses of inclinometer data it is found that there are two sliding surfaces existed in the majiagou landslide and that the deeper sliding surface is the critical one it accounts for nearly 80 of the deformation of the landslide this information necessitated the recording of the displacement at the deeper sliding surface together with the rainfall water level pore water pressure temperature of the landslide using a real time monitoring system after analyzing the multi parameter data in detail it is found that observed deformation is mainly governed by reservoir water levels while precipitation has some minor effects the reservoir water level is the determining factor of landslide deformation when it exceeds 160 m or lower than 150 m whereas the reservoir water level varies from 150 m to 160 m the fluctuation velocity plays a dominant role the relationship between the variation of seepage field and kinematic evolution of majiagou landslide is recognized the average displacement rate of majiagou landslide is within 0 1 mm day signifying that the landslide is still creeping presently the results are significant with respect to stability evaluation and formulation of early warning plans for the reservoir landslide

has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years 1 by analyzing the geochemistry of chinese loess this study examines if the flux of calcite dust from the chinese loess plateau to the north pacific influenced the evolution of marine 87sr 86sr ratios between 2 5 million years ago ma and the present calcite comprises 10 wt of chinese loess and contains 1 104 nmol of sr g with an 87sr 86sr ratio of 0 711 a compilation of literature data suggests that the calcite dust flux emanating from eastern asia has averaged either 2 1013 or 1 1014 g yr since the onset of northern hemisphere cooling 2 5 ma the factor of 5 difference between the estimates reflects discrepancies inherent to methods for determining dust fluxes to seawater at present these discrepancies remain unresolved calcite dust is completely dissolved during transport in the atmosphere and ocean thus the marine sr input from eolian calcite dissolution has averaged either 2 108 or 1 109 mol yr a mass balance model demonstrates that the lower estimate has very little influence on seawater 87sr 86sr ratios whereas the higher estimate has possibly elevated seawater 87sr 86sr ratios by 18 since 2 5 ma when combined with previously reported effects of northern hemisphere glaciation on the riverine sr flux this shift is sufficient to reproduce the entire plio pleistocene marine sr record while more research is required to constrain dust flux estimates these findings suggest that the atmospheric supply of eolian calcite to seawater may represent a previously overlooked process linking climate change to the marine sr cycle

landslide deformation behavior influenced by water level fluctuations of the three gorges reservoir china abstract water level fluctuations that occurs during filling drawdown operations in man made reservoirs can result in accelerations or reactivations or even catastrophic failure of large landslides for disaster mitigation a monitoring system comprising manual and automatic gps systems borehole inclinometers and groundwater piezometers was installed to investigate the slope deformation behavior of a large reactivated landslide known as the shuping landslide at the three gorges reservoir china the long term monitoring data 2003 2015 focused on the landslide deformation which was triggered by water level fluctuations is presented in this study the cumulative displacement curves showed a step like behavior suggesting a lower base activity superimposed by phases of acceleration which appeared during reservoir drawdown periods and rainy seasons based on statistical pearson correlation analysis the increase in landslide activity is dominated by reservoir water drawdown rather than rainfall the durations of the slide acceleration phases are much shorter than the reservoir water drawdown durations based on in site piezometer monitoring data and numerical simulation the potential causes are the hydraulic processes in the slope with much smaller groundwater drawdown velocities and hydraulic gradients in the initial stage of the reservoir water drawdown period

lithological and seasonal control on rainfall thresholds for the possible initiation of landslides in central italy we compiled a catalogue of 442 rainfall events with landslides in the abruzzo marche and umbria regions central italy between february 2002 and august 2010 for each event we determined the duration d in hours and the cumulated total event rainfall e in mm using rainfall measurements obtained from a dense network of 150 rain gauges landslides were mapped as single points using google earth and were attributed a level of mapping accuracy p in four classes p1 1 km2 p10 10 km2 p100 100 km2 p300 300 km2 using this information we determined cumulated event rainfall rainfall duration ed thresholds which are entirely equivalent to rainfall intensity duration id thresholds and avoid unnecessary conversions to determine the ed thresholds we modified a statistical method first proposed to determine id thresholds adopting a bootstrapping statistical technique we expanded the method to determine the uncertainty associated with the parameters that define the power law threshold model and the sensitivity of the thresholds to the number of d e data points in the empirical data set we determined ed thresholds for 1 and 5 exceedance probability levels i for the entire study area and for the three individual regions in the study area abruzzo marche and umbria ii for three main lithological domains in the study area post orogenic sediments flysch deposits carbonate rocks and iii for two seasonal periods may september october april comparison of the ed thresholds indicates that the cumulated amount of rainfall necessary to trigger landslides in flysch deposits is larger than in post orogenic sediments and carbonate rocks however the ed thresholds for post orogenic sediments and carbonate rocks were statistically indistinguishable in the study area also the seasonal thresholds were statistically different for rainfall durations shorter than 12 h and longer than 100 h but were indistinguishable in the range 12 d 100 h the results obtained are directly applicable to landslide forecasting based on empirical rainfall thresholds and have implications for landslide hazard and risk assessment as well as for landslide erosion and landscape evolution studies both in the study area and in the neighboring regions

ridge segmentation and the magnetic structure of the southwest indian ridge at 50 30 e 55 30 e and 66 20 e implications for magmatic processes at ultraslow spreading centers 1 the aim of this paper is to investigate the relationships between the segmentation and the magnetic structure of the ultraslow spreading southwest indian ridge contrary to faster spreading ridges magnetization usually decreases from high values along the neovolcanic axis to low values in the nontransform discontinuities there is a direct correlation between the deepening of the axial valley and the decrease of the magnetization from the neovolcanic axis toward the deepest parts of the axial discontinuities we suggest that less frequent eruptions as the distance from the segment center and the length of these discontinuities increase result in thinner extrusive lavas and thus control the along axis magnetization variations by thinning the magnetic source layer a unique segment centered at 50 28 e shows a marked low magnetization anomaly at its center similarly to the segments of the slow spreading mid atlantic ridge we suggest that in this segment both the mantle temperature and the magmatic activity are high enough for the lavas not to be highly fractionated a higher rate of melt production to the west of gallieni transform fault may have created some form of reservoir where mixing of melts occurs and where crystalline fractionation is low producing low magnetization lavas to the east magma chambers may be smaller with cooler mantle temperatures resulting in restricted mixing and significant fractionation which may lead to relatively high intensity magnetization lavas finally we propose that serpentinization of peridotites has no significant contribution to the variation of the magnetization along the axial valley off axis in thin crust areas upper mantle rocks may become progressively more altered as distance from the axis increases the strong faulting and alteration of a thin basaltic cap and underlying upper mantle rocks can produce the disappearance of the magnetic reversal pattern and the increase of the magnetization which is observed along the traces of the largest amagmatic discontinuities by contrast in thicker crust areas the upper mantle rocks are shielded from the alteration and the serpentinization process may be delayed resulting as on the mid atlantic ridge in slightly more positive magnetization values along the traces of axial discontinuities regardless of polarity

source regions and formation of the loess sediments on the high mountain regions of northwestern china loess on the high mountains of northwestern china is largely controlled by the topographic features distributed mainly on the northern slopes of the tianshan and kunlun mountains as well as in the ili valley between the northern and central tianshan ranges loess distributed in different regions has different ages with the oldest early pleistocene loess occurring in the ili valley geochemical mineralogical and granulometric analyses demonstrate that the loess in the three different regions has different provenance the loess on the northern tianshan and kunlun mountains is mainly derived from the junggar and taklimakan deserts respectively whereas the loess in the ili valley is derived mainly from the sary ishikotrau desert located in the republic of kazakhstan however these deserts serve mostly as holding areas for the silts rather than original source regions the production of the silt sized particles is mainly associated with glacial abrasion and tectonic induced rock denudation thus the loess in the studied regions can be described as mountainous loess rather than simply glacial loess or desert loess it is unlikely that the mechanisms of loess formation are the same in different regions given their dependence on specific geomorphological conditions and associated processes

mineralogical variation of sr nd isotopic and elemental compositions in loess and desert sand from the central loess plateau in china as a provenance tracer of wet and dry deposition in the northwestern pacific we determined sr and nd isotopic compositions and major trace and rare earth element ree compositions of evaporite and detrital minerals in loess and desert sand from the central loess plateau clp where 80 of the loess deposits in china are found the loess exhibited a narrow range of variation in 87sr 86sr 0 715 0 001 a sequential extraction experiment on the loess however showed that water and acetic acid hoac soluble minerals mainly halite and calcite hydrochloric acid hcl soluble minerals chlorite and phosphate and hcl insoluble minerals illite kaolinite smectite vermiculite feldspar and quartz have distinct 87sr 86sr ratios approximately 0 7111 0 0004 0 7141 0 0004 and 0 7195 0 0010 respectively the water and hoac soluble ratios were regionally uniform and were close to the 87sr 86sr value of river water from the huanghe yellow river and the maximum 87sr 86sr value of spring rainwater in japan suggesting selective solution of eolian halite and calcite into the chinese river water and into the japanese rainwater the mineralogical elemental and sr nd isotopic compositions of hcl soluble and insoluble minerals in the clp loess were different from those of the northern desert sand but were indistinguishable from those of its fine grained fraction supporting the view that the loess is composed of the fine grained fraction of desert sand that was transported to the southeast in the atmosphere the 87sr 86sr end and gd yb values of hcl insoluble minerals in the clp loess were almost identical to those of airborne dust soil minerals and deep sea sediments in the northwestern pacific considered to be of eolian origin suggesting dissolution of the loess evaporite minerals during atmospheric transportation these relationships demonstrate the usefulness of sr isotopes of water and hoac soluble minerals and sr and nd isotope ratios and ree compositions of acid insoluble minerals in loess as provenance markers for wet and dry deposition respectively

mechanism of the anlesi landslide in the three gorges reservoir china abstract many gentle dip translational rock slides have taken place in the three gorges reservoir china in order to study the mechanism of these translational rock slides the authors use the anlesi landslide as a typical case study to investigate in detail field investigations show that the slip zones of the anlesi landslide were formed from a white mudstone in jurassic red strata x ray diffraction and infrared ray analysis showed that the main mineral components of the slip zones are montmorillonite illite feldspar and quartz laboratory tests indicate that the slip zone soils are silty clay of medium swelling potential the shear strength decreasing significantly as the slip zone attracts water and saturates the main factors contributing to the anlesi landslide are recent tectonic activity incompetent beds and intensive rainfall recent tectonic activity had caused shear failure along the incompetent beds and joints within the sandstone with the effect of intensive rainfall water percolates to the incompetent beds along tectonic fissures resulting in swelling of the soil material and high groundwater pressures within fissures in the strata as a consequence the anlesi slope is prone to slide along these incompetent beds flac3d software was used to simulate the mechanism of the anlesi landslide considering the rheological properties of soil and rock the simulation results demonstrate that the stress displacement and failure area changes with simulated creep time the maximum displacement in the x direction reaches 7 59 m after 200 year simulated creep therefore the mechanism of the anlesi landslide can be illustrated considering the rheological properties of jurassic red strata

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

modelling of the landslide induced impulse waves in the artvin dam reservoir by empirical approach and 3d numerical simulation abstract due to the burgeoning energy demand in turkey there has been a significant increase in the number of dams and hydroelectric power plants constructed 250 dams have been built in the past 10 years consequently various engineering problems were encountered due to landslides near reservoirs both during and after the construction generally two dimensional 2d and three dimensional 3d empirical equations have been used to calculate the physical properties and propagation of the landslide induced impulse waves however 3d numerical simulation based methodologies are rarely used although they can model the complex geometry of dam reservoirs better using detailed topographic data in this study therefore 3d numerical analysis is carried out for a potential generation of impulse waves using the data of paleo landslide at the artvin dam reservoir ne turkey and the results are compared with the calculated results by empirical equations a finite element method based shear strength reduction analysis fem ssr was performed to analyse the slope stability after the establishment of the correct propagation model the equations were utilised with different input parameters and 3d numerical analysis based simulations to evaluate the characteristics of the impulse waves in the numerical model created using the flow 3d software the drift flux model was used to simulate the probable landslides the reynolds averaged navier stokes equations were used in a free surface modelling technique together with the volume of fluid vof model for simulating the wave generation the renormalised group model rng for viscous flow and k e turbulence model for fluid fluid coupled condition were used as the boundary conditions the results indicated that the values obtained from the proposed empirical equations and 3d numerical analysis were not similar thus if the reservoir geometry is very complex and the wave propagation distance is more than a few kilometers as in this study highly detailed engineering geological studies should be performed to accurately define the boundary conditions and three dimensional numerical analyses should be performed to construct the impulse wave model

theoretical and numerical study on the block flexure toppling failure of rock slopes abstract block flexure toppling failure is frequently encountered in rock slopes in this paper we first proposed two theoretical models to calculate the factor of safety against block flexure toppling namely step by step analysis model lem ssam and overall analysis model lem oam then we developed two special matlab codes for a quick stability estimation based on the proposed methods respectively next the universal distinct element code udec was used to study the failure mechanisms of block flexure toppling in order to realistically simulate the excavation of slope and obtain the detailed damage information of joints we developed two fish functions in udec finally we conducted a comparative analysis of the limit equilibrium method and the numerical simulations through twelve theoretical models the results show that many aspects of block flexure toppling failure have been captured using udec combined with the developed fish functions the lem oam and udec agree well while a larger factor of safety is obtained using the lem ssam it is found that the dip angles and friction angles of the joints dipping steeply into face have a great influence on block flexure toppling failure while the influence of the cross joint spacing is less significant

towards a complete understanding of the triggering mechanism of a large reactivated landslide in the three gorges reservoir abstract the primary aim of this study is to research the characteristics of a slide motion and its relationships with environmental triggers with reference to the quchi landslide which is a large slow moving reactivated landslide in the three gorges reservoir region since 2006 this instability has been involved in a slow moving process with clearly visible signs ground fissures cracking of houses and road the landslide consists of 18 mm3 rock masses threatening quchi town and a road that is crucial for local transportation for civil protection purposes a continuous monitoring system has been put into use since 2009 combining four years of meteorological and hydrological data with gps displacement measurements and in situ observations allows a detailed identification of the key processes involved the deformation is thought to be closely related to precipitations and fluctuating reservoir levels slope movements have a highly distinctive pattern that is characterized by high deformation starting in june and lasting into september when the reservoir level drops and rainfall increases followed by a rapid transition to constant deformation until the next wet season in order to investigate in detail the influences of rainfall and fluctuating water levels on the hydromechanical behavior of the landslide a series of two dimensional numerical simulations are performed using the universal distinct element code udec the modeling reveals that precipitation mainly mobilizes the slope materials on the upper part of the slope while the other trigger factor fluctuating water levels destabilizes the foot of the slope into a multistage failure with a remarkable retrogressive evolution the slide is most likely to collapse in a complex pattern characterized by en masse sliding on the upper part of the slope and a retrogressive rupture at its foot

characteristics mechanism and development tendency of deformation of maoping landslide after commission of geheyan reservoir on the qingjiang river hubei province china abstract based on field investigation of the constituent structure and geological formation of the maoping landslide the authors made an in depth study of the deformation characteristics and triggering mechanism of the reservoir induced slide through comprehensive analysis of the about 13 years observation data the maoping landslide the largest ancient landslide in geheyan reservoir with a volume of 23 5 million m3 is located on the left bank of the qingjiang river 66 km upstream of geheyan dam in april 1993 reservoir inundation reactivated the landslide which resulted in relocation of a village of 290 people since then the landslide body has been experiencing persistent deformation with an observed maximum displacement of 2841 4 mm up to october 2005 therefore further development of deformation of the landslide becomes a great concern for the safety of the reservoir and dam the analysis results show that the maoping landslide is an ancient landslide that is an accumulation of several consequent slides along the bank slope and experienced several secondary slumps in its front in later stages the ongoing deformation of the reactivated landslide is controlled by mechanical properties of materials and hydraulic effects induced by reservoir the slip process is of creep deformation as a whole and appears to be attenuating in later stage which indicates very low possibility of the high speed slip and integral failure of the slide

investigation of the hsien du shan rock avalanche caused by typhoon morakot in 2009 at kaohsiung county taiwan abstract the hsien du shan rock avalanche at kaohsiung county taiwan was triggered by heavy rainfall brought by typhoon morakot in 2009 heavy rainfall began on the day of august 6 and continued to the morning of august 9 when the slope failure and landslide occurred in this post event investigation physical mechanical and hydraulic properties of the rocks soils at this large landslide site are evaluated the in situ hydraulic conductivity of the soils at the source area was found to be too low k 1 48 10 6 m s for rainfall to vertically infiltrate to the deep sliding surface which was found to have a maximum depth of 85 6 m the post failure simulations using discontinuous deformation analysis dda suggest that the geometry of the sliding surface governs the failure behavior and two continuous progressing failures likely occurred at the beginning of the hsien du shan rock avalanche slope deformation was observed by the local residents before the hsien du shan rock avalanche occurred as a geomorphologic precursor in addition water accumulation along the sliding surface governs the behavior of the sliding surface therefore in the future an early warning system of a rock avalanche can be developed by simultaneously applying high resolution airborne lidar to detect slope deformation and using geo electric measurements to image the infiltration of surface water to the sliding surface

influence of filling drawdown cycles of the vajont reservoir on mt toc slope stability abstract in the present work the 1963 vajont landslide has been back analyzed in detail to examine the influence of reservoir operations filling and drawdown on mt toc slope stability the combined seepage slope stability analyses carried out show that the main destabilizing factor that favored the 1963 vajont landslide was the reservoir induced water table that formed as a consequence of rapid seepage inflow within the submerged toe of the slope decrease in the factor of safety fos up to 12 compared to the initial slope stability condition i e in the absence of the vajont reservoir rainfall would only have been a decisive factor if the initial stability condition of the mt toc slope had already been very close to failure decrease in fos caused by heavy or prolonged rainfall is about 3 4 for the worst case scenario analyzed the permeability of the shear zone material occurring at the base of the prehistoric vajont rockslide has been evaluated at 5 10 4 m s and back calculated values of the friction angles range from 17 5 to 27 5 when considering mountain reservoirs slope failures can occur during both filling and drawdown phases in the vajont case owing to the highly permeable materials of the shear zone slope stability decreased during filling and increased during drawdown another displacement dependent phenomenon of a mechanical nature progressive failure of the ne landslide constraint has to be considered to understand the slope collapse that occurred during the last drawdown 26 september 9 october 1963 the results of the combined seepage slope stability models indicate that permeability of bank forming material and filling drawdown rates of reservoirs can strongly influence slope stability slow lowering of the reservoir level is a necessary measure to reduce the occurrence of very dangerous transient negative peaks of fos

influence of filling drawdown cycles of the three gorges reservoir on deformation and failure behaviors of anaclinal rock slopes in the wu gorge abstract the upper wu gorge on the yangtze river has been the site of tens of reservoir induced landslides since the filling of the three gorges reservoir in 2003 these landslides have been occurring in heavily fractured carbonate rock materials along the rim of the reservoir in the wu gorge a detailed investigation was carried out to examine the influence of reservoir operations filling and drawdown on slope stabilities in the upper wu gorge field investigations reveal many collapses of various types occurred at the toe of the anaclinal rock slopes owing to the long term intensive river erosion caused by periodic fluctuation of the reservoir level analysis of data from deformation monitoring suggests that the temporal movement of the slopes shows seasonal fluctuations that correlate with reservoir levels and drawdown conditions with induced slope acceleration peaking when reservoir levels are lowest this may illustrate that the main mechanism is the reservoir drawdown which induces an episodic seepage force in the highly permeable materials at the slope toes and thus leads to the episodic rockslides the coupled hydraulic mechanical hm modeling of the g2 landslide which occurred in 2008 shows that collapse initiated at the submerged slope toe which then caused the upper slope to collapse in a rock topple rock slide pattern the results imply that preventing water erosion at the slope toe might be an effective way for landslide prevention in the study area

isotope geochemistry of quaternary deposits from the arid lands in northern china abstract quaternary deposits of various types lacustrine desert sand river loess and loess like deposits from the southwestern tarim basin north tianshan northeast china and the central loess plateau exhibit an nd 0 range from 5 to 12 8 and a 147 sm 144 nd range from 0 110 to 0 140 their nd depleted mantle model ages are between 1 50 and 1 92 ga with a mean value of 1 7 ga th sc ratios vary over a wide range from 0 1 to 2 comparison of these geochemical signatures with those of the old australian shales and modern pacific ocean dust suggests a continuous input of mantle derived material into the crust over geological time the deposits from the north tianshan show clearly different chemical and isotopic features with significantly higher sm nd high 143 nd 144 nd low 87 sr 86 sr and low la lu and th sc ratios relative to those in the deposits from the other areas this indicates a geological control on the local source which has an overall young age and an enrichment of basic components the ce 0 values of two loess samples from the central loess plateau are 1 8 and 3 9 corresponding to depleted mantle model ages of 2 2 and 3 4 ga like the rb sr system the evolution of the la ce isotopic system in the crust may be to some extent decoupled from the sm nd system due to la ce fractionation by sedimentary processes the loess deposits and the desert sand are not distinguishable in isotopic composition but show somewhat different chemical compositions we conclude that the loess can have originated from desert processes since the difference in the chemistry of the desert sand and loess may result from mineral sorting during desert processes and aeolian transportation the loess deposits on the central loess plateau chemically and isotopically resemble the desert loess deposits in the southwestern tarim basin but do not resemble those of the north tianshan accordingly the loess on the plateau may have a source region in the tarim basin but clearly not in the north tianshan

a complex rock topple rock slide failure of an anaclinal rock slope in the wu gorge yangtze river china abstract this paper presents the results of an investigation of the gongjiafang landslide with the volume of about 500 000 m 3 in the three gorges reservoir region tgr occurred on 23 november 2008 in this study detailed geological and geomorphological surveys in situ and laboratory tests and numerical simulation are carried out to reveal the failure mechanism of this landslide the anaclinal rock slope is characterized mainly by a set of outward dipping and non persistent joints a hard stratum limestone in the middle portion and an underlying soft base argillaceous limestone interbedded with shale because of the long term intensive river erosion caused by periodic fluctuation of the reservoir water level the soft rock masses at the toe of the slope were softened or even washed away inducing the first sliding toppling failure at the toe the collapse at the toe leaves the hard strata in the middle unsupported like a beam thus a conceptual cantilever beam model is proposed to explain the failure mechanism of the landslide the dem simulation further highlights the failure process with a complex rock topple rock slide failure mode i e first composite sliding and toppling occurred at the toe a composite shear and flexure failure of the middle cantilever beam and a simultaneous overall sliding failure of the rock masses in the upper part of the slope the results imply that preventing water erosion at the toe could be an effective way in landslide prevention and treatment in the study area

provenance of dust in the pacific ocean eolian dust preserved in deep sea sediment cores provides a valuable indicator of past atmospheric circulation and continental paleoclimate in order to identify the provenance of eolian dust nd and sr isotopic compositions and rb sr and rare earth element ree concentrations have been determined for the silicate fractions of deep sea sediments from the north and central pacific ocean different regions of the pacific ocean are characterized by distinct air borne inputs producing a large range in end 10 to 1 stsr 86sr 0 705 0 721 la yb 5 15 eun eu 0 6 1 0 and sr nd 4 33 the average nd isotopic composition of pacific deep sea sediments eno 6 is more radiogenic than the average from the atlantic ena 8 in contrast the average 1475m 14and ratio for pacific sediments 0 114 is identical to that of atlantic sediments and to that of global average riverine suspended material the values of ena and 147sm 144nd are positively correlated for the pacific samples but negatively correlated for atlantic samples reflecting a fundamental difference between the dominant components in the end members with radiogenic nd island arc components in the pacific and lree enriched intraplate ocean island components in the atlantic samples from the north central pacific have distinctive unradiogenic end values of 10 87sr 86sr 0 715 high la yb 12 and low eun eu 0 6 and sr nd 3 6 these data are virtually identical to the values for loess from asia and endorse the use of these sediments as indicators of asian paleoclimate and paleowind directions island arc contributions appear to dominate in the northwest pacific resulting in higher end 1 to 1 and lower 87sr 86sr 0 705 and la yb 5 sediments from the eastern pacific tend to have intermediate sr and nd isotopic compositions but regionally variable sr nd and ree patterns they appear to be derived from the west margin of the north and south american continents rather than from asia our results confirm that dust provenance can be constrained by isotopic and geochemical analyses which will facilitate reconstructions of past atmospheric circulation and continental paleoclimate

the portuguese bend landslide abstract the portuguese bend landslide in coastal southern california is an active slow moving mass of blocks and debris that extends from the shoreline to moderate altitudes along part of the southerly margin of the palos verdes hills these hills form a peninsula that is underlain by cenozoic sedimentary and volcanic rocks draped anticlinally over a core of mesozoic schist in the southerly parts of the peninsula inherently weak units in the altamira shale member of the miocene monterey formation dip seaward in general concordance with the ground surface ground failure has been widespread in this area it evidently began in mid to late pleistocene time and it has continued intermittently to the present the portuguese bend landslide represents a reactivation of movement of the eastern part of a complex of prehistoric landslides occupying an area of approximately two square miles this latest episode of movement began in 1956 presumably in response to placement of fill during a road construction project the active slide subsequently was enlarged by sequential failure of adjoining blocks of ground and by september 1969 about 54 500 000 metric tons of debris was slowly moving downslope in an area of approximately 104 ha movement has been continuous since recent failure began in 1956 although the velocity of the active slide decreased markedly after that year between 1962 and 1972 the velocity fluctuated only slightly about an average value of about 1 cm per day the active slide is an irregular prism roughly triangular in plan view the southern side of the triangle trends approximately 1100 m east west along a stretch of shoreline that essentially coincides with the toe of the slide the other two sides of the triangle trend northeast and northwest from the ends of the toe and meet about 1200 m north of the shoreline the thickness of the moving mass differs considerably from one place to another reflecting both topographic irregularities and major undulations in the underlying surface of movement the maximum thickness is approximately 75 m movement is occurring along a distinct basal failure surface the eastern part of the slide is underlain by bedrock and is bordered by bedrock with a general structure that limits further deep seated propagation of failure to the east and northeast in contrast the western part of the slide is underlain and bordered by extensive ancient landslide deposits that are marginally stable further encroachment of the active slide westward and northwestward into these materials was viewed as a distinct possibility at the time the dissertation was prepared and has occurred since then continued movement of the portuguese bend landslide since 1956 has been due to four main factors a rise in the water table during the period 1957 1968 has been documented in the northwestern part of the moving mass and is attributable mainly to infiltration of surface runoff entering numerous open fissures that cut the surface of the slide the toe of the active slide daylights along the shoreline and is subjected to storm wave erosion so that any natural build up of resisting forces is prevented in this area the redistribution of mass as the slide has moved along an undulatory failure surface has been responsible for local fluctuations in the driving and resisting forces finally smoothing of irregularities in the failure surface by the moving slide mass must have decreased some of the forces resisting movement

reconstructing the geochronological evolution of large landslides by means of the trenching technique in the yesa reservoir spanish pyrenees abstract detailed geomorphological mapping has revealed that the slopes upstream of the yesa dam are affected by several flysch landslides the largest landslides correspond to la refaya rotational slide 11 million m3 situated just upstream of the spillway and el vertedero translational slide 6 million m3 located 1 5 km upstream of the dam a portion of el vertedero landslide 3 million m3 was reactivated in 2006 due to overloading caused by an earth heap a higher earth dam will be built on the downstream side of the existing gravity concrete dam to raise the maximum water level of the reservoir by 23 m the retrodeformation analysis of the deposits exposed in two trenches excavated in the upper part of these landslides together with the obtained absolute ages c14 and osl have provided information on the kinematics and evolution of these slope movements the main findings derived from the 45 m long trench dug in the closed depression developed at the foot of the head scarp of la refaya landslide include 1 the landslide is older than 12 ka and has undergone a cumulative rotation higher than 17 yielding a mean rotation rate of about 1 4 millennium 2 most of the rotation 14 occurred before 5 8 ka and according to the trench stratigraphy the kinematics of the landslide has been dominated by progressive displacement no evidence of catastrophic reactivation has been found the 45 m long trench excavated across the scarp and bench situated at the head of the non reactivated portion of el vertedero translational slide reveals that 1 the landslide is older than 38 ka 2 the trenched portion has undergone at least one reactivation subsequent to 20 ka and has remained inactive for a long time as suggested by the highly degraded bedrock scarp with a slope of 18 compared to the 60 dip of the underlying failure plane based on this study corrective measures with an estimated cost of 11 5 million euros have been designed for this slope the investigation illustrates the usefulness and cost effectiveness of the trenching technique allied with geochronological methods to obtain information on the precise limits age failure mechanism kinematics progressive vs episodic displacement movement rate and chronological evolution of landslides

susceptibility of reservoir induced landslides and strategies for increasing the slope stability in the three gorges reservoir area zigui basin as an example abstract the construction of the huge three gorges reservoir affected a large region and the resultant geological and environmental impacts have caused global concern the remarkable 30 m annual fluctuation in the reservoir water level poses a significant threat to slope stability in this area four hundred sixty two landslides were identified in the zigui basin using historical records satellite images field investigations and unmanned aerial vehicle uav observations enabling the construction of a complete landslide database and distribution map three failure modes of landslides in the zigui basin are used to illustrate the major factors that govern reservoir induced landslides the results show that 1 99 of identified landslides occur on slopes angle 80 occur at elevations below 600 m 2 jurassic niejiashan formation is highly prone to landslides 3 low reservoir levels of 145 m to 155 m greatly reduce slope stability based on the information entropy method that use the conditional probability of different influencing factors and principal component analysis as inputs the relative contributions of various influencing factors are quantified and a landslide susceptibility map was drawn this susceptibility map helps define the countermeasures that will best reduce fatalities and property losses for areas having different landslide conditions and susceptibilities

sr isotopic and elemental characteristics of calcites in the chinese deserts implications for eolian sr transport and seawater sr evolution abstract calcite content sr concentrations and isotopes of calcites in the chinese deserts are systematically studied in this paper calcite contents which are calculated according to acid soluble ca contents in the deserts are generally higher in the sandy deserts than in the sandy lands and decrease roughly from northwest to northeast of china acid soluble sr is well correlated with calcite in the chinese deserts implying acid soluble sr comes mainly from the calcite dissolution sr concentrations in calcites calculated on the basis of calcite contents and acid soluble sr concentrations in the deserts have an inverse relation to calcite contents essentially mirroring the degree of sr substitution for ca in the calcite development desert calcites have regional variations in sr isotopic ratios calcite sr isotopic ratios depend on geological settings and chemical weathering the badain jaran and tengger deserts are probably affected by additional factors such as the remote groundwater cycle or overturning of underlying sand deposits only four deserts taklimakan qaidam badain jaran and tengger appear to be potential sources of eolian deposits in the chinese loess plateau clp isotopic signatures of calcite sr and silicate nd further indicate that the tengger desert was not an important source for eolian deposits in the clp eolian calcite was probably enriched due to wind sorting from the potential sources to the clp and suffered weathering leaching after it accumulated in the clp sr isotopic compositions and ca sr molar ratios of calcites are different between the deserts and the lingtai profile due to the integrated effect of wind sorting and weathering leaching it is essential to calculate accurately the 87sr 86sr ratio and sr concentration of eolian calcite entering the oceans according to geochemical data of the chinese deserts because of the importance of the chinese deserts in the global dust cycle the calculated sr concentration and 87sr 86sr ratio of eolian calcite entering the north pacific ocean are 11 75 mol g and 0 71032 respectively the calculated values in this study are close to the recommended values by jacobson jacobson a d 2004 has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years geochem geophys geosyst 5 12 1 9 q12002 doi 10 1029 2004gc000750 using the same model as that of jacobson 2004 the effect of asia dust on the evolution of seawater sr isotopes is evaluated 87sr 86sr seawater increases by 0 3 10 5 if the lower dust flux of 2 34 108 mol sr yr is used in the model suggesting the little effect of asian dust on the seawater sr record in the quaternary the increase in 87sr 86sr seawater is 1 5 10 5 if the higher value of 1 17 109 mol sr yr is used as observed in the quaternary sr record these results further support the suggestions of jacobson 2004

numerical and theoretical study of bi planar failure in footwall slopes abstract bi planar failure is the commonest type of failure in steep and high footwall slopes this paper presents an investigation of the bi planar failure mechanism and a stability analysis model for footwall slopes based on the study of eleven diabase mines in hunyuan county shanxi province china first a detailed investigation of the site and tests were carried out to obtain a geological model and calculation parameters for the slope then the failure process in footwall slopes was investigated by a trigon approach performed using the universal distinct element code udec software package a mechanism was then obtained for bi planar compression shear failure by combining the results obtained for the stress displacement and crack development subsequently based on the limit equilibrium and frictional plasticity theories a new columnar mechanical model was proposed for bi planar footwall slope failure the results demonstrate that the udec trigon approach was well suited to simulating bi planar failure in steep and high footwall slopes employing this approach a sliding failure surface that initiates develops and propagates in the discontinuity and intact rock could be correctly captured and the evolution of the damage in the toe of the slope could be quantitatively investigated the results also indicate that shear failure first occurs at persistent discontinuities and then compression shear failure occurs in the intact rocks in addition the failure surface of the rock emanates from the toe of the slope is oriented upwards at an angle to the persistent discontinuity thus forming the through sliding surface this angle can be determined using frictional plasticity theory the critical heights and safety factors of footwall slopes could be readily obtained by employing this new columnar mechanical model giving results that are consistent with the results of numerical simulations furthermore the results of a parameter sensitivity analysis show that the dip angle of the toe breakout surface increases as the slope angle increases however the angle between the toe breakout and internal shear surfaces remains unchanged as the slope angle increases moreover the critical height of the footwall slope decreases linearly as the slope angle increases the method proposed provides theoretical guidance for the stability analysis of steep and high footwall slopes the results produced should also help engineers to gain a better understanding of the mechanisms of bi planar failure in such rock slopes

analysis and modeling of the combined effects of hydrological factors on a reservoir bank slope in the three gorges reservoir area china abstract more than 5000 landslides have been identified in the three gorges reservoir tgr area since the impoundment in 2003 which posed great threats to the residential houses transportation on the yangtze and dam stability this paper focuses on the evaluation of the coupled influence of rainfall and reservoir water on deformation characteristics and failure evolution of the outang landslide in china based on field investigations a statistical pearson cross correlation coefficient analysis multi technique monitoring data and a numerical model this instability is a reactivated ancient landslide with a volume of approximately 90 mm3 located in the three gorges reservoir the slope behavior is featured with a short period of fast displacement and a relatively long period of semi constant displacement rates per hydrological year and displacements velocities quicken gradually upslope rainfall and reservoir water level are the main triggering factors of slope movement existing in the upper and the lower parts of the landslide respectively based on the numerical results the failure evolution of this landslide is a compounded push retrogression type failure process involving a a first rupture at the toe caused by the reservoir water level that will rapidly mobilize a second and subsequent collapses upwards retrogression type and b the rock mass at the upper part will be pushed out and failed downslope push type due to precipitation these results provide a comprehensive analysis of the outang landslide which is critical for its management as well as for disaster prevention and mitigation of analogous reservoir induced landslides

iron geochemistry of loess and red clay deposits in the chinese loess plateau and implications for long term asian monsoon evolution in the last 7 0 ma abstract recently some groups of authors have demonstrated that the tertiary red clay deposits underlying the pleistocene loess paleosol sequence in the chinese loess plateau are wind blown in origin thus extending the eolian record in the plateau from 2 6 ma back to about 7 0 ma and providing a good opportunity to reconstruct long term monsoon changes as magnetic susceptibility the widely used paleomonsoon proxy of loess deposits is problematic in reconstructing the monsoon history recorded in the red clay the development of other proxies is urgently needed in this study we analyzed the ratios of citrate bicarbonate dithionite cbd extractable fe2o3 to total fe2o3 concentrations in four loess sections along a north south transect of the loess plateau and in the lingtai loess red clay sequence of 305 m thick the fe2o3 ratio in the loess sections clearly shows higher values in soil units than in loess horizons and a southward increase in this ratio is also remarkable along the transect these are in good agreement with the temporal spatial variations in the east asia summer monsoon intensity identified by other monsoon proxies and soil development observations the fe2o3 ratio thus attests to being a good proxy indicator of the summer monsoon evolution the lingtai fe2o3 ratio record shows high values over three time intervals 4 8 4 1 ma 3 4 2 6 ma and during the interglacial periods of the past 0 8 ma the increase in summer monsoon intensity over the three intervals also coincides with the well developed soil characteristics it is therefore concluded that the east asia summer monsoon has experienced a non linear evolution since the late miocene the occurrence of a monsoon prime at about 4 8 4 1 ma implies that the tibetan plateau one of the most important boundary conditions in maintaining the monsoon circulation must have been uplifted to a critical height at that time

the landslide of cortes de pallas spain a large landslide in cretaceous limestone and marl formations reactivated by quarry excavations has been stabilized by weight transfer procedures designed by using a conventional limit equilibriu

the sensitivity of upper ocean structure to time varying wind direction observations and models show that sudden changes in the magnitude of the wind stress which occur within a time interval of one half inertial period are most effective in increasing surface current speeds and mixing the upper layers of the ocean the purpose of the present study is to quantify the effects of concurrent time dependent wind direction the mellor yamada level 2 1 2 turbulence closure model is used a series of model runs was executed in order to determine the relative sensitivity of mixed layer depth and sea surface temperature to wind speed as compared with the rate of change of wind direction the results indicate that the accuracy and time resolution of wind direction should be given special consideration in the design and interpretation of field experiments which will be used for testing prognostic mixed layer models

geomorphic evolution of the yangtze gorges and the time of their formation abstract the three gorges of the yangtze link its upper rocky valley to downstream alluvial sections a series of stepped landforms exist in the three gorges area the sichuan basin upstream and the jianghan basin downstream these landforms are characterized by two planation surfaces one erosional surface and up to seven terraces the higher planation surface named the exi surface 1800 2000 m a s l and the lower planation surface 1200 1500 m were probably formed in the tertiary prior to 3 4 3 6 ma b p no correlation seems to exist between the drainage networks of earlier period with the present yangtze system it is suggested that the erosional surface found in the study area at 800 1200 m in elevation above sea level was formed in late pliocene of early pleistocene during this period following the last planation event the ancestral yangtze might have begun to adjust its drainage network the seven terraces well developed along the eastern sichuan basin and the three gorges date from early to late pleistocene 1 16 0 01 ma b p the chronostratigraphic evidence and diagnostic sediments are generally comparable in time and space from the sichuan basin through the three gorges to the jianghan basin therefore the present study proposes that the three gorges were cut not later than the initiation of the earliest terrace the fluvial landforms in the yangtze gorges are characterized also by valley in valley cross sections i e an older u shaped valley cut by a younger v shaped valley a tectonic rise accompanied by a rapid downcutting of the river channels predominated in the region

patterns of movement in reactivated landslides abstract the primary aim of this research was to study the relationship between landslide motion and its causes with reference to large slow moving reactivated translational rock slides surface displacements of the 22 106 m3 utiku landslide in central north island new zealand were measured using continuous gps cgps for three years the nature of the movement of such slides has often been difficult to determine because of poor temporal and spatial monitoring resolutions after removal of tectonic plate motion the temporal pattern of the landslide s surface motion could be understood to arise from irregular episodes of faster up to 21 mm day and slower up to 26 mm yr post failure landslide displacement and seasonal cyclic displacements of about 20 mm yr 10 mm per half year in alternating directions intervals of faster motion gave rise to displacements of between 10 and 120 mm per event faster displacement was associated mostly with basal sliding mechanism 1 involving deformation within a thin clay seam as recorded by borehole inclinometer surveys slower surface displacement involved permanent internal deformation of the larger landslide mass consisting of plastic deformation within the landslide body and or slip along existing internal planes of weakness and slip on the slide base mechanism 2 it accounted for up to 26 mm yr of displacement at a mean angle of about 49 from the horizontal indicating that the slide mass was thinning as it moved down slope seasonal cyclic displacements were synchronous with changes in pore pressure suggesting that it is a shrink swell process mechanism 3 associated with wetting and recharge of groundwater during the wetter winter months leading to a downslope movement and soil shrinkage leading to upslope rebounds during the dryer summer months the brief periods of faster displacement were triggered by seasonal peaks in pore pressure linked to long periods 12 to 20 weeks of increased precipitation and lowered evapotranspiration faster displacement however was not arrested by lowering pore pressure or by any other monitored factor similarly periods of slower displacement did not correlate with pore pressure changes or with any other monitored factor this study has shown that the annual movement pattern of a reactivated landslide is a combination of these processes that generate a complex overall movement record the field measurements showed real variability arising from variations in rainfall and pore pressure which were overprinted with measurement noise that may mask some other processes

evolution of the large landslide induced by typhoon morakot a case study in the butangbunasi river southern taiwan using the discrete element method abstract in 2009 typhoon morakot delivered high intensity rainfall and triggered many sites of large landslide which projected areas were larger than 10 000 m 2 from the satellite image especially in southern taiwan according to dtm analysis the material volume of the large landslide in butangbunasi river was more than four times larger than that of the nearly famous landslide disaster in hsiaolin village nevertheless the different movement of these two large landslides led to different disaster impacts based on literatures and field works the large hsiaolin landslide was a catastrophic landslide which had high velocity and less energy loss in the kinematic process the source area of the large landslide in the butangbunasi river on the other hand was composed of several landslide events and the kinetic energy dissipated when the landslide materials attained to riverbed in sequence in this study we divided the butangbunasi river large landslide into five slope units namely a b c d and e landslide events to recognize the mechanism of the large landslide and the simulation by using the particle flow code 3d pfc3d which is based on the discrete element method provided the kinematic process of the large landslide in the butangbunasi river it is noticed that most of the initial energy dissipated during the movement which the fist happening landslide event counteracted the crash of the follow up events and the residual energy gradually declined by the collision interaction of landslide blocks until the end of the large landslide the result helps to reconstruct the evolution of the large landslide from small scale landslide events and contributes to predict the affected region of the disaster it also reveals that even though the impact of the large landslide is reduced by sequent small scale landslide events there still remain secondary disasters such as landslide dam which show a high potential risk in the river valley and midstream

geohazards in the three gorges reservoir area china lessons learned from decades of research abstract the impoundment of the 660 km long reservoir behind the huge three gorges dam the world s largest hydropower station increased regional seismicity and reactivated severe geohazards before the reservoir filling was initiated in 2003 the region had approximately two earthquakes per year with magnitudes between 3 0 and 4 9 after the full impoundment in 2008 approximately 14 earthquakes per year occurred with magnitudes between 3 0 and 5 4 in addition hundreds of landslides were reactivated and are now in a state of intermittent creep many landslides exhibit step like annual pattern of displacement in response to quasi regular variations in seasonal rainfall and reservoir level additional problems include rock avalanches impulse waves and debris flows the seriousness of these events motivated numerous studies that resulted in 1 better insight into the behavior and evolution mechanism of geohazards in the three gorges reservoir area tgra 2 implementation of monitoring and early warning systems of geohazards and 3 design and construction of preventive countermeasures including lattice anchors stabilizing piles rock bolts drainage canals and tunnels and huge revetments this paper reviews the hydro geologic setting of tgra geohazards examines their occurrence and evolution in the past few decades offers insight learned from extensive research on tgra geohazards and suggests topics for future research to address the remaining challenges

grain size distribution and depositional processes of the mineral component of abyssal sediments lessons from the north pacific grain size analyses of the mineral component of abyssal pacific surface sediments show two distinctly different size distributions that can be associated with sediments that are dominantly eolian and dominantly hemipelagic respectively in the range of 1 to 30 m eolian grains show a distinct size mode at about 2 m 9 and little material coarser than about 16 m 6 hemipelagic grains are characterized by a much flatter size distribution that has a broad size mode near 2 m 9 and important amounts of material coarser than 16 m 6 this ability to distinguish between hemipelagic and eolian grains will obviate some long standing concerns in the interpretation of deep sea sediments examples of the utility of this technique are given for the north pacific and south atlantic

mesoscale characterization of coupled hydromechanical behavior of a fractured porous slope in response to free water surface movement mesoscale characterization of coupled hydromechanical behavior of a fractured porous slope in response to free water surface movement y guglielmi a f cappa a b j rutqvist b c f tsang b and a thoraval c b geosciences azur cnrs unsa ird upmc sophia antipolis france lawrence berkeley national laboratory earth sciences division berkeley usa c ineris ecole des mines de nancy nancy france a corresponding author fax 33 4 92 94 26 10 e mail address guglielmi geoazur unice fr y guglielmi abstract to better understand the role of groundwater level changes on rock slope deformation and damage a carbonate rock slope 30 m 30 m 15 m was extensively instrumented for mesoscale hydraulic and mechanical measurements during water level changes the slope is naturally drained by a spring that can be artificially closed or opened by a water gate in this study a 2 hour slope dewatering experiment was analyzed changes in fluid pressure and deformation were simultaneously monitored both at discontinuities and in the intact rock using short base extensometers and pressure gauges as well as tiltmeters fixed at the slope surface field data were analyzed with different coupled hydromechanical hm codes rocmas flac 3d and udec field data indicate that in the faults a 40 kpa pressure fall occurs in 2 minutes and induces a 0 5 to 31 10 6 m normal closure pressure fall is slower in the bedding planes lasting 120 minutes with no normal deformation no pressure change or deformation is observed in the intact rock the slope surface displays a complex tilt towards the interior of the slope with magnitudes ranging from 0 6 to 15 10 6 rad close agreement with model for both slope surface and internal measurements is obtained when a high variability in slope element properties is introduced into the models with normal stiffnesses of k n faults 10 3 k n bedding planes and permeabilities of k h faults 10 3 k h bedding planes a nonlinear correlation between hydraulic and mechanical discontinuity properties is proposed and related to discontinuity damage a parametric study shows that 90 of slope deformation depends on hm effects in a few highly permeable and highly deformable discontinuities located in the basal saturated part of the slope while the remaining 10 are related to elasto plastic deformations in the low permeability discontinuities induced by complex stress strain transfers from the high permeability zones the periodicity and magnitude of free water surface movements cause 10 to 20 variations in those local stress strain accumulations related to the contrasting hm behavior for high and low permeable elements of the slope finally surface tilt monitoring coupled with internal localized pressure deformation measurements appears to be a promising method for characterizing the hm properties and behavior of a slope and for detecting its progressive destabilization key words fracture rock slope mesoscale in situ poroelastic measurements hydromechanics numerical modeling tiltmeter monitoring damage 1 introduction understanding coupled groundwater and mechanical processes in complex fractured porous rocks is essential for the safety and efficiency of subsurface and slope stability engineering and thus for the security and economic well being of the general public although poorly documented water is often mentioned as a triggering mechanism for failure of rocks with well developed pre existing fractures networks and thus the cause for rock

zonation of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river on the basis of the investigation and statistic analysis of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river the major factors that are found to have affected the slope stabilities are outlined and a zonation of landslide hazards of the region is made using an integrated information model it is divided into destructive disastrous slightly disastrous likely disastrous and essentially non disastrous areas the first two cover an area of less than 5 of the total region and are at a distance of more than 20 km from the three gorges dam and so a landslide over there will impose no direct impact to the tgp but may effect to some degree the navigation of the yangtze river and nearby highway transportation reservoir slopes and building of cities and towns

tsunami squares modeling of landslide generated impulsive waves and its application to the 1792 unzen mayuyama mega slide in japan abstract the frequent occurrence of landslide tsunami has aroused great social concern hence an efficient approach for modeling the phenomena is required urgently herein we present and supplement a meshless numerical model named tsunami squares ts ts simulates both the landslide and its generated wave using an updated numerical scheme that has enhanced computational efficiency ts also provides an artful way of approximating linear dispersive wave propagation and non linear wave inundation that makes it quite capable of simulating real scale events a well designed test that compares ts output with an analytical formula for a tsunami propagation calculation provides firm validation of the approach we then applied the tsunami squares to simulate the 1792 unzen mayuyama mega slide and generated tsunami this event remains the largest volcanic disaster in the history of japan landslide dynamics simulated by ts coincide with historical reports and the known geometry of landslide deposits the model output of tsunami runup heights well match the observed values recorded by the locations of historical tsunami stones this well documented and data rich case further validates the tsunami squares model and the excellent reproduction of the 1792 event provides new insights for better understanding of landslide tsunami hazards