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

an experimental micromechanical study of sand grain contacts behavior from different geological environments abstract grain scale tests can provide useful information about geological materials interface properties and to understand the possible role of geological environments on their behavior this paper presents an experimental micromechanical study investigating the behavior of two quartz sands at the grain scale namely river sand and beach sand which are obtained from two different geological environments the results of the study are compared with leighton buzzard sand lbs quartz grains with the latter material being extensively examined in previous research works basic characterization of the grains is conducted in terms of chemical composition particle shape and roughness it was observed that the grains of the beach sand are relatively rougher and less rounded compared to the river sand grains a custom built new generation micromechanical apparatus was used to quantify the micromechanical behavior of the sand grains at their contacts from the two different materials it was observed that both materials showed a similar range of young s moduli which are obtained from hertzian fitting the river sand grains showed fairly steady state behavior during shearing which was not very obvious for the grains of the beach sand this different observation in steady state was attributed partly to grain morphology effects the stiffness degradation of both sands followed similar trends the average value of the inter particle coefficient of friction for river sand and beach sand grains are about 0 15 and 0 22 respectively whereas for lbs grains the inter particle coefficient of friction lies in between that of river sand and beach sand the high roughness and morphology of the beach sand grains are factors which have contributed to the observed trends and the differences between the variable types of sands

self excitation process due to local seismic amplification responsible for the reactivation of the salcito landslide italy on 31 october 2002 1 an integrated numerical and geophysical approach was used to investigate the role of local seismic amplification in the reactivation of the salcito landslide italy after the molise earthquake of 31 october 2002 numerical stress strain analysis with flac 5 0 fdm software performed in dynamic configuration showed that the 1 hz frequency was consistent with landslide instability conditions the fourier spectrum of the triggering earthquake showed two main peaks occurring at 1 and 2 hz respectively which could be related to local effects the analysis of h v spectral ratios of ambient noise records obtained in the landslide area evidenced amplification effects in the 1 3 hz range on the basis of an engineering geology model numerical modeling of both 1 d and 2 d seismic wave propagation was conducted using linear and nonlinear solutions the simulation outputs showed 1 a 1 hz amplification ascribable to 2 d effects due to a landslide mass lying within a basin like geological structure 2 a double peak amplification at about 2 and 3 hz respectively ascribable to 1 d resonance of the landslide mass and 3 1 d plus lateral wave effects within the landslide mass in the 2 5 3 5 hz frequency range these findings suggest that local amplification of ground motion by the salcito landslide mass may generate a self excitation process responsible for its reactivation

development of a loess mudstone landslide in a fault fracture zone a landslide occurred on the morning of december 16 2013 in liujiabao village tianshui city gansu province china the 260 000 m3 of landslide material traveled a distance of 190 m downslope and damaged a village road and several farmhouses before it stopped on the middle of the slope these landslide materials are still threatening the lives and property of people in the downslope residential areas a field survey revealed that this landslide was strongly affected by the geological setting six normal faults that extend from east to west developed in the neogene mudstone of this region these faults form a fault fracture zone with a width of 80 m the authors performed a detailed investigation of the geological features of these six normal faults and their spatial and faulting relationships to the landslide were examined finally the evolutionary progress of the loess mudstone landslide controlled by the fault fracture zone is discussed

influence of kinematics on landslide mobility and failure mode geometry of discontinuities greatly influences the kinematic behavior of slopes and landslides discontinuous deformation analysis dda is used here to analyze two typical examples of slope failure demonstrating that accurate representation of the geometry of the discontinuities is essential for identification of kinematically correct failure modes then static stability analyses of the vaiont italy landslide of october 9 1963 are used to show that the dda results compare favorably with previously published limit equilibrium studies using similar geometries and that the location and number of discontinuities have a significant effect on the predicted stability and failure velocities of the landslide dynamic dda simulations of the vaiont landslide show that the peak velocity increases up to 50 as the number of blocks increases indicating that internal disintegration of the landslide mass results in increasing acceleration and higher peak velocity dda analyses simulating pore pressure rise resulting from frictional heating of the basal slide plane show that the peak velocity similarly increases up to 50 as the number of blocks increases the magnitude of the increase in peak velocity as a result of disintegration i e increasing number of blocks suggests that as much attention should be paid to the geometry of discontinuities as is typically paid to shear strength and pore pressure

ring shear tests on soil from the vaiont landslide slip surface the paper presents results from ring shear tests carried out on two samples from the slip surface of the vaiont landslide in north italy the tests were carried out at slow and fast rates of shearing in order to determine values of the coefficient of friction appropriate to static and dynamic aspects of the landslide both samples showed a significant loss of strength negative rate effect up to 60 below the slow residual strength when sheared at rates of shearing greater than 100 mm min the observed loss of strength may explain the high acquired velocity of the landslide or alternatively some combination of this and other mechanisms may have taken place le papier presente les resultats d essais de cisaillement par anneau effectues sur deux echantilions preleves sur la surface de cisaillement du glissement de terrain vaiont dans le nord de l italie les essais ont ete menes avec des vitesses de cisaillement lentes et rapides de maniere a pouvoir determiner les valeurs des coefficients de frotteme

geomorphic threshold conditions for ephemeral gully incision abstract ephemeral gully erosion in cultivated land is an important source of sediment that is frequently being overlooked and not accounted for in soil erosion studies furthermore little is known about the factors controlling ephemeral gully erosion in this paper the available information on the initiation and location of ephemeral gullies is summarised focusing on the relationship between the upslope drainage area a and the critical slope gradient s cr for ephemeral gully initiation by plotting the non linear relationship between critical slope gradient measured immediately upstream of the incision head and drainage area at the incision head for gullied sites it was possible to draw a straight line on log log paper through the lower most points for each of the available datasets representing a critical slope area relationship for incision consequently below this line no incision occurs this line or critical relation can also be written as a power function between critical slope and area although many factors vary between the different datasets the exponent of the drainage area relationship 0 4 showed very little variation the observed critical slope area relationship can be related to a simple model of channel initiation by overland flow furthermore this relationship can be used to identify potentially unstable sites where control measures should be undertaken

assessment of gully erosion in eastern ethiopia using photogrammetric techniques abstract eastern ethiopia is severely affected by soil erosion as it is revealed by the commonly occurring deep and wide gullies these gullies are dynamically expanding into agricultural lands at an alarming rate they are also the chief sources of sediment causing siltation of lakes that are valuable sources of both drinking and irrigation water in the alemaya and harar areas a quantitative assessment of gully dynamics and the associated soil loss and a prognosis of areas susceptible to further gullying were deemed crucial aerial photographs from two different dates 1966 and 1996 with approximate scales of 1 45 000 were used to study the development and dynamics of gullies as indicated by volume changes between the two dates they were digitized at a pixel size of 20 m digital elevation models dem with grid widths of 20 and 2 m were derived from stereo image pairs separately gully breaklines and borderlines were measured for the identified gully systems gully profiles were positioned at regular intervals of 20 m along the gully length giving rise to gully sections that are portions of a gully between neighbouring profiles gully volume was computed for every gully section soil loss was estimated from the computed gully volumes using soil bulk density it showed that soil loss per unit of gully surface is very high 1 7 tons m 2 of gully surface over the 30 years time period indicating the severity of gully erosion in the subcatchment there was significant agreement between breakline measured and field measured gully depth and width for selected points this is an indication of the potential of the method for reliable gully volume estimation and hence quantification of soil loss due to gully erosion the possibility of predicting hill slope areas susceptible to further gullying based on the topographic attributes such as specific contributing area and local slope from an interpolated detailed dem with 2 m resolution was tested it was found that wetness index alone or a combination of the wetness index and the compound topographic index at the threshold values established in literature would give better results as viewed from better connectivity of flow lines and higher conformity of the predicted susceptible areas to natural gully headcut and expansion in a landscape reality

initiation and displacement of landslide induced by earthquake a study of shaking table model slope test landslide researches often focus on factor of safety critical acceleration and displacement for an earthquake induced landslide the initiation and displacement of the landslide were important factors for definition of failure in this research the shaking table model slope test is adopted for study of slope failure initiation based on analyses of limit equilibrium particle image velocimetry piv analysis and acceleration time history recorded within the model slope based on the analyses landslide initiation could be defined as surface and local movement of the slope slope failure could be defined based on the massive movement of the slope the piv analysis provides good information for identifying both surface movement and massive movement the landslide displacement determined from the slope movement provides consistent results compared to observed displacements

analysis of a rock slide stabilized with a toe berm a case study in british columbia canada abstract practical experience has shown that slope movement can be controlled by the placement of a berm near the toe of the moving mass during construction of the revelstoke project british columbia canada excavation of a large highway rock cut triggered movement of a 250 000 m 3 rock slide a 15 000 m 3 toe berm was used as a temporary measure to control the displacements of the slide and allow permanent remedial measures to be completed the rock slide was extensively investigated and monitored the sarma limit equilibrium method and the three dimensional distinct element program 3dec were used to investigate the stabilizing effect of the toe berm on the slope deformations in addition 3dec was used to investigate the effect of internal discontinuities on slope displacements the numerical model responded in a manner that is in general agreement with field observations and supported the observations that a small toe berm can be an effective remedial measure in controlling slope displacements

modelling gully erosion for a small catchment on the chinese loess plateau the rolling hills region of the chinese loess plateau is one of the areas with the highest erosion rates on earth a striking feature of this area is the occurrence of many large permanent gullies a 3 5 km2 catchment was selected to study the processes of erosion and to adapt the storm based limburg soil erosion model lisem to the conditions prevailing on the loess plateau part of this work consisted of mapping and measuring the largest gully headcuts the amount of loose soil material beneath the headcuts was also estimated observations suggest that gully headcuts are relatively stable i e do not migrate rapidly but that gullies can nevertheless produce significant amounts of sediment during overland flow events erosion of headcuts occurs mainly by soil falls in between storms the loose soil material produced by these soil falls accumulates on the gully bottom as the lisem simulates storm erosion the development of gullies over time can be ignored and only the amount of material produced by them during runoff events needs to be studied a digital elevation model dem was used to estimate the position of existing gully heads by applying an adapted form of the montgomery and dietrich science 255 1992 826 index using the assumption that headcuts are vertical it is possible to calculate headcut height from the slope angle map a simple stability model which assumes soil falls on gully headcuts to be a function of soil moisture content and headcut height was applied this daily based model can then be used to simulate the accumulation of loose soil material below the headcut the results show that while the dem is not accurate enough to allow the detection of individual headcuts this method can be used to produce a reasonable estimate of the amount of loose soil material available a map showing the amount of loose soil material accumulated can then serve as input for a storm based erosion model such as lisem

sph based analysis of the post failure flow behavior for soft and hard interbedded earth slope abstract this study proposed a smoothed particle hydrodynamics sph model that could consider two types of soils with different viscosities to reveal the flow mechanism of a soft and hard interbedded earth slope the flow processes of an actual unstable slope in the lushan hot spring district and the saleshan landslide were simulated and the applicability of proposed sph model was validated by comparing the flow process and the flow velocity with dem results and surveyed data thereafter with a conceptual simulating case for the soft and hard interbedded earth slope materials were divided into two types and eight groups consisting of 64 cases were analyzed with different viscosities according to the variation curves of the run out and the flow velocity with time the flow behavior is controlled by the properties of both the soft layer and hard layer and increasing the viscosity of the hard layer can greatly reduce the run out and the maximum velocity the result provided a basis for the mitigation of possible layered earth slope disasters in engineering geology

vegetation cover and geomorphodynamics on abandoned fields in the central ebro basin spain abstract a dense vegetation cover is the key to soil erosion control on abandoned fields in semi arid environments in the study area maria de huerva in the semi arid central ebro basin spain investigations were carried out on two abandoned fields of different ages 5 and approx 75 years young fallow land abandoned field for a period of 5 years 1994 1998 the vegetation cover and the intensity of geomorphodynamics were recorded on two 24 36 m unbounded test plots for 8 5 specific dates based on the states of vegetation cover and geomorphodynamics at two points change maps were developed these change maps were combined to change relation maps it can be seen that an increase in vegetation cover does not generally lead to a stabilisation in the geomorphodynamic process activity

the prehistoric vajont rockslide an updated geological model abstract this study presents the detailed reconstruction of the entire structure of the prehistoric vajont rockslide about 270 300 million m 3 of rocks and debris for the first time describing the complex geometry and the characteristic superimposition of distinct rigid blocks on a very thick shear zone the prehistoric vajont rockslide was characterized by an enormous en masse motion of a rigid overlying rock mass 100 130 m thick that moved downslope sliding onto a very thick shear zone 40 50 m thick on average made up of a chaotic assemblage of blocks limestone angular gravel and high plasticity clays montmorillonitic clays coarse loose sediments still exposed on the 9 october 1963 detachment surface are always associated with large blocks made of strongly fractured rock masses fonzaso formation middle upper jurassic preserving the stratification the blocks of stratified and folded limestone sequences appear to be sheared off from the underlying bedrock and can be considered as displaced rock masses planed off by the motion of the overlying rigid rock mass rock mass shavings the prehistoric vajont rockslide was characterized by a multistage failure with a marked retrogressive evolution the first rupture pian del toc block rapidly destabilized the upper slope mobilizing a second rock mass block pian della pozza block that in turn determined the multiple rupture of the revealed shear zone material massalezza lobe even if the exact timing of the different phases is not known the entire multistaged failure process was very rapid at the end of the multistage retrogressive failure the slope morphology of the northern toe of mt toc was drastically changed and the large failed rock mass settled into the preexisting vajont valley assuming the unusual chair like geometry the vajont rockslide represents a very significant example on how a complex geological situation if not adequately analyzed and reconstructed can lead to dangerous misinterpretations or even to erroneous engineering geological and geotechnical models accurate fieldwork and modern technologies can be fundamental in solving such a very intriguing geological puzzle

modelling the erosional susceptibility of landslide catchments in thick loess chinese variations on a theme by jan de ploey abstract in his 1990 paper catena 17 175 183 jan de ploey proposed a system whereby catchments are viewed as functional units in which geomorphic work results from the combined effects of water erosion and mass movements his measure of erosional susceptibility of catchments es introduced the gravitational potential in addition to the kinetic energy of the eroding agents this modelling of the erosional susceptibility of catchments in terms of energy was being used to explore time dependent variations of es when jan de ploey died also at this time he extended an invitation to the present authors to test and extend his model using our data base on the landslide dominated catchments in the thick loess country of north central china this paper presents a series of new equations expressing variations in es using a data base for over 200 landslides in the loess covered mountainous terrain relative relief up to 1500 m of the lanzhou region of eastern gansu province these equations express the loss of potential energy of the landslide mass in relation to the relative relief and the pressure energy input in the form of rainfall these indices of erosional susceptibility can be used to analyse the differences in response from one catchment to another and through time between the characteristics of vegetation cover including land use hydrology geomechanical behaviour and mechanisms of movement on slopes using certain assumptions on percentage area of catchments affected by mass movement and long term mean annual precipitation in the lanzhou region the es equation suggests an estimate for non clayey materials of about 10 4 m 2 s 2 which is a significantly higher susceptibility value than the mean worldwide value for non clayey materials obtained by de ploey

short term bank gully retreat rates in mediterranean environments abstract in this study short term headcut retreat was monitored from 46 active bank gullies selected in the guadalentin and the guadix basin in southeast spain the measurements were carried out manually using an orthogonal reference system fixed by erosion pins around the gully heads between april 1997 and april 1999 with a 1 year interval the average volumetric retreat rate for all gullies was 4 0 m 3 year 1 corresponding with an average linear retreat rate of 0 1 m year 1 but more erosion took place during the first monitored year 1997 1998 compared to the second 1998 1999 an interplay of spatial variations in rainfall distribution and tension crack activity is assumed to be responsible for the important difference in annual headcut retreat compared to the small difference in annual rainfall amounts statistical analysis showed that the present drainage basin area a p was the most important topographical factor explaining average gully headcut retreat rate both in terms of annual eroded volume v e and annual linear retreat r l and expressed by the power relationships v e 0 04 a p 0 38 r 2 0 39 and r l 0 01 a p 0 23 r 2 0 39 the v e a p relationship was compared with the relationship between original drainage basin area a o and total eroded bank gully volume vol i e vol 1 71 a o 0 60 r 2 0 65 the importance of runoff generation from a drainage basin is shown by the positive correlation of linear headcut retreat and the runoff curve number cn representative for the conditions in the drainage basin high cn values tend to coincide with higher annual eroded volumes in the relationship between present drainage basin area a p and annual eroded volume v e but this effect was not observed in the relationship between original drainage basin area a o and total eroded bank gully volume vol stepwise multiple regression selected the relevant environmental parameters explaining annual eroded volume and linear retreat in both equations the present drainage basin area explained the largest part of the variation the cn was selected as another common parameter height of the headcut was the second most important variable explaining annual eroded volume indicating the role of energy transfers and undercutting at the headcut linear retreat was further explained by the average slope of the present drainage basin area representing the effect of decreasing transmission losses and increasing flow velocity with steeper catchment slopes and by the sand content decreasing the cohesion of the soil material promoting soil fall and headcut retreat spatial extrapolation of the measured volumetric retreat rate of 4 0 m 3 year 1 revealed that active bank gully heads contribute up to 6 of the sediment yearly filling up the puentes reservoir estimated gully ages i based on the ergodic principle and ii by linear extrapolation of actual gully retreat rates in the past range between 63 years and 1539 and between 64 and 1720 years respectively the high correlation between the gully ages estimated by the two methods is attributed to the fact that most gullies have not reached the evolutionary stage of significantly declining retreat rates since medium term gully retreat rates are more dependent on drainage basin area compared to the short term retreat rates obtained in this study the estimated gully ages represent maximum values assuming that present land use and climate conditions prevailed over the last two millennia

the role of sidewall processes in gully development some n s w examples little attention has been paid to the role of sidewall processes in gully development simple estimates of linear incision sidewall erosion ratios at two localities in new south wales australia suggest that sidewall erosion is responsible for more than half the gully volume studies at three localities where overland flow and throughflow are limited to only one sidewall indicate that these processes are responsible for 10 30 per cent of gully volume these observations have important implications for gully management

assessment of bank gully development and vegetation coverage on the chinese loess plateau abstract gully erosion is a serious environmental problem and the primary source of sediment loss on the loess plateau of china yet previous research focusing on bank gullies is limited an assessment of bank gully development is needed as a basis for predicting erosion rates under the effects of vegetation cover and land use change to estimate bank gully retreat rates under different land uses assess the factors leading to bank gully development and model gully area growth rate at the catchment scale 30 catchments with an average area of 39 0 ha were selected in the southeastern part of the loess plateau quickbird images 0 61 m resolution obtained in 2003 and 2010 were interpreted to delineate bank gully features and a 5 m resolution digital elevation model was used to extract topographic factors the results showed that from 2003 to 2010 the maximum retreat rates of bank gully heads in the 30 investigated catchments ranged between 0 23 and 1 08 m yr 1 with an average of 0 51 m yr 1 the ratio of bank gully growth area to valley area changed from 0 49 to 9 45 depending on land use with average increases of 3 94 4 00 and 2 09 for the three land use types identified i e mixed use grassland and forestland respectively correlation analysis indicated that the effects of topographic factors on bank gullies decreased as vegetation coverage increased in upslope drainage areas and that vegetation coverage exceeding 60 in upslope drainage areas can significantly control bank gully development a model was built to predict the bank gully area growth rate ra m2 yr 1 with upslope drainage area ai m2 local slope gradient s m m 1 and the proportion of the area with vegetation coverage below 60 in upslope drainage areas 0 6 at the catchment scale the regression equation is in the form ra 0 1540 0 6ai 0 24s 3 2588 compared with previous studies vegetation is a factor in this model which would be helpful for assessing the influence of vegetation cover on bank gully development

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

assessment of the effects of historical strong earthquakes on large scale landslide groupings in the wei river midstream abstract regional active tectonics and historical earthquake records indicate the importance of the triggering effects of historical strong earthquakes on groups of large scale landslide occurrences in the wei river midstream section in this study a method to assess the triggering effects of historical earthquakes on regional large scale landslides is presented the greatest epicentral distances of seismically induced landslides were calculated the triggering effects of four key historical strong earthquakes with epicenters within 300 km of the wei river midstream section were analyzed these are the ms 7 0 qishan earthquake of 780 bce the ms 8 0 tianshui earthquake of 1654 ce the ms 8 25 huaxian earthquake of 1556 ce and the ms 8 5 haiyuan earthquake of 1920 ce taking the qishan earthquake as an example a seismically induced landslide displacement and hazard assessment method based on the newmark displacement model was developed the degree of spatial matching of the results for historical earthquake triggered landslides and the distribution of actual large scale landslide deposits were compared quantitatively using the success rate curve method the results show that of the four historical earthquakes the tianshui earthquake had the strongest effect of inducing large scale landslides regionally along the wei river midstream section

a slope movement in a complex rock formation deformation measurements and dem modelling abstract the case history of a deep seated slope movement in a complex rock formation marly arenaceous formation is analyzed the movement monitored for more than 20 years was recognized after the discovery of intense cracking in the concrete lining of a hydraulic tunnel running across the slope the time history of displacements shows that the ongoing deformation process is essentially a stationary creep phenomenon also influenced by transient variations in pore pressure distribution the shearing zone is mainly formed by tectonized clay gouge and is characterized by a mobilized strength close to residual the slope has been modelled by dem approach as a complex blocky structure defined by several joint sets bedding planes inclined and sub vertical joints different hypotheses about the geometry of the slip surface compatible with field evidences are discussed as well as their influence on the critical friction angle of the slope the type of model adopted for rock mass with continuous or staggered joints influences the pre failure deformation mode but the failure conditions are not as much affected finally the response of dem models to the increase in water level at the toe of the slope and to the rise of the groundwater table inside the slope has been analyzed the results of simplified models without flow calculation and coupled hydro mechanical analyses are compared finding some relevant differences

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

a general analytical solution for the evolution of cliffs accounting for strength degradation seismic action formation of tension cracks and seepage abstract the evolution of natural slopes over time is ruled by several concurrent physical phenomena namely the strength of its component geomaterials and their weakening over time due to weathering processes the occurrence of seismic events seepage and the formation of tension cracks the paper presents analytical solutions obtained considering a succession of discrete failure events landslides progressively altering the slope morphology over time the model derived in the framework of limit analysis assuming plane strain conditions provides a tool for the assessment of whether manufacts and or infrastructures located on a slope subject to various natural degradation phenomena will be affected by the occurrence of failures unlike current empirical and semi empirical models of slope evolution the analytical solution that is here presented is derived by applying principles of soil and rock mechanics therefore it is of general validity so that no ad hoc calibration against past observations of the evolving slope is needed this analytical technique only requires knowledge of the geotechnical parameters characterising the geomaterials comprising the slope of interest namely angle of shearing resistance cohesion c tensile strength unit weight together with knowledge of the relevant seepage scenarios strength degradation processes and seismic events likely to occur results show that that earthquake loading and seepage can substantially decrease slope stability increase the volume of material sliding away during each landslide event and alter the evolution of the slope over time while tensile strength exhibits a less strong influence especially as strength degradation progresses dimensionless ready to use charts are provided for the benefit of practitioners

criteria for rapid sliding ii thermo hydro mechanical and scale effects in vaiont case abstract thermally induced excess pore pressures have been included into a two wedge evolutive model of vaiont landslide the problem requires the solution of a system of four coupled balance equations for the shear bands and the surrounding rock as well as the joint equation of motion of the entire slide the model predicts the high velocities observed and is consistent with other data slide geometry residual strength and conditions on the sliding surface the interpretation of a sensitivity analysis suggests that there exists a threshold permeability band in the range 10 8 to 10 10 m s which separates potentially fast motions from slow motions this conclusion is maintained if the scale of the landslide is reduced

the mechanism of the 1941 tsaoling landslide taiwan insight from a 2d discrete element simulation tsaoling is located in southwestern taiwan 10 km east of the frontal thrusts of the mountain belt five large historical landslide events were recorded from 1862 to 1999 no details of the earliest landslide event 1862 are available thus this paper deals with the 1941 landslide event using the particle flow code in two dimensions pfc 2d to simulate the mechanism of the tsaoling landslide in 1941 this study shows that the landslide block developed cracks and slid down 0 2 1 8 m on the sliding plane the cracks concentrated in certain zones which corresponded to future landslide detachment planes during the vibration simulation the cracks spread from the shear plane to ground surface monitoring the variations of the displacements velocity and stress during vibration simulation showed that the peak velocity and stress in the transition zones occurred at 3 s the displacement of the left part of the block exceeded 1 3 m and the displacement of the right part was less than 1 3 m during vibration simulation these results suggest that the left part of the block was pushed down by the right part ultimately inducing a landslide during an earthquake

patterns and controls of gully growth along the shoreline of lake huron an empirical approach was used to examine the morphology and behaviour of gullies along the eastern shoreline of lake huron canada gully and watershed dimensions and percentage vegetation cover of a sample of 44 gullies were measured from aerial photographs between 1930 and 1992 gullies with larger watersheds had higher area growth rates larger gullies continue to expand over time while small gullies are more likely to become stable growth rates increased between 1955 and 1978 because of increased snowfall extreme flow events the extension of municipal drains and the use of subsurface drainage after 1970 efforts to rehabilitate gullies using drain pipes and check dams contributed to a decrease in gully growth rates 1997 john wiley sons ltd

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

dem simulations of transverse pipe soil interaction on sand realistic modelling of transverse i e vertical and lateral pipe soil interaction plays an important role in predicting the behaviour of untrenched offshore pipelines that are designed to undergo

surface sealing as influenced by slope angle and position of simulated stones in the top layer of loose sediments the influence of five different slope angles and two different positions of simulated stones in the top layer of a sandy and a silty sediment on surface sealing intensity is examined in the laboratory sealing intensity is assessed by studying changes of percolation rate through a sediment layer with simulated rainfall duration and by measuring cohesion of the 5 mm thick upper sediment layer a measure of seal strength by means of a torvane slope has a negative influence on sealing intensity for a constant per cent of simulated stone cover sealing intensity is lowest in the case of stones placed on the sediment surface compared to the case of stones pushed into the surface layer explanations for these findings are given and some implications are further discussed

characteristics and controlling factors of bank gullies in two semi arid mediterranean environments abstract bank gullies are gullies that are formed due to a height drop caused by a terrace or a river bank which develop by headward retreat in erodible hillslopes this study aims i to investigate the morphology of actively eroding bank gullies i e geometrical characteristics resulting from past erosion and active erosion processes shaping the gully and ii to find relationships with environmental site characteristics such as topographical parameters material properties and climate the ultimate goal is to identify the most important controlling factors of past and present bank gully erosion fifty five active bank gullies formed in different lithologies by various erosion processes have been selected in the guadalentin basin and the surroundings of guadix southeast spain for each bank gully site geometrical and topographical parameters of both the channel and the drainage basin were measured erosion features indicating activity at the gully head such as tension cracks plunge pools undercutting fluting piping and rill or sheet erosion on sloping side walls were mapped and samples were taken from distinct lithological layers that were considered to influence the type and intensity of erosion processes a relationship could be shown between the presence of piping and fluting and a number of material characteristics including particle size distribution dispersion behaviour and electrical conductivity on the other hand lithology appeared not to be a differentiating factor on gully development in the long run as expressed by the total eroded volume v this parameter was most strongly related to the drainage basin area in which the entire bank gully had been formed a o explaining 66 of the variance the relationship is v 1 75 a o 0 59 no significant difference was found between regression lines through sub datasets of different soil textural classes finally multiple regression was used to include both topographical parameters and material characteristics in an explanatory and or predictive equation for the total eroded bank gully volume the results of the analyses using the entire dataset including the sites in the guadalentin as well as in the guadix area have been compared with the results for the separate study areas differences are not only related to topographical and lithological characteristics but may also be the consequence of a different climate in the two areas

on the seismic response of deep seated rock slope instabilities insights from numerical modeling abstract earthquake induced landslides constitute a critical component of seismic hazard in mountainous regions while many seismic slope stability analysis methods exist with varying degrees of complexity details of interactions between seismic waves and incipient landslides are not well understood and rarely incorporated in particular for deep seated slope instabilities we present a series of 2d distinct element numerical models aimed at clarifying interactions between earthquakes and large rock slope instabilities the study has two main goals 1 to explore the role of amplification in enhancing co seismic slope deformation a relationship widely discussed in literature but rarely tested quantitatively and 2 to compare our numerical results with the well established newmark method which is commonly used in seismic slope stability analysis we focus on three amplification phenomena 1 geometric topographic amplification 2 amplification related to material contrasts and 3 amplification related to compliant fractures slope height topography seismic velocity contrasts and internal strength and damage history were varied systematically in a series of models with a relatively simple scalable geometry for each model we compute the spatial amplification patterns and displacement induced by real earthquake ground motions we find that material contrasts and internal fracturing create both the largest amplification factors and induced displacements while the effect of geometry is comparably small newmark type sliding block methods underestimate displacements by not accounting for material contrasts and internal fracturing within the landslide body both common phenomena in deep seated slope instabilities although larger amplification factors tend to be associated with greater displacements we did not identify a clear link between ground motion frequency content spectral amplification and induced displacement nevertheless observation of amplification patterns can play an important role in seismic slope stability analyses as 1 strong amplification related to material contrasts or compliant fractures is an indicator of potentially large co seismic displacements and 2 amplification patterns can be used to constrain geological and numerical models used for seismic stability analysis the complexity of wave slope interactions as well as the potential to severely underestimate hazard using newmark type methods motivates use of rigorous numerical modeling for quantitative seismic hazard and risk assessment of large landslides

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

effects of rainwater softening on red mudstone of deep seated landslide southwest china abstract red mudstone landslides are widespread in southwest of china the development and distribution of deep seated landsides with slow inclination are closely related to the special soft rock properties of the red mudstone layers most previous studies focused on the failure mechanisms of rain induced shallow landslides studies on deep seated landslides in red layer zones are still limited in order to ascertain the basic failure mechanisms of red layer landslides with a gentle inclination a fatal landslide named as shibangou landslide which occurred in sichuan china was investigated this paper aims to 1 conduct laboratory tests on the reduction in shear strength of a red layer to identify the water rock coupling effect 2 investigate variations in the microscopic structure of the soft rock found within a red layer after rainfall infiltration 3 discuss the failure mechanisms of red layer landslides with slow inclination results from shear test of mudstone from the shibangou landslide revealed that there is a tendency that behavior of soft rock can be transferred to soil in different days of immersion the delineation threshold of shear strength of the red layer is determined as 6 days of immersion microstructures of clay minerals become loose and porous due to the contacts between the particles transferred from the face edges face face associations into edge edge and face edge associations therefore the intramolecular and cemented expansions of illite are the basic mechanisms which lead to structural damage structural decay and strength attenuation of soft rock in red layer under the condition of rainwater infiltration

3d numerical modeling using smoothed particle hydrodynamics of flow like landslide propagation triggered by the 2008 wenchuan earthquake abstract the extremely strong wenchuan earthquake triggered thousands of landslides in sichuan province china flow like landslides such as the tangjiashan wangjiayan and donghekou landslides were among the most destructive causing many casualties and serious economic damage it is therefore important to identify the flow mechanisms and investigate the specific characteristics of these flow like landslides this paper presents a three dimensional model based on smoothed particle hydrodynamics sph to simulate rapid landslide motion across 3d terrain the navier stokes equations in a cfd framework are used as governing equations and artificial viscosity is incorporated into the pressure terms in the momentum equation to dissipate energy to avoid numerical oscillation and particle penetration thus improving the stability of the numerical results a non newtonian fluid model the bingham model has proven suitable for describing the relationship between the shear strain rate and the shear stress in highly deformed soil materials in the proposed model it is used as the constitutive model to describe the fluidization characteristics of flow like landslides combined with the mohr coulomb yield criterion the model incorporates a no slip boundary condition to consider the effect of a solid boundary on slope movement ghost particles are created and assigned an artificial velocity the viscous force caused by the solid boundary is calculated using the relative velocities between the fluid and the boundary particles open multiprocessing openmp an api for multi platform shared memory parallel programming is used to improve the efficiency of the sph code running to show the validity of the proposed approach a benchmark problem of 3d dam break was simulated the calculated distances of the surge front at different times agree well with the test results numerical modeling of the propagation of the tangjiashan wangjiayan and donghekou landslides was performed by the application of sph models to real flow like landslides the whole flow processes of these flow like landslides across the 3d terrain are represented the landslides change direction split or join in and spread or contract in their flow path in response to the local topography time history curves of the velocity and displacement were obtained to analyze the movement characteristics of the landslide mass the shapes of the deposition zones after slide occurrence were investigated comparisons of the sph simulated geometry and the surveyed landslide configurations for the tangjiashan wangjiayan and donghekou landslides were conducted and show a high degree of similarity this indicates that the proposed 3d sph model can accurately represent the evolution of the final slide shape the prediction of the fluidization characteristics of earthquake induced flow like landslides can notably reduce sudden loss of life as it provides a means for mapping hazardous areas for estimating the hazard intensity and for identification and design of appropriate protective measures

thermoporomechanics of creeping landslides the 1963 vaiont slide northern italy 1 the catastrophic vaiont landslide southern alps italy of 9 october 1963 moved 2 7 108 m3 of rock that collapsed in an artificial lake causing a giant wave that killed 1917 people the landslide was preceded by 2 3 years of creep that ended with the final collapse of the rock mass slipping at about 30 m s 1 assuming that creep was localized in a clay rich water saturated layer in this study we propose shear heating as the primary mechanism for the long term phase of accelerating creep we study only the creeping phase of the slide and we model this phase using a rigid block moving over a thin zone of high shear strain rates introducing a thermal softening and velocity strengthening law for the basal material we reformulate the governing equations of a water saturated porous material obtaining an estimate for the collapse time of the slide our model is calibrated upon real velocity measurements from the vaiont landslide and provides an estimation of the critical time of failure up to 169 days before the collapse we also show that the slide became critical 21 days before the collapse when shear heating started localizing in the clay rich layer inducing a tendency for slip localization and thermal runaway instability in a plane the total loss of strength in the slipping zone during the last minutes prior to the slide is explained by the onset of thermal pressurization triggered by the temperature rise within the clay rich layer

investigation of rock fragmentation during rockfalls and rock avalanches via 3 d discrete element analyses this paper investigates the characteristics of dynamic rock fragmentation and its influence on the postfailure fragment trajectory a series of numerical simulations by discrete element method dem were performed for a simple rock block and slope geometry where a particle agglomerate of prismatic shape is released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point the rock block is modeled as an assembly of bonded spherical particles with fragmentation arising from bond breakages bond strength and stiffness were calibrated against available experimental data we analyzed how dynamic fragmentation occurs at impact together with the generated fragment size distributions and consequently their runout for different slope topographies it emerges that after impact the vertical momentum of the granular system decreases sharply to nil while the horizontal momentum increases suddenly and then decreases the sudden boost of horizontal momentum can effectively facilitate the transport of fragments along the bottom floor the rock fragmentation intensity is associated with the input energy and increases quickly with the slope angle gentle slopes normally lead to long spreading distance and large fragments while steep slopes lead to high momentum boosts and impact forces with efficient rock fragmentation and fine deposits the fragment size decreases while the fracture stress and fragment number both increase with the impact loading strain rate supporting the experimental observations the fragment size distributions can be well fitted by the weibull s distribution function

rotational translational landslides in the neogene basins at the northeast margin of the tibetan plateau abstract rotational translational landslides are common in neogene basins throughout the world and are of high risk to the public to understand the mechanism of rotational translational failure the spatial distribution and deformation of rotational translational landslides in the northeast of the tibetan plateau are investigated in this study the spatial distribution of these landslides is dependent on the regional tectonics and geomorphology crustal stresses and lithological properties the rotational translational landslides are concentrated in the neogene mudstone basins and the intensities of these landslides are observed to gradually decrease from the hinterland of the plateau to the marginal basins the bedding parallel shear zones within the location of the rotational translational landslides are present in the overconsolidated neogene mudstones with high clay content nearly horizontal tectonic stresses and erosion cause the formation of horizontal shear stresses in the sliding masses in this stress environment materials with low internal friction angle

monitoring of gully erosion on the loess plateau of china using a global positioning system abstract with the development of a technique global positioning system gps has become progressively less expensive lighter and easier to use the accuracy of gps has been improved and it appears applicable to the continuously monitoring morphology changes on the earth surface with small and slow change the objective of this study is to use gps to measure the morphology of gullies in a small catchment near suide shaanxi province china there are three main gully types in the study area bank gullies floor gullies and hill slope gullies and this study mainly focuses on the hill slope gullies the hill slope gullies in the study area are mainly discontinuous and are developing rapidly the gully density in the study area is very large the retreat rate of hill slope gullies is 0 16 2 02 m year 1 the relationships between the upslope drainage area a and the critical slope gradient s for hill slope gullies is s 0 1839a 0 2385 the values of as2 range from 41 to 814 m2 for the hill slope gully headcuts and most of them fell into the range of 100 300 m2 both of these relationships are suggested as indexes for estimating the location of gully headcuts

spatial distribution of gully head activity and sediment supply along an ephemeral channel in a mediterranean environment abstract in this study we examined the factors that control the spatial distribution of bank gully heads along a reach of an ephemeral river rambla salada in an area threatened by desertification in southeast spain the activity of 458 gully heads was assessed in the field by pre defined criteria such as sharp edges presence of a plunge pool tension cracks recent deposited sediments flow marks and vegetation re growth the results showed that land use has a significant impact on bank gully head activity recent land use changes involving the extension of almond cultivation appears to intensify bank gully head activity also lithology has a clear impact on the bank gully extension it was further investigated whether the gully heads were important sediment sources that contributed to reservoir sedimentation the density of very active bank gully heads along the study reach was one per 17 m of channel length average annual retreat volumes were derived from measurements at 46 active gully heads 4 0 m3 y 1 by selecting all the channel sections in the catchment of the puentes reservoir with a similar pattern of bank gullies using aerial photographs an estimate of basin wide sediment production of bank gully heads was established it was estimated that the retreat of active bank gully heads alone in the 12 760 ha study area representing 12 of the total catchment area of the puentes reservoir produced 6 of the sediment filling up the reservoir considering that the sediment is also derived from other sources such as channel walls channel beds and hillslopes the overall conclusion is that bank gully expansion in southeast spain is a major point source of sediment and therefore a major process of land degradation

landslides induced by the 2008 wenchuan earthquake sichuan china the 2008 wenchuan earthquake with a magnitude of mw 7 9 induced numerous slope movements on the hanging walls of fault surface ruptures and on steep inner valleys along the minjiang river landslide moving directions showed preferred orientations normal to the fault ruptures indicating the effect of the directivity of the seismic wave the most common landslides were of carbonate rocks which are easily dissolved and decrease the contact surfaces the largest non volcanic landslide in history was induced in bedded dolomite by the earthquake and was preceded by gravitational deformation with ridge top depressions valley fill materials were mobilized at 36 locations probably by pore water pressure build up

long term coupled effects of hydrological factors on kinematic responses of a reactivated landslide in the three gorges reservoir abstract a reservoir induced landslide is a common geomorphological problem in the tgr three gorges reservoir region china this study considers the quchi landslide as an example of a large scale partially reactivated ancient landslide in the tgr region the possible kinematic responses and corresponding triggering mechanisms are investigated by analyzing eight year monitoring data sets field surveys observations and laboratory tests the reactivated zone is primarily located in the south western part of the ancient landslide and it mainly moves along the deep sliding surface the long term monitoring data sets show that the presence of faster movements from june to september rainy season followed by slower deformation in the remaining nine months of the hydrological year both strong rainfall and drawdown during the low period of rwl reservoir water level are important hydrological factors responsible for the occurrence of faster movements an rwl of 160 m a s l above sea level during drawdown is considered the key water level for the initiation of faster movements the motion pattern is primarily retrogressive and the displacement velocity increases towards the toe at present the stability of the reactivated zone is indeterminate a multistage failure with significant retrogressive evolution can possibly occur in the future the findings in this study can help in managing reservoir landsides and designing landslide reinforcements in the regions of the word with geological settings similar to that of the tgr region

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

medium term gully headcut retreat rates in southeast spain determined from aerial photographs and ground measurements this paper deals with gully retreat rates at different time scales whereby the short term time scale may span a time interval of 1 5 years the medium term time scale a time interval of 5 50 years and the long term time scale a time interval of more than 50 years an analysis of high altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully head retreat rates for 12 permanent gullies in southeast spain guadalentin and guadix study areas over a 40 43 year time interval medium term time scale this resulted in an average retreat rate ve of 17 4 m3 year 1 a power relationship between drainage basin area a and medium term volumetric gully head retreat rate ve 0 069a0 380 r2 0 51 n 21 was found by combining the gully head retreat rates obtained in this study with those obtained by a dendrochronological method the exponent b and the coefficient of determination r2 of the power relationships ve aab increases from the short term to the long term time scale expressing the increasing importance of drainage basin area in gully development with time considerable differences between gully head retreat rates measured at the short and medium term time scales at individual gullies showed the importance of land use changes and unsuccessful management practices on gully head retreat and the episodic nature of gully head retreat when piping and tension cracking are involved higher gully head retreat rates are obtained at the medium term time scale compared to the short term time scale but the differences are not significantly different at 10 the medium term methods tend to measure proportionally more high gully retreat rates but less extreme values compared to the short term method this is explained by a more equal distribution of extreme rainfall events both in space and time at a longer term time scale and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully

data for activity law and hydraulics mechanism of landslides with different sliding surface and permeability in the three gorges reservoir area china abstract the three gorges hydropower station is the largest hydropower station worldwide and the largest project ever built in china there are about 2619 ancient landslides affected by reservoir level fluctuation in the three gorges reservoir tgr area more than 670 landslides have been reactivated and eight landslides have failed since the impoundment of the reservoir in june 2003 which seriously threatens people s safety and property in this study taking a large number of re active and failed landslides as statistical samples the activity and displacements of the reservoir landslide with special regard to different sliding surface and permeability are analyzed and discussed it is noted that a significant correlation between the landslide movement and the reservoir filling process the re active landslides are mainly concentrated in the initial stage of water storage and the frequency of activation as well as the degree of deformation decrease gradually after the third phase of water storage 175 m then the four dominant combinations of the inducing factors of re active landslide are presented a drawdown of water level straight line sliding surface 20 40 degree of immersion and weak permeability b drawdown of water level arc sliding surface 40 60 degree of immersion and medium permeability c raising of water level fold line sliding surface 20 40 degree of immersion and good permeability d raising of water level chair shaped sliding surface 0 20 degree of immersion and good permeability furthermore when the rate of the reservoir level fluctuation is greater than the permeability coefficient the shape of sliding surface is from the straight line the arc the fold line the chair shaped and the hydraulics effect of reservoir water on landslide shifts from the seepage pressure effect to the buoyant effect meanwhile the impact of the reservoir water filling on the landslide reactivation changes from favorable to worse and the impact of the reservoir water drawdown on the landslide reactivation changes from worse to favorable

development of gullies and sediment production in the black soil region of northeastern china abstract gully erosion is an important environmental hazard in the black soil region of northeastern china it is a primary sediment source in the region which needs appropriate soil conservation practices gully incision in rolling hills typical of this region was monitored using real time kinematic gps to assess the rates of gully development and the resultant sediment production from 2002 to 2005 gully heads in the study area retreated between 15 4 and 33 5 m giving an average retreat rate of 8 4 m yr 1 field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr 1 which is equivalent to 326 to 2355 t yr 1 with gully head retreat accounting for 0 to 21 7 4 4 in average the sediment delivery ratio was especially high during the summer rainy season 56 in average sediment production by ephemeral gullies and permanent gullies was 1 5 times greater than that from surface erosion gully heads retreated faster in the spring freeze thaw period than in the summer the stage of gully development could be identified based on short term changes in the gully erosion rate

comparison of gully erosion estimates using airborne and ground based lidar on santa cruz island california abstract gully erosion removes comparatively large volumes of soil from small areas it is often difficult to quantify the loss of soil because the footprint of individual gullies is too small to be captured by most generally available digital elevation models dems such as the usgs national elevation dataset airborne lidar light detection and ranging has the potential to provide the required data density but an even newer class of ground based sensors may provide better local resolution at lower cost in this study we compared digital elevation models produced by airborne and ground based lidar systems with ground based geomorphic and geodetic survey data to determine their utility in quantifying volumetric soil loss due to gully erosion in a heavily degraded watershed 7 55 10 2 km 2 on southwestern santa cruz island in southern california volumetric estimates of the eroded sediment were produced by comparing the lidar derived dems of the gully system to a modeled pre erosion surface average point densities were significantly higher for the ground based lidar system and provided more detailed information however its limited scanning footprint and side looking orientation presented serious challenges in collecting continuous data from deeply incised gullies making the airborne system preferable for this type of investigation and likely for most applications where heavy topographic shadowing is prevalent

the role of seismic triggering in a deep seated mudstone landslide china historical reconstruction and mechanism analysis abstract deep seated mudstone landslides are widely distributed in northwest china the zhengjiamo landslide occurred in 734 ce near taijing tianshui region it was triggered by the main shock of the historical ms 7 0734 ce earthquake the earthquake also induced a wide range of landslides in this area with hundreds of fatalities and many houses destroyed by landslide debris based on a detailed field survey borehole data and mapping a detailed geological reconstruction of the slope was achieved and the geo mechanical features of the claystone involved in the landslide were obtained using the particle flow code to simulate the mechanism of the zhengjiamo landslide the features of the landslide dynamics were obtained using a 5 stage model during the landslide process the slip mass at the front and upper edges exhibited higher mobility than at the rear and bottom edges furthermore the contact bond strength of the sliding body gradually weakened the model indicates that the particle bond strength has a larger influence on the maximum runout distance and landslide debris morphology than the type of weak intercalated layers the slip mass presented a rotational slide pattern and remained on the slip plane throughout the sliding process finally the earthquake uplifted the slope toe which prevented the slip mass from gliding the modelled scenario provided a reasonably good fit to the actual topography verifying the modelling results after the historical earthquake with the clay minerals swelling and shrinking under rainfall and efflorescence conditions the structure of the soft rock changed contributing to the weakening of the sliding rock mass the landslide gradually crept and evolved to its current topography

dynamic distinct element analysis of the 800 m high aknes rock slope dynamic analysis of the 800m high aknes rock slope using udec dynamic distinct element analysis of the 800 m high aknes rock slope

the tsaoling landslide triggered by the chi chi earthquake taiwan insights from a discrete element simulation article i nfo in the village of tsaoling in yunlin county taiwan a major landslide was triggered by the chi chi earthquake in 1999 with more than 125 10 6 m 3 of rock displaced the kinematic behaviour of this landslide is simulated using a 2d discrete element model pfc2d code our numerical model is composed of discs bonded together the initial boundary conditions are applied along the ball wall contacts by using derived velocities integrated from the strong motion data with a duration of 160 s including the peak acceleration near tsaoling the constraints are mainly issued from the final geometry of the landslide including its capacity to cross the river valley and reach a significant elevation on the opposite mountain flank they also result from a variety of geological and hydrological observations including the local levels of material disruption and the location of survivors our modelling thus indicates that a low friction coefficient about 0 15 and a medium strength are required to account for the actual landslide characteristics a self lubrication mechanism probably accounts for the low residual friction our model also suggests that the maximum velocity of sliding reached 50 m s a result that cannot be checked in the absence of actual measurements in addition to friction the strength of sliding block is of special importance because it controlled the possibility for the upper layer fragments to roll and get buried and hence the probability of survival

finite element analysis of progressive failure of carsington embankment progressive failure occurs when brittle soils are loaded non uniformly the average shear stress at collapse is less than peak strength the effect cannot be examined by conventional limit equilibrium stability analysis the carsington embankment slipped in 1984 just before it reached full height the slide was 30 m deep and 500 m long and instrumentation had been installed and read up to the moment of collapse the strengths of the soils involved were carefully established as was the exact geometry of the slip limit equilibrium analysis showed that at collapse the average shear stress mobilized was less than peak strength with a safety factor based on peak strength of 1 2 since the soils involved were brittle progressive failure was a probable cause of the discrepancy finite element analyses were performed in which strain softening soil properties were assumed some of these analyses are reported here the pre failure displacements the collapse height and collapse mechanism were recovered by t

dynamic response characteristics and deformation evolution of loess slopes under seismic loads abstract the loess plateau is one of the most seismically and geologically active regions in china the related catastrophic earthquakes and geological disasters have caused more than 1 4 million deaths in the plateau in this study the slopes on the edge of the loess tableland in pingliang city gansu province the core area of the loess plateau are investigated based on large scale shaking table model tests and discrete element numerical simulation particle flow code pfc 2d the dynamic response characteristics and deformation evolution process of fissured and non fissured loess slopes under different seismic loads are studied the test results show that with increasing seismic load input the peak ground displacement pgd of the loess slopes increases gradually with increasing slope height for the two types of slopes the acceleration amplification effects in the slope with horizontal direction load are larger than those of the vertical direction load the amplification factor of the peak ground acceleration pga at the shoulder of the fissured slope is significantly larger than that of the non fissured slope according to the numerical simulation results of the fissured slope when the seismic load is small the bond failures are distributed densely in the initial fissured structural plane and at the model bottom regarding the non fissured slope the bond failures in the slope are mainly distributed at the bottom of the model with increasing acceleration amplitude the number of bond failures in the slopes increases rapidly when the input load increases to 0 40 g two potential slip surfaces occur in the shallow surface of the fissured slope and a potential slip surface appears at the back edge of the non fissured slope

gully head erosion processes on a semi arid valley floor in kenya a case study into temporal variation and sediment budgeting a three year monitoring programme of gully head retreat was established to assess the significance of sediment production in a drainage network that expanded rapidly by gully head erosion on the low angled alluvio lacustrine njemps flats in semi arid baringo district kenya this paper discusses the factors controlling the large observed spatial and temporal variation in gully head retreat rates ranging from 0 to 15 m a 1 the selected gullies differed in planform and in runoff contributing catchment area but soil material and land use were similar the data were analysed at event and annual timescales the results show that at annual timescale rainfall amount appears to be a good indicator of gully head retreat while at storm event timescale rainfall distribution has to be taken into account a model is proposed including only rainfall p and the number of dry days dd between storms which explains 56 per cent of the variation in retreat rate of the single headed gully of lam1 a detailed sediment budget has been established for lam1 and its runoff contributing area rca by measuring sediment input from the rca the sediment output by channelized flow and linear retreat of the gully head for nine storms it can be seen that erosion shifts between different components of the budget depending on the duration of the dry period dd between storms sediment input from the rca was usually the largest component for the smaller storms the erosion of the gully head occurred as a direct effect of runoff falling over the edge ghwaterfall and of the indirect destabilization of the adjacent walls by the waterfall erosion and by saturation ghmass storage the latter component ghmass storage was usually much larger that the former ghwaterfall the sediment output from the gully was strongly related to the runoff volume while the linear retreat because of its complex behaviour was not overall the results show that the annual retreat is the optimal timescale to predict retreat patterns more detailed knowledge about relevant processes and interactions is necessary if gully head erosion is to be included in event based soil erosion models copyright 2001 john wiley sons ltd

low to high velocity frictional properties of the clay rich gouges from the slipping zone of the 1963 vaiont slide northern italy the final slip of about 450 m at about 30 m s of the 1963 vaiont landslide italy was preceded by 3 year long creeping phase which was localized in centimeter thick clay rich layers 60 70 smectites 20 30 calcite and quartz here we investigate the frictional properties of the clay rich layers under similar deformation conditions as during the landslide 1 5 mpa normal stress 2 10 7 to 1 31 m s slip rate and displacements up to 34 m experiments were performed at room humidity and wet conditions with biaxial torsion and rotary shear apparatus the clay rich gouge was velocity independent to velocity weakening in both room humidity and wet conditions in room humidity experiments the coefficient of friction decreased from 0 47 at v 0 70 m s full lubrication results from the formation of a continuous water film in the gouge the vaiont landslide occurred under wet to saturated conditions the unstable behavior of the landslide is explained by the velocity weakening behavior of the vaiont clay rich gouges the formation of a continuous film of liquid water in the slipping zone reduced the coefficient of friction to almost zero even without invoking the activation of thermal pressurization this explains the extraordinary high velocity achieved by the slide during the final collapse

statistical analysis of an earthquake induced landslide distribution the 1989 loma prieta california event the 1989 loma prieta california earthquake moment magnitude m 6 9 generated landslides throughout an area of about 15 000 km2 in central california most of these landslides occurred in an area of about 2000 km2 in the mountainous terrain around the epicenter where they were mapped during field investigations immediately following the earthquake the distribution of these landslides is investigated statistically using regression and one way analysis of variance anova techniques to determine how the occurrence of landslides correlates with distance from the earthquake source slope steepness and rock type the landslide concentration defined as the number of landslide sources per unit area has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness the landslide concentration differs substantially among the various geologic units in the area the differences correlate to some degree with differences in lithology and degree of induration but this correlation is less clear suggesting a more complex relationship between landslide occurrence and rock properties

evidence of hillslope directional amplification from accelerometer recordings at qiaozhuang sichuan china abstract this work reports the results of an accelerometer monitoring aimed at revealing the seismic response of hillslopes in the town of qiaozhuang in qingchuan county near the north eastern end of the fault ruptured during the 2008 mw 7 9 wenchuan earthquake in sichuan province serious damage and slope failures were induced by this earthquake in the town center and on the hills in the peri urban zone this suggested the possible occurrence of amplification phenomena five accelerometer stations were emplaced at two topographic reliefs to investigate their response to ground motion during the last part of the wenchuan seismic sequence about 50 aftershocks were recorded whose magnitude ml varied between 1 2 and 5 5 and epicentral distance ranged from a few to 90 km the accelerometer records provided evidence of directional amplification which was investigated by analyzing the polar diagrams of normalized arias intensity ia and the horizontal to vertical spectral ratios hvsr evidence of the anisotropic dynamic response and site specific resonance frequencies was obtained for both topographic reliefs however the ground shaking maxima orientations differed depending on the local geological setting in one case they were transversal and in the other case sub parallel to the relief elongation no preferential direction of maximum shaking was observed at the site in the valley furthermore evidence of resonance was derived from the calculation of spectral ratio between the sites on the slope and those at the foot of the hills the resonance was more pronounced at higher elevations which suggested a possible occurrence of topographic amplification resonance frequencies were lower 3 5 hz on the smaller hill consisting of sub vertically layered phyllites and higher up to 7 hz on the larger hill made mainly of limestones whereas an opposite relation between resonance frequency and hill size could be expected from a purely topographic effect this and the presence of amplification factors larger than 2 suggest that in addition to topographic effects local geology also played a significant role in differentiating the site response

a morphologic characterisation of the 1963 vajont slide italy using long range terrestrial photogrammetry abstract the 1963 vajont slide in northeast italy is an important engineering and geological event although the landslide has been extensively studied new insights can be derived by applying modern techniques such as remote sensing and numerical modelling this paper presents the first digital terrestrial photogrammetric analyses of the failure scar landslide deposits and the area surrounding the failure with a focus on the scar we processed photogrammetric models to produce discontinuity stereonets residual maps and profiles and slope and aspect maps all of which provide information on the failure scar morphology our analyses enabled the creation of a preliminary semi quantitative morphologic classification of the vajont failure scar based on the large scale tectonic folds and step paths that define it the analyses and morphologic classification have implications for the kinematics dynamics and mechanism of the slide metre and decametre scale features affected the initiation direction and displacement rate of sliding the most complexly folded and stepped areas occur close to the intersection of orthogonal synclinal features related to the dinaric and neoalpine deformation events our analyses also highlight for the first time the evolution of the vajont failure scar from 1963 to the present

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

criteria for rapid sliding i a review of vaiont case vaiont slide has been represented by a model of two interacting evolutive wedges mass conservation during the motion implies that the upper wedge transfers mass to the lower one through an internal shearing plane the model respects available in situ observations it was formulated in dynamics terms outcomes of the analysis are the determination of safety factors of the valley before dam impoundment and the calculation of run out distance once the motion starts rock strength degradation as motion develops has also been included this degradation even if it is intense was unable to explain the very high estimated landslide velocities

influence of lixiviation by irrigation water on residual shear strength of weathered red mudstone in northwest china implication for its role in landslides reactivation abstract irrigation in loess tableland areas of northwest china has induced a large number of landslides around their edges of which loess red mudstone landslide is one of the most frequent types salt sinters commonly observed at the toes of these landslides where the weathered red mudstone wrm outcrops have raised the possibility that removal of soluble salts in the wrm by irrigation water could be crucial in the reduction of its shear strength and thus in the occurrence of these landslides in order to investigate the effects of lixiviation by irrigation water on residual shear strength of the wrm samples of the wrm close to two landslides in lanzhou city one of the largest cities in northwest china were tested after being treated under different conditions these included 1 saturation with the yellow river water the only source of irrigation 2 saturation with groundwater and 3 saturation and leaching with deionized water based on the results of these tests specific mechanisms of residual shear strength reduction of the wrm due to lixiviation by irrigation water were discussed in terms of physico chemical interactions between the wrm and water it was found that lixiviation reduced residual shear strength and residual friction angle r of the wrm by up to 65 and 62 respectively after being leached 6 times this coincided with a dramatic dissolution and leaching of soluble salts from the wrm particle size distribution showed that the more the wrm was leached the more the clay fraction and the lesser coarser fractions this suggested that reduction in residual shear strength of the wrm could be attributed to mainly disaggregation of particles coarser than clay and to a lesser degree to weakening of interparticle forces among individual clays it was further postulated that variation in clay mineralogy may influence performance of particle disaggregation

quantitative risk analysis for earthquake induced landslides emamzadeh ali iran abstract earthquake induced landslides are among the most destructive slope movements not only because of their size and magnitude but also because of the synergistic action with the earthquake the consequences are higher due to the earthquake shaking and the landslide effect studies on landslides triggered by seismic activities are not as extensive as rainfall induced landslides in this study a quantitative risk analysis approach was used to calculate the risk for people exposed to the threat of earthquake induced landslide in emamzadeh ali north of iran emamzadeh ali was selected as it has already experienced some landslides and is located in a tectonically active region a numerical model was used in this study to carry out the stability analysis of the slope under both static and dynamic conditions a quantitative probabilistic approach was developed for determining the frequency and magnitude of the process in addition the values of vulnerability for each building were calculated the highest risks individual risk to life and societal risk to life are in the area of the stone mine on the head of the slope and close to the toppling activities north east of the study area

right lateral shear and rotation as the explanation for strike slip faulting in eastern tibet the convergence of two continents can be accommodated by crustal thickening and by lateral transport of crust out of the path of the converging continents1 3 the principal features suggesting that lateral transport is important are major strike slip faults striking roughly orthogonally to the orientation of convergence between the continents displacement on such faults is imagined to allow lateral transport of material with respect to the converging continents possibly accounting for a large fraction of the convergence between the two continents the most spectacular example of such strike slip faulting is in the eastern part of the tibetan plateau where three major left lateral faults with slip rates of 10 mm yr 1 and several smaller roughly parallel faults dominate the regional strain field2 3 cobbold and davy4 suggested that these faults may be rotating in a clockwise fashion here we put bounds on that rate of rotation and conclude that the image of lateral transport on such faults2 known also as continental escape extrusion or expulsion is an illusion and that instead the left lateral slip on east striking planes in eastern tibet is a manifestation of north striking right lateral simple shear if this conclusion is correct the east striking left lateral faults and the crustal blocks between them are rotating clockwise at 1 2 myr 1 the east west dimension of eastern tibet is shortening at 10 20 mm yr 1 and little material is moving eastward out of india s path into eurasia by left lateral simple shear

aznalcollar dam failure part 2 stability conditions and failure mechanism an analysis of the conditions that led to the failure of the aznalcollar dam is made in the paper pore water pressures prevailing in the foundation clay at the time of the failure have been established on the basis of piezometric observations made after the failure a simplified consolidation analysis is first presented to interpret pore water pressure generation and dissipation and to evaluate the evolution of shear stresses along the potential failure plane both limit equilibrium and finite element analysis are used to back analyse the failure and to derive representative strength parameters along the failure surface three dimensional effects introduced by the layered nature of the foundation clay are then described they provide an explanation for the location of the slide which affected only the south eastern portion of the embankment the failure is examined in the final part of the paper from the perspective offered by the current knowledge of the strength behaviour of brittle clays the signifi

recent gully erosion in the el cautivo badlands tabernas se spain abstract detailed geomorphic observations in el cautivo badland area in the semiarid se of spain show a recent renewal of linear channel erosion following a period of aggradation prior to this renewal the landscape was characterized by smooth colluvial pediments on the north east facing aspects and relatively steep crusted microhillslopes on south west facing aspects first order valleys within the badland landscape were smooth floored and filled with silty deposits connected with pediment colluvial deposits the conditions under which valley bottom deposition was replaced by channel incision were analyzed by a study of flow hydraulics magnitude frequency of eroding events vs resistance of valley floor to water flow and the pollen sequence in the recently cut deposits changes in the vegetation carpeting the valley bottom seem to be responsible for the deposition erosion alternation rather than changes in the magnitude frequency of major runoff events given the high sensitivity of flow hydraulics to changes in roughness present rainfall rates would not on their own be able to erode a well vegetated valley bottom yet the pollen sequence in the valley fills demonstrates a progressive deterioration in climatic conditions with the eventual disappearance of groups that require a constant level of soil moisture alnus corylus cyperaceae an increase in yearly rainfall or a change in temporal patterns would increase infiltration leading to permanent denser vegetation on footslopes and valley floors helped by the natural water harvesting system this vegetation cover would reduce the flow velocity and induce the deposition of the colluvium and valley fills whereas erosion on headslopes would have been active enough to supply the sediments that were deposited downslope or on the valley bottoms the reactivation of linear erosion would seem therefore to be a consequence of the decay of this permanent vegetation induced by an increase in the duration or severity of drought periods which meant that the water storage capacity of the valley fillings was insufficient to support it

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

a method for dendrochronological assessment of medium term gully erosion rates abstract a method based on dendrochronology to estimate gully erosion rates was developed as an alternative of traditional methods for assessing medium term gully retreat rates such as field monitoring of headcuts or aerial photo interpretation of gully retreat the method makes use of trees or parts of a tree affected by gully erosion revealing information on the history of the erosion process by datable deviations of their normal growth pattern hence defined as datable objects these include roots exposed by erosion browsing scars made by ungulates on exposed roots or on above ground parts of fallen trees exposed and dead root ends root suckers stems branches and leading shoots of fallen trees and a sequence of trees within a gully the method is based on the differentiation between three main conditions depending on the relation between the dynamics of the datable object part of the tree and the development of the gully the first condition implies that the datable object was created before erosion of the gully volume to be dated e g exposed tree roots according to the second condition the datable object developed as an immediate consequence of the erosion event e g growth reactions of a fallen tree the third condition implies that the datable object was created some time after the erosion event took place e g trees colonising the gully bed each principle has consequences for the accuracy and the correct interpretation of the estimated erosion rate i e whether the true erosion rate is underestimated exact or overestimated in spite of methodological limitations and dendrochronological dating problems the method was successfully applied in southeast spain conservative estimations of gully head retreat rate resulted in an average medium term 3 46 years value of 6 m3 year 1 n 9 for gully sidewall processes the average minimum erosion rate per unit sidewall length amounted 0 1 m3 year 1 m 1 n 9 a strong correlation was found between the headcut retreat rate vm ortho m3 year 1 and the drainage basin area a m2 of the gullies expressed by vm ortho 0 02a0 57 r2 0 93 n 9 comparing the findings from this study with those obtained by short term headcut retreat monitoring suggests a high reliability of the estimated retreat rates supporting the applicability of the developed dendrochronological method

heavy rainfall triggered loess mudstone landslide and subsequent debris flow in tianshui china abstract continuous and heavy precipitation triggered a large loess landslide at the southern dagou village of mapaoquan town tianshui city gansu province of china on july 21 2013 the landslide debris rapidly turned into a debris flow that was deposited in the ravine mouth with the volume of 1 9 105 m3 detailed field mapping three dimensional laser scanning aerial photograph interpretation and laboratory tests were carried out to study the formation and moving characteristics of the landslide and subsequent debris flow the results showed that 1 the peak flow velocity and peak discharge of the debris flow were estimated to be approximately 7 2 m s and 730 m3 s respectively the velocity had a tendency to first increase and then decrease from the head to entrance in the dagou gully 2 the analysis of rainfall conditions showed that the effective antecedent rainfall within 7 days and hourly rainfall intensity which triggered the slide debris flows was 239 mm and 20 mm h respectively compared with the critical rainfall in this area the effective antecedent rainfall was found to be more significant in triggering this event 3 the mean and effective particle sizes were approximately 0 73 1 3 mm and 0 036 0 087 mm respectively and had the same distribution along the gully as the velocity which confirmed the process of the variation in the flow velocity 4 the scale amplification was very obvious in the formation and moving process of the slide debris flows

gully and sheet erosion on subtropical mountain slopes their respective roles and the scale effect abstract as most mountains in tropical and subtropical zones the western sierra madre suffers active present erosion which may create some constraints to the social and economic development in the area the objectives of this study of soil degradation in the western sierra madre are to determine the respective roles of gully and sheet erosion this research is based on field observations field measurements of runoff and soil losses at the plot as well as the watershed scales as an analysis of an exhaustive census of the few gullies located in an experimental area measured soil losses in the western sierra madre are high although there are few gullies most of the sediment yield seems to originate in widespread degraded areas where stoniness is the main evidence of a previous stage of erosion previously overgrazing and deforestation were determined as the factors of the appearance of new soil surface characteristics which explain the high runoff and sediment productions the soil compacted by cattle trampling reduces infiltration the decrease of the vegetation cover triggers a rise in the splash effect and thus a soil sealing these processes induce an increase in runoff and soil losses the main erosion type has been described as sheet erosion it is characterised by the removal of fine soil particles and the remains of gravels pebbles and blocks which constitute a pavement on the soil gullies generally appear on the bottom of wide valleys and depressions where soils are thick it is shown that sheet erosion is two orders of magnitude higher than gully erosion at the hillslope scale due to the spatial distribution of land use and the geological context such as the heavily degraded areas close to the main rivers the reduction of runoff and soil loss rates within the extension of a considered area commonly observed in hydrology only applies up to the elementary catchments scale 1 to 50 km 2 above this area runoff coefficient and soil loss rates increase

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide