behavior of concrete faced rockfill dams during initial impoundment centrifuge tests to investigate the behavior during initial reservoir filling of a concrete faced rockfill dam cfrd with face slab stiffnesses that vary by a factor of about two are described the two centrifuge models exhibited similar deformations at the crest and along the face slab with crest settlements averaging 0 19h and maximum face slab deformations averaging 0 88h the centrifuge test results suggest that the face slab stiffness had little effect on deformations at least for the range of stiffnesses examined here a parametric study of transition supporting zone stiffness was performed using a numerical model calibrated using the centrifuge results the numerical results indicated that face slab deformation is more influenced by transition zone stiffness than face slab stiffness supporting the centrifuge results deformation measurements for 25 in service cfrds including six korean cfrds one of which was used as the basis for the centrifuge model dam are presented and compared w

the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

discrimination of grain size subpopulations in pyroclastic deposits a cubic spline curve fit to histograms of grain size data from pyroclastic deposits affords a rapid means to distinguish subpopulations in complex size distributions using interactive microcomputer graphics the operator can isolate and quantitatively characterize subpopulations by a method of successive gaussian subtractions percentile measures of the entire size range are not needed and segments of the whole size distribution can be analyzed independently recurrent subpopulations with similar means and standard deviations are consistent among the more than 140 samples of pyroclastic surge deposits from sugarloaf in arizona and vulcano in italy the entire data set can be replicated by synthetic curves consisting of various proportions of five identified gaussian components each of which the authors attribute to a specific mechanism of transport and deposition

characterization of glacial silt and clay using automated mineralogy glacial erosion produces vast quantities of fine grained sediment that has a far reaching impact on earth surface processes to gain a better understanding of the production of glacial silt and clay we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the st elias mountains yukon canada sediments were collected from proglacial streams while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation for both rock fragments and sediments we observe a log normal distribution of grain sizes and a sub micrometer terminal grain size we find that the abrasion of silt and clay results in both rounding and the exploitation of through going fractures the abundance of inter versus intragranular fractures depends on mineralogy and size unlike the relatively larger grains where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes the comminution of fines leads to a grain size composition and rounding that is continuously distributed across size and highly dependent on source rock properties

petrology of glacial sand implications for the origin and mechanical durability of lithic fragments the petrology of first cycle unmodified and second cycle reworked sand at the termini of eleven valley glaciers eroding coarse to fine grained bedrock types is determined in order to evaluate the origin and mechanical durability of lithic sands first cycle sands are coarse to medium grained poorly sorted fine skewed non modal lithic sands with an average composition of q21f6l73 grain size distributions do not vary with composition or source rock types although sands derived from finer grained source rocks contain more lithic fragments than sands from coarser grained sources by contrast second cycle sands are medium grained poorly sorted fine to coarse skewed arkosic to lithic sands with an average composition of q19f40l41 and contain fewer lithic fragments than do first cycle sands we propose that the origin mechanical durability and survival potential of lithic fragments are related to the types and abundances of their internal planes of weakness and the particular stress field of the transporting medium as a result of abrasion glacial clasts and lithic fragments are subjected to shear stress so that fractures propagate along intracrystal and intercrystal planes of weakness resulting in a continuous grain size spectrum of lithic fragments and monomineralic grains irrespective of the type of source rock upon subsequent aqueous transport in the proglacial environment lithic fragments are subjected to point loading during saltation in addition to shear stress point loading produces extensional fractures which preferentially propagate along intercrystal planes of weakness so the lithic fragments break into smaller monomineralic grains and or lithic fragments lithic fragments of very coarse sand size are abundant in first cycle sands thus refuting at least for glacial sands the widely held view that grains of this size are deficient in nature the presence of fewer grains of this size in second cycle sands indicates that very coarse sand size lithic fragments can survive recycling but in greatly reduced proportions due to breakage

effect of stone content on water flow velocity over loess slope non frozen soil abstract stony soils are commonly found worldwide and are considerably studied for their hydrological characteristics and effect on soil erosion water flow velocity is an important parameter in understanding the effect of stone content on hydrodynamics and soil erosion in this study laboratory experiments were used to measure rill flow velocity by using electrolyte tracer method under different hydraulic conditions flow rates of 1 2 4 and 8 l min slope gradients of 5 10 15 and 20 and stone mass contents amounting to 0 10 20 and 50 nine sensors which were 1 m apart along the 8 m long rill were used to measure flow velocity by tracing solute transport measured flow velocity increased with slope gradient and flow rate the highest increase in flow velocity was measured from 15 to 20 which were also affected by flow rate effects of discharge rate on flow velocity presented the largest difference when flow rate increased from 2 l min to 8 l min at slope gradients higher than 5 the effects of different factors were quantified by a regression model with high accuracy of 0 99 maximum flow velocity of water was predicted at 15 23 of stone content flow velocity increased with 0 15 23 of stone content but decreased at higher values this study aims at further understanding the hydrodynamics of soil erosion and sediment transport behaviors in hillslopes with different stone contents to obtain information for quantifying soil erosion on stony slopes

effect of tree thinning and skidding trails on hydrological connectivity in two japanese forest catchments abstract land use composition and patterns influence the hydrological response in mountainous and forest catchments in plantation forest management operations fmo modify the spatial and temporal dynamics of overland flow processes however we found a gap in the literature focussed on modelling hydrological connectivity hc in plantation forest under different fmo in this study we simulated hc in two steep paired forest subcatchments k2 and k3 33 2 ha composed of japanese cypress chamaecyparis obtusa endl and japanese cedar cryptomeria japonica d don plantations 59 of the total area against a tree thinning intensity of 50 at different time additionally construction of new skidding trails and vegetation recovery was simulated on five thinning based scenarios that covered a 40 month test period july 2010 october 2013 as a future scenario six check dams located in the main streams were proposed to reduce sediment and radionuclide delivery an updated version of borselli s index of runoff and sediment connectivity was run using the d infinity flow accumulation algorithm and exploiting three 0 5 m resolution digital elevation models on the basis of the pre fmo scenario hc increased at catchment scale owing to tree thinning and the new skidding trails this change was more noticeable within the area affected by the fmo where hc increased by 11 4 and 10 5 in the cypress and cedar plantations in k2 respectively and by 8 8 in the cedar plantation in k3 at hillslope plot and stream scales the evolution in the values of hc was less evident except the increment by 5 4 observed in the streams at k2 after the fmo progressive vegetation recovery after the fmo triggered a slight reduction of connectivity in all compartments of both subcatchments forest roads and especially skidding trails presented the highest values of hc appearing as the most efficient features connecting the different vegetation patches with the stream network the spatial and temporal evolution of hc over the five past scenarios correlated well with the observed changes in runoff yield as well as with the available values of rainfall interception and throughfall before during and after the fmo the simulation of the proposed scenario recommends the construction of check dams as effective landscape features to somewhat reduce hc and thus to decrease the sediment and radionuclide delivery rates from the two subcatchments

the effect of grain texture on the occurrence of microstructural properties in subglacial till in this paper we examine whether till grain size affects the range and occurrence of micromorphological features associated with subglacial shear our till samples were collected from two glaciers in iceland and varied in texture from a coarse sandy clast rich till fjallsjokull to a fine grained silty sandy till vestari hagafellsjokull we found a wide range of deformational microstructures that included skelsepic plasmic fabric intraclasts of pre existing eroded bedrock basalt and weathered clay and mini shear zones between clasts we classified our micromorphological data into three classes rotational intermediate and linear in addition to these observations we performed extensive microfabric analysis at different scales on all of our samples we found that the coarse grained till contained a greater number and variety of microstructures than the fine grained till in addition the fine grained till showed a distinct lack of rotational structures that we attribute to the lack of significantly sized clasts in the matrix we argue that the varied texture of the coarse grained till provides a greater degree of perturbation within the shearing layer and so more distinct microstructures form in a more fine grained till shearing is more homogeneous since there are less perturbations in the matrix and this leads to a more singular kind of microstructure our observations suggest that subglacial shear occurs within a multi layered patchwork of different grain sizes competence and pore water pressures it is these factors that are so crucial in determining the occurrence and type of microstructural evidence we see in subglacial tills

factors controlling sediment yield from small intensively cultivated catchments in a temperate humid climate abstract data on sediment yield from 26 small cultivated catchments 10 10 000 ha in central belgium were collected based on sedimentation rates in small flood retention ponds area specific sediment yield varies from 0 4 to 20 6 t ha 1 year 1 for catchments ranging from 7 to 4873 ha various catchment properties were analysed in order to understand this large variation in sediment yield catchment area alone explains 64 of the observed variance in area specific sediment yield although no other parameter could explain more it is concluded that catchment area is not a valid parameter to link with sediment yield overall catchment geomorphology e g presented by the hypsometric integral is much more important in controlling sediment yield the lack of data however made this not very clear a multiple regression model including three morphological catchment properties is a valuable tool to predict total sediment yield t year 1 from catchments in central belgium this model has an efficiency of 0 81 furthermore it was concluded that the within catchment spatial distribution of parameters for instance slope steepness is very important but difficult to obtain one single representative value the use of spatially distributed erosion and sediment delivery models is therefore necessary accurate sediment yield data like the one presented in this study however are needed to validate these models

fractal dimensions of diamictic particle size distributions simulations and evaluation it has been proposed that deformation tills have fractal particle size distributions reflecting scale invariant debris comminution processes numerical simulations however show that fractal dimensions m typical of deformation tills can be produced by the mixing of gaussian parent populations analogous to the mechanical mixing of coarse medium and fine grained sorted sediments the simulated distributions have high r2 values 0 98 and narrow 95 confidence limits indicating that fractal analysis cannot distinguish diamictons that have been created by shearing from those formed by other mechanisms such as the mixing of preexisting sediments the fractal dimensions of diamictons reflect the relative amounts of coarse and fine material in the distribution but are not uniquely diagnostic of particular genetic processes

numerical analysis of concrete faced rockfill dams considering the effect of face slab cushion layer interaction in this study the effect of concrete slab cushion layer interface on the performance of face slabs in concrete face rockfill dams cfrd is investigated using the finite element method the body of the cfr dam is simulated by the cap elasto plasticity model while the interface zone between the concrete slab and the gravelly cushion layer is simulated explicitly by an advanced interface constitutive model developed in the framework of critical state soil mechanics cssm and state parameters and capable of simulating volumetric behavior and stress path dependency the effect of elastic and elasto plastic material behavior and water level on the stress and displacement responses of the concrete slab is examined and the influence of the roughness at the interface area between the concrete slab at the contact face and the cushion layer on the performance of the face slab is investigated comparison of the results with and without the explicit consideration of the interface behaviour showed the importance

investigation of the relationship between precipitation extremes and sediment discharge production under extensive land cover change in the chinese loess plateau abstract to quantify the effects of rainfall and catchment characteristics on sediment yield is of essential importance for sustainable land management precipitation extremes are the external cause of the majority of serious soil erosion and suspended sediment yield ssy events in the chinese loess plateau clp which has undergone extensive land use cover change lucc the investigation of the linkage between climate variables and ssy production is crucial to the precise implementation of ecological restoration strategies thereby reducing soil loss in the clp in this study a partial least squares regression plsr approach is used to investigate this issue using 1961 2015 data from 16 main catchments in the clp this period includes the reference period 1961 1979 period i integrated soil conservation project period 1980 1999 period ii and the grain for green program period 2000 2015 period iii the results indicate that the dominant climate factors driving ssy are precipitation extremes including maximum precipitation events heavy precipitation daily precipitation 25 mm consecutive wet days erosive precipitation daily precipitation 12 mm and annual total precipitation the effects of the precipitation extremes on sediment yield generation are stronger in drier catchments the influence of the precipitation extremes on sediment generation can be strengthened by cultivation and weakened by revegetation especially reforestation the climate driven sediment yield decreased by 951 t km 2 yr 1 during period ii and 505 t km 2 yr 1 during period iii in comparison with period i the dominant cause of the sediment yield reduction was lucc with the contribution increasing from 73 in period ii to 92 in period iii this study provides a greater understanding of the effects of climate variation and lucc on sediment yield and is beneficial for better catchment management

quantitative analysis of factors controlling sediment yield in mountainous watersheds abstract sediment and turbidity are primary causes of impaired river ecosystems remedial action for these impairments requires the identification of their sources and controlling factors this paper examines the combined effects of watershed complexity in terms of land use and physiography on the specific sediment yield of the upper du river watershed 8973 km2 in china the land use composition land use pattern morphometric variables and soil properties of the watershed were calculated at the subwatershed scale and considered to be potentially influential factors because these watershed characteristics are highly codependent a partial least squares regression plsr was used to elucidate the linkages between the specific sediment yield and metrics composed of 19 selected watershed characteristics the first order factors were identified by calculating the variable importance for the projection vip the results revealed that the land use composition and land use pattern exerted the largest effects on the specific sediment yield and explained 65 2 of the variation in the specific sediment yield a set of physiographic indices was also found to have a large effect on the specific sediment yield and explained 17 7 of the observed variation in the specific sediment yield the following are the dominant first order factors of the specific sediment yield at the subwatershed scale the areal percentages of agriculture and forest patch density value of the shannon s diversity index contagion value of the hypsometric integral and saturated soil hydraulic conductivity the watershed size exerted a substantial effect on the sediment delivery ratio sdr the vip values also suggested that the shannon s diversity index contagion and hypsometric integral are important factors in the sdr with a readily available digital spatial database and rapid developments in geographic information system gis technology this practical and simple plsr approach could be applied to a variety of watersheds

spatial and temporal variation of sediment yield in the landscape example of huanghe yellow river regional scale relations between specific sediment yield and drainage basin area in the huanghe basin reveal varying landscape sedimentary dynamics declining specific sediment yield with area is typical of disturbed agricultural areas while increasing yields indicate the remobilization of stored sediment by bank and floodplain erosion along major tributaries using the developed relations areally adjusted sediment yield maps are created over the entire huanghe basin maps of the loess plateau for periods before and after 1970 reveal major changes in sediment yield indicating that land management may have a major effect on sediment dynamics within a short period of time copyright 2008 by the american geophysical union

fragmentation model of the grain size mix of sediment supplied to basins abstracta key factor in the downstream dispersal and fractionation of sediment is the grain size distribution of sediment supplied by upstream catchments modeling of the grain size distribution of modern bedload in the main trunk channels of tectonically uplifting catchments including the sediment at their outlets and the weathering products of a range of bedrock lithologies in southern italy and sicily reveals fractal dimensions of 2 3 2 7 similar to the fractal dimension of many natural materials undergoing fragmentation we examine the impact of changing statistical properties of the grain size distribution of the sediment supply in simulating grain size trends in sedimentary basins model simulations show a marked movement of the gravel front and patterns of progradation and retrogradation in basin stratigraphy these grain size trends and sedimentary architectures are generated simply by variations in the grain size mix of the sediment supply without variations in base level or sediment discharg

effects of lithology and geomorphology on sediment yield in karst mountainous catchments abstract due to the characteristics of the lithology and the complexity of the geomorphology the karst areas of southwest china are experiencing severe soil erosion knowledge of the effects of lithology and geomorphology on sediment yield are therefore essential for developing measures to effectively control sediment delivery in this region the objective of this study was to investigate the relative importance of lithological and geomorphological factors for sediment yield in 40 selected karst mountainous catchments in southwest china because of the high co dependence of these variables a partial least squares regression plsr model was used to explore the quantitative relationships between annual sediment yield and 30 lithological and geomorphological factors results showed that the lithology and geomorphology were critically important to annual sediment yield and could explain 65 9 of the total variance in sediment yield the dominant lithological and geomorphological factors controlling annual sediment yield were karst coverage drainage density basin relief plane curvature elevation maximum elevation average slope dolomite coverage relative relief and catchment area this importance or these contributions of lithological and geomorphological factors to annual sediment yield provides a good reference for selecting key factors when developing soil erosion models this study yields a greater understanding of the influences of lithology and geomorphology on sediment yield and is helpful for better catchment management in karst regions

research paperseffect of stone content on water flow velocity over loess slope frozen soil soils in high altitude or latitude regions are commonly rich in stone fragments which are frequently frozen the hydrodynamics of water flow over frozen stony slopes must be investigated to understand soil erosion and sediment transportation the objective of this laboratory experiments was to measure water flow velocity over frozen slopes with different stone contents by using electrolyte trace method the experiments were performed under slope gradients of 5 10 15 and 20 flow discharge rates of 1 2 4 and 8 l min and stone contents of 0 10 20 and 50 on mass basis nine equidistant sensors were used to measure flow velocity along flume from the top of the slope results indicated that stone content significantly affected flow velocity under increasing slope gradient the increase in stone content rapidly reduced the flow velocity the flow velocities over frozen slopes were 1 21 to 1 30 times of those over non frozen slopes under different slope gradients and flow rates when the stone content increased from 0 to 20 proportions gradually decreased from 52 to 25 and 13 additionally flow velocities over frozen and non frozen soil slopes became gradually similar with increasing stone content this study will help elucidate the hydrodynamics soil erosion and sediment transport behaviors of frozen or partially unfrozen hillslopes with different stone contents

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

microstructural control of quartz sand grain shape and texture implications for the discrimination of debris transport pathways through glaciers abstract previous studies of the surface textures of glacially transported quartz sand grains have rarely distinguished between the influence which quartz grain microstructure and transport history independently exert on the appearance of grains in this paper we identify two distinct categories of quartz sand grain both of which can be found in subglacial and supraglacial debris translucent grains are derived from monocrystalline quartz which is largely free of dislocation structures while opaque grains are derived from polycrystalline quartz which displays a wide range of dislocation structures whilst subglacially derived grains show no differences in terms of their angularity fourier shape or surface texture from supraglacially derived grains of the same category translucent grains from both environments are consistently more angular and less rough than opaque grains and their surfaces are delimited primarily by planar fractures rather than blocky surfaces these differences in the appearance of translucent and opaque grains appear to reflect the manner in which the process of brittle fracture operates on undeformed and deformed quartz microstructure may therefore exert a greater influence on the appearance of glacially transported quartz sand grains than their specific transport history

spatially distributed erosion and sediment yield modeling in the upper indus river basin 1 spatially distributed erosion rates and sediment yields are predicted in the mountainous upper indus river basin with coupled models of erosion and sediment delivery potential erosion rates are calculated with the thornes model in combination with a surface runoff model sediment delivery ratios sdrs are hypothesized to be a function of travel time of surface runoff from catchment cells to the nearest downstream channel modeled monthly erosion rates for the upper indus river basin indicate that 87 of the annual gross erosion takes place in the three summer months the erosion risk map suggests that the areas with the greatest erosion potential are concentrated in subbasins with high relief and a substantial proportion of glacierized area lower erosion rates can be explained by the arid climate and low relief on the tibetan plateau and by the dense vegetation and lower relief in the lower monsoon subregion high erosion rates 1 0 mm a 1 occur over 66 4 of the basin area the model predicts an average annual erosion rate of 3 2 mm a 1 or 868 mt a 1 which is approximately 4 5 times the long term observed annual sediment yield of the basin the predicted annual basin sediment yield is 244 mt a 1 which compares reasonably well to the measured value of 195 1 mt a 1 the overall sediment delivery ratio in the basin is calculated as 0 28 model results indicate that higher delivery ratios sdr 0 6 are found in 18 of the basin area mostly located in the high relief subbasins the sediment delivery ratio is lower than 0 2 in 70 of the basin area the indus subbasins generally show an increase of sediment delivery ratio with basin area model evaluation based on accuracy statistics suggest very good to satisfactory performance ratings for predicted sediment yields the presented modeling framework requires relatively few data all of which can be derived from global data sets it therefore can be used to predict erosion and sediment yield in other ungaged or poorly gaged drainage basins

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

fabric signature of subglacial till deformation breidamerkurjokull iceland the foreland of breidamerkurjokull iceland is the only locality where tills known to have undergone subglacial deformation are exposed till on the foreland has a two tiered structure consisting of a dilatant upper horizon c 0 5 m thick and a compact lower till these horizons correspond to the ductile deforming a horizon and the brittle ductile b horizon observed below the glacier by g s boulton and co workers the relationship between known strain history and a variety of macrofabric elements is examined for these two genetic facies of deformation till the upper horizon exhibits variable a axis fabrics and abundant evidence for clast re alignment reflecting ductile flow and rapid clast response to transient strains in contrast the lower horizon has consistently well organized a axis fabrics with a narrow range of dip values recording clast rotation into parallel with strain axes during brittle or brittle ductile shear the data indicate that till strain history imparts identifiable macrofabric signatures providing important analogues to guide the interpretation of pleistocene tills

a sedimentological and isotopic study of the origin of supraglacial debris bands kongsfjorden svalbard hubbard b glasser n f hambrey m j etienne j l 2004 a sedimentological and isotopic study of the origin of supraglacial debris bands kongsfjorden svalbard journal of glaciology 50 169 157 170 rae2008

embankment dam on liquefiable foundation dynamic behavior and densification remediation earthquake induced liquefaction is a major concern for embankment dam safety many liquefaction induced earth embankment failures or near failures have been reported around the world during various earthquakes such embankment damages were particularly destructive when the underlying saturated granular soils liquefied resulting in cracking settlement lateral spreading and slumping of the embankment through a series of four highly instrumented geotechnical centrifuge model tests seismic behavior of a zoned embankment dam with saturated sandy soil foundation was studied under moderate earthquake conditions the beneficial effects of foundation densification were investigated valuable insights into the dynamic behavior of the employed embankment foundation systems are provided test results suggest that there may be an optimum depth of densification treatment beneath an earth dam beyond which the reduction of the earthquake induced deformations are relatively minor and that relatively small and isolated zones e g at depth of loose material within a densified volume of soil may not impair the overall effectiveness of treatment and do not necessarily result in damaging displacements

treatment for a fully weathered rock dam foundation abstract the main dam at the upper reservoir of tianhuanping pumped storage power station is a rockfill dam with an asphalt concrete impervious lining on the upstream face it is constructed on a non homogeneous fully weathered rock foundation in this paper we present the case study on the treatment for this non homogeneous fully weathered rock dam foundation the treatment includes the partial excavation of the fully weathered rock in different depths with respect to the dam deformation and the enlargement of the transition curvature at the junctions of the inclined dam face and the reservoir floor as well as the reinforcement for the asphalt concrete impervious lining with a layer of polyester mesh at the parts where tensile strains of the lining are large a three dimensional 3d finite element analysis is carried out for the main dam to provide the basis for the proposed compound treatment method to account for the effect of the intermediate principal stress 2 on the deformation and strength of soils a simple constitutive soil model is proposed for the finite element fe analysis so far this project has operated well for more than 5 years without any maintenance for the main dam s asphalt concrete impervious lining illustrating the success of the treatment for the fully weathered rock dam foundation

measurement of rill and ephemeral gully flow velocities and their model expression affected by flow rate and slope gradient abstract water flow velocities in rill and ephemeral gully are useful for estimating hydrodynamics in the study on soil erosion laboratory experiments were conducted to measure erosive rill and ephemeral gully flow velocities including nine unit width flow rates of 0 17 0 33 0 67 1 33 2 67 5 33 10 67 21 33 and 42 67 10 3 m2 s 1 and five slope gradients of 8 7 17 6 26 8 36 4 and 46 6 on sandpaper slope glued with silt loam soil materials to imitate fixed rill and ephemeral gully beds using an electrolyte tracer method the flow velocities measured in this research ranged from 0 31 to 3 34 m s 1 for sediment free water flow the flow velocity fitted well with unit width flow rate and slope gradient by a power function yielding an improved model with higher coefficient of determination than that related flow velocity to flow rate alone the improved model is applicable for flow velocity and soil erosion predictions

the response of soil erosion and sediment export to land use change in four areas of europe the importance of landscape pattern the response of erosion and sediment export to past land use change has been studied in four agricultural areas of europe three of these areas were subject to land abandonment or de intensification and one to intensification of land use practices erosion and sediment yield were modeled using the watem sedem model which combines the rusle equation with a sediment routing algorithm spatial relationships between the rusle c factor i e land use and other erosion and sediment export determining factors slope soil erodibility and distance to rivers were investigated as these account for non linearity in the response of erosion and sediment export to land use change erosion and sediment export have decreased enormously in the de intensified areas but slightly increased in the intensively cultivated area the spatial pattern of land use change in relation to other erosion and sediment export determining factors appears to have a large impact on the response of soil erosion and sediment export to land use change that the drivers of abandonment of arable land and erosion coincide indicates that de intensification leads to a more favourable landscape pattern with respect to reduction of erosion and sediment export this mechanism applies not only within the study areas but also among the european study areas where the process of intensification of some areas and de intensification of others might result in an overall decrease of erosion and sediment yield through time c 2007 elsevier b v all rights reserved

construction of concrete faced rockfill dams with weak rocks constructing concrete faced rockfill dams cfrds with weak rocks has great advantages as a result of the use of local materials cost effectiveness extensive adaptability simple construction and short construction period however the behaviors of cfrds constructed with weak rocks are not well understood this paper reports the physical mechanical and hydraulic properties of weak rockfill during placement and compaction in three dam projects in china these properties were obtained from laboratory and field tests important considerations such as the control of crushing and crusting and the increase of the permeability of weak rocks are discussed numerical studies on the settlements and slope stability of the dams were conducted and their results were compared with the field measurements this study provides the opportunities for further understanding the behaviors of cfrds with weak rocks

on subglacial stone pavements in till four pavements from central and western canada display uneven pavement surfaces abundant tilted and inverted stones reversed lee ends fine crossing striae in various directions weak striae around curves worn facets distributed evenly on rounded stones and till fabric girdles collectively inconsistent with the popular concept of stones firmly held in till being abraded by overriding ice based on these data new models are offered that involve stone rotation in viscously deforming till to produce deformation pavements in the specific model increased pore water pressure under moving ice locally mobilizes previously formed lodgment and or erosional pavements into deformation pavements in the more general model stones released from the sole of a wet based glacier rotate interact and settle into a viscous suspension zone in deforming till according to velocity density and viscosity gradients stone axes and striae settle into various orientations following dewatering and till stiffening conceptu

particle and aggregate mobility in till microscopic evidence of subglacial processes abstract microscopic studies of tills show that the deforming bed of glaciers is made up of minute rotational elements or wheels consisting of a nucleus alone or a nucleus with spiralling arms of fine grains these fine grains can move from one wheel to the next providing a process of high grain mobility within a deforming subglacial till recognition of this process explains a variety of glacial distribution patterns i e the mineralogical reflection of subjacent lithologies in the till matrix the side by side occurrence of far travelled erratics and locally derived matrix and the shape of geochemical anomalies

the interpretation and classification of subglacially deformed materials abstract a general classification of subglacially deformed materials is proposed based on sediment properties and their relationship to styles of subglacial strain deformation till is defined as homogenized usually diamictic material formed by glacially induced shear of subsole materials three types are recognized type a formed by pervasive ductile deformation type b formed by brittle shear and comminution till produced by the reduction of void space by in situ crushing and abrasion the term glacitectonite is adopted for materials that have undergone subglacial shear but retain some of the structural characteristics of the parent material original structures may be truncated by glacitectonic fabric elements type a or distorted but not truncated type b the principles of strain and material response particle orientation mechanisms fabric development and drainage conditions are reviewed examples of deformation tills and glacitectonites from breidamerkurjokull iceland slettmarkbreen norway loch lomond scotland and east yorkshire england are used to illustrate the nature of subglacially deformed materials and their relationship to former subglacial strain and drainage conditions the geologic evidence suggests a continuum of bed strengths can be recognized in deforming substrata ranging from high strength low strain type b deformation till and comminution till to low strength high strain type a deformation till

factors controlling specific sediment yield in the upper indus river basin northern pakistan estimates of sediment yield are essential in water resources analysis modelling and engineering in investigations of continental denudation rates and in studies of drainage basin response to changes in climate and land use the availability of high resolution global environmental datasets offers an opportunity to examine the relationships between specific sediment yield sysp and drainage basin attributes in a geographical information system gis environment this study examines sysp at 14 long term gauging stations within the upper indus river basin twenty nine environmental variables were derived from global datasets the majority with a 1 1 km resolution the sysp ranges from 194 to 1302 t km 2 yr 1 for sub basins ranging from 567 to 212 447 km2 the high degree of scatter in sysp is greatly reduced when the stations are divided into three groups upper glacierized sub basins lower monsoon sub basins and the main indus river percentage snow ice cover lcs emerges as the single major land cover control for sysp in the high mountainous upper indus river basin a regression model with percentage snow ice cover lcs as the single independent variable explains 73 4 of the variance in sysp for the whole indus basin a combination of percentage snow ice cover lcs relief and climate variables explains 98 5 of the variance for the upper glacierized sub basins for the lower monsoon region a regression model with only mean annual precipitation p explains 99 4 of the variance along the main indus river a regression model including just basin relief r explains 92 4 of the variance in sysp based on the r2adj and p value statistics the variables used are capable of explaining the majority of variance in the upper indus river basin copyright 2007 john wiley sons ltd

spatial heterogeneity of soil detachment capacity by overland flow at a hillslope with ephemeral gullies on the loess plateau abstract ephemeral gullies are typical erosional landforms and widespread on the chinese loess plateau to better understand the spatial variability in soil detachment capacity dc by overland flow and its influence at a hillslope with an ephemeral gully this study investigates a hillslope on the loess plateau using classical statistics geostatistical analysis and principal component analysis undisturbed soil samples were collected from 202 sites along nine 90 m transects in two completely developed ephemeral gullies and were scoured in a laboratory flume under consistent hydraulic conditions the results indicate that dc varied widely from 0 0004 to 1 25 kg m 2 s 1 with a mean of 0 22 kg m 2 s 1 the coefficient of variation also shows a high variability in dc the ephemeral gullies were divided into four sections uppermost upper middle and lower slopes and dc differed significantly among the four sections a semivariogram of dc indicated a moderate spatial dependence the sampling interval significantly affects the spatial pattern of dc when the sampling interval decreased from 10 to 2 m the nugget variance decreased whereas structured variance spatial dependence and range increased distribution maps of dc derived from kriging interpolation showed that samples in the lower slope position have greater dc than the other positions dc significantly correlates with clay content sand content median soil grain size bulk density cohesion water stable aggregate and litter mass density principal component analysis pca and a minimum data set mds method identified that the median soil grain size bulk density and litter mass density were the major factors affecting the spatial variability in dc

numerical analysis of the causes of face slab cracks in gongboxia rockfill dam abstract there are face slab cracks on the gongboxia concrete face rockfill dam cfrd which is located on the yellow river in china they generally occur as vertical cracks at the top of the panel near the water level the region where gongboxia cfrd is located is subjected to low temperatures during the winter months and high temperatures during the summer months also this region experiences large temperature fluctuations during the day and night in this study the causes of crack formation in the face slabs of the dam are numerically analyzed from the perspective of structural and temperature induced stresses the results show that temperature induced stress is the main reason for the slab cracks on the gongboxia cfrd the structure induced stresses lead to more cracks in the steep dam section than in the riverbed dam section and the occurrence of vertical cracks are likely caused by slight variations in the water level

three dimensional analysis of water infiltration into the gouhou rockfill dam using saturated unsaturated seepage theory the gouhou dam was a concrete faced rockfill dam built in a steep canyon that collapsed in 1993 due to internal erosion during the initial reservoir filling in this paper the process of water infiltration into the originally unsaturated rockfill dam is studied using three dimensional saturated unsaturated seepage theory the three dimensional characteristics of seepage through the dam bounded by steep abutments the effect of material anisotropy and the effect of rockfill stratifications are studied the three dimensional results are compared with those from two dimensional analyses the three dimensional simulations show that seepage water flows faster and the hydraulic gradients are greater near the abutment boundary in the dam as such the evolution of the seepage failure in the three dimensional cases is faster than that in the two dimensional analyses and the two dimensional analyses will underestimate the risk of seepage failure particularly near the abutment boundary if the materials in the

a hypothesis on the relative roles of crushing and abrasion in the mechanical genesis of a glacial sediment relatively new techniques of optical microscopy and interferometry have been used combined with fractal and modal analyses to study possible deformation mechanisms in glacial sediment from langjokull iceland previous studies have shown that the langjokull till has reached an ultimate grading during deposition and transport the results presented here add information on the deformation mechanisms that it may have suffered until and after reaching this ultimate grading the modal and fractal analyses suggest high mechanical weathering this is supported by the shape and texture of particles determined using the different imaging techniques of laser scanning optical microscopy combined with three dimensional image construction interferometry and scanning electron microscopy the larger particles have highly weathered surfaces indicating severe abrasion to their surface during transport the finer particles show less abrasion stamp and higher angularity they also bear evidence of relatively fresh fractures this seems to indicate that as the sediment became better distributed during transport breakage moved from the larger to the smaller particles with the larger grains only suffering abrasion this supports the hypothesis of fractal breakage in this type of soil

experiments on the dynamics and sedimentary products of glacier slip abstract experimental work in glacial geomorphology is focused almost entirely on processes in the thin shear zone at the beds of sliding glaciers where ice at its pressure melting temperature moves over either rigid rock or deformable till experiments with rotary shear devices illuminate constitutive behavior there central to the dynamics of fast moving glaciers and provide a foundation for interpreting the sedimentary record of glacier slip and associated sediment transport results from experiments designed to study ice sliding over a rigid wavy bed shear deformation of till and plowing of clasts across the surface of a till bed point to a common conclusion drag at the bed can decrease with increasing slip velocity thereby concentrating driving stress elsewhere and promoting rapid glacier flow this rate weakening behavior at glacier beds is in contrast to the viscous slip resistance assumed in ice sheet models and most efforts to determine distributions of basal drag from glacier surface velocities ring shear experiments in which various basal tills and more idealized materials are sheared to high strains provide quantitative insight into grain size evolution mixing at contacts between basal tills microstructure development particle fabric development and development of anisotropy of magnetic susceptibility preferred orientations of principal magnetic susceptibilities provide the most dependable and complete description of till shear patterns when applied to basal tills of the geologic record magnetic till fabrics measured along thick till sections and calibrated experimentally indicate that deformation of the bed by two lobes of the laurentide ice sheet was shallow

fluted moraine formation and till genesis below a temperate valley glacier slettmarkbreen jotunheimen southern norway clast fabric and morphological data have been used to determine the origin of fluted subglacial tills exposed by recent retreat of the slettmarkbreen glacier norway a new method for the interpretation of clast fabric data allows aspects of the strain and depositional history of the till to be reconstructed the till formed by a combination of lodgement and subsole deformation by slip along discrete shear planes lodgement was dominant for the larger size fractions 125 mm while the smaller material was more susceptible to deformation the fluted till surface reflects the tendency for the till matrix to deform into regions of low confining pressure in the lee of lodged boulders downglacier components of till flow are thought to have resulted in significant sediment transfer towards the margin

pleistocene glacitectonic landforms and sediments around central magellan strait southernmost chile evidence for fast outlet glaciers with cold based margins abstract proglacial and subglacial glacitectonic sediments and landforms around the margins of the strait of magellan southernmost chile record the advance and retreat of outlet glaciers of the patagonian ice cap during the last glacial cycle the spatial arrangement of glacitectonic landforms in the area is inferred to have resulted from the advance of ice lobes with cold based margins and wet based interiors as the ice advanced subglacial basins were excavated beneath the glacier margins and the eroded material was pushed up into thrust moraines probably because frozen bed conditions formed a thermal dam against the free drainage of subglacial meltwater these ice marginal glacitectonic landforms were then overridden and streamlined into drumlins and flutes as thicker wet based ice passed over the area evidence for permafrost near sea level in patagonia during the last glaciation suggests that mean annual temperatures were several degrees lower than indicated by recent modelling studies the results indicate that future modelling experiments should incorporate more realistic basal boundary conditions particularly the presence of a weak deforming layer at the glacier bed to improve climatic reconstructions of southern south america

analysis of factors determining sediment yield variability in the highlands of northern ethiopia in many developing countries sustainable land management and water resources development are threatened by soil erosion and sediment related problems in response to such threats there is an urgent need for improved catchment based erosion control and sediment management strategies the design and implementation of such strategies require data on erosion rates and understanding of the factors that control the delivery of sediment through the catchment system in this study reservoir sedimentation and corresponding catchment attribute data were used to investigate the major factors controlling sediment yield variability in a mountainous dryland region of northern ethiopia sediment yield data were acquired for representative 11 catchments above reservoirs geomorphological and anthropogenic catchment attributes were extracted for each reservoir from different sources including digital elevation models satellite images and field surveys different statistical analyses such as pearson s correlation principal components and multiple regression were implemented to analyze the relationship between sediment yield and catchment characteristics and to determine the major factors controlling the variability of sediment yield the results show that terrain form gully erosion surface lithology and land cover explain most of the variability in sediment yield among the catchments the implications of the results for relevant management intervention targeted at ameliorating the major causative factors of erosion are also outlined

geomorphological consequences of a glacier advance across a paraglacial rock avalanche deposit abstract glacial reworking of paraglacial rock slope sediment has been inferred from long deglaciated terrains to contribute significantly to glacial sediment transfer at feegletscher switzerland we provide the first description of the geomorphological consequences of glacier advance across paraglacial rock avalanche sediment this produced a small arcuate end moraine that encloses a zone of hummocky debris the sedimentology of these landforms is conditioned by rock avalanche sediment and can be differentiated from purely glacial sediments indicating that the contribution of glacially reworked rock avalanche debris may be recognisable in deglaciated terrain remarkably much of the overridden rock avalanche debris has maintained its angularity and delicate brecciation features despite up to 40 years of glacial action we suggest that the surface carapace facies of the rock avalanche deposit comprising large openwork blocks limited the effectiveness of glacial erosion processes the carapace facies will have resisted significant erosion by the relatively thin glacier because of its high shear strength and because it was able to transmit subglacial meltwater efficiently thus enhanced debris transfer associated with reworking of paraglacial rock avalanche sediment should not necessarily be expected during the initial stages of glacier advance

grain textural analysis across a range of glacial facies a technique proposed by hooke and iverson 1995 to identify deformed subglacial sediments is reviewed and tested based on two main objectives first an investigation of whether the fractal dimension can distinguish between non deformed and deformed facies for which we compare supraglacial and subglacial facies explicitly second an evaluation of whether the fractal dimension can be used as a diagnostic criteria to discriminate between different styles and degrees of basal deformation this is tested using a range of sediments from the deformation continuum suggested by hart and boulton 1991b sixteen subglacial samples were selected from quaternary sites in england and three supraglacial samples from the modern haut glacier d arolla switzerland the mean fractal dimension for the subglacial diamicton matrix facies was 2 92 similar to findings of 2 90 by hooke and iverson 1995 for their basal tills the supraglacial facies displayed a mean fractal dimension of 2 83 which is unusually high for facies which are assumed to be undeformed a mann whitney u test showed that fractal dimensions of supraglacial and subglacial diamicton matrix facies were not significantly different no significant difference was found between the fractal dimensions of the different tectonic facies within the subglacial group it may be impossible to separate the subglacial and supraglacial facies because of complex debris paths within the glacier grain fracture or parent lithology may affect the particle size distribution of subglacial facies

modelling time dependent behaviour of murro test embankment this paper investigates the time dependent behaviour of murro test embankment in finland the embankment was built in 1993 on a soft natural clay deposit which exhibits large strain anisotropy destructuration and viscosity the study is based on extensive experimental data from triaxial and oedometer tests on intact and reconstituted soil samples which shed light on the influence of time on mechanical properties including testing designed for studying soil anisotropy and destructuration the interpretation of the results is done in the framework of a recently developed elasto viscoplastic model evp sclay1s which is used to simulate the soft soil deposit coupled with biot s consolidation theory the determination of model parameters from the test results demonstrates that the model can be relatively easily used for practical applications using these parameters two dimensional finite element analyses have been made as large deformation analysis the comparisons between calculations and measurements de

fully coupled dynamic analysis of an earth dam the paper studies the seismic behaviour of an existing homogeneous earth dam using a fully coupled finite element effective stress approach in conjunction with a recently developed multi surface elasto plastic constitutive model for structured soils the model is calibrated using laboratory test results for the embankment material and the foundation soils the initial state variables stress hardening parameters are determined by simulating a simplified geological history of the foundation soil dam construction stages and reservoir impounding prior to the application of the earthquake shaking at the bedrock level the paper critically reviews the role of the constitutive model parameters the hysteretic damping introduced by the model and the additional viscous damping parameters in the accumulation of permanent displacements and in the development and subsequent dissipation of excess pore water pressures due to the seismic loading the analyses carried out with reference to a set of earthquake reco

a case study on the post construction deformation of concrete face rockfill dams concrete face rockfill dams cfrds are considered to be fundamentally safe especially against leakage and to be a low cost alternative at many sites their design is based on empirical experienc

a statistical review of the behaviour of concrete face rockfill dams based on case histories the concrete face rockfill dam cfrd has become a preferred dam type but its design remains largely based on past experiences understanding the behaviour of cfrds is critical to the design and s

sedimentary processes at the base of a west antarctic ice stream constraints from textural and compositional properties of subglacial debris samples of sediments from beneath ice stream b at camp upb west antarctica provide the first opportunity to study the relationship between sediment properties and physical conditions in a sub ice stream environment piston coring in holes bored by hot water drilling yielded five 1 3 m long undisturbed subglacial sediment cores we analyzed granulometry composition and particle morphology in these cores the upb cores are composed of a clay rich unsorted diamicton containing rare marine diatoms sedimentary particles in these cores bear no evidence of the recent crushing or abrasion that is common in other subglacial sedimentary environments the presence of reworked diatoms and their state of preservation as well as the relative spatial homogeneity of this diamicton suggest that the upb cores sampled a several meter thick till layer and not in situ glacimarine sediments the till does incorporate material recycled from the subjacent poorly indurated tertiary glacimarine sediments of the ross sea sedimentary basin which extends beneath this part of the west antarctic ice sheet we propose that the lack of significant comminution in the upb till is ultimately due to its setting over these easily erodible clay rich source sediments the resulting fine grained till matrix inhibits glacial comminution because it facilitates buildup of high pore water pressures and hinders interparticle stress concentrations our observations are consistent with the conjecture that subglacial deformation of weak fine grained tills does not produce significant comminution of till debris elson 1988 based on our findings we hypothesize that extensive layers of weak till may develop preferentially where ice overrides preexisting poorly indurated fine grained sediments since such weak till layers create a permissive condition for ice streaming sub glacial geology may have an indirect but strong control over the location extent and basal mechanics of ice streams

deformation till in the great lakes region implications for rapid flow along the south central margin of the laurentide ice sheet structural and lithologic data indicate that while deposited under actively moving ice considerable portions of three muddy calcareous subglacial tills in the great lakes region probably experienced some component of ductile deformation viscous till flow and ductile shear are invoked to explain a combination of features such as recumbent isoclinal folds unlithified sediment clasts mixed ostracode shells reversed stone lee ends girdle and transverse fabrics irregular stone pavements fine striae following stone curves and inconsistent stone striae and a axes deforming fine textured subglacial till is considered as a subhorizontal shear zone rheologically layered with associated structures in descending order ductile e g isoclinal folds brittle ductile e g fissility and brittle e g till wedges rheology would be controlled mainly by till pore water content matrix texture and stone content spatial and temporal superposition of rheologies and subglacial processes probably occur