karstification beneath dam sites from conceptual models to realistic scenarios summary dam sites and reservoirs located above soluble rock are often damaged by increased leakage through the sub surface within the life time of the structure the high hydraulic gradients driving the water through the fracture and fissure system of the bedrock have a strong impact on the aquifer evolution the increased permeability if not prevented leads to an imminent danger of high leakage rates breakthrough as well as a result the structural safety of the dam site itself is at risk past experience has shown that this may have large environmental and economical consequences for a better understanding of the evolution of karst aquifer systems in the vicinity of dam sites a three dimensional conceptual model is presented we show the evolution of the karst aquifer for simple three dimensional dam site setups keeping the symmetry and simplicity of the models we can relate our results to the two and one dimensional scenarios presented in the past implementing a statistical fracture network and topographic information to this basic setup we show that these complex three dimensional properties of the real aquifers have a significant influence on the karstification and cannot always be addressed by two and one dimensional models

soil hydraulic properties of two loess soils in china measured by various field scale and laboratory methods abstract knowledge of hydraulic properties is essential for understanding water movement in soil however very few data on these properties are available from the loess plateau of china we determined the hydraulic properties of two silty loam soils on agricultural land at sites in mizhi and heyang in the region undisturbed soil cores were collected from seven layers to one meter depth to determine saturated hydraulic conductivity soil water retention curves and unsaturated hydraulic conductivity by the hot air method additional field methods internal drainage and guelph permeameter were applied at the heyang site to compare differences between methods soil water retention curves were flatter at mizhi than at heyang water contents at saturation and wilting point 1500 kpa were higher at heyang than at mizhi however unsaturated hydraulic conductivity was lower at heyang than at mizhi with maximum differences of more than six orders of magnitude nevertheless the two soils had similar saturated hydraulic conductivities of about 60 cm day 1 comparison between the methods showed that soil water retention curves obtained in the laboratory generally agreed well with the field data field saturated conductivities had similar values to those obtained using the soil core method unsaturated hydraulic conductivities predicted by the brooks corey model were closer to field data than corresponding values predicted by the van genuchten model

contribution of entrainment and vertical plumes to the winter cascading of cold shelf waters in a deep lake observations made from vertical moorings of thermistors and current meters are used to analyze the relative contribution of the entrainment of overlying water and the cold plumes convecting from the surface to the cascade of dense shelf waters down the sides of lake geneva assuming a steady state and ignoring the effects of the earth s rotation a simple model was introduced and 25 individual slugs of gravity currents were analyzed the average drag coefficient which includes the effects of friction on the slope and the interface between the gravity current and the ambient water is found to be equal to c d 4 6 1 5 x 10 3 the volume flux in the gravity current increases with downslope distance a consequence of both the entrainment of water into the gravity current and the supply of cold water from the plumes entrainment was found to be on average 1 9 0 9 times the contribution of vertical plumes suggesting that the latter may be important in the dynamics of the cascade

easter microplate evolution geochemical evidence confirms that there is current active spreading on both the east and west rift zones of the easter microplate and northwards propagation of the east rift with the active tip at 25 s the east rift is influenced by lateral flow of plume derived material from a hotspot located beneath either sala y gomez or easter island spreading rate variation does not seem to be influential in controlling the composition of erupted basalts

ferrobasalts from the spiess ridge segment of the southwest indian ridge highly vesicular microporphyritic basaltic rocks have been dredged from the slow spreading spiess ridge segment of the southwest indian ridge all the samples recovered are hyalocrystalline with plagioclase clinopyroxene and olivine as phenocryst and microphenocryst phases titanomagnetite occurs as euhedral microphenocrysts in some of the more evolved samples in terms of bulk rock and quench glass chemistry the lavas are characterised by highly evolved compositions e g feo 10 3 14 2 tio2 2 0 3 4 k2o 0 50 1 1 mgo 6 0 3 5 zr 160 274ppm nb 14 32ppm and can be classified as ferrobasalts isotopic and incompatible element ratios of the lavas e g 87sr 86sr 0 70325 0 70333 zr nb 8 4 11 3 y nb 2 3 1 4 indicate their strongly enriched nature see also dickey et al 6 quantitative major and trace element modelling indicates that most of the compositional variations observed can be attributed to low pressure fractional crystallisation of plagioclase clinopyroxene and minor olivine and titanomagnetite the range in composition can be accounted for by up to 65 fractional crystallisation we suggest that the extreme differentiation of the spiess ridge lavas is related not to spreading rate but to rate of magma supply the basaltic melts appear to have evolved in a newly established zone of magmatic activity associated with the most recent northward jump of the bouvet triple junction where they were effectively isolated from significant admixture of primitive magmas

a new method for determining the hydraulic aperture of rough rock fractures using the support vector regression abstract understanding fluid flow in rock fractures is relevant to many engineering applications including underground nuclear waste disposition oil and gas exploitation dam and slope design as well as contaminant transport rough rock fracture is usually idealized as two parallel plates separated by the hydraulic aperture the determination of which is key to solving seepage problems in fractured rock using the cubic law the mechanical aperture and fracture morphology are the main aspects affecting the hydraulic aperture here an innovative hydraulic aperture prediction equation for two dimensional fractures is established based on the mechanical aperture and fracture morphology six parameters were firstly selected to predict the hydraulic aperture including three mechanical aperture parameters and three fracture morphology parameters a training database was then established from numerical experiments of 300 fracture models which were built based on barton s 10 standard profiles and their combinations the numerical experiments were conducted with fluent software based on the database a hydraulic aperture prediction model was established using the support vector machine theory and the particle swarm optimization algorithm which was transformed into an explicit equation finally 20 natural fractures were used to validate the performance of this equation with the comparisons of four existing empirical equations the results show that this method worked well in predicting the hydraulic aperture this method provides an alternative and effective way to directly determine the hydraulic aperture using the geometry information of rough rock fractures

salman farsi dam reservoir a successful project on a karstified foundation sw iran the salman farsi dam is constructed on the ghareh aghaj river at the northern limb of changal anticline sw iran the anticline is composed of the calcareous asmari formation af sandwiched between two marly formations the pabdeh gurpi pgf and razak rf the af is divided into three units lower laf marl and limestone middle maf karstified limestone and upper uaf marl and marly limestone the dam is constructed on the maf and the reservoir is in direct contact with the maf uaf and rf a huge relict cave was discovered during excavation of grouting galleries in the maf in this research the potential leakage passage plp is defined as parts of the karst aquifer located lower than the normal water level nwl of reservoir in which the reservoir water has potential to be leaked toward downstream assuming no grout curtain construction the plp is composed of the inlet windows transfer passage and discharge zones at the salman farsi dam the plp is determined by three alternative schematic models considering hydrogeological and geological settings at this dam site the grout curtain was properly designed from the maf toward the downstream laf at the narrowest part of the plp and bypassing the huge cave the grout curtain was successful in blocking the plp based on the negligible leakage and high differences between water level in the pair piezometers at the upstream and downstream sides of the grout curtain it is recommended to determine the plp in future dam construction in karst terrains

spectral analysis of volcanic glass chemistry along the east pacific rise 13 23 s an analysis is presented for the variation in chemistry of 162 normal mid ocean ridge basalt glass groups collected with an average spacing of about 10 km along a 1100 km section of the east pacific rise between 13 and 23 s long wavelength periodicities have been determined for oxides al2o3 cao cr2o3 feo k2o mgo mno na2o nio p2o5 sio2 tio2 for ratios feo mgo k p and k ti for feo na2o and sio2 corrected for fractionation to 8 0 wt mgo and for bathymetry the data were modeled as the sum of a long wavelength periodic component and a residual random component the power spectrum of the periodic component was determined using the maximum entropy method the spectral phase of significant spectral peaks was determined by cross correlation with a cosine wave with the wavelength of the respective peaks in most cases the characteristics of the random component were found to be consistent with a normal distribution spatial aliasing considerations and the variance of the random component place confidence limits upon the spectral features the results of the spectral analyses indicate substantial correlation in the power spectra of the oxides the oxide data have spectral peaks with wavelengths in the vicinity of 575 and 225 km and a local minimum in spectral power at wavelengths between 300 and 500 km in general oxide components compatible in the crystallizing minerals olivine and plagioclase are approximately 180 out of phase with the incompatible oxides indicating that fractionation is an important process in controlling compositional variations along this portion of the east pacific rise unlike the fractionation sensitive oxide data periodic variations are not pronounced for k ti indicating that the length scales of mantle composition being melted are uncorrelated with those of magmatic temperature variation the analysis of fractionation corrected values of na8 0 and fe8 0 indicates that degree and depth of partial melting show a strong spectral peak near a wavelength about 430 km there is also significant power in the spectrum of na8 0 near 260 km and of fe8 0 near 200 km bounding the average spectral peak for the oxides at 225 km there appears to be strong coupling between the degree and depth of melting and magmatic temperature at two length scales around 225 km and 400 600 km corresponding to wavelengths of geoid undulations observed in the vicinity of the east pacific rise and suggesting a relationship with convection

saturated unsaturated flow through leaky dams this research investigated seepage flow through leaky dams using the well known finite element method different areas locations and hydraulic conductivities of leaks were examined an area of leak equal to 4 4 of the core area increased the seepage flow through the dam to be about 9 5 times the seepage flow through tight nonleaky core this happened for a dam having a downstream horizontal drainage filter when the drainage filter did not exist the increase of flow because of the same area of leak was about seven times the flow through a tight core when the leak existed at the centerline of the core in the out of plane direction its impact was slightly greater than when it existed at the edge of the core moreover as the location of the leak moved up vertically its impact was observed to be less it was also observed that when the leak existed in curtain wall driven into underneath the dam its impact was not significant compared with the case when it existed in the core

geochemical studies of abyssal lavas recovered by dsrv alvin from eastern galapagos rift inca transform and ecuador rift 1 major element variations in natural glasses and spacial distribution of lavas fifty three major element chemical analyses of volcanic glasses collected by alvin from the eastern gapalagos rift inca transform ecuador rift plate boundary are used to assess tectonic controls on petrogenesis and subrift magma chamber evolution these lavas span a compositional range that includes mid ocean ridge basalts morb feti basalts basaltic andesites and andesites this entire chemical spectrum of rocks was recovered on each of several dives within the eastern galapagos rift along short 2 km traverses of the seafloor at the axis of accretion this juxtapositon of chemically diverse lavas supports the idea that very small shallow level isolated magma bodies are the eruptive sources for fractionated accretionary lavas in this rift segment a distinct difference in chemical diversity occurs between two of the dives 1002 and 998 in the eastern rift lavas recovered east of the break exhibit high degrees of fractionation while rocks from west of this divide have only morb compo sitions this break occurs approximately 60 km west of the galapagos rift inca transform intersection and it is believed to mark an important east to west transition in subrift accretionary dynamics east of this break accretion is perturbed by transform cold edge plus attempted rift propagation effects while west of it a more stable accretionary environment large buffered magma chambers which erupt only morb spectrum lavas prevails only extremely fe and ti enriched lavas were recovered from the southern intersection of the inca transform with the galapagos rift the abundance of feti basalts at this locale is considered to be an effect of attempted rift propagation through thick cold nazca plate lithosphere rocks from the ecuador rift northern inca transform intersection have similar morb chemistries and are among the least fractionated basalts recovered from the cocos nazca plate boundary

global systematics of unaveraged mid ocean ridge basalt compositions comment on global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness by e m klein and c h langmuir

simple magma supply geometry inferred beneath a segment of the mid atlantic ridge the petrological characteristics of axial basalts along the global mid ocean ridge system shed light on the processes of magma supply involved in the formation of ocean crust several models of magma supply1 4 predict regular patterns of chemical variation along the strike of mid ocean ridge axes here we present chemical data from closely spaced samples of axial basalts from the mid atlantic ridge between the rio grande and moore fracture zones at 26 s this segment of the ridge is far from active hotspots and erupts normal mid ocean ridge basalt the samples show regular patterns of chemical variation along the ridge axis indicating systematic and correlated differences in depth and extent of partial melting and extent of shallow fractionation these patterns support the existence of a deep central supply system but preclude along axis melt migration and the presence of large well mixed chambers below this segment of the southern mid atlantic ridge

the geological problems of the large dams constructed on the euphrates river turkey abstract in order to use the energy and irrigation potential of the euphrates river a series of dams have been designed upstream to downstream keban karakaya karababa ataturk birecik and karkamis the first three of these dams have been completed construction on the birecik and karkamis dams is underway the initial plans involved a 60 m high golkoy dam downstream of the karakaya dam with the ataturk dam 60 m lower than it is currently in the belief that the cost of irrigation by the ataturk dam s water would be high the increase of the height of ataturk dam was preferred to the construction of the golkoy dam the keban dam s basement is formed by karstic rock named keban marble from the author and his colleagues studies it has been shown that water would leak from the left side of keban dam reservoir forming a spring in the keban creek in order to prevent this water leakage an intensive grouting programme was applied in spite of this when the reservoir was filled 26 30 m3 s of water leaked from the keban creek a more recent study on the volume of leakage showed it to be reduced to 7 8 m3 s with this amount remaining constant the karakaya dam is constructed on metamorphic rocks thus only allowing minimal water leakage however on the downstream side of the right slope the tillo bego senketo landslides have been an important risk to the dam if such landslides cause an artifical lake by blocking the euphrates river the karakaya hydroelectric power station could be flooded limestone forms the foundations for the ataturk dam on and around the damsite there is epithermal water 24 26 c below the aquifer deeper than 300 m with the level of the grouting curtain down to 180 200 m the grouting curtain would not be able to prevent the leakage because the level of karstification extends below the grouting curtain in february 1993 the total volume of leaking water from the damsite and its vicinity reached 10 m3 s when the reservoir level was 517 m when the reservoir is full 542 m the volume of leaking water is expected to increase under the clay core of the dam extending from the surface to 30 40 m depth high grouting pressure could not be applied so water leaked at this part of the grouting curtain and thus the amount of leaked water could not be measured

hydrogeochemical interpretation of water seepage through a geological barrier at a reservoir boundary a geological barrier such as a mountain ridge surrounding a large reservoir generally plays some part in preventing water leakage from the reservoir but water flows out naturally according to the hydraulic gradient because the reservoir water level is typically higher than that outside the hydrogeological geochemical and isotopic properties of water in the daechung dam area were analysed to characterize the source and the phenomenon of the groundwater flowing through the geological barrier our geochemical analysis showed that the concentrations of anions and cations tended to increase due to the longer residence time of the water as the distance between the sampling site and reservoir increased elevation differences calculated using oxygen and hydrogen isotopes between the highest and lowest sampling sites ranged between 350 and 420 m based on the altitude effect on isotope concentration but the actual difference was only 35 m these results including analysis of the rate of water seepage from the reservoir ca 2 3 to 14 4 of natural recharge indicate the possibility that groundwater in the study area originated from reservoir water that was derived from upstream water and rainfall in the high mountainous area of the upper watershed copyright 2013 john wiley sons ltd

magma supply in back arc spreading centre segment e2 east scotia ridge segment e2 is situated in the back arc east scotia ridge the segment is unusual in that it has an axial topographic high underlain by a seismically imaged melt lens the axis of the segment which is 70 km long was sampled at 2 km spacing there is strong correlation between compositions and bathymetry and there is no evidence that lateral flow of magmas along dykes within the segment was more than 25 km magmas are more evolved towards the summit indicating that magma fractionation took place within the imaged melt lens na8 0 is roughly constant at 2 6 implying uniform degree of partial melting except for some samples at the summit that have na8 0 2 2 compositions closest to n morb occur at the segment tips and lree hree ratios increase toward the summit none of the magmas were derived from depleted sub arc mantle nevertheless most compositions in the segment were modified by slab derived components the low na8 0 samples have high ba nb compared with the rest of the segment dredged lavas from the lateral flanks of the summit have the most extreme compositions including ones derived from plume mantle and are end members for magma mixing processes that controlled compositions

identification of sources and causes of leakage on a zoned earth dam in northern taiwan hydrological and isotopic evidence abstract seepage through an earth dam body must be regulated as a well planned process if it is not properly managed the abnormal seepage may cause dam failure this study employed stable isotopic and statistical methods to identify the source and cause of an abnormal leakage on the zoned earth dam of the xin shan reservoir located in northern taiwan water samples from the dam area over a 2 a period were collected and analyzed for their stable o and h isotope compositions in addition a 4 a period of hydrological data including rainfall reservoir level well level seepage of filter drainage and leakage were statistically analyzed with a stepwise multiple regression approach both the stable isotopic and hydrological results indicate that the abnormal leakage on the dam shell comes from the filter drainage in the dam the reason for abnormal leakage is due to unexpected and significant precipitation sourced water flowing into the dam s body the dam filter fails to drain out the incoming water sufficiently thus generating the abnormal seepage in addition the defect in the dam filter may also cause the drainage filter to drain off reservoir seepage inadequately therefore it is suggested that checking the filter function and preventing excessive precipitation sourced water from flowing into the dam are the two top priorities for the follow up remedial strategy of the dam

sequential tracer tests for determining water seepage paths in a large rockfill dam nakdong river basin korea the rockfill dam of this study has a clay core filter zone and sandy gravel shell and it is located in the nakdong river basin in korea filling the reservoir began in august 1994 and it was full by april 1998 when the reservoir level was approximately 150 m three settlement holes were found in the dam crest to determine possible seepage paths and potential damaged areas within the rockfill dam 15 tracer tests were performed during two periods during the two test periods six and nine tracer tests were conducted when the average water levels of the reservoir were 145 m and 142 m respectively rhodamine wt rwt and bromide ion were used as tracers for each test 1800 to 4000 l of tracer solution were injected into the riprap for about 5 h the 15 injection points were uniformly distributed from the right to left sides of the embankment and the two tracers were injected alternately tracer concentrations were monitored at 26 observation wells which were divided into four groups by their geographical positions right side of the crest left side of the crest right side of the dam toe and left side of the dam toe for each tracer test more than 30 water samples were taken during a period of 96 h at each observation well based the breakthrough curves obtained from the sequential tracer tests it was inferred that the most probable seepage paths and potential damaged area were in the left side of the crest tongue wing zone and to a lesser extent in the right side of the dam abutment

application of the mise a la masse method to detect the bottom leakage of water reservoirs abstract leakages of reservoirs are responsible for the loss of water resources and the spread of contaminants we develop a methodology to detect leaks located at the bottom side of a reservoir with the minimally invasive mise a la masse method which involves the potential electrodes located at the ground surface around the reservoir and the current source and sink placed in and out of the reservoir respectively this method allows localizing the secondary current distribution associated with leakage using the distribution of potential recorded on a set of electrodes during the mise a la masse experiment an initial model based on the distribution of root mean square values between the observation and the simulation data is first given to the inversion algorithm the tikhonov regularization which includes a weighting matrix and a minimum support function is used to strengthen the detection resolution of the leak 29 sandbox experiments show that the proposed method and inversion algorithm can localize a single leak for a leak with a crack shape the inversion algorithm detects the location of the leak with a small bias when the leak lasts a conductive zone may occur below the leak due to the increase of water content or ionic strength of the pore water the occurrence of such a conductive body could affect the localization of the leak because the conductivity distribution may not be well resolved the effect is analyzed using synthetic experiments the results show that the bias between the real leak and inversion results increases with the position and size of the undetected conductive zone two small scale field tests were conducted to test the performance of the mise a la masse method the two leaks are properly identified this study provides an efficient approach to detect the bottom leakage of reservoirs

chemistry of deep 3500 5600 m pacific morb why is the pacific anomalous in contrast with the atlantic and indian oceans the pacific shows the global correlations of axial depth and basalt chemistry only weakly or not at all for unaveraged data in the past this observation has been partly explained by the limited depth window of available pacific samples we report on new very young basalt samples collected by submersible from pacific ridges at 3500 5600 m nearly doubling the depth interval of pacific samples these samples from the pito deep hess deep and the garrett transform do not conform to the global correlation of depth vs chemistry and show the local trend of chemical variation the pacific as a whole is thus unusual compared to the atlantic and indian oceans we propose that the anomalous behavior of the pacific is due mostly to its relatively rapid spreading rate and tectonic shifts leading to an absence of a dynamic equilibrium between mantle temperature and seafloor depth observed elsewhere

axial depth anomalies from 10 to 50 north along the mid atlantic ridge correlation with other mantle properties abstract we present an analysis of intermediate to long wavelength a few hundred to a few thousand kilometers axial depth anomalies along the mid atlantic ridge between 10 and 50 n the maximum depth of the rift valley is chosen as the elevation datum for oceanic crust of zero age the large depth anomalies are correlated for short wavelengths less than a few hundred kilometers with some fracture zones irrespective of their offset and for intermediate to long wavelengths with mantle properties expressed in 1 excess elevation near triple junctions 2 trace element and isotope geochemistry of the basaltic liquids emplaced at the ridge axis and 3 anomalies in the earth s gravity field we suggest that the correlations may be explained in two ways the depth anomalies of intermediate to long wavelength may represent the sites of upwelling and downwelling of the deep mantle alternatively the depth anomalies could be due to a regionalization in temperature or mineralogy in the asthenosphere

the volcanic tectonic cycle of the famous and amar valleys mid atlantic ridge 36 47 n evidence from basalt glass and phenocryst compositional variations for a steady state magma chamber beneath the valley midsections amar 3 the 1978 amar expedition extended the investigation of the mid atlantic ridge that was begun by the 1973 1974 famous expedition from the northern end of the famous rift the original famous area to the narrow central and southern end of the famous rift narrowgate region and into the broad amar valley south of fracture zone b available field and geochemical data allow us to characterize in detail the volcanic tectonic cycle for these two segments of the mid ocean ridge system a dynamic model of the crust forming processes within these two rift valley segments is deduced from 1 variations in the chemical composition of the erupted basaltic liquids as preserved in chilled glassy margins 2 composition and petrographie relationships of megacrysts and phenocrysts that represent cumulus crystallization onto the floor of a shallow magma chamber of a primitive magma that has reached pyroxene saturation early in its evolution and 3 detailed stratigraphie and regional observations that characterize the periodicity of volcanic construction and superimposed tectonism related to the ongoing extension of the valley floor each volcanic cycle is composed of several eruptive episodes that are initially typified by rapidly extruded sheet flows of primitive composition the decreasing extrustion rates at the end of an eruptive event are associated with more evolved liquid compositions that reflect fractionation within the shallow conduits intermixing of magmas is indicated by the relatively limited variability in glass composition not explicable in terms of simple fractionation processes the common evidence of crystal resorption and the apparent disequilibrium between megacrysts phenocrysts and their enclosing glass this indicates control by a crustal magma chamber liquid and crystal compositions and textural relations can best be explained by a three stage crystallization history 1 crystallization of olivine plagioclase and clinopyroxene onto the floor of a magma chamber 2 partial resorption of mineral phases by a superheated undersaturated liquid above the floor 3 intratelluric crystallization of olivine and plagioclase clinopyroxene during rise of melt to the surface through the conduit system above the magma chamber a magma chamber model is suggested for the amar famous rift valleys that satisfies both seismic and geological constraints we propose that a small steady state magma chamber is maintained beneath the topographically higher midsections of each valley segment amar and narrowgate regions but that these thin and terminate near the intersecting fracture zones expansion and contracton of the central magma body is controlled by the fluctuating imbalance between magma supply and chamber crystallization the famous narrowgate rift is currently in a contraction period so that in the northern famous region primitive liquid has erupted at mount venus and mount pluto without intercepting and mixing into the steady state chamber that supplies the mixed magmas to the narrowgate region

analysis of rainstorm induced slide debris flows on natural terrain of lantau island hong kong abstract lantau island the largest outlying island of the territory of hong kong experienced a severe rainstorm on 4 5 november 1993 which induced 800 slope failures on natural terrain there detailed field investigations were carried out to study the failure modes in relation with various influencing factors it was found that the occurrence of slide debris flows has a close relationship with bedrock geology slope gradient vegetation cover and micro landform the failure modes of slide debris flows may be classified into translational slides and rotational slides and the former are predominant analysis of the hydrological response of colluvial slopes during the rainstorm indicated that the majority of the failures were caused by the development of a perched water table in the thin surface layer of colluvium of volcanic origin due to infiltration during the heavy rain undisturbed soil samples from south lantau have been subjected to anisotropically consolidated undrained compression tests at comparatively low stress levels constant deviatoric stress path tests cqd simulating the stress path in the field at in situ stress levels have been performed to investigate soil behavior the cqd test results indicate that the material of slopes at undisturbed state is brought to dilation because of the increase in pore water pressure caused by infiltration of rain water for a translational slide the displacement resulting from dilation may destroy cohesion along the failure surface and locally within the interior of the slide the surplus water during the intense rainstorm was able to equilibrate the reduction in pore pressure caused by dilation and the dilation and displacement may be further increased the strain softening after significant strains triggered debris flow mobilization however for a rotational slide the increase in pore water pressure caused by surplus water infiltration during the intense rainstorm could not equilibrate the reduction in pore pressure caused by dilation much or even all of the sliding block could not mobilize into a debris flow

dam sites in soluble rocks a model of increasing leakage by dissolutional widening of fractures beneath a dam abstract water flowing through narrow fissures and fractures in soluble rock e g limestone and gypsum widens these by chemical dissolution this process called karstification sculptures subterranean river systems which drain most of their catchment close to dam sites unnaturally high hydraulic gradients are present to drive the water impounded in the reservoir downstream through fractures reaching below the dam under such conditions the natural process of karstification is accelerated to such an extent that high leakage rates may arise which endanger the operation of the hydraulic structure model simulations of karstification below dams by coupling equations of dissolutional widening to hydrodynamic flow are presented the model scenario is a dam 100 m wide in limestone or gypsum the modelling domain is a two dimensional slice 1 m wide directed perpendicular to the dam it extends 375 m vertically and 750 m horizontally the dam is located in its center this domain is divided by fractures and fissures into blocks of 7 5 7 5 1 m the average aperture width of the fractures is 0 02 cm we performed model runs on standard scenarios for a dam site in limestone with the height h of impounded water 150 m a horizontal impermeable apron of width w 262 m and a grouting curtain reaching down to a depth of g 97 m in a second scenario we changed these construction features to g 187 m and w 82 m to calculate widening of the fractures well established experimental data on the dissolution of limestone and gypsum have been used as they occur in such geochemical settings all model runs show similar characteristic behaviour shortly after filling the reservoir exhibits a small leakage of about 0 01 m 3 s 1 which increases steadily until a breakthrough event occurs after several decades with an abrupt increase of leakage to about 1 m 3 s 1 within the short time of a few years then flow in the fractures becomes turbulent and the leakage increases to 10 m 3 s 1 in a further time span of about 10 years the widths of the fractures are visualized in various time steps small channels propagate downstream and leakage rises slowly until the first channel reaches the surface downstream then breakthrough occurs the laminar flow changes to turbulent and a dense net of fractures which carry flow is established we performed a sensitivity analysis on the dependence of breakthrough times on various parameters determining breakthrough these are the height of impounded water h the depth g of grouting the average aperture width a 0 of the fractures and the chemical parameters which are c eq the equilibrium concentration of ca with respect to calcite and the ca concentration c in of the inflowing water the results show that the most critical parameter is a 0 at fracture aperture widths of 0 01 cm breakthrough times are above 500 years for values of a 0 0 02 cm however breakthrough times are within the lifetime of the structure we have also modelled dam sites in gypsum which exhibit similar breakthrough times however after breakthrough owing to the much larger dissolution rates of gypsum the time until unbearable leakage is obtained is only a few years the modelling can be applied to complex geological settings as phreatic cave conduits below the dam or a complex stratigraphy with varying properties of the rock with respect to hydraulic conductivity and solubility a few examples are given in conclusion our results support the assumption that increasing leakage of dam sites may be caused by dissolutional widening of fractures

major element chemistry of galapagos rift zone magmas and their phenocrysts abstract basalts dredged from the galapagos rift zone between 85 w and 100 w were analyzed by electron microprobe to determine the chemistry of the glass exteriors and included phenocrysts microphenocrysts and quench minerals the basalts come from both normal mid ocean ridge segments and from ridge segments that cross the galapagos platform the basalts fall into two chemical and geographical groups group a basalts come from outside the central region of the galapagos platform i e outside 89 92 5 w and are chemically similar to basalts from normal ocean ridge segments group b basalts come from the center of the galapagos platform 89 92 5 w and are enriched in incompatible elements like plume influenced basalts from the mid atlantic ridge the spinel olivine plagioclase and clinopyroxene phenocrysts in both groups of basalts are low pressure equilibrium phases but the chemical difference among basalts from within each group indicates high pressure fractional crystallization is also responsible for the chemical evolution of some of these basalts presently no crystallization or partial melting model can relate the chemistry of the two groups of basalts and the compositional influence of a large ion lithophile elements and water rich mantle beneath the galapagos platform is a viable alternate hypothesis the eruption temperature of magmas from the normal ridge segments as determined by olivine liquid thermometry is 1217 10 c suggesting steady state conditions but on the galapagos platform the eruption temperatures are lower and more variable than on the normal ridge 1186 c 30 c suggesting a more complex plumbing system and the absence of a steady state magma chamber beneath the platform

identification of leakage and potential areas for internal erosion combining ert and ip techniques at the negratin dam left abutment granada southern spain abstract at the negratin dam southern spain two main springs derived from the water reservoir were detected on the west side of the mountain ridge matching the location of the left abutment of the dam the seepages appear when the level of the stored water exceeds 622 m above sea level m a s l where some paleochannels are embedded in the silts the water level was at 631 m a s l on the day of the measurements 13 12 23 close to the historical maximum 633 78 m a s l although the water crossing the leaks does not drag particles nowadays this sector may potentially cause internal erosion or piping phenomena implying a loss of water resources and slope instability problems the infiltration areas were evaluated by electrical resistivity and induced polarization methods measured along one profile on the mountain ridge between the water reservoir and the springs we determine that the infiltrations zones are characterized by low resistivity and high chargeability distributed in small areas we demonstrate that these methods are a reliable tool to detect and characterize infiltration zones and they are the first step to planning mitigation actions to avoid the piping phenomena

dynamical response to differential rates of temperature change over sloping topography lough corrib ireland 1 an enclosed water body subjected to a uniform surface heat flux exhibits differential rates of temperature change between shallow peripheral waters and adjacent deeper waters the result is the formation of horizontal temperature gradients in regions of sloping topography referred to as topographic temperature gradients ttgs an integrated observational and numerical study has been undertaken considering the impact of ttgs on the basin scale dynamics of lough corrib ireland temperature time series recorded during the winter of 2001 revealed sustained surface temperature gradients parallel to sloping boundaries cold dense water formed in peripheral regions of the lake cascaded down slope under the influence of gravity forming density plumes that extended over horizontal scales of kilometers plumes were typically 8 12 m thick and traveled down slope at speeds in the range 4 10 cm s 1 down slope cascading of cool water was typically initiated when the daily mean surface heat flux fell below 55 w m 2 meaning cascading occurred almost persistently throughout the period of seasonal cooling from early september until early january while cascading plumes exhibited a diurnal periodicity individual cascading events were linked to the passing of weather systems persisting for between 5 hours and 3 6 days the cascading of dense water formed an important mechanism for the transport of peripheral waters to depth greatly increasing rates of lake overturning and preventing stagnation during cool calm conditions the offshore transport owing to cascading was balanced by a weaker and more diffuse onshore flow within the upper 5 m of the water column quasi geostrophic alongshore currents evident in the modeled velocity field formed a basin scale anticyclonic gyre during calm conditions

controlling factors of loess landslides in western china based on detailed field data from recent geo hazards surveys in the loess plateau region of western china this study analyzes the key factors that control loess landslides the evolution phase of river valleys the geological structure of slopes and the geometry of slopes are all found to play a role in determining the occurrence distribution and other characteristics of loess landslides groundwater and vegetation also contribute to their formation a combination of human engineering activities and precipitation events are the principal triggering factors for the instability of loess slopes

soil deformation measurement using particle image velocimetry piv and photogrammetry a deformation measurement system based on particle image velocimetry piv and close range photogrammetry has been developed for use in geotechnical testing in this paper the theory underlying this system is described and the performance is validated digital photography is used to capture images of planar soil deformation using piv the movement of a fine mesh of soil patches is measured to a high precision since piv operates on the image texture intrusive target markers need not be installed in the observed soil the resulting displacement vectors are converted from image space to object space using a photogrammetric transformation a series of validation experiments are reported these demonstrate that the precision accuracy and resolution of the system are an order of magnitude higher than previous image based deformation methods and are comparable to local instrumentation used in element testing this performance is achieved concurrent with an order of magnitude increase in the number of meas

volatiles in basaltic glasses from the east pacific rise at 21 n implications for morb sources and submarine lava flow morphology pillow rim glasses from a suite of moderately evolved lavas erupted along the axis of the east pacific rise epr at 21 n were analyzed by high temperature mass spectrometry for volatile content concentrations of h2o f and cl in the 21 n glasses are low and correlate inversely with mg yielding well defined trends these and other geochemical data indicate derivation of the 21 n glasses from similar parental magmas produced from a highly depleted nearly homogeneous source 1 total volatile h2o f and s contents are lower and co2 content is somewhat higher in these samples than in previously analyzed mid atlantic ridge mar glasses 21 n glasses are similar in volatile content to glasses from the galapagos spreading center gsc at 95 w except in cl lower and co2 higher unlike most mar and gsc glasses co2 is the dominant volatile in all of the 21 n glasses with mg 62 all of the epr and gsc glasses contain reduced carbon species co and ch4 unlike most previously analyzed mar samples these data indicate that sources for mid ocean ridge basalts are extremely volatile poor 0 10 wt and are probably dominantly reduced below quartz fayalite magnetite buffer sheet flow and pillow basalts contain identical volatile contents thus volatile abundance is not a factor controlling flow morphology extrusion rate and or surface topography are probably the most important factors influencing flow morphology in submarine basalts h2o release patterns are however related to flow morphology mass pyrograms for sheet flow and pillow basalt glasses both show bimodal h2o release behavior at the same temperatures 800 c and1000 c 50 c however the dominant h2o release peak for sheet flow glasses is at the lower temperature for pillow rim glasses it is at the higher temperature infrared spectroscopic studies indicate that h2o in these glasses is present only as hydroxyl groups thus the cause of differences in the bimodal h2o release and how it is related to flow morphology is unclear

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

galapagos hot spot spreading center system 1 spatial petrological and geochemical variations 83 w 101 w we report on the petrology and geochemistry of basalts dredged at 40 50 km intervals along the galapagos spreading center between 83 sup 0 w and 101 sup 0 w 40 stations emphasis is on spatial variations of whole rock major elements rare earths trace metals of the first transition series and the nature of phenocryst assemblages and their abundances these results provide new constraints on the nature and scale of mantle source heterogeneities melting conditions thermal field and dynamics of crustal formation of the region we suggest that ridge segments outside the high magnetic amplitude zone are at a steady state as a result of passive seafloor spreading basalts from these segments are apparently derived from an asthenosphere relatively uniformally depleted in incompatible elements which appears of worldwide extent we reject vogt and deboer s 1976 model invoking damming at fracture zones of subaxial asthenosphere flow of crystal slushes and increasing fractional crystallization down the flow line because this model would not explain the gradients in ree observed about the galapagos platform our preferred model combines the mantle plume binary mixing model of schilling 1973 with the concept of recurring rift propagation proposed by hey 1977a we further propose that pulsating mantle plume flux perhaps inmore the form of a chain of blobs may initiate the development of new rifts and their propagation the present position of the tips of such new propagating rifts locate the wave fronts of such pulsating mantle plume flow a two million year period is suggested for the last 4 m y from wilson and hey s 1979 information rigorous testing of our preferred model is possible less

s wave velocity basalt chemistry and bathymetry along the mid atlantic ridge major element chemistry of mid ocean ridge basalt s wave velocity and bathymetry along the mid atlantic ridge are correlated on an intermediate length scale and the large anomalies in these observations are associated with hotspot locations the best correlations are for at depths of 100 200 km and there is no correlation for depths of 300 km or deeper s wave velocities are low directly under the mid atlantic ridge above 100 km but the low velocity regions shift away from the ridge at greater depth and a sinuous strip of asthenospheric low velocity extends along the atlantic hotspots from the azores to tristan da cunha these features suggest that common physical processes in the upper mantle produce these anomalies an inspection of the history of the atlantic ocean suggests that the asthenospheric low velocity strip may record earlier ridge position or possible upwelling in the mantle possible interaction between hotspots and the ridge blurs the distinction between passive and active upwellings

karstification beneath the birs weir in basel switzerland a 3d modeling approach we present a three dimensional model describing the evolution of a gypsum karst aquifer along the birs river near basel in switzerland here a small dam site was built in 1890 to generate hydro electric power after subsidence of a nearby highway geophysical and geological field studies have been carried out and a detailed hydrogeological model has been developed these observations identified a karstified weathered zone as the reason for the subsidence to prevent any further damage remedial construction measures have been carried out we employ our numerical model karstaquifer which simulates the temporal evolution of a karst system by dissolution increasing the porosity in the aquifer we used results from geological and geophysical investigations as a priori information for implementing the initial boundary conditions into our three dimensional numerical model our model accounts for topography precipitation and geology and especially for the anisotropy of the local bedrock it can successfully reproduce the weathered zone in its current horizontal and vertical extent we cm also simulate the possible evolution of the aquifer following a remedial construction phase therefore taken together with the geophysical and geological observations and the groundwater model our three dimensional karst aquifer evolution model enhances the understanding of the development of this heterogeneous karst aquifer system c 2012 elsevier b v all rights reserved hydrogeologie der nordwestschweiz grundwasser

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

submersible observations at the axis of the ultra fast spreading east pacific rise 17 30 to 21 30 s abstract manned submersible observations conducted with the diving saucer cyana at the axis of the east pacific rise at four sites near 21 30 21 10 18 30 and 17 30 s demonstrate that the ridge evolves between two end members the volcanic end member is characterized by a non rifted or only slightly rifted topographic ridge with widespread but diffuse water venting the tectonic end member is marked by a well defined axial graben whose floor can be the locus of intense sulfide deposition at one site a small stockwork mineralization exposed through normal faulting was observed at the base of the graben wall the dives illustrate the discontinuous nature of volcanic tectonic and hydrothermal activities even in the case of the fastest accretion found in the ocean

assessing preferential seepage and monitoring mortar injection through an earthen dam settled over a gypsiferous substrate using combined geophysical methods abstract for several decades the sant llorenc de montgai reservoir has experienced different problems that could affect the safety of the engineering structure for this reason several corrective actions have been taken over the years here we present a study involving complementary geophysical methods including electrical resistivity tomography seismic refraction tomography and frequency domain electromagnetic surveys the analysis of the inverted electrical resistivity tomography cross sections combined with the seismic refraction results and land subsidence monitoring data show the likely mechanism of abnormal seepage the areas where mortar injections were applied as a corrective measure are also clearly delineated in addition the evolution of the state of the embankment has been established from two successive electrical resistivity tomography surveys in the last two decades the results show areas where corrective mortar injections have been effective while in other areas new abnormal seepage has been detected the lithological heterogeneity of the bedrock especially the dissolution of gypsum rich rocks induced subsidence effects and caused abnormal seepage in different areas along the embankment our results indicate how corrective solutions can be optimized to reduce the cost of corrective engineering interventions

laboratory characterization of rainfall induced loess slope failure loess slopes are widely distributed throughout the northwestern region of china and are prone to slope failure in response to heavy rainfall we undertook three groups of flume experiments in the laboratory to study loess slope dynamics under artificial rainfall conditions additionally a laser scanner was used to observe loess landslide deformation characteristics and failure development a numerical analysis of unsaturated seepage in loess slopes because of rainfall infiltration was performed moisture content pore water pressure and slope deformation were monitored to quantify the relationship between rainfall infiltration and loess slope stability movement of the wetting front near the slope surface was triggered by rainfall and related to rainfall intensity and duration which is consistent with the numerical solution rainfall infiltration increased pore water pressure producing gravity driven landslides we observed that landslide development began with local failure in the toe slope that gradually retreated toward the crown forming a multi sliding displacement and eventually resulting in total slope failure

diversity and spatial zonation of volcanic rocks from the east pacific rise near 21 n a substantial range of petrologic rock types has erupted on the accreting plate boundary near 21 n on the east pacific rise epr young olivine basalts have fo89 86 phenocrysts low bulk tio2 1 1 1 3 ba 7 10 ppm and high ni contents 100 ppm older plagioclase olivine pyroxene pop basalts have fo86 81 phenocrysts high tio2 1 4 1 7 ba 9 40 ppm and low ni 100 ppm the youngest olivine basalts erupt immediately around a segmented axial fissure system progressively older more fractionated pop basalts have spread farther from the same fissure system producing a stratigraphically controlled zonal pattern of basalt type distribution around the eruptive fissures a topographic and morphologic en echelon displacement of the ridge axis fissure of 1 7 km to the nw near 20 54 n offsets this zonal distribution pattern low pressure crystal fractionation of olivine plagioclase and clinopyroxene 2 5 1 from an olivine basalt parent would yield pop basalts of the observed zr ti y p and major element chemistry however very incompatible elements ba and k are too variably enriched in pop basalts for this model to be viable small variable degrees of mantle partial melting is not a viable model either because of the substantial depletion of ni which correlates with incompatible element enrichment and because of the precise low pressure cotectic character of pop basalts the in situ fractionation model of langmuir 1987 can explain these features the relative abundance of fractionated lavas their small scale areal chemical zonation the petrochemical correlation between types and geophysical evidence point to the existence of shallow fractionating magma reservoirs beneath the epr at 21 n

minor and trace element geochemistry of volcanic rocks dredged from the galapagos spreading center role of crystal fractionation and mantle heterogeneity a wide range of rock types abyssal tholeiite fe ti rich basalt andesite and rhyodacite were dredged from near 95 w and 85 w on the galapagos spreading center computer modeling of major element compositions has shown that these rocks could be derived from common parental magmas by successive degrees of fractional crystallization however the p2o5 k2o ratio averages 0 83 at 95 w and 1 66 at 85 w and implies distinct mantle source compositions for the two areas these source regions also have different rare earth element ree abundance patterns with la sm ef 0 67 at 95 w and 0 46 at 85 w the sequence of fractionated lavas differs for the two areas and indicates earlier fractionation of apatite and titanomagnetite in the lavas from 95 w the mantle source regions for these two areas are interpreted to be depleted in incompatible and volatile elements although the source region beneath 95 w is less severely depleted in la and k incompatible trace element abundances in 26 samples are used to infer that the range of fe ti rich basalt from 85 w represents 19 to 35 residual liquid following crystal fractionation of a mineral assemblage of plagioclase clinopyroxene and lesser olivine the most highly differentiated samples have also had less than 1 titanomagnetite removed most samples from 85 w can be related to a common parental magma that contained approximately 9 wt feo 1 wt tio2 and had an mg number mg 100 mg mg fe2 of about 65 although the samples from 95 w cannot all be derived from a common parental magma the inferred parental magmas may have been derived by varying degrees of partial melting of a common source the fractionation sequence consists of two parts an initial iron enrichment trend followed by a silica enrichment trend we interpret the trace element data to indicate that the most iron rich lavas represent about 32 residual liquid derived by crystal fractionation of plagioclase clinopyroxene and lesser olivine from a parental magma with an mg number of about 66 the silica enrichment trend results from crystallization of titanomagnetite and some apatite fractionation of pigeonite which is a minor phase in the major element models cannot be distinguished from clinopyroxene fractionation by using trace elements

an integrated hydrological model for rain induced landslide prediction this paper describes an extension to the combined hydrology and stability model chasm to fully include the effects of vegetation and slope plan topography on slope stability the resultant physically based numerical model is designed to be applied to site specific slopes in which a detailed assessment of unsaturated and saturated hydrology is required in relation to vegetation topography and slope stability applications are made to the hawke s bay region in new zealand where shallow seated instability is strongly associated with spatial and temporal trends in vegetation cover types and the mid levels region in hong kong an area subject to a variety of landslide mechanisms some of which may be subject to strong topographic control an improved understanding of process mechanism afforded by the model is critical for reliable and appropriate design of slope stabilization and remedial measures copyright 2002 john wiley sons ltd

origin of the oceanic lithosphere in a global examination of mid ocean ridge basalt morb glass compositions we find that na8 fe8 depth variations do not support modeling of morbs as aggregates of melt compositions generated over a large range of temperature and pressure however the na 8 fe8 variations are consistent with the compositional systematics of solidus melts in the plagioclase spinel lherzolite transition in the cao mgo al2o3 sio2 na2o feo cmasnf system for natural compositions the p trange for melt extraction is estimated to be 1 2 1 5 gpa and 1250 12808c this p trange is a close match with the maximum p t conditions for explosive pressurerelease vaporization of carbonate bearing melts it is proposed that fracturing of the lithosphere induces explosive formation and escape of co2 vapor this provides the vehicle for extraction of morbs at a relatively uniform tand p the upper portion of the co2 bearing and slightly melted seismic low velocity zone flows toward the ridge rises at the ridge axis to lower lithosphere depths melts much more extensively during this rise and releases morb melts to the surface driven by explosively escaping co2 vapor the residue and overlying crust produced by this melting then migrate away from the ridge axis as new oceanic lithosphere the entire process of oceanic lithosphere creation involves only the upper 140 km when lithospheric stresses shift fracture formation to other localities escape of co2 ceases the vehicle for transporting melt to the surface disappears and ridges die inverse correlations of na8 vs fe8 for morb glasses are explained by mantle heterogeneity and positive variations superimposed on the inverse variations are consistent with progressive extraction of melts from short ascending melting columns the uniformly low temperatures of morb extraction are not consistent with the existence of hot plumes on or close to ocean ridges in this modeling the southern atlantic mantle from bouvet to about 268n is relatively homogeneous whereas the atlantic mantle north of about 268 ns hows significant long range heterogeneity the mantle between the charlie gibbs and jan mayen fracture zones is strongly enriched in feo mgo perhaps by a trapped fragment of basaltic crust iceland is explained as the product of this enrichment not a hot plume the east pacific rise galapagos ridge gorda ridge and juan de fuca ridge sample mantle that is heterogeneous over short distances the mantle beneath the red sea is enriched in feo mgo relative to the mantle beneath the northern indian ocean

investigation of leakage at ataturk dam and hydroelectric power plant by means of hydrometric measurements abstract ataturk dam with its 84 5 million m 3 fill volume and 169 m height above the foundation is one of the largest dams in the world its 1 2 million m 2 grout curtain surface area is the largest constructed in the world to date the bozova fault crosses the dam axis in the left bank and extends towards the downstream valley the grout curtain constructed in karstic limestone is 180 m deep in the thalweg and partially extends to 250 300 m depths in some local zones on both the right and left sides of the valley in this study we have investigated leakage at the ataturk dam and hydroelectric power plant by means of hydrometric measurements the hanging grout curtain indicates that leakage at ataturk dam is of vital importance in defining the longevity of the dam hydrometric measurements including discharge temperature and electrical conductivity of springs and leakages were carried out for 9 years periodically in addition to monitoring performed before during and after construction the leakage increased as the reservoir water level rose seasonally but it was also discovered that this regular increase was not observed in the last three measurements the decrease in leakage volume in the last three measurements proved the integrity of the grout curtain and the efficiency of the microsol grout works recent seepage levels are within design limits and therefore have no serious effect on the stability of the dam structures

moisture content pore water pressure and wetting front in granite residual soil during collapsing erosion with varying slope angle abstract collapsing erosion is very severe in subtropical regions that are covered extensively by granite residual soil however detailed information about hydraulic responses during collapsing erosion especially for different slope angles remains unclear therefore to control collapsing erosion it is important to attain a more comprehensive understanding of the complex hydraulic responses due to rainfall in this study an artificial rainfall simulator and an experimental device were used to evaluate the collapsing erosion process with particular consideration of the influence of slope angle flume experiments using three slope angles 0 10 and 20 were performed under artificial rainfall this study explored the evolutions and hydraulic responses of collapsing erosion of granite residual soil by simultaneously monitoring moisture content pore water pressure and wetting front during heavy rainfall the results showed that collapsing erosion occurred faster with steeper slope angle collapse occurred in an upslope direction when the corresponding moisture content of the soil was between 30 and 40 pore water pressure increased until the development of collapsing erosion but was released when the soil mass collapsed the descending process of the wetting front on a gentle slope and a steep slope can be divided into two stages and three stages respectively this study presents an improved characterization of collapsing erosion and provides valuable evidence for slope angle impacts on infiltration events during collapsing erosion under heavy rainfall

evaluation and rehabilitation of dam seepage problems a case study kafrein dam abstract the intention of this study is to locate the probable sources of the kafrein dam seepage problem a methodology known as excitation response analysis will be considered analytical expressions depicting the groundwater level response in the underlying aquifer as a result of changes in the reservoir water level were derived from a linearized groundwater flow equation for one dimensional semi infinite isotropic and homogeneous porous media the results revealed that a large proportion of the seepage water originates from a site at a distance about 1 km from the observation point m1 and streamlines along the existing faults emphasis in this work was also placed on controling and mitigating the seepage problem

delineation of leakage pathways in an earth and rockfill dam using multi tracer tests abstract in this study a multiple tracer analysis was carried out to investigate the leakage pathway of the xixiayuan dam located on the yellow river in china composite geomembrane and a concrete cutoff wall are used jointly to control seepage filling of the reservoir began on may 30 2007 with water level rising to 133 6 m asl above sea level on october 2 2007 thereafter the water level fluctuated between 133 0 m asl and 133 6 m asl until a leakage point emerged on october 15 2007 from october 16 to 18 2007 two other water leakage points were found emerging from the top of a drainage channel located at the downstream toe of the left earth rockfill dam to determine the possible leakage pathways 10 additional investigation boreholes were installed single borehole artificial isotope dilution tests were carried out to quantify the vertical and horizontal flow velocities in boreholes at high and low reservoir water levels temperatures and water levels were measured in boreholes reservoir water and leakage points an interconnection test using salty water tracer was performed between borehole and leakage point as a result of these studies the possible seepage location was identified to be near boreholes zz5 and zz6 excavation and inspection at the estimated seepage location confirms the presence of a construction defect

the 3d analysis and estimation of transient seepage in earth dams through plaxis 3d software neural network case study kord oliya dam isfahan province iran the issue of seepage and its management is essential in earth dams which if exceeded from a certain stage the destruction of dam is probable despite the studies run through consulting engineers the hydraulic behaviors of both body and foundation cannot be predicted to understand the function of such structures the geotechnical software plaxis 3d based on fem is applied to determine the transient seepage analysis on the subject earth dam for 1 year the outputs in downstream drain are compared with the actual obtained results from seepage at the same points with 15 day intervals for 1 year as an experimental sample the obtained data here thorough plaxis 3d in addition to available actual seepage permeability coefficients in x y and z directions transient head upstream soil specific gravity for both the wet and dry conditions poisson coefficient c and elasticity modulus material are trained through a neural network algorithm here an equation is yield through which the seepage is calculated in transient head upstream at any point of the subject earth dam this equation has a great accuracy of p value 0 05 and is applied in calculating the actual seepage of earth dams in critical situations such as earth dam failure due to piping operation or dam body erosion

hydrologic characteristics of a large rockfill dam implications for water leakage abstract the unmun dam a rockfill dam with a clay core filter zone and sandy gravel shell is located in the nakdong river basin near cheongdo gun in korea in the dam area the cretaceous gyeongsang supergroup andesite lies over intrusive granite these form the intrusive contact near the main dam and cofferdam areas the stratigraphic units in upward sequence consist of cretaceous granite and andesite weathered soft rock and a soil layer of silty clay with gravel the reservoir was first filled in august 1994 and was full by april 1998 right after complete filling three sinkholes were found in the dam crest near stations 2 12 and 10 when the reservoir level was at around 150 m the amount of leakage increased with rise of the reservoir level mainly caused by rainfall events as a countermeasure for the abnormal leakage and dam rehabilitation comprehensive surveys were performed on the dam including observational drillings grouting geophysical surveys and tracer tests by korea water resources corporation kowaco there were also further investigations for hydrologic characterization of the dam to identify water leakages the groundwater levels at the 26 observation wells installed on the crest and dam toe were measured to evaluate the relationship between the reservoir level and groundwater level and the influences on the dam leakage groundwater level at the left side of the embankment was high compared with a normal phreatic line it was only 4 m lower than the reservoir level while 6 65 m lower than that at its right side fluctuation of the groundwater levels in the crest wells coincided well with the reservoir level without a significant lag time which reflected a good hydraulic connection between the reservoir and the dam interior hydraulic conductivity estimated from 149 hydraulic tests at 9 monitoring wells constructed in the dam core showed a wide range between 1 42 10 4 and 4 35 10 8 cm s with a geometric mean of 3 13 10 6 cm s furthermore water quality at the monitoring wells were much different from that of the reservoir high levels of turbidity and electrical conductivity were observed at the monitoring wells in the left side of the bank all these hydrologic characteristics reflected possible occurrence of the leakage on the dam especially in the left embankment this paper presents a summary of several investigation studies on the hydrologic characteristics of the rockfill dam which implied abnormal water leakage

assessment of water seepage through a geologic barrier surrounding a large reservoir using groundwater levels soil condition and a numerical model though the geologic barrier surrounding a dam reservoir plays an important role in preventing water seepage to the outside of a reservoir a detailed survey to assess bedrock conditions of the whole reservoir boundary is seldom performed when designing a dam in this study a variety of investigations and analyses have been conducted to reveal a seepage phenomenon through a reservoir boundary composed of highly fractured metamorphic rocks at the daechung multipurpose dam at the study site groundwater levels at monitoring wells located close to a reservoir tend to change proportionally to reservoir water levels usually with a rapid response time of 1 day or less soil moisture content also changes with respect to the reservoir water level and the area where seepage from the reservoir is a possibility has a relatively high soil moisture content the similarity of measured seepage rates at the outflow site and the seepage rate estimated by darcy s law suggests strong connectivity and high density of the fractures the estimated seepage rate using a numerical model for the northernmost valley zone 1 is approximately 127 2 m3 day in the case of high reservoir water level and 24 3 m3 day in the case of low water level continuous monitoring to obtain time series data for water levels quality and bedrock displacement is recommended to assess the sustainable stability of this geologic barrier

investigation of groundwater chemistry at a dam site during its construction a case study of xiangjiaba dam china water quality can be used to reflect the hydro geological features and seepage restrictions around grout curtains xiangjiaba dam a large hydropower station constructed in southwest of china was investigated as a case study groundwater samples were collected and analysed qualitatively using hydrochemistry diagrams after which the presence of four major water groups was determined by hierarchical cluster analysis and saturation indices of each group were calculated finally inverse geochemical models of the groups were developed using phreeqc to elucidate the dissolution precipitation quality of different minerals and the relative contributions of different seepage sources the hydro geochemical methods used were found to be useful for revealing seepage behaviour within the domain during construction of a hydropower station

shocks in a box an analogue model of subduction earthquake cycles with application to seismotectonic forearc evolution 1 we introduce and test an experimental approach to simulate elastoplastic megathrust earthquake cycles using an analogue model and apply it to study the seismotectonic evolution of subduction zones the quasi two dimensional analogue model features rate and state dependent elastic frictional plastic and viscoelastic material properties and is scaled for gravity inertia elasticity friction and viscosity the experiments are monitored with a high resolution strain analysis tool based on digital image correlation particle imaging velocimetry piv providing deformation time series comparable to seismologic geodetic and geologic observations in order to separate elastic and nonelastic effects inherent the experimental deformation patterns we integrate elastic dislocation modeling edm into a hybrid approach we use the analogue earthquake slip and interseismic locking distribution as edm dislocation input and forward model the coseismic and interseismic elastic response the residual which remains when the edm prediction is subtracted from the experimental deformation pattern highlights the accumulation of permanent deformation in the model the setup generates analogue earthquake sequences with realistic source mechanisms and elastic forearc response and recurrence patterns and reproduces principal earthquake scaling relations by applying the model to an accretionary type plate margin we demonstrate how strain localization at the rupture peripheries may lead to a seismotectonically segmented forearc including a tectonically stable shelf and coastal high 20 plate convergence accommodated by internal shortening overlying the area of large megathrust earthquake slip fifty to 75 of plate convergence is accommodated by internal shortening in the slope region where earthquake slip tapers out toward the trench the inner forearc region remains undeformed and represents a basin

unsaturated soil mechanics in rainfall induced flow landslides abstract rainfall induced flow landslides in coarse grained soils pose significant threats to populations and structures due to their high velocities long travel distance and the absence of definite warning signs during the pre failure stage the triggering phase of these phenomena is frequently related to rainfall events which significantly reduce matric suction in the shallower soil layers in this paper the processes leading to the onset of such phenomena are illustrated and some observations on their modelling are briefly recalled the failure stage at different scales is then modelled with reference to a case study from southern italy which draws on high quality experimental data sets from extensive in situ and laboratory investigation

formation process and mechanism of seepage channels around grout curtain from microseismic monitoring a case study of zhangmatun iron mine china abstract the grout curtain in zhangmatun iron mine china suffers from the leakage of water due to the influence of multiple factors including inadequate grouting area weak rock and mining disturbance water seepage through rock mass around the grout curtain further deteriorates the water plugging effect of the grout curtain and poses a potential hazard to workers underground thus a microseismic ms monitoring system was established in the zhangmatun iron mine in the present paper a ms monitoring analysis method for assessing a potential seepage channel is proposed using the proposed ms monitoring analysis method the dip dip angle and center depth of the potential seepage plane across the grout curtain in zhangmatun iron mine are determined to be 126 1 e 53 97 and 275 m respectively the spatial and temporal behaviors of density distribution source parameters and cracking type of the seismic source are analyzed to reveal the initiation propagation coalescence of seepage channel located at the southwest of the iron mine four types of local seepage channel formation processes are summarized by correlating the mechanism of microcracking two main weak areas around the grout curtain at the levels of 230 m and 318 m are identified and two seepage paths whose water discharge points are localized to the roof of stope 9 10 and sidewall of stope 10 are determined respectively our study helps to get a better understanding of damage and failure of rock mass around grout curtain and thus provides a basis for taking reinforcement measures to secure the stability of grout curtain in mines

geotechnical characterization of carbonate marls for the construction of impermeable dam cores abstract fine grained more or less cohesive carbonate materials are extremely widespread in terms of surface area and are therefore commonly used as materials to construct impermeable cores for dams however it has not been adequately documented whether the carbonate content in fine grained soils significantly affects their engineering behaviour the present study shows that the carbonate content substantially influences the engineering behaviour of clayey material for this we subjected 32 samples to different laboratory tests such as the normal proctor the atterberg limits granulometric analysis oedometric and undrained triaxial tests the resulting parameters were correlated with the carbonate content of the samples the materials studied in this work had been used in the construction of the impermeable core of the san clemente dam belonging to the hydrographic basin of the guadalquivir river southern spain these marls present as their prime characteristic a carbonate content of the fine fraction consistently exceeding 50 giving them special importance in the study of this phenomenon in this study a direct relationship was found between the geotechnical properties of the soils studied and their degree of compaction with the carbonate content and the type of minerals in the clay being the main factors determining the behaviour of these soils finally we conclude that the percentage of carbonates should be used as a classification criterion for the soils used to construct the cores of earth filled dams

basalt geochemistry of the explorer ridge area northeast pacific ocean forty two fragments of young fresh basalts dredged from the explorer ridge paul revere ridge fracture zone and dellwood knolls have been analysed for 34 major minor and trace elements and 87sr 86sr ratios have been determined in seven of the fragments the explorer ridge basalts have major element compositions similar to most mid ocean ridge basalts morb particularly to the iron rich basalts of the southern juan de fuca ridge the basalts exhibit variability in trace element content largely attributable to crystal fractionation at low pressure with respect to morb the incompatible minor and trace elements are weakly to strongly enriched in the explorer samples and are most strongly enriched in basalts from explorer deep adjacent ridge segments erupt basalts with variable incompatible element concentrations and ratios this could be an indicator of a chemically heterogeneous mantle source or may be the result of intermittent injection of enriched magmas from a hotspot beneath explorer deep

petrologic and geologic variations along the southern explorer ridge northeast pacific ocean mid ocean ridge basalts morb from the well defined southern explorer ridge segment ser in the northeast pacific ocean are moderately to strongly enriched in incompatible elements enriched morb were erupted at the highest and widest part of the segment culmination where the magma supply may be the greatest and also at the northern and southern ends of the ser variations in basalts incompatible element enrichment occur over short distances and suggest that the underlying mantle is heterogeneous on a small scale the variations also preclude the existence of a long lived well mixed magma chamber beneath the robust culmination instead magma chambers are probably temporally and spatially isolated as evidenced by the presence of highly differentiated lavas less enriched transitional morb were erupted along the central part of the ser 11 27 km south of the culmination and were supplied to the ridge separately from a less enriched pan of the mantle a more continuous magma chamber cannot be ruled out for this section on geochemical grounds all of the morb from the ser have undergone significant amounts of fractional crystallization unlike certain segments of the east pacific rise the most evolved morb were erupted near the culmination of the ridge segment aphyric lavas have been recovered only from the vicinity of the culmination while phyric lavas have erupted along the entire length of the ser there is no correlation between composition and total crystal abundances despite the requirement of multiple parental magmas most of the lavas from the culmination and the distal ends of the ridge fall on a common liquid line of descent indicating that they formed at similar depths and extents of partial melting the transitional morb from the central part of the ridge have probably formed by lesser extents of partial melting and separated from their mantle source at greater depths based on abundances of na and moderately incompatible elements such as sm and zr enriched high melt fraction lavas at the magma starved southern end of the ser closely resemble lavas from the culmination either the southernmost lavas have flowed laterally within the crust from near the culmination or there is another melting anomaly that supplies the southern end of the ser if the latter case is true correspondence between ridge morphology and mantle thermal state is poor

occurrence of landsliding on slopes where flowsliding had previously occurred an investigation in a loess platform north west china abstract loess slides in south jingyang platform shaanxi province usually occur on slopes where loess flowslides had previously occurred numerical modeling shows that flowslide occurrence causes conditions that increase shear stress and water content in the subsequent slopes both of these factors move the soil stress states towards its theoretical failure line under these conditions only small increases in water content can cause soil collapse this leads to the backscarps of former flowslides being much more prone to landsliding wetting test results show that the loess can collapse suddenly as the water content gradually increases therefore the wetting process induced by continued irrigation may result in the subsequent slides during constant water content tests of the loess material soil shear strength increases with the development of specimen deformation therefore slide mobilization which may be a relatively slow process is dependent on whether the wetting conditions exist finally a slope evolution model for loess platforms is proposed in this study

evidence for variable upper mantle temperature and crustal thickness in and near the australian antarctic discordance abstract the southeast indian ridge seir in and near the australian antarctic discordance aad exhibits at a constant spreading rate almost the full range of the many geophysical and geochemical parameters characteristic of the slow mid atlantic ridge and fast east pacific rise we used satellite derived gravity data in combination with seamarc ii bathymetry in and near the aad to examine regional density variations in the upper mantle beneath the aad through three dimensional gravity analysis we found that at least two end member models satisfy the gravity observations regional crustal thickness variations of at least 3 km along the seir near the aad or a temperature anomaly of the order of 150 c in the upper mantle beneath the seir these new observations combined with other geophysical and geochemical characteristics of the australian antarctic discordance provide further evidence that the temperature structure of a mid ocean ridge is a controlling factor in addition to spreading rate in the crustal accretionary process numerical models of mantle flow beneath mid ocean ridges offer one means of investigating the dynamic effect of a variable upper mantle temperature on the accretionary process our results indicate that temperature is important especially at intermediate and slower spreading rates where thermal effects can dominate mantle flow beneath a mid ocean ridge and result in increasing crustal production with decreasing spreading rate at the constant intermediate spreading rate of 37 mm yr characteristic of the seir in and near the aad our numerical models show that significant crustal thinning 2 4 km can occur with relatively small variations in upper mantle temperature all else being equal thus combined with our end member gravity models these observations and results suggest that both anomalously cool upper mantle and thin crust exist beneath the aad

late cenozoic regional uplift and localised crustal deformation within the northern arabian platform in southeast turkey investigation of the euphrates terrace staircase using multidisciplinary techniques we present the results of detailed field investigations of the fluvial succession exposed along the euphrates valley adjoining the ataturk dam in the northern part of the arabian platform within se turkey this work which has used differential gps surveying to obtain accurate heights of deposits and shuttle radar topographic mission imagery for location purposes has included documentation of many fresh sections exposed by quarrying the work has been supplemented by unspiked kar dating of late middle miocene to late miocene basalt flows which are widespread in the region providing a chronology for the early stages of development of this river system following regional emergence above sea level in the early middle miocene for example beside the ataturk dam lake at siverek iskelesi basalt dated to 10 24 0 22 ma 2 caps a polymict euphrates gravel some 80 m above the modern river this is the oldest euphrates terrace currently recognised however amounts and rates of fluvial incision are shown to vary across the northern arabian platform in a complex manner due to the interaction between regional uplift and localised vertical crustal motions caused by slip on active reverse faults beneath anticlines the study reach downstream of the ataturk dam includes the footwall of one such fault beneath the bozova anticline we estimate that the resulting rate of localised subsidence superimposed onto the regional uplift that has also been occurring has been 0 01 mm a 1 during the present phase of crustal deformation which began at 3 7 3 6 ma but was higher maybe 0 03 mm a 1 during the previous phase which began at 6 ma when the pattern of plate motions in the surrounding region was different a large palaeo lake centred north of the present study region around the city of adiyaman is inferred to have existed during this 6 ma to 3 7 3 6 ma phase of plate motion apparently because the relatively rapid localised hanging wall uplift on the northern flank of the bozova anticline dammed the euphrates valley near the site of the modern ataturk dam the uppermost part of a thick fluvial aggradation west of the euphrates near karababa bridge inferred to date from around the mid pliocene reaches 100 m above the modern river and after correction for an estimated 30 m of localised subsidence and by 50 m for subsequent downstream lengthening of the euphrates channel indicates 180 m of subsequent regional uplift the euphrates then incised to within 20 m of its present level by the mid early pleistocene then a switch to regional subsidence accompanied the deposition of a second thick fluvial aggradation the top of which is 70 m above the modern river subsequent renewed regional uplift following the mid pleistocene revolution has resulted in the development of a succession of fluvial terraces typically inset into these older aggradations which are correlated with the cold stages of milankovitch climate cycles the early part of the euphrates chronology constrained mainly by the disposition of basalt flows indicates 800 m of regional uplift since the early middle miocene of which an estimated 330 m is masked by the subsequent downstream lengthening of the river components of localised uplift and subsidence caused by slip on reverse faults beneath anticlines are superimposed onto this regional pattern the hanging wall uplift being much larger in one case roughly five times larger than the footwall subsidence our results provide for the first time detailed documentation of the complex development of the euphrates valley in se turkey during the late cenozoic due to the interaction between regional uplift and localised crustal deformation this work also demonstrates the benefits of applying multidisciplinary techniques to investigate an important but hitherto poorly documented river system

petrology and sr nd and pb isotope geochemistry of mid ocean ridge basalt glasses from the 11 45 n to 15 00 n segment of the east pacific rise 1 basaltic glasses from the geophysically well studied section of the east pacific rise epr between 11 45 n to 15 00 n range from normal mid ocean ridge basalts morb to transitional morb and their major element variations correlate with isotopic and trace element indices of enrichment to first order basalts enriched in na8 0 incompatible elements 87sr 86sr and 206pb 204pb but low in fe8 0 and 143nd 144nd are more prevalent along the shallow portions of the ridge axis in detail the samples can be divided into two chemical and geographical groups the southern bathymetric dome extending from the 11 45 n overlapping spreading center to 14 10 n and the northern group extending from 14 10 n to the orozco transform the boundary between these two groups is apparent in a change in isotopic composition results indicate that there are three mantle source components that produce the compositional variability observed among samples from the 11 45 n to 15 00 n segment of the epr a depleted mantle component a seamount type enriched mantle component and an indian morb like mantle component south of 14 10 n the geochemical variability is dominated by binary mixing between a depleted mantle component and an enriched component similar to near ridge seamounts north of 14 10 n the low 206pb 204pb high 207pb 204pb indian morb like component exerts a major influence on the geochemical variability of the axial lavas regional averages of major element composition e g na8 0 and fe8 0 show relatively limited variability consistent with the restricted range in depth for this region and plot within the pacific field of the previously defined global trends major element variations among individual samples however parallel the global array and their correlation with indices of mantle enrichment supports the idea that the pacific type local trend results from small scale heterogeneities in the mantle beneath the epr our results also indicate that tectonic segmentation and magmatic boundaries are probably not causally related in this study area and that the sizes of the present magma chambers are not a dominant factor in determining the compositional variability of erupted lavas

factor and cluster analyses of water chemistry in and around a large rockfill dam implications for water leakage based on water chemistry data a rockfill dam in south korea was investigated to identify major parts of substantial dam water leakage sinkholes in the dam crest and abnormal water leakage through the dam were observed since the first impounding of the dam previous investigations including observational drillings hydraulic tests geophysical surveys and tracer tests revealed the development of a high permeability zone in the clay core and an abnormally high phreatic line zone in the left embankment sequential tracer tests provided further evidence of locations of preference and rapid water leakage pathways in this study we examined the usefulness of water chemistry data to confirm previous findings of water leakage factor analysis of the water chemistry data revealed major processes controlling the chemical composition which include the wash out and successive dissolution of fill materials in the dam interior interaction between percolating water and dam core materials and contamination of seeping water by grouting materials and previous tracer tests distinct spatial distribution of similar chemical groups was illustrated by cluster analysis and confirmed the location of major water leakage at the left abutment adjoining the spillway

the lar dam an example of infrastructural development in a geologically active karstic region abstract the problems associated with the construction of the lar dam iran provide a classic example of problems that can result from infrastructural development in an active geological terrain which includes the regional carbonate units the lar dam lies in a heavily faulted and fractured region close to the active damavand volcano the fracturing has enhanced the production of karst and sinkholes in the limestone below the dam and acidic ground water run off from the damavand volcano increases the dissolution of the carbonate beds along the fractures to produce sinkholes below the dam the initial problem of building the dam in such a region is compounded by the relationship between water loss due to enhanced sinkhole development and the remedial measures being taken to lessen this leakage drainage of the sub reservoir caverns through leakage along fractures can lead to loss of hydrostatic support for the developing sub reservoir caverns and their consequent collapse furthermore rapid changes in subterranean water levels would lead to rock shattering hammer effects particularly during rapid rises in water level

water losses from a reservoir built in karst the example of the boljuncica reservoir istria croatia the paper presents the case of the boljuncica reservoir which began operation in 1973 it is situated on the istria peninsula croatia this is a multipurpose reservoir which was built in order to protect the downstream area from flood to store water for irrigation and to control sediment transport the reservoir is situated on the contact zone between water impermeable eocene flysch and deep eocene and cretaceous limestone the bottom of the reservoir is covered partly by both flysch and quaternary deposits water losses from the reservoir bottom are so large that the main service intended for the reservoir the storage of water for irrigation is impossible after every intensive precipitation which occurs often in this region the reservoir fills very quickly the problem is that its retention of water is very short and lasts only a few days the water volume of the reservoir at the spillway altitude of 93 00 m a s l is about 6 5 106 m3 because of water losses from the reservoir bottom the mean annual volume of water stored in it during the period of 1977 2005 was only 0 5 106 m3 which is less than 8 of the full reservoir volume on the reservoir bottom many new swallow holes opened through the sediment cover after each time it filled and emptied with water special attention is paid to the groundwater level analyses interdisciplinary analyses and investigations of hydrological and hydrogeological factors causing the formation of swallow holes and water losses from the boljuncica reservoir are discussed the example given in this paper explains one unsuccessful case of building a reservoir in dinaric karst caused mainly due to insufficient geological hydrogeological and hydrological investigations in order to prevent water losses from the boljuncica reservoir very complex and expensive work needs to be done but its success regarding the reasonable reduction of water losses from the reservoir is in question

convectively driven transport in temperate lakes penetrative convection in the surface layer of a midsize temperate lake 5 km2 was investigated in both summer and winter using a conductivity temperature depth ctd logger mounted on an autonomous underwater vehicle auv flown repeatedly along horizontal transects at selected depths in summer the epilimnion cooled differentially during a calm evening 240 and 297 w m22 on the east and west sides of the lake respectively these cooling rates agree well with the average net heat flux of 270 w m22 estimated from meteorological data density currents were driven by this differential cooling in winter ctd profiles during a sunny day showed four distinct thermal layers beneath the ice 50 cm thick consistent with radiative penetrative convection a stratified diffusive layer just beneath the ice top 1 6 m a well mixed convective layer that deepens at 1 14 m d21 and warms at 0 015u cd 21 during the observation period an entrainment layer 1 5 m thick and a weakly stratified quiescent layer to bottom auv transects flown at constant depths in each layer revealed a 150 m wide region displaying evidence of penetrative convection surrounded by regions with negligible heat changes these high resolution horizontal ctd measurements provided insight into previously unresolved physical dynamics of the well mixed layer of a temperate lake in quasi shear free conditions that would have been difficult to quantify during summer months and impossible under winter ice cover without the use of an auv platform in temperate lakes during periods of little or no wind exposure penetrative convection driven by a destabilizing buoyancy flux will be the dominant source of vertical mixing in the upper layers of the water column above the temperature of maximum density penetrative convection

landslide fluidization process by flume experiments abstract an almost real size slope model was used to study the generation process of landslide fluidization during torrential rain experiments were conducted by filling an inclined flume with loose sand and spraying water over the flume with a rainfall simulator to induce the sand to collapse both the movement volumetric strain and the pore water pressure of the sand were monitored throughout the experiments from the start of spraying to the cessation of the landslide our experiments showed the following 1 landslide fluidization caused by undrained sudden loading undergoes three stages compaction of the sand layer by the sliding mass from upper slope generation of excess pore water pressure in saturated zone and induction of fast shearing 2 fluidization at the collapse source area also undergoes three stages destruction and compaction of sand layer skeleton by outbreak of shearing increase of pore water pressure in saturated zone and shift to fast shearing but these three stages take place almost simultaneously

detection of leakage paths at the wanyao dam body in southwest china by hydrochemical analysis and tracer testing leakage at the wanyao dam body was studied using a combined approach of field exploration hydrochemical analysis and tracer testing the objective of study was to determine the location of the water leakage paths at the dam a hydraulic connection was observed between exploration boreholes of dam crest and drain holes at drainage gallery during the period of drilling this connection shows that there were some defects in the dam the hydrochemical compositions and characteristics of the water samples involved the main anions and cations total dissolved solids electrical conductivity ph and water temperature which were analyzed and evaluated by correlation and cluster analysis the results indicated that a close hydraulic connection existed between water from the dam body and reservoir water particularly reservoir water from sections iii and ix tracer testing results demonstrated further existence of leakage paths between reservoir water and sections iii and ix also there were multiple leakage paths in section ix compared with a single path of section iii furthermore the leakage location of upstream concrete faces in the vertical and horizontal directions was determined accurately with the measured electrical conductivity of receiving points the experimental data provide a strong foundation and basis for maintaining and reinforcing the dam

analysis of the causes of large scale loess landslides in baoji china landslide hazards are common in western china understanding the mechanism of landslides in loess covered regions is particularly important for landslide risk assessment a detailed landslide survey including large scale slide drilling and geophysical exploration was carried out at the edge of the loess plateau on the north side of the wei river in china we reconstructed the geomorphological evolution model of the wei river and analyzed slope structures and lithology engineering geologic conditions and active fault properties in the landslide regions were investigated the results showed that paleogeomorphology of the north slope of the river gradually lowered from south to north ancient landforms showed a gradual transition to the south sanmen lake basin from the piedmont alluvial plain during the pliocene to early pleistocene the lake basin in the southern part of the study area gradually retreated and the wei river formed in the early pleistocene the main river flow shifted northward because of neotectonic movement and periodic climate changes until the holocene and then gradually moved southward to produce the current landforms the active wei river fault at the edge of the loess plateau acted as a route of water infiltration weakening the structural planes erosion and rise of the groundwater table caused old occurrence during the late pleistocene and ancient occurrence before the late pleistocene landslides to form on the edge of the plateau along active fractures and interfaces of pliocene sand gravel and clay these were multiple deep seated rotational slides and or multiple perched translational landslides slope stability analysis indicated that the complex landslides that occurred in the loess areas in recent years were closely related to the distribution of water and pliocene clay

back arc basin basalt systematics the mariana east scotia lau and manus back arc basins babs have spreading rates that vary from slow 100 mm yr and extension axes located from 10 to 400 km behind their island arcs axial lava compositions from these babs indicate melting of mid ocean ridge basalt morb like sources in proportion to the amount added of previously depleted water rich arc like components the arc like end members are characterized by low na ti and fe and by high h2o and ba la the morb like end members have the opposite traits comparisons between basins show that the least hydrous compositions follow global morb systematics and an inverse correlation between na8 and fe8 this is interpreted as a positive correlation between the average degree and pressure of mantle melting that reflects regional variations in mantle potential temperatures lau manus hotter than mariana scotia this interpretation accords with numerical model predictions that faster subduction induced advection will maintain a hotter mantle wedge the primary compositional trends within each bab a positive correlation between fe8 na8 and ti8 and their inverse correlation with h2o 8 and ba la are controlled by variations in water content melt extraction and enrichments imposed by slab and mantle wedge processes systematic axial depth as a proxy for crustal production variations with distance from the island arc indicate that compositional controls on melting dominate over spreading rate hydrous fluxing enhances decompression melting allowing depleted mantle sources just behind the island arc to melt extensively producing shallow spreading axes flow of enriched mantle components around the ends of slabs may augment this process in transform bounded back arcs such as the east scotia basin the re circulation by mantle wedge corner flow to the spreading axes of mantle previously depleted by both arc and spreading melt extraction can explain the greater depths and thinner crust of the east lau spreading center manus southern rifts and mariana trough and the very depleted lavas of east scotia segments e8 e9 the crust becomes mid ocean ridge mor like where the spreading axes further away from the island arc and subducted slab entrain dominantly fertile mantle

hydrogeochemical modeling of the water seepages through tannur dam southern jordan this paper reveals the geochemical processes of dissolution precipitation and cation exchange that took place during water rock interaction between water seepages through the tannur dam the schoeller diagram indicates that there are three major water types originating during water rock interaction the first water type is characterized by low salinity that ranges from 1 300 to 2 800 s cm which represents the reservoir water and the water in the right side of the central gallery the second water type is in the left side of the central gallery which exhibits medium salinity that reaches about 4 400 s cm the third water type is characterized by very high salinity that reaches a value of around 8 500 s cm and represents the water in the right existing adit the increase of salinity can be explained due to the dissolution of carbonate and sulfate minerals that form the matrix of the foundation and the abutment rocks and the dissolution of the grout curtain which is composed of cement and bentonite hydrogeochemical modeling using a computer code phreeqc was used to obtain the saturation indices of specific mineral phases which might be related to interaction with water seepages and to identify the chemical species of the dissolved ions the thermodynamic calculations indicate that most of the water samples were undersaturated with respect to gypsum anhydrite and halite and were saturated and or supersaturated with respect to calcite and dolomite ca hco3 2 is the primary water type as a result of dissolution of carbonate minerals such as calcite and dolomite prevailing at the dam site however cation exchange processes are responsible for the formation of the na2so4 water type from the caso4 type that formed due to the dissolution of gypsum

an integrated hydrogeological approach to evaluate the leakage potential from a complex and fractured karst aquifer example of abolabbas dam iran the design and construction of dams are risky in karst regions with active tectonic settings and strong heterogeneity due to their leakage potential hydrogeological characterization by karst specific methods can be used to reduce the risk of improper dam construction numerous karstic dams have been constructed in the world in simple tectonic settings in this study a combination of geological and hydrogeological investigations is used with extensive data collection to evaluate the leakage potential of the abolabbas dam construction project at the malagha karst aquifer a tectonized highland karst region in the southwest of iran two thrust faults which bounded the malagha karst aquifer overthrusting caused extensive crushed zones continuous lengths with high permeabilities in most of the boreholes extensive open joints and small size solution cavities the results of artificial tracer tests imply that the flow regime is diffuse the flat water table diffuse flow regime extensive crushed zones and continuous high permeabilities most probably imply that the groundwater flows through an extensive network of joints without main conduits to drain the system despite a diffuse flow regime an extensive grout curtain both in length and depth is required to prevent leakage because the loose materials of the crushed zones will be washed out without it under high hydraulic gradients after dam impoundment the impermeable formation is too deep due to overthrusting therefore a huge leakage may occur under the hanging grout curtain the results allow a clearer understanding of the location and properties of fracture zones erodible materials high permeability zones groundwater flow regime and zones of preferential flow which are essential for reducing the failure of dam construction in such environments overall it is demonstrated that integrating different complementary methods can help to minimize the uncertainties inherent in engineering problems in similar karst scarce data regions

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