increased lateral abutment resistance from gravel backfills of limited width lateral pile cap tests were performed on a pile cap with three backfills to evaluate the static and dynamic behavior one backfill consisted of loose silty sand while the other two consisted of 0 91 and 1 82 m wide dense gravel zones between the pile cap and the loose silty sand the 0 91 and 1 82 m wide dense gravel zones increased the lateral resistance by 75 to 150 and 150 to 225 respectively relative to the loose silty sand backfill despite being thin relative to the overall shear length the 0 92 and 1 82 m wide gravel zones increase lateral resistance to approximately 54 and 78 respectively of the resistance that would be provided by a backfill entirely composed of dense gravel the dynamic stiffness for the pile cap with the gravel zones decreased about 10 after 15 cycles of loading while the damping ratio remained relatively constant with cycling dynamic stiffness increased by about 10 to 40 at higher deflections while the damping ratio decreased from an initial value of about 0 30 to around 0 26 at higher deflections

liquefaction evidence for strong earthquakes of holocene and latest pleistocene ages in the states of indiana and illinois usa abstract sand and gravel filled clastic dikes of seismic liquefaction origin occur throughout much of southern indiana and illinois nearly all of these dikes originated from prehistoric earthquakes centered in the study area in this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the holocene and at least one during the latest pleistocene the recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects but some have been recognized only by geotechnical testing at sites of liquefaction most paleo earthquakes presently recognized lie in indiana but equally as many may have occurred in illinois studies in illinois have not yet narrowly bracketed the age of clastic dikes at many sites which sometimes causes uncertainty in defining the causative earthquake but even in illinois the largest paleo earthquakes probably have been identified prehistoric magnitudes were probably as high as about moment magnitude m 7 5 this greatly exceeds the largest historic earthquake of m 5 5 centered in indiana or illinois the strongest paleo earthquakes struck in the vicinity of the concentration of strongest historic seismicity elsewhere paleo earthquakes on the order of m 6 7 have occurred even where there has been little or no historic seismicity both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back calculating prehistoric magnitudes methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere

lateral resistance of full scale pile cap with gravel backfill a static lateral load test was performed on a full scale 33 pile group driven in saturated low plasticity silts and clays the steel pipe piles were attached to a concrete pile cap creating a fixed head end constraint a gravel backfill was compacted in place on the backside of the cap lateral resistance therefore was provided by pilesoilpile interaction as well as base friction and passive pressure on the cap in this case passive resistance contributed 40 of total resistance the logspiral method provided the best agreement with measured resistance estimates of passive pressure computed by the rankine method greatly underestimated the resistance while the coulomb method overestimated resistance cap movement needed to fully mobilize passive resistance in the gravel backfill was about 6 of the cap height this is somewhat larger than reported in other studies due likely to the underlying clay layer p multipliers developed for the free head pile group gave reasonable estimates of the pilesoilpile resistance for the fixed head pile group once gaps adjacent to the pile were considered

liquefaction failure and remediation king harbor redondo beach california liquefaction failure including large lateral displacements and associated settlement severely damaged marina facilities at redondo beach king harbor during the northridge earthquake of january 17 1994 although minor ground deformation apparently occurred in several areas of the harbor severe damage was restricted to the central portion of mole b one of four offshore fills constructed as a part of marina improvements in 1960 61 local ground conditions and methods used to remediate liquefaction are presented and discussed two ground modification techniques were used to mitigate the liquefaction potential of the reconstructed mole b facilities the major portion of the failure area was treated with vibroreplacement stone columns vibratory displacement and installation of the gravel columns not only densified the foundation soils but also provide additional strength and drainage capacity compaction grouting was used to densify foundation soils in the vicinity of existing improvements that were considered sensitive to construction induced ground vibrations these ground improvement techniques effectively reduced the liquefaction potential and allowed the marina improvements to be reconstructed on shallow foundations similar to the original design

time dependent ground motion amplification characteristics at reclaimed land after the 1995 hyogoken nambu earthquake two sets of borehole array records obtained from the great hanshin earthquake as well as its fore and after shocks are investigated one of the stations is located at port island in kobe city where severe liquefaction occurred and the records from the main event include the typical phenomena of liquefaction the other station is located at rokko island in kobe city where the liquefaction phenomenon was not predominant as it was at port island the non linear ground motion amplification depending on the level of input ground motion as well as its spectral characteristics is carefully investigated two numerical techniques for seismic response ground analysis are applied for these stations one is the frequency dependent equivalent linearization technique for frequency domain analysis and the other is the effective stress based liquefaction analysis the discussion is focused on the amplification characteristics of these two reclaimed lands depending on their reclamation history the time dependent amplification ratio for peak ground motion and spectral contents is demonstrated caused by the recovery of soil rigidity due to the decrease in excess pore water pressure after the main event

the densification of granular soils using vibro methods the method of densifying in situ sandy soils using deep vibration vibro was first developed in germany over 60 years ago since then the technique has been extended to improve a wide range of soil types for structures of up to 30 storeys in height a major development in the vibro market worldwide over the last 25 years has been the treatment of soils to resist the effects of liquefaction during seismic events it is well known that the presence of silt and clay fines inhibits the physical in situ densification of sandy soils experience has shown that a maximum fines content of about 15 would normally permit the performance of vibro compaction methods without the addition of stone aggregate however the development of new vibrators and modified construction techniques has enabled sands with significantly higher fines content to be treated the paper describes how densification of granular soils has progressed with the development of new equipment the greater appreciation in the manner in which soils

development of pervious concrete pile ground improvement alternative and behavior under vertical loading permeable granular columns are used to increase the time rate of consolidation reduce liquefaction potential improve bearing capacity and reduce settlement however their behavior depends on the confinement provided by surrounding soil which limits their use in very soft clays and silts and organic and peat soils this research effort aims to develop a new ground improvement method using pervious concrete piles pervious concrete piles provide higher stiffness and strength that are independent of surrounding soil confinement while offering permeability comparable to granular columns this proposed ground improvement method can improve the performance of different structures supported on poor soils to achieve the goal of the research project four vertical load tests were performed on one granular column and three pervious concrete piles in this paper the material properties of pervious concrete the developed installation method and the vertical load response of pervious concrete and aggregate piles are presented and the variation of soil stresses and displacement during pile installation are briefly discussed the experimental test results show that the ultimate load capacity of the pervious concrete pile was 4 4 times greater than that of an identical granular column in addition the ultimate load capacity of a pervious concrete pile installed using the developed technique was 2 6 times greater than a precast pervious concrete pile the used installation method created nonuniform lateral soil displacement and increased vertical and horizontal soil stresses

large scale passive earth pressure load displacement tests and numerical simulation passive earth pressure is recorded in two different tests using a 6 7 m long 2 9 m wide soil container in these tests sand with 7 silt content is densely compacted behind a moveable test wall to a supported height of 1 68 m 5 5 ft lateral load is applied to the vertical reinforced concrete wall section which displaces freely along with the adjacent backfill in the horizontal and vertical directions the recorded passive resistance is found to increase until a peak is reached at a horizontal displacement of 2 7 3 of the supported backfill height decreasing thereafter to a residual level in this test configuration a triangular failure wedge shape is observed due to the low mobilized wall soil friction backfill strength parameters are estimated based on this observed failure mechanism from these estimates along with triaxial and direct shear test data theoretical predictions are compared with the measured passive resistance using the test data a calibrated finite element model is employed

modeling the stone column behavior in soft ground with special emphasis on lateral deformation abstractamong various ground improvement techniques soft soil reinforcement by stone columns is one of the most common and convenient methods with numerous benefits including increased bearing cap

development of a sequential extraction procedure for iron implications for iron partitioning in continentally derived particulates abstract the development of a sequential extraction procedure for iron in modern and ancient sediments is presented the scheme recognizes seven operationally derived iron pools 1 carbonate associated fe fe carb including siderite and ankerite 2 easily reducible oxides fe ox1 including ferrihydrite and lepidocrocite 3 reducible oxides fe ox2 including goethite hematite and akaganeite 4 magnetite fe mag 5 poorly reactive sheet silicate fe fe prs 6 pyrite fe fe py and 7 unreactive silicate fe fe u as such this is the first extraction scheme specifically developed to allow the separate identification of magnetite and the first to allow a complete evaluation of fe carbonate phases such as siderite and ankerite the scheme was developed following tests on pure mineral phases to evaluate the minerals solubilized by each technique and to determine optimum extraction times further tests on mixtures of pure minerals and on grain size separated sediments from two major us rivers and two glacial meltwaters validate the specificity of the scheme for different pools of iron minerals and demonstrate a high degree of reproducibility for each analytical stage the data obtained for the riverine and glacial sediments are additionally discussed in relation to the dominant modes of transport of different iron minerals in fine grained continental sediments

influence of sea level rise on iron diagenesis in an east florida subterranean estuary abstract subterranean estuary occupies the transition zone between hypoxic fresh groundwater and oxic seawater and between terrestrial and marine sediment deposits consequently we hypothesize in a subterranean estuary biogeochemical reactions of fe respond to submarine groundwater discharge sgd and sea level rise porewater and sediment samples were collected across a 30 m wide freshwater discharge zone of the indian river lagoon florida usa subterranean estuary and at a site 250 m offshore porewater fe concentrations range from 0 5 m at the shoreline and 250 m offshore to about 286 m at the freshwater saltwater boundary sediment sulfur and porewater sulfide maxima occur in near surface oc rich black sediments of marine origin and dissolved fe maxima occur in underlying oc poor orange sediments of terrestrial origin freshwater sgd flow rates decrease offshore from around 1 to 0 1 cm day while bioirrigation exchange deepens with distance from about 10 cm at the shoreline to about 40 cm at the freshwater saltwater boundary doc concentrations increase from around 75 m at the shoreline to as much as 700 m at the freshwater saltwater boundary as a result of labile marine carbon inputs from marine sgd this labile doc reduces fe oxides which in conjunction with slow discharge of sgd at the boundary allows dissolved fe to accumulate upward advection of fresh sgd carries dissolved fe from the fe oxide reduction zone to the sulfate reduction zone where dissolved fe precipitates as fe sulfides saturation models of fe sulfides indicate some fractions of these fe sulfides get dissolved near the sediment water interface where bioirrigation exchanges oxic surface water the estimated dissolved fe flux is approximately 0 84 m fe day per meter of shoreline to lagoon surface waters accelerated sea level rise predictions are thus likely to increase the fe flux to surface waters and local primary productivity particularly along coastlines where groundwater discharges through sediments

in situ evaluation of k0 in eastern canada clays an approximate value of the horizontal effective stress in an overconsolidated clay deposit is often determined from an estimate of the effective stress ratio k0 using the equation it is also generally considered that the parameter is approximately equal to sin for evaluating k0 in sensitive clays of eastern canada a testing program has been initiated on three different sites representing a large range of overconsolidation ratios three different in situ devices were used the cambridge self boring pressuremeter the flat dilatometer and hydraulic fracturing the results show that the different techniques give essentially the same k0 values they also give k0 values larger than those expected with an parameter typically between 0 75 and 1 15 key words clay dilatometer horizontal stress hydraulic fracturing in situ tests self boring pressuremeter

performance of embankments on liquefiable soils improved with dense granular columns observations from case histories and centrifuge experiments abstractdense granular columns dgcs are generally known to mitigate the liquefaction hazard through a combination of 1 installation induced ground densification 2 enhanced drainage and 3

evaluation of in situ anisotropy from crosshole and downhole shear wave velocity measurements downhole and cross hole shear wave velocity determinations are becoming a routine part of dynamic site evaluation studies the in situ measurements are frequently performed in boreholes using a variety of techniques a seismic cone system has been developed for determining both downhole and crosshole shear wave velocity the system consists of a source and two receivers all embodied in penetrometers at any depth three different polarized sets of shear wave signals can be generated and are recorded by both receivers located at different distances from the source it has been suggested from laboratory tests in large chambers that the measured shear wave velocities can be used to evaluate the in situ stress conditions tests have been performed at research sites in vancouver to evaluate the in situ stress dependence of the measured shear wave velocities the results of this study suggest that variations in structural anisotropy are the predominant factors controlling the directional shear wave velocities

geotechnical site characterization in the greater memphis area using cone penetration tests abstract the determination of seismic ground hazards in memphis and shelby county tennessee is facilitated by the use of electronic cone penetration tests that can provide up to four independent readings with depth from a single sounding one series of soundings is being performed for site specific mapping to determine the presence and extent of potentially liquefiable sediments in situ soil resistance to liquefaction and initial soil stiffness for ground motion amplification studies another series of soundings is being conducted in conjunction with field paleoliquefaction mapping in the new madrid seismic zone to better define the intensity magnitude and geographic extent of ground failures caused by large past earthquake events as well as information about the source sands in this paper an overview is given on the types of multi channeled penetrometer data that are being collected including vertical profiles of cone tip stress qt sleeve friction fs penetration porewater pressure u1 or u2 downhole shear wave velocity vs and or electrical conductivity ke representative soundings are presented from select sites to illustrate repeatability data post processing methods and that derived downhole vs profiles are generally in good agreement with non invasive surface techniques at two memphis test sites cyclic stress based procedures for liquefaction are discussed with relation to data from a paleoliquefaction site in germantown tennessee and estimates of the minimum magnitude of the historic event are discussed while estimates of the earthquake magnitude are preliminary pending additional study on attenuation relationships and site response in the deep soils of the mississippi embayment it is inferred from evaluation of in situ test data using cyclic stress based techniques that the december 1811 new madrid earthquake was likely larger than a mw 7 5 event

mitigation of liquefaction and associated ground deformations by stone columns soil liquefaction and associated ground failures have been a major source of damage during the past earthquakes the risk of liquefaction and associated ground deformation can be reduced by various ground improvement methods including the stone column gravel drain technique this paper presents the current state of the stone column technologies as a liquefaction countermeasure a comprehensive review is provided aiming to a identify key considerations for the general use of stone columns as a liquefaction countermeasure b provide insights for design and construction c compile the latest research developments and d identify sources of useful information case histories of field applications and observed field performance are cited to portray different stone column applications and observed effectiveness the paper identifies areas where more research is needed and includes recommendations for future research and development

centrifuge modeling of prefabricated vertical drains for liquefaction remediation drainage methods for liquefaction remediation have been in use since the 1970s and have traditionally included stone columns gravel drains and more recently prefabricated vertical drains this paper presents the results from a dynamic centrifuge test designed to evaluate the performance of a liquefiable site treated with prefabricated vertical drains the centrifuge model consisted of gently sloping untreated and treated liquefiable soil deposits overlain by a clay crust the model was subjected to multiple shaking events that included both recorded earthquake acceleration time histories and sinusoidal input motions comparisons of deformations and excess pore water pressures in the untreated and treated areas showed that drains were effective in expediting the dissipation of excess pore water pressures and reducing deformations however depending on the characteristics of the input ground motion the peak excess pore pressures in the treated area were not always substantially smaller than in the untr

model for predicting displacement dependent lateral earth pressure a model for predicting displacement dependent lateral earth pressure was proposed based on an earth pressure displacement relationship commonly observed in practice the proposed model is a monot

a depth consistent spt based empirical equation for evaluating sand liquefaction abstract focusing on the deficiencies of the current liquefaction evaluation methods typically on deep sandy layers of 10 m to 20 m a new liquefaction evaluation formula which is based on the 156 spt data from liquefaction investigation in china mainland is proposed the formula is plausible for wide depth range up to 20 m the formula which takes a hyperbolic function form fits the liquefaction data at shallow depth and predicts satisfactorily deep liquefaction the liquefaction dataset available from china earthquakes and foreign earthquakes i e kobe earthquake and chichi earthquake are statistically summarized the deficiencies of prevailing liquefaction evaluation methods and the csr method by seed are pinpointed to validate the proposed formula a liquefaction dataset consist of 312 liquefaction data from china mainland and foreign countries is used for re evaluation the results indicate that the new formula is quite feasible for wide sandy layer buried depth different seismic intensities and varying groundwater tables comparing with the current chinese code methods and the csr method the new formula which approaches to an asymptote eliminates the abnormality of the csr method that decreases inversely when the depth exceeds a certain value the new formulae solve the deficiency of chinese codified liquefaction evaluation methods that are conservative for intensity vii at shallow depth

a comparative study of manganese dynamics in the water column and sediments of intertidal systems of the north sea abstract the dynamics of the redox sensitive trace metal manganese mn and its response to biological activity were investigated in the water column and shallow pore waters of the german wadden sea southern north sea in 2008 and 2009 two systems one from the southern backbarrier area of spiekeroog island and one from the eastern part sylt romo wadden sea of the german bight were compared the major aim was to examine to which extent biogeochemical findings are specific for a particular tidal basin or transferable to other basins of the german wadden sea although both study areas reveal hydrodynamical sedimentological and ecological differences qualitatively pronounced similarities in mn dynamics are observed thus complex cycling of dissolved mn with increasing values in spring and late summer due to elevated biological activity as well as a depletion period in early summer were observed in both study areas this finding suggests a seasonal behaviour of mn being generally representative for the tidal basins of the southern north sea quantitative differences are significant as the backbarrier area of spiekeroog island shows much higher concentrations of dissolved mn in the water column especially during spring we suggest that this difference is due to a larger sediment area water volume ratio in the spiekeroog backbarrier area combined with a higher release of dissolved mn from the tidal flat sediments as seen in pore water profiles from surface sediments site specific differences are also seen in further tidal systems of the north frisian wadden sea which are characterised by individual hydrodynamical and sedimentological conditions several transects leading from offshore locations towards the coast also revealed a highly variable mn level overall the north frisian wadden sea most likely represents a less important source for dissolved mn than the east frisian wadden sea furthermore our data suggest that site specific properties of the different tidal basins have to be considered in budget calculations for the entire wadden sea

fractionation processes in deccan traps magmas comments on the paper by g sen mineralogy and petrogenesis of the deccan trap lava flows around mahabaleshwar india

pyritization a palaeoenvironmental and redox proxy reevaluated abstract pyrite as a proxy for the redox states of bottom waters was evaluated in the context of modern salt marsh sediments two sites 40 m apart with very different physicochemical properties were sampled seasonally the sites differed from each other in 1 the amount of tidal flushing 2 vegetation 3 redox condition below the sediment water interface 4 carbon content and 5 solid phase iron oxyhydroxide and iron sulfide content of the sediment the calculated degree of pyritization dop varies between 0 44 and 1 0 depending on the site and the season different dop values were obtained for the same samples when different techniques were applied for extraction of reactive iron framboidal pyrite was dominant however other textural forms of pyrite were also observed the size distribution of the individual pyrite crystals and the framboids was fairly narrow with the majority of them having diameters

passive earth pressures theories and tests the magnitude of the passive earth pressure that resists the movement of a structure is controlled by the amount the structure moves and the direction in which it moves strength and stiffness of the soil that resists its movement friction or adhesion on the interface between the structure and soil and shape of the structure the log spiral theory corrected for 3d effects provides an accurate means of computing ultimate passive pressures a hyperbolic expression together with estimated values of soil modulus and ultimate resistance provides a means of estimating the relationship between structural movement and passive resistance it is essential that the soil strength and stiffness used in making these estimates should be appropriate for the soil and the drainage conditions involved the results of an undrained passive pressure load test in stiff sandy silt and a drained passive pressure load test in well graded gravel are compared with passive pressures computed using the methods discussed reasonable agreement between the calculated and measured values shows that the log spiral theory corrected for 3d effects and the hyperbolic load deflection relationship provide an adequate means of estimating passive resistance for a wide range of conditions

pathways of organic carbon oxidation in three continental margin sediments we have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of denmark and norway rates of nh4 and sigma co2 liberation sediment incubations were used with o2 penetration depths to conclude that o2 respiration accounted for only between 3 6 17 4 of the total organic carbon oxidation dentrification was limited to a narrow zone just below the depth of o2 penetration and was not a major carbon oxidation pathway the processes of fe reduction mn reduction and sulfate reduction dominated organic carbon mineralization but their relative significance varied depending on the sediment where high concentrations of mn oxide were found 3 4 wt mn only mn reduction occurred with lower mn oxide concentrations more typical of coastal sediments fe reduction and sulfate reduction were most important and of a similar magnitude overall most of the measured o2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon we suspect that the importance of o2 respiration in many coastal sediments has been overestimated whereas metal oxide reduction both fe and mn reduction has probably been well underestimated

advective pore water input of nutrients to the satilla river estuary georgia usa abstract in situ benthic flux measurements pore water nutrient profiles water column nutrient distributions sediment grain size distributions and side scan sonar observations suggest that advective transport of pore waters may be a major input pathway of nutrients into the satilla river estuary coastal georgia usa in situ benthic chamber incubations demonstrate the occurrence of highly variable but occasionally very large sea floor fluxes of silicate phosphate and ammonium locally occurring benthic microbial mineralization of organic matter as estimated by s35 sulphate reduction rate measurements is insufficient to support these large fluxes we hypothesize that the observed interlayering of permeable sandy sediments with fine grained organic rich sediments in the estuary provides conduits for advective transport of pore water constituents out of the sediments because permeable layers may extend significant distances beneath the salt marsh the large fluxes observed may be supported by remineralization occurring over large areas adjacent to the estuary advective transport may be induced by pressure gradients generated by a variety of processes including landward recharge by meteoric or rain waters if sand layers extend far enough into the maritime coastal lands alternatively tidal variations across the salt marsh sediment surface may hydraulically pump water through the sediment system because these fluxes appear to be concentrated into small layers this source may be a significant input of nutrients to the estuary even if permeable sandy layers comprise a very small proportion of the seabed

relationships between crustal contamination and crystallisation in continental flood basalt magmas with special reference to the deccan traps of the western ghats india the upper part of the deccan traps sequence bushe to mahabaleshwar formations shows a statistically significant tendency for the most mafic lavas to be the most contaminated by crustal materials this is the reverse of the relationship shown by suites evolving by contamination accompanied by fractional crystallisation afc the observed correlations e g between mg number and sr isotope initial ratios are partly an accidental consequence of the fact that the most mafic lavas are more abundant in the lower part of the sequence while contaminant availability declines in the upper part it is probable however that the correlations are augmented by increased contamination of hotter magma batches during ascent through dykes a process during which fractional crystallisation is suppressed by magmatic turbulence the absence of afc relationships suggests that most of the contamination took place during the ascent stage rather than in a magma chamber other continental flood basalt provinces such as the parana and etendeka do show afc relationships and it is speculated that this may be a result of magma chamber contamination coupled with flow rates which prevent contamination during ascent

dynamic centrifuge tests to evaluate reinforcing mechanisms of soil cement columns in liquefiable sand abstractfour centrifuge tests were performed to investigate the reinforcing mechanisms of soil cement columns in liquefiable sand two unimproved baseline models and two models improved with soil cement columns were subjected to sine sweep and earthquake base motions of varying intensities to observe acceleration pore pressure lateral displacement and settlement responses the dynamic records were processed to derive the effective natural frequency of the profiles and to obtain the dynamic stress strain responses for unimproved and improved soil it was found that the shear reinforcement mechanisms of columns was not effective in reducing cyclic stress ratios in the treated soil liquefaction triggering occurred nearly at same time for both unimproved and improved soil cases and the magnitude of the resulting soil settlement was not significantly reduced when the bases of the columns were free to rotate the columns rocked within the soil and produced negligible shear stiffening of the soil profile w

ohmic conductivity of a compacted silty clay in its natural state loess can be considered as an unstable soil which develops large deformations when moistened in argentina loess is used in most geotechnical constructions including embankments and liners the interest of this work to evaluate the potential application of electrical conductivity measurements for monitoring the effects introduced by remolding and compaction in the soil samples of loess were compacted at varied densities and mixed with electrolytes of different concentrations electrical conductivity was measured with a two electrode cell the effects introduced on the measured conductivity by frequency degree of saturation soil density temperature and electrolyte type and concentration are addressed additionally hydraulic permeability tests were performed on compacted specimens of loess and the relationship between electrical and hydraulic conductivity was determined it is concluded here that the ohmic conductivity of compacted specimens depends mainly on the salt concentr

influence of prefabricated vertical drains on the seismic performance of similar neighbouring structures founded on liquefiable deposits increasing the resilience of structures to seismically induced soil liquefaction is a major objective for the earthquake engineering community increasingly soil drains are being used to mitigate

trace element cycling in a subterranean estuary part 2 geochemistry of the pore water abstract submarine groundwater discharge sgd is an important source of dissolved elements to the ocean yet little is known regarding the chemical reactions that control their flux from sandy coastal aquifers the net flux of elements from sgd to the coastal ocean is dependent on biogeochemical reactions in the groundwater seawater mixing zone recently termed the subterranean estuary this paper is the second in a two part series on the biogeochemistry of the waquoit bay coastal aquifer subterranean estuary the first paper addressed the biogeochemistry of fe mn p ba u and th from the perspective of the sediment composition of cores charette et al charette m a sholkovitz e r hansell c m 2005 trace element cycling in a subterranean estuary part 1 geochemistry of the permeable sediments geochim cosmochim acta 69 2095 2109 this paper uses pore water data from the subterranean estuary along with bay surface water data to establish a more detailed view into the estuarine chemistry and the chemical diagenesis of fe mn u ba and sr in coastal aquifers nine high resolution pore water groundwater profiles were collected from the head of the bay during july 2002 there were non conservative additions of both ba and sr in the salinity transition zone of the subterranean estuary however the extent of sr release was significantly less than that of its alkaline earth neighbor ba pore water ba concentrations approached 3000 nm compared with 25 50 nm in the surface waters of the bay the pore water sr salinity distribution suggests a 26 elevation in the amount of sr added to the subterranean estuary the release of dissolved ba to the mixing zone of surface estuaries is frequently attributed to an ion exchange process whereby seawater cations react with ba from river suspended clay mineral particles at low to intermediate salinity results presented here suggest that reductive dissolution of mn oxides in conjunction with changes in salinity may also be an important process in maintaining high concentrations of ba in the pore water of subterranean estuaries in contrast pore water u was significantly depleted in the subterranean estuary a result of sgd driven circulation of seawater through reducing permeable sediments this finding is supported by surface water concentrations of u in the bay which were significantly depleted in u compared with adjacent coastal waters using a global estimate of sgd we calculate u removal in subterranean estuaries at 20 106 mol u y 1 which is the same order of magnitude as the other major u sinks for the ocean our results suggest a need to revisit and reevaluate the oceanic budgets for elements that are likely influenced by sgd associated processes

geochemistry of iron and manganese in soils and sediments of a mangrove system island of pai matos cananeia sp brazil abstract five zones along a transect of 180 m were selected for study on the island of pai matos sao paulo brazil four of the zones are colonised by vascular plants spartina sp laguncularia lg avicennia av and rhizophora rh and were denominated soils and the other zone which lacks vegetation was denominated sediment sd the geochemical conditions differed significantly in soils and sediment and also at different depths the soils were oxic eh 350 mv or suboxic eh 350 100 mv at the surface and anoxic eh

equivalent linear computation of response spectra for liquefiable sites the spectral envelope method abstracta simplified methodology is proposed for the computation of elastic response spectra at liquefiable sites based on the widely used equivalent linear frequency domain site response analysis method the actual response spectrum is obtained as the upper bound envelope of the thus calculated response spectra corresponding to the preliquefaction and the postliquefaction segments of the seismic excitation the former computed for the natural soil properties and the latter for the properties of the liquefied soil the time of liquefaction onset which separates the two seismic excitation segments is defined in terms of the minimum factor of safety against liquefaction within the liquefiable layer additional guidelines are provided for the estimation of the excess pore pressure buildup and the associated soil softening during the preliquefaction segment of the seismic excitation as well as for the definition of the liquefied soil stiffness and the hysteretic damping ratio the proposed methodology h

abundance and speciation of iron across a subtropical tidal marsh of the min river estuary in the east china sea abstract iron has profound influence on anaerobic organic matter oxidation and fe s c biogeochemical cycling in tidal marshes to examine the abundance and speciation of iron six iron species poor crystalline fe iii crystalline fe iii non sulfidic fe ii porewater fe2 fes and fes2 were investigated in a cross transect span 250 m depth 1 2 m in a tidal marsh of the min river estuary in the east china sea the results suggested that sediment characteristics ph redox condition conductivity chloride sulfate and organic matter create a highly heterogeneous geochemical framework in the cross transect correspondingly the zonation of iron species differed significantly across the tidal marsh poor crystalline fe iii 48 24 mol g 1 and crystalline fe iii 75 32 mol g 1 accumulated on the surface of the high tide zone and decreased with elevation the non sulfidic fe ii minerals 140 61 mol g 1 accounted for the largest proportion of the six iron species the porewater fe2 was enriched within the deep layer of the upland region ph 6 2 6 5 and exhibited a maximum of 11 49 mm the aqueous sulfide concentration was below detection fes 39 6 mol g 1 and fes2 57 25 mol g 1 accumulated closer to the lower extremity tidal water brought o2 and removed certain amounts of dissolved organic carbon dissolved inorganic carbon and fe iii bearing particles in an element budget during tidal inundation variations of topography tidal hydrology seawater intrusion and organic matter altered the dominant organic matter oxidation pathway and further affected iron mineralization

simulation of downhole and crosshole seismic tests on sand using the hydraulic gradient similitude method a method of simulating downhole and crosshole seismic shear wave tests in a model under controlled stress conditionsis described the downhole and shear wave in horizontal plane sh crosshole shear waves are generated and received along the principal stress axes using piezoceramic bender elements the k0in situ stress conditions including loading and unloading stress paths are simulated by the hydraulic gradient similitude method which allows high stresses simulating field conditions to be obtained the horizontal stress during the tests is directly measured by a lateral total stress transducer the test data are used to evaluate various published empirical equations that relate shear wave velocity and soil stress state it is found that although the various empirical equations can predict the in situ shear wave velocity profile reasonably well only the equation that relates the shear wave velocity to the individual principal stresses in the directions of wave propagation and particle motion can pred

assessment of the coefficient of the earth pressure at rest from shear wave velocity measurements the paper presents an attempt to evaluate the feasibility of predicting the value of the coefficient of the earth pressure at rest k of natural soil deposits on the basis of the measured velocities of the seismic shear waves the experimental data presented were obtained from seismic tests performed in a calibration chamber on laboratory prepared specimens of seven granular materials with grades ranging from fine sand to gravelly sand the relationship between k and the shear wave velocity established using the calibration chamber results was used successfully to predict k at two well documented sites for which both cross hole seismic and seismic piezocone penetration test results are available cet expose dicrit un essai destine a evaluer la faisabilite dune pr6vision de la valeur du coefficient de pression au sol au repos ko des depots de sol naturels en se basant sur les velocies mesurees des ondes sismiques transversales les donn6es experimentales qui sont presentees dans cet exposa viennen

a geological map of the southern deccan traps india and its structural implications a geological map of an area of over 125 000 km 2 within the southern deccan traps india is presented which is based upon variations in the basalt geochemistry it represents a synthesis of new data and earlier work the use of large data sets has allowed stratigraphic boundaries to be established with greater accuracy over a much larger area than before the geochemical sections demonstrate that the southward overstepping stratigraphic style encountered along the ghats ridge has an essentially north to south polarity and that there appears to be detectable overstep in an east to west sense however the stratigraphy defines a pronounced coastward dipping monoclinal flexure across the western ghats ridge between 16 n and 18 n the data are consistent with two models of eruption the first considers the deccan eruptive focus to have been fixed throughout the volcanic episode producing an essentially annular flow pattern the second considers the flow pattern to have been generated from a southerly migrating eruptive centre resulting from the northerly drift of india over a fixed hotspot both hypotheses are consistent with recent quantitative models which suggest that rapid and voluminous flood basalt eruptions are the result of continental rifting events associated with plume generated thermal 9highs9 until a causal link between established plume hotspot trails and impact sites can be satisfactorily demonstrated we find it unnecessary to invoke a cataclysmic impact event as an explanation for the deccan eruptions

passive pressure coefficients critical failure surface and its kinematic admissibility using a combination of a logarithmic spiral and a straight line as a failure surface comprehensive charts have been developed to determine the passive earth pressure coefficients and the positions of the critical failure surface for positive as well as negative wall friction angles translational movement of the wall has been examined in detail considering the soil as either an associated flow dilatant material or a non dilatant material to determine the kinematic admissibility of the limit equilibrium solutions

iron geochemical zonation in a tidally inundated acid sulfate soil wetland abstract tidal inundation is a new technique for remediating coastal acid sulfate soils cass here we examine the effects of this technique on the geochemical zonation and cycling of fe across a tidally inundated cass toposequence by investigating toposequence hydrology in situ porewater geochemistry solid phase fe fractions and fe mineralogy interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation redistribution and subsequent mineralogical transformations of fe within the landscape reductive dissolution of fe iii minerals including jarosite kfe3 so4 2 oh 6 resulted in elevated concentrations of porewater fe2 30 mmol l 1 in former sulfuric horizons in the upper intertidal zone tidal forcing generated oscillating hydraulic gradients driving upward advection of this fe2 enriched porewater along the intertidal slope subsequent oxidation of fe2 led to substantial accumulation of reactive fe iii fractions up to 8000 mol g 1 in redox interfacial tidal zone sediments these fe iii precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation schwertmannite fe8o8 oh 6so4 was the dominant fe mineral phase in the upper intertidal zone at mainly low ph 3 4 this was followed by increasing lepidocrocite feooh and goethite feooh at circumneutral ph within lower intertidal and subtidal zones relationships were evident between fe fractions and topography there was increasing precipitation of fe sulfide minerals and non sulfidic solid phase fe ii in the lower intertidal and subtidal zones precipitation of fe sulfide minerals was spatially co incident with decreases in porewater fe2 a conceptual model is presented to explain the observed landscape scale patterns of fe mineralisation and hydro geochemical zonation this study provides valuable insights into the hydro geochemical processes caused by saline tidal inundation of low lying cass landscapes regardless of whether inundation is an intentional strategy or due to sea level rise

sulfur biogeochemical cycling and novel fe s mineralization pathways in a tidally re flooded wetland abstract sulfur biogeochemical cycling and associated fe s mineralization processes exert a major influence over acidity dynamics electron flow and contaminant mobility in wetlands benthic sediments and groundwater systems while s biogeochemical cycling has been studied intensively in many environmental settings relatively little direct information exists on s cycling in formerly drained wetlands that have been remediated via tidal re flooding this study focuses on a tidal wetland that was drained in the 1970s causing severe soil and water acidification and subsequently remediated by controlled re flooding in 2002 we examine so 4 2 reduction rates and fe s mineralization at the tidal fringe 7 years after the commencement of re flooding the initial drainage of the wetland examined here caused in situ pyrite fes2 oxidation resulting in the drained soil layers being highly acidic and rich in so 4 2 bearing fe iii minerals including jarosite kfe3 so4 2 oh 6 tidal re flooding has neutralized much of the previous acidity with the pore water ph now mostly spanning ph 5 7 the fastest rates of in situ so 4 2 reduction up to 300 nmol cm 3 day 1 occur within the inter tidal zone in the near surface soil layers to 60 cm below ground surface the so 4 2 reduction rates correlate with pore water dissolved organic c concentrations thereby suggesting that electron donor supply was the predominant rate determining factor elemental s was a major short term product of so 4 2 reduction comprising up to 69 of reduced inorganic s in the near surface soil layers this enrichment in elemental s can be partly attributed to interactions between biogenic h2s and jarosite a process that also contributed to enrichment in pore water fe2 up to 55 mm and so 4 2 up to 50 mm the iron sulfide thiospinel greigite fe3s4 was abundant in near surface soil layers within the inter to sub tidal zone where tidal water level fluctuations created oscillatory redox conditions there was evidence for relatively rapid pyrite re formation within the re flooded soil layers however the results indicate that pyrite re formation has occurred mainly in the lower formerly drained soil layers whereas the accumulation of elemental s and greigite has been confined towards the soil surface the discovery that pyrite formation was spatially decoupled from that of elemental s and greigite challenges the concept that greigite is an essential precursor required for sedimentary pyrite formation in fact the results suggest that greigite and pyrite may represent distinct end points of divergent fe s mineralization pathways overall this study highlights novel aspects of fe s mineralization within tidal wetlands that have been drained and re flooded in contrast to normal undisturbed tidal wetlands as such the long term biogeochemical trajectory of drained and acidified wetlands that are remediated by tidal re flooding cannot be predicted from the well studied behaviour of normal tidal wetlands

the pressure distribution along stone columns in soft clay under consolidation and foundation loading the mechanism whereby foundation loading is transmitted through the column has received little attention from researchers this paper reports on some interesting findings obtained from a laboratory based model study in respect of this issue the model tests were carried out on samples of soft clay 300 mm in diameter and 400 mm high the samples were reinforced with fully penetrating stone columns of three different diameters made of crushed basalt four pressure cells were located along each stone column the 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions the results show that the dissipation of excess pore water pressure developed during the initial application of total stresses when the foundation was subjected to no loading generated considerable stresses within the column and that this was directly attributable to the development of negative skin friction the pressure distributions

root reinforcement of soils under compression it is well recognized that roots reinforce soils and that the distribution of roots within vegetated hillslopes strongly influences the spatial distribution of soil strength previous studies have focussed on the contribution of root reinforcement under conditions of tension or shear however no systematic investigation into the contribution of root reinforcement to soils experiencing compression such as the passive earth forces at the toe of a landslide is found in the literature an empirical analytical model coros for the quantification of root reinforcement in soils under compression is presented and tested against experimental data the coros model describes the force displacement behavior of compressed rooted soils and can be used to provide a framework for improving slope stability calculations laboratory results showed that the presence of 10 roots with diameters ranging from 6 to 28 mm in a rectangular soil profile 0 72 m by 0 25 m increased the compressive strength of the soil by about 40 2 5 kn at a displacement of 0 05 m while the apparent stiffness of the rooted soil was 38 higher than for root free soil the coros model yields good agreement with experimentally determined values of maximum reinforcement force and compression force as a function of displacement these results indicate that root reinforcement under compression has a major influence on the mechanical behavior of soil and that the force displacement behavior of roots should be included in analysis of the compressive regimes that commonly are present in the toe of landslides

assessing the coefficient of the earth pressure at rest from shear wave velocity and electrical resistivity measurements abstract determination of earth pressure coefficient k 0 in natural soil deposits is a significantly important issue in geotechnical engineering this paper evaluates the feasibility of predicting k 0 values from measurements of vertical and horizontal shear wave velocities v s vh v s hh and v s hv and vertical and horizontal electrical resistivities s v s h a series of seismic piezocone tests scptu improved crosshole ch tests and soil resistivity tests using a modified laboratory apparatus were carried out at two research sites in jiangsu province of china and results were used to develop two existing k 0 shear wave velocity correlations for prediction of k 0 the seismic and electrical resistivity test results showed that both the shear wave velocity ratios v s hh v s hv or v s hv v s vh and the horizontal to vertical electrical resistivity ratio s h s v may provide a good indicator of the inherent soil anisotropy at these sites the existing v s k 0 prediction framework largely requires determining c s hv c s hh ratio and a simple procedure for evaluating this ratio based on the measured horizontal and vertical electrical resistivities the k 0 values predicted by shear wave velocity at both sites are also compared with values determined by jaky s formula and mayne kulhwy s formula in normally consolidated nc soils the k 0 values predicted from these methods showed good agreement however for over consolidated oc soils at shallow depths certain variations between different methods are noted further investigations of the effects of overconsolidation ratio on k 0 predictions will lead to the correction factors for better prediction of k 0 for oc soils this paper has confirmed that reasonable predictions of k 0 for natural soil deposits can be made using the proposed methodology

importance of crystal settling in the differentiation of deccan trap basaltic magmas recent research on the mechanism of differentiation of magmas has seriously challenged the idea of crystal settling and invited alternative interpretation in terms of convective f ractionation here we present data for basalts that suggest that the older hypothesis should still be regarded as significant in the evolution of this magma type we describe mixed sequences of aphyric and porphyritic eruptions among which only the denser liquids have brought suspended crystals to the surface discriminating strongly in favour of plagioclase the least dense solid phase by implication ferromagnesian minerals have been selectively lost by crystal set tling from the porphyritic magmas and all crystallizing phases have been lost from the less dense aphyric magmas

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

speciation and spatial distribution of solid phase iron in surface sediments of the east china sea continental shelf abstract speciation and reactivity characterization of solid phase fe in marine sediments are of significance to understanding its heterogeneous mineralogy and crystallinity the diagenetic cycling of fe and its regulating roles on many other elements in sediments in this study a combination of sequential and single step extractions was used for the determination of seven fe pools in surface sediments of the east china sea ecs continental shelf 1 carbonate associated fe fe ii carb plus acid volatile sulfide fe fe ii avs 2 easily reducible amorphous poorly crystalline fe oxides fe ox1 3 reducible crystalline fe oxides fe ox2 4 magnetite fe mag 5 poorly reactive sheet silicate fe fe prs 6 pyrite fe fe py and 7 unreactive silicate fe fe u total fe fe t in the sediments is largely determined by terrestrial aluminosilicate particles as indicated by a great similarity of the fe t with that of the yangtze river and global riverine particulates the size of fe prs is found to be the largest pool followed by fe u fe ox2 fe mag fe ii avs carb fe ox1 and fe py the large fe prs may result from neoformation of fe rich clay minerals via reverse weathering and subsequent ageing the small sizes of fe ii avs carb and fe py pools is believed to be the result of low so 4 reduction due to generally low labile organic matter together with the oxic suboxic dynamic environments of the surface sediments the occurrence of fe ox1 fe ox2 and fe prs in the sediments is closely associated with the clay fraction as indicated by a high spatial correlation between the former and the latter highly reactive fe fe hr in the sediments is comparable to that in global marine sediments but apparently lower than in the yangtze river and global riverine particulates due probably to sequestration in the yangtze estuary the ratios of fe hr fe t fe pr fe t and fe u fe t in the ecs surface sediments consistently show more similarity to those in the yangtze river particulates than in the global continental margin or deep sea sediments the surface sediments maintain a high level of buffering capacity toward sulfidation suggested by a large fraction of highly reactive fe iii oxides fe iii hr in fe hr

liquefaction induced softening of load transfer between pile groups and laterally spreading crusts laterally spreading nonliquefied crusts can exert large loads on pile foundations causing major damage to structures while monotonic load tests of pile caps indicate that full passive resistance may be mobilized by displacements on the order of 1 7 of the pile cap height dynamic centrifuge model tests show that much larger relative displacements may be required to mobilize the full passive load from a laterally spreading crust onto a pile group the centrifuge models contained six pile groups embedded in a gently sloping soil profile with a nonliquefied crust over liquefiable loose sand over dense sand the nonliquefied crust layer spread downslope on top of the liquefied sand layer and failed in the passive mode against the pile foundations the dynamic trace of lateral load versus relative displacement between the free field crust and pile cap is nonlinear and hysteretic and depends on the cyclic mobility of the underlying liquefiable sand ground motion characteristics and cyclic degradation and cracking of the nonliquefied crust analytical models are derived to explain a mechanism by which liquefaction of the underlying sand layer causes the soil to pile cap interaction stresses to be distributed through a larger zone of influence in the crust thereby contributing to the softer load transfer behavior the analytical models distinguish between structural loading and lateral spreading conditions load transfer relations obtained from the two analytical models reasonably envelope the responses observed in the centrifuge tests

consolidation theory for a composite foundation considering radial and vertical flows within the column and the variation of soil permeability within the disturbed soil zone to remedy the contradiction between the equal strain assumption and the flow continuity assumption at a soil column interface the traditional flow continuity assumption was abandoned and the radial and vertical flows within a stone column were incorporated to consider the column consolidation and deformation in a coupled fashion moreover two possible variation patterns of the horizontal permeability coefficient of soil within the disturbed soil zone were included to reflect the detrimental influence on the surrounding soil due to column construction in addition a linearly changed total vertical stress along the column depth was assumed to achieve a more realistic stress distribution in practice by considering the above mentioned characteristics the governing equations for this type of consolidation problem were developed the solutions for the governing equations were subsequently derived by using a new initial condition obtained from the equilibrium condition and equal strain assumption on the

the bhuj india earthquake lessons learned for earthquake safety of dams on alluvium abstract the bhuj india earthquake of 26 january 2001 m s 7 9 caused dams built on alluvium to sustain damage ranging from cosmetic to severe major damage was caused almost entirely by soil liquefaction in the alluvium the critical factor was the level of earthquake ground motion the bhuj earthquake showed that peak horizontal accelerations phas 0 2 g were generally safe phas 0 2 g were hazardous when unconsolidated granular foundation soils were water saturated n values of 0 2 g must be evaluated over the full area beneath a new dam and all soils deemed susceptible to liquefaction must be either removed or treated for remediating an old dam reliable options are removal and replacement of liquefiable alluvium beneath upstream and downstream portions of the dam combined with building berms designed to provide stability for the dam should there be a strength loss in soils beneath the dam

the coefficient of earth pressure at rest laboratory experiments on undisturbed specimens of a large number of soft clay deposits as well as previous measurements on clays and granular soils were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest k0 i after sedimentation primary consolidation ii during secondary compression aging iii after active or passive preshearing away from the laterally constrained condition iv during a decrease in effective vertical stress and v during an increase in effective vertical stress in the recompression or compression range in terms of the slope of the effective horizontal versus effective vertical stress path the behavior of k0 is explained using the concept of mobilized angle of friction in laterally constrained deformation condition the jaky equation provides in terms of the angle of internal friction a good estimate of k0 of sedimented normally consolidated young clays and granular soils as well as of of presheared clays and sands

evaluation of the lateral earth pressure coefficients at rest in granular soil deposits using the anisotropic components of s wave velocity abstract determination of the lateral earth pressure coefficients at rest k0 in natural soil deposits is an important issue in geotechnical and geological engineering in this study evaluation of this parameter in a granular soil deposit was examined by using two anisotropic components of the s wave velocity sv and sh wave components to this end thirteen pairs of p and s wave seismic refraction profiles were acquired at two different granular sites in iran the collected shot gathers were processed from which the sv and sh wave velocities were derived the sv wave velocities were obtained by using the multichannel analysis of surface waves masw method while the sh wave velocities were extracted by utilizing the multichannel analysis of love waves malw technique the reference k0 values in the soil deposits were calculated by the mayne and kulhawy s formula based on the friction angles and overconsolidation ratios ocr determined from laboratory tests the curves of the reference k0 values versus the sh sv velocity ratios at both sites strongly confirmed the feasibility of k0 evaluation from the velocity components to develop a global equation for k0 evaluation in granular soil deposits a general regression analysis was conducted on the obtained data from this study combined with those reported in the literature the results showed that reliable values of k0 can be estimated using the sh sv velocity ratios the findings of this study may appropriately serve as references for economic and non invasive in situ k0 identification in granular soil deposits using the surface wave methods

static and seismic passive earth pressure coefficients on rigid retaining structures the passive earth pressure problem is investigated by means of the kinematical method of the limit analysis theory a translational kinematically admissible failure mechanism composed of a sequence