magnetostratigraphy of the willwood formation bighorn basin wyoming new constraints on the location of paleocene eocene boundary abstract the lower eocene willwood formation in the bighorn basin of wyoming preserves a rich and diverse mammalian and floral record the paleomagnetic behavior of the sequence of floodplain paleosols of varying degrees of maturation ranges from excellent to poor we present a magnetostratigraphic section for a composite section near worland wyoming by using a set of strict criteria for interpreting the step wise alternating field and thermal demagnetization data of 266 samples from 90 sites throughout the composite section correlation to the geomagnetic reversal time scale was achieved by combining magnetostratigraphic and biostratigraphic data from this section from a section in the clark s fork basin in northern wyoming and from dsdp site 550 with the isotopic data determined on a tuff near the top of our section our correlation suggests that the bighorn basin composite section in the worland area spans from within chron c24r to near the top of chron c24n or from approximately 55 to 52 ma this correlation places the paleocene eocene boundary within the vicinity of the base of the section cryptochron c24r 6 of cande and kent is tentatively identified some 100 m above the base of the section the temporal framework provided here enables correlation of the mammalian biostratigraphy of the bighorn basin to other continental sequences as well as to marine records it also provides independent chronological information for the calculation of sediment accumulation rates to constrain soil maturation rates we exclude an age as young as 53 ma for the paleocene eocene boundary and support older ages as recommended in recent time scales the location of a tuff dated at 52 8 0 3 ma at the older boundary c24n 1 is consistent with the age of 52 5 ma estimated by cande and kent and inconsistent with that of 53 7 ma from harland et al

undrained cyclic shear behaviour of weathered tephra weathered tephra is prevalent across volcanic islands like the north island of new zealand and is composed of volcanic airfall materials that have been subjected to various soil processes understa

in situ dynamic piezocone penetrometer tests in natural clayey soils a reappraisal of strain rate corrections cone penetration testing with pore pressure measurement cptu is a cost and time efficient way of collecting in situ geotechnical parameters of near surface marine soils for cable and pipeline tr

effect of sleeves and skirts on mitigating spudcan punch through in sand overlying normally consolidated clay punch through failure of mobile jack up rigs is still a main concern for spudcan foundations using centrifuge model tests and numerical modelling this paper examines the mitigating effect of top

response of normally consolidated kaolin clay under irregular cyclic loading and comparison with predictions from the accumulation procedure the accumulation procedure on contour diagrams of shear strain is used in geotechnical design to account for the effect of cyclic loading on offshore foundations in this paper contour diagrams of

imaging a shallow aquifer in temperate glacial sediments using seismic reflection profiling with dmo processing we acquired a seismic reflection profile to image a shallow 100 m aquifer system on a small island in puget sound north of seattle washington the aquifer system is comprised of temperate glacial sedimentary strata with the primary aquifer lying approximately 45 m below the surface we chose the site because there are water well boring descriptions available and a sea cliff parallels the profile location providing stratigraphic control a 20 lb 9 kg weight drop was used as an energy source to acquire a 30 fold common midpoint cmp reflection profile along a 400 m line analysis of the recorded wavefield was not straightforward because of complex stratigraphy and the presence of a laterally variable thin bed 5 15 m of high impedance lodgement till within a few meters of the surface we used finite difference modeling to determine that conventional cmp processing would provide a reasonable approximation for imaging strata in the primary target zone roughly 20 m below the high velocity till fo

rainfall infiltration in a landslide soil deposit importance of inverse particle segregation abstract coarse particles move towards the front and surface of the deposit while fine particles stay in the rear and bottom accordingly the coefficient of permeability of the soil statistically tends to decrease from the surface to the bottom and from the toe to the apex of the deposit this feature can be described by trend functions that describe the changes in particle size and permeability inside the soil deposit in this paper attempts are made to include the physical background in the characterization of geotechnical uncertainties the objectives of this paper are to simulate non stationary fields of particle size and coefficient of permeability in a landslide soil deposit and to analyse rainfall infiltration in the non stationary random fields the soil deposit is assumed to consist of inter layers parallel to the slope surface the soil deposit is also assumed to be axisymmetric therefore any vertical section of the deposit can be selected to generate two dimensional non stationary random fields each of the non stationary random fields is formulated by adding a trend surface to a residual stationary random field with orthogonal major and minor scales of fluctuation the produced random fields follow an exponential correlation structure subsequently steady state rainfall infiltration in the anisotropic non stationary heterogeneous random fields is analysed the effects of variations of saturated permeability and scale of fluctuation on the pore water pressure regime are also investigated

spatial connectivity in a highly heterogeneous aquifer from cores to preferential flow paths 1 this study investigates connectivity in a small portion of the extremely heterogeneous aquifer at the macrodispersion experiment made site in columbus mississippi a total of 19 fully penetrating soil cores were collected from a rectangular grid of 4 m by 4 m detailed grain size analysis was performed on 5 cm segments of each core yielding 1740 hydraulic conductivity k estimates three different geostatistical simulation methods were used to generate 3 d conditional realizations of the k field for the sampled block particle tracking calculations showed that the fastest particles as represented by the first 5 to arrive converge along preferential flow paths and exit the model domain within preferred areas these 5 fastest flow paths accounted for about 40 of the flow the distribution of preferential flow paths and particle exit locations is clearly influenced by the occurrence of clusters formed by interconnected cells with k equal to or greater than the 0 9 decile of the data distribution 10 of the volume the fraction of particle paths within the high k clusters ranges from 43 to 69 in variogram based k fields some of the fastest paths are through media with lower k values suggesting that transport connectivity may not require fully connected zones of relatively homogenous k the high degree of flow and transport connectivity was confirmed by the values of two groups of connectivity indicators in particular the ratio between effective and geometric mean k on average about 2 and the ratio between the average arrival time and the arrival time of the fastest particles on average about 9 are consistent with flow and advective transport behavior characterized by channeling along preferential flow paths

imaging low velocity anomalies with the aid of seismic tomography abstract theoretical considerations snell s law suggest that low velocity fanomalies are undersampled and therefore should be poorly resolved by inversion schemes based on ray tracing methods a synthetic study considering a 40 20 m low velocity anomaly 300 m s placed at the center of a 400 50 m block with gradient background velocity model from 3000 m s at the surface to 4000 m s at the base indicates that the low ray density in ray tracing coverage diagrams of tomographic inversion studies can be used as evidence for the existence of low velocity anomalies combined normal incidence seismic reflection images and the velocity models obtained by tomographic inversions of first arrival travel times form an efficient scheme to resolve low velocity anomalies such as fracture zones furthermore the velocity models derived from tomographic inversions are used in a wave equation datuming algorithm to account for statics caused by a strongly laterally variable shallow surface weathering layer and provide seismic reflection images of fracture zones low velocity anomaly within a granitic pluton

post erosion mechanical response of internally unstable soil of varying size and flow regime one of the leading causes of dam failure is internal erosion the impact of erosion of non plastic fine particles known as suffusion on the soil structure and strength has been studied experiment

high resolution reflection seismics applied to detection of groundwater resources in glacial deposits sweden a large proportion of sweden s ground water resources is contained in sand gravel glaciofluvial deposits that overlie precambrian crystalline basement and are covered by clay the depth to the sand gravel deposits varies from near surface to about 100 m and their thickness is generally 10 20 m traditionally due to logistics short refraction seismic profiles and penetration tests have been used to localize the sand gravel deposits below the clay and to determine their thickness however when the overlying clay deposits are thick or the glacial deposits show significant 2 d structure refracting waves may not penetrate into the sand gravel deposits or into the crystalline basement reflection seismic methods provide an alternative mapping method and a test profile was acquired over glacial deposits where the structure is well known standard processing shows in general excellent agreement between the seismic image and the structure determined from penetration tests

a pore size distribution function based method for estimation of hydraulic properties of sandy soils abstract hydraulic property of soil is key information required for understanding the groundwater flow in the soil including saturated and unsaturated zone the water flow in soil is governed by the geometrical pore space characteristics of soil structure i e pore size distribution function even though the concept of pore size distribution function had been proposed decades ago the pore size distribution function is rarely used to estimate the hydraulic properties in engineering practice in practice the effective particle size i e d10 and void ratio e are commonly used for the estimation of saturated coefficient of permeability ks for sandy soils neither d10 nor e can accurately represent the geometrical pore space in soil with the development of unsaturated soil mechanics it is observed that the pore size distribution function can be expressed in another form which is named as soil water characteristic curve swcc in this study the coefficients of permeability of sandy soils were estimated using the concept of pore size distribution function or swcc the comparison between the estimated results using the proposed equation and the measured data from laboratory tests in nanyang technological university ntu showed that the proposed equation in this note provided good estimation of ks

large deformation finite element analysis of pipe penetration and large amplitude lateral displacement seabed pipelines must be designed to accommodate thermal expansion which is commonly achieved through controlled lateral buckling and to resist damage from submarine slides in both cases the pipe moves laterally by a significant distance and the overall pipeline response is strongly influenced by the lateral pipe soil resistance here the process of pipe penetration and lateral displacement is investigated using a large deformation finite element method with a softening rate dependent soil model being incorporated the calculated soil flow mechanisms pipe resistances and trajectories agree well with plasticity solutions and centrifuge test data it was found that the lateral resistance is strongly influenced by soil heave during penetration and the berm formed ahead of the pipe during lateral displacement for light pipes the pipe rises to the soil surface and the soil failure mechanism involves sliding at the base of the berm in contrast heavy pipes dive downwards and a deep shearing zon

relating in situ hydraulic conductivity particle size and relative density of superficial deposits in a heterogeneous catchment summary estimating the permeability of superficial deposits is fundamental to many aspects of catchment science but can be problematic where insufficient in situ measurements are available from pumping tests in piezometers consequently common practice is to estimate permeability from the material description or where available particle size distribution using a formula such as hazen in this study we examine the relationships between particle size relative density and hydraulic conductivity in superficial deposits in morayshire northern scotland a heterogeneous environment typical of many catchments subject to previous glaciations the superficial deposits comprise glaciofluvial sands and gravels glacial tills and moraines raised marine sediments and blown sands thirty eight sites were investigated hydraulic conductivity measurements were made using repeated guelph permeameter measurements cone resistance was measured in situ with a panda dynamic cone penetrometer material descriptions were made in accordance with bs5930 1999 and disturbed samples were taken for particle size analysis overall hydraulic conductivity k varied from 0 001 m d to 40 m d glacial till had the lowest k median 0 027 m d and glacial moraine the highest k median 30 m d however within each geological unit there was great variability in measured hydraulic conductivity values multiple linear regression of the data indicated that log d 10 and relative density indicated by cone resistance or bs5930 1999 soil state description were independent predictors of log k and together gave a relationship with an r 2 of 0 80 material description using the largest fraction e g sand or gravel had little predictive power therefore in heterogeneous catchments the permeability of superficial deposits is most strongly related to the finest fraction d 10 and relative density of the material in situ guelph permeameter measurements at outcrops with good geological characterisation provide an easy and reliable method of determining the permeability of particular units of superficial deposits

synoptic reconstruction of a major ancient lake system eocene green river formation western united states numerous 40ar 39ar experiments on sanidine and biotite from 22 ash beds and 3 volcaniclastic sand beds from the greater green river piceance creek and uinta basins of wyoming colorado and utah constrain 8 m y of the eocene epoch multiple analyses were conducted per sample using laser fusion and incremental heating techniques to differentiate inheritance 40ar loss and 39ar recoil when considered in conjunction with existing radioisotopic ages and lithostratigraphy biostratigraphy and magnetostratigraphy these new age determinations facilitate temporal correlation of linked eocene lake basins in the laramide rocky mountain region at a significantly increased level of precision to compare our results to the geomagnetic polarity time scale and the regional volcanic record the ages of eocene magnetic anomalies c24 through c20 were recalibrated using seven 40ar 39ar ages overall the ages obtained for this study are consistent with the isochroneity of north american land mammal ages throughout the study area and provide precise radioisotopic constraints on several important biostratigraphic boundaries applying these new ages average sediment accumulation rates in the greater green river basin wyoming were approximately three times faster at the center of the basin versus its ramp like northern margin during deposition of the underfilled wilkins peak member in contrast sediment accumulation occurred faster at the edge of the basin during deposition of the balanced filled to overfilled tipton and laney members sediment accumulation patterns thus reflect basin center focused accumulation rates when the basin was underfilled and supply limited accumulation when the basin was balanced filled to overfilled sediment accumulation in the uinta basin at indian canyon utah was relatively constant at 150 mm k y during deposition of over 5 m y of both evaporative and fluctuating profundal facies which likely reflects the basin margin position of the measured section the most rapid sediment accumulation for the entire system 1 m k y occurred between 49 0 and 47 5 ma when volcaniclastic materials from the absaroka and or challis volcanic fields entered the green river formation lakes from the north our new ages combined with existing paleomagnetic and biostratigraphic control permit the first detailed synoptic comparison of lacustrine depositional environments in all the green river formation basins coupled with previously published paleocurrent observations our detailed correlations show that relatively freshwater lakes commonly drained into more saline downstream lakes the overall character of eocene lake deposits was therefore governed in part by the geomorphic evolution of drainage patterns in the surrounding laramide landscape freshwater overfilled lakes were initially dominant 53 5 52 0 ma possibly related to high erosion rates of remnant cretaceous strata on adjacent uplifts expansion of balanced fill lakes first occurred in all green river formation basins at 52 0 51 3 ma and again between 49 6 and 48 5 ma evaporative underfilled lakes occurred in various basins between 51 3 and 45 1 ma coincident with the end of the early eocene climatic optima and subsequent onset of global cooling defined from marine record however evaporite intervals in the different depocenters were deposited at different times rather than being confined to a single episode of arid climate evaporative terminal sinks were initially located in the greater green river and piceance creek basins 51 3 48 9 ma then gradually migrated southward to the uinta basin 47 1 45 2 ma this history is likely related to progressive southward construction of the absaroka volcanic province which constituted a major topographic and thermal anomaly that contributed to a regional north to south hydrologic gradient the greater green river and piceance creek basins were eventually filled from north to south with absarokaderived detritus at sedimentation rates 1 2 orders of magnitude greater than the underlying lake deposits

bearing capacity under cyclic loading offshore along the coast and on land the 21st bjerrum lecture presented in oslo 23 november 2007 le chargement cyclique est important pour la conception de fondations de structures autant en mer sur la cote et sur la terre et pour la stabilite des pentes ceci est illustre a l aide de plusieurs exemples cet article discute du comportement du sol soumis a un chargement cyclique pour la structure et les pentes et demontre que la resistance au cisaillement cyclique et le mode de defaillance sous chargement cyclique dependent fortement du cheminement des contraintes et de la combinaison des contraintes en cisaillement moyennes et cycliques des diagrammes de resistance au cisaillement cyclique pour l argile sable et silt qui peuvent etre utilises pour la conception sont presentes des comparaisons entre les calculs et les essais modelises indiquent que la capacite de la fondation soumise a un chargement cyclique peut etre determinee a partir de la resistance au cisaillement cyclique obtenu par des essais en laboratoire

goodbye hazen hello kozeny carman the century old hazen formula for predicting the permeability of sand is based only on the d10 particle size whereas the half century old kozeny carman formula is based on the entire particle size distribution the particle shape and the void ratio as a consequence the hazen formula is less accurate than the kozeny carman formula it is recommended that the former be retired and the latter be adopted

discussion of network model for hydraulic conductivity of sand bentonite mixtures chapuis et al 114 the authors have presented a very interesting research paper in which a network model is used to predict the hydraulic conductivity of sand bentonite mixtures sbms several points of the paper are examined and discussed here in the light of previously published concepts laboratory test results and field data on the same topic past experience is also used to further investigate through questions posed to the authors the capability of their model

physical properties of hydrate bearing sediments 1 methane gas hydrates crystalline inclusion compounds formed from methane and water are found in marine continental margin and permafrost sediments worldwide this article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate bearing sediments formation phenomena include pore scale habit solubility spatial variability and host sediment aggregate properties physical properties include thermal properties permeability electrical conductivity and permittivity small strain elastic p and s wave velocities shear strength and volume changes resulting from hydrate dissociation the magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate bearing sediments to changes in mechanical thermal or chemical boundary conditions these predictions are vital for mitigating borehole local and regional slope stability hazards optimizing recovery techniques for extracting methane from hydrate bearing sediments or sequestering carbon dioxide in gas hydrate and evaluating the role of gas hydrate in the global carbon cycle

delayed collapse of cut slopes in stiff clay delayed failure of railway cutting slopes in stiff clays excavated in the nineteenth and early twentieth centuries has been studied for some forty years known failures have generally been deep seated more recently failures have been a problem in the slopes of motorway cuttings and embankments although generally these have been shallow the average operational strength at failure in these slides has been significantly less than the peak strength and progressive failure has been postulated as the probable cause of this progressive failure can now be analysed using advanced numerical techniques a series of coupled finite element analyses have been conducted assuming strain softening soil with properties based on the brown london clay and the results are reported they show that progressive failure is considerable and fully explain the observed field behaviour the delays experienced in the field are also recovered by the analyses progressive failure is generated primarily by the high lateral stresse

undrained bearing capacity factors for conical footings on clay introduction the bearing capacity of circular foundations on undrained clay is of fundamental importance in many geotechnical problems in particular there are a number of designs of offshore foundations where the foundation can be treated approximately as a large circular footing for instance some gravity bases the spudcan foundations of jack up units and the more recently developed caisson foundations in most cases the footing is not placed at the ground surface and it is important to take into account the depth of embedment furthermore the base of a spudcan is generally not flat but approximates a shallow cone for foundations on soft clays the effect of the increase of strength of the soil with depth needs to be taken into account and this is particularly important for large foundations the purpose of this note is to present calculations of bearing capacity factors for shallow circular foundations accounting for embedment cone angle rate of increase of strength with depth and surface roughness of the foundation the results have widespread application particularly in the offshore industry the soil is assumed to be rigid plastic with yield determined by the tresca condition with an undrained strength su the method of characteristics is used for the bearing capacity calculation as described by shield 1955 eason shield 1960 houlsby 1982 and houlsby wroth 1982a for application to undrained axisymmetric problems some previous results have been published for this problem using similar numerical techniques e g houlsby wroth 1982b salencon matar 1982 houlsby wroth 1983 tani craig 1995 martin 2001 but the study presented here involves a much more comprehensive coverage of the parameters where comparisons can be made with the previous solutions the factors differ by up to about 0 5 which gives some indication of the level of accuracy attainable with this numerical technique exceptionally the rough footing results given by tani craig 1995 are higher by up to about 5 but this may be due to a problem with their numerical integration procedures see martin randolph 2001

the variability of critical shear stress friction angle and grain protrusion in water worked sediments the erodibility of a grain on a rough bed is controlled by among other factors its relative projection above the mean bed its exposure relative to upstream grains and its friction angle here we report direct measurements of friction angles grain projection and exposure and small scale topographic structure on a variety of water worked mixed grain sediment surfaces using a simple analytical model of the force balance on individual grains we calculate the distribution of critical shear stress for idealized spherical grains on the measured bed topography the friction angle projection and exposure of single grain sizes vary widely from point to point within a given bed surface the variability within a single surface often exceeds the difference between the mean values of disparate surfaces as a result the critical shear stress for a given grain size on a sediment surface is characterized by a probability distribution rather than a single value on a given bed the crtitical shear stress distributions of different grain sizes have similar lower bounds but above their lower tails they diverge rapidly with smaller grains having substantially higher median critical shear stresses large numbers of fines trapp ed within pockets on the bed or shielded by upstream grains are effectively lost to the flow our calculations suggest that critical shear stress as conventionally measured is defined by the most erodible grains entrained during transient shear stress excursions associated with the turbulent flow this implies a physical basis for the indeterminacy of initial motion these observations suggest that transport rate shear stress relationships may be controlled in part by the increasing numbers of grains that become available for entrainment as mean shear stress increases they also suggest that bed textures and grain size distributions may be controlled within the constraints of an imposed shear stress and sediment supply regime by the influence of each size fraction on the erodibility of other grain sizes present on the bed

shallow seismic reflection study of a glaciated valley shallow seismic reflection data were recorded along two long 1 6 km intersecting profiles in the glaciated suhre valley of northern switzerland appropriate choice of source and receiver parameters resulted in a high fold 36 48 data set with common midpoints every 1 25 m as for many shallow seismic reflection data sets upper portions of the shot gathers were contaminated with high amplitude source generated noise e g direct refracted guided surface and airwaves spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source generated noise and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi continuous reflection zones the uppermost reflection zone at 20 to 50 ms 15 to 40 m depth originated from a boundary between

40ar 39ar geochronology of the eocene green river formation wyoming discussion smith et al 2003 1 hereafter referred to as smith et al present seven new isotopic ages from the green river formation in the greater green river basin these data provide welcome new information in the ongoing effort to develop a coherent and reliable geochron ological framework for this

measuring physical and hydraulic properties of peat from x ray tomography abstract organic soils cover a large percentage of the canadian land mass in the form of peatlands 14 and other organic terrains including arctic and alpine tundra and taiga 25 sphagnum mosses are the dominant peat forming species in all of these terrains understanding the processes by which this material conducts retains and redistributes moisture and energy is crucial to the successful development of physically based methods of measuring and modelling their hydrological response sphagnum peat was sampled from scotty creek in the wetland dominated zone of discontinuous permafrost near fort simpson northwest territories canada physical properties of the peat samples were measured from standard methods and x ray tomographic images of sub samples were obtained at 5 levels of volumetric moisture content between 0 4 and 0 7 the volumetric moisture content measured using the tomographic images closely approximated the gravimetric measurements properties of the pore spaces were measured in both two and three dimensions the active porosities measured in 2d and 3d were very similar and matched closely with values reported in the literature specific surface area 3d however was larger than the specific perimeter 2d the 2d analysis suggests a relatively gradual transition from small to large pores while in 3d the distribution is dominated by a single large pore space whose volume and surface area are 3 orders of magnitude larger than the next largest pore and 99 of the total inter particle pore volume this single large pore space contains the flow network this study elucidated the volume and configuration of this network for discrete ranges of soil water pressure that typically occur in the field the flow network diminished from 17 6 to 9 0 of a sample volume as its volumetric moisture content lowered from 0 65 to 0 42 this volume loss was accommodated by the thinning and disaggregation of moisture films although as the sample lost moisture the flow network maintained a relatively even spatial distribution

frac sand crushing characteristics and morphology changes under high compressive stress and implications for sand pack permeability sand consisting of round quartz grains is widely used as a proppant during hydraulic fracturing to produce natural gas from tight shale formations this paper presents results from sand characteriz

high resolution calibration of eocene strata 40ar 39ar geochronology of biotite in the green river formation the sixth tuff of the wilkins peak member of the green river formation is an important potential calibration point for magnetic stratigraphy mammalian evolution and lacustrine processes however two recent 40 ar 39 ar ages based on laser fusion of biotite from this important bed are not in agreement with one other most large euhedral biotite from the basal 1 cm give concordant age spectra when incrementally heated however some crystals yield discordant age spectra and have plateau and integrated ages that are scattered toward both older and younger apparent ages electron probe microanalysis indicates that intergrown alteration phases occur in a small fraction of sixth tuff biotite crystals and likely contributed to open system processes that led to the observed discordance and age scatter a new age of 49 62 0 10 ma is obtained from 22 concordant incremental heating experiments this age agrees with a new 49 78 0 08 ma age for the sanidine from the layered tuff which is stratigraphically 24 m below the sixth tuff

groundwater exploration using combined controlled source and radiomagnetotelluric techniques radiomagnetotelluric rmt 14 250 khz combined with controlled source magnetotelluric csmt 1 12 khz measurements were applied to the exploration of groundwater located in sandy formations at depths as great as 20 m below thick clay lenses a combination of approximately 30 radio frequencies and controlled source frequencies is essential for penetrating the thick clay layers the electromagnetic transfer functions of impedance tensor and tipper vectors point toward a structure that is largely two dimensional although clear three dimensional effects can be observed where the sandy formation is close to the surface the determinant of the impedance tensor was chosen for inversion using two dimensional models the final two dimensional model fits the data to within twice the estimated standard errors which is considered quite satisfactory given that typical errors are on the level of 1 on the impedance elements comparison with bore hole results and shallow reflection seismic sections show that the

numerical investigation of spudcan penetration in multi layer deposits with an interbedded sand layer for calculating spudcan penetration resistance in an interbedded sand layer between two clay layers the recently developed mechanism based design methods for surface sand over clay deposits are extended to account for the influence of the overlying clay layer a series of large deformation finite element ldfe analyses were carried out varying layer geometries and strength parameters the numerical results and existing centrifuge test data are used to calibrate the extended design methods the performance of the modified design methods and those suggested in the iso standard 19905 1 is compared confirming the accuracy of the former methods in estimating the peak penetration resistance in the sand layer ldfe analyses were also carried out adding a strong fourth layer with the corresponding effects on the increasing peak resistance in the second sand layer and squeezing behaviour or limiting squeezing depth in the third soft clay layer discussed design formulas are also developed to estimate th

fine tuning the calibration of the early to middle eocene geomagnetic polarity time scale paleomagnetism of radioisotopically dated tuffs from laramide foreland basins age calibration of the early to middle eocene geomagnetic polarity time scale remains highly uncertain due to conflicting magnetostratigraphic radioisotopic and astrochronologic results in this study new paleomagnetic polarity determinations of 29 ash fall tuffs preserved in strata of five laramide foreland basins were used in conjunction with previously published 40 ar 39 ar ages from the same tuffs to evaluate eight different calibration models for the early to middle eocene part of the geomagnetic polarity time scale reliable paleomagnetic information was recovered from 23 tuffs of which 17 showed normal polarity and six showed reversed polarity after comparison of the models with the paleomagnetic and radioisotopic data from the tuffs and an array of independent chronostratigraphic observations the new willwood model is herein selected as the best alternative to the current geomagnetic polarity time scale calibration for the early to middle eocene three important implications are apparent in our proposed model first the early eocene is shortened by 0 6 m y and the middle eocene is lengthened by 0 8 m y compared with the 2004 geomagnetic polarity time scale also the early eocene climatic optimum is estimated to have lasted from 52 9 to 50 7 ma 1 m y longer than previously suggested and overlapping in time with the inferred age of the wasatchian bridgerian faunal transition our new model agrees with a previous astronomical model when it is tied to the oldest proposed age for the paleocene eocene thermal maximum at 56 33 ma

equivalent images derived from very low frequency vlf profile data we describe the implementation of a new fast imaging technique for filtering very low frequency vlf data measured on profiles into corresponding equivalent current systems in the earth single frequency vlf data using magnetic measurements alone are often used to delineate lateral changes in electrical conductivity e g fracture zones in crystalline terrains or changes in lithology in the sedimentary cover here an attempt is made to add depth information to the conductivity distribution by realizing that the single frequency vlf profile data contain information about 1 the background medium through their decay away from the conductors 2 the position and 3 the depth of the dominating conductors through the relative contribution of in phase and quadrature components to the vlf anomaly in addition to the rate of change of the anomaly close to the conductors synthetic data from a model containing a shallow and a deeper conductor are filtered to show that the estimated current distributions coincide well with the horizontal position of the conductors but even they provide some smeared images of the depth distribution of the conductors a comparison with models obtained from regularized inversion of the same data shows good correspondence the vlf field data from an area with clay lenses overlying wet sand and crystalline basement are filtered into current distributions that grossly mimic the electrical conductivity distribution of the clay lenses as obtained from radiomagnetotelluric measurements along the same profile

waves generated by subaerial slides with various porosities abstract waves generated by subaerial slides were investigated experimentally in a two dimensional wave tank slide volume initial position slope angle and equilibrium water depth were kept constant while the slide material was varied five different slide types were employed one block slide and four granular slides with grain diameter ranging from 3 mm to 25 mm the slides were accelerated by gravity with different impact velocities and froude numbers varying from 0 34 to 0 93 amplitudes of the generated waves were measured with non intrusive acoustic wave gauges while the slide position during rundown was recorded with a high speed video camera empirical functions for prediction of maximum amplitudes that have been reported in the literature were employed for comparison with the generated waves differences between predictions based on the empirical functions and experimental results were discussed together with possible effects of permeability

dynamic analysis of a smooth penetrometer free falling into uniform clay the finite element analysis of free falling objects penetrating soil deposits is one of the most sophisticated and challenging problems in geomechanics a robust numerical method will be described here for dealing with such complex and difficult problems the approach is based on the arbitrary lagrangian eulerian ale method of analysis the main features and challenges of which are described briefly in the paper the ale method is then employed to perform a parametric study of a perfectly smooth penetrometer free falling into a uniform layer of clay which deforms under undrained conditions the effect of the mechanical properties of the clay soil on the penetration characteristics is presented and an approximate closed form expression is derived for the dynamic penetration factor ndp comparisons are made between the deduced values of ndp and published values of the conventional cone factor nc and comparisons are made with experimental data to validate the approach

a geochemical clogging model with carbonate precipitation rates under hydrothermal conditions abstract a step wise numerical calculation method was developed to provide predictions of when and where carbonate deposits might be found through reservoirs during co 2 sequestration flow experiments through porous media using a supersaturated carbonate fluid were also performed in order to observe flow rates in order to evaluate precipitation rates and permeability change in the formation calculated flow rates based on the proposed geochemical clogging model were compared with the experimentally observed data both high and low temperature cases were studied to understand how hydrothermal conditions can affect precipitation rates of carbonate according to chemical kinetics growth rates of minerals are generally proportional to the saturation index s i that depends on temperature thus a supersaturated fluid has the advantage of improving the filtration and the amount of c fixation however when the ratio of filtration coefficient to pore fluid velocity u increases the permeability around the injection point tends to be significantly reduced by carbonate accumulation and thus this might result in insufficient injection of co 2 therefore it is essential to understand how to control both and u so that the precipitation of carbonate can be located as far away from the inlet as possible

pollutant advective spreading in beach sand exposed to high energy tides abstract this paper presents field measurements in which dye solute was injected into coastal sand to investigate contaminant advection in intertidal beach sand the measurements show the pathways of a contaminated plume in the unsaturated zone during both the flood and ebb tides a prescribed amount of dye tracer solution was directly injected through the topsoil with average porosity 0 3521 0 01 at predetermined locations of the river mersey s outer estuarial beach during ebb tide the injected dye was monitored sampled and photographed over several tidal cycles the distinctive features of the plume full two dimensional cross sections sediments and water table depth were sampled in situ close to the injection point differing from previous contaminant monitoring tests in aquifers the advective movement is attributed to tidal impact which is different from contaminant transport in aquifers the experimental results show that plumes have significantly large spatial variability diverging upwards and converging downwards with a conical geometric shape which is different from the usual spherical elliptical shape reported in literature the mean vertical motion of the plume reaches three times the top width within ten tidal cycles exceeding the narrow bottom width by a factor of order 2 the observed transport features of the plume within the beach sand have significant relevance to saltwater intrusion surface water and groundwater quality the field observations are unique and can serve as a valuable benchmark database for relevant numerical studies

estimating hydraulic and thermal conductivities of crushed granite using porosity and equivalent particle size this paper presents an experimental study of the effect of porosity and particle size on the hydraulic conductivity and thermal conductivity of sand sized crushed granite particles with diameters ranging from 0 08 10 mm the results show that the hydraulic conductivity varies with particle size and porosity but thermal conductivity varies primarily with porosity estimating methods found in the literature are used in an attempt to predict the measured hydraulic and thermal conductivities of the crushed granite materials the results show that the hydraulic conductivity model of chapuis generally yields accurate estimated values for d102n3 1 n 2 larger than 0 01 mm2 below this critical point the estimating method progressively yields larger values of hydraulic conductivity a new set of empirical parameters are proposed to extend the use of this method to crushed granite materials at low d102n3 1 n 2 values it is also shown that predicted thermal conductivity values obtained with the cote and konrad

constraining helicopter electromagnetic models of the okavango delta with seismic refraction and seismic reflection data abstractelectrical resistivity models derived from exceptionally high quality helicopter transient electromagnetic data recorded across the okavango delta in botswana one of the world s great inland deltas or megafans include three principal layers 1 an upper heterogeneous layer of dry and water saturated sand 2 an intermediate electrically conductive layer that likely comprises saline water saturated sand and clay and 3 a lower fan shaped electrically resistive layer of freshwater saturated sand gravel and or crystalline basement if part of the lower layer comprises a freshwater aquifer it would be evidence for a recently proposed paleo okavango megafan and a major new source of freshwater in an attempt to constrain the interpretation of the lower layer we acquired two high resolution seismic refraction and re ection data sets at each of two investigation sites one near the center of the delta and one along its western edge the interface between unconsolidated sediments and basement near

effect of soil contraction tendency on static liquefaction triggering analysis static liquefaction failure occurs when the shear stress applied by a monotonic triggering load exceeds the undrained yield peak shear strength of the saturated liquefiable cohesionless soil in this study the effect of soil contraction tendency on static liquefaction failure of cohesionless soils is characterised by an empirical relationship between soil brittleness index and undrained yield strength from a database of 702 laboratory shear tests performed by the author and collected from past literature the application of this relationship for estimating the static liquefaction triggering strength of cohesionless soils is validated by comparison with several cases of liquefaction failures

database of friction angles of sand and consolidation characteristics of sand silt and clay abstractthe paper presents diagrams of the 1 drained and undrained effective stress friction angles of sand 2 dilatancy angle of sand 3 parameters in a nonlinear constrained modulus expression for virgin loading unloading and reloading on sand and silt and 4 diagrams with the coefficient of permeability for sand silt and clay the database parameters are suitable for preliminary assessments or applications when assumed parameters are acceptable the database can also be helpful in planning and interpreting site specific tests and in reducing the number of site specific tests for important projects the parameters should be determined by site specific tests

permeability of mine tailings measured in triaxial cell the execution of permeability tests using a triaxial cell makes it possible to eliminate the uncertainties that characterize tests performed using conventional equipment this paper contains the re

terminal infill of eocene lake gosiute wyoming u s a abstract deposition of lacustrine sediments in the greater green river basin was progressively terminated in the middle eocene as volcaniclastic detritus prograded across the basin the lacustrine sediment of the laney member was replaced by deposition of the deltaic and fluvial sediments of the volcaniclastic bridger and washakie formations and the sand butte bed of the laney member the transition from the deposition of lacustrine to alluvial sediment also records a reversal in the direction of drainage across the basin that occurred between 49 5 ma and 48 9 ma prior to this transition drainage entered the basin from the east and the arkosic detritus of the cathedral bluffs member of the wasatch formation was deposited in the washakie and great divide subbasins at the same time evaporitic sediments of the wilkins peak member of the green river formation accumulated simultaneously in the bridger basin indicating that the clastic sediment was baffled east of the rock springs arch an intrabasinal structural high the subsequent transition to deposition of the laney member is traditionally interpreted as an isochronous expansion of lake gosiute across the greater green river basin alternatively the transition may have been diachronous with continued accumulation of the wilkins peak member in the bridger basin coinciding with the earliest deposition of the laney member in the washakie basin by 48 9 ma the dominant drainage was clearly from the west which reflects the capture of an external drainage network through the northwest corner of the basin that delivered extrabasinal volcaniclastic detritus to the greater green river basin more broadly these results illustrate that the geomorphic evolution of the landscape influenced the character of sedimentary fill in the nonmarine greater green river basin

experimental characterization of coupled diffusion reaction mechanisms in low permeability chalk abstract reactions caused by the diffusion of reactants from different sources can alter rock diffusivity and are therefore the critical mechanisms for evaluating short and long term behavior of low permeability rocks used as confinement layers for underground storage for instance this paper presents and discusses a set of two diffusion driven reaction experiments focusing on precipitation of two end member types of sulfate minerals gypsum caso4 2h2o and barite baso4 in low permeability chalk the time resolved changes in porosity and effective diffusion coefficient de were evaluated along the duration of the experiments 140 days by analyzing the behavior of passive tracers and evaluating the amount of precipitated gypsum or barite from measuring the reactant concentration evolution in the reservoirs at both ends of the sample then sem eds and x ray microtomography ct imaging were used to characterize the initial rock structure and the precipitated materials results showed that the change in porosity from 45 to about 43 corresponding to the volume of sulfate precipitated are similar for gypsum and barite conversely the precipitation impact on diffusion properties of the water tracers that were injected 70 days after the beginning of the precipitation step is distinctly different for the each of the studied sulfate mineral the precipitation of barite generated a more significant impact than gypsum deintact 4 15 10 10 m2 s 1 vs debarite 1 1 10 10 m2 s 1 and degypsum 2 5 10 10 m2 s 1 post mortem imaging revealed a thin precipitated zone 250 m in the center of the sample for the barite precipitation experiment whereas isolated quasi spherical clusters resulted from the gypsum precipitation the ct images at higher resolution showed that the precipitation of barite is heterogeneous at small scale which explains the hto diffusion curve for gypsum the post mortem imaging around the quasi spherical clusters showed a significant presence of initial macropores of the connected porosity that were still unfilled these intact chalk zones allowed hdo to diffuse through the precipitated zone lowering the impact on water tracer diffusivity these experimental results indicate that the morphology and the distribution of barite precipitates is mainly controlled by homogeneous and heterogeneous nucleation phenomena whereas gypsum precipitation is mainly controlled by the spatial variability of the initial porous system properties reactive surface area tortuosity pore network structure

discussion of hydraulic conductivity of saturated granular soils determined using a constriction based technique 1 1 appears in the canadian geotechnical journal 49 5 607 613 doi 10 1139 t2012 016

application of portable free fall penetrometer for geotechnical investigation of arctic nearshore zone the arctic is currently undergoing rapid changes with regard to sea ice extent permafrost thaw and coastal erosion in addition to hydrodynamic processes the sediments in the arctic nearshore zon

a multi method field experiment to determine local groundwater flow in a glacier forefield we implemented multiple independent field techniques to determine the direction and velocity of groundwater flow at a specific stream reach in a glacier forefield time lapse experiments were conducted using two electrical resistivity tomography ert lines installed in a cross pattern a circular array of groundwater tubes was also installed to monitor groundwater flow via discrete salt injections both inter borehole and ert results confirmed this stream section as a losing reach and enabled quantification of the flow direction both techniques yielded advection velocities varying between 5 7 and 21 8 m day estimates of groundwater flow direction and velocity indicated that groundwater infiltrates from the stream nearby and not from the adjacent lateral moraine groundwater age estimated from radon concentration measurements supported this hypothesis despite uncertainties inherent to each of the methods deployed the combination of multiple field techniques allowed drawing consistent conclusions about local groundwater flow we thus regard our multi method approach as a reliable way to characterize the two dimensional groundwater flow at sites where more invasive groundwater investigation techniques are difficult to carry out and local heterogeneities can make single measurements unreliable copyright 2014 john wiley sons ltd

study on the hydraulic conductivity of boom clay the hydraulic conductivity is a parameter in geotechnical engineering practice that is key in seepage and consolidation analysis experimental results show that the hydraulic conductivity is mainly governed by the soil porosity and correlations with void ratio are usually proposed the validity of these correlations has been verified for soft clays and sands however few studies have included stiff clays in this work the hydraulic conductivity of boom clay a stiff clay taken from the essen site in belgium was determined from both consolidation and constant head percolation tests the data obtained was then analyzed to evaluate the existing correlations to predict the hydraulic conductivity in addition as these correlations usually require a referred hydraulic conductivity at a known void ratio the existing methods are often difficult to use in practice thus a new method was developed allowing the prediction of hydraulic conductivity without the referred value which was based on two existing co

linking the wasatchian bridgerian boundary to the cenozoic global climate optimum new magnetostratigraphic and isotopic results from south pass wyoming new paleomagnetic and stable isotopic results from the northeastern margin of the greater green river basin south pass wyoming provide a refined geochronological context for the wasatchian bridgerian land mammal age boundary and suggest the existence of large amplitude milankovich scale carbon and oxygen isotopic oscillations in this area during the early eocene analysis of 55 paleomagnetic sites through a 310 m section of wasatch green river and bridger formations indicates several reversals that can be correlated to the geomagnetic polarity time scale using radiometric age constraints this correlation places the wasatchian bridgerian boundary in chron c23r at about 52 ma approximately two million years older than previous estimates this new correlation suggests that the mammalian turnover which characterizes the wasatchian bridgerian boundary is coincident with the onset of the cenozoic global climate optimum the warmest interval of the entire cenozoic intrabasinal magnetostratigraphic correlation supports earlier claims that community composition and biostratigraphic datums of basinmargin faunas can differ significantly from coeval basin center faunas oxygen and carbon isotopic composition of paleosol carbonates show in phase cyclic variations on the order of 6 and 3 5 respectively based on the preferred magnetostratigraphic correlation the four best defined cycles represent 397 thousand years indicating potential forcing by variations in orbital eccentricity oxygen isotopic variations may be tracking wet dry cycles amplified by adjacent changes in levels of paleolake gosuite carbon isotopic variations may be tracking the vegetative response to these climate variations alternative interpretations involve cyclic changes in pedogenesis driving correlated variations in isotopic inheritance from parent paleozoic carbonate material and the possibility that c4 plants existed in marginal habitats earlier in geological time than previously thought q 2001 elsevier science b v all rights reserved

specific surface and hydraulic conductivity of fine grained soils abstractthe kozeny carman k c equation can be used to predict the saturated hydraulic conductivity of a soil provided enough information is given regarding the porosity and the specific surface the main limitation of the k c equation lays in the determination of the specific surface of the soil a parameter that is not regularly measured but can be estimated with analytical or empirical relations a method to evaluate the soil s specific surface is proposed which combines the contribution of the plastic clayey fraction and that of the granular silty sandy particles the applicability of the proposed method and its effect on the performance of the k c equation have been verified by comparing the k c estimated hydraulic conductivity with the result of approximately 130 hydraulic conductivity tests on saturated soil specimens in the triaxial apparatus the results show that the k c equation and the method for estimating the specific surface predict within an order of magnitude the saturated hydraulic co

cyclic tests on high quality undisturbed block samples of soft marine norwegian clay the results of a study with undrained cyclic triaxial and direct simple shear dss tests on high quality undisturbed samples obtained from large blocks of a soft marine norwegian clay are presented several tests with different average shear stresses shear stress amplitudes loading frequencies and sample geometries have been performed on block samples taken from different depths in tests with small average shear stresses failure occurred due to large shear strain amplitudes while large permanent shear strains were observed in tests with higher average shear stresses diagrams quantifying the undrained cyclic strength permanent shear strain shear strain amplitude and permanent pore water pressure dependent on average shear stress shear stress amplitude and number of cycles have been developed based on the test results the undrained cyclic strength was found strongly dependent on loading frequency block samples from shallower depth showed a somewhat higher undrained cyclic strength no influen

bearing capacity on sand overlying clay soils a simplified conceptual model the derivation of a new conceptual model for predicting the peak penetration resistance of circular footings installed vertically into sand overlying soft clay is presented in this paper based on visualisation experiments and finite element analyses a failure mechanism of a frustum of sand being forced into the underlying clay with the outer angle reflecting the dilation in the sand is assumed the analytical basis of the new conceptual model follows the approach for silo analysis and takes into account the stress level and dilatant response of the sand a comprehensive analysis of the performance of the new model and other existing analytical methods in retrospectively predicting the peak resistance of a database of 49 geotechnical centrifuge tests is provided significant improvements over existing punching shear and load spread models are shown as a result of incorporating the strength properties of the sand in a consistent manner the new model has application to the offshore mobile jack up

peat hydraulic conductivity in cold regions and its relation to pore size and geometry subsurface flow through peat plays a critical role in the hydrology of organic covered permafrost terrains which occupy a large part the continental arctic sub arctic and boreal regions hillslope drainage in these terrains occurs predominantly through the active flow zone between the relatively impermeable frost table and the water table above it the hydraulic conductivity profile within this zone controls the subsurface drainage of snowmelt and storm water peat hydraulic conductivity profiles were examined at three sites in north western canada each representing a widely occurring organic covered permafrost terrain type three independent measures of saturated hydraulic conductivity were used tracer tests constant head well permeameter tests and laboratory measurements of undisturbed samples at all three sites the conductivity profiles contained very high values 10 1000 m d 1 within the top ca 0 1 m where the peat is only lightly decomposed a large reduction with increasing depth below the ground surface in the transition zone and relatively low values in a narrow range 0 5 5 m d 1 below ca 0 2 m depth where the peat is in an advanced state of decomposition digital image analysis of resin impregnated peat samples showed that hydraulic conductivity is essentially controlled by pore hydraulic radius the strong dependence of hydraulic conductivity on hydraulic radius implies that peat soils subjected to similar degrees of decomposition and compaction have a similar hydraulic conductivity regardless of the location this explains the similarity of the depth conductivity profiles among all three terrain types copyright 2008 john wiley sons ltd

a comparison of terpenoid and leaf fossil vegetation proxies in paleocene and eocene bighorn basin sediments abstract plant derived terpenoids long recognized as biomarkers can help reveal the major taxonomic groups of land plants present in ancient environments even if rocks and sediments do not preserve plant macro or microfossils previous studies have used simple di to triterpenoid ratios to reconstruct floral changes in the geologic past but few have compared terpenoid ratios with estimates of floral composition from fossils further reconstructions have not taken into account differences in biomarker production i e concentration relative to leaf biomass between different types of plants here we have examined terpenoids from early cenozoic fluvial rocks from the bighorn basin wyoming usa where fossil flora has been studied in detail we analyzed the distributions of diterpenoids triterpenoids and n alkanes from leaf wax in a total of 43 samples from 15 stratigraphic horizons of late paleocene 63 ma to early eocene 53 ma in age in nearly all samples triterpenoids derived from angiosperms were significantly lower in abundance than conifer specific diterpenoids a finding that contrasted with plant fossil evidence for the same rocks this suggests that di to triterpenoid ratios severely underestimate the abundance of angiosperms in paleovegetation angiosperms dominated n alkane production among modern plants and we propose a new paleovegetation proxy based on the ratio of diterpenoids conifers to n alkanes angiosperms corrected for lipid production estimated from extant vegetation using diterpenoids and alkanes we infer the composition of paleovegetation to be similar to that inferred from plant fossils although the approach works well for the bighorn basin we stress the new paleovegetation proxy will need to be evaluated for other time periods communities paleogeography and depositional environments with pollen or megafossil data available

evaluating the hydraulic conductivity at three different scales within an unconfined sand aquifer at lachenaie quebec this paper presents the evaluation of scale effects for the hydraulic conductivity k of a sand data were obtained using several methods at a site that was densely instrumented with piezometers within an area of about 100 m 100 m the 3 1 3 6 m thick sand deposit rests on a thick nonfissured champlain sea clay deposit at the small scale local k values were obtained from the grain size curves of sand samples and also from ground penetrating radar surveys at the intermediate scale k values were obtained from field variable head tests using piezometers at the large scale k values were obtained from pumping test drawdowns in steady state conditions in this sand aquifer the careful evaluations at three scales gave similar narrow distributions for the hydraulic conductivity and therefore no scale effect is evidenced key words hydraulic conductivity sand scale effect gradation monitoring well pumping

pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate bearing reservoirs in the krishna godavari basin offshore india abstract physical properties of the sediment directly overlying a gas hydrate reservoir provide important controls on the effectiveness of depressurizing that reservoir to extract methane from gas hydrate as an energy resource the permeability of overlying sediment determines if a gas hydrate reservoir s upper contact will provide an effective seal that enables efficient reservoir depressurization compressibility stiffness and strength indicate how overlying sediment will deform as the in situ stress changes during production providing engineering data for well designs assessing these properties requires minimally disturbed sediment india s national gas hydrates program expedition 2 nghp 02 provided an opportunity to study these seal sediment properties reducing disturbance from gas exsolution and bubble growth by collecting a pressure core from the seal sediment just above the primary gas hydrate reservoir at site nghp 02 08 in area c of the krishna godavari basin the effective stress chamber esc and the direct shear chamber dsc devices in the suite of pressure core characterization tools pccts were used to measure permeability compressibility stiffness and shear strength at the in situ vertical stress geotechnical properties of the predominantly fine grained seal layer at in situ vertical stress are in typical clay sediment ranges with low measured permeability 0 02 md high compressibility c c 0 26 0 33 and low shear strength 404 kpa though pressure and temperature were maintained throughout the collection and measurement process to stabilize gas hydrate the lack of effective stress in the pressure core storage chamber and the chamber pressurization with methane free water caused core expansion and gas hydrate in a thin coarser grained layer to dissolve the pccts can reapply in situ stress with incremental loading steps during a consolidation test to account for sediment compaction gas hydrate dissolution can be limited by storing cores just above freezing temperatures and by using solid spacers to reduce the storage chamber s free volume

long term persistence of oil from the exxon valdez spill in two layer beaches oil spilt from the tanker exxon valdez more than 20 years ago still persists in the gravel beaches of prince william sound alaska field data and numerical modelling indicate that some of the oil was trapped in the anoxic environment of the lower layers of the beaches when the water table was low oil spilled from the tanker exxon valdez in 1989 refs 1 2 persists in the subsurface of gravel beaches in prince william sound alaska the contamination includes considerable amounts of chemicals that are harmful to the local fauna3 however remediation of the beaches was stopped in 1992 because it was assumed that the disappearance rate of oil was large enough to ensure a complete removal of oil within a few years here we present field data and numerical simulations of a two layered beach with a small freshwater recharge in the contaminated area where a high permeability upper layer is underlain by a low permeability lower layer we find that the upper layer temporarily stored the oil while it slowly and continuously filled the lower layer wherever the water table dropped below the interface of the two layers as a result of low freshwater recharge from the land once the oil entered the lower layer it became entrapped by capillary forces and persisted there in nearly anoxic conditions that are a result of the tidal hydraulics in the two layered beaches we suggest that similar dynamics could operate on tidal gravel beaches around the world which are particularly common in mid and high latitude regions4 5 with implications for locating spilled oil and for its biological remediation

influence of state and compressibility on liquefied strength of sands critical state soil mechanics is a useful framework to understand sand behavior in this paper a relationship is developed for estimating undrained critical shear strength of sands based on the critical state framework the application of this relationship is demonstrated by comparison with laboratory test results and sand liquefied strength from field liquefaction flow failure case histories using this relationship the effects of effective stress variation and density on undrained critical shear strength are studied for different combinations of critical state line parameters corresponding to several reference sands the parametric study indicates that depending on sand void ratio undrained critical shear strength may increase remain the same or decrease as sand shearing compressibility represented by the slope of the critical state line increases the underlying mechanisms of field failures in dense sands and reverse behavior of compressible sands are explained through this relationship it is su

40ar 39ar geochronology of the eocene green river formation wyoming the deposits of eocene lake gosiute that constitute the green river formation of wyoming contain numerous tuff beds that represent isochronous correlatable stratigraphic markers tuff beds selected for 40ar 39ar analysis occur within laminated mudstone are matrix supported and lack evidence of reworking these tuffs contain 2 15 euhedral phenocrysts of quartz plagioclase sanidine biotite and minor amphibole pyroxene and zircon encased in a matrix of altered glassy ash air abrasion and handpicking under refractive index oils were required to obtain clean unaltered phenocrysts of sanidine 40ar 39ar age determinations from single crystal and 1 mg multigrain aliquots of sanidine and biotite allowed the identification and exclusion of xenocrystic contamination laser fusion experiments on phenocrysts from the rife firehole c bed grey main sixth and analcite tuff beds from the tipton wilkins peak and laney members yielded weighted mean ages 2 analytical uncertainties of 51 25 0 31 ma 50 70 0 14 ma 50 56 0 26 ma 50 39 0 13 ma 49 96 0 08 ma 49 70 0 10 ma and 48 94 0 12 ma respectively ages for sanidine and biotite from the main tuff are indistinguishable when presumably xenocrystic contaminants are excluded from the age calculation moreover the 40ar 39ar ages are consistent with the stratigraphic order of the tuff beds and with provenance in the absaroka and challis volcanic fields our 40ar 39ar based age model indicates that sediment accumulated three times more rapidly 327 86 m yr during the evaporative wilkins peak phase than the freshwater to saline tipton 88 34 m yr and laney 104 18 m yr phases the much lower accumulation rates for the tipton and laney members are permissive of an annual origin for 1 mm thick laminae and precessional forcing of 1 3 m thick depositional cycles in these units however previously described cycles in the wilkins peak member have average durations that are significantly shorter than the 19 23 k y precessional modes the green river formation encompasses an 5 m y period between ca 53 5 and 48 5 ma spanning magnetic chrons 24n through 21r the green river formation was therefore deposited during the warmest period of the cenozoic corresponding to the early eocene climatic optimum as defined by the global marine o isotope record deposition of bedded evaporites trona of the wilkins peak member began at ca 51 ma or 2 m y after the onset of the highest inferred temperatures of the climatic optimum the bridgerian wasatchian faunal turnover occurred subsequently during wilkins peak time at ca 50 6 ma thus our 40ar 39ar ages strongly suggest that wilkins peak evaporite deposition and the turnover from wasatchian to bridgerian fauna were not directly caused by the initiation of maximum greenhouse conditions

experimental investigation of spudcan penetration in multi layer clays with interbedded sand layers highly layered soils are prevalent in several areas of current offshore activity and in particular in emerging provinces and fields however no investigation has been carried out for spudcan penetration in stratified sediments with more than two layers this paper reports centrifuge modelling of spudcan foundations penetrating through 3 6 clay layers with interbedded stronger clay silica sand and carbonate sand layers the aim was to provide insight into the behaviour of spudcan foundations in stratified sediments comprising layers of different drainage conditions and mineralogy the motivation for this paper emanated directly from the future needs identified by the recent revised version of iso 19905 1 it was found that the downward soil deformation was extended into 3 4 underlying layers of sand and clay with thickness ratios t d less than 0 6 the limiting squeezing depth was 0 17 0 18d when approaching stiff clay moderate clay layers and 0 28d when approaching dense sand stiff clay layers these

mapping brittle fracture zones in three dimensions high resolution traveltime seismic tomography in a granitic pluton summary fractured and altered zones within a granitic pluton are mapped in three dimensions by means of high resolution seismic traveltime tomography the input traveltimes were picked from offset and azimuth variable vertical seismic profiles ovsp acquired in three boreholes and from seismic shot gathers of four cdp high resolution seismic reflection profiles recorded on the surface for the ovsp data a hydrophone streamer placed in the boreholes recorded the acoustic energy generated a signal with a frequency content between 15 to 150 hz by a vibroseis truck at source points distributed every 30 m in a rectangular grid of 620 m by 150 m the combination of borehole and surface seismic data resulted in an increase in the ray density of the shallow subsurface the tomographic algorithm uses a variable model grid with a finer grid spacing close to the surface were ray density is highest and the velocity variations are strongest therefore the resulting velocity models feature more detail at shallow levels a simple and smooth starting velocity model was derived from p wave velocity logs careful surface geological mapping and borehole geophysical data p and s wave velocity logs and poisson s ratio depth functions provided key constraints for a physically reasonable 3 d interpretation of the tomograms the low velocity anomalies constrained by the tomographic images were interpreted as unconsolidated rock fractures and altered zones which correlate with structures mapped at the surface or velocity anomalies identified in the logs subsequent resolution analysis revealed that the derived velocity model is well constrained to depths of 60 m

memory enhanced plasticity modeling of sand behavior under undrained cyclic loading abstractthis work presents a critical state plasticity model for predicting the response of sands to cyclic loading the well known bounding surface sanisand framework by dafalias and manzari is en

chronology of the wasatchian land mammal age early eocene magnetostratigraphic results from the mccullough peaks section northern bighorn basin wyoming a reply the mccullough peaks section of the willwood formation in the northern bighorn basin wyoming has produced a rich fossil record of early eocene mammals spanning much of the wasatchian land mammal age the wasatchian is an especially significant period in mammalian evolution since it marks the first appearance of several modern orders of mammals including perissodactyla artiodactyla and true primates magnetostratigraphic analysis of paleosol horizons in the mccullough peaks region is used to correlate wasatchian land mammal zones to the geomagnetic polarity time scale a total of 135 paleomagnetic samples were analyzed from 37 levels in a 1480 m section that ranges from wasatchian zone wa 0 earliest sandcouleean subage to the base of zone wa 7 earliest lostcabinian subage progressive thermal demagnetization of samples from red b type and mottled red gray ab type soil horizons provides the most reliable results the characteristic magnetization is carried by hematite with unblocking temperature

predicting the resistance profile of a spudcan penetrating sand overlying clay assessment of the risk of punch through failure of spudcan foundations on sand overlying clay requires prediction of the full penetration resistance profile from touchdown and through punch through to equilibrium of the vertical resistance at depth in the underlying clay layer this study uses the coupled eulerian lagrangian approach a large deformation finite element analysis method to model the complete penetration resistance profile of a spudcan on sand overlying clay the sand is modeled using the mohr coulomb model while the clay is modeled using a modified tresca model to account for strain softening the numerical method is then used to simulate a series of spudcan penetration tests performed in a geotechnical centrifuge on medium dense sand overlying clay the punch through behavior observed in the experiments is replicated and the penetration resistance profiles from numerical analyses are generally a reasonable match to the experimental measure ments the influences of the sand layer height to foundation diameter ratio sand clay interface shear strength and strength gradient in clay on the penetration resistance profiles are explored in a complementary parametric study the penetration resistance in the underlying clay layer is well predicted using a simple linear expression for the bearing capacity factor for the spudcan and underlying sand plug this expression is combined with an existing failure stress dependent model for predicting peak resistance to form a simplified method for prediction of the full penetration resistance profile this new method provides estimates of the vertical penetration that the spudcan will run during the punch through event it is validated against both medium dense and dense sand centrifuge tests

strength of undisturbed versus reconstituted silt and silty sand specimens the differences in undrained stress strain strength behavior between undisturbed and reconstituted silt and silty sand specimens tested at the same void ratio and initial stress state may be dramatic in all tests reported herein the undisturbed specimens showed dilative and ductile behavior whereas in all but a very few cases the accompanying reconstituted specimens at the same or lower density showed contraction much lower undrained strength and brittle behavior the test series included samples from a natural fluvial silt deposit as well as from silty sand hydraulically placed in a tailings dam when reconstituting specimens for laboratory testing it is not sufficient to only satisfy the criteria of correct density and grain size distribution but somehow the same fabric also must be reproduced otherwise deformation and stability analyses based on the results of reconstituted specimens or on in situ tests calibrated against such results may be misleading most of the reconstituted specimens

laboratory study on subgrade fluidization under undrained cyclic triaxial loading a long term issue that has hampered the efficient operation of heavy haul tracks is the migration of fluidized fines from the shallow soft subgrade to the overlying ballast i e mud pumping this

in situ liquefaction resistance of clean sands over a wide density range the paper describes a method of obtaining undisturbed samples of saturated clean sand by freezing it in situ using a single freezer pipe tests have shown that the method can yield high quality samples that retain the density and the undrained cyclic strength of the sand in situ undrained cyclic triaxial tests were run on in situ frozen samples and on samples obtained with conventional tube samplers the liquefaction resistance of the frozen samples of clean sands correlates well with a normalized iv value of the standard penetration test over a wide range of tv values the in situ liquefaction resistance of the clean sands estimated from the results of the undrained cyclic tests on the frozen samples is consistent with a criterion based on field performance data during earthquakes for dense sands the samples obtained with the tube samplers are looser and much weaker than those obtained by the in situ freezing method the reverse is true for very loose sands the correlation between relative density an

estimating in situ relative density and friction angle of nearshore sand from portable free fall penetrometer tests the friction angle of sand in the nearshore zone of cannon beach yakutat alaska was estimated from the deceleration measured by a portable free fall penetrometer pffp at 72 test locations a c

undrained shear strength of granular soils with different particle gradations a series of undrained tests were performed on granular soils consisting of sand and gravel with different particle gradations and different relative densities reconstituted in laboratory despite large differences in grading only a small difference was observed in undrained cyclic shear strength or liquefaction strength defined as the cyclic stress causing 5 double amplitude axial strain for specimens having the same relative density in a good contrast undrained monotonic shear strength defined at larger strains after undrained cyclic loading was at least eight times larger for well graded soils than poorly graded sand despite the same relative density this indicates that devastating failures with large postliquefaction soil strain are less likely to develop in well graded granular soils compared to poorly graded sands with the same relative density although they are almost equally liquefiable however if gravelly particles of well graded materials are crushable such as decomposed granite soils undrained monotonic strengths are considerably small and almost identical to or lower than that of poorly graded sands

physical property characteristics of gas hydrate bearing reservoir and associated seal sediments collected during nghp 02 in the krishna godavari basin in the offshore of india abstract india s national gas hydrate program expedition 02 nghp 02 was conducted to better understand geologic controls on gas hydrate occurrence and morphology targeting coarse grained sediments along the lower continental slope offshore eastern india this study combines seismic logging while drilling data and a petroleum system approach to provide a regional geologic and lithologic context for 1 gas hydrate morphology and distribution and 2 effects of fine grained sediments clays and other grains smaller than 63 m on gas production in nghp 02 area b in the krishna godavari basin area b seismic data show a buried anticline syncline structure with strong reflectors r1 and r2 that delineate two of the five lithologic units unit i shallowest ii r1 iii iv r2 and v below the bas of gas hydrate stability throughout area b gas hydrate morphology depends on its placement within these units specifically core and grain scale measurements indicate fines content exerts a primary control on the gas hydrate distribution and morphology units i ii and iii are generally fine grained on the anticline crest these units host primarily grain displacing gas hydrate veins linked to pore occupying gas hydrate in thin localized coarser grained deposits diatoms in unit iii increase porosity with depth reaching 70 where it contacts unit iv the gas hydrate reservoir associated with reflector r2 the unit iii lithology and porosity allow fluid and dissolved phase methane to escape unit iv and form gas hydrate in the fine grained overburden within unit iv fine grained layers are interbedded with coarser grained gas hydrate reservoir sands and the fines content even in the sands is high enough to impact hydraulic and mechanical properties during gas production fluid motion during gas production can mobilize fines which can then clog pore throats limiting production rates pore water freshening during gas hydrate dissociation can increase fines mobilization particularly given the smectite identified in the fine grained interbeds

thermal plume transport from sand and gravel pits potential thermal impacts on cool water streams summary we investigated the potential thermal impacts from below water table aggregate extraction on a cool water stream supporting brook trout salvelinus fontinalis and cool water macroinvertebrates we monitored thermal plumes emanating from an aggregate pit through an unconfined glacial outwash aquifer our objectives were to complete a detailed assessment to quantify the persistence of thermal plumes in the subsurface and establish a framework for guiding these investigations as the growing demand for aggregate increases pressures to pursue extraction in ecologically sensitive areas during a 10 year period we measured ground and surface water temperatures in an outwash aquifer and cool water stream including two periods of intensive monitoring 22 months and 2 5 years focusing on plume movement from one aggregate pit we quantified the aquifer hydraulic conductivity k at the laboratory and field scale and characterized the effective thermal conductivity at an unprecedented level of detail the mean k s from the multi scale tests span two orders of magnitude 1 8 10 4 to 1 7 10 2 m s 1 and are related to the test support volume the saturated has a mean of 2 42 w m 1 k 1 ranges from 2 14 to 2 69 w m 1 k 1 and is correlated to stratigraphic units gravel sand and till the annual temperature amplitude in the pit is 10 c above up gradient ground water and our results show that alternating warm and cool plumes persist in the aquifer for 11 months and migrate up to 250 m down gradient the observed plume velocity 1 2 m d 1 lags the ground water velocity 2 8 m d 1 due to thermal retardation furthermore hydraulic conductivity is shown to vary with the scale of the test and ground water velocities estimated from pumping tests may overestimate thermal plume velocities while we focused on plume migration our results demonstrate that assessing impacts on the aquatic community requires an integrated multi disciplinary study this work can guide such assessments

hydrodynamics in a gravel beach and its impact on the exxon valdez oil 1 this paper investigated the interaction of groundwater and seawater in a tidally influenced gravel beach field observations of water table pore water salinity were performed the two dimensional finite element model marun was used to simulate observed water table and salinity based on field observations and model calibrations a two layered beach structure was identified which is characterized by a high permeability surface layer underlain by a low permeability lower layer the salt wedge seaward of the low tide line was almost invariant in comparison with the strong fluctuations of the salinity plume in the surface layer of the intertidal zone the presence of the two layers prevented the presence of a freshwater discharge tube between the upper saline plume and salt wedge this is in contrast with the previous works where freshwater discharge tube was observed the tide induced submarine groundwater discharge sgd was estimated at 9 m3 d 1 m 1 a large value that is probably due to the large tidal range of 4 8 m and the very permeable surface layer the freshwater seawater dynamics revealed here may provide new insights into the complexity intensity and time scales of mixing between fresh groundwater and seawater in tidal beaches the simulated water table of the beach was higher than the interface between the surface layer and the lower layer which prevented exxon valdez oil from penetrating into the lower layer in 1989

influence of clod size and water content on gas permeability of a compacted loess1 the northwestern region of china is mainly semi arid to arid and loess is ubiquitous this natural resource has considerable potential to be transformed into earthen final covers for local landfills but first its suitability must be ascertained through extensive tests in this study a device was developed to measure the gas permeability of unsaturated compacted loess specimens experiments were carried out to investigate the influence of clod size compaction water content and post compaction water content on the gas permeability of the compacted loess to maintain an identical soil structure the post compaction water content was changed using the osmotic technique it was found that the compaction water content and resultant soil clod size exerted a combined effect on the gas permeability such that at low water contents the gas permeability remained fairly constant but at high water contents the clods became relatively large and the effect of the clod size dominated the water blockage effect from

correlations between index tests and the properties of remoulded clays correlations have been developed which relate the compressibility undrained shear strength and permeability of remoulded clays to their atterberg limits and activity the relationships can be used to model a hydraulic fill such as fine grained dredged material or mine tailings prior to deposition they can also be used to estimate the engineering properties of normally consolidated natural clay such as marine sediments the correlations cover a wide range of plasticity index and liquidity index for a wide variety of clays it was found that the activity plays a major role in the compressibility and undrained shear strength and is thus also related to the sensitivity of clays the activity apparently does not affect the permeability but other factors remain to be investigated because compressibility undrained shear strength and permeability are interrelated it can be concluded that if one is known then the other two can be derived hence these three engineering properties are seen as different

friction angle measurements on a naturally formed gravel streambed implications for critical boundary shear stress we report the first measurements of friction angles for a naturally formed gravel streambed for a given test grain size placed on a bed surface friction angles varied from 10o to over 100o friction angle distributions can be expressed as a function of test grain size median bed grain size and bed sorting parameter friction angles decrease with increasing grain size relative to the median bed grain size and are a systematic function of sorting with lower friction angles associated with poorer sorting the probability distributions of critical shear stress for different grain sizes on a given bed surface as calculated from our friction angle data show a common origin but otherwise diverge with larger grains having narrower and lower ranges of critical shear stresses the potential mobility of a grain as defined by its probability distribution of critical shear stress may be overestimated for larger grains in this analysis because our calculations do not take into account the effects of grain burial and altered near bed flow fields

seismic reflections from depths of less than two meters three distinct seismic reflections were obtained from within the upper 2 1 m of flood plain alluvium in the ar kansas river valley near great bend kansas reflections were observed at depths of 0 63 1 46 and 2 10 m and confirmed by finite difference wave equation modeling the wavefield was densely sampled by placing geophones at 5 cm intervals and near source nonelastic deformation was minimized by us ing a very small seismic impulse source for the reflections to be visible within this shallow range low seismic p wave ve locities 300 m s and high dominant frequency content of the data 450 hz were essential the practical implementa tion of high resolution seismic imaging at these depths has the potential to complement ground penetrating radar gpr chiefly in areas where materials exhibiting high electrical con ductivity such as clays prevent the effective use of gpr potential applications of these results exist in hydrogeology and environmental quaternary and neotectonic geology

assessing the punch through hazard of a spudcan on sand overlying clay a complete analytical method to describe the full load penetration resistance profile of a mobile jack up spudcan footing penetrating a sand over clay stratigraphy is described it is based on both large deformation finite element analyses and geotechnical centrifuge experiments the coupled eulerian lagrangian cel approach is used to accommodate the large deformations of a spudcan footing penetrating sand overlying clay modified mohr coulomb and tresca models describe the sand and clay behaviour with modifications accounting for the effects of strain softening on the response of the soil the cel results are shown to match centrifuge tests well allowing the numerical study to be extended parametrically and with confidence to cover the range of layer geometries sand relative densities and footing shapes that are of practical interest to offshore jack ups the results are used to a assess the performance of an existing model to predict the peak resistance in the sand layer extending its range of

high resolution aquifer analog of fluvial aeolian sediments of the guarani aquifer system the guarani aquifer system gas represents one of the biggest aquifers in the world and is the most relevant groundwater resource in south america for the first time by combining field and laboratory measurements a high resolution aquifer analog model of fluvial aeolian sediments of the gas in sao paulo state brazil is constructed three parallel sections of frontal outcrops 28 m 5 8 m and two parallel sections of lateral outcrops 7 m 5 8 m are recorded during open pit mining of sandy sediments and describe in detail the three dimensional distribution of the local lithofacies and hydrofacies variations of hydraulic conductivity k and porosity n are resolved on the centimeter scale and the most permeable units of the fluvial aeolian facies association are identified the constructed aquifer analog model shows moderate hydraulic heterogeneity and a mean k value of 1 36 10 4 m s which is greater than the reported range of k values for the entire gas in sao paulo state the results suggest that the examined sedimentary unit constitutes a relevant portion of the gas in sao paulo state in the context of groundwater extraction and pollution moreover the constructed aquifer analog is considered an ideal basis for future numerical model experiments aiming at in depth understanding of the groundwater flow and contaminant transport patterns at this gas portion or at comparable fluvial aeolian facies associations

intrinsic permeability of materials ranging from sand to rock fill using natural air convection tests air convection within coarse rock fills enhances winter time heat extraction from underlying soils modeling this phenomenon requires the knowledge of intrinsic permeability this study focuses on the measurement of intrinsic permeability using natural air convection within a 1 m3 test cell upward heat flow conditions are applied to various specimens test results are analyzed using a theoretical solution of natural convection in a square enclosure four materials were studied with effective particle sizes d10 ranging from 90 to 150 mm and porosities ranging from 0 37 to 0 41 the results showed that intrinsic permeability increases with increasing d10 the experimental results were adequately predicted by the kozeny carman and chapuis equations only slight deviations were observed which is considered acceptable given that these equations were developed for materials with much smaller values of d10 the experimental results of this study confirm the value of intrinsic permeability recently used in a