experimental behaviour of compacted marls jurassic marls from abadia portugal were used in the construction of some motorway embankments large fragments of this evolving material remained after the construction process and their degradation was of concern because of the expected change of the engineering properties of the compacted material the material exhibits a very complex behaviour which is difficult to reproduce with existing constitutive models for unsaturated structured materials this paper focuses on understanding and providing data on the interaction between the pure marls rock and the aggregate behaviour it presents the main results of tests performed to characterise the hydro mechanical behaviour of compacted marls in specimens prepared with different grading size distributions and subjected to oedometer tests where both stress and suction changes were applied the experimental data obtained were analysed considering the presence of fragments and their degradation the marl matrix was characterised to complete the existing

pre alpine variscan inheritance a key for the location of the future valaisan basin western alps the boundary between the helvetic and the penninic brianconnais zones has long been recognized as a major fault penninic front in the western alps a narrow oceanic domain has been postulated at least along part of this boundary the valaisan ocean however the information provided by the pre triassic basement has not been fully exploited and will be discussed here in detail the igneous and metamorphic history of the pre triassic basement shows significant differences between the external massifs from the helvetic zone with abundant late carboniferous granites and the basement of the brianconnais zone including the internal massifs dora maira gran paradiso monte rosa devoid of carboniferous granites a major coal bearing basin the zone houillere opened along this boundary this limnic intramontane basin has never been properly investigated the zone houillere is not comparable with the external paralic flexural basins on both sides of the variscan belt but shows similarities with the saar saale basin like the latter we interpret the zone houillere as a transtensional basin opened along a major crustal scale fault zone namely the east variscan shear zone the permian magmatism and sedimentation displays contrasting distributions being absent or very localized in the helvetic zone and widespread in the penninic zone the above data indicate that the structural inheritance from the variscan belt plays a major role in defining the future location of the valaisan basin i e the boundary between the european palaeomargin and the brianconnais microcontinent

new models for evolution of magma poor rifted margins based on a review of data and concepts from west iberia and the alps direct observation and extensive sampling in ancient margins exposed in the alps combined with drill hole and geophysical data from the present day iberia margin result in new concepts for the strain evolution and near surface response to lithospheric rupturing at magma poor rifted margins this paper reviews data and tectonic concepts derived from these two margins and proposes that extension leading to thinning and final rupturing of the continental lithosphere is accommodated by three fault systems each of them characterized by a specific temporal and spatial evolution during rifting of the margin by its fault geometry and its surface response the data presented in this paper suggest that margin architecture and distribution of rift structures within the future margin are controlled first by inherited heterogeneities within the lithosphere leading to a contrasting behaviour of the future distal and proximal margins during an initial stage of rifting the place of final break up appears to be determined early in the evolution of the margin and occurs where the crust has been thinned during a first stage to less than 10 kilometres during final break up the rheology of the extending lithosphere is controlled by the thermal structure related to the rise of the asthenosphere and by serpentinization and magmatic processes

brittle deformation during alpine basal accretion and the origin of seismicity nests above the subduction interface geophysical observations on active subduction zones have evidenced high seismicity clusters at 20 40 km depth in the fore arc region whose origin remains controversial we report here field observations of pervasive pseudotachylyte networks interpreted as evidence for paleo seismicity in the now exhumed valpelline continental unit dent blanche complex nw alps italy a tectonic sliver accreted to the upper plate at c 30 km depth during the paleocene alpine subduction pre alpine granulite facies paragneiss from the core of the valpelline unit are crosscut by widespread mm to cm thick pseudotachylyte veins co seismic heating and subsequent cooling led to the formation of ti rich garnet rims ilmenite needles ca rich plagioclase biotite microliths and hercynite micro crystals 39ar 40ar dating yields a 51 54 ma age range for these veins thus suggesting that frictional melting events occurred near peak burial conditions while the valpelline unit was already inserted inside the duplex structure in contrast the base of the valpelline unit underwent synchronous ductile and brittle seismic deformation under water bearing conditions followed by a re equilibration at c 40 ma 39ar 40ar on retrograded pseudotachylyte veins during exhumation related deformation calculated rheological profiles suggest that pseudotachylyte veins from the dry core of the granulite unit record upper plate micro seismicity mw 2 3 formed under very high differential stresses 500 mpa while the sheared base of the unit underwent repeated brittle ductile deformation at much lower differential stresses 40 mpa in a fluid saturated environment these results demonstrate that some of the seismicity clusters nested along and above the plate interface may reflect the presence of stiff tectonic slivers rheologically analogous to the valpelline unit acting as repeatedly breaking asperities in the basal accretion region of active subduction zones

hydromechanical behaviour of compacted granular expansive mixtures experimental and constitutive study compacted granular mixtures of high density bentonite pellets have been evaluated as an alternative buffer material to fill the empty space around nuclear waste disposal canisters in horizontal drifts despite the obvious benefits of these compacted mixtures the backfilling operation becomes easier and the gaps between the host rock and the buffer are minimised there are several aspects of concern such as the effective blockage of the large inter pellet pores due to granule swelling this blockage improves the water permeability properties and the tendency to develop initial collapses before reaching an adequate swelling pressure selected test results of a comprehensive laboratory experimental programme are presented to gain insight into the hydromechanical response of this multi porosity compacted material to improve the information on local transient behaviour simulation assisted techniques using a double structure constitutive model are used the paper presents a physically based one dimension

relation between flow through and volumetric changes in natural expansive soils abstract geology and climate govern the evolution and behavior of natural expansive soils in the semi arid canadian prairies the regina clay deposit has a flat topography a homogenous composition and contains hair line fissures this research focuses on understanding the relation between flow through and volumetric changes in the natural expansive soil based on analysis of test data it is concluded that flow occurs through macro pores or fissures 5 10 8 m s during structural volume change and through micro pores or matrix 10 9 m s during normal and residual volume changes the hydraulic conductivity decreases by several orders of magnitude and becomes asymptotic vapor flow 2 10 14 m s during residual volume change a complete assessment of soil behavior requires water retention swell shrink and hydraulic conductivity curves the proposed straight line representation of the functions components is useful for predicting field response of expansive soils

a microstructurally based effective stress for unsaturated soils current alternative choices of stress state variables in unsaturated soils are described and compared with a special focus on the use of an effective stress experimental data on stiffness and shear strength evolution with suction suggest that the proportion of suction contributing to the effective stress is often much smaller than predicted by the term suction times degree of saturation generally used in effective stress expressions of the bishop type it is suggested that effective stress in unsaturated soils should be related to soil microstructure an effective degree of saturation is defined as describing the volume of water partially filling the soil macroporosity this effective degree of saturation defines the proportion of the prevailing suction that actually contributes to the effective stress two alternative expressions piecewise linear and non linear are proposed for the effective degree of saturation they offer a similar performance available data on stiffness and shear strength varia

experimental zircon melt and zircon garnet trace element partitioning and implications for the geochronology of crustal rocks garnet is the most commonly used mineral in thermobarometry whereas zircon is the most robust chronometer to date high grade metamorphic rocks to provide a basis for correlation of zircon and garnet growth we determined experimentally the trace element partitioningbetweenzircon ahydrousgraniticmeltandgarnetat20kbarand800 1000 cforp y rareearthelements ree zr hf th andu inrespecttomelt zirconpreferentiallyincorporatesallinvestigatedelementsapartfromreewithatomicnumberlowerthansm at this pressure and in the chosen composition the distribution coefficient between zircon and melt d zrn melt for ree increases with increasingatomicnumberofthereeandwithdecreasingtemperature dyb is 20at1000 c butmorethananorderofmagnitude higher at800 c the solubilityofzrinhydrousgraniticmelts buffered by zirconisabouta factoroftwo lower at20kbar than what has been previously established for mid crustal pressures large garnet produced in the experiments allowed determination of garnet melt trace element partitioning d grt melt at temperatures of 800 1000 c conditions relevant for partial melting of crustal rocks there is a systematic increase indree with decreasing temperature zircon contains significantly more heavy ree than garnet at temperatures of 800 850 c zircon garnetpartitioncoefficientsofheavy reedecreasewithincreasingtemperaturefromdlu of12at800 cto 1 4at1000 c middle reepartitioningisclosetounityforthewholeinvestigatedtemperaturerange differentempiricallydetermined zircon garnet partition coefficients from granulites and ultra high temperature granulites can potentially be explained by the experimentallydeterminedchangeofpartitioningasafunctionoftemperature thesedatacanassistinestablishingequilibriumbetween garnetandzirconzonesinnaturalrocks andintheconstructionofdetailedpressure temperature timepathsinhigh grademetamorphic rocks

suction controlled multistage triaxial testing on clayey silty soil abstract multistage triaxial testing offers a potentially reliable and time saving alternative method of determining the shear strength of soils under suction controlled conditions while addressing the issues related to soil variability and lack of replicates however evidence of its suitability for testing geomaterials in unsaturated conditions is rather limited in this work a series of suction controlled multistage triaxial tests were performed on compacted specimens of clayey silty soil wherein each test was performed on the same soil specimen at a constant suction under drained condition but at varying net confining pressures the point of termination of the shearing stage was defined through a selection process involving either the stiffness or the volume change in monotonically sheared specimen based on whichever prevents premature failure of the specimen this was the first attempt where all the stages of a multistage triaxial test were compared against that from single stage triaxial tests for validation of the approach moreover the influence of errors introduced by multistage triaxial testing on the shear strength predictions of unsaturated soil was considered by constructing a three dimensional failure envelope on p s space using a well known relation and comparing them against those obtained from single stage triaxial tests it was also noted that for determining the shear strength parameters of soil the multistage testing reduced the testing times to half of that required by single stage triaxial testing which would translate into significant reduction of cost of testing thereby making unsaturated soil testing much more appealing to the practitioners

a constitutive model for soft clayey rocks that includes weathering effects microstructural and mineralogical observations of clay stones reveal the presence of clay aggregates bonded by a skeleton of inert minerals such as calcium carbonate the behaviour of these natural materials evolves from a rock like behaviour when undisturbed to clay like soil when weathered or when subjected to straining a model has been developed to simulate the constitutive behaviour of these transitional materials following the proposal made by vaunat gens the material is conceived as a composite medium made of a clay matrix and a quasi brittle bonding microstructure the basic model has been modified and extended to reproduce the expansive behaviour of the clay matrix a fundamental aspect to simulate weathering effects induced largely by drying wetting cycles the clay matrix reacts to stress and suction changes whereas the bond component is not affected by suction changes an elasto plastic double structure model for expansive clay soils describes the clay matrix the bonding structure fol

challenges to modelling heave in expansive soils there are challenges associated with the numerical modelling of unsaturated expansive soils the challenges are primarily related to the quantification of the void ratio constitutive surface the characterization of the void ratio constitutive surface at low stresses and or suction and the solution of coupled equations with several nonlinear unsaturated soil property functions this study suggests that the void ratio constitutive surface of an expansive soil subject to a monotonic wetting path can be estimated from volume change indices obtained from conventional laboratory tests the constitutive surfaces for both the soil structure and the water phase can be described using mathematical equations that allow net normal stress and suction to be reduced to zero the solutions for two typical volume change problems are presented using both a coupled approach and an uncoupled approach the first example problem simulates water leakage from a pipe under a flexible cover the second example problem simulate

a fossil ocean continent transition of the mesozoic tethys preserved in the schistes lustres nappe of northern corsica abstract the analysis of field relationships between allochthonous crystalline slivers ultramafic units and associated sedimentary cover in the high pressure schistes lustres units of northern corsica allows reconstruction of the pre orogenic architecture of a fossil mesozoic ocean continent transition oct of the tethys basin the studied area encompassing the serra di pigno and col de teghime areas cap corse is composed of an assemblage of prealpine basement sheets made up of serpentinized mantle rocks permian gabbros and gneisses locally associated with paleozoic metabasites and micaschists the sedimentary cover includes numerous intervals of calc schists marbles quartzites micaschists and dolomitic metabreccias yielding a great variety of lithostratigraphical successions the metasedimentary sequences do not show affinities with the typical cover series of the prepiemontais margin domains this implies an origin from a more internal domain oceanward for the studied units in addition the sedimentary cover of the ultramafic basement units do not display the characters of the classical alpine ophiolites but bear lithological features showing affinities with both continental and oceanic environments we assume that the high variability of the sedimentary successions as well as the presence of a basement composed of continental and upper mantle rocks is consistent with an origin at an oct the acidic basement slivers are regarded as former extensional allochthons of continental crust abandoned during breakup on a newly exhumed seafloor of peridotite composition such extensional allochthons will then logically constitute the most internal continental slices buried at great depth during alpine subduction this work shows that a lot has to be expected from a revision of the schistes lustres lithostratigraphy in the light of the new concepts of the evolution of the oct domains

compaction behaviour of clay this paper presents an experimental study of the compaction behaviour of non active clay one dimensional static compaction tests were carried out at high and medium water content with matric suction monitoring using trento high capacity tensiometers at lower water contents a transistor psychrometer was used to measure post compaction suction samples were compacted on the dry side of optimum to cover a wide range of compaction water contents and vertical stresses three water content regions were identified in the compaction plane depending on whether post compaction suction increased decreased or remained constant as the degree of saturation was increased at constant water content hydraulic paths of specimens subjected to loading unloading cycles at constant water content have clearly shown that post compaction suction may increase as the degree of saturation increases this non intuitive behaviour was demonstrated to be associated with the coupling between mechanical and water retention behaviour to this end a coupled mechanical water retention model was formulated irreversible one dimensional mechanical paths were modelled by a boundary surface in the space average skeleton vertical stress modified suction and void ratio irreversible hydraulic wetting paths were modelled by a boundary surface in the space suction degree of saturation and void ratio this study was completed by investigating the pore size distribution of compacted samples through mip tests

a revised subduction inception model to explain the late cretaceous double vergent orogen in the precollisional western tethys evidence from the northern apennines the meso cenozoic alpine belts of the mediterranean area are characterized by complex architectures result of a complex subduction and collision evolution that preserve also a legacy of the rifting related configuration of the continental margins the northern apennines is a segment of these belts originated during closure of the ligure piemontese ocean and collision between the europe and adria plates the different configuration of the adria and europe margins inherited from asymmetric rifting is recorded in the ligurian units that preserve incorporation into the subduction factory of fragments of the oceanic domain internal ligurian units and portions of the ocean continent transition zone octz toward adria external ligurian units we provide here unpublished data on the stratigraphy and sedimentology of these units together with a review of what is already established in literature both datasets combined testify that at 80 m a an accretionary prism was growing between the deposition basins of the two groups of units and fed both basins with clasts from the ocean realm the continental crust and the subcontinental mantle we propose that closure of the ligure piemontese ocean occurred through subduction that nucleated at the transition from the oceanic plate and the thinned adria margin and developed a double vergent prism by accreting oceanic material and continental extensional allochthons from the octz we believe the revised site of subduction initiation and the pre collisional architecture inherited from the rifting and spreading phases allow reconciling most of the discrepancies between the various interpretation proposed in literature for the pre collisional evolution of the apennines

evaluation of strain and stress states of a compacted highly expansive soil using a thin walled oedometer abstract investigation of the volume change behavior of expansive soils typically utilizes conventional oedometer which provide estimates of vertical strain and swelling pressure under fully lateral restrained conditions in this study testing was conducted on compacted highly expansive clay using a thin walled oedometer to evaluate the state of stresses during inundation in both vertical and lateral directions in addition to the vertical strain first calibration correction and verification of the thin wall oedometer were described second an experimental program was developed to evaluate the volume change behavior during inundation for a wide range of vertical stresses at inundation i under two conditions i constant vertical stress at inundation and ii constant volume results of tests under constant vertical stress at inundation indicate the dependency of strain state of expansive soil on the inundation vertical stress moreover the vertical stress at inundation i was observed to affect the vertical stress state after inundation for constant volume condition investigating the equilibrium vertical stress state after inundation under constant volume condition showed that there is one relation termed as swell collapse equilibrium line scel that represents the equilibrium condition after inundation for specimens subjected to different initial sample conditions prior to inundation general trends of strain softening behavior for the evolution of lateral stresses with time were observed particularly for the swelling zone stress path followed by tested samples was depicted interpretation of results in light of barcelona expansive model bexm was also performed an enlargement of yield envelop after loading to stresses greater than past stress history was observed

hydro mechanical analysis of volcanic ash slopes during rainfall rainfall induced landslides in volcanic ashes represent a major natural hazard in many regions around the world due to their loose structure volcanic ash slopes are prone to rainfall induced landslides the paper presents a continuum modelling approach for the analysis of wetting induced instability phenomena at the onset of failure in loose volcanic ash slopes a numerical simulation of a landslide prone volcanic slope in costa rica is carried out with a 2d hydro mechanical finite element slope model a constitutive model based on the effective stress concept extended to partially saturated conditions is used to reproduce the volcanic ash hydro mechanical behaviour the model parameters were calibrated through a previous extensive laboratory testing campaign simulation results allow to anticipate the behaviour of the slope during rainfall infiltration and to analyze the development of the failure mechanism results of the coupled numerical model demonstrate the important role of wetting and drying cycles slope geometry and bedrock on the timely evolution of matric suctions and wetting induced deformations moreover it is observed that the pore collapse upon wetting enhances the development of a localised shear failure mechanism in unsaturated conditions

pervasive eclogitization due to brittle deformation and rehydration of subducted basement effects on continental recycling the buoyancy of continental crust opposes its subduction to mantle depths except where mineral reactions substantially increase rock density sluggish kinetics limit such densification especially in dry rocks unless deformation and hydrous fluids intervene here we document how hydrous fluids in the subduction channel invaded lower crustal granulites at 50 60 km depth through a dense network of probably seismically induced fractures we combine analyses of textures and mineral composition with thermodynamic modeling to reconstruct repeated stages of interaction with pulses of high pressure hp fluid at 650 670 c rehydrating the initially dry rocks to micaschists sims oxygen isotopic data of quartz indicate fluids of crustal composition hp growth rims in allanite and zircon show uniform u th pb ages of 65 ma and indicate that hydration occurred during subduction at eclogite facies conditions based on this case study in the sesia zone western italian alps we conclude that continental crust and in particular deep basement fragments during subduction can behave as substantial fluid sinks not sources density modeling indicates a bifurcation in continental recycling chiefly mafic crust once it is eclogitized to 60 are prone to end up in a subduction graveyard such as is tomographically evident beneath the alps at 550 km depth by contrast dominantly felsic hp fragments and mafic granulites remain positively buoyant and tend be incorporated into an orogen and be exhumed with it felsic and intermediate lithotypes remain positively buoyant even where deformation and fluid percolation allowed them to equilibrate at hp

from permo triassic lithospheric thinning to jurassic rifting at the adriatic margin petrological and geochronological record in valtournenche western italian alps abstract slices of polycyclic metasediments marbles and meta cherts are tectonically amalgamated with the polydeformed basement of the dent blanche tectonic system along a major alpine shear zone in the western alps becca di sale area valtournenche valley a combination of techniques structural analysis at various scales metamorphic petrology geochronology and trace element geochemistry was applied to determine the age and composition of accessory phases titanite allanite and zircon and their relation to major minerals the results are used to reconstruct the polyphase structural and metamorphic histories comprising both pre alpine and alpine cycles the pre alpine evolution is associated with low pressure high temperature metamorphism related to permo triassic lithospheric thinning in meta cherts microtextural relations indicate coeval growth of allanite and garnet during this stage at 300 ma textures of zircon also indicate crystallisation at ht conditions ages scatter from 263 to 294 ma with a major cluster of data at 276 ma in impure marble u pb analyses of titanite domains with variable al and f contents yield apparent 206pb 238u dates range from permian to jurassic chemical and isotopic data suggest that titanite formed at permian times and was then affected by extension related fluid circulation during the triassic and jurassic which redistributed major elements al and f and partially opened the u pb system the alpine cycle lead to early blueschist facies assemblages which were partly overprinted under greenschist facies conditions the strong alpine compressional overprint disrupted the pre alpine structural imprint and or reactivated earlier structures the pre alpine metamorphic record preserved in these slices of metasediments reflects the onset of the permo triassic lithospheric extension to jurassic rifting

evolution of microstructure in compacted london clay during wetting and loading the influence of fabric on mechanical behaviour is explicitly considered in some of the current constitutive models for unsaturated soils these are based on assumptions regarding the interaction b

assessing internal stress evolution in unsaturated soils 1 internal stresses in soils evolve as a result of the various interactions among soil particles and the pore fluids in response to natural or human induced activities whether attributed to suction structure or the various physicochemical forces that may develop assessing the internal stresses in soils has been an active area of research in soil science and engineering this paper presents the restrained ring method as an experimental tool for measuring the stresses that develop in a drying soil when it is restrained from shrinking freely the internal stress that develops can be related to the water content of the soil this method is validated using results for both silty clay loam and clay loam soils tensile stress at failure estimated from the restrained ring method was compared to tensile strength ranges of similar soils and a good correlation was observed moreover internal stresses measured by the restrained ring method were compared with existing empirical relationships using suction and degree of saturation this comparison concluded that suction is not the sole contributor to the soil s internal stress

swelling and softening behaviour of la biche shale free swell semiconfined swell and one dimensional oedometer swell tests were performed on la biche shale specimens in solutions of different salinities the swelling behaviour of la biche shale w

from passive margins to orogens the link between ocean continent transition zones and ultra high pressure metamorphism a lithostratigraphic association consisting of serpentinized mantle rocks continent derived allochthons mid oceanic ridge gabbros of jurassic age and post rift sediments typical of an ocean continent transition is found in the eclogitic piemonte units in the western alps in situ u pb geochronology was performed on zircons from an orthogneiss sampled at the bottom of a sliver of continental basement in contact with serpentinites primary magmatic zircons of permian age were overgrown by a second generation of zircon at ca 166 150 ma likely related to melt infiltration associated with the intrusion of the underlying gabbroic body this indicates that continental basement slices and oceanic basement rocks were already juxtaposed in the jurassic and they were probably part of hyper extended crust related to the opening of the tethys therefore the complex lithological association described here which is also characteristic of several ultra high pressure melange zones worldwide was acquired prior to the orogenic event during which it was only partly reworked ocean continent transitions are in positions favorable to reach ultra high pressure conditions following negatively buoyant oceanic lithosphere into subduction and then being accreted to the orogen in response to the arrival of more buoyant continental lithosphere resisting subduction the ocean continent transition is now found in the immediate footwall of a 500 m thick shear zone which accommodated multiple episodes of deformation during eocene oligocene time suggesting an important link between alpine deformation and rift related structures

recent developments in gravity wave effects in climate models and the global distribution of gravity wave momentum flux from observations and models recent observational and theoretical studies of the global properties of small scale atmospheric gravity waves have highlighted the global effects of these waves on the circulation from the surface to the middle atmosphere the effects of gravity waves on the large scale circulation have long been treated via parametrizations in both climate and weather forecasting applications in these parametrizations key parameters describe the global distributions of gravity wave momentum flux wavelengths and frequencies until recently global observations could not define the required parameters because the waves are small in scale and intermittent in occurrence recent satellite and other global datasets with improved resolution along with innovative analysis methods are now providing constraints for the parametrizations that can improve the treatment of these waves in climate prediction models research using very high resolution global models has also recently demonstrated the capability to resolve gravity waves and their circulation effects and when tested against observations these models show some very realistic properties here we review recent studies on gravity wave effects in stratosphere resolving climate models recent observations and analysis methods that reveal global patterns in gravity wave momentum fluxes and results of very high resolution model studies and we outline some future research requirements to improve the treatment of these waves in climate simulations copyright 2010 royal meteorological society and crown in the right of canada

experimental observations of the stress regime in unsaturated compacted clay when laterally confined construction processes often involve reformation of the landscape which will inevitably encompass compaction of artificially placed soils a common application of fill materials is their use as backfill in many engineering applications for example behind a retaining wall the post construction behaviour of clay fills is complex with respect to stresses and deformation when the fills become saturated over time heavily compacted fills swells significantly more than the lightly compacted fills this will produce enhanced lateral stresses if the fill is laterally restrained the work presented in this paper examines how the stress regime in unsaturated clay fills changes with wetting under laterally restrained conditions specimens of compacted kaolin with different initial conditions were wetted to various values of suction under zero lateral strain at constant net overburden pressure which allowed the concept of k0 the ratio between the net horizontal stress and the net vertical stress to be examined

modified state surface approach to the study of unsaturated soil behavior part ii general formulation in the previous companion paper a modified state surface approach was proposed to algebraically represent unsaturated soil behavior under isotropic stress conditions the present paper proposes a

suction in compacted states examines the possible magnitude of suction in compacted states of clayey soils from the test results it is concluded that suction is zero in monotonically loaded unsaturated states this implies that suction in compacted states should be equal to the compaction stress itself however as data previously reported in literature have often shown suction is strongly related to the water content and not much affected by the compaction stress

changes in tensile strength and microstructure of loess due to vibration abstract loess soils typically have an open and metastable structure humidification and vibration can modify their microstructure and thus influence their mechanical behavior in the present study to investigate the influence of train vibration on the tensile strength behavior of loess the tensile tests were performed on loess specimens that had been vibrated at a low amplitude for a long period using a modified horizontal extensograph in addition the microstructures of vibrated and non vibrated loess specimens before and after the tensile tests were characterized changes in the loess microstructure due to vibration and that in the tensile test were analyzed the results show that the relationship between uniaxial tensile strength and water content in soil specimen could be represented using a power function the axial displacement at failure varies at the same manner as tensile strength with respect to water content in comparison to intact loess occurrence of less clay bridges and clay buttresses between aggregates or coarse particles is identified in the disturbed specimens while aggregates are seen to be a very little more loose in vibrated specimens after the tensile tests than that before the tensile tests this indicates that vibration reduces the tension resistance and ductility of loess soil structure which could be attributed to loss of bonding strength as a result of breakage of clay cementations and disintegration of aggregates in the tensile test the soil structure goes through two distinct phases of change i e stretching phase and cracking phase in the stretching phase the tensile deformations take place throughout the specimen without altering the contacts between soil particles significantly in the cracking phase weak cementations fail to resist tensile deformation and suffer from breakage once a through crack is developed the specimen breaks in two leading to a catastrophic drop of tensile stress

the water retention curve and relative permeability for gas production from hydrate bearing sediments pore network model simulation the water retention curve and relative permeability are critical to predict gas and water production from hydrate bearing sediments however values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges this study utilizes the combined techniques of micro focus x ray computed tomography ct and pore network model simulation to identify proper values for those key parameters such as gas entry pressure residual water saturation and curve fitting values hydrates with various saturation and morphology are realized in the pore network that was extracted from micron resolution ct images of sediments recovered from the hydrate deposit at the mallik site and then the processes of gas invasion hydrate dissociation gas expansion and gas and water permeability are simulated results show that greater hydrate saturation in sediments lead to higher gas entry pressure higher residual water saturation and steeper water retention curve an increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate hydrate morphology has more significant impacts than hydrate saturation on relative permeability sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability in this sense the brooks corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate bearing sediments

unified hardening uh model for overconsolidated unsaturated soils naturally deposited clays are often unsaturated and overconsolidated within the frameworks of the barcelona basic model bbm for normally consolidated unsaturated clays and the unified hardening

effects of repeated hydraulic loads on microstructure and hydraulic behaviour of a compacted clayey silt soils used in earth construction projects are mostly unsaturated and they undergo frequent drying wetting cycles repeated hydraulic loads due to changes in climatic conditions or variations of t

yielding and plastic behaviour of boom clay an underground research laboratory url has been excavated in a deposit of boom clay at a depth of 223 m by the sck cen belgian organisation near the city of mol this url is devoted to research into nuclear waste disposal this paper presents the results of an investigation carried out in the triaxial apparatus on specimens that were trimmed from blocks extracted during excavation sequences in the url in order to characterise the mechanical behaviour of the natural boom clay and to examine the effect of initial and induced anisotropy on its constitutive behaviour two series of triaxial tests were carried out special attention was devoted to the yield behaviour and the effects of stress history experimental results showed a clear relation between the shape of yield curves and stress history the yield curve of the clay in its initial state was oriented along the k0 line illustrating the anisotropy of fabric that was generated during the soil deposition subsequent isotropic compression up to 9 mpa

a thermomechanical model for saturated clays a thermomechanical model for saturated clays is proposed within the framework of recent extensions of the cam clay model the results of some tests found in the literature are analyzed and the main features of the thermomechanical behaviour of clays are identified the effect of the overconsolidation ratio ocr on the volume change of a soil expansion contraction submitted to heating is well established using experimental data obtained for selected soils by various authors however existing models need to be modified to correctly model this feature for this reason a new volumetric thermal plastic mechanism is developed that allows for the prediction of plastic strains at higher ocr values the overconsolidation effect observed when heating a normally consolidated soil is also modelled particular attention is paid to the coupling and hardening phenomena related to the combined effects of stress and temperature a qualitative validation is made by examining the response of the model under a given th

swelling phenomena and effective stress in compacted expansive clays the central aim of this paper is to discuss the applicability of the effective stress principle as defined by terzaghi total stress minus pore water pressure to predict the behaviour of expansive

paleozoic to triassic ocean opening and closure preserved in central iran constraints from the geochemistry of meta igneous rocks of the anarak area the anarak area belongs to an ophiolitic belt along the northern border of the central east iranian microcontinent and is thought to contain fragments of the former paleotethys and neotethys oceans a wide range of meta igneous rocks from the late paleozoic to triassic anarak metamorphic complex amc and nearby meraji area have been studied to constrain the origins and modes of emplacement of oceanic remnants in central iran our samples occur as layers and lenses embedded in extensive sequences of deformed meta sediments and smaller bodies of serpentinized ultramafic rocks petrographical and geochemical data combined with field and satellite observations allow recognition of seven types of meta igneous rocks preserved from low grade to blueschist facies conditions their origins based on relative abundances of immobile trace elements include subduction zone mid ocean ridge ocean intraplate and continental rift settings these data and existing geochronological constraints show the amc formed an accretionary complex formed exhumed incrementally during the carboniferous permo triassic and triassic igneous rocks from meraji formed in the early devonian due to opening of the paleotethys and belong to a rift sequence extending over 300 km along the edge of the central east iranian microcontinent the amc and nearby rock associations record the evolution of the paleotethys during a complete wilson cycle between ca 450 and 225 ma with implications for 1 continental rifting 2 ocean opening 3 subduction initiation 4 ocean intraplate and continued mid ocean volcanism 5 ridge subduction and 6 final closure of the ocean during continent continent collision alternate interpretations of the anarak metabasites are possible but require radical departures from the widely accepted model for tectonic evolution of the paleotethys with the existence of paleotethyan backarc basin s and permian or earlier collision of continental blocks in central iran in any case our results show accretionary complexes preserved along suture zones contain an important record of the evolution of oceanic crust from ancient ocean basins

mechanical behaviour of heavily compacted bentonite under high suction changes the paper reports the results of an experimental study carried out on a bentonite compacted to a dry density of up to 1 7 mg m3 a high value for this type of soil the soil fabric has been studied using a variety of techniques revealing a clear bimodal pore distribution that corresponds to two distinct structural levels a microstructural one and a macrostructural one the main testing programme has been performed using oedometers especially designed to apply a very large range of suctions by applying the axis translation technique using nitrogen as the gas fluid it has been possible to reach suctions up to 15 mpa the higher suction range has been achieved by applying a controlled atmosphere where the relative humidity has been fixed by a solution of sulphuric acid or salts in this way suctions up to 550 mpa could be reached the maximum vertical stress that could be applied in the apparatus was 10 mpa two types of test have been carried out a tests in which a combination of loading paths at constant suction and drying wetting paths at constant load were applied b swelling tests under constant volume conditions in order to determine the swelling pressure and the stress path followed during wetting the results of the experimental programme are examined taking into account the role of the soil fabric in controlling observed mechanical behaviour in addition the results of the laboratory tests are reproduced and interpreted using a generalised plasticity model that considers explicitly the interaction between macrostructure and microstructure in this way it is possible to achieve a more complete understanding of the mechanisms that underlie observed behaviour and in particular the interplay between the two structural levels

the geometry and timing of orogenic extension an example from the western italian alps contacts between rocks recording large differences in metamorphic grade are indicative of major tectonic displacements low p upon high p contacts are commonly interpreted as extensional i e material points on either side of the contact moved apart relative to the palaeo horizontal but dating of deformation and metamorphism is essential in testing such models in the western alps the piemonte ophiolite consists of eclogites t 550 600 c and p 18 20 kbar structurally beneath greenschist facies rocks t 400 c and p 9 kbar mapping shows that the latter form a kilometre wide shear zone the gressoney shear zone gsz dominated by top se movement related to crustal extension rb sr data from micas within different gsz fabrics which dynamically recrystallized below their blocking temperature are interpreted as deformation ages ages from different samples within the same fabric are reproducible and are consistent with the relative chronology derived from mapping they show that the gsz had an extensional deformation history over a period of c 9 myr between c 45 36 ma this overlaps in time with the eclogite facies metamorphism the gsz operated over the entire period during which the footwall evolved from eclogite to greenschist facies and was therefore responsible for eclogite exhumation the discrete contact zone between eclogite and greenschist facies rocks is the last active part of the gsz and truncates greenschist facies folds in the footwall these final movements were therefore not a major component of eclogite exhumation pressure estimates associated with old and young fabrics within the gsz are comparable indicating that during extensional deformation there was no significant unroofing of the hangingwall since there are no known extensional structures younger than 36 ma at higher levels in this part of the alps exhumation since the final juxtaposition of the two units at 36 ma seems to have been dominated by erosion key words deformation age eclogite exhumation rb sr dating tectonic

a framework for the behaviour of unsaturated expansive clays the paper presents a framework for describing the mechanical behaviour of unsaturated expansive clays it is an extension of an existing formulation developed for unsaturated soils of low activity the extended framework is based on the distinction within the material of a microstructural level where the basic swelling of the active minerals takes place and a macrostructural level responsible for major structural rearrangements by adopting simple assumptions concerning the coupling between the two levels it is possible to reproduce major features of the behaviour of unsaturated expansive clays some selected qualitative comparisons between model predictions and experimental results reported in the literature are presented despite the simplified hypotheses made a very encouraging agreement is obtained key words capillarity clay model unsaturation suction expansive soils

soil structure of a highly weathered old alluvium the old alluvium in san juan puerto rico is an early pleistocene deposit that has undergone substantial post depositional weathering in a tropical climate preliminary geotechnical laboratory testing found that the soil exhibits some unusual index and consolidation properties compared with stereotypical sedimentary soils for instance both the swelling index and the coefficient of consolidation are greatly affected by the maximum past stress applied to the soil in order to understand its unusual behaviour a variety of experiments were performed to characterise its composition and microstructure direct observations of the microstructure used environmental scanning electron microscopy and indirect examinations included slaking cation exchange capacity selective chemical dissolution particle size analyses and atterberg limits the results clearly indicate that the weathered deposit possesses a complex microstructure the intact material consists of a stiff network of aggregates interconnected by fe

kinematics of syn and post exhumational shear zones at lago di cignana western alps italy constraints on the exhumation of zermatt saas ultra high pressure rocks and deformation along the combin fault and dent blanche basal thrust kinematic analyses of shear zones at lago di cignana in the italian western alps were used to constrain the structural evolution of units from the piemont ligurian oceanic realm zermatt saas and combin zones and the adriatic continental margin dent blanche nappe during palaeogene syn and post exhumational deformation exhumation of zermatt saas u hp rocks to approximately lower crustal levels at ca 39 ma occurred during normal sense top s e shearing under epidote amphibolite facies conditions juxtaposition with the overlying combin zone along the combin fault at mid crustal levels occurred during greenschist facies normal sense top se shearing at ca 38 ma the scarcity of top se kinematic indicators in the hanging wall of the combin fault probably resulted from strain localization along the uppermost zermatt saas zone and obliteration by subsequent deformation a phase of dominant pure shear deformation around 35 ma affected units in the direct footwall and hanging wall of the combin fault it is interpreted to reflect nw se crustal elongation during updoming of the nappe stack as a result of underthrusting of european continental margin units and the onset of continental collision this phase was partly accompanied and followed by ductile bulk top nw shearing especially at higher structural levels which transitioned into semi ductile to brittle normal sense top nw deformation due to vanzone phase folding from ca 32 ma onwards our structural observations suggest that syn exhumational deformation is partly preserved within units and shear zones exposed at lago di cignana but also that the combin fault and dent blanche basal thrust experienced significant post exhumational deformation reworking and overprinting earlier structures

recognizing remnants of magma poor rifted margins in high pressure orogenic belts the alpine case study magma poor rifted margins are being increasingly recognized in present day atlantic type systems however findings of fossil areas floored by exhumed mantle or hyper extended crust are comparatively rare within orogenic belts that were originated through the inversion of pre existing rifted margins this discrepancy may be due to the common reactivation of lithological contacts during subduction orogeny potentially masking pre orogenic relationships and most importantly to the frequent lack of a preorogenic layer cake architecture hindering retro deformation of multiply deformed tectonic units this study outlines a methodology to detect sections of magma poor hyper extended rifted margins without a layer cake architecture in multiply deformed metamorphosed terrains this approach is defined by comparison to well studied examples of fossil analogues preserved in weakly deformed parts of alpine orogens in the latter domains continental basement and hydrated peridotites were exhumed at the basin floor during jurassic rifting along long offset detachment systems extensional geometries locally resulted in tectonic sampling of laterally discontinuous slivers of allochthonous continental basement and pre rift sediments fromthe hanging wall blocks lithostratigraphic associations consisting of continental basement rocks directly juxtaposed with syn to post rift meta sediments and or serpentinized subcontinental mantle are widespread within sections of alpine type orogenic belts that underwent high to ultra high pressure metamorphism however similar associations may arise from a variety of processes other than rift related lithospheric thinning in magma poor environments including subduction melange dynamics or deposition of sedimentary melanges along convergent divergent margins the partial preservation of rift related lithostratigraphic associations may still be assessed despite the lack of biostratigraphic evidence by 1 the consistency of the lithostratigraphic architecture over large areas despite pervasive alpine deformation which rules out chaotic mixing during subduction exhumation 2 the presence of clasts of basement rocks in the neighboringmeta sediments indicating the original proximity of the different lithologies 3 evidence of brittle deformation in continental basement and ultramafic rocks pre dating alpine metamorphism indicating that theywere juxtaposed by fault activity prior to the deposition of post rift sediments and 4 the similar alpine tectono metamorphic evolution of ophiolites continental basement and meta sediments a re assessment of basement cover relationships in the north western alps following this approach combined with published studies on exhumedmantle domains sampled in the rest of thewestern alps indicates that several tectono metamorphic units fromthemost deformed metamorphosed part of the belt between the canavese line and the penninic front sample hyper extended lithosphere related to the jurassic opening of the western tethys relative plate motion during cretaceous tertiary basin inversion was largely accommodated at the transition between areas floored by hyper extended crust or hydrated subcontinental mantle and domains consisting of thicker continental crust as a result distal margins were preferentially subducted whereas the proximal domains and the brianconnais paleo high underwent relatively minor deformation and metamorphism the high pressure alpine tectono metamorphic units were probably detached from the downgoing lithosphere along a hydration front that is typically observed in present day distal margins the recognition of preserved pre alpine relationships between continental basement post rift sediments and or serpentinized ultramafic rocks calls for a re assessment of the relative role of subduction and rifting dynamics in establishing the present day orogen architecture

burial rates during prograde metamorphism of an ultra high pressure terrane an example from lago di cignana western alps italy abstract estimation of burial rates and duration of prograde metamorphism of ultra high pressure uhp rocks t 590 630 c p 2 7 2 9 gpa of the zermatt saas ophiolite from lago di cignana italy may be made through combined lu hf and sm nd garnet geochronology in conjunction with petrologic estimates of the prograde p t path we report a lu hf garnet omphacite whole rock isochron age of 48 8 2 1 ma from the uhp locality at lago di cignana which stands in contrast to the sm nd age of 40 6 2 6 ma amato et al earth planet sci lett 171 1999 425 438 obtained from the same sample and mineral material the sm nd and lu hf ages as well as other ages determined on metamorphic garnet zircon and white mica amato et al earth planet sci lett 171 1999 425 438 mayer et al eur union geosci 10 1999 abstr 809 rubatto et al contrib mineral petrol 132 1998 269 287 dal piaz et al int j earth sci 90 2001 668 684 from lago di cignana and elsewhere in the zermatt saas ophiolite lie within a range of 50 38 ma which we interpret to encompass the duration of prograde metamorphism and possibly the duration of garnet growth the difference in measured sm nd and lu hf ages from cignana can be accounted for by expected core to rim variations in lu hf sm and nd the measured yttrium content in garnet which may be a proxy for lu is highest in garnet core and lowest in the mineral rim generally following a profile that is predicted by rayleigh fractionation preferential enrichment of lu in the core produces a lu hf age that is weighted toward the older garnet core sm nd ages as predicted by rayleigh fractionation of sm and nd during garnet growth however reflect later grown garnet as compared to lu hf ages the difference in sm nd and lu hf ages from a single sample should therefore be a minimum estimate for the duration of garnet growth and prograde metamorphism so long as sm nd and lu hf blocking temperatures were not exceeded for a long period of time based on the 12 myr duration of prograde garnet growth estimated in this study burial rates for rocks at lago di cignana were on the order of 0 23 0 47 cm yr these values correlate with continuous shortening rates of 0 4 1 4 cm yr between the european plate and the african adriatic promontory between 50 and 38 ma which is on the order of that calculated for plate velocities from plate reconstructions suggesting that the zermatt saas ophiolite may have remained well coupled to the down going slab to uhp conditions

microstructure and cementation of two carbonatic fine grained soils this paper presents an investigation of the microstructure and cementation of two carbonatic fine grained soils obtained from a deposit of lacustrine origin formed during the wisconsin glaciation

prediction of the wetting induced collapse behaviour using the soil water characteristic curve abstract collapsible soils go through three distinct phases in response to matric suction decrease during wetting pre collapse phase collapse phase and post collapse phase it is reasonable and conservative to consider a strain path that includes a pre collapse phase in which constant volume is maintained and a collapse phase that extends to the final matric suction to be experienced by collapsible soils during wetting upon this assumption a method is proposed for predicting the collapse behaviour due to wetting to use the proposed method two parameters critical suction and collapse rate are required the former is the suction value below which significant collapse deformations take place in response to matric suction decease and the later is the rate at which void ratio reduces with matric suction in the collapse phase the value of critical suction can be estimated from the water entry value taking account of both the microstructure characteristics and collapse mechanism of fine grained collapsible soils the wetting soil water characteristic curve thus can be used as a tool five sets of data of wetting tests on both compacted and natural collapsible soils reported in the literature were used to validate the proposed method the critical suction values were estimated from the water entry value with parameter a that is suggested to vary between 0 10 and 0 25 for compacted soils and to be lower for natural collapsible soils the results of a field permeation test in collapsible loess soils were also used to validate the proposed method the relatively good agreement between the measured and estimated collapse deformations suggests that the proposed method can provide reasonable prediction of the collapse behaviour due to wetting

kinematic reworking and exhumation within the convergent alpine orogen abstract kinematic data from the internal zones of the western alps indicate both top to se and top to nw shearing during synkinematic greenschist facies recrystallisation rb sr data from white micas from different kinematic domains record a range of ages that does not represent closure through a single thermal event but reflects the variable timing of synkinematic mica recrystallisation at temperatures between 300 and 450 c the data indicate an initial phase of accretion and foreland directed thrusting at ca 60 ma followed by almost complete reworking of thrust related deformation by se directed shearing this deformation is localised within oceanic units of the combin zone and the base of the overlying austroalpine basement and forms a regional scale shear zone that can be traced for almost 50 km perpendicular to strike the timing of deformation in this shear zone spans 9 ma from 45 to 36 ma the se directed shear leads to local structures that cut upwards in the transport direction with respect to tectonic stratigraphy and such structures have been interpreted in the past as backthrusts in response to ongoing alpine convergence however on a regional scale the top to se deformation is related to crustal extension not shortening and is coincident with exhumation of eclogites in its footwall during this extension phase deformation within the shear zone migrated both spatially and temporally giving rise to domains of older shear zone fabrics intercalated with zones of localised reworking top nw kinematics preserved within the combin zone show a range of ages the oldest 48 ma may reflect the final stages of emplacement of austroalpine units above piemonte oceanic rocks prior to the onset of extension however much of the top to nw deformation took place over the period of extension and may reflect either continuing or episodic convergence or tectonic thinning of the shear zone 40ar 39ar data from the region are complicated due to the widespread occurrence of excess 40ar in eclogite facies micas and partial ar loss during alpine heating reliable ages from both eclogite and greenschist facies micas indicate cooling ages in different tectonic units of between 32 and 40 ma these ages are slightly younger than rb sr deformation ages and suggest that cooling below ca 350 c occurred after juxtaposition of the units by se directed extensional deformation our data indicate a complex kinematic history involving both crustal shortening and extension within the internal zones of the alpine orogen to constrain the palaeogeographic and geodynamic evolution of the alps requires that these data be integrated with data from the more external zones of the orogen complexity such as that described is unlikely to be restricted to the western alps and spatially and temporally variable kinematic data are probably the norm in convergent orogens recognising such features is fundamental to the correct tectonic interpretation of both modern and ancient orogens

mechanical behaviour of unsaturated marine sediments experimental and theoretical approaches abstract the costa target areas exhibit different slope failure events which reflect different triggering mechanisms including gas hydrates dissociation gas hydrates stability law depends on temperature pore pressure gas chemistry and pore water salinity any change in the equilibrium parameters may convert the hydrate to gas plus water causing significant weakening of the sediment and generating a rise of pore pressure a significant consequence of the hydrate melting is the gas production which alters significantly the behaviour and mechanical properties of the marine sediments and could be very hazardous when the sediment is unloaded in undrained conditions the behaviour of the unsaturated marine sediment has to be accurately identified in order to quantify the geological risks associated to the hydrate dissociation see for instance sultan n cochonat p foucher j p mienert j this volume effect of gas hydrates melting on seafloor slope instability thus in this work five tests were carried out on synthetic marine sediments in order to identify the gas effect on the hydro mechanical behaviour of unsaturated marine sediments based on the experimental results obtained from this study on previous constitutive models alonso e e gens a josa a 1990 a constitutive model for partially saturated soils geotechnique 40 3 405 430 gens a alonso e e 1992 a framework for the behaviour of unsaturated expansive clays can geotech j 29 1013 1032 and on the relationship of van genuchten van genuchten m th 1980 a closed form equation for predicting the hydraulic conductivity of unsaturated soils soil sci soc am j 44 892 898 a new mathematical formulation was proposed to simulate the behaviour of the unsaturated soil qualitative comparison between experimental results and model predictions shows the capacity of the proposed model to reasonably reproduce the essential features of the hydro mechanical behaviour of marine unsaturated sediment experimental and simulation results show that unloading tidal cycles erosion natural slope instabilities excavation a submarine unsaturated sediment slope in shallow water is much more hazardous than unloading the same submarine slope in deep water

work input analysis for soils with double porosity and application to the hydromechanical modeling of unsaturated expansive clays a mechanical approach for unsaturated expansive soils considering double porosity has been developed based on the porous media theory in this approach the adsorbed and the capillary water as well as the micropores and macropores are two distinct phases an interaggregate stress considered as the work conjugate of the macrostructural strain increment has been defined both physicochemical and capillary effects of the pore water have been introduced at the macroscopic level other work conjugate variables relevant for the constitutive modeling of double porosity unsaturated media have also been identified consisting of the modified suction as conjugate of the increment of the macrostructural degree of saturation and the microstructural effective stress as conjugate of the microstructural volumetric strain increment a hydromechanical model for unsaturated expansive clays taking into account the interaction between the micro and the macrostructures in expansive clays can thus be built based on the bou

modelling the thermomechanical volume change behaviour of compacted expansive clays compacted expansive clays are often considered as a possible buffer material in high level deep radioactive waste disposals after the installation of waste canisters the engineered clay barriers are subjected to thermohydromechanical action in the form of water infiltration from the geological barrier heat dissipation from the radioactive waste canisters and stresses generated by clay swelling under almost confined conditions the aim of the present work is to develop a constitutive model that is able to describe the behaviour of compacted expansive clays under these coupled thermo hydromechanical actions the proposed model is based on two existing models one for the hydromechanical behaviour of compacted expansive clays and another for the thermomechanical behaviour of saturated clays the elaborated model has been validated using thermo hydromechanical test results on compacted mx80 bentonite comparison between the model prediction and the experimental data shows that this model is able to reprod

a microstructure based elastoplastic model to describe the behaviour of a compacted clayey silt in isotropic and triaxial compression the paper focuses on the hydromechanical behaviour of an unsaturated compacted clayey silt accounting for fabric changes induced by drying wetting cycles occurring at low stress levels the respon

mechanical behaviour of unsaturated kaolin with isotropic and anisotropic stress history part 1 wetting and compression behaviour over the last 40 years considerable progress has been made in understanding the complex behaviour of unsaturated soils research using constitutive modelling has extended the critical state framework and the concept of yielding in saturated soils to encompass unsaturated soils experiencing suction however validation testing of the framework for unsaturated soils has shown disagreement with the basic propositions the main reason for this disparity is the anisotropic properties of the soil specimens tested as a result of preparation using one dimensional compaction the paper describes the detailed testing carried out to justify this statement as part of the work presented samples of unsaturated kaolin were prepared using isotropic compression the suctions in these samples were reduced to predefined values by wetting under low isotropic loading the pore size distributions the pressure volume relationships and yielding under subsequent isotropic loading are compared with tests on samples prepared by

episodic formation of neotethyan ophiolites tibetan plateau snapshots of abrupt global plate reorganizations during major episodes of supercontinent breakup abstract neotethyan ophiolites along the bangong nujiang and yarlung tsangpo sutures tibetan plateau consist of mantle peridotite cumulates isotropic gabbro diabase plagiogranite and basaltic lava they comprise morb iab oib and boninitic rocks and mostly belong to supra subduction zone ssz type compositionally different rocks crystallized synchronously over a distance of 2000 km along the bangong nujiang and yarlung tsangpo sutures during the short periods of 190 182 and 132 120 ma respectively resembling the izu bonin mariana ibm proto arc the early jurassic bangong nujiang ophiolites formed in forearc settings during subduction initiation while the middle jurassic early cretaceous bangong nujiang ophiolites and the early cretaceous yarlung tsangpo ophiolites formed in forearc settings at pre existing subduction zones crystallization of the neotethyan ssz ophiolites from the eastern mediterranean middle east tibetan plateau to southeast asia and formation of the associated metamorphic rocks temporally coincided with major supercontinent breakup events 1 initial breakup of pangea in central atlantic and westernmost tethys 190 ma 2 separation of west and east gondwana 170 160 ma and initial opening of piemont ligurian tethys 175 164 ma 3 initial breakups of east and west gondwana 135 125 ma and 4 final breakup of gondwana 104 96 ma far field forces associated with abrupt global plate reorganizations may have triggered subduction initiation or transient interplate coupling decoupling at pre existing subduction zones leading to episodic formation of the neotethyan ssz ophiolites and rapid exhumation of metamorphic rocks in subduction zones the formation events of neotethyan ssz ophiolites and associated metamorphic rocks represent snapshots of global plate reorganizations during the major episodes of supercontinent breakup

relationship between soil structure and mechanical behavior for an expansive unsaturated clay to investigate the soil structure and mechanical behavior of an unsaturated expansive clay soil triaxial and mercury intrusion tests have been performed and are presented in this paper also an optical test system was developed for studying the internal structure evolution of the unsaturated expansive soil during shear loading tests the research results show a linear relationship between the cohesion intercept and the degree of saturation of the unsaturated clay for the test data for the tested soil the pore size distribution curves were found to be bimodal the measurement results from mercury intrusion tests confirm that the micropores of guangxi expansive soils of this study remain constant and that the macropores vary with the dry density of soil samples comparing the volumetric strain curves with the soil particle area curves some correlation and dependence on the macropore variation of soil samples during shear loading tests can be shown to exist key words soil structure mechanical behavior

subduction interface processes recorded by eclogite facies shear zones monviso w alps abstract the monviso ophiolite lago superiore unit constitutes a well preserved almost continuous upper fragment of oceanic lithosphere subducted at c 80 km depth thereby providing a unique opportunity to study mechanical coupling processes and meter scale fluid rock interactions occurring at such depths in present day subduction zones it is made of i a variably thick 50 500 m section of eclogitized basaltic crust associated with minor calcschist lenses overlying a 100 400 m thick metagabbroic body and of ii a c 1 km thick serpentinite sole we herein focus on the three major eclogite facies shear zones found at the top of the unit at the boundary between basalts and gabbros and between gabbros and serpentinites respectively strain localization occurred at lithological interfaces irrespective of material strength while ductile deformation dominates along the shear zones local brittle behavior is demonstrated by the existence of numerous eclogite breccias of fe ti metagabbros and widespread garnet fractures possibly linked with intermediate depth eclogite facies micro seismicity these m to hm sized fragments of fe ti metagabbros were later sheared and disseminated within serpentinite schists along the gabbro serpentinite boundary lower shear zone lsz pervasive and focused fluid flow is attested in the lsz by significant alteration of bulk rock compositions weakening of the rocks and widespread crystallization of hydrous parageneses by contrast the intermediate shear zone isz shows evidence for more restricted short range fluid flow the activity of both the isz and lsz ceased during early lawsonite eclogite facies exhumation when deformation localized deeper within the serpentinite sole allowing for the detachment and preservation of this large ophiolitic fragment

oceanic detachment faults focus very large volumes of black smoker fluids it is generally assumed that the seawater derived fluids that feed black smoker vent fields on the seafloor are discharged vertically from depths of 1 3 km we present new oxygen and strontium isotope data that show that fluids at black smoker temperatures of 300 400 c were focused along a low angle detachment fault at 15 45 n near the mid atlantic ridge isotopic alteration is the most extreme ever reported from oceanic rocks altered at similar temperatures indicating intensely focused fluid flow both in recharge and discharge parts of the hydrothermal system rare earth element mobility in the fault rocks demonstrates isotopic alteration by evolved hydrothermal fluids not conductively heated seawater the fault zone protolith was predominantly ultramafic but also included mafic rocks with metasomatic alteration to talc tremolite chlorite schists resulting mainly from chemical exchange between these lithologies during fluid flow fluids in equilibrium with this assemblage would be similar to ultramafic hosted black smoker fluids we present a new model in which hydrothermal circulation around detachment faults evolves from basalt hosted tag type to footwall ultramafic hosted rainbow type to low temperature ultramafic hosted lost city type key features of our model are the intrusion of gabbro bodies immediately below the detachment to provide a heat source for circulation and focusing of fluid flow into the detachment fault to allow venting away from the neovolcanic axis