middle devonian olistostromes in the rheno hercynian zone rheinisches schiefergebirge an indication of back arc rifting on the southern shelf of laurussia abstract the rheinisches schiefergebirge in the rheno hercynian zone of the mid european variscides was geographically situated on laurussia s southern shelf during the devonian in its eastern part lahn dill area givetian coarse clastic sediments formerly misinterpreted as transgressional conglomerates are recognised as olistostrome deposits intercalated in basinal sediments that document a phase of rifting on the southern shelf of laurussia the clastic components redeposited as olistolithes and rounded boulders are locally derived rocks of emsian and givetian age the olistostromes show facies patterns comparable with other syn rift deposits the proximal facies is characterised by olistolithes and slideflow debrites overlain by debrites and intercalated with turbidites the distal facies is represented by intercalation of debrites and turbidites both grade upwards into basinal sedimentation based on conodont stratigraphy the redeposition lasted from the middle varcus zone to the disparilis zone during the middle varcus zone footwall uplift raised the sedimentary column of the source area by about 500 m above which brought it above sea level rifting of the laurussian shelf as a result of hinterland transtension and extension caused by the oblique collision of peri gondwana with laurussia provides the most plausible explanation for the development of the olistostromes olistolithes and slideflow debrites in the eastern rheinisches schiefergebirge

performance of a buried pipeline along the dip of a slope experiencing accidental sliding contrary to highways major pipelines often have to be installed crossing hills or mountain ridges following the dip of the slope slope movements that may be triggered by an earthquake heavy rai

sand deformation around an uplift plate anchor abstractthis paper presents an experimental investigation on soil deformation around uplift plate anchors in sand by using digital image correlation dic the experimental setup consists of a camera loading frame plexiglass mold and computer which is developed to capture soil deformation during anchor uplifting a series of model tests are performed to investigate the influence of particle size soil density and anchor embedment depth on soil deformation a set of images captured during anchor uplifting are used to calculate soil displacement fields by dic the failure surface is studied by tracking the points with maximum shear strain values on the basis of this study it is found that soil deformation and the pullout resistance of plate anchors are substantially influenced by soil density and anchor embedment depth whereas particle size within the studied range has limited influence in dense sand the shape of the failure surface changes from a truncated cone above a shallow anchor to a combine

numerical calibration of the devonian carboniferous boundary two new u pb isotope dilution thermal ionization mass spectrometry single zircon ages from hasselbachtal sauerland germany the hasselbachtal section sauerland germany is an auxiliary global stratotype of the devonian carboniferous boundary and one of the most important reference sections for the evolution of the latest famennian to earliest tournaisian pelagic fauna biostratigraphically well controlled altered volcanic ash layers metabentonites intercalated in the section afford a perfect opportunity for a numerical fixing of this important paleozoic period boundary we have performed u pb isotope dilution thermal ionization mass spectrometry id tims analyses on sub microgram sized single zircons and zircon fragments extracted from two metabentonites beds 79 and 70 in the lowermost tournaisian part of the section bed 79 metabentonite is positioned directly above the devonian carboniferous boundary within the siphonodella sulcata conodont zone five concordant analyses form a cluster with a 2 0 6 pb 3 3 8 u concordia age of 360 5 0 8 ma zircons of the next younger metabentonite bed 70 in the lower siphonodella duplicata conodont zone yielded a tightly grouped cluster of 10 concordant analyses with a 2 0 6 pb 2 3 8 u concordia age of 360 2 0 7 ma on the basis of these two new single zircon ages and previously published late famennian u pb id tims ages the devonian carboniferous boundary is reinterpolated herein to 360 7 0 7 ma

tectonic underplating versus out of sequence thrusting beneath the lesser himalaya insights from the analogue modeling of the nepal himalaya fold and thrust belt abstract the nepal himalaya fold and thrust belt is a classical two decollement thrust fold system the belt has been extensively studied by analogue and numerical modeling but the formation mechanism of the mid crustal duplex structure beneath the northern part of the lesser himalaya remains debated the formation of this thrust duplex has been attributed either to tectonic underplating along new ramps in response to the subducting indian plate or to out of sequence thrusting along preexisting ramps we conducted a series of experiments using analogue models employing a model setup that was faithful to the geological setting of the nepal himalaya we used industrial computed tomography ct and particle image velocimetry piv to generate detailed deformation maps the analogue models successfully reproduce the main structure of the nepal himalaya fold and thrust belt showing that the two competing processes i e underplating along new ramps and out of sequence thrusting along preexisting ramps operate alternately to form the duplex structure the models also show that underplating is associated with extensive foreland sedimentation analogous to the foreland molassic sedimentation in the sub himalaya which leads to a systematic recession of the deformation front and a smaller horse finally the recognition that out of sequence thrusting occurs in the interval between major underplating events provides important insights into the origin of the 2015 m w 7 8 gorkha earthquake

the limiting pressure on a circular pile loaded laterally in cohesive soil in the analysis of the undrained loading of laterally loaded piles an important quantity is the ultimate lateral resistance at depth to purely horizontal movement if the soil is modelled as a perfectly plastic cohesive material then the calculation of this quantity reduces to a plane strain problem in plasticity theory in which the load is calculated on a long cylinder which moves laterally through an infinite medium an exact calculation of the load on such a cylinder is presented if this load is non dimensionalized with respect to the soil strength and the diameter of the pile it is found that the load factor varies between for a perfectly smooth pile and for a perfectly rough pile this result is discussed in the context of previous calculations for the lateral load capacity of piles and is compared with approximate calculations using cavity expansion theory and a wedge failure near the soil surface la resistance laterale limite en profondeur au seul mouvement horizontal represente un parametre im

effects of multipropped excavation on an adjacent floating pile abstractdeep excavations inevitably induce stress relief and soil movement which may affect the safety and serviceability of nearby existing pile foundations although the effects of excavation on

crack initiation in clay observed in beam bending tensile cracking in clay is an important phenomenon that affects the strength and permeability of clays in many facilities such as dams embankments and landfill liners as well as being a precursor to slope failures in the natural terrain this study investigates the stress strain criteria for cracking in clays by performing four point bending tests on consolidated kaolin clay beams load controlled and strain controlled tests were performed on clay beams with varying initial suction to understand the stress strain criteria for crack initiation in clay at no stage was the negative pore pressure permitted to exceed the air entry value of the clay so the clay remained saturated throughout strains in the clay were obtained by particle image velocimetry analysis of digital images of the clay beam and suction measurements were obtained from pore pressure and tension transducers installed within the clay beams results from this investigation showed that the threshold tensile strain to cracking in kaolin

the effects of quartz dauphine twinning on strain localization in a mid crustal shear zone abstract we use microstructural electron backscatter diffraction ebsd and crystal vorticity axis cva analyses to evaluate the effects of quartz dauphine twinning on strain localization we compare a granodiorite mylonite and a tonalite mylonite from the grebe shear zone a mid crustal transpressional shear zone in fiordland new zealand ebsd analysis reveals identical quartz grain boundary migration dynamic recrystallization microstructures in both samples with abundant dauphine twinning only in the granodiorite mylonite bulk cva patterns further distinguish the untwinned and dauphine twinned samples indicating a transition from simple shear to pure shear dominated transpression respectively the quartz cva pattern from the dauphine twinned sample indicates that twinned and untwinned grains record a transition from simple shear to pure shear dominated deformation respectively pole figures of the dauphine twinned sample reveal high temperature slip systems in the untwinned and dauphine twinned grains we conclude that dauphine twinning formed early in transpression and rendered the twinned grains less deformable relative to the untwinned grains over time the effectiveness of dauphine twinning in localizing strain is therefore strongly influenced by its timing relative to the evolving shear zone kinematic deformation geometry

the palaeozoic variscan oceans revisited abstract geological evidence supported by biogeographical data and in accord with palaeomagnetic constraints indicates that one ocean models for the variscides should be discarded and confirms instead the existence of three gondwana derived microcontinents which were involved in the variscan collision avalonia north armorica franconia and thuringia subdivided by a failed vesser rift and south armorica central iberia armorica bohemia all divided by small oceans in addition parts of south eastern europe including adria and apulia are combined here under the new name of palaeo adria which was also peri gondwanan in the early palaeozoic oceanic separations were formed by the break up of the northern gondwana margin from the late cambrian onwards most of the oceans or seaways remained narrow but much like the alpine cenozoic oceans gave birth to orogenic belts with hp uhp metamorphism and extensive allochthons the saxo thuringian ocean between north and south armorica and the galicia moldanubian ocean between south armorica and palaeo adria only the rheic ocean between avalonia and peri gondwana was wide enough to be unambiguously recorded by biogeography and palaeomagnetism and its north western arm closed before or during the emsian in europe ridge subduction under the northernmost part of armorica in the emsian created the narrow and short lived rheno hercynian ocean it is that ocean and not the rheic whose opening and closure controlled the evolution of the rheno hercynian foldbelt in south west iberia south west england germany and moravia czech republic devonian magmatism and sedimentation set within belts of early variscan deformation and metamorphism are probably strike slip related the first arrival of flysch on the forelands and or the age of deformation of foreland sequences constrains the sequential closure of the variscan seaways galicia moldanubian in the givetian saxo thuringian in the early famennian rheno hercynian in the tournaisian additional mid to late devonian and partly early carboniferous magmatism and extension in the rheno hercynian saxo thuringian and galicia moldanubian basins overlapped with variscan geodynamics as strictly defined the early carboniferous episode was the start of episodic anorogenic heating which lasted until the permian and probably relates to tethys rifting

development of a prototype for modelling soil pipe interaction and its application for predicting uplift resistance to buried pipe movements in sand this paper presents a testing rig for measuring the reactions on rigid pipes buried in sand during episodes of relative displacement following a detailed presentation of the 1g prototype the test

extraction of spudcan foundations in single and multilayer soils abstractdifficulties are often encountered in a variety of seabed sediments during extraction of spudcan foundations of mobile jack up rigs this paper reports results from centrifuge model tests undertaken to provide insight into spudcan foundation behavior during vertical extraction through single double and multilayer soils the model tests included half spudcan tests against a transparent window allowing the soil flow to be captured continuously by a digital camera and subsequently quantified through particle image velocimetry piv analysis and separate full spudcan tests to measure the uplift resistance the observed soil failure mechanisms provide insight with respect to the profile of extraction resistance the mechanisms reveal evolving failure modes at different spudcan extraction depths and in particular changes in the failure patterns because of varying layer geometry soil types and properties for single double and multilayer clays suction at the spudcan base shearing along a trunc

carboniferous submarine volcanism at herbornseelbach lahn dill area germany a 100 m thick sequence of carboniferous submarine dominantly basaltic volcanic rocks at herbornseelbach lahn dill area is subdivided into six units two pillow volcanoes show a characteristic change from basal megapillows up to 5 m across through normal pillows 0 5 to 0 8 m across to a top facies of small pillows 0 5 m across and or breccias of scoriaceous clasts and discontinuous lava stringers sheet flows 0 5 to 4 m thick can be distinguished from sills by asymmetric cooling structures and textures vesicle concentrations near the top basal flow wrinkles and ponding of sediments on irregular flow tops

evolution of the rheic ocean the rheic ocean which separated laurussia from gondwana following the closure of iapetus is arguably the most important ocean of the palaeozoic its suture extends from mexico to turkey and its closure produced the climactic variscan alleghanian ouachita orogeny that assembled the supercontinent pangaea following protracted cambrian rifting that represented a continuum from neoproterozoic orogenic processes the rheic ocean opened in the early ordovician with the separation of several neoproterozoic arc terranes from the continental margin of northern gondwana separation occurred along the line of a former neoproterozoic suture following the onset of subduction in the outboard iapetus ocean the timing of rift drift transition and drive for subsequent spreading was likely governed by slab pull accounting for the rapid rate 8 10 cm yr at which the rheic ocean widened during the ordovician the ocean broadened at the expense of iapetus and attained its greatest width 4000 km in the silurian by which time baltica had sutured to laurentia and the neoproterozoic arc terranes had accreted to laurussia closing iapetus in the process closure of the rheic ocean began in the devonian and was facilitated by northward subduction beneath southern baltica and southward subduction beneath northwest gondwana closure was largely complete by the mississippian as gondwana and laurussia sutured to build pangaea north africa colliding with southern europe to create the variscan orogen in the devonian carboniferous and west africa and south america suturing to north america to form the alleghanian and ouachita orogens respectively during the carboniferous permian the rheic ocean consequently plays a dominant role in the basement geology of southern europe in the appalachian ouachita orogeny of north america and in the palaeozoic sedimentary structural and tectonothermal record from middle america to the middle east with its closure the ocean brought about the assembly of pangaea and brought the palaeozoic era to an end

acoustic emission sensing of pipe soil interaction full scale pipelines subjected to differential ground movements abstractthis paper presents the first full scale demonstration of the potential use of pipe soil interaction generated acoustic emission ae for early detection of buried pipe deformation full sc

numerical and experimental study on influence of installation effects on behaviour of helical anchors in very dense sand the use of helical anchors has been increasing in recent years however the current understanding of its behaviour does not allow for reliable estimates of uplift capacity and load displacement re

u pb zircon dating of paleozoic volcanic rocks from the rheno hercynian zone new age constraints for the steinkopf formation lahn dill area germany small and volumetrically subordinate outcrops of alkali rhyolitic to trachytic metavolcanic rocks are widespread in the lahn dill area of the rheinisches schiefergebirge germany these occurrences are either related to late early devonian or to middle devonian episodes of volcanic activity an unambiguous age assignment for the time of eruption could not be established so far most volcanic rocks of the study area are not suitable for application of u pb geochronology a notable exception is the steinkopf rock suite in the sw lahn dill area but a straightforward interpretation of the la icp ms u pb data is hampered by complex zircon populations recording various processes including crystallization from newly formed melt inheritance assimilation of country rocks variable degrees of pb loss and fluid assisted zr mobility a plausible evaluation of u pb zircon data of two metatrachytes and a metavolcaniclastic rock document a coherent age group at ca 390 384 ma and a probable eruption age at ca 385 ma suggesting a relationship to middle devonian givetian igneous processes zircon bearing veinlets in a metatrachyte indicate post eruptive infiltration of external hydrothermal fluids and or internal zr redistribution in late devonian to early carboniferous time 364 10 ma but this process is of rather limited importance

zirconolite allanite and hoegbomite in a marble skarn from the bergell contact aureole implications for mobility of ti zr and ree zirconolite allanite and hoegbomite are present as accessory phases in a metasomatically altered spinel calcite marble from the contact with the bergell intrusives switzerland italy textural relationships indicate a step wise alteration of spinel to 1 hoegbomite or corundum magnetite 2 margarite and 3 chlorite replacement of spinel by hoegbomite can be described by the substitution 1 94 mg2 fe2 zn2 mn2 ca2 ti4 0 12 oh where al3 and fe3 are held constant the average composition of the bergell hoegbomites is given by the formula fe 0 97 2 mg0 69zn0 04ti0 17al3 94fe 0 06 3 o7 98 oh 0 02 and seems to be imposed by the composition of pre existing spinel during the first two steps of spinel alteration calcite was replaced by anorthite phlogopite and the rare earth element ree bearing minerals zirconolite allanite and sphene were formed allanites have characteristic chondrite normalized ree patterns with enrichment in the light ree the zirconolite patterns show a marked increase in concentration from la to ce followed by an almost constant section sphene lacks detectable la and its ree patterns vary from grain to grain contemporaneous formation of phlogopite ree bearing minerals and hoegbomite during replacement of the spinel calcite marble indicates that the metamorphic fluid introduced potassium along with ree and other high valence cations ti4 zr4 u4 th4a3804265 nb5a3804265 y3a3804265 possibly as polynuclear complexes the abundance of fluorine bearing phlogopite and fluor apatite as well as their close association with ree bearing minerals and hoegbomite suggests f and po 4 3 as likely ligands for complexing of the above mentioned elements

accretion of a rifted passive margin the late paleozoic rhenohercynian fold and thrust belt middle european variscides in the western rhenish massif the rhenohercynian fold and thrust belt of the middle european varsicides exposes a telescoped complete devonian to early carboniferous passive margin this permits the analysis of geometry and kinematic processes of passive margin accretion to an erogenic wedge during variscan collision 330 300 ma the sedimentary cover of the passive margin was shortened by some 50 or 180 km crustal scale balancing and restoration reveals a wide symmetric rift with a central graben a marginal plateau separated this failed lower devonian rift from an emsian middle devonian oceanic basin in the south remnants of which are preserved in the southernmost imbricates and the giessen harz nappes the seismically well imaged aachen midi detachment faille du midi acted as the basal decollement of this thin to thick skinned orogenic wedge it shows a ramp and flat geometry from the blind tip down to middle crustal levels owing to its position below the base of the basin fill the thick synrift sequence and structure controlled structural evolution during contraction by localizing thrust branch lines and by inversion of rift structures synthetic to the subduction direction with formation of basement footwall shortcuts moreover the three dimensional detachment geometry shows large scale oblique ramp flat features which control the architecture of the belt and the distribution of metamorphic grade rocks and fabrics from the detachment show that the latter was located at the transition into the ductile field at the fossil 300 400 c isotherm in the restored section the detachment trajectory displays a saucershaped geometry rising to the surface at the rear and at the front this suggests that the basal detachment propagated into the passive margin by ductile failure during lithospheric flexure under the load of an advancing upper plate the regional pattern of synkinematic metamorphic grade shows varying modes of margin accretion basal underplating into the orogenic wedge by the shelf slope and marginal plateau with formation of duplex stacks and elongate thrust sheets and frontal accretion of the remaining thicker failed rift in the north into the propagating wedge with formation of several imbricate fans cyclical changes in accretion history and or critical taper are suggested by spaced domains of out of sequence thickening these are also related to internal domainal kinematic partitioning of the wedge controlled by oblique collision

the mobility of zirconium and other immobile elements during hydrothermal alteration abstract development of zircon and other zr phases in hydrothermal deposits indicates that zr can be highly mobile in these systems mobility is most common in but not restricted to f rich hydrothermal systems related to alkalic f rich igneous suites these suites can range from peralkaline through metaluminous to peraluminous a few examples are neither alkalic nor f rich three locations in the trans pecos magmatic province texas u s a demonstrate this hydrothermal zr mobility all three igneous systems are alkalic and f rich but vary in alkali al ratios peralkaline rhyolites and trachytes in the christmas mountains contain as much as 2100 ppm zr mostly in aegirine or arfvedsonite zircon is rare or absent fluorspar replacement deposits in limestone at contacts with the rhyolites contain as much as 38 000 ppm zr occurring as small disseminated zircons the deposits also are enriched in a variety of incompatible elements including be rare earth elements ree y nb mo hf pb th and u the sierra blanca intrusions a series of mildly peraluminous f rich rhyolite laccoliths contain as much as 1000 ppm zr mostly as zircon hydrothermal zircon occurs as overgrowths on magmatic grains as veinlets connected to overgrowths and in fluorspar replacement bodies in adjacent limestone the highest zr concentrations in fluorspar are 200 ppm metaluminous quartz monzonite from the infiernito caldera contains 400 600 ppm zr mostly as zircon euhedral zircon in quartz fluorite veins in the quartz monzonite indicates mobility of zr zirconium concentrations in the veins are unknown but the paucity of zircon suggests little zr enrichment relative to the host zircon and more rarely zirconolite occur in skarn in the ertsberg district of irian jaya indonesia unlike in texas related igneous rocks are metaluminous and the hydrothermal system was f poor worldwide hydrothermal zircon other zr phases and ti and al bearing phases occur in skarn epithermal precious metal veins volcanogenic massive sulfide deposits and mylonites we propose that differences in zr mineralogy of igneous source rocks is an important factor in determining the availability of zr to hydrothermal fluids although zr concentrations in the sierra blanca and christmas mountains rhyolites are similar zr enrichment in fluorspar was much greater in the christmas mountains we suggest that hydrothermal solutions could easily break down aegirine and arfvedsonite to release zr but that zircon was only moderately attacked therefore far more zr was available for transport and subsequent deposition in the christmas mountains than at sierra blanca availability of other trace elements probably is also governed by their mineral host although zr mobility is most common in f rich hydrothermal systems related to alkalic and f rich igneous systems mobility at ertsberg may have been promoted by sulfate complexing

kinematics of active earthflows revealed by digital image correlation and dem subtraction techniques applied to multi temporal lidar data earthflow type landslides are persistent natural hazards having deep socio economic and environmental consequences they have significantly contributed to the geomorphic evolution of mountainous slopes in europe since the late glacial an understanding of their complex kinematics is crucial to better constrain the processes governing their occurrence and mobility in this work we explored the possibility to quantify displacement vectors on a spatially distributed basis and to quantify volumetric transfer at the slope scale with regard to a large flow type landslide located in the northern apennines of italy for this purpose we applied digital image correlation dic and digital elevation model differencing demod techniques to multi temporal airborne lidar surveys of 2006 2007 and 2009 the dic was applied to greyscale slope gradient maps retrieved after precise co registration of lidar surveys thereby movement patterns over various sectors of the landslide were reconstructed and quantified most notably up to 20 m in the head zone up to 51 m in the lower main track and up to about 27 m at the landslide toe the demod analysis revealed significant mass transfer from the source to the tracks and toe zone with the upper flow tracks acting as temporal storage of large amounts of material the mass balance indicated that significant amounts of advancing landslide debris were eroded by a local stream an integrated analysis of demod and dic results allowed for a discussion of governing processes such as the transition from slide to flow the influence of underlying topography on earthflow mobility and the role of undrained loading as a mechanism of toe zone reactivation in conclusion the successful application of dic and demod to the case study underlines the added value of high resolution dems in the analysis of earthflow kinematics toward a better understanding of their role in the geomorphic evolution of slopes copyright 2012 john wiley sons ltd

deformation thermometry based on quartz c axis fabrics and recrystallization microstructures a review abstract for quartz rich tectonites two types of deformation thermometer are currently commonly employed 1 the quartz c axis fabric opening angle thermometer that provides an estimate of deformation temperatures when fabrics were locked in during dislocation creep and dynamic recrystallization 2 the quartz recrystallization thermometer that indicates a range of likely deformation temperatures based on observed microstructures and inferred mechanisms of dynamic recrystallization a critically important caveat in applying both thermometers is the assumption that deformation temperature is the primary controlling factor in recrystallization mechanisms and fabric development however fabric opening angles and recrystallization mechanisms are also sensitive to other variables such as strain rate and water weakening in this paper the development of these thermometers is reviewed and their potential sensitivities to competing factors such as temperature strain rate water weakening and in the case of opening angles 3d strain type are discussed examples of the application of these potential thermometers to naturally deformed quartz rich rocks are given and case studies of correlations between deformation temperatures estimated by these thermometers and temperatures of synkinematic metamorphism determined by petrology based thermobarometers are highlighted in the review attention is focused on problems associated with applying these thermometers to natural deformation and examples of such problems are discussed

rheology of a coaxial shear zone in the virginia blue ridge wet quartzite dislocation creep at 250 280 c abstract cambrian quartzite along the western margin of the blue ridge near front royal virginia records significant penetrative strain under subgreenschist facies conditions strain analyses of the quartzite indicate general flattening and octahedral shear strain values up to 1 25 x z up to 5 7 1 samples with x z as low as 1 5 1 have crystallographic preferred orientations that record a dominance of basal slip and patterns consistent with coaxial flattening in most samples quartz has undergone minor amounts of dynamic recrystallization with mean grain sizes 4 5 m locally the quartzite is brittlely deformed and subgrains and recrystallized bulges are present along fractures and extinction bands fluid inclusion planes and fluid inclusions along deformation lamellae are abundant and quartz ftir analyses yield average h 106si values of 1100 3300 indicating fluid flow and high intragranular water content during deformation higher strain samples generally record lower water contents which may indicate that fluids migrated to grain boundaries during deformation dissolution microstructures are rare in high strain samples and we interpret most strain to have been accommodated by dislocation creep thermal modeling of zircon low temperature thermochronology data coupled with quartz c axis opening angle thermometry suggest deformation temperatures were likely 250 280 c these deformation temperatures are lower than what is typically considered the brittle plastic transition in quartz we attribute localization of this high strain zone and dislocation creep at these temperatures to hydrolytic weakening and a relatively low strain rate estimated to be 10 15 s 1

uplift mechanisms of pipes buried in sand reliable design against upheaval buckling of offshore pipelines requires the uplift response to be predicted this paper describes a model scale investigation into the mechanisms by which uplift resistance is mobilized in silica sand and illustrates how the observed mechanisms are captured in prediction models a novel image based deformation measurement technique has been used the results show that peak uplift resistance is mobilized through the formation of an inverted trapezoidal block bounded by a pair of distributed shear zones the inclination of the shear zone is dependent on the soil density and therefore dilatancy after peak resistance shear bands form and softening behavior is observed at large pipe displacements either a combination of a vertical sliding block mechanism and a flow around mechanism near the pipe or a localized flow around mechanism without surface heave is observed depending on the soil density and particle size

carboniferous permian volcanic evolution in central europe u pb ages of volcanic rocks in saxony germany and northern bohemia czech republic nine shrimp u pb ages on zircon and two pb pb single zircon ages have been determined from late paleozoic volcanic rocks from saxony and northern bohemia samples came from the teplice altenberg volcanic complex the meissen volcanic complex the chemnitz basin the dohlen basin the brandov olbernhau basin and the north saxon volcanic complex the teplice altenberg volcanic complex is subdivided into an early namurian phase mikulov ignimbrite 326 8 4 3 ma thus older than assumed by previous studies and a late caldera forming phase teplice ignimbrite 308 8 4 9 ma the age of the latter however is not well constrained due to a large population of inherited zircon and possible hydrothermal overprint the leutewitz ignimbrite product of an early explosive volcanic episode of the meissen volcanic complex yielded an age of 302 9 2 5 ma stephanian a volcanic rocks intercalated in the brandov olbernhau basin bob 302 2 8 ma chemnitz basin cb 296 6 3 0 ma dohlen basin db 296 3 0 ma and the north saxon volcanic complex nsvc c 300 290 ma yielded well constrained stephanian to sakmarian ages the largest late paleozoic ignimbrite forming eruption in central europe the rochlitz ignimbrite has a well defined middle asselian age of 294 4 1 8 ma ages of palingenic zircon revealed that the namurian westphalian magmatism assimilated larger amounts of crystalline basement that formed during previous paleozoic geodynamic phases the precambrian inherited ages support the chronostratigraphic structure assumed for the saxo thuringian zone of the variscan orogen the present results help to improve the chronostratigraphic allocation of the late paleozoic volcanic zones in central europe at the same time the radiometric ages have implications for the interbasinal correlation and for the geodynamic evolution of the variscan orogeny

experimental characterization of deformation coefficient of earth pressure at rest stiffness and contact force distributions of sand during secondary compression and rebound this paper aims to provide a comprehensive picture of the sand responses during secondary compression and rebound based on experimental characterizations the experiment was carried out on dry leighton buzzard sand using a modified direct shear box equipped with tactile pressure sensors for the stress measurements and bender elements for stiffness i e ghv and ghh monitoring it was found that secondary compression and rebound followed the same deformation trends as primary compression and rebound to continuously contract and expand respectively the deformation characteristics determined the changes in the associated soil properties therefore the opposite soil behavior during secondary compression and rebound was observed during secondary compression the corresponding void change deviatoric strains eq and the deviatoric strain rate e q increased with increasing vertical stress v or deviatoric stress q because the sample crept more easily under a higher v or q the compression deformation ga

evidence for regional dauphine twinning in quartz from the santa rosa mylonite zone in southern california a neutron diffraction study preferred orientation in granitic mylonites from the santa rosa mylonite zone in southern california is investigated with time of flight neutron diffraction quartz and biotite display strong preferred orientation whereas feldspar alignment is weak for quartz a c axis maximum in the intermediate fabric direction is consistent with dynamic recrystallization pole figures for positive and negative rhombs such as rz 10 11 and zz 01 11 are distinct over a wide region suggesting that the pattern reflects tectonic deformation and was not

dem simulations of transverse pipe soil interaction on sand realistic modelling of transverse i e vertical and lateral pipe soil interaction plays an important role in predicting the behaviour of untrenched offshore pipelines that are designed to undergo

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

base stability of multi propped excavations in soft clay subjected to hydraulic uplift excavations in soft clay underlain with an aquifer may be destabilized by hydraulic uplift previous studies on this subject are based mainly on field observations dewatering from the aquifer is a

rate effects on the vertical uplift capacity of footings founded in clay this paper describes results from a series of uplift tests performed in a drum centrifuge on shallow square footings founded on clay and sand with an overlying sand backfill the test series investigated footings of various widths loaded at displacement rates extending over five orders of magnitude additional tests were performed to examine the influence on uplift capacity of the direction of load inclination the uplift tests performed on footings founded on sand enabled estimations to be made of the suction that developed at the base of the footings founded on clay it is shown that the suction mobilised at very fast rates may be assessed using existing undrained bearing capacity approaches and a rate corrected operational undrained strength similar to that measured in triaxial extension the uplift rates required to reach fully undrained conditions are almost two orders of magnitude higher than those for footings loaded in compression and the upward footing displacements required to generate maxim

physical modelling to demonstrate the feasibility of screw piles for offshore jacket supported wind energy structures screw piles potentially offer quieter installation and enhanced axial tensile capacity over straight shafted driven piles as such they have been suggested as a possible foundation solution for of

statistical evaluation of model factors in reliability calibration of high displacement helical piles under axial loading an industry survey suggests an increasing application of high displacement helical piles with greater shaft and helix diameters to support various structures in this paper a database of 84 static

pipe uplift in saturated sand rate and density effects a key parameter for assessing the unburial behaviour of offshore pipelines such as during upheaval buckling is the soil uplift resistance despite much research on uplift response two variables remain relatively unexplored the effect of low relative density backfill and partially drained soil response to address this shortcoming an investigation into the plane strain uplift resistance of pipe segments in saturated sand was carried out the model tests targeting drained and partially drained soil behaviour demonstrate that soil state strongly influences the pipe soil failure mechanism and hence the mobilised uplift resistance in very loose sand the normalised peak uplift resistance remained constant beyond a critical embedment depth indicating a possible transition between different failure mechanisms faster rate tests result in positive excess pore pressures which serve to further reduce the uplift resistance tests at varying uplift rates and densities identified a transition relative densit

towards a simple and reliable method for calculating the uplift capacity of plate anchors in sand this paper investigates the uplift capacity of horizontal plate anchors in sand through finite element analyses and centrifuge experiments finite element simulations adopt a sophisticated bounding

centrifuge experiments on the settlement of circular foundations on clay centrifuge experiments were conducted to investigate the mechanisms governing the settlement of shallow circular foundations on clay model tests were performed on both soft and firm beds of overconsolidated kaolin clay foundation loads were applied as dead weight and also through pneumatic loading a perspex window in the centrifuge package allowed digital images to be captured of a vertical cross section during and after the application of loading soil displacements deduced by particle image velocimetry piv allow deformation mechanisms to be presented for undrained penetration creep and consol idation caused by transient flow a technique is presented for discriminating consolidation settlements from the varying rates of short and long term creep the mobilizable strength design msd method is shown to make useful predictions of the undrained penetration using an estimated stress strain behaviour of the clay with allowances made for anisotropy and rate effects subsequent creep and consolidation settlements were then determined using established correlations

volcanism and reef development in the devonian a case study from the lahn syncline rheinisches schiefergebirge germany abstract new data from the rheinisches schiefergebirge in germany offer insights into a complex marine basinal facies setting on the southern shelf area of the old red continent this interdisciplinary approach has the aim of providing a reconstruction of depositional and palaeoecological conditions of volcanic island induced reef growth during the middle devonian time devonian volcanic activity culminated in a givetian frasnian phase producing mainly alkali basaltic to basanitic melts some volcanic buildups reached sea level and gave rise to the development of reefs during times of reduced volcanic activity reef communities in the lahn syncline were dominated by corals and stromatoporoids in terms of conodont stratigraphy they began to flourish during the middle varcus subzone in the givetian and lasted until the late falsiovalis subzone in the frasnian a facies model is presented for the entire area that clarifies the association of volcanism and reef development

non catastrophic landslides induced by the mw 7 6 chi chi earthquake in central taiwan as revealed by piv analysis abstract the chi chi earthquake occurred in the western foothills of central taiwan which triggered coseismic and catastrophic chiufengershan dip slope landslides tsaoling rockslides and surface stripping of the jiujiufeng area after a few days of the chi chi event the hongtsaiping area in central taiwan was reported to have several meters of slide in a small scale area the reported landslides are dissimilar to the catastrophic events to better understand the characteristics of such non catastrophic and unobvious landslide we try to characterize in detail the sliding directions their magnitudes and region of the landslide we analyzed three orthorectified aerial photographs of the hongtsaiping area which were taken in 1998 06 13 1999 11 18 and 2002 10 26 using the particle image velocimetry piv technique through the method we correlated the image pixels of the two aerial photographs in order to derive the displacement vector field the results of the piv analysis have helped us not only find the areas where sliding had happened but also evaluate the azimuth and magnitudes of the sliding event the piv analysis in the hongtsaiping area covers a dimension of about 3228 2448 pixels in an area of about 1 2 km2 our results show that the maximum horizontal displacement of the landslide is about 24 m towards nw in the study area this unobvious but wide coverage landslide may need further investigation in mechanisms combining with available or new geological data

experimental investigation of the uplift behaviour of circular plate anchors embedded in sand an experimental investigation of the uplift behaviour of relatively large scale model circular plate anchors up to 400 mm in diameter embedded in loose medium dense and dense dry sand is described uplift capacity is strongly influenced by anchor diameter embedment ratio and sand density in tests on shallow half cut models a gently curved rupture surface emerged from the top edge of the anchor to the sand surface at approximately 2 to the vertical where is the angle of shearing resistance for a deep anchor a balloon shaped rupture surface emerged at 0 8 to the vertical immediately above the anchor and was confined within the sand bed the load displacement behaviour of full shaped models was three phase and two phase for shallow and deep anchors respectively alternative methods of determining the critical embedment ratio are considered and values of 4 8 5 9 and 6 8 are proposed for loose medium dense and dense sand respectively empirical equations are presented which yield breakout

damage to sewerage systems during the 2004 earthquake in niigata ken chuetsu japan the 2004 earthquake in niigata ken chuetsu japan caused widespread damage to sewer pipelines due to uplift behaviors caused by ground settlement after liquefaction sewer pipelines which are important lifelines suffer damage when sewerage systems cease to operate over a long period of time manholes ejected from the ground s surface can disrupt traffic to study the failure mechanism after the earthquake the nagaoka city government conducted an open cut survey of the damaged sewerage systems the main features of the collected data included the locations of damaged sections and the inclination of the sewer pipes before and after the earthquake in the present study the cause of damage to the sewerage systems was investigated using the datasets and the standard penetration test spt borehole logs the relationship between the sewer pipeline damage and the geological settings in the affected area reveals that the groundwater depth and the geotechnical properties of the original subsoils acted as the key parameters influencing the manhole uplift behavior also the uplift mechanism was investigated through centrifuge modeling tests and these findings agree well with the test results obtained in this study

hydrothermal mobility of ti zr and ree examples from the bergell and adamello contact aureoles italy contact metamorphic marbles affected by metasomatic fluids at the contact to the bergell and adamello intrusives contain various accessory minerals zirconolite allanite titanite rutile geikielite hoegbomite which provide new evidence for the hydrothermal mobility of ti and zr in both examples ti and zr migrated along with u th y and ree in a metasomatic fluid rich in potassium the composition of the main minerals fluorine rich phlogopite pargasite and titanian clinohumite and the abundance of fluor apatite demonstrate that fluorine and phosphorus were important components of the fluid the textural relationships indicate that the formation of the accessory phases is linked to the crystallization of the hydrous minerals

a low cost landslide displacement activity assessment from time lapse photogrammetry and rainfall data application to the tessina landslide site abstract acquiring useful and reliable displacement data from a complex landslide site is often a problem because of large localized and scattered erosive processes and deformations the inaccessibility of the site the high cost of instrumentation and maintenance however these data are of fundamental importance not only to hazard assessments but also to understanding the processes at the basis of slope evolution in this framework time lapse photogrammetry can represent a good compromise the low accuracy is compensated for by the wide ranging and dense spatial displacement information that can be obtained with inexpensive equipment nevertheless when large displacement monitoring data sets become available the problem becomes the choice of the most suitable statistical model to describe the probability of movement and adequately simplify the complexity of a scattered intermittent and spatially inhomogeneous displacement field in this paper an automated displacement detection method which is based on the absolute image differences and digital correlations from a sequence of photos was developed and applied to a photographic survey activity at the head of the tessina landslide northeastern italy the method allowed us to simplify and binarize the displacement field and to recognize the intermittent activity and the peculiar behaviours of different parts of the landslide which were identified and classified by combining geomorphological and geological information moreover for the first time sliding correlations between these areas were quantitatively estimated using time series based binary logistic regression and the definition of a probability based directed graph of displacement occurrence that connected the source zones to the lower depletion basin and the main collector channel using rainfall data event based logistic and poisson regression models were applied to the upper zones of the landslide to estimate the probability of movement of each scarp and the persistence of the displacement as a result of certain rainfall events the results of these statistical analyses highlighted the capability of this approach to quantitatively evaluate the pattern of displacement occurrences and to assess the evolution of a landslide site to gain insight into geomorphological processes

a finite element approach for determining the full load displacement relationship of axially loaded shallow screw anchors incorporating installation effects screw anchors have been recognised as an innovative solution to support offshore jacket structures and floating systems due to their low noise installation and potential enhanced uplift capacity

the role of subgrain boundaries in partial melting abstract evidence for partial melting along subgrain boundaries in quartz and plagioclase is documented for rocks from the lost creek gneiss of the llano uplift central texas the wet mountains of central colorado and the albany fraser orogen southwestern australia domains of quartz or plagioclase crystals along subgrain boundaries are preferentially involved in partial melting over unstrained domains of these minerals material along subgrain boundaries in quartz and plagioclase has the same morphology as melt pseudomorphs present along grain boundaries and is commonly laterally continuous with this former grain boundary melt indicating the material along subgrain boundaries can also be categorized as a melt pseudomorph subgrain boundaries consist of arrays of dislocations within a crystal lattice and unlike fractures would not act as conduits for melt migration instead the presence of former melt along subgrain boundaries requires that partial melting occurred in these locations because it is kinetically more favorable for melting reactions to occur there preferential melting in high strain locations may be attributed to strain energy which provides a minor energetic contribution to the reaction and leads to preferential melting in locations with weakened bonds and or the presence of small quantities of water associated with dislocations which may enhance diffusion rates or locally lower the temperature needed for partial melting

the effect of dauphine twinning on plastic strain in quartz we present an electron backscatter diffraction analysis of five quartz porphyroclasts in a greenschist facies t 300 400 c granitoid protomylonite from the arolla unit of the nw alps mechanical dauphine twinning developed pervasively during the incipient stage of deformation within two porphyroclasts oriented with a negative rhomb plane z almost orthogonal to the compression direction z twin orientation twinning was driven by the anisotropy in the elastic compliance of quartz and resulted in the alignment of the poles of the planes of the more compliant positive rhomb r nearly parallel to the compression direction r twin orientation in contrast we report the lack of twinning in two porphyroclasts already oriented with one of the r planes orthogonal to the compression direction one twinned porphyroclast has been investigated with more detail it shows the localization of much of the plastic strain into discrete r twins as a consequence of the higher amount of elastic strain energy stored by r twins in comparison to z twins the presence of dauphine twins induced a switch in the dominant active slip systems during plastic deformation from basal regions without twinning to and pervasively twinned regions dynamic recrystallization is localized along an r twin and occurred dominantly by progressive subgrain rotation with a local component of bulging recrystallization part of the recrystallized grains underwent rigid body rotation approximately about the bulk vorticity axis which accounts for the development of large misorientation angles the recrystallized grain size piezometer for quartz yields differential stress of 100 mpa the comparison of this palaeostress estimate with literature data suggests that mechanical dauphine twinning could have a potential use as palaeopiezometer in quartz bearing rocks

uplift soil pipe interaction in granular soil soil pipeline interaction for uplift in granular soil is evaluated by means of a two dimensional finite element fe continuum model with a mohr coulomb mc yield surface for peak strength a strain softening relationship tied to critical void conditions and an equivalent modulus that is consistent with soil deformation at maximum uplift resistance the model accounts for soil migration beneath the pipe through fe mesh adjustment coordinated with upward pipe displacement a systematic comparison of model results with multiple full scale test measurements of pipe in dry sand show excellent agreement both with respect to maximum force and force displacement relationships including post peak performance the relationship between peak upward force and pipe depth is developed for various sand densities all of which show maximum force at a depth to diameter ratio of 30 hyperbolic and bilinear models for vertical upward force versus displacement are presented the analytical approach described in this pape

landslides triggered by excavation in the loess plateau of china a case study of middle pleistocene loess slopes abstract the frequent occurrence of catastrophic landslides caused by excavation in a loess slope is one of the commonly encountered engineering problems in the loess plateau middle pleistocene loess slopes were selected as a case study for current research the distribution of excavation induced loess landslides was studied by field investigation on the basis of centrifuge model tests the deformation features and failure mechanism of a homogeneous loess slope and a double paleosol interlayer loess slope under different excavation slope angles were analyzed and compared it was shown that the response of horizontal earth pressures in the lateral region of the excavation zone has a close relationship with the failure of the slope displacement measurements showed that the deformation stages of loess slopes due to excavation are independent of the paleosol interlayer the excavation slope inclinations and soil properties significantly affected the failure process and division of the slope the characteristics that excavation induced loess landslides always occur in hysteresis and abruptness were interpreted by the analysis of the failure process the influence of blade penetration during the excavation performed was quantitatively estimated finally based on the result of stress path tests an improved unloading constitutive model was proposed to simulate the deformation of soils in the lateral and bottom of the excavation area

uplift of shallowly buried pipe sections in saturated very loose sand offshore pipelines are often buried to protect them from damage and to provide additional thermal insulation in sandy soils the pipes are trenched using jet trenching or ploughing in both cases the nature of the trenching operation means that the backfill material can be placed over the pipe in an extremely loose state if the pipe then undergoes a small displacement or vibration liquefaction of the backfill material may occur and the resistance to upward movement of the pipe can be reduced to explore this experimentally an instrumented model pipe section was pulled vertically upwards at different rates in very loose saturated fine uniform sand representative of a north sea sand the instrumentation allowed for the measurement of the force on the pipe section as well as the excess pore water pressure regime around the pipe the results show that for sand at a relative density of zero there is a reduction of capacity at the faster uplift rates a simple analytical model using the vertical sl

calcite twins their geometry appearance and significance as stress strain markers and indicators of tectonic regime a review twin lamellae are a widespread feature in calcites of any type and origin twinning in calcite is an important intracrystalline deformation mechanism with low critical resolved shear stress and virtually no temperature dependence in contrast to most slip systems in rock forming minerals twinning therefore permits intracrystalline deformation at very low temperature and very little confining pressure twinning alone however cannot lead to large strains because only one independent slip system is effectively available twins lead to discontinuous shearing on the grain scale which gives rise to considerable strain incompatibilities at grain boundaries twinning consequently leads to strain hardening detailed observations of the geometry of twin lamellae show that incompatibilities at grain boundaries are eliminated by pressure solution on the grain scale at low temperature and dynamic recovery processes at higher temperatures twins are found in various tectonic environments and record very small strains in rocks deformed under very little cover different twinning strain and twinning stress methods and palaeopiezometers are critically reviewed all methods are limited to strains of less than 15 shortening or extension by twinning twinning nevertheless is an important although not directly measurable contribution to the total strain in highly strained calcite rocks at least up to middle greenschist facies under which conditions it is the most effective contributor to the formation of strong lattice preferred orientations in calcite tectonites the appearance of calcite twin lamellae changes systematically as a function of deformation temperature micro twins and straight narrow 1 5 m but fewer twins are developed above approximately 200 c curved twins twinned twins and completely twinned grains indicate the progressive importance of other slip systems and larger intracrystalline strains are possible at ca 250 c and above ancient straight twin lamellae are modified into irregular geometries by recrystallization and grain boundary migration the appearance of calcite twins is proposed as an approximate but rapid and easy to use geothermometer in low temperature environments

iron ore of the lahn dill type formed by diagenetic seeping of pyroclastic sequences a case study on the schalstein section at gansberg weilburg investigations on the reconstruction of processes and facies relationships from submarine volcanics of devonian age in the lahn syncline rhenish mountains western germany reveal a complex development of secondary alteration this is well illustrated by a mafic pyroclastic sequence schalstein at the gansberg near weilburg where alteration processes are visible by petrographic and geochemical means and can be further classified by cathodoluminescence iron ore formation of lahn dill type is recognized as part of this alteration process resulting from diagenetic seeping until recently a direct magmatic source for the lahn dill type iron ore has been the generally accepted model these bodies have therefore been viewed as a rather unique stratiform deposit whose occurrence was virtually confined to this type area however it is here considered that the formation of the iron ore corresponds well with existing models of alteration processes within recent oceanic environments which are of a more universal occurrence

two new emsian early devonian u pb zircon ages from volcanic rocks of the rhenish massif germany implications for the devonian time scale so far only few biostratigraphically well constrained isotopic ages constitute the geochronological framework of the devonian period to expand this sparse dataset two new u pb isotope dilution thermal ionization mass spectrometry id tims zircon ages were obtained from volcanic rocks of the rhenish massif germany these rocks are interbedded in emsian lower devonian marine sedimentary successions that are well documented by index fossils given that the u pb zircon data represent primary crystallization and eruption ages they provide an important contribution to the devonian time scale the older sample a stratiform volcaniclastic layer hans platte is collected from bundenbach hunsruck the type locality of the lower emsian hunsruck slate a cluster of five coherent single zircon analyses obtained from this layer yielded a weighted mean 206 pb 238 u age of 407 7 0 7 ma which is regarded as the time of eruption of the pyroclastic rock biostratigraphically the layer can be assigned to the upper part of the polygnathus excavatus conodont zone the younger u pb age was obtained from the global stratotype section and stratigraphic point section at wetteldorf eifel where the k bentonite hercules i is intercalated 13 m below the lower middle devonian boundary in the uppermost part of the polygnathus costatus patulus conodont zone some of the 19 single zircon analyses obtained from this bentonite appear to document significant influences of inheritance the 13 youngest points are however concordant and form an elongated cluster along concordia with 206 pb 238 u ages between 392 2 and 407 7 ma given the risky assumption that this age scattering is exclusively caused by varying amounts of inheritance the youngest point of this cluster represents the analysis with the least or no inheritance in this case its 206 pb 238 u age of 392 2 1 5 ma should approach the eruptional age of the bentonite the ages presented here in combination with u pb id tims zircon and monazite ages from other workers allow a recalibration of the early emsian to early eifelian interval of the devonian time scale the result is a duration of the emsian stage excluding the basal emsian p kitabicus conodont zone of more than 17 2 ma and an emsian eifelian early middle devonian boundary age of 391 8 0 4 ma