combined u pb geochronology and lu hf isotope systematics by lam icpms of zircons from granites and metasedimentary rocks of carrazeda de ansiaes and sabugal areas portugal to constrain granite sources abstract the carrazeda de ansiaes and sabugal areas in the central iberian zone of the iberian variscan belt contain abundant s type granites formed during the post thickening stage of the variscan orogeny syn to post d3 i e the last ductile deformation phase magmatic zircons and inherited zircon cores from two granites g and g5 magmatic zircons from three other granites g1 g4 and g6 and detrital zircons from a chlorite phyllite and a metagraywacke were dated by lam icpms hf isotope data were obtained by the same method to constrain the sources for granites some granites have zircons with negative ehft values g from 8 to 4 g1 from 8 to 1 g4 from 6 to 3 suggesting an origin from heterogeneous crustal anatectic melts or from mantle derived magmas contaminated in the crust magmatic zircons from granites g5 and g6 show a larger variation yielding also some positive ehft values g5 from 8 to 6 g6 from 4 to 4 indicating crystallization from mildly contaminated mantle derived magmas or from a lower crustal source u pb isotope data of inherited zircon cores from granites g and g5 show that neoproterozoic ages dominate but only the inherited zircon cores from granite g have similar initial 176hf 177hf ratios to those from a chlorite phyllite of the formation of ervedosa do douro carrazeda de ansiaes area suggesting that this metasedimentary unit could have been involved in the genesis of the granite g on the other hand the lu hf data suggest that the metagraywacke from sabugal area should not be considered a component involved in the partial melting process that formed the granite g5 the occurrence of mesoproterozoic detrital zircons in both metasediments suggests that these rocks are likely to have evolved from a peri amazonian realm close to west avalonian terranes during the neoproterozoic early palaeozoic however a west african craton provenance could also be considered if a long distance river transportation of mesoproterozoic zircons from the southwest baltica or arabian nubian shield is admitted the u pb isotope data obtained in detrital zircons from both metasedimentary rocks suggest that their maximum depositional ages are ca 578 ma for the chlorite phyllite and ca 577 ma for the metagraywacke

field and laboratory testing of st peter sandstone the purpose of this project was to evaluate mechanical properties of st peter sandstone by in situ testing and to compare the field data with laboratory results direct shear tests were conducted to evaluate the strength dilatancy behavior and thin section microscopy was used to help explain the significant friction angles associated with the material st peter sandstone is nearly cohesionless but it possesses a friction angle of 57 63 at low confinement the large angle of internal friction at failure may be due to locking of sand particles or to postdepositional quartz overgrowths tests on pulverized densely packed sand and loosely packed sand were conducted in the same manner as the intact specimens and yielded friction angles of about 42 and 34 pressuremeter tests were performed in situ and the results were interpreted using an elasto plastic analysis in terms of total stresses by appropriate consideration of system stiffness young s modulus was found to be about 0 5 gpa slightly lower than the laboratory value although unload reload cycles were not attempted assuming associative behavior the friction angle was estimated to be at least 56

one dimensional compression and consolidation of shales abstract this paper presents a comprehensive methodology for analysing the compression and consolidation behaviour of shales an apparatus was designed to perform oedometric high pressure tests by applying a maximum vertical total stress of 100 mpa and simultaneously controlling the pore water pressure of the specimen an analytical method was formulated to analyse the shale consolidation behaviour which allows information to be gathered on the coefficient of consolidation stiffness poroelastic properties secondary compression and permeability of the tested material as a function of the applied stress conditions results obtained on opalinus clay shale using the developed methodology are presented and discussed

rate effect experiments on round tipped penetrometer insertion into uniform snow snow penetrometers are being developed to detect stratigraphy indicative of slab avalanches results are presented here from experiments performed to assess the relationship between the velocity of a round tipped penetrometer through uniform snow and the resulting force response the range of velocities used is commensurate with that used to drive a manually driven penetrometer through the snow a characteristic spike is noted in profiles during the initial stage of deformation which appears to be more pronounced for the harder snow layers tested an investigation of snow deformation using video analysis of a split axis rod deforming snow against a clear plastic window indicates that the spike in the force signal corresponds to the development of a compaction zone below the penetrometer tip once shear forces that develop in the compacted snow are overcome deformation proceeds in a steady state and there is little or no relationship between the force response and velocity over the velocity range of our experiments

reassessment of continental growth during the accretionary history of the central asian orogenic belt we argue that the production of mantle derived or juvenile continental crust during the accretionary history of the central asian orogenic belt caob has been grossly overestimated this is because previous assessments only considered the palaeozoic evolution of the belt whereas its accretionary history already began in the latest mesoproterozoic furthermore much of the juvenile growth in central asia occurred in late permian and mesozoic times after completion of caob evolution and perhaps related to major plume activity we demonstrate from zircon ages and nd hf isotopic systematics from selected terranes within the caob that many neoproterozoic to palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous precambrian crust or through mixing of old continental crust with juvenile or short lived material most likely in continental arc settings at the same time juvenile growth in the caob occurred during the latest neoproterozoic to palaeozoic in oceanic island arc settings and during accretion of oceanic island arc and precambrian terranes however taking together our data do not support unusually high crust production rates during evolution of the caob significant variations in zircon ehf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources we reiterate that the chemical characteristics of crustally derived granitoids are inherited from their source s and cannot be used to reconstruct tectonic settings and thus many tectonic models solely based on chemical data may need re evaluation crustal evolution in the caob involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history and we see many similarities with the evolution of the sw pacific and the tasmanides of eastern australia

cone penetration testing cpt in antarctic firn an introduction to interpretation commercial cone penetration testing cpt equipment was adapted to allow penetrative testing in hard polar firn to depths of 10 m the apparatus is hydraulically driven rate controllable and able to penetrate firn with a resistance of 10 mpa it can be mounted on many types of typical polar vehicles requiring connection to only hydraulics and 12 v electricity data recorded include both cone tip resistance and sleeve friction a parameter not previously examined through such testing this paper describes the development and calibration of the equipment and examines factors including snow density penetration rate and cone size and shape that are shown to affect cpt interpretation cpt can be used efficiently in polar environments to potentially provide estimates of physical parameters in hard firn to substantial depth

the 1 75 1 68ga anorthosite mangerite alkali granitoid rapakivi granite suite from the northern north china craton magmatism related to a paleoproterozoic orogen abstract the amgrs is a suite of anorthosite mangerite alkali granitoid rapakivi granite in the northern north china craton ncc new zircon shrimp and laser ablation inductively coupled plasma mass spectrometry la icpms u pb dating of the damiao anorthosite changsaoying k feldspar granite lanying anorthosite and quartz syenite and the gubeikou k feldspar granite yielded emplacement ages of 1726 9 ma 1753 23 ma 1739 43 ma 1712 15 ma and 1692 19 ma respectively combined with previous geochronological data from the damiao norite and mangerite and shachang rapakivi granite it indicates that the whole amgrs was intruded between 1750 ma and 1680 ma the damiao anorthosites and norites exhibit a high mg and this decreases from mafic up to 63 to felsic t dm c ages ranging from 2 32 ga to 2 43 ga and 2 70 ga to 2 88 ga respectively this suggests that these rocks are the fractional crystallization products of one parental magma zircon hf and whole rock sr nd pb isotopic systematics combined with high la yb 10 and intermediate th ta ratios suggest that the parental magma of the amgrs could have been derived from em i lithosphere mantle enriched by recycled archean continent crustal materials accompanied by some assimilation of lower crustal components the mafic to felsic compositions of the amgrs are different from typical bimodal rocks formed in an anorogenic intra continent rift setting but resemble those emplaced during post collisional post orogenic extensional tectonic setting this is compatible with their age of

a brief introduction to cone penetration testing cpt in frozen geomaterials the cone penetration test has been successfully used to classify soil for 100 years however it has received only limited contemporary use in frozen geomaterials the historical and contemporary use of the cone penetration test in various frozen geomaterials is considered here and contemporary data from recent work in polar snow are examined it is probable that many material physical properties e g density strength and microstructure can be obtained directly from cone penetration testing it appears under utilized as a contemporary scientific and engineering investigative tool in frozen geomaterials

3m analytical method evaluation of shaft friction of bored piles in sands abstractthis study presents 3m an analytical method to estimate the skin friction of bored piles in sands it is based on the fundamental mechanic behavior of sands and keeps track of the major mechanisms occurring in the soil close to the pile during loading these include the development of a shear band its potential expansion as induced by soil dilatancy and the ensuing increment of horizontal stresses owing to the restraining effect of surrounding soils the resulting analytical equations are easy to apply and insert in a worksheet the procedure to evaluate the shear band expansion is calibrated against results of direct shear tests at constant normal load whereas the increment of horizontal stresses is evaluated by the closed form solution for the expansion of a cylindrical cavity into a dilatant elastic perfectly plastic medium the effectiveness of the 3m method in predicting shaft friction has been checked against numerical results centrifuge and full scale pile load tests nevertheless pr

discussion of test fill on soft plastic marine clay at onsoy norway 1 the comprehensive technical article by berre 2014 on the plastic marine clay at onsoy norway merits further examination we attempted to determine c cc for onsoy clay using the cc and c values in table 1 the computed values of c cc based on tests oed 1x to oed 4x were however dissimilar and some of the values of c cc for example for test oed 4x do not seem reasonable fortunately the author has carefully defined the cc and c values that are listed in table 1 it turns out according to the list of symbols that the compression index cc has been calculated for the steepest part of the a versus a plot above pc on the other hand the values of a at which c wasmeasured are clearly shown on figs 20 to 23 for computing c cc for any soil c and cc must be defined at the same consolidation pressure e g a or v mesri and godlewski 1977 mesri and castro 1987 it is readily possible to determine from figs 20 to 23 the values of tangent cc 1 eo where eo is the initial or preconstruction void ratio at consolidation pressures at which secondary compression was allowed to determine c note that the values of eo ei are also listed in table 1 the values of cc determined from figs 20 to 23 together with the corresponding values of c from table 1 are listed in table d1 the computed values of c cc for the four oedometer tests data are nearly identical and the average c cc for onsoy marine clay is near the most representative value of 0 04 for inorganic soft clays terzaghi et al 1996 table 16 1 p 110 berre 2014 reports a ko value for onsoy plastic clay equal to 0 60 determined by hydraulic fracturing tests in the field it is interesting to compare the ko value of 0 60 by hydraulic fracture with the values of ko computed by the empirical equations proposed by mesri and hayat 1993 for ko of soft clay deposits

mechanical properties of a carbonate sand from a dredged hydraulic fill this paper focuses on the properties of a crushable uncemented carbonate sand retrieved from an artificial island to be used for petroleum production offshore of the united arab emirates the sa

early cretaceous potassic volcanic rocks in the jiangnan orogenic belt east china crustal melting in response to subduction of the pacific izanagi ridge abstract eastern china is characterized by widespread mesozoic magmatism that was closely related to subduction of the paleo pacific plate but the genetic relationship between magmatism and subduction is not always clear the jiangnan orogenic belt job is a neoproterozoic collisional belt between the yangtze and cathaysian blocks early cretaceous felsic magmas from the tianmushan basin in the eastern job form a 3000 m thick volcanic sequence erupted within an extremely short period of time 132 130 ma these rocks are potassic k2o 3 86 6 05 and peraluminous a cnk 1 0 1 23 and are compositionally similar to experimental melts derived from predominantly clay poor and k rich metasediments or granodiorites at crustal conditions they are lile and lree enriched la yb cn 9 0 14 6 and display variable eu anomalies and nb ta depletion the weakly variable and negative whole rock end t 5 4 to 2 5 and heterogeneous zircon ehf t values 6 7 to 3 5 of these rocks are similar to those of basement rocks beneath the job suggesting a genetic relationship with basement no magmas with clear subduction related composition occurred at this time in the area and the compositions of the potassic rocks more closely resemble high temperature melts of extensively thinned crust in continental rift environments our data favors a model that the early cretaceous potassic magmas formed as subduction of the pacific izanagi ridge resulted in upwelling asthenosphere providing the high temperatures required to extensively melt the lower middle crust in the eastern job

engineering properties of fibrous peats this state of the art paper presents an interpretation of the permeability compressibility and shear strength of fibrous peats using data from laboratory tests on undisturbed block samples of two fibrous peats as well as extensive laboratory and field data from the literature on fibrous peat deposits engineering properties of fibrous peats are significantly different from those of most inorganic soils however the same fundamental mechanisms and factors determine behavior of both inorganic soils and fibrous peats fibrous peat deposits possess very high initial permeability typically 1 000 times the initial permeability of soft clay and silt deposits upon compression the permeability of fibrous peats decreases dramatically with a ratio of permeability change index to in situ void ratio equal to 0 25 as compared to 0 50 for soft clay and silt deposits fibrous peats display extreme compressibility to the increase in effective vertical stress with compression index values right after preconsolidation pressure 5 to 20 times the corresponding compressibility of typical soft clay and silt deposits among geotechnical materials fibrous peats display the highest ratios of secondary compression index to compression index in the range of 0 05 to 0 07 the values of coefficient of earth pressure at rest for normally consolidated young fibrous peat deposits are in the range of 0 30 to 0 35 as compared to 0 45 to 0 65 for inorganic soils the values of friction angle from triaxial compression tests for fibrous peats are in the range of 40 to 60 as compared to less than 35 for soft clay and silt compositions for fibrous peats the ratios of undrained shear strength in compression to preconsolidation pressure are usually in the range of 0 50 to 0 75 as compared to 0 32 for soft clay and silt deposits for surficial fibrous peat deposits the ratio of vane shear strength to preconsolidation pressure is near 1 0 as compared to 0 12 to 0 35 for inorganic soft clay and silt deposits for fibrous peats the ratio of undrained young s modulus to undrained shear strength is in the range of 20 to 80

u pb geochronology and hf nd isotope compositions of the oldest neoproterozoic crust within the cadomian orogen new evidence for a unique juvenile terrane new u pb dates combined with nd and hf isotopic data from rocks within the port morvan area of the baie de st brieuc region of brittany identify a unique portion of the neoproterozoic cadomia terrane two gneisses near port morvan yielded u pb dates of 754 6 0 8 ma and 746 0 0 9 ma ages that are more than 130 myr older than the oldest units formed during the main phase of early cadomian magmatism two trondhjemite boulders from the monogenetic facies of the cesson conglomerate yielded identical ages of 665 2 0 5 ma and 665 5 0 7 ma and a cobble from the polygenetic facies yields a 207pb 206pb date of 637 2 ma individual detrital zircons from a sandstone associated with the cesson conglomerates yield concordant u pb dates ranging from 650 3 ma to 624 1 0 6 ma initial nd values for the rocks in this region range from 5 0 to 6 6 indicative of a substantial input from depleted mantle initial hf values determined on zircons from these neoproterozoic rocks including the detrital zircons range from 6 7 to 14 5 consistent with the nd isotopic results maximum initial hf values for two 2 ga icartian gneisses considered basement to cadomia average 8 4 and 8 7 in contrast to the results of the port morvan rocks 616 608 ma syn tectonic intrusions from normandy and the british channel islands all have negative initial nd values 10 4 to 8 3 consistent with significant contamination by ancient crust such as the 2 ga gneisses the oldest arc related magmas should have interacted most extensively with cadomian basement buffering younger mantle derived magmas that were generated in subsequent magmatic episodes the rocks within the port morvan region are thus inconsistent as examples of the earliest cadomian intrusions as they show no evidence of interaction with 2 ga basement instead the older ages and mantle like isotopic composition of these rocks suggest they are part of an independent terrane that formed prior to and independently from the cadomian arc possible terrane scale structural boundaries have recently been identified including the newly recognized port morvan thrust fault and the nw dipping main cadomian thrust

estimating horizontal stresses for mudrocks under one dimensional compression abstract we examine horizontal stresses in mudrocks for the case of one dimensional mechanical compression through laboratory measurements of the horizontal to vertical effective stress ratio i e k 0 previous empirical relationships which predict horizontal stresses as a function of depth or overburden stress are site specific and cannot easily be generalized the k 0 values of various resedimented mudrocks from a diverse range of geologic origins have been investigated for effective stresses ranging from 0 1 to 100 mpa the value of k 0 during normal compression k 0nc varies systematically as a function of both stress level and mudrock composition k 0nc generally increases with stress level and values as high as 0 90 have been measured at effective stresses approaching 100 mpa this finding implies that high horizontal stresses can develop at depth solely due to normal mechanical compression and that tectonic stresses creep or geologic unloading are not necessary correlations have been developed which allow k 0nc to be estimated from a mudrock s liquid limit an easily and inexpensively measured property which reflects both the quantity and type of clay minerals present in a mudrock high liquid limit smectite rich mudrocks display a more rapid increase in k 0nc with increasing stress compared to more silty low liquid limit mudrocks k 0 measurements made on laboratory resedimented specimens compare well with measurements made on intact core samples as well as in situ tests tests carried out to examine k 0 for overconsolidated materials show that k 0 during unloading can be well approximated by a power law function originally proposed by schmidt 1966 an original equation is proposed to describe k 0 during reloading our experimental results reveal sediment behavior at high stress levels that has not been previously observed and provide useful information on how horizontal stresses evolve within basins

mechanical properties of two expansive clay soils from sudan the mechanical responses of two highly expansive plastic alluvial soils from sudan are reported when wetted from their in situ state such soils frequently lead to damage of civil engineering structures disturbed samples of a black cotton clay and a more plastic red clay were collected from two locations in the vicinity of khartoum intrinsic properties were established from reconstituted samples using oedometer and triaxial apparatus natural undisturbed block samples of the black cotton clay were obtained and tested in an unsaturated state as found in situ basic characteristics of both soils are presented detailed information on the intrinsic properties of both clay soils was established and found to conform with burland s earlier published framework shear planes formed during shearing in almost all triaxial samples and strengths reduced to post rupture values k0 consolidated reconstituted samples exhibited a more brittle response to undrained shearing compared with isotropically consolidated sam

pseudo static lateral earth pressures on broken back retaining walls displacement of retaining walls during earthquakes causes damage to the structures founded on their backfill the displacement of the wall can be reduced by decreasing the lateral earth pressure applied on its back this can be achieved in a broken back wall as the size of the failure wedge formed behind the wall is reduced therefore the calcula tion of lateral earth pressures is essential in assessing the safety of and designing broken back retaining walls in this study a series of reduced scale shaking table model experiments were performed on broken back quay walls composed of concrete blocks with two different rear face shapes in comparison with a vertical back wall earth pressures increased at the upper forward i e seaward leaning rear face segments of the wall whereas they decreased at lower backward i e landward leaning elevations because of the wide application of the pseudo static method of mononobe okabe in engi neering practice and design codes lateral earth pressures have also been estimated using this approach the comparison between the measured lateral earth pressures and those calculated using the mononobe okabe method shows fairly good agreement in predicting the overall distribution of lateral active earth pressure during and after the shaking resume le deplacement des murs de soutenement durant un seisme cause des dommages aux structures ayant des fonda tions installees sur le remblai de ces murs de soutenement le deplacement du mur peut etre reduit en diminuant la pres sion laterale des terres appliquees au dos du mur cette diminution peut etre accomplie par l utilisation d un mur a dos brise puisque la zone de fracture formee derriere le mur est reduite ainsi il devient essentiel de calculer les pressions la terales des terres pour evaluer la securiteet pour concevoir des murs de soutenement a dos brise dans cette etude des es sais al echelle reduite a l aide d un modele de table asecousses sont effectues sur des murs a dos brisede quais faits de blocs de beton avec deux formes de dos differentes comparativement aun mur ados vertical la pression des terres aug mente dans les sections de la face arriere du mur orientees vers le devant et le haut c a d vers la mer tandis que la pression des terres diminue dans les sections orientees vers le derriere et vers le bas c a d vers le sol les pressions late rales des terres sont aussi estimees al aide de l approche pseudo statique de mononobe okabe puisque cette approche est largement utilisee dans l ingenierie et la conception la comparaison entre les pressions laterales des terres mesurees et celles calculees a l aide de la methode mononobe okabe montre la concordance des resultats apredire la distribution glo bale des pressions laterales actives des terres pendant et apres les secousses mots cles methode mononobe okabe mur de soutenement pression laterale des terres seisme essai sur table a secous ses mur a dos brise traduit par la redaction

normally loaded inclined strip anchors in cohesionless soil plate anchors are among the most effective anchorage systems that are widely used to resist horizontal and inclined uplift loads in many offshore and onshore applications previous research on plat

the cone penetration test in unsaturated sands laboratory controlled cone penetration test results for an unsaturated sand are presented obtained using a suction controlled calibration chamber the cone penetration resistances are found to increase significantly owing to the presence of suction when compared with those for saturated or dry states for a given relative density and net confining stress increases of as much as 50 for a relative density of 0 33 and net confining stress of 50 kpa are recorded when suction is included in the effective stress the same semi empirical expressions used for saturated sands are found to link penetration resistance to the relative density and effective confining stress the expressions may also be used to back calculate the suction changes in a soil profile when cone penetration resistances for two unsaturated states are known it is also shown that failure to account for suction influences may lead to significant and non conservative overestimations of relative density or peak friction angle

discussion of cyclic tests on high quality undisturbed block samples of soft marine norwegian clay the article by wichtmann et al 2013 presents a comprehensive set of laboratory test data on the cyclic undrained shear strength of soft marine norwegian onsoy clay the tests were performed on specimen quality designation sqd b specimens andresen and kolstad 1979 terzaghi et al 1996 cut from block samples taken by the sherbrooke sampler lefebvre and poulin 1979 this article is a valuable contribution because compared to data and interpretation for sands undrained cyclic strength data for soft clays are rare e g andersen and lauritzen 1988 andersen et al 1988 furthermore the previous norwegian geotechnical institute ngi tests on soft marine norwegian drammen clay were performed on specimens consolidated to the compression range beyond the pre consolidation pressure p whereas the tests on onsoy clay have been performed using high quality specimens subjected to the in situ effective stress condition ho vo before undrained shear a meaningful impression of undrained shear strength behavior of soft clay deposits is obtained by normalizing undrained shear strength with respect to pre consolidation pressure as both su and p represent points on the yield envelope skempton 1948 mesri 1975 mesri and huvaj 2007 the cyclic undrained shear strengths of sands have been commonly normalized with respect to effective overburden pressure vo because it is not readily possible to determine pre consolidation pressure of sand deposits this discussion concerns cyclic triaxial shear data on specimens cut from samples taken in the depth range of 10 50 to 11 37 m and consolidated before undrained shear to the in situ effective stress condition the onsoy clay samples had a pore water salt content of 32 5 g l natural water content of 63 to 65 liquid limit of 63 and plasticity index of 33 to 34 lunne et al 2006 at the depth range of the samples the end of primary eop pre consolidation pressure p corresponds to p vo 1 4 note that i reduced values of p from the constant rate of strain crs tests by a factor of 0 912 because the imposed strain rates i in the ngi tests were about 10 times the eop strain rate p mesri et al 1994 the in situ values of ko ho vo can be determined according to the following empirical equations mesri and hayat 1993

rate controlled cone penetration tests in permafrost cone penetration tests cpts were carried out in the summers of 1999 and 2000 in a permafrost mound near umiujaq in northern quebec canada to study the cryostratigraphy and assess the creep behaviour of permafrost a new linear pushing system using an actuator technology was specifically designed and developed to accurately control the penetration rate of the cone in the permafrost this system has a load capacity of about 113 kn at a maximum penetration rate of 1 5875 cm s and a stroke of 120 cm and can provide constant penetration rates as low as 4 10 6 cm s it can be disassembled in pieces for easy hand transport and use in remote locations two different types of cpt were performed in the permafrost mound stratigraphic profiling and creep test the first type is a quasi static cpt at a penetration rate of 0 1 cm s providing a stratigraphic profile of permafrost in terms of the measurement of penetrometer sensors as a function of depth the second type is a series of quasi static cpts at incre

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

present trends and the future of zircon in geochronology laser ablation icpms in situ u th pb geochronology was born some two decades ago with the introduction and development of high resolution secondary ion mass spectrometry sims or shrimp sensitive high mass resolution ion microprobe compston et al 1984 williams 1998 compston 1999 davis et al this volume ireland and williams this volume this technique clearly demonstrated the existence of age heterogeneities within the single crystals of zircon and other accessory phases and therefore the need for high spatial resolution tens to hundreds of cubic micrometers geochronological data in situ dating by ion probe is capable of achieving an analytical precision that is only an order of magnitude worse than the conventional isotope dilution thermal ionization mass spectrometry id tims dating technique it has the advantage however of more readily identifying concordant portions of grains does not require chemical treatment of samples prior to the analysis is essentially nondestructive and can achieve greater sample throughputs a major obstacle to the wider use of ion probe dating has always been the high cost of instrumentation and hence relative scarcity of suitably equipped geologic laboratories laser ablation inductively coupled plasma mass spectrometry la icpms emerged in 1985 and rapidly became an important analytical tool for trace element determinations in geological samples jackson et al 1992 it was soon realized that the large variations in radiogenic pb and pb u isotopic ratios found in nature could be resolved by icpms techniques and when coupled to a laser icpms could be used as a dating tool similar to the ion probe the pioneering work of feng et al 1993 fryer et al 1993 hirata and nesbitt 1995 and jackson et al 1996 illustrated the potential usefulness of laser sampling for in situ dating by icpms particularly well however these studies and others that followed also revealed the major

axial capacity of bored piles in very stiff intermediate soils there is a major shortage of good quality load test data for bored piles in stiff to hard intermediate soils such as silts and clayey sands this paper presents the results and interpretation of an

in situ u pb geochronology and hf isotope analyses of the rayner complex east antarctica in situ zircon u pb and hf isotopic analysis via laser ablation microprobe inductively coupled plasma mass spectrometer lam icpms of samples from kemp and macrobertson lands east antarctica suggests that the kemp land terrane evolved separately from the rest of the rayner complex prior to the ca 940 ma rayner structural episode several archaean metamorphic events in rocks from western kemp land can be correlated with events previously reported for the adjacent napier complex recently reported ca 1 600 ma isotopic disturbance in rocks from the oygarden group may be correlated with a charnockitic intrusion in the stillwell hills before ca 1 550 ma despite being separated by some 200 km t hf dm ages indicate felsic orthogneiss from rippon point the oygarden group havstein island and the stillwell hills share a ca 3 660 3 560 ma source that is indistinguishable from that previously reported for parts of the napier complex more recent additions to this crust include proterozoic charnockite in the stillwell hills and the vicinity of mawson station these plutons have distinct 176hf 177hf ratios and formed via the melting of crust generated at ca 2 150 2 550 ma and ca 1 790 1 870 ma respectively

assessing mass balance with the cone penetration test this letter briefly outlines why a friction sleeve equipped cone penetrometer may be a useful tool for assessing surface mass balance of polar ice masses

integrating s wave seismic reflection data and cone penetration test data using a multiangle multiscale approach a cone penetration test cpt is the most common geotechnical testing method used to estimate in situ the strength properties of soil although cpt provides valuable information this information is restricted to the location of the measurement we propose a new concept to integrate shallow s wave reflection seismic data with cpt data in order to obtain laterally continuous subsoil information in this vein a valid quantitative means to relate seismic reflections to cpt data is a primary requirement the approach proposed here is based on the characterization of the scaling behavior of the local fine scale s wave velocity information extracted from the seismic reflection data and the same behavior of the cpt cone resistance the local velocity contrast information is extracted by linearized zoeppritz inversion of the amplitude preserved prestack reflection data we have formulated a multiscale analysis approach employing the continuous wavelet transform in order to quantitatively characterize the nature

compaction behavior of argillaceous sediments as function of diagenesis the paper presents the results of laboratory compaction tests on samples of kimmeridge clay taken from two different locations in the uk the main objective of the laboratory tests is to determine how diagenesis affects the hydro mechanical properties and compaction behavior of argillaceous sediments the two kimmeridge clays used in the tests are essentially from the same parent material but have undergone different degrees of mechanical and chemical diagenesis the laboratory tests are designed to determine the effects of mechanical loading and chemical processes on changes in porosity permeability compressibility strength and effective horizontal stress in argillaceous materials another objective of the study is to investigate the adequacy of soil mechanical constitutive models in predicting the response of argillaceous materials to conditions corresponding to burial depths in sedimentary basins the tests on kimmeridge clay are carried out to as high as 150 mpa effective vertical stress corresponding to about 9 km in burial the results indicate that mechanical compaction and burial depth cannot explain the differences in the hydro mechanical behavior of the tested materials the differences in hydro mechanical response are attributed to chemical diagenesis by precipitation of minerals in the pores of the sediment other observed effects of chemical diagenesis on hydro mechanical behavior of lithified sediments are 1 increase in apparent pre consolidation stress 2 decrease in compressibility 3 decrease in permeability and 4 decrease in effective horizontal stress implications of the results to fluid flow and overpressure development in sedimentary basins are discussed

numerical simulation and shaking table test of geotextile bag retaining wall structure this study analyzed the dynamic behavior of flexible retaining walls constructed with geotextile bags the behavior of geotextile bag retaining wall system was simulated using a large scale shaking table in which 1 g n of one directional dynamic load was applied the dynamic behavior of the retaining wall was analyzed with simulated ground consisting of a geotextile bag in which 0 154 0 44 g n of ground acceleration was applied using historic and artificial seismic waves by el centro and hachinohe dynamic characteristics of the geotextile bag retaining wall structure in response to acceleration displacement and earth pressure were also analyzed based on results of large scale shaking table test and numerical analysis with the finite element method results showed that the dynamic active earth pressure increased with increasing ground acceleration at an action point of 0 6 h in addition the higher the point of passive positive earth pressure and the lower the increment of active positive earth pressure the more gradual the slope of the geotextile bag retaining wall

effect of particle fabric on the coefficient of lateral earth pressure observed during one dimensional compression of sand the effect of initial particle fabric on the one dimensional compression response of fraser river sand was investigated one dimensional compression with lateral stress measurement was carried out

cone penetration tests in unsaturated silty sands very little is known about how to interpret cone penetration tests cpts when performed in unsaturated soils the few published studies on cpts in unsaturated soils have focused on either clean sands or silt in this study new results of laboratory controlled cpts in an unsaturated silty sand are presented silty sand exhibits hydraulic hysteresis and suction hardening suction is observed to have a pronounced effect on measured cone penetration resistance for an isotropic net confining stress of 60 kpa it is observed that higher suctions give rise to cone penetration resistances that are 50 larger than those for lower suctions a semi theoretical correlation is presented that links measured cone penetration resistances to initial relative density and mean effective stress suction has an influence on cone penetration resistances through suction hardening as well as its contribution to effective stress for this silty sand it is shown that failing to account for suction may result in significant ov

stress history and sampling disturbance effects on monotonic and cyclic responses of overconsolidated bootlegger cove clays this paper examines the influence of reproducing the stress history of a natural soil deposit during laboratory reconsolidation on the subsequent response and behavior of heavily overconsolidated b

reliability of self boring pressuremeter in sand the cone penetration test cpt is viewed by a majority in the geotechnical engineering profession as a preferred in situ testing tool while the self boring pressuremeter test sbpmt is sometimes

scour effects on p y curves for shallowly embedded piles in sand soil scour around a shallowly embedded pile can significantly compromise its lateral response reducing both stiffness and capacity estimation of the lateral pile response must take into account both the scour hole geometry and the overconsolidation effects on the remaining soil a series of centrifuge model tests with various scour profiles were conducted at a scale of 1 250 to investigate the effects of both local and general scour on the response of a laterally loaded pile measured pile moment distributions and force displacement data at the pile head were used to derive p y curves quantifying the lateral pile soil interaction the p y curves derived from various scour profiles were compared for equivalent depths below the new scour base and below the original soil surface for the general scour cases the p y curves for given depths below the post scour surface are essentially identical to those at the same depths without scour in contrast for the local scour cases the p y response at a given de

in situ hafnium and lead isotope analyses of detrital zircons from the devonian sedimentary basin of ne greenland a record of repeated crustal reworking an intramontane collapse basin developed within the hanging wall above the large scale extensional fjord regional detachment of ne greenland in middle to late devonian times the continental clastic sediments within the basin are derived locally from laurentian source rocks which makes them well suited for a study of the crustal evolution of the source terrain this is the first integrated in situ pb and hf isotope study to be presented and zircon data on a selected sandstone from the basin are combined with sm nd whole rock data on sand siltstones nd whole rock ages of two samples of sandstones and a siltstone are 2 0 2 1 ga peak frequencies of zircon 207pb 206pb ages at 1 764 1 912 ma and 176hf 177hf values at 0 28142 0 28163 tdm 2 47 to 2 06 for the sandstone suggest the generation of a considerable volume of juvenile continental crust in the ultimate zircon provenance at 1 9 2 0 ga the hf isotopic compositions of archaean zircons in the sandstone are distinct from those of the source materials of proterozoic protocrust at 1 9 2 0 ga but zircons with elevated hf tdm ages of up to 2 47 ga can be related to a component of archaean crust or reworked archaean material in the ultimate zircon source area zircon 207pb 206pb ages are also recorded at 1 480 1 572 1 318 and 1 014 ma grenvillian the hf isotope compositions of these zircons are consistent with reworking of the proterozoic protocrust at these times with little or no juvenile input the proterozoic zircons form two distinct groups defined by 176yb 177hf 0 05055 and 176yb 177hf 0 03301 and the latter group overlaps with yb hf isotope data on the archaean zircons the two groups may represent zircons derived from evolved granites and intermediate to mildly felsic rocks respectively the repeated reworking of the continental crust also comprised erosion and deposition of sediments in the proterozoic the krummedal sequence and the eleonore bay supergroup ebs and intrusion of caledonian anatectic granites in the ebs which both represent provenance components to the devonian sediments no discrete caledonian pb pb zircon ages are recorded but caledonian magmatism may be represented by strongly discordant zircons which form arrays with a lower intercept age at ca 400 ma and an upper intercept at 1 600 2 000 ma one undated zircon records a 176hf 177hf ratio of 0 282218 higher than that of the proterozoic protocrust in caledonian late caledonian times 380 450 ma which may represent a caledonian mantle contribution

mineral dissolution and the evolution of k0 adequate knowledge of the in situ state of stress can be essential to the analysis of geotechnical systems however the measurement and prediction of k0 remain difficult in particular limited attention has been given to the evolution of k0 during the formation history of the soil and diagenetic processes such as mineral dissolution experimental and numerical results show that grain mass loss due to mineral dissolution produces a pronounced horizontal stress drop under zero lateral strain conditions the state of stress may reach the active shear failure ka condition and internal shear planes may develop while horizontal stress recovery often follows upon further dissolution marked differences in fabric are observed between the pre and postdissolution soil structures

calibration chamber tests of a cone penetrometer in sand the results of a series of tests using a cone penetrometer in sand in a large calibration chamber are reported sand at three different densities and a range of stress states was studied the principal finding from the tests is that cone resistance in sand depends primarily on the horizontal stress and the angle of friction but is relatively unaffected by the vertical stress a relationship between qc h and tc is proposed and compared with previous work in calibration chambers l article presente les resultats d une serie d essais effectues avec un penetrometre a cone dans du sable dans une chambre d etalonnage le sable a ete etudie avec trois densites differentes dans un intervalle d etats de contrainte les essais ont demontre surtout que la resistance au cone dans le sable depend d abord de la contrainte horizontale et de l angle de friction mais reste relativement peu influencee par la contrainte verticale on propose une relation entre qc h et tc et on la compare avec des recherches anteri

a new instrument for determining strength profiles in snow cover thermo resistographe realise a l aide d une jauge de contrainte et un systeme d acquisition de donnees microprocesseur z80

mechanical behaviour of fine grained sediments experimental compaction and three dimensional constitutive model abstract the usual undimensional description of deformations of sediments based on a phenomenological relationship between porosity and the vertical effective stress does not give information about the horizontal stress and moreover is irrelevant for sedimentary structures in which deformation process is not only vertical modelling three dimensional deformation processes in sedimentary basins requires a three dimensional mechanical constitutive model for sediments a special dometric cell was conceived in g 3s this cell allows the measurement of the lateral stress during dometric compaction and so enables us to elaborate a three dimensional model of mechanical behaviour four varieties of fine grained sediments were studied by this cell in a large scale of strain and stresses the modified cam clay model was used for fitting the experimental data and it was shown that this model can reproduce the mechanical compaction of sediments up to 50 mpa of vertical effective stress about 3 km burial depth if its parameters are deduced from dometric zero lateral strain data

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

mesozoic plutons of the yidun arc sw china u pb geochronology and hf isotopic signature abstract the yidun arc is a triassic volcanic arc located between the songpan garze fold belt and the qiangtang block southwest china to constrain the age of a number of the major granitic plutons from the yidun arc laser ablation icp ms u pb analysis of zircon was conducted hafnium isotope data was also acquired through laser ablation multicollector icpms analysis of zircon with the aim of gaining insight into the age and nature of the source region of the plutons three age groups have been identified from seven granite samples early middle triassic 245 to 229 ma late triassic 219 to 216 ma and cretaceous 105 to 95 ma hafnium analysis shows the triassic granites to have negative and variable e hf values and mesoproterozoic 1 6 ga depleted mantle model ages which is interpreted to reflect derivation from an isotopically heterogeneous largely crustal source the cretaceous granite shows higher and less variable e hf values and slightly younger model ages 1 3 ga and is interpreted to be derived from melting of a more homogeneous crustal source a depleted mantle model age of 1 5 ga is calculated from the pooled triassic and cretaceous samples the source region for these magmas may be tentatively correlated with mesoproterozoic material of the yangtze craton which has been suggested to underlie the yidun arc however further work is necessary to demonstrate this suggestion

seismic earth pressure on retaining structures a simple kinematic method to predict the seismic earth pressure against retaining structures is developed the fundamental solution to the free field seismic response considering nonlinear plastic behavior of soil is included in the retaining wall analysis for the first time perturbation to the free field response caused by soil structure interaction effects for different types of wall movement is considered results from this kinematic method are compared with those obtained from finite element analysis and observed from laboratory shaking table tests performed on model retaining walls

design of driven piles in sand estimation of the axial capacity of piles driven into sand involves considerable uncertainty and design rules are generally not consistent with the physical processes involved this paper reviews current understanding of the factors that determine the axial capacity of piles driven into sand and outlines a new framework for design which takes account of the physical processes is consistent with the existing database of load test results and is sufficiently flexible to permit refinement as new data become available it allows for the effects of confining stress on the frictional and compressibility characteristics of sand and hence on end bearing capacity in keeping with field observations shaft friction is assumed to degrade with driving of the pile past a particular location from an initial maximum value linked to the local end bearing capacity the resulting design approach is compared with field data and effects of factors such as the direction of loading are discussed l estimation de la resi

response of sands to multidirectional dynamic loading in centrifuge tests abstractdynamic centrifuge tests were performed to investigate multidirectional loading effects on the shear and volumetric response of saturated sands under partially drained level ground conditi

carbonates and cementation of glacially derived cohesive soils in new york state and southern ontario cet article presente des resultats se rapportant a la teneur en carbonate de silts et d argiles naturels en fonction de la profondeur de l emplacement geographique et de l origine geologique on etudie aussi l influence de cette teneur en carbonate sur le comportement geotechnique l effet sur la pression de preconsolidation apparente est illustre en detail pour l un des sites etudies la repartition des carbonates a l interieur des varves d un depot glacio lacustre est egalement presentee pour demontrer la variabilite potentielle de la cimentation naturelle des sols les donnees en provenance de quinze sites etayent les relations proposees entre teneur en carbonate et pression de preconsolidation apparente

interpretation of cone penetration testing in silty soils conducted under partially drained conditions abstractthe standard penetration rate used in cone penetration tests cpts is 20 mm s regardless of soil type which yields fully drained penetration in sand and fully undrained penetration in clay however for silty soils that represent an intermediate grain size composition and unique characteristics compared with sand and clay the standard rate of penetration results in partially drained penetration often leading to misinterpretation of this soil type in this study 15 cpts with penetration rates varying from 0 5 to 60 mm s were performed at a test site in northern denmark where the subsoil consisted primarily of sandy silt with clay bands the results illustrated that when the penetration rate is reduced the cone resistance increases but the pore pressure decreases the transition between undrained and fully drained penetration was determined by converting the results into a normalized penetration rate also evaluated and presented in this paper is how cone resistance obtained under parti

the kinetic friction of snow three components of the kinetic friction of snow are described but only the lubricated component of friction is treated in detail this component depends upon the thickness of water films which support a slider on snow grains over a small fraction of its area the thickness of the film decreases with ambient temperature in a manner which is sensitive to the thermal conductivity of the slider the minimum value of friction at any temperature is reached at an intermediate value of speed because friction decreases as the slider first begins to move and the films form but then increases at higher speeds because of the shear resistance at sub freezing temperatures a small area in the front part of the slider is dry and the friction is high once the water film is formed it increases in thickness towards an equilibrium value which can be very sensitive to slider properties speed and temperature it appears that the mechanisms may be very different for hydrophobic and hydrophilic sliders from the equations derived here it is clear why friction decreases with repeated passes over the same snow

zircon u pb ages and hf isotope compositions of the neoproterozoic magmatic rocks in the helan mountains north china the periodic dispersal and assembly of continental fragments has been an inherent feature of the continental crust based on the discovery of large scale supercontinent cycle and the theory of plate tectonics several supercontinents have been identified such as columbia nuna rodinia gondwana and pangaea neoproterozoic magmatic events related to the break up of rodinia are globally well preserved although neoproterozoic magmatic events were very weak in the north china craton ncc they are crucial in reconstructing the geometries of the ncc and could facilitate the completion of the neoproterozoic configuration of the supercontinent in this study c 853 835 ma magmatic rocks are identified in the western margin of the ncc precise zircon u pb age determination yields 206pb 238u average ages of 835 5 5 3 ma hl 39 and 853 7 4 5 ma hl 30 in situ zircon hf isotope compositions of the samples reveal that their parental magma was formed by the reworking of ancient crust evolved from mesoproterozoic mantle in summary the discovery of neoproterozoic magmatic rocks in the western margin of the ncc and reported synchronous rocks in other parts of the ncc indicate that the ncc might be conjoined with the supercontinent rodinia during the neoproterozoic this discovery is of significant help in unravelling the early neoproterozoic history of the ncc and the evolution of the supercontinent rodinia

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

discrete element model dem simulations of cone penetration test cpt measurements and soil classification this paper presents a study on the simulation of cone penetration tests cpts using the discrete element model dem method this study s main objective is to investigate the effect of different m

cone penetration testing in snow the application of the electric cone penetrometer test in snow has been investigated and compared with results from the ram penetrometer test which is normally used for snow profiling and slope stability analysis a special cone penetrometer system was built consisting of a sensitive 1 cm2 electric cone depth transducer and battery operated chart recorder the instruments were tested in april 1985 at three different locations in the swiss alps and the test results were compared with those of the ram penetrometer tests the tests yielded repeatable results up to a depth of 4 m with a high resolution of different snow layers the electric cone tests show more layers than found in the ram profile and snow pit analyses in soft snow the ram resistances appear to be on average about 30 lower than cone resistance values recommendations are given for the future use of electric cone penetration testing in snow key words snow snowpack analysis cone penetration test ram penetrometer cone resistance ram

determination of erosion thickness by numerical back analysis the case study of badenian clays in the carpathian foredeep czech republic abstract the paper describes an application of the geotechnical numerical back analysis in estimating the thickness of eroded sedimentary overburden in shallow basinal sediments the approach is based on the back analysis of the coefficient of earth pressure at rest k 0 and on estimating the unloading from the obtained k 0 value this approach is compared with the conventional methods represented by baldwin butler s compaction curves and casagrande s concept of preconsolidation stress the results of these two commonly used methods are incorrect if the sedimentary profile is affected by ageing effects such as cementation secondary compression etc the method is demonstrated on the lower miocene marine clay often called tegl which was deposited in the carpathian foredeep in the vicinity of brno czech republic the numerical back analysis was applied to galleries and adits opened during site investigation of the kralovo pole tunnels in brno the application of baldwin butler s equation suggested the erosion thickness of 180 270 m and casagrande s method of 100 800 m while the numerical back analysis of 0 40 m

episodic growth of the gondwana supercontinent from hafnium and oxygen isotopes in zircon it is thought that continental crust existed as early as 150 million years after planetary accretion but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records for example the striking global peaks in juvenile igneous activity 2 7 1 9 and 1 2 gyr ago imply rapid crustal generation in response to the emplacement of mantle super plumes rather than by the continuous process of subduction yet uncertainties persist over whether these age peaks are artefacts of selective preservation and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle these model ages are only meaningful if the host magma lacked a mixed or sedimentary source component but the latter can be diagnosed by oxygen isotopes which are strongly fractionated by rock hydrosphere interactions here we report the first study that integrates hafnium and oxygen isotopes all measured in situ on the same precisely dated detrital zircon grains the data reveal that crust generation in part of gondwana was limited to major pulses at 1 9 and 3 3 gyr ago and that the zircons crystallized during repeated reworking of crust formed at these times the implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts

the behavior of a compressible silty fine sand publications associated with sands are often limited to clean i e little fines content uniform uncemented silica or quartz sand on the other hand the importance of mineral content particle

coefficient of earth pressure at rest for sands subjected to vibration an oedometer instrumented to measure horizontal pressure was used to examine the behavior of the coefficient of earth pressure at rest ko of clean sands subjected to vertical vibration reconstit

behavior of hydrocarbon reservoir sands and sandstones most new oil and gas reservoirs are discovered in sands and weak sandstones and the petroleum industry has therefore generated an extensive amount of data from laboratory tests on these materials some of these data are reexamined in this paper within the context of recent soil mechanics research of key importance to petroleum engineers is the compressibility of the sands and this is shown to be related both to the current density and stress level of the soil and to the location of its normal compression line when present the cement bonds between the particles appear to be weaker than the particles themselves so that the major yield point during compression is still associated with breakage of the particles rather than of the cement bonds the paper also examines the behavior of the sands and sandstones in shearing allowing a more general understanding of the mechanics of the materials to be developed

relating shaft friction of buried piles and cpt resistance in clayey sands this paper examines factors controlling the ultimate shaft friction developed on buried piles in normally consolidated clay sand mixtures and explores the relationship between this friction and the

the source of granitic gneisses and migmatites in the antarctic peninsula a combined u pb shrimp and laser ablation hf isotope study of complex zircons zircons gneisses and migmatites collected from the antarctic peninsula have different core rim hafnium isotope ratio relationships depending on whether evidence for zircon dissolution is present or absent two samples contain inherited zircon that is partially dissolved in these samples the 176hf 177hf rations of the inherited zircon and new magmatic zircon rims are on average indistinguishable and consistent with in situ melting in such cases the hafnium isotopic composition of the melt was probably strongly influenced by the dissolved zircon component at the source variation in 176hf 177hf within the magmatic zircon rims from grain to grain suggests that hf isotopes were only partially homogenized during melt migration alternatively zircon growth may have taken place within small volumes of partial melt other samples do not preserve textural evidence for zircon dissolution during melt generation in these samples the 176hf 177hf values of the inherited zircon and new magmatic zircon rims are different the zircon rims apparently suggest a source of less evolved hafnium than that contained within the inherited zircon whether this relates to a separate juvenile source or alternatively is derived from minerals other than zircon at the source cannot be resolved inherited zircon irrespective of age has been strongly influenced by the reworking of a juvenile late mesoproterozoic source suggesting that such crust underlies the antarctic peninsula our results therefore suggest that hf isotope analyses provide great potential for future studies investigating the source and processes involved in the generation of crustal melts

earth pressures against rigid retaining walls this paper outlines the results of unique shaking table experiments to determine neutral and active static and dynamic stresses and the points of application of corresponding total thrust generated by granular soils against rigid retaining walls and compares the experimental data with the well known coulomb and mononobe okabe equations a new criterion is proposed for identification of the wall deformation level at which the active state of stress develops this criterion states that active stress develops when the angle of friction between the wall and the backfill soil reaches its maximum value based on the above criterion experimental results show that the backfill soil enters the active state at much lower wall displacement levels than generally believed an equation is proposed for calculating the displacement necessary to initiate active static or dynamic stress this equation reveals that the displacement necessary to initiate active state increases with the height of the wall and decreases with backfill soil strength

components and episodic growth of precambrian crust in the cathaysia block south china evidence from u pb ages and hf isotopes of zircons in neoproterozoic sediments abstract detailed lam icpms u pb dating and lam mc icpms lu hf isotope analysis were carried out on zircons from nine samples of basement metamorphic rocks in the southern cathaysia block south china the chemical compositions of these metamorphic rocks and zircon morphology indicate that their protoliths were sedimentary zircon u pb dating results show they mainly formed during the late neoproterozoic the precambrian crust of the cathaysia block can be divided into two distinct tectonic domains the wuyishan terrane to the northeast and the nanling yunkai terrane to the southwest the nearly e w boundary between these two terranes is also supported by geophysical petrological and geochemical evidence and the basement rocks of the two terranes are comprised of different components the wuyishan terrane is characterized by dominant paleoproterozoic 1 86 ga and lesser neoarchean magmatism and the southern central part of the terrane suffered strong neoproterozoic and early paleozoic tectonothermal reworking the zircon data suggest that there were five important episodes of juvenile crust generation 3 6 ga 2 8 ga 2 6 2 4 ga 1 85 ga and 0 8 0 7 ga in the wuyishan terrane strong paleoproterozoic 1 85 ga magmatism in northern wuyishan and neoproterozoic 0 8 0 7 ga magmatism in central and southern wuyishan both principally involved the remelting of old crust with minor input of juvenile material in contrast the nanling yunkai terrane contains abundant neoarchean and grenvillian zircons some evidence of mesoproterozoic activity and rare paleo to meso archean and neoproterozoic zircons u pb ages and hf isotopic compositions of the detrital zircons from the late neoproterozoic to early paleozoic meta sedimentary rocks in the nanling yunkai area suggest that the growth of juvenile crust mainly occurred at 3 6 ga 3 3 ga 2 5 2 6 ga 1 6 ga 1 0 ga and 0 8 0 7 ga neoarchaean 2 6 2 5 ga grenvillian 1 0 ga and neoproterozoic 0 8 0 7 ga magmatism mainly involved the recycling of old crust minor remnants of 4 1 ga crust may remain in the terrane this crustal history is distinct from that of the wuyishan terrane and analogous to those recorded for the eastern india east antarctic domain of northern gondwanaland suggesting that they probably were once linked

growth and reworking of the early precambrian continental crust in the north china craton constraints from zircon hf isotopes abstract we synthesize more than 2600 hf isotope data on the archean paleoproterozoic zircons from the north china craton ncc recalculation of the data based on single stage and two stage hf model ages of the eastern block of the ncc shows peak ages of 3902 13 ma and 3978 18 ma respectively and also small peaks at 3 5 4 0 ga the majority of zircon ehf t values are positive suggesting the possibility of the crust and the mantle differentiation at ca 3 9 4 0 ga in the eastern block of the ncc most magmatic zircons from the whole of ncc have their hf model age range of 2 4 2 9 ga and the single stage model ages is cluster at 2698 4 ma whereas the two stage model ages concentrate at 2714 5 ma implying that the protoliths were juvenile crustal rocks the most prominent peak at 2 7 ga indicates that this period marks the most important stage of the crust mantle differentiation and crust formation of the ncc the widespread 2 5 ga rocks in the ncc and the absence of the 2 5 ga peaks in hf model ages are consistent with the partial melting and reworking of the juvenile rocks at 2 5 ga furthermore the 2 5 1 7 ga zircon hf isotope features are also related to the reworking of the crustal rocks our results from the integration of a large database suggest that the eastern block and the trans north china orogen have undergone similar crust mantle differentiation and magmatism leading to the conclusion that the essential cratonization of the north china took place at the end of neoarchean

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

hf nd o isotopic evidence for melting of recycled sediments beneath the sulu orogen north china article the mantle source of late mesozoic mafic magmas in the southeastern north china craton is generally con sidered to have been enriched by deeply subducted continental lithosphere of the yangtze block the mechanisms through which enrichment occurs are still unclear here we document an early cretaceous zircon u pb age at 115 2 ma dioritic intrusion with some geochemical features similar to sanukitoids i e al2o3 n 17 5 ba 1692 1819 ppm sr 1042 1111 ppm and 18 ozircon 6 2 0 2 f rom the sulu orogen in north china compared with the regional older 120 130 ma mafi cm agmas dykes the diorite has less radiogenic sr 87 sr

behaviour of a sensitive marine sediment microstructural investigation the aim of this study is to characterise along various stress paths the microstructural evolution of a deep water marine sediment from the gulf of guinea gog results obtained at the macroscopic level have shown that the phenomenological behaviour of the gog sediment is explained by the properties of remoulded samples given by the isotropic and critical state lines and by the properties of the intact samples given by the damage evolution of the inter aggregate bonds microstructural investigations conducted by mercury intrusion porosimetry and scanning electron microscopy demonstrate that the volumetric strains measured at the macroscopic level come from inter aggregate pore variations associated with the degrading of the inter aggregate bonds the mechanism responsible for reorienting the particles appears to apply in the case of the remoulded sediment as for the natural sediment it is first necessary to increase the isotropic consolidation stress towards higher values in order to break the bonds between the aggregates before it becomes possible to activate the particle reorientation mechanism and thus approach the remoulded behaviour

earth pressure at rest of sovind marl a highly overconsolidated eocene clay abstract the present study evaluated the earth pressure at rest k 0 of sovind marl a highly overconsolidated eocene clay this clay exhibits extremely high plasticity indices of up to 300 a highly fissured structure and preconsolidation stresses up to 6800 kpa continuous loading oedometer clo tests at a constant rate of strain were performed in the danish clo apparatus this apparatus applies test water at 200 kpa and measures total horizontal stresses via pressure gauges placed in a stiff oedometer ring horizontal and vertical stresses were measured from in situ stresses to various stress levels to estimate continuous k 0 development in the clay normally consolidated earth pressures at rest were 0 42 and 0 68 for sovind marl at two different ages overconsolidated k 0 k 0 oc reached values as high as 6 to 8 in the in situ stress range the correlation between k 0 oc and the overconsolidation ratio ocr reported by meyerhof in 1976 was inconsistent with the k 0 oc development of sovind marl however the development of ocr in the laboratory under the previously applied test stresses ocr lab as an alternative to preconsolidation stresses showed congruent results regardless of sample age when an value of 1 05 was used

influence of placement method on the in situ density of hydraulic sand fills the range of densities achievable by hydraulic placement of sand straddles the boundary between values giving acceptable potential performance and those giving unacceptable potential performance this has led to concerns over the safety of structures using hydraulic fills such as the artificial drilling islands in the canadian beaufort sea liquefaction failures of hydraulically placed sand have occurred at four or more of these islands until recently the factors affecting in situ density were little understood data obtained from several artificial islands are presented and these are used to demonstrate the overwhelming influence of method of placement on in situ density the possible reasons for this influence and the implications for design are discussed recommendations are made for research that together with conclusions drawn in the paper should allow hydraulic fills to be used with more confidence in the future key words sand hydraulic fill liquefaction cone penetration test

rate effects on penetrometer resistance in kaolin this paper describes the results from a centrifuge investigation into the rate dependence of t bar and ball penetrometer resistance in kaolin four t bar diameters and two ball diameters were installed in kaolin with overconsolidation ratios of 1 2 and 5 at penetration velocities varying over five orders of magnitude the penetration resistances are compared with the properties of kaolin as measured in element tests to assist in the development of a framework that describes this resistance over the full velocity range consistent trends emerge when the soil viscosity is assumed to affect the penetration resistance in both the partially drained and undrained conditions enabling the dependence of the t bar and ball resistances on diameter velocity and soil characteristics to be quantified

soil behaviour through field instrumentation an improved version of the observational method is developed and proposed the method uses field measurements as the direct inputs to the framework of the constitutive behaviour and analyses the be

provenance of late palaeozoic metasediments of the sw south american gondwana margin a combined u pb and hf isotope study of single detrital zircons combined u pb and lu hf isotope measurements of single detrital zircon grains in carboniferous metasediments from patagonia delineate the source areas of the sediments the detritus represented by four metasandstone samples was deposited prior to onset of subduction in late carboniferous time along the south patagonian proto pacific gondwana margin a broad series of detrital zircon age peaks 0 35 0 7 ga 0 9 1 5 ga and a large spread 0 3 3 5 ga in the age spectra require numerous sources a fifth metasediment was deposited after the onset of subduction this syncollisional sample shows two distinct u pb age peaks at c 290 ma and 305 ma this points to a few sources only patagonia west antarctica initial hf isotope compositions of selected u pb dated zircons from the carboniferous metasediments reveal zircon protoliths originating from both recycled crust and juvenile sources ehf t 0 4 3 5ga 14 to 12 a comparison with crustal compositions of possible source areas indicates that the detritus mainly originated from the interior of gondwana extra andean patagonia the argentine sierra de la ventana southernmost africa east antarctica as well as northern chile and northwestern argentina the sediment transportation paths are consistent with an autochthonous palaeogeographical position of patagonia with respect to gondwana in carboniferous time

in situ lateral stress measurement in glaciolacustrine seattle clay using the pressuremeter pressuremeter testing was conducted for the state route sr 99 bored tunnel project in seattle washington to estimate in situ soil stress deformation parameters along the tunnel alignment many of the tests were conducted in a very stiff to hard glaciolacustrine clay known as seattle clay this unit is historically known for deep seated slope failures and many of these failures have been attributed to the release of high locked in lateral stresses estimation in situ lateral stresses along the tunnel alignment was a primary focus of the exploration program due to the hard consistency of this unit and the potential for cobbles neither self boring pressuremeter nor dilatometer testing was feasible therefore prebored pressuremeter testing was used using several lateral stress estimation techniques including a novel in situ creep testing approach the in situ lateral stresses in the seattle clay were estimated to be significantly higher than what would be expected by assuming a simple laterally constrained vertical loading and unloading stress path due to glaciation deformational features commonly encountered in seattle clay indicate its stress history also has included significant lateral shearing the memory of this shearing within the fabric of the clay may influence the in situ stress state and response to lateral unloading

seismic passive earth pressures in soils seismic passive earth pressure coefficients were computed by the method of limit equilibrium using a pseudostatic approach for seismic forces composite curved rupture surfaces were considered in the analysis while earlier studies using this type of analysis were mainly for sands seismic passive earth pressure coefficients were obtained in the present study considering the effects of cohesion surcharge and own weight the minimum seismic passive force was obtained by adding the individual minimum values of these components and the validity of the principle of superposition was examined other parameters considered in the analysis were wall batter angle ground surface slope soil friction angle wall friction angle wall adhesion to soil cohesion ratio and horizontal and vertical seismic accelerations the seismic earth pressure coefficients were found to be highly sensitive to the seismic acceleration coefficients both in the horizontal and vertical directions results of the study are presented in the form of figures and tables comparisons of the proposed method with available theories in the seismic case are also presented

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

analysis of piezocone penetration under different drainage conditions with the two phase material point method abstractthe piezocone penetration test cptu is commonly used to identify a soil s profile and estimate its material properties depending on the soil type ranging from clay to sand undrained partially drained or drained conditions may occur during cone penetration in silt and sand clay mixtures the cptu penetration is characterized by partially drained conditions which are often neglected in data interpretation the effect of drainage on cptu measurements has been mainly studied experimentally numerical analyses are rare because taking into account large soil deformations soil water and soil structure interactions and nonlinear soil behavior is still a challenging task this paper presents and discusses numerical simulations of cptu in saturated soils with the two phase material point method soil behavior is described with the modified cam clay model this study investigates the effects of pore pressure dissipation during penetration cone roughness and horizontal stress state comparing the