thermal history of the h chondrite parent body implications for metamorphic grade and accretionary time scales abstract multiple temperature age constraints for eight h chondrite samples have been used to provide insight into the thermal history of their parent body through combination with numerical models of thermal evolution assuming internal heating by 26al and conductive cooling the effect of spreading accretion out over time is the principal focus of this work a wide range of body size and date of accretion is systematically tested for different values of accretion rate in order to quantify and illustrate the parameter space that is consistent with the available thermo chronological data we conclude that the h chondrite samples considered have a thermal history consistent with a parent body that at some stage had a concentric onion shell internal structure that body had a radius no larger than 130 km and accretion most probably took place over a time interval on the order of 0 0 0 2 myr approximately 2 myr after cai condensation in any case the time interval of accretion is unlikely to have been more than 0 5 myr supporting evidence in favour of rapid accretion possibly through reassembly of the fragments of an earlier generation of bodies furthermore the h chondrites studied here are inferred to have come from a wide depth range within the body where they experienced metamorphism indicating that preservation of the onion shell structure is unlikely the presence of an insulating regolith does not modify this conclusion as appropriate thermal histories for the three h6 samples considered cannot be reproduced at depths near the surface asteroid 6 hebe may be the parent body of the h chondrites but the high bulk density of the latter is difficult to reconcile with a rubble pile structure of pure h chondrite material finally optimized thermal histories are used to constrain the temperatures characterizing boundaries between petrological types 800 1000 and 1140 k for the h3 4 h4 5 and h5 6 boundaries respectively in detail the type 6 samples studied here are inferred to have experienced a similar peak temperature on the order of 1180 k but spent different times at that temperature while samples of lower metamorphic grade experienced different peak temperature but spent more or less the same time within 10 k of peak temperature on the order of 1 ma these results constitute a quantitative framework within which variations in petrographic and textural properties may be interpreted

diffusion kinetics of fe2 and mg in aluminous spinel experimental determination and applications the diffusion coefficients of fe2 and mg in aluminous spinel at 20 kb 950 to 1325 c and at 30 kb 1125 c have been determined via diffusion couple experiments and numerical modeling of the induced diffusion profiles the oxygen fugacity fo2 was constrained by graphite encapsulating materials the retrieved self diffusion coefficients of fe2 and mg at 20 kb 950 to 1325 c fit well the arrhenian relation d d0exp q rt where q is the activation energy with d0 fe 1 8 2 8 10 5 d0 mg 1 9 1 4 10 5 cm2 s q fe 198 19 and q mg 202 8 kj mol comparison with the data at 30 kb suggests an activation volume of 5 cm3 mol from analysis of compositional zoning in natural olivine spinel assemblages in ultramafic rocks previous reports concluded that d fe mg in spinel with cr cr al 0 5 is 10 times that in olivine the diffusion data in spinel and olivine have been applied to the problems of preservation of mg isotopic inhomogeneity in spinel within the plagioclase olivine inclusions in allende meteorite and cooling rates of terrestrial ultramafic rocks

evolution of protoplanetary disk inferred from 26 al chronology of individual chondrules abstract we review the 26al ages of chondrules in various type 3 0 chondrites the 26al ages of chondrules are 1 3 myr after calcium aluminum rich inclusion cai for ll3 0 co3 0 and acfer 094 ungrouped c 3 0 available data for chondrules in cr chondrites indicate that many chondrules are relatively younger 3 myr although data from chondrules in cr3 0 are not yet available to confirm their younger ages the total ranges for the 26al ages of chondrules in a single chondrite group are more than 0 5 1 myr however most chondrules show relatively narrow range of ages in a single chondrite group 0 2 0 4 myr 1 sd which might be short enough to preserve the group specific chemical and isotope signatures against radial diffusion of solid in the disk distinct oxygen isotope reservoirs might exist in the protoplanetary disk simultaneously which could be spatially separated

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

live iron 60 in the early solar system isotopic analyses of nickel in samples from the differentiated meteorite chervony kut revealed the presence of relative excesses of 60ni ranging from 2 4 up to 50 parts per 104 these isotopic excesses are from the decay of the now extinct short lived nuclide 60fe and provide clear evidence for the existence of 60fe over large scales in the early solar system not only was 60fe present at the time of melting and differentiation that is fe ni fractionation of the parent body of chervony kut but also later at the time when basaltic magma solidified at or near the surface of the planetesimal the inferred abundance of 60fe suggests that its decay alone could have provided sufficient heat to melt small diameters of several hundred kilometers planetary bodies shortly after their accretion

field experiments and numerical simulations of confined aquifer response to multi cycle recharge recovery process through a well summary shanghai is one of the cities suffering from land subsidence in china land subsidence has caused serious financial losses thus artificial recharge measures have been adopted to compensate the drawdown in shallow confined aquifers and thereby control land subsidence in this study a multi cycle recharge recovery field experiment was performed to investigate the response of a shallow confined aquifer to artificial recharge through a well in the experiment a series of recharge recovery cycles with different recharge volumes and durations with and without artificial pressure were performed the water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi cycle recharge recovery process meanwhile a finite difference method fdm numerical model was established and its parameters were obtained via a reversed numerical analysis on the experimental data the responses of the shallow confined aquifer to the multi cycle recharge recovery process were simulated in detail using the model the calculation results showed that the water level dropped significantly when the recharge ended moreover the efficiency of a multi cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time the relationship between recharge frequency and efficiency expressed as h 0 29498 f 0 40163 and r 2 0 97264 respectively was obtained through the fdm numerical simulation in the recharge intervals the optimal recharge efficiency was achieved when the water level rose to 40 of the peak

a short duration of chondrule formation in the solar nebula evidence from 26al in semarkona ferromagnesian chondrules abstract the 26 al 26 mg systems of five ferromagnesian chondrules from the least metamorphosed ordinary chondrite semarkona ll3 0 were studied using a secondary ion mass spectrometer their glass or plagioclase portions contain excesses of 26 mg and in two chondrules the 26 mg excesses are well correlated with 27 al 24 mg which demonstrates the in situ decay of 26 al the initial 26 al 27 al ratios in these chondrules obtained from the slope of isochrons show a narrow range of between 6 10 6 and 9 10 6 indicating their short formation duration of less than 1 my if the solar nebula was initially homogeneous in al isotopes the chondrule formation ages are 2 my younger than those of cais our results based on the study of the least metamorphosed uoc are consistent with the previous studies on al rich chondrules that the chondrule formation started at least 2 my after cais alternatively the older records before 2 my were erased by chondrule recycling process it further suggests that the young apparent ages 3 to 5 my after cais for chondrules in type 3 4 uocs are due to the disturbance of the 26 al 26 mg system possibly during parent body metamorphism the result is not consistent with the extended nebular time scale of 5 my and the chondrule formation by planetary processes the ni isotopic analysis of the feo rich olivines in a type ii chondrule in semarkona did not show any detectable excess 60 ni in spite of their high fe ni ratios the upper limit of the initial 60 fe 56 fe ratio of the solar system was estimated to be 3 4 10 7 which is consistent with the previous estimate 0 2 1 9 10 7 from eucrites this result confirms that the 60 ni excess previously observed from cais was not due to the decay of the short lived nuclide 60 fe but a ni isotopic anomaly of nucleosynthetic origin

60fe 60ni systematics in the eucrite parent body a case study of bouvante and juvinas abstract eucrites are basaltic meteorites that cooled rapidly but are in many instances thermally metamorphosed and impact brecciated the exact timing of these events remains unclear in this study ni isotopic compositions and fe ni elemental ratios are presented for two non cumulate eucrites bouvante and juvinas including mineral separates from the latter the samples are characterized by variable well resolved 60 ni excesses consistent with the former presence of live 60 fe t 1 2 2 62 ma at the time of eucrite crystallization a significant fraction of ni with a terrestrial like composition appears to be surface correlated this ni may be the product of terrestrial contamination or was introduced by a chondritic impactor during brecciation altogether the data provide evidence for a complex and probably multi stage history of fe and or ni redistribution which impedes the interpretation of the chronological data

thermal metamorphic history of a ca al rich inclusion constrained by high spatial resolution mg isotopic measurements with nanosims 50l abstract mg isotope data were collected by nanosims with high precision and high spatial resolution from a coarse grained type b ca al rich inclusion cai ek1 6 3 in the allende cv3 chondrite to evaluate the time scale of parent body thermal metamorphism the cai melilite and fassaite contain excesses of 26mg 26mg from the in situ decay of 26al the inferred initial ratio 26al 27al 0 5 8 2 4 10 5 is consistent with many previously reported coarse grained cais from cv chondrites e g macpherson et al 1995 however the anorthite has heterogeneous 26al 27al 0 ranging from 1 8 10 5 to 3 3 10 6 the 26al 26mg systematics within the anorthite is consistent with thermal diffusion of mg isotopes during metamorphism we also show that the heterogeneous distribution of 26mg in anorthite could have resulted from thermal diffusion of 26mg over a 0 6 0 8 ma time span mg diffusion thus may be responsible for the 26al 27al 0 heterogeneity within anorthite in cais

bleached chondrules evidence for widespread aqueous processes on the parent asteroids of ordinary chondrites we present the first detailed study of a population of texturally distinct chondrules previously described by kurat 1969 christophe michel levy 1976 and skinner et al 1989 that are sharply depleted in alkalis and al in their outer portions these bleached chondrules which are exclusively radial pyroxene and cryptocrystalline in texture have porous outer zones where mesostasis has been lost bleached chondrules are present in all type 3 ordinary chondrites and are present in lower abundances in types 4 6 they are most abundant in the l and ll groups apparently less common in h chondrites and absent in enstatite chondrites we used x ray mapping and traditional electron microprobe techniques to characterize bleached chondrules in a cross section of ordinary chondrites we studied bleached chondrules from semarkona by ion microprobe for trace elements and h isotopes and by transmission electron microscopy chondrule bleaching was the result of low temperature alteration by aqueous fluids flowing through finegrained chondrite matrix prior to thermal metamorphism during aqueous alteration interstitial glass dissolved and was partially replaced by phyllosilicates troilite was altered to pentlandite but pyroxene was completely unaffected calcium rich zones formed at the inner margins of the bleached zones either as the result of the early stages of metamorphism or because of fluid chondrule reaction the mineralogy of bleached chondrules is extremely sensitive to thermal metamorphism in type 3 ordinary chondrites and bleached zones provide a favorable location for the growth of metamorphic minerals in higher petrologic types the ubiquitous presence of bleached chondrules in ordinary chondrites implies that they all experienced aqueous alteration early in their asteroidal histories but there is no relationship between the degree of alteration and metamorphic grade a correlation between the oxidation state of chondrite groups and their degree of aqueous alteration is consistent with the source of water being either accreted ices or water released during oxidation of organic matter ordinary chondrites were probably open systems after accretion and aqueous fluids may have carried volatile elements with them during dehydration individual radial pyroxene and cryptocrystalline chondrules were certainly open systems in all chondrites that experienced aqueous alteration leading to bleaching

overrun length of avalanches overtopping catching dams cross comparison of small scale laboratory experiments and observations from full scale avalanches 1 results from small scale and full scale experiments on avalanche dam interactions are presented and compared these experiments were analyzed with respect to the overrun length i e the distance that the avalanche traveled beyond a catching dam the differences and similarities in the results are discussed through a cross comparison of the small scale experiments and by comparing them with observations from ryggfonn on avalanche dam interactions further we establish a simple relationship that appears to be valid for small scale experiments with granular materials as well as for full scale avalanche experiments the relationship relates the overrun length to the speed of the approaching avalanche and the effective height of the catching dam

ground response to multiple parallel microtunneling operations in cemented silty clay and sand abstractthis paper presents a case history of the successful application of observational method to instruction microtunneling with successive pipe jacking the microtunneling project is the construction of four parallel pipes under guan river in jiangsu china four parallel tunnels with external diameter of 4 160 mm and horizontally spaced at 4 8 m apart were jacked over 450 m in cemented silty clay and sand by two slurry balance microtunnel boring machines mtbm at a depth of 4 6 m under the river bed since the overburden soil is very thin proper control of tunneling operations was of utmost importance for maintaining the stability of the river bed in order to optimize the operation parameters prior to construction under the river bed a field trial was conducted which included measurement of ground surface settlement subsurface settlement and lateral displacement of the subsurface soils as well as excess pore water pressure and earth pressure the relationship between ground response and const

quantified whole section trace element mapping of carbonaceous chondrites by synchrotron x ray fluorescence microscopy 1 cv meteorites abstract we present the application of a new synchrotron based technique for rapid mapping of trace element distributions across large areas of the cv3 meteorites allende and vigarano this technique utilizes the australian synchrotron x ray fluorescence microscopy xfm beam line with its custom designed and built x ray detector array called maia xfm with maia allows data to be collected using a 2 m spot size at very low dwell times 0 1 0 5 ms resulting in maps of entire thin sections in 5 h maia is an energy dispersive detector system with a large collection solid angle which allows full spectral acquisition and high sensitivity hence there is no need to constrain the elements of interest a priori we collected whole section maps 2 cm 1 cm from 3 thick sections of allende and a single map 2 cm 1 5 cm from a thick section of vigarano our experimental conditions provide data for elements with 20 z 40 k shell ca through zr and the l emissions of os ir pt au and pb we illustrate the unique capabilities of this technique by presenting observations across myriad length scales from the centimeter scale down to the detection of sub micrometer particles within these objects our initial results show the potential of this technique to help decipher spatial and textural variations in trace element chemistry between cais chondrules matrix and other chondritic components we also illustrate how these datasets can be applied to understanding both nebular and parent body processes within meteorites

a dual well step drawdown method for the estimation of linear and non linear flow parameters and wellbore skin factor in confined aquifer systems summary in this study a method based on dual well step drawdown test i e a combination of an aquifer and a well performance test for the determination of hydrodynamic parameters namely storage coefficient and hydraulic conductivity mechanical wellbore finite thickness skin factor non linear wellbore and non linear aquifer parameters in an homogeneous confined aquifer is presented in order to put together aquifer and well tests the interpretation procedure is based on the application of superposition principle to a large time logarithmic approximation of the solution the advantages of this method that can be considered an extension of jacob step test 1947 and cooper jacob approximation 1946 are that i it is possible to determine simultaneously aquifer and well properties in a single test ii the method is based on a large time approximation and it is therefore independent from wellbore storage iii if the well skin is absent the aquifer parameters storage coefficient and hydraulic conductivity can be derived just from a single well test iv the interpretation procedure is easy to apply and robust and does not require any specific numeric code or software the same procedure can be easily adapted to gas well testing it is also shown that even in the presence of linear and non linear flow skin effect and wellbore storage the hydraulic conductivity and not the storage coefficient of the aquifer can be correctly estimated by the cooper and jacob 1946 method applied to a single rate pumping test using exclusively the large time drawdown data measured at the pumping well

evaluation of the blocking effect of retaining walls on groundwater seepage in aquifers with different insertion depths abstract in the design of a deep retaining wall it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers in this study both laboratory tests and numerical simulation with finite element method fem were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer the test results indicate that the effective insertion depth ratio j of a retaining wall in shanghai aquifer sand is about 70 a three dimensional numerical model 3d fem was conducted to analyze the laboratory test results the fem results show that fem is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer based on the same aforementioned procedure a 3d fem model is established to investigate the blocking effect in the confined aquifer in shanghai deposit both laboratory test and fem results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio j of retaining structures in an aquifer the optimal value of j approximately 70 is achieved for retaining wall based on the synthetic results from laboratory test fem analysis and the equation of pujades et al for either unconfined aquifers or confined aquifers of shanghai

statistical and hydro mechanical coupling analyses on groundwater drawdown and soil deformation caused by dewatering in a multi aquifer aquitard system abstract groundwater withdrawn in a multi aquifer aquitard system maas may cause vertical cross flow supplement and result in groundwater drawdown and soil deformation in both aquifers and aquitards this study investigates the responses of groundwater and deep soils to dewatering in the maas through statistical and numerical analyses field data of ten pumping tests conducted in the maas in shanghai urban area are collected and a statistical analysis for groundwater drawdown and ground settlement is performed field measurements indicate that the drawdowns are distributed linearly along radial distance in logarithmic coordinates however the ground settlements are disproportional to the drawdowns and show a trilinear distribution along the radial direction to examine the inconsistent distributions of the groundwater drawdown and the ground settlement representative dewatering models are developed numerically and solved explicitly by the coupled biot s three dimensional consolidation theory numerical results of dewatering in maas are compared to those obtained by a non coupling formula moreover effect of a micro confined aquifer on drawdown and soil deformation is discussed it is found that soil compression in each stratum is closely related to the decline of the pore pressure whilst small expansions are observed in early dewatering stages due to the hydro mechanical coupling effect the ground surface settlement near the pumping well obtained by the coupled numerical method is significantly smaller than that by the non coupling formula owing to horizontal and vertical cross flow supplement an additional aquifer embedded in aquitard above the pumping aquifer can relief both the groundwater drawdown and ground surface settlement significantly

cr diffusion in orthopyroxene experimental determination 53mn 53cr thermochronology and planetary applications we have determined cr diffusion coefficients d in orthopyroxene parallel to the a b and c axial directions as a function temperature at f o2 corresponding to those of the wustite iron wi buffer diffusion is found to be significantly anisotropic with d c d b d a conforming to an earlier theoretical prediction increase of f o2 from wi buffer conditions to 4 5 log unit above the buffer at 950 and 1050 c leads to decrease of d cr by a factor of two to three possibly suggesting significant contribution from an interstitial diffusion mechanism we have used the diffusion data to calculate the closure tem peratures tc of the mn cr decay system in orthopyroxene as a function of initial temperature t0 grain size a and cooling rate for spherical and plane sheet geometries we also present graphical relations that permit retrieval of cooling rates from knowledge of the resetting of mn cr ages in orthopyroxene during cooling t0 and a application of these relations to the mn cr age data of the cumulate eucrite serra de mageyields a tc of 830 980 c and cooling rates of 2 27 c myr at tc and 1 13 c myr at 500 c it is shown that the cooling of serra de mageto the closure temperature of the mn cr system took place at its original site in the parent body and thus implies a thickness for the eucrite crust in the commonly accepted hed parent body vesta of greater than 30 km this thickness of the eucrite crust is compatible only with a model of relatively olivine poor bulk mineralogy in which olivine constitutes 19 7 of the total asteroidal mass

a laboratory study of the retarding effects of braking mounds on snow avalanches a series of laboratory experiments in a 6 m long chute using glass particles of mean diameter 100 m were performed to investigate the interaction of a supercritical granular flow with obstacles it was found that the collision of the flow with a row of mounds led to the formation of a jet whereby a large fraction of the flow was launched from the top of the mounds and subsequently landed back on the chute the retarding effect of the mounds was investigated quantitatively by direct measurements of the velocity of the flow its runout length and the geometry of the jet the effects of several aspects of the layout of the mounds on their retarding effects were examined it was observed that a row of steep mounds with an elongated shape in the transverse direction to the flow and with a height several times the flow depth led to dissipation of a large proportion of the kinetic energy of the flow

responses of retaining wall and surrounding ground to pre excavation dewatering in an alternated multi aquifer aquitard system abstract pre excavation dewatering ped is an important construction stage in deep excavation field measurements show that retaining walls can develop obvious deflections during ped which has been rarely considered in the past the characteristics of ped induced wall deflection and the relationship of this deflection to surrounding ground deformation are still unclear in this study a ped test is simulated by a numerical model the model is verified by field observations and used to investigate the responses of retaining wall and surrounding ground to ped results indicate that the maximum wall defection hm and surface settlement vm can all reach centimeter level under common conditions of ped the ratio of vm to hm varies at the range of 0 45 0 67 wall and soil deformations will be more obvious if the soils within the dewatering depth hd have better permeability the relative positions between hd and strata i e aquifer or aquitard have great influence on the ped induced deformations if an aquifer appears below hd further increasing hd can induce a rapid growth of wall and soil deformations if thick aquitard appears below hd the deformation increments by further increasing hd are not apparent however once hd exceeds the center of the thick aquitard and reaches a thick confined aquifer the wall deflections and soil deformation zones behind the wall will enlarge significantly meanwhile a large bending moment in the retaining wall will arise around the bottom of the confined aquifer the designers should consider this condition and allocate enough steel rebars there preventing the appearance of wall cracks in the confined aquifer

ground settlements and drawdown of the water table around an excavation in the vicinity of an excavation in a saturated soil ground settlements are often caused by the combined effects of stress release and drawdown of the water table these settlements may be crucial if the excavation is carried out in a congested area a case history of excavation adjacent to closely constructed blocks of buildings is discussed in this study ground settlements and water surface levels were monitored during the excavation period as the settlement of the surrounding area was of concern the authors have previously developed a fully coupled numerical method that allows the computation of the displacements and pore pressures in a soil taking account of the drawdown of the water table which may accompany excavation this method is used here for back analysis of a full scale excavation that has been comprehensively documented comparisons between the field measurements and the calculated results are given in this paper key words consolidation excavation finite element seepage transient

numerical study on the responses of groundwater and strata to pumping and recharge in a deep confined aquifer abstract groundwater drawdown and strata settlements induced by dewatering in confined aquifers can be relieved by artificial recharge in this study numerical simulations of a field multi well pumping recharge test in a deep confined aquifer are conducted to analyze the responses of groundwater and strata to pumping and recharge a three dimensional numerical model is developed in a finite difference software which considers the fluid mechanical interaction using the biot consolidation theory the predicted groundwater drawdown and ground settlements are compared to the measured data to confirm the validation of the numerical analysis of the pumping and recharge both numerical results and measured data indicate that the effect of recharge on controlling the groundwater drawdown and strata settlements correlates with the injection rate and well arrangements since the groundwater drawdown induced by pumping can be controlled by artificial recharge soil compression can be relieved by reducing the changes of effective stress of the soils consequently strata settlement induced by pumping can be relieved by artificial recharge and ground settlements can be eliminated if an appropriate injection rate and well arrangement are being determined moreover the changes of the pore pressure and seepage force induced by pumping and recharge will also result in significant horizontal deformations in the strata near the recharge wells

field tests of pumping recharge technology for deep confined aquifers and its application to a deep excavation abstract the execution of deep excavation above confined aquifers asks for dewatering measurements to reduce the hydrostatic pressure so that the safety of the deep excavation can be assured dewatering will inevitably cause deformations in the surrounding strata to reduce the dewatering induced strata movement an innovative pumping recharge technology has been developed in which the dewatering is carried out in the excavation and the recharge is conducted near the protected facilities however the capacity and efficiency of this technology in deep confined aquifers need to be further investigated this paper presents two in situ pumping recharge tests in a deep confined aquifer under a deep foundation pit the feasibility of artificial recharge in the deep confined aquifer has been verified by conducting a single well pumping and multi well recharge test with different discharge and injection rates then a multi well pumping recharge test was carried out in accordance with the requirement and circumstance of construction to evaluate the capacity and efficiency of recharge in controlling the drawdown and ground settlement the results showed that multi well recharge could form a water curtain which has a water proof function to reduce the groundwater drawdown meanwhile by controlling the groundwater head of the confined aquifer during the recharge the pumping induced settlement of the surrounding area can be reduced or even eliminated the pumping effect in the pit would be affected by the recharge around the protected facilities so it is necessary to take in situ pumping recharge tests to determine the layout of wells and the discharge and injection rate finally the artificial recharge was applied to the construction of a deep excavation in shanghai and the drawdown and the ground settlement around the protected buildings were effectively controlled by recharge

fossil records of high level of 60fe in chondrules from unequilibrated chondrites abstract the short lived now extinct nuclide sln 60fe which decays to 60ni with a half life of 2 62 ma is uniquely of stellar origin hence its solar system initial abundance yields information about the source of slns and the astrophysical environment in which the solar system was born only a few chondrules 19 from unequilibrated ordinary chondrites have reported resolved 60ni excesses using in situ secondary ion mass spectrometry implying fe 60 fe 56 0 6 10 7 in the early solar system and among these very few 3 have higher excesses implying fe 60 fe 56 7 10 7 mishra et al 2010 mishra and goswami 2014 telus et al 2012 at variance multi collector inductively coupled plasma mass spectrometer studies of bulk samples and mineral separates from differentiated meteorites angrites achondrites and chondrules suggest a low abundance of 60fe 56fe of 1 4 10 8 which would rule out the need for an external seeding of the early solar with stellar 60fe quitte et al 2011 tang and dauphas 2012 two semarkona chondrules and one efremovka chondrule analyzed in the present study have mass fractionation corrected excess of up to 75 permil and give 60fe isochrons with initial 60fe 56fe ratios of 7 8 3 7 10 7 3 8 1 6 10 7 and 2 2 1 1 10 7 2 for efremovka ch 1 semarkona ch 12 and semarkona ch j5 respectively the higher values of 60fe 56fe ratios seen in the chondrules of these least altered meteorites samples concur with and lend greater credence to the suggestion of a massive star as the source of 60fe and possibly of other short lived nuclides to the early solar system however no definitive explanation e g sample bias effects of metamorphism 60fe heterogeneity to the apparent disagreement with studies of bulk chondrules and chondrule fragments has been found

clay mineraloid weathering products in antarctic meteorites abstract clay mineraloids are associated with gypsum k fe sulfates possibly jarosite cryptocrystalline rust and possibly with zeolites and or secondary alkali feldspars as terrestrial weathering products in stony meteorites from the allan hills alh and elephant moraine eet collection areas in victoria land antarctica weathering formed fracture fillings in fusion crusts of eucrites eeta79004 and eeta79005 diogenites alha77256 and eeta79002 shergottite eeta79001 and h5 chondrite alh82102 and decomposition products of glass and plagioclase in interior samples of achondrites clay mineraloids displayed massive to incipient vermicular forms with elemental compositions that suggest smectite and mica like phases deposits were too small to yield pure material for phase identification although x ray diffractometry and differential scanning calorimetry of bulk samples suggested that the clay mineraloids were not well crystallized a typical structural formula calculated on a smectite basis follows k 0 26 ca 0 04 al 0 97 ti 0 02 fe 3 0 77 mg 0 03 si 4 00 o 10 oh 2 n 2 o net charge 0 28 excessions 0 58 si 0 02 cl 0 09 so 4 0 02 po 4 hydrocryogenic diagenesis can initiate clay mineral formation on timescales of 10 4 10 6 y even with only limited supplies of liquid water cosmochemists must take care not to confuse possible weathering induced elemental and isotopic fractionations in antarctic meteorite samples with signatures of pre terrestrial cosmic processes given proper sample selection and testing though occurrence of clay mineraloid and other weathering products should probably not impede progress in studies of antarctic meteorites

influence of the opening timing of recharge wells on settlement caused by dewatering in excavations abstract in deep excavation engineering the head of the confined aquifer below the excavation bottom must be lowered when the anti uprush safety factor is not satisfied however the drawdown of the confined aquifer may cause ground settlement around the excavation and endanger adjacent buildings tunnels or municipal pipes artificial recharge ar is a measure that has been applied in such situations to recover the water level and control the settlement however practical engineering cases have shown that ar could control only the development of settlement and could hardly recover the settlement caused by long term dewatering therefore three recharge schemes namely recharge first simultaneous pressure relief and recharge and pressure relief first are studied using numerical modeling the results show that the opening timing of the recharge wells and pressure relief wells has a significant impact on the final settlement in different recharge schemes different stress paths of the soil in the confined aquifer and overlying aquitards cause different plastic compressive deformations to reduce plastic deformation recharge should begin at the same time as pressure relief when the surrounding environment of the deep excavation must be strictly protected additionally the case study and numerical simulation both show that the most significant settlement or uplift occurs in the deep soil layer rather than at the ground surface a phenomenon that occurs because the vertical displacement of the soil adjacent to the relief and recharge wells is larger than that in the soil far away leading to a vertical soil arching in the strata above the confined aquifer

granular flow simulation in a centrifugal acceleration field the use of the geotechnical centrifuge to obtain scaled physical models is a useful tool in geomechanics when dealing with granular flows however the traditional scaling principles are challenge

return period calculation and passive structure design at the taconnaz avalanche path france this paper aims to show how recent knowledge developed in the field of avalanche research can be used for a real case study the taconnaz avalanche path where passive structures already existed but had to be improved first a morphological analysis of the site is done and historical data are analysed second each recorded event is back calculated using a numerical model of dense flow avalanches for each surveyed avalanche parameters at the entry of the runout zone upstream of the defence structures are defined third a statistical analysis of these parameters allows characterization of 100 year return period events fourth physical and numerical models of dense avalanches interacting with defence structures are combined in order to design the most effective passive structure able to contain the reference scenarios finally physical and numerical modelling of the interaction between the powder avalanche and the designed defence structure is performed to show that the proposed improvements do not increase the residual risk due to the powder part in areas downstream of the defence structures

froude characterization for unsteady single surge dry granular flows impact pressure and runup height the impact and pileup mechanisms of unsteady granular flows impacting a rigid barrier are governed by the froude conditions fr velocity and depth vary along the length of the flow there is curr

characteristics of groundwater seepage with cut off wall in gravel aquifer i field observations1 this paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in hangzhou china the groundwater system at the tes

diffusion kinetics of cr in olivine and 53mn 53cr thermochronology of early solar system objects we have determined the diffusion coefficient of cr in olivine as function of temperature oxygen fugacity fo2 and crystallographic orientation and used these data to develop a quantitative understanding of the resetting of the short lived 53 mn 53 cr decay system in olivine during cooling within meteorite parent body the diffusion of cr in olivine was found to be anisotropic and effectively indepen dent of fo2 between wustite iron buffer and two orders of magnitude above this buffer the diffusion data were used to calculate the spatially averaged mean closure temperature of the 53 mn 53 cr decay system in olivine as function of the initial temperature cooling rate and grain size and also the closure age profile of this system in olivine single crystal as function of radial distance and a dimensionless parameter that incorporates the effects of various parameters that affect the closure age we also present a thermochronolgic formulation that permits retrieval of cooling rates from the extent of resetting of the bulk 53 mn 53 cr closure age of olivine during cooling this method was applied to determine the cooling rate of the pallasite omolon which showed 53 mn 53 cr bulk age of olivine that is 10 myr younger than the age of the solar system the calculated cooling rate which is 20 40 c myr at 985 1000 c is in good agreement with the metallographic cooling rate at 500 c when the two results are considered in terms of a cooling model in which the reciprocal temperature increases linearly with time the inferred cooling rate of omolon which seems to be a sample from the core mantle boun dary yields a burial depth of 30 km in a parent body of at least 100 km radius

formation of non magmatic iron meteorite group iie abstract instrumental neutron activation inaa data for metal in 22 nonmagmatic iie meteorites show narrow ranges in ir and other refractory siderophiles the ir range is a factor of 2 6 a factor of 2 smaller than in nonmagmatic iab mg and orders of magnitude smaller than in the large magmatic groups siderophile data show no evidence of fractional crystallization iie irons can be split into two sets a larger main set and a set of 6 cu or fes rich irons elemental concentrations in metal from veins in h5 chondrite portales valley fall within the iie range with the exceptions of co high and ga low h group chondrite and au normalized iie abundances for siderophiles show that iie irons are 30 higher than h in refractory siderophiles re ir and w and are about 30 lower than h chondrites in the volatiles ga and sb inconsistent with proposals that iie irons formed from h chondrites the iie fractionations contrast with those in l chondrites which are about 15 lower than h in the three refractory elements and 40 higher than h in volatiles indicating that iie irons did not form from h chondrites but from a more reduced and siderophile rich kind of ordinary chondrite hh chondrites most o isotope data support a close relationship between iie irons and h or hh chondrites lower 17o in primitive chondritic silicates support an hh classification literature isotopic data for ru and mo also show that iie metal formed from an ordinary chondrite parent it appears that the silicates and metal were formed by melting of a single asteroid there is no evidence for radiogenic 26al heating this the rapid cooling recorded in the sizes of parental gamma crystal in the metal and the absence of fractional crystallization strongly support the hypothesis that iie melting was the result of impacts to summarize the weight of the evidence favors the conclusion that iie meteorites were formed by one or more impacts on an hh asteroid the target probably had a composition like the chondritic materials in netschaevo but was unequilibrated and had much higher porosity

shock waves dead zones and particle free regions in rapid granular free surface flows shock waves dead zones and particle free regions form when a thin surface avalanche of granular material flows around an obstacle or over a change in the bed topography understanding and modelling these flows is of considerable practical interest for industrial processes as well as for the design of defences to protect buildings structures and people from snow avalanches debris flows and rockfalls these flow phenomena also yield useful constitutive information that can be used to improve existing avalanche models in this paper a simple hydraulic theory first suggested in the russian literature is generalized to model quasi two dimensional flows around obstacles exact and numerical solutions are then compared with laboratory experiments these indicate that the theory is adequate to quantitatively describe the formation of normal shocks oblique shocks dead zones and granular vacua such features are generated by the flow around a pyramidal obstacle which is typical of some of the defensive structures in use today

towards rational use of baffle arrays on sloped and horizontal terrain for filtering boulders baffle arrays are used to filter boulders from granular flows such that the impact load exerted on barriers is reduced however current guidelines provide limited recommendations on baffle design

the microstructure of semarkona and bishunpur abstract the ordinary chondrites semarkona and bishunpur appear to have experienced in situ hydrous alteration here we report the results of the first detailed tem examination of them which supports this conclusion in semarkona all but the most magnesian mafic minerals have been destroyed and primary sulphides most likely troilite have been partially altered to phyllosilicates and ni rich pyrrhotite in bishunpur alteration is confined to the production of smectite from an amorphous feldspathic material in the chondrule rims and interchondrule matrix during hydrous alteration of both meteorites the temperature probably did not exceed 260 c the equilibrium composition of the gas present during the alteration of semarkona was not solar but was dominated by h2o the formation of smectite does not require the presence of liquid water however evidence for the redistribution of elements such as ca zn and si over tens of microns or more implies that there was at least some transient grain boundary fluid present the alteration in semarkona and bishunpur is far from complete thermodynamic modelling suggests that more altered ordinary chondrites would be mineralogically similar to the cm and ci carbonaceous chondrites superficially the mineralogy mineral chemistry and bulk chemistry of semarkona matrix rims resemble those of some chondritic interplanetary dust particles cidps the ordinary chondrite parent bodies may therefore be a source of some cidps

finite element analysis for rockfall and debris flow mitigation works1 landslide risks arising from boulder falls and debris flows are commonly mitigated using rigid and flexible barriers debris barrier interaction is a complicated process so current design methods

experimental analysis on the impact force of viscous debris flow a miniaturized flume experiment was carried out to measure impact forces of viscous debris flow the flow depth 7 2 11 2 cm velocity 2 4 5 2 m s and impact force were recorded during the experiment the impact process of debris flow can be divided into three phases by analyzing the variation of impact signals and flow regime the three phases are the sudden strong impact of the debris flow head continuous dynamic pressure of the body and slight static pressure of the tail the variation of impact process is consistent with the change in the flow regime the head has strong rapid impact pressure which is shown as a turbulent type flow the body approximates to steady laminar flow accordingly the process of debris flows hitting structures was simplified to a triangle shape ignoring the pressure of the tail in order to study the distribution of the debris flow impact force at different depths and variation of the impact process over time the impact signals of slurry and coarse particles were separated from the original signals using wavelet analysis the slurry s dynamic pressure signal appears to be a smooth curve and the peak pressure is 12 34 kpa when the debris flow head hits the sensors which is about 1 54 0 36 times the continuous dynamic pressure of the debris flow body the limit of application of the empirical parameter a in the hydraulic formula was also noted we introduced the power function relationship of a and the froude number of debris flows and proposed a universal model for calculating dynamic pressure the impact pressure of large particles has the characteristic of randomness the mean frequency of large particles impacting the sensor is 210 50 287 29 times per second and it is 336 114 490 69 times per second for the debris flow head which is greater than that in the debris flow body peak impact pressure of particles at different flow depths is 40 160 kpa which is 3 2 1 5 times the impact pressure of the slurry at the bottom of the flow 3 1 0 9 times the flow in the middle and 3 3 0 9 times the flow at the surface the differences in impact frequency indicate that most of the large particles concentrate in the debris flow head and the number of particles in the debris flow head increases with height this research supports the study of solid liquid two phase flow mechanisms and helps engineering design and risk assessment in debris flow prone areas c 2015 the authors earth surface proccesses and landforms published by john wiley sons ltd

evaluation of the effectiveness of an alternative to control groundwater inflow during a deep excavation into confined aquifers this paper presents a case study of groundwater control for a deep excavation into confined aquifers in fuzhou china field pumping tests were first carried out prior to the excavation to investigate the groundwater conditions at the site and as well as to evaluate the feasibility of previous designed dewatering systems 34 m diaphragm walls together with pumping wells the results showed that under the condition of previous dewatering systems it would have been extremely difficult to safely lower the water level inside the excavation a co working scenario of partially penetrating curtains and horizontal waterproof curtain with jet grouting was then proposed to control groundwater inflows additional water tightness assessment tests wat were then performed that allowed to confirm the efficiency of the proposed method from the feedbacks of wat this proposed scenario not only successfully lowered the water lever inside the excavation below the excavation bottom maximum drawdown up to 14 9 m but also it minimized the drawdown outside the excavation less than 0 2 m furthermore an approach was proposed to approximately estimate the hydraulic conductivity of the jet grouting at the real site from the result of wat the hydraulic conductivity of jet grouted soil is three orders of magnitude lower than that of the original sediments

mechanisms of weathering of meteorites recovered from hot and cold deserts and the formation of phyllosilicates abstract petrographic mineralogical and chemical analysis of naturally weathered equilibrated ordinary chondrites collected from hot deserts and antarctica has revealed striking similarities and also pronounced differences in weathering between the two environments terrestrial weathering in all meteorites studied is dominated by oxidation and hydration of fe ni metal producing fe oxides and oxyhydroxides that have partially replaced the metal grains and have also occluded primary intergranular pores to form veins troilite weathers readily in hot desert environments but undergoes very little alteration under antarctic conditions most of the primary porosity of ordinary chondrites has been occluded by the time that 15 to 25 of the initial fe 0 and fe 2 has been oxidised to fe 3 in both environments results from modelling the volume changes upon alteration of primary minerals to a range of weathering products demonstrates that the primary porosity of most meteorites is sufficient to accommodate weathering products dilation of primary pores and brecciation which has been observed in parts of some meteorites will only occur if the meteorite is especially metal rich or has a low primary porosity these weathering products are absent from recent falls but have formed in a fall after 100 yr of museum storage cl bearing akaganeite and hibbingite are common weathering products in antarctic finds but occur in abundance in only one hot desert meteorite daraj 014 the majority of fe rich weathering products in meteorites from both environments contain low but variable concentrations of si mg and ca in most meteorites a proportion of these elements are inferred to be present as a very finely crystalline mineral with a 1 0 nm lattice fringe spacing where seen within intragranular fractures this mineral has a topotactic relationship with olivine and orthopyroxene in the heavily weathered antarctic finds alha 78045 and 77002 si is concentrated in cronstedtite a fe rich phyllosilicate an unidentified hydrous si fe ni mg mineral or gel has also partially replaced taenite in alha 78045 in addition to fe rich weathering products hot desert meteorites contain sulphates ca carbonate and silica whereas such minerals are largely absent from antarctic finds the abundance of silicate weathering products in antarctic meteorites is unexpected and indicates that olivine and pyroxene undergo significant chemical weathering in these environments as preterrestrial cronstedtite is abundant in cm2 carbonaceous chondrites the antarctic environment may be a powerful analog for aqueous alteration in the asteroidal parent bodies of primitive meteorites

mobility of iron and nickel at low temperatures implications for 60fe 60ni systematics of chondrules from unequilibrated ordinary chondrites abstract the fe and ni isotopic composition of ferromagnesian silicates in chondrules from unequilibrated ordinary chondrites uocs have been used to estimate the initial abundance of the short lived radionuclide 60 fe in the early solar system however these estimates vary widely and there are systematic discrepancies in initial 60 fe 56 fe ratios inferred from in situ and bulk analyses of chondrules a possible explanation is that the fe ni isotope system in uoc chondrules has not remained closed a necessary condition for isotopic dating and fe and ni have been redistributed since the chondrules formed in order to evaluate this we collected high spatial resolution x ray fluorescence xrf maps of uoc chondrules to better understand the distribution and mobility of fe and ni at the low metamorphic temperatures of these chondrites we used synchrotron x ray fluorescence microscopy to map the distribution of fe ni and other elements in portions of 71 chondrules from 8 uocs types 3 00 3 2 the synchrotron xrf maps show clear enrichment of fe and or ni in fractures ranging down to micrometer scale in chondrules from all uocs analyzed for this study regardless of petrologic type and regardless of whether fall or find indicating that there was significant exchange of fe and ni between chondrules and matrix and that the fe ni system was not closed sixty percent of chondrules in semarkona ll3 00 have fe and ni enrichment along fractures while 80 100 of chondrules analyzed from the other uocs show these enrichments mobilization was likely a result of fluid transport of fe and ni during aqueous alteration on the parent body and or during terrestrial weathering in situ and bulk fe ni analyses that incorporate extraneous fe and ni from chondrule fractures will result in lowering the inferred initial 60 fe 56 fe ratios

experiments on the flow behaviour of granular materials at high velocity in an open channel a series of laboratory flume experiments has been conducted to investigate the flow behaviour of dry sand at high velocities the first incentive for this experimental programme was an attempt to explain the high mobility of apparently dry masses of rapidly moving broken rock during rock avalanches sturzstroms test velocities of over 5 m s and most other parameters of the tests were found to be dimensionally similar to those for a typical rock avalanche yet the conclusion was negative even the most rapid of the experiments indicated flow behaviour which is in conformity with the constant volume uniform coulomb friction relationship as applicable to slow shearing this conclusion was confirmed independently both by direct measurements of base friction and mean density of the flows and by detailed observations of flow uniformity acceleration and velocity profiles the surprising mobility of st umlrzstroms therefore requires a different explanation une serie de tests a canaux a ete entreprise dans le

evaluation of optimized depth of waterproof curtain to mitigate negative impacts during dewatering abstract dewatering using a combination of waterproof curtain and pumping wells is commonly adopted to ensure the stability of foundation pits in multi aquifer strata however dewatering is likely to result in environmental problems this paper investigates the impact on surroundings owing to the interaction between the waterproof curtain and pumping wells by numerical simulation the depth of the diaphragm wall penetrating the dewatering aquifer d and the filter length of pumping wells l are varied in the simulation the relationship between approximate hydraulic gradient i or ground settlement outside the foundation pit s with curtain depth ratio rd d over the thickness of the dewatering confined aquifer ha or filter length ratio rl l ha can be divided into three change parts namely initial gradual middle sharp and final gentle part three values of rd and rl namely effective suggested and control value are proposed rd and rl should vary between the effective and control value the suggested value of rd and rl is recommended in actual engineering by comprehensive consideration the effective suggested and control value of rd can be calculated by a linear equation according to the value of rl

scaling and design of landslide and debris flow experiments abstract scaling plays a crucial role in designing experiments aimed at understanding the behavior of landslides debris flows and other geomorphic phenomena involving grain fluid mixtures scaling can be addressed by using dimensional analysis or more rigorously by normalizing differential equations that describe the evolving dynamics of the system both of these approaches show that relative to full scale natural events miniaturized landslides and debris flows exhibit disproportionately large effects of viscous shear resistance and cohesion as well as disproportionately small effects of excess pore fluid pressure that is generated by debris dilation or contraction this behavioral divergence grows in proportion to h3 where h is the thickness of a moving mass therefore to maximize geomorphological relevance experiments with wet landslides and debris flows must be conducted at the largest feasible scales another important consideration is that unlike stream flows landslides and debris flows accelerate from statically balanced initial states thus no characteristic macroscopic velocity exists to guide experiment scaling and design on the other hand macroscopic gravity driven motion of landslides and debris flows evolves over a characteristic time scale l g 1 2 where g is the magnitude of gravitational acceleration and l is the characteristic length of the moving mass grain scale stress generation within the mass occurs on a shorter time scale h gl 1 2 which is inversely proportional to the depth averaged material shear rate a separation of these two time scales exists if the criterion h l

dewatering of a deep excavation undertaken in a layered soil in order to carry out deep excavations under the water table in urban environments the safety of the work site and of the adjacent buildings is a major cause for concern one of the most common and effective methods of undertaking these excavations involves combining the cut and cover method with a dewatering system the success of a construction depends on the stability of the excavation bottom the effects produced outside the excavation by dewatering soil movements and or the state of the enclosure defects in the diaphragm walls this study proposes a realistic multidisciplinary procedure to address these issues the work emphasizes the importance of soil characterisation and underlines the need to perform a watertightness assessment test wtat before the excavation stage the procedure was applied to the excavation of a deep shaft of the high speed train hst tunnel in barcelona an earlier geological characterisation at large scale ruled out the use of deep pumping wells however a subsequent hydrogeological characterisation which involved borehole logging grain size analyses natural gamma ray and pumping tests revealed the presence of thin transmissive layers inside the low hydraulic conductivity materials the dewatering system was designed by considering different model scenarios and the safest design was selected for the excavation depths of the enclosure and of the pumping wells differed in accordance with the scenarios the impacts settlements due to pumping and the stability in each scenario were computed the state of the enclosure underwent a wtat before the start of the excavation but after constructing the enclosure to verify its low permeability the test consisted in pumping inside the enclosure and monitoring the groundwater behaviour outside the enclosure numerical interpretation of this test showed a defect in the diaphragm walls below the excavation bottom since this defect was not repaired because of its location below the bottom of the excavation the dewatering system had to be redesigned to ensure safety surface settlements which were also a source of concern were small they were computed using coupled hydro mechanical models

the onset of metamorphism in ordinary and carbonaceous chondrites ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by xray mapping techniques a variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe scanning electron microscopy sem transmission electron microscopy tem and cathodoluminescence cl methods the distribution of cr in feo rich olivine systematically changes as metamorphism increases between type 3 0 and type 3 2 igneous zoning patterns are replaced by complex ones and cr rich coatings develop on all grains cr distributions in olivine are controlled by the exsolution of a cr rich phase probably chromite cr in olivine may have been partly present as tetrahedrally coordinated cr3 separation of chromite is nearly complete by petrologic type 3 2 the abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type tem shows this to be the result of crystallization of albite residual glass compositions systematically change during metamorphism becoming increasingly rich in k glass in type i chondrules also gains alkalis during metamorphism both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules the matrix in the least metamorphosed chondrites is rich in s and na the s is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules alkalis initially leave the matrix and enter chondrules during early metamorphism feldspar subsequently nucleates in the matrix and na re enters from chondrules these metamorphic trends can be used to refine classification schemes for chondrites cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3 0 and 3 1 into types 3 00 through 3 15 on this basis the most primitive ordinary chondrite known is semarkona although even this meteorite has experienced a small amount of metamorphism allan hills alh a77307 is the least metamorphosed co chondrite and shares many properties with the ungrouped carbonaceous chondrite acfer 094 analytical problems are significant for glasses in type ii chondrules as na is easily lost during microprobe analysis as a result existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised

physical and numerical modelling of dry granular flows under coriolis conditions in this paper quantitative observations of dry granular flows subject to varying magnitude and direction of coriolis acceleration are presented in order to assess the robustness of the savage hutt

the distribution of short lived radioisotopes in the early solar system and the chronology of asteroid accretion differentiation and secondary mineralization abstract we evaluate initial 26 al 27 al i 53 mn 55 mn i and 182 hf 180 hf i ratios together with 207 pb 206 pb ages for igneous differentiated meteorites and chondrules from ordinary chondrites for consistency with radioactive decay of the parent nuclides within a common closed isotopic system i e the early solar nebula the relative initial isotopic abundances of 26 al 53 mn and 182 hf in differentiated meteorites and chondrules are consistent with decay from common solar system initial values here denoted by i al ss i mn ss and i hf ss respectively i mn ss and i hf ss 9 1 1 7 10 6 and 1 07 0 08 10 4 respectively correspond to canonical i al ss 5 1 10 5 i hf ss so determined is consistent with i hf ss 9 72 0 44 10 5 directly determined from an internal hf w isochron for cai minerals i mn ss is within error of the lowest value directly measured for cais we suggest that erratically higher values measured for cais in carbonaceous chondrites may reflect proton irradiation of unaccreted cais by the early sun after other asteroids destined for melting by 26 al decay had already accreted the 53 mn incorporated within such asteroids would have been shielded from further local spallogenic contributions from within the solar system the relative initial isotopic abundances of the short lived nuclides are less consistent with the 207 pb 206 pb ages of the corresponding materials than with one another the best consistency of short and long lived chronometers is obtained for 182 hf 180 hf i and the 207 pb 206 pb ages of angrites 182 hf 180 hf i decreases with decreasing 207 pb 206 pb ages at the rate expected from the 8 90 0 09 ma half life of 182 hf the model solar system age thus determined is t ss hf w 4568 3 0 7 ma 26 al 27 al i and 53 mn 55 mn i are less consistent with 207 pb 206 pb ages of the corresponding meteorites but yield t ss mn cr 4568 2 0 5 ma relative to i al ss 5 1 10 5 and a 207 pb 206 pb age of 4558 55 0 15 ma for the lew86010 angrite the mn cr method with i mn ss 9 1 1 7 10 6 is useful for dating accretion if identified with chondrule formation primary igneous events and secondary mineralization on asteroid parent bodies all of these events appear to have occurred approximately contemporaneously on different asteroid parent bodies for i mn ss 9 1 1 7 10 6 parent body differentiation is found to extend at least to 5 ma post t ss i e until differentiation of the angrite parent body 4563 5 ma ago or 4564 5 ma ago using the directly measured 207 pb 206 pb ages of the d orbigny clan angrites the 1 ma difference is characteristic of a remaining inconsistency for the d orbigny clan between the al mg and mn cr chronometers on one hand and the 207 pb 206 pb chronometer on the other differentiation of the iiiab iron meteorite and ureilite parent bodies probably occurred slightly later than for the angrite parent body and at nearly the same time as one another as shown by the mn cr ages of iiiab irons and ureilites respectively the latest recorded episodes of secondary mineralization are for carbonates on the ci carbonaceous chondrite parent body and fayalites on the cv carbonaceous chondrite parent body both extending to 10 ma post t ss

characteristics of groundwater seepage with cut off wall in gravel aquifer ii numerical analysis this paper presents a numerical investigation into the leakage behavior of cut off walls in gravel strata due to dewatering in a deep excavation pit the calculated values of the groundwater head and surface settlement using a model agree well with the measured values values of the hydraulic conductivity k and storage coefficient ss of each soil layer are obtained from the test results when the cut off wall is 43 m deep the leakage through the cut off wall in gravel is analyzed by considering a variation in hydraulic conductivity in different sections of the cut off wall the simulated results show that a significant leakage occurred in the 54 m deep cut off wall although leakage did occur in the full cut off wall in the confined aquifer the full cut off wall is still more efficient in preventing groundwater seepage than the partial cut off wall the relative depths of the cut off wall and of the wells have a significant effect on ground surface settlement during the withdrawal of groundwater the

in situ 60fe 60ni systematics of chondrules from unequilibrated ordinary chondrites abstract the initial 60fe 56fe of chondrules from unequilibrated ordinary chondrites uocs can potentially constrain the stellar source of short lived radionuclides and develop the 60fe 60ni t1 2 2 6 ma system for early solar system chronology however progress with the 60fe 60ni system has been hindered by discrepancies between initial ratios inferred from bulk and in situ fe ni analyses telus et al 2016 show that discrepancies between these different techniques stem from late stage open system fe ni mobilization here we report in situ analyses of the fe ni isotopic composition of ferromagnesian silicates in chondrules from uocs using the ion microprobe of the 24 chondrules analyzed for this study a few chondrules have resolved excesses in 60ni of up to 70 however the correlations with fe ni are weak although complications from fe ni redistribution make it difficult to interpret the data we show that the initial 60fe 56fe for uoc chondrules is between 5 10 8 and 3 0 10 7 this is consistent with a late supernova source for 60fe but self enrichment of the molecular cloud is another possible mechanism for incorporating 60fe in the solar system discrepancies between bulk and in situ analyses remain but likely stem from late stage open system fe ni mobilization

landslide mobility analysis for design of multiple debris resisting barriers multiple debris resisting barriers have been commonly used worldwide to mitigate debris flows in drainage lines however a well developed methodology to assess the mobility of debris flows with co

interaction between dry granular flow and rigid barrier with basal clearance analytical and physical modelling some types of barriers are designed with a clearance between the bottom of the barrier and the channel bed this feature allows small discharges to pass thereby reducing the maintenance required o

deformation characteristics of a clayey interbed during fluid injection surface deformation due to fluid withdrawal has long been observed at the surface above aquifers and oil reservoirs uplift associated with fluid injection has also been observed although the processes of subsidence and uplift are reversible in a poroelastic setting the presence of clayey interbeds can result in ground deformation behavior non reversible because of their low permeability and nonlinear behavior in this investigation a cam clay model is used in conjunction with a poroelastic model to simulate the presence of a laterally extensive lens shaped clayey interbed in a sandstone aquifer during fluid injection spatial and temporal changes associated with this interbed during aquifer pressurization are captured and can be clearly differentiated from the deformation of the surrounding poroelastic aquifer formation results for pore pressures and ground surface deformation patterns can be categorized into three distinct time intervals an early time interval where the aquifer is pressurized but not the interbed leading to a lower region above the interbed an intermediate time interval in which the interbed pressures slowly increase approaching the pressure of the adjacent aquifer leading to a potentially large surface uplift above the interbed and a late time interval in which pressure equilibration is achieved between the interbed and aquifer and a highly non symmetrical irregular surface deformation pattern results which may be higher or lower than the background depending on the interbed characteristics reservoir configuration is found to be an important factor influencing ground deformation behavior with more obvious deformation always occurring in a laterally confined aquifer as opposed to a laterally infinite aquifer

characteristics of dewatering induced drawdown curve under blocking effect of retaining wall in aquifer summary for deep excavation pits that require the pumping of confined groundwater a combination of a retaining wall and dewatering with large diameter wells is usually adopted during excavation to improve safety since a retaining wall has a much lower hydraulic conductivity than the surrounding material in the aquifer blocking of seepage to prolong the seepage path of the groundwater outside of the pit is effective the retaining walls used during excavation dewatering cause hydraulic head drawdown inside the pit much faster than outside the pit thus difference in hydraulic head between inside and outside of the pit increases to investigate the mechanism of the blocking effect numerical simulation using the finite difference method fdm was conducted to analyze the effects of pumping in the pit the fdm results show that drawdown varies along the depth of the confined aquifer the influence factors of drawdown inside and outside the pit include insertion depth of retaining walls anisotropy of a confined aquifer and screen length of pumping wells in addition fdm results also show that the drawdown time curve can be divided into four stages in stage i drawdown inside the pit is very small and outside the pit it is almost zero in stage ii drawdown increases quickly with time in stage iii the drawdown curve is parallel to the cooper jacob curve on semi log axes and in stage iv the drawdown becomes constant these characteristics of the drawdown curve under the blocking effect of a retaining wall in an aquifer provide a way of estimating hydrogeological parameters according to pumping test results

organic thermometry for chondritic parent bodies abstract a unique spectroscopic feature has been identified in a study of twenty five different samples of meteoritic insoluble organic matter iom spanning multiple chemical classes groups and petrologic types using carbon x ray absorption near edge structure xanes spectroscopy the intensity of this feature a 1s exciton appears to provide a precise measure of parent body metamorphism the intensity of this exciton is also shown to correlate well with a large negative paramagnetic shift observed through solid state 13c nmr experiments reveal that upon heating primitive iom is transformed into material that is indistinguishable from that in thermally processed chondrites including the development of the 1s exciton a thermo kinetic expression is derived from the experimental data that allows the intensity of the 1s exciton to be used to estimated the effective temperature integrated over time a good correlation is observed between the intensity of the 1s exciton and previously published microraman spectral data these data provide a self consistent organic derived temperature scale for the purpose of calibrating raman based thermometric expressions

diffusion in polycrystalline materials grain boundaries mathematical models and experimental data geological relevance of grain boundary diffusion as a rule of thumb diffusion along grain boundaries is several orders of magnitude faster than within minerals and hence it could enable mass transport on much larger spatial scales within geological time scales therefore earth scientists are interested in the transport properties of grain and interphase boundaries and other short circuit diffusion paths such as dislocations or a fluid network since they may provide very efficient transport paths controlling a variety of processes operating on very different spatial scales for example on a micron scale corona formation around minerals is a common phenomenon that is typically controlled by grain boundary diffusion similarly element and isotopic exchange between a physically separated mineral pair used for example as a geothermometer requires transport along grain boundaries metasomatic reaction zones on the centimeter to meter scale are not always simply related to fluid flow but are also induced by fluid assisted diffusive fluxes between two different rock types imposed on each other due to tectonic processes e g miller et al 2009 it has been also argued that the observed strong gradual fractionation of li isotopes on the meter scale was a result of diffusion where a strong contribution comes from grain boundary diffusion within these rocks teng et al 2006 further new data on grain boundary diffusion of siderophile elements and carbon in polycrystalline mgo suggest that grain boundary diffusion provides an efficient mechanism to exchange these elements between the mantle and the core even on the kilometer scale within reasonable time scales hayden and watson 2007 2008 in addition to the significant role of grain boundary diffusion for element transfer in rocks grain boundary diffusion can also dominate the bulk physical properties of rocks e g their viscosity coble creep or electrical conductivity which is for example relevant for the interpretation of

dry granular flow interaction with dual barrier systems multiple barriers are commonly installed along predicted geophysical flow paths to intercept large flow volumes the main criterion for multiple barrier design is volume retained the velocity of t

investigation of field installation effects of horizontal twin jet grouting in shanghai soft soil deposits this paper presents a case study of an investigation into the responses of the surrounding ground to the horizontal twin jet grouting method htjgm in soft soil deposits of shanghai during the fi

surface settlements at a soft soil site due to bedrock dewatering abstract construction of a 16 m deep 55 m wide almost square underground structure through 8 m of soft soils and 8 m of sandstone and siltstone led to the development of widespread settlements the affected area extended to distances of over 200 m from the perimeter of the structure the floor slab of the underground structure was not designed for water pressure thus operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure subsurface investigation and monitoring data obtained over 5 75 year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure an analytical study was undertaken to project the long term settlement a simple analytical model could be used to simulate the complex hydrogeological problem reasonably the details of hydrogeologic setting subsurface investigation and monitoring activities and the analytical model for projecting long term settlements are presented in this paper

petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites

abundance distribution and origin of 60fe in the solar protoplanetary disk abstract meteorites contain relict decay products of short lived radionuclides that were present in the protoplanetary disk when asteroids and planets formed several studies reported a high abundance of 60fe t1 2 2 62 0 04 myr in chondrites 60fe 56fe 6 10 7 suggesting that planetary materials incorporated fresh products of stellar nucleosynthesis ejected by one or several massive stars that exploded in the vicinity of the newborn sun we measured 58fe 54fe and 60ni 58ni isotope ratios in whole rocks and constituents of differentiated achondrites ureilites aubrites heds and angrites unequilibrated ordinary chondrites semarkona ll3 0 and nwa 5717 ungrouped petrologic type 3 05 metal rich carbonaceous chondrite gujba cba and several other meteorites cv el h ll chondrites iiiab iva ivb iron meteorites we derive from these measurements a much lower initial 60fe 56fe ratio of 11 5 2 6 10 9 and conclude that 60fe was homogeneously distributed among planetary bodies this low ratio is consistent with derivation of 60fe from galactic background 60fe 56fe 2 8 10 7 in the interstellar medium from ray observations and can be reconciled with high 26al 27al 5 10 5 in chondrites if solar material was contaminated through winds by outer layers of one or several massive stars e g a wolf rayet star rich in 26al and poor in 60fe we present the first chronological application of the 60fe 60ni decay system to establish the time of core formation on vesta at 3 7 1 7 2 5 myr after condensation of calcium aluminum rich inclusions cais

thermal evolution model for the h chondrite asteroid instantaneous formation versus protracted accretion abstract we present a model of the thermal evolution of asteroids assuming an onion shell model for the h chondrite parent body we obtain constraints for the h chondrite asteroid parameters by fitting empirical h chondrite cooling ages of estacado guarena kernouve mt browne richardton allegan nadiabondi ste marguerite and forest vale by using a genetic algorithm for parameter optimisation the model improves previous calculations on the thermal history calculated in the instantaneous accretion approximation considering sintering and porosity dependent heat conduction the model is extended to include a finite growth time of the parent body to study whether the meteoritic record constrains the duration of the growth phase of the parent body where it assembles most of its mass it is found that only short accretion times of up to 0 1 ma are compatible with the empirical data on h chondrite cooling histories best fit models yield excellent agreement with the cooling age data particularly they indicate that i 26 al was the major heat source driving metamorphism while 60 fe contributed rather marginally ii maximum temperatures remained below partial melting temperatures throughout the body indicating that no partial differentiation occurred on the h chondrite parent asteroid iii the h chondrite asteroid formed 2 ma after cais briefly after most ordinary chondrite chondrules formed if 26 al abundance defines a chronological sequence

aquifer recharge using a partially penetrating well with clogging induced permeability reduction abstract well and aquifer clogging is one of the most serious problems restricting the application of managed aquifer recharge mar to address the clogging issue this study proposes an innovative model using partially penetrating wells ppw in confined aquifers while considering the clogging related permeability as an exponentially decayed function of time based on analysis of in situ observation data a combination of hankel transform and finite fourier cosine transform is adopted to solve the model the quasi solutions at early and late times and steady state are also derived using the developed analytical solution the developed solutions can be used to investigate the independent or combined effect of clogging induced permeability reduction well configuration and aquifer anisotropy on groundwater flow dynamics in confined aquifers or inversely used for estimating parameters associated with the clogging effect and aquifer property based on a semi log graphic approach the findings of this study can help for better understanding of the flow behaviors in the confined aquifers suffering clogging and find application in the estimation and prediction of well and aquifer clogging in mar using aquifer injection wells