intercontinental trilobite based correlation of the moroccan early middle cambrian refined correlations of lower middle cambrian boundary strata and middle cambrian strata between cambrian paleocontinents require an improved understanding of local stratigraphic ranges of well defined trilobite genera and species the conventional definition of the base of the middle cambrian in spain base of acadoparadoxides mureroensis zone has led to problems even when correlations into other west gondwanan regions i e moroccan are attempted because paradoxides acadoparadoxides mureroensis and protolenid species from immediately underlying strata have been regularly misidentified the a mureroensis zone is shown to correlate into strata above the base of the moroccan middle cambrian and paradoxidid trilobites a guide to the middle cambrian have a lower occurrence in morocco these correlations are strengthened by a reevaluation of higher middle cambrian trilobite genera and species in morocco and their use in correlation into spain and baltica two new genera and eight new species of middl

advances in experimental investigation on hydraulic fracturing behavior of bentonite based materials used for hlw disposal bentonite based materials bbm in the form of blocks or rings have been commonly proposed as buffer materials for high level radioactive waste disposal in a real repository hydraulic fracturing is likely to be present when the ground water pressure exceeds to hydraulic resistance and the existence of technological gaps increases the risk of hydraulic fracturing based on the previous studies of hydraulic fracturing of bbm and technological interfaces the present work systematically analyzes the experimental achievements results show that the fracturing pressure of bbm and interfaces increases with hydration time initial dry density bentonite content and overburden pressure while it decreases with initial water content and gap thickness the temperature effect on hydraulic fracturing depends on the predominant cation of bentonite for na bentonite the higher temperature leads to the larger swelling pressure and thus the stronger hydraulic resistance tensile failure shear failure and synthesis failures are increasingly accepted for hydraulic fracturing mechanism the hydraulic fracturing of highly compacted bbm is mainly controlled by tensile failure while the initial shear failure can be found for bbm with a low enough density since hydraulic fracturing is expected to occur several times during the repository operation the long time monitoring of hydro mechanical behavior is of vital importance until the technological gaps are completely sealed furthermore the failure mechanism of hydraulic fracturing of bbm should be further researched as well as the sealing properties of interfaces under thermo hydro mechanically coupled conditions are proposed to be studied thoroughly

reply to the discussion by degago and grimstad on experimental investigation on the creep behavior of an unsaturated clay 1 in their discussion degago and grimstad 2015 affirmed the importance of thework of lai et al 2014 in dealingwith the creep behavior of unsaturated clay by attempting to benefit from the existing vast knowledge in saturated soils and extending it to unsaturated soils however some questions regarding discrepancies were raised the key point of these discrepancies is is there any general agreement on whether hypothesis a or b is better in this regard based on a thorough study and a critical assessment of selected test results degago 2011 demonstrated that the measured timedependent compressibility of clays agrees well with hypothesis b while hypothesis a represents an extreme case however the authors lai et al 2014 claim that there is still no general agreement on whether hypothesis a or b is better and their approach was firstly developing a creepmodel in a conventional way as for saturated soils and then trying to correlate the matric suction with the parameters of the model in fact to the best of the authors knowledge since 1977 this concern has continued to be a topic of active discussion among researchers and remains an issue that needs to be resolved degago 2011 although the authors lai et al 2014 fully agree that some important developments have been made in the past three decades or so degago 2011 they still think that this topic remains interesting for discussion hypothesis b is perhaps more reasonable while hypothesis a is simpler

a new simplified method for calculating consolidation settlement of multi layer soft soils with creep under multi stage ramp loading abstract in normal practice a multi stage surcharge loading is applied gradually to achieve a certain strength of soft soils and thus it is important to study the settlement of soft soils under multi stage ramp loading in this study a new simplified method is developed to calculate the settlement of multi layer soft soils exhibiting creep subjected to the multi stage loading under a one dimensional straining condition the zhu and yin method is utilized to obtain the average degree of consolidation for multi layer soils under each loading stage the effects of creep compression on excess pore water pressure and total settlement during consolidation stage are elaborated subsequently two typical projects ska edeby with 46 years recorded settlement data and highway embankment in the berthierville area are selected as the typical multi layer soil profiles cases with three different loadings and two different over consolidation ratio ocr values are analyzed using the finite element modeling namely the new simplified method and the hypothesis a method with the use of the results from finite element analysis as the reference the new simplified method offers a good estimation of the settlement for all the cases and outperforms the hypothesis a method in terms of accuracy

palaeogeographical controls on the cambrian trilobite immigration and evolutionary patterns reported in the western gondwana margin abstract southward drifting of the western gondwanan margin during the cambrian has been demonstrated by means of both palaeomagnetic methods and lithological indicators of climate such as carbonates and evaporites recent improvements in biostratigraphical correlations permit an enhanced understanding of the climatic and palaeobiogeographical constraints that controlled the distribution of cambrian benthic communities palaeogeographical and biogeographical reconstructions based on trilobites are reported in this paper in order to test interaction between migration speciation and extinction rates the variability of the documented biogeographical patterns is directly related to species diversity in which wider distribution coincides with transgressive trends and subsequent connection of neighbouring platforms early cambrian trilobite faunas show a high degree of both substrate control and endemicity although transgressions led to parallel shifts in faunal compositions by contrast mid cambrian trilobite faunas are relatively uniform across western gondwana and latest mid and late cambrian associations document influence of an increased similarity with asian trilobite faunas

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

c o and sr isotope stratigraphy across the lower middle cambrian transition of the cantabrian zone spain and the montagne noire france west gondwana c o and sr isotopes have been analysed for three sections of the cantabrian zone northern spain and the southern montagne noire france that cross the lower middle cambrian transition or bilbilian leonian transition in its iberian sense the base of the leonian middle cambrian is regionally defined by the first appearance of the trilobite acadoparadoxides mureroensis which is well constrained in the cantabrian zone but absent in the montagne noire in the bilbilian parts of the three sections nearshore to peritidal strata are capped by erosive unconformities the succeeding leonian relative sea level rise is recorded in similar fashion in both environments leading to the deposition of aggradational bioclastic limestones and or transgressive limestone shale couplets the so called griotte facies overlain by offshore shales which relate to platform drowning and coastal smothering during the leonian caesaraugustan transition bilbilian leonian carbonates show a long term trend to higher 13c values that was punctuated by a succession of positive excursions in cremenes valdore cantabrian zone and ferrals les montagnes montagne noire two bilbilian 13c shifts an older uncertain peak at 0 1 0 01 and a younger certain shift at 0 6 1 7 and two leonian shifts peaking at 1 1 1 2 and 1 3 respectively are apparent at genestosa cantabrian zone a fifth early middle caesaraugustan shift is identified peaking at 2 1 these positive excursions and increasing trend are similar to published trends from the lower middle cambrian transition in siberia and australia although in those areas only two 13c excursions have been reported so far the marked negative 13c excursion reported from the lower middle cambrian boundary of laurentia and china is not recorded in our dataset oxygen isotope and trace element ca mn and sr data indicate that our 13c trends are unlikely to be diagenetic features while the lack of correlation with relative sea level fluctuations facies changes or benthic community dynamics means that they could be of potential for global stratigraphic correlation sr isotope compositions for the cantabrian zone succession exhibit consistent values upsection which suggests that seawater 87sr 86sr remained around 0 7089 0 7090 our more limited dataset for the montagne noire region confirms this value and both are consistent with published constraints from laurentia for seawater 87sr 86sr across the lower middle cambrian boundary the only other 87sr 86sr study to cover the boundary interval reported significantly lower 87sr 86sr values not vert similar0 7087 0 7088 indicating perhaps that the lower middle cambrian boundary in siberia lies stratigraphically below its equivalent levels in europe and laurentia however we consider it more likely that these siberian samples have been diagenetically altered to less radiogenic values

experimental investigation on the creep behavior of an unsaturated clay to better understand the long term deformation of landslides with consideration of the influence of water content variation a series of triaxial creep tests with suction control was conducted on clay specimens taken from one large scale landslide in the three gorges reservoir area in china results indicate that in the double logarithmic coordinates the axial strain increases linearly and the axial strain rate decreases linearly with the elapsed time the axial strain and strain rate increase with increasing deviator stress levels and decreasing matric suction for theoretical analysis based on the simulation of the test results by an empirical creep model developed for saturated soils a linear relationship was established between suction and one of the parameters of the model then a revised model with consideration of suction effects was developed in the revised model a power function was adopted for the description of the strain time relationship and a hyperbolic function was employed for the stress strain relationship verification indicated that the calculated results were in good agreement with the experimental ones

finite element analysis of an embankment on a soft estuarine deposit using an elastic viscoplastic soil model a new elastic viscoplastic evp soil model has been used to simulate the measured deformation response of a soft estuarine soil loaded by a stage constructed embankment the simulation incorporate

a new elastic viscoplastic model for time dependent behaviour of normally and overconsolidated clays theory and verification this paper presents a new three dimensional elastic viscoplastic 3d evp constitutive model for the time dependent stress strain behaviour of both normally consolidated and overconsolidated clays there are two major new developments in the 3d evp model i incorporation of a nonlinear creep function with a limit for the creep volume strain under isotropic stressing conditions ii adoption of a new loading surface function with a smooth shape on the plane based on the equivalent time concept of yin and graham the formulation of the new 3d evp model is derived using the new nonlinear creep function and loading surface function a new approach to determining all model parameters is presented the 3d evp model is calibrated using data from one conventional isotropic stress creep test and consolidated undrained triaxial tests on soft hong kong marine deposits hkmd the model is verified by comparing model results with those from both normally and overconsolidated triaxial tests on hkmd and a mixtu

viscoplastic constitutive approach for rate sensitive structured clays this paper extends an existing elastic viscoplastic evp constitutive model using a state dependent viscosity parameter to describe the engineering response of undisturbed structured clay the term structure refers to the effects of fabric and weak cementation bonds between clay particles the extended constitutive model is coupled with the biot consolidation theory and is formulated to describe the intrinsic or unstructured response of clay using overstress viscoplasticity an elliptical cap yield surface drucker prager failure envelope and a hardening law from critical state theory the clay structure is mathematically accounted for by assuming that the initial fluidity of structured clay at yield and failure is very low and that the fluidity increases with increasing plastic strain this process is usually referred to as destructuration the formulation is evaluated using saint jean vianney sjv clay by comparing calculated and measured behaviour during consolidated isotropically undrained triaxi

evaluation of the transitional inelastic behaviour of unsaturated clay sand mixtures this paper examines and compares the mechanical behaviour of two different unsaturated clay mixtures comprised of bentonite clay saskatchewan or wyoming and quartz sand the two mixtures have bee

influence of suction on the strength and stiffness of compacted sand bentonite this paper examines the constitutive behaviour of unsaturated mixtures of compacted sand bentonite material two different techniques have been used to modify soil suction in laboratory specimens to examine the influence of suction on the behaviour of compacted materials the two methods generated inherent differences in material fabric and therefore in stress strain behaviour the difference in microstructure generated by these two preparation techniques created different properties for the two series of specimens this paper compares the behaviour of the two series of specimens and relates the observed mechanical behaviour to the initial soil fabric created by the two different preparation techniques specimens of similar compacted material were taken from two full scale in ground experiments conducted at atomic energy of canada limited s underground research laboratory at lac du bonnet manitoba and sheared using the same triaxial equipment the results are compared to the results of shearing laborator

evaluation of the viscous behaviour of clay using generalised overstress viscoplastic theory in this paper generalised elastic viscoplastic evp theory combined with a power law is used to derive simplified equations relating undrained shear strength and preconsolidation pressure to strain rate an additional equation is derived relating the strain rate parameter in evp theory to the secondary compression index the derived equations are used to evaluate the rate sensitive and drained creep response of 20 clays reported in the literature the evaluation shows strong evidence that the rate sensitivity and time dependency of clay in compression can be described simultaneously using the generalised evp theory and power law in addition the constitutive parameter governing rate sensitivity in evp theory appears to be unique for constant rate of strain tests such as undrained triaxial compression and drained oedometer compression as well as stress controlled tests such as drained oedometer creep to conclude an approach to select the viscous parameters for clay is provided

discussion of experimental investigation on the creep behavior of an unsaturated clay 1 time dependency is a crucial behavior of soils and the authors have done extensive research in their investigation based mostly on saturated soils given the importance of understanding and dealing with unsaturated geomaterials the work of lai et al 2014 is interesting they have conducted suction controlled creep tests in a triaxial apparatus at various levels of deviatoric stress and matric suction in addition they presented a numerical study that attempts to incorporate the effect of matric suction on deviatoric creep in doing so it is only natural that they attempt to benefit from the existing vast knowledge in saturated soils and extend it to unsaturated soils this however demands a clear understanding of the progress that has been achieved so far the discussers would like to point out some of the main discrepancies between the authors work and existing knowledge and attempt to briefly

the measurement of soil stiffness in the triaxial apparatus this paper describes a simple technique for accurately measuring the mean local axial strains of triaxial samples over a central gauge length the technique makes use of an axial displacement gauge which is a development of one devised by burland symes 1982 which makes use of electrolytic levels the device can resolve to less than 1 m over a range of 15 mm is simple to mount on the specimen and is not damaged when the sample is taken to failure the results of undrained triaxial tests are presented for a wide spectrum of soil types ranging from sands through intact reconstituted and remoulded low plasticity till undisturbed london clay to intact unweathered chalk the test results show that conventional external measurements of displacement contain errors which are frequently so large that their use in the determination of soil stiffness at working levels of stress is invalid the errors mainly result from tilting of the sample bedding at the end platens and the effects of compliance in the app

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

drained creep of undisturbed cohesive marine sediments long term drained triaxial creep and direct simple shear creep tests were conducted on undisturbed marine specimens from the gulf of mexico and the north central pacific results indicated that time dependent deformations can be represented by a power law equation and the creep strain rate can be represented by an equation similar to that suggested earlier by other researchers however it was found that the m parameter suggested by these scientists was not a constant but dependent on stress level and sediment plasticity ageing effects were evidenced in triaxial specimens by the increase of shear strength with both test duration and stress level the results provided a guide for the development of mathematical stress strain time relationships that will be developed in a separate paper key words drained triaxial creep simple shear creep stress strain time behavior

interpretation of increased deformation rate in aquifer iv due to groundwater pumping in shanghai shanghai is a typical example of a region in china suffering from severe land subsidence previous investigations have shown that land subsidence is strongly related to groundwater pumping in both the temporal and spatial domains a series of field investigations shows that the deformation rate of aquifer iv aqiv has increased contributing significantly to the total subsidence in shanghai to predict the deformation behavior of aqiv in shanghai due to groundwater pumping four different models have been applied in this study i a model based on groundwater flow theory ii an elastic model based on cauchy mechanics iii a creep model incorporated into cauchy mechanics and iv a recently proposed land subsidence model by budhu based on cosserat mechanics based on a number of assumptions budhu s concept was extended to consider the time dependent behavior of groundwater potential in aquifers and the consolidation behavior of overburdened aquitards the calculated results of aqiv s deformation we

modelling unanticipated pore water pressures in soft clays field observations in thin soft clay layers may show pore water pressures that increase for some time after the loading is applied reasons for these observations are not well understood the paper shows how an elastic viscoplastic constitutive model incorporated into the consolidation equation can predict these pore water pressure increases in soils that exhibit significant creep behaviour or secondary compression the phenomenon has been related to relaxation in regions of the profile from which drainage has not yet begun key words clay consolidation creep secondary compression viscous relaxation pore water pressure elastic plastic

an improved elastic viscoplastic soil model this paper develops an improved and accessible framework for modelling time dependent behaviour of soils using the concepts of elasticity and viscoplasticity the mathematical description of viscop

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

shear strength characteristics of statically compacted unsaturated kaolin the shear strength characteristics of statically compacted unsaturated soil specimens of commercial kaolin ip 15 were determined using conventional triaxial shear testing apparatus extending total stress analysis the testing program consists of two different types of confined compression shear strength tests on unsaturated soil specimens in the first series of tests the specimens were sheared immediately after the application of the confining pressure under undrained loading conditions in the second series of tests the specimens were first allowed to come to equilibrium with respect to volume change and suction value under the applied confining pressure and sheared at two different rates of strain a psychrometer was used for measuring suction values in addition conventional consolidated undrained tests were also conducted on specimens that were saturated using the back pressure technique before shearing comparisons with respect to the shear strength behavior are provided for both saturated a

fingerprinting gondwana versus baltica provenance nd and sr isotopes in lower paleozoic clastic rocks of the malopolska and łysogory terranes southern poland abstract neodymium and strontium isotope compositions of clastic material in lower paleozoic rocks in addition to detrital zircon and mica geochronology and faunal data are used to constrain the geotectonic provenance of the malopolska and ysogory terranes in southern poland being characterized by markedly different geological histories during early paleozoic times malopolska and ysogory were most often interpreted as exotic terranes but their identity provenance and accretionary history are still being discussed this study presents the first systematic nd and sr isotope survey of the lower paleozoic siliciclastic rocks cambrian clastic rocks of malopolska differ in their nd and sr isotope compositions from those of ysogory the former are characterized by a wide range of the end 505 ma values from 11 7 to 5 7 sr isotope ratios from 0 712 to 0 767 and model ages t2dm predominantly younger than 1 9 ga whereas the end t values of the latter vary within a fairly narrow range of the end 505 ma from 11 0 to 8 3 sr isotope ratios from 0 722 to 0 754 and model ages are older than 1 9 ga new nd data combined with detrital zircon ages provide evidence that malopolska must have been supplied with clastic material from amazonian sources during cambrian times being also progressively sourced from the baltic svecofennian crust in the middle cambrian detritus recognized in ysogory has mostly been derived from the svecofennian basement of fennoscandia but it has also a small addition from cadomian sources all provenance and biogeographic data suggest that malopolska was situated close to the amazonian craton near the western end of the cadomian belt during the early cambrian and it was not until the late middle cambrian that malopolska collided with the baltica margin during the late cambrian ysogory occupied a position between baltica and the cadomian belt but it was probably not yet accreted to the baltic crust at that time

dynamic fault interaction during a fluid injection induced earthquake the 2017 mw 5 5 pohang event the november 15th 2017 mw 5 5 pohang earthquake south korea has been linked to hydraulic stimulation and fluid injections making this the largest induced seismic event associated with an enhanced geothermal system egs to understand its source dynamics and fault interactions we conduct the first 3d high resolution spontaneous dynamic rupture simulations of an induced earthquake we account for topography off fault plastic deformation under depth dependent bulk cohesion rapid velocity weakening friction and 1d subsurface structure a guided fault reconstruction approach that clusters spatio temporal aftershock locations including their uncertainties is used to identify a main and a secondary fault plane that intersects under a shallow angle of 15 based on simple mohr coulomb failure analysis and 180 dynamic rupture experiments in which we vary local stress loading conditions fluid pressure and relative fault strength we identify preferred two fault plane scenarios that well reproduce observations we find that the regional far field tectonic stress regime promotes pure strike slip faulting while local stress conditions constrained by borehole logging generate the observed thrust faulting component our preferred model is characterized by overpressurized pore fluids non optimally oriented but dynamically weak faults and a close to critical local stress state in our model earthquake rupture jumps to the secondary fault by dynamic triggering generating a measurable non double couple component our simulations suggest that complex dynamic fault interaction may occur during fluid injection induced earthquakes and that local stress perturbations dominate over the regional stress conditions these findings therefore have important implications for seismic hazard in active geo reservoir

cambrian trilobites from brzechow holy cross mountains poland and their significance in stratigraphic correlation and biogeographic reconstructions a revision of the trilobite fauna from brzechow in the holy cross mountains poland shows that the assemblage consists of palaeolenus medius bednarczyk issafeniella orlowinensis samsonowicz kingaspidoides sanctacrucensis czarnocki paradoxides acadoparadoxides oelandicus sjogren p a cf mureroensis sdzuy and p a sp it is earliest middle cambrian in age according to the west gondwana standard of geyer landing 2004 and can be correlated with the cephalopyge notabilis zone of morocco moreover the co occurrence of the ranges of p a oelandicus with p a cf mureroensis might suggest that p a oelandicus appears earlier in the brzechow sandstones than in scandinavia thus the strata exposed here do not find their correlative in the scandinavian succession as a result the banian agdzian boundary lower middle cambrian boundary according to the west gondwana standard probably lies within the kamieniec formation and also below the brzechow sandstones in the upper part of the ocieseki formation close similarity of the discussed assemblage with contemporaneous assemblages from morocco jordan or new brunswick indicates that the fauna is generally of peri gondwanan and gondwanan aspect

impact of pore fluid salinity on the mechanical behavior of unsaturated bentonite sand mixture high salinity of local groundwater and the thermal gradient present within the deep geological repository environment make it necessary to investigate the effect of the pore fluid salinity on the hydro mechanical behavior engineered barriers at different degrees of saturation this study examines the impact of cacl2 salt solution at two concentrations i e 100 and 250 g l on the compressibility and shear strength behavior of the bentonite sand buffer bsb within a range of saturations both as compacted and desiccated bsb specimens were studied desiccated specimens were prepared in a constant suction environment using the vapor equilibrium technique and high pressure cells were used to carry out the triaxial shear experiments experimental results were compared with the available data from the literature for bsb materials prepared with distilled water in order to get a better understanding of the impact of the salinity the comparison shows that the existence of salt in the specimens has notable effect on the total suction levels compressibility and shear strength of the material

evaluation of the predictive ability of two elastic viscoplastic constitutive models two elastic viscoplastic constitutive formulations are evaluated using laboratory and field data from sackville new brunswick and gloucester ontario both constitutive models have been implemented in a finite element program and formulated for undrained analysis and fully coupled analysis based on biot consolidation theory a laboratory study of the rate sensitive behaviour of sackville clay is described the response of sackville clay during consolidated anisotropic undrained cau triaxial creep cau triaxial compression and incremental oedometer consolidation is compared with the calculated behaviour the comparisons demonstrate the general ability of three parameter elastic viscoplastic constitutive models to satisfactorily describe the rate dependent behaviour of sackville clay the measured response of gloucester clay during long term rowe cell consolidation tests is compared with the calculated behaviour and the predictive ability of both constitutive formulations is evaluated using the field p

use and misuse of the isotache concept with respect to creep hypotheses a and b time dependent settlements of thick in situ clay layers are normally analysed based on results of thin laboratory specimens however the time used to complete primary consolidation is significantly different for laboratory specimens and in situ soil layers two totally different cases referred to as creep hypotheses a and b have been used as a basis of discussion to assess the effect of creep during the primary consolidation phase several laboratory and field experiments have been conducted to study the effect of soil layer thickness on the time dependent compressibility of a soil layer some of these tests seemed to support hypothesis a others hypothesis b and in some cases showed a behaviour between the two as a result this question has continued to be a controversial topic among researchers and remains to be an issue that needs to be resolved in this study some relevant experimental investigations from the literature are thoroughly studied and critically reviewed and also explained consistently using the isotache concept this work indicates that the isotache approach can capture the main characteristics of the time dependent compressibility of clays during both the primary and secondary consolidation phases it is also shown that the misuse of the isotache concept as reported in the literature may give a confusing picture of reality based on the considered data it is demonstrated that the measured time dependent compressibility of clays agrees well with hypothesis b

suction and rate dependent behaviour of a shear zone soil from a landslide in a gently inclined mudstone sandstone sequence in the sichuan basin china abstract bedding controlled landslides in alternated mudstone and sandstone beds in cataclinal slopes are common in the sichuan basin and in the three gorges area in china they are characterised by very gentle dip angles of the beds

in situ and laboratory stress strain relationships the question of whether or not the end of primary consolidation curve from laboratory oedometer tests is representative of in situ behaviour has been the subject of much discussion the behaviour of the berthierville test embankment is described and in situ effective stress strain curves are defined for two well defined clay sublayers these compressibility curves are then compared with laboratory end of primary consolidation curves similar comparisons are also made for sublayers under three other well instrumented embankments all the results show that the laboratory end of primary consolidation curve strongly underestimates in situ settlements and thus that theory a is not valid on s est souvent demande si la courbe de la fin de consolidation primaire obtenue a partir d essais oedometriques en laboratoire represente effec tivement le comportement en place l article decrit le comportement du remblai experimental de berthierville et definit les courbes contrainte deformation effectives en place pour de

the 2003 r m hardy lecture soil parameters for numerical analysis in clay engineers in geotechnical practice work on increasingly complex problems with increasingly powerful numerical tools effective solutions to design problems need good information about the site and parameters or functions that describe how the soil will behave under the proposed loadings these loadings can include heating drying or wetting time effects and chemical changes as well as the more common structural loads this paper outlines issues that need to be considered when laboratory tests are used to produce soil properties for use in numerical analyses the focus is on soft to moderately stiff saturated clays similar considerations for in situ tests stiff clays and sands are not considered key words clay testing characterization properties constitutive modeling

performance of a reinforced embankment on a sensitive champlain clay deposit an existing elastoviscoplastic constitutive model is modified using concepts of the state dependent fluidity parameters and the damage law to incorporate the effect of soil structure and its destructuration the model is employed to simulate the performance of a well documented case study of the reinforced test embankment constructed over a sensitive champlain clay deposit at saint alban quebec the finite element calculations using both the original nonstructured and modified structured elastoviscoplastic soil models are compared with the observed field data from a test embankment brought to failure the results from the structured elastoviscoplastic soil model show better agreements with the field data when compared with those analyzed using the nonstructured elastoviscoplastic soil model the modified model captures many features of the reinforced embankment behaviour such as vertical settlement excess pore water pressure responses and reinforcement force however they also reveal the fact

the permeability of natural soft clays part ii permeability characteristics reply the permeability characteristics of a number of intact natural soft clays from quebec the usa and sweden have been investigated in the laboratory the variation of permeability with void ratio is best represented in terms of a linear e vs lg k relation which is generally valid in the range of volumetric strains encountered in engineering practice the permeability at the in situ void ratio is shown to be a complex function of such parameters as the void ratio the clay fraction the plasticity index and the fabric of the clay permeability anisotropy is negligible in marine clays the e vs lg k relationships of the various clays tested are well ordered in terms of an empirical parameter ip clay fraction irrespective of the geological origin of the clay the slope of the e vs lg k relationship referred to as permeability change index ck is simply related to the initial void ratio by ck 0 5eo keywords permeability clays laboratory tests permeability anisotropy permeability void ratio re

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

measurements of suction versus water content for bentonite sand mixtures compacted soils have been widely used as landfill barriers because of favorable characteristics such as low coefficient of permeability and high swelling compacted bentonite sand mixtures are norm

modelling time dependent behaviour of murro test embankment this paper investigates the time dependent behaviour of murro test embankment in finland the embankment was built in 1993 on a soft natural clay deposit which exhibits large strain anisotropy destructuration and viscosity the study is based on extensive experimental data from triaxial and oedometer tests on intact and reconstituted soil samples which shed light on the influence of time on mechanical properties including testing designed for studying soil anisotropy and destructuration the interpretation of the results is done in the framework of a recently developed elasto viscoplastic model evp sclay1s which is used to simulate the soft soil deposit coupled with biot s consolidation theory the determination of model parameters from the test results demonstrates that the model can be relatively easily used for practical applications using these parameters two dimensional finite element analyses have been made as large deformation analysis the comparisons between calculations and measurements de

assessment and statistical evaluation of suction characteristics obtained via filter paper technique on zeolite bentonite mixtures filter paper technique fpt is known to measure both matric and total suctions in a wide measurement range however it has many individual errors due to the uncertainty of calibration curve and sensitivity of the measurements to the temperature and relative humidity variations besides the astm procedure for fpt does not specify any sample preparation and repetition for experiments in this regard this study covers the reliability of suction measurements using the fpt and its application on zeolite bentonite mixtures zbms which were proposed for use of liner material in the literature a calibration curve for whatman no 42 filter paper was constructed and compared to the other calibration curves given in the literature due to large scatter of calibration curves total suction measurement is found to be inconvenient for suction values under 1000 kpa an improvement in sample preparation and necessary minimum numbers of tests are also suggested when preparing the test specimen the compacted sample is recommended not to be cut but to be compacted separately as upper and lower parts where the contact filter paper to be placed in between in order to obtain good contact area to measure the matric suction accurately the necessary minimum numbers of tests for 10 accuracy band in a confidence level of 95 for astm procedure on zbms are suggested repetitions were found to vary depending on the suction type and bentonite content repetitions of six and eight times are recommended for 10 zbms for matric and total suction measurements respectively similarly for 20 zbms the repetitions of six and ten times are found for matric and total suction measurements respectively in addition the influence of index properties and compaction states on suction was also investigated matric suction values decrease from dry of optimum water content to the wet of optimum water content and approach to zero for higher water contents the suction values are found to increase with decreasing water contents where the dry density and the void ratio were constant on the other hand for a given water content matric suction values are found to be increasing with increasing dry densities while the void ratio was decreasing being more evident at relatively higher saturation degrees

modeling the viscoplastic behaviour of clays during consolidation application to berthierville clay in both laboratory and field conditions to analyze the effects of strain rate and viscoplastic strain on consolidation of natural clay this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a un

time dependent behaviour of the bearpaw shale in oedometric loading and unloading time dependent behaviour can have a significant influence on the compressibility characteristics of soils however most of the research on this topic has investigated the behaviour of soft soils in this paper the time dependent behaviour of a hard clay shale bearpaw shale is investigated using both one dimensional multi staged loading msl oedometer and constant rate of strain crs oedometer consolidation tests conducted on 25 0 and 16 9 mm diameter specimens the results show that soft clays and hard clay shales that share the same c e cc ratio where c e is the secondary compression index and cc is the incremental compression index will show the same approximately 7 change in pre consolidation pressure for an increase of one log cycle of strain rate despite the many orders of magnitude difference in pre consolidation pressure in the case of the bearpaw shale this 7 change in pre consolidation pressure corresponds to approximately 700 kpa the time dependent behaviour of the bearpaw shale d

syn rift unconformities punctuating the lower middle cambrian transition in the atlas rift morocco the cambrian tamdroust and bab n ali volcanic complexes represent two magmatic episodes developed in the latest ediacaran cambrian atlas rift of morocco their rifting pulses were accompanied by accumulation of volcanosedimentary edifices dominated by effusive lava flows in the former and explosive acidic aprons in the latter associated with active tilting and uplift sealing of their peneplaned horst and graben palaeotopographies led to the onset of distinct onlapping geometries and angular discordances capping eroded basements ranging from the ediacaran ouarzazate supergroup to the cambrian asrir formation previous interpretations of these discordances as pull apart or compressive events are revised here and reinterpreted in an extensional rifting context associated with active volcanism the record of erosive unconformities stratigraphic gaps condensed beds and onlapping patterns across the traditional lower middle cambrian or cambrian series 2 3 transition of the atlas rift must be taken into consideration for global chronostratigraphic correlation based on their trilobite content

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

elastic plastic modelling of unsaturated soil using results from a new triaxial test with controlled suction this paper examines the constitutive behaviour of a compacted highly plastic sand clay mixture three series of tests evaluated components of a possible elastic plastic constitutive model for unsaturated stress strain behaviour the tests examined the influence of suction on yield stress under external isotropic loading and the influence of suction on shear strength the results examine the behaviour of highly plastic clay subjected to generalised triaxial stresses that include shear isotropic and suction loading the data represent an important new resource of information on a densely compacted strongly expansive sand bentonite mixture that was loaded independently by external stresses and internal suctions the suctions were also measured by sensors buried in the specimens they have been interpreted in an elastic plastic framework to produce values for some of the material properties needed for the model the results and associated discussion provide new insights into the behaviour of unsaturated

viscous behaviour of st roch de l achigan clay quebec this paper describes the viscous behaviour of st roch de l achigan clay a champlain sea clay from quebec canada the general geotechnical profile of the soil deposit was first established with st