a state dependent elasto plastic model for saturated and unsaturated soils a state dependent elasto plastic constitutive model for both saturated and unsaturated soils is presented in this paper the model which is developed under an extended critical state framework uses two independent stress state variables net normal stress and matric suction in addition the influence of a simplified non linear soil water characteristic curve on mechanical behaviour is incorporated in the model by using a bi linear function most importantly a state dependent dilatancy formulation is introduced to account for the effects of stress level or stress ratio internal state density and soil suction in this paper details of the model formulation and the determination of model parameters are described and reported by using the new model numerical simulations of triaxial tests have been carried out on both saturated and unsaturated fine grained sandy silt and coarse grained gravelly sand weathered soils the simulated triaxial tests include undrained shear tests on saturated specimens

measurements of elastic and electrical properties of an unconventional organic shale under differential loading abstractwe have developed an experimental approach to simultaneously measure the stress dependence of ultrasonic wave velocities at 1 mhz and therefore the components of the undrained elastic stiffness tensor as well as the components of the complex conductivity tensor in the frequency range from 100 mhz to 10 hz we performed the experiments on a cylindrical core sample from the haynesville formation porosity of approximately 0 08 bound water excluded and clay content mostly illite approximately 30 40 wt we performed experiments under controlled confining and pore fluid pressures achieving differential pressure states representative of autochthonous reservoir conditions directional measurements were made using independent acquisition arrays piezoelectric crystals and nonpolarizing electrodes distributed azimuthally on the core sample external surface the bedding plane being along the axis of the cylindrical core sample ultrasonic waveforms were recorded on a high resolution oscilloscope

quasi steady state a real behaviour reply discussions 189 the authors would like to thank the discusser for his interest in the paper the discusser disagrees with the main conclusion in the paper that the qss behaviour or the postpt increase in shear stress in undrained triaxial test on loose saturated sand may be a test induced behaviour it is useful to reiterate some of the arguments for this con clusion which are as follows 1 in undrained triaxial tests on loose unimin sand constant pore pressure constant shear stress constant effective normal stress constant sample vol ume and constant strain rate are reached over a strain range between 9 15 thereafter the shear resistance continuously increases with further straining e g fig 4 in other words the requirements of the definition of the steady state are fully satisfied with in this strain range however the post pt increase in shear resistance conflicts with the concepts of the critical void ratio and the steady state 2 the drained be haviour of loose sands corresponding to the undrained qss behaviour is that after peak the shear resistance remains constant while the sample volume remains constant only temporarily and then continuously increases e g fig 7 3 the post pt increase in shear resistance in undrained tests or the continuous increase in sample volume in drained tests on loose sands usually commences at a strain of about 15 this study ishihara 1993 this strongly suggests that the increase is likely an error caused by the triaxial test system 4 for a given consolidation void ratio the higher the friction force between end platens and a sample the larger is the shear resistance of the sample e g figs 9 and 13 5 the radial dilation of a specimen with lubricated end platens is much larger than that without lubrication e g fig 12 the results of the drained tests indicate as stated in the paper that the deviator stress and the volumetric strain may reflect responses within different zones of a loose sand specimen at large strain the measured deviator stress reflects the shear resistance controlled locally by the failure zone and remains constant at large strain because the effective confining stress maintains constant during drained shear and the failure zone has reached an ultimate state the measured volumetric strain however reflects the global volume change and continuously changes at large strain since zones other than the failure zone have not reached an ultimate state after peak in the case of undrained triaxial tests the volume change is restrained during shear and the dilation tendency of global volume at large strain results in continuous decrease in pore pressure and then causes the post pt increase in deviator stress even though the failure zone may have reached an ultimate state as in the drained triaxial tests the above results also indicate that the end restraint due to the fiction between end platens and a specimen can significantly affect the dilation at its ends therefore it is reasonable to question whether the post pt increase in deviator stress during undrained shear is a real behaviour of loose sands the discusser argues that the results of the hollow cylinder torsional tests shown in fig 13 disproves the assumption that the post pt increase in deviator stress is mainly caused by the end restraint the reasons for his comment are that when b

laboratory determination of the full electrical resistivity tensor of heterogeneous carbonate rocks at elevated pressures we describe a measurement system capable of determining the full resistivity tensor of core samples at elevated geologically representative pressures using a galvanic method it is suitable for heterogeneous rocks where it is difficult to measure tensorial resistivity without bias from sample selection and heterogeneity we demonstrate the efficacy of the system using both synthetic data and measurements on carbonate rock core samples the apparatus employs a computer controlled array of 16 electrodes to inject current into and measure boundary voltages on a 5 cm diameter cylindrical sample a computationally efficient fe algorithm is used to retrieve the full resistivity tensor from the measured voltages the algorithm uses isotropic finite element code to calculate anisotropic solutions for samples of arbitrary geometry initial results from jurassic limestone and triassic dolomite samples reveal cm scale heterogeneity and significant bulk anisotropy consistent with rock fabric observed in x ray computed tomography scan images

geology and ore genesis of the yu erya gold deposit eastern hebei province china abstract the large yu erya gold deposit 65 t of contained gold averaging 2 3 g t au in the eastern part of the hebei province of china is spatially associated with the yu erya granite and a group of ne and nne trending faults the alteration associated with mineralization is characterized by the assemblage pyrite quartz sericite albite and carbonate four stages of mineralization in chronological order are 1 quartz and medium to coarse grained pyrite 2 quartz fine grained pyrite and gold 3 quartz polymetallic sulfide tellurobismuthite and gold and 4 quartz pyrite and carbonate most of the gold was deposited during the second and third stages of alteration from mesothermal fluids these fluids were relatively rich in h 2 o co 2 k ca 2 cl and s and low salinity the h o and sulfur isotope ratios determined for the mineralized samples indicate a magmatic source and the pb isotope data indicate that the au mineralization originated from the mantle and lower crustal materials geochronological data indicate that the gold mineralization event was restricted to 200 163 ma whereas the associated magmatism occurred between 200 and 150 ma this mesozoic gold mineralization is related to the subduction of the mongolia okhotsk and paleo pacific oceans along the edges of the north china craton

a critical state constitutive model for liquefiable sand this paper presents a critical state constitutive model for sands over a wide range of void ratios and consolidation pressures in a triaxial plane a single set of parameters including a unique critical state line reached at large strain is also used in the model and differences in behavior in triaxial compression and extension are modeled by accounting for anisotropy at small and medium ranges of strain the model uses a capped yield surface ys which is characterized by its size and shape following evidence in past literature the stress ratio at the peak point of the capped ys of loose sands is approximated by the stress ratio measured at the peak point of their undrained effective stress path yielding parameters obtained using this stress ratio are also applied in modeling dense sand behavior and drained loading these parameters account for the effects of inherent anisotropy void ratio and confining pressure on yielding stresses and are readily determined from laboratory tests but further r

characterisation and multifaceted anisotropy assessment of corvio sandstone for geological co2 storage studies we present a comprehensive characterisation of the physical mineralogical geomechanical geophysical and hydrodynamic properties of corvio sandstone this information together with a detailed assessment of anisotropy is needed to establish corvio sandstone as a useful laboratory rock testing standard for well constrained studies of thermo hydro mechanical chemical coupled phenomena associated with co2 storage practices and for geological reservoir studies in general more than 200 core plugs of corvio sandstone 38 1 and 50 mm diameters 2 1 length to diameter ratio were used in this characterisation study with a rock porosity of 21 7 1 2 dry density 2036 32 kg m 3 and unconfined compressive and tensile strengths of 41 3 28 and 2 3 0 14 mpa respectively geomechanical tests show that the rock behaves elastically between 10 and 18 mpa under unconfined conditions with associated young s modulus and poisson s ratio of 11 8 2 8 gpa and 0 34 0 01 gpa respectively permeability abruptly decreases with confining pressure up to 10 mpa and then stabilises at 1 md ultrasonic p and s wave velocities vary from about 2 8 3 8 km s 1 and 1 5 2 4 km s 1 respectively over confining and differential pressures between 0 1 and 35 mpa allowing derivation of associated dynamic elastic moduli anisotropy was investigated using oriented core plugs for electrical resistivity elastic wave velocity and attenuation permeability and tracer injection tests corvio sandstone shows weak transverse isotropy symmetry axis normal to bedding of 10 for velocity and 20 for attenuation

uniqueness of steady state and liquefaction potential a given sand is presumed to have a unique steady state line the proximity of an initial state to the steady state line is considered to be a measure of liquefaction potential this line of reasoni

electron microprobe analyses of ore minerals and h o s isotope geochemistry of the yuerya gold deposit eastern hebei china implications for ore genesis and mineralization abstract the yuerya gold deposit in eastern hebei province china is located on the eastern margin of the north china craton and is hosted by mesozoic yanshanian granitoid rocks and adjacent mesoproterozoic gaoyuzhuang formation carbonates the auriferous quartz veins in this deposit are dominated by pyrite with subordinate sphalerite chalcopyrite and galena in a quartz dominated gangue that also contains calcite dolomite barite apatite and fluorite gold is present as native gold and electrum which are generally present as micron size infillings in microfissures within pyrite and less commonly as tiny inclusions within pyrite quartz and tellurobismuthite the pyrite in this deposit has high co ni ratios and contains elevated concentrations of both of these elements suggesting that the yuerya gold deposit has a magmato hydrothermal origin and that the ore forming fluids that formed the deposit leached trace elements such as co ni as and au during passage through archean metamorphic rocks mesoproterozoic carbonates and the yanshanian yuerya granitoid pyrite in the study area has s se ratios and s isotopic compositions that suggest that the sulfur and by inference the gold within the deposit was sourced from magmato hydrothermal fluids that were probably originally derived from archean metamorphic rocks and yanshanian granitoids tellurobismuthite in the study area is closely intergrown with gold and was the single telluride phase identified during this study the fineness of gold associated with tellurobismuthite is greater than the fineness of gold associated with pyrite although the fine particle size of the gold surrounded by tellurobismuthite means that the recovery of this gold is difficult in turn meaning that the tellurobismuthite has little significance to the economics of the yuerya gold deposit only trace amounts of sulfides are associated with the tellurobismuthite within the yuerya gold deposit suggesting that this mineral was deposited under conditions of low fs2 and or high fte2 in addition the presence of tellurides within the yuerya gold deposit reflects a genetic relationship between the deposit and magmatism quartz from mineralized veins in the study area has 18o values of 11 2 12 9 and the fluids that formed these veins have d values of 78 3 to 72 1 the 34s values of pyrite within the deposit are rather restricted 2 3 3 5 these data combined with the trace element geochemistry of sulfides within the deposit suggest that the formation of the yuerya gold deposit was closely related to both archean metamorphic rocks and the yanshanian yuerya granitoid

towards establishing criteria for identifying trigger mechanisms for soft sediment deformation a case study of late pleistocene lacustrine sands and clays onikobe and nakayamadaira basins northeastern japan five main deformation units discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment were selected for study within late pleistocene lacustrine sands and clays in the onikobe and nakayamadaira basins northeastern japan the deformed units show evidence of deformation by a variety of mechanisms including fluidization liquefaction brittle failure and cohesive flow driving forces are thought to be primarily reverse density gradient systems but also include gravitational body force shear stress and unequal loading the main trigger mechanisms are firstly earthquakes secondly overloading from volcanic sands and thirdly to a lesser extent subaqueous currents consideration is given to criteria that allow the trigger mechanism to be identified this study shows that the following criteria can be used to identify a seismic triggering agent i setting ii the extent of the deformation units iii absence of evidence relating to other potential trigger mechanisms and iv evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment conversely the following criteria while they are important in interpreting the driving force and deformation mechanism have no relevance to the trigger mechanism i sediment composition ii deformation structures being restricted to a single stratigraphic interval 1 m thick not necessarily correlatable over large areas and iii similarity to structures in the literature

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

mineralogical characteristics of metallic minerals in yuerya gold deposit of eastern hebei province and their combination significance the yuerya gold deposit is one of the important gold deposits in eastern hebei province the study of the compositional variations of metallic minerals and the mode of occurrence of elements from the yuerya gold deposit is of great significance in further understanding the metallogenic mechanism and providing the basis for further prospecting the research on metallic minerals of the yuerya gold deposit was carried out by means of field survey and microscopic study as well as the electron probe micro analysis epma hydrogen oxygen and sulfur isotopes were also analyzed to probe into the sources of ore forming hydrothermal fluids and sulfur the gold bearing minerals of the yuerya gold deposit include quartz pyrite and tellurobismuthite and the gold mineral is electrum the sulfur average content of pyrite is 52 34 wt a comparison with the theoretical content of sulfur shows that the pyrite from yuerya gold deposit is generally sulfur depletion suggesting that the mineralization of deposit was related to the hydrothermal fluid this study laid emphasis on the gold bearing mineral tellurobismuthite which belonged to the medium and high temperature mineral and had certain genetic relationship with the formation of electrum based on a comparison between the amount of gold carried by electrum in pyrite and that in tellurobismuthite the authors have come to the conclusion that the amount of gold carried by tellurobismuthite was greater than the amount of gold carried by pyrite by analyzing hydrogen oxygen and sulfur isotope the authors consider that the ore forming fluid came from magmatic water and the sulfur came from deep seated magma taking the mineralogical characteristics and combination signicance of pyrite chalcopyrite sphalerite galena tellurobismuthite and electrum into account the authors hold that the yuerya gold deposit belongs to middle deep medium temperature magmatic hydrothermal deposit and that we should pay special attention to the enrichment area of te and bi in the prospecting for deep ore bodies

anomalous electrical resistivity anisotropy in clean reservoir sandstones we report novel laboratory measurements of the full electrical resistivity tensor in reservoir analogue quartzose sandstones with clay contents less than 1 5 we show that clean homogeneous visually uniform sandstone samples typically display between 15 and 25 resistivity anisotropy with minimum resistivity normal to the bedding plane thin section petrography analysis of fabric anisotropy and comparison to finite element simulations of grain pack compaction show that the observed anisotropy symmetries and magnitudes can be explained by syn depositional and post depositional compaction processes our findings suggest that electrical resistivity anisotropy is likely to be present in most clastic rocks as a consequence of ballistic deposition and compaction compaction may be deduced from measurements of electrical anisotropy and the anisotropy observed at larger scales in well logging and controlled source electromagnetic data with maximum resistivity normal to bedding is most likely the result of meso scale 10 1 m 101 m periodic layering of electrically dissimilar lithologies

undrained shear strength of soils under flow deformation the initial stress and density condition leading to flow deformation and the resultant undrained strength of clean and silty sands are examined based on the un drained triaxial tests the effective major stress at consolidation 1c is found to serve as a primary parameter in defining a series of characteristic state lines and undrained strength ratios the largest possible undrained strength ratio sus 1c under flow deformation was found not to differ largely among soils though the range of such initial density conditions differs the estimation of undrained strength would therefore be practically useful in determining the occurrence of flow deformation

predicting the onset of static liquefaction of loose sand with fines abstractloose sandy soil subject to undrained shearing manifests deviatoric strain softening and such a behavior has been referred to as collapse static liquefaction or instability this paper uses the term instability and characterizes its triggering by the corresponding effective stress ratio referred to as the instability ratio is to capture the influence of fines on is the state parameter as originally proposed by been and jefferies was generalized to an equivalent granular state parameter this is achieved simply by replacing the void ratio e with the equivalent granular void ratio e the conversion from e to e was achieved by a predictive approach and backanalysis is not required it was hypothesized that provided the fines content is less than the threshold value is and at the start of undrained shearing can be described by a single relationship irrespective of the fines content two published databases and a series of undrained triaxial tests results are used to eva

multiple scale facies and reservoir quality variations within a dolomite body outcrop analog study from the middle triassic sw german basin abstract this study focuses on a porous dolomite body in the proximal part of an epeiric carbonate ramp triassic muschelkalk south german basin analogous to hydrocarbon bearing dolomite reservoirs in the middle east e g khuff and arab formations the dolomite body is made up of shoal lagoonal and peritidal facies types and is built by a three fold hierarchy of cycles 3rd order to 5th order the best reservoir quality occurs in finely crystalline lagoonal dolo mudstones mean k 37 8 md 20 2 with micro intercrystalline and vuggy porosity coarsely crystalline shoal related dolo grainstones show variable reservoir potential mean k 30 1 md 4 4 due to late diagenetic modification reservoir quality significantly decreases in the non dolomitized foreshoal section mean k 4 5 md 3 6 stratigraphically the most porous dolomite occurs in the upper regressive portion of the 3rd order cycle reservoir quality progressively decreases towards the limy bottom of the section outcrop mapping showed high lateral continuity for the distribution of facies types and poroperm values on the scale of several 10s of meters within correlated 5th order cycles considerable facies and poroperm heterogeneity is already observed on the 100s of meters scale on a 1000s of meters scale the facies and lithology distribution is controlled by the geometry of a gently inclined carbonate ramp during regression a progradational pattern is recognized marked by a basinward migration of backshoal facies and a down dip decrease of dolomite body thickness lithology facies and poroperm data from outcrops and cores were used for 3d modeling with the software petrel the modeled variations in the poroperm distribution are consistent with the degree of heterogeneity expected for a combination of laterally persistent lithology and highly variable facies results of this study may help to better understand the reservoir heterogeneity of inner ramp dolomite bodies and can be applied to improve characterization and modeling of similar dolomite reservoirs

sensitivity and inversion of marine electromagnetic data in a vertically anisotropic stratified earth the controlled source electromagnetic csem and magnetotelluric method mt are two techniques that can be jointly used to explore the resistivity structure of the earth such methods have in recent years been applied in marine environments to the exploration and appraisal of hydrocarbons in many situations the electric properties of the earth are anisotropic with differences between resistivity in the vertical direction typically much higher than those in the horizontal direction in cases such as this the two modes of the time harmonic electromagnetic field are altered in different ways implying that the sensitivity to the earth resistivity may vary significantly from one particular resistivity component scalar horizontal or vertical to another depending on the measurement configuration range azimuth frequency or water depth in this paper we examine the sensitivity of the electromagnetic field to a vertically anisotropic earth for a typical set of configurations compare inversion results of synthetic data characterizing a vertically anisotropic earth obtained using the isotropic and anisotropic assumptions and show that correctly accounting for anisotropy can prevent artefacts in inversion results

shear displacement amplitude dependent pore pressure generation in undrained cyclic loading ring shear tests an energy approach by conducting a series of shear torque controlled stc and shear displacement controlled sdc ring shear tests under undrained conditions the effects of cyclic loading frequency shear displacement rate and overconsolidation ratio ocr on the pore pressure generation were examined and analyzed by means of an energy approach cyclic stc tests demonstrated that as the frequency of loading increased the shear energy wtotal as well as the total shear displacement ltotal until liquefaction substantially decreased while the number of cycles to liquefaction n increased with frequency nevertheless sdc tests showed that wtotal ltotal n did not vary with frequency this dependency of wtotal on the loading frequency in stc tests was inferred to be due to the different resultant shear displacement amplitude after shear failure but before liquefaction during cyclic shearing the results of stc tests on samples with different ocrs showed that all these three parameters of wtotal ltotal n incr

undrained behavior of silty sand and the role of isotropic and k0 consolidation abstractthe characteristic features of undrained behavior of a silty sand are investigated for a range of initial conditions e p for both isotropic consolidation ciu and k0 consolidation k0u

cyclic characterization of wave induced oscillatory and residual response of liquefiable seabed the paper presents a robust modeling method for a fully coupled effective stress analysis of the wave induced liquefaction scenarios based on the biot consolidation theory in this context emphasis is placed on the implementation of a well calibrated cyclic soil model and an empirical shear volume coupling equation which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle unlike most of the previous investigations using the amplitude of shear stress over the wave period or the phase resolved oscillatory shear stresses as the source term for calculating the residual pore pressure in this study the source term is related to the rate of plastic volumetric deformation and implemented into the biot consolidation equation to consider both generation and partial dissipation of excess pore pressure during wave propagation then the proposed modeling method is incorporated into a dynamic finite difference analysis procedure model calibrations are carried out in terms of individual soil element behavior and seabed response under progressive waves respectively overall good agreement demonstrates the reliability of the modeling method for the prediction of wave induced seabed response finally the paper highlights the potentials of proposed modeling framework to simulate the basic features of wave induced seabed response i e the coupling of progressive buildup of pore pressure and cyclic softening of soil skeleton by means of numerical examples the obtained results show that the cyclic behavior of liquefiable seabed under wave actions can be well captured by the proposed model

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

electric pore fabric of the nubia sandstones in south egypt characterization and modelling summary this study testifies the reliability of the electric pore fabric technique applied on the nubia sandstones in south egypt through a comparison with pre assigned magnetic pore fabric and permeabilityalreadymeasuredforthreeperpendiculardirectionsintheserocks discrepancies between the different techniques were attributed to the fact that the magnetic pore fabric technique has the ability to detect and define accurately the pore volume distribution in 3 d whereas the electric pore fabric technique has the ability to detect the shortest paths for the electric current fluid flow although the magnetic pore fabric is a bulk property the permeability measurements and the electric pore fabric are quantifying transport properties both the magnetic and electric pore fabrics refer mostly to slightly and moderately anisotropic fabrics the integration between both techniques revealed two main directions for fluid migration swinging to the n s and the e w directions one difficulty of the electric pore fabric technique is due to the surface conductivity effects either from the presence of some clay minerals or cracks therefore interpreting the obtained electric pore fabric must be carried out in care for the cracked and clayey rocks the surface conductivity effect could be accounted for by using the true formation factor for calculating the electric pore fabric parameters the electric pore fabric technique can be compared to the 3 d permeability measurements which show very similar directions

derisking exploration prospects using integrated seismic and electromagnetic data a falkland islands case study the british geological survey has concluded that the north falkland basin contains the second richest documented source rock in the world they predict that as much as 100 billion barrels of oil have been expelled much of which could still be trapped beneath the regional seal richards and hillier 2000 despite this encouraging hypothesis during the 50 year exploration history of the area only six wells have been drilled these all lie in a small area and to date there has been no commercial production although live oil has been recovered to the surface

laboratory study of the electrical and hydraulic properties of rocks under simulated reservoir conditions abstract experimental results are presented for resistivity and permeability measurements on clay free sandstone and shaly synthetic rock samples at simulated reservoir conditions of pressure and temperature some details of a novel multi sample high pressure and temperature rock testing system and a new technique for making synthetic shaly samples are also presented a significant influence of pressure and temperature on both the electrical and the hydraulic properties of sandstone and synthetic rocks has been observed the combined effect of pressure and temperature on the electrical properties of the sandstones tested is approximately the sum of their individual effects the effect of clay minerals on the electrical and hydraulic properties of rocks has also been investigated the experimental results obtained lead to a better understanding of the mechanisms of the pressure and temperature effects on the geophysical properties of sedimentary rocks

characterization of electrical properties of organic rich shales at nano micro scales abstract a new experimental protocol is explored to characterize electrical properties of hydrocarbon bearing mudrocks at nano micro scales two current flow regimes of peak force tunneling atomic force microscopy pf tuna have been used 1 the vertical out of plane current regime with hundred micrometer diameter top electrodes obtains homogenized conductivity quantitatively 2 the horizontal in plane current regime was shown powerful to visualize the conductive paths related to connectivity and tortuosity for heterogeneous and anisotropic shales results show that the approach works well with one to two layers of adsorbed water 25 55 relative humidity under low frequency 0 5 20 hz for shale rocks current maps with sub nanometer resolution emphasize the dominant role of hydrated ions associated with the hydrophilic clay minerals in driving the dielectric response of shales while conductivity of pyrite and kerogen cannot be neglected for mature organic rich shale conductive network the acquired i v curves at microscale provide a reliable mean to evaluate homogenized conductivity of such multiscale multi component heterogeneous material under controlled environmental conditions the procedure discussed herein serves as a complement for fine grained rocks and minerals of ionic electronic hybrid conductive mechanism under partially water saturation these results can be used to develop accurate electrical models specifically for shale rocks with heterogeneous and sophisticated microstructure the methodology can be also extended to other micro or meso porous geomaterials such as cementitious and bituminous nanoporous media

integrated geophysical and hydromechanical assessment for co2 storage shallow low permeable reservoir sandstones geological reservoirs can be structurally complex and can respond to co2 injection both geochemically and geomechanically hence predicting reservoir formation behaviour in response to co2 injection and assessing the resulting hazards are important prerequisites for safe geological co2 storage this requires a detailed study of thermal hydro mechanical chemical coupled phenomena that can be triggered in the reservoir formation most readily achieved through laboratory simulations of co2 injection into typical reservoir formations here we present the first results from a new experimental apparatus of a steady state drainage flooding test conducted through a synthetic sandstone sample simulating real co2 storage reservoir conditions in a shallow 1 km low permeability 1md 26 porosity sandstone formation the injected pore fluid comprised brine with co2 saturation increasing in steps of 20 brine co2 partial flow rates up to 100 co2 flow at each pore fluid stage an unload loading cycle of effective pressure was imposed to study the response of the rock under different geomechanical scenarios the monitoring included axial strains and relative permeability in a continuous mode hydromechanical assessment and related geophysical signatures ultrasonic p wave and s wave velocities vp and vs and attenuations qp 1 and qs 1 respectively and electrical resistivity on average the results showed vp and vs dropped 7 and 4 respectively during the test whereas qp 1 increased 55 and qs 1 decreased by 25 from the electrical resistivity data we estimated a maximum co2 saturation of 0 5 whereas relative permeability curves were adjusted for both fluids comparing the experimental results to theoretical predictions we found that gassmann s equations explain vp at high and very low co2 saturations whereas bulk modulus yields results consistent with white and dutta ode model predictions this is interpreted as a heterogeneous distribution of the two pore fluid phases corroborated by electrical resistivity tomography images the integration of laboratory geophysical and hydromechanical observations on representative shallow low permeable sandstone reservoir allowed us to distinguish between pure geomechanical responses and those associated with the pore fluid distribution this is a key aspect in understanding co2 injection effects in deep geological reservoirs associated with carbon capture and storage practices

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

defining an appropriate steady state line for merriespruit gold tailings failure of the merriespruit gold tailings dam in 1994 in south africa was unusual in that never before had a gold tailings dam in south africa failed in such a catastrophic fashion conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading primarily because of the method of deposition which allows significant consolidation to occur due to sun drying this paper demonstrates that the concept of a steady state line which separates dilative from contractive behaviour upon undrained loading is applicable to merriespruit tailings four particle size distributions of merriespruit tailings were tested to determine the influence of the percent finer than 75 m on the position of the steady state line the tailings with the greater percentage of fines gave a steady state line that plotted above all the others which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low fines tailings samples