variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

an 800 kyr record of global surface ocean δ18o and implications for ice volume temperature coupling abstract the sequence of feedbacks that characterized 100 kyr glacial cycles of the past million years remains uncertain hampering an understanding of the interconnections between insolation ice sheets greenhouse gas forcing and climate critical to addressing this issue is an accurate interpretation of the marine 18 o record the main template for the ice ages this study uses a global compilation of 49 paired sea surface temperature planktonic 18 o records to extract the mean 18 o of surface ocean seawater over the past 800 kyr which we interpret to dominantly reflect global ice volume the results indicate that global surface temperature inferred deep ocean temperature and atmospheric co2 decrease early during each glacial cycle in close association with one another whereas major ice sheet growth occurs later in glacial cycles these relationships suggest that ice volume may have exhibited a threshold response to global cooling and that global deglaciations do not occur until after the growth of large ice sheets this phase sequence also suggests that the ice sheets had relatively little feedback on global cooling simple modeling shows that the rate of ice volume change through time is largely determined by the combined influence of insolation temperature and ice sheet size with possible implications for the evolution of glacial cycles over the past three million years

characterization of hydraulic properties of rocks using probability of fluid induced microearthquakes the use of borehole fluid injections is typical for exploration and development of hydrocarbon or geothermal reservoirs such injections often induce small magnitude earthquakes the nature of processes leading to triggering of such microseismicity is still not completely understood here we consider induced microseismicity using as examples two case studies of geothermal reservoirs in crystalline rocks and one case study of a tight gas sandstone reservoir in all three cases we found that the probability of induced earthquakes occurring is very well described by the relaxation law of pressure perturbation in fluids filling the pore space in rocks this strongly supports the hypothesis of seismicity triggered by pore pressure moreover this opens additional possibilities of using passive seismic monitoring to characterize hydraulic properties of rocks on the reservoir scale with high precision

geological and hydraulic characterisation of the excavation disturbed zone in the opalinus clay of the mont terri rock laboratory abstract the fracture network in the excavation disturbed zone edz of an argillaceous formation the opalinus clay in the mont terri rock laboratory in northwest switzerland is characterised using structural and hydrogeological techniques sampling of unloading fractures is done by analysing resin injected overcores taken from the edz resulting in a structural data set of fracture orientations frequencies and extent of the edz these parameters are derived in tunnel sections which were excavated by blasting pneumatic hammering and road header techniques pneumatic and hydrogeological tests are subsequently carried out to derive hydraulic parameters such as permeability and transmissivity distributions of the fracture network synthesis of the structural and hydrogeological data led to a conceptual model of the edz in the mont terri rock laboratory which is defined by a 2 m plastically deformed zone around the tunnel this plastic zone is further divided into an inner 1 m zone consisting of an air filled fracture network and an outer zone with mostly saturated and isolated fractures transmissivities in the inner zone are orders of magnitude higher than those of the undisturbed opalinus clay finally a methodology is proposed for the structural and hydrogeological characterisation of the edz this methodology is not site specific and is thus applicable at any argillaceous underground facility

a classification for the pressure sensitivity properties of a sandstone rock frame a three parameter formula is proposed to describe the sensitivity of the bulk modulus or shear rigidity for a sandstone rock frame under applied isotropic loading the theoretical basis for this relation is the use of excess compliance as a pseudo function to describe all internal weaknesses in the rock regardless of their origin the law is fitted to 179 sets of laboratory measurements on unsaturated reservoir core and outcrop sandstones that have low to moderate porosity and a range of clay fractions and cementation a stress index defined to quantitatively rank the reservoir sands indicates that laboratory derived pressure sensitivity is highest 10 per mpa maximum for the clean moderate porosity paleocene sands from the forties formation and west of shetlands whereas the lower porosity cemented and more consolidated permian sands rank as least pressure sensitive 1 per mpa maximum higher porosity sands are stress sensitive because of the overall rock frame compressibility all of t

seismic investigation of the excavation damaged zone in opalinus clay a mini sonic borehole probe was used to investigate the excavation damaged zone edz around an underground opening in the opalinus clay in the mont terri rock laboratory in switzerland the edz could be determined by using seismic parameters as interval velocities and amplitudes of first arrivals derived from measurements in eight radial drilled boreholes the extent of the edz is about 1 m but varies between 0 6 and 2 2 m

evidence for a middle pleistocene glaciation of mis 8 age in the southern north sea abstract in the cores of borehole 89 2 situated at 54 00 01 n and 5 00 04 e about 70 km north of the frisian islands in the southern north sea two diamictons levels are found at 70 and 100 m below sea floor i e 110 and 140 below present sea level respectively both diamictons appear to be older than saalian mis 6 in contrast to earlier interpretations the upper diamicton is overlain by about 20 m of shallow marine sands followed by a chaotic alternation of fine grained clay rich eemian mis 5e sediments and sands deposited in a glacially excavated basin it was originally assumed that this diamicton was saalian mis 6 in age and lined the base of the basin seismic lines crossing the borehole location however show that the upper diamicton is truncated by the basin and consequently must be older than saalian this is corroborated by new investigations on the saalian eemian transition in the netherlands and new data on the age of the molluscs and foraminifera in the sands directly overlying the upper diamicton the age data based on measurements of the isoleucine epimerisation of mollusc shells and foraminiferal tests favour an mis 8 age

on the relationship between stress and elastic strain for porous and fractured rock modeling the mechanical deformations of porous and fractured rocks requires a stress strain relationship experience with inherently heterogeneous earth materials suggests that different varieties of hooke s law should be applied within regions of the rock having significantly different stress strain behavior we apply this idea by dividing a rock body conceptually into two distinct parts the natural strain volume change divided by rock volume at the current stress state rather than the engineering strain volume change divided by the unstressed rock volume should be used in hooke s law for accurate modeling of the elastic deformation of that part of the pore volume subject to a relatively large degree of relative deformation i e cracks or fractures this approach permits the derivation of constitutive relations between stress and a variety of mechanical and or hydraulic rock properties we show that the theoretical predictions of this method are generally consistent with empirical expressions from field data and also laboratory rock experimental data

in situ monitoring of tunnel deformation evolutions from auxiliary tunnel in deep mine abstract deformation caused by excavation is of great effects on tunnel stability and tunnel support design monitoring using instruments that are installed in place within the examined tunnel cannot record a large amount of surrounding rock deformation that usually takes place ahead and close to the tunnel face for this important reason the overall deformation process was observed using instruments installed prior to excavation from auxiliary tunnel in a 900 m deep coal mine tunnel two monitoring methods i e multipoint extensometers and wave velocity tomography were used at two monitoring sections with different rock lithology the results showed that a large amount of deformation at both monitoring sections had already been occurred when the excavation face passed the monitoring sections at a very small distance the size of the plastic zone at monitoring section 1 is identified as 1 8 m 0 36 d d denotes the diameter of the examined tunnel and the velocities within this zone decreased from 4 5 km s to 2 km s the primary deformation was generated in a distance from 0 8 d ahead the excavation face to 2 3 d behind the excavation face the induced deformation was also observed after the primary deformation period and some additional deformation was still occurred in the plastic zone although the size of plastic zone remains constant the displacements and p wave velocities at the two monitoring sections showed little differences

geohydromechanical processes in the excavation damaged zone in crystalline rock rock salt and indurated and plastic clays in the context of radioactive waste disposal abstract the creation of an excavation disturbed zone edz or excavation damaged zone edz is expected around all man made openings in geologic formations macro and micro fracturing and in general a redistribution of in situ stresses and rearrangement of rock structures will occur in this zone resulting in drastic changes of permeability to flow mainly through the fractures and cracks induced by excavation the edz may have significant implications for the operation and long term performance of an underground nuclear waste repository various issues of concern need to be evaluated such as processes creating fractures in the edz the degree of permeability increase and the potential for sealing or healing with permeability reduction in the zone in recent years efforts along these lines have been made for a potential repository in four rock types crystalline rock salt indurated clay and plastic clay and these efforts have involved field laboratory and theoretical studies the present work involves a synthesis of the ideas and issues that emerged from presentations and discussions on edz in these four rock types at a cluster conference and workshop held in luxembourg in november 2003 first definitions of excavation disturbed and edzs that may be applicable to all four rock types are proposed then an approach is suggested for the synthesis and intercomparison of geohydromechanical processes in the edz for crystalline rock salt indurated clay and plastic clay comparison tables of relevant processes associated factors and modelling and testing techniques are developed a discussion of the general state of the art and outstanding issues is also presented a substantial bibliography of relevant papers on the subject is supplied at the end of the paper

modelling a mine by test at the mont terri rock laboratory switzerland abstract an instrumented mine by test was conducted at the mont terri rock laboratory switzerland in 1997 1998 to assess issues associated with tunnel excavation in a middle jurassic claystone known as the opalinus clay excavation induced stresses resulted in unusually large deformations and the development of an excavation disturbed zone edz around the tunnel where the observed dominant mode of yielding consisted of extensional fracturing from field and laboratory observations it has been observed that opalinus clay exhibits responses that often are not represented adequately by linear elastic or elasto plastic models in particular strong non linear elastic behaviour at low stresses was observed in laboratory tests this behaviour has been captured by a phenomenological based model known as the stress dependent modulus sdm model the concepts of the sdm model have been extended to a piece wise pore pressure formulation that captures the hydromechanical rockmass response these models were implemented into a finite difference method numerical code and used to simulate the short term deformations and pore pressure response of the ed b mine by test these simply calibrated models provided a reasonable fit to the field data particularly in regions of unloading where rockmass deformations were not dominated by dilation

investigation of damage induced permeability of opalinus clay abstract an excavation damaged zone edz around emplacement boreholes for radioactive waste represents a potential pathway for radionuclides due to its increased porosity and crack permeability as clay is one of the potential host rocks for radioactive waste disposal opalinus clay samples from the underground rock laboratory at mont terri were investigated regarding their hydraulic properties and related crack occurrence after excavation and during stress dependent crack closure after determination of their hydraulic properties in untreated conditions the samples were artificially cracked by tensile strength tests the cracked samples were put into a triaxial pressure cell and the permeability and effective porosity were measured during stepwise increase and decrease of confining pressure when the pressure was increased a continuous decrease of permeability was found which was similar for all test samples and a mathematical expression was identified when the pressure was decreased no increase of permeability was observed until the samples were completely depressurized leading to the assumption that during pressurization some kind of sealing process took place resulting in a permanent crack closure in addition to the dependence on pressure a time dependent permeability reduction and thus crack closure at constant pressure was found indicating a creep compaction behaviour of the clay by knowing the initial permeability immediately after excavation of an emplacement borehole the permeability reduction due to time dependent stress variation can be calculated for use in long term safety analyses

observations in a cavity beneath grinnell glacier abstract during a 3 year period several aspects of the glacier rock interface were studied in a cavity beneath 5 8 m of ice near the terminus of grinnell glacier montana u s a continuous week long records of the summer sliding rate revealed a very uniform speed of about 12 m a during the summer a value about 20 per cent higher than the average annual sliding rate several decimetre sized rock fragments were broken from the glacier bed near the lee sides of bedrock ledges and transported down glacier in the course of a two week long experiment the glacier abraded its bed significantly and non uniformly it is of interest that significant quarrying and abrasion occurred under thin ice with relatively little entrained debris key words glacier sliding subglacial erosion introduction subglacial cavities provide easy access to the bases of glaciers where information can be gathered on a variety of processes and features at the ice rock interface a more complete understanding of these processes is essential for continued advances in studies of the dynamics of temperate glaciers and of erosion and deposition by glaciers a number of topical questions can be addressed through studies conducted in subglacial cavities for example is the sliding motion of the ice steady or is it jerky as might be expected if sliding is influenced significantly by rock to rock friction what is the debris content of the ice what can be observed regarding the poorly understood phenomena of glacial quarrying and abrasion is there any indication that at the base of a temperate glacier ice might locally freeze to its bed site description

a minimum thermodynamic model for the bipolar seesaw 1 the simplest possible model is proposed to explain a large fraction of the millennial climate variability measured in the isotopic composition of antarctic ice cores the model results from the classic bipolar seesaw by coupling it to a heat reservoir in this thermal bipolar seesaw the heat reservoir convolves northern time signals with a characteristic timescale applying the model to the data of grip and byrd we demonstrate that maximum correlation can be obtained using a timescale of about 1000 1500 years higher correlations are obtained by first filtering out the long term variability which is due to astronomical and greenhouse gas forcing and not part of the thermal bipolar seesaw the model resolves the apparent confusion whether northern and southern climate records are in or out of phase synchronous or time lagged

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

global glacier dynamics during 100 ka pleistocene glacial cycles ice volume during the last ten 100 ka glacial cycles was driven by solar radiation flux in the northern hemisphere early minima in solar radiation combined with critical levels of atmospheric co 2 drove initial glacier expansion glacial cycles between marine isotope stage mis 24 and mis 13 whilst at 100 ka periodicity were irregular in amplitude and the shift to the largest amplitude 100 ka glacial cycles occurred after mis 16 mountain glaciers in the mid latitudes and asia reached their maximum extents early in glacial cycles then retreated as global climate became increasingly arid in contrast larger ice masses close to maritime moisture sources continued to build up and dominated global glacial maxima reflected in marine isotope and sea level records the effect of this pattern of glaciation on the state of the global atmosphere is evident in dust records from antarctic ice cores where pronounced double peaks in dust flux occur in all of the last eight glacial cycles glacier growth is strongly modulated by variations in solar radiation especially in glacial inceptions this external control accounts for 50 60 of ice volume change through glacial cycles internal global glacier climate dynamics account for the rest of the change which is controlled by the geographic distributions of glaciers

the mechanical behaviour of weak mudstone opalinus clay at low stresses abstract over the last 10 years argillaceous rocks mudrocks such as the jurassic claystone opalinus clay have gained acceptance as a potential host formation for geological disposal of nuclear waste observations from tunnels in opalinus clay at the mont terri rock laboratory switzerland suggest that the excavation induced response is not linear elastic the micro structure of the opalinus clay has been identified as a source for this response it has been demonstrated that diagenetic processes over the last 180 ma have been responsible for the formation of strong diagenetic bonds locking latent strain energy into the micro structure of opalinus clay a conceptual model of the micro structure including the effects of diagenetic processes has been developed as a framework to interpret the mechanical behaviour of the opalinus clay samples recovered at mont terri rock laboratory have been subjected to processes that have resulted in bond breakage and the release of locked in latent strain energy this tends to reduce the strength and deformation properties of samples and induces low stiffness non linearity of the stress strain curve at low stress levels numerical modelling of the sampling stress path at mont terri rock laboratory shows that unloading was the dominant factor resulting in this response as a result samples can shed light on the unloading response of the rockmass to excavation this non linear behaviour has been quantified by means of routine laboratory compressive tests

the glacial history of the pindus mountains greece abstract geomorphological evidence for pleistocene glaciation has been mapped in the pindus mountains of northwest greece and the chronology of glaciation in this area has been established through soil profile analysis and u series dating of secondary carbonates calcite formed within glacial deposits three glacial stages are evident in the sedimentological and geomorphological records the earliest and most extensive recorded glaciation predates 350 000 yr b p and was characterized by extensive valley glaciers and ice fields a more recent glaciation occurred before the last interglacial and was characterized by glaciers that reached midvalley positions the last phase of glaciation in greece is recorded by small cirque glacier moraines and relict periglacial rock glaciers the glacial and periglacial sequence on mount tymphi has been used in conjunction with a reference parastratotype the long lacustrine sequence at ioannina to provide a chronostratigraphical framework for cold stage deposits in g

porosity and elastic anisotropy of rocks under tectonic stress and pore pressure changes elastic properties of rocks depend on tectonic stress using the theory of poroelasticity as a constraint we analyze features of these dependencies related to changes in rock pore space geometry we develop a formalism describing elastic moduli and anisotropy of rocks as nonlinear functions of confining stress and pore pressure this formalism appears to agree with laboratory observations to a first approximation elastic moduli and seismic velocities as well as porosity depend only on the difference between the confining tectonic stress and pore pressure however in general both the confining stress tensor and the pore pressure must be taken into account as independent variables the stress dependent geometry of the pore space fully controls the stress induced changes in elastic moduli and seismic velocities specifically the compliant porosity plays the most important role despite the fact that in many rocks the compliant porosity is a very small part of total porosity changes in compliant porosi

a numerical study of the mechanical response to excavation and ventilation around tunnels in clay rocks abstract as an attempt to more accurately model the nonlinear elastic response and excavation damaged zone edz behavior induced by excavation and ventilation in clay shale we have incorporated and implemented a recently developed stress strain relationship called the two part hooke s model tphm within the tough flac3d code tphm is based on a macroscopic scale approximation using a natural strain based hooke s law to describe elastic deformation for a fraction of pores subject to a large degree of deformation an engineering strain based hooke s law is used for the other part we carried out a series of numerical verification tests on the deformation behavior of small scale clay and shale samples based on tphm a comparison with an elastic model described by the conventional hooke s law the single part hooke s model sphm indicates that the tphm can more accurately capture observed mechanical deformation in the low stress region of clay shale rocks furthermore based on numerical simulations of elastic response and edz behavior around a tunnel opening in opalinus clay induced by excavation and ventilation we found a larger radial elastic deformation on the roof and floor of the tunnel and considerably different stress distributions than were found with sphm although desaturation was influenced by ventilation only and occurred within a narrow zone around the tunnel opening a suction state in the rock mass developed over quite a long radial distance which had a substantial effect on the macroscopic behavior of the rock matrix during the desaturation process throughout the tunnel the mode and extension of damage zones calculated by tphm showed clear differences from those calculated by sphm the results based on tphm are more consistent with observations indicating the need and importance of incorporating more accurate constitutive models for modeling coupled processes

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

a stalagmite record of abrupt climate change and possible westerlies derived atmospheric precipitation during the penultimate glacial maximum in northern china abstract the geochemistry and petrography of a stalagmite from wanxiang cave in central china provide a paleoclimate record of the penultimate glacial maximum pgm suggesting unexpectedly abundant non monsoonal atmospheric precipitation at the nadir of the pgm eleven u th 230 th ages from 149 to 140 ka bp place the stalagmite in marine isotope stage 6b coincident with the greatest benthic marine 18 o calcite values of mis 6 carbon and oxygen stable isotope data measurements of layer specific width positions of surfaces of non deposition or dissolution changes in the character and thickness of seemingly annual layers changes in concentration of organic acids within the stalagmite s calcite and patterns in the mg concentration of that calcite all combine to give a coherent paleoclimate record these data suggest that the stalagmite represents a wetter period than before or after its growth with the wettest and coldest phase at 145 to 144 ka bp this extreme in climate yields a striking correlation with the lr04 stack of oxygen isotope records from marine benthic forams if the latter is subjected to a 4500 year chronological adjustment previously suggested by u th data from corals the timing of the wudu stalagmite s deposition combines with findings elsewhere to suggest that the pgm was the most extreme of later pleistocene glacial maxima petrography and u th age determinations suggest dramatic changes in climate during the pgm at the beginning 149 146 ka bp and end 143 140 ka bp of the stalagmite s growth abrupt century scale drying caused lengthy hiatuses as dripwater to the stalagmite diminished on the other hand delivery of water to the stalagmite during the wettest phase 145 144 ka bp caused dissolution of previous layers of the stalagmite enhanced atmospheric precipitation during the cold of a glacial maximum is unexpected because within the spectrum of holocene climate cooler conditions lessen the impact of the east asian monsoon changes in the character of stalagmite layers indeed suggest weakened to negligible influence of the east asian monsoon during the nadir of the pgm however data from the stalagmite are compatible with atmospheric precipitation from westerly winds that today reach only northwestern china but that may have been deflected southward in the pgm by southward migration of the siberian high this unexpected significance of the westerlies during the pgm may be a result of the hypothesized extreme nature of the pgm relative to other glacial maxima of the later pleistocene

hazard and seismic reinforcement analysis for typical large dams following the wenchuan earthquake abstract the primary aim of this research is to analyze the hazards and seismic performance of reservoirs and typical large dams based on a field investigation following the wenchuan 8 0 earthquake the current seismic performance standards being achieved are discussed and further suggestions are given for super high dams based on field investigations statistics are also given on damaged small reservoirs and damage severities due to the many various types of earthquake threat it is of interest to note that the major structures of the medium sized hydropower stations on the minjiang river did withstand the wenchuan earthquake despite earthquake intensity exceeding engineering design expectations all the dams remained overall stable the shapai roller compacted concrete rcc arch dam and the zipingpu concrete faced rockfill cfr dam suffered damage the main earthquake induced hazards to the dam structures and to both abutments are detailed case study analyses of the hazards and reinforcement provision revealed that 1 the wenchuan earthquake proved very dangerous for small reservoirs with destroyed reservoirs widely distributed the risk of failure of small dams can be classified into three levels based on field investigation 2 the damage to and behavior of the large dams in the area affected by the earthquake prove that the chinese codes relating to the seismic design of large dams are appropriate 3 appropriate reinforcement can increase the overall stiffness of abutments riverbed foundation and the adjacent slopes further improving the seismic performance of dams 4 the design and management of emergency responses to cope with extreme conditions should be improved and a unified response platform covering all hydropower engineering projects in each valley should be established the effects to be expected and the seismic design measures to be taken still pose great challenges for engineers in respect of large dams

assessment of excavation damaged zone around roadways under dynamic pressure induced by an active mining process abstract this study presents an investigation of the excavation damaged zone edz around roadways under dynamic pressure during longwall mining based on their geological conditions a total of fourteen typical roadways seven roadways under dynamic pressure seven roadways under static pressure in daxing coal mine liaoning province china were selected to investigate the characteristics of their edz under both dynamic and static pressure with borehole camera detection and nonmetallic ultrasonic detection techniques the results of the investigation indicate that the edz width around roadways under dynamic pressure was larger than those under static pressure due to mining induced disturbance and the effect of unstable overlying rocks in adjacent goaf the existence of faults and other adverse geological conditions can also contribute to the expansion of edzs the findings were incorporated in designing a more appropriate roadway support system if the width of edz is larger than the bolt length then the employment of bolts alone will not be sufficient to maintain roadway stability reinforcement with cables must be added to the support system the reason is that cables have an overhanging effect and can be anchored in the excavation influenced zone eiz which is adjacent to the edz in stable surrounding rock masses the installation of cables could increase the volume of stable strata participating in the support system