sedimentary record of mesozoic deformation and inception of the turpan hami basin northwest china the turpan hami basin is a major physiographic and geologic feature of northwest china yet considerable uncertainty exists as to the timing of its inception its late paleozoic and mesozoic tectonic history and the relationship of its petroleum systems to those of the nearby junggar basin to address these issues we examined the late paleozoic and mesozoic sedimentary record in the turpan hami basin through a series of outcrop and subsurface studies mesozoic sedimentary facies regional unconformities sediment dispersal patterns and sediment compositions within the turpan hami and southern junggar basins suggest that these basins were initially separated between early triassic and early jurassic time prior to separation upper permian profundal lacustrine and fan delta facies and triassic coarse grained braided fluvial alluvial facies were deposited across a contiguous junggar turpan hami basin permian through triassic facies were derived mainly from the tian shan to the south as indicated by northward directed paleocurrent directions this is consistent with the sedimentary provenance of triassic sandstone mean qm29f29lt42 qp23lvm49lsm28 and qm51p25k24 and conglomerate 32 granitic clasts in the northern turpan hami basin we interpret a relative increase in quartz and feldspar concentration and a relative decrease in volcanic lithic grains in the northern turpan hami basin to reflect unroofing in the tian shan and exposure of late paleozoic granitoid rocks in addition two basinwide unconformities of late permian early triassic and early triassic middle late triassic age attest to deformation within the turpan hami basin and associated continued uplift and erosion of the tian shan

evolution and mass accumulation of the cenozoic hoh xil basin northern tibet abstract this work reconstructs the depositional history and estimates the mass of sediments stored in the hoh xil basin northern tibet the largest cenozoic sedimentary basin in the hinterland of the tibetan plateau the mass estimate is derived from over 75 geologic sites and 21 measured stratigraphic sections with a total thickness of 13 478 m the results show that the hoh xil basin underwent six stages of development from the early eocene to the early miocene with a hiatus in sedimentation in the late oligocene the fenghuoshan group was deposited during the first four stages 56 0 52 0 52 0 43 0 43 0 38 2 and 38 2 31 5 myr the yaxicuo group comprises stage 5 31 5 30 0 myr the wudaoliang group covered the entire basin during the last stage 23 0 to 16 0 myr the strata of the fenghuoshan and yaxicuo groups were strongly deformed mainly during the late oligocene whereas only minor tilting has occurred since then in the wudaoliang group the depositional history indicates that the hoh xil basin could have been formed as a piggyback basin and that the onset of northeastward growth of the central tibet was from the early eocene about 56 myr to the late oligocene the analyses of subsidence history and mass accumulation indicate that both accelerated subsidence and sudden increases of accumulation rate occurred at the four periods of about 52 0 40 5 34 5 and 31 5 myr in three sub basins and over the entire basin from the early eocene to the early oligocene during the four periods the deposits were either lacustrine turbidite sandstone or fan delta conglomerate which resulted from the tectonic movement on the basis of the mechanism of northeastward growth of the piggyback basins and the consistency of accelerated subsidence depositional systems and mass accumulation we suggest the continental collision and early uplift of the tibetan plateau controlled the formation and evolution of the hoh xil basin the event that occurred at 52 0 myr could represent the continental collision between india and asia whereas the other three events that happened during about 40 30 myr could show the early uplift of the tibetan plateau this study on sedimentary records in the hoh xil basin along with widespread magmatic activity in eastern and western tibet suggests a diachronous uplift history for the tibetan plateau from east to west

permian sedimentary record of the turpan hami basin and adjacent regions northwest china constraints on postamalgamation tectonic evolution the permian marks an important yet poorly understood tectonic transition in the tian shan region of northwestern china between devonian carboniferous continental amalgamation and recurrent mesozoic cenozoic intracontinental orogenic reactivation the turpan hami basin accommodated up to 3000 m of sediment and is ideally positioned to provide constraints on this transition new stratigraphic data and mapping indicate that extension dominated early permian tectonics in the region whereas flexural foreland subsidence controlled late permian basin evolution lower permian strata in the northwestern turpan hami basin consist of coarse grained debris flow and alluvial fan deposits interbedded with mafic to intermediate volcanic sills and flows in contrast lower permian rocks in the north central and northeastern turpan hami basin unconformably overlie a late carboniferous volcanic arc sequence these lower permian strata include possible shallow marine carbonate rocks and thick volcanic and volcaniclastic rocks that are in turn overlain by littoral to profundal lacustrine facies above a regional lower permian upper permian unconformity regional sedimentation patterns record the development of a more integrated sedimentary basin the upper permian is entirely nonmarine and can be correlated east west along the depositional strike of the basin the lower upper permian consists of a broad belt of braided fluvial deposits shed northward these strata are overlain by fluctuating littoral and profundal lacustrine facies and associated fluvial facies the uppermost permian is characterized by shallow lake plain and fluvial environments the early permian association of diffuse volcanism and partitioning of subbasins by normal faulting is consistent with an early phase of lithospheric extension local relationships indicate west east extension in the turpan hami basin along faults oriented normal to late devonian carboniferous collisional sutures within the tian shan the cause of extension in the wake of carboniferous orogenesis remains enigmatic however the temporal and spatial relationships of the two strain regimes suggest that they are genetically related upper permian stratigraphy and unconformities and local late permian triassic contractional deformation record foreland basin development when the turpan hami region became a wedge top basin with respect to the north tian shan fold and thrust belt flexurally induced late permian subsidence is also manifested in the larger junggar basin to the north where 4000 m of strata are preserved in the foredeep region the turpan hami and junggar basins were depositionally connected for much of the late permian when a vast lacustrine system developed across northwestern china this lacustrine paleogeography was only occasionally interrupted possibly by structural damming during uplift of the orogenic wedge

validation of models and empirical equations to estimate deformations in jointed rock through the monitoring of a 40 storey tower foundation abstract there is a pressing need in rock mechanics for the calculation of deformations and stresses of structures in rock with this aim the rock mass modulus must be estimated and a model chosen to perform the calculations monitoring the foundation of twin towers in tenerife island has allowed validating both the rock mass modulus estimated from empirical equations and the model in this paper only the second tower tower n with a structural height of 137 4 m above foundation has been studied because the first tower had been previously presented by justo et al int j rock mech min sci 2006 43 267 81 the foundations of both towers are supported by jointed vesicular and weathered basalt and scoria the parameters have been deduced from the simple empirical equations proposed by several authors as a function of geological strength index gsi or rock mass rating rmr three dimensional elastic and advanced elasto plastic finite element fe programs have permitted calculation of the displacements of tower n the stresses in the slab and the factor of safety fos of the excavation the installation of rod extensometers at different depths below the slab has permitted comparison between measured and calculated displacements good fit has been obtained in this type of rock these results increase our confidence in the use of classification schemes to estimate the deformations in jointed rock in construction processes that involve unloading reloading it is important to use a material model that considers these processes the use of advanced elasto plastic methods increases the calculated settlements even if there are no failure points as the pre consolidation stress and the mobilized angle reached during the excavation phase are exceeded at many points during the loading phase tension cut off points also increase deformations with respect to linear elastic behaviour the hardening soil model improves fit between measured and calculated settlements as well

sandstone petrology and geochemistry of the turpan basin nw china implications for the tectonic evolution of a continental basin the evolution of the turpan basin nw china from the permian to the tertiary was reconstructed from sandstone petrology and geochemistry the sandstones are mostly feldspathic litharenite and litharenite and were deposited mainly in fluvial and lacustrine environments sandstone samples show large variations in the contents of quartz and lithic fragments a general increase in compositional maturity is observed from the permian to the tertiary in particular quartz content is only 11 in the permian increases to 27 in the triassic 35 in the lower jurassic 36 in the upper jurassic and more than 47 in the cretaceous and tertiary the geochemistry of sandstones also varies with time late permian sandstones have lower sio2 67 48 and higher fe2o3 4 87 and mgo 1 75 values whereas triassic and jurassic samples show high sio2 74 15 77 5 respectively and low fe2o3 4 06 2 8 and mgo 0 95 0 79 contents in the cretaceous and tertiary fe2o3 and mgo contents increased again k2o na2o and al2o3 also vary considerably within the study site the tectonic evolution of the basin can be subdivided into three stages from petrologic and geochemical data the first stage covers the permian the second stage the triassic and jurassic and the third stage the cretaceous and tertiary there are two large discontinuities in sandstone composition among these three stages these discontinuities signify the influence of collision and convergence of the tarim block at the end of the permian and the gangdise block between the jurassic and the cretaceous with the eurasian plate the source rock regions of the basin varied with time in permian triassic and jurassic time the paleo jueluotage shan mountains were the dominant source region for the turpan basin while in the cretaceous and tertiary the paleo bogda shan mountains were an important source region in the tertiary and later the bogda shan mountains continued to be strongly uplifted during the collision of the indian plate with the eurasian plate and were the dominant source region the trace element ratios eu eu gd n yb n la yb and la th subscript n refers to chandrite normalized values show that the source rocks of the sedimentary rocks were derived from upper continental crust the data from the turpan basin show that combined petrologic and geochemical analysis of sandstone suites can be used to track changes in the sediment supply from adjacent areas if 1 a long term record of the basin fill is available 2 the source signal is preserved by proximal depositional conditions and 3 diagenetic alteration of sediments is limited provenance derived variations in sandstone compositions are therefore a key in unraveling regional tectonic histories

stochastic analysis of strength and deformability of fractured rocks using multi fracture system realizations this thesis presents a systematic numerical modeling framework to simulate the stress deformation and coupled stress deformation flow processes by performing uniaxial and biaxial compressive tests on fractured rock models with considering the effects of different loading conditions different loading directions anisotropy and coupled hydro mechanical processes for evaluating strength and deformability behavior of fractured rocks by using code udec of discrete element method dem a series of numerical experiments were conducted on discrete fracture network models dfn at an established representative elementary volume rev based on realistic geometrical and mechanical data of fracture systems from field mapping at sellafield uk the results were used to estimate the equivalent young s modulus and poisson s ratio and to fit the mohr coulomb and hoek brown failure criteria represented by equivalent material properties defining these two criteria the results demonstrate that strength and deformation parameters of fractured rocks are dependent on confining pressures loading directions water pressure and mechanical and hydraulic boundary conditions fractured rocks behave nonlinearly represented by their elasto plastic behavior with a strain hardening trend fluid flow analysis in fractured rocks under hydro mechanical loading conditions show an important impact of water pressure on the strength and deformability parameters of fractured rocks due to the effective stress phenomenon but the values of stress and strength reduction may or may not equal to the magnitude of water pressure due to the influence of fracture system complexity stochastic analysis indicates that the strength and deformation properties of fractured rocks have ranges of values instead of fixed values hence such analyses should be considered especially in cases where there is significant scatter in the rock and fracture parameters these scientific achievements can improve our understanding of fractured rocks hydro mechanical behavior and are useful for the design of large scale in situ experiments with large volumes of fractured rocks considering coupled stress deformation flow processes in engineering practice

comparison between plate jacking and large flat jack test results of rock mass deformation modulus the results of two types of loading tests for the determination of the in situ rock mass deformation modulus em namely large flat jack lfj and plate jacking tests pjt which were carried out side by side during the exploratory phase of the karun 3 hydro electric project in iran have been compared correlated and analysed the comparison includes sixteen pjts and twelve lfj tests pjt moduli obtained from displacements measured in depth are much higher than the lfj moduli and are sometimes even higher than the modulus of the intact rock material however this investigation has proved that they can be well correlated with the corresponding lfj results and reduced by factors established in this comparison the analyses showed that uncertainties connected to pjt results are caused by the restraining effects of the adjoining rock and the disturbing effects of blast damage and also that the scattering of results occurs due to insufficient volumes of rock mass tested a new empirical relationship for indirect estimates of em based on the rmr classification scheme is made from field data presented in this investigation and other reliable published data

multicomponent magnetization in western dolpo tethyan himalaya nepal tectonic implications abstract a palaeomagnetic study has been carried out in the tethyan himalaya th the northern margin of greater india twenty six palaeomagnetic sites have been sampled in triassic low grade metasediments of western dolpo two remanent components have been identified a pyrrhotite component characterized by unblocking temperatures of 270 335 c yields an in situ mean direction of d 191 7 i 30 9 k 29 5 95 5 7 n 23 sites the component fails the fold test at the 99 confidence level kin situ kbed 6 9 and is therefore of postfolding origin for reason of the low metamorphic grade this pyrrhotite magnetization is believed to be of thermo chemical origin geochronological data and inclination matching indicate an acquisition age around 35 ma the second remanence component has higher unblocking temperatures 400 c and up to 500 580 c range and resides in magnetite a positive fold test and comparison with expected triassic palaeomagnetic directions suggest a primary origin the postfolding character of the pyrrhotite component and its interpreted age of remanence acquisition implies that the main himalayan folding is older than 35 ma in the western dolpo area this study also suggests that the second metamorphic event neo himalayan was more significant in the dolpo area than the first eo himalayan one a clockwise rotation of 10 15 is inferred from the pyrrhotite component which is compatible with oroclinal bending and or rotational underthrusting models this rotation is also supported by the magnetite component indicating that no rotation of the tethyan himalaya relative to india took place before 35 ma

in situ stress measurements interpretations in large underground marble quarry by 3d modeling abstract this paper describes the studies and the in situ stress measurements carried out to support the stability analysis of underground ornamental stones quarries in particular this paper describes the findings evidence and analysis carried out at the ravaccione and fantiscritti quarries which are located in the carrara basin italy the main activities carried out during the study are starting with the characterization of the rock mass which has been done through the interpretation of data obtained from in situ geostructural surveys combining the geometrical and mechanical characteristics of the discontinuities with the mechanical features of the rock matrix in order to assess the proper rock index in accordance with the more diffused classification systems further consideration regarding the tectonic stress orientation are done through the observation of kinematic indicators on brittle structures such as faults fractures s l joints s s and fractures with no evidence of movement and systems of conjugated fractures in order to evaluate the tectonic stress main orientation for the studied area then several in situ measurements of actual state of stress on various location inside the ravaccione and fantiscritti quarries where carried out using csiro cells this preliminary work lead to the geometric reconstruction of the rock mass carried out using the computer code resoblock this phase allowed once the current excavation geometry was given to define the geometry of a discontinuous rock mass model on which thereafter a numerical simulations was carried out using the computer code 3dec at last the comparison between the numerical model results and the in situ tests allowed the back analysis of the site and lead to a most satisfying model calibration to be used for the provisional analysis of further excavation development

controls of oil family distribution and composition in nonmarine petroleum systems a case study from the turpan hami basin northwestern china controls on oil family distribution in tectonically complicated nonmarine petroliferous basins are commonly difficult to isolate because of the varying ages of potential source rocks the complex assemblage of organic rich sedimentary facies and the geographic variability of burial histories the turpan hami basin of northwestern china is an oil bearing intermontane basin where stratigraphic sedimentologic and geochemical controls are sufficient to address each of these issues independently and to determine how they influence the current distribution and composition of liquid hydrocarbons source rock age is one of three major statistically significant discriminators affecting oil family composition both lower middle lower or middle jurassic and upper permian rocks are important source rocks for the basin a newly developed diterpane biomarker parameter can distinguish permian rocks and their correlative oils from jurassic coals and mudrocks and their derivative oils source facies is a second key control on petroleum occurrence and character a variety of biomarker parameters that reflect source rock depositional conditions are indexed to rock samples from interpreted depositional environments by erecting rock to oil correlation models the biomarker parameters separate oil families into end member groups group 1 oils lower middle jurassic peatland swamp facies high land plant input less reducing conditions group 2 oils lower middle jurassic profundal lacustrine facies high algal input more reducing conditions and group 3 oils upper permian lacustrine facies high algal stratified anoxic conditions burial history exercises a third major control on petroleum distribution source rock maturation modeling can demonstrate that relatively uninterrupted burial in the asymmetrically subsiding northern turpan hami area taibei depression exhausted upper permian sourced rocks by the late cretaceous which led to southward migration of upper permiansourced oils group 3 into triassic reservoirs of southern and southwestern turpan hami tainan and tokesun depressions subsequent to uplift of the central basin thrust that currently partitions taibei from tainan lower middle jurassicsourced oils were expelled in the taibei depression by paleoceneeocene time which locally charged jurassic and cretaceous reservoirs groups 1 and 2 forming turpan hami s largest oil accumulations in the basin

carboniferous permian tectonic evolution and sedimentation of the turpan hami basin nw china implications for the closure of the paleo asian ocean abstract the tectonic evolution and sedimentary characteristics of the carboniferous permian rocks of the turpan hami basin have been analysed initially a joint inversion of gravity magnetic seismic data and the established model of electrical profiles was synthesized to create a new geological interpretation discussion on the tectonic characteristics of piedmont zone in the northern part of the basin then followed according to the analysis of balanced cross sections the tectonic evolutionary history of carboniferous permian sedimentary rocks of the turpan hami basin can be divided into three stages an extensional stage in the carboniferous a tectonic transition stage in the early permian and a compression and inversion stage after the middle permian it is found that the tectonic evolution controlled the sedimentary facies under these three stages and the sedimentation evolution has undergone marine facies marine lacustrine transitional facies and lacustrine facies meanwhile based on the recent seismic gravity magnetic and electrical data and combined with the field surveying of outcrops the residual distribution of carboniferous permian strata is characterized by the widely distributed residual upper carboniferous except for the southern liaodun uplift and locally in the eastern area and the denudation of middle permian strata mainly distributed in the turpan depression and the turpan hami depression after comprehensive analysis of the sedimentary facies and erosion of permian strata it is concluded that the tectonic evolution and sedimentation of the turfan hami basin can be used as a constraint on permian subduction related accretionary orogenesis of northern xinjiang nw china and the closure time of the paleo asian ocean

evolution of the turfan basin chinese central asia the turfan basin extends approximately 550 km east west by 100 km north south within northwest china and is located between branches of the intracontinental tien shan orogenic belt at present it is an intermontane foreland basin loaded by southward transported thrust sheets at its northern margin this deformation is a long distance manifestation of the india asia collision but the orientation and location of cenozoic structures is strongly influenced by the pre cenozoic history of the region the exposed basement marginal to the turfan basin consists of volcanics granitoids volcaniclastics and deepwater sedimentary rocks associated with the north tien shan island arc and subduction accretion complexes north of the north tien shan fault this arc had accreted to the central tien shan by late carboniferous to early permian times the north tien shan fault represents a major boundary between paleozoic arcs and accretionary complexes to the north and proterozoic basement of the central tien shan and tarim block to the south postcollisional thrusting appears to have provided a tectonic load for lower permian subsidence and sedimentation early postcollisional strata are turbidites but there was a shoaling of facies until the deposition of permo triassic conglomerates no marine sediments have been deposited in the region since the paleozoic at least two mesozoic episodes of compressional deformation are recorded at the northern margin of the basin which was an intermontane foreland basin during this era lower jurassic fluvial and lacustrine clastic rocks lie above a regional unconformity an oligocene unconformity marks the onset of coarse clastic sedimentation in the cenozoic and probably indicates the start of major compressional deformation related to the india asia collision sedimentation rates have increased through the cenozoic the neotectonics of the turfan basin are dominated by a southward directed thrust system emergent within the basin at the fire mountains range southward directed thrusting appears to have been a feature of mesozoic age tectonics and possibly the late paleozoic tectonics of the basin the most important neotectonic structures in the turfan basin follow older structural trends

maintaining geological reality in application of gsi for design of engineering structures in rock abstract in rock engineering design significant advances have occurred in recent years in numerical modelling capability with increasing trends to ever greater use of synthetic rock mass models and discrete fracture network dfn modelling but all too often with little comparative improvement in geologic base data as a consequence there is even more need that reliable estimates be available of strength and deformation characteristics of the rock masses on which or within which engineering structures are to be created be it a tunnel a foundation or a slope geological strength index gsi characterization linked with hoek brown strength determination as a basis for modelling has been widely adopted by engineers and geologists involved in design and construction of engineering structures the need for geological definition of rock mass properties required as inputs into numerical analysis constitutes one of the greatest reasons for application of the gsi chart allowing characterization of even difficult to describe rock masses including tackling even the most problematic of weak and complex rock masses back analyses of tunnels slopes and foundation behaviour using gsi and its reliable application in rock engineering designs attest to its reliability with continuing use worldwide the gsi system has continued to evolve but greater understanding is needed in the definition of input constants for establishing both gsi and intact rock properties this need for improved evaluation particularly from a geological perspective is addressed in this paper geological processes of tectonism weathering and alteration all affect gsi evaluation of these factors which are each critical to proper gsi definition are analyzed based on real rock mass cases suggested ranges in variability of intact rock parameters uniaxial compressive strength ci and material constant mi for common rock masses are presented in the context of a composite new gsi chart this chart allows selection of appropriate gsi ranges for any specific rock suite specific key engineering geological characteristics that differentiate igneous metamorphic and sedimentary one from each other are highlighted through discussion of various example rock units including gneisses granites ophiolites limestones schists siltstones mudstones shales and molassic and flysch formations illustrations are given of how geological differentiation dictates variability in geotechnical properties of most common rock masses

depositional style and subsidence history of the turpan basin nw china the turpan basin has a complex polycyclic sedimentary and tectonic history from late permian to late tertiary time main stratigraphic boundaries are unconformities that bound tectonically induced sedimentary cycles the depositional style reflects a continental environment exhibiting changes from alluvial fan fluvial to lacustrine conditions within each cycle more than 7000 m of clastic sediments accumulated during the evolution of the basin paleocurrent analysis reveals a complex pattern of sediment dispersal pathways into the basin on the southern margin of the basin the transport direction is always directed from south to north indicating sediment sources in the jueluotage shan while in the northern part the late jurassic uplift of the bogda shan provided an important source area from the early cretaceous onwards with transport directions from north to south after basin formation during the late permian the turpan basin underwent first thermal subsidence and then flexural subsidence the thermal subsidence took place during the late permian and early triassic following the period of magmatic activities in this region the flexural subsidence was throughout the middle triassic to early tertiary induced by collisions and accretions onto the south asian continental margin of the qiangtang block in the late triassic early jurassic the gangdise block in latest jurassic earliest cretaceous and the indian subcontinent in the latest cretaceous early cenozoic

the effect of sample disturbance on laboratory properties of lac du bonnet granite laboratory properties of lac du bonnet granite samples collected at depths ranging from near surface to 1000 m were established the laboratory properties indicated that either the in situ properties were changing with depth or the samples were changing with depth comparison of p wave velocities in the samples and in situ confirmed the latter i e sample disturbance was affecting the laboratory properties the strength of the damaged samples indicated that sample disturbance affected the cohesion of the material not the frictional properties and that the cohesion loss cannot be accounted for by applying a confining stress sample disturbance started to affect the laboratory properties of lac du bonnet granite when the maximum far field in situ stress exceeded about 10 of the unconfined compression strength key words sample disturbance core discing cohesion brittle rocks damage microcracks stress dependent young s modulus

triaxial strength and deformability of intact and increasingly jointed granite samples abstract triaxial strength tests were performed on artificially jointed standard size granite specimens with two sub vertical and three sub horizontal 2 3 joints a fully servo controlled press was used to load the samples and attain residual strength these tests add to an existing test database for intact and artificially jointed 1 2 joints samples of the same rock the main parameters from each test were used to analyse tendencies in particular changes in elasticity and peak and residual strength in line with increased jointing peak strength and apparent young s modulus decreased from the intact to the jointed specimens reflecting a tendency analogous to that deriving from the use of classification systems to characterize rock masses mohr coulomb and hoek brown failure criteria were fit to peak and residual strength tests results in the case of the hoek brown criterion it seems that an equivalent of the geological strength index gsi which reflects structure at the specimen scale could be of use in estimating the decrease in strength of increasingly jointed samples residual strength envelopes were practically the same for the intact and jointed specimens our results for granite would suggest that the so called rock mechanics scale effect at large i e the relevant change in material properties from rock samples at lab scale to that of the rock mass including the occurrence of natural discontinuities at the engineering work scale is more due to structure number orientation spacing and features of occurring joints than to sample scale effect i e the variation in properties when testing different size from a few mm to some decimetres unjointed intact rock samples at the laboratory

yield envelope assessment as a preliminary screening tool to determine carbon capture and storage viability in depleted southern north sea hydrocarbon reservoirs abstract this paper describes a laboratory study of the hydro mechanical properties of samples from the sherwood sandstone group ssg an onshore analogue of the finer grained lower porosity portions that make up the bunter sandstone formation bsf the study provides a yield envelope for this sandstone and demonstrates that it is a competent sandstone at relevant reservoir depths a theoretical yield envelope has been calculated based on the anticipated in situ stress induced by depletion and reinjection showing that only the high porosity 35 large grain diameter 290 m end member of the bsf is likely to result in deformation of the reservoir rock stress analysis of four fields within the southern north sea suggest that depletion of 10 mpa will not result in permanent deformation of the reservoirs assuming similar porosity and grainsize characteristics to the ssg tested furthermore re inflation is unlikely to result in permanent deformation should the injection pressure not exceed the initial pre production reservoir pore pressure

integrating damage zone heterogeneities based on stochastic realizations of fracture networks for fault stability analysis in the domain of reservoir engineering fault stability assessment is traditionally performed by assimilating fault systems to surfaces however faults are complex and heterogeneous geological systems whose compartmentalized architecture generally corresponds to an inner core surrounded by outer often fractured damage zones dz to date few studies have assessed the potential role of the dz characteristics anisotropy complex spatial distribution etc on the shear behavior of the whole system the main challenge being the proper numerical integration of fracture networks in reservoir simulators the present study was motivated by the stochastically generated fracture networks representative of dz investigated on outcrops cirques de navacelles south of france we propose here a methodology relying on homogenization techniques for deriving the spatial distribution of effective anisotropic hydro poro elastic dz properties from these stochastic fracture networks using them as inputs of 2d finite element coupled hydro mechanical models of a reservoir scale fault zone the key role of the spatially varying dz stiffness and biot s coefficients are highlighted neglecting them might lead to a high over estimation of the maximum sustainable injection pressure by nearly 50 in the considered cases

sedimentary evidence of early late permian mid latitude continental climate variability southern bogda mountains nw china abstract a preliminary early late permian mid latitude continental climatic record in nw china was interpreted mainly from sedimentary climate indicators and type and stacking pattern of depositional systems and cycles in a 1178 m fluvial lacustrine section depositional systems analysis delineated five types of primary fluvial and lacustrine depositional cycles which were grouped into three high intermediate and low orders semi arid subhumid and humid climate types in terms of relative precipitation evaporation ratio were interpreted and climate variability was identified at sub cycle and high intermediate and low order cycle scales early kungurian climate fluctuated between subhumid to humid and middle late kungurian climate shifted gradually from subhumid semi arid to semi arid roadian climate fluctuated widely from humid to semi arid with strong precipitation seasonality at sub cycle and high order cycle scales wordian climate was dominantly humid with short subhumid intervals and ended with a peak semi arid condition capitanian climate was mainly subhumid to humid as the start of a long interval of dominantly humid strongly wet dry conditions into the wuchiapingian time the late kungurian wordian semi arid condition is incompatible with modern mid latitude east coast humid climate suggesting different mechanisms operating in pangea and panthalassa the highly variable roadian wordian climate may have started terrestrial mass extinction that climaxed at the end of permian

what generated the late permian to triassic unconformities in the southern junggar basin and western turpan basin tectonic uplift or increasing aridity abstract the upper permian to triassic sedimentary successions of the southern junggar basin and western turpan basin are characterized by widespread unconformities however the origin of these unconformities remains highly controversial three sections namely the jimsar section in the southern junggar basin and the aiweiergou and yuergou sections in the western turpan basin have been systematically studied using detrital zircon u pb geochronology heavy mineral assemblages and whole rock geochemical analyses detrital zircon ages show that both upper permian and triassic samples from each section have similar age distributions with a major age group at 250 380 ma a subordinate age group at 380 540 ma and sporadic precambrian ages suggesting that the main provenance areas were the north tian shan and the northern margin of the yili central tian shan with a secondary source area in the yili central tian shan ree distributions and trace element crossplots also indicate that upper permian and triassic samples display similar characteristics in both basins all were sourced from felsic or mixed mafic felsic rocks with only a minor component of ancient or recycled sediments detrital provenance and geochemical analyses agree in showing no significant changes in the source to sink sediment transport system from the late permian to the triassic however field observations heavy minerals analysis and geochemistry do suggest that both the southern junggar basin and western turpan basin experienced an arid climate during this interval both upper permian and triassic sediments in the two basins contain abundant hematite display low cia values and th u ratios and have mudcracks redbeds and other indicators of arid climate therefore we suggest that the regional unconformities in the two basins were not generated by regional tectonic uplift but most likely resulted from an increasingly arid climate

stability analysis and optimization of the support system of an underground powerhouse cavern considering rock mass variability input parameters such as rock mass strength parameters and deformation modulus considered in the design of underground openings involve some uncertainty the current uncertainty in these parameters is due to the inherent variability of these parameters to quantify these parameters and design underground openings the statistical methods must be utilized in this research a statistical method was used to define the gsi of rock mass geological strength index block volume vb and joint conditions jc using the gsi distribution function obtained from field data and intact rock strength characteristics the statistical distribution functions of rock mass parameters were defined using the monte carlo method the statistical analysis of the stability in azad pumped storage powerhouse cavern was carried out through the point estimate method the appropriate support system was suggested according to the support pressure and the plastic zone around the cavern this study showed the application of the statistical method by combining the uncertainties of the intact rock strength and discontinuity parameters in the assessment of the strength and deformability of rock masses and the support selection process in comparison with the deterministic methods

empirical and numerical approaches for geomechanical characterization of coal seam reservoirs abstract the effects of fractures or joints on geomechanical properties of coal when transitioning from small samples to larger field scales have long been recognized two geomechanical characterization methodologies for of a coal seam for reservoir engineering are presented which attempt to account for these scale effect the first is a well established empirical rock mass classification method the geological strength index gsi the second is a newly developed numerical technique termed the synthetic rock mass srm gsi was developed to empirically account for the influence of rock joint density and joint surface conditions on the behaviour of the rock mass the established gsi to strength and deformation theories are reviewed and an approach to account for joint stiffness based on the minimum confining stress is presented the srm approach to jointed rock mass geomechanical characterization is a numerical modeling technique which combines the bonded particle model for rock and discrete fracture network simulation the intact or matrix of the srm is calibrated to laboratory data the dfn inserted creating a numerical representation of the rock mass which can then be tested at any scale in each case the approaches attempt to geomechanically characterize strength modulus etc the large scale behaviour of the coal seam where the properties can then be used for continuum type simulation reservoir simulation borehole stability etc

an example of estimating rock mass deformation around an underground opening using numerical modeling abstract in rock engineering rock strength is regarded as an important rock mass parameter and it is widely estimated using the uniaxial compressive strength ucs test a ucs test in laboratory requires sampling and preparation of core samples which necessitates time consuming and expensive studies furthermore preparation of cores is almost impossible for a weak rock material taken from foliated laminated or thinly bedded rock masses of low rock quality designation rqd values 0 20 in this case determination of ucs by laboratory test may be impossible in compliance with isrm or astm standards to overcome this difficulty indirect tests such as point load index pli schmidt hammer sh rebound number tests are often employed to predict the ucs however indirect tests are likely to yield ucs values with large standard deviations depending on the geological origin of the rock mass the block punch index bpi has recently been developed to overcome the drawbacks of ucs and indirect tests and to minimize the errors arisen from the structural deficiencies and large standard deviations in this study determination of rock mass behavior in laminated foliated bornova melange yellowish brown flysch and grayish black flysch and well jointed yamanlar volcanics altindag formation where the second phase of the izmir metro tunnels was excavated is aimed the bpi ratings were directly used in rmr calculations and indirectly used to estimate the ucs values of rock materials then the obtained results were input into numerical models along with the rock mass strength ucs rm and deformation modulus of rock mass e rm the results obtained from the numerical models agreed with that obtained results from inner tunnel convergence and ground settlement measurements

stability assessment of jinlong village landslide sichuan the jinlong village landslide is located in zitong county sichuan and approximately 150 km east of wenchuan the landslide has exhibited creep deformation for nearly 30 years field investigations indicated that the slope deformation was caused by the combined effects of unfavorable topographic and geological conditions and earthquakes the sliding surface is along a contact between silty clay and mudstone the wenchuan earthquake accelerated the creep causing bulging of the ground surface shear test results of the silty clay near the sliding surface indicated that the residual strength is consistent with the stability state of the landslide the factors of safety were calculated using the limit equilibrium method lem and the method of fast lagrangian analysis of continua in two dimensions the results using the lem indicate that the stability is clearly affected by seismic shaking and when the peak ground acceleration is 0 08g the slope reaches the limit state the shear failure surface given by numerical simulation develops on the contact between the clay and silty mudstone which confirmed the assumed sliding surfaces location using the lem

carbazole distributions in rocks from non marine depositional environments abstract pyrrolic nitrogen compounds have been studied from extracts of the rocks collected from the tertiary saline lacustrine strata in the qaidam basin and the middle lower jurassic coal bearing strata in the turpan basin nw china biomarker signatures revealed the presence of three sample groups related to saline lacustrine conditions in the qaidam basin and freshwater lake and swamp depositional settings in the turpan basin significant differences in carbazole distributions were observed among the sample groups from different depositional environments generally a strong predominance of 1 4 1 5 dimethylcarbazoles over 1 3 1 6 dimethylcarbazoles was found for the qaidam rocks from the saline lacustrine settings with a ratio of 1 3 1 6 1 4 1 5 dimethylcarbazole ranging from 0 35 to 0 66 while enhanced amounts of 1 3 1 6 dimethylcarbazoles relative to 1 4 1 5 dimethylcarbazoles were detected for the turpan samples from the swamp environments with the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio 0 8 samples from the freshwater lake environments in the turpan basin showed intermediate values for the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio in addition a predominance of 2 4 dimethylcarbazole over 2 6 dimethylcarbazole was observed for the qaidam samples whereas most turpan samples showed elevated amounts of 2 6 dimethylcarbazole relative to 2 4 dimethylcarbazole moreover 3 methylcarbazole occurred as the least abundant c 1 carbazole isomer for most qaidam rocks while the turpan samples from swamp settings often showed an enhanced abundance of 3 methylcarbazole the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio was observed to have a positive correlation with 3 4 methylcarbazole 2 6 2 4 dimethylcarbazole and pr ph respectively these observations may indicate that c 1 and c 2 carbazoles with a methyl group at c 3 c 6 prevailed for swamp settings whereas isomers with a methyl at c 4 c 5 were dominant for the freshwater or saline lacustrine environments although variations in benzocarbazoles were detected in the bitumens an obvious correlation was not observed for the different depositional environments

topographic evolution of the tianshan mountains and their relation to the junggar and turpan basins central asia from the permian to the neogene abstract the modern tianshan mountains and their surrounding basins have mainly been shaped by the far field effects of the cenozoic india asia collision however precollision topographic evolution of the tianshan mountains and its impacts on the junggar and turpan basins remain unclear due to the scarcity of data detrital zircon u pb dating of 14 new and 23 published samples from permian to neogene strata in the northern western tianshan mountains northern and southern bogda mountains and central turpan basin are combined with sedimentary characteristics lithofacies petrofacies and paleocurrent data to investigate the temporal and spatial changes in sediment provenances based on the age characteristics of the source rocks in the tianshan mountains the detrital zircons are divided into three groups pre carboniferous zircons mainly from the central tianshan mountains carboniferous to permian zircons mainly from the north tianshan and bogda mountains and mesozoic zircons mainly from syn depositional volcanic activity the topographic evolution of the tianshan mountains and their relation to the junggar and turpan basins can be generally divided into six stages 1 positive relief tianshan and bogda mountains and a rifted marine basin formed during the early permian to early middle permian following late carboniferous orogenesis as evidenced by interbedded alluvial fan conglomerates and postcollisional extension related volcanic rocks along the basin margins by marine deposits far from the basin margins and by the predominance of carboniferous to permian detrital zircons 2 fluvial to lacustrine deposits in the modern southern junggar and turpan basins are characterized by abundant pre carboniferous zircons and consistently northward flowing paleocurrents indicating the submergence of the bogda mountains and a contiguous junggar turpan continental depression basin during the late middle permian to the triassic 3 the bogda mountains began to uplift in the early jurassic resulting in opposing paleocurrent directions a sudden increase in sedimentary lithic detritus and the dominance of carboniferous to permian detrital zircons along the southern and northern margins of this range 4 in contrast to the uplift of the bogda mountains the other parts of the tianshan mountains experienced gradual peneplanation from the early jurassic to the middle jurassic as confirmed by widespread fluvial to lacustrine deposits even inside the modern tianshan mountains and by the dominance of pre carboniferous detrital zircons 5 the dominance of carboniferous to permian zircons in the southern junggar basin suggests the west tianshan mountains were uplifted during the late jurassic while the dominance of pre carboniferous zircons in the central turpan basin indicates continuous peneplanation in the eastern tianshan mountains 6 the initial shape of the tianshan mountains junggar basin turpan basin system was constructed in the late jurassic but was modified in the cenozoic by the india asia collision resulting in much higher western tianshan and bogda mountains low eastern tianshan mountains and well developed foreland basins these cenozoic changes were recorded by the rapid cooling of apatites the dominance of carboniferous to permian zircons in the southern junggar basin and northern turpan basin and the dominance of pre carboniferous zircons in the central turpan basin

integrated provenance analysis of a complex orogenic terrane mesozoic uplift of the bogda shan and inception of the turpan hami basin nw china we employ petrographic and advanced geochemical tech niques to better document the evolution of the turpan hami basin based on the unique geologic histories of the arc terranes that served as potential sources of turpan hami deposits first a provenance study of permian through cretaceous sandstone of the turpan hami basin reveals temporal and spatial changes in dominant source ter ranes that provided detritus to the basin volcanic lithic rich upper permian sandstone mean qm 19f18lt63 q p 7lvm89lsm4 q m 48p39k13 followed by more quartzose compositions in triassic sandstone mean qm 41f19lt40 q p 20lvm75lsm5 q m 68p21k11 indicate progressive un roofing of the extinct northern and central tian shan arc terranes to the south of turpan hami a sharp change to sedimentary lithic rich lower jurassic sandstone mean qm 47f16lt37 q p 16lvm42lsm42 qm 75p12k13 overlain by a return to volcanic lithic rich middle ju rassic sandstone mean qm 39f21lt40 q p 14lvm51lsm35 q m 65p21k14 points to the initial uplift and unroofing of the largely andesitic bogda shan to the north which first shed its sedimentary cover as it emerged to become the partition between the turpan hami and southern jung gar basins second geochronological trace element and sm nd isotopic varia tions among granitoids in the late paleozoic tian shan orogenic belt provide a further test of mesozoic uplift of the bogda shan on the basis of previous models of crustal compositions throughout the south central and north tian shan bogda shan and east and west jung gar terranes we infer that isotopically enriched granitic cobbles av erage endi 5 20 50 n 5 6 contained in lower triassic deposits in the north central turpan hami basin were derived from the continen tal crustal central tian shan terrane south of turpan hami and not from the more oceanic north tian shan bogda shan and east and west junggar terranes north of the turpan hami basin we therefore infer that the ancestral bogda shan had not been uplifted by the early triassic and that prior to this time a unified junggar turpan hami basin existed during late permian deposition of extensive lacustrine deposits

simplified method for estimating the hoek brown constant for intact rocks abstractthe constant mi is a fundamental parameter required for the hoek brown hb criterion to estimate the strength of rock materials to calculate mi values triaxial tests need to be carried out however triaxial tests are time consuming and expensive in this research a simplified method is proposed that can estimate mi values using information on rock types and the uniaxial compressive strength ucs of intact rocks to evaluate the reliability of the proposed method mi values estimated from the proposed method are used in the hb criterion to predict intact rock strength the predicted intact rock strength is then tested against experimental intact rock strength using existing triaxial tests and tests in the authors laboratory results from the comparison show that mi values calculated from the proposed method can be used reliably in the hb criterion for estimating intact rock strength when triaxial test data are not available

bayesian estimation of the normal and shear stiffness for rock sockets in weak sedimentary rocks abstract the design of socketed foundations in weak sedimentary rocks is often governed by settlement the shear stiffness of the rock socket sidewalls and the normal stiffness of the rock socket base are the main parameters that affect the settlement of rock sockets at service load conditions and are needed for settlement calculation in load transfer method or using the theory of elasticity in this paper in situ load test data for socketed foundations in weak rocks are collected the shear stiffness of the rock socket sidewalls and the normal stiffness for the rock socket base are respectively estimated based on the measured side shear stress and shear displacement and base contact pressure and normal displacement relationships the parameters affecting shear and normal stiffnesses are discussed a bayesian approach is used to develop probabilistic models for the rock socket shear and normal stiffnesses which are functions of both rock properties and the rock socket size

development of stratigraphically controlled eolian modified unconsolidated gravel surfaces and yardang fields in the wind eroded hami basin northwestern china

jurassic paleogeography of the tian shan an evolution driven by far field tectonics and climate abstract the strongly intracontinental tian shan region in central asia represents a key area to understand the long term evolution of continents in general and asia in particular if its paleozoic and cenozoic geodynamics are well understood its mesozoic evolution remains poorly constrained in order to decipher the paleogeographic and large scale tectonic evolution of the tian shan area during the jurassic we compiled detailed field analyses of sedimentary rocks acquired within and around the chinese tian shan region together with previously published data we present three paleogeographical maps corresponding to the late early early middle jurassic late middle early late jurassic and late jurassic early cretaceous transition periods we provide a large scale picture of the jurassic paleogeographic and climatic evolution of the tian shan region and discuss the geological evolution of the range together with the possible driving mechanisms during the early to early middle jurassic the topographic evolution of the tian shan range was dominated by progressive planation of late paleozoic to early mesozoic relief locally interrupted by short lived tectonic uplift throughout the region contemporaneous sedimentation was characterized by alluvial to lacustrine strata deposited under humid conditions during this period recurrent limited deformation events associated with strike slip and compressive tectonics occurred that cannot be explained by far field effect of the qiangtang collision but could instead be associated to the coeval subduction related extension affecting the caspian turan domains during the late middle to early late jurassic the planation of the paleozoic early mesozoic tian shan range then continued a shift to more semi arid conditions during the late jurassic is also recorded in the sedimentary series all over the region at that time few evidences of deformation exists in the tian shan or within the caspian turan domains we propose that the late middle early late jurassic corresponded to a period of relative tectonic quiescence in the area finally the late jurassic early cretaceous transition was marked by a tectonic reactivation leading to the inversion of the yarkand fergana basin and to localized relief building in the tian shan this renewed transpressive deformation phase could be mainly related to the coeval accretion of the helmand block to the south west and possibly to the onset of the accretion of the lhasa block along the southwestern margin of eurasia finally this period was also characterized by the climax of aridification which played a major role on the emplacement of extensive alluvial fan systems in the basins surrounding the range

pre miocene deformation of the himalayan superstructure hidden valley central nepal abstract throughout the himalaya the tethyan sedimentary sequence forms the detached carapace or superstructure to exhumed mid crustal rocks in central nepal low metamorphic grade cambrian to jurassic rocks of this carapace preserve five phases of deformation structurally dominated by second phase d 2 north verging back folds that oppose the vergence of the orogen the folds are overprinted and cross cut by the c 22 ma south tibetan detachment system and the manaslu leucogranite new structural mapping in hidden valley provides further constraints on the character of d 2 megascopically large asymmetric north verging folds define d 2 microscopically it is characterized by an axial planar cleavage balanced cross sections and bed length restoration of f 2 folds indicate a minimum of 32 38 shortening and 180 thickening during d 2 these data indicate that north verging folds played a significant role in pre miocene crustal thickening of the himalayan superstructure the formation of these folds is compatible with wedge extrusion or channel flow of the underlying mid crustal rocks whereby their geometry reflects early coupling between the upper and middle crust

the upper jurassic lower cretaceous alluvial fan deposits of the kalaza formation central asia tectonic pulse or increased aridity the topographical evolution of tectonic systems as well as the sedimentation pattern and depositional environments in the associated basins are controlled by both tectonics and climate in the region of the tien shan central asia the jurassic lower cretaceous period was marked by complex low intensity tectonic deformation and major climate changes from humid to arid conditions jurassic to semi arid conditions cretaceous using the sediment record in the junggar tarim and fergana basins to describe the tectonic evolution of the tien shan area during the mesozoic thus requires differentiation between the tectonic and climatic influences on sedimentation the conglomerates of the upper jurassic lower cretaceous kalaza formation were commonly associated with renewed tectonic activity resulting from the docking of the lhasa block along the southern margin of asia from sedimentology and sequence stratigraphy analyses of several sections in the junggar tarim and fergana basins we reassess the main factors controlling the deposition of this formation we show that while some tectonic activity persisted throughout the jurassic cretaceous transition the switch from the sandy deposits of the upper jurassic qigu formation to the coarse deposits of the kalaza formation is largely linked to the development of an arid climate

determination of deformation modulus in a weak rock mass by using menard pressuremeter abstract the deformation modulus of heavily jointed andesitic rock mass was investigated by using 41 menard pressuremeter test results and geotechnical information obtained from seven geotechnical boreholes the geotechnical borehole logs and laboratory test results provided by a mining company were used for the assessment of rock mass characterization the log and the test results were taken into account in the rock mass classification work the well known empirical equations were employed to predict the deformation modulus of the rock mass the predictions and the pressuremeter test results were compared and their performance indicators were presented non linear multiple regression methods were used for predictive modelling of the deformation modulus of the rock mass by considering the available data rock quality designation rqd discontinuity condition rating dc of the rock mass rating rmr system and uniaxial compressive strength of the intact rock ci were taken into consideration as input parameters in four new prediction equations to be used for determination of deformation modulus one more equation was proposed by the addition of the depth as a predictive parameter the influence of the depth and vertical to horizontal stress ratio k on the deformation modulus was preliminarily examined by using finite element modelling initially the rock mass was assumed to be an isotropic elastic brittle plastic medium later on the rock mass was modelled as a discontinuum by imposing a discrete fracture network dfn keeping all of the mechanical properties constant different depth and k parameters were applied to the pressuremeter models no influence of the depth and k on the deformation modulus was observed for the isotropic medium while the depth contributed to an increase in the modulus in the anisotropic discontinuum analysis the numerical modelling findings constituted a basis for the inclusion of the depth parameter into the new predictions

junggar basin northwest china trapped late paleozoic ocean abstract the junggar basin originated during the late paleozoic as either a remnant lower to mid paleozoic ocean basin or a mid carboniferous back arc intra or inter arc basin bounded by emergent volcanic arcs south of the siberian craton the retreating junggar sea left behind a regressive sedimentary section comprising at least 3 4 km of marine volcaniclastics in the southern junggar area sandstones deposited in the junggar basin since the devonian are exclusively volcaniclastic demonstrating that precambrian basement rocks have never been exposed in the basin and supporting the hypothesis that the junggar is underlain by oceanic crustal materials the mid carboniferous junggar ocean may have been a remnant ocean basin of early to mid paleozoic age or alternatively may have been an extending intra or inter arc basin formed behind an emergent volcanic arc in the northern turpan region subsequent strike slip deformation and the general sparsity of geologic and geophysical data from the junggar area make it difficult to distinguish between these models late early permian through triassic sediments of the junggar basin are exclusively non marine deposited in a flexurally subsiding foreland basin during initial uplift of the ancestral tian shan mountains the sedimentary section deposited during the late permian early triassic appears to be inconsistent with a proposed rifting episode during this period

discussion on the paper by m orhan n s isik t topal m ozer effect of weathering on the geomechanical properties of andesite ankara turkey environmental geology 50 1 85 100

paleoenvironments and paleogeography of the lower and lower middle jurassic coal measures in the turpan hami oil prone coal basin northwestern china detailed facies and paleogeographical analyses of extensive borehole and outcrop data from lower and lower middle jurassic oil prone coal bearing sequences in the turpan hami oil producing basin of northwest china have led to the reconstruction of a basinwide depositional model a total of 20 distinct lithofacies have been identified and grouped into braided fluvial plain meandering fluvial plain braided delta meandering channel delta and lacustrine depositional systems coal forming swamps occur in each depositional system but the preferred sites of accumulation are interdelta bay and lower delta plain environments in the braided delta and meandering channel depositional systems and it is in these sites that major oil prone source rocks are located a series of age specific basinwide paleogeographical maps have been constructed leading to a depositional model for the basin results indicate that the basin experienced cyclic flooding to produce swamps and lakes and that these characterize the deposition of the lower and lower middle jurassic coal measures analyses indicate that both the bogda and harlik mountains were uplifted prior to the early jurassic and a lake separated the two mountain regions during the early and early middle jurassic from these results it is interpreted that major oil prone coal sequences are to be found in the western part of the taibei depression of the basin and thus the full economic potential of the basin has yet to be fully realized

the evolution of the north german basin and the metamorphism of the lower crust in an integrated analysis metamorphic processes in the accreted crust potential field anomalies temperature field and subsidence history are summarized into a model for the development of the north german basin the model integrates observed phenomena such as the high nitrogen content in natural gases in permian sandstone reservoirs and the structure of the crust with model calculations rock density increase subsequent volume reduction and loss of volatiles during metamorphism lead to a depression at the surface of the earth the load of the sediments which will be deposited in the depression enhances the subsidence and the ongoing metamorphism the model provides an alternative to the application of existing tectonic stretching models for the explanation of the subsidence of sedimentary basins

palaeosol stratigraphy across the permian triassic boundary bogda mountains nw china implications for palaeoenvironmental transition through earth s largest mass extinction abstract upper permian and lower triassic palaeosols from northeastern tethyan localities exposed within the bogda mountains nw china provide a wealth of information regarding long term palaeoclimatic and palaeoenvironmental variations wuchiapingian palaeosols are characterized by intense redoximorphy accumulation of vascular plant matter accumulation of clay minerals and fe oxides slickensides and clastic dikes suggesting a soil moisture regime that ranged from perennially wet to distinctly seasonal in soil moisture budget changsinghian to early induan palaeosols include subsurface accumulations of clay and carbonate as well as surficial accumulations of organic matter indicative of sub humid to sub arid soil moisture and variable soil moisture regimes induan to olenekian palaeosols contain pedogenic caco 3 accumulations and gypsum pseudomorphs indicating a drier environment characterized by net soil moisture deficiency elemental composition of palaeosol matrix was used to estimate palaeoprecipitation through the chemical index of alteration minus potassium cia k proxy estimates from various wuchiapingian strata indicate relatively stable palaeoprecipitation during the late changsinghian and early induan palaeoprecipitation appears to have decreased from 1100 to 230 180 mm year over less than 100 m of vertical stratigraphic section in the induan and olenekian palaeoprecipitation appears much less stable than in wuchiapingian with values vacillating from 290 to 1014 mm year the transition to a relatively unstable precipitation state coincides generally with the permian triassic boundary and may reflect climatic disturbances associated with the end permian extinction event in addition to altered atmospheric circulation patterns resulting from regional tectonics moisture availability and expansion of the subtropical high pressure belt

planation surfaces of the tian shan range central asia insight on several 100 million years of topographic evolution abstract in central asia numerous fragments of planation surfaces are visible within the present day topography however their precise timing of formations is still poorly constrained and it is not clear if they are remnants of a single extensive planation surface or if they represent different planation episodes by reconstructing the landscape evolution of the tian shan region and by analyzing the relations between the planation surfaces preserved within the eastern tarim basin and the sedimentary record we demonstrate that the numerous erosional surfaces preserved within the tian shan range represent different episodes of surfaces genesis these erosion events span from the late paleozoic to the early cenozoic the widespread preservation of large fragments of these surfaces within the tian shan range implies that this region did not undergo strong relief building during most of its mesozoic evolution but was dominated by plains associated to small hills along episodically active discrete tectonic structures finally the preservation of these surfaces within the active tian shan range implies a long term strong non equilibrium state of the topography during its cenozoic evolution this was probably promoted by the arid to semi arid climate prevailing since the late paleogene onset of relief building

numerical analysis of a large landslide induced by coal mining subsidence mining induced subsidence is one of the challenging problems in geotechnical engineering the surface topography of the ground over mining excavations plays a key role in the mechanism of subsidence when a mining operation is performed beneath mountainous or hilly terrain it may trigger landslides this study therefore aims to analyse the impacts of underground mining on the stability of slopes by using numerical modelling a coal mining induced landslide at nattai north australia is investigated as a typical case study in this area mining operations beneath the sydney basin escarpments initiated the largest contemporary landslide and mass movement known in australia cunningham 1988 discontinuous numerical modelling is employed to analyse the mechanisms of the ground movements leading to this landslide the role of geological and geotechnical factors such as rock mass characteristics bedding and joints are discussed through the numerical modelling the outcomes of the analyses reveal that mining induced stresses lead to the shear and compressive failure of weak strata at the escarpment base particularly around its toe the failure of the base materials as well as the caving of the overlaying bedded rocks into the extracted panel facilitated the detachment of the massive sandstone this rock column ahead of the escarpment was overlaying the weak strata the numerical results also indicate that the aforementioned rock column remained almost unaffected during mining however the failure of the weak strata at the toe of the escarpment initiated the simultaneous forward sliding and toppling of the rock column this mode of failure which is known as ski jump type of failure was previously observed and explained by pells et al 1987

three dimensional analysis of a deep seated landslide in central taiwan the unstable slope which is located at lushan central taiwan slid when heavy rainfall occurred in recent decades posing a threat to a nearby village slope stability analysis in three dimensions is more realistic and can advance comprehension of the sliding mechanism the landslides caused by two heavy rainfall events are simulated in sequence using finite element modeling the three dimensional 3d modeling is established according to the data of extensive investigations including field reconnaissance borehole drilling laboratory experimentation and monitoring of groundwater tables and displacements in particular it requires skills for the generation of a sliding surface and the division of the 3d model the difference in lithology and a joint set initiated the instability of the slope forming the fractures on the slope the sliding surface with greatest depth over 100 m has not yet extended to the lower slope resulting in greater displacements on the upper and middle slopes than those on the lower slope the 3d numerical modeling not only reasonably simulates the displacements induced by the rainfall events but also enables 3d visualization and details of the sliding mechanism also it is capable of revealing the features that cannot be explained in a 2d analysis

indirect determination of the modulus of deformation of rock masses based on the gsi system today as a result of the increase in the number of large tunnel constructions and underground excavations required for civil engineering and waste disposal and the operation of deep open pit mines determination of rock mass properties has become one of the most important stages in design and construction for rock engineering when rocks and rock masses are classified for geotechnical purposes this needs to be on the basis of strength or static modulus of deformation to give an indication of their stability or deformational response in addition the strength and modulus of deformation are the necessary input parameters of the rock masses to be utilized by numerical methods the modulus of elasticity of the rock material is undoubtly the geomechanical parameter that best represents the mechanical behaviour of rock material a similar conclusion can also be made for rock masses however the modulus of deformation of rock masses should be determined in situ by carrying out special tests which normally implies considerable costs and operational difficulties because of such difficulties the determination of the modulus of deformation of the rock masses continues to attract the attention of rock engineers and engineering geologists given the importance of having the value of the modulus of deformation available and at the same time the operational and economical difficulties mentioned above many researchers mentioned below were led to consider several cost effective and not too time consuming indirect procedures that can provide information on the modulus of deformation these attempts

ambient resonance of mesa arch canyonlands national park utah we analyzed the resonance characteristics of a prominent natural arch in canyonlands national park mesa arch as measured from ambient seismic data evaluating spectral and polarization attributes we distinguished the first four resonant frequencies of the arch 2 9 6 0 6 9 and 8 5 hz as well as basic properties of the associated mode shapes we then affirmed experimental data using 3 d numerical modal analysis providing estimates of material properties and clarifying vibrational mode shapes monitoring resonant frequencies over time we searched for shifts associated with changing environmental conditions and long term progressive damage we measured 3 direct daily variation in resonant frequency associated with changing rock temperature thermal stress and stiffening of the rock matrix independent tilt data showed similar diurnal cycles associated with thermoelastic stresses and deformation of the arch we observed no permanent resonant frequency shifts related to irreversible damage of mesa arch during our study period

fault dislocation modeled structure of lobate scarps from lunar reconnaissance orbiter camera digital terrain models 1 before the launch of the lunar reconnaissance orbiter known characteristics of lobate scarps on the moon were limited to studies of only a few dozen scarps revealed in apollo era photographs within 20 of the equator the lunar reconnaissance orbiter camera now provides meter scale images of more than 100 lobate scarps as well as stereo derived topography of about a dozen scarps high resolution digital terrain models dtms provide unprecedented insight into scarp morphology and dimensions here we analyze images and dtms of the slipher racah x 1 mandel shtam 1 feoktistov simpelius 1 and oppenheimer f lobate scarps parameters in fault dislocation models are iteratively varied to provide best fits to dtm topographic profiles to test previous interpretations that the observed landforms are the result of shallow low angle thrust faults results suggest that these faults occur from the surface down to depths of hundreds of meters have dip angles of 35 40 and have typical maximum slips of tens of meters these lunar scarp models are comparable to modeled geometries of lobate scarps on mercury mars and asteroid 433 eros but are shallower and 10 steeper than geometries determined in studies with limited apollo era data frictional and rock mass strength criteria constrain the state of global differential stress between 3 5 and 18 6 mpa at the modeled maximum depths of faulting our results are consistent with thermal history models that predict relatively small compressional stresses that likely arise from cooling of a magma ocean

tunnelling through the young himalayas a case history of the maneri uttarkashi power tunnel abstract a 8 56 km long circular tunnel with a finished diameter of 4 75 m has been constructed for the maneri hydel hydro electric project on the river bhagirthi the tunnel passes through quartzitic and metabasic rock formations of the young himalayas the tunnel excavation was accomplished from four headings one from the upstream end at maneri two from an intermediate adit at heena and one from the downstream end near uttarkashi where an 80 mw power house is located problems of tunnel face collapse with or without heavy ingress of water cavity formation and large tunnel closures leading to buckling of steel ribs on account of squeezing ground conditions were encountered methods to combat these problems are described the absence of advance knowledge of the frequently chanigng rock mass and ground water conditions and therefore the inability of the tunnelling engineers to modify the construction method and the support system was responsible for these problems predic values of support pressure obtained from the empirical methods of terzaghi barton et al and the one proposed by singh et al have been compared with the observed values of checking the reliability of various methods particularly for poor rock masses

engineering geological and geotechnical investigations along the head race tunnel in teesta stage iii hydroelectric project india abstract an investigation of the engineering geological properties and geotechnical parameters of rock masses along a horseshoe shaped head race tunnel hrt in the teesta stage iii hydroelectric project sikkim india was carried out to analyze the rock mass properties for optimum support system the empirical methods field tests and numerical modeling were employed to determine rock mass properties several empirical equations and statistical analysis were performed to obtain the rational and reasonable results the tunnel passes through different geological formations and critical zones the field investigations indicate the presence of five joint sets which contribute towards the development of unforeseen wedges along the tunnel alignment the attitudes of joints were measured by brunton compass and analyzed with dips v 5 1 software the potential wedge block analysis and factor of safety fs were determined using unwedge v 3 0 software the rock mass classification assessment of tunnel stability and necessary support types were carried out with q rmr and rmi systems as empirical tunnel support design methods the numerical method phase2 v 6 0 was used to quantify plastic zone and squeezing potential of the tunnel the installed support systems as per empirical methods were cross checked by means of numerical modeling field observations and engineering judgments according to the results from different methods 3 0 4 4 m rock bolts shotcrete 0 1 0 15 m wire mesh and final concrete lining were proposed it was observed that the plastic and deformed zones surrounding the excavation area got appreciably reduced after the recommended support installation

end bearing response of open ended pipe piles embedded in rock abstract prediction of bearing capacity of steel pipe piles in rock masses is an important consideration in civil engineering especially as such prediction influences the safety of the supported superstructures as well as the pile integrity in pile driving operations provided that the rock mass is described as a linear elastic and perfectly plastic material obeying the hoek brown failure criterion a finite element analysis is performed to investigate the embedment depth effect on the annular base bearing capacity and the failure mechanism of typical open ended pipe piles in sedimentary rock masses the pipe pile has smooth walls and rough toe surface annular toe resistance of pipe piles can serve as an estimate of the rock mass resistance to driving in a fully coring mode which is usually expected for large diameter open ended pipe piles pipe pile results are also extended to circular piles and embedded strip foundations socketed in rock masses the analysis is shown to highlight the influence of the annular geometry of the pipe pile causing an unsymmetrical failure mechanism with respect to pipe wall center as well as an inclination of rock mass reaction which if sufficiently large may lead to pile convergence and damage during pile driving operations the failure mechanism legitimates the plug tendency to rise up in the pipe and explains the plug formation the study demonstrates that in most practical applications the bearing capacity of pipe piles approaches a limiting value which is less than or at most equal to the end bearing capacity of an embedded strip foundation of width equal to the pipe wall thickness a comparison has been made with experimental data it is shown that the results are relatively in good agreement with test data in terms of rock mass resistance and the mechanism of rock plug formation

jurassic tectonostratigraphic evolution of the junggar basin nw china a record of mesozoic intraplate deformation in central asia mesozoic basins in northwest china provide important records for investigating relationships between intraplate deformation in central asia and tectonic processes at asian boundaries the present study using well seismic outcrop and thermochronology data in the junggar basin and neighboring areas describes the main features of jurassic strata in the basin analyzes the jurassic evolution of the basin and neighboring mountain belts and discusses possible mechanisms of jurassic intraplate deformation in central asia during the early middle jurassic episodic uplift of surrounding mountain belts kept the junggar basin a contractional closed basin and alluvial fan fluvial delta and lacustrine depositional environments successively developed from surrounding ranges to the central basin during the late jurassic the western and central parts of the basin were folded and uplifted and deposition migrated mainly to the eastern basin during the latest jurassic earliest cretaceous pre cretaceous strata in the eastern and northeastern junggar basin were folded and uplifted and coarse grained sediments were transported from surrounding uplifts to the central basin we suggest that jurassic episodic deformation events in the junggar basin and other areas of central asia are related to the qiangtang collision during the late triassic early jurassic the closure of the western mongol okhotsk ocean at the early middle jurassic boundary a collision of a microcontinent in the pamir with the southern asian margin during the late middle jurassic early late jurassic the collision of the kolyma omolon block with siberia at the end of the jurassic and the subsequent closure of the eastern mongol okhotsk ocean during the latest jurassic earliest cretaceous

a specific upscaling theory of rock mass parameters exhibiting spatial variability analytical relations and computational scheme abstract in this paper the representation of geological conditions in a numerical simulation model is considered by the expression geological conditions we mean the 3d volume geometry of the geological formations the spatial variability exhibited by the rock parameters inside each of these geological volumes and the necessary upscaling of the rock deformability and strength parameters that are determined in the laboratory from cores collected in the field a specific theory is outlined of how to go from laboratory tests geological information and field measurements and observations to the full scale numerical or ground model that includes apart from initial and boundary conditions and ground water the rock constitutive laws and associated material parameters for use in simulation models the term specific used in the title of this paper stems from the fact that other possible approaches for the same problem may be applied i e empirical rock mass classification systems explicit modeling of joints in the rock by the distinct element or finite element methods homogenization techniques etc the method used to take into account the spatial variability of rock mass properties by virtue of geostatistical theory and 3d modeling tools is also outlined with an example case study

engineering geological studies of the diversion tunnel focusing on stabilization analysis and support design iran abstract in this paper a detailed engineering geological assessment of rock masses and support design studies at garmi chay dam site has been carried out this project is located in the northwest of iran and will be used for flow control and water storage the diversion tunnel of the dam has a diameter of 5 5 m and a length of 420 m and will be driven in slightly to highly weathered micaschist and trachy andesite rock units the geological studies include field and laboratory investigations that based on the results for more exact investigation tunnel alignment was divided into three geotechnical zones these zones consist mainly of highly weathered gray micaschists dark red trachy andesites and slightly weathered gray micaschists respectively then for every zone support capacity of rock masses was evaluated by means of empirical and numerical methods the rock mass classification systems rmr q gsi rsr src and rmi the convergence confinement method and a 2d finite element computer software phase2 were used for empirical and numerical method respectively according to the results acquired from these methods some stability problems were expected in the tunnel especially in highly weathered micaschist zone so that in practice two big collapses occurred because of high weathering low constants of rock masses and their soil like behavior the stability analysis by analytical method does not give illogical results in lightly weathered micaschist zone the support system suggested by empirical method was applied and its performance was evaluated by means of numerical modeling after installation the support suggested by phase2 program the thickness of plastic zone and deformations around the tunnel decreased significantly consequently the agreement of these methods with each other was resulted and using combination of them was recommended for more reliable support design

deformation failure and permeability of coal bearing strata during longwall mining abstract to mitigate water shortage a few groundwater reservoirs are being built at the daliuta coal mine shaanxi province china it is essential to investigate the deformation failure and permeability of coal bearing strata during longwall mining and their influences on the construction of groundwater reservoirs in this paper the local geology was introduced briefly and the complete stress strain and permeability for different rock samples were investigated using laboratory experiments and then a three dimensional coupling model between stress and permeability was proposed after that a series of numerical simulation was performed to investigate the dynamics of stress permeability coefficient using flac3d it turns out that due to the relatively low mechanical strength of the coal bearing strata at the daliuta coal mine there are only two zones above the goaf that is caving zone and fracture zone and the fracture zone extends directly to the surface the rock mass permeability is closely related to the stress strain and the permeability decreases with the rise of stress in the stage of elastic deformation while it increases significantly in the stages of plastic deformation and failure the maximum value of permeability coefficient appears in the stage of strain softening and the value varies greatly with the rock lithology during the advancement of longwall face the redistribution range is much wider for permeability than for rock failure and the permeability is the largest on the periphery of goaf rock mass with increased permeability is horizontally oval shaped and vertically saddle shaped the permeability of coal seam roof and floor experiences three stages decrease increase and gradual recovery during coal mining the results are in good agreement with those of physical modeling and field observation the outcomes may contribute to the site selection and construction of the groundwater reservoir at the daliuta coal mine

using geological strength index gsi to model uncertainty in rock mass properties of coal for cbm ecbm reservoir geomechanics abstract the use of geostatistics has become an important concept to characterize uncertainty in reservoir simulations only recently has the concept been applied to geomechanics and coupled reservoir geomechanical simulations the work presented here describes how the geological strength index gsi is used to represent the fractured reservoir properties of a coalseam reservoir and link changes in flow properties with stress changes as well as to strength and deformation the approach is demonstrated by using a spherical geostatistical model to create 11 gsi realizations and one constant gsi model two years of primary methane production and then 3 months co 2 storage were simulated using each of the 12 models as inputs much higher cumulative gas and gas production rate profiles were observed for models with a mean gsi below 80 than the 80gsi model all models above 80 gsi show much lower cumulative gas and gas production rates than the 80gsi model the same trend held true for the co 2 injection component of the operation stress path profiles for three monitoring points in the reservoir showed large variability but similar paths whereas monitoring points in the overlying caprock showed very low variability for each realization

engineering geological study of the second part of water supply karaj to tehran tunnel with emphasis on squeezing problems abstract this research is concerned with the assessment of squeezing potential along the second part of water supply karaj to tehran tunnel one of the new components of water conveyance system in the north of iran is the karaj to tehran water conveyance tunnel that has been excavated by a double shield tbm this research has been performed on the second part of the tunnel with 14 km long passes mainly through the pyroclastic and igneous rocks of eocene age the geological studies include field and laboratory investigations based on the results and for more exact investigation tunnel alignment has been divided into 20 geological engineering units rock mass classifications have been performed for all units then rock mass properties were calculated using empirical equations because of high overburden up to 800 m and the presence of faults and crushed zones it was necessary to evaluate squeezing potential along the critical section of the tunnel therefore empirical and semi empirical approaches and a new method as critical strain have been used for evaluation of squeezing potential some experimental equations were used for estimation of critical strain and also phase 2 program has been used to calculate tunnel convergence consequently squeezing index was estimated this index is used for determination of squeezing degree as a result fair squeezing potential was found in crushed zones along the tunnel route

the development of a coal measure classification cmc and its use for prediction of geomechanical parameters abstract many studies have been performed to predict the strength and deformation moduli for both rock masses and discontinuities however in most empirical equations in the literature that have been proposed for the estimation of the strengths and deformation moduli the rock mass is assumed isotropic although it is known that the strength and deformation of a stratified rock mass varies depending on the loading direction in relation to the orientation of the lamination planes there exists at present no commonly accepted method for characterising this anisotropy this paper outlines the development of a rock mass rating system for coal measure rock masses that can be used to empirically predict the engineering properties of stratified rock masses the output from the classification system is two numerical ratings representing the different engineering properties of the strata in directions parallel and perpendicular to stratification a detailed description on the methodology used to develop the classification system has been given and the derivation and rating of the various rock mass parameters is outlined the methodology of deriving the in situ stratified rock mass input parameters and geomechanical computational analysis is illustrated for the case of two rock bolted roadways within a representative deep uk coal mine the model predictions were validated against the actual in situ monitoring data of displacements within the immediate roof of the roadway

geomechanics stability assessment of world war i military excavations at the canadian national vimy memorial site france abstract the canadian national memorial site vimy ridge france commemorates the efforts and loss of life of canadian troops in the first world war wwi the site comprises the monument a visitors centre the grange tunnels and restored trenches and several cemeteries a substantial portion of the battlefield terrain remaining from wwi is preserved at this site including trenches shell holes and military mining craters the ground surface is further disturbed by subsidence of the ground surface into underground excavations left from the war a significant number of subsidence events have been recorded within the last decade there is concern that ground surface subsidence could compromise the safety of visitors or workers at the site the excavations of concern include dugouts headquarters and hospitals and were excavated in chalk possible excavation types dimensions and support were investigated in the historical literature to assess the potential for ground subsidence the geological setting was investigated and the chalk was mapped and sampled to determine the geomechanical characteristics of the material the chalk was accessed in quarry excavations and in tunnels and declines that have been discovered and re opened in recent years finally the influence of excavation geometry and depth chalk condition and effects of weathering on the excavation stability were assessed using numerical simulation using a finite element program and considering voussoir beam stability interpretation of the results of this analysis allow development of general relationships between span depth and possible failure to isolate excavation classes that pose a long term hazard and to reduce the priority for those that are unlikely to fail to surface as well as those that are likely to have failed soon after construction

assessment of rock mass strength for underground excavations abstract when the stability of underground openings is assessed one must concern with local and global failure modes local failures may take place as long as rock blocks are kinematically movable into openings while global failure modes are associated with the stress state and the strength of rock mass surrounding openings this fact is always confused in underground rock engineering first the authors briefly describe several approaches how to assess the strength of rock masses together with some new proposals for underground excavations then the estimations by these methods are compared with each other as well as with experimental data finally the validity of these methods are discussed and some recommendations are made for practical applications

empirical estimation of rock mass modulus the deformation modulus of a rock mass is an important input parameter in any analysis of rock mass behaviour that includes deformations field tests to determine this parameter directly are time consuming expensive and the reliability of the results of these tests is sometimes questionable consequently several authors have proposed empirical relationships for estimating the value of rock mass deformation modulus on the basis of classification schemes these relationships are reviewed and their limitations are discussed based on data from a large number of in situ measurements from china and taiwan a new relationship based upon a sigmoid function is proposed the properties of the intact rock as well as the effects of disturbance due to blast damage and or stress relaxation are also included in this new relationship