tidal forcing of basal seismicity of ice stream c west antarctica observed far inland the seismicity rate beneath the downglacier 85 km of ice stream c west antarctica is modulated by the tide the tide beneath the ross ice shelf modifies the force balance of the ice stream basal environment enough to change the rate of basal microearthquake generation by an order of magnitude this tidal forcing travels up the ice stream as an attenuating wave at approximately 1 6m s 1 and is detectable 85km from the grounding line we successfully model this behavior as an elastic ice stream underlain by a viscous substrate of viscosity and thickness hb and calculate that the substrate has an apparent stiffness hb of o 108 pa s m 1 this finding suggests that the conditions of the till layer at the bed of ice stream c are similar to those of ice stream b and that the reason for the recent stagnation of ice stream c is other than loss of till we further find that the ice stream at the grounding line is more strongly affected by ice shelf processes than by the basal shear stress

parametric assessment of salt cavern performance using a creep model describing dilatancy and failure abstract the present paper discusses a systematic approach to study the time dependent performance of underground storage caverns in rock salt an elasto viscoplastic constitutive model capable of describing dilatancy short term failure and long term failure during creep of rock salt was implemented in a lagrangian finite element formulation using the finite element formulation a series of numerical analyses was performed to investigate the influence of the cavern geometry and non salt interbeds on the performance of underground storage caverns excavated in rock salt in the framework of large displacements the attained results demonstrated the capability of the proposed approach in performance assessment of the underground caverns

influence of the leaching phase on the mechanical behavior of salt caverns abstract big caverns can be leached out from salt formations during the leaching process cold water is injected in the cavern through tubing warmer brine is withdrawn through an annular space thermal balance is relatively intricate because salt dissolution is an endothermic process whereas brine and water exchange heat through the steel tubing inside the well as a whole the rock mass is cooler around the cavern after leaching than before resulting in a small reduction of cavern creep

spatial extent of a hydrothermal system at kilauea volcano hawaii determined from array analyses of shallow long period seismicity 2 results we present a probabilistic method to locate the source of seismic events using seismic antennas the method is based on a comparison of the event azimuths and slownesses derived from frequency slowness analyses of array data with a slowness vector model several slowness vector models are considered including both homogeneous and horizontally layered half spaces and also a more complex medium representing the actual topography and three dimensional velocity structure of the region under study in this latter model the slowness vector is obtained from frequency slowness analyses of synthetic signals these signals are generated using the finite difference method and include the effects of topography and velocity structure to reproduce as closely as possible the behavior of the observed wave fields a comparison of these results with those obtained with a homogeneous half space demonstrates the importance of structural and topographic effects which if ignored lead to a bias in the source location we use synthetic seismograms to test the accuracy and stability of the method and to investigate the effect of our choice of probability distributions we conclude that this location method can provide the source position of shallow events within a complex volcanic structure such as kilauea volcano with an error of 200 m

grounding zone ice thickness from insar inverse modelling of tidal elastic bending ice thickness measurements in antarctic ice shelf grounding zones are necessary for calculating the mass balance of individual catchments but remain poorly constrained for most of the continent we describe a new inverse modelling optimization approach to estimate ice thickness in the grounding zone of antarctic outlet glaciers and ice shelves using spatial patterns of tide induced flexure derived from differential interferometric synthetic aperture radar insar we demonstrate that the illposedness of the inverse formulation of the elastic plate equations for bending can be controlled by regularization in one dimension the model recreates smooth synthesized profiles of ice thickness from flexure information to within 1 2 we test the method in two dimensions and validate it in the grounding zone of beardmore glacier a major outlet glacier in the transantarctic mountains using interferograms created from terrasar x satellite imagery acquired in 2012 we compare our results with historic and modern ice thickness data radio echo sounding from 1967 and ground penetrating radar from 2010 we match both longitudinal and transverse thickness transects to within 50m root mean square error using an effective young s modulus of 1 4gpa the highest accuracy is achieved close to the grounded ice boundary where current estimates of thickness based on surface elevation measurements contain a systematic bias towards thicker ice

geomechanical model test for stability analysis of high arch dam based on small blocks masonry technique abstract rock mass deformation and strength property simulation plays a key role in the rupture tests of arch dam geomechanical model subject to the limit of geometry scale usually the simulation of tectonic discontinuities such as faults disturbed belts crush belts and weak interlayer were ignored as safety buffer which may yield overstated safety factors in this paper small block masonry technique and low strength binder invented make the simultaneous simulation of the rock mass and tectonic discontinuities available which is more coincident with real engineering conditions based on the material test of blocks and binder the small blocks masonry technique has been successfully applied in the rupture test of xiluodu arch dam with the assistance of high accuracy monitoring and measuring system the stress strain and displacement distribution of the dam abutments and rock foundations are obtained by analyzing these monitoring results the failure process mode and mechanism of the dam body and abutments are derived for further identification of weakness at last the comparative analysis with other arch dam geomechanical rupture test results yields the evaluation of the dam s global stability and necessary reinforcement measures

deformation characteristics of rock salt with mudstone interbeds surrounding gas and oil storage cavern abstract this paper discusses the deformation differences that occur due to the presence of thin mudstone layers in underground storage caverns in rock salt both plasticity and viscosity are considered in the displacement calculations the results show that both creep deformation and deformation distinction i e the differences in the creep behavior between the salt rock and the mudstone are very large under the condition of high effective stresses when the inner diameters of salt caverns are 40 60 m the maximum radial convergence can reach 24 m and the deformation distinction can reach up to 6 m 30 years after the completion of cavern by solution mining the affected areas are however are restricted to the vicinity of the cavern the tightness of the cavern may not be violated if the distance between the caverns is greater than this amount the extension of plastic and dilatancy zones in rock salt is limited to three times the cavern diameter when elasto plastic mudstone interbeds are included tensile failure zones are present in the vicinity of the cavern and the plasticity zone stretches through the entire layer this could cause a loss of cavern tightness or stability if the mudstone interbeds creep although the creep rate is 2 orders lower than that of rock salt yielding is strongly de escalated but the deformation distinction is not affected

tidal and spatial variability of flow speed and seismicity near the grounding zone of beardmore glacier antarctica gps measurements of tidal modulation of ice flow and seismicity within the grounding zone of beardmore glacier show that tidally induced fluctuations of horizontal flow are largest near the grounding line and decrease downstream seismic activity is continuous but peaks occur on falling and rising tides beamforming methods reveal that most seismic events originate from two distinct locations one on the grid north side of the grounding zone and one on the grid south side the broad pattern of deformation generated as beardmore glacier merges with the ross ice shelf results in net extension along the grid north side of the grounding zone and net compression along the grid south side during falling tides seismic activity peaks on both sides because of increased vertical flexure across the grounding line during rising tides seismic activity in the region of extension on the grid north side is relatively low because the tidal influence on both horizontal strain rate and vertical flexure is small on the grid south side during rising tides however tidally induced horizontal strain rates promote increased seismicity in regions of long term compressional flow paths our study highlights how concurrent geodetic and seismic measurements provide insight into grounding zone mechanics and their influence on ice shelf buttressing

experimental investigation of mechanical properties of bedded salt rock abstract because of salt cavern utilization for liquid gas and solid waste storage salt rock mechanical properties are needed for assessments of facility stability and safety bedded salt deposits are widespread and used as much or more than diapiric salt bodies as storage facility hosts but experimental data on the mechanical properties of bedded salt rock with impurities are far less common than data available on relatively pure diapiric salt rocks through laboratory uniaxial and triaxial compression experiments on rock salt halite interlayers anhydrite and bedded composite specimens anhydrite halite and mudstone halite differences in mechanical properties of the various lithologies are explored in the composite specimens the weakest or the most deformable component governs the behavior also the properties of bedded composite lithology specimens tend to be in between the property ranges of the pure lithologies the elastic modulus of the bedded salt rock increases from 5 3 to 24 1 gpa with an increase in the confining stress from 0 to 15 mpa with some evidence of sample damage the ductile transition for halite at the strain rates used is at about 3 10 mpa with increasing 3 the anhydrite halite composite lithology deformation showed strain hardening and a strong trend to ductile behavior as the halite bands tended to dominate the behavior strain incompatibility effects exist along interfaces between creeping and non creeping phases in anhydrite halite composite lithologies mudstone halite rocks tended to be extremely weak compared with all other specimens

physical model test and numerical simulation for the stability analysis of deep gas storage cavern group located in bedded rock salt formation abstract the stability of gas storage cavern complex constructed in bedded salt rock formation might be influenced by multiple factors during the operation process in order to assess these effects three dimensional rheological model tests were conducted in this study physical model with four ellipsoid caverns were constructed with scaled in situ stresses applied through independent sets of hydraulic jacks and internal pressure applied by digital controlled latex balloons influences of different factors on the deformation properties of surrounding rock were systematically evaluated including the gas recovery and injection rate the loss of pressure the extremely low and high gas pressure and the pillar width and pressure difference between adjacent caverns test results revealed that the deformation of the cavern wall was accelerated when the gas extraction injection rate exceeds 0 65 mpa d loss of internal pressure dramatically promoted the deformation tertiary creep stage arose when the internal pressure was too low 3 mpa or too high 22 mpa internal pressure difference and pillar width worked together to affect the deformation properties tests results obtained in this study provided physical evidence for the safety analysis of cavern group as well as the optimization of design and operation scheme these results can also serve as benchmark for the validation of numerical models

local acceleration monitoring and its application in physical modelling of underground mining abstract a micro electro mechanical systems mems inertial sensor was introduced to perform local acceleration monitoring lam in a physical model to showcase mining induced strata movements to prove the feasibility of lam a physical model experiment was performed using four sensors mounted on the roof strata acquired acceleration signals were processed by a moving average and median filter analysed with respective trend variation and fluctuation along with excavation sequence to identify the movement of roof strata a key reference was the mid span section that characterized by adjacent sensors with opposite acceleration change direction to assess the stability of strata a clear evidence is the synchronicity loss of two adjacent sensors in terms of acceleration change in the presented experiment the first weighting and the fracture position can be predicted 1 5 h prior to final failure this study represents a novel attempt to apply lam in a physical modelling experiment and tentatively interpret signals in accordance with strata movement the proposed lam based approach succeeded in identifying the movement and assessing the stability of the strata results presented in this paper verify the validity of lam in terms of noise analysis sensibility and rationality this lam technique is capable of serving as an easy to implement high precision and low cost method in mining and geotechnical related physical modelling research

physical modelling of subsidence from sequential extraction of partially overlapping longwall panels and study of substrata movement characteristics field examples of subsidence from sequential extraction of overlapping coal longwall panels have shown that complex and unexpected subsidence effects can occur physical models comprising sand and plaster obeying relevant similarity rules were used to investigate the subsidence mechanisms displacements within the models were measured using a combination of optical transducers photogrammetry and laser scanning the observed results were compared with finite element models the models demonstrate that the incremental subsidence and substrata movement profiles after lower seam extraction can be separated into three different zones these zones undergo different horizontal and vertical movement characteristics the zone of overlap of the two longwall panels undergoes greater total subsidence compared to a single seam of equivalent thickness the limit angle of the subsidence also differs at the two ends of the lower extraction as a result of the effects of the previously mined out area above

high internal pressure induced fracture patterns in rock masses surrounding caverns experimental study using physical model tests abstract this research has experimented with artificial rock specimens that contain a circular or oblong hole using a novel physical modeling approach to investigate the failure behavior of rock masses surrounding a cavern with high internal pressure the knowledge of fracture initiation and propagation in rock masses is crucial to the selection of underground storage construction sites and a stability evaluation method specifically this research attempts to investigate the fracture initiation and propagation direction of the rock mass that encloses an underground gas air storage cavern with high internal pressure under varying control conditions the experiments are carried out with 200 time scaled down artificial rock specimens under varying stress ratio k i overburden stress vi and the joint s dip angle the internal pressure applied to the hole is gradually increased until the fracture is initiated and propagates photogrammetric analysis is utilized to identify the rock mass response induced by increasing internal pressure and the occurrence of failure path the experimental results indicate that the fracture initiation point and propagation direction of failure path are strongly influenced by the in situ stress ratio k the findings also reveal that the site with an initial in situ stress ratio greater than one is suitable for use as a high internal pressure underground cavern in addition in the presence of a nearby joint the site with a smaller dip angle joint is more desirable for the same in situ stress ratio an oblong shaped cavern is more stable than a circular cavern tunnel of similar size although both cavern configurations exhibit the similar failure patterns

ice flow of the antarctic ice sheet we present a reference comprehensive high resolution digital mosaic of ice motion in antarctica assembled from multiple satellite interferometric synthetic aperture radar data acquired during the international polar year 2007 to 2009 the data reveal widespread patterned enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent this view of ice sheet motion emphasizes the importance of basal slip dominated tributary flow over deformation dominated ice sheet flow redefines our understanding of ice sheet dynamics and has far reaching implications for the reconstruction and prediction of ice sheet evolution

tides and the flow of rutford ice stream west antarctica 1 surface speeds of rutford ice stream west antarctica are known to vary by around 10 20 depending on location with a fortnightly periodicity corresponding to a springneap tidal cycle the reasons for these periodic variations in flow are unclear here the possible role of tidal stress transmission upstream of the grounding line in affecting rates of basal motion is investigated it is found that nonlinear rheological effects within the till when coupled with transmission of tidal stresses within the ice that are linearly related to tidal amplitude can give rise to the type of periodic oscillations in flow observed this nonlinear interaction between tidal forcing and till deformation increases the mean ice flux across the grounding line by a few percent above what might be expected in the absence of tidal forcing periodic velocity fluctuations of this type have not been observed on other ice streams however modeling suggests that this may be due to lack of data and that such flow variations are likely to be common features of active ice streams draining into the ronne ice shelf as well as of other ice streams subjected to similar tidal forcing

failure analysis of thick interlayer from leaching of bedded salt caverns abstract a mathematical model is proposed to calculate the critical collapse span of a thick interlayer during the leaching of a gas storage salt cavern in bedded rock salt in the proposed model the ratio of the height of the damaged zone to the interlayer thickness is introduced this approach overcomes the negative effects on the calculation accuracy of the fact that the damaged rock does not fall off from the thick interlayer but is linked to it by contact forces brine immersion tests have been carried out to obtain the solution characteristics and the influence of brine immersion on tensile strength and on elastic modulus of interlayer samples of a salt formation from yingcheng city hubei province china experimental results show that these mechanical parameters decrease with immersion in brine and more so with decreasing brine density to validate the proposed model a 3d geomechanical model has been built of a salt cavern under construction in a bedded rock salt formation of yingcheng city the stresses and deformations of the thick interlayer obtained by the analytical solution and by the numerical simulation are compared and show good agreement the critical collapse span of the thick interlayer decreases greatly with a decrease of the ratio of damaged zone height to interlayer thickness and interlayer depth increases with increasing tensile strength and thickness of interlayer and is independent of the elastic modulus of the interlayer the proposed model has been used in the planning of the leaching of the underground salt cavern gas storage of yingcheng city hubei province china

a novel joint space wavenumber analysis of an unusual antarctic gravity wave event as part of a collaborative research program between british antarctic survey u k and utah state university usa all sky airglow images were recorded at halley station antarctica 75 5 s 26 7 w an unusual mesospheric gravity wave event was observed in the oh nightglow nominal height 87 km over a period of 3 hours on the 27 28 may 2001 the characteristics of the bore wave event were determined by application of the one dimensional spatial s transform analysis this is the first time such analysis has been performed on airglow data by employing these local spatial spectral analysis the evolution of the wave packet can be measured the wave parameters phase velocity wave number wavelength period were inferred from as little as 2 images separated in time which is a powerful ability when a data set of images is irregularly sampled in time as is often the case in airglow imager studies several interesting and novel results were obtained regarding the dynamic evolution of the wave the horizontal wavelength of the bore wave packet was seen to decrease as the packet evolved coincident with this observation the horizontal phase speed decreased with an associated decrease in wave packet amplitude

characteristics of seismic and acoustic signals produced by calving bering glacier alaska 1 we recorded 126 calving and iceberg breakup events from the terminus of the bering glacier during five days in august 2008 using seismometers and three small aperture arrays of infrasound sensors the seismic signals were typically emergent narrow band and lower frequency similar to records at other glaciers the acoustic records were characterized by shorter duration higher frequency signals with more impulsive onsets we demonstrate that triangular infrasound arrays permit improved locations of calving events over seismic arrivals that rely on a relatively complicated poorly known velocity model twenty six of 35 well located events occurred on icebergs in vitus lake rather than the glacier face while our data do not permit a complete description of the source process the distinctive frequency contents and durations in the seismic and infrasound data suggest that the two data types record different aspects of the same process

engineering properties of rock salt and simplified closed form deformation solution for circular opening in rock salt under the true triaxial stress state abstract underground structures and storage caverns are increasingly being constructed in rock salt due to its unique self healing ability and impervious nature rock salts are likely to experience and develop time dependent behavior deformation hence the characterization of rock salt for its properties including viscosity are pertinent for design of these structures in addition the material in underground openings experiences true triaxial stresses and hence it is vital to study the behaviour of such structures under true triaxial loading conditions this paper presents results of extensive laboratory testing carried out on specimens of khewra rock salt for its physico mechanical properties physical and engineering properties such as mineralogy density sonic wave velocity resistivity point load index and shear strength properties were measured a simplified closed form solution which deploys three dimensional strength criterion mogi coulomb with maxwell viscoelastic behaviour is developed to assess the stress and deformation behaviour of circular opening in plane strain condition the closed form solution assumes that the material exhibits the maxwell behavior when the stresses are lower than the yield stress and the material behavior is the combination of maxwell and mogi coulomb elastoplastic material when the stresses are equal to the yield stress in addition a cylindrical wellbore problem is solved with the proposed closed form solution and the deformation of the wellbore was estimated for the different time intervals

investigating tidal flexure on an ice shelf using kinematic gps the positions of ice stream grounding zones are uniquely sensitive to changes in the mass balance of the ice sheet present methods for locating groundingzone features are either imprecise or require considerable effort in interpretation and so are of little value for change studies we present a new method which uses the kinematic gps technique to locate the position of the limit of tidal flexure the method involves the collection of at least two surface elevation profiles along the same track through the grounding zone at different times during the tidal cycle the elevation profiles obtained coincide upstream of the limit of flexure but diverge downstream of the limit of flexure subtracting the profiles produces a tidal def1ection profile which shows directly the response of the ice shelf to the tidal forcing we present two examples of the use of this method both on rutford ice stream antarctica the first is across the grounding zone and shows that the method is capable of measuring grounding positions to around 200 m precision the second taken across an active shear margin shows a tidal deflection profile with an absence of steps that would indicate the presence of fracture planes penetrating from the ice base to sea level

large scale geomechanical model testing of an underground cavern group in a true three dimensional 3 d stress state the stability of a large cavern group at great depth is discussed on the basis of large scale three dimensional 3 d geomechanical model tests and numerical simulations the model tests are described in detail improvements in the tests were made in terms of experimental techniques and advanced measurement methods the model tests utilized active loading on six sides of a rock mass in a true 3 d stress state during the model construction precast blocks were fabri cated and monitoring holes were defined prior to test initiation newly developed combination ball sliding walls were in stalled on each of the major loading surfaces to reduce the friction induced by model deformation a unique grouting and installation technique employing prestressed cables was adopted in the tests a digital photogrammetric technique dis placement sensing bars using fiber bragg grating fbg technology and mini multipoint extensometers were developed for measuring deformation overloading tests were then conducted for different overburden depths and 3 d numerical analyses were performed to simulate the testing procedures conclusions regarding the stability of the cavern group were developed based on a comparison between the experimental and numerical results resume la stabilited un groupe de grandes cavernes profondes est discutee en utilisant des essais en modele geomeca nique 3 d agrande echelle et des simulations numeriques les essais sont decrits en details dans l article des ameliora tions ont eteapportees aux essais par rapport aux techniques experimentales et aux methodes de mesures les essais comportent des chargements actifs sur 6 faces d une masse de roche de facon a representer un etat des contraintes en 3 d durant la construction du modele des blocs pre moules ont etefabriques et des ports de suivi ont etedefinis avant le de but des essais sur chacune des surfaces majeures de chargement des murs en combinaison bille glissement recemment de veloppes ont eteinstalles afin de reduire la friction induite par les deformations du modele une technique de scellement et d installation unique utilisant des cables precontraints a eteutilisee durant les essais une technique photogrammetrique digitale des sondes de deplacements munies de la technologie d un reseau de fibre bragg et de minis extensiometres multi points ont etedeveloppes afin de mesurer les deformations des essais en surcharge ont eteeffectues pour des pro fondeurs de mort terrain differentes ensuite des analyses numeriques en 3 d ont eteeffectuees dans le but de simuler les procedures de l essai des conclusions en lien avec la stabilitedu groupe de cavernes ont etedeveloppees selon des com paraisons entre les resultats experimentaux et numeriques mots cles essai en modele geomecanique simulation numerique groupe de grandes cavernes souterraines etat des contraintes 3 d reel analyse de stabilite traduit par la redaction

diurnal and semidiurnal tide induced lateral movement of ronne ice shelf antarctica 1 recent gps observations from a spatially extensive network across ronne ice shelf show significant daily ice flow variations at all sites the almost synchronous horizontal displacements occur at diurnal and semidiurnal tidal periods during spring tides displacements velocities and strains near the ice front have superimposed oscillations that are 300 of their mean values and occur over a six hour period resulting in regular ice shelf flow reversals close to ice stream grounding lines however the horizontal diurnal and semidiurnal signals decay and almost vanish from our analysis we conclude that ice shelves respond primarily elastically to tidal tilting thus accounting for the observed diurnal and semidiurnal flow variations and their amplification toward the ice shelf front our findings suggest that detailed modeling of these data could provide improved ice shelf and ice stream models for correctly simulating ice shelf flow and predicting future ice sheet evolution citation makinson k m a king k w nicholls and g hilmar gudmundsson 2012 diurnal and semidiurnal tide induced lateral movement of ronne ice shelf antarctica geophys res lett 39 l10501 doi 10 1029 2012gl051636

safety evaluation of salt cavern gas storage close to an old cavern abstract uniaxial compression tests triaxial compression tests brazilian disk splitting tests direct shear tests and triaxial creep tests have been carried out on samples cored from jintan mining district to determine their mechanical parameters based on the formation characteristic and the sonar survey data of an old cavern a 3d geomechanical model has been built of a cavern close to an old brine cavern the effects of the distance between new and old caverns on the safety of the rock mass around the caverns are investigated deformation plastic areas and volumes effective strains safety factors and volume shrinkages are selected as the indexes to assess the safety of the caverns the width of the pillar between the new and old caverns is optimized based on the calculated results experimental results show that the interlayer has large effects on the mechanical parameters of jintan bedded rock salt and should be considered in the numerical simulations numerical calculations indicate that the distance between the new and old caverns has large influences on the deformations effective strains and safety factors but has little effect on the plastic areas and volumes and volume shrinkages of the rock mass around the caverns although the dimensions of these old brine caverns are much smaller than those of the new ones a distance between the new and old caverns of no less than two times the maximum diameter of the new cavern is proposed as the shape of the old cavern is poor

evolution of stress induced borehole breakout in inherently anisotropic rock insights from discrete element modeling the aim of this study is to better understand the mechanisms controlling the initiation propagation and ultimate pattern of borehole breakouts in shale formation when drilled parallel with and perpendicular to beddings a two dimensional discrete element model is constructed to explicitly represent the microstructure of inherently anisotropic rocks by inserting a series of individual smooth joints into an assembly of bonded rigid discs both isotropic and anisotropic hollow square shaped samples are generated to represent the wellbores drilled perpendicular to and parallel with beddings at reduced scale the isotropic model is validated by comparing the stress distribution around borehole wall and along x axis direction with analytical solutions effects of different factors including the particle size distribution borehole diameter far field stress anisotropy and rock anisotropy are systematically evaluated on the stress distribution and borehole breakout propagation simulation results reveal that wider particle size distribution results in the local stress perturbations which cause localization of cracks reduction of borehole diameter significantly alters the crack failure from tensile to shear and raises the critical pressure rock anisotropy plays an important role on the stress state around wellbore which lead to the formation of preferred cracks under hydrostatic stress far field stress anisotropy plays a dominant role in the shape of borehole breakout when drilled perpendicular to beddings while a secondary role when drilled parallel with beddings results from this study can provide fundamental insights on the underlying particle scale mechanisms for previous findings in laboratory and field on borehole stability in anisotropic rock

application of 3d laser scanner optical transducers and digital image processing techniques in physical modelling of mining related strata movement a physical testing protocol for modelling mining related problems has been presented a new method for monitoring fracture propagation pattern has been introduced laser based and optical devices have been used for physical modelling of subsidence multiple seam subsidence has been measured by photogrammetry dic analysis optoncdt and 3d tls

a study of isolated draw zones in block caving mines by means of a large 3d physical model block caving methods rely on gravity to break and transport large amounts of ore and waste despite the importance of gravity flow there is debate within the literature about the influence that the height of draw particle size and particle size distribution has on the geometry of extraction and movement zones this paper presents the results of an experimental programme conducted in the largest three dimensional 3d physical model to investigate the mechanisms of flow of cohesionless materials when drawing from a single drawpoint experimental results showed that isolated draw zones are mainly influenced by mass drawn and height of draw particle size was found to have a slight effect on extraction zones and no significant effect on movement zone width particle size composition wide or narrow distributions and drawpoint width were found not to have a major role on drawzone geometry those conclusions were based on statistical analysis of experimental data to define the controlling parameters in isolated draw model theory principles were used to investigate within the physical modelling framework the possibility of directly scaling the geometry of the extraction zones which indicated that flow zones could be scaled in cohesionless materials under a set of assumptions a mechanistic model of isolated draw is also postulated from experimental data from observations of stresses and the imz s geometry

geomechanical investigation of roof failure of china s first gas storage salt cavern abstract jk a cavern is the first operating cavern of jintan underground gas storage which is also the first operating salt cavern gas storage in china in 2015 the sonar survey carried out under working conditions indicated that a massive roof collapse of the jk a cavern had taken place to prevent similar accidents from happening again finding the causes and the collapse time of jk a cavern would be valuable by using the target salt formation information rock properties and monitored gas pressure a 3d geomechanical model of jk a cavern has been built the responses of the rock mass around jk a cavern under leaching sealing tests debrining and gas injection delivery have been investigated a safety evaluation system consisting of cavern volume shrinkage dilatancy safety factor displacement vertical stress and equivalent strain is proposed to find the likely collapse time and the reason for the jk a cavern roof collapse results show that there are two main causes for the cavern roof failure 1 a large span flat roof detrimental for bearing loads once local damage takes place massive collapse may be triggered by the self weight of the loosened rock 2 the decrease speed of the internal gas pressure is too fast the loads applied to the cavern roof cannot be transferred in a timely fashion which causes a stress concentration zone to form and local damage develops the roof collapse of jk a cavern took place 1 3 years after its gas injection delivery started numerical analysis results show that dilatancy safety factor and vertical stress have high accuracy and sensitivity in the prediction of the cavern roof collapse there is a high potential for a roof collapse of jk a cavern to happen again we propose that the gas pressure and pressure decrease rate are to be controlled strictly in the later operating period to prevent any collapses in the future