determination of residual strength parameters of jointed rock masses using the gsi system abstract the geological strength index gsi system proposed in 1995 is now widely used for the estimation of the rock mass strength and the rock mass deformation parameters the gsi system concentrates on the description of two factors rock structure and block surface conditions the guidelines given by the gsi system are for the estimation of the peak strength parameters of jointed rock masses there are no guidelines given by the gsi or by any other system for the estimation of the rock mass residual strength that yield consistent results in this paper a method is proposed to extend the gsi system for the estimation of a rock mass s residual strength it is proposed to adjust the peak gsi to the residual gsir value based on the two major controlling factors in the gsi system the residual block volume v b r and the residual joint condition factor j c r methods to estimate the residual block volume and joint condition factor are presented the proposed method for the estimation of rock mass s residual strength is validated using in situ block shear test data from three large scale cavern construction sites and data from a back analysis of rock slopes the estimated residual strengths calculated using the reduced residual gsir value are found to be in good agreement with field test or back analyzed data

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

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

water in albitic glasses infrared spectroscopy has been calibrated to provide a precise and accurate method for determining the concentrations of molecular water and hydroxyl groups in hydrous albitic glasses at total water contents less than 4 wt most of the water is dissolved as hydroxyl groups at higher total water contents molecular water becomes the dominant species for total water contents above 4 wt the amount of water dissolved as hydroxyl groups is nearly constant at about 2 wt and additional water is incorporated as molecular water these trends in the concentrations of the h bearing species are similar to those observed in other silicate glasses using infrared and nmr spectroscopies the ratio of molecular water to hydroxyl groups at a given total water content is independent of the pressure and only weakly dependent on the temperature of equilibration molecular water and hydroxyl group concentrations in glasses provide constraints on the dissolution mechanisms of water in silicate liquids several mixing models involving homogeneous equilibria of the form h 2o o 2 2oh among melt species in albitic melts have been developed these models can account for the measured species concentrations if the effects of non ideal behavior or mixing of polymerized units are included or by allowing for several different anhydrous species we used two thermodynamic models of hydrous albitic melts to calculate phase equilibria the first assumes that henry s law holds for molecular water in albitic liquids i e that the activity of molecular water in the melt is proportional to its mole fraction as determined by infrared spectroscopy the second describes the speciation and thermodynamics of hydrous albitic melts using the formalism of a strictly regular solution these models can account reasonably well for the position of the vapor saturated solidus of high albite and the pressure and temperature dependence of the solubility of water in albitic melts to the extent that these models are successful our approach provides a direct link between measured species concentrations in hydrous albitic glasses and the macroscopic thermodynamic properties of the naalsi 3o 8 h 2o system

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

earthquake triggered rock falls and their role in the development of a rock slope the case of skolis mountain greece abstract inventory of pre earthquake and earthquake triggered landslides is used to provide insight into the interplay between climatic and tectonic forcing in the development of the rock slopes of the skolis mountain in the nw peloponnese aerial photograph analysis and surface mapping indicate that the skolis mountain is characterized by long term climatically and tectonically controlled rock falls forming taluses temporally these taluses show a slow progressive inflation in surface area from 1945 to 2007 however the post earthquake surface area of the rock falls increased three times similarly 75 rock fall sites before the earthquake increased into 89 after the movri mountain earthquake mw 6 4 in addition during the earthquake a series of isolated rock falls descended skolis slopes causing threat of the santomerion village and blocking significant part of the dirt roads around it these boulders are clustered in three areas beyond the base of taluses the rock slope failures are controlled by a complex array of discontinuities that are conveniently related to rock mass classification following the geological strength index these discontinuities are associated with joints and faults caused during the formation of the hellenides fold and thrust belt and or related tectonic damage we infer that a dense pattern of fractures in limestone plays a crucial role in the reactivation of movement within the rock falls during the 2008 movri mountain earthquake all these data are used to define two borders the taluses base and the rock fall hazard border beyond the base of taluses for defining these borders we use the angle drawn from the boulders release zone down its maximal runout points our results indicate that the border defined by the 33 corresponds to the climatically driven rock falls while the 24 border is defined as the boulders maximum runout during earthquakes

estimation of rev for fractured rock masses based on geological strength index abstract the representative elementary volume rev of fractured rock masses is a significant index to investigate the rock mass behaviors in the continuum mechanics in this research a new indicator to estimate the rev size of fractured rock masses based on the geological strength index gsi is proposed for this purpose a new method that combines the pfc based synthetic rock mass srm model with the hoek brown hb failure criterion is proposed to investigate the strength and deformation properties of fractured rock masses under biaxial stress conditions extensive numerical analyses are carried out to estimate variation of the uniaxial compression strength ucs deformation modulus e and gsi of the brunswick mine rock mass with increasing the size of the srm models up to a rev size results show that the gsi based indicator gives relatively larger rev size compared with the traditional ucs or deformation modulus e based indicators compared with the traditional indicators the proposed gsi based indicator has merits of not only reflecting the geometrical characteristics of rock structures but also containing both geometrical and mechanical properties of discontinuities

combining digital elevation model analysis and run out modeling to characterize hazard posed by a potentially unstable rock slope at turtle mountain alberta canada abstract turtle mountain in alberta canada has become an important field laboratory for testing different techniques related to the characterization and monitoring of large slope mass movements as the stability of large portions of the eastern face of the mountain is still questionable in order to better quantify the volumes potentially unstable and the most probable failure mechanisms and potential consequences structural analysis and runout modeling were preformed the structural features of the eastern face were investigated using a high resolution digital elevation model hrdem according to displacement datasets and structural observations potential failure mechanisms affecting different portions of the mountain have been assessed the volumes of the different potentially unstable blocks have been calculated using the sloping local base level slbl method based on the volume estimation two and three dimensional dynamic runout analyses have been performed calibration of this analysis is based on the experience from the adjacent frank slide and other similar rock avalanches the results will be used to improve the contingency plans within the hazard area

automatic characterization of rock mass discontinuities using 3d point clouds abstract direct contact measurements for rock mass discontinuities are generally difficult to perform time consuming biased and often dangerous this paper presents an automatic characterization method for rock mass discontinuities that uses 3d point clouds which can be obtained through non contact measuring techniques such as photogrammetry and light detection and ranging lidar in this method five discontinuity parameters namely the orientation trace spacing roughness and aperture are extracted automatically the overall methodology is as follows 1 orientation is determined by using an improved k means clustering method 2 trace segments are detected by using the normal tensor voting theory and four post processing techniques are employed to compute the trace length 3 spacing is calculated by plotting virtual normal scan lines on the projected traces 4 roughness is evaluated by the correlation between the joint roughness coefficient jrc and the root mean square of the discontinuity surface profile and 5 aperture is obtained by computing the average minimum width based on sub pixel edge detection the proposed method was applied to a drill and blast rock tunnel where the extracted discontinuity parameters were used to calculate the rock mass rating rmr value and geological strength index gsi of the rock mass the application results showed that photogrammetry was more objective and efficient for acquiring rock mass discontinuity information and that it could be used as a potential alternative to the traditional discontinuity mapping method

analysis of spalling failure in marble rock slope a case study of neyriz marble mine iran the expansion of the neyriz marble mine into deeper levels caused an unexpected failure particularly in the toes of lower benches this phenomenon can impact the overall stability of the quarry and results in undesirable environmental and technical consequences to understand the failure mechanism a comprehensive study including laboratory testing in situ field testing and theoretical analyses are carried out the theory of the brittle failure which was mainly developed based on the experiences gained during excavation in granite rocks is adopted and augmented in this study to explain the governing mechanism of failure mechanical properties of the marble are determined using conventional rock mechanics tests and the in situ stress field was evaluated using a modified under coring test analyzing the laboratory and field data with the available empirical criteria for brittle failure shows that the level of stress in the lower bench is high enough to initiate the brittle failure finally constitutive models developed for this failure mode are adopted in conjunction with numerical modeling to investigate the observed failure in the quarry two modeling strategies based on elastic and elastic plastic analyses are considered comparing the predicted failure surface with the observed failure profile it can be concluded that the brittle failure criteria can very well capture the failure mechanism in this marble quarry this shows that the criteria proposed to describe spalling failure around underground excavation in granite can be effectively employed for assessing the brittle failure in deep open cast and quarry mines in good quality rocks such as marble

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

convergence of synthetic rock mass modelling and the hoek brown strength criterion abstract synthetic rock mass modelling is based on estimating the mass scale properties of rock directly from properties of the intact material and observed jointing geometry and strength this technique explicitly represents characteristics of the rock mass that are implicit in the widely applied empirical hoek brown strength criterion we demonstrate here that the two approaches converge in mass strength and the strength envelope when the necessary conditions for the empirical method are satisfied however the synthetic rock mass approach is advantageous whenever the necessary conditions of the empirical method are not satisfied as an example we use the synthetic rock mass method to describe an anisotropic strength envelope for a rock mass with four independent joint sets where the orientation specific strength has a significant impact on rock mass stability in addition we show that rock mass strength is controlled strongly by joint persistence and the resultant connectivity of discontinuities and only weakly by joint density and intensity

composite rock slope kinematics at the current randa instability switzerland based on remote sensing and numerical modeling abstract kinematic analysis of slope instabilities in brittle rock is crucial for understanding the reaction of the rock mass to external forcing factors in steep terrain inaccessibility often limits collection of relevant data and remote sensing techniques must be applied this is the case at the current randa rock slope instability in southern switzerland where a total volume of about 5 6 million m3 moves at a rate of up to 30 mm yr a large portion of the unstable rock mass is exposed in an 800 m high inaccessible cliff the main scarp of the may 1991 rock slope failure between 2005 and 2007 a comprehensive suite of remote sensing techniques including photogrammetry lidar and gb dinsar was combined with 3d geodetic measurements to characterize the rock mass structure and displacement patterns photogrammetry and lidar data were measured simultaneously from a helicopter using a system allowing for oblique view angles which provided optimal observations of the steep rock cliff we used these datasets to map large scale structures and extract their orientation and minimum persistence as well as to characterize the 1991 failure scarp the northern part of the may 1991 failure surface shows a transition from stepped planar sliding at the base to failed rock bridges in the center to tensile failure close to the vertical head scarp kinematic analysis of the discontinuity sets in the currently moving rock mass shows that both toppling and translational sliding are feasible failure mechanisms toppling is more likely for steep faces above 2200 m whereas translational failure is more likely in the lower portion of the instability interpretation of gb dinsar displacement maps revealed similar kinematic behavior and also allowed identification of a basal rupture zone and lateral release plane bounding the instability displacement vectors derived from geodetic surveying provided new insights into the 3d kinematic behavior of the instability all information extracted from different data sets were integrated in a conceptual model which was then investigated with 2d numerical simulation using the discontinuum code udec the numerical models were able to reproduce the hypothesized kinematic behavior well

structurally controlled instability damage and slope failure in a porphyry rock mass abstract rock slopes fail through structurally controlled mechanisms global circular failures or complex mechanisms depending on structural patterns and rock mass damage here structural geology rock mass characterisation terrestrial laser scanning tls ground based radar interferometry gb insar and finite element modelling are integrated to explore relationships between structure damage and global slope failure at mt gorsa trentino italy there a porphyry quarry has been excavated in complex strongly anisotropic rhyolitic ignimbrite rock masses the slope was affected by a major rockslide in 2003 and undergoes continuing instability site investigations and gb insar monitoring revealed that the 2003 failure was a roto translational rockslide involving about 400 000 m3 of disrupted rock structural analysis of tls and field data shows that the slope is affected by widespread structurally controlled mechanisms sliding toppling strain localization in kink bands the non obvious relationships between structurally controlled and global roto translational slope failure mechanisms are investigated by characterising rock mass damage in different slope sectors a new approach to quantify rock mass damage by mapping the geological strength index and interpreting its topographic signatures in tls point clouds is presented a persistent geological marker is systematically mapped in tls point clouds and correlations between attitude variability statistics and rock mass damage are established providing an efficient assessment tool rock mass damage increases in kinematic domains affected by structurally controlled instability gsi 35 40 and is maximum in areas of ongoing global instability gsi 15 20 the 2003 rockslide occurred inside a damaged rock mass zone with gsi

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

dehumidification property of eskisehir derbent ciftligi white tuffs in turkey in anatolia throughout the centuries caverns in tuffs have been used for food storage the aim of this study is to investigate experimentally the dehumidification property of tuffs and to confirm whether tuffs play any part in the humidity of the ecosystem in storage according to tests carried out on the eskisehir derbent ciftligi white tuffs and six different rock types from turkey it was found that the atmospheric moisture absorption ability of tuffs is relatively higher than those of other tested rocks this suggests that the dehumidification property is a unique characteristic of tuffs it may allow for the tuff walls to work as an air dehumidifier for storing food

from the source area to the deposit collapse fragmentation and propagation of the frank slide the combination of structural data from the source area and descriptive data from the deposit s carapace as well as remote sensing and statistical analysis allows a better understanding of the collapse fragmentation and propagation processes of the frank slide rock avalanche the in situ observed conservation of the stratigraphic sequence of the turtle mountain anticline s normal limb in the deposit is interpreted as the consequence of the collapse mode involving simple shearing of the mass accompanied by a rotational movement i e a simple shear parallel to the topography and a breakage of the hinge followed by overthrusting of the normal limb on the inverse limb coherence between the block size distributions of the source area and the deposit carapace is interpreted as a demonstration of the primary control of preexisting fracturing on the fragmentation processes remote sensing indexes allow us to uncover a priori hidden morphological features preserved on the surface of the deposit i e longitudinal and compressional features as well as lobes their location on the carapace provides evidence of lateral heterogeneity in the propagation highlighted by three different types of propagation behaviors this comprehensive study not only provides elements that contribute to an understanding of the frank slide rock avalanche but it also provides insight into essential parameters to take into account in further modeling of these types of phenomena

the effects of blast damage zone thickness on rock slope stability the selection of blast damage zone t of the hoek brown hb criterion is significant in open pit slope design and stability analysis traditional slope numerical analysis adopts a single value of blast damage factor d to the entire rock mass which results in underestimation of slope stability in this research the parallel layer model plm which rock mass is divided into a number of layers parallel to slope surface with a decreasing value of d applied to each layer in slope modeling is used in the limit equilibrium method to investigate the effect of blast damage zone t on the stability of rock slopes based on extensive parametric studies a blast damage zone weighting factor ft is proposed to quantify the influence of t on the evaluation of the factor of safety fos of given slopes results show that the selection of t in the slope model plays an important role in terms of calculation of fos especially when the ratio of t to slope height h is less than 1 0 finally based on ft and the existing stability charts a stability model is proposed for estimating the fos of slopes with various slope geometries and rock mass properties the reliability of the proposed stability model is tested against numerical solutions the results show that fos estimated from the proposed stability model exhibits only 5 6 average discrepancy from numerical solutions using 1254 sets of data the proposed stability model is simple and straightforward and can be used for the preliminary rock slope stability analysis considering blast damage zone effects

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

assessment of periglacial slope stability for the 1988 tschierva rock avalanche piz morteratsch switzerland the tschierva rock avalanche occurred on october 29 1988 in the area of the piz morteratsch switzerland releasing a total volume of 300 000 m3 the avalanche ran out over 1 km destroying a hiking trail before stopping on the tschierva glacier we analyze the setting of this periglacial slope failure combining geomechanical and cryosphere investigations to identify the primary factors contributing to the rock avalanche an approach to slope stability assessment is presented that copes with existing data limitations in an inaccessible alpine terrain results from the analyses of morphology geology glaciation history permafrost hydrology and meteorological data allowed preliminary inferences to be made regarding the influence of these factors on slope stability conceptual kinematic and numerical slope stability modeling critically analyzed the role of kinematic degrees of freedom glacier retreat and water infiltration from above the detachment zone results highlight the strong influence of discontinuity orientation with respect to the slope face the role of a fault zone with increased joint density and long term progressive development of persistent discontinuities induced by glacier retreat and groundwater loading cycles in leading to the rock avalanche the role of permafrost could not be clearly assessed however observations and analyses indicate that permafrost had no dominant influence on the slope failure extraordinary precipitation prior to the event is suggested to have played a role in triggering the rock avalanche especially in combination with observed superficial ice that could have sealed the rock face generating high water pressures our results emphasize the importance of analyzing multiple contributing factors when assessing alpine rock slope failures with careful consideration of data limitations prevailing in such areas

use of digital terrestrial photogrammetry in rocky slope stability analysis by distinct elements numerical methods abstract current approaches to rocky slope stability analysis require knowledge of the geometrical structural setting as well as the physical mechanical properties of the intact material and its discontinuities the physical mechanical properties are derived from in situ and laboratory tests whereas the geometrical characteristics come from field attitude measurements frequently the inaccessibility of walls does not allow direct measurement of discontinuity surfaces by traditional geological methods in such cases data can only be obtained by statistical methods although this approach is significant and provides spatial meaning it is ineffective for deterministic analysis this paper provides a solution to this problem by applying digital terrestrial photogrammetric techniques employing a reamed bar an aerostatic balloon and a helicopter results demonstrate that the accuracy and the quantity of geometrical and engineering geological data coming from the photogrammetric survey allow for numerical simulation of the relationship between rock elements as a function of their physical mechanical properties and load conditions the 3dec code was chosen among the different methods available to model the discontinuous media through distinct elements the proposed methodology was applied to a quarry located in the carrara marble district the apuan alps italy the largest and most exploited mining region in europe the economic value of the area required a detailed study of the presence of instability phenomena so that marble extraction could continue in safe conditions

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

impact of the intermediate stress component in a plastic potential function on rock mass stability around a sequentially excavated large underground cavity abstract although plastic potential functions considering an intermediate principal stress component are widely employed for elasto plastic analyses its effect on excavation induced stress re distribution is not adequately examined and verified based on in situ stress measurements the present study addressed this issue by not only examining the analytical solutions of elasto plastic models but also conducting a case study based on large cavern excavation and the continual measurement of the in situ stress at a great depth the analytical solutions indicate a clear difference in volumetric plastic strain increment between different plastic potential functions with the same yield function specifically when 2 1 exceeds 0 6 the drucker prager dp plastic potential function produces an increase in volumetric strain rate larger than that of the mohr coulomb mc potential function hence suggesting the increase in confining stress in the surrounding rock mass for the case study the numerical analyses of the large cavern excavation with the different potential functions demonstrated that both the potential functions yield comparable excavation induced stress change at the stress monitoring point however the failure state transition of the surrounding rock mass is non identical when the mc potential function is employed the surrounding rock mass continuously undergoes failure throughout the excavation stages whilst for the model with the dp potential function unloading takes place due to the volumetric expansion of failed rock masses associated with the intermediate principal stress component as the excavation stage proceeds this was found to be more consistent with field observations thus we concluded that the intermediate principal stress in a plastic potential function plays a vital role in the evolution of volumetric plastic strain thereby exerting an influence on the overall stability of rock mass structures especially for a fractured rock mass and when the intermediate stress is relatively large compared to the minor principal stress value

multi approach stability analyses of large caverns excavated in low angled bedded sedimentary rock masses in singapore abstract the first commercial underground rock caverns for hydrocarbon storage in south east asia the jurong rock caverns project jrc project have recently been completed in singapore the storage capacity of 5 caverns is 1 47 million cubic meters and 3 5 million cubic meters of rocks were excavated in this project geologically it was excavated in low angled bedded meta sedimentary mudstone pyroclastic rocks and sandstone although traditional arch roofed style excavations are typical for tunnel and cavern for stability condition flat roofed profiles tend to form in low angle stratified sedimentary rock mass in this study the stability of such flat roofed tunnel and cavern with structurally controlled stability was analyzed using geotechnical classification systems including the stability graph method analytical voussoir techniques and numerical models accordingly and once presented the main features of the project characterization of the rock masses is presented some classification system approaches providing a convenient but probably over estimated support and reinforcement recommendation are illustrated then basic wedge stability analysis is briefly illustrated voussoir analogue techniques are applied to unsupported cavern profiles showing instability but clear stability for the supported case discontinuous models of the final designed cavities are presented showing a good agreement with indicative measurements on place and stress distributions associated with the excavation sections are analyzed using examine2d to show that abutment relaxation was unlikely to occur in jrc project the study shows that classification systems are useful tools but application of analytical techniques and numerical models contribute to a better understanding of the excavation and reinforcement process

discrete element modelling of deformation and damage of a roadway driven along an unstable goaf a case study abstract roadways driven alongside a previously extracted longwall panel goaf are a common situation in underground coal mining the unstable goaf can have a significant detrimental impact on the stability of the roadway this paper presents a combined srm udec trigon numerical approach to investigate the failure mechanism of a roadway driven alongside an unstable goaf the synthetic rock mass srm method is used to derive the rock mass properties and the newly developed udec trigon approach is used for simulating brittle fracture and consequent roadway damage the results indicate that the roadway suffers asymmetric damage characterized by a major rib convexity a severe floor heave and a relatively stable roof with limited fracturing this failure mechanism is consistent with field observations a quantitative evaluation of the damage around the roadway indicates that shear failure plays a major role in the roadway damage our study suggests that the proposed combination of srm and the udec trigon is well suited to the evaluation of failure mechanisms around underground coal mine excavations

constraining coalbed methane reservoir petrophysical and mechanical properties through a new coal structure index in the southern qinshui basin northern china implications for hydraulic fracturing structurally deformed coal sdc influences not only gas outbursts during coal mining but also coalbed methane cbm production different sdcs have different mechanical strengths and physical properties the structurally constrained petrophysical and mechanical properties of a cbm reservoir from the southern qinshui basin sqb northern china have been investigated by using a coal structure index csi the csi was established as a quantitative criterion for the deformation of sdcs based on surface conditions and blockiness using the data of 783 coring samples from 109 cbm wells the results show that undeformed coal and slight brittle sdcs are dominant in the sqb with ductile sdcs distributed locally both compressive strength and tensile strength decline exponentially with increasing csi average avg coal structure is a crucial factor for coal seam fracturing with an increasing csi avg the major fracture length will first increase to the maximum of 266 m at a csi avg of 45 and then decrease rapidly however branch fractures are independent of the csi avg the major fracture height attained a minimum of 4 39 m at a csi avg of 40 and then slowly increased therefore slightly brittle sdcs should be beneficial for fracturing at least for high rank coals the presence of variable sdcs can have a considerable impact on cbm reservoir petrophysical and mechanical properties finally a csi model that strives to establish the relation between structure deformation and cbm reservoir physical and mechanical properties in coal is expected to effectively guide hydraulic fracturing

a slope movement in a complex rock formation deformation measurements and dem modelling abstract the case history of a deep seated slope movement in a complex rock formation marly arenaceous formation is analyzed the movement monitored for more than 20 years was recognized after the discovery of intense cracking in the concrete lining of a hydraulic tunnel running across the slope the time history of displacements shows that the ongoing deformation process is essentially a stationary creep phenomenon also influenced by transient variations in pore pressure distribution the shearing zone is mainly formed by tectonized clay gouge and is characterized by a mobilized strength close to residual the slope has been modelled by dem approach as a complex blocky structure defined by several joint sets bedding planes inclined and sub vertical joints different hypotheses about the geometry of the slip surface compatible with field evidences are discussed as well as their influence on the critical friction angle of the slope the type of model adopted for rock mass with continuous or staggered joints influences the pre failure deformation mode but the failure conditions are not as much affected finally the response of dem models to the increase in water level at the toe of the slope and to the rise of the groundwater table inside the slope has been analyzed the results of simplified models without flow calculation and coupled hydro mechanical analyses are compared finding some relevant differences

hoek brown parameters for predicting the depth of brittle failure around tunnels a review of underground openings excavated in varying rock masstypes and conditions indicates that the initiation of brittlefailure occurs when the damage index di expressed as theratio of the maximum tangential boundary stress to the laboratoryunconfined compressive strength exceeds approx0 4 when thedamage index exceeds this value the depth of brittle failure around a tunnel can be estimated by using a strengthenvelope based solely on cohesion which in terms of thehoek brown parameters implies that m 0 it is proposed that inthe brittle failure process peak cohesion and friction are notmobilized together and that around underground openings thebrittle failure process is dominated by a loss of the intrinsiccohesion of the rock mass such that the frictional strengthcomponent can be ignored for estimating the depth of brittlefailure an essential component in designing support for theopening case histories were analyzed using the hoek brownfailure criterion with traditional frictional parameter

geological discontinuity persistence implications and quantification abstract persistence of geological discontinuities is of great importance for many rock related applications in earth sciences both in terms of mechanical and hydraulic properties of individual discontinuities and fractured rock masses although the importance of persistence has been identified by academics and practitioners over the past decades quantification of areal persistence remains extremely difficult in practice trace length from finite outcrop is still often used as an approximation for persistence this paper reviews the mechanical behaviour of individual discontinuities that are not fully persistent and the implications of persistence on the strength and stability of rock masses current techniques to quantify discontinuity persistence are then examined this review will facilitate application of the most applicable methods to measure or predict persistence in rock engineering projects and recommended approaches for the quantification of discontinuity persistence furthermore it demonstrates that further research should focus on the development of persistence quantification standards to promote our understanding of rock mass behaviours including strength stability and permeability

long term dynamics of rockslides and damage propagation inferred from mechanical modeling 1 long term observations of large active rockslides show accelerating deformation over many thousands of years since the last deglaciation the effect of deglaciation on slope stability is however poorly understood due to 1 limited long term observations and 2 a complex interaction between glacier retreat and hydrogeological mechanical and morphological processes to assess the sensitivity of rockslide dynamics to these different processes a model of progressive damage through intact rock mass is developed in this study based on the finite element method this model uses time to failure laws based on rock laboratory creep experiments it is able to reproduce progressive damage localization along shear bands associated with strain rate acceleration as observed during tertiary creep the model reproduces the different phases of deformation associated with morphologies typical of large rockslides this model is thus suitable for simulating the dynamics of large rockslides and the transition from initiation to rapid sliding the sensitivity of rockslide kinematics and morphology to different mechanical properties is analyzed this analysis shows that the time evolution of the rockslide can be inferred with the knowledge of only one time parameter independent of the knowledge of the mechanical properties of the rock mass this parameter is here chosen as the time when the summit slope displacement has reached 10 m a parameter that can be estimated with cosmogenic dating the model is then used to study the effects of deglaciation on the valley flank stability and the formation of large rockslides this study shows that the deglaciation velocity can affect the morphology of the rockslide with the shear band of the rockslide emerging at higher elevation as the velocity decreases we also show that the response to the deglaciation can last several thousands of years after the glacier retreat

incorporating scale effect into a failure criterion for predicting stress induced overbreak around excavations abstract the evaluation of the depth of brittle failure around excavations is of major importance in order to optimize the design of underground excavations and ensure the safety of workers and equipment the current proposed approaches to evaluate it are related to a single scale of study intact rock or rock mass scale therefore they are scale dependent and cannot be applied for all excavation diameter in this paper a generalized failure criterion including the scale effect for predicting stress induced overbreak around excavations is developed this failure criterion is based on the damage initiation relation 1 a 3 b c the scale effect is included into it through a relation proposed to evaluate the b parameter and depending on the scale of study the fit parameters of the relation proposed have been defined considering a database at both rock mass and intact rock scales arising from a literature review for intact rock scale the b parameter is defined as a function of the diameter of the excavation expressed following a potential form for rock mass scale the b parameter is defined equal to 0 35 regardless the diameter of the excavation based on the proposed b parameter relation the depth and extension of the brittle failure around excavations can be evaluated for any scale of study

investigation of mechanical properties of jointed granite under compression using lattice spring based synthetic rock mass modeling approach abstract joint waviness is one of the important parameters of joint that need to be considered in civil and mining engineering design of structures built in or on jointed rock masses however this parameter is often overlooked by designers in this study the mechanical properties of laboratory scale jointed granite with both planar and non planar joints of different joint configurations are investigated using the lattice spring based synthetic rock mass ls srm modeling approach jointed granite models are calibrated using the laboratory test results and the calibrated lattice model parameters are used to perform both conventional triaxial and true triaxial compression tests in addition the influences of joint orientation intensity and persistence on the strength and deformability of jointed granite with both planar and non planar joints are investigated the simulation results show that the strength and deformation modulus of the jointed rock decrease with the increase of joint intensity and persistence the strength and deformation modulus of the jointed rock are higher for the ones with non planar joints under the true triaxial loading condition the strength and deformation modulus of the jointed granite depend strongly on the magnitude and orientation of the intermediate principal stress

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

numerical characterization for rock mass integrating gsi hoek brown system and synthetic rock mass method abstract rock mass characterization is a key issue to derive mechanical properties of jointed rock mass in this research the strength modulus and post peak behaviour of rock masses with varied joint orientations and confining stresses are characterized by integrating an empirical geological strength index gsi hoek brown system and a synthetic rock mass srm numerical method the srm model is a 3d distinct element model supporting explicit simulation of discontinuous joints and crack propagation in the rock mass the rock mass structure as denoted by a discrete fracture network is correlated to the gsi system through a quantitative factor of rock block size the strength and modulus are then derived from the gsi hoek brown system and used as references for a series of synthetic rock mass models a comparative study shows that when the predominant joints are steeply inclined in the rock mass subjected to axial loading the empirical gsi hoek brown system provides reliable mechanical properties when the joints are less favorable to shear sliding the gsi hoek brown system underestimates the rock mass strength cracking characteristics are also investigated in selected srm models where few cracks are simulated when inclined joints are inserted in the rock mass and low confining stresses are applied this research finally shows the method to construct continuum rock mass models using the numerical parameters of the srm models the numerical results suggest that the global failure zone is thin when the post peak is elasto brittle and the failure zone is much wider when the post peak is elasto plastic the involvement of the additional failed zones is responsible for the post peak ductility the paper is meant to explore new methods to derive high quality geo data for jointed rock mass

generalized crack initiation and crack damage stress thresholds of brittle rock masses near underground excavations abstract the rock mass failure process is characterized by several distinct deformation stages which include crack initiation crack propagation and coalescence it is important to know the stress levels associated with these deformation stages for engineering design and practice extensive theoretical experimental and numerical studies on the failure process of intact rocks exist it is generally understood that crack initiation starts at 0 3 to 0 5 times the peak uniaxial compressive stress in confined conditions the constant deviatoric stress criterion was found to describe the crack initiation stress level here generalized crack initiation and crack damage thresholds of rock masses are proposed the crack initiation threshold is defined by 1 3 a cm and the crack damage threshold is defined by 1 3 b cm for jointed rock masses where a and b are material constants and cm is the uniaxial compressive strength of the rock masses for a massive rock mass without joints cm is equal to cd the long term uniaxial strength of intact rock after examining data from intact rocks and jointed rock masses it was found that for massive to moderately jointed rock masses the material constants a and b are in the range of 0 4 to 0 5 0 8 to 0 9 respectively and for moderately to highly jointed rock masses a and b are in the range of 0 5 to 0 6 0 9 to 1 0 respectively the generalized crack initiation and crack damage thresholds when combined with simple linear elastic stress analysis assist in assessing the rock mass integrity in low confinement conditions greatly reducing the effort needed to obtain the required material constants for engineering design of underground excavations

multi peak deformation behavior of jointed rock mass under uniaxial compression insight from particle flow modeling abstract evaluation of mechanical properties of jointed rock mass is very important for geological engineering problems related to underground opening slope stability dam foundation and hydraulic fracturing etc it is generally known that both strength and deformability of rock mass may change with joint geometry and arrangement by pfc particle flow code modeling this paper aims at understanding the damage mechanism of the multi peak deformation behavior of jointed rock mass with different joint orientations and continuity factors under uniaxial compression observed in the physical model tests with the smooth joint contact model not only has the inherent roughness in conventional joint model been avoided but also we can monitor the joint aperture number of closed joints and forces acting on the joints during the damage process it is shown that mobilization of joint strength plays an important role in the multi peak deformation behavior of rock mass if the joint strength is slightly mobilized or immobilized i e most joints keep open during the test strain softening occurs however if the joint strength is significantly or fully mobilized yielding platform or strain hardening may happen

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

a study on the uplift mechanism of tongjiezi dam using a coupled hydro mechanical model during filling in 1992 of the tongjiezi reservoir in southwest china it was noticed that the dam body and the rock masses on the right side of the valley were uplifted up to 22 2 mm and 24 3 mm respectively after reservoir filling in 1993 the uplift continued but the rate decreased and the measured maximum uplift increased from 22 2 mm to 27 5 mm in the dam body and from 24 3 mm to 28 9 mm in the rock masses from 1993 to 2004 based on the geological features of the dam site and observed geomechanics data a numerical method is used to evaluate the representative elementary volume rev and to identify the parameters related to the mechanical and hydraulic properties of the rock mass furthermore a coupled hydro mechanical model is presented to describe the uplift process the simulated results agree well with those measured in addition the time dependent deformation is studied in the laboratory and numerically it is concluded that with the specific hydrogeological conditions at the tongjiezi dam site hydro mechanical coupling during and after the reservoir impoundment is the main factor contributing to the uplift and the time dependent deformation is due to the rheological behavior of rock masses under seepage pressure

applying photogrammetry and semi automated joint mapping for rock mass characterization abstract rock engineering in blocky rock masses demands a sound knowledge about the joint network since it consists of planes of weakness than can lead to block instabilities however collecting data about the joint network is time consuming seldom very detailed and depends strongly on the experience of the mapping geologist additionally the characterization is reduced to the identification of the most relevant joint structures with their characteristic orientation and spacing other parameters like the in situ block shape and the block size distribution or the main orientation of the blocks are seldom collected or determined if at all with the emergence and increasing application of digital surface mapping techniques in rock mass characterization like shapemetrix3d or the discontinuity set extractor the time needed on site could be reduced and the degree of detail in the mapping of discontinuities is improved significantly the work presented in this study displays a continuous work flow from the data collection in the field to the determination of the block size and shape distribution generated by the intersection of joint sets for the process a marble quarry in styria austria was digitized using photogrammetry the joint sets are semi automatically identified with the discontinuity set extractor whose results are transferred into the software shapemetrix3d where the joint set spacing along with its standard deviations are determined these parameters are used to generate statistical representation of representative rock mass units using 3dec itasca consulting group inc and determine the block sizes block shapes and main orientation of the blocks in a row of simulations

a cohesion loss model for determining residual strength of intact rocks abstract residual strength of rock is required in stability evaluation of underground excavations such as tunnels and caverns accurate determination of residual strength of rock can facilitate cost effective design of these underground structures this study investigates the methods for determining residual strength of intact rocks firstly previous methods for determining residual strength of intact rocks are examined from a literature review and a new method which uses the concept of cohesion loss is proposed the proposed cohesion loss model is based on the framework of the widely used hoek brown h b strength model it is simple and contains only one parameter that controls the nonlinearity of the residual strength envelope the cohesion loss model is validated using two sets of test data and the results show that the model can represent residual strength envelopes of intact rocks satisfactorily finally the model parameter is studied by examining a large amount of test data collected from previous publications it is found that the model parameter varies for different rock types and shows a decreasing trend as the rock strength increases overall the results in this study show that the proposed model can capture the residual strength of intact rocks

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

influence of fracture induced weakening on coal mine gateroad stability abstract the ground stability of gateroads is a major concern in underground coal mines especially when the surrounding strata are weak and fractured this paper presents a novel numerical modelling technique for gateroad stability analysis based on a case study conducted at zhaogu no 2 mine china considering the occurrence of fracturing and its weakening effect on the stiffness of the rock mass a tension weakening model is implemented into flac3d whereby the stiffness of the rock mass is progressively decreased with the failure state a relationship between the intensity of fractures and the residual strength of the rockmass is built in the numerical model a parametric study of the tension weakening model is carried out and the results are compared to elastic perfectly plastic and strain softening models it is shown that the tension weakening model exhibits noticeable effects on ground deformation and rock support loading which are observed from field measurements thus the tension weakening model offers a more realistic simulation of the gateroad behavior than elastic plastic and strain softening models the proposed model can be utilized for other applications involving rock reinforcement of mine openings under similar geotechnical conditions

influence of plastic shear strain and confinement dependent rock dilation on rock failure and displacement near an excavation boundary abstract excavation induced rock failure and displacement near an underground opening boundary is closely associated with rock mass dilation a better understanding of rock mass dilation around the excavation helps us to predict or anticipate displacements and extent and shape of the failed zone and subsequently assist design of proper ground support systems a calibrated cohesion weakening and frictional strengthening cwfs model with a constant dilation angle can capture the stress induced brittle failure shape in hard rocks however the use of a constant dilation angle in either cwfs mohr coulomb perfectly elasto plastic or mohr coulomb strain softening models cannot simulate the displacement distribution near the excavation reasonably in the present study numerical simulations are performed to study excavation induced displacement around tunnels located in different rock mass types i e coarse grained hard rock medium grained hard rock fine medium grained soft rock and fine grained soft rock using a mobilized dilation angle model that depends on both confining stress and plastic shear strain it is illustrated from a few examples that displacement distributions obtained from the dilation angle model are more reasonable when compared with the general trend measured underground

geological analysis and stability assessment of a sea arch in palinuro southern italy abstract the study aims to describe the geological and geostructural layouts of an unstable sea arch located in a very attractive tourist area of southern italy on the basis of ad hoc field surveys and laboratory tests the problems of an in depth geo mechanical characterization of the rock mass are discussed in details and its main strength parameters are derived an indirect assessment of the possible geostatic stress field due to the neotectonic events which affected this sector of apennine range during the last 100 000 years is proposed and validated by means of numerical non linear fe analyses the results suggest that the presence of a lateral thrust acting into the promontory located at the back of the arch is very likely and its effects would agree well with the failures occurred in the past on the arch surfaces it is concluded that any possible intervention should be carefully designed on the basis of the highlighted factors and further investigations

structural characterization of turtle mountain anticline alberta canada and impact on rock slope failure abstract this paper proposes a structural investigation of the turtle mountain anticline alberta canada to better understand the role of the different tectonic features on the development of both local and large scale rock slope instabilities occurring in turtle mountain the study area is investigated by combining remote methods with detailed field surveys in particular the benefit of terrestrial laser scanning for ductile and brittle tectonic structure interpretations is illustrated the proposed tectonic interpretation allows the characterization of the fracturing pattern the fold geometry and the role of these tectonic features in rock slope instability development ten discontinuity sets are identified in the study area their local variations permitting the differentiation of the study zone into 20 homogenous structural domains the anticline is described as an eastern verging fold that displays considerable geometry differences along its axis and developed by both flexural slip and tangential longitudinal strain folding mechanisms moreover the origins of the discontinuity sets are determined according to the tectonic phases affecting the region pre folding folding post folding the localization and interpretation of kinematics of the different instabilities revealed the importance of considering the discrete brittle planes of weakness which largely control the kinematic release of the local instabilities and also the rock mass damage induced by large tectonic structures fold hinge thrust

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

large deformation finite element modelling of earthquake induced landslides considering strain softening behaviour of sensitive clay large scale landslides in sensitive clays cannot be explained properly using the traditional limit equilibrium or lagrangian based finite element fe methods in the present study dynamic fe anal

mechanical anisotropy of columnar jointed basalts an example from the baihetan hydropower station china abstract columnar jointed basalts are characterized by a self organized joint network of discontinuities and pose a difficult challenge for geotechnical engineering design due to their inherent anisotropic nature we explore here the anisotropic characteristics of the columnar basalt formation in the chinese baihetan hydropower station including aspects of the geometrical rock structure deformation and strength anisotropy site investigations reveal that a typical cross section of the columnar basalt blocks is mainly quadrangular and pentagonal with an average edge length of 0 152 m three types of joints with different macro and micro characteristics form the columnar jointed rock mass and are identified by scanning electron microscopy in situ ultrasonic tests further confirm that the columnar basalt prisms exhibit transverse isotropy with the plane of isotropy perpendicular to the column axis as can also be observed in the field strength anisotropy is confirmed by point load and uniaxial compression tests the mechanical and anisotropic characteristics of baihetan s jointed basalt mass can be explained by its multi scale joints pattern by means of goodman s stiffness equation we find that the anisotropic coefficients obtained for its deformability and strength are similar for all testing methods employed including in situ p wave velocity point load tests and uniaxial compression tests this result confirms the strong anisotropic effect in these rock masses and facilitates an issue that must be considered when assigning input parameters for various classification and numerical analyses schemes

geomechanical properties and permeability of coals from the foothills and mountain regions of western canada abstract static and dynamic geomechanical properties and hydraulic permeability were determined for six large blocks of bituminous coal sampled from active mines in the foothills and mountain regions of western canada testing showed a nonlinear shear strength envelope and brittle failure during triaxial loading the dominant failure mode was along distinct shear planes effective compressive strengths increased from 8 6 mpa to 80 8 mpa with increasing confining pressure the mohr coulomb failure criterion showed that the coals had friction angle of 29 8 to 39 8 and cohesion ranging between 3 4 mpa and 8 0 mpa with increasing confining stress the non linear hoek brown failure envelope was also fit to the data which provided a better estimation of the strength values for static young s modulus ranged from 1119 mpa to 5070 mpa and poisson s ratio ranged from 0 26 to 0 48 also varying with the confining stress concurrent ultrasonic measurements indicate that the values for dynamic moduli are consistently higher than those obtained from quasi static measurements permeability of the coals tested at simulated in situ stress conditions and parallel to bedding surfaces was highly variable ranging from 2 09 md in seam 3 greenhills mine to less than 0 001 md in seam 10 elkview mine this variation may be rationalized based on variations in maceral composition stress history degree of shearing and the mode of deformation brittle or ductile of the coal seams in these tectonically complex regions

estimation of rock mass deformation modulus and strength of jointed hard rock masses using the gsi system abstract rock mass characterization is required for many applications in rock engineering practice including excavation design support design stope design amongst others for these purposes it is necessary to obtain design input parameters such as deformation moduli and strength parameters for numerical modeling although such parameters can ultimately be determined from in situ tests at the preliminary design stage where access to underground is limited the practical way to obtain these parameters is to apply a rock mass classification system to characterize the rock mass and estimate the rock mass properties over the years many classification systems such as rqd rock mass rating q and geological strength index gsi systems have been developed amongst them the q system is widely used for rock support system design and the gsi system is used for estimating design parameters the gsi system is the only rock mass classification system that is directly linked to engineering parameters such as mohr coulomb hoek brown strength parameters or rock mass modulus however the application of the existing gsi system is hindered by the facts that the use of the system is to some extent subjective and requires long term experience in the present study a quantitative approach to assist in the use of the gsi system is presented it employs the block volume and a joint condition factor as quantitative characterization factors the approach is built on the linkage between descriptive geological terms and measurable field parameters such as joint spacing and joint roughness the newly developed approach adds quantitative means to facilitate use of the system especially by inexperienced engineers the gsi system is applied to characterize the jointed rock masses at two underground powerhouse cavern sites in japan gsi values are obtained from block volume and joint condition factor which in turn are determined from site construction documents and field mapping data based on gsi values and intact rock strength properties equivalent mohr coulomb strength parameters and elastic modulus of the jointed rock mass are calculated and compared to in situ test results the point estimate method is implemented to approximate the mean and variance of the mechanical properties of the jointed rock masses it is seen that both the means and variances of strength and deformation parameters predicted from the gsi system are in good agreement with field test data

new constraints on bedrock erodibility and landscape response times upstream of an active fault abstract considerable progress has been made in modelling the response of rivers to tectonic perturbation in order to decode the tectonic signals embedded in river long profiles and planform geometry whilst studies have showed the importance of rock type on the morphology of rivers responding to tectonics on a local scale these effects are often not captured in landscape evolution models in fact current models of fluvial response to tectonic perturbation such as active faulting require carefully collected data sets to fully constrain or calibrate key parameters including the effect of bedrock lithology on substrate erodibility and timescales for tectonic signal propagation in bedrock river systems here we constrain the role of bedrock in controlling fluvial incision for a 240 km2 catchment draining into the gulf of corinth which has excellent tectonic constraints and a variety of bedrock lithologies an active normal fault at the downstream end of the catchment the east eliki fault is known to have initiated at 0 7 ma with average quaternary uplift and incision rates of 1 00 1 25 mm yr the initiation of the east eliki fault is recorded in the river as a prominent knickzone 7 16 km upstream of the fault detailed field data collected within this catchment at 500 m intervals along the main channel length at this tectonically well constrained field site show an order of magnitude increase in river channel slopes y x 0 02 to 0 18 and stream powers 1 kwm 2 to 27 kwm 2 at the lithological boundary between weak and resistant bedrock the weak conglomerates and strong limestones have schmidt hammer compressive strengths of ca 30 and 50 respectively based on in situ rock strength measurements consequent erodibility values of 1 8 0 3 10 14 and 5 6 2 10 15 ms2kg 1 show a factor of three to four decrease in erodibility for a two fold increase in rock strength a simple simulation of tectonic signal propagation through the river catchment based on these erodibility values indicates that the observed plan view position of the knickpoint is consistent with our calculated knickpoint positions based on erodibility values derived from incision rate and stream power data however the tectonic signal associated with faulting would have propagated completely through the catchment within 1 ma if it were entirely composed of weak rock for similar climatic and tectonic conditions indicating that lithology has a major control on landscape response times our results help constrain the effect of lithology on river channel geometry and allow erosional parameters to be derived that are crucial for effective modelling of tectonic rates from topography

numerical investigation of the scale effect and anisotropy in the strength and deformability of coal abstract the decrease in strength and stiffness of coal with increase in specimen size has long been recognized as scale effect in this study a synthetic rock mass srm approach has been used to investigate this scale effect and the anisotropy of coal a discrete fracture network dfn for the coal was created and then embedded into bonded particle models to form a range of varying size of srm coal specimens unconfined compression tests on the srm specimens showed that the srm approach is capable of quantitatively reproducing the dependency of the strength and stiffness on the size of the coal specimens the strength and stiffness anisotropy of coal can also be reproduced the numerical results are shown to be in good agreement with published laboratory and field test results

a method to predict geomechanical properties and model well stability in horizontal boreholes abstract a methodology is proposed to quickly assess the stability risk for horizontal wells drilled in coal seams the first task involves the estimation of strength and deformation parameters of the coal by indirect methods such as the use of core description to assign a geological strength index gsi the second task involves the use of a finite element analysis called flac to investigate factors such as the depth of fluid penetration while drilling the horizontal well and the stability of the wellbore during simulated production these two factors are important because coal fines generated by the drill bit action are carried by the drilling fluid into the cleat system of the coal thereby plugging the permeability pathways and causing formation damage on the other hand a wellbore that may become unstable during pressure drawdown would require a perforated or slotted production liner in this study the conditions of drilling and production necessary for a stable horizontal well drilled into a mannville coal seam at 750 800 m in the central alberta plains were studied modeling showed that the depth of fluid penetration would be at least 2 2 m if there is no filter cake formation while drilling underbalanced drilling fluid penetration would be minimal if a filter cake is formed under overbalanced conditions furthermore flac analysis showed that drilling a smaller diameter hole 5 cm would be preferable because this size results in a stable wellbore during production compared to the standard 15 cm diameter hole