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This study summarizes the experience of conducting and maintaining mining operations in unstable zones in mines in Kazakhstan, assessing the mining and geological technical conditions of their operation under difficult mining and geological conditions. A field study and analytical modeling with an assessment of the stability of the boundary mass using the Barton mining method enabled the development of a technology for sinking mining operations with combined fasteners and friction anchors in ore mines. [ABSTRACT FROM AUTHOR]

Roof fall in underground coal mines is a time-dependent process involving various behaviors such as intact and failed rock, strain-softening, and strength degradation. Current laboratory tests have observed these behaviors, but no comprehensive model represents all of these critical behaviors. To investigate the time-dependent manners of intact and failed sandstone rocks under unconfined conditions using unconfined relaxation testing in underground coal mines in Iran. Unconfined compression and relaxation tests were conducted on sandstone specimens to study the time-dependent behavior of intact and failed sandstone rocks. Two tests were conducted, with one group initiating relaxation examinations in the pre-failure region and the other in the post-failure region. The results show that intact and failed rock specimens' relaxation behaviors differ. The stress relaxation curves in the pre-failure area exhibit a smooth stress relaxation behavior. In contrast, those in the post-failure region exhibit stepped behavior with sudden and significant stress drops. The viscous parameters defined at distinct failure conditions did not show significant differences, and their average represents the time-dependent properties of failed rock. The developed model, which combines the Burgers and strain-softening models, can accurately describe the time-dependent strain-softening behavior of rocks and simulate laboratory tests. This study demonstrates the feasibility of using unconfined relaxation testing to determine the time-dependent properties of intact and failed rocks under unconfined conditions. The developed model provides a comprehensive representation of the time-dependent behavior of rocks, including strain-softening, strength degradation, and viscous behaviors. [ABSTRACT FROM AUTHOR]

Stability problems in rock stress fields were highlighted. It is a direct source of force for crustal deformation, rock destruction, and earthquake occurrence. Through large-scale international cooperation, the global GPS velocity field and world stress map were updated. Plates with the soul of a power source are no longer a bunch of rigid tectonics, and for the first time the dynamism of their movements and internal stresses are revealed. This paper describes the methods of in-situ measurement of stress, the principles of division of stress tensor regimes, and the basic features of stress maps. In response to the earthquake focal mechanism, the author has drawn a variety of 3D perspective drawings, so that readers can easily grasp the geologic meaning of the earthquake focal mechanism in a way that is easy to read and understand by looking at the drawings. Finally, the background of the local dynamics is analyzed with two examples comparing the similarities and differences between the measured stress maps and the earthquake focal mechanism.

Located in the southern part of Central Anatolia Region, Manazan Caves is situated in the east of Yeşildere Valley. It is a five-storey mass dwelling carved into a human-made high rock mass. Although there are no exact data to determine when the caves were carved, it is assumed that the caves were carved and settled in the Byzantine period during the 6th − 7th centuries. The geological and geotechnical data analyses were conducted in Manazan Caves. As a result of these analyses, it was observed that rock blocks of different sizes fell into the field in various times of the year, and there were instabilities in some individual rock blocks. In the study area, the movement mechanisms of rock slopes due to discontinuity were analysed by using various computer programs (DIPS, RockFALL, GEO5); and in order to ensure the safety of life and property and to protect this heritage cave, the current rockfall potential and risk along with slope instabilities were determined, and the fundamental prevention measures to be taken were discussed. [ABSTRACT FROM AUTHOR]

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During the construction of a mountain tunnel, water inflow and rock instability are common occurrences due to unfavorable geological conditions, posing serious threats to construction safety. This study focuses on a proposed mountain tunnel and employs multiple formulas to predict potential water inflow during excavation. Based on the amount of water inflow and deformation of surrounding rocks, comprehensive determinations are made for the thickness of grouting rings and permeability coefficients. The results demonstrate that: 1) Different formulas yield slightly varied outcomes but overall trends remain consistent; considering various calculations, the normal water inflow for this tunnel is approximately 115.5908 x 10³ m³/d with a maximum at 210.9100 x 10³ m³/d 2) Increasing grouting ring thickness or decreasing permeability coefficient can effectively reduce water inflow, but the reduction range is gradually narrowed. 3) Pre-grouting curtains have an evident effect in enhancing stability; however, their effectiveness decreases with increased thickness. 4) Taking into account both safety and economic factors, it is recommended that the grouting ring thickness be set at 8 m with a permeability coefficient equaling one 100th that of surrounding rocks for this tunnel project. [ABSTRACT FROM AUTHOR]

The empty-space subsequent filling mining method is the main mining scheme for underground metal mines to achieve large-scale mechanized mining. The stage height, one of the main parameters of this method, affects the various production process aspects of the mine and influences the stability of the goaf. In order to determine the stage height scientifically and rationally in the empty-space subsequent filling mining method, a formula for the stabilized critical safe height of a high goaf in an underground metal mine was derived based on Pu's arch equilibrium theory, Bieniawski's pillar strength limit theory, and the Kastner equation and combined with the results of an orthogonal analysis to rank the importance of the main factors in the formula. A copper mine in Jiangxi Province was used as a case study, with the reliability of the formula verified by numerical simulation and industrial testing. The factors in the formula influencing the critical stabilized safe height of the goaf were, in descending order, the compressive strength of the rock body, the width of the two-step mining pillar, the width of the one-step mining room, the mining height, and the depth of mining. Based on the calculation results, the recommended stage heights are 30 m (−378 m middle section) and 25 m (−478 m middle section) in the area of poor rock body stability and 50 m in the area of better rock body stability. The simulation results show that the goaf is significantly affected by the compressive stress under the condition of a certain rock body stability and that the compressive stress increases with increasing goaf height. The minimum recommended values of the sidewall safety coefficients in areas of poor and better rock stability are 1.04 and 1.06, respectively. The volume deviation coefficients of the three industrial test mines were all controlled within 3%, indicating that no obvious collapse and destabilization phenomenon occurred in the goaf. This paper provides some theoretical and applied guidance for the stage height design of similar underground metal mines using the empty-space subsequent filling mining method. [ABSTRACT FROM AUTHOR]

Investigating the construction mechanics of a ventilation tunnel using the TBM (Tunnel Boring Machine) pilot and enlargement method with reliable rock mechanics parameters ensures the safety of on-site excavation operations. Leveraging the construction project of the ventilation tunnel at the Wuhai Pumped Storage Power Station, TGP sidewall forecasting was employed to explore the geological conditions within a 50 m range of the tunnel's side. A systematic study of the construction mechanics of the TBM pilot and enlargement method was conducted, along with corresponding construction recommendations and engineering applications. This research indicates that sidewall forecasting can supplement the deficiencies in geological exploration reports, with excavation revealing conditions consistent with the forecast. Deformation at the interface, including the arch crown and sidewall, mainly concentrates during the construction phase from the completion of full-section excavation to the beginning of expansion. As the working face advances, the upper rock mass within the ventilation tunnel outline experiences tension, with stress concentration in the shoulder and bottom corner rock masses. The plastic zone before expansion primarily concentrates within the ventilation tunnel outline, shifting to the sidewall after expansion, with the left shoulder's plastic zone depth slightly exceeding that of the right. The proposed method effectively ensures construction safety, and the research findings have valuable implications for similar projects. [ABSTRACT FROM AUTHOR]

Establishing the degree and numerical parameters of fracturing of the host rock massif in the contour of the roof of the mine opening allows us to establish the technological parameters of the fastening. Monitoring and forecasting the assessment of the stability of mine workings in the mines of the Karaganda coal basin will allow us to determine the patterns of manifestations of rock pressure in workings depending on mining and geological factors and mining operating conditions based on computer modeling of geomechanical processes in the host mixed coal rock mass around the workings under study. It is necessary to create technological schemes for conducting mining operations based on modeling of zonal disintegration of rock masses and passports for fastening mine workings for various mining, geological and mining technical conditions of coal mine development in order to reduce the cost of operating mine workings in compliance with the standard speed of their implementation for preparing the front of the mining excavation. The use of arched metal-frame support does not allow increasing the pace of mining and the productivity of miners, reducing the metal intensity of the support and its cost, and also applying comprehensive mechanization of work to maintain mine workings. Depending on the type of polymer composition, the adhesion of the fastening chemical composition to sandstone is 0.03 - 0.15 MPa and increases from a smooth rod to a threaded one and is maximum for an anchor rod with a variable profile. [ABSTRACT FROM AUTHOR]

Purpose is to assess a natural field of rock mass stress within Vostochnaya Sary-Oba deposit using in-situ measurements. It will help identify stress distribution as well as high-stress areas that may be dangerous for mining operations. Methods. The research has applied a technique of well hydraulic fracturing to study parameters of the initial stress field within the deposit. For the purpose, two metering points in two measuring (horizontal and vertical) wells were used. Hydraulic fracturing has been tested at each installation location. Findings. The in-situ measurement results have helped obtain quantitative parameters of stress-strain state of the rock mass. It has been understood that the available tectonic disturbances may result from the shape of structural folds as well as from tectonic fissility. Operating azimuth of the maximum horizontal stress within the points coincides, it is equal to 70° ± 10. Originality is the use of a new approach to assess the stress rock mass state within Vostochnaya Sary-Oba deposit while applying in-situ measurements and well hydraulic fracturing. The abovementioned favours more accurate and reliable assessment of rock stress state at the field being quite important for mining safety and for the development of the efficient supporting procedures and ore extraction procedures. Practical implications. The research results are applicable to adapt project documents for the deposit mining, a supporting technique selection, and ore extracting. Moreover, they will help make the substantiated choice of a structure and geotechnical parameters taking into consideration safety of operations as well as quality of ore mining. In addition, the results help develop measures to prevent rock mass outburst and fall in mine workings. [ABSTRACT FROM AUTHOR]

Investigating the construction mechanics of a ventilation tunnel using the TBM (Tunnel Boring Machine) pilot and enlargement method with reliable rock mechanics parameters ensures the safety of on-site excavation operations. Leveraging the construction project of the ventilation tunnel at the Wuhai Pumped Storage Power Station, TGP sidewall forecasting was employed to explore the geological conditions within a 50 m range of the tunnel’s side. A systematic study of the construction mechanics of the TBM pilot and enlargement method was conducted, along with corresponding construction recommendations and engineering applications. This research indicates that sidewall forecasting can supplement the deficiencies in geological exploration reports, with excavation revealing conditions consistent with the forecast. Deformation at the interface, including the arch crown and sidewall, mainly concentrates during the construction phase from the completion of full-section excavation to the beginning of expansion. As the working face advances, the upper rock mass within the ventilation tunnel outline experiences tension, with stress concentration in the shoulder and bottom corner rock masses. The plastic zone before expansion primarily concentrates within the ventilation tunnel outline, shifting to the sidewall after expansion, with the left shoulder’s plastic zone depth slightly exceeding that of the right. The proposed method effectively ensures construction safety, and the research findings have valuable implications for similar projects.

Relevance. The stress-strain state of the rock massif during open-pit mining of mineral deposits, as well as during construction in excavations of significant size, depends on both the mechanical properties of rocks and the structural and textural features of the rock massif. In particular, the presence of cracks in the near-slope zone of the ledge can significantly weaken its stability, and the direction and angle of crack incidence relative to the ledge slope change the location of stress zones within the massif relative to the surface of the outcrop. The identification of zones of increased mechanical stresses in order to predict the behavior of rock massifs with different structural-textural properties is an urgent scientific and practical task. The main aim is identification of the stress concentration zones in the near-slope part of the ledge in the rock massif with different structural-textural properties during open-pit mining. Methods: mathematical modeling of rock massifs with regard to their physical and mechanical properties and structural and textural features using the finite element method, processing the results of experimental studies. Results. The paper introduces the description of the mathematical model of the elastic behavior of a natural fractured rock massif with an outcrop surface in the form of a ledge, as well as the laws of stress concentration distribution in it. The stress-strain state of loaded and unloaded massifs in the undisturbed and disturbed by cracks of different orientation states is described, and their values for ledges with different structure are compared. The authors have revealed the increased values of tensile stresses in the massif in the direction of crack incidence from the ledge slope compared to the undisturbed state and in the direction of crack incidence toward the ledge slope.

Rock mass failure is gradually becoming more common as the number of geotechnical engineering projects continues to increase. In this paper, the probability density distributions of initial and peak frequency events in the acoustic emission (AE) from two types of rock (phosphate rock and granite) undergoing failure are analyzed. Feature events (FEs) in this AE are proposed and obtained. The probabilities of events with an initial frequency of 1,000 kHz and peak frequency of 625 kHz are found to be higher than those with other frequencies. The evolutionary behavior of the cumulative probability distributions (CPDs) of the FEs as the rocks fail is subsequently investigated. The characteristic FEs of the AE and their CPD evolution behavior in the two rocks are then compared and contrasted. The CPD curves derived for both types of rock consist of four stages: slow rise—concave rise—rapid rise—slow rise. The differences related to the FEs for the two rocks are also found. The duration of the last stage (near rock failure) is quite different for phosphate rock and granite. The peak frequencies of the FEs are the highest and the smallest in the two rocks, respectively. Our method of analyzing the AE data and results provide a theoretical method for analyzing the stability of rock masses and predicting their failure.

Comprehensive knowledge and analysis of in situ rock strength and geo-mechanical characteristics of rocks are crucial in hydrocarbon and mineral exploration stage to maximize wellbore performance, maintain wellbore stability, and optimize hydraulic fracturing process. Due to the high cost of laboratory-based measurements of rock mechanics properties, the log-based prediction is a viable option. Nowadays, the machine learning tools are being used for estimation of the in situ rock properties using wireline log data. This paper proposes a machine learning approach for rock strength (uniaxial compressive strength) prediction. The main objectives are to investigate the performance of data-driven predictive model in determining this vital parameter and to select features of predictor log variables in the model. The backpropagation multilayer perception (MLP) artificial neural network (ANN) with Levenberg–Marquardt training algorithm as well as the least squares support vector machine (LS-SVM) with coupled simulated annealing (CSA) optimization technique is employed to develop the dynamic data-driven models. Capturing nonlinear, high dimensional, and complex nature of real field log data, the rock strength models' performances are evaluated using statistical criteria to ensure concerning the model reliability and accuracy. The model predictions are compared and validated against the measured values as well as the results obtained from existing log-based correlations. Both the MLP-ANN and the CSA-based LS-SVM connectionist strategies are able to predict the rock strength so that there is a very good match between the model results and corresponding measured values. The input log parameters are ranked based on their contributions in prediction performance. The acoustic travel time and gamma ray are found to have the highest relative significance in estimating rock strength. New correlations are also developed to obtain the in situ rock strength of the siliciclastic sedimentary rocks using the most important log parameters such as dynamic sonic slowness, formation electron density, and shalyness effect. The developed correlations can be used to obtain quick estimation of dynamic uniaxial compressive strength profile using wireline logging data, instead of static data from the surface measurements or laboratory data. It is expected that the proposed models and tools will enable oil and gas engineers to better predict rock strength and thus enhance wellbore performance. [ABSTRACT FROM AUTHOR]

Cobbles, boulders, and rocks often are used in a bed protection layer near a structure to protect the underlying sand bed against erosion by combined current and waves. The design of a bed protection layer consisting of loose rocks (rubble mound) requires knowledge of the stability and movement (as bed load) of very coarse materials. If some movement (or damage) is acceptable, the rock diameter can be designed to be smaller. This paper addresses the stability and movement of very coarse materials (cobbles, boulders, and rocks) based on the concept of the critical Shields mobility number. It is shown that the bed load transport of large cobbles, boulders, and rocks can be described by the equations of Meyer-Peter and Mueller (MPM) and Cheng. Both are valid for relatively small Shields mobility numbers. New and general equations for the design of a bed protection layer (including some permissible damage) in conditions with a current with or without waves are proposed based on the Shields mobility parameter and the bed load transport equation of Cheng. Laboratory and field data of critical velocities for pebbles, cobbles, boulders, and rocks have been analyzed and compared to the computed results of the proposed equations. Practical applications are given to demonstrate the general applicability of the proposed equations. [ABSTRACT FROM AUTHOR]

An optimization model was developed to obtain the ideal values of the primary support parameters of tunnels, which are wide-ranging in high-speed railway design codes when the surrounding rocks are at the III, IV, and V levels. First, several sets of experiments were designed and simulated using the FLAC3D software under an orthogonal experimental design. Six factors, namely, level of surrounding rock, buried depth of tunnel, lateral pressure coefficient, anchor spacing, anchor length, and shotcrete thickness, were considered. Second, a regression equation was generated by conducting a multiple linear regression analysis following the analysis of the simulation results. Finally, the optimization model of support parameters was obtained by solving the regression equation using the least squares method. In practical projects, the optimized values of support parameters could be obtained by integrating known parameters into the proposed model. In this work, the proposed model was verified on the basis of the Liuyang River Tunnel Project. Results show that the optimization model significantly reduces related costs. The proposed model can also be used as a reliable reference for other high-speed railway tunnels.

For the purpose of continuous production design in the deeper levels of underground mine JAMA Bor, at first the rock stability analysis of ore deposit 'Borska Reka' was performed before beginning of design the exploitation. Analysis was performed on the designed roadway model at the XVII level in ore deposit Borska Reka, with the scope of confirmation the relevance of data collected from previous research and studies. Analyses presented in this paper were performed by using software package Phase2, Rocscience Inc., which calculations are based on stress-strain condition analysis with finite element method to analyze behavior of rocks. It can be used for a wide range of engineering projects.

Abstract An empirical formula was developed for predicting the stability of isolated quarry rocks on relatively flat beds under waves with or without current in terms of the damage ratio. The damage ratio was examined using 100 crushed stones (median mass M 50 = 293 g and mass density ρ s = 2.62 g/cm3) as scale models of quarry rocks and replicas with a lower density (ρ s = 1.38 g/cm3) by placing them on beds of different roughness in a wave flume, not only under periodic waves with periods of 2–3.5 s, but also in symmetric and asymmetric oscillatory flows (periods: 8–12 s), simulating waves without and with current in a circulating water channel. Comparison between hydrodynamic forces expressed in terms of three non-dimensional mobility indices: the maximum velocity, maximum semi-velocity amplitude (U a), and maximum acceleration relative to the friction force (expressed in terms of the median coefficient of friction) suggested that the damage ratio was most closely related to the U a -based mobility index (ψ 2). Nevertheless, significant differences remained between data from the wave flume and circulating water channel tests. The variation in the damage ratio, which included the effects of the oscillatory-velocity asymmetry, oscillation period, superimposed steady current, mass density of stones, and bottom friction, was reasonably well described via the product of ψ 2 and a function of a Keulegan–Carpenter number. The results of the field tests on quarry rocks (with M 50 = 2.04 t) placed on a thin sand layer overlaying hard substrate show that the minimum stable mass is consistent with the prediction. Highlights • A model is presented for isolated rock stability under waves with or without current. • Wave flume and circulating water channel experiments are conducted. • The model well explains the observed damage ratio of rocks. • A formula is also presented for estimating the friction coefficient used in the model. • A reasonable agreement is found in a field test. [ABSTRACT FROM AUTHOR]

Deep mining is widely carried out across the world. Due to large cover depth, both stress magnitude and fracture development are greatly enlarged, increasing the complexity in mining conditions. Correspondingly, a series of ground control problems emerge in deep coal mines, such as face collapsing, roof falling and support jamming. This study mainly focusses on the variation in roof activity along face length direction, which helps to strengthen roof control of a deep longwall panel. Geological radar detection reveals that the development of mining-induced fractures present an increasing trend from the maingate to tailgate side, implying the variation in roof activity along face length direction. Microseismic (MS) monitoring is moreover conducted, with which both spatial distribution and dynamic evolution of MS events in roof strata are thoroughly analyzed. Due to stronger influence provided by fault structures, the concentration of MS number mainly occurs to the tailgate section. Thus, roof microseismicity is brisker in the referred section, accounting for 63.7% of the total events. The sensitivity of MS energy to fault structures is weaker than that of MS number. Energy concentration can be observed in the whole panel width. In the maingate section, the energy proportion reaches 44.1%, indicating stronger roof microseismicity. Such asymmetrical distribution in roof microseismicity is sensitive to fault activation, fracture influence and mining disturbance. The location of fault structures, spatial variation in fracture parameters and the difference in stress rotation characteristics contribute to asymmetrical distribution in roof microseismicity on two sides of the target panel. Based on MS characteristics, a coordinative movement method is innovatively proposed for hydraulic supports, which weakens cyclic disturbance of support movement on roof strata at the face area. The method is proved to be effective by the improvement in roof stability and mining efficiency. • Mining induced microseismic events of a deep longwall panel are monitored. • Asymmetrical distribution of roof microseismicity in face length direction is identified. • Fault activation, fracture influence and mining disturbance leads to asymmetrical distribution. • A coordinative movement method is proposed for hydraulic supports based on microseismic detection. [ABSTRACT FROM AUTHOR]

The strength decay that occurs in the post-peak stage, under low confinement stress, represents a key factor of the stress-strain behaviour of rocks. However, for soft rocks this issue is generally underestimated or even neglected in the solution of boundary value problems, as for example those concerning the stability of underground cavities or rocky cliffs. In these cases, the constitutive models frequently used in limit equilibrium analyses or more sophisticated numerical calculations are, respectively, rigid-plastic or elastic-perfectly plastic. In particular, most of commercial continuum-based numerical codes propose a variety of constitutive models, including elasticity, elasto-plasticity, strain-softening and elasto-viscoplasticity, which are not exhaustive in simulating the progressive failure mechanisms affecting brittle rock materials, these being characterized by material detachment and crack opening and propagation. As a consequence, a numerical coupling with mechanical joint propagation is needed to cope with fracture mechanics. Therefore, continuum-based applications that treat the simulation of the failure processes of intact rock masses at low stress levels may need the adoption of numerical techniques capable of implementing fracture mechanics and rock brittleness concepts, as it is shown in this paper. This work is aimed at highlighting, for some applications of rock mechanics, the essential role of post-peak brittleness of soft rocks by means of the application of a hybrid finite-discrete element method. This method allows for a proper simulation of the brittle rock behaviour and the related mechanism of fracture propagation. In particular, the paper presents two ideal problems, represented by a shallow underground cave and a vertical cliff, for which the evolution of the stability conditions is investigated by comparing the solutions obtained implementing different brittle material responses with those resulting from the assumption of perfectly plastic behaviour. To this purpose, a series of petrophysical and mechanical tests were conducted on samples of soft calcarenite belonging to the Calcarenite di Gravina Fm. (Apulia, Southern Italy), focusing specific attention on the post-peak behaviour of the material under three types of loading (compression, indirect tension and shear). Typical geometrical features representative of real rock engineering problems observed in Southern Italy were assumed in the problems examined. The numerical results indicate the impact of soft rock brittleness in the assessment of stability and highlight the need for the adoption of innovative numerical techniques to analyse these types of problems properly. [ABSTRACT FROM AUTHOR]

Geologic carbon storage is considered as a requisite to effectively mitigate climate change, so large amounts of carbon dioxide (CO2) are expected to be injected in sedimentary saline formations. CO2 injection leads to the creation of acidic solution when it dissolves into the resident brine, which can react with reservoir rock, especially carbonates. We numerically investigated the behavior of reservoir-caprock system where CO2 injection-induced changes in the hydraulic and geomechanical properties of Apulian limestone were measured in the laboratory. We found that porosity of the limestone slightly decreases after CO2 treatment, which lead to a permeability reduction by a factor of two. In the treated specimens, calcite dissolution was observed at the inlet, but carbonate precipitation occurred at the outlet, which was closed during the reaction time of three days. Additionally, the relative permeability curves were modified after CO2–rock interaction, especially the one for water, which evolved from a quadratic to a quasi-linear function of the water saturation degree. Geomechanically, the limestone became softer and it was weakened after being altered by CO2. Simulation results showed that the property changes occurring within the CO2 plume caused a stress redistribution because CO2 treated limestone became softer and tended to deform more in response to pressure buildup than the pristine rock. The reduction in strength induced by geochemical reactions may eventually cause shear failure within the CO2 plume affected rock. This combination of laboratory experiments with numerical simulations leads to a better understanding of the implications of coupled chemo-mechanical interactions in geologic carbon storage.

Degradation of permafrost rock wall decreases stability and can initiate rock slope instability of all magnitudes. Rock instability is controlled by the balance of shear forces and shear resistances. The sensitivity of slope stability to warming results from a complex interplay of shear forces and resistances. Conductive, convective and advective heat transport processes act to warm, degrade and thaw permafrost in rock walls. On a seasonal scale, snow cover changes are a poorly understood key control of the timing and extent of thawing and permafrost degradation. We identified two potential critical time windows where shear forces might exceed shear resistances of the rock. In early summer combined hydrostatic and cryostatic pressure can cause a peak in shear force exceeding high frozen shear resistance and in autumn fast increasing shear forces can exceed slower increasing shear resistance. On a multiannual system scale, shear resistances change from predominantly rock-mechanically to ice-mechanically controlled. Progressive rock bridge failure results in an increase of sensitivity to warming. Climate change alters snow cover and duration and, hereby, thermal and mechanical processes in the rock wall. Amplified thawing of permafrost will result in higher rock slope instability and rock fall activity. We present a holistic conceptual approach connecting thermal and mechanical processes, validate parts of the model with geophysical and kinematic data and develop future scenarios to enhance understanding on system scale. [ABSTRACT FROM AUTHOR]

In focus is the methodology of the support design for a tunnel in disseminated ore mining in Zapolyarny Mine, Transpolar Division, Norilsk Nickel. The calculation of the rock bolting parameters in the zone of influence of stoping is exemplified. [ABSTRACT FROM AUTHOR]

Cyclic diurnal and annual temperature variations acting upon rocks belong to the permanent factors rarely considered as triggering factors of slope movements. The importance of temperature changes is viewed mainly as the precursor of failures where triggers are rainfall, seismic activity or other natural factors. This paper aims to determine the limit conditions where plastic deformation develops in situation where the block or several blocks fallen into open discontinuity create a "wedge-like" behaviour causing non-elastic displacement of block resting on an inclined plane. A physical model was prepared to study this phenomenon. The study was performed in thermal dilatometer where the displacements were measured using LVDT sensors for blocks with different block/wedge ratios, while the temperature cycled in a controlled manner. Together 9 physical models of sandstone blocks were tested within range of ΔT = 35 °C, which corresponds to annual temperature change and permanent displacements of the block was measured in order to confirm the existence of expected type of failure mechanism. Further series of cyclic tests at 9 models were performed in order to determine the threshold temperature change at which the plastic deformation for different block/wedge ratios occurs. The results confirmed the existence of plastic deformation resulting from cyclic wedging mechanism for block/wedge ratio 0.4 and total model size of 50mm reached permanent displacement of 2.23 × 10-3 mm for a block resting on an inclined plane of 7°. For the same conditions the temperature change which causes permanent displacement of the block by wedging mechanism was found out to be as low as 6 °C. The results of physical model are in agreement with proposed analytical solution by Pasten (2013) and measurements of Bakun-Mazor et al., (2013) at Masada site in Israel. A thorough testing of the rock material in saturated conditions together with physical models was carried out, which confirmed the existence of the plastic deformations with amplitudes ten times larger compared to the dry conditions. [ABSTRACT FROM AUTHOR]

Abstract: A great number of numerical simulations of multiple schemes were conducted to investigate the stability of underground cavern complexes in three representative hydropower stations in China. The purpose was to study the displacement law of side walls of underground openings under different conditions. In the calculation, four major typical rocks, four overburden thicknesses, and five geo-stress conditions were taken into account. The best-fit formulae to predict the displacement of key points on the side walls of underground openings were obtained by using the dimensionless technique. The formulations can describe the effects of rock quality, overburden thickness, horizontal in situ stress, the height of the power house and the spacing between openings. The formulation/methodology was used to predict the side wall displacements of nine underground complexes in China. A comparison analysis showed that the predicted values were in close agreement with those obtained by field measurements and by back analysis. [Copyright &y& Elsevier]

Optimal parameters of room-and-pillar mining have been established by numerical modeling based on in-situ data on topography, geological structure and physico-mechanical properties for three marble quarries in Turkey. Vertical stresses in pillars are estimated and rock stability classification is developed. [ABSTRACT FROM AUTHOR]

An analysis is performed for the distribution of stresses in the elements of slicing system in mining the “Internatsionalnaya” kimberlite pipe. The parameters and conditions of carrying out the stoping operations in experimental-industrial block by ascending slices are substantiated. [ABSTRACT FROM AUTHOR]