Subjects -> EARTH SCIENCES (Total: 771 journals)     - EARTH SCIENCES (527 journals)    - GEOLOGY (94 journals)    - GEOPHYSICS (33 journals)    - HYDROLOGY (29 journals)    - OCEANOGRAPHY (88 journals) EARTH SCIENCES (527 journals)            First | 1 2 3
 Showing 401 - 371 of 371 Journals sorted alphabetically Physical Science International Journal Physics in Medicine & Biology       (Followers: 15) Physics of Life Reviews       (Followers: 1) Physics of Metals and Metallography       (Followers: 18) Physics of Plasmas       (Followers: 10) Physics of the Earth and Planetary Interiors       (Followers: 34) Physics of the Solid State       (Followers: 5) Physics of Wave Phenomena Physics World       (Followers: 18) Physik in unserer Zeit       (Followers: 9) Pirineos Planet       (Followers: 4) Plasma Physics Reports       (Followers: 7) Polar Record       (Followers: 2) Positioning       (Followers: 4) Pramana       (Followers: 13) Precambrian Research       (Followers: 7) Preview Proceedings of the Geologists' Association       (Followers: 6) Proceedings of the Linnean Society of New South Wales       (Followers: 2) Proceedings of the Yorkshire Geological Society       (Followers: 1) Progress in Earth and Planetary Science       (Followers: 16) Pure and Applied Geophysics       (Followers: 12) Quarterly Journal of Engineering Geology and Hydrogeology       (Followers: 4) Quaternary Quaternary Australasia Quaternary Geochronology       (Followers: 8) Quaternary International       (Followers: 14) Quaternary Research       (Followers: 19) Quaternary Science Advances Quaternary Science Reviews       (Followers: 26) Radiocarbon       (Followers: 12) Remote Sensing       (Followers: 58) Remote Sensing Applications : Society and Environment       (Followers: 10) Remote Sensing in Earth Systems Sciences       (Followers: 5) Remote Sensing Letters       (Followers: 46) Remote Sensing Science       (Followers: 29) Rendiconti Lincei Reports on Geodesy and Geoinformatics       (Followers: 8) Reports on Mathematical Physics       (Followers: 2) Research & Reviews : Journal of Space Science & Technology       (Followers: 18) Resource Geology       (Followers: 6) Resources, Environment and Sustainability       (Followers: 2) Results in Geochemistry Results in Geophysical Sciences Reviews in Mineralogy and Geochemistry       (Followers: 4) Reviews of Modern Physics       (Followers: 31) Revista Cerrados Revista de Ciências Exatas Aplicadas e Tecnológicas da Universidade de Passo Fundo : CIATEC-UPF Revista de Ingenieria Sismica Revista de Investigaciones en Energía, Medio Ambiente y Tecnología Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales Revista de Teledetección Revista Geológica de Chile Revue Française de Géotechnique Rock Mechanics and Rock Engineering       (Followers: 7) Rocks & Minerals       (Followers: 3) Russian Geology and Geophysics       (Followers: 3) Russian Journal of Mathematical Physics Russian Journal of Pacific Geology Russian Physics Journal       (Followers: 1) Science China Earth Sciences       (Followers: 3) Science News       (Followers: 11) Science of Remote Sensing       (Followers: 7) Scientific Annals of Stefan cel Mare University of Suceava. 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Similar Journals
 Rock Mechanics and Rock EngineeringJournal Prestige (SJR): 2.328 Citation Impact (citeScore): 3Number of Followers: 7      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1434-453X - ISSN (Online) 0723-2632 Published by Springer-Verlag  [2469 journals]
• Novel Rock Image Classification: The Proposal and Implementation of
RockNet

Abstract: Rock classification provides vital information to geosciences and geological engineering practices. Reaping the benefits of the advances of computer vision-based deep learning artificial intelligence (AI) technology, this study aims to develop a next-generation convolutional neural network (CNN) to perform automatic rock classification. Two major challenging issues have been particularly addressed. First, most of the previous rock classifications are simply transfer learning of CNNs that are trained by life-like scenarios. Second, classifying rock types with similar textures leads to severe overfitting of CNNs. In this study, a novel CNN called RockNet is proposed and implemented to classify seven common Hong Kong rock types, namely fine-grained granite, medium-grained granite, coarse-grained granite, coarse ash tuff, fine ash tuff, feldspar phyric rhyolite, and granodiorite. With the aid of dynamic expansion, squeeze and excitation, and other strategies, RockNet can classify rock types with similar texture patterns/colors but different grain sizes. As compared with the other ten landmark CNNs and seven feature-based algorithms, RockNet has the best performance in precision (90.9%), recall (90.4%), and f1-score (90.5%). By implementing the alerting level, which restricts the training loss hovering above a small constant, and prevents the validation loss from rising, the overfitting has been efficiently eliminated. The proposal and implementation of RockNet highlight the value of interdisciplinary research and will continuously pave the way for better coupling AI and geosciences.
PubDate: 2022-08-11

• Probabilistic Time Estimation of Tunneling Projects: The Uri Headrace
Tunnel

Abstract: Probabilistic time estimation is an essential part of proper risk management in tunneling projects. In recent decades, several models have been developed for this purpose, one of which was developed by Isaksson and Stille (Rock Mech Rock Eng 38:373–398, 2005). In this paper, Isaksson and Stille’s probabilistic time and cost estimation model was improved and then applied to estimate the total tunneling time of the headrace tunnel in the Uri hydropower project in India. The improvements allow the user to more accurately account for different types of geological features and disruptive events. The result of the estimation is a distribution of tunneling time. The outcome illustrates how a proper understanding of the geological setting of the project and its effect on construction performance can contribute to effective risk management.
PubDate: 2022-08-11

• On the Interpretability of Machine Learning Using Input Variable
Selection: Forecasting Tunnel Liner Yield

Abstract: To validate the application of machine learning (ML) to rock engineering practice, it is crucial that algorithm developers use appropriate methods to quantify how closely the ML reproduces the observed rock mass deformation. Input variable selection (IVS) is one approach that examines how ML uses the given data, or inputs, to forecast rock mass behavior. Three IVS methods were developed for two convolutional neural network (CNN) architectures that predict tunnel liner yield at the Cigar Lake Mine, which exhibits time-dependent squeezing deformation. One model architecture focused on accurately predicting the higher tunnel liner yield classes, while the second architecture prioritized prediction accuracy across all tunnel liner yield classes. The three IVS methods investigated herein were channel activation strength (CAS), input omission (IO), and partial correlation (PC). The IO and PC approaches proposed are novel approaches proposed for CNNs using a spatial and temporal geomechanical dataset. Performance of all models was compared using the corrected Akaike information criterion (AICc), where lower values indicate better performance. Each IVS method was used to produce a unique ranking for each model architecture and training/testing data split: CAS produced an activation ranking, IO produced an Omission Ranking, and PC produced a correlation ranking. The activation rankings showed that the geology input had the lowest activation strength in the CNN relative to the other inputs (ground freezing, primary installed support class, and radial tunnel displacement). Geology had the highest omission ranking, resulting from it having the most negative impact on performance as compared to the other inputs when it was omitted from the models entirely. The PC approach, using the Correlation Rankings, found that the highest model performances were reached when the most recent radial tunnel displacement was added into the pool of candidate inputs. The three IVS approaches and their respective rankings proved to be useful for analyzing the CNN inputs in terms of importance and confirming underlying assumption about the deformation mechanics at Cigar Lake Mine. Collectively, the IVS analyses indicated that all of the available digitized inputs for the Cigar Lake Mine CNNs are needed to produce good model performances. Each IVS method revealed different insights into this CNN development. Undertaking IVS for ML developed using geomechanical datasets allows for verification of the algorithms and thereby a better understanding of the nuance of the rock mass deformation. At Cigar Lake Mine, these findings may be used to assist in forecasting the schedule and budget for ground support rehabilitation.
PubDate: 2022-08-11

• Confined Tensile Testing of Porous Sandstone

Abstract: The confined tension region of a failure surface, where both tensile and compressive normal stresses are present, is experimentally challenging to investigate and consequently not fully characterized. In particular, strength tests of rock at stress states associated with low mean stress are rare. To address this limitation, axisymmetric extension experiments on dog-bone specimens are used in combination with axisymmetric extension and compression experiments on right-circular cylinders of Dunnville sandstone to define the confined tension region and evaluate linear (Mohr–Coulomb and Paul-Mohr–Coulomb) with tension cut-offs and non-linear (Hoek–Brown and Fairhurst) failure criteria. The strength tests indicate that a failure criterion that includes a tension cut-off best captures failure in the low mean stress regime, − T/3 < P < Co/3, where T = uniaxial tensile strength, P = mean stress, and Co = uniaxial compressive strength. Fracture surfaces of the dog-bone specimens were examined for failure mode based on surface roughness and it was found that there is a transition of decreasing roughness from tensile (opening) failure to hybrid (opening and sliding) failure to shear (sliding) failure.
PubDate: 2022-08-10

• Thermo-Poromechanical Properties of Pierre II Shale

Abstract: During the injection of carbon dioxide (CO2) for CO2 capture and storage (CCS) operations, the near-well (including casing, cement, and rock around it) can undergo several thermal loadings. These loadings can significantly increase or decrease the pore pressure and can thus lead to mechanical failure of the cement sheath and rock formation. When these failures appear in the caprock, they can compromise the integrity of the storage site. The understanding of thermo-mechanical behaviour of a potential caprock shale is, therefore, of great importance for the success of CCS operations. In this paper, experiments were performed on Pierre II shale, under confining and initial pore pressures comparable to field conditions. A 60 °C loading amplitude (between 30 and 90 °C) was applied on the shale material both under undrained and drained conditions. The results, analysed within the framework of anisotropic thermo-poro-elasticity, highlight the anisotropic behaviour of the thermal expansion coefficients, as well as of the Skempton coefficient. The thermal pressurization coefficient was also evaluated and showed a potential pore pressure change as high as 0.11 MPa/°C.
PubDate: 2022-08-10

• Experimental Investigation of Thermal Strengthening in Sichuan Marble

Abstract: It is well documented that temperatures higher than 400 ℃ can significantly lower rock strength due to thermally induced decomposition and microcracks. However, rock strength increase under temperatures 25–400 ℃ has also been reported. It remains elusive whether thermal strengthening does exist or it is just an illusion caused by rock heterogeneity. To uncover such a mystery, we carried out triaxial compression tests on Sichuan marble under 25–200 ℃. Rock heterogeneity was at a low level and data dispersion was limited in our experiment. We managed to observe a clear trend of strength increase with temperature, justifying the existence of thermal strengthening in Sichuan marble. To unveil the mechanism of thermal strengthening, five factors, as predominant and comprehensive as we could concern, were investigated. After careful examination and analysis, thermal expansion was inferred to be the main reason leading to the thermal strengthening in Sichuan marble. The mechanism may lie in tighter compaction between mineral grains due to thermal expansion. Since thermal expansion is a physical process that can occur in all crystalline rocks upon heating, thermal strengthening holds a high potential to be a general property of crystalline rocks in the moderate temperature range. To our best knowledge, this study is the first to explicitly confirm the existence of thermal strengthening and comprehensively investigate the underlying mechanisms. The findings provide a new understanding of the thermal effect on rock strength, which may aid rock engineering design under a thermo-mechanical coupling working condition.
PubDate: 2022-08-09

• Numerical Study on the Fracturing Mechanism of the Belt Conveyor Roadway
in Dagushan Open-Pit Mine and Control Measures Evaluation

Abstract: Dagushan Iron Mine is a large-scale open-pit mine. In this mine, the belt conveyors residing in the rock slope are employed for ore haulage. However, after the − 210 m bench was excavated, many fractures occurred in one of the roadways placing the belt conveyors. In this paper, this engineering case was introduced in detail and the fracturing mechanism was investigated numerically. A numerical model containing complex stratigraphy and geological conditions was built for fracturing mechanism analysis. The strain-softening constitutive model was adopted to describe the post-failure behavior of rock mass. The model was validated with field monitoring data and spot observations, and then used to analyze the interactions between the roadway and rock slope induced by bench excavation. The deformation and stress evolutions in the rock slope and the fracturing process of concrete lining were further clarified for this roadway-landslide system. The numerical results show that the − 210 m bench excavation activated the F14 and F15 faults (with activity initiating low and extending upwards) and generated large shear bands, forming an isolated potential sliding strip. The large displacement of the potential sliding strip acting on the roadway led to the fracturing of the concrete lining. The rock masses around the roadway have also been damaged severely. The control measures of slope cutting were suggested for future production and evaluated using the numerical model. It was found that the suggested control measures could manage the convergent deformation of the roadway to within the appropriate limit and ensure that the belt conveyor can be used for ore haulage until nearly the end of production. The suggested control measures are feasible and practical, and provide a reference for addressing similar engineering problems.
PubDate: 2022-08-08

• Experimental Investigation of Incompatible Deformation Characteristics of
Ultra-Deep Composite Rock Salt

Abstract: Rock salt formation has a worldwide distribution. In China, a typical area for rock salt formation is in Tarim Basin, Xinjiang Uygur Autonomous Region, Northwest of China. Because of the ultra-deep depth and tectonic movement, the rock salt is interbedded with mudstone and other components. As a result, the creep behavior and mechanism remain uncertain, which brings a big challenge for safe drilling and wellbore integrity. In this paper, we compared different types of rock salt, including fine-grain size pure salt outcrop, composite rock salt outcrop with coarse grain size, and ultra-deep halite core with mudstone interlayer from Tarim basin. The result reveals that the halite core is mainly comprised of salt and clay minerals, highly transparent, and the "hardest" among all the samples. It is hard to define the grain size of the core since the salt crystal seems to be in a whole piece. Besides, we notice distinct fluctuations with composite rock salt in creep tests, which is missed in the fine grain pure rock salt. The halite core is less sensitive to temperature compared with the outcrop. In addition, a finer grain size means a faster creep rate. DIC (Digital Image Correlation) analysis shows that a prominent strain area near the composite interface due to the deformability difference. In addition, it validated the creep fluctuation phenomenon since we could observe it intuitively. The substance of creep doesn't attribute to crystal deformation but fine grain dislocation.
PubDate: 2022-08-07

• The Brittle–Ductile Transition and the Formation of Compaction Bands in
the Savonnières Limestone: Impact of the Stress and Pore Fluid

Abstract: Carbonate sediments play a prominent role on the global geological stage as they store more than $$60\%$$ of world’s oil and $$40\%$$ of world’s gas reserves. Prediction of the deformation and failure of porous carbonates is, therefore, essential to minimise reservoir compaction, fault reactivation, or wellbore instability. This relies on our understanding of the mechanisms underlying the observed inelastic response to fluid injection or deviatoric stress perturbations. Understanding the impact of deformation/failure on the hydraulic properties of the rock is also essential as injection/production rates will be affected. In this work, we present new experimental results from triaxial deformation experiments carried out to elucidate the behaviour of a porous limestone reservoir analogue (Savonnières limestone). Drained triaxial and isotropic compression tests were conducted at five different confining pressures in dry and water-saturated conditions. Stress–strain data and X-ray tomography images of the rock indicate two distinct types of deformation and failure regimes: at low confinement (10 MPa) brittle failure in the form of dilatant shear banding was dominant; whereas at higher confinement compaction bands orthogonal to the maximum principal stress formed. In addition to the pore pressure effect, the presence of water in the pore space significantly weakened the rock, thereby shrinking the yield envelope compared to the dry conditions, and shifted the brittle–ductile transition to lower effective confining pressures (from 35 MPa to 29 MPa). Finally, permeability measurements during deformation show a reduction of an order of magnitude in the ductile regime due to the formation of the compaction bands. These results highlight the importance of considering the role of the saturating fluid in the brittle–ductile response of porous rocks and elucidate some of the microstructural processes taking place during this transition.
PubDate: 2022-08-07

• Effect of Crack Angle on Mechanical Behaviors and Damage Evolution
Characteristics of Sandstone Under Uniaxial Compression

Abstract: Hydraulic fracturing has been extensively utilized to control strata in coal mines. However, the mechanical characteristics and damage evolution of the fracturing rock mass have not been thoroughly explored. In this study, the effects of fracture dip angle on sandstone mechanical properties, failure modes, energy characteristics, and damage progression were investigated through uniaxial compression and acoustic emission monitoring systems. The results indicate that with the increase in the fracture angle, the compressive strength and elastic modulus of sandstone display an asymmetrical “U”-shaped change trend, and the failure mode of the sample is a mixed tension-shear failure. Throughout the loading process, the acoustic emission ringing counts and energy signals were imperceptible in the early stages, but rapidly increased to the peak value as the sample approached failure. Moreover, the acoustic emission amplitude signal showed the phase characteristic of active-calm-reactive to the peak point. With the increase in fracture inclination, the total strain energy and elastic energy at the peak point of sandstone also show an asymmetric “U”-shaped change trend. The energy storage capacity, dissipation capacity, and energy release intensity of the rock were characterized using a quadratic function relationship with the crack angle, θ, indicating that the difficulty of rock failure driven by energy follows a difficult-easy-difficult trend. In addition, a coupling damage model considering macro cracks and micro defects was established, demonstrating that the theoretical results are in good agreement with the experimental results.
PubDate: 2022-08-07

• A Dual Fractal Approach to Thermal–Hydrological–Mechanical
Interactions of Unconventional Reservoir

Abstract: As one of the most essential clean energy sources, the extraction and utilization methods of Coal Bed Methane (CBM) have been widely investigated and analyzed. A good understanding of the CBM seepage behavior in complex reservoir fracture–matrix structure is fundamental to the exploitation. In this study, we propose a new approach to investigate the interactions between macroscopic behavior and reservoir microstructure by the following parameters: (1) matrix fractal dimension; (2) fracture fractal dimension; (3) maximum fracture length; (4) maximum pore diameter. The results indicate that the fractal seepage model proposed in this study is more effective than the classical cubic seepage model for investigating thermal conduction, seepage and fracture–matrix interactions in coal seam. When the fractal dimension increases by 0.4, the permeability increases by about 10%. In addition, reservoir permeability is inversely proportional to coal seam temperature and directly proportional to fracture–matrix fractal dimension, maximum fracture length and maximum pore diameter. Furthermore, we also investigate the evolution of reservoir permeability with the extraction process, coal seam temperature and gas pressure under various microstructural parameters. It can be concluded that different structural parameters will draw various effects on coal seam gas seepage, which cannot be obtained by the cubic permeability model.
PubDate: 2022-08-06

• Experimental and Numerical Studies on the Anisotropic Mechanical
Characteristics of Rock-Like Material with Bedding Planes and Voids

Abstract: Mechanical and fracture behaviors of rocks are largely dependent on the rock structure and existing flaws. This study mainly focuses on the combined effects of bedding plane and void on the tensile mechanical behaviors of layered rock. Brazilian tensile tests accompanied by acoustic emission (AE) and image collecting testing were first conducted on layered rock-like material with different bedding plane inclination angles. The experimental results showed that Brazilian tensile strength (BTS) and accumulated AE energy decreased with the increasing bedding plane inclination angle. The failure patterns of testing specimen transformed from central failure to layer activation failure. The relationships between BTS values and accumulated AE energy can be fitted by a linear function. Based on the cohesive zone model, the effects of bedding plane strength and spacing were further investigated, and the effects of bedding plane strength and void size on tensile behaviors of numerical specimen containing void were discussed. The numerical results indicated that both bedding plane strength and spacing had strong influences on BTS values and failure patterns of numerical specimen. The existing void has a strong attenuation on tensile behavior of numerical specimen. The tensile mechanical behaviors were strongly influenced by bedding plane strength and void size.
PubDate: 2022-08-06

• Evaluating the Effect of Anisotropy on Hydraulic Stimulation in a Slate
Geothermal Reservoir

Abstract: Most geothermal reservoirs in Taiwan are distributed in metamorphic rock masses, especially slate. The presence of slate foliation causes rock masses to exhibit high anisotropy and heterogeneity. This study conducted an anisotropic coupled hydro-mechanical analysis to evaluate the influence area of hydraulic stimulation in slate for the operation of a geothermal power plant. A failure criterion for slate incorporated with a transversely isotropic poroelastic model were established to describe the behavior of slate, and a fracture aperture model was used to simulate the stress-dependent permeability of open fractures. The developed model was validated using a benchmark problem of geothermal techniques under an isotropic condition. The effects of anisotropy on the mechanical behavior of the fracture and rock matrix were also investigated. These results indicate that the analysis results indicated that anisotropy significantly affects stress and strain distributions. When the anisotropic angle is 135°, a substantial increase in pressure, deviatoric stress, and volumetric strain occur at the center of fracture walls. However, larger damage zones are generated in the case of the anisotropic angle is 0° and 90°. The proposed model was further applied to analyze the injection response in a slate geothermal site. The analysis results revealed that the proposed model can reasonably simulate the anisotropic coupled hydro-mechanical behavior of slate geothermal reservoir.
PubDate: 2022-08-06

• Experimental Study on the Effects of Water Saturation on the Microseismic
and Acoustic Emission Characteristics of Sandstone in Different Stress
States

Abstract: To investigate the evolution characteristics of microseismic (MS) and acoustic emission (AE) of sandstone before and after water saturation in different stress states and the precursory information of rock failure, Brazilian splitting, direct shear, and uniaxial and biaxial compression tests were carried out on natural and saturated specimens of sandstone, and the whole failure process of each specimen was monitored by an MS system combined with an AE system. The results show that: (1) water increased the number and duration of MS waveform signals detected during the post-σpeak stage, increased the overall level of the MS b value, and reduced the accumulative absolute AE energy (EAE,ab) and single abrupt increases in EAE,ab. These changes evince the effects of water on the strength and deformation of the sandstone and reflect the degradation and softening of the sandstone due to saturation. Furthermore, water was found to significantly affect the mechanical properties and acoustic characteristics of the sandstone, and the effect varied with the stress state of the sandstone. (2) A notable abrupt increase in the MS fractal dimension (Dt), a notable abrupt decrease in the MS b value, or the first post-σpeak decrease in the AE Dt to a Dt,min less than 0.1 often suggests imminent rock failure. The overall average b value of MS signals during the failure process of a rock can be used as a criterion for determining whether it is in a saturated state. (3) Due to the difference in the frequency range, acquisition mode and activeness indexes of MS and AE signals, MS is more sensitive to large-scale fracture events and AE is more sensitive to small-scale fracture events. Combining the respective advantages of AE and MS signals and using both of them to monitor the failure process of rocks can facilitate a more comprehensive understanding of their intrinsic failure mechanisms and, therefore, help to provide more accurate predictions of rock failure.
PubDate: 2022-08-05

• Failure and Instability Characteristics of Coal-Rock Parting-Coal
Structures with Rough Discontinuities

PubDate: 2022-08-05

• Development and Numerical Modeling Approached to Individual Rock Test
Chamber Based on In-situ Condition Preserved

Abstract: Better understanding mechanical behavior of in-situ rocks is significant for oil exploration and underground mining. Traditional coring samples fail to keep the fidelity that can represent in-situ conditions such as underground temperature, pore pressure, and stress level, so in-situ condition-preserved coring technology was developed and realized. How to test these novel in-situ condition-preserved coring samples is of great concern due that existing experimental devices cannot be adopted to load them directly. In this manuscript, an innovative pseudo-triaxial apparatus was presented which can apply various loading on these in-situ condition-preserved rock samples and investigate their mechanical behavior. This apparatus called as Separatable Pressure-preserved Testing Capsule (SPTC in short form) can be used by putting it into any existing uniaxial test machine just with some simple connecting. To achieve pressure-preserved loading, balance chambers and an oil bag are introduced as two critical structures. The design concept was demonstrated and discussed. Moreover, shapes, dimensions, and materials of the testing capsule are determined after a serial of numerical simulations using the FEM software COMSOL. Furthermore, numerical simulations of rock samples with and without pore pressure were carried out under hydrostatic pressure and deviatoric stress loading. The results show that the safety strength measured from non-pressure-preserved rock samples is relatively large than that from pressure-preserved rock samples. Such improper estimation might cause mistaken design that probably result in the occurrence of underground engineering disasters. These simulation results also verify that such apparatus used to test pressure-preserved rock samples is necessary to obtain the veritable mechanical parameters of in-situ rocks.
PubDate: 2022-08-04

• Dynamic Mechanical Behaviors of Rock's Joints Quantified by Repeated

Abstract: Joints widely exist in engineering rock masses and significantly affect their dynamic response to different loadings. Here, utilizing the state-of-the-art 3D laser scanning technology, which allows the digitalization of the joint surface’s topography, and the Digital Image Correlation scanning technology that records the time series of the strain and mass point vibration, we build our unique experimental apparatus on the basis of a conventional split Hopkinson pressure bar with which we perform a series of repeated experiments on samples that are intact, with rough and smooth joint surfaces. This series of experiments provide us opportunities to look into the joint's dynamic mechanical behavior and energy evolution through multiple repeated impact loadings. We observe that the transmitted coefficient decreases with a larger joint roughness coefficient and the number of impacts. The stress wave and energy attenuation of rock masses with rough joints are much greater than those with smooth joints. Further, we observe the rough joints are more damaged than the smooth joints. The quantitative analysis carried through this experiment allows us to describe the process of a stress wave propagating through a joint in the rock mass with three consecutive stages: (1) joint closure; (2) joint compaction; and (3) coordinating deformation. The stress wave and energy attenuation of rock masses caused by the joint occur mainly at the stages 1 and 2.
PubDate: 2022-08-02

• Rock Properties and Modelled Stress State Uncertainties: A Study of
Variability and Dependence

Abstract: The safety and sustainability of subsurface applications requires a profound knowledge of the local stress state which is frequently assessed using 3D geomechanical-numerical models. Various factors lead to generally large uncertainties in these models. The variabilities in the rock properties as one of the sources of uncertainties and their influence on the modelled stress state is addressed herein. A generic 3D geomechanical-numerical model is used to investigate the influence of different distributions of variability and their effect on different stress states. The variability in rock properties clearly affects the uncertainties in the stress state in a positive correlation with differences that depend on the affected component of the stress tensor. The basic observation is that largest uncertainties are observed in the normal components of the stress tensor where the variabilities apparently are most effective. The same rock property variabilities affect the shear components uncertainties to a significantly lesser extent. Variabilities in the Young’s modulus and the Poisson’s ratio chiefly affect the uncertainties in $$\sigma _{xx}$$ and $$\sigma _{yy}$$ . The density variability, however, leads to highest uncertainties in $$\sigma _{zz}$$ . In general, variabilities in the Young’s modulus are most effective, followed by the Density and then the Poisson’s ratio. Furthermore, an influence of the tectonic stress regime on how the variability in the rock properties affects the stress state is observed. At the same time only a small effect is observed for different stress magnitudes. The eventual uncertainties in a modelled stress state depend not only on the uncertainties in the rock properties but also whether the uncertainties are found mainly in the Young’s modulus, the Poisson’s ratio or the Density. These findings indicate the importance to regard variabilities in rock properties as a source for significant uncertainties in geomechanical-numerical models. It is proposed to use the derived relations for an inexpensive quantification of uncertainties by means of a post-computation assignment of uncertainties to a stress model.
PubDate: 2022-08-01

• Evaluating the Response of a Tunnel Subjected to Strike-Slip Fault Rupture
in Conjunction with Model Test and Hybrid Discrete–Continuous Numerical
Modeling

Abstract: The current paper evaluates the response of a tunnel subjected to strike-slip fault rupture with experimental and numerical approaches. Some state-of-art techniques were adopted in the analysis. A new formula containing sodium silicate was used for the similar material. Endoscope technique was used in the model test to log the crack propagating inside the tunnel. And hybrid discrete–continuous modeling was introduced to perform a sophisticated numerical investigation. Two small-scale model tests were carried out, in which the interaction of the tunnel with the fault rupture, the deformation pattern, and the strain evolution and crack propagation in the tunnel liner were observed. The model tests indicate that the failure of the tunnel mainly resulted by the faulting-induced circular cracks concentrated in the vicinity of the shear zone and longitudinal cracks at the passive side portion. Then, the hybrid DEM-FDM model was constructed and calibrated based on the experimental data, with which the response and mechanism of the tunnel subjected to strike-slip fault rupture were numerically investigated to identify the influences of some important factors. The longitudinal and transverse deformation profiles of the tunnel were found to be dominated by the rock mass condition and the buried depth of the tunnel. And the tunnel’s design factors have significant effects on the stress and failure mode of the liner. For a soft or thin tunnel liner, the failure zones were more concentrated. The tunnel would fail in a ‘shear’ mode. In contrast, for a hard or thick liner, the magnitude of the tensile strain is less, yet the tension failure area is larger. The tunnel would fail in a ‘squeeze’ mode. Based on the obtained results, suggestions on the design of tunnel liner against the strike-slip fault rupture were proposed.
PubDate: 2022-08-01

• Coupled Thermo-Hydro-Mechanical Modeling on the Rongcheng Geothermal
Field, China

Abstract: Numerical reservoir modeling plays an important role in understanding and predicting the performance of geothermal reservoirs to varying exploitation schemes. In this study, four parameters including thermal breakthrough time, water level and vertical displacement at the production wells and the recoverable energy in the licensed region are selected to assess the potential exploitation schemes. An integrated model combining the simplified 1D geothermal well model and the 3D geothermal reservoir model is developed to simulate the fully coupled thermo-hydro-mechanical (THM) processes in geothermal reservoirs including multiple wells, and the measured surface settlement data in the Geysers geothermal field is used to validate the reasonability and efficiency of the developed modeling method. A case study of the Rongcheng geothermal field, China, is presented to clarify the important role of coupled THM processes in the sustainable exploitation of geothermal resources. The results show that the developed integrated model is a robust simulation tool to understand and predict the performance of city-scale geothermal fields under different patterns of well groups. The production wells may not reach the designed lifetime due to various natural or artificial reasons, so the optimal well patterns should be designed to maximize the recoverable geothermal energy considering the natural properties of geothermal reservoirs.
PubDate: 2022-08-01

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