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Microwave energy is a promising application in future rock breakage operations in the civil, mining, processing, and space industries. Rock engineering projects frequently experience mechanical vibration and blasting impacts. Thus, understanding the dynamic fracturing behavior of microwave-treated rock is essential for its future application in microwave-assisted mechanical rock breakage. A customized industrial microwave system with a multimode resonant cavity was used to heat red sandstone at different microwave power levels (up to 4 kW) for a constant exposure time (4 min). The rock surface temperature distribution after microwave treatment was measured by an infrared camera. Dynamic splitting tests were conducted using a split Hopkinson pressure bar (SHPB) system in combination with a high-speed camera. Experimental results indicate that the rock dynamic splitting strength is negatively related to the microwave power, and the maximum reduction is 47.8%. Microwave treatment induced an obvious nonuniform temperature distribution and C-shaped surface cracks on disc specimens. During the dynamic splitting test, the crack induced by dynamic loading always initiates from the crack tip induced by microwave irradiation and then propagates along the loading diameter. The distribution of the inner high-temperature zone in the disc specimen is symmetric along the horizontal centerline of the disc specimen. Key words: microwave treatment, dynamic splitting behavior, infrared temperature, rock fracturing, dynamic nominal tensile strength. Le recours a l'energie micro-ondes represente un potentiel prometteur dans les futures operations de bris de roche dans les industries civiles, minieres, de transformation et spatiales. La vibration mecanique et les impacts des explosions sont frequents dans les projets d'ingenierie des roches. Il est donc essentiel de comprendre le comportement dynamique de fracturation de la roche traitee par micro-ondes pour son application future dans les operations de rupture mecanique de la roche assistee par micro-ondes. On a utilise un systeme micro-ondes industriel personnalise equipe d'une cavite resonnante multimode afin de chauffer du gres rouge a differents niveaux de puissance micro-ondes (jusqu'a 4 kW) durant un temps d'exposition constant (4 min). La distribution de la temperature de la surface de la roche apres le traitement par micro-ondes a ete mesuree par une camera infrarouge. Des essais de fendage dynamique ont ete realises a l'aide d'un systeme de barre de pression Hopkinson fendue (SHPB) associe a une camera a grande vitesse. Selon les resultats experimentaux, la limite de fendage dynamique de la roche est negativement liee a la puissance des micro-ondes, et la reduction maximale est de 47,8 %. Le processus de traitement par micro-ondes a provoque une distribution non uniforme de la temperature et des fissures superficielles en forme de C sur les specimens de disques. Pendant l'essai de fendage dynamique, la fissure induite par le chargement dynamique commence toujours a partir de la pointe de la fissure induite par l'irradiation par micro-ondes, puis se propage le long du diametre de chargement. La distribution de la zone interne a haute temperature du specimen de disque est symetrique le long de la ligne centrale horizontale du specimen de disque. [Traduit par la Redaction] Mots-cles: traitement par micro-ondes, comportement dynamique de fendage, temperature infrarouge, fracturation de la roche, resistance nominale dynamique a la traction., 1. Introduction Safe and efficient continuous rock breakage significantly affects the progress of rock engineering projects. As the most commonly used rock breakage technique, drilling and blasting have been widely [...]

Using metallurgical solid waste Titanium-extracted Residual Slag (TRS) as mine-filling cementitious material is crucial to reduce the filling cost and promote the utilization of solid waste resources. In this paper, taking the strength of the backfill at different curing ages as the response target, the Design-expert mixing design was used to optimize the proportioning experiment of titanium-extracted residual slag, titanium gypsum, silicate cement, and total tailings, to analyze the interactions and influences of the materials on the strength of the backfill, and to analyze the hydration mechanism of the titanium-extracted residual slag-based filling cementitious materials under the optimal proportioning. The results show that: (1) the order of the sensitivity of each component to the strength of backfill is: composite activator > cement > titanium gypsum > titanium-extracted residual slag, and there are different degrees of interaction between them; (2) the optimal ratio of titanium-extracted residual slag-based filling cementitious materials is TRS:titanium gypsum:cement:composite activator = 55:25:17:3; (3) early strength formation of backfill is mainly related to its hydration products ettringite and C-S-H, the rapid nucleation and cross-growth of ettringite in the early stage forms an effective physical filling effect, which is the main reason for the formation of high early strength, and the later strength of backfill benefited from the continuous accumulation of C-S-H encapsulation and bonding, which further densified its internal structure; (4) the use of titanium-extracted residual slag-based filling cementitious materials contributes to safe, green, and economic mining. [ABSTRACT FROM AUTHOR]

The study of the constitutive model under stress loading for rock after undergoing freeze-thaw weathering cycles (FTWCs) treatment has important theoretical significance for the site operation and numerical calculation of rock mass engineering in cold regions. In this work, a series of FTWCs treatment tests of sandstone were carried out, and the evolution characteristics of the T 2 spectrum distribution curve for sandstone before and after FTWCs treatment were analyzed utilizing nuclear magnetic resonance (NMR) technology. The schematic diagram of freeze-thaw damage evolution for sandstone was drawn, and the damage evolution mechanism was analyzed. Evolution laws of the stress-strain curves, peak and residual strength, peak and residual strain, and Young's modulus of sandstone under different FTWCs and confining pressures were analyzed by conventional triaxial compression tests. A piecewise constitutive model under triaxial stress loading for sandstone after undergoing FTWCs treatment was established, and the model considered the significant influence of FTWCs on the nonlinear deformation in the compaction stage and residual strength. By introducing error analysis indexes, the proposed model and published models were compared with the experimental data, it was found that the proposed model's performance is better than the published models, which indicated that the proposed model has good performance and strong universality. [ABSTRACT FROM AUTHOR]

To study the dynamic response of granite to different levels of microwave power, an intelligent microwave rock-breaking instrument is used to irradiate different power from three directions. The servo universal testing machine is used to carry out a uniaxial compression test on the granite after microwave damage to analyze the strength damage characteristics and the degree of pore damage. Pore fractal characteristics are analyzed based on nuclear magnetic resonance to establish the microwave damage degradation model. In parallel, the energy evolution process of granite under the influence of various power levels is analyzed using the theory of energy dissipation. Simultaneously, based on the energy dissipation theory, we analyze the energy evolution process of granite under the action of different powers. The results show that with higher microwave power, the peak strength and modulus of elasticity show a linear decreasing law. The degree of fragmentation is more obvious, showing the damage characteristics with two big ends and little in the middle. The higher the power, the greater the porosity and the more sensitive the micropore becomes to microwaves. Additionally, the damage degradation model established to evaluate the microwave damage of the rock showed that it was feasible. The higher the power, the lower the total energy, elastic energy, and dissipation energy, and the granite is gradually transformed from elastic deformation to plastic deformation. The elastic energy ratio decreases, the dissipation energy ratio increases, and the degree of damage becomes more and more serious. This study provides theoretical support for exploring the mechanical behavior and mechanism of microwave-assisted rock breaking and is of great practical significance. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of rock are greatly influenced by hydrochemical corrosion. The chemical corrosion impact and deformation properties of the meso-pore structure of rock under the action of different hydrochemical solutions for the stability evaluation of rock mass engineering are of high theoretical relevance and applied value. Based on actual data, a support vector machine (SVM) rock constitutive model based on artificial bee colony algorithm (ABC) optimization is constructed in this article. The impact of porosity (chemical deterioration), confining pressure, and other aspects is thoroughly examined. It is used to mimic the triaxial mechanical behavior of rock under various hydration conditions, with high nonlinear prediction ability. Simultaneously, the statistical damage constitutive model and the ABC-SVM constitutive model are used to forecast the sample's stress–strain curve and compare it to the experimental data. The two models' correlation coefficients (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE) are computed and examined. The correlation coefficient between the ABC-SVM constitutive model calculation results and the experimental results is found to be larger (R2 = 0.998), and the error is smaller (RMSE = 0.7730, MAPE = 1.51), indicating that it has better prediction performance on the conventional triaxial constitutive relationship of rock. It is a highly promising new way of describing the rock's constitutive connection. [ABSTRACT FROM AUTHOR]

There are some problems in the application of slurry preparation technology, such as wide fluctuation range of underflow concentration, long settling time and low efficiency of solid–liquid separation. This is an important basis for researching the thick settling law of tailings slurry under the action of mechanical vibration and its influencing factors to solve these problems. To this end, a small vibration thickening testing machine and vibrating rod were designed and developed. Physical simulation experiments were conducted to analyze the settling characteristics of tailings slurry under different vibration duration, start time, vibration frequency, and vibration inertia single factors. The results show that: (1) Mechanical vibration can effectively accelerate the settling speed of tailings particles, but the relationship between them is a non-positive correlation, and mechanical vibration time control with in 5 mins is the best. With the delay of starting the vibration time, the final mass concentration first increases and then decreases. (2) As the vibration frequency increases, the final mass concentration of tailings settlement first increases and then decreases. When the eccentric vibrator speed is 6000 r/min, the best slurry settlement effect is achieved. (3) When the vibration inertia of the eccentric oscillator is 0.158 g·cm2 and the final mass concentration reaches 70.1%, the settling time only takes 210 min. (4) The lower the slurry concentration, the faster the settling speed. As the initial concentration increases, the final thickening time is also gradually prolonged. The research results provide some insights for the rapid thickening technology of rake-free paste thickeners. [ABSTRACT FROM AUTHOR]

A large amount of traffic safety information has been generated. This will further promote the sustainable development of transport. However, its content, form, and structure are complex and scattered, lacking effective information integration and a comprehensive framework. Combined with the concept of safety analysis, a traffic safety management knowledge graph was designed for structured data, which include 54 types of node entities and 14 types of relationship entities. Six types of information were collected and imported, including illegal acts, vehicle failure, emergency response, legal norms, organization information, and road-related information. Ultimately, a knowledge query function was realized using Cypher, and an automatic Q&A function was created based on rule matching. A traffic accident knowledge graph was constructed for unstructured data, with people and institutions involved, vehicles involved, and accidents as the core, including 21 types of node entities and 22 types of relationship entities. Comparing the node entity extraction performance of Bert, Bert-CRF, Bert-BiLSTM, and Bert-BiLSTM-CRF models, Bert BiLSTM-CRF performs the best. The Bert model was used for relationship entity extraction. The traffic accident knowledge graph can structurally display accident information and support a query function to facilitate safety analysis. [ABSTRACT FROM AUTHOR]

It has been demonstrated that microwave pretreatment can weaken rocks, reduce tool wear, and improve mechanical rock breaking efficiency. The dielectric properties of rock minerals are a major factor affecting the ability of rocks to absorb microwaves, so it is important to conduct experimental research on rock modification to improve the microwave absorption capacity of rocks. The concept of "microwave-assisted absorbing reagents" has been proposed to increase the microwave absorption capacity of rocks. Sandstone specimens are first pretreated with strong dielectric substances before being exposed to microwave radiation to increase their microwave absorption capacity, then they are exposed to microwave fields and finally conducted to uniaxial compression tests. Enhancement in microwave absorption capacity of sandstone specimens is showed by P-wave velocity, nuclear magnetic resonance, and mechanical tests before and after microwave treatment. The results showed that barium titanate suspension and water are both effective microwave-assisted absorbing agents. The specimens treated with barium titanate suspension exhibited better microwave absorption capacity; in 5 kW microwave power irradiation, its p-wave velocity falls by 14.04%, porosity rises by 25.43%, and uniaxial compressive strength falls by 24.98%. Additionally, the failure form of sandstone specimens changes from brittle to plastic once it has fully absorbed microwave energy. [ABSTRACT FROM AUTHOR]

The F317 fault, as a major tectonic zone in the Jianshan mine area, influences the geotectonic features and geomechanical properties of the mine area. Mining operations need to be conducted within these tectonic systems, so it is important to fully study and understand the characteristics and evolution of these tectonic systems to develop reasonable mining plans and safety measures. Aiming at the problem that the existence of the F317 fault affects the stability of the west road during the mining of the security pillar at The Jianshan underground mine in Panzhihua Iron Mine, the mechanical model of the fault surface was established through the theory of material mechanics. The mechanical criterion of fault slip during the security pillar retrieval process was obtained and combined with the contact surface theory in the numerical analysis software FLAC3D. Two numerical calculation models with and without the F317 fault were established to analyze the change characteristics of the maximum tensile stress and displacement of the road protection zone under different simulation scenarios. The influence of the fault's presence on the surface road's stability during the security pillar retrieval process was obtained. The study results show that changes in positive and shear stresses at the fault face caused by the security pillar retrieval process are the main factors influencing the fault slip. The upper side of the fault tends to slip along the fault face during the security pillar retrieval process, which theoretically prevents the transfer of subsidence displacement caused by underground mining to the roadside (foot side of the fault). The presence of the F317 fault has less effect on the tensile stresses at the road protection zone. Still, the fault allows the tensile stresses to be concentrated at the top and bottom of the quarry and at the isolated pillar, which is more likely to cause the rock to be stretched and squeezed. Without the F317 fault, the maximum subsidence displacement at the road protection zone is 30.59 mm, the maximum X-directional displacement is 42.17 mm (both of which are greater than the safe displacement limit by 20 mm), and the maximum Y-directional displacement is 19.75 mm, which is less than the safe displacement limit by 20 mm. Compared with the case without the F317 fault, the displacement at the road protection zone with the F317 fault is smaller, with a maximum subsidence displacement of 16.92 mm, a maximum X-directional displacement of 19.63 mm, and a maximum Y-directional displacement of 3.35 mm, all of which are less than the safe displacement limits. Therefore, the presence of the F317 fault provides some protection to the west side of the road from collapse due to underground mining. [ABSTRACT FROM AUTHOR]

In the drifts of underground metal mines, the extraction of rock mass discontinuity characteristics from point cloud models generated with laser scanning has become the main approach. However, the exposure of discontinuities is restricted in drifts, and the size of discontinuities cannot be measured directly. Therefore, it is necessary to use a reasonable sampling tool to estimate the mean trace length of the discontinuities that are mapped in the point cloud model. In this paper, a method to estimate the mean trace length of discontinuities using a three-dimensional (3D) model of a drift (3DM) is proposed. Through the point cloud data of a drift obtained using 3D laser scanning, the information on discontinuities in the surrounding rock was extracted; then, the mean trace length was estimated using 3DEC to set sampling windows on the roof and sidewall in the 3DM. By analyzing the difference between the circular sampling window and the rectangular sampling window using simulated cases, the estimation results showed that the mean trace length obtained using circular measuring windows in the 3DM was closer to the true trace length. Finally, the method was used in a practical engineering case in Jianshan Iron Mine, Panzhihua, Sichuan, China. [ABSTRACT FROM AUTHOR]

Predicting the strength evolution of fiber-reinforced cement mortar under freeze-thaw cycles plays an important role in engineering stability evaluation. In this study, the microscopic pore distribution characteristics of fiber-reinforced cement mortar were obtained by using nuclear magnetic resonance (NMR) technology. The change trend of T2 spectrum curve and porosity cumulative distribution curve showed that the freeze-thaw resistance of cement mortar increased first and then decreased with the fiber content. The optimal fiber content was approximately 0.5%. By conducting mechanical experiments, it is found that the uniaxial compressive strength (UCS) of the samples exhibited the 'upward convex' evolution trends with freeze-thaw cycles due to cement hydration, and based on fractal theory, the negative correlation between UCS and Dmin was established. Eventually, a freeze-thaw strength prediction model considering both porosity and pore distribution was proposed, which could accurately predict the strength deterioration law of cement-based materials under freeze-thaw conditions. [ABSTRACT FROM AUTHOR]

Freeze-and-thaw (F&T) weathering cycles induced by day–night and seasonal temperature changes cause a large number of rock mass engineering disasters in cold areas. Investigating the impact of F&T weathering process on the strength and deformation characteristics of frozen–thawed rocks is therefore of critical scientific importance for evaluating the stability and optimizing the design of rock mass engineering in these areas. In this research, the evolution characteristics of F&T damage were analyzed based on T2 spectrum distribution curves of sandstone specimens before and after F&T weathering cycles. The coupling impact of the quantity of F&T weathering cycles and confining pressure on pre-peak and post-peak deformation behaviors of sandstone specimens were analyzed in detail. By introducing the confining pressure increase factor (CPIF), the impact of confining pressure on the triaxial compressive strength (TCS) of sandstone specimens after undergoing different quantities of F&T weathering cycles was further investigated. A novel strength evolution model was proposed that could effectively describe the coupling impact of the quantity of F&T weathering cycles and confining pressure on TCS of rocks after undergoing the F&T weathering process. The proposed strength evolution model was cross-verified with experimental data from the published literature and all correlation coefficients were above 0.95, which proved that the strength evolution model proposed in this paper was reasonable; in addition, this model has strong applicability. [ABSTRACT FROM AUTHOR]

Infrared radiation thermal imaging technology is proposed for rock mechanics tests. Through the infrared radiation temperature and stress–strain curves of sandstone with different porosity during the process of uniaxial compression loading obtained by an infrared camera and uniaxial compression testing machine, the characteristics of infrared radiation on sandstone are systematically analyzed during uniaxial compression loading. The results show that: (1) The strength of sandstone decreases with the increase of porosity, the infrared thermography of sandstone has obvious characteristics of stage evolution and is closely related to the deformation and failure stage of rock in the process of uniaxial compression; (2) During the rock failure process, infrared thermography is differentiated, and the high-temperature radiation zone can reflect the location, size and shape of rock fractures; (3) During the uniaxial compression loading process, the evolution law of the average infrared radiation temperature (AIRT) is closely related to the porosity and uniaxial compressive of the rock, and it is possible to invert all processes of rock failure. The research results demonstrate that the technique of infrared thermal imaging can be applied to rock mechanics tests, and the evolution law of the infrared radiation characteristics can provide a reference for stability analysis of the underground rock engineering. [ABSTRACT FROM AUTHOR]

Multiple compression tests on rock-like samples of pre-existing cracks with different geometries were conducted to investigate the strength properties and crack propagation behavior considering multi-crack interactions. The progressive failure process of the specimens was segmented into four categories and seven coalescence modes were identified due to different crack propagation mechanisms. Ultimately, a mechanical model of the multi-crack rock mass was proposed to investigate the gradual fracture and damage evolution traits of the multi-crack rock on the basis of exploring the law of the compression-shear wing crack initiation and propagation. A comparison between theory and experimental results indicated that the peak strength of the specimens with multiple fractures decreased initially and subsequently increased with the increase in the fissure inclination angles; the peak strength of specimens decreased with the increase in the density of fissure distribution. [ABSTRACT FROM AUTHOR]

With an increase in mining depth, the problem of heat damage in metal mine working face has become increasingly prominent. In order to effectively reduce the temperature of the working face and provide a comfortable working environment for the miners, based on the concept of "cooling on demand", a mobile refrigeration system for high-temperature working face was designed, and a field test was carried out in Dahongshan Copper Mine, Yunnan Province. At the same time, based on the experimental conditions, the parameter optimization research of the mobile refrigeration system was carried out. The results showed that: (1) The mobile refrigeration system could reduce the wet bulb temperature of the working face at the test site to below 30 °C, which is in line with the "Safety Regulations for Metal and Non-Metallic Mines" (GB16423-2020); (2) when the diameter of the air supply pipe was 600 mm and the air supply velocity was 12 m/s, the target cooling area could meet the continuous operation requirements stipulated in the "Safety Regulations for Metal and Non-metallic Mines" in China; (3) for every 2 °C decrease in supply air temperature, the average wet bulb temperature in the target cooling area decreased by 0.9 °C; (4) for every 10% decrease in supply air humidity, the wet bulb temperature and relative humidity in the target cooling area decreased by 0.76 °C and 4.38% on average, respectively. The research results provide new ideas and methods for the prevention and control of heat damage in metal mines. [ABSTRACT FROM AUTHOR]

Mineral resources are increasingly being developed in cold and permafrost regions. However, the mechanical and physical properties of cemented tailings backfill (CTB) cured at normal temperature are no longer applicable. To clarify the reasons for this variability, a series of tests were performed. The mechanical properties of CTB with different cement–tailings ratios (CTR, 1:4, 1:8, 1:12, 1:16, and 1:20) were tested at different curing ages (3, 7 and 28 days) and curing temperatures (20 °C, 5 °C, −5 °C, and −20 °C). The differences of CTB in mechanical and physical properties under positive- and negative-temperature curing conditions were analyzed, and the microscopic failure process of CTB under negative-temperature curing conditions was discussed. The results revealed that the mechanical properties and deformation behavior of CTB under positive- and negative-temperature curing conditions were different. The frozen CTB had higher early strength than the standard-temperature curing condition (20 °C), and the lower the temperature, the higher the early strength. The low-temperature curing condition, on the other hand, was not beneficial to CTB's long-term strength. The low-temperature curing condition was not conducive to the long-term strength of CTB. After yielding, strain hardening and strain softening appeared in the deformation behavior of frozen backfill, indicating ductility. In contrast to the typical-temperature curing condition, the frozen CTB showed a new failure pattern that has little relation to curing time or CTR. Furthermore, the failure process of frozen backfill was reviewed and studied, which was separated into four stages, and altered as the curing time increased. The results of this study can act as a guide for filling mines in permafrost and cold climates. [ABSTRACT FROM AUTHOR]

Driven by the commitment of achieving peak carbon dioxide emissions before 2030 and carbon neutrality before 2060, China is promoting the optimization of its energy and industry structures. In the electricity supply industry, a large number of different types of sophisticated large and giant hydropower stations are planned or being constructed in western China. In future decades, hydropower may take the dominant position in China's electricity supply. Rock fracturing behavior plays a vital role in geotechnical hazard prevention and geotechnical engineering design. With the construction of hydropower stations, rock mechanics investigation will be of great concern. This study presents a hybrid model that coupled the finite element method and peridynamic theory to simulate the indirect tensile strength of marble. Sensitivity analyses of the loading rate, mesh size, and fracture energy release rate are performed. The numerical results indicate that both the loading rate and mesh size significantly affect the numerical representation of rock properties. After the calibration of the fracture energy release rate, Brazilian tensile strength modeling is successfully conducted, and the numerical results are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

To analyse the different mechanism of polycarboxylate superplasticizer and polyester fibre and its effect on cement mortar during freeze-thaw cycles, by taking cement mortar as main research object and the proportion of additive as variables, the varying pattern of the mechanical properties, size and distribution of the pores of the cement mortar during freeze-thaw cycles were studied by the NMR technology for the first time. The influence of different proportion of additive on the changes of the surface scaling, mass, compressive strength, splitting tensile strength and elastic modulus of cement mortar after 0, 25, 50, 75 and 100 times freeze-thaw cycles was studied. Meanwhile, the T2 spectra change law of the cement mortar under different freeze-thaw environment was analysed and the change rule between freeze-thaw cycle, additive proportion and the pore size within the cement mortar was obtained. Also, the relationship between the mechanical parameters and pore properties was studied. This study on the damage evolution mechanism of additive cement mortar during freeze-thaw process is of great theoretical and practical significance to the analysis and prevention of freeze-thaw disasters in cold area. [ABSTRACT FROM AUTHOR]

Rock compressive strength is an important mechanical parameter for the design, excavation, and stability analysis of rock mass engineering in cold regions. Accurate and rapid prediction of rock compressive strength has great engineering value in guiding the efficient construction of rock mass engineering in a cold regions. In this study, the prediction of triaxial compressive strength (TCS) for sandstone subjected to freeze-thaw cycles was proposed using a genetic algorithm (GA) and an artificial neural network (ANN). For this purpose, a database including four model inputs, namely, the longitudinal wave velocity, porosity, confining pressure, and number of freeze-thaw cycles, and one output, the TCS of the rock, was established. The structure, initial connection weights, and biases of the ANN were optimized progressively based on GA. After obtaining the optimal GA-ANN model, the performance of the GA-ANN model was compared with that of a simple ANN model. The results revealed that the proposed hybrid GA-ANN model had a higher accuracy in predicting the testing datasets than the simple ANN model: the root mean square error (RMSE), mean absolute error (MAE), and R squared ( R 2 ) were equal to 1.083, 0.893, and 0.993, respectively, for the hybrid GA-ANN model, while the corresponding values were 2.676, 2.153, and 0.952 for the simple ANN model. [ABSTRACT FROM AUTHOR]

In the operations of underground rock engineering, such as mining, the formation of goafs is often accompanied by unloading and energy effects. In this study, a cyclic loading and unloading stress test is carried out to analyze the strength characteristics of the loaded samples under different loading and unloading ranges as well as different numbers of cycles. The rock force is accompanied by substantial energy changes. To better fit the energy analysis under cyclic loading and unloading conditions, thermal infrared radiation characteristic analysis is performed during rock loading and unloading. An infrared radiation camera is adopted to detect the infrared characteristics of the rock force process after cyclic loading and unloading. Multiangle detection is implemented on the temperature, temperature field, and frequency histogram. The analysis shows that cyclic loading and unloading first strengthen and then weaken the rock. Moreover, the failure caused by the local stress concentration leads to a sharp increase in the temperature. There are significant temperature fluctuations before and after failure, and the temperature field after failure can be divided into three zones, namely, the normal temperature zone, heating zone, and mutational temperature zone, to comprehensively reflect that rock compression failure which is accompanied by the process of energy accumulation and release. On the basis of infrared energy analysis, the index of the energy release rate is introduced, and the loading and unloading analysis model is constructed. The research results reveal that rock failure is accompanied by the process of energy accumulation and release, which provides evidence for the analysis of the spatial stability of the rock mass under cyclic loading and unloading conditions and engineering excavation. [ABSTRACT FROM AUTHOR]

To study the evolutionary characteristics of mesostructural damage to saturated limestone under different loading and unloading paths, three types of loading and unloading tests involving three different loading rates and initial peak stresses were performed. Nuclear magnetic resonance technology and scanning electron microscopy were used to investigate the evolutionary characteristics of pore water during the loading and unloading of the limestone. The results indicated that, with an increase in the initial peak stress, the rock viscoplasticity gradually decreased, and the variation of pore radius and the reduction of bound water decreased. With an increasing loading rate, the mesostructure evolution law under disturbance-increasing amplitude (DIA) cycling was opposite to those under increasing amplitude (IA) and repeated-increasing amplitude (RIA) cycling. With the increasing loading stress level, the porosity decreased and then increased. Under increasing amplitude cycling, a larger initial porosity resulted in higher pore compaction and expansion limits. Reducing the initial peak stress inhibited the pore expansion, whereas it had the opposite effect under RIA and DIA cycling. During loading and unloading, bound water exists in pores of organic matter and mesopores, and free water exists in macropores of intergranular and transgranular fractures. These changes indicate certain laws under different loading and unloading paths. The results of this study indicate that the mesostructure characteristics of rock depend on the loading and unloading paths. [ABSTRACT FROM AUTHOR]

The evolution of the rock pore structure is an important factor influencing rock mechanical properties in cold regions. To study the mesoscopic evolution law of the rock pore structure under freeze-thaw weathering cycles, a freeze-thaw weathering cycle experiment was performed on red sandstone from the cold region of western China with temperatures ranging from -20°C to +20°C. The porosity, T2 spectral distribution, and magnetic resonance imaging (MRI) characteristics of the red sandstone after 0, 20, 40, 60, 80, 100, and 120 freeze-thaw weathering cycles were measured by the nondestructive detection technique nuclear magnetic resonance (NMR). The results show that the porosity of sandstone decreases first and then increases with the increase of the freeze-thaw weathering cycles and reaches the minimum at 60 of freeze-thaw weathering cycles. The evolution characteristics of porosity can be divided into three stages, namely, the abrupt decrease in porosity, the slow decrease in porosity, and the steady increase in porosity. The evolution characteristics of the T2 spectrum distribution, movable fluid porosity (MFP), and MRI images in response to the freeze-thaw weathering process are positively correlated with the porosity. Analysis of the experimental data reveals that the decrease in the porosity of the red sandstone is mainly governed by mesopores, which is related to the water swelling phenomenon of montmorillonite. Hence, the pore connectivity decreases. As the number of freeze-thaw cycles increases, the effect of the hydrophysical reaction on the porosity gradually disappears, and the frost heaving effect caused by the water-ice phase transition gradually dominates the pore evolution law of red sandstone. [ABSTRACT FROM AUTHOR]

Featured Application: A new safety supervision system architecture, by introducing the permissioned blockchain technology proposed in this paper, will be applied in special equipment safety supervision of China, which will solve many safety supervision loopholes in this field. In addition, we will also try to apply the design ideas of the system to other fields that also require safety supervision; the mining industry is the most likely target. With the use of the traditional safety supervision system of special equipment, the job burnout of supervision participants and other supervision problems emerge endlessly, which leads to the supervision for the prevention of safety accidents being greatly weakened. In recent years, the significance of introducing new technology to improve the original supervision system for safety accident prevention has been constantly growing. In this paper, based on the current situation of China's special equipment safety supervision, we summarize several specific requirements for improving the supervision system, namely efficient accident responsibility tracing, more transparent, more efficient data sharing, and integrating more functions. On this basis, we have designed a new system architecture, by introducing the permissioned blockchain technology, which can meet all the improvement requirements and adapt to the technical features of safety supervision work. The extensibility design of the system architecture can meet the new requirements in future work. The design idea of the system architecture can not only be used in the field of special equipment, but can also be used for reference by other fields with safety supervision requirements. [ABSTRACT FROM AUTHOR]