Methodology for identifying the damage state of sandstone using Mel-frequency cepstral coefficient of acoustic emission

Rock mass structure rupture is an important factor that seriously restricts the construction and safe operation of underground space engineering projects such as mines, subways and tunnels. Realizing the identification of rock mass fracture state is one of the hotspots and emphases of current research. In this study, some experiments of sandstone loading failure under different conditions were carried out, the acoustic emission Mel-frequency cepstral coefficient (MFCC) and its fluctuation difference during the whole loading process were extracted, the variation law of the coefficient and its fluctuation difference during the whole loading failure process was studied, and the correlation characteristics of coefficient No.1 (According to the calculation of acoustic emission Mel-frequency cepstral coefficients, it can be seen that a set of acoustic emission Mel-frequency cepstral coefficient includes 12, and coefficient No.1 refers to the first Mel-frequency cepstral coefficient) and its fluctuation difference with the fracture state of sandstone were analyzed. Based on this, a method to identify sandstone fracture state using the Mel-frequency cepstral of acoustic emission was proposed, and the identification criteria was constructed. The identification effect was finally verified. The results show that with loading increase, the coefficient No.1 increases as a whole, and the coefficient value and its discreteness increase significantly in the failure stage and show significant regular fluctuations. The fluctuation difference of the coefficient has the characteristics of periodic variation. The size of the fluctuation difference and its fluctuation can characterize the fracture of sandstone. The overall increase and sudden increase of the fluctuation difference can reflect the macroscopic fracture of sandstone in the unstable deformation and post-peak failure stage, and the sudden increase level of the fluctuation difference can reflect the fracture degree of sandstone. The acoustic emission Mel-frequency cepstral coefficient and its fluctuation difference show good response characteristics to sandstone fracture, which is less affected by different loading conditions, thus they have applicability in reflecting sandstone fracture. The coefficient No.1 and its fluctuation difference have a good correlation with the fracture state of sandstone. The correlation can be divided into three stages as: in the micro-fracture stage of sandstone, the coefficient No.1 and its fluctuation difference are intensively distributed; in the unstable deformation stage just prior to the peak load, the distribution range increases sharply, the overall value increases and the high abnormal value appears; in the post-peak failure stage, the distribution range further increases, the overall value is higher, and more high abnormal values appear. The identification method and criteria of sandstone fracture state were constructed by using the 75% site value and outliers of coefficient No.1 and the 75% site value and outliers of the fluctuation difference of coefficient No.1. The effect of the identification criteria was tested by the confusion matrix of the three-classification model. The accuracy and precision of identification are 90.43% and 94.45%, respectively, which indicate the identification effect is good. The results can provide a reference for the identification of the fracture state of other types of coal and rocks, and for the monitoring and early warning of coal rock instability

Strategic positioning of the Russian Far East gold mining industry

© The Authors, published by EDP Sciences, 2020. The objectives of this paper is to investigate internal and external factors influencing the gold mining in Russian Far East. Justification of the methodological and practical recommendations as well as effective strategies which in full measure correspond to the range of economic and technical factors aimed to increase the effectiveness of gold mining industry in Russia are presented. In this paper, we analysed the current state and main development trends, identified strengths and weaknesses of the internal environment, as well as opportunities and threats of the external environment for the gold mining enterprises based on SWOT analysis. Based on the analysis identified directions of production strategies improvements, sound strategic response and strategic management mechanisms to mitigate the challenges of current times. Their implementation will allow companies using the strengths to reduce the negative impact of weaknesses and prevent key threats, that will significantly increase the competitiveness and economic efficiency of the Russian gold mining industry

Features of choosing the schemes for selective mining of ores and justifying their rational parameters while using heap leaching schemes for processing

The article presents data from theoretical and experimental studies related to the search for a solution to an urgent geotechnological problem - selective mining of standard quality ore, substandard and diluted ores, taking into account the peculiarities of their processing by heap leaching. For complex-structural large-scale ore deposits of the stockwork morphological-structural type, multilevel heterogeneity is typical. The morphology and structure of the objects of direct extraction - ore bodies within the production blocks - vary significantly. The expediency of selective mining and separate heap leaching (or heap oxidation and leaching) of gold and copper from conditioned ores of various geological and technological types and grades is justified. In addition, it is advisable to selectively extract and separately process by heap leaching or flux in a controlled manner before it off-balance and diluted ores, as well as mineralized overburden and tailings of high-grade ores

Strategic positioning of the Russian Far East gold mining industry

The objectives of this paper is to investigate internal and external factors influencing the gold mining in Russian Far East. Justification of the methodological and practical recommendations as well as effective strategies which in full measure correspond to the range of economic and technical factors aimed to increase the effectiveness of gold mining industry in Russia are presented. In this paper, we analysed the current state and main development trends, identified strengths and weaknesses of the internal environment, as well as opportunities and threats of the external environment for the gold mining enterprises based on SWOT analysis. Based on the analysis identified directions of production strategies improvements, sound strategic response and strategic management mechanisms to mitigate the challenges of current times. Their implementation will allow companies using the strengths to reduce the negative impact of weaknesses and prevent key threats, that will significantly increase the competitiveness and economic efficiency of the Russian gold mining industry

Lithofacial characteristic and cyclic analysis of the Middle Triassic of the Pronchishchev Range (north of Middle Siberia)

The object of study is clastic Middle Triassic of the central part of the Pronchishchev Range. The territory of researches is located on the border of Ust’-Anabar and Lena-Olenek facies districts and has poor geological knowledge. During field study of outcrops and test pits new data for Triassic of the right bank of the Peschanaya River were obtained. Lithofacial analysis and analysis of cyclical structure of the Anisian and Ladinian were carried out. The stratigraphic subdivision of the strata was made according to the results of a comprehensive bio- and lithostratigraphic analysis. The succession includes the Karangatinskaya and the Tuora-Khainskaya (Anisian), the Ust’-Olenekskaya and Olimpiiskaya (Ladinian) formations. The lithofacial analysis showed that the sedimentation occurred in mainly sea-shallow conditions with constant exposure of normal waves. Upward the succession a part of coastal sediments increase. Stages of fast sea level rising took place. The analysis of cyclical structures showed that the studied deposits represent the series of regressive sedimentological cycles of decameter scale with а transgressive orientation. They form the large regressive sedimentary cycle with a pronounced binomial structure. It has been found that the Anisian part of the studied section has very similar features of a structure with Leno-Olenek type sections. The structure of the Ladinian part is also similar to the sections of the Lena-Olenek type and is characterized by a slightly reduced thickness of the Olympic formation. It is typical for the western part of the Lena-Olenek facies district. Structural features of the selected cycles allow you to use them in lithostratigraphic correlations of geological sections within the considered sedimentation basin. This is especially true for sites with rare and relatively uniform fossil fauna

An Intelligent Rockburst Prediction Model Based on Scorecard Methodology

Rockburst is a serious hazard in underground engineering, and accurate prediction of rockburst risk is challenging. To construct an intelligent prediction model of rockburst risk with interpretability and high accuracy, three binary scorecards predicting different risk levels of rockburst were constructed using ChiMerge, evidence weight theory, and the logistic regression algorithm. An intelligent rockburst prediction model based on scorecard methodology (IRPSC) was obtained by integrating the three scorecards. The effects of hazard sample category weights on the missed alarm rate, false alarm rate, and accuracy of the IRPSC were analyzed. Results show that the accuracy, false alarm rate, and missed alarm rate of the IRPSC for rockburst prediction in riverside hydropower stations are 75%, 12.5%, and 12.5%, respectively. Setting higher hazard sample category weights can reduce the missed alarm rate of IRPSC, but it will lead to a higher false alarm rate. The IRPSC can adaptively adjust the threshold and weight value of the indicator and convert the abstract machine learning model into a tabular form, which overcomes the commonly black box problems of machine learning model, as well as is of great significance to the application of machine learning in rockburst risk prediction

A method to predict rockburst using temporal trend test and its application

Rockbursts have become a significant hazard in underground mining, underscoring the need for a robust early warning model to ensure safety management. This study presents a novel approach for rockburst prediction, integrating the Mann-Kendall trend test (MKT) and multi-indices fusion to enable real-time and quantitative assessment of rockburst hazards. The methodology employed in this study involves the development of a comprehensive precursory index library for rockbursts. The MKT is then applied to analyze the real-time trend of each index, with adherence to rockburst characterization laws serving as the warning criterion. By employing a confusion matrix, the warning effectiveness of each index is assessed, enabling index preference determination. Ultimately, the integrated rockburst hazard index Q is derived through data fusion. The results demonstrate that the proposed model achieves a warning effectiveness of 0.563 for Q, surpassing the performance of any individual index. Moreover, the model's adaptability and scalability are enhanced through periodic updates driven by actual field monitoring data, making it suitable for complex underground working environments. By providing an efficient and accurate basis for decision-making, the proposed model holds great potential for the prevention and control of rockbursts. It offers a valuable tool for enhancing safety measures in underground mining operations

S 235 B explained: an accreting Herbig Be star surrounded by reflection nebulosity

The intent of this study is to determine the nature of the star and associated nebulosity S 235 B, which are located in a region of active star formation still heavily obscured by the parent molecular cloud. Low-resolution (R = 400) long-slit spectra of the star and nebulosity, and medium- (R = 1800) and high-resolution (R = 60000) spectra of the central star are presented along with the results of Fabry-Perot interferometric imaging of the entire region. Based on the long-slit and Fabry-Perot observations, the nebulosity appears to be entirely reflective in nature, with the stellar component S 235 B* providing most of the illuminating flux. The stellar source itself is classified here as a B1V star, with emission-line profiles indicative of an accretion disc. S 235 B* thus belongs to the relatively rare class of early-type Hebrig Be stars. Based on the intensity of the reflected component, it is concluded that the accretion disc must be viewed nearly edge-on. Estimates of the accretion rate of S 235 B* from the width of the Halpha profile at 10 per cent of maximum intensity, a method which has been used lately for T Tauri stars and Brown Dwarfs, appear to be inconsistent with the mass outflow rate and accretion rate implied from previous infrared observations by Felli et al., suggesting this empirical law does not extend to higher masses