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Nonlinear criterion for strength mobilization in brittle failure of rock and its extension to the tunnel scale

International Journal of mining Science and technology 2022年第4期32卷 685-705页

作者： Rodolfo Cabezas Javier Vallejos Faculty of Engineering and technology Universidad San SebastianSantiagoChile Advanced Mining Technology Center Universidad de ChileSantiagoChile Department of mining Engineering Universidad de ChileSantiagoChile

As underground excavations are getting deeper and field stresses increase, the behavior of intact rock blocks plays an increasingly important role in understanding and estimating the overall rock mass strength. To model the brittle behavior of intact rock blocks, the stress–strain curve is usually idealized considering a linear strength mobilization approach(cohesion-weakening-friction-strengthening, CWFS),however, it is well recognized that rock presents a nonlinear behavior in terms of the confining stress.This study extends the strength mobilization in brittle failure of rock using nonlinear criteria. To determine the model parameters, a standard statistical method that uses the complete laboratory stress–strain curves of the intact rock is employed. Several hypotheses of linear and nonlinear models are statistically compared for different types of rock and confining stress levels. Results demonstrate that the best approach to model the brittle failure of rock is to consider a nonlinear strength envelope, such as the Hoek-Brown criterion assuming a residual uniaxial compressive strength different from zero and a mi parameter that increases, both with simultaneous mobilization. This model helps to recreate highconfining conditions and a more realistic transition between peak and post-peak strength. The obtained parameters are discussed and compared with literature values to verify the validity and to develop guidelines for the estimation of parameters, providing an objective mobilization criterion. Finally, the nonlinear model was applied to a finite element code and extended to a tunnel scale in the brittle rock under high-stress conditions. A reasonable fit between the simulations and the in-situ overbreak measurements was found.

关键词： Nonlinear strength Strength mobilization Brittle failure Intact rock Scaling

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Improving the Control Energy in Model Reference Adaptive Controllers Using Fractional Adaptive Laws

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IEEE/CAA Journal of Automatica Sinica 2016年第3期3卷 332-337页

作者： Norelys Aguila-Camacho Manuel A.Duarte-Mermoud Department of Electrical Engineering and the Advanced Mining Technology Center University of Chile IEEE

This paper presents the analysis of the control energy consumed in model reference adaptive control(MRAC)schemes using fractional adaptive laws, through simulation studies. The analysis is focused on the energy spent in the control signal represented by means of the integral of the squared control input(ISI). Also, the behavior of the integral of the squared control error(ISE) is included in the analysis.The orders of the adaptive laws were selected by particle swarm optimization(PSO), using an objective function including the ISI and the ISE, with different weighting factors. The results show that, when ISI index is taken into account in the optimization process to determine the orders of adaptive laws,the resulting values are fractional, indicating that control energy of the scheme might be better managed if fractional adaptive laws are used.

关键词： Control energy fractional adaptive laws modelreference adaptive control

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Liberation characteristics of coal middlings comminuted by jaw crusher and ball mill

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International Journal of mining Science and technology 2013年第5期23卷 669-674页

作者： Xie Weining He Yaqun Zhu Xiangnan Ge Linhan Huang Yajun Wang Haifeng School of Chemical Engineering and technology China University of Mining & Technology advanced Analysis & Computation center China University of Mining & Technology

The associated minerals make coal middlings possess a relatively high ash content.Subsequent liberation through size reduction can cause recovery increase.However,effect of comminution facilities on mineral liberation of middlings was ignored.This paper studied the liberation characteristics of middlings crushed with different kinds of fragmentation forces.Middlings of 3 mm+0.5 mm sampled from a dense medium cyclone were comminuted by a jaw crusher and a ball mill to 0.5 mm with similar size distribution respectively.The generating mechanism of fnes was also analyzed.Full densimetric analyses indicate that mineral liberation of the product crushed by the jaw crusher is better than that by the ball mill at each fraction.For sizes of 0.125 mm+0.074 mm and 0.074 mm,yields of the product with ash content 11%comminuted by jaw crusher are nearly 20%higher than that by the ball mill.Sectional micrographs observed by the scanning electron microscopy(SEM)also show the same law for these two fractions and some intergrowth particles still exist in the fraction of 0.5 mm+0.25 mm.

关键词： Coal middlings Fragmentation force Liberation Float and sink test Sectional micrograph

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Simulation research and application on response characteristics of detecting water-filled goaf by transient electromagnetic method

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International Journal of Coal Science & technology 2022年第2期9卷 167-192页

作者： Tingye Qi Fan Zhang Xiaoming Pei Guorui Feng Huiru Wei College of mining Engineering Taiyuan University of TechnologyTaiyuan 030024China Research center of Green mining Engineering technology in Shanxi Province Taiyuan 030024China

Water inrush disasters poses a great threat to the safe exploitation of coal resources.To solve this problem,the transient electromagnetic method(TEM)was proposed to accurately detect the water accumulation in the goaf.The electromagnetic response characteristics of diferent water-flled goaves were studied by electromagnetic feld theory,numerical simulation and feld verifcation.Through the models of 100%water accumulation,50%water accumulation,0%water accumulation,100%water accumulation with collapsed rock,50%water accumulation with collapsed rock and 0%water accumulation with collapsed rock goaf,the characteristics of induced voltage attenuation curves were studied.Meanwhile,the relationship between the attenuation voltage value and area of the transmitting coil,the depth of the goaf,the background resistivity,and the delay time were also simulated.The results illustrate that the attenuation curve of induced voltage presented a regular exponential decay form in the 0%water accumulation model but existed abnormal exaltation for voltage in water-flled model.Through the linear ftting curve,it can be seen that the abnormal intensity of the induced voltage becomes stronger as the distance between the measuring point and the center of the target decrement.Moreover,the abnormal amplitude of the induced voltage increases with the rise of the water accumulation and collapsed rock will weakly reduce the low-resistivity anomalous efect on the water-accumulated goaf.In addition,the response value of the attenuation voltage increased as the area of the transmitting coil increases,but decreased with increasing delay time and increasing background resistivity and depth of the target body.The feld detection results of the Majiliang coal mine also confrmed the theoretical analysis and the numerical simulation.

关键词： Transient electromagnetic method Water-accumulated goaf Forward and inverse simulation Attenuation curve of induced voltage

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An image segmentation method of pulverized coal for particle size analysis

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International Journal of mining Science and technology 2023年第9期33卷 1181-1192页

作者： Xin Li Shiyin Li Liang Dong Shuxian Su Xiaojuan Hu Zhaolin Lu Affiliated Hospital of China University of mining and technology Xuzhou 221002China School of Information and Control Engineering China University of Mining and TechnologyXuzhou 221116China School of Chemical Engineering&technology China University of Mining and TechnologyXuzhou 221116China advanced Analysis and Computation center China University of Mining and TechnologyXuzhou 221116China

An important index to evaluate the process efficiency of coal preparation is the mineral liberation degree of pulverized coal,which is greatly influenced by the particle size and shape distribution acquired by image segmentation.However,the agglomeration effect of fine powders and the edge effect of granular images caused by scanning electron microscopy greatly affect the precision of particle image segmentation.In this study,we propose a novel image segmentation method derived from mask regional convolutional neural network based on deep learning for recognizing fine coal powders.Firstly,an atrous convolution is introduced into our network to learn the image feature of multi-sized powders,which can reduce the missing segmentation of small-sized agglomerated particles.Then,a new mask loss function combing focal loss and dice coefficient is used to overcome the false segmentation caused by the edge effect.The final comparative experimental results show that our method achieves the best results of 94.43%and 91.44%on AP50 and AP75 respectively among the comparison algorithms.In addition,in order to provide an effective method for particle size analysis of coal particles,we study the particle size distribution of coal powders based on the proposed image segmentation method and obtain a good curve relationship between cumulative mass fraction and particle size.

关键词： Pulverized coal Image segmentation Deep learning Particle size analysis

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Design and application of solid, dense backfill advanced mining technology with two pre-driving entries

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International Journal of mining Science and technology 2015年第1期25卷 127-132页

作者： Zhang Qiang Zhang Jixiong Guo Shuai Gao Rui Li Weikang School of Mines China University of Mining & Technology Key Laboratory of Deep Coal Resource mining Ministry of Education of China China University of Mining & Technology

New solid backfill mining technology provides unique technical advantages for ‘‘three-under'' coal mining which refers to coal resources trapped under buildings, railways, and water bodies. This technology has a much higher recovery rate and can effectively control the surface subsidence. However, successful application of this technology depends heavily on geological conditions. To avoid the disadvantages associated with downward mining and overhead backfilling with this new technology, a new advanced solid backfill mining design with two pre-driving entries is proposed here to ensure the backfill effect. Taking Huayuan coal mine as an example, this paper tests the double gob-side entries retaining with no pillar left scheme and optimizes an integrated technology setup for backfill mining and gob-side entry retaining. Field applications show that the recovery rate increased from 40% for strip mining to 85% for backfill mining. Moreover, the new backfill technology allowed for better control over the surrounding rock deformation caused by the gob-side entry retaining effect and better control of ground subsidence as compared to strip mining.

关键词：开采技术充填开采应用程序开采设计条目驱动回填技术采空区侧

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Unidirectional transport in amorphous topological photonic crystals

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中国科学:物理学、力学、天文学英文版 2023年第7期66卷 62-68页

作者： Yuting Yang Xinyue Qian Liwei Shi Xiaopeng Shen Zhi Hong Hang School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221116China School of Physical Science and technology&Collaborative Innovation center of Suzhou Nano Science and technology Soochow UniversitySuzhou 215006China Institute for advanced Study Soochow UniversitySuzhou 215006China

Many works on topological insulators have focused on periodic lattice systems,where short-and long-range order is considered.Here we construct a two-dimensional amorphous photonic crystal with short-range order and a controllable level of long-range order and experimentally investigate the transport of topological edge states in this amorphous system.We demonstrate that topology properties remain constant with unidirectional edge state propagation,immune to specific disorder strength.The partition phenomena of edge states are also observed at the intersection of four topological channels in microwave experiments.This proposed amorphous configuration provides new opportunities to explore the relationship between short-range order and topology and may alleviate the fabrication difficulties of topological optical devices for practical applications.

关键词： photonic crystal amorphous material topological insulator

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Effect of calcination temperature on the pozzolanic activity of maize straw stem ash treated with portlandite solution

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International Journal of Minerals,Metallurgy and Materials 2022年第6期29卷 1161-1169页

作者： Tingye Qi Haochen Wang Guorui Feng Yujiang Zhang Jinwen Bai Yanna Han College of mining technology Taiyuan University of TechnologyTaiyuan 030024China Shanxi Province Research center of Green mining Engineering technology Taiyuan 030024China Shanxi Coal-based Resources Green-efficient mining Engineering Research center Taiyuan 030024China Key Laboratory of Shanxi Province for Mine Rock Strata Control and Disaster Prevention Taiyuan 030024China

The effect of calcination temperature on the pozzolanic activity of maize straw stem ash(MSSA)was evaluated.The MSSA samples calcined at temperature values of 500,700,and 850℃ were dissolved in portlandite solution for 6 h,thereby obtaining residual samples.The MSSA and MSSA residual samples were analyzed using Fourier transform infrared spectroscopy,X-ray powder diffraction scanning electron microscopy,and X-ray photoelectron spectroscopy to determine vibration bonds,minerals,microstructures,and Si 2p transformation behavior.The conductivity,pH value,and loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were also determined.The main oxide composition of MSSA was silica and potassium oxide.The dissolution of the Si^(4+) content of MSSA at 500℃ was higher than those of the other calcination temperatures.The conductivity and loss of conductivity of MSSA at 700℃ were higher than those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700℃.C-S-H was easily identified in MSSA samples using X-ray powder diffraction,and small cubic and nearly spherical particles of C-S-H were found in the MSSA residual samples.In conclusion,the optimum calcination temperature of MSSA having the best pozzolanic activity is 500℃,but excessive agglomeration must be prevented.

关键词： calcination temperature pozzolanic activity maize straw stem ash portlandite solution

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Numerical modelling of spatially and temporally distributed on‑fault induced seismicity:implication for seismic hazards

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International Journal of Coal Science & technology 2023年第1期10卷 108-123页

作者： Atsushi Sainoki Adam Karl Schwartzkopf Lishuai Jiang Hani Mitri Faculty of advanced Science and technology KumamotoUniversityKumamotoJapan School of Engineering The University of Western AustraliaPerthAustralia State Key Laboratory of mining Disaster Preventionand Control Shandong University of Scienceand TechnologyShandongChina Department of mining and Materials Engineering McGillUniversityMontrealCanada

Induced seismicity is strongly related to various engineering projects that cause anthropogenic in-situ stress change at a great depth.Hence,there is a need to estimate and mitigate the associated risks.In the past,various simulation methods have been developed and applied to induced seismicity analysis,but there is still a fundamental diference between simulation results and feld observations in terms of the spatial distribution of seismic events and its frequency.The present study aims to develop a method to simulate spatially distributed on-fault seismicity whilst reproducing a complex stress state in the fault zone.Hence,an equivalent continuum model is constructed,based on a discrete fracture network within a fault damage zone,by employing the crack tensor theory.A fault core is simulated at the center of the model as a discontinuous plane.Using the model,a heterogeneous stress state with stress anomalies in the fault zone is frst simulated by applying tractions on the model outer boundaries.Subsequently,the efective normal stress on the fault plane is decreased in a stepwise manner to induce slip.The simulation result is validated in terms of the b-value and other seismic source parameters,hence demonstrating that the model can reproduce spatially and temporally distributed on-fault seismicity.Further analysis on the parameters shows the variation of frequency-magnitude distribution before the occurrence of large seismic events.This variation is found to be consistent with feld observations,thus suggesting the potential use of this simulation method in evaluating the risk for seismic hazards in various engineering projects.

关键词： Induced seismicity Fracture network Fault damage zone Crack tensor theory

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Triboelectric properties of ilmenite and quartz minerals and investigation of triboelectric separation of ilmenite ore

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International Journal of mining Science and technology 2018年第2期28卷 223-230页

作者： Yang Xing Wang Haifeng Peng Zhen Hao Juan Zhang Guangwen Xie Weining He Yaqun Key Laboratory of Coal Processing and Efficient Utilization China University of Mining and TechnologyMinistry of EducationXuzhou 221116China School of Chemical Engineering and technology China University of Mining&TechnologyXuzhou 221116China Jinan Yuxing Chemical Co.Ltd. Jinan 250119China advanced Analysis&Computation center China University of Mining&TechnologyXuzhou 221116China

Triboelectric separation, as an entirely dry technology, is a prospective method to process fine minerals.The aim of this paper is to investigate the performance of triboelectric separation of ilmenite and quartz minerals in a lab unit and to get ready for the separation of ilmenite ore. A tribocharge measurement system was used to test the triboelectric properties of ilmenite and quartz particles with tribochargers respectively made of PVC, PPR, PMMA, Teflon, copper, stainless steel and quartz glass. The results show that the ilmenite particles charged positively while quartz charged negatively when tribocharged with PVC tribocharger. The mixture of 12% ilmenite and 88% quartz was prepared for the triboelectric separation. The recovery of ilmenite increases with the increase of airflow rate, decreases with the increasing feed rate, and grows up firstly and then decreases with the increasing voltage. A maximum ilmenite recovery of 51.71% with ilmenite content 32.72% was obtained at 40 m^3/h airflow rate, 6 g/s feed rate and 20 kV voltage. According to the optimal parameters of the separation of ilmenite and quartz mixture,fine ilmenite ore with 7.55% Ti content was beneficiated using the unit and the Ti content increased to 12.32% in concentrate product.

关键词： Triboelectric separation Tribocharge Ilmenite Quartz Ilmenite ore

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