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Continuous-discontinuous element method for three-dimensional thermal cracking of rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第11期15卷 2917-2929页

作者： wen nie Junlin Wang Chun Feng Yiming Zhang School of Civil and Transportation Engineering Hebei University of TechnologyTianjin300401China Institute of Mechanics Chinese Academy of SciencesBeijing100190China

Thermal cracking of rocks can significantly affect the durability of underground structures in engineering practices such as geothermal energy extraction,storage of nuclear waste and tunnelling in freezeethaw cycle induced *** is a scenario of strong coupled thermomechanical process involving discontinuity behaviours of *** this context,a numerical model was proposed to investigate the thermal cracking of rocks,in a framework of the continuous-discontinuous element method(CDEM)for efficiently capturing the initiation and propagation of multiple cracks.A simplex integration strategy was adopted to account for the influences of temperature-dependent material *** benchmark tests were considered and the obtained results were compared with analytical solutions and numerical results from the *** results show that the fracture degree of the cases when considering temperature-dependent material parameters had 10%differences approximately compared with the cases with constant parameters.

关键词： Rock thermal cracking Continuous-discontinuous element Simplex integration Temperature dependence Numerical simulation

Modified Sadowski formula-based model for the slope shape amplification effect under multistage slope blasting vibration

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International Journal of Mining Science and Technology 2024年第5期34卷 631-641页

作者： Xiaogang Wu Mingyang Wang Hao Lu Yongjun Zhang wen nie State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact Army Engineering University of PLANanjing 210007China State Key Laboratory of Metal Mine Safety and Health Ma’anshan 243000China School of Civil Engineering Qingdao University of TechnologyQingdao 266520China

Blasting operations,which are crucial to open-pit mine production due to their simplicity and efficiency,require precise control through accurate vibration velocity *** conventional Sadowski formula mainly focuses on blast center distance but neglects the amplification effect of blasting vibration waves by terraced terrain,from which the calculated blasting vibration velocities are smaller than the actual values,affecting the safety of the *** address this issue,our model introduces the influences of slope and time into Sadowski formula to measure safety through blast vibration *** the northern section of the open-pit quartz mine in Jinchang City,Gansu Province,China,the data of a continuous blasting slope project are referred *** findings reveal a noticeable vibration amplification effect during blasting when a multi-stage slope platform undergoes a sudden cross-sectional change near the upper overhanging *** amplification vibration coefficient increases with height,while vibration waves within rocks decrease from bottom to ***,platforms without distinct crosssectional changes exhibit no pronounced amplification during *** addition,the vibration intensity decreases with distance as the rock height difference change *** results obtained by the proposed blast vibration displacement equation incorporating slope shape influence closely agree with real-world *** to Pearson correlation coefficient(PPMCC)analysis,the average accuracy rate of our model is 88.84%,which exceeds the conventional Sadowski formula(46.92%).

关键词： Multistage slope Slope shape influence factor Continuous blasting Sadowski formula Amplification effect

Microcrack analysis of Sanya grantite fragments from rockburst tests

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Mining Science and Technology 2010年第2期20卷 238-243页

作者： HE, Manchao nie, wen HAN, Liqiang LING, Lijing state key laboratory of geomechanics and deep underground engineering beijing 100083china school of mechanics & civil engineering china university of mining & technologybeijing 100083china school of mechanics & civil engineering china university of mining & technologybeijing 100083china

Fractures running along a plane reflect the cracking *** this paper uniaxial and rockburst tests on a group of granite specimens from Sanya province are *** electron microscopic imaging was used to characterize the *** fracture mechanics were used to analyze the microcracks in terms of both the crack type and the mineral constituent.A statistical analysis showed that the area of inter-granular cracking exceeds that of intra-granular *** types of crack were observed in the cracked *** percentage of intra-granular cracks in fragments from rockburst tests exceeds that from uniaxial compression *** results also showed that feldspar deformation was the main cause of fracture and that the consolidation along quartz grain boundaries was another weak area in the *** along quartz grains had enough energy to enter the quartz crystal in the rockburst *** these results contribute to further research on rockburst mechanics.

关键词： granite rockburst medium fragment quartz feldspar fractal analysis

Micro-and macro-fractures of coarse granite under true-triaxial unloading conditions

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Mining Science and Technology 2011年第3期21卷 389-394页

作者： He Manchao nie wen Zhao Zhiye Cheng Cheng School of Mechanics and Civil Engineering China University of Mining ＆ Technology Beijing 100083 China State Key Laboratory of Geomechanics and Deep Underground Engineering Beijing 100083. China School of Civil and Environmental Engineering Nanyang Technological University Singapore

We studied the mechanical behavior of rock under different boundary conditions, based on the fractal characteristics of fractures in terms of microscopic and macroscopic investigations. Three rectangular granite specimens of similar dimensions were tested by a triaxial rock testing machine under uniaxial compression （UC）, confined compression （CC） and true-triaxial unloading conditions （RB） under rock burst boundary conditions. The failure processes of these specimens were investigated via examinations of their fracture behavior on a macro-scale by laser profilometers and on a micro-scale by a scanning electron microscopic （SEM） imaging technique. The SEM images, showing the spailing features of RB frag- ments, are compared with the grain dislocations under UC and CC conditions. Based on a variogram method, two fractal parameters, i.e., fractal dimensions （Dr^d） and the scale dependent fractal parameter Kv, were induced to present the surface roughness of scanning profiles in all directions. The fitted ellipses of Dr^d distribution show that RB surface has the smallest eccentricity, followed by the CC surface, while the UC surface had the largest eccentricity. As a result of this assessment, we conclude that rocks are affected by shear traction in an intermediate stress direction, which will cause fractures generated during rock bursts to twist rather than to tilt as shown in the uniaxial compression and the confined compres- sion tests.

关键词： Rock burstsSurface roughness Stress distribution Fractal dimension Coarse granite

A Straightforward Direct Traction Boundary Integral Method for Two-Dimensional Crack Problems Simulation of Linear Elastic Materials

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Computers, Materials & Continua 2019年第3期58卷 761-775页

作者： Chao Zhang Chunhe Yang Shangwei Wu Xiaolong Zhang wen nie State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Quanzhou Institute of Equipment Manufacturing Haixi InstitutesChinese Academy of SciencesQuanzhouFujian362000China College of Safety Engineering Chongqing University of Science and TechnologyChongqing401331China.

This paper presents a direct traction boundary integral equation method(DTBIEM)for two-dimensional crack problems of *** traction boundary integral equation was collocated on both the external boundary and either side of the crack *** displacements and tractions were used as unknowns on the external boundary,while the relative crack opening displacement(RCOD)was chosen as unknowns on either side of crack surfaces to keep the single-domain *** one side of the crack surfaces was concerned and needed to be discretized,thus the proposed method resulted in a smaller system of algebraic equations compared with the dual boundary element method(DBEM).A new set of crack-tip shape functions was constructed to represent the strain field singularity exactly,and the SIFs were evaluated by the extrapolation of the *** examples for both straight and curved cracks are given to validate the accuracy and efficiency of the presented method.

关键词： Fracture mechanics direct traction integral method relative crack opening displacement stress intensity factor.

Regression analysis of major parameters affecting the intensity of coal and gas outbursts in laboratory

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International Journal of Mining Science and Technology 2017年第2期27卷 327-332页

作者： Geng Jiabo Xu Jiang nie wen Peng Shoujian Zhang Chaolin Luo Xiaohang State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam Chongqing UniversityChongqing 400044China

Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coal and gas outbursts is significant in the evaluation of the intensity of the outburst. In this paper, we discuss the correlation between these major factors and the intensity of the outburst using Analysis of Variance(ANOVA) and Contingency Table Analysis(CTA). Regression analysis is used to evaluate the impact of these major factors on the intensity of outbursts based on physical experiments. Based on the evaluation, two simple models in terms of multiple linear and nonlinear regression were constructed for the prediction of the intensity of the outburst. The results show that the gas pressure and initial moisture in the coal mass could be the most significant factors compared to the weakest factor-porosity. The P values from Fisher's exact test in CTA are: moisture(0.019), geostress(0.290), porosity(0.650), and gas pressure(0.031). P values from ANOVA are moisture(0.094), geostress(0.077), porosity(0.420), and gas pressure(0.051). Furthermore, the multiple nonlinear regression model(RMSE: 3.870) is more accurate than the linear regression model(RMSE: 4.091).

关键词： Coal and gas outburst Gas pressure Regression analysis ANOVA CTA

Value of enhanced computed tomography in differentiating small mesenchymal tumours of the gastrointestinal from smooth muscle tumours

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World Journal of Gastrointestinal Surgery 2023年第9期15卷 2012-2020页

作者： wen-Jun nie Zhao Jing Mo Hua Department of Radiology Changzhou Geriatric Hospital Affiliated to Soochow UniversityChangzhou No.7 People’s Hospital Radiology DepartmentChangzhou 213011Jiangsu ProvinceChina Medical Area Eastern Theater General HospitalQinhuai District Medical AreaNanjing 210000Jiangsu ProvinceChina

BACKGROUND Computed tomography(CT)technology has been gradually used in the differen-tiation of small mesenchymal tumors of the stomach and intestines from smooth muscle *** To explore the value of enhanced CT in the differentiation of small mesenchymal tumors of the stomach and intestines from smooth muscle *** Clinical data of patients with gastric mesenchymal or gastric smooth muscle tu-mours who were treated in our hospital from May 2018 to April 2023 were retrospectively *** were divided into the gastric mesenchymal tumor group and the gastric smooth muscle tumor group respectively(n=50 cases per group).Clinical data of 50 healthy volunteers who received physical examinations in our hospital during the same period were selected and included in the control *** levels of carcinoembryonic antigen(CEA),alpha-fetoprotein(AFP),carbohydrate antigen 19-9(CA19-9),CA-125 and cytokeratin 19 fragment antigen 21-1 were compared among the three *** value of CEA and CA19-9 in the identification of gastric mesenchymal tumours was analysed using the receiver operating characteristic(ROC)*** Kappa statistic was used to analyse the consistency of the combined CEA and CA19-9 test in identi-fying gastric mesenchymal *** CEA levels varied among the three groups in the following order:The gastric mesenchymal tumour group>the control group>the gastric smooth muscle tumour ***19-9 levels varied among the three groups in the following order:The gastric mesenchymal group>the gastric smooth muscle group>the control group,the difference was statistically significant(P<0.05).ROC analysis showed that the area under the curve of CEA and CA19-9 was 0.879 and 0.782,*** Enhanced CT has shown value in differentiating small mesenchymal tumors of the stomach and intestines from smooth muscle tumors.

关键词： Smooth muscle tumour Stomach Intestines Differentiation

Generating large steady-state optomechanical entanglement by the action of Casimir force

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Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2276-2284页

作者： nie wen Jie LAN Yue Heng LI Yong ZHU Shi Yao Department of Physics Tsinghua University Beijing Computational Science Research Center Department of Applied Physics East China Jiaotong University

In this paper, we study an optomechanical device consisting of a Fabry-P6rot cavity with two dielectric nanospheres trapped near the cavity mirrors by an external driving laser. In the condition where the distances between the nanospheres and cavity mirrors are small enough, the Casimir force helps the optomechanical coupling to induce a steady-state optomechanical entanglement of the mechanical and optical modes in a certain regime of parameters. We investigate in detail the dependence of the steady- state optomechanical entanglement on external control parameters of the system, i.e., the effective detuning, the pump powers of the cavity, the cavity decay rate and the wavelength of the driving field. It is found that the large steady-state optomechanical entanglement, i.e. EN = 5.76, can be generated with experimentally feasible parameters, i.e. the pump power P = 18.2 μW, the cavity decay rate K = 0.5 MHz and the wavelength of the laser AL=1064 nm, which should be checked by optical measurement.

关键词： optomechanics Casimir effect entanglement

Analysis of diffusion behavior of harmful emissions from trackless rubber-wheel diesel vehicles in underground coal mines

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International Journal of Mining Science and Technology 2022年第6期32卷 1285-1299页

作者： Yun Hua wen nie Qiang Liu Xiaofei Liu Chengyi Liu Weiwei Zhou Fengning Yu College of Safety and Environmental Engineering Shandong University of Science and TechnologyQingdao 266590China State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China

To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle.A computational fluid dynamics(CFD)model of the diffusion of harmful emissions was hence established and *** the perspective of risk analysis,the diffusion behavior and distribution of hazardous substances emitted by the diesel vehicle were studied under 4 different conditions;moreover,we identified areas characterized by hazardous levels of *** the vehicle idled upwind in the roadway,high-risk areas formed behind and to the right of the vehicle:particularly high concentrations of pollutants were measured near the rear floor of the vehicle and within 5 m behind the *** the vehicle idled downwind,high-risk areas formed in front of it:particularly high concentrations of pollutants were measured near the floor and within 5 m from the front of the *** the above cases,the driver would not breathe highly polluted air and would be relatively *** the vehicle idled into the chamber,however,high-risk areas formed on both sides of the vehicle and near the upper *** entry of the vehicle caused a greater increase in the concentration of pollutants in the chamber and in the driver’s breathing zone compared with reverse entry.

关键词： Diesel vehicle Harmful emissions Diffusion behavior CFD model Underground coal mine