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Recovering 3D structural properties of galaxies from SDSS-like photometry

Research in Astronomy and Astrophysics 2015年第10期15卷 1613-1628页

作者： elmo tempel Antti Tamm Rain Kipper Teeter Tenjes Tartu Observatory Institute of Physics University of Tartu

Because of the 3D nature of galaxies, an algorithm for constructing spatial density distribution models of galaxies on the basis of galaxy images has many advan- tages over approximations of the surface density distribution. We present a method for deriving the spatial structure and overall parameters of galaxies from images and estimate its accuracy and derived parameter degeneracies on a sample of idealised model galaxies. The test galaxies consist component with varying proportions and of a disc-like component and a spheroidal properties. Both components are assumed to be axially symmetric and coplanar. We simulate these test galaxies as if they had been observed in the SDSS project through ugriz filters, thus gaining a set of realis- tically imperfect images of galaxies with known intrinsic properties. These artificial SDSS galaxies were thereafter remodelled by approximating the surface brightness distribution with a 2D projection of a bulge＋disc spatial distribution model and the restored parameters were compared to the initial ones. Down to the r-band limiting magnitude of 18, errors in the restored integral luminosities and colour indices re- main within 0.05 mag and errors in the luminosities of individual components within 0.2 mag. Accuracy of the restored bulge-to-disc luminosity ratio （B/D） is within 40% in most cases, and becomes worse for galaxies with low B/D, but the general balance between bulges and discs is not shifted systematically. Assuming that the intrinsic disc axial ratio is ≤ 0.3, then the inclination angles can be estimated with errors 〈 5° for most of the galaxies with B/D 〈 2 and with errors 〈 15° up to B/D = 6. Errors in the recovered sizes of the galactic components are below 10% in most cases. The axial ratios and the shape parameter N of Einasto＇s distribution （similar to the Sersic index） are relatively inaccurate, but can provide statistical estimates for large samples. In general, models of disc components are more accurate than

关键词： methods: numerical -- galaxies: general -- galaxies: photometry --galaxies: structure

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矸石充填体机械压缩过程及宽条带岩层沉降分析

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煤矿安全 2024年第2期55卷 125-132页

作者：轩召军许磊相峥蔡玲祥郭帅 DAVIDE elmo 山东康格能源科技有限公司山东济宁272075 山东省充填开采工程技术研究中心山东济宁272075 河南理工大学土木工程学院河南焦作454000 河南理工大学河南省地下工程与灾变防控重点实验室河南焦作454000 禹州神火广鑫矿业有限公司河南禹州452570 英属哥伦比亚大学NBK矿业工程学院加拿大温哥华V6T 1Z4

以亭南煤矿1102宽条带矸石充填工作面为工程背景,采用理论分析、数值模拟、室内试验、现场实测等方法研究了矸石机械压缩过程及岩层沉降规律。结果表明:散体矸石经2 MPa夯实后压缩了27.05%,变成矸石充填体,矸石充填体在可充填空间内机... 详细信息

以亭南煤矿1102宽条带矸石充填工作面为工程背景,采用理论分析、数值模拟、室内试验、现场实测等方法研究了矸石机械压缩过程及岩层沉降规律。结果表明:散体矸石经2 MPa夯实后压缩了27.05%,变成矸石充填体,矸石充填体在可充填空间内机械压缩过程及架后压缩率为(各阶段压缩与可充填空间高度比值):骨架调整段(7.42%),缓慢压缩段(5.39%);机械压缩等价采高为可充填空间高度与矸石充填体2个阶段可充压缩率的乘积;1102工作面矸石充填体在骨架调整段和缓慢压缩段的等价采高分别为0.94 m和1.10 m;1102工作面走向和倾向主断面地表下沉曲线均为“碗”形,骨架调整段到缓慢压缩段过程中,地表变形曲线变化不大,最终最大下沉量分别为39 mm和41 mm。

关键词：矸石充填充填开采等价采高矸石夯实宽条带岩层沉降

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夯实矸石压缩-固结蠕变成岩过程及等价采高模型分析

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河南理工大学学报（自然科学版） 2024年第6期43卷 27-37页

作者：许磊王思雨 elmo Davide 丁书学刘洪林李文峰洪紫杰河南理工大学土木工程学院河南焦作454000 河南省地下空间开发及诱发灾变防治国际联合实验室河南焦作454000 英属哥伦比亚大学NBK矿业工程研究所温哥华V6T 1Z4加拿大新疆大学地质与矿业工程学院新疆乌鲁木齐830046 洛斯阿拉莫斯国家试验室洛斯阿拉莫斯87545新墨西哥美国

目的为了研究被夯实矸石压缩-固结蠕变成岩过程及其等价采高模型,方法以亭南煤业公司1102矸石充填工作面为工程背景,采用理论分析、数值模拟、室内试验、现场实测等方法进行研究。结果结果表明:矸石充填工作面最大控顶距=端面距+截割深... 详细信息

目的为了研究被夯实矸石压缩-固结蠕变成岩过程及其等价采高模型,方法以亭南煤业公司1102矸石充填工作面为工程背景,采用理论分析、数值模拟、室内试验、现场实测等方法进行研究。结果结果表明:矸石充填工作面最大控顶距=端面距+截割深度+顶梁长度+架后触矸距离;顶板回转下沉量等于最大控顶距乘以支架后倾角度正弦值;架后可充填空间高度等于采高减去顶板回转下沉量、欠接顶量、架后底鼓量。被夯实矸石在可充填空间内压缩-固结蠕变成岩的4个阶段及可充压缩率分别为骨架调整段(7.42%),缓慢压缩段(5.39%),固结沉降段(0.34%),蠕变成岩段(12.38%)。由该等价采高模型可知,1102工作面4阶段等价采高为骨架调整段0.94 m,缓慢压缩段1.10 m,固结沉降段1.11 m,蠕变成岩段1.48 m。结论通过概率积分法预测、数值模拟和沉陷观测对比可知,1102工作面走向和倾向主断面地表下沉曲线均为碗形。前两阶段地表下沉曲线平缓,后两阶段地表下沉曲线陡峭。

关键词：矸石充填等价采高矸石压实固结成岩

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Development of a spring analogue approach for the study of pillars and shafts

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International Journal of Mining Science and Technology 2018年第2期28卷 267-274页

作者： Amichai Mitelman Davide elmo Doug Stead NBK Institute of Mining Engineering University of British Columbia Department of Earth Sciences Simon Fraser University

In civil and mining operations that involve ground excavation and support, the loads are distributed between the ground and support depending on their relative stiffness. This paper presents the development of conceptual single-degree-of-freedom models, which are used to derive equations for estimating displacements and stresses for ground-support interaction problems encountered in pillars in room-andpillar mining(natural support system), and liners for circular vertical shafts(artificial support systems).For pillar assessment, mine-pillar interaction curves can be constructed using a double spring ***, the effectiveness of different support systems can be evaluated depending on their effect upon the mine-pillar system. For shaft design, an initial estimation of the required lining strength and thickness can be readily made based on a double ring analogue. For both problems, the results from the proposed approach compare well with those obtained by finite element numerical simulations.

关键词： Room and pillar Shafts Ground-support interaction Spring analogue Rockbolts

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Influence of data analysis when exploiting DFN model representation in the application of rock mass classification systems

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第6期10卷 1046-1062页

作者： Takako Miyoshi Davide elmo Steve Rogers NBK Institute of Mining University of British ColumbiaVancouverCanada Golder Associates Ltd. VancouverCanada

Discrete fracture network(DFN) models have been proved to be effective tools for the characterisation of rock masses by using statistical distributions to generate realistic three-dimensional(3 D) representations of a natural fracture network. The quality of DFN modelling relies on the quality of the field data and their interpretation. In this context, advancements in remote data acquisition have now made it possible to acquire high-quality data potentially not accessible by conventional scanline and window mapping. This paper presents a comparison between aggregate and disaggregate approaches to define fracture sets, and their role with respect to the definition of key input parameters required to generate DFN models. The focal point of the discussion is the characterisation of in situ block size distribution(IBSD) using DFN methods. An application of IBSD is the assessment of rock mass quality through rock mass classification systems such as geological strength index(GSI). As DFN models are becoming an almost integral part of many geotechnical and mining engineering problems, the authors present a method whereby realistic representation of 3 D fracture networks and block size analysis are used to estimate GSI ratings, with emphasis on the limitations that exist in rock engineering design when assigning a unique GSI value to spatially variable rock masses.

关键词： Data collection Discrete fracture network(DFN) Classification system Geological strength index(GSI)

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Overhanging rock slope by design:An integrated approach using rock mass strength characterisation,large-scale numerical modelling and limit equilibrium methods

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第1期10卷 72-90页

作者： Paul Schlotfeldt Davide elmo Brad Panton Golder Associates Ltd. VancouverCanada NBK Institute of Mining The University of British ColumbiaVancouverCanada

Overhanging rock slopes(steeper than 90°) are typically avoided in rock engineering design, particularly where the scale of the slope exceeds the scale of fracturing present in the rock mass. This paper highlights an integrated approach of designing overhanging rock slopes where the relative dimensions of the slope exceed the scale of fracturing and the rock mass failure needs to be considered rather than kinematic release of individual blocks. The key to the method is a simplified limit equilibrium(LE) tool that was used for the support design and analysis of a multi-faceted overhanging rock slope. The overhanging slopes required complex geometries with constantly changing orientations. The overhanging rock varied in height from 30 m to 66 m. Geomechanical modelling combined with discrete fracture network(DFN)representation of the rock mass was used to validate the rock mass strength assumptions and the failure mechanism assumed in the LE model. The advantage of the simplified LE method is that buttress and support design iterations(along with sensitivity analysis of design parameters) can be completed for various cross-sections along the proposed overhanging rock sections in an efficient manner, compared to the more time-intensive, sophisticated methods that were used for the initial validation. The method described presents the development of this design tool and assumptions made for a specific overhanging rock slope design. Other locations will have different geological conditions that can control the potential behaviour of rock slopes, however, the approach presented can be applied as a general guiding design principle for overhanging rock cut slope.

关键词： Rock slopes Discrete fracture network(DFN) Rock mass strength characterisation Numerical modelling Limit equilibrium(LE) methods

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Modelling of blast-induced damage in tunnels using a hybrid finite-discrete numerical approach

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第6期6卷 565-573页

作者： Amichai Mitelman Davide elmo NBK Institute of Mining Engineering University of British ColumbiaVancouver Canada

This paper presents the application of a hybrid finite-discrete element method to study blast-induceddamage in circular tunnels. An extensive database of field tests of underground explosions above tunnelsis used for calibrating and validating the proposed numerical method; the numerical results areshown to be in good agreement with published data for large-scale physical experiments. The method isthen used to investigate the influence of rock strength properties on tunnel durability to withstand blastloads. The presented analysis considers blast damage in tunnels excavated through relatively weak（sandstone） and strong （granite） rock materials. It was found that higher rock strength will increase thetunnel resistance to the load on one hand, but decrease attenuation on the other hand. Thus, undercertain conditions, results for weak and strong rock masses are similar. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Blast damage Tunnels Numerical analysis Finite-discrete method

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New approaches to quantify progressive damage and associated dynamic rock mass blockiness

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第2期15卷 285-295页

作者： Ladan Karimi Sharif Davide elmo Doug Stead NBK Institute of Mining Engineering The University of British ColumbiaVancouverCanada Department of Earth Science Simon Fraser UniversityBurnabyCanada

In the past decade, numerical modelling has been increasingly used for simulating the mechanical behaviour of naturally fractured rock masses. In this paper, we introduce new algorithms for spatial and temporal analyses of newly generated fractures and blocks using an integrated discrete fracture network (DFN)-finite-discrete element method (FDEM) (DFN-FDEM) modelling approach. A fracture line calculator and analysis technique (i.e. discrete element method (DEM) fracture analysis, DEMFA) calculates the geometrical aspects of induced fractures using a dilation criterion. The resultant two-dimensional (2D) blocks are then identified and characterised using a graph structure. Block tracking trees allow track of newly generated blocks across timesteps and to analyse progressive breakage of these blocks into smaller blocks. Fracture statistics (number and total length of initial and induced fractures) are then related to the block forming processes to investigate damage evolution. The combination of various proposed methodologies together across various stages of modelling processes provides new insights to investigate the dependency of structure's resistance on the initial fracture configuration.

关键词： Numerical modelling Spatial analysis Temporal analysis Discrete fracture network(DFN) Finite-discrete element method(FDEM)modelling Block calculations Graph structure

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Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 609-625页

作者： Pooya Hamdi Doug Stead Davide elmo Simon Fraser University 8888 University Drive NBK Institute of Mining Engineering University of British Columbia

Heterogeneity is an inherent component of rock and may be present in different forms including mineralheterogeneity, geometrical heterogeneity, weak grain boundaries and micro-defects. Microcracks areusually observed in crystalline rocks in two forms： natural and stress-induced; the amount of stressinducedmicrocracking increases with depth and in-situ stress. Laboratory results indicate that thephysical properties of rocks such as strength, deformability, P-wave velocity and permeability areinfluenced by increase in microcrack intensity. In this study, the finite-discrete element method （FDEM）is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks usingthe proposed micro discrete fracture network （mDFN） approach. The characteristics of the microcracksrequired to create mDFN models are obtained through image analyses of thin sections of Lac du Bonnetgranite adopted from published literature. A suite of two-dimensional laboratory tests including uniaxial,triaxial compression and Brazilian tests is simulated and the results are compared with laboratory *** FDEM-mDFN models indicate that micro-heterogeneity has a profound influence on both the mechanicalbehavior and resultant fracture pattern. An increase in the microcrack intensity leads to areduction in the strength of the sample and changes the character of the rock strength envelope. Spallingand axial splitting dominate the failure mode at low confinement while shear failure is the dominantfailure mode at high confinement. Numerical results from simulated compression tests show thatmicrocracking reduces the cohesive component of strength alone, and the frictional strength componentremains unaffected. Results from simulated Brazilian tests show that the tensile strength is influenced bythe presence of microcracks, with a reduction in tensile strength as microcrack intensity increases. Theimportance of microcrack heterogeneity in reproducing a bi-linear or S-shape failure

关键词： Finite-discrete element method(FDEM) Micro discrete fracture network(μDFN) Brittle fracture

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Long-term mechanical behavior and characteristics of cemented tailings backfill through impact loading

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International Journal of Minerals,Metallurgy and Materials 2020年第2期27卷 140-151页

作者： Yu-ye Tan elmo Davide Yu-cheng Zhou Wei-dong Song Xiang Meng Key Laboratory of High-Efficient Mining and Safety of Metal Mines(Ministry of Education of China) University of Science and Technology BeijingBeijing 100083China School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China Norman B.Keevil Institute of Mining Engineering Applied Science SchoolUniversity of British ColumbiaVancouverBC Canada V6T 1Z4

Cemented tailings backfill(CTB)structures are important components of underground mine *** is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to disturbance by dynamic loading,such as excavation and *** this study,the authors present the results of a series of Split-Hopkinson pressure bar(SHPB)single and cyclic impact loading tests on CTB specimens to investigate the long-term dynamic mechanical properties of *** stress-strain relationship,dynamic strength,and dynamic failure characteristics of CTB specimens are analyzed and discussed to provide valuable conclusions that will improve our knowledge of CTB long-term mechanical behavior and *** instance,the dynamic peak stress under cyclic impact loading is approximately twice that under single impact loading,and the CTB specimens are less prone to fracture when cyclically *** findings and conclusions can provide a new set of references for the stability analysis of CTB materials and help guide mine designers in reducing the amount of binding agents and the associated mining cost.

关键词： cyclic impact loading cemented tailings backfill dynamic mechanical properties Split–Hopkinson pressure bar dynamic peak stress

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