检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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

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

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

深部不同断面巷道分区破裂形态与围岩结构控制

在线全文

学校读者我要写书评

暂无评论

岩土工程学报 2023年第4期45卷 720-729页

作者：许磊郭帅 Davide elmo 刘洪林洪紫杰肖同强河南理工大学土木工程学院河南焦作454000 河南省地下工程与灾变防控重点实验室(河南理工大学) 河南焦作454000 英属哥伦比亚大学NBK矿业工程学院温哥华V6T 1Z4 新疆大学地质与矿业工程学院新疆乌鲁木齐830046 河南理工大学能源科学与工程学院河南焦作454000

采用理论分析、现场实测、模拟分析的方法,研究了各向等压条件下等效开挖矩形、直墙半圆拱和圆形断面分区破裂形态及围岩稳定结构。结论:3个断面分区破裂形态不同,矩形断面分区破裂呈“■”状分布,直墙半圆拱断面分区破裂呈多层的“■... 详细信息

采用理论分析、现场实测、模拟分析的方法,研究了各向等压条件下等效开挖矩形、直墙半圆拱和圆形断面分区破裂形态及围岩稳定结构。结论:3个断面分区破裂形态不同,矩形断面分区破裂呈“■”状分布,直墙半圆拱断面分区破裂呈多层的“■”状分布,圆形断面分区破裂呈“花瓣”状分布;三个断面位移特征相似,位移等值线浅部呈正立的“鸡蛋壳”形,深部呈“碗”形;支承压力在主破裂面处降低,在最外层主破裂面头部集中,在破裂面之间完整岩层处升高,呈分区集中,“波谷—波峰—波谷”震荡增高的特征向外传播;理想正方形破裂面弦长有an+1=2(1/2)an(n=1,2,3,4)关系;浅部围岩分区破裂形成后,相当于深部围岩的伪开挖,3个断面均存在多层“■”形围岩承载结构。巷道稳定原理就是促进多层承载结构相互依存,共同承载。具体措施:加密、加粗、加长锚杆(索)支护结构,建立浅部与深部多层承载结构相互联系,在浅部形成稳定锚固体促进深部围岩稳定,主破裂面精准注浆修复围岩破裂面和限制主破裂面滑移。

关键词：分区破裂围岩结构深部巷道破裂形态

切近位关键层卸压沿空掘巷关键参数与工程应用

在线全文

学校读者我要写书评

暂无评论

采矿与安全工程学报 2023年第1期40卷 91-100页

作者：许磊李明伟郭亮肖同强刘洪林 DAVIDE elmo 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 陕西时代能源化工有限公司陕西榆林719000 河南理工大学能源科学与工程学院河南焦作454000 新疆大学地质与矿业工程学院新疆乌鲁木齐830046 英属哥伦比亚大学NBK矿业工程学院加拿大温哥华V6T 1Z4

以马家岩煤矿40103回风巷(沿空掘巷)为背景,采用理论分析、数值模拟和工程实践等方法研究切顶卸压沿空掘巷关键参数等问题。结果表明:关键层位于4~8倍采高范围时为近位关键层,位于4~8倍采高范围外时为远位关键层;掘进期间在块体A(悬臂结... 详细信息

以马家岩煤矿40103回风巷(沿空掘巷)为背景,采用理论分析、数值模拟和工程实践等方法研究切顶卸压沿空掘巷关键参数等问题。结果表明:关键层位于4~8倍采高范围时为近位关键层,位于4~8倍采高范围外时为远位关键层;掘进期间在块体A(悬臂结构)下完成;切角垂直于顶板时卸压效果最好,有利于岩块C_(i)的滑落,但倒梯形切顶结构更有利于超前巷道顶板稳定,选取75°为切顶角度;切顶长度越深卸压效果越好,超过关键层后,再增加切长,支承压力继续降低但降低幅度逐渐减小。通过对比切顶(切长20 m,角度75°)与不切顶条件下不同煤柱宽度支承压力,可发现:实体煤侧支承压力依然呈“单峰”状分布,大煤柱(>10 m)上支承压力呈非对称“马鞍”状分布,小煤柱(<10 m)支承压力呈“钟形”分布,切顶可降低支承压力峰值,但不改变其位置。炮孔间距不大于爆破裂隙损伤半径的2倍,可根据现场及时调整。最终确定护巷煤柱宽度8 m,切顶长度20 m,角度75°,炮孔间距1.0 m,支护方案为锚杆+金属网+钢带+锚索补强联合支护。掘进期间两帮相对位移量156 mm,顶板下沉量186 mm,底鼓量101 mm;10 d左右实现自稳;回采期间两帮相对最大移近速度42 mm/d,顶板最大下沉速度47 mm/d,底鼓最大速度63 mm/d。

关键词：沿空掘巷近位关键层切顶卸压小煤柱

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

在线全文

学校读者我要写书评

暂无评论

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

多器官床旁即时超声在新型冠状病毒肺炎中的应用:国际专家共识

在线全文

学校读者我要写书评

暂无评论

中国呼吸与危重监护杂志 2021年第2期20卷 77-84页

作者：王臻(译) Arif Hussain Gabriele Via Lawrence Melniker Alberto Goffi Guido Tavazzi Luca Neri Tomas Villen Richard Hoppmann Francesco Mojoli Vicki Noble Laurent Zieleskiewicz Pablo Blanco Irene W.Y.Ma Mahathar Abd.Wahab Abdulmohsen Alsaawi Majid AI Salamah Martin Balik Diego Barca Karim Bendjelid Belaid Bouhemad Pablo Bravo-Figueroa Raoul Breitkreutz Juan Calderon Jim Connolly Roberto Copetti Francesco Corradi Anthony J.Dean AndréDenault Deepak Govil Carmela Graci Young-Rock Ha Laura Hurtado Toru Kameda Michael Lanspa Christian B Laursen Francis Lee Rachel Liu Massimiliano Meineri Miguel Montorfano Peiman Nazerian Bret P.Nelson Aleksandar N.Neskovic Ramon Nogue Adi Osman JoséPazeli elmo pereira-junior Tomislav Petrovic Emanuele Pivetta Jan Poelaert Susanna Price Gregor Prosen Shalim Rodriguez Philippe Rola Colin Royse Yale Tung Chen Mike Wells Adrian Wong Wang Xiaoting Wang Zhen Yaseen Arabi 中国人民解放军空军军医大学航空航天医学系陕西西安710032 Department of Cardiac Sciences King Abdulaziz Medical City and King Abdullah International Medical Research Center 不详

新型冠状病毒肺炎(简称新冠肺炎,COVID-19)自首次报道以来,已造成全球超一亿人感染,给各国的公共卫生体系造成了巨大威胁。新冠肺炎的临床表现以呼吸系统体征和症状为主,80%的患者症状轻微,约5%为危重症患者,常表现为急性呼吸窘迫综合征... 详细信息

新型冠状病毒肺炎(简称新冠肺炎,COVID-19)自首次报道以来,已造成全球超一亿人感染,给各国的公共卫生体系造成了巨大威胁。新冠肺炎的临床表现以呼吸系统体征和症状为主,80%的患者症状轻微,约5%为危重症患者,常表现为急性呼吸窘迫综合征(ARDS)。前期,由于缺乏相关研究,面对日益紧迫的临床困境,医务人员不得不借鉴采取一些经验性措施以应对疫情。

关键词：体征和症状肺炎公共卫生体系呼吸系统首次报道专家共识疫情

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

在线全文

学校读者我要写书评

暂无评论

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)

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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