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Application of a vertex chain operation algorithm on topological analysis of three-dimensional fractured rock masses

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Frontiers of Structural and Civil engineering 2017年第2期11卷 187-208页

作者： Zixin ZHANG Jia WU Xin HUANG Department of Geotechnical Engineering School of Civil Engineering Tongji University Shanghai 200092 China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University State Key Laboratory for Geomechanies and Deep Underground Engineering Xuzhou 221008 China a shanghai Tunnel Engineering & Rail Transit Design and Research Institute Shanghai 200235 China

Identifying the morphology of rock blocks is vital to accurate modelling of rock mass structures. This paper applies the concepts of directed edges and vertex chain operations which are typical for block tracing approach to block assembling approach to construct the structure of three-dimensional fractured rock masses. Polygon subtraction and union algorithms that rely merely on vertex chain operation are proposed, which allow a fast and convenient construction of complex faces/loops. Apart from its robustness in dealing with finite discontinuities and complex geometries, the advantages of the current methodology in tackling some challenging issues associated with the morphological analysis of rock blocks are addressed. In particular, the identification of complex blocks with interior voids such as cavity, pit and toms can be readily achieved based on the number and the type of loops. The improved morphology visualization approach can benefit the pre-processing stage when analyzing the stability of rock masses subject to various engineering impacts using the block theory and the discrete element method.

关键词： morphology block assembling vertex operation discontinuities

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Effects of fault zones on failure mechanism of tunnel, an experimental study

Effects of fault zones on failure mechanism of tunnel, an ex...

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China-Europe Conference on Geotechnical engineering, 2016

作者： Vu, Ba Thao Zhu, Hehua Xu, Qianwei Zhuang, Xiaoying Department of Geotechnical Engineering Hydraulic Construction Institute Vietnam Academy for Water Resources Hanoi Viet Nam State Key Laboratory of Disaster Reduction in Civil Engineering College of Civil Engineering Tongji University Shanghai China Urban Rail Transit and Railway Engineering Department Tongji University Shanghai China Institute of Structural Mechanics Leibniz University Hanover Hanover Germany

ISBN: (纸本)9783319971148

This paper presents a large-scale experiment for studying the effects of fault zones on the failure process and failure pattern of tunnel. Firstly, appropriate synthetic materials representing fault zones and rock mass were developed. The mix of fine sand and grease was adopted to model the fault zones. Secondly, an experimental model was then performed to investigate the effects of fault zones on the progressive failure of tunnels. It was found that the presence of fault zones caused the asymmetry of convergent deformations and failure patterns. The fault zone itself failed initially and became a slip surface, which then led to the failure of surrounding rock masses and eventually caused the collapse of the tunnel. Failure mechanisms of tunnels with a fault zone obtained by model tests are helpful for the implementation of optimum support designing. © Springer Nature Switzerland AG 2018.

关键词： Failure (mechanical)

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Experimental Study on Mechanical Properties of Soft Clay under Different Stress Paths

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IOP Conference Series: Earth and Environmental Science 2020年第1期619卷

作者： Yuan Lu Wenhui Ke Xiangguo Huang Mingzhao Xiao Bin Chen Juehao Huang Jian Chen State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 People's Republic of China University of Chinese Academy of Sciences Beijing 100049 People's Republic of China Hubei Key Laboratory of Geo-Environmental Engineering Wuhan 430071 People's Republic of China The Soft Soil Research Center in Ningbo University of Technology State Key Laboratory of Geomechanics and Geotechnical Engineering Ningbo 315211 People's Republic of China Wuhan Municipal Construction Group Co. Ltd Wuhan Hubei 430023 China Ningbo Rail Transit Group Co. Ltd. Ningbo 315040 China.

In actual engineering, when the soil element is subjected to load, the stress state will change accordingly. In this paper, undrained triaxial stress path tests for Ningbo reshaped saturated soft clay under different confining pressures are carried out. The test uses the GDS bidirectional vibrating triaxial instrument. The stress path dependence of saturated soft clay is studied. The stress-strain relationship and undrained shear strength under different stress path conditions are mainly analyzed. The test results show that the stress-strain relationship of the stress path test is obviously non-linear, basically strain hardening. The stress-strain curves of saturated remolded soft clay under different stress paths and consolidation pressures can be expressed in hyperbolic form. The initial stiffness E0 basically increases with the increase of the deflection angle of the stress path. The test results have certain reference significance for foundation pit and tunnel engineering.

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A Novel Approach for Mining Road Information from Low Precision GPS Data

A Novel Approach for Mining Road Information from Low Precis...

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International Conference on Networking and Network Applications (NaNA)

作者： Siqie Zhang Changle Li Xun Zhou State Key Laboratory of Integrated Services Networks Xidian University Xi'an Shaanxi China State Key Laboratory of Rail Transit Engineering Informatization (FSDI) Xi'an China

Road curvature and lane number information (hereinafter to be referred as road information) play an important and necessary role in transportation research. In order to avoid the drawbacks, i.e., high cost and poor time effectiveness, of traditional ways existing to obtain the road information, it has become a hot topic to mine road information through GPS data. In this paper, we propose a novel approach for mining road information from low precision GPS data, which including: a) Analyze and test the distribution of real world GPS data; b) Propose the weighted approximation least squares method (WALSM) to mine the curvature information of the road so as to establish the optimal center line of the road; c) Establish the GPS Data Distribution Variance - Road Width Discrete Model (DV-RWDM) so as to get the road lane number information. We demonstrate our approach using real world low precision GPS data and the results show that we can mine the road information with high accuracy. This provide us a lower cost and high timeliness guideline for the processing and application of low precision GPS data.

关键词： Global Positioning System Roads Gaussian distribution Data mining Least mean squares methods Data models Trajectory

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Dynamic Characteristics of Saturated Soft Clay under Constant Confining Pressure Cyclic Loading

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IOP Conference Series: Earth and Environmental Science 2020年第1期619卷

作者： Yuan Lu Fusheng Liu Youyan Bian Yu Zhong Bin Chen Juehao Huang Jian Chen State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 People's Republic of China University of Chinese Academy of Sciences Beijing 100049 People's Republic of China Hubei Key Laboratory of Geo-Environmental Engineering Wuhan 430071 People's Republic of China The Soft Soil Research Center in Ningbo University of Technology State Key Laboratory of Geomechanics and Geotechnical Engineering Ningbo 315211 People's Republic of China China Railway Siyuan Survey and Design Group Co. Ltd Wuhan Hubei 430063 China Wuhan Metro Group Co. Ltd. Wuhan Hubei 430070 China Ningbo Rail Transit Group Co. Ltd. Ningbo 315040 China.

The research on the dynamic characteristics of soft clay under cyclic loading has high value. This paper takes Ningbo saturated soft clay as the research object and uses the GCTS true triaxial test system to analyze the effects of consolidated confining pressure and cyclic deviator stress on the axial cumulative strain. The experimental results found that when the number of vibrations and the cyclic stress ratio are the same, the axial cumulative plastic strain increases with the increase of the consolidation confining pressure. When the dynamic stress amplitude is the same, the axial cumulative strain decreases with the increase of the consolidation confining pressure. Under different confining pressures, as the number of vibrations increases, the cumulative axial strain increases. The development law of axial cumulative strain under different cyclic stress ratios is inconsistent, and there is a critical cyclic stress ratio. The experimental results provide a certain reference for engineering seismic design.

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Strength of undisturbed and reconstituted frozen soil at temperatures close to 0 ℃

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Research in Cold and Arid Regions 2017年第4期9卷 404-411页

作者： XiaoDong Zhao GuoQing Zhou GuiLin Lu Yue Wu Wei Jiao Jing Yu State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology Xuzhou Jiangsu 221116 China Xuzhou Urban Rail Transit Co. Ltd. Xuzhou Jiangsu 221000 China

The strength of warm frozen soils in permafrost is fundamentally significant to estimate and predict the ground settlements from construction activities. A study was therefore initiated to assess the strength and its behaviors of undisturbed and reconstituted frozen soils at temperatures close to 0 ℃. A series of triaxial compression tests(TCT) were performed by using a developed testing apparatus and a matching specimen-preparation method. The confinement was applied from air pressure, the temperature in the specimen was maintained using two-end refrigeration, and multi-stage loading on a single specimen was adopted to determine the strength. The test results showed that the strength, both for the undisturbed and reconstituted frozen-soil specimens, was significantly dependent on the temperatures and independent of the applied confining pressures. Additionally, the strength of undisturbed frozen soils was about 1.6 times more than that for reconstituted frozen soils. These observations were closely associated with the structures existing between pore-ice and gravels with large diameters.

关键词： warm frozen soils strength behaviors undisturbed specimen

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Research for the Influence of Inlet Gas Humidification on PEMFC

Research for the Influence of Inlet Gas Humidification on PE...

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2017 2nd International Conference on Applied Mechanics and Mechatronics engineering(AMME 2017)

作者： Lei FAN Yong-feng LIU Pu-cheng PEI Sheng-zhuo YAO Fang WANG Beijing Key Laboratory of Performance Guarantee on Urban Rail Transit Vehicles School of Mechanical-electronic and Automobile Engineering Beijing University of Civil Engineering and Architecture State Key Laboratory of Automotive Safety and Energy Tsinghua University

In order to study the influence of inlet gas humidification on the performance of proton exchange membrane fuel cell（PEMFC）, a new inlet gas humidification efficiency（IGHE） model is proposed. Two parts including the water content of inlet gas humidification and the water content produced by electrochemical reaction consist of the total water content of PEM. The inlet gas humidification efficiency is derived. Firstly, the flow chart of calculation was given. Secondly, the experimental system was established and experiments had been done at the operating temperature of 70 ℃ and at 40% RH, 55% RH, 70% RH and 85% RH, respectively. Finally, the polarization curves of the IGHE model and experimental were compared and analyzed at 85% RH. The results show that the difference of experimental and IGHE model is minimum（0.03 V） at 85% RH when the current density of PEMFC is 250 mA/cm.

关键词： Inlet gas humidification PEMFC Relative humidity Polarization curve

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Rheological Behaviors of Fresh Cement Pastes with Polycarboxylate Superplasticizer

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Journal of Wuhan University of Technology(Materials Science) 2016年第2期31卷 286-299页

作者：张艳荣孔祥明高亮 WANG Jiaxin State Key Lab of Rail Traffic Control and Safety School of Civil Engineering beijing Jiaotong University beijing 100044 China Department of Civil Engineering Tsinghua University Beijing 100084 China beijing Key Laboratory of Track Engineering beijing Engineering and Technology Research Center of Rail Transit Line Safety and Disaster Prevention Beijing Jiaotong University Beijing 100044 China

The rheologicalbehaviors of fresh cement paste with polycarboxylate superplasticizer were systematically *** including superplasticizer to cement ratio（Sp/C）,water to cement ratio（w/c）,temperature,and time were *** cement pastes with Sp/Cs in the range of 0 to 2.0% and varied W/Cs from 0.25 to 0.5 were prepared and tested at 0,20 and 40 °C,*** and rheologicaltests on cement pastes were conducted to characterize the development of the rheologicalbehavior of fresh cement pastes over *** exprimentalresults indicate that the initialflowability and flowability retention over shelf time increase with the growth in superplasticizer dosage due to the plasticizing effect and retardation effect of *** temperature usually leads to a sharper drop in initialflowability and flowability ***,for the cement paste with high Sp/C or w/c,the flowability is slightly affected by *** stress and plastic viscosity show similar variation trends to the flowability under the abovementioned influentialfactors at low Sp/*** the case of high Sp/C,yield stress and plastic viscosity start to decline over shelf time and the decreasing rate descends at elevated ***,two equations to roughly predict yield stress and plastic viscosity of the fresh cement pastes incorporating Sp/C,w/c,temperature and time are developed on the basis of the existing models,in which experimentalconstants can be extracted from a database created by the rheologicaltest results.

关键词： cement paste flowability yield stress plastic viscosity model

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Acoustic emission characterization of frozen sandstone in compression test 50

Acoustic emission characterization of frozen sandstone in co...

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50th US Rock Mechanics / Geomechanics Symposium 2016

作者： Liu, Bo Zhang, Gong Xu, Wei Liu, Lulu School of Mechanics and Civil Engineering China University of Mining and Technology Beijing China State Key Laboratory of Deep Geomechanics and Underground Engineering Beijing China General Contract Department of Rail Transit and Municipal Engineering Beijing Uni-Construction Group Co Ltd. Beijing China

ISBN: (纸本)9781510828025

Artificial freezing has been proved to be an effective method and technology to prevent water seepage and shaft flooding accidents in soft water-rich rock strata in western area of China. Many studies have been undertaken using frozen rocks to understand the mechanical and physical properties as well as their degradation mechanisms. However, the existing researches on the real-time dynamic damage process of frozen rocks are very limited, so that the damage mechanisms of frozen rock under compressive loading condition remain unknown. In this study, acoustic emission (AE) method and digital microscope were adopted to study the mechanical properties and microstructure of sandstone samples taken from Meilin Temple Mines at depth of 700 m in Ordos, China. The uniaxial compression tests were performed at four different sub-zero temperatures. The AE signals (e.g., energy) were recorded during freezing and loading processes at negative temperatures. The results showed that AE activities mainly occurred in the initial freezing phase and reduced afterwards. In the uniaxial compression test, AE signals were also observed in the initial loading stage, while no obvious results was observed from rock samples in room temperature. Based on the monitored acoustic emission data, the internal micro-crack change of frozen sandstone was revealed and the damage process was analyzed to evaluate the real state of frozen sandstone at the shaft construction site.

关键词： Freezing

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Modelling and optimisation of train electric drive system based on fuzzy predictive control in urban rail transit

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International Journal of Simulation and Process Modelling 2016年第5期11卷 363-373页

作者： Huang, Yeran Cao, Fang Ke, Bwo-Ren Tang, Tao State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing Laboratory of Urban Mass Transit Beijing Key Laboratory of Urban Mass Transit Automation and Control China Department of Electrical Engineering National Penghu University of Science and Technology Penghu880 Taiwan

This paper establishes an elaborate model of train electric drive system to simulate the train operation process. The transmission loss and train length are taken into account when calculating voltage of contact line and resistance force with equivalent slope. Considering the influence of voltage and slope variation on control performance, we propose original model original control with fixed voltage (OMOC-FV) and original model original control with slope (OMOC-S) to compare with the most commonly used PI control method, i.e., modified model original control (MMOC). Moreover, focusing on variable parameters and complex dynamics of induction motor, a fuzzy predictive control method, called modified model modified control (MMMC), is proposed to track the target speed profile accurately and to achieve the voltage stability. The effectiveness of elaborate model and the performance of MMMC are evaluated based on the data of Beijing Yizhuang line. © 2016 Inderscience Enterprises Ltd.

关键词： Induction motors

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