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  • 3051.
    Yi, Xiaoping
    Luleå tekniska universitet.
    Fracture toughness and crack growth in short rod specimens of rocks1987Licentiate thesis, monograph (Other academic)
  • 3052.
    Yi, Xiaoping
    et al.
    Central South University of Technology, Changsha.
    Sun, Zongqi
    Central South University of Technology, Changsha.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stephansson, Ove
    Kungliga tekniska högskolan, KTH.
    Fracture toughness of Kallax gabbro and specimen size effect1991In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 28, no 2/3, p. 219-223Article in journal (Refereed)
  • 3053.
    Yi, Xiaoping
    et al.
    Laurentian University.
    Sun, Zongqi
    Central South University of Technology, Changsha.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stephansson, Ove
    Luleå tekniska universitet.
    Specimen size effect of the fracture toughness of Kallax gabbro1992In: Rock mechanics: proceedings of the 33rd U.S. Symposium, Sweeney Convention Center, Santa Fe, New Mexico 3 - 5 June 1992 / [ed] J R Tillerson; W Waversik, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1992, p. 847-856Conference paper (Refereed)
  • 3054.
    Yin, Ying
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Feng, Xiaoxing
    A Comparative study with Swedish and China’s Eco-cities: From planning to implementation, taking the Hammarby Sjöstad, Sweden, and Wuxi Sino-Swedish Eco-City, China, as cases2012In: Natural Resources And Sustainable Development II, Pts 1-4, Trans Tech Publications Inc., 2012, Vol. 524-527, p. 2741-2750Conference paper (Refereed)
    Abstract [en]

    This paper targets to improve understanding and explain influential factors of different planning and implementing process of two eco-cities, Hammarby Sjöstad, Sweden, and Sino-Swedish Low-carbon Eco-city, China. The study is approached by examining and comparing the two eco-cities in perspectives of plans formulation, policy and regulations foundation, planning management and implementing mechanisms. Lessons from Hammarby Sjöstad are that integrative planning and management, follow-up and evaluations of implementing results, and lifestyle transitions all need to be concerned, as well as environmental technologies. In Sino-Swedish lowcarbon eco-city, lack of local technologies, supporting policies and regulations, inactive cross-sector cooperation and public participation are summarized as main obstacles. To approach these, efforts are made on formulating local regulations, government documents, and coordinating cross-sector cooperation, promoting mutual learning. Finally, concluding that, besides environmental technologies, the foundation of legislations, policies and environmental objectives, integrative approaches, public awareness are key areas need to be promoted for popularizing sustainability in China.

  • 3055.
    Yiu, Benjamin
    et al.
    Western Australian School of Mines, Kalgoorlie.
    Halim, Adrianus
    Western Australian School of Mines, Kalgoorlie.
    Selection of Haulage Fleet at Daisy Milano Gold Mine2014In: Mining Education Australia (MEA) Journal of Research Projects Review, ISSN 2203-529X, Vol. 3, no 1, p. 69-76Article in journal (Refereed)
    Abstract [en]

    In the underground mining industry, one of the long-term operational issues involves longer haulage routes as the mine gets deeper with the life of mine. This longer travel route has a great impact on the productivity and cost of the operation. Choosing the best haulage fleet will result in improved productivity and lower cost per tonne of material moved. For this reason, it has motivated Daisy Milano Gold Mine, owned by Silver Lake Resources, to analyse their current Toro 50 Plus trucks against the Atlas Copco MT5010 truck. During a three month trial of both haulage options, trucking parameters were collected from a specifically designed trucking plod.This research used a time motion study to perform productivity calculations and cost analysis of the two haulage options.Based on the assumptions made in this research, the conclusion is that the Atlas Copco MT5010 should be utilised as the preferred truck option at Daisy Milano. The Atlas Copco MT5010 has a higher average productivity of 254 tkm/hr tonnes kilometre per hour) compared to the Toro 50 Plus with an average productivity of 160 tkm/hr. In terms of cost ($ per tkm) the MT5010 is the cheaper option by over 35 per cent when compared to the Toro 50 Plus ($0.85 versus $1.31).

  • 3056.
    Yosef Nezhad Arya, Nessa
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Second-order FE Analysis of Axial Loaded Concrete Members According to Eurocode 22015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A nonlinear finite element analysis was performed for an axial loaded reinforced concrete column subjected to biaxial bending taking into account second-order effects. According to Eurocode there are two ways to take second-order effects into consideration: nonlinear FE analysis and hand calculation based on the simplified methods explained in Eurocode 2. Since simulating this kind of structures in ABAQUS is difficult, several simulations were made to find the correct model with satisfying accuracy.

    The nonlinear analysis focused on material modelling of concrete and its nonlinear behaviour. The simulation took into consideration the inelastic behaviour of concrete along with the confinement effect from transverse reinforcement.

    The finite element model was verified by comparing the obtained results from FEA to the results from a benchmark experiment. The mean values needed for simulating the FE model was derived from the mean compressive strength of concrete. After verification, another FE model using design parameters was analysed and the results were compared to the results from calculations based on simplified methods according to Eurocode 2 to see how much they agreed with each other. In a parametric study, the effect of eccentricity, compressive and tensile strength of concrete, fracture energy, modulus of elasticity, column cross-section dimension and length, steel yield stress and stirrup spacing were studied.

    A comparison between outcomes from the simplified methods and ABAQUS, calculated with design parameters showed that the bearing capacity from FE analysis was 21-34 % higher than the one obtained with the simplified methods. It is recommended that in further studies, analyse different slender reinforced concrete column with different L/h with FE-simulation to investigate if FEA always gives a more accurate result. For this case, and probably for columns with complex geometries, a finite element analysis is a better choice. 

  • 3057.
    Yu, Huan
    et al.
    School of Reliability and Systems Engineering, Beihang University.
    Yang, Jun
    School of Reliability and Systems Engineering, Beihang University.
    Lin, Jing (Janet)
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Zhao, Yu
    School of Reliability and Systems Engineering, Beihang University.
    Reliability evaluation of non-repairable phased-mission common bus systems with common cause failures2017In: Computers & industrial engineering, ISSN 0360-8352, E-ISSN 1879-0550, Vol. 111, p. 445-457Article in journal (Refereed)
    Abstract [en]

    Phased-mission common bus (PMCB) systems are systems with a common bus structure, performing missions with consecutive and non-overlapping phases of operations. PMCB systems are found throughout industry, e.g., power generating systems, parallel computing systems, transportation systems, and are sometimes characterized by their common cause failures. Reliability evaluation of PMCB systems plays an important role in system design, operation, and maintenance. However, current studies have focused on either phased-mission systems or common bus systems because of their complexity. The challenge in practice is to consider phased-mission systems together with common bus structures and common cause failures. To solve this problem, we propose an evaluation algorithm for PMCB systems with common cause failures by coupling the structure function of a common bus performance sharing system and an existing recursive algorithm. To weigh the efficiency of the proposed algorithm, its complexity is discussed. To improve the reliability of PMCB systems, we adopt the genetic algorithm method to search for the optimal allocation strategies of the service elements. We use both analytical and numerical examples to illustrate the application of the proposed algorithm.

  • 3058.
    Zakirov, Artur
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Zakirov, Timur
    Mälardalen University, School of Business, Society and Engineering.
    Fire risk assessment of a single exit metro station: Evacuation, fire and rescue perspective2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work aims to evaluate the risks at the single exit metro station Zinkensdamm with regard to evacuation and possibilities for fire and rescue operation. The work also includes a comparison of the same station having two exits. The results from the newly-conducted METRO-project were used as the starting point for the evaluation. The report is based on a comprehensive literature review on single exit underground stations and their potential hazards. The evaluation was conducted by comparing the time available for evacuation with the time at which critical conditions occur in case of fire. The results show that for the chosen fire scenario a successful evacuation cannot always be guaranteed. Based on the results, different measures are suggested to improve the fire safety inside the station, such as further improving the train cars' furnishings and installing a sprinkler system in the track area or inside the train cars.

  • 3059.
    Zalejska-Jonsson, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Building and Real Estate Economics.
    In the Business of Building Green: The value of low-energy residential buildings from customer and developer perspectives2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An overarching aim of this research was to investigate the comprehensive value of green residential buildings as seen from two perspectives: that of the developer and that of the occupant (the customer). The dissertation consists of studies presented in seven papers.  The studies conducted to investigate the developer’s perspective focused on construction cost and potential profit (papers I and VII). The customer’s perspective was examined with three approaches: the impact that energy and environment have on the decision to purchase (or rent) an apartment (paper V), willingness to pay for a green apartment (paper VI) and finally, the occupants’ satisfaction with the dwelling and indoor environment (papers II, III and IV). 

    The first paper examines whether increased investment costs are profitable, taking into account the reduction in operating costs. The investment viability is approached by comparing investment in conventional and green residential building, particularly passive houses, using real construction and post-occupancy conditions. The increased investment costs in energy-efficient building were also the focus of paper VII. In this paper, the aim was to study how technologies used in energy-efficient residential building construction affect the available saleable floor area and how this impacts on the profitability of the investment. Potential losses and gains of saleable floor area in energy-efficient buildings were assessed using a modelled building and analysed with the help of the average construction cost.

    Papers II and IV present results from a study of occupants’ satisfaction and indoor environmental qualities. Both papers aim at comparing and analysing responses from occupants living in green and conventional buildings. Paper III focuses on a similar subject, but investigates occupants’ satisfaction among all adults living in multi-family buildings in Sweden, providing a national context for the results presented in papers II and IV. The results indicate that occupants are generally satisfied with their dwellings, but indoor environment proved to have a statistically significant effect on overall satisfaction.

    The results in paper V indicate that energy and environmental factors have a minor impact on customers’ decision to purchase or rent an apartment. However, availability of information on building energy and environmental performance may have an effect on the likelihood of the buyers’ being interested in environmental qualities and consequently an impact on their decision. The study presented in paper VI shows that customer interest in energy and environmental factors has a significant impact on stated willingness to pay for green dwellings. The paper discusses the stated willingness to pay for low-energy buildings and buildings with an environmental certificate and attempts to assess the rationale of the stated willingness to pay for low-energy dwellings given potential energy savings.

  • 3060.
    Zandi, Maryam
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Estimating Nighttime and Daytime PopulationsUsing Space Syntax: A Case Study of the Greater Copenhagen Area2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Space syntax uncovers hidden perspectives on geographic spaces and facilitates the study of the structure and form of spaces. Correlations of the human movement and space configurations are interesting observations revealed by space syntax. Much research demonstrates that urban configurations can affect the distribution of human flows in space and even form of land use patterns. The high correlation between the human movement and space structures can lead to the hypothesis that through this high correlation, it is possible to obtain information about a particular type of human activity and the number of people in a region. The present research investigates this possibility and tries to generate models for predicting the number of people who live in a region and the number of people who work in that region.

    The project takes a street network and calculates the space syntax’s measures and length of the streets. Based on regional boundaries in which the measures are located, sum, average, maximum and minimum of all measures are computed and assigned to the related regions. Next, correlations between them and nighttime (the number of people who live in the region) and daytime (the number of people who work in the region) populations are calculated. The significance test is run to check if the calculated correlations are real. From the significant correlations, the measures with high correlations are selected for the regression analyses and different regression models are generated. Finally the project selects the model which has 79% correspondence with the population counts as the result.

    The main application of this method is in Location-Based Services (LBS) which collect users’ trajectories via mobile positioning and communication technologies. However, hidden information in trajectories can be abused and can threaten the privacy and security of the users. Indeed this research is a preface for a new approach for trajectory anonymization. The method - based on the street network properties - counts the number of people that live in a region and work in another, to construct regions for the user such that the count is above a threshold then it cloaks the user’s trajectory within the constructed regions.  

  • 3061.
    Zhang, J.
    et al.
    Northeastern University at Qinhuangdao.
    Tang, C.
    School of Civil and Hydraulic Engineering, Dalian University of Technology.
    Kou, S.
    Luleå tekniska universitet.
    Liang, Z.
    School of Civil and Hydraulic Engineering, Dalian University of Technology.
    Xu, T.
    School of Civil and Hydraulic Engineering, Dalian University of Technology.
    Mechanism of periodically distributed fracture in reinforced concrete beam under uniaxial tension2007In: Yingyong Lixue Xuebao, ISSN 1000-4939, Vol. 24, no 4, p. 646-651Article in journal (Refereed)
    Abstract [en]

    A numerical code RFPA3D(Three-Dimension Realistic Failure Process Analysis) is employeel to simulate the three-dimensional failure process of reinforced concrete under uniaxial tension. Then the analysis focuses on the stress distribution during the failure process and failure mechanism of the concrete and reinforcement. The numerical tests indicate the periodically distributed fracture in the reinforced concrete structure and the numerical analysis reproduces the complete process of the fracture initiation, infilling and saturation, 3D numerical tests with different thickness of concrete covers reveal that the eritical value of the fracture spacing increases and the crack numbers decreases with increasing ratio of the thickness of the concrete cover to that of the steel bar

  • 3062.
    Zhang, Liangwei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    An Approach of Big Data Analytics for Fault Detection2014In: Newsletter of European Safety and Reliability Association, p. 3-5Article in journal (Other (popular science, discussion, etc.))
  • 3063.
    Zhang, Liangwei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Big Data Analytics for eMaintenance: Modeling of high-dimensional data streams2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Big Data analytics has attracted intense interest from both academia and industry recently for its attempt to extract information, knowledge and wisdom from Big Data. In industry, with the development of sensor technology and Information & Communication Technologies (ICT), reams of high-dimensional data streams are being collected and curated by enterprises to support their decision-making. Fault detection from these data is one of the important applications in eMaintenance solutions with the aim of supporting maintenance decision-making. Early discovery of system faults may ensure the reliability and safety of industrial systems and reduce the risk of unplanned breakdowns. Both high dimensionality and the properties of data streams impose stringent challenges on fault detection applications. From the data modeling point of view, high dimensionality may cause the notorious “curse of dimensionality” and lead to the accuracy deterioration of fault detection algorithms. On the other hand, fast-flowing data streams require fault detection algorithms to have low computing complexity and give real-time or near real-time responses upon the arrival of new samples. Most existing fault detection models work on relatively low-dimensional spaces. Theoretical studies on high-dimensional fault detection mainly focus on detecting anomalies on subspace projections of the original space. However, these models are either arbitrary in selecting subspaces or computationally intensive. In considering the requirements of fast-flowing data streams, several strategies have been proposed to adapt existing fault detection models to online mode for them to be applicable in stream data mining. Nevertheless, few studies have simultaneously tackled the challenges associated with high dimensionality and data streams. In this research, an Angle-based Subspace Anomaly Detection (ABSAD) approach to fault detection from high-dimensional data is developed. Both analytical study and numerical illustration demonstrated the efficacy of the proposed ABSAD approach. Based on the sliding window strategy, the approach is further extended to an online mode with the aim of detecting faults from high-dimensional data streams. Experiments on synthetic datasets proved that the online ABSAD algorithm can be adaptive to the time-varying behavior of the monitored system, and hence applicable to dynamic fault detection.

  • 3064.
    Zhang, Liangwei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Big Data Analytics for Fault Detection and its Application in Maintenance2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Big Data analytics has attracted intense interest recently for its attempt to extract information, knowledge and wisdom from Big Data. In industry, with the development of sensor technology and Information & Communication Technologies (ICT), reams of high-dimensional, streaming, and nonlinear data are being collected and curated to support decision-making. The detection of faults in these data is an important application in eMaintenance solutions, as it can facilitate maintenance decision-making. Early discovery of system faults may ensure the reliability and safety of industrial systems and reduce the risk of unplanned breakdowns.

    Complexities in the data, including high dimensionality, fast-flowing data streams, and high nonlinearity, impose stringent challenges on fault detection applications. From the data modelling perspective, high dimensionality may cause the notorious “curse of dimensionality” and lead to deterioration in the accuracy of fault detection algorithms. Fast-flowing data streams require algorithms to give real-time or near real-time responses upon the arrival of new samples. High nonlinearity requires fault detection approaches to have sufficiently expressive power and to avoid overfitting or underfitting problems.

    Most existing fault detection approaches work in relatively low-dimensional spaces. Theoretical studies on high-dimensional fault detection mainly focus on detecting anomalies on subspace projections. However, these models are either arbitrary in selecting subspaces or computationally intensive. To meet the requirements of fast-flowing data streams, several strategies have been proposed to adapt existing models to an online mode to make them applicable in stream data mining. But few studies have simultaneously tackled the challenges associated with high dimensionality and data streams. Existing nonlinear fault detection approaches cannot provide satisfactory performance in terms of smoothness, effectiveness, robustness and interpretability. New approaches are needed to address this issue.

    This research develops an Angle-based Subspace Anomaly Detection (ABSAD) approach to fault detection in high-dimensional data. The efficacy of the approach is demonstrated in analytical studies and numerical illustrations. Based on the sliding window strategy, the approach is extended to an online mode to detect faults in high-dimensional data streams. Experiments on synthetic datasets show the online extension can adapt to the time-varying behaviour of the monitored system and, hence, is applicable to dynamic fault detection. To deal with highly nonlinear data, the research proposes an Adaptive Kernel Density-based (Adaptive-KD) anomaly detection approach. Numerical illustrations show the approach’s superiority in terms of smoothness, effectiveness and robustness.

  • 3065.
    Zhang, Liangwei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Dynamic fault detection from high-dimensional data streams2015In: Newsletter of European Safety and Reliability Association, no June, p. 2-4Article in journal (Other (popular science, discussion, etc.))
  • 3066.
    Zhang, Liangwei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Karim, Ramin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Big Data Mining in eMaintenance: An Overview2014In: Proceedings of the 3rd international workshop and congress on eMaintenance: June 17-18 Luleå, Sweden : eMaintenance, Trends in technologies & methodologies, challenges, possibilites and applications / [ed] Uday Kumar; Ramin Karim; Aditya Parida; Philip Tretten, Luleå: Luleå tekniska universitet, 2014, p. 159-170Conference paper (Refereed)
    Abstract [en]

    Maintenance related data are tending to be increasingly huge involume, rapid in velocity and vast in variety. Data with thesecharacteristics bring new challenges with respect to data analysisand data mining, which requires new approaches andtechnologies. In industry, related research and applications, somecontributions have been provided to utilize Big Data technologiesfor extraction of information through pattern recognitionmechanisms via eMaintenance solutions. Today, the existingcontributions are not enabling a holistic approach for maintenancedata analysis and therefore are insufficient. However, theimmense value hidden inside the Big Data in eMaintenance isarousing more and more attention from both academia andindustry. Hence, this paper aims to explore eMaintenancesolutions for maintenance decision-making through utilization ofBig Data technologies and approaches. The paper discusses BigData mining in eMaintenance through a general manner byemploying one of the widely accepted frameworks with the nameof Cross Industry Standard Process for Data Mining (CRISPDM).In addition, the paper outlines features of maintenance dataand investigates six sub-processes (i.e. business understanding,data understanding, data preparation, modeling, evaluation anddeployment) of data mining applications defined by CRISP-DMwithin the domain of eMaintenance.

  • 3067.
    Zhang, Liangwei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lin, Janet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Karim, Ramin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Adaptive Kernel Density-based Anomaly Detection for Nonlinear Systems2018In: Knowledge-Based Systems, ISSN 0950-7051, E-ISSN 1872-7409, Vol. 139, no 1, p. 50-63Article in journal (Refereed)
    Abstract [en]

    This paper presents an unsupervised, density-based approach to anomaly detection. The purpose is to define a smooth yet effective measure of outlierness that can be used to detect anomalies in nonlinear systems. The approach assigns each sample a local outlier score indicating how much one sample deviates from others in its locality. Specifically, the local outlier score is defined as a relative measure of local density between a sample and a set of its neighboring samples. To achieve smoothness in the measure, we adopt the Gaussian kernel function. Further, to enhance its discriminating power, we use adaptive kernel width: in high-density regions, we apply wide kernel widths to smooth out the discrepancy between normal samples; in low-density regions, we use narrow kernel widths to intensify the abnormality of potentially anomalous samples. The approach is extended to an online mode with the purpose of detecting anomalies in stationary data streams. To validate the proposed approach, we compare it with several alternatives using synthetic datasets; the approach is found superior in terms of smoothness, effectiveness and robustness. A further experiment on a real-world dataset demonstrated the applicability of the proposed approach in fault detection tasks.

  • 3068.
    Zhang, Liangwei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lin, Janet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Karim, Ramin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    An Angle-based Subspace Anomaly Detection Approach to High-dimensional Data: With an Application to Industrial Fault Detection2015In: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 142, p. 482-497Article in journal (Refereed)
    Abstract [en]

    The accuracy of traditional anomaly detection techniques implemented on full-dimensional spaces degrades significantly as dimensionality increases, thereby hampering many real-world applications. This work proposes an approach to selecting meaningful feature subspace and conducting anomaly detection in the corresponding subspace projection. The aim is to maintain the detection accuracy in high-dimensional circumstances. The suggested approach assesses the angle between all pairs of two lines for one specific anomaly candidate: the first line is connected by the relevant data point and the center of its adjacent points; the other line is one of the axis-parallel lines. Those dimensions which have a relatively small angle with the first line are then chosen to constitute the axis-parallel subspace for the candidate. Next, a normalized Mahalanobis distance is introduced to measure the local outlier-ness of an object in the subspace projection. To comprehensively compare the proposed algorithm with several existing anomaly detection techniques, we constructed artificial datasets with various high-dimensional settings and found the algorithm displayed superior accuracy. A further experiment on an industrial dataset demonstrated the applicability of the proposed algorithm in fault detection tasks and highlighted another of its merits, namely, to provide preliminary interpretation of abnormality through feature ordering in relevant subspaces.

  • 3069.
    Zhang, Liangwei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lin, Janet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Karim, Ramin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sliding Window-based Fault Detection from High-dimensional Data Streams2017In: IEEE Transactions on Systems, Man & Cybernetics. Systems, ISSN 2168-2216, Vol. 47, no 2, p. 289-303, article id 7509594Article in journal (Refereed)
    Abstract [en]

    High-dimensional data streams are becoming increasingly ubiquitous in industrial systems. Efficient detection of system faults from these data can ensure the reliability and safety of the system. The difficulties brought about by high dimensionality and data streams are mainly the ``curse of dimensionality'' and concept drifting, and one current challenge is to simultaneously address them. To this purpose, this paper presents an approach to fault detection from nonstationary high-dimensional data streams. An angle-based subspace anomaly detection approach is proposed to detect low-dimensional subspace faults from high-dimensional datasets. Specifically, it selects fault-relevant subspaces by evaluating vectorial angles and computes the local outlier-ness of an object in its subspace projection. Based on the sliding window strategy, the approach is further extended to an online mode that can continuously monitor system states. To validate the proposed algorithm, we compared it with the local outlier factor-based approaches on artificial datasets and found the algorithm displayed superior accuracy. The results of the experiment demonstrated the efficacy of the proposed algorithm. They also indicated that the algorithm has the ability to discriminate low-dimensional subspace faults from normal samples in high-dimensional spaces and can be adaptive to the time-varying behavior of the monitored system. The online subspace learning algorithm for fault detection would be the main contribution of this paper.

  • 3070.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    A 3DEC numerical analysis of the interaction between uneven rock surface and shotcrete lining: Validation of physical model and evaluation of influence of unevenness on the support effect of shotcrete2013Report (Other academic)
    Abstract [en]

    Although shotcrete (sprayed concrete) has been widely used as rock support in mines and in civil engineering projects, the complex interaction between shotcrete and rock has not been studied well. The main reason is that the performance of shotcrete is influenced by a number of important parameters.Experiences from previous research and past projects show that the unevenness of rock surface has a large impact on the number of failures at the interface and in the lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. Although people have done some experimental and numerical analysis, the influence of the complex unevenness of three dimensional shaped surfaces on the shotcrete – rock interaction has not been well studied.The project here focuses on the influence of the surface unevenness of a circular opening on the support effect of shotcrete. The work was done by using a 3D numerical simulation (3DEC) and was conducted in two stages. In stage 1, the numerical model was validated by comparing with physical model tests by Chang (1994). In stage 2, based on the well validated numerical model, the influence of unevenness on the support effect of shotcrete was further investigated.

  • 3071.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hansen-Haug, Jouni
    Lundin Mining.
    Woldemedhin, Biruk
    LKAB.
    Töyrä, Jimmy
    LKAB.
    Boskovic, Mirjana
    LKAB.
    Nyström, Anders
    Boliden.
    Marklund, Per-Ivar
    Boliden.
    Mozaffari, Shahram
    Boliden.
    Establishment of experimental sites in three Swedish mines to monitor the in-situ performance of ground support systems associated with mining-induced seismicity2016In: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E . N ordlund, T.H. Jones and A. Eitzenberger (eds), 2016Conference paper (Refereed)
    Abstract [en]

    In order to assess the performance of ground support components and systems when subjected to seismic activity and strong ground motion, Luleå University of Technology together with three Swedish mining companies (Lundin Mining, LKAB and Boliden) started a three year research project in September 2014. The aim of the project is to develop new methods for evaluating the rock support performance in-situ that use all available information about i) the source of the seismic event (obtained from the seismic network in the mine and additional seismic sensors), ii) seismic loading (ground motion) recorded by temporary local seismic networks, and iii) the consequences of the seismic loading in terms of damage to the underground excavations and the rock support.The sites with high potential of seismic damage were defined after the historical damaging seismic events were reviewed and the mining-induced stress disturbance was investigated with 3D numerical models. As of 31 December 2015, four sites in three different mines have been instrumented. Geophones (in depth and at surface), multi-points extensometers and instrumented bolts were installed to monitor the ground motion, the deformation of the rock mass and the elongation of the bolts. Observation boreholes were drilled to investigate the rock lithology, structures as well as fracture distribution and development. The data from locally installed geophones will be integrated with seismic data recorded by the mine-wide network. For each monitoring point, all of the instruments and observation boreholes were located at very close area within 0.5-1 m distance from each other. These results will be used to establish the relationship between the dynamic loading and the response of rock mass and rock bolts. Additionally, laser scanning is used to measure the surface deformation of the whole volume of instrumented sites with time. Two damaging seismic events occurred near the instrumented sites after the instruments were installed and the results of site investigation show that installed instruments have captured the response of the rock mass and bolts due to production blasting and seismic events.

  • 3072. Zhang, Ping
    et al.
    Li, Ning
    Xi'an University of Technology.
    Li, Xibing
    School of Resources and Safety Engineering, Central South University, Changsha.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Compressive failure model for brittle rocks by shear faulting and its evolution of strength components2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 5, p. 830-841Article in journal (Refereed)
    Abstract [en]

    A physical theory for brittle failure is presented that aims to explain both the phenomenological and micro-structural observations. The objective of this model is to capture the important attributes inferred from micro-structural experiments so as to arrive at constitutive relations that describe macroscopic failure behaviour. Based on experimental results, the micromechanical failure character- isation is summarised first. The localised failure process of rock will experience two stages: the brittle breakage stage (bond rupture of rock bridge) and the sliding stage (frictional resistance of failure plane mobilisation). A physical model is developed by dividing the sample into elastic and localised shear zones. Furthermore, the deformation process of the localised shear zone is divided into bond loss and frictional resistance mobilisation in two stages. To combine the micro-characteristics with the macromechanical properties, the chain models in localised shear zone, and the homogenisation method are adopted. The model is validated against the experimental data of Yumlu and Ozbay's. Subsequently, the localised progressive failure characteristics of rock are analysed by changing the model's parameters. The intrinsic effects and influential factors such as geometrical effects (size effect, shape effect), the strain softening phenomenon and Class II stress-strain curves are revealed. Finally, in order to be used easily by engineers, the simplified description of rock failure process and its evolution of strength components are given based on the model.

  • 3073.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mikromechanical modeling of fire-induced thermal damae in a laboratory model tunnel2015Conference paper (Other academic)
  • 3074.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mainali, Ganesh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, Christine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jansson, Robert
    SP Sveriges Tekniska Forskningsinstitut.
    Experimental study of thermal spalling on rock blocks exposed to different fire/heating conditions2011In: Bergmekanikdag 2011: Föredrag, Stiftelsen bergteknisk forskning - Befo , 2011, p. 53-63Conference paper (Other academic)
  • 3075.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mainali, Ganesh
    Saiang, Christine
    Jansson, Robert
    SP Technical Research Institute of Sweden.
    Adl-Zarrabi, Bijan
    SP Technical Research Institute of Sweden.
    Experimental study on thermal spalling of rock blocks exposed to fire2010In: Bergmekanikk i Norden 2010 = Rock mechanics in the Nordic countries 2010 / [ed] Charlie C. Li, Kongsberg, Norway, 9.-12. June 2010, 2010, p. 294-305Conference paper (Refereed)
  • 3076.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Swan, Graham
    Rock Mechanics and Mine Design.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    1D numerical simulation of velocity amplification of P-waves travelling through fractured rock near a free surface2015In: The Southern African Journal of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 1543-9518, Vol. 115, no 11, p. 1121-1126Article in journal (Refereed)
    Abstract [en]

    The most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four-to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time. In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0-3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion

  • 3077.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yi, Changping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzadegan, Shahin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Nordqvist, Anders
    LKAB.
    Numerical back-analysis of simulated rockburst field tests by using coupled numerical technique2013In: Ground Support 2013: Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction / [ed] Yves Potvin; B.G.H. Brady, Perth, Australia: Australian Center for Geomechanics , 2013, p. 565-581Conference paper (Refereed)
    Abstract [en]

    In order to assess the capacity of ground support systems when submitted to dynamic loading, simulated rockburst tests utilizing blasting have been performed for many years in different countries with limited success. In general, the blasts need to be carefully designed in order to reach the goal; however, different blast layouts (e.g. blasthole angle, burden) have been used based on researcher’s experience without conducting detailed analyses, the exception being a field test by CSIR. Recently, field trials have been conducted at the LKAB Kiirunavaara underground mine with some unexpected results which show that either the whole tested panel was destroyed or only a few fractures were formed without any ejections being observed. The aim of this paper is to investigate the failure mechanism in the simulated rockburst tests and improve the blast design by back-analyzing the test results using a coupled numerical modeling technique. The blast was simulated by using finite element method (LS-DYNA) and the dynamic interaction between the blasting generated waves and the opening was simulated by using discrete element modeling (UDEC) with the dynamic input from LS-DYNA. The numerical modeling showed that blasting can create both radial fractures radiating from the blasthole and fractures parallel or sub-parallel to the surface of the tested panel caused by reflected tensile stress waves. By comparing the results of the numerical modeling with the measured data, it is shown that the collapse failure was mainly controlled by the creation of a cone-shaped area formed by radial fractures and the burden seems to be a critical factor. In order to obtain fractures caused by reflected tensile stress waves and reduce blasting induced radial fractures, 2 parallel blastholes are suggested with larger burden (> 5 m) for future tests. Furthermore, the limitation of the current numerical modeling has also been discussed. The coupled numerical technique has shown its advantage when simulating blasting as well as interaction between waves and opening and it can thus be used as a tool for extrapolating results from simulated rockburst experiments if detailed geological structure and ground support system can be incorporated in the model and the model can be well calibrated.

  • 3078. Zhang, Ping
    et al.
    Yin, J.J.
    Hunan University.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Li, N.
    Xi'an University of Technology.
    Determination and verification of the longitudinal deformation profile in a horse-shoe shaped tunnel using two-stage excavation2008In: MassMin 2008: Proceedings of the 5th International Conference and Exhibition on Mass Mining, Lulea, Sweden 9-11 June 2008 / [ed] Håkan Schunnesson; Erling Nordlund, Luleå: Luleå tekniska universitet, 2008, p. 845-854Conference paper (Refereed)
  • 3079.
    Zhang, Z. X.
    et al.
    Luleå tekniska universitet.
    Kou, S. Q.
    Luleå tekniska universitet.
    Jiang, L. G.
    University of Science and Technology, Beijing.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of loading rate on rock fracture: fracture characteristics and energy partitioning2000In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 37, no 5, p. 745-762Article in journal (Refereed)
    Abstract [en]

    By means of the Scanning Electron Microscope (SEM), an examination was performed of the fracture surfaces (including their vertical sections) of both Fangshan gabbro and Fangshan marble specimens fractured at the loading rates k = 10-2 ≈ 106 MPa m1/2 s-1. The results showed that one or more branching cracks near the fracture surfaces of dynamic rock specimens were clear and the cracks increased with increasing loading rates. However, such branching cracks were rarely seen near the static fracture surfaces. In addition, with the aid of the Split Hopkinson Pressure Bar (SHPB) testing system and a high-speed framing camera, the energy partitioning in the dynamic fracture process of a short rod (SR) rock specimen was analysed quantitatively. The total energy WL absorbed by an SR specimen in the dynamic fracture process mainly consisted of the fracture and damage energy WFD and the kinetic energy WK of flying fragments. The energies WL and WK could be quantitatively calculated through stress wave measurement and high-speed photography in the SHPB testing system. Thus, the fracture and damage energy WFD could be obtained. The results showed that: (1) the energy WK increased with an increase in the impact speed of the striker bar or the loading rate; (2) the energy WFD for dynamic rock fracture was markedly greater than that for static rock fracture, and the WFD increased with an increase in the impact speed of the striker bar or the loading rate; and (3) the value WL/WB (WB is the energy input into the loading system) in the case of dynamic fracture is much lower than that in the case of static fracture. In addition, the ratio decreases with an increase in the loading rate or the impact speed of the striker bar. This means that the energy utilisation decreases when the loading rate or the impact speed of the striker bar rises. Finally, some application problems are discussed in the paper.

  • 3080.
    Zhang, Z X
    et al.
    Luleå tekniska universitet.
    Kou, S Q
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Measurements of cutter forces and cutter temperature of boring machine in Äspö Hard Rock Laboratory2001Report (Other academic)
    Abstract [en]

    This report presents both the testing methods used and the testing results obtained for cutter forces and cutter temperature during field boring in Äspö Hard Rock Laboratory. In order to estimate the strains induced by cutter forces in the cutter shaft and choose proper transducers, first a numerical simulation was performed. The simulation results indicated that the cutter forces should be measurable by ordinary strain gauges. Furthermore, an independent three-direction loading system for laboratory calibration was set up to solve force-coupling problems appearing in field measurements. By means of the established measuring system, which was proved successful in the laboratory, the normal forces, tangential forces, and side forces of two button cutters in the boring machine were measured in the field. In addition, the temperature in the shaft of the front cutter was measured. After the measurements of the cutter forces and cutter temperature, rock core samples were taken from the bottom and the wall of the testing borehole. Then the samples were cut, polished, and examined by means of the Scanning Electron Microscope (SEM). After that, the lengths of major cracks induced by the cutters in the rock samples were measured, and an approximate relationship between the length of the medium cracks and the relevant cutter forces was obtained. This relationship was compared with the theoretical relationship established before. Finally, according to the measured results, the cracked zones around the borehole were described. The results show that: (1) there are two kinds of cracked zones: one in the borehole wall and the other in the bottom of the borehole. The depth of the cracked zone in the borehole bottom is much larger than that in the borehole wall because the maximum normal force of the front cutter is always much larger than that of the gauge cutter. (2) Each cracked zone includes a densely cracked zone and all the longest medium cracks caused by mechanical boring. (3) According to the measurements for four rock core samples, the maximum depth of the cracked zone in the borehole bottom is 27.1 mm, and the maximum depth of the densely cracked zone is 2.5-3 mm.

  • 3081. Zhang, Z. X.
    et al.
    Kou, S. Q.
    Yu, J
    Yu, Y
    Jiang, L. G.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of loading rate on rock fracture1999In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 36, no 5, p. 597-611Article in journal (Refereed)
    Abstract [en]

    By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10−2–106 MPa m1/2 s−1. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness KIc of the rock was nearly a constant, but the dynamic fracture toughness KId of the rock (≥104 MPa m1/2 s−1) increased with the loading rate, i.e. log(KId)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates (≥106 MPa m1/2 s−1) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.

  • 3082.
    Zhang, Z X
    et al.
    Luleå tekniska universitet.
    Yu, J
    University of Science and Technology, Beijing.
    Kou, S.Q.
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of high temperatures on dynamic rock fracture2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 2, p. 211-225Article in journal (Refereed)
    Abstract [en]

    The dynamic fracture toughness of Fangshan Gabbro and Fangshan Marble subjected to high temperature was measured by means of the split Hopkinson pressure bar (SHPB) system. The specimens for measuring the fracture toughness were manufactured according to the requirements for the Short Rod (SR) specimen suggested by ISRM. Two cases were investigated: (1) the SR specimens of the gabbro and marble were fractured at high temperature (100-330 degrees C), and (2) the specimens of the rocks were first pre-heat-treated at 200 degrees C for the marble and 600 degrees C for the gabbro, and then fractured at room temperature. The experimental results showed that under dynamic loading the fracture toughness of both the gabbro and the marble tested in the above-mentioned cases increased with increasing loading rates. The relationship between the fracture toughness and the loading rates in the two cases is similar to that obtained in the room temperature environment, i.e., without high temperature. (This is defined as the third case.) It can be concluded that temperature variation affects the dynamic fracture toughness of the two rocks to a limited extent within the temperature ranges tested. This is different from the results obtained under the static loading condition. Furthermore, by means of the scanning electronic microscope (SEM), the vertical sections of the fracture surfaces for some gabbro specimens were examined. In addition, the fractal dimensions of the fracture surfaces of some specimens were measured by means of fractal geometry. The results showed that under dynamic loading: (1) macro-crack branching near the fracture surfaces was universal; (2) the fractal dimensions increased with increasing loading rates; (3) in the sections of the specimens tested at high temperature there were many micro-cracks that were probably induced by thermal cracking. On the basis of the above macro- and micro-experimental investigation, an energy analysis of the process of dynamic rock fracture was performed. The results showed that the energy utilisation in dynamic fracture was much lower than that in static fracture.

  • 3083.
    Zhang, Zhi-qiang
    et al.
    Xi’an University of Technology, Xi’an, P.R. China.
    Li, Ning
    Xi’an University of Technology, Xi’an, P.R. China.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Han, S.
    Xi’an University of Technology, Xi’an, P.R. China.
    Effect of fault on tunnel stability with different distribution2013In: Global View of Engineering Geology and the Environment: International Symposium & 9th Asian Regional Conference of IAEG / [ed] Faquan Wu; Shengwen Qi, London: CRC Press, Taylor & Francis Group , 2013, p. 279-285Conference paper (Refereed)
    Abstract [en]

    For tunnel engineering, the fault that locates near tunnel always plays an important role on the stability of the surrounding rock mass and the safety of the supporting system. To investigate the influence of the fault on the tunnel stability, systematic numerical experiments are carried out via the FINAL code. Through these numerical experiment results, the displacement and the distribution of the stress in surrounding rock mass are analyzed for these cases of the different locations and dips of fault around tunnel periphery, and the stress in the sprayed concrete layer are analyzed as well. To simulate the characteristics of the fault located in the rock mass, the COJO element, embedded in the FINAL code, is used in all numerical experiments. The quantized results reflecting the rules of the change for the displacement, stress, plastic region in the surrounding rock mass are obtained also in this paper.

  • 3084.
    Zhang, Zongxian
    Luleå tekniska universitet.
    Laboratory studies of dynamic rock fracture and in-situ measurements of cutter forces for a boring machine2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    All forms of rock failure usually happen within a very wide range of loading rates covering static and dynamic loading. Since rock failure always results from fracture - the propagation of one or more cracks- the first part of the thesis is focused on laboratory studies of the influences of loading rates on rock fracture. This part has mainly investigated macro/micro fracture characteristics of rock, energy partitioning in the process of rock fracture, and the influences of high temperatures on rock fracture. In the second part of the thesis, the research has dealt with in-situ measurements of the cutter forces and cutter temperatures of a boring machine. Then a number of core rock samples were taken from the borehole. After that, the cracks induced by mechanical boring were examined by using a scanning electron microscope (SEM). Finally, an approximate relationship between the length of the medium cracks and the respective normal forces measured in-situ was established.

  • 3085.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    In-situ measurements of cutter forces on boring machine at Äspö Hard Rock Laboratory. Part 2: Characteristics of cutter forces and examination of cracks generated2003In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 36, no 1, p. 63-83Article in journal (Refereed)
    Abstract [en]

    By means of spectral analysis, the measured normal forces, tangential forces, and side forces acting on two button cutters on the boring machine in Äspö Hard Rock Laboratory were analysed and the basic characteristics of the cutter forces were determined. After the measurements of the cutter forces, some rock core samples were taken from the bottom and the wall of the test borehole. These samples were cut, polished, and examined by means of a Scanning Electron Microscope (SEM). The lengths of the major cracks in the rock samples were measured, and a relation between the length of the median cracks and the relevant cutter forces was investigated.

  • 3086.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    In-situ measurements of TBM cutter temperature in Äspö Hard Rock Laboratory, Sweden2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 4, p. 585-590Article in journal (Refereed)
  • 3087.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Tan, Xiangchun
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    In-situ measurements of cutter forces on boring machine at Äspö Hard Rock Laboratory. Part 1: Laboratory calibration and in-situ measurements2003In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 36, no 1, p. 39-61Article in journal (Refereed)
    Abstract [en]

    This paper presents the testing methods used and the results obtained in an investigation of the cutter forces on a Boretec DS 1.6 boring machine during field boring in Äspö Hard Rock Laboratory. Two button cutters, one front cutter and one gauge cutter, were used in the field measurements. A total of 6 strain gauges were bonded on the shaft of each cutter. And each group of two gauges was used to measure a one-orthogonal cutter force component, i.e. the normal force, tangential force, and side force, respectively. In order to measure the cutter forces successfully, a telemetry system composed of a transmitter and a receiver was employed to transfer the signals from the strain gauges to a computer.A three-direction-loading system was employed in the laboratory calibration so as to solve the force-coupling problem appearing in the cutter force measurements. Correspondingly, a mathematical treatment of the force-coupling problem was performed. Then, by means of the established testing system, which was proved successful in the laboratory, the normal force, tangential force, and side force of the two button cutters on the boring machine were measured in the field. In addition, the penetration rate, thrust, and rotation speed of the boring machine were also recorded in the field. The results show the following. (1) A force-coupling phenomenon really exists and it should be considered. (2) All three directional force components always show quite a high peak value every few seconds. (3) The cutter forces of the front cutter are always much larger than the respective cutter forces of the gauge cutter. Moreover, as expected, the normal force of each cutter is much larger than the tangential force and side force of the cutter in question.

  • 3088.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Yu, J.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    On study of influences of loading rate on fractal dimensions of fracture surfaces in Gabbro2001In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 34, no 3, p. 235-242Article in journal (Refereed)
    Abstract [en]

    Studies of the effects of loading rates on rock fracture were performed for decades. However, the previous work on static or dynamic rock fracture was mainly limited to a macro-experimental study. The present investigation measures the fractal dimensions of the fracture surfaces of the gabbro specimens fractured at various loading rates covering static and dynamic loading, and explores the relationship between the fractal dimensions and the fracture toughness of the rock.

  • 3089.
    Zhang, Z.X.
    Luleå tekniska universitet.
    An empirical relation between mode I fracture toughness and the tensile strength of rock2002In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 39, no 3, p. 401-406Article in journal (Refereed)
  • 3090.
    Zhang, Z.X.
    Luleå tekniska universitet.
    Estimate of loading rate for a TBM machine based on measured cutter forces2004In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 37, no 3, p. 239-248Article in journal (Refereed)
    Abstract [en]

    Various aspects of a tunnel boring machines (TBM) were presented. The loading rate of a TBM machine can be estimated on the basis of its cutter force measurements. The method can also be used to estimate the loading rate of other similar rock breakage machines. On the basis of the cutter forces measured in the field, the loading rate of the Boretech D1.6 boring machine was estimated. Results show that the loading rate of the machine is within a typical quasi-static loading

  • 3091.
    Zhang, Z.X.
    et al.
    Luleå tekniska universitet.
    Kou, S.Q.
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fracture behaviour of rock under dynamic loading1999In: Comptes-rendus / 9 Congrès international de mécanique de roches, Paris, France 1999 / [ed] Gerard Vouille; Pierre Berest, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1999, Vol. 2, p. 1127-1130Conference paper (Refereed)
  • 3092. Zhang, Z.X.
    et al.
    Kou, S.Q.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Measurements of cutter forces for a TBM machine in Aspo underground2000In: Pacific rocks 2000: "rock around the rim". Proceedings of the 4th North American Rock Mechanics Symposium / [ed] Jami Girard, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 2000, Vol. 4, p. 11-17Conference paper (Refereed)
  • 3093. Zhang, Z.X.
    et al.
    Kou, S.Q.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yu, J.
    University of Science and Technology of China.
    Jiang, L.G.
    University of Science and Technology of China.
    Dynamic fracture behaviour of rock at high temperatures1999In: Rock mechanics for industry: proceedings of the 37th US Rock Mechanics Symposium /Vail/Colorado/USA/6-9 June 1999 / [ed] Bernard Arnadei, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1999, p. 325-331Conference paper (Refereed)
  • 3094.
    Zhang, Z.X.
    et al.
    LKAB, Research & Development, 983 81 Malmberget.
    Lindqvist, Per-Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Naarttijärvi, Torbjörn
    LKAB, Research & Development, 983 81 Malmberget.
    Wikström, K.
    LKAB, Research & Development, 983 81 Malmberget.
    A feasibility study on controlling ground vibrations caused by blasts in Malmberget underground mine2010In: Fragblast, ISSN 1385-514X, E-ISSN 1744-4977, Vol. 8, no 1, p. 3-21Article in journal (Refereed)
    Abstract [en]

    In order to control or reduce the ground vibrations caused by underground blasts in Malmberget mine, a number of blast tests were carried out during production blasts and a series of single shot waveforms were obtained. Then the single shot waveforms from the same ring or different rings were analysed and compared with each other. The results showed that the single shots are reproducible, meaning that the ground vibrations caused by underground blasts can be controlled by means of the interference of the vibration waveforms measured. Finally, a formal test using electronic detonators and employing an optimum delay time of 8 ms was done in production. The test for an 11-borehole ring shows that the maximum vertical ground vibrations are reduced to the maximum vertical vibrations of a single shot. Particularly, the total vibration history for the 11-borehole-ring blast is shortened to about 200 ms over a velocity of 2 mm/s. However, the total vibration history of a normal production blast of 11-borehole ring is always 1400 ms over a velocity of 2 mm/s, namely the total vibration time of a production blast can be reduced to one seventh of that of the common production blasts by using the vibration control method. This indicates that the vibration control method introduced in the paper is feasible for underground mining blasts

  • 3095.
    Zhao, Guanyi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Satellite Positioning.
    Fusion of Ladybug3 omnidirectional camera and Velodyne Lidar2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The advent of autonomous vehicles expedites the revolution of car industry. Volvo Car Corporation has an ambition of developing the next generation of autonomous vehicle. In the Volvo Car Corporation, Active Safety CAE group, enthusiastic engineers have initiated a series of relevant research to enhance the safety function for autonomous vehicle and this thesis work is also implemented at Active Safety CAE with their support.   

    Perception of vehicle plays a pivotal role in autonomous driving, therefore an idea of improving vision by fusing two different types of data from Velodyne HDL-64E S3 High Definition LiDAR Sensor and Ladybug3 camera respectively, is proposed.

     This report presents the whole process of fusion of point clouds and image data. An experiment is implemented for collecting and synchronizing multi-sensor data streams by building a platform which supports the mounting of Velodyne, Ladybug 3 and their accessories, as well as the connection to GPS unit, laptop. Related software/programming environment for recording, synchronizing and storing data will also be mentioned.

    Synchronization is mainly achieved by matching timestamps between different datasets. Creating log files for timestamps is the primary task in synchronization.

    External Calibration between Velodyne and Ladybug3 camera for matching two different datasets correctly is the focus of this report. In the project, we will develop a semi-automatic calibration method with very little human intervention using a checkerboard for acquiring a small set of feature points from laser point cloud and image feature correspondences. Based on these correspondences, the displacement is computed. Using the computed result, the laser points are back-projected into the image. If the original and back-projected images are sufficiently consistent, then the transformation parameters can be accepted. Displacement between camera and laser scanner are estimated through two separate steps: first, we will estimate the pose for the checkerboard in image and get its depth information in camera coordinate system; and then a transformation relation between the camera and the laser scanner will be computed within three dimensional space. 

    Fusion of datasets will finally be done by combing color information from image and range information from point cloud together. Other applications related to data fusion will be developed as the support of future work. 

    In the end, a conclusion will be drawn. Possible improvements are also expected in future work. For example, better accuracy of calibration might be achieved with other methods and adding texture to cloud points will generate a more realistic model.

  • 3096. Zhao, Xiaogang
    et al.
    Zhou, Yi
    Zhao, Jianyu
    KTH, School of Architecture and the Built Environment (ABE).
    Zhan, Guo
    Yang, Peng
    Safety Prediction of Soleplate Corrosion State in Petroleum Storage Tank Based on Grey Theory Model2016In: 3rd International Conference on Applied Engineering, AIDIC - associazione italiana di ingegneria chimica, 2016, p. 271-276Conference paper (Refereed)
    Abstract [en]

    The corrosion protection of petroleum storage tank is important for safety work in petroleum depot. Precise prediction of soleplate corrosion may reflect the security state of a storage tank, and it can provide scientific references to the anti-corrosion and maintenance in safety management. Grey Model GM (1,1) in the Grey Theory is a good prediction method based on small volume of original data, and it is introduced and applied to predict the soleplate corrosion of No. G-2 petroleum storage tank in Luquan oil depot. In order to improving the calculation speed, the GM (1,1) model is programmed by MATLAB and is further utilized in data processing. Compared with the measurements, the prediction results meet them very well, which shows that this model is practical. Meanwhile, the prediction results also reflect the status and the corrosion rate of a petroleum tank which is of great importance for the future safety management and maintenance works. Meanwhile, the GM (1,1) is suitable for wide applications in other relative fields in oil depots.

  • 3097.
    Zhou, Guanghong
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Low-Carbon City Initiatives in China: Planning Approaches, Dilemmas and Opportunities2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In order to reduce greenhouse gas (GHG) emissions, tackle climate change and move toward sustainable development, the central government in China has proposed low-carbon city development as the national strategy and relevant initiatives have been taken by local governments. This thesis analyses current low-carbon city programmes and planning approaches in China, identifies limitations and proposes a metabolic approach that could be used to account for physical resources, monitor GHG emissions and involve stakeholders in the planning process.

    There are currently two parallel programmes for low-carbon initiatives in China: the “Low-Carbon City” programme and the “Low-Carbon Eco-City” programme. Around thirty cities in the Coastal, Central and Western regions of China have been selected as the national pilot areas for these programmes. This widespread distribution marks a change the previous priority set on development in the Coastal region, meaning that more cities have opportunities to explore low-carbon pathways and obtain support from the state. The large number of cities involved shows China’s determination to transition to low-carbon development in different city contexts. The selected cities have set up local administrative groups to manage low-carbon development and have established integrated approaches to reduce GHG emissions from urban sectors such as energy, transportation, buildings and waste. Some plans have been developed by the cities themselves, while others have involved international cooperation. However, because of limited knowledge on low-carbon city development, an absence of established standards and procedures and the Chinese top-down planning system, low-carbon planning faces specific challenges, such as lack of information about GHG flows, GHG monitoring and stakeholder involvement.

    To overcome these challenges and improve low-carbon city approaches in China, this thesis proposes a holistic approach to low-carbon city development, by integrating Industrial Ecology into urban planning. Such work would benefit greatly from adopting a metabolic approach, within which a metabolic approach-based standard is used to understand low-carbon city from GHG flows; a DPSIR framework is used to address root causes of GHG emissions; and an Eco-Cycle Model is used to describe urban metabolism and account for physical resources, monitor GHG emissions and involve stakeholders in the planning process.

    The thesis also recommends better collaboration between relevant government departments and stakeholders. Moreover, instead of simply transferring approaches developed elsewhere, international cooperation needs to combine the local context and knowledge in China with international knowledge and experience. In return, experiences from China can help improve low-carbon city approaches in other parts of the world.

  • 3098.
    Zhou, Yang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Nonlinear analysis of reinforced concrete slab on partially softening ground: Ickelinjär analys av armerad betongplatta på delvis uppmjuknande grund2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Reinforced concrete slabs are a conventional type of foundation that is widely used in residential, commercial and industrial buildings. Most of the slab foundations are constructed directly on the ground without another structural medium in between and some of the slabs are therefore influenced by ground softening. A slab foundation is designed to transfer vertical loads and bridge imperfections in the ground, but excessive soil distortion may destroy the support conditions of the slab and through this influence the stability of the superstructures.

    The aim of this project is to study how ground softening and its further development influence a typical concrete slab. Furthermore, an approximate analytical method to evaluate the condition of a slab due to ground softening was studied. A practical case has been studied to capture the actual failure behaviours of a reinforced concrete slab, based on a previous project. For the case studied, possible future mining activities close to a high bay warehouse may cause damaging settlement in the underground. The fault that may appear softens the soils underneath the foundation, which may deteriorate and cause collapse of the concrete slab under the warehouse. Two types of failure scenarios were studied; subsoil softening and subsoil collapse.

    The Finite Element Method (FEM) was used to analyse the behaviour of the slab and the development of the failures in the subsoil. A commercial FEM software package, Abaqus, was used as the analytic tool, with a built-in Concrete Damaged Plasticity model (CDP) that for the concrete material model. Both linear and nonlinear material properties have been used in the analyses with same softening effect of the subsoil. A large number of models were analysed to simulate the development of the fault and capture the failure modes of the slab at different stages.

    Excessive tensile cracks and vertical deformations were found in both failure scenarios studied. A possible internal stability problem of the warehouse due to this was also found. The nonlinear behaviour of the concrete slab was captured through the failure scenarios before damage. It is shown that the serviceability of the reinforced concrete slab can be influenced by softening ground, and a more realistic description of the possible failures was here obtained based on the nonlinear model compared to previous elastic analyses.

    Keywords:     Reinforced concrete slab, Nonlinear, Ground softening, Finite Element Method (FEM), Abaqus, Concrete Damaged Plasticity (CDP).

  • 3099. Zhou, Yi
    et al.
    Zhao, Xiaogang
    Zhao, Jianyu
    KTH, School of Architecture and the Built Environment (ABE).
    Chen, Du
    Research on Fire and Explosion Accidents of Oil Depots2016In: 3rd International Conference on Applied Engineering, AIDIC - associazione italiana di ingegneria chimica, 2016, Vol. 51, p. 163-168Conference paper (Refereed)
    Abstract [en]

    Fire and explosion accidents occurred frequently in oil depots in China which lead to great casualties, severe environmental pollution and large economic losses. Case studies of 435 fire and explosion accidents of oil depots in China from 1951 to 2013 are reviewed in this paper. From the analysis of time scale, area, facilities & equipment, ignition sources, types of accident substances, and responsibility, the statistic results show that the most dangerous area is the loading and unloading operation area, and the most vulnerable facilities & equipment are the storage tanks. Meanwhile, the proportions of ignition sources are so evenly distributed that the prevention of fire and explosion should be equally concentrated to several impact factors. The vapor cloud explosion could be the most common accident type in oil depots, and the management responsibility dominates in all of the accident causes. According to data analysis, special lessons learned from these accidents are proposed, and the majority of fire and explosion accidents in oil depots would have been prevented or avoided if security management had been improved.

  • 3100.
    Zhu, Huiming
    et al.
    College of Business Administration, Hunan University.
    Guan, Haoyun
    College of Business Administration, Hunan University.
    Lin, Jing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Yu, Keming
    Brunel University.
    Zeng, Zhaofa
    College of Business Administration, Hunan University.
    Bayesian multivariate monitoring models for process mean vectors based on multistage predictive distributions2011In: Hunan Daxue Xuebao (Ziran Kexue Ban), ISSN 1674-2974, Vol. 38, no 3, p. 82-86Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to utilize sample information in different stages and solve the parameter uncertainty risk in statistical process control. This paper introduces a reference prior distribution for the parameters in quality models, and constructs the warning lines and action lines to monitor the mean vectors change according to the predictive distribution as well as the relationship between the multivariate t distribution and F distribution. When the current stage is under control, the parametric posterior distribution is considered to be their priori distribution in the next stage, in which the sequential Bayesian mean vector control method is established.

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