Laboratory experimental study of the evaporation and mechanical behaviour of deposited tailings
- Authors: Zheng, Binbin , Wang, Jiahe , Zhang, Dongming , Zhao, Lei , Wang, Wensong
- Date: 2021
- Type: Text , Journal article
- Relation: Environmental Science and Pollution Research Vol. 28, no. 47 (2021), p. 67565-67576
- Full Text: false
- Reviewed:
- Description: Surface deposition has been widely used in the mining industry to manage mill tailings. Tailings are generally discharged in the form of a slurry into tailings ponds. The slurried tailings are deposited in layers that undergo complex processes, e.g. evaporation, desiccation and consolidation. The evaporation of the deposited tailings controls their geotechnical engineering behaviour, which is necessary to characterise the physical properties. In this study, a constant temperature device was employed in evaporation tests to investigate two classes of deposited tailings, and the effects of the initial concentration, particle size, exposure area and deposited layer thickness on the evaporation processes were analysed. The test results showed four stages in the evaporation processes of deposited coarse and fine tailings. Dewatering of the deposited tailings occurred during the first two stages, which were keys to improving the desiccation efficiency of the tailings in the pond. The exposure area and deposited layer thickness also had a considerable influence on evaporation. The evaporation rate increased with the exposure area and layer thickness. Direct shear tests were performed to measure the shear strength of intact tailings during evaporation and used to determine the variation law of the mechanical properties of the test tailings. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
From convex to nonconvex: A loss function analysis for binary classification
- Authors: Zhao, Lei , Mammadov, Musa , Yearwood, John
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at10th IEEE International Conference on Data Mining Workshops, ICDMW 2010 p. 1281-1288
- Full Text:
- Reviewed:
- Description: Problems of data classification can be studied in the framework of regularization theory as ill-posed problems. In this framework, loss functions play an important role in the application of regularization theory to classification. In this paper, we review some important convex loss functions, including hinge loss, square loss, modified square loss, exponential loss, logistic regression loss, as well as some non-convex loss functions, such as sigmoid loss, ø-loss, ramp loss, normalized sigmoid loss, and the loss function of 2 layer neural network. Based on the analysis of these loss functions, we propose a new differentiable non-convex loss function, called smoothed 0-1 loss function, which is a natural approximation of the 0-1 loss function. To compare the performance of different loss functions, we propose two binary classification algorithms for binary classification, one for convex loss functions, the other for non-convex loss functions. A set of experiments are launched on several binary data sets from the UCI repository. The results show that the proposed smoothed 0-1 loss function is robust, especially for those noisy data sets with many outliers. © 2010 IEEE.
Learning from noisy data: Robust data classification
- Authors: Zhao, Lei
- Date: 2012
- Type: Text , Thesis , PhD
- Full Text:
- Description: The problem of learning from noisy data sets has been the focus of much attention for many years. Three different types of noise could be defined that generate difficulties in data classification. The first type is related to the noisy features and labels where data entry and data acquisition are inherently prone to errors. The second type is from the redundant features, which may confuse the classification algorithm and degrade the classification performance. The last type could be generated by insufficient features where some features may become quite ambiguous in the absence of related hidden complementary features. In order to address these problems, robust methods for data classification have been studied in many areas, such as bio-informatics, genetics, medicine, education and electronic engineering. This thesis aims to study classification methods that are robust for noisy data sets. Different problems caused by the three types of noise listed above are investigated. New robust methods for data classification are proposed. "From Abstract"
- Description: Doctor of Philosophy
Cracking mechanism along the north batter of Maddingley Brown Coal Open Pit Mine, Victoria, Australia
- Authors: Zhao, Lei , You, Greg
- Date: 2018
- Type: Text , Book chapter
- Relation: Engineering Geology and Geological Engineering for Sustainable Use of the Earth's Resources, Urbanization and Infrastructure Protection from Geohazards, Proceedings of the 1st GeoMEast International Congress and Exhibition, Egypt 2017 on Sustainable Civil Infrastructures (Part of the Sustainable Civil Infrastuctures book series) 8 p. 115-129
- Full Text: false
- Reviewed:
- Description: Cracks manifested on the north batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia in November 2013. The crack opened varies from trace to approximately 150 mm wide was located at about 20 m back from the coal face and extended for approximately 50 m on the eastern side and terminated 10 m away from the access road. Site investigations and remedy measures were implemented immediately after the cracking. This study involves in a three dimensional modeling on the cracking mechanism using finite element method (FEM) encoded in Plaxis 3D software program. From the study, it was found that the initial model based on north batter being stable for many decades tended to lead a circular critical path while the model after overburden removal showed a trend of block sliding. The safety factor of initial north batter was 1.38 through safety analysis while it was decreased to 1.17 for the coal batter after overburden removal. But the simulated shear and tensile strains indicated that the coal batter after overburden removal in fact experienced block failure. Furthermore, the simulated location of cracking was in good agreement with the actual location, and the simulated heave of the coal seam was in good agreement with the experience in Victoria brown coal open pit mining The observed vertical crack would be a combined action of the overburden removal and the groundwater flow in the unconfined aquifer.
Stability study on the northern batter of MBC Open Pit using Plaxis 3D
- Authors: Zhao, Lei , You, Greg
- Date: 2018
- Type: Text , Journal article
- Relation: Arabian Journal of Geosciences Vol. 11, no. 6 (2018), p. 1-11
- Full Text:
- Reviewed:
- Description: Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data.
A new loss function for robust classification
- Authors: Zhao, Lei , Mammadov, Musa , Yearwood, John
- Date: 2014
- Type: Text , Journal article
- Relation: Intelligent Data Analysis Vol. 18, no. 4 (2014), p. 697-715
- Full Text: false
- Reviewed:
- Description: Loss function plays an important role in data classification. Manyloss functions have been proposed and applied to differentclassification problems. This paper proposes a new so called thesmoothed 0-1 loss function, that could be considered as anapproximation of the classical 0-1 loss function. Due to thenon-convexity property of the proposed loss function, globaloptimization methods are required to solve the correspondingoptimization problems. Together with the proposed loss function, wecompare the performance of several existing loss functions in theclassification of noisy data sets. In this comparison, differentoptimization problems are considered in regards to the convexity andsmoothness of different loss functions. The experimental resultsshow that the proposed smoothed 0-1 loss function works better ondata sets with noisy labels, noisy features, and outliers. © 2014 - IOS Press and the authors. All rights reserved.
Three-dimensional numerical study on the batter instability mechanism of Maddingley Brown Coal Open Pit, Victoria, Australia using PLAXIS 3D
- Authors: Zhao, Lei
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: With the increased size of excavation due to long-term open cut mining, batter instability has become a major geo-hazard in Victorian Brown Coal Open Pits where facilitate some largest brown coal mining operations in the world. Block failure is a unique failure mode in Victorian brown coal mines, which is often associated with cracks and rainfall. Maddingley Brown Coal Mine (MBC) is located in Bacchus Marsh, Victoria, Australia. Slope instability has also been a major geo-problem since the open pit mining commenced in MBC in 1940s. Making clear the cracking mechanism and the correlations between rainfall and batter instability have important implications in better understanding and predicting batter failures in Victorian brown coal mines. In this research, three-dimensional geologic models were developed to investigate the mechanism of brown coal batter instability. The finite element program encoded in Plaxis 3D was employed to conduct the complex two-phase (fluid-solid) coupled numerical simulations. The results revealed the cracking mechanism of coal batter and the effects of rainfall on batter stability. It was found that the brown coal batter with overburden tends to lead a circular critical path while the batter after overburden removal shows a trend of block sliding as interpreted by the shear and tensile strains simulated. The existence of joints and the hydrostatic water pressure in the joints could adversely affect the stability of brown coal batter towards block failure. Precipitation can increase the deformation, excess pore pressure, total pore pressure, active pressure and decrease the matric suction, and thereby decrease the shear strength, effective stress, and batter stability. The results from the three-dimensional hydro-mechanically coupled finite element study were well agreed with the field monitored data, theoretical calculations, and Victorian brown coal mining experience.
- Description: Doctor of Philosophy
Rainfall-induced deformation behavior of cracks on brown coal open pit batter in Australia
- Authors: Zhao, Lei , You, Greg
- Date: 2019
- Type: Text , Conference paper
- Relation: 9th International Conference on Geotechnique, Construction Materials and Environment, 20-22 November 2019, Tokyo Japan p. 458-463
- Full Text: false
- Reviewed:
- Description: After a 26mm rainfall in 24 hours, noticeable ground movements were observed on the north batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia in February 2014. The batter is brown coal sandwiched by confining beds. Cracks manifested on the north batter months before the rainfall event, and then an emergency buttress was immediately constructed to maintain the batter stability. A three-dimensional geologic model is developed to study the rainfall-induced ground movement in this paper. The finite element program encoded in Plaxis 3D is employed to conduct the complex two-phase (fluid-solid) coupled numerical simulation. It is found that the simulated deformation is well agreed with the observed data from field survey markers. There are ground movements along the length of cracks on both sides with larger movement towards the pit bottom. These movements are the results of the combined reactions of surface run-off and sudden increased underground water level. The 26mm rainfall event did not cause instability of the batter.
Study on the stability of brown coal batter with opened cracks on Maddingley brown coal mine
- Authors: Zhao, Lei , You, Greg
- Date: 2020
- Type: Text , Journal article
- Relation: Sn Applied Sciences Vol. 2, no. 6 (Jun 2020), p. 14
- Full Text:
- Reviewed:
- Description: After a 26-mm precipitation in February 2014, noticeable ground movements were recorded on the north batter of Maddingley brown coal open pit, Victoria. To investigate the rainfall effect on the stability of the brown coal batter with opened cracks, a three-dimensional geologic model was developed, and the finite element program encoded in Plaxis 3D was employed to conduct a complex two-phase (fluid-solid) coupled numerical simulation. It was found that the simulated deformations were well agreed with the field survey data. There were ground movements along the length of cracks on both sides of the crack with larger movement towards the pit bottom. The coupled effect of hydrostatic forces from the crack in the rear of the batter and from the clay layer underlain the batter caused the block to slide, or batter failure. From the results, it revealed that both short-term high rainfall intensity precipitation and long enduring low rainfall intensity precipitation could cause the brown coal batter with opened cracks instable.
- Description: Australian Research Training Program (RTP) Scholarship Federation University Australia George Collins Memorial Scholarship.
Rainfall affected stability analysis of Maddingley brown coal eastern batter using plaxis 3D
- Authors: Zhao, Lei , You, Greg
- Date: 2020
- Type: Text , Journal article
- Relation: Arabian Journal of Geosciences Vol. 13, no. 20 (2020), p.
- Full Text:
- Reviewed:
- Description: Rainfall is a common factor that triggers the instability of Victorian Brown Coal (VBC) open pits which facilitate some of the largest brown coal mining operations. There has been no relevant study on rainfall-induced slope instability of VBC open pits in literature. In this paper, a three-dimensional (3D) two-phase (fluid-solid) coupled finite element method (FEM) was employed to investigate the stability of Maddingley Brown Coal (MBC) eastern batter under different rainfall conditions. It was found that the batter tends to lead a circular failure path during large rainfall. With the increase in either precipitation period or rainfall intensity, the deformation, excess pore pressure and active pressure increased, while the matric suction decreased. The hydrostatic force in the confined aquifer underlying the brown coal seam increased during rainfall; meanwhile, the resisting force decreased. As a result, the shear strength decreased and thereby the stability of the batter decreased. The safety factor and the critical failure path of the eastern batter simulated in this study were consistent with the previous study on the Northern batter. This study is a strong supplement to the literature on rainfall-induced instability of VBC batters. In the meantime, it is significant to provide a reference to the application of sophisticated 3D numerical modelling for studying slope instability of brown coal and similar mineral deposits. © 2020, Saudi Society for Geosciences.
- Description: The study is supported by the Australian Research Training Program (RTP) Scholarship and Federation University Australia George Collins Memorial Scholarship
Causation analysis of risk coupling of gas explosion accident in chinese underground coal mines
- Authors: Zhang, Jinjia , Xu, Kaili , You, Greg , Wang, Beibei , Zhao, Lei
- Date: 2019
- Type: Text , Journal article
- Relation: Risk Analysis Vol. 39, no. 7 (2019), p. 1634-1646
- Full Text: false
- Reviewed:
- Description: The coal mine production industry is a complex sociotechnical system with interactive relationships among several risk factors. Currently, causation analysis of gas explosion accidents is mainly focused on the aspects of human error and equipment fault, while neglecting the interactive relationships among risk factors. A new method is proposed through risk coupling. First, the meaning of risk coupling of a gas explosion is defined, and types of risk coupling are classified. Next, the coupled relationship and coupled effects among risk factors are explored through combining the interpretative structural modeling (ISM) and the NK model. Twenty-eight representative risk factors and 16 coupled types of risk factors are obtained through analysis of 332 gas explosion accidents in coal mines in China. Through the application of the combined ISM-NK model, an eight-level hierarchical model of risk coupling of a gas explosion accident is established, and the coupled degrees of different types of risk coupling are assessed. The hierarchical model reveals that two of the 28 risk factors, such as state policies, laws, and regulations, are the root risk factors for gas explosions; nine of the 28 risk factors, such as flame from blasting, electric spark, and local gas accumulation, are direct causes of gas explosions; whereas 17 of the risk factors, such as three-violation actions, ventilation system, and safety management, are indirect ones. A quantitative analysis of the NK model shows that the probability of gas explosion increases with the increasing number of risk factors. Compared with subjective risk factors, objective risk factors have a higher probability of causing gas explosion because of risk coupling.
Reliability analysis of shear strength parameters of rock mass derived using the Hoek-Brown criterion
- Authors: Wen, Yiming , Wang, Chun , Zhao, Lei , You, Greg , Yang, Jianzhong , Zeng, Xiaoyan , Yang, Ze , Sun, Wei , Cheng, Yong , Lin, You
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Mines, Metals and Fuels Vol. 66, no. 8 (2018), p. 438-443
- Full Text: false
- Reviewed:
- Description: Determining the mechanical parameters of a rock mass is a difficult but crucial matter in studies pertaining to stability. In this study, the Hoek-Brown criterion is used to derive the shear strength parameters of a rock mass; the parameters are subsequently optimized through reliability analyses, including the nonlinear Mohr-Coulomb envelope, optimized slopes, and least square variance methods. Further, through a case study of the Jianshan open pit mine, the c and ϕ values of the orebody were comparatively studied using the proposed method. The nonlinear Mohr-Coulomb envelope method and the optimized slopes method can attain reliability values exceeding 80%, as required by Chinese standards.
A new supervised term ranking method for text categorization
- Authors: Mammadov, Musa , Yearwood, John , Zhao, Lei
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at 23rd Australasian Joint Conference on Artificial Intelligence, AI 2010 Vol. 6464 LNAI, p. 102-111
- Full Text:
- Reviewed:
- Description: In text categorization, different supervised term weighting methods have been applied to improve classification performance by weighting terms with respect to different categories, for example, Information Gain, χ2 statistic, and Odds Ratio. From the literature there are three term ranking methods to summarize term weights of different categories for multi-class text categorization. They are Summation, Average, and Maximum methods. In this paper we present a new term ranking method to summarize term weights, i.e. Maximum Gap. Using two different methods of information gain and χ2 statistic, we setup controlled experiments for different term ranking methods. Reuter-21578 text corpus is used as the dataset. Two popular classification algorithms SVM and Boostexter are adopted to evaluate the performance of different term ranking methods. Experimental results show that the new term ranking method performs better. © 2010 Springer-Verlag.
Regularization methods in the study of drug reaction relationships
- Authors: Mammadov, Musa , Zhao, Lei , Zhang, Jianjun
- Date: 2010
- Type: Text , Conference proceedings
- Full Text: false
Sensitivity analysis, determination and optimization of granite RHT parameters
- Authors: Li, Hongchao , Chen, Yong , Liu, Dianshu , Zhao, Lei , You, Greg
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Beijing Institute of Technology (English Edition) Vol. 28, no. 1 (2019), p. 94-102
- Full Text: false
- Reviewed:
- Description: The RHT model has 34 parameters, among which 19 parameters can be obtained by experiments or theoretical calculations and the remaining 15 parameters are difficult to acquire. In this study, firstly, 10 Hopkinson impact tests were conducted to acquire the typical stress-strain curves of granite under dynamic loads. Through the sensitivity analysis, it is found that 13 of the 15 difficultacquired parameters are effective to affect the shape of the stress-strain curve, and the other two parameters have no effect. Following the initial determination of model parameters with reference to the concrete RHT model, a new approach is proposed to optimize the 13 influential parameters through the LS-DYNA numerical simulation and orthogonal experiments. Finally, the determined granite RHT model parameters are verified by the results of Hopkinson impact tests conducted in this study and the bullet penetration test by Wang et al. Both results of the numerical simulations are in a good agreement with the tested results, which validates the suitability of the proposed method to acquire RHT model parameters for granite and the other rocks.
Experimental study on the time-dependent dynamic mechanical behaviour of C60 concrete under high-temperatures
- Authors: Li, Hong-chao , Liu, Dian-shu , Zhao, Lei , You, Greg , Liang, Shu-feng , Wang, Yu-tao
- Date: 2015
- Type: Text , Journal article
- Relation: Journal of Beijing Institute of Technology (English Edition) Vol. 24, no. 3 (2015), p. 313-320
- Full Text: false
- Reviewed:
- Description: To study the dynamic mechanical behavior of C60 concrete at high temperatures, impact tests under different steady-state temperature fields (100, 200, 300, 400 and 500℃) were conducted under a variety of durations at the corresponding constant high temperature, namely 0, 30, 60, 90 and 120 min, employing split Hopkinson pressure bar (SHPB) system. In addition, the impact tests were also conducted on the specimens cooled from the high temperature to the room temperature and the specimen under room temperature. From the analysis, it is found that C60 concrete has a time-dependent behavior under high-temperature environment. Under 100, 200, 300, 400 and 500℃ steady-state temperature fields respectively, as the duration at the corresponding constant high temperature increases, the dynamic compressive strength and the elastic modulus decrease but the peak strain generally ascends. After cooling to the room temperature, the dynamic compressive strength and the elastic modulus descend as well, but the peak strain increases first and then decreases slightly, when the duration increases. For specimens under and cooled from the high-temperature, as the temperature increases, the dynamic compressive strength and the peak strain raise first and then reduce gradually, and the dynamic compressive strength of specimen under high temperature is higher than that of the specimen cooled from the same high temperature. © 2015, Editorial Department of Journal of Beijing Institute of Technology. All right reserved.
Sensitivity analysis determination and optimization of rock RHT parameters
- Authors: Li, Hong-chao , Chen, Yong , Liu, Dian-shu , Huang, Yonghui , Zhao, Lei
- Date: 2018
- Type: Text , Journal article
- Relation: Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology Vol. 38, no. 8 (2018), p. 779-785
- Full Text: false
- Reviewed:
- Description: Among the total 34 parameters of RHT constitutive model, there are 19 parameters can be confirmed from experiment or theoretical study, but the left ones, N, pcomp, ft *, fs *, A, n, Q0, gc *, ξ, D1, εp m, Af, nf, B and gt *, are generally hard to acquire. A sensitivity study of the 15 hard-acquired parameters was conducted through numerical simulation of uniaxial and triaxial compression of limestone using LS-DYNA. And then a new method was proposed in this paper to acquire all 34 parameters of RHT model in terms of red sandstone by orthogonal experiment coupled with static test, sonic wave test, SHPB impact test and LS-DYNA numerical simulation. The simulated result of red sandstone is in a well line with the result from SHPB impact test of red sandstone, which evidenced the RHT model of red sandstone is effective. © 2018, Editorial Department of Transaction of Beijing Institute of Technology. All right reserved.
Study on Parameters Determination of Marble RHT Model
- Authors: Li, Hong-chao , Liu, Dian-shu , Zhao, Lei , Li, Chen , Zhang, Zhenyuan
- Date: 2017
- Type: Text , Journal article
- Relation: Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology Vol. 37, no. 8 (2017), p. 801-806
- Full Text: false
- Reviewed:
- Description: RHT model includes 34 parameters. The values of A, n, fs *, ft *, Q0, gc *, ξ, D1, εp m, Af, nf, pcomp and N are hard to be determined due to the complicated experimental methods. In previous researches on simulation of rock blasting based on RHT model, many scholars quoted directly from the relevant parameters of concrete or they simply modified values of concrete parameters with little consideration of the kinds of rock material. To get the fairly accurate relevant parameter values of marble, the orthogonal experiment method and LS-Dyna numerical computation were used in this paper to determine and optimize the above parameters on the basis of static tests, wave velocity tests and SHPB impacting experiments. This paper also made a comparison between the simulation curves before and after the optimizing and the stress-strain curves of marble specimen processed by the SHPB impacting experiment. The final results show that the errors between the simulate curve and SHPB impacting experiment curve were decreased dramatically after the parameters had been processed by the orthogonal experiment. The appropriate parameters of the marble RHT model were obtained. © 2017, Editorial Department of Transaction of Beijing Institute of Technology. All right reserved.