The paper basically deals on reliability of the hydraulic shovel machines used in coal mines. Reliability of machines defined as the probability of the machine that will carry out its specified function satisfactory for stated period of time and without undergoing failure when used under specified condition for the specified period of time. Reliability of machine depends on its failure, if the failure is frequent then we can say that machine is less reliable and vice-versa. Due to recent deployment of sophisticated and capital intensive mining machinery equipment in mining industry, interest in the field of maintenance and operational reliability has been created. Keeping this in view a reliability investigation is initiated for hydraulic shovel in a reputed mine. The goal is to estimate the operational reliability of these mining machines for coal production in order to enhance its profit. Failure data for period of 1.5 years are analyzed using various probability distribution methods. The importance of testing the reliability data for the presence of trends and serial correlation is also emphasized. The project aimed at analyzing the reliability of the two hydraulic shovel machine using suitable distribution methods and to study the IFR and DFR using TTT-plotting method.
Keywords: Reliability; hydraulic shovel; time between failure (TBF); mean time to failure (MTTF); time to test (TTT); increasing failure rate (IFR); decreasing failure rate (DFR); parametric method
Based on the principle of phase sensitive detection (PSD) technology, the multi-frequency digital PSD algorithm is deduced to achieve the constrained relationship of sampling frequency, sampling number and signal frequency in the PSD of multi-frequency signals. The results of simulation experiment show that the amplitude detection error is controlled within 0.5% and the phase detection error is controlled within 0.2% when the signal to noise ratio (SNR) is as low as -10dB.
Keywords: Electrical logging, multi-frequency signals, PSD
This paper studies characteristics of deformation failure and fracture growth of fractured coal-rock combination with RFPA2D numerical analysis software. Peak strength of the combination increases with increase of the dip of fracture and the peak strength when dip of fracture is 90° approaches to the peak strength without fracture. Under the same dip of fracture, peak strength of the combination when fracture is in the rock is higher than that in the coal, and fracture in the coal has more significant effect on the strength of the combination than in the rock. If fracture locations in combination are different, the characteristics of fracture growth are different. If dips of fracture in the same location are different, the fracture growth characteristics are different, too. However, fracture growth connection in coal is the main cause of overall failure of the combination body. During the loading, sound emission appears in two ends of fracture and the new fracture in the rock in upper end of the fracture, which mainly is caused by tensile failure. While in the coal, the new fracture in the end of fracture is caused by tensile failure; failures in other part are caused by both tensile failure and shear failure.
Keywords: Combination body, connected fissure, RFPA2D, sound emission
The multi-line parallel tunnels belong to a complex layout in the underground space that has emerged in the wake of the continuous development of metro construction. When a new tunnel that travels through the existing ones in parallel with over a long distance is constructed, not only an adverse impact will produce on existing parallel tunnels, but also surface subsidence will be occurred. Contrapose the construction pattern that four-line parallel shield tunnels breakthrough soft soil stratum, a 3D elastic-plastic finite element dynamic model is built to simulate and analyze the whole process of four-line parallel shield construction. Study shows that, in the process of shield excavation, the interactive effects between horizontal lines are relatively weak, but in the vertical direction, it presents more intense; after the completion of the excavation for four-line parallel tunnels, the surface subsiders are not symmetrical, but appear right above the last excavation line; first excavation should run from the upper tunnels, followed by the lower tunnels, since it is conducive to the surface settlement control and reducing the interactive effects between various lines. In this paper, the findings can provide a theoretical basis and prophase guidance for such construction in the future.
Keywords: Four-line parallel, shield tunnel, soil deformation, excavation sequence, finite element analysis
A method based on principal component analysis (PCA) and Fisher discrimination analysis is proposed targeting water inrush from mine floor. Based on the analysis of a large number of measured data from past projects, 13 factors affecting and controlling water inrush from floor are selected as the discrimination indexes. Firstly, the dimension of multi-index floor water inrush data is reduced by principal component analysis, and 4 principal component factors are extracted. Then the PCA-Fisher discrimination model of mine floor water inrush risk is established based on Fisher discrimination analysis theory, and its discrimination effect is verified by recurrent discrimination analysis and an example of its application is presented. The application results show that the results of the discrimination model are consistent with the actual situation, with an accuracy of 100%, which can provide a more effective method for discriminating the water inrush risk from mine floor.
Keywords: Floor water inrush, risk discrimination, principal component analysis, Fisher discrimination analysis
Targeting at slow tunnelling advance rate problem of the coal roadway with large section and compound roof in Zhaozhuang mine, on the basis of site investigation and statistical analysis, revealed that the engineering geological conditions, support parameters and construction technology are the main factors affecting tunnelling efficiency, and then through the numerical simulation to optimize the roadway support parameters, the theoretical calculation of a reasonable cycle step, the EJM270/4-2 header with bolting machine with higher tunnelling efficiency and tunnelling and bolt integration was selected, the improved excavation construction programme compared to the original construction programme, increased the cycle pace, shortening the cutting of coal, support and other major processes of working time. Field practice results show: not only ensured the safety of tunnelling construction and the stability of surrounding rock, but also increased the monthly footage from 210 m/month to 262 m/month, tunnelling speed increased by 24.7%, at the same time, the roadway molding was better, the labour intensity of workers was reduced, and good benefits have been achieved.
Keywords: Large section, compound roof, cycle step, bolting machine, rapid excavation
In order to effectively solve the hazards of heading slope landslide of tunnel entrance project in fractured strata, the geological conditions, human activities, meteorology, hydrology, and other factors of Feilongshan tunnel entrance are analyzed; by comprehensively taking into consideration of factors such as the environment, project duration, and safety of the landslide area, this paper proposes comprehensive control measures centered on anti-sliding, and systematically studies the effectiveness of slope-brushing protection, pipe-shed support, counter-pressure backfill mortar rubbles and other measures for controlling heading slope landslide of the tunnel entrance. The on-site monitoring results shows that the change trend of the vector displacement and plane displacement at each measuring point after the remediation is relatively stable, all within the allowable deformation range; the comprehensive remediation plan has clear construction process flow, obvious technical effects, and high construction efficiency and safety. The research results provide a technical basis and reference for the remediation of tunnel entrance landslide in complex and fractured strata.
Keywords: Tunnel entrance, heading slope landslide, remediation plan
This paper presents a three-dimensional finite difference numerical analysis of cap-pile system under earthquake. The deformation law of the cap-pile system and the variation characteristics of the axial force and moment of the pile are obtained. Under the action of earthquake, the settlement of the cap is increasing, and finally did not retrace, while the axial force and bending moment of the pile, present the trend of increasing first and then reducing, and the withdrawal efforts are great. The force and displacement are not completely corresponding relationship under the action of the earthquake. The moment of the pile swings at 0 o’clock under earthquake.
Keywords: Pile cap; pile foundation; seismic force; force characteristics
The Dabaoshan Mo-polymetallic deposit is located in the Nanling Metallogenic Belt, China. It consists of porphyry Mo, skarn Mo and strata”-bound Cu–Pb–Zn mineralization, of which rutile was only found in potassium feldspar alteration zones surrounding porphyry Mo orebodies. Petrographic observation combined with in–situ major elements mapping analysis by EPMA show that there are two generations of rutile, namely rutile I and rutile II. Rutile I with larger grain sizes(approximating to 100×200 μm2) occur closer to the mineralization center of porphyry Mo orebodies than rutile II with smaller grain sizes(nearly 20×15 μm2). Besides, rutile I grains are chemically zoned (in W and Cr), while rutile II are less likely to show chemically zoning. Rutile I grains have high W contents (4.79–9.57 wt%) and Cr contents (2.24–3.09wt%) in coherent zones. Slower diffusion rate on crystal face of W6+, which is the cation with the highest chemical valence and smallest radius, is an important factor accounting for chemical zoning in rutile I. Above all, the rutile in biotite and K–feldspar alteration zones surrounding porphyry Mo orebodies, especially those with large grian sizes,W-Cr anomaly and chemical zoning, are critical indicator of economic mineralization and mineralization center.
Keywords: W-bearing rutile, EPMA, Dabaoshan, South China
As the global temperature is on the rise due to global warming, the issue of climate change is indeed a hot topic among the climate scientists and policy-makers worldwide. Claiming anthropogenic emissions as the primary cause of the prevailing climate change, every human activity is now under heavy scrutiny. Among others, mining is one of the fundamental activities which caters to the supply of raw materials to other basic industries and fulfils most of the energy needs of the human race and is believed to be a major contributor to the anthropogenic emissions. The present paper discusses a few case studies conducted in some Indian mines to estimate their respective carbon emissions. The accounting of carbon emissions due to mining activities is called as ‘greenhouse gas inventory’. A brief look over the GHG inventory of some mines provides a succinct idea about contribution of mining industry to global emissions. The results highlight that emissions from mining industry are significant and cannot be overlooked. Thus it is required to develop clean technology to be implemented in mines to lower its emissions.Read more