The existing studies on the routing problem of emergency logistics vehicles emphasize on qualitative analysis over quantitative research. To solve the problem, this paper combines qualitative and quantitative methods into a mathematical model of the routing problem, and adopts the genetic algorithm (GA) to enhance the transport efficiency and reduce the accident loss. Due to the lack of research on the maximum number of iterations, control parameters, etc., the rationality of the proposed iteration number and parameters was tested through a case simulation on Matlab R2011b. Through repeated tests, it is proved that the GA, the maximum number of iterations and the control parameters can find the optimal solution for the routing problem and achieve the desirable effect. In addition, the authors discussed the impacts of different crossover probabilities and mutation probabilities on the solution time and accuracy. This research provides strong supports to emergency management agencies in transport route design, allocation of relief items, manpower and vehicles, and reduction of disaster loss.
Keywords: Coal emergency logistics vehicles, genetic algorithm (GA), routing problem, maximum number of iterations, control parameters
Aiming at understanding the evolution characteristics of permeability in coal masses containing gas during creep, samples of coal containing gas were collected from the No. 3 coal seam of Rundong coal mine, Yangcheng, China for analysis. The seepage is tested during the creep process in multi-stage axial load apparatus under different confining pressures using a self-developed multi-stage triaxial stress loading device allowing analysis of seepage during creep processes. Experimental results shows that: (1) obvious attenuation creep deformation and static deformation appeared during the creep process caused by multi-stage loading under low stresses, and the permeability decreased during the loading process and creep stage. The permeability decreased at a high rate in the initial stages of testing, gradually reaching a stable value and, it changed in the opposite sense to the axial deformation. Moreover, high confining pressures had certain inhibiting effects on the change in permeability of the coal samples; (2) The permeability varied slightly in the attenuated, and steady, stages under the failure stress of creep, and it decreased in the attenuated stage, while it linearly increased under steady state conditions. In the accelerated stage, the permeability increases significantly and it is several times greater than the initial permeability in the steady creep stage when the coal body is damaged; (3) In the creep damage stage, the changes in the permeability and volumetric strain conformed to an exponential function.
Keywords: Short-term creep, seepage, tectonic coal, multi-stage loading, permeability
In northeastern Chongqing, the Longmaxi formation shale has experienced several tectonic uplifts of various scales during the geological evolution, hence forming shale gas enrichment zones featuring thrust fold belt. Based on field geology, drilling core characteristics observation and physical simulation experiment, and combined with methane isothermal adsorption experiment, this paper carries out a quantitative analysis on the variation rules of gas content during the late uplift of thrust belt in northeastern Chongqing, and discusses escape modes of Longmaxi formation shale gas by stages. The results show that the reservoir experiences two major tectonic uplifts after hydrocarbon generation ends, during which the changes in adsorption capacity are mainly affected by the combination of temperature and pressure. The content of adsorbed gas in the reservoir slightly increases, and the content of free gas decreases rapidly, thus the total gas content decreases. The simplified geological model and simulation restoration of tectonic burial history in northeast Chongqing are constructed. The shale remodelling in the study area is divided into four stages. The initial tectonic uplift amplitude was about 1,400m, and the total gas content was reduced; the second uplift amplitude was about 1,100m, and the total gas content was further reduced.
Keywords: Shale gas, gas escape, gas content, Longmaxi formation, northeast Chongqing
Few studies can be found on the origin of coalbed methane in Tunlan minefield of Xishan coalfield, Taiyuan, which leads to incomprehensive understanding of the overall characteristics of coalbed methane genesis in Xishan coalfield. Based on the chemical composition and isotope test data of 6 gas wells in Xishan coalfield, this paper discusses the origin of coalbed methane. The results show that the average volume fractions of methane, ethane, nitrogen, carbon dioxide and argon are 89.93%, 0.03%, 6.64%, 0.30% and 0.12% respectively. and the values of carbon isotope and hydrogen isotope are -43.85%~-41.3% and -238.27%~-222.45%. carbon dioxide isotope value is- 12.8%~-6.0%. Data of chemical composition and isotopic test in Tunlan minefield shows that the coalbed methane has undergone secondary transformation, which is due to coal degradation. Secondary biogenic methane has been formed, which is the mixed genetic coalbed methane, and the secondary biogenic gas accounts for about 35%.
Keywords: Carbon isotope, coalbed methane, secondary biogenic gas, thermal degradation, Xishan coalfield
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.
Keywords: Hoek-Brown criterion, non-linear Mohr- Coulomb envelope, least square variance, reliability
The sporadic near-misses in the process of coal mine transportation causes interference to the safe and smooth production of coal mine. In order to scientifically prevent and control the occurrence of near-misses in coal mine transportation, the influential factors of near-misses in coal mine transportation have to be defined so as to take corresponding control strategies. Based on the initial established evaluation index system of influencing factors of near-misses in coal mine transportation, this paper constructed the structural equation model. Then questionnaire was designed, and questionnaire survey was carried out. The reliability and validity of the sample data were tested using SPSS24.0 and the model was verified and corrected using AMOS21.0. Results show that near-misses in coal mine transportation are influenced by such factors as transportation equipment system, organization and management system, quality of staff and workplace environment, with the influence degree of the above factors presenting a descending order. Moreover, the system of organization management exerts different degree of impact on the transportation equipment system, quality of staff and the workplace environment and the impact gets smaller and smaller following this order. Finally, the paper put forward the strategy of implementing standard operating procedures, establishing management mechanisms, strengthening safety culture construction, carrying out closed-loop education and training strategies, etc.
Keywords: Coal mine, transportation near-miss, safety management, influential factors
This paper aims at making accurate prediction of embankment slope failures. To this end, the acoustic emission(AE) technique is introduced to monitor the slope stability of embankments, and the similarity simulation is carried out indoor on embankment slopes with waveguide rods of different diameters and gravels with distinctive particle sizes. In the simulation tests, the AE feature data of the embankment slope models are obtained during the failure process. Then, the fractal theory is applied to analyse the features and variation patterns of the AE energy fractal dimensions of the embankment slopes throughout the failure process. The author also analyses the features and variation patterns of AE energy fractal dimension during embankment slope failure. The test results show that the fractal dimension remained at a low level at the onset, continued to increase during the test, and eventually peaked at the middle phase of the test. In the final phase, the fractal dimension started to decrease. The AE fractal dimension also peaked at the slip-impending phase and then drop all of a sudden. This research offers a valuable detection means for the forecast of embankment slope failure.
Keywords: Acoustic emission (AE), embankment slope, fractal dimension, similarity simulation
The crane of some single-storied steel structure mold workshop runs under load, causing obvious vibration of an adjacent two-storied steel structure office building along the crane running direction. Vibration test was done by using CRAS random signal and vibration analysis system DH-5922. As test results reveal, in case of cantilever brake, the office building resonates with the mold workshop, with a resonant frequency of 3.3 Hz; for the office building, the maximum vibration velocity is 2.26 mm/s, and the maximum vibration level is 105.72 dB, neither meeting ambient vibration requirements of the office area. In this regard, plans to reinforce the office building stiffness were proposed, and the reinforcement effect was simulated by using FEM (finiteelement method) midas. As simulation results reveal, the plan to add a cross brace is more conducive to the vibration damping of office building than the plan to expand the sectional area in the resonance direction. As results of acceptance testing after reinforcement show, for the office building, the fundamental frequency increases to 4.2 Hz; there is not resonance with the mold workshop any longer; the maximum vibration velocity decreases to 0.49 mm/s by 75%; the vibration level decreases to 82.38 dB by 22%. All of these values meet ambient vibration requirements of office area. The building stiffness was well improved. The proposed solution can be used as reference for the vibration test and problems solving of similar items.
Keywords: Single-storied steel structure workshop, office building, resonance, cross-bracing reinforcement
Fire in coal mines is a global problem which started due to numerous reasons. Thousands of coalfield fires are burning globally in every continent except Antertica. Jharia coalfield in India is one such place where number of coal reserves are under fire. The fire is spreaded over a vast area. The first coal fire in Jharia coalfield was reported in 1916 and are still burning inspite of best efforts to extinguish them.Read more
Crown pillar is a horizontal pillar left to protect the upper level workings when stope advances along the up dip direction and approaches to the upper level in cut and fill method of mining. These horizontal pillars are the main support structures for stopes during excavation. In this study the vertical movement of the pillars at crown level has been analysed by varying the rock mass parameters such as geological strength index (GSI), uniaxial compressive strength (UCS or ƒãci), modulus of elasticity (E), depth of pillar from surface (D) and thickness of horizontal pillar (T) using finite element method.These analyses have been conducted based on 135 non-linear numerical models considering Drucker-Prager failure criterion in plane strain condition. Results of finite element models are represented in terms of displacements in rock mass of the pillars. Displacement profiles of rock mass along the predefined paths are obtained, presented and analyzed for different models having variation in geo-mining conditions. Finally, the most important parameters affecting the convergence significantly are identified which may be incorporated in the design of the optimum crown pillar thickness.
Keywords: Geo-mining parameters, crown pillar; numerical modelling; vertical displacement, FEM, orebody width, pillar depth