Impact of the Mining Dimensions on the Stability of Backfilled Pier-Columns

Owing to alternate mining of the new and old mining areas on sites, the mining thickness and width of the working face for pier-column backfilling varies. Thus, there is an urgent need to determine the impact on the bearing performance of the backfilled pier-column after changing the mined dimensions. This study consisted of three-dimensional numerical simulations, physical experiments, and field testing. These methods were performed to study the impact on the stability of the backfilled pier-column after changing the dimensions of the working face. The numerical and physical simulation results revealed that the mining thickness has a greater impact on the stability of the backfilled pier-columns than the width. Field testing results proved that the designed parameters for the backfilled pier-column in situ satisfy the bearing requirements; thus, it can effectively support the overlying strata of the goaf after mining. When increasing the mining thickness, the stress borne by the pier-column increased, and its stability decreased. Upon increasing the mining width, the variation in the stress exerted onto the pier-column was remarkably small, and the change of the elastoplastic zone of the pier-column was also minimal.

Substantiating rational schedule to load trucks using draglines while mining a pit of Motronivskyi MPP

Purpose. To substantiate a rational schedule for the combined dragline-truck operation taking into consideration a coefficient of mining in the context of the pit. Methodology. Mathematical and graphical modeling was involved while determining a coefficient of mining concentration in the pit as well as feasibility analysis to select a rational procedure scheme for dragline operation. Findings. Recommendations for the selection of rational dragline operation, while truck loading in the context of Motronivsko-Annivskyi pit, have been developed taking into consideration mining concentration degree in the pit. It has been determined that bottom dragline unloading into a truck, located in the central part of bench mining width, as well as the dragline position at 0.5 A distance from the bench crest, is the most efficient plan of action for the conditions. Technological scheme to develop Motronivsko-Annivskyi pit has been proposed. Originality. Dependence of the mining concentration in the pit upon the parameters of development system elements according to different technological schemes has been derived. The dependence helps estimate development cost for overburden rocks using draglines with direct unloading into trucks. Practical value. Technological schemes for the combined dragline dump truck operation have been developed. Their use makes it possible to cut the prime cost of overburden activities. Implementation of the proposed solutions helps cut stripping cost by UAH 79.65 million a year if annual overburden volume is Qrozkryvu - Qstripping = 13.5 million m3/year.

Research on a Numerical Simulation and Prediction Model of Floor Mining Failure Depth in the Chenghe Mining Area

Ordovician limestone water on the floor is a serious threat to the safety of coal mine production in the Weibei coalfield, and prediction of the floor failure depth is the key for evaluating the mining conditions under pressure. This paper combines the hydrogeological conditions of the no. 5 coal seam and uses the FLAC3D program to determine the floor failure depth under two-factor (mining depth and width) and multifactor (mining depth, width, and height) conditions via numerical calculations and analysis. We obtain the fitting formula for the floor failure depth and analyze the influence of various factors on it. The results show that when the mining width does not exceed 200 m, the mining width has the greatest influence on the floor failure depth, followed by mining depth and mining height. In this paper, the working face floor failure depths measured values of 18 flat seams in China are taken as samples for comparison with the values calculated via empirical formulas and fitting formulas, and the maximum and minimum absolute errors and relative errors are analyzed. The nonlinear fitting regression formulas offered in this paper are found to provide strong predictive value, high accuracy, and a relatively small error range. The reliability and rationality of the models are further verified, thus providing a reference for future mining operations under safe aquifer water pressure conditions in the Weibei coalfield.

Surface and New Building Deformation Analysis of Deep Well Strip Mining

Aiming at the problem of surface movement and long-term stability of a work plane of deep well strip mining in Shandong Province, an observation station is set up on the surface of strip mining, and the surface deformation value during strip mining is measured with advanced measuring instruments; on the stable surface of the old mining area, the surface deformation monitoring work is also carried out for new buildings. In addition, the FLAC3D simulation method is used to determine the subsidence factor of different mining depth, mining width, mining length, and mining thickness, and the mathematical model between the subsidence factor and mining depth, mining width, mining length, and mining thickness is established. After the surface of the old goaf is basically stable after strip mining, the high-rise buildings are built. By changing the size of the new buildings and the amount of the load imposed on the surface, the surface deformation is simulated and calculated, and the relationship between the different load positions, load sizes, loading building sizes, and the surface activated deformation is obtained. The measured value of the surface deformation confirms that the load of the new buildings can induce the activation of the old goaf and make the surface generate secondary deformation, but the activated deformation makes the new building within the range of 1, so the new building is safe.

A Roadheader-Assisted Coal Cutter Based on Tensile Failure Mechanism of Coal

This paper proposes a new roadheader-assisted coal cutter (RACC) based on the tensile failure mechanism of coal. An innovative mining method, called the cutting inside and spalling outside mining (CISOM) method, is developed based on this new RACC. The mechanical model is established, and the working mechanism of the new CISOM method is illustrated using a column model and a beam model. The mechanical models reveal that the tensile stress causes greater deflection than compressive stress. The deflection and mining width demonstrates a quadratic relationship. To understand the stratum behaviors and improve mining efficiency, the stability of a working face owned by Jincheng Coal Mining Group in Shanxi is analyzed using UDEC numerical simulation. Numerical results indicate that the optimal values of the parameter are 0.8 m width for the inside cutting and 0.4 m width for the outside spalling at #1305 working face. The newly developed RACC was successfully applied at #1305 working face. The field results showed that the recovery rate of CISOM method is over 90%; i.e., it is improved by 20% in comparison with the traditional method.

The shift step optimization of belt conveyor in self-advancing semi-continuous mining technology based on SIMIO

Purpose This paper aims to develop a computer simulation processing method to simulate the mining operation of self-advancing semi-continuous mining technology and optimize the shift step of belt conveyor by using simulation modeling framework based on intelligent objects (SIMIO). The method would effectively solve the challenge of field testing such large-scale equipment. Design/methodology/approach The four operational modes of self-advancing semi-continuous mining technology at single bench had been illustrated. The operational system of this technology was analyzed and broken down to single units. By analyzing the time constitution of one operation cycle, the theoretical optimization model of shift step can be established and the optimization criteria is the time utilization ratio being maximum. Once the simulation flow was determined, a three-dimensional (3D) computer simulation model of this mining technology was developed by adapting the SIMIO simulating software to the theoretical model. The models were run to investigate the outputs from different operational modes using geological and mining data from East open-pit mine. Findings The result of these simulations showed that the four-mining-width one-shift (FMWOS) is at maximum production capacity during all operation modes. If transfer equipment is necessary, then this mode can adapt, but system will become more complex. There are minor differences between two-mining-width one-shift and three-mining-width one-shift. If transfer equipment is not necessary, then the two-mining-width one-shift can adapt during actual production. Originality/value The simulation results show that the proposed method can achieve the optimal shift step of a belt conveyor and effectively reduce the time loss caused by the coordination of multiple pieces of equipment while simultaneously improving operational efficiency.

Mining Project Design under Villages and Comparison Analysis of Mining Method

In order to solve the problem of coal mining under villages of regions of Yaoqiao Mine, through comprehensive analysis, the author considers that strip mining has feasibility in realistic, meanwhile, a series of mining width and retaining width was studied for strip mining and eventually a mining project was put forward to meet the unique conditions. By comparing application conditions and range of application between continuous miner used in strip type of Wongawilli coal mining method and shortwall shearer mining method, the author analyzes the economic benefit and draws a conclusion that shortwall shearer mining method has better applicability. Those all provide a new way to mining under villages in Yaoqiao Mine and the conclusion can also be used for reference in similar mining conditions.

Analysis of Separation and Dislocation Characteristics of Layered Roof in the Mined-Out Areas

The computational model based on the shallow mined-out areas was built by using FLAC3D, and the separation and dislocation characteristics of the layered roof in the mined-out areas were analyzed under different conditions. The results showed that the maximum value of the layered roof separation increased with the increase of the mining width, and that value decreased with the increase of lateral pressure and the cohesion between layers. The separation curves of the layered roof showed the shape variation from the symmetry flat arch to the asymmetric steeple arch and then to the linear form, the maximum separation value of the layered roof exhibited a three-stage tendency of a gradual increase, a steep reduction and a slight change, and the maximum dislocation value of the layered roof presented a two-stage tendency of firstly slow growth and then rapid growth with the increase of the dip angle of coal seam.