Research On System Optimization And Application Of Dragline Stripping Technology In Surface Mine

Dragline stripping is the mainstream technology of surface mining in foreign countries, which played a significant role in mining. The technology has less equipment than others, logging and dumping join closely, so the system is of high reliability. Dragline is the key equipment in this technology, which has many advantages such as: lower cost of production, larger production capacity, higher production. Dragline stripping technology was successfully applied in Heidaigou surface mine, which represent the advanced level of surface mining technology in our country. However, due to the study of dragline stripping started later than other foreign developed countries, there still exist a gap in terms of process design and optimization.Therefore, this paper did further studies to the operating characteristic, operating method, the theory of parameter design and application of dragline, the achievement could use in the design and application of similar technology, which have great meaning to theory and practice of disciplines in surface mining study and the design theory, mining tech, application and so on.The major research contents and achievements are as follows:(1) By means of long-term investigate and survey with operation process, we acquired the major technology parameters of equipment and working face, and formed the standard formulation of basic operation procedures. We cleared and defined each step of operation procedures, defined and explained the terminology of dragline operation.(2) In order to improve the efficiency of dragline operation,statistical study was made on time consuming of dragline single-operation cycle in Heidaigou surface mine. Then the distribution of time consuming and the restriction factor of efficiency in each operation step were obtained. The results show that mining methods and geometry of soil bench are the main influence factors of digging efficiency. Time consuming of equipment rotation is the main factor that influence the efficiency of single operation cycle, so rotation angle ratio of acceleration and deceleration process should be 3/2 in rotating and 4/5 in returning step respectively; Time consuming of bucket ascension is the key factor which restricts the efficiency of coal trench excavation. Reference table of dragline operation is made according to the restrictive relation between bucket ascension and equipment rotation; made evaluation criteria for equipment operation level, and provide reference to improve the management level and operation technique of dragline, and offer basis for improving the efficiency of equipment operation.(3) As the key equipment of dragline stripping, dragline has gigantic linear dimension, moves too slowly to frequent mobilize, its operating radius varies along with operating state, and needs extremely strict working environment. By means of long-term data acquisition and measurement, draw the conclusions as follows: the average operating radius of brushing work is about 94 m, the minimum excavation radius of initial state of excavating is 28.4m, the maximum reasonable radius of bench excavating is about 80 m, the reasonable radius of coal ditch excavating is about 70 m. Operating radius is an important parameter which influence excavating and dumping operation.(4) In the field operation, dragline bench height and shifting distance of excavating work dynamically change, Based on 8750-65 dragline parameters and on-site operation conditions, paper deduced different kinds of operation mode including initial state, reverse shifting, unidirectional advancing, round trip advancing, etc., concludes the relations of working bench height, shifting distance, shifting steps and advancing distance, recommends 8750-65 dragline apply roundtrip advancing mode.(5) This paper calculated the maximum of dumping volume, newly increased waste volume, twice casting volume and other major parameters under various process layout method, determined the position of the first and second operating center line. Take shifting time, geotechnical property, equipment characteristics into account, design 4 machine positions for dragline, and put forward circling shifting method. Take the change of coal seam occurrence condition into account, analyzed working platform elevating and declining work, and design reasonable operating method.(6) Based on the rock flow-direction and flow rate optimization theory, we put forward the optimization theory of project transformation for gravity center circle, and deduct the optimization theory. Results shows: rotational angle is constant value under certain working face parameters, and has no relation with transfer order and route of waste. According to the relation between time consuming and rotational angle in waste transportation, we divided the time consuming function into concave function and convex function, with the total minimum of time consuming as the optimization goal, optimized the transfer order and route of waste, results shows: the relation between time consuming and rotational angle accord with concave function, which should apply variance distance dumping method.(7) Based on the optimization theory of project transformation for gravity center circle, simulation optimization was made. According to the field condition, we made 3D model of dragline stripping working face, and determined the center of the circle of gravity, by means of long-term investigate and survey we achieved the probability distribution of time consuming, which provide the basis to simulation optimization under various bench height. Results shows: operating efficiency reached the maximal when bench height is 13m; on this condition, dragline operating efficiency declined after did extra bench expanding work by itself. The simulation results identify with field experimentation results and verify the reliability of the simulation model.(8) Field application studies show that: Integral cost of overburden removing declined along with the rising of bench height. However, we have to decline the bench height in order to improve production, and the bench height only can be designed up to 11 m to insure 32 Mt yearly output of coal. When the coal production rises from 25Mt/a to 32Mt/a, the unit cost of dragline system rises from 9.26yuan/m3 to 9.69yuan/m3, Stripping unit material costs increased by 4.64%. Consider that the production capacity of dragline is the restrict factor of current stripping ability, we raise dragline various propel speed method, by changing the stripping zone of dragline system, dynamically adjust the propel speed of stripping working face, so the operating efficiency can be enhanced and cost of stripping can be reduced.