Research On Remnant Coal, Fully-mechanized Mining Technologyand Strata Behavior Regularity With The Old Mining Method

It has been a long time to mine coal of high quality in shallow overburden. However, a huge amount of residual coal resources are wasted, with less than 20% of coal utilized. Some research are made on key engineering technology, mainly about the old mining remnant coal, the mechanized second mining method, the strata behavior regularity in this paper.The old coal mining methods mainly include the roadway method, the room and pillar method and the column type method. After collecting and analyzing the practical engineering plan ichnographies of residual coal resources of over 100 coal mines during different historical periods, coal percentage recovery and the characters of residual coal resources were investigated. Some main results obtained are as follows: 1) There are 223.75 ton of the old mining remnant coal in Shanxi province and 801 ton in China; 2) There are a lot of water and gas accumulation in roadway goaf. Meanwhile the range and amount of water accumulation is unclear. As the remnant coal has been formed for a long time, the coal fractures are generally developmental, which led to low gas content less than 5m3/t, and gas pressure is generally lower than 0.5MPa.After lucubration, this paper present some basic principles of fully mechanized coal mining methods: 1) with the physical exploration first, it can be figured out the distribution of remnant coal and goaf, as well as the situation of water and gas in the goaf. 2) the remnant should be divided into different districts by grouting and then the districts are mined orderly. 3)by technical scheme in fully mechanized mining area and large working face, heavy mechanized mining equipment is chosen.With analog simulation experiments, this paper compared the room and pillar method, the column type method and those two mixed. Based on that, lots of numerical modeling experiments were investigated. Stretch and plastic failure, vertical stress distribution and displacement laws were analyzed, in which the angle between the work face and goaf is parallel 0°, 20°, 40°, 45°, 60°, 90°. The results show: If the angle is above 30°between the work face and the roadway during the mechanized second mining, the mining process can be taken smoothly, which will not lead to roof subsidence and collapse in the front of the work face. However, when the angle is below 30°, the mining process can not be taken smoothly. There will be great stress difference between the edge and middle of remnant coal pillars, which can be up to 2~3times. There are detailed descriptions of recovery process of Xiqu 22102 surface, including roadway experience, observational data, simulations and engineering practice, which verified the mentioned conclusions.The methods and technical proposal of fully-mechanized remnant coal mining, charged by the author, were taken in the design of the residual coal mining of Xiegou Coal Mine 18107 work face. The main conclusion can be draw: 1) the water in the roadway gob area poured out when tunneling the return airway, the management of the water before the pushment of working face can be conducted by applying the specific drainage measure. 2) when the the old goaf mining lane expose, gas consistency in the goaf was 0.8%-3.4%, by applying the negative pressure ventilation system and local ventilation the attenuation of the gas can meet the requirement of production. 3) when layout the work face of residual coal mining, the angle between work face and the tendency of goaf is above 30°and there are no roof caving accident along the period. 4)during the process of second mining of Xiegou Coal Mine 18107 work face, the working resistance of mining hydraulic support is 1.2-1.65 more than usual. The distribution of the working resistance of mining hydraulic support is heterogeneous. The working resistance of mining hydraulic support where is the goaf on the front is more 40% than that where is the coal on the front.According to research conclusions and revealed rules in this paper, the feasibility study reports and preliminary designs of Xihe coal mine, Shanxi Jinneng Group, have been completed.