Slope Stability Under The Condition Of High-Wall Coal Mining-Replacement Seam In Open Pit Mine With Thick-Seam Coal Seam

The situation of high-wall overburden coal resources in China’s surface coal mines is more serious,and this problem is especially prominent in the open pit mines with huge thick coal seams,which is one of the important problems of green mining in surface coal mines.The main difficulty is to improve the recovery rate of coal resources overlapped by the high-wall while ensuring the stability of the high-wall slope.This thesis addresses this difficulty and proposes the method of using geopolymer with higher mechanical strength as backfill material for the replacement coal seam based on high-wall coal mining.The actual situation of a surface mine in Xinjiang is combined,and the operation equipment and process of this method are described.By means of theoretical derivation and numerical simulation,the factors affecting the stability of the slope in the process of coal seam replacement and their influence laws are revealed.The main results obtained are as follows:(1)The main equipment types and parameters were defined through field and data research;the backfill material ratios and mechanical parameters were determined through tests and numerical simulations;the spacing between adjacent cavities on the40 m working berm was determined to be 0.7m and the number of cavities was determined to be 6m based on the Mark-Bieniawski empirical formula;and the replacement process was described,starting with the replacement of cavities with odd numbers and then the replacement of cavities with even numbers.The replacement process is described,starting with an odd numbered refuge,followed by an even numbered refuge.(2)Explained that the stability of coal pillar directly affects the stability of the overall slope,considering that the replacement coal seam operation will disturb the original coal seam and lead to the destruction and destabilization of the coal pillar,which affects the operation and the stability of the overall slope;combined with the existence of the topping rate of the replacement material and its own porosity and redistribution by gravity,the calculation method was determined as the discretecontinuous coupling method;established a numerical simulation calculation model for the coal pillar,analyzed the vertical stress,displacement and shear strain increment distribution of the coal pillar,explored the stability of the coal pillar under different stages,and ensured the stability of the coal pillar in the operation process.(3)Based on the simplified Bishop method,the expression of slope stability coefficient under the replacement coal seam was derived,and the factors affecting the stability coefficient were clarified.Based on the influence law of engineering example and replacement scheme on slope stability coefficient,the best replacement scheme is determined under the engineering example,with replacement depth of 450 m and replacement height of 5.5m;the change law of stability coefficient,displacement change and plastic zone distribution under the replacement operation is discussed to ensure the stability of slope during the replacement operation;in order to improve the resource recovery rate,from the perspective of stability coefficient and shear strain increment,the downward multilayer In order to improve the resource recovery rate,the slope stability under the constraint condition of replacement coal seam of downward multi-layer is discussed.There are 39 figures,10 tables and 74 references in this thesis.