Study On The Relationship Between The Advancing Speed And Strata Behaviors Of Fully-mechanized Working Face

With the rapid development of coal mining industry, the proportion of fully mechanized coal mining in China has increased significantly. Keeping reasonable retreating speed is a key factor in realizing safety and high-efficiency of mining process. However, the relationship between working face advancing speed and strata behavior is still needed to be analyzed. In this paper, numerical modeling, physical experiments and field data on strata pressure analysis are combined to further analyze the relationship between the retreating speed and strata pressure, specifically, numerical simulation was adopted to analyze the plastic zone, stress field, displacement field of the working face, Similarity simulation experiments were applied to study the stress distribution of coal seam in overburden strata caving, and displacement features of coal body in front of working face. Besides, the field measurement was carried out to verify the results. Results show that:1) The main factors affecting the working face advancing speed were summarized. Through the calculation of analytic hierarchy process(AHP), the factors,including, Spontaneous combustion, gas emissions, coal mining machine performance, scraper conveyor performance, mine pressure and roof activities were rated 0.11、0.17、0.10、0.10、0.26 and 0.24, which indicates that strata behavior is the most significant factor in influencing the advancing speed of 20105 fully mechanized mining face.2) The plastic zone, stress field, displacement field of the mining face with different advancing speeds was analyzed through numerical simulation. With the acceleration of working face advancing speed, vertical stress moves closer to the coal wall as the retreating speed increases, the stress concentration factor increases while the stress decreasing zone decreases. With the decrease of working face advancing speed, the plastic damage area extends to the deep part of coal body. Low advancing speed will result in larger horizontal displacement. Accelerating the advancing speed is beneficial to prevent the rib spalling and roof controlling.3) Similarity simulation experiments were conducted to analyze the stress distribution of coal seam in front of the working face and displacement characters of overlying strata caving. The results show that: With the increase of advancing speed of the working face, the periodic weighting length will increase slightly, but the periodic pressure duration length increases obviously, meanwhile the peak value of bearing pressure will increase, the peak value position will be much more close to the working face, the high pressure area above the working face will enlarge, leading to the increase of sudden caving probability, in the actual production, the exorbitant gathering elastic energy is likely to induce the underground rock burst,and some other disasters.4) This paper completed the field data analysis of the 20105 fully mechanized working face of Yanghuopan mine. Bracket working resistance curve of the working face with different advancing speed was drawn. The results show that: accelerating the speed of working face possess little effect on the periodic roof weighting pace, but will increase the increase the pressure duration length, which further verifies the above experimental results. During the working face periodic roof pressure, the geological disasters, such as, roof fracture, surface subsidence and water storage roof intruding into the working face will happen. Thus the working face advancing speed should be organized in a relatively high speed to avoid long time stay.