Abstract:The dynamic pressure load of the mined out area above makes the advancing of fully mechanized coal faces difficult. To solve this problem, a case study was made of the 31201 work face, 3-1# coal seam. As the pressure is great during advancement, and as large areas of over-burdened supports often occur, the duration and length of periodic pressure steps in different areas, as well as the energy released were monitored, and a pressure occurrence pattern was thus developed. Based on the pressure pattern, oriented drilling and blasting was used to relieve the pressure caused by the concentrated pillars in the mine-out area above. According to the field data, when 31201 work face was passing the area of concentrated pillars, roof stability was greatly enhanced and pressure was reduced markedly, with no over-burdened supports; the average periodic pressure step and duration were 8.65m and 2.3m respectively. The scope and severity of surface cracks were also greatly reduced, and the goal of “bringing roof movement under control and relieving roof pressure step by step” was realized.
