Research And Application Of Fracture Law And Deep Hole Presplit Blasting Weakening Technology In Hard And Thick Roof

In order to solve the problem about large area flap top under the condition of hard and thick roof, based on the physical and mechanical features of 101 fully-mechanized face of east-one mining area in Yuanlin coal mine, fracture law and deep hole presplit blasting technology in hard and thick roof was researched. By using elasticity analytical method and numerical simulation, first pressure pace、periodical pressure pace、plastic zone of roof strata and pressure curve of abutment in front of coal wall、weakening design before first roof breaking and reasonable step of periodical caving were researched. Based on particle peak vibration velocity(PPV), range of rock damage for deep hole presplit blasting was figure up. Based on finite element software ABAQUS, change of rock stress in different time and hole spacing on effect of blasting was analyzed and compared. Deep hole presplit blasting technology in hard and thick roof was put forward. Main research work and achievements are as follows:(1)Through analysis the thick and hard roof feature of 101 fully-mechanized face, the first roof caving step is about 55m~60m, the periodical roof caving step is 30m~35m. Weakening design before first roof breaking is side kerve. Reasonable space for roof advanced caving deep hole blasting is 30 m.(2)Deep hole blasting in 101 fully-mechanized face can make different damage about 11 m range. Numerical simulation determined that the blast hole space is 2m.(3)Deep holes’ diameter、length、angle、explosive payload and sealing length were layout by calculation and engineering analogy.Deep hole presplit blasting technology in hard and thick roof industrial experiment in 101 fully-mechanized face and mining pressure field testing and analysis show that:since 101 fully-mechanized face was weakening and mining, the original roof caving average space is 10m~20m. Roof falling was plenitude. the support working resistance in the upper face、central face and lower face were basically normal range. The goaf hanging arch area were reduced and verifies effectiveness of proposed technique.