Pilling Characteristics Of Caving Debris And Its Influences On Mine Pressure In Longwall Mining Steeply Dipping Coal Seam

The steeply dipping seam is defined by coal seam which pitch is 35°~55°. When coal seam pitch is more than 35°,The broken roof is no longer stay in place, b ut along the working face floor downward slide and roll, and fill the lower goaf region, and form a non-symmetrical filled belt. The belt changes the working- face roof constraint condition, resulting in non-evenly and non-symmetry of mine pressure behavior. Researching on the filling gangue characteristic and showing the influence of mine pressure in in steeply dipping coal seam have an important significance to enrich mining theory and technology in steeply dipping seam.In this paper, studied on the 1125?1123 working- faces in ChangShanzi coal mine, Launched the research by means of similar physical simu lation, numerical simulation, theoretical analysis and on-site underground pressure observation. The main conclusions are as follows:(1)After mining, the broken roof will slide and roll downward the lower goaf region, form a compacting caving debris area, fully filling area and small amount of filling area, and form a non-symmetrical filling belt. The characteristics of compacting caving debris area is strong with a certain intensity grading, the central goaf is filled with loose gangue, larger and the support strength is lower than upper area. The upper area has a small amount filling in goaf. It has an obvious partition characteristics.(2)The caving debris surrounding rock failure zone shifted to unfilled region. Filling higher the ratio, the less plastic zones development, The filling gangue effectively slowed down the mine pressure appears in the lower part of working- face. The stress release arch shifted to unfilled area when the goaf is being filled, and the higher the proportion of filling, the stress release arch smaller the range, and the smaller stress value. The overlying rock caving arch shifted to unfilled region, The vertical displacement of roof decreased with the increase of fil ing ratio.(3)The upper half of the rock beam is under tension, the lower part is under compression, and the filling gangue will support the rock beam, therefore the asymmetry stress distribution is caused. The basic roof fracture will breake in the upper part of the basic roof in steeply dipping seam. The basic roof can be broken to form an asymmetric triangular arch.(4)According to the 1125?1123working- faces geological conditions of C hangShanzi coal mine, the support stress state was monitored and analyzed, The result showed that the basic roof will fracture from the lower end of 45.7m, located in the middle position of 31# support area.The caving debris length is about 52.9m. The monitoring results showed that the central support had a maximum load, followed by the upper support and the lower was minimum. The Mine pressure first occurred at the middle working- face, then the upper working- face area, the lower working- face area. The mine pressure had obvious time sequence. The engineering practice and physical similar simulation, theoretical analysis a re in good agreement.