Support Technology of Large Cross Section Open-off Cut for Fully Mechanized Top Coal Caving Mining Face in Ultra Thick Seam

In order to solve the support dificulty of the open-off cut with a span of 10 m for the fully mechanized top coal caving mining face in Tashan Mine, the th eoretical analysis and the numerical calculation method was applied to set up the high strength bolt, the built-up anchor, the W steel band, the steel mesh and the concr ete combined support as the large span open-off cut support mode in order to form a group bolt closed effect and to keep the surrounding rock stability of the open-off C ut and the safety.During the test, the anchorage force of the anchor reached at 1401 60 kN, the max separation value of the roof in the anchorage zone was 7 mm and th e max convergence value between the roof and floor was 38 mm.The test results showed that the bolt-built-up anchor-concrete combined support proposed in the desig n could improve the integrated bearing force of the support structure, could effectively control the surrounding rock deformation of the open-off cut and could ensure the safety application of the large cross section open-off cut.