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 difficulty of the open-off cut with a span of 10 m for the fully mechanized top coal caving mining face in Tashan Mine,the theoretical 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 concrete 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 cut and the safety.During the test,the anchorage force of the anchor reached at 140~160 kN,the max separation value of the roof in the anchorage zone was 7 mm and the 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 design 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.