Study on deformation law and control of surrounding rock in roofcutting gateway retained along goaf in deep medium thick seam

In order to ensure a successful application of the gateway retained technology along the goaf with the roof cutting pressure released to a deep medium thick seam,a theoretical analysis,site measurement,numerical simulation and other methods were comprehensively applied to the study on the deformation law and control technology of the surrounding rock structure in the gateway retained along the goaf.The study results showed that after the roof cutting pressure releasing conducted,the pilot concentrated stress influence scope and strength of the gateway both were decreased.The surrounding rock in the gateway would have two features of a long stabilized time and continued deformation.The surrounding rock in the gateway with a distance over 440 m behind the coal mining face was stable basically.In the initial movement stage of the roof,a “constant resistant anchor + single props” was applied to the pilot support.In the roof serious movement stage,a “hydraulic lifting frame support + single prop shield” was applied to the enhanced support.In the roof gently slow movement stage,the hydraulic lifting frame supports and single prop were withdrawn.In the roof relative stable stage,a cross support at the fault zone and chamber was enhanced,a extensible U type steel retaining support was applied to the broken rock sidewall and could effectively control the surrounding rock deformation of the gateway with a good effect of the gateway.