Non-pillar mining technology of medium thick seam with roof cutting and pressure released retained gateway and complex roof

In order to realize a non pillar mining with a roof cutting and pressure released retained gateway, the support parameters of the constant resistance and high deformation anchor was rationally designed. With the medium thick seam of No. 21304 coal mining face with the complex roof in Chengjiao Mine as the engineering background, a FLAC3D numerical simulation was applied to analyze the pre-fractured roof cutting height and cutting angle affected to the stress and displacement of the surrounding rock along the retained gateway. the directional blasting radius and charging structure of the single borehole drilled with the slotting were determined by the site test. A tracing and monitoring study was conducted on the constant resistance anchor stressed, roof bedding, support pressure and cylinder yielding, gateway lateral stress and others individually. The study results showed that the non pillar mining with the roof cutting and pressure released retained gateway in Chengjiao Mine determined the key location of the surrounding rock deformation along the gateway and designed the support technique of the constant resistance and high deformation anchor. The rational roof cutting height was 8 m and the rational cutting angle was 15°. In the site test, the direction blasting radius and changing structure of the slotting single borehole were applied and the implemented effect was excellent. The tracing monitoring was conducted on the constant resistance anchor stressed, roof bedding, support pressure and cylinder yielding, gateway lateral stress and others and the whole effect of the retained gateway was good.