Study on the method of pressure relief by roof cutting and absorbing energy in deep coal mines

With the mining depth increases, under the condition of high stress and intensive disturbance, large deformation problem of roadway surrounding rock is more serious. Therefore, energy design criteria of support materials to control large deformation of roadway surrounding rock are established. Based on energy design criteria, the method of pressure relief by roof cutting and absorbing energy is proposed, which can be noted that the stress transfer path of overburden roof is cut off by using the technique of directional roof cutting to make roadway in the low stress state, and constant-resistance anchor cable with extraordinary characteristics of absorbing energy can effectively control the roof subsidence and deformation of roadway. A field engineering case using this method was performed in Guotun coal mine with burial depth of 890 m; field test results are as follows: (1) compared with the influence zone without roof cutting, support stress, advancing abutment stress, and lateral abutment stress in the influence zone of roof cutting is significantly reduced; (2) constant-resistance anchor cables have large deformation ability and extraordinary absorbing energy characteristic to meet energy design criteria; (3) compared with the influence zone without roof cutting, micro-seismic events, maximum energy, and total energy are obviously reduced in the influence zone of roof cutting; (4) the displacement of the gob-side roadway by using this method meets the engineering requirements. The field engineering case proves that this method can make the gob-side roadway in the state of low stress condition and improve the ability of absorbing energy of support system to effectively control large deformation of roadway surrounding rock.