Abstract: The traditional gob-side entry retaining with filling is cumbersome and slow, which cannot satisfy the requirements of modern high-intensity mining. Thus, a non-pillar mining technology by cutting roof is proposed to form a roadway along the empty. However, the design of key parameters is one of core problems of this technology, which has a great influence on the stability of gob-side entry retaining. In this study, theoretical analysis, numerical simulation and field tests are conducted to investigate the key parameters systematically at the 21304 working face of Chengjiao mine. We derive the formulas for the height and the angle of cutting roof by using the self-bearing of bulking rocks and the stability principle (S-R) of surrounding rock. A mechanical model of energy-cavity blasting is established and further used to determine the explosive payload and spacing of borehole in combination with numerical simulation and field tests. The results show that the mechanical relationship between the roof and stratum of mining goaf can be cut off if the designed parameters of cutting roof are proper. Additionally, the roof can collapse along pre-cutting and gangue of bulking rock can support the overlying roof. Moreover, the rotary sinking, disturbance to roadway and deformation of surrounding rock of roadway are all controlled by cutting roof. The key parameters for the 21304 working face of Chengjiao mine are obtained by theoretical calculation, numerical simulation and field tests. The field application indicates that the lateral roof of roadway can be quickly cut down into the roadside after robbing and all indicators can meet the requirements of this site.

Key words: pressure relief by roof cutting, gob-side entry retaining, key parameters, numerical simulation, engineering application