When mining coal from the working face, the main roof withstands the overlying strata. The main roof’s first weighting and periodic weighting may cause accidents, such as crushing the working face hydraulic supports. A mechanical model of the main roof was constructed, and the contributing factors of first and periodic weights on the main roof were examined in order to prevent such accidents. The thickness of the main roof was found as the most contributory factor to the main roof’s stability. Therefore, a new directional roof crack (DRC) technique is proposed, which produces directional cracks in the main roof through directional blasting and makes part of it collapse in advance so as to reduce the thickness and relieve the first and periodic weighting. To verify the effectiveness of DRC, the mechanism of DRC was analysed. A mechanical model of the hydraulic support was constructed, and the DRC techniques were tested on-site. Field experiments with a complete set of monitoring schemes showed that, with DRC technology, the roof periodic weighting interval decreased by 35.36%, and the hydraulic support pressure decreased by 17.56%. The theoretical analysis was consistent with the measured results. Therefore, the DRC technology is feasible and effective to ensure mining safety at the working face.

There are many problems associated with the surrounding rocks of the gob-side entry retaining by roof cutting (GERRC) as they are difficult to stabilise in deep mines. The following needs to be studied to understand the problems such as the pressure relief mechanism, evolution law of the surrounding-rock stress and the key technologies of GERRC in deep mines. Cracks are formed by advanced directional blasting to sever the path of stress transmission from the roof of the goaf to the roof of the entry and reduce the lateral cantilever length of the roof. Therefore the surrounding-rock stress and roof structure are optimised. The broken and expanded gangue formed by the collapse of the strata in the range of roof cutting fills the mining space adequately, which avoids a rapid pressure increase caused by the roof breaking impact and slows down the movement of overlying strata. The deformation of the deep surrounding rocks is transformed from “abrupt” to “slow”, and the surrounding-rock deformation of the retained entry in deep mines is significantly reduced. The average pressure and periodic pressure of the supports near the blasting line can be reduced by the blasting cracks to a certain extent, mainly due to the reduction of the length of the immediate roof cantilever and the effective load of the main roof. The combined support technologies for GERRC in deep mines were proposed, and field tests were performed. The monitoring results show that the coordinated control system can effectively control the deformation of deep rock masses, and all indexes can meet the requirements of the next working face after the retained entry is stabilised.