The gob-side entry 150∼180 m behind the 14201 working face at Majialiang Coal Mine suffered serious dedeformation. Technology to control the behavior of the high-located main key stratum (HMKS) is studied for mining safety. The failure type and the breaking span of HMKS were determined based on the key stratum theory and the voussoir beam model. By monitoring the entry deformation and surface subsidence, it was found that sliding of HMKS was the main cause of large deformation of the gob-side entry. A new technique was proposed to grout in separated-beds during the mining operation. Physic simulation results indicated that this technique is efficient in controlling the sliding of the HMKS and avoiding strong dynamic loading, with the peak of the abutment stress reduced by 59%. Grouting stations were set up at a spacing of 150 m behind the working face according to the technique principles and key parameters of the technique, and the geological conditions at Majialiang Mine. Before the HMKS slides, high-water content materials with a water to cement ratio of 1.5:1 are injected into the bed separation space in order to change the formation of the separation space and prevent the breaking of the key strata.

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