Mechanical Characteristics and Control Technology of Floor in Gob-Side Entry Retaining

Abstract

The effect of abutment pressure caused by the mining influence of two working faces can easily lead to floor heave in gob-side entry retaining. According to the distribution law of abutment pressure loading on the floor of gob-side entry retaining, a mechanical calculation model is established based on the elastoplastic theory. The calculation results based on the production geology of track entry of 1024 working face in Zhongxin coal mine shows that the vertical stress and plastic zone in the floor increase with the advancing of working face at the stage of leading influence during first mining, increase first and then decrease at the stage of entry retaining during first mining, and increase at the stage of leading influence during second mining. Especially, the vertical stress distribution and plastic zone appear asymmetrical characteristic. In addition, the similarity model test of gob-side entry retaining demonstrates the forming process and shape of the main fracture plane of floor, that also proves the asymmetrical characteristics of floor heave. Finally, based on idea that high strength of roof and two sides can reduce the abutment pressure loading on the floor, the technology of strengthening support of roof and two sides is proposed to control floor heave in gob-side entry retaining, and the technology is proved by the calculation results based on the above mechanical calculation model. The research fruits can enrich theory of gob-side entry retaining technology to improve its application value.