Study on deformation law of crossing layer drilling superimposed floor roadway

Floor extraction roadway through layer drilling is a pivotal strategy for gas control in areas prone to coal and gas outbursts. However, the efficacy of this method is often compromised due to the impacts of overburden pressure and mining-induced stress, leading to deformation and blockage of the floor through-layer drilling, thus diminishing the extraction efficiency. In this study, we focus on extraction roadways equipped with perforated floors, employing uniaxial compression testing and numerical simulation analyses of perforated specimens to elucidate the deformation dynamics of such roadways under loading conditions. The FISH command flow has been successfully implemented within the FLAC ^3D computational framework, facilitating a rigorous quantitative analysis of the plastic zone volume and failure mode in both perforated specimens and perforated floor configurations. Our findings elucidate that the drilling angle, drilling section, and coal-rock interface are pivotal determinants influencing the deformation dynamics of through-layer drilling operations. Notably, the compressive strength of the hole section, the hole body section, and the hole bottom section within the perforated specimen exhibits a decremental trend, with the corresponding deformation magnitude escalating progressively. Specifically, the compressive capacity diminishes in the following sequence: hole section, hole body section, and hole bottom section. The present investigation reveals that drilling operations at low dip angles are particularly susceptible to complications such as hole sticking and hole collapse. Consequently, the adoption of borehole protection strategies at the rock interface is recommended to mitigate the risk of hole collapse.