Study on Instability Characteristics of the Directional Borehole on the Coal-Seam Roof: A Case Study of the Tingnan Coal Mine

Directional long drilling on the roof is an effective gas control measure in goaf, but there little research stability of surrounding rock. In this study, geological conditions #4 coal seam Tingnan Coal Mine, Shaanxi Province, China taken as application background, and deformation characteristics boreholes under four typical rock were first analyzed based Universal Distinct Element Code (UDEC) numerical simulation. Secondly, stress, strain, plastic borehole with different diameters carried out using Fast Lagrangian Analysis Continua 3D (FLAC 3D). The effect casing was also simulated. results showed that mudstone lower than fine-grained sandstone coarse-grained sandstone. larger diameter, stability. tended to be unstable, especially when diameter 160 mm 200 mm. Traditional pipes can provide some protection, for large boreholes, protection poor. Based above research, uniaxial compression tests various internal support tubes, such ‘line-shaped’, ‘Y-shaped’, ‘cross-shaped’. cross-shaped pipe had highest compressive strength, which 4–5 times other types protective a good effect. reliable technical directional roofs through strata have important implications popularization technique.