Integrated FLAC3D simulation and field monitoring of bolt-cable supports in three deep coal-mine roadway cases

This paper examines the intricate engineering conditions encountered in typical deep coal mine roadways, specifically focusing on the effects of tectonic stress, the influence of narrow coal pillar gob-side gateways, and the elevated in-situ stress prevalent in deep mining environments. Utilizing the Zhaolou Coal Mine No.5309 track gateway, Dongtan Coal Mine No.3302 track gateway, and Baodian Coal Mine No.5312 belt gateway as case studies, this research conducts a systematic numerical simulation and on-site monitoring of a bolt–cable combined support system. Through employing FLAC 3D , three-dimensional numerical models are methodically established to analyze the distribution characteristics of surrounding rock displacement, stress, and plastic zones within each roadway under various existing support systems. The above gateways, in order, represent the dominance of deep-stress, tectonic, and narrow-pillar gob-side failures; these cases exhibit mining convergences of 125–655 mm, roof subsidence of 175–205 mm, bolt loads below 190 kN, and cable utilization under 26%. The rationality of the support system is further validated through on-site geomechanical tests, which include methodical assessments of surrounding rock structures, in-situ stress evaluations, and analyses of surrounding rock strength. The results from on-site monitoring demonstrate that during both excavation and mining phases, roof subsidence and sidewall convergence in all three roadways remain within the limits prescribed by design criteria, and the net cross-sectional dimensions of the roadways are in compliance with the “Coal Mine Safety Regulations” (Decree No. 17 of the Ministry of Emergency Management). The combined bolt-cable support system consistently operates within an elastic range, with bolt axial forces remaining below the yield tensile threshold and the utilization rate of cable bearing capacity being comparatively low. This indirectly suggests that the deformation of the surrounding rock met the established design requirements. The findings of this research provide substantial theoretical insights and serve as valuable engineering references for the design of support systems in deep mining roadways under complex geological conditions.