Objective Surface multistage hydraulic fracturing of hard roofs using horizontal wells serves as an important technique for rock burst control in mines. However, fracturing technique under improper control might pose adverse impacts on excavated mining roadways underground, causing roadway deformation, mesh failure with block falling, and the flow of fracturing fluids into the roadways.

Methods This study investigated certain mining face of the Zhaoxian Coal Mine in the Yonglong mining area, Shaanxi Province. Targeting different characteristics and phenomena of roadways following hydraulic fracturing, this study analyzed the reasons why fracturing fluids flowed into roadways during hydraulic fracturing using theoretical analysis, numerical calculations, and numerical simulation. Accordingly, the fracturing technique was optimized, followed by verification through engineering application.

Results During hydraulic fracturing, surrounding rock deformations and mesh failure with block falling in the mining roadways occurred due to the combined effects of the original formation stress and hydraulic fracturing-induced stress on the surrounding rocks of the roadways. Fracturing fluids flowed into the roadways in three ways: (1) hydraulically stimulated fractures connected directly to roadway tunneling-induced fractures; (2) hydraulically stimulated fractures connected to roadway tunneling-induced fractures via natural fractures in rock layers, and (3) hydraulically stimulated fractures connected to roadway tunneling-induced fractures via matrix pores in rock layers. Fracture control technologies, such as the optimization of fracturing parameters and pumping procedures, were proposed. Based on the influencing mechanisms of early-stage fracturing on the roadways, fracture control technologies were adopted for the remaining fracturing stages, with no secondary response characteristics observed in the excavated roadways. Microseismic monitoring showed that the hydraulically stimulated fractures measured 52‒55 m in height and 304‒335 m in length, extending across the entire target mining face and 64‒95 m beyond the mining roadways on its both sides. These results demonstrated that the advance prevention and control of rock bursts in hard roofs were achieved while incorporating the safety of excavated roadways. Compared to the adjacent mining face, the target mining face exhibited significantly decreased average step distance in periodic weighting of 6.6 m, as well as distinctly reduced average daily total energy, maximum energy, and average daily frequency of microseismic events of 2.46 kJ, 5.02 kJ, and 4.7, respectively, during mining. Furthermore, no microseismic events with energy of 10⁴ J or above occurred during the mining process.

Conclusions The results of this study indicate that under specific geological conditions, it is necessary to conduct reasonable fracturing technique design and fracturing parameter optimization. These measures allow for more effective control of fracture propagation morphology, prevent adverse impacts of hydraulic fracturing on roadways, and ensure the effective control of disasters in hard roofs.