• Quantified confining-pressure-driven stress migration along the bolt–grout–rock interface using BOTDA distributed sensing. • Established a strain-transfer-coefficient-based calibration framework to convert BOTDA strain profiles into bolt axial-force evolution. • Integrated pull-out tests, numerical simulation, and coal-mine roadway deployment to verify the consistency of along-bolt response patterns. • Demonstrated that increased confinement suppresses interface slip and improves anchorage stability, supporting roadway support safety assessment. With the normalization of deep mining in coal mines, high confining pressure environments pose challenges to support systems. However, traditional monitoring methods for bolt stress suffer from low sensitivity and poor real-time performance, making them inadequate for dynamically monitoring support systems under deep mining conditions. To reduce the frequency of anchor support inspections, this study integrates Brillouin optical time-domain analysis (BOTDA) fiber optic sensing technology with physical and numerical simulations, and adopts an experimentally validated strain-transfer coefficient as a calibration framework to interpret BOTDA-measured strains and evaluate the confining-pressure-dependent stress distribution of anchor bolts. Pull-out tests show that distributed fiber optics can monitor minute strains in anchor rod bodies. Based on the monitored changes in anchor bolt strain, it is possible to identify areas of concentrated strain in anchor rods that have been altered by surrounding pressure, and to discover the general causes of strain changes in each group. Numerical simulation indicates that as the confining pressure increases, the peak stress at the exposed end of the anchor rod decreases, the stress distribution becomes more uniform, and the internal displacement of the anchor rod decreases. In engineering practice, fiber optic sensors show good agreement with conventional load cells and successfully detected sudden axial force changes in the roadways of Kongzhuang Coal Mine, demonstrating higher sensitivity and identifying an axial force anomaly. This study establishes a coupled monitoring–simulation framework based on distributed BOTDA sensing, quantitatively revealing the confining-pressure–dependent stress evolution mechanism of anchor bolts and extending fiber-optic sensing applications from laboratory testing to practical coal-mine engineering. These findings elucidate the mechanical response of anchorage systems under confining pressure, providing a fiber optic monitoring approach for safety assurance of anchor bolt support in deep coal-mine roadways.
Zhang et al. (Sun,) studied this question.