Abstract
After roadway excavation, the deformation and failure of roadway surrounding rocks typically results in roadway damage or collapse. Conventional monitoring techniques, such as extensometers, stress meters, and convergence stations, are only capable to detect the stress or strain data with the shallow layers of surrounding rocks, and they require arduous manual works. Moreover, in the abovementioned monitoring techniques, the monitoring instruments are installed behind the excavation face; therefore, the strain and deformation occurring in front of excavation face cannot be detected. In order to eliminate these shortcomings, an innovative monitoring system for surrounding rock deformation control has been developed base on Brillouin optical time domain reflectometry. Compared with conventional monitoring systems, the proposed system provides a reliable, accurate, and real-time monitoring measure for roadway surrounding rock deformation control over wide extension. The optical fiber sensors are installed in boreholes which are situated ahead of the excavation face; therefore, the sensors can be protected well and the surrounding rock deformation behaviors can be studied. The proposed system has been applied within a TBM-excavated roadway in Zhangji coal mine, China. The surrounding rock deformation behaviors have been detected accurately, and the monitoring results provided essential references for surrounding rock deformation control works.
Highlights
In recent 20 years, as the depletion of coal resources in shallow strata, coal mining operations have been moving to deeper strata [1]
These emerging problems have resulted in large deformation and failures of surrounding rocks and roadway collapse which seriously threaten the safety of miners and limit output capacity of coal productions
The conventional monitoring techniques such as extensometers, stress meters, and convergence stations which have been typically applied in shallow roadways cannot meet the requirement of monitoring works in deep strata due to the lower precision and excessive manual operations
Summary
In recent 20 years, as the depletion of coal resources in shallow strata, coal mining operations have been moving to deeper strata [1]. For overcoming the problems of surrounding rock deformation monitoring in deep coal mines, many emerging measurement techniques have been conducted at working faces of coal mining and roadway excavation in underground coal mines. The monitoring of the whole section of the roadway, includes a deeper layer of surrounding rocks and excavation faces, has been a crucial issue of ensuring safety production in underground coal mines. This paper focuses on developing a BOTDR-based monitoring system for surrounding rock control of roadways in underground coal mines. (2) The optical fiber sensors need to be installed in deep boreholes for surrounding rock deformation measurement, and the steel wire-reinforced fibers are easier to insert into boreholes due to higher stiffness of the steel wire.
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